JPH0347849A - Partially crosslinked thermoplastic elastomer foam and production thereof - Google Patents

Abstract

PURPOSE:To obtain the title foam having excellent heat resistance, thermal molding and processing characteristics, etc., by blending a specific ionizing radiation partially crosslinkable thermoplastic elastomer with a thermal decomposition type blowing agent in a molten state, molding, irradiating the blend with ionizing radiation, heating and foaming. CONSTITUTION:(A) An ionizing radiation partially crosslinkable thermoplastic elastomer which comprises (i) 100-10 pts.wt. ionizing radiation crosslinking type olefin-based copolymer rubber, (ii) 70-90 pts. wt. ionizing radiation crosslinking type olefin based plastics and (iii) 1-90 pts.wt. ionizing radiation thermal decomposition type olefin-based plastics and has 0.1-100g/10 minutes melt index is blended in a molten state with (B) a thermal decomposition type blowing agent at <= the decomposition temperature of the component B to give an expandable composition, which is molded and irradiated with ionizing radiation to give an unfoamed partially crosslinkable thermoplastic elastomer molded article. The molded article is heated and expanded at <= the decomposition temperature of the component B to give the objective foam.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a partially crosslinked thermoplastic elastomer foam and a method for producing the same, and more particularly, it relates to a partially crosslinked thermoplastic elastomer foam and a method for producing the same, and more particularly, to a partially crosslinked thermoplastic elastomer foam that has excellent heat resistance, chemical resistance, tensile properties, flexibility, and rubber elasticity. ,
The present invention relates to a partially crosslinked thermoplastic elastomer foam having excellent thermoformability and a low to high expansion ratio, and a method for producing the same.

Technical Background of the Invention Conventionally, elastomer foams have been produced by adding a vulcanizing agent and a blowing agent to natural rubber or synthetic rubber, kneading the mixture, and then molding the mixture into a predetermined shape and heating it. A method of obtaining an elastomer foam by vulcanization and foaming is known.

However, in the above method, when the rubber is molded into a predetermined shape by continuous extrusion, since the raw material is rubber, a compound such as a blowing agent is kneaded into the rubber in advance in batches to obtain a mixed material. It is necessary to perform this step before continuous extrusion, and in order to make it easier to feed this kneaded material to the extruder, it is necessary to perform a step of previously forming the kneaded material into a ribbon shape before continuous extrusion. In addition, the above method has the problem that it is not possible to obtain a wide sheet-like molded product or a molded product with a complex irregular shape, and the shape of the molded product is easily deformed during foaming, so it is difficult to obtain a foamed product with a fixed shape. There is a problem that the foamed product cannot be obtained, and furthermore, it is difficult to thermoform the obtained foamed product.

As a method to solve these problems, it is already known to use soft olefin plastics, such as thermoplastic resins such as ethylene-vinyl acetate copolymer and low-density polyethylene, instead of natural rubber or synthetic rubber. However, according to this method, not only can the above-mentioned steps be omitted, but also there is a high degree of freedom in the shape of the molded product of the mixed wire product that is continuously extruded. Moreover, if the molded product of the hybrid mixture is once crosslinked by radiation irradiation or treatment with a chemical crosslinking agent and then foamed, the shape retention of the molded product during foaming will be improved.

However, basically, soft olefin plastics have drawbacks such as inferior heat resistance and tensile properties compared to rubber, and there is a problem that the uses of the resulting foams are greatly limited.

Furthermore, Japanese Patent Application Laid-Open No. 49-129757 discloses that a mixture of a foamed base material consisting only of a crosslinkable resin, an ethylene-propylene elastomer and a polyethylene resin, and a pyrolyzable foaming agent is molded into a desired shape. A production method has been proposed in which a highly foamed synthetic resin foam is obtained by crosslinking with ionizing radiation and then heating and foaming.

However, in this case, as the foam base material component does not contain a component that can be decomposed by irradiation with ionizing radiation, only a component that can be crosslinked by irradiation with ionizing radiation is used.
The resulting foam is not a partially cross-linked foam but a fully cross-linked foam, and although it has excellent flexibility, it has poor thermoformability, manufacturing stability, and surface smoothness, which limits its uses. There is a point.

On the other hand, partially crosslinked materials consisting of peroxide crosslinked olefin copolymer rubber, peroxide crosslinked olefin plastics, and peroxide decomposition type olefin plastics are used as materials that exhibit intermediate performance between soft olefin plastics and vulcanized rubber. It is known, for example, from JP-A No. 48-28838, that the resulting composition can be used as a thermoplastic elastomer.

In addition, a method for manufacturing a foam using such a polyolefin thermoplastic elastomer as a foaming base material was published in 1983.
0-11937, specifically, a partially crosslinked material consisting of a peroxide decomposition type olefin plastic, a lightly crosslinked peroxide crosslinked olefin copolymer rubber, and a peroxide crosslinked olefin plastic. A manufacturing method has been proposed in which a thermoplastic elastomer and a thermally decomposable foaming agent are kneaded and molded into a desired shape, and then heated and foamed as they are to obtain a foam.

However, in the above method, instead of partially crosslinking at the time of foaming, the foaming agent is simply mixed with the partially crosslinked thermoplastic elastomer and foamed with the raw material that has already been partially crosslinked, so the foaming ratio is at most 3 times. Only foams with low expansion ratios can be obtained. Therefore, there is a problem in that the foam obtained by this method is limited to use in large, thick-walled products such as vehicle exterior materials.

Additionally, the Japan Rubber Association Journal, Vol. 61, No. 2, Page 70, also refers to the manufacturing method of thermoplastic elastomer foam, but in this case as well, the thermoplastic elastomer after crosslinking is used as the base material. Even if a foaming method such as using a chemical foaming agent and a gas in combination is devised, only a foam with a specific gravity of about 0.2 at most, and in practical terms a specific gravity of 0.7, can only be obtained with extremely low foaming.

Therefore, there is a problem in that the foam obtained by this method is also limited to use in large, thick-walled products such as vehicle exterior materials.

The inventors of the present invention have conducted intensive research to solve the above problems, and have developed an olefin copolymer rubber that does not crosslink due to ionizing radiation, in addition to an ionizing radiation crosslinkable olefin copolymer rubber that crosslinks due to ionizing radiation. A thermally decomposable blowing agent is added to an ionizing radiation partially crosslinkable thermoplastic elastomer containing an ionizing radiation decomposable olefin plastic as an essential component to form a foamable composition, and a molded article of this foamable composition is exposed to ionizing radiation. When the material was irradiated and further heated to foam, it not only showed excellent flexibility, but also excellent manufacturing stability and surface smoothness, as well as excellent heat processability due to the fluidity of the non-crosslinked portion during thermoforming. They have discovered that a partially crosslinked thermoplastic elastomer foam can be obtained that can be used in a wide range of applications, and have completed the present invention.

Purpose of the Invention The present invention aims to solve the problems associated with the prior art as described above. The object of the present invention is to provide a partially crosslinked thermoplastic elastomer foam having a low expansion ratio to a high expansion ratio, and a method for producing the same.

Summary of the Invention The partially crosslinked thermoplastic elastomer foam according to the present invention comprises:
(a) Ionizing radiation crosslinked olefin copolymer rubber 1
00 to 10 parts by weight, (b) ionizing radiation crosslinkable olefin plastic O to 90 parts by weight, and (c) 1 to 90 parts by weight of ionizing radiation decomposition type olefin plastic [However, component (a), (b) The total weight of components () and (c) is 100 parts by weight, and the melt index is 0.1 to 100 g/
An unfoamed partially crosslinked thermoplastic elastomer molded article composed of a foamable composition consisting of a partially crosslinkable thermoplastic elastomer (A) and a pyrolyzable blowing agent (B) after 10 minutes of ionizing radiation is foamed. It is characterized by the fact that

The method for producing a partially crosslinked thermoplastic elastomer foam according to the present invention includes (a) 100 to 10 parts by weight of an ionizing radiation crosslinked olefin copolymer rubber, and (b) 0 to 10 parts by weight of an ionizing radiation crosslinked olefin copolymer rubber. 90 parts by weight and (c) ionizing radiodegradable olefin plastic 1
~90 parts by weight [However, component (a), component (b) and (
c) The total weight of the ingredients is 100 parts by weight;
A pyrolytic type 1 blowing agent (B) is added to a thermoplastic elastomer (A) partially crosslinkable by ionizing radiation with a melt index of 0.1 to 100 g/10 min at a temperature below the decomposition temperature of the pyrolytic blowing agent (B). a step of molding a foamable composition obtained by melt-kneading at a temperature into a predetermined shape and then irradiating it with ionizing radiation to obtain an unfoamed partially crosslinked thermoplastic elastomer molded body; It is characterized by comprising the step of heating and foaming the plastic elastomer molded article at a temperature equal to or higher than the decomposition temperature of the pyrolyzable foaming agent (B).

DETAILED DESCRIPTION OF THE INVENTION The partially crosslinked thermoplastic elastomer foam and the method for producing the same according to the present invention will be specifically described below.

First, the partially crosslinked thermoplastic elastomer foam according to the present invention will be explained.

The partially crosslinked thermoplastic elastomer foam of the present invention is a foam obtained by foaming an unfoamed partially crosslinked thermoplastic elastomer molded product, and this unfoamed partially crosslinked thermoplastic elastomer molded product basically has ionizable properties. Radiation partially crosslinkable thermoplastic elastomer] 2 (A) and a thermally decomposable foaming agent (B). The ionizing radiation partially crosslinkable thermoplastic elastomer (A) comprises (a) an ionizing radiation crosslinkable olefin copolymer rubber, (b) an ionizing radiation crosslinkable olefin plastic, and (c) an ionizing radiation crosslinkable olefin copolymer rubber. (d) A mineral oil softener can be included as necessary.

Ionizing radiation partially crosslinkable thermoplastic elastomer (A) In the present invention, ionizing radiation partially crosslinkable thermoplastic elastomer (A) refers to the decomposition reaction and crosslinking that occur when an olefinic thermoplastic elastomer is irradiated with ionizing radiation. In competitive reactions, there are parts where the molecular weight of the polymer in the composition increases as a result of many crosslinking reactions, and parts where the molecular weight of the polymer in the composition decreases as a result of many decomposition reactions4) Partially crosslinked thermoplastic elastomer.

(a) Ionizing radiation crosslinked olefin copolymer rubber] 3 The (a) ionizing radiation crosslinked olefin copolymer rubber used in the present invention is, for example, ethylene-propylene-nonconjugated diene rubber, ethylene-butadiene rubber, etc. Copolymer rubber is an amorphous random elastic copolymer mainly composed of olefins, and when irradiated with ionizing radiation, it crosslinks and its fluidity decreases or becomes non-flowable. Refers to polymer rubber. Among these, ethylene-propylene-nonconjugated diene rubber (here, nonconjugated diene refers to dicyclopentadiene, 1.4-
Hexadiene, cyclooctadiene, methylene norbornene, ethylidene norbornene, etc.) are preferred, and ethylene-propylene-nonconjugated diene copolymer rubber, especially ethylene-propylene-ethylidene norbornene copolymer rubber, has an appropriate crosslinked structure. (4) Particularly preferred in that a partially crosslinked thermoplastic elastomer foam can be obtained.

Mooney viscosity ML1+4(1
00°C) is preferably in the range of 10 to 1°80, particularly 40 to 140. If the Mooney viscosity is less than 440, the melt tension of the foamable composition obtained will be low, and the resulting foam will be The diameter of the bubbles may become larger. On the other hand, if the Mooney viscosity exceeds 140, the moldability (fluidity) of the foamable composition may be poor, and the appearance of the resulting foam may deteriorate.

The iodine value (degree of unsaturation) of this copolymer rubber is preferably 16 or less. When a copolymer rubber having an iodine value within the above range is used, a partially crosslinked thermoplastic elastomer foam with a good balance between foaming and crosslinking can be obtained.

In the present invention, (a) ionizing radiation crosslinkable olefin copolymer rubber includes (a) ionizing radiation crosslinking olefin copolymer rubber, (b) ionizing radiation crosslinkable olefin plastic, and (c) 10 parts by weight per 100 parts by weight of the ionizing radiolytic olefin plastic
It is used in an amount of ~100 parts by weight, preferably 40-90 parts by weight, more preferably 50-80 parts by weight.

5 (b) Ionizing radiation crosslinked olefinic plastic The (b) ionizing radiation crosslinked olefinic plastic used in the present invention is one that is crosslinked by irradiation with ionizing radiation and has reduced fluidity, or Refers to olefin-based plastics that no longer flow, specifically:
High-pressure low-density polyethylene, medium-low-pressure low-density polyethylene, high-density polyethylene, other ethylene/α-olefin copolymers, or copolymers of α-olefin and 15 mol% or less of other polymerizable monomers copolymer, such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate Examples include resinous polymeric substances such as copolymers. Among these,
In particular, low-density polyethylene is preferred in that 4) a partially crosslinked thermoplastic elastomer foam having an appropriate crosslinked structure can be obtained.

(b) Melt index of ionizing radiation crosslinked olefin plastic (ASTM D 123)
8-65T, 190°C) is 0.1-50 g/
10 minutes, preferably in the range of 2 to 20 g/10 minutes.

In the present invention, (b) ionizing radiation crosslinkable olefinic plastic includes (a) ionizing radiation crosslinking olefinic copolymer rubber, (b) ionizing radiation crosslinkable olefinic plastic, and (c) ionizing radiation crosslinkable olefinic plastic. 0 to 100 parts by weight of the total weight of decomposable olefin plastic
90 parts by weight, preferably 5-50 Tf! parts by weight, more preferably 10 to 30 parts by weight.

(c) Ionizing radiation decomposition type olefin plastic The (c) ionizing radiation decomposition type olefin plastic used in the present invention is an olefin type plastic whose molecular weight decreases and fluidity increases by irradiation with ionizing radiation. Specifically, isotactic polypropylene or a copolymer of propylene and a small amount of other α-olefin, such as propylene-ethylene copolymer, 7-propylene-1-butene copolymer, propylene-1- Hexene copolymers, propylene/4-methyl-pentene copolymers, etc. are used.

(c) Melt index of ionizing radiodegradable olefin plastic (ASTM D 1238:2
30°C, 2][Og) ranges from 1 to 80 g/l 0 min, preferably from 5 to 50 g/10 min.

The (c) ionizing radiation-degradable olefin plastic used in the present invention has the role of improving the fluidity and heat resistance of the foamable composition.

In the present invention, (c) ionizing radiation-degradable olefin-based plastics include (a) ionizing radiation-crosslinked olefin-based copolymer rubber, (b) ionizing radiation-crosslinked olefin-based plastic, and (c) ionizing radiation-crosslinked olefin-based plastics. 1 to 9 parts per 100 parts by weight of the total weight of decomposable olefin plastic
It is used in an amount of 0 parts by weight, preferably 10 to 80 parts by weight, more preferably 20 to 50 parts by weight. (c) If the amount of the ionizing radiolytic olefin plastic exceeds 50 parts by weight, the flexibility and rubber elasticity of the foam obtained may decrease. On the other hand, if the amount of (c) ionizing radiodegradable olefin plastic is less than 20 parts by weight, the heat resistance and fluidity of the foamable composition will be impaired, resulting in 4) Heat resistance of partially crosslinked thermoplastic elastomer foam and thermoformability may deteriorate.

(d) Mineral oil-based softeners (d) Mineral oil-based softeners are used to weaken the intermolecular forces of rubber during roll processing, making it easier to process, and to soften carbon black, white carbon, etc. High boiling point petroleum fractions are used to aid in dispersion, or to reduce the hardness of vulcanized rubber and increase its flexibility or elasticity.Specifically, paraffinic,
A naphthenic or aromatic mineral oil is used.

Such (d) mineral oil-based softener contains the above component (a).
, (b), (c) and (d) sum type ff1loO
0 to 50 parts by weight, preferably 10 to 20 parts by weight
Used in parts by weight. (d) If the amount of the mineral oil softener is less than 10 parts by weight, sufficient fluidity improvement effect may not be obtained; on the other hand, if it exceeds 20 parts by weight, the partially crosslinked thermoplastic elastomer may not be obtained. The heat resistance and tensile properties of the foam may deteriorate, and (d) the mineral oil softener may ooze out onto the surface of the foam, resulting in unfavorable effects such as impairing the appearance of the foam.

Melt index (ASTM-D) of the ionizing radiation partially crosslinkable thermoplastic elastomer (A) used in the present invention
-1238-65T, 230℃) is 0.1 to 10
0 g/10 min, preferably 5-80 g/l.

minutes, more preferably within the range of 10 to 40 g/10 minutes. When the melt index of the ionizing radiation partially crosslinkable thermoplastic elastomer (A) is within the above range, the ionizing radiation partially crosslinkable thermoplastic elastomer can be used during blending or when molding into a desired shape before crosslinking and foaming. (A) has excellent thermal flow properties.

The ionizing radiation partially crosslinkable thermoplastic elastomer (A) as described above is preferably prepared using a conventionally known kneading device, such as an open type mixing roll, a non-open type Banbury mixer, an extruder, or a kneader-1 continuous mixer. uses a non-open crosstalk device to perform the above (a),
Each component of (b) and (c) or the above (a), (b)
, (c) and (d) are melt-mixed.

The above melt-kneading is preferably carried out in an atmosphere of an inert gas such as nitrogen or carbon dioxide. Moreover, the conditions for the above-mentioned melt cross-wire are that the cross-wire temperature is usually 150 to 280°C, preferably 170 to 240°C, and the cross-wire time is 1 to 20 minutes, preferably 3 to 10 minutes.

Pyrolytic foaming agent (B) As the pyrolytic foaming agent (B) used in the present invention, conventionally known pyrolytic foaming agents can be used. Specifically, diethyl azodicarboxylate, azo Dicarbonamide, barium azodicarboxylate, 4.4"-oxybis(benzenesulfonylhydrazide), 3.3'-
Disulfone hydrazidophenyl sulfonic acid, N, N'-
Examples include dinitrosopentamethylenetetramine. Among them, it is most preferable to use azodicarbonamide in view of the resin temperature suitable for molding the resin composition used in the present invention. The amount of the pyrolytic blowing agent to be blended depends on the expansion ratio of the desired foam, but it usually includes the above-mentioned (a) ionizing radiation crosslinked OLEF, in-based copolymer rubber, and (b) ionizing radiation crosslinking. type olefin plastic and (c)
1 to 50 parts by weight, preferably 1 to 100 parts by weight of the total weight of the ionizing radiolytic olefin plastic.
It is used in an amount of ˜30 parts by weight. If the amount of the foaming agent is too small, foam molding becomes difficult, while if it is too large, defoaming is likely to occur, resulting in unevenness on the surface of the foam.

In the present invention, the foamable composition constituting the unfoamed partially crosslinked thermoplastic elastomer molded article includes sulfur, p-quinonedioxime, I)-dibenzoylquinonedioxime,
Ionizing radiation crosslinking coagents such as N-methyl-N,4-dinitrosoaniline, nitrobenzene, diphenylguanidine, trimethylolpropane-N,N'-+n-phenylene dimaleimide, or divinylbenzene, ethylene glycol dimethacrylate. ,
Polyfunctional vinyl monomers such as diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate can be blended. Efficient crosslinking reactions can be expected with such compounds.

In the present invention, the crosslinking aid or polyfunctional vinyl monomer as described above is preferably 0.05 to 5.0 parts by weight per 100 parts by weight of the thermoplastic elastomer (A) partially crosslinkable by ionizing radiation. More preferably 0.1 to 1
．． It is used in an amount of 5 parts by weight. If the amount of the crosslinking auxiliary agent or polyfunctional vinyl monomer exceeds 5.0 parts by weight, the crosslinking reaction will proceed excessively and the thermoformability of the foam will be poor if the irradiation dose of ionizing radiation is large. On the other hand, when the irradiation dose of ionizing radiation is small, the crosslinking aid or polyfunctional vinyl monomer exists as an unreacted monomer in the unfoamed partially crosslinked thermoplastic elastomer molded body, and when this molded body is foam-molded, 3. The physical properties of the foam obtained change depending on the thermal history.

Therefore, in the present invention, it is preferable to avoid excessive blending of the crosslinking aid or polyfunctional vinyl monomer as described above.

Further, in the present invention, in addition to the above-mentioned ionizing radiation partially crosslinkable thermoplastic elastomer (A) and the pyrolyzable blowing agent (B), the foamable composition constituting the unfoamed partially crosslinked thermoplastic elastomer molded article is added. If necessary, additives such as a foaming aid, a wetting agent, an adhesive (=I gradient agent, a flame retardant, etc.) may be added within a range that does not impair the object of the present invention.

Examples of foaming aids include organic acid aids such as stearic acid, lauric acid, and salicylic acid; metal salt aids such as fatty acid zinc, calcium, lead, and barium; and conventional foaming aids such as urea aids. Known foaming aids are used.

Specifically, the wetting agent is DOPSDBP.

Conventionally known wetting agents such as DIDP, chlorinated paraffin, polybutene, liquid paraffin, and glycerin are used.

4 Tackifiers include chlorinated paraffin, polybutene,
Conventionally known tackifiers such as liquid paraffin, compounds that are essentially hydrocarbon compounds such as oil, rosin, terpene resins, and petroleum resins are used.

As the flame retardant, liquid or semi-solid compounds such as trichloroethyl phosphite and tetrakis(2-chloroethyl)ethylene diphosphonate are used.

Compounds that are essentially hydrocarbon compounds such as chlorinated paraffins and polybutenes, rosins, terpene resins, petroleum resins,
Furthermore, by using a phosphorus-based flame retardant such as phosphite or phosphonate, waterproofness, flexibility, and adhesion to other material surfaces can be improved, making the partially crosslinked thermoplastic elastomer foam of the present invention waterproof. It can be used as a sealing material.

In addition, in the present invention, the foamable composition constituting the unfoamed partially crosslinked thermoplastic elastomer molded article includes conventionally known heat-resistant stabilizers, weather-resistant stabilizers, antistatic agents, pigments, dyes, fillers, nucleating agents, Additives such as lubricants, slipping agents, anti-blocking agents, etc. can be added to the extent that they do not impair the purpose of the present invention.

As heat-resistant stabilizers, phenol type, sulfide type,
Conventionally known heat-resistant stabilizers such as phenylalkane-based, phosphite-based, and amine-based stabilizers are used.

As the pigment, specifically, conventionally known pigments such as carbon black, titanium oxide, zinc white, red iron oxide, ultramarine blue, navy blue, azo pigment, nitroso pigment, lake pigment, and phthalocyanine pigment are used.

Specific fillers include calcium carbonate, calcium silicate, clay, kaolin, talc, silica, diatomaceous earth, mica powder, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, molybdenum disulfide, graphite, and glass. Fibers, glass spheres, glass balloons, carbon fibers, etc. may be used within the range that does not impair the fluidity and rubbery properties of the foamable composition.

4) The degree of crosslinking of the partially crosslinked thermoplastic elastomer in the partially crosslinked thermoplastic elastomer foam 6 of the present invention is:
Gel fraction (thermal xylene,
(130°C), the range is 2 to 90%, preferably 10 to 70%, and more preferably 15 to 60%.

The thermal xylene extracted gel content is measured as follows. i.e. sample pellets (size of each pellet:
Weigh out approximately 0.3g of 3+nmX 3mmX 3mm),
This weight is defined as the initial weight (X).

Next, this sample pellet was immersed in 80 ml of boiling xylene in a closed container for 5 hours, filtered through a 325 mesh screen, air-dried the residue on the screen, and then vacuum-dried at 80°C for 5 hours. The amount of this dry residue is defined as the final weight (Y).

If the thermoplastic elastomer contains heat xylene insoluble fillers, pigments, etc., calculate the weight of these heat xylene insoluble fillers, pigments, etc. from the weight of the sample pellet and the weight of the dry residue. Let the reduced weight be the initial type ffi (X) and the final weight (Y), respectively.

From these initial weights (X) and final form ffi (Y)7, the hot xylene extracted gel content is determined by the following formula.

Final weight (Y) Hot xylene extracted gel content (%) =
X100 Initial Weight (X) A partially crosslinked thermoplastic elastomer foam in which the gel fraction of the thermoplastic elastomer is within the above range has excellent rubber elasticity and heat resistance.

Partially crosslinked thermoplastic elastomer foams as described above are
It is obtained according to the manufacturing method according to the present invention as described below.

As the first step of the production method according to the present invention, (a) 100 to 10 parts by weight of ionizing radiation crosslinkable olefin copolymer rubber, (b) 0 to 90 parts by weight of ionizing radiation crosslinkable olefin plastic, and ( c) 1 to 90 parts by weight of ionizing radiolytic olefin plastic [However, (a)
The total weight of component (b) component and (c) component is 100
Parts by weight], melt index 0.1~
100g/] 0 minute ionizing radiation partially crosslinkable thermoplastic elastic 8 A pyrolytic blowing agent (B) is melt-kneaded into a blower (A) at a temperature below the decomposition temperature of the pyrolytic blowing agent (B). The foamable composition obtained is molded into a predetermined shape and then irradiated with ionizing radiation to obtain an unfoamed partially crosslinked thermoplastic elastomer molded article.

The above ionizing radiation partially crosslinkable thermoplastic elastomer (
The manufacturing method of A) is as described above.

The above melt-kneading method includes, for example, mixing pellets of the thermoplastic elastomer (A) partially crosslinkable with ionizing radiation and the pyrolytic blowing agent (B). After mixing using a known kneader such as lavender,
If necessary, knead using an extruder, mixing roll, kneader, or Banbury mixer. The kneading is preferably carried out at a temperature below the decomposition temperature of the thermally decomposable blowing agent (B). Additionally, additives such as foaming aids, wetting agents, weathering stabilizers, heat stabilizers, anti-boiling agents, and coloring agents can be added at any stage of the melt-mixing process.

9 Next, a crosslinking aid, a vulcanization accelerator, etc. are added to the kneaded product obtained as described above, if necessary, and the mixture is mixed with a known mixing machine such as a tumbler Brabender, V-type Brabender, or Henschel mixer. After uniform mixing, preferably at a temperature of 50° C. or lower, the mixed material is passed through an open mixing roll or a non-open Banbury mixer 1 extruder,
Cross-dispersion is performed using a known kneader such as a kneader-continuous mixer. The kneading is preferably carried out at a temperature below the decomposition temperature of the thermally decomposable blowing agent.

Next, the foamable composition obtained by melt-kneading as described above is heated to a temperature at which the pyrolyzable blowing agent (B) does not decompose and is shaped into a predetermined shape, such as a sheet, a film, an irregular shape, a pipe, or a tube. A non-crosslinked, non-foamed thermoplastic elastomer molded product is obtained.

The above-mentioned molding can be performed using a conventionally known molding machine such as a hot press, an injection molding machine, an extruder, or a calender roll.

Further, in the present invention, each component (a) 0 (b) and (c) of the ionizing radiation partially crosslinkable thermoplastic elastomer (A) or (a), (b), (
Melt-kneading of each component c) and (d), melt-kneading of the ionizing radiation partially crosslinkable thermoplastic elastomer (A) and additives such as a pyrolytic blowing agent (B), and further melt-kneading of the components obtained by this melt-kneading. The process leading to the molding of the foamable composition is
It can be carried out in one step using an injection molding machine, a single screw extruder, a multi-screw extruder, etc.

Next, the uncrosslinked, unfoamed thermoplastic elastomer molded article obtained as described above is irradiated with ionizing radiation to obtain an unfoamed, partially crosslinked thermoplastic elastomer molded article. Ionizing radiation used in the present invention includes, for example, α rays, β rays,
rays, gamma rays, X-rays, neutron beams, electron beams, etc. are suitable;
The irradiation dose of ionizing radiation is 0.1 to 10.0 in terms of absorbed dose.
Mrad, particularly preferably within the range of 0.25 to 5.0 Mrad. Among the above-mentioned ionizing radiations, electron beams and gamma rays are preferably used in the present invention.

Next, as the second step of the production method according to the present invention, the unfoamed partially crosslinked thermoplastic elastomer molded article obtained in the above step is heated at a temperature equal to or higher than the decomposition temperature of the pyrolytic blowing agent (B). to foam.

The above-mentioned foaming is usually carried out by heating the unfoamed partially crosslinked thermoplastic elastomer molded article by a conventionally known heating method such as hot air circulation heating, salt bath heating, infrared heating, or heating using a hot press.
A method is adopted in which the thermally decomposable foaming agent (B) contained in the unfoamed partially crosslinked thermoplastic elastomer molded article is thermally decomposed and foamed.

Effects of the Invention The partially crosslinked thermoplastic elastomer foam according to the present invention has
Certain ionizing radiation partially crosslinkable thermoplastic elastomers (
Since it is a foam formed by foaming an unfoamed partially crosslinked thermoplastic elastomer molded article composed of a foamable composition consisting of A) and a pyrolyzable foaming agent (B), it has excellent heat resistance,
It has excellent chemical resistance, tensile properties, flexibility, and rubber elasticity, as well as excellent thermoforming processability.

Further, according to the manufacturing method of the present invention, a partially crosslinked thermoplastic elastomer foam having the above-mentioned effects can be obtained, and a part with a low expansion ratio of 3 times or less and a high expansion ratio of more than 3 times can be obtained. The effect is that a crosslinked thermoplastic elastomer foam is obtained.

The partially crosslinked thermoplastic elastomer foam of the present invention ranges from a low expansion ratio of 3 times or less to a high expansion ratio of over 3 times, and has excellent heat resistance, weather resistance, chemical resistance, tensile properties,
It not only has flexibility and rubber elasticity, but also has excellent thermoforming processability. Taking advantage of this property, it can be used as interior and exterior materials for vehicles, sealing materials for vehicles, home appliances, civil engineering construction, etc., and sound absorbing and sound insulating materials. Widely applicable. For example, in applications for vehicle interior and exterior materials, high expansion ratio foams have properties such as feel, cushioning, resilience, and sound absorption, in addition to the above-mentioned properties of foam, so they can be used as door skin materials. The foam is suitable for materials such as ceiling materials, seat leather, etc., and the foam with a low expansion ratio can be used for dash boards, weather strips, etc. In addition, when using the foam of the present invention for these applications, the foam of the present invention has excellent thermoforming processability, so it can be used in complex processes such as vacuum forming, pressure forming, hot press forming, welding process forming, etc. Shapes can be easily formed. In addition, in the application of sealing materials, from low-foam to high-foam materials, it can be applied to sealing materials used for waterproofing, windproofing, and soundproofing of vehicles, home appliances, civil engineering construction, etc.; Suitable for heat-resistant sound absorbing and sound insulating materials such as room sound absorbing materials.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. In addition, molding of the foam and evaluation of basic physical properties in Examples were performed according to the following conditions and evaluation methods.

[Molding of foam] (1) Extrusion molding A sheet of uncrosslinked and unfoamed thermoplastic elastomer was extrusion molded using the following equipment and conditions.

Molding machine: Single screw extrusion molding machine [manufactured by Aji Nippon Steel, model number P40
-25AB, 40mmφ], twin-screw extrusion molding machine [manufactured by Ikegai Iron Works ■, model number PCM-30, 30mmφ] 4 Molding temperature = 160°C Molding speed 2 0.1 to 10 m/min (2) Foam molding The following equipment and conditions A sheet of uncrosslinked and unfoamed thermoplastic elastomer was foam-molded.

Foaming furnace: Hot air circulation furnace [manufactured by Micro Denshi ■, model number MIIV-
08L] Foaming heating temperature: 200-230°C Heating time: 2 minutes 30 seconds [Evaluation method of basic physical properties] (1) Expansion ratio Value obtained by dividing the density of unfoamed product, 0.89 g/cnt, by the apparent density of foamed molded product is the foaming ratio.

(2) Tensile properties: Tensile strength at break and elongation at break of foam according to JIS-6
3. Measure according to the measurement method prescribed in the old regulations.

(3) Flexibility The flexibility of the foam is evaluated by the flexibility index (N).

N = (25% compressive strength) x (expansion ratio) 5 Here, the 25% compressive strength is J Is- -B7[17
- Measured according to the measurement method specified in 1976,
Further, the expansion ratio is expressed as the reciprocal of the apparent density of the foam.

(4) Average cell cross-sectional diameter Under a microscope with a magnification of 50 times, the number of cells per 3.3 mm square was n
, it is expressed as the average bubble cross-sectional diameter - (L3) 2/πn.

(5) Aged processability The thermoforming processability of the foam is evaluated by performing vacuum forming according to the following forming conditions.

(Vacuum forming conditions) Surface temperature: 260°C Vacuum forming time: 100 seconds (Evaluation method) Examine whether the sheet is cut due to deep drawing and changes in appearance such as wrinkles.

Those with excellent thermoforming processability are ◎, and those with good thermoformability are 01.
Fairly good results are represented by △, and poor results are represented by ×.

6 (6) Heating dimensional changes of foamed materials are determined by heat treatment in accordance with the measuring method specified in J Is-B7 [17].
Evaluate based on each heat shrinkage rate in the thickness direction.

Vertical and horizontal 1. After marking a square with Oc+n angles and measuring the thickness, heat treatment is performed in a hot air oven at 80° C. for 22 hours. Next, after cooling the sample to room temperature, the length, width, and thickness dimensions are measured to determine the dimensional change (thermal shrinkage rate) due to this treatment.

(7) Appearance of the molded product Observe the presence or absence of irregularities on the surface due to degassing. Those with smooth surfaces are ranked 5, and those with irregularities observed here and there are ranked 3.
, 1 indicates that the surface is noticeably rough due to defoaming, 4 indicates a surface condition between 5 and 3, and 2 indicates a surface condition between 3 and 1.

Example 1 Molecular weight 32000 (Mn), molecular weight distribution 9.3 (
Mw/Mn), Mooney viscosity ML (100℃) ■
+4 65, ethylene-propylene nor7 bornene copolymer rubber with an iodine value of 12 (hereinafter abbreviated as El DH) 6
0 parts by weight, melt index (ASTM-D-123
8-857゜230℃) 3.0g/10min, density 0.9
10g/- of polypropylene (hereinafter abbreviated as 1) 1) 1
0 parts by weight, melt index (ASTM-D-123
8-65T, 190°C) 1.6g/10min, density 0.
92], 20 parts by weight of low-density polyethylene (hereinafter abbreviated as LDPE) and 10 parts by weight of naphthene (paraffin)-based process oil (hereinafter abbreviated as oil) were mixed in a Henschel mixer. After that, 1
Melt-kneaded in the first kneading section with a twin-screw extruder at 60°C,
Next, 10 parts by weight of azocica-bonamide (hereinafter abbreviated as ADCA) as a blowing agent was added between the first kneading section and the second mixing section;
0.5 parts by weight of triallyl cyanurate (hereinafter abbreviated as TAC) as a crosslinking aid was quantitatively supplied from the injection port after the second kneading section and kneaded.

The kneaded product thus obtained was prepared with a lip width of 1 m.

A continuous sheet of uncrosslinked, unfoamed thermoplastic elastomer was obtained by extruding it into a sheet from a flat die with a lip thickness of 3 mm.

8 Next, this continuous sheet was irradiated with an IMrad electron beam, and then the continuous sheet was heated and foamed at 200 to 230°C using a hot air circulation furnace to obtain a sheet-like foam.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 2 A round bar shaped foam was obtained in the same manner as in Example 1, except that a round irregularly shaped die (nozzle diameter 5 mmφ) was used instead of the flat die. .

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 3 After kneading the raw materials for the foam base material in Example 1 using a Banbury mixer, the kneaded product was passed through a roll and pellets were produced using a sheet cutter. Then,
After mixing 10 parts by weight of these pellets, 10 parts by weight of ADCA, and 5 parts by weight of TACo using a Henschel mixer, this mixture was continuously extruded into a sheet shape using a single-screw extruder at a molding temperature of 160°C. A continuous sheet of uncrosslinked, unfoamed thermoplastic elastomer having a thickness of 3 m s and 9 m s was obtained.

Next, this continuous sheet was irradiated with an IMrad electron beam, and then the continuous sheet was heated and foamed at 20.0 to 230°C using a hot air circulation furnace to obtain a sheet-like foam.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 4 A round bar shaped foam was obtained in the same manner as in Example 3, except that a round irregularly shaped die (nozzle diameter 5 mmφ) was used instead of the flat die. .

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 5 A sheet-like foam was obtained in the same manner as in Example 1, except that the amounts of PP, LDPE, and ADCA were changed to 30 parts by weight, 0 parts by weight, and 5 parts by weight, respectively. Ta.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 6 0 A round bar shaped foam was obtained in the same manner as in Example 5, except that a round irregularly shaped die (nozzle diameter 5IIIφ) was used instead of the flat die. .

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 7 A sheet-like foam was obtained in the same manner as in Example 3, except that the amounts of PP, LDPE, and ADCA were 30 parts by weight, 0 parts by weight, and 5 parts by weight, respectively. Ta.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 8 In Example 7, except that a round irregularly shaped die (nozzle diameter 5 mraφ) was used instead of the flat die.
In the same manner as in Example 7, a foam having an irregular shape of a round bar was obtained.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 9 A sheet-shaped foam was obtained in the same manner as in Example 1, except that the amount of ADCA was changed to 2 parts by weight.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 10 A round bar shaped foam was obtained in the same manner as in Example 9, except that a round irregularly shaped die (nozzle diameter 5 mm) was used instead of the flat die. Ta.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 11 EPDM 60 parts by weight, melt index (AST
M-D-65T, 230°C) 2.0 g/10 min, 10 parts by weight of PP with a density of 0.910 g/-, LDPE20
Pellets were produced using a Banbury mixer using the raw material for the foam base material containing 10 parts by weight of oil and 10 parts by weight of oil.

Next, 5 parts by weight of TACo was added to 0.5 parts by weight of divinylbenzene.
After the solution melted and dispersed in parts by weight was uniformly adhered to the surface of the pellet, the pellet was extruded at 200° C. under a nitrogen atmosphere using an extruder.

Pellets obtained by mixing 100 parts by weight of the thermoplastic elastomer obtained by the above method and 2 parts by weight of ADCAI in a blender mixer are continuously extruded into a sheet shape at a molding temperature of 160°C using a single screw extruder. Width: 1 m s
A continuous sheet of uncrosslinked, unfoamed thermoplastic elastomer having a thickness of 3 mm was obtained.

Next, this continuous sheet was irradiated with an IMrad electron beam, and then the continuous sheet was heated and foamed at 200 to 230° C. using a hot air circulation furnace to obtain a sheet-like foam.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 12 A sheet-like foam was obtained in the same manner as in Example 11, except that the amount of ADCA was changed to 5 parts by weight.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 13 In Example 11, the blending amounts of PP and LDPE were
Example 1 except that they were 30 parts by weight and 0 parts by weight, respectively.
A sheet-like foam was obtained in the same manner as in 1.

3 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 14 A sheet-like foam was obtained in the same manner as in Example 13, except that the amount of ADCA was changed to 5 parts by weight.

Table 1 shows the evaluation of the basic physical properties of the obtained foam.

4 Table 1 Table 1 (continued) [Note Ha): Ionizing radiation crosslinkable olefin copolymer rubber (b): Ionizing radiation crosslinking olefin plastic (c): Ionizing radiation decomposition type olefin plastic (d) : Mineral oil ADCA: Azodicarbonamide TAC: ) Realyl cyanuride-1.56 Table 1 (continued) Example 15 In Example 1, 55 parts by weight of EPDM and 15 parts by weight of PP were added.
Parts by weight, melt index (ASTM-D-1238
-B5T, 190°C) 1.9 g/l, 0 min, density 0.
25 parts by weight of 920 g/cJ LDPE, 5 parts by weight of oil, 5 parts by weight of ADCA, and 0.0 parts of trimethylolpropane trimethacrylate-1 instead of TAC. Sfflfm
Section 1. A sheet-like foam was obtained in the same manner as in Example 1, except that irradiation with an electron beam of 5 M rad was performed.

Table 2 shows the evaluation of the basic physical properties of the obtained foam.

Example 16 A sheet-like foam was obtained in the same manner as in Example 15, except that the amounts of EPDM, PP, and LDPE were changed to 65 parts by weight, 10 parts by weight, and 20 parts by weight, respectively. Ta.

Table 2 shows the evaluation of the basic physical properties of the obtained foam.

Example 17 In Example 15, EPDM, PP.

A sheet-shaped foam was obtained in the same manner as in Example 15, except that the blending amounts of LDPE and oil were 708 parts by weight, 10 parts by weight, ]O parts by weight, and 10 parts by weight, respectively.

Table 2 shows the evaluation of the basic physical properties of the obtained foam.

Table 2 Special fl’l’ Applicant Nil Petrochemical” Ida, Price iJ.

Claims (1)

[Scope of Claims] 1) (a) 100 to 10 parts by weight of ionizing radiation crosslinkable olefin copolymer rubber, (b) 0 to 90 parts by weight of ionizing radiation crosslinkable olefin plastic, and (c) ionizable A melt index of 0.1 to 100 g/10 consisting of 1 to 90 parts by weight of a radiodegradable olefin plastic [however, the total weight of components (a), (b) and (c) is 100 parts by weight] An unfoamed partially crosslinked thermoplastic elastomer molded article composed of a foamable composition consisting of a thermoplastic elastomer (A) partially crosslinked by ionizing radiation and a pyrolyzable blowing agent (B) is foamed. Partially cross-linked thermoplastic elastomer foam characterized by: 2) The partially crosslinked thermoplastic elastomer foam according to claim 1, wherein the ionizing radiation partially crosslinkable thermoplastic elastomer (A) contains (d) a mineral oil softener. 3) (d) The blending amount of mineral oil-based softener is (a) component, (
Total weight of component b), component (c) and component (d) 10
3. The partially crosslinked thermoplastic elastomer foam according to claim 2, wherein the amount is in the range of 0 to 50 parts by weight relative to 0 parts by weight. 4) The degree of crosslinking of the thermoplastic elastomer in the partially crosslinked thermoplastic elastomer foam is determined by the gel fraction (thermal xylene,
4. The partially crosslinked thermoplastic elastomer foam according to any one of claims 1 to 3, characterized in that the crosslinked thermoplastic elastomer foam has a content of 2 to 90% at a temperature of 130°C. 5) Claims 1 to 4, characterized in that the partially crosslinked thermoplastic elastomer foam has a foaming ratio of more than 3 times.
3. The partially crosslinked thermoplastic elastomer foam according to any one of paragraphs. 6) (a) 100 to 10 parts by weight of ionizing radiation crosslinkable olefin copolymer rubber, (b) 0 to 90 parts by weight of ionizing radiation crosslinking olefin plastic, and (c) ionizing radiation decomposition type olefin plastic 1 to 90 parts by weight [however, the total weight of components (a), (b), and (c) is 100 parts by weight], with a melt index of 0.1 to 100 g/10 minutes. A foamable composition obtained by melt-kneading a crosslinkable thermoplastic elastomer (A) and a thermally decomposable blowing agent (B) at a temperature below the decomposition temperature of the thermally decomposable blowing agent (B) is mixed into a predetermined shape. obtaining an unfoamed partially crosslinked thermoplastic elastomer molded article by irradiating it with ionizing radiation; 1. A method for producing a partially crosslinked thermoplastic elastomer foam, comprising the steps of heating and foaming at a temperature above. 7) The method for producing a partially crosslinked thermoplastic elastomer foam according to claim 6, wherein the ionizing radiation partially crosslinkable thermoplastic elastomer (A) contains (d) a mineral oil softener. 8) (d) The blending amount of mineral oil softener is (a) component, (
Total weight of component b), component (c) and component (d) 10
8. The method for producing a partially crosslinked thermoplastic elastomer foam according to claim 7, wherein the amount is in the range of 0 to 50 parts by weight relative to 0 parts by weight. 9) The degree of crosslinking of the thermoplastic elastomer in the partially crosslinked thermoplastic elastomer foam is determined by the gel fraction (thermal xylene,
130° C.) from 2 to 90%. 10) The method for producing a partially crosslinked thermoplastic elastomer foam according to any one of claims 6 to 9, wherein the expansion ratio of the partially crosslinked thermoplastic elastomer foam is more than 3 times.