DE69513394T2 - Thermoplastic elastomer reinforced with fine fibers and process for its production - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Scope of the invention

The invention relates to a fine fiber-reinforced thermoplastic elastomer composition, a process for producing the thermoplastic elastomer composition, an elastic material reinforced with fine fibers and a process for producing the elastic material.

More particularly, the invention relates to a fine fiber reinforced thermoplastic elastomer composition, wherein a matrix comprising an elastic component and a polyolefin component is reinforced by a fine fiber polyamide component, a process for producing the thermoplastic elastomer composition with high efficiency, a A fine fiber reinforced elastic material comprising the thermoplastic elastomer composition and an additional elastic component and having excellent elastic modulus, tensile strength and processability, and a method for producing the elastic material.

The fine fiber reinforced elastomer composition and the fine fiber reinforced elastic material are suitable for the production of external parts for tires, e.g. for the tread and sidewall, of internal parts for tires, e.g. for the carcass, braided edge, belt and bead, and of industrial products, e.g. for hoses, belts and straps, rubber rollers and rubber crawler belts.

2. Description of the state of the art

As is known, polyolefin resin materials such as polypropylene and ethylene-propylene copolymer materials have been widely used for manufacturing bumpers and interior trim parts for automobiles and casings and parts for household electrical appliances.

Most of these polyolefin resin materials have an elastic polymer, such as EPDM (ethylene propylene diene terpolymer), mixed in to improve their impact resistance.

For example, Japanese Patent Application Laid-Open (Kokai) No. 01-104636 discloses a polymer composition comprising a polypropylene resin and an ethylene-propylene copolymer rubber grafted to an organic short-fiber material using a coupling agent.

Furthermore, Japanese Laid-Open Patent Application (Kokoku) No. 02-248448 discloses a thermoplastic resin composition comprising a thermoplastic resin and a blend of a chlorinated polyethylene with short-fiber polyamide.

Further, Japanese Patent Laid-Open (Kokai) No. 2-251550 discloses a fiber-reinforced composition comprising chlorinated polyethylene and a polyamide which is in the form of fine fibers and dispersed in the chlorinated polyethylene.

Conventional fiber-reinforced elastomeric materials comprise a composition containing short fibers dispersed in a vulcanizable rubber material, e.g., natural rubber-polyisoprene, polybutadiene rubber, or ethylene-propylene copolymer rubbers, to improve its elastic modulus and mechanical strength. The conventional fiber-reinforced elastomeric materials are prepared by blending an elastomeric material with short fibers including those of nylon, polyester, or water-insolubilized polyvinyl alcohol and optionally vulcanizing the blend.

The conventional fiber-reinforced elastomer materials produced by the above-mentioned method are found to be inadequate in terms of mechanical strength and elongation when used as a material for manufacturing automobile tires. There is therefore a need for a new fiber-reinforced elastomer material which has improved mechanical strength and elongation properties.

In response to this need, attempts have been made to provide an improved elastomeric material which, under using fine, short fibers, e.g. nylon fibers, which have an average thickness of less than 1 µm. A fiber-reinforced elastomeric material of this type can be obtained by the following procedure: melt-kneading a mixture of a vulcanizable rubber material, a nylon-type resin and a binder at a temperature equal to or higher than the melting temperature of the nylon resin, extruding the kneaded melt through an extrusion die at a temperature equal to or higher than the melting temperature of the nylon resin to form a thread, and stretching or press-rolling the thread. Optionally, a vulcanizing agent is also added to the mixture to vulcanize the stretched or press-rolled material. This type of method is disclosed in Japanese Patent Laid-Open (Kokai) No. 58-79037, wherein a precondensate of a resol type alkylphenol-formaldehyde resin is used as a binder, or in Japanese Patent Laid-Open (Kokai) No. 59-43041, which uses a precondensate of a novolak type alkylphenol-formaldehyde resin as a binder, or in Japanese Patent Laid-Open (Kokai) No. 63-81137, wherein a silane coupling agent is used as a binder.

In conventional elastomeric materials, it is known that when an elastic polymer is mixed into the polyolefin resin, the resulting blend material exhibits reduced rigidity and mechanical strength, reduced yield stress and reduced creep resistance. In order to prevent the reduction in rigidity, mechanical strength, yield stress and creep resistance, glass fibers and/or an inorganic filler are mixed into the poly olefin resin. However, an increased proportion of the glass fibers or the inorganic filler causes the resulting molded article to have an unsightly appearance and an increased specific gravity. In general, the conventional fiber-reinforced elastomer compositions have advantages in that they not only have excellent tensile strength and elastic modulus but also have high tear strength and high elongation. However, the conventional fiber-reinforced elastomer composition has a disadvantage that because the fine fibers, e.g., fine nylon fibers, are dispersed in an elastic matrix, the resulting composition is difficult to granulate and therefore can only be produced in the form of a sheet or coarse material. Furthermore, the conventional fiber-reinforced elastomer composition has a disadvantage that when the reinforcing fibers, e.g., nylon fibers, are mixed in large amounts, the resulting composition is too rigid.

As a result of the above-mentioned disadvantages, the conventional elastomer composition must be manually divided when an additional vulcanizable elastic material and/or a vulcanizing agent is mixed therein. Also, in some cases, it is difficult to uniformly disperse the reinforcing fibers and the additional vulcanizable elastic material in the elastomer composition. To overcome these disadvantages, it is necessary to prolong the time of the melt-kneading treatment or to mix an additional vulcanizable elastomer material or other additive into the elastomer composition after the elastomer composition is softened by heating. This necessity has caused a decrease in the productivity of the fiber-reinforced elastomer composition. stomer composition and an increase in production costs.

The conventional fiber-reinforced elastomer composition is advantageous in that it exhibits a high elastic modulus and high fatigue resistance in the orientation direction of the reinforcing fibers. However, the conventional fiber-reinforced elastomer composition has the disadvantage that the elastic modulus and the fatigue resistance in the direction perpendicular to the orientation direction of the reinforcing fibers are noticeably low.

SUMMARY OF THE INVENTION

An object of the invention is to provide a fine fiber-reinforced thermoplastic elastomer composition having improved impact resistance, rigidity, mechanical strength, creep resistance and a low specific gravity; a process for producing the thermoplastic elastomer composition; a fine fiber-reinforced elastic material comprising the thermoplastic elastomer composition; and a process for producing the elastic material.

Another object of the invention is to provide a fine fiber reinforced thermoplastic elastomer composition which can be produced with high productivity at low cost and which has excellent elastic modulus and fatigue resistance not only in the direction parallel to the direction of orientation of the reinforcing fibers but also in the direction perpendicular or transverse to the orientation direction of the reinforcing fibers; a process for producing the thermoplastic elastomer composition; a fine fiber-reinforced elastic material comprising the thermoplastic elastomer composition; and a process for producing the elastic material.

The fine fiber reinforced elastomer composition according to the invention comprises:

(a) 100 parts by weight of an elastic component comprising at least one elastic polymer having a glass transition temperature of 0ºC or lower;

(b) 30 to 500 parts by weight of a polyolefin component, which comprises at least one polyolefin; and

(c) 10 to 500 parts by weight of a polyamide component which comprises at least one thermoplastic amide polymer with amide group-containing structural units, wherein

(i) the elastic component (a) and the polyolefin component (b) are in the form of a matrix and wherein in the matrix the elastic component (a) is in the form of a plurality of islands in a lake formed by the polyolefin component (b);

(ii) the polyamide component (c) is in the form of fine fibres and dispersed in the matrix; and

(iii) the elastic component (a), the polyolefin component (b) and the polyamide component (c) are chemically bonded to one another via at least one binder (d).

The process according to the invention for producing a fine fiber-reinforced thermoplastic elastomer composition comprises the steps:

(1) Melt-kneading a mixture comprising:

(a) 100 parts by weight of an elastic component comprising at least one elastic polymer having a glass transition temperature of 0°C or lower; (b) 30 to 500 parts by weight of a polyolefin component comprising at least one polyolefin; and (d) a binder, at a temperature equal to or higher than the melting temperature of the mixture to provide a matrix mixture in which the elastic component (a) is dispersed in the form of a plurality of islands in a lake formed by the polyolefin component (b);

(2) further kneading the matrix mixture together with (c) 10 to 500 parts by weight of a polyamide component comprising at least one thermoplastic amide polymer having amide group-containing structural units at a temperature equal to or higher than the melting temperature of the polyamide component (c) to provide a preliminary composition, the polyamide component (c) being dispersed in the form of fine particles in the matrix mixture; and

(3) extruding the preliminary composition through an extrusion die at a temperature equal to or higher than the melting temperature of the polyamide component (c), while cooling and stretching or press-rolling the extruded preliminary composition at a temperature lower than the melting temperature of the polyamide component (c) to convert the fine particles of the polyamide component (c) into fine fibers dispersed in the matrix mixture and to cause chemical bonding to be established between the components (a), (b) and (c) via the binder (d), thereby obtaining a fine fiber-reinforced thermoplastic elastic composition.

The fine fiber reinforced elastic material according to the invention comprises:

(A) the fine fiber reinforced thermoplastic elastomer composition as mentioned above and

(B) an additional elastic component which comprises at least one elastic polymer having a glass transition temperature of 0°C or lower and is mixed with the fine fiber reinforced thermoplastic elastomer composition (A) by kneading,

wherein, with respect to 100 parts of the total weight of the elastic component (a) and the additional elastic component (B), the polyolefin component (b) is present in an amount of 1 to 40 parts by weight and the polyamide component (c) is present in an amount of 1 to 70 parts by weight.

The process for producing the fine fiber reinforced elastic material according to the present invention comprises kneading the fine fiber reinforced thermoplastic elastomer composition (A) as mentioned above with an additional elastic component (B) comprising at least one elastic polymer having a glass transition temperature of 0°C or lower, at a temperature equal to or higher than the melting temperature of the polyolefin component (b) and lower than the melting temperature of the polyamide component (c),

wherein, with respect to 100 parts of the total weight of the elastic component (a) and the additional elastic component (B), the polyolefin component (b) is present in an amount of 1 to 40 parts by weight and the polyamide component (c) is present in an amount of 1 to 70 parts by weight.

BRIEF DESCRIPTION OF THE INVENTION

Fig. 1 shows chemical reactions between an elastic component (a), a polyolefin component (b) modified with a silane coupling agent (d) and a polyamide component (c) modified with a silane coupling agent (d');

Fig. 2 is a graphical representation of the stress-strain curves of the sheets made from the fiber-reinforced elastomer compositions of Example 2 and Comparative Example 1;

Fig. 3 is a micrograph showing the fibers formed from the polyamide component (c) dispersed in the sheet made from the fine fiber reinforced elastomer composition according to Example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The fine fiber reinforced elastomer composition according to the invention comprises:

(a) 100 parts by weight of an elastic component,

(b) 30 to 500 parts by weight of a polyolefin component and

(c) 10 to 500 parts by weight of a polyamide component in the form of fine fibers and dispersed in a matrix formed from the elastic component (a) and the polyolefin component (b).

The elastic component (a) comprises at least one elastic polymer having a glass transition temperature of 0°C or lower, preferably in the range of -120°C to -20°C.

The elastic polymer usable for the elastic component (a) is preferably selected from the group comprising: natural rubber; polyaliphatic diene elastomers, e.g. isoprene rubber, butadiene rubber, styrene-butadiene copolymer rubbers, acrylonitrile-butadiene copolymer rubbers, butyl rubbers, chlorinated butyl rubbers, brominated butyl rubbers, acrylonitrile-chloroprene copolymer rubbers, acrylic nitrile-isoprene copolymer rubbers, acrylate-butadiene copolymer rubbers, vinylpyridine-butadiene copolymer rubbers, vinylpyridine-styrene-butadiene terpolymer rubbers, styrene-chloroprene copolymer rubbers, styrene-isoprene copolymer rubbers, carboxylated styrene-butadiene copolymer rubbers, carboxylated acrylonitrile-butadiene copolymer rubbers, styrene-butadiene block copolymers, styrene-isoprene block copolymers, carboxylated styrene-butadiene block copolymers and carboxylated styrene-isoprene block copolymers; polyolefin elastomers, e.g. B. ethylene-propylene copolymer rubbers, ethylene-propylene-diene terpolymers, ethylene-butene copolymer rubbers, ethylene-butene-diene terpolymers, chlorinated polyethylene and chlorosulfonated polyethylene; polymethylene elastomers having a polymethylene group as the main chain, e.g. acrylic rubbers, ethylene-acrylic rubbers, polychlorotrifluoroethylene, fluorine-containing rubbers and hydrogenated acrylonitrile-butadiene rubbers; elastomers having an oxygen atom-containing organic group as the main chain, e.g. epichlorohydrin polymers, ethylene oxide-epichlorohydrin-allyl glycidyl ether terpolymers and propylene oxide-allyl glycidyl ether copolymers; silicone rubbers, e.g. H. polyphenylmethylsiloxane, polydimethylsiloxane, polymethylethylsiloxane and polymethylbutylsiloxane; and elastomers having a nitrogen and oxygen atom-containing organic group as a main chain, e.g. nitroso rubbers, polyester urethane rubbers and polyether urethane rubbers.

The elastic polymers that can be used for the elastic component (a) also include epoxy; silane or maleic acid modification products of the above-mentioned elastic polymers. Furthermore, the elastic polymers suitable for the elastic component (a) are preferably selected from thermoplastic styrene block copolymers, olefinic elastomers, urethane Elastomers, polyester elastomers, polyamide elastomers, 1,2-polybutadiene elastomers and vinyl chloride elastomers.

The polyolefin component (D) comprises at least one polyolefin. The polyolefin component preferably has a melting temperature of 80°C to 250°C or a Vicat softening temperature of 50°C to 200°C.

The polyolefin which can be used for the polyolefin component (b) is preferably selected from homopolymers and copolymers of olefins having 2 to 8 carbon atoms; copolymers of at least one olefin having 2 to 8 carbon atoms, at least one member being selected from the group comprising aromatic vinyl compounds, e.g. styrene, chlorostyrene and α-methylstyrene, vinyl acetate, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters and vinylsilane compounds, and halogenated polyolefins.

In detail, the polyolefin is preferably selected from the group comprising: high density polyethylene, low density polyethylene, polypropylene, propylene-ethylene block copolymers, ethylene-propylene random copolymers, linear low density polyethylene, poly-4-methylpentene-1, polybutene-1, polyhexene-1, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-acrylic acid copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-propyl acrylate copolymers, ethylene-butyl acrylate copolymers, ethylene-2-ethylhexyl acrylate copolymers, ethylene-hydroxyethyl acrylate copolymers, ethylene-vinyltrimethoxysilane copolymers, Ethylene-vinyltriethoxysilane copolymers, ethylene-vinylsilane copolymers, ethylene-styrene copolymers, chlorinated polyethylenes, brominated polyethylenes and chlorosulfonated polyethylenes.

More preferably, the polyolefin is selected from the group comprising: high density polyethylene, low density polyethylene, polypropylene, ethylene-propylene block copolymers, ethylene-propylene random copolymers, linear low density polyethylene, poly-4-methylpentene-1, ethylene-vinyl acetate copolymers and ethylene-vinyl alcohol copolymers. Of the series of polymers mentioned above, polyolefins whose melt flow index is in the range of 0.2 to 50 g/10 min are the most preferred for the polyolefin component (b).

The above-mentioned polyolefins can be used alone or as a blend of two or more of these polyolefins.

The polyamide component (c) comprises at least one thermoplastic amide polymer which carries structural units containing amide groups in the main chain and whose melting temperature is preferably 135°C to 350°C, more preferably 160°C to 265°C.

The amide polymer suitable for the polyamide component (c) is preferably selected from thermoplastic polyamides and polyureas. The thermoplastic polyamides are even more preferably used for the polyamide component (c) because the thermoplastic polyamides are capable of forming tough fibers by melt extrusion and stretching processes.

The thermoplastic polyamide suitable for the polyamide component (c) is preferably selected from the group comprising: nylon 6, nylon 66, nylon 6-nylon 66 copolymers, nylon 610, nylon 612, nylon 46, nylon 11, nylon 12, nylon MXD6, polycondensates of xylylenediamine with adipic acid, polycondensates of xylylenediamine with azelaic acid, polycondensates of Xylylenediamine with sebacic acid, polycondensates of tetramethylenediamine with terephthalic acid, polycondensates of hexamethylenediamine with terephthalic acid, polycondensates of octamethylenediamine with terephthalic acid, polycondensates of trimethylhexamethylenediamine with terephthalic acid, polycondensates of decamethylenediamine with terephthalic acids, polycondensates of undecamethylenediamine with terephthalic acid, polycondensates of dodecamethylenediamine with terephthalic acid, polycondensates of tetramethylenediamine with isophthalic acid, polycondensates of hexamethylenediamine with isophthalic acid, polycondensates of octamethylenediamine with isophthalic acids, polycondensates of trimethylhexamethylenediamine with isophthalic acid, polycondensates of decamethylenediamine with isophthalic acid, polycondensates of Undecamethylkendiamine with isophthalic acid and polycondensates of dodecamethylenediamine with isophthalic acid.

From the series of the above-mentioned thermoplastic polyamides, more preferably at least one member selected from nylon 6, nylon 66, nylon 6-nylon 66 copolymers, nylon 610, nylon 612, nylon 46, nylon 11 and nylon 12 is used for the polyamide component (c).

The thermoplastic polyamide preferably has a molecular weight of 10,000 to 200,000.

In the thermoplastic elastomer composition of the present invention, a mixture of the elastic component (a) with the polyolefin component (b) forms a matrix, and the polyamide component (c) is dispersed in the form of fine fibers in the matrix.

In the matrix, the elastic component (a) is in the form of several islands in a polyolefin component (b) formed lake. More preferably, in the matrix, the elastic component (a) and the polyolefin component (b) are chemically bonded to one another at the interfaces between the components (a) and (b) via the binder (d).

As mentioned above, a major portion of the polyamide component (c) dispersed in the matrix is in the fine fiber form. Preferably, 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more of the polyamide component (c) is dispersed in the form of fine fibers in the matrix.

The fine fibers of the polyamide dispersed in the matrix preferably have an average thickness of 1 µm or less, more preferably 0.05 to 0.8 µm, and have an average aspect ratio (ratio of fiber length to fiber thickness) of 10 or more.

Preferably, the polyamide component (c) is chemically bonded to the elastic component (a) and the polyolefin component (b) at interfaces between the components via the binder (d'). The binder (d') for the polyamide component (c) can be the same or different from the binder (d) for the elastic component (a) and the polyolefin component (b).

The percentage of component (c) bonded to components (a) and (b) is preferably 0.1 to 20%, more preferably 0.5 to 10%, based on the total weight of component (c). The percentage bonded to polyamide component (c) is determined by the following method.

A fine fiber reinforced thermoplastic elastomer composition of the present invention is refluxed with a solvent capable of dissolving only the elastic component (a) and the polyolefin component (b), for example xylene, to remove the components (a) and (b); then, the weight Wc of the remaining polyamide component (c) is determined.

Then, the percentage value of Wc based on the total weight Wco of the polyamide component (c) is calculated, namely Wc/Wco · 100. This percentage value is referred to below as the percent bond content of the polyamide component (c).

The chemical bonding of the polyamide component (c) to the elastic component (a) and the polyolefin component (b) in the thermoplastic elastomer composition of the present invention can be confirmed by the following method.

A fine fiber reinforced thermoplastic elastomer composition according to the invention is treated with a solvent which can dissolve only the elastic component (a) and the polyolefin component (b), for example xylene, under reflux of the solvent, the remaining polyamide component (c) is dissolved in another solvent and subjected to NMR analysis. In the resulting NMR spectrum, certain peaks are observed which originate from the elastic component (a) and the polyolefin component (b). Thus, the peaks indicate that parts of the elastic component (a) and the polyolefin component (b) are chemically bonded to the surface areas of the fibers formed by the polyamide component (c). The chemical bonds are derived from the binder (d'). The binders (d) and (d') are explained in detail below.

In the thermoplastic elastomer composition according to the invention, components (a), (b) and (c) are present in the following contents.

Based on 100 parts by weight of the elastic component (a), the polyolefin component (b) is present in amounts of 30 to 500 parts by weight, preferably 30 to 300 parts by weight, more preferably 40 to 200 parts by weight. When the content of the polyolefin component (b) is less than 30 parts by weight per 100 parts by weight of the elastic component (a), the resulting fine fiber reinforced thermoplastic elastomer composition exhibits a low creep resistance. Namely, when the resulting elastomer composition is subjected to a load for a given time so that it may undergo elongation and the load is then removed, the residual elongation, i.e., creep, of the elastomer composition is too large. Further, when the content of the polyolefin component (b) is more than 500 parts by weight, the creep resistance of the elastomer composition is low. , the resulting fine fiber-reinforced thermoplastic elastomer composition shows unsatisfactory impact strength.

The polyamide component (c) is present in amounts of 10 to 500 parts by weight, preferably 20 to 400 parts by weight, more preferably 30 to 300 parts by weight per 100 parts by weight of the elastic component (a). If the content of the polyamide component (c) is less than 10 parts by weight, the resulting thermoplastic elastomer composition exhibits unsatisfactory creep resistance. Furthermore, if the content of the polyamide component (c) exceeds 500 parts by weight, the content of the reinforcing fine fibers in the thermoplastic elastomer composition is too small, making it difficult to use the resulting thermoplastic elastomer composition in to produce a molded article having a smooth surface.

The above-mentioned fine fiber reinforced thermoplastic elastomer composition can be produced by the process of the present invention.

The method according to the invention includes

(1) a mixture comprising: (a) 100 parts by weight of an elastic component comprising at least one elastic polymer having a glass transition temperature of 0°C or lower; (b) 30 to 500 parts by weight of a polyolefin component comprising at least one polyolefin; and (d) a binder, is melt-kneaded at a temperature equal to or higher than the melting temperature of the mixture to provide a matrix mixture in which the elastic component (a) is dispersed in the form of a plurality of islands in a lake formed by the polyolefin component (b);

(2) the matrix mixture thus obtained is further kneaded together with (c) 10 to 500 parts by weight of a polyamide component which comprises at least one thermoplastic amide polymer having amide group-containing structural units, at a temperature equal to or higher than the melting temperature of the polyamide component (c) to provide a preliminary composition, the polyamide component (c) being dispersed in the matrix in the form of fine particles; and

(3) extruding the obtained preliminary composition through an extrusion die at a temperature equal to or higher than the melting temperature of the polyamide component (c), while cooling and stretching or press-rolling the extruded preliminary composition at a temperature lower than the melting temperature of the polyamide component (c) to convert the fine particles of the polyamide component (c) into fine fibers dispersed in the matrix mixture and to cause a chemical bond to be established between the components (a), (b) and (c) via the binder (d), thereby obtaining a fine fiber-reinforced thermoplastic elastic composition.

In an exemplary embodiment of the melt-kneading step (1), the polyolefin component (b) is melt-kneaded together with the binder (d) to modify the component (b) with the binder (d), then the polyolefin component (b) modified with the binder (d) is mixed with the elastic component (a), and this mixture is melt-kneaded at a temperature equal to or higher than the melting temperature of the mixture to further modify the elastic component (a) with the binder (d) and provide a matrix mixture.

In another embodiment of the melt-kneading step (1), the elastic component (a), the polyolefin component (b) and the binder (d) are mixed together and then the mixture is subjected to the melt-kneading treatment.

The melt-kneading treatment can be carried out using a conventional equipment for melt-kneading resins or rubber. The melt-kneading treatment can be carried out in any of the following ways: the melt-kneading equipment can be, for example, a Banbury mixer, kneader, kneading extruder, open kneading roll mill, monoaxial kneader and biaxial kneader. In view of the fact that the melt-kneading treatment can be carried out in a continuous manner and can be completed within a short time, biaxial extruder-kneaders are most preferably used for the process of the invention.

In the process of the present invention, the binder (d) is preferably used in amounts of 0.1 to 2.0 parts by weight, more preferably 0.2 to 1.0 parts by weight, based on 100 parts by weight of the polyolefin component (b). If the content of the binder (d) is less than 0.1 part by weight per 100 parts by weight of the polyolefin component (b), the resulting matrix may exhibit unsatisfactory mechanical strength. Further, if the content of the binder (d) is more than 2.0 parts by weight, the resulting matrix may exhibit unsatisfactory elastic modulus.

The binder (d) may comprise at least one member selected from conventional coupling agents for organic polymeric materials. The coupling agents include silane coupling agents, titanate coupling agents, phenol-formaldehyde precondensates, e.g., novolak-type alkylphenol-formaldehyde precondensates, resole-type alkylphenol-formaldehyde precondensates, novolak-type phenol-formaldehyde precondensates and resole-type phenol-formaldehyde precondensates, unsaturated carboxylic acids, unsaturated carboxylic acid derivatives and organic peroxides.

The most preferred coupling agents are silane coupling agents because they cause the elastic component (a) and the polyolefin component (b) does not gel or gels less and is therefore firmly bound together.

The silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, vinyl tris-(β-methoxyethoxy)silane, vinyltriacetylsilane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ- Glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylethyldimethoxysilane, N-β-(aminoethyl)-amino-propyltrimethoxysilane, N-β-(aminoethyl)-amino-propylmethyldimethoxysilane, N-β-(aminoethyl)-amino-propylethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-[N-(β-methacryloxyethyl)-N,N-dimethylammonium-(chloride)]-propylmethoxysilane and styryldiaminosilane. From the series of these compounds Preferred silane coupling agents are those which have reactive groups which can be easily eliminated by taking up a hydrogen atom from hydrogen atom-containing groups such as alkoxyl groups of the compound to be reacted with the silane coupling agents and/or polar groups and vinyl groups.

The titanate coupling agents suitable for the present invention include isopropyl isostearyl titanate, isopropyl tri-(N-aminoethyl) titanate, tetra-(2,2-diallyloxymethyl-1-butyl)-bis-(ditridecyl)-phosphite titanate, bis-(dioctyl pyrophosphate)-oxyacetate titanate, isopropyl trioctanoyl titanate, isopropyl isostearyl diacryl titanate, and isopropyl dimethacroyl diacryl.

The unsaturated carboxylic acids and unsaturated carboxylic acid derivatives which can be used for the invention include α,β-unsaturated carboxylic acids, cycloaliphatic unsaturated carboxylic acids, alkenylcarboxylic acids and derivatives of in the above-mentioned carboxylic acids. The unsaturated carboxylic acids and these derivatives are preferably selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, vinylbenzoic acid, vinylphthalic acid, endobicyclo-(2,2,1)-5-hapten-2,3-carboxylic acid, di-4-cyclohexene-1,2-carboxylic acid, octadecenylsuccinic acid and anhydrides, esters and metal salts of the above-mentioned acids.

The organic peroxides which can be used in the present invention include 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-tert-butylperoxycyclohexane, 2,2-di-tert-butylperoxybutane, n-butyl-4,4-di-tert-butylperoxyvalerate, 2,2-bis(4,4-di-tert-butylperoxycyclohexane)propane, 2,2,4-trimethylpentylperoxyneodecanoate-α-cumylperoxyneodecanoate, tert-butylperoxyneohexanate, tert-butylperoxypivalate, tert-butylperoxyacetate, tert-butylperoxylaurate, tert-butylperoxybenzeneate and tert-butylperoxyisophthalate. Among these compounds, preferred organic peroxides are those whose 1-minute half-life temperature is equal to or approximately 30°C higher than the melt-kneading temperature, particularly in the range of 80°C to 260°C, more particularly in the range of 110°C to 200°C.

Regarding the above-mentioned binders, the silane coupling agents are the most preferred because they do not allow the elastic component (a) and the polyolefin component (b) to gel or cause them to gel to a lesser extent.

When the silane coupling agents are used as binders, the organic peroxide can be used together with the silane coupling agent. The use of the organic peroxide together with the silane coupling agent has the following advantages.

The organic peroxide causes the formation of radicals on the molecular chains of the polyolefin component (b), and the radicals react with the silane coupling agent, so that the reaction of the polyolefin component (b) with the coupling agent is promoted.

In this case, the organic peroxide is preferably used in amounts of 0.01 to 1.0 parts by weight per 100 parts by weight of the polyolefin component (b).

Where the elastic component (a) comprises natural rubber, polyisoprene or styrene-isoprene-styrene block copolymers, organic peroxide can be dispensed with. When the elastic polymer such as natural rubber, polyisoprene or styrene-isoprene-styrene block copolymer having an isoprene structure is kneaded at high temperatures, the main chains of the polymer are severed by mechanochemical reactions and certain peroxide groups containing -COO· radicals are formed at the ends of the severed molecules. The peroxide groups have the same function as the organic peroxides.

In the further kneading step (2) of the process of the present invention, a mixture of the matrix mixture with 10 to 500 parts by weight of a polyamide component (c) is prepared at a temperature not lower than the melting temperature of the polyamide component (c) to provide a preliminary composition. During the further kneading step (2), the polyamide component (c) is dispersed in the form of fine particles in the matrix mixture. Before the further kneading step (2), the polyamide component (c) may or may not be modified with a binder (d').

The modification of the polyamide component (c) with the binder (d') can be carried out by melt-kneading the polyamide component (c) mixed with the binder (d') at a temperature equal to or higher than the melting temperature of the polyamide component (c).

The binder (d') for the polyamide component (c) is selected from the same compounds that can also be used for the binder (d) for the elastic component (a) and the polyolefin component (b). Furthermore, the binder (d') used for the polyamide component (c) can be the same or different from the binder (d) used for the elastic component (a) and the polyolefin component (b).

Preferably, the binder (d') for the polyamide component (c) comprises at least one member selected from the group consisting of silane coupling agents, titanium coupling agents, unsaturated carboxylic acids, unsaturated carboxylic acid derivatives and organic peroxides.

The most preferred binders (d') are the silane coupling agents because they do not lead to gelling of the polyamide component (c) or cause it to gel less.

The silane coupling agents are selected from those which contain reactive groups, e.g. alkoxyl groups which are able to bond to nitrogen groups in the amide groups (-NHCO-) of the polyamide component (c) via a water or alcohol elimination reaction. Silane coupling agents of this type are preferably selected from vinylalkoxysilanes, e.g. vinyltrimethoxysilane, vinyltriethoxysilane and vinyl-tris-((3-methoxyethoxy)-silane, vinyltriacetylsilane, γ-methacryloxypropyltri methoxysilane, γ-[N-(β-methacryloxyethyl)-N,N-dimethylammonium-(chloride)]-propylmethoxysilane, N-β-aminoethyl)-8-amino-propyltrimethoxysilane and γ-ureidopropyltriethoxysilane and styryldiaminosilane.

The melt-kneading treatment for the polyamide component (c) mixed with the binder (d') can be carried out using the conventional melt-kneading equipment which can also be used for the melt-kneading step (1).

In the further kneading step (2), the unmodified polyamide component (c) or the polyamide component (c) modified with the binder (d') or a mixture of the unmodified polyamide component (c) with the binder (d') is mixed into the matrix mixture, and the resulting mixture is subjected to a further kneading treatment at a temperature that is equal to or higher than the melting temperature of the polyamide component (c) which is unmodified or modified with the binder (d').

When using the binder (d'), the content of the binder (d) is preferably 0.1 to 5.5 parts by weight, more preferably 0.2 to 5.5 parts by weight, even more preferably 0.2 to 3 parts by weight, per 100 parts by weight of the total amount of the polyamide component (c) and the binder (d').

The binder (d') applied to the polyamide component (c) leads to an effective improvement in the chemical bonding of the polyamide component (c) to the elastic component (a) and the polyolefin component (b) in the matrix, so that the creep resistance of the resulting fine fiber-reinforced thermoplastic elastomer composition according to the invention is improved.

If the content of the binder (d') is more than 5.5 parts by weight, the polyamide component (c) may be overmodified and thus may not be formed into fine fibers, whereby the resulting elastic composition may exhibit unsatisfactory creep resistance.

Even if the binder (d') is not used, parts of the polyamide component (c) can be chemically bonded to the elastic component (a) and the polyolefin component (b) - modified with the binder (d) at the interfaces between the components (c) and the components (a) and (b) - during the further kneading step.

In the case that the elastic component (a) has a certain melting temperature, the temperature in the further kneading treatment is preferably equal to or higher than the melting temperature of the elastic component (a).

If the temperature in the further kneading treatment is lower than the melting temperature of the polyamide component (c), the polyamide component (c) cannot be dispersed in the form of fine particles in the matrix, resulting in that in the extrusion step (3) the polyamide component (c) cannot be dispersed in the form of fine fibers in the matrix.

Preferably, step (2) of further kneading is carried out at a temperature which is at least 30°C above the melting temperature of the polyamide component (c).

When the polyamide component (c) is modified with the binder (d'), the further kneading treatment (2) is preferred and using conventional melt kneading equipment such as a Banbury mixer, a melt kneader, a kneading extruder, an open kneading mill, a monoaxial kneader or a biaxial kneader.

When the polyamide component (c) is not modified with the binder (d'), the step (2) of further kneading is preferably carried out using a melt-kneading device capable of kneading at a high shear rate, for example, a Banbury mixer or a biaxial kneader.

When the polyamide component (c) is modified with the silane coupling agent, the -NH group of the polyamide component (c) is bonded via the silane coupling agent in such a way that a hydrogen atom is removed from the -NH group and the remaining nitrogen atom reacts with the silane coupling agent to form a nitrogen-silicon bond. In addition, when the polyamide component (c) modified with the silane coupling agent is kneaded into the matrix mixture, the silane coupling agent residue of the modified polyamide component (c) reacts with main chains or side chains of the elastomer molecules in the elastic component (a) to form nitrogen-silicon-carbon bonds between the polyamide component (c) and the elastic component (a). Furthermore, the polyamide component (c) modified with the silane coupling agent can react with the polyolefin component (b) to form nitrogen-silicon-carbon bonds therebetween.

The resulting preliminary composition is subjected to the extrusion step (3) of the process according to the invention.

In the extrusion step (3), the preliminary composition is melt-extruded through an extrusion die, e.g., a melt spinneret or T-die, slot or blow die, at a temperature equal to or higher than the melting temperature of the polyamide component (c), and the extruded stream of the preliminary composition is cooled and stretched or press-rolled at a temperature lower than the melting temperature of the polyamide component (c).

Preferably, the extrusion temperature is at least 20°C, preferably 20°C to 50°C above the melting temperature of the polyamide component (c).

During the melt extrusion process, the particles of the polyamide component (c) are bonded into fine fibers, and during the stretching or press rolling process, the fine fibers formed from the polyamide component (c) are stretched to improve the orientation and mechanical strength of the fine fibers. The stretching or press rolling process is carried out at a temperature lower than the melting temperature of the polyamide component (c).

When the preliminary composition is extruded through a melt spinneret, the extruded melt stream in the form of a thread or yarn is cooled during drawing or drafting, and the drawn thread is wound onto a bobbin or drum. The term "drawing" or "drafting" refers to a process in which the extruded thread is wound at a winding speed higher than the extrusion speed through the die. The drawing or drafting ratio is the ratio of the winding speed to the extrusion speed.

In the extrusion step (3) of the process according to the invention, the stretch ratio is preferably 1.5 to 100, more preferably 2 to 70, even more preferably 3 to 50.

If the stretch ratio is greater than 1, the extruded thread is stretched during cooling.

The extruded filament may be subjected to a continuous rolling operation by means of a press roll or roller. Alternatively, the preliminary composition is melt-extruded through a T-die or a blowing die and the extruded ribbon is drawn (stretched) with cooling and then wound onto a take-up roll. Alternatively, the extruded ribbon may be subjected to a continuous rolling operation by means of a press roll or roller.

As a result of the extrusion step (3), a fine fiber reinforced thermoplastic elastomer composition in the form of a thread, yarn or tape is obtained. The thermoplastic elastomer composition can be granulated using a granulating device or used as a yarn prepreg.

The fine fiber reinforced elastic material according to the invention comprises:

(A) the fine fiber reinforced thermoplastic elastomer composition of the invention as mentioned above and

(B) an additional elastic component which comprises at least one elastic polymer having a glass transition temperature of 0°C or lower, preferably -20°C or lower, and which is reinforced with the above-mentioned fine fiber thermoplastic elastomer composition (A) by kneading.

In the elastic material according to the invention, the polyolefin component (b) is present in amounts of 1 to 40 parts by weight, preferably 2 to 30 parts by weight, and the polyamide component (c) is present in amounts of 1 to 70 parts by weight, preferably 2 to 55 parts by weight, per 100 parts of the total weight of the elastic component (a) and the additional component (B).

The elastic polymer for the additional elastic component (B) can be selected from the same components as can be used for the elastic component (a). The additional elastic component (B) can consist of a single elastic polymer or a mixture of two or more elastic polymers.

The composition of the additional elastic composition (B) may be the same as that of the elastic component (a) or different therefrom.

In the elastic material of the present invention, if the content of the polyolefin component (b) is more than 40 parts by weight per 100 parts of the total weight of the elastic component (a) and the additional elastic component (B), the resulting elastic material exhibits unsatisfactory elasticity. On the other hand, if the content of the polyolefin component (b) is less than 1 part by weight, the resulting elastic material exhibits unsatisfactory physical properties, e.g., poor fatigue resistance.

With a content of the polyamide component (c) of more than 70 parts by weight, the resulting elastic material shows a unsatisfactory tensile strength, elongation at break and processability. When the content of the polyamide component (c) is less than 1 part by weight, the resulting elastic material shows unsatisfactory mechanical strength. Generally, the weight ratio of the thermoplastic elastomer composition (A) to the additional elastic component (B) is not limited to a specific ratio as long as the contents of the olefin component (b) and the polyamide component (c) are within the above-mentioned specific ranges based on the total weight of the elastic component (a) and the additional elastic component (B). However, when the weight ratio of the additional elastic component (B) to the elastomer composition (A) is in the range of 20:1 to 0.1:1, more preferably in the range of 10:1 to 0.5:1, the resulting elastic material shows improved processability by kneading.

In the elastic material according to the invention, the elastic component (a) and the additional component (8) can be vulcanizable or vulcanized.

In the method for producing the fine fiber reinforced elastic material of the present invention, the fine fiber reinforced thermoplastic elastomer composition (A) of the present invention with an additional elastic component (B) comprising at least one elastic polymer having a glass transition temperature of 0°C or lower is subjected to a kneading-mixing treatment at a temperature equal to or higher than the melting temperature of the polyolefin component (b) and lower than the melting temperature of the polyamide component (c). The contents of the polyolefin component (b) and the polyamide component (c) are adjusted as mentioned above.

When the kneading-mixing process is carried out at a temperature lower than the melting temperature of the polyolefin component (b), the fine fibers formed by the polyamide component (c) are not uniformly dispersed in the matrix.

When the kneading-mixing treatment is carried out at a temperature higher than the melting temperature of the polyamide component (c), the fine fibers formed by the polyamide component (c) are melted and take the form of spherical particles.

The kneading-mixing temperature is preferably at least 5ºC above the melting temperature of the polyolefin component (c).

For the process for producing the elastic material, the fine fiber-reinforced thermoplastic elastomer composition is preferably in granulated form because the granules can be easily and evenly mixed with the additional elastic component (B), which is preferably in the form of granules, and the fine reinforcing fibers formed by the polyamide component (c) can be evenly distributed in the resulting elastic material.

In the method for producing the elastic material, when the elastic component (a) and the additional elastic component (8) are vulcanizable, the fine fiber reinforced thermoplastic elastomer composition (A) and the additional elastic component (B) may be mixed with a vulcanizing agent and optionally with a vulcanization accelerator by kneading.

The vulcanizing agent is preferably used in amounts of 0.1 to 5.0 parts by weight, more preferably 0.5 to 3.0 parts by weight, per 100 parts by weight of the total weight of the elastic component (a) and the additional elastic component (B). The vulcanization accelerator is preferably used in amounts of 0.01 to 2.0 parts by weight, more preferably 0.1 to 1.0 parts by weight, per 100 parts by weight of the sum of the elastic component (a) and the additional elastic component (B).

The vulcanizing agent usable in the invention can be selected from conventional vulcanizing agents, e.g. sulfur, organic peroxides such as dicumyl peroxide and conventional hydroperoxide vulcanizing resins, e.g. alkylphenol-formaldehyde resins, melamine-formaldehyde resins and triazine-formaldehyde resins, and metal oxides, e.g. magnesium oxide, zincoside and lead monoxide.

The vulcanization accelerator usable in the invention can be selected from conventional vulcanization accelerators, e.g. aldehyde-ammonium compounds, aldehyde-amine compounds, guanidine compounds, thiourea compounds, thiazole compounds, thiuram compounds, dithiocarbonate compounds and xanthate compounds.

When the vulcanizing agent is mixed into the fine fiber reinforced thermoplastic elastomer composition (A) and the additional elastic component (B), the resulting elastic material is preferably vulcanized at a temperature ranging from 100 to 180°C and below the melting temperature of the polyamide component (c). If the vulcanization temperature is higher than the melting temperature of the polyamide component (c), the properties of the polyamide component (b) are reduced. component (c) are melted and take the form of spherical particles. The resulting vulcanized material cannot be reinforced by the fine fibers.

The fine fiber reinforced elastic material optionally contains an additive comprising at least one member selected from, for example, reinforcing materials such as carbon black, white carbon black, activated calcium carbonate, superfinely ground magnesium silicate, high polystyrene resins, phenolic resins, lignin, modified melamine resins, coumarone-indene resins and petroleum resins; fillers such as calcium carbonate, basic magnesium carbonate, kaolin, zinc oxide, diatomaceous earth, regenerated rubbers, powdered rubbers, hard rubber powder; stabilizers such as amine-aldehyde compounds, amine-ketone compounds, amines, phenolic compounds, imidazole compounds, sulfur-containing antioxidants and phosphorus-containing antioxidants; and colorants.

In the thermoplastic elastomer composition of the present invention, a plurality of fine reinforcing fibers formed from the polyamide component (c) are dispersed in the matrix comprising the elastic component (a) and the polyolefin component (b) and chemically bonded to the components (a) and (b) at the interfaces therebetween. However, as a whole, the elastomer composition is thermoplastic. For this reason, the elastomer composition of the present invention is processable by the same molding methods as the ordinary thermoplastic resins, such as injection molding, extrusion molding and press molding. The resulting molded articles exhibit high rigidity and mechanical strength and are lightweight.

The fine fiber reinforced thermoplastic elastomer composition of the present invention can be used as a yarn prepreg. The yarn prepreg can be used to make a mat, or it can be woven in a plain weave, tire cord weave or satin weave manner, or it can be subjected to molding on a punching machine.

The elastic material made from the fine fiber reinforced thermoplastic elastomer composition (A) and the additional elastic component (B) contains a plurality of fine fibers derived from the polyamide component (c) dispersed in a matrix comprising the elastic component (a) and the additional elastic component (B), with parts of the polyolefin component (b) grafted onto the fine fibers formed by the polyamide component (c) to form crystalline lamellae projecting outwardly from the surfaces of the fine fibers. The crystalline lamellae serve as anchors for the fine fibers and improve the interfacial adhesion between the fine fibers and the elastic matrix. Another part of the polyolefin component (b) is grafted onto the elastic component (a) in the form of fine particles having a size of 0.1 µm or less and uniformly distributed in the elastic matrix to reinforce the resulting elastic material.

Accordingly, the fine fiber reinforced elastic material according to the invention exhibits, compared with the conventional fiber reinforced elastic material, a high hardness, a high elastic modulus, an excellent fatigue resistance, a low temperature rise (at the same hardness) and also in the direction perpendicular to the orientation of the fine fibers an improved modulus of elasticity and improved fatigue resistance.

EXAMPLES

The invention is explained in more detail using the following examples.

In the examples, the following tests were carried out.

(1) Density: ASTM D1505

(2) Tensile modulus of elasticity:

The complex elastic modulus was determined using a Vibron DDV-11 (trademark) of Orientec Co. at a temperature of 23ºC.

(3) Yield strength: ASTM D638

(4) Tear strength: ASTM D638

(5) Creep: A specimen of length L0 was stretched under a load of 50 kg/cm2 for one hour; then the load was removed and the length L of the specimen was measured.

The creep of the sample was calculated using the following equation:

Creep (%) = (L - L0 )/L0 · 100

The smaller the creep value, the higher the creep resistance.

(6) Fine fiber formation of a polyamide component (c) in a fine fiber reinforced thermoplastic elastomer composition: A fine fiber reinforced thermoplastic elastomer composition was treated in a mixed solvent consisting of 50 parts by volume of o-dichlorobenzene and 50 parts by volume of xylene at a temperature of 100°C while refluxing the solvent to remove the elastic component (a) and the polyolefin component (b). The remaining polyamide component (c) in the form of fine fibers was observed and determined under a microscope.

(7) Average thickness of fine fibers derived from the polyamide component (c): The thickness of 200 fine fibers derived from the polyamide component (c) was measured under a microscope and an average value was calculated from the measured thicknesses.

(8) Formability: A fine fiber reinforced thermoplastic elastomer composite material was formed into a sheet with a thickness of 1 to 2 mm by means of a hot press at a temperature of 180ºC. The surface smoothness of the resulting sheet was observed with the naked eye and evaluated as follows

Grade Formability

4 The resulting sheet had a very smooth surface.

3 The resulting flat material had a satisfactory surface.

2 The resulting sheet material had a rough surface.

1 The formation of the sheet was difficult, or the resulting sheet had a very rough surface.

(9) Elastic modulus, tensile strength and elongation at break of a fine fiber reinforced elastic material: A dumbbell specimen No. 3 was made from a fine fiber reinforced elastic material by punching and subjected to the test for elastic modulus, tensile strength and elongation at break of the elastic material according to JIS K 6251.

(10) Fatigue resistance under constant loading rate: A dumbbell specimen No. 3 was made of a fine fiber reinforced elastic material by punching and stretched until failure by repeatedly applying a load of 70 kg/cm2; the number of load applications until failure was recorded.

(11) Temperature rise (AT)

The temperature rise (ΔT) of the elastic material during the vulcanization process was measured using a Goodrich Flexmeter (trademark) in accordance with ASTM D 623.

Examples 1 to 4

In each of Examples 1 to 4, a fine fiber reinforced thermoplastic elastomer composition was prepared from the following components.

As the elastic component (a), an ethylene-propylene copolymer of EPDM type (brand: EP-22, a product of Nihon Goseigomu K. K.) having a glass transition temperature of -60ºC was used. As the polyolefin component (b), a polypropylene resin (brand: Ubepolypro J109, manufactured by Ube Industries, Ltd.) having a melting temperature of 165ºC to 170ºC and a melt flow index of 9 g/10 min was used. Furthermore, as the polyamide component (c), a resin of nylon 6 type (brand: Ubenylon 1022B, a product of Ube Industries, Ltd.) having a melting temperature of 215ºC to 220ºC and a molecular weight of 30,000 was used.

The polyolefin component (b) was modified with 0.5 parts by weight of γ-methacryloxypropyltrimethoxysilane and 0.1 part by weight of n-butyl-4,4-di-(tert-butylperoxy)valerate per 100 parts by weight of the polyolefin component (b) by a melt-kneading treatment at a temperature of 180°C using a twin-screw extruder.

The polyamide component (c) was modified with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane in an amount of 1.0 part by weight per 100 parts by weight of the component (c) by a melt-kneading treatment at a temperature of 240°C using a twin-screw extruder.

The modified polyolefin component (b) in the amount given in Table 1 was mixed with the elastic component (a) in the amount shown in Table 1, and the mixture was melt-kneaded in a Banbury mixer at a temperature of 180ºC for 5 minutes to provide a matrix mixture. The matrix mixture was drawn off at a temperature of 170ºC and then made into granules.

The granules of the matrix mixture were mixed with the modified polyamide component (c) in the amount shown in Table 1, and this mixture was subjected to a melt-kneading treatment in a twin-screw extruder at a temperature of 240°C and then granulated to prepare a preliminary composition. The preliminary composition in the form of granules was melt-extruded in a filamentary form by means of a single-screw extruder, cooled and wound up at a stretch ratio of 10, and then made into granules using a granulator. The winding process was carried out at room temperature. The granules were formed into a sheet having a thickness of 1 mm using a press and applying a temperature of 180°C. The resulting sheet showed smooth surfaces.

A part of the sheet was taken out to prepare a test piece. The test piece was subjected to tests (6) and (7), respectively, in which the elastic component (a) and the polyolefin component (b) were removed by means of the mixed solvent and the remaining polyamide component (c) was observed under the microscope. It was confirmed that the polyamide component (c) was in the form of fine fibers having an average thickness of 0.2 to 0.3 µm. When the remaining fine fibers were measured by NMR, the resulting NMR spectrum showed peaks attributable to the (nylon 6)-polyamide component (c) and the elastic (EPDM)- Component (a) and the (PP)-polyolefin component (b).

Dumbbell-shaped test specimens were made from the other parts of the sheet material made from the fine-fiber-reinforced elastomer composition and subjected to testing for physical properties. The results of the tests are shown in Table 1.

The tensile elastic moduli of the test specimens were from 3690 to 4612 kg/cm², and the tensile strengths were from 79 to 190 kg/cm², as shown in Table 1. The tensile elastic modulus and the tensile strength increased with increasing the content of the fine fibers derived from the polyamide component (c).

The sheet material made from the fine fiber reinforced thermoplastic elastomer composition according to Examples 1 to 4 showed no yield stress.

The creep resistance ranged from 1% in Example 4 to 10% in Example 1. The creep resistance increased with increasing content of the fine fibers derived from the polyamide component (c).

A stress-strain curve of the sheet material made from the fine fiber reinforced elastomer composition according to Example 2 is shown in Fig. 2.

Further, Fig. 3 shows the fine fibers formed by the polyamide component (c) in the sheet made from the fine fiber-reinforced thermoplastic elastomer composition of Example 1.

Comparison example 1

The same procedures and tests were carried out as in Example 1, but using amounts of components (a), (b) and (c) as shown in Table 1. Specifically, no polyamide component (c) was used and the matrix mixture prepared from the modified polyolefin component (b) and the elastic component (a) was formed into a sheet. The sheet was then subjected to the tests.

The results of the tests are shown in Table 1. Although the tensile elastic modulus of the resulting sheet material from the elastomer composition was obtained as 3611 kg/cm², which is similar to that of Examples 1 to 4, the tensile strength of the sheet material was 68 kg/cm² and the yield stress was 45 kg/cm², which is significantly lower than the results of Examples 1 to 4.

Furthermore, the flat material showed a creep resistance of 150% under a load of 50 kg/cm², which is a significantly high value.

The stress-strain curve of the sheet material made from the thermoplastic elastomer composition of Comparative Example 1 is shown in Fig. 2.

Comparison example 2

The same procedures and tests were carried out as in Example 1, but the polyamide component (c) was used in an amount of 500 parts by weight.

The preliminary composition prepared as granules was drawn into a filament form at the same stretching as in Example 1, and the filament was formed into a sheet by compression molding. The resulting sheet was not suitable for testing the physical properties.

The sheet was subjected to fine fiber observation according to test (b). It was found that the polyamide component (c) was distributed in the form of a film in the matrix.

Comparison example 3

The same procedures and tests were carried out as in Example 1, but no polyolefin component (b) was used.

The preliminary composition was extruded into a filament form as in Example 1, and the extruded filament was granulated. The resulting thermoplastic elastomer composition prepared as granules was molded into a sheet by compression molding under a compression temperature of 180°C.

The resulting flat material was subjected to tests for physical properties.

The flat material showed a tensile elastic modulus of 2580 kg/cm² and a tensile strength of 52 kg/cm², i.e. significantly lower values than those of Examples 1 to 4.

The results of microscopic observation of fine fibers after tests (6) and (7) confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.3 µm.

The test results are shown in Table 1.

Example 5

The same procedures and tests as in Example 1 were carried out to prepare a fine fiber reinforced thermoplastic elastomer composition, except that the polyamide component (c) was not modified with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

The preliminary composition was extruded in filament form, using the same stretch ratio as in Example 1, and processed into pellets. The resulting thermoplastic elastomer composition prepared as pellets was converted into a sheet in the same manner as in Example 1 using a temperature of 100°C. The resulting sheet was then subjected to the tests.

Although in this example the polyamide component (c) was modified with the silane coupling agent, the resulting sheet material made of the fine fiber reinforced thermoplastic The elastomer composition exhibited a tensile elastic modulus of 4920 kg/cm² and a tensile strength of 218 kg/cm², which are excellent values. Furthermore, the sheet material showed essentially no yield stress and the creep was very low at 1%.

The microscopic observation according to tests (6) and (7) confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.2 µm.

The results of the tests are shown in Table 1. Table 1

Annotation:

(*)1 PP: Polypropylen

(*)2 EPDM: Ethylene-propylene-diene terpolymer

(*)3 PA6: Nylon 6

Example 6

The same procedures and tests were carried out as in Example 1, except that the polyolefin component (b) was used in an amount of 50 parts by weight and the polyamide component (c) was used in an amount of 75 parts by weight.

The preliminary composition was extruded in the form of a filament, using the same stretch ratio as in Example 1, and granulated. The resulting thermoplastic elastomer composition in the form of granules was converted into a sheet by compression molding at a temperature of 180°C in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

Although in this example the elastic component (a), EPDM, was used in an increased content of 200 parts by weight, the resulting sheet material made of the fine fiber reinforced elastomer composition showed a tensile elastic modulus of 3090 kg/cm² and a tensile strength of 89 kg/cm², which are quite satisfactory values. Furthermore, the sheet material showed no yield stress and a low creep of 7%.

Microscopic observation after tests (6) and (7) confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.2 µm.

The test results are shown in Table 2.

Example 7

The same procedures and tests were carried out as in Example 1, except that the polyolefin component (b) was used in an amount of 77 parts by weight and the polyamide component (c) was used in an amount of 88 parts by weight.

The preliminary composition was extruded in filament form, using the same stretch ratio as in Example 1, and processed into pellets. The resulting thermoplastic elastomer composition prepared as pellets was converted into a sheet by compression molding at a temperature of 180°C in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

In this example, although the elastic component (a), namely EPDM, was used in an increased content of 130 parts by weight, the resulting sheet of the fine fiber reinforced thermoplastic elastomer composition had a tensile elastic modulus of 3560 kg/cm2 and a tensile strength of 100 kg/cm2, the sheet showed substantially no yield stress, and the creep was small at 6%.

The microscopic observation after tests (6) and (7) confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.3 µm.

The results of the tests are shown in Table 2.

Example 8

The same procedures and tests were carried out as in Example 1, except that the polyolefin component (b) was used in an amount of 200 parts by weight and the polyamide component (c) was used in an amount of 150 parts by weight.

The preliminary composition was extruded in the form of a filament using the same stretch ratio as in Example 1 and granulated. The resulting thermoplastic elastomer composition in the form of granules was formed into a sheet by compression molding using a temperature of 180°C in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

In this example, the resulting sheet made of the fine fiber reinforced thermoplastic elastomer composition had a tensile elastic modulus of 4870 kg/cm² and a tensile strength of 102 kg/cm², which are quite satisfactory values. Furthermore, the sheet showed essentially no yield stress and the creep was very low at 2%.

From the microscope observation after tests (6) and (7), it was confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.3 µm.

The results of the tests are shown in Table 2. Table 2

Example 9

The same procedures and tests were carried out as in Example 1, except that the elastic component (a) consisted of a natural rubber (SMR-L) in an amount of 100 parts by weight. The natural rubber had a glass transition temperature of -63ºC.

The preliminary composition was extruded and granulated in the form of a filament using the same stretch ratio as in Example 1. The resulting thermoplastic elastomer composition in the form of granules was formed into a sheet by compression molding at a temperature of 180°C in the same manner as in Example 1. The resulting sheet was then subjected to tests.

In this example, the resulting sheet made of the fine fiber reinforced thermoplastic elastomer composition showed a tensile elastic modulus of 4050 kg/cm² and a tensile strength of 103 kg/cm², which are quite satisfactory values. Furthermore, the sheet showed essentially no yield stress and the creep was small at 4%.

The microscopic observation after tests (6) and (7) confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.3 µm.

The test results are summarized in Table 3.

Example 10

The same procedures and tests as in Example 1 were carried out, except that the elastic component (a) consisted of 100 parts by weight of an acrylonitrile-butadiene copolymer rubber having a glass transition temperature of -46°C and available under the trademark N-520 from Nihon Goseigomu K.K.

The preliminary composition was extruded in filament form using the same stretch ratio as in Example 1 and granulated. The resulting thermoplastic elastomer composition prepared as granules was converted into a sheet by compression molding at a temperature of 100°C in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

In this example, the resulting sheet made of the fine fiber reinforced elastomer composition had a tensile elastic modulus of 4220 kg/cm² and a tensile strength of 103 kg/cm², which are quite satisfactory. Furthermore, the sheet showed essentially no yield stress and the creep was very small at 3%.

As a result of the microscope observation after tests (6) and (7), it was confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.3 µm.

The results of the tests are shown in Table 3.

Example 11

The same procedures and tests were carried out as in Example 1, except that the elastic component (8) consisted of 100 parts by weight of a hydrogenated rubber available under the trademark Epichlomer C from Daiso K. K, and having a glass transition temperature of -25°C.

The preliminary composition was extruded in the form of a filament, using the same stretch ratio as in Example 1, and made into pellets. The resulting thermoplastic elastomer composition in the form of pellets was made into a sheet by compression molding at a temperature of 180°C in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

In this example, the resulting sheet made of the fine fiber reinforced thermoplastic elastomer composition had a tensile elastic modulus of 4570 kg/cm² and a tensile strength of 114 kg/cm², which are excellent values. Also, the sheet showed essentially no yield stress and the creep was very low at 2%.

As a result of microscopic observation according to tests (6) and (7), it was confirmed that the polyamide component (c) was in the form of fine fibers having an average thickness of 0.3 µm.

The test results are shown in Table 3. Table 3

Annotation:

(*)4 NR Natural rubber

(*)5 NBR: Acrylonitrile-butadiene copolymer rubber

Example 12

The same procedures and tests were carried out as in Example 11, except that the polyolefin component (b) was formed from an ethylene-vinyl acetate copolymer available under the trademark EVA copolymer 215 from UBE Industries, Ltd. and having a Vicat softening temperature of 73°C and a melt flow index of 2 g/10 min.

The preliminary composition was extruded into a filament form using the same stretch ratio as in Example 1 and granulated. The resulting thermoplastic elastomer composition prepared as granules was formed into a sheet by compression molding at a temperature of 180°C in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

In this example, the resulting sheet of the fine fiber reinforced thermoplastic elastomer composition had a tensile elastic modulus of 1850 kg/cm² and a tensile strength of 101 kg/cm², which are satisfactory. In addition, the sheet showed substantially no yield stress and had a creep value of 10%.

Microscopic observation after tests (6) and (7) confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.3 µm.

The test results are shown in Table 4.

Example 13

The same procedures and tests were carried out as in Example 1, except that the polyolefin component (b) was a polyethylene resin available under the trademark Ube Polyethylene FO19 from Ube Industries, Ltd., having a melting point of 107°C and a melt flow index of 0.9 g/10 min.

The polyolefin component (b) was modified with 0.5 parts by weight of γ-methacryloxypropyltrimethoxysilane and 0.1 part by weight of n-butyl 4,4-di-(tert-butylperoxy)valerate per 100 parts of the polyolefin component (b) by a melt-kneading treatment at a temperature of 150°C using a single-screw extruder.

The polyolefin component (b) was modified in the same way as in Example 1.

The preliminary composition was extruded in the form of a filament, using the same stretch ratio of 10 as in Example 1, and granulated. The resulting elastomer composition in the form of granules was converted into a sheet by compression molding at a temperature of 180°C in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

In this example, the resulting sheet of the fine fiber reinforced thermoplastic elastomer composition had a tensile elastic modulus of 1910 kg/cm2 and a tensile strength of 101 kg/cm2, which are satisfactory. Furthermore, the sheet showed substantially no yield stress, and the creep was small at 10%.

From the microscopic observation according to tests (6) and (7), it was confirmed that the polyamide component (c) was in the form of fine fibers with an average thickness of 0.2 µm.

The test results are shown in Table 4.

Comparison example 4

The same procedures and tests were carried out as in Example 11, but without using a polyamide component (c).

The preliminary composition was extruded in the form of a filament using the same stretch ratio as in Example 1 and granulated. The resulting thermoplastic elastomer composition in the form of granules was formed into a sheet by compression molding at a temperature of 180°C in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

In this comparative example, the resulting sheet material made of the fine fiber reinforced thermoplastic elastomer composition showed a tensile elastic modulus of 362 kg/cm² and a tensile strength of 56 kg/cm², which is unsatisfactory. Furthermore, the specimen fractured during the creep test (5).

The results of the tests are shown in Table 4.

Comparison example 5

The same procedures and tests were carried out as in Example 12, but without using a polyamide component (c).

The preliminary composition was extruded in filament form using the same stretch ratio as in Example 1, and granulated. The resulting thermoplastic elastomer composition in the form of granules was converted into a sheet by compression molding at a temperature of 180ºC in the same manner as in Example 1. The resulting sheet was then subjected to the tests.

In this comparative example, the resulting sheet material made of the fine fiber-reinforced thermoplastic elastomer composition showed a tensile elastic modulus of 254 kg/cm² and a tensile strength of 74 kg/cm², which are unsatisfactory values. In addition, the specimen fractured during the creep test (5).

The test results are shown in Table 4. Table 4

Annotation:

(*)6 PE: Polyethylen

(*)7 EVA: Ethylene-vinyl acetate copolymer

In the following examples and comparative examples, six kinds of fine fiber reinforced thermoplastic elastomer compositions were prepared and used to manufacture fine fiber reinforced elastic materials.

(1) Production of fine fiber reinforced thermoplastic elastomer compositions (No. 1 to No. 6) [Thermoplastic elastomer composition No. 1]

As the elastic component (a), a natural rubber (brand: SMR-L) with a glass transition temperature of -63ºC was used. As the polyolefin component (b), a polypropylene resin (brand: Ubepolypro J109, manufactured by Ube Industries, Ltd.) with a melting temperature of 165ºC to 170ºC and a melt flow index of 9 g/10 min. Furthermore, a nylon 6 type resin (trade name: Ubenylon 1030B, a product of Ube Industries, Ltd.) with a melting temperature of 215ºC to 220ºC and a molecular weight of 30,000 was used as the polyamide component (c).

The polyolefin component (b) was modified with 0.5 parts by weight of γ-methacryloxypropyltrimethoxysilane and 0.1 part by weight of n-butyl-4,4-di-(tert-butylperoxy)valerate per 100 parts by weight of the polyolefin component (b) by a melt-kneading treatment at a temperature of 180°C using a single-screw extruder.

The polyamide component (c) was modified with 1.0 part by weight of N-β- (aminoethyl)-γ-aminopropyltrimethoxysilane per 100 parts by weight of the component (c) by a melt-kneading treatment at a temperature of 240°C using a single-screw extruder.

The modified polyolefin component (b) was mixed in an amount of 100 parts by weight with 100 parts by weight of the elastic component (a), and the mixture was melt-kneaded in a Banbury mixer at a temperature of 180°C for 5 minutes to provide a matrix mixture. The matrix mixture was drawn off at a temperature of 170°C and then granulated.

The granules of the matrix mixture were mixed with 100 parts by weight of the modified polyamide component (c), and this mixture was melt-kneaded in a biaxial kneader at a temperature of 240°C and then processed into granules to provide a preliminary composition. The preliminary composition prepared as granules was a monoaxial extruder in the form of a thread, with cooling and winding at a stretch ratio of 10, and then processed into granules using a granulating device.

The resulting specimen of the fine fiber-reinforced thermoplastic elastomer composition was subjected to tests (6) and (7), in which the elastic component (a) and the polyolefin component (b) were removed by means of the mixed solvent consisting of o-dichlorobenzene and xylene, and the remaining polyamide component (c) was observed under a microscope. It was confirmed that the polyamide component (c) was formed into fine fibers having an average thickness of 0.2 µm.

[Thermoplastic elastomer composition No. 2]

The procedure for preparing thermoplastic elastomer composition No. 1 was followed, except that the polyamide component (c) (nylon 6) was used in an increased amount of 200 parts by weight per 100 parts by weight of the polyolefin component (b).

The resulting granules were refluxed with a mixed solvent comprising o-dichlorobenzene and xylene to remove the elastic component (a) and the polyolefin component (b), and the remaining polyamide component (c) was subjected to tests (6) and (7).

It was confirmed that the polyamide component (c) was in the form of fine fibers having an average thickness of 0.2 µm.

[Thermoplastic elastomer composition No. 3 (comparison)]

The same procedure was followed as for the preparation of elastomer composition No. 1, except that the elastic component (a) (natural rubber) was used in an amount of 100 parts by weight, the polyamide component (c) (nylon 6) was used in an amount of 50 parts by weight per 100 parts of the polyolefin component (b), and no polyolefin component (b) was used.

The resulting thermoplastic elastomer composition was refluxed with a mixed solvent comprising o-dichlorobenzene and xylene to remove the elastic component (a) and the polyolefin component (b), and the remaining polyamide component (c) was subjected to tests (6) and (7).

It was confirmed that the polyamide component (c) was in the form of fine fibers having an average thickness of 0.2 µm.

The thermoplastic elastomer composition No. 3 could not be processed into granules at all.

[Thermoplastic elastomer composition No. 4]

The procedure for preparing thermoplastic elastomer composition No. 1 was followed, except that the elastic component (a) (natural rubber) was used in an amount of 100 parts by weight, the polyolefin component (b) was used in an amount of 75 parts by weight, and the polyamide component (c) (nylon 6) was used in an amount of 87.5 parts by weight.

The resulting granules were refluxed with a mixed solvent comprising o-dichlorobenzene and xylene to remove the elastic component (a) and the polyolefin component (b), and the remaining polyamide component (c) was subjected to tests (6) and (7).

It was confirmed that the polyamide component (c) was in the form of fine fibers having an average thickness of 0.2 µm.

The composition of the thermoplastic elastomer compositions No. 1 to No. 4 and the form of the polyamide component (c) in the compositions are shown in Table 5. Table 5

Annotation:

(*)8 PP: Polypropylen

(*)9 HDPE: High density polyethylene

(*)10 NR: Natural rubber

(*)11 Nylon6

[Thermoplastic elastomer composition No. 5]

As the elastic component (a), 100 parts by weight of the natural rubber (brand: SMR-L) was used. As the polyolefin component (b), a high-density polyethylene resin (brand: Chemilets HD 3070, manufactured by Maruzene Polymer KFC) having a melting temperature of 130ºC and a melt flow index of 8 g/10 min was used in an amount of 75 parts by weight. In addition, as the polyamide component (c), a nylon 6 type resin (brand: Ubenylon 1030B, a product of Ube Industries, Ltd.) having a melting temperature of 215ºC to 220ºC and a molecular weight of 30,000 was used in an amount of 87.5 parts by weight.

The elastic component (a) in an amount of 100 parts by weight and 75 parts by weight of the polyolefin component (b) were mixed with 0.56 parts by weight of γ-methacryloxypropyltrimethoxysilane and 0.1 part by weight of n-butyl 4,4-di-(tert-butylperoxy)valerate, and the mixture was melt-kneaded in a Banbury mixer at a temperature of 180°C for 5 minutes to provide a matrix mixture. The matrix mixture was melt-kneaded together with 87.5 parts by weight of the unmodified polyamide component (c) in a biaxial kneader at a temperature of 245°C to provide a preliminary composition. The preliminary composition prepared as granules was melt-extruded into a filamentary form using a single-screw extruder, cooled and wound up at a stretch ratio of 10, and then made into granules using a granulator.

The resulting specimen of the fine fiber reinforced thermoplastic elastomer composition was subjected to tests (6) and (7), in which the elastic component (a) and the polyolefin component (b) were determined by means of the mixed solvent of o-dichlorobenzene and xylene and the remaining polyamide component (c) was observed under a microscope. It was confirmed that the polyamide component (c) was formed into fine fibers having an average thickness of 0.2 µm.

[Thermoplastic elastomer composition No. 6] As the elastic component (a), 100 parts by weight of the natural rubber (SMR-L brand) was used. As the polyolefin component (b), 75 parts by weight of the same high-density polyethylene resin as mentioned above was used. Further, as the polyamide component (c), the same nylon 6 type resin as mentioned above was used in an amount of 130 parts by weight.

The elastic component (a) in an amount of 100 parts by weight and 75 parts by weight of the polyolefin component (b) were mixed with 0.75 parts by weight of γ-methacryloxypropyltrimethoxysilane and 0.1 part by weight of n-butyl 4,4-di-(tert-butylperoxy)valerate and 130 parts by weight of the unmodified polyamide component (c) and the mixture was melt-kneaded in a Banbury mixer at a temperature of 240°C for 5 minutes and then withdrawn and processed into pellets at a temperature of 260°C to provide a preliminary composition. The preliminary composition prepared as granules was melt-extruded into a filamentary form by a monoaxial extruder at a temperature of 245°C, with cooling and winding at a stretch ratio of 10, and then granulated by a granulating device.

The resulting fine fiber reinforced thermoplastic elastomer composition produced as granules was subjected to tests (6) and (7), in which the elastic component (a) and the polyolefin component (b) were respectively mixed solvent of o-dichlorobenzene and xylene and the remaining polyamide component (c) was observed under a microscope. It was confirmed that the polyamide component (c) was formed into fine fibers having an average thickness of 0.2 µm.

Examples 14 to 19

In each of Examples 14 to 19, the following components were mixed together in the amounts shown in Table 6: an elastomer composition of the type shown in Table 6, an additional elastic component (B) consisting of the same natural rubber as for the elastic component (a) and thus having a glass transition temperature of -63 °C, carbon black (HAF), processing oil, zinc oxide, stearic acid, an antioxidant consisting of N-phenyl-N'-isopropyl-p-phenylenediamine (available under the trademark 810-NA from OUCHI SINKO CHEMICAL INDUSTRIES CO., LTD), sulfur (vulcanizing agent) and a vulcanization accelerator consisting of N-oxydiethylene-2-benzothiazolylsulphenamide (available under the trademark Vulcanizing acceleration NS from OUCHI SINKO CHEMICAL INDUSTRIES CO., LTD). The mixing process was carried out in such a way that the natural rubber and the fine-fiber-reinforced thermoplastic elastomer composition were first kneaded in a Brabender Plastograph set at a temperature of 160ºC for 30 seconds, then the carbon black, the plasticizer oil, the zinc oxide, the stearic acid and the anti-aging agent were added to the mixture one after the other, the mixture was kneaded for 4 minutes, and this mixture was then cured with sulfur as a vulcanization accelerator on an open Kneading roller mill at a temperature of 80ºC.

The resulting mixture was vulcanized at a temperature of 145ºC for 30 minutes. A fine fiber-reinforced elastic material was obtained.

The resulting fine fibers derived from the polyamide component (c) were present in the contents given in Table 6, based on the total weight of the elastic component (a) and the additional elastic component (B), namely in a range from 5 wt% (Example 14) to 50 wt% (Example 19).

In the resulting elastic materials of Example 13 to Example 18, the polyamide component (c) consisting of nylon 6 was uniformly distributed in the form of fine fibers in the matrix consisting of the natural rubber (NR).

The resulting elastic material was subjected to measurements regarding elastic modulus (100% modulus and 300% modulus), tensile strength and elongation at break, as mentioned previously.

The 100% moduli and 300% moduli for Examples 13 to 18 were significantly higher than those of the comparative elastic material which did not contain the polyamide component (c). Specifically, in Examples 13 to 18, the 100% moduli were in a range from 66 kg/cm² (Example 13) to 254 kg/cm² (Example 4), which was significantly higher than the modulus obtained for the comparative elastic material which did not contain the fine fibers derived from the polyamide component (c), namely 21 kg/cm². Similar Results similar to those for the 100% module were obtained for the 300% module.

The test results are shown in Table 6.

Comparison example 6

The thermoplastic elastomer composition No. 3 according to Table 6, an additional elastic component (B) consisting of the same natural rubber as for the elastic component (a), carbon black (HAF), plasticizer oil, zinc oxide, stearic acid, an anti-aging agent consisting of N-phenyl-N'-isopropyl-p-phenylenediamine, sulfur (vulcanizing agent) and a vulcanization accelerator consisting of N-oxydiethylene-2-benzothiazolylsulphenamide were mixed together in the amounts indicated in Table 6. The mixing process was carried out as in Example 14.

The resulting mixture was vulcanized at a temperature of 145ºC for 30 minutes. A fine fiber-reinforced elastic material was obtained.

The resulting fine fibers derived from the polyamide component (c) were present in a content of 30 wt.% based on the total weight of the elastic component (a) and the additional elastic component (B). It was demonstrated that the fine fibers derived from the polyamide component (c) consisting of nylon 6 were unevenly distributed in the matrix comprising the natural rubber (NR).

The resulting elastic material was subjected to measurements of elastic modulus (100% modulus and 300% modulus), tensile strength and elongation at break, as mentioned previously.

Although the 100% modulus of 174 kg/cm² was satisfactory, the elongation at break of 110% was too low.

The results of the tests are shown in Table 6.

Comparison example 7

An elastic material was prepared by following the same procedure as in Example 14 except that no fine fiber reinforced thermoplastic elastomer composition (A) was used and the additional elastic component (B) formed from the same natural rubber as in Example 13 was used in an increased content of 100 parts by weight. In the resulting elastic material, the reinforcing fine fibers derived from the polyamide component (c) were not present.

The resulting elastic material had a 100% modulus of 21 kg/cm² and a 300% modulus of 109 kg/cm², which is extremely low and totally unsatisfactory compared to the values obtained for Examples 14 to 19.

The test results are shown in Table 6.

Example 20

A fine fiber reinforced elastic material was prepared and tested using the same procedure as in Example 14, except that the additional elastic component (B) consisted of 75 parts by weight of the natural rubber and 20 parts by weight of a butadiene rubber (BR, available under the trademark Ubepol BR 150 from Ube Industries Ltd.) having a glass transition temperature of -108°C.

The resulting fine fibers formed from the polyamide component (c) were present in a content of 5 wt.% based on the total weight of the elastic component (a) and the additional elastic component (B).

In the resulting elastic materials, the polyamide component (c) consisting of nylon 6 was evenly distributed in the form of fine fibers in the matrix.

The resulting elastic material was subjected to measurements regarding elastic modulus (100% modulus and 300% modulus), tensile strength and elongation at break, as mentioned above.

The 100% modulus was 62 kg/cm², the 300% modulus was 182 kg/cm², and the elongation at break was 450%, all of which are satisfactory values. The results of the tests are shown in Table 6.

Comparison example 8

An elastic material was prepared and tested by following the same procedure as in Example 20 except that in the additional elastic component (B) the natural rubber was used in an amount of 80 parts by weight and no fine fiber reinforced thermoplastic elastomer composition was used. In the resulting elastic material the reinforcing fine fibers were not present.

The resulting elastic material was subjected to measurements regarding 100% modulus and 300% modulus, tensile strength and elongation at break.

The obtained 100% modulus was 27 kg/cm², the 300% modulus was 131 kg/cm², which is significantly lower than the results for Example 20.

Examples 21 and 22

In Example 21, the same procedures and tests were carried out as in Example 14, except that the fine fiber reinforced thermoplastic elastomer composition No. 5 was used in an amount of 15 parts by weight instead of the thermoplastic elastomer composition No. 1.

The fine fibers formed by the polyamide component (c) were in a content of 5 wt.%, based on the total weight of the elastic component (a) and the additional elastic component (B), and evenly distributed in the Kneading and mixing of the combined elastic components (a) and (B).

The test results are shown in Table 6.

In Example 22, the same procedures and tests were carried out as in Example 14, except that the fine fiber reinforced thermoplastic elastomer composition No. 6 was used in place of the thermoplastic elastomer composition No. 1 in an amount of 11.7 parts by weight and the additional elastic component (B) was used in an amount of 96.2 parts by weight.

The fine fibers derived from the polyamide component (c) were present in a content of 5 wt.% based on the total weight of the elastic component (a) and the additional elastic component (B), and evenly distributed in the elastic components (a) and (B) combined by kneading.

The results of the tests are shown in Table 6. Table 6

Examples 23 to 25

In each of Examples 23 to 25, the fine fiber reinforced thermoplastic elastomer composition No. 4 shown in Table 5, an additional elastic component (B) consisting of the same natural rubber as for the elastic component (a), carbon black (HAF), processing oil, zinc oxide, stearic acid, an anti-aging agent consisting of N-phenyl-N'-isopropyl-p-phenylenediamine (available under the trademark 810-NA from OUCHI SINKO CHEMICAL INDUSTRIES CO., LTD), sulfur (vulcanizing agent) and a vulcanization accelerator consisting of N-oxydiethylene-2-benzothiazolylsulphenamide (available under the trademark Vulcanizing accelerator NS from OUCHI SINKO CHEMICAL INDUSTRIES CO., LTD) were mixed together in the amounts shown in Table 7. The mixing process and the vulcanization process were carried out in the same manner as in Example 14. A fine fiber-reinforced elastic material was obtained.

The resulting fine fibers derived from the polyamide component (c) were present in contents of 3 wt% (Example 23) to 7 wt% (Example 25) as shown in Table 7, based on the total weight of the elastic component (a) and the additional elastic component (B).

In the resulting elastic materials of Example 23 to Example 25, the polyamide component (c) consisting of nylon 6 was uniformly distributed in the form of fine fibers in the matrix comprising the natural rubber (NR).

The resulting elastic material was subjected to measurements in terms of elastic modulus (100% modulus, 200% modulus and 300% modulus), tensile strength and elongation at break and fatigue resistance at constant loading rate (load: 70 kg/cm²) as mentioned above.

The tests were carried out not only in the direction parallel to the orientation direction of the fine fibers derived from the polyamide component (c), but also perpendicular to the orientation direction of the fine fibers derived from the polyamide component (c).

The results of the tests are shown in Table 7. The resulting fine fiber reinforced elastic material showed clearly excellent values for the 100%, 200% and 300% moduli, tensile strength, elongation at break and fatigue resistance as compared with those obtained for Comparative Example 7. Furthermore, it was confirmed that the difference in the moduli and the fatigue resistance at a constant load rate between the direction parallel and perpendicular to the orientation direction of the fine fibers dispersed in the elastic materials is small.

Comparison example 9

The same procedures and tests as in Example 23 were carried out except that the fine fiber reinforced thermoplastic elastomer composition No. 4 was omitted and the additional elastic component (B) (NR) was used in an amount of 100 parts by weight. In the resulting elastic material, the reinforcing fine fibers were not present.

The test results are shown in Table 7.

Essentially no direction-dependent differences were found in the moduli and fatigue resistance at constant loading rate. However, these physical properties were significantly worse than those obtained in Example 23 to Example 25.

Comparison example 10

A fine fiber reinforced elastic material was prepared and tested by following the same procedure as in Example 23, except that the fine fiber reinforced thermoplastic elastomer composition No. 3 containing no polyolefin component (b) was used in an amount of 15 parts by weight and the additional elastic component (B) formed from the natural rubber was used in an amount of 90 parts by weight.

In the resulting fine fiber reinforced elastic material, the fine fibers derived from the polyamide component (c) (nylon 6) are dispersed in a content of 5 wt.%, based on the total weight of the elastic component (a) and the additional elastic component (B).

The test results are shown in Table 7.

The values of the moduli and tensile strength of the resulting elastic material parallel to the orientation direction of the fine fibers were approximately equal to those obtained for Example 24.

In contrast, the modulus and fatigue strength perpendicular to the orientation direction of the fine fibers were significantly lower than in Examples 21 to 23. Table 7

Claims (33)

1. A fine fiber reinforced thermoplastic elastomer composition comprising (a) 100 parts by weight of an elastic component comprising at least one elastic polymer having a glass transition temperature of 0ºC or less; (b) 30 to 500 parts by weight of a polyolefin component, which comprises at least one polyolefin; and (c) 10 to 500 parts by weight of a polyamide component, which comprises at least one thermoplastic amide polymer with structural units containing amide groups, wherein (i) the elastic component (a) and the polyolefin component (b) are in the form of a matrix and wherein in the matrix the elastic component (a) is in the form of a plurality of islands in a lake formed by the polyolefin component (b); (ii) the polyamide component (c) is in the form of fine fibers and dispersed in the matrix; and the elastic component (a), the polyolefin component (b) and (iii) the polyamide components (c) are chemically bonded to one another by means of at least one binder (d). 2. Thermoplastic elastomer composition according to claim 1, wherein the elastic polymer of the elastic component (a) is selected from the group of natural rubber, polyaliphatic diene elastomers, polyolefin elastomers, Polymethylene elastomers, elastomers with an oxygen-containing backbone, silicone elastomers and elastomers which contain nitrogen and oxygen atoms in their backbone. 3. A thermoplastic elastomer composition according to claim 1 or 2, wherein the polyolefin component (b) has a melting temperature of 80°C to 250°C and has a lower melting temperature than the polyamide component (c) or a Vicat softening temperature of 50°C to 200°C. 4. Thermoplastic elastomer composition according to any one of the preceding claims, wherein the polyolefin for the polyolefin component (b) is selected from homopolymers and copolymers of olefins having 2 to 8 carbon atoms; copolymers of at least one olefin having 2 to 8 carbon atoms with at least one member selected from the group consisting of aromatic vinyl compounds, vinyl acetate, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters and vinylsilane compounds; and halogenated polyolefins. 5. Thermoplastic elastomer composition according to any one of the preceding claims, wherein the polyolefin component (b) has a melt index of 0.2 to 50 grams/10 minutes. 6. Thermoplastic elastomer composition according to any one of the preceding claims, wherein the polyolefin for the polyolefin component (b) is selected from the group consisting of high-density polyethylenes, low-density polyethylenes, polypropylenes, ethylene-propylene block copolymers, ethylene-propylene random copolymers, linear low-density polyethylenes, poly(4-methylpentene-1), ethylene-vinyl acetate copolymers, and ethylene-vinyl alcohol copolymers. 7. Thermoplastic elastomer composition according to any one of the preceding claims, wherein the thermoplastic amide polymer for the polyamide component (c) has a melting temperature of 135°C to 350°C. 8. A thermoplastic elastomer composition according to any one of the preceding claims, wherein the thermoplastic amide polymer for polyamide component (c) is selected from the group consisting of nylon-6, nylon-66, nylon-6-nylon-66 copolymers, nylon-610, nylon-612, nylon-46, nylon-11 and nylon-12. 9. A thermoplastic elastomer composition according to any one of the preceding claims, wherein at least 70% by weight of the polyamide component (c) is in the form of a plurality of fine fibers dispersed in the matrix. 10. A thermoplastic elastomer composition according to any one of the preceding claims, wherein the fine fibers of the polyamide component (c) have an average thickness of 1 µm or less and an aspect ratio of 10 or more. 11. Thermoplastic elastomer composition according to any one of the preceding claims, wherein the polyamide component (c) is chemically bonded to the elastic component (a) and the polyolefin component (b) at a bonding ratio of 0.1 to 20% by weight. 12. A thermoplastic elastomer composition according to any one of the preceding claims, wherein the binder (d) comprises at least one member selected from the group consisting of silane coupling agents, titanate coupling agents, phenol-formaldehyde precondensates, unsaturated carboxylic acids, unsaturated saturated carboxylic acid derivatives and organic peroxides. 13. Thermoplastic elastomer composition according to any one of the preceding claims, wherein the binder (d) is used in an amount of 0.1 to 2 parts by weight per 100 parts by weight of the elastic component (b). 14. A thermoplastic elastomer composition according to any one of the preceding claims, wherein the thermoplastic amide polymer for the polyamide component (c) is modified with a binder (d') which comprises at least one member selected from the group consisting of silane coupling agents, titanium coupling agents, unsaturated carboxylic acids, unsaturated carboxylic acid derivatives and organic peroxides. 15. The thermoplastic elastomer composition according to claim 14, wherein the binder (d') is used in an amount of 0.1 to 5.5 parts by weight per 100 parts by weight of the polyamide component (c). 16. A process for producing a fine fiber-reinforced thermoplastic elastomer composition, comprising the steps of: (1) Melt-kneading a mixture comprising (a) 100 parts by weight of an elastic component comprising at least one elastic polymer having a glass transition temperature of 0°C or less, (b) 30 to 500 parts by weight of a polyolefin component comprising at least one polyolefin, and (d) a binder, at a temperature equal to or higher than the melting temperature of the mixture to obtain a matrix mixture in which the elastic component (a) is in the form of a plurality of of islands in a lake of the polyolefin component (b); (2) continuing to knead the matrix mixture together with (c) 10 to 500 parts by weight of a polyamide component comprising at least one thermoplastic amide polymer having structural units containing amide groups, at a temperature equal to or higher than the melting temperature of the polyamide component (c), to provide a preliminary composition in which the polyamide component (c) is dispersed in the form of fine particles in the matrix mixture; and (3) extruding the preliminary composition through an extrusion die at a temperature equal to or higher than the melting temperature of the polyamide component (c), while cooling and stretching or press-rolling the extruded preliminary composition at a temperature lower than the melting temperature of the polyamide component (c) to convert the fine particles of the polyamide component (c) into fine fibers dispersed in the matrix mixture, and to chemically bond the components (a), (b) and (c) to each other through the binder (d), thereby obtaining a thermoplastic elastic composition reinforced with fine fibers. 17. The method according to claim 16, wherein in the melt-kneading step (1), the polyolefin component (b) is melt-kneaded together with the binder (d) and then a blend of the polyolefin component (b) modified with the binder (d) is melt-kneaded with the elastic component (a) at a temperature equal to or higher than the melting temperature of the blend. 18. The method according to claim 16 or 17, wherein in the melt-kneading step (1), the elastic component (a), the polyolefin component (b) and the binder (d) are mixed together and then the mixture is subjected to a melt-kneading treatment. 19. The method according to any one of claims 16 to 18, wherein before the further kneading step (2), the polyamide component (c) is modified with a binder (d') by melt kneading, the binder comprising at least one member selected from the group consisting of silane coupling agents, titanium coupling agents, unsaturated carboxylic acids, unsaturated carboxylic acid derivatives and organic peroxides. 20. The process according to claim 19, wherein the binder (d') is used in an amount of 0.1 to 5.5 parts by weight per 100 parts by weight of the polyamide component (c). 21. The method according to any one of claims 16 to 20, wherein both the melt-kneading step (1) and the further kneading step (2) are carried out by using at least one kneading machine selected from the group consisting of Banbury mixers, kneaders, kneading extruders, open kneading rolls, monoaxial kneaders and biaxial kneaders. 22. A process according to any one of claims 16 to 21, wherein the further kneading step (2) is carried out at a temperature lower than the melting temperatures of the elastic component (a) and the polyamide component (c). 23. A process according to any one of claims 16 to 22, wherein the further kneading step (2) is carried out at a temperature which is at least 30°C higher than the melting temperature of the polyamide component (c). 24. A process according to any one of claims 16 to 23, wherein in the extrusion step (3) the extrusion process is carried out at a temperature of at least 30°C above the melting temperature of the polyamide component (c). 25. A process according to any one of claims 16 to 24, wherein in the extrusion step (3) the extruded composition is stretched at a stretch ratio of 1.5 to 100. 26. Fine fiber reinforced elastic material, comprising: (A) the fine fiber-reinforced thermoplastic elastomer composition according to any one of claims 1 to 15 and (B) an additional elastic component which comprises at least one elastic polymer having a glass transition temperature of 0°C or less and which is mixed with the fine fiber reinforced elastomer composition (A) by kneading, wherein, with respect to 100 parts of the total weight of the elastic component (a) and the additional elastic component (8), the polyolefin component (b) is present in an amount of 1 to 40 parts by weight and the polyamide component (c) is present in an amount of 1 to 70 parts by weight. 27. An elastic material according to claim 26, wherein the additional elastic component (B) is present in a weight ratio to the fine fiber reinforced thermoplastic elastomer composition (A) of 20:1 to 0.1:1. 28. Elastic material according to claim 26 or 27, wherein the elastic component (a) and the additional elastic component (B) are vulcanizable. 29. Elastic material according to one of claims 26 to 28, wherein the elastic component (a) and the additional elastic component (B) are vulcanized. 30. A process for producing a fine fiber-reinforced elastic material, which comprises kneading-mixing the fine fiber-reinforced thermoplastic elastomer composition (A) according to any one of claims 1 to 15 with an additional elastic component (B) comprising at least one elastic polymer having a glass transition temperature of 0°C or less at a temperature equal to or higher than the melting temperature of the polyolefin component (b) and lower than the melting temperature of the polyamide component (c), wherein, with respect to 100 parts of the total weight of the elastic component (a) and the additional elastic component (B), the polyolefin component (b) is present in an amount of 1 to 40 parts by weight and the polyamide component (c) is present in an amount of 1 to 70 parts by weight. 31. A process according to claim 30, wherein the fine fiber-reinforced thermoplastic elastomer composition (A) and the additional elastic component (B) are mixed together by kneading with (C) a vulcanizing agent, and the resulting mixture is subjected to vulcanization at a temperature of 100°C to 180°C and lower than the melting temperature of the polyamide component (c). 32. The process according to claim 31, wherein the vulcanizing agent is used in an amount of 0.1 to 5 parts by weight per 100 parts of the total weight of the elastic component (a) and the additional elastic component (B). 33. A process according to claim 31 or 32, wherein the vulcanization process is carried out in the presence of a vulcanization accelerator in an amount of 0.01 to 2 parts by weight per 100 parts of the total weight of the elastic component (a) and the additional elastic component (B).