JP7001014B2 - Adhesion method between diene rubber and silicone rubber - Google Patents

Description

The present invention relates to a method for satisfactorily adhering a diene rubber and a silicone rubber.

The diene rubber has a double bond in the main chain, and specific examples thereof include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, chloroprene rubber, and acrylonitrile butadiene rubber.
Among them, natural rubber and isoprene rubber, which is known as a substitute for it, both contain cis-1,4-polyisoprene as the main component, and the cured product of this polyisoprene has excellent mechanical strength and wear resistance. , The price is also stable. Therefore, it is widely used for automobile tires, aircraft tires, hoses, belts, footwear (sole), and the like. However, it also has the drawback of being inferior in heat resistance, weather resistance, and oil resistance.

On the other hand, silicone rubber has excellent heat resistance, cold resistance, and weather resistance, is tasteless and odorless, and has excellent tactile sensation after molding. Therefore, if the surface of the cured polyisoprene can be coated with silicone rubber or integrally molded, for example, there is a possibility that high-strength rubber having excellent heat resistance and weather resistance can be provided at low cost.
However, until now, there has been no method for stably adhering the cured polyisoprene to the silicone rubber. The first reason for this is that the silicone rubber is non-adhesive. In addition, sulfur-based vulcanizers, carbons, anti-aging agents (amines, quinoline, phenols, etc.) may be added to the cured polyisoprene, and these additives are added to the silicone rubber near the interface. It may also delay or inhibit the curing of.

In Patent Document 1 (Japanese Unexamined Patent Publication No. 62-176406), the inner and outer surfaces of a latex sponge of natural rubber or synthetic rubber are previously treated with a primer or treated with a self-adhesive organopolysiloxane, and then this treatment is performed. A technique for adhering a non-self-adhesive organopolysiloxane cured layer to a surface has been proposed. For example, in Example 1, an NBR latex sponge is immersed in a primer composition consisting of a methanol solution containing 3-glycidoxypropyltrimethoxysilane, air-dried, and this is a toluene solution of a one-component room temperature curable silicone rubber composition. Soaked in and air-dried.
However, the latex sponge is a sponge having a large surface area with fine irregularities on the surface, and the surface treatment is performed by immersing the sponge in a toluene solution containing a primer composition and an organopolysiloxane. However, it is difficult to bond the diene rubber and the silicone rubber on a flat surface by such a method.

In Patent Document 2 (Japanese Unexamined Patent Publication No. 11-25926), a silicone base material is surface-treated, a silane coupling agent is applied and heat-dried, and then a polymer is back-coated on the silicone base material and heat-dried. .. In Example 1, a silicone rubber catheter is immersed in a sulfuric acid aqueous solution, washed with water, immersed in a tetrahydrofuran solution of N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, dried at room temperature, heat-treated, and then immersed in a nanotube solution of polyurethane. It is soaked, dried at room temperature, and heat-treated.
However, surface treatment is performed in which sulfuric acid treatment and immersion in a tetrahydrofuran solution are repeated, and it is difficult to bond the diene rubber and the silicone rubber on a flat surface as in Patent Document 1.

Japanese Unexamined Patent Publication No. 62-176406 Japanese Unexamined Patent Publication No. 11-255926

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for satisfactorily adhering a diene rubber and a silicone rubber.

As a result of diligent studies to achieve the above object, the present inventor has silane compound having an alkenyl group, silane compound having a (meth) acrylic group, and silane hydrolysis on the surface of an unvulcanized or cured product of diene rubber. A primer composition containing an organic metal compound having properties as an essential component is applied and dried to form a primer layer, a silicone rubber composition is applied to the surface of the primer layer, and the mixture is heat-cured to form a silicone rubber layer. By doing so, it was found that strong adhesion is developed between the diene rubber and the silicone rubber, which led to the present invention.

Therefore, the present invention provides the following method for adhering a diene rubber and a silicone rubber.
1. 1. A method of adhering a diene rubber and a silicone rubber to the surface of an unvulcanized or cured product of the diene rubber.
The following (A) to (C) components (A) silane compounds having an alkenyl group,
(B) A silane compound having a (meth) acrylic group,
(C) silane hydrolyzable organometallic compound,
Includes a step of applying a primer composition containing the above as an essential component and drying to form a primer layer, and a step of applying a silicone rubber composition to the surface of the primer layer and heat-curing to form a silicone rubber layer. , How to bond diene rubber and silicone rubber.
2. 2. 1. The method for adhering a diene-based rubber to a silicone rubber according to 1, wherein the diene-based rubber is a natural rubber or an isoprene rubber.
3. 3. The method for adhering a diene-based rubber and a silicone rubber according to 1 or 2, wherein the component (A) is an alkoxysilane having at least one vinyl group in one molecule.
4. The method for adhering a diene-based rubber to a silicone rubber according to any one of 1 to 3, wherein the component (B) is an alkoxysilane having at least one (meth) acrylic group in one molecule.
5. Described in any one of 1 to 4, wherein the component (C) is a metal alkoxide compound or a metal chelate compound having silane hydrolyzability, and the metal is one or more selected from titanium, tin, zirconium, and aluminum. How to bond the metal rubber and silicone rubber.

According to the method for adhering a cured diene rubber to a silicone rubber of the present invention, it is possible to produce a molded product in which the diene rubber and the silicone rubber are firmly adhered to each other.

Hereinafter, the present invention will be described in detail.
[Diene rubber]
Specific examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, chloroprene rubber, and acrylonitrile butadiene rubber. Of these, natural rubber or isoprene rubber is preferable.

Diene-based rubber has a diene component that serves as a cross-linking point in a part of the main chain or the side chain, and sulfur vulcanization is often performed using a sulfur-based vulcanizing agent. From the viewpoint of safety, organic peroxide vulcanization using an organic peroxide-based vulcanizing agent is often adopted.

[Sulfur-based vulcanizer]
Examples of the sulfur-based curing agent used for the diene-based rubber include sulfur (powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, etc.) and sulfur compounds (sulfur chloride, sulfur dichloride, morpholine disulfide, dithiodicaprolactam, alkylphenol, etc.). Disulfide, etc.), but is not particularly limited thereto. The sulfur-based vulcanizing agent may be used alone or in combination of two or more.

[Organic peroxide vulcanizer]
Examples of the organic peroxide-based sulfide used for the diene-based rubber include 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane and 1,3-bis (t-butylperoxyisopropyl). ) Benzene, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-bis (t-butylperoxy) -2,5-dimethyl-3-hexine and the like, but are particularly limited thereto. It is not something that is done. The organic peroxide-based vulcanizing agent may be used alone or in combination of two or more.

The amount of the sulfur-based vulcanizing agent or the organic peroxide-based vulcanizing agent added may be appropriately selected according to the vulcanization rate, but usually, the sulfur-based vulcanizing agent or the sulfur-based vulcanizing agent or 100 parts by mass of the diene-based rubber is used. The organic peroxide-based vulcanizer is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass. If the amount added is less than 0.1 parts by mass, crosslinking does not proceed sufficiently, while if it exceeds 5 parts by mass, problems such as scorch and discoloration may occur.

In addition, fillers (carbon, silica, calcium carbonate, clay, etc.), antiaging agents (amines, quinolines, phenols, etc.), vulcanization accelerators, plasticizers, etc. should be added to the diene rubber as appropriate. Can be done.

Further, the diene-based rubber may be diluted with an organic solvent before use. Examples of the organic solvent for dilution include hydrocarbon solvents such as hexane, toluene and rubber volatile oil, halogenated hydrocarbons such as chlorobenzene, esters such as butyl acetate, and ketones such as methyl isobutyl ketone. However, due to the complexity of the process and the working environment, it is preferable to use the diene rubber as it is without diluting it with an organic solvent.

The heating temperature at the time of vulcanization may be adjusted according to the vulcanization rate, but can be cured at 120 to 200 ° C., preferably 150 to 200 ° C.

The vulcanization time is determined based on the 90% vulcanization time (T90) obtained in accordance with JIS K 6300-2: 2001. It is preferable to set a time longer than T90 by 5 to 20 minutes, and more preferably 5 to 10 minutes longer. However, when the coating film is heat-cured in the step of forming the primer layer described later, a primer composition is applied. If the vulcanization time of the diene rubber is set to be shorter than T90 before the work, and the heat treatment time after applying the primer composition is set to be longer than T90, the adhesiveness is improved. It is preferable because it is stable.

[Silicone rubber composition]
As the silicone rubber composition, for example, (D) organopolysiloxane and (E) reinforcing silica are essential components, and an organic peroxide-based curing agent or an addition reaction-based curing agent is selected depending on the curing form.

[(D) Organopolysiloxane]
The organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule is a main agent (base polymer) for forming a cured silicone rubber, and the organopolysiloxane has the following average composition formula. Those represented by (I) and containing an alkenyl group bonded to at least two silicon atoms in one molecule can be used, and one kind alone or two or more kinds can be used as appropriate.
R ¹ _a SiO _{(4-a) / 2} (I)
(In the formula, R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon atoms of 1 to 10, preferably 1 to 8, and a is 1.5 to 2.8, preferably 1. It is a positive number in the range of 8 to 2.5, more preferably 1.9 to 2.1.)

In the formula (I), R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon atoms of 1 to 10, specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, and the like. Alkyl groups such as butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group and decyl group, phenyl group, trill group, xylyl group, naphthyl group and the like aryl Aralkyl groups such as groups, benzyl groups, phenylethyl groups and phenylpropyl groups, vinyl groups, allyl groups, propenyl groups, isopropenyl groups, butenyl groups, hexenyl groups, cyclohexenyl groups, alkenyl groups such as octenyl groups, and alkenyl groups thereof. Part or all of the hydrogen atom of the group is substituted with a halogen atom such as fluorine, bromine, chlorine, a cyano group, etc., for example, a chloromethyl group, a chloropropyl group, a bromoethyl group, a trifluoropropyl group, a cyanoethyl group and the like. However, it is preferable that 90 mol% or more of the total R ¹ and particularly all R ¹ excluding the alkenyl group are methyl groups.

Further, one molecule contains an alkenyl group (preferably having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, still more preferably a vinyl group) bonded to at least two silicon atoms. , The content of alkenyl groups in organopolysiloxane is 1.0 × 10 ^-6 mol / g to 5.0 × 10 ^-3 mol / g, especially 3.0 × 10 ^-6 mol / g to 1.0. It is preferably × 10 ^-3 mol / g. If the amount of alkenyl group is less than 1.0 × 10 ^-6 mol / g, the rubber hardness is low and sufficient strength may not be obtained, and if it exceeds 5.0 × 10 ^-3 mol / g, cross-linking may occur. The density may become too high, resulting in brittle rubber.

The alkenyl group may be bonded to a silicon atom at the end of the molecular chain, a silicon atom in the middle of the molecular chain, or both, but at least the silicon atom at both ends of the molecular chain. It is preferable that the molecule has an alkenyl group bonded to.

Further, the structure of this organopolysiloxane is preferably basically a linear structure, but may be a branched structure, a cyclic structure, a three-dimensional network structure, or the like. The molecular weight is not particularly limited and can be used from a liquid having a low viscosity at room temperature (25 ° C.) to a raw rubber having a high viscosity, but the organopolysiloxane has a weight average degree of polymerization of 100 to 20,000. Is preferable, and those having a value of 200 to 10,000 are more preferable. If the weight average degree of polymerization is less than 100, the silicone rubber composition has a low viscosity, the share may not be sufficient at the time of stirring, and silica may not be dispersed well. If it exceeds 20,000, the silicone rubber composition is high. It may become viscous and difficult to mold. The weight average degree of polymerization can be determined as a polystyrene-equivalent weight average degree of polymerization by gel permeation chromatography (GPC). Further, this organopolysiloxane may be a mixture of two or more types of organopolysiloxanes having different molecular structures and weight average degrees of polymerization.

[(E) Reinforcing silica]
The reinforcing silica of the component (E) is indispensable for imparting sufficient strength to the silicone rubber, and examples thereof include fumed silica (dry silica) and precipitated silica (wet silica).
The component (E) may be used alone or in combination of two or more. The specific surface area of silica according to the BET method is preferably 50 to 400 m ² / g, more preferably 100 to 350 m ² / g. If the specific surface area is less than 50 m ² / g, the mechanical strength may be insufficiently imparted, and if it exceeds 400 m ² / g, the viscosity of the silicone rubber composition may increase and the handleability may deteriorate. be.

These reinforcing silicas may be used as they are, but they may be treated in advance with a surface hydrophobizing agent, or may be treated by adding a surface treatment agent at the time of kneading with the component (D). It is preferable to use it. Any known surface treatment agent such as alkylalkoxysilane, alkylchlorosilane, alkylsilazane, silane coupling agent, titanate-based treatment agent, fatty acid ester, etc. can be used, and one type may be used, or 2 Seeds or more may be used simultaneously or at different timings.

The blending amount of (E) reinforcing silica in the silicone rubber composition is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the component (D). By setting the blending amount of the component (B) to 5 parts by mass or more, more sufficient rubber strength can be obtained. On the other hand, if it exceeds 50 parts by mass, the viscosity of the silicone rubber composition may increase and the handleability may deteriorate.

In the silicone rubber composition, as other components, if necessary, a reinforcing agent such as silicone resin, a filler such as quartz powder, diatomaceous earth, calcium carbonate, a nitrogen-containing compound, an acetylene compound, a phosphorus compound, a nitrile compound, and a carboxy can be added. It is also possible to blend a hydrosilylation reaction control agent such as rate, tin compound, mercury compound, sulfur compound, ethynylcyclohexanol, and a heat resistant agent such as iron oxide and cerium oxide.

[(F) Organic Peroxide Curing Agent]
Examples of the organic peroxide-based curing agent used in the silicone composition include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, and 2,4-dikumil. Peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 1,3-bis (t-butylperoxyisopropyl) benzene, t-butylcumyl peroxide, di-t-butyl Examples thereof include peroxide, 2,5-bis (t-butylperoxy) -2,5-dimethyl-3-hexine, and the like, and the present invention is not particularly limited to these, and one type alone or two or more types may be used in combination. You may.

When an organic peroxide-based curing agent is used, the amount added to the silicone rubber composition may be appropriately selected according to the curing rate, but is 0.1 to 10 parts by mass with respect to 100 parts by mass of the component (D). Is preferable, and 0.2 to 2 parts by mass is more preferable. When using an organic peroxide-based curing agent, if the amount of the organic peroxide-based curing agent added is too small, cross-linking may be insufficient and the rubber physical properties such as strength and elongation may be inferior. It may cause problems such as discoloration.

[Addition reaction curing agent]
As the addition reaction system curing agent used in the silicone composition, (G) organohydrogenpolysiloxane and (H) hydrosilylation catalyst are used in combination.

[(G) Organohydrogenpolysiloxane]
The organohydrogenpolysiloxane is an organohydrogenpolysiloxane having at least two, preferably three or more hydrogen atoms (hydrosilyl groups) bonded to silicon atoms in one molecule, and has the following average composition formula (II).
R ² _b H _c SiO _{(4-bc) / 2} (II)
(In the formula, R ² is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon atoms of 1 to 10. B is 0.7 to 2.1 and c is 0.001 to 1. And b + c is a positive number satisfying 0.8 to 3).
It is preferably an organohydrogenpolysiloxane that is liquid at room temperature as indicated by.

In formula (II), R ² is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms of the same or different species from each other, and specifically, an alkyl group such as a methyl group, an ethyl group or a propyl group. , Cycloalkyl groups such as cyclohexyl groups, aryl groups such as phenyl groups and trill groups, aralkyl groups such as benzyl groups, 2-phenylethyl groups and 2-phenylpropyl groups, and some or all of the hydrogen atoms of these groups. Examples thereof include a group in which the above is substituted with a halogen atom or the like, for example, a 3,3,3-trifluoropropyl group or the like.

Further, b is 0.7 to 2.1, preferably 0.8 to 2, c is 0.001 to 1, preferably 0.01 to 1, and b + c is 0.8 to 3, preferably 0. It is a positive number that satisfies 9 to 2.7.

The organohydrogenpolysiloxane has at least 2 (usually 2 to 300) hydrosilyl groups, preferably 3 or more (for example, about 3 to 200), and more preferably 4 or more (for example, 4 to 100) in one molecule. It may be at the end of the molecular chain, in the middle of the molecular chain, or both. Further, the organohydrogenpolysiloxane may have a number of silicon atoms (or degree of polymerization) of usually 2 to 300, preferably 3 to 200, and more preferably 4 to 100 in the molecule. Further, the viscosity at 25 ° C. is preferably 0.5 to 1,000 mPa · s, preferably 1 to 500 mPa · s, and particularly preferably 5 to 300 mPa · s. This viscosity can be measured with a rotational viscometer (for example, BL type, BH type, BS type, cone plate type, etc.) (hereinafter, the same applies).

Organohydrogenpolysiloxanes include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, and methylhydrogensiloxane / dimethylsiloxane cyclic. Copolymer, Tris (dimethylhydrogensiloxy) methylsilane, Tris (dimethylhydrogensiloxy) phenylsilane, both-terminal trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both-terminal trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane co-weight Combined, both-ended dimethylhydrogensiloxy group-blocked methylhydrogenpolysiloxane, both-ended dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, both-ended dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both-ended trimethyl Syloxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, both-terminal trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, (CH ₃ ) ₂ HSiO _1/2 unit and SiO _4/2 unit Copolymers consisting of (CH ₃ ) ₂ HSiO _1/2 units, SiO _4/2 units and (C ₆ H ₅ ) SiO _3/2 units, and methyl groups in these exemplary compounds. Examples thereof include those obtained by substituting a part or all with another alkyl group or phenyl group.

When this organohydrogenpolysiloxane is used, the blending amount is preferably 0.1 to 30 parts by mass, more preferably 0.3 to 10 parts by mass with respect to 100 parts by mass of the organopolysiloxane of the component (D).
Further, in this organohydrogenpolysiloxane, the molar ratio of Si—H groups to the total alkenyl groups of the component (D) is preferably in the range of 0.5 to 5, more preferably 0.8 to 3. It can also be blended so as to be about 1 to 2.5. When using organohydrogenpolysiloxane, if the amount of organohydrogenpolysiloxane is too small, cross-linking may be insufficient and the rubber physical characteristics such as strength and elongation may be inferior. If too much, there are too many cross-linking points. (The crosslink density is too high), and the rubber properties may be inferior as well.

[(H) Hydrosilylation catalyst]
Examples of the hydrosilylation catalyst include platinum black, second platinum chloride, platinum chloride acid, a reaction product of platinum chloride acid and a monovalent alcohol, a complex of platinum chloride acid and olefins, and a platinum-based catalyst such as platinum bisacetacetate. Platinum-based catalysts, rhodium-based catalysts and the like can be mentioned.

When this hydrosilylation catalyst is used, the blending amount can be a catalytic amount, and usually 0.5 to 1,000 ppm in terms of platinum metal mass is preferable with respect to the component (D), and 1 to 1 to 1. The range of 500 ppm is more preferable.

Further, the silicone rubber composition of the present invention may be diluted with an organic solvent before use. Examples of the organic solvent for dilution include hydrocarbon solvents such as hexane, heptane, benzene, toluene, xylene and rubber volatile oil, and halogenated hydrocarbons such as chloroform and chlorobenzene. However, due to the complexity of the process and the working environment, it is preferable to use the diene rubber as it is without diluting it with an organic solvent.

The curing temperature of the silicone rubber composition of the present invention is preferably 100 to 200 ° C. for 10 seconds to 2 hours, more preferably 120 to 200 ° C. for 20 seconds to 30 minutes. After molding the silicone rubber composition on the primer layer (that is, after the primary curing), it is preferable to perform post-cure (secondary curing) for the purpose of improving the adhesiveness and the compression set of the cured product. The post-cure conditions are usually 100 to 220 ° C. for 30 minutes to 100 hours, preferably 120 to 200 ° C. for 1 to 8 hours.

[Primer composition]
The primer composition of the present invention contains (A) a silane compound having an alkenyl group, (B) a silane compound having a (meth) acrylic group, and (C) an organic metal compound having a silane hydrolyzable property as essential components.
The alkenyl group develops the adhesiveness to the silicone rubber composition, and the (meth) acrylic group develops the adhesiveness to the diene-based rubber cured product. The strength of the primer layer itself is obtained by forming a three-dimensional network by siloxane bonds between the silanes.

[(A) Silane compound having an alkenyl group]
The silane compound having an alkenyl group of the present invention is an alkoxysilane having at least one alkenyl group in one molecule, and may contain a partial hydrolyzate of the alkoxysilane. (A) The silane compound having an alkenyl group can be used alone or in combination of two or more.

Examples of the alkenyl group include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, a hexenyl group, a cyclohexenyl group, an octenyl group and the like, but it is preferable to use a vinyl group because of its availability.
As the alkoxy group, it is preferable to use a methoxy group or an ethoxy group because of easy availability, and specifically, vinyltrimethoxysilane or vinyltriethoxysilane is preferable.

The blending amount of the component (A) is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass in the primer composition. If the blending amount of the component (A) is less than 0.01% by mass, sufficient adhesiveness may not be exhibited, and if it exceeds 5% by mass, the primer layer may become too thick and strength may not be obtained.

[(B) (Silane compound having a (meth) acrylic group]
The silane compound having a (meth) acrylic group of the present invention is a silane compound having at least one (meth) acrylic group in one molecule, and alkoxysilane is preferable. It may contain a partial hydrolyzate of the alkoxysilane. The silane compound having a (meth) acrylic group can be used alone or in combination of two or more. The (meth) acrylic group indicates an acrylic group and / or a methacrylic group.

Specific examples thereof include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, and γ-acryloxypropyltriethoxysilane.

The blending amount of the component (B) is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass in the primer composition. If the blending amount of the component (B) is less than 0.01% by mass, sufficient adhesiveness may not be exhibited, and if it exceeds 5% by mass, the primer layer may become too thick and the strength may not be obtained.
The total amount of the component (A) and the component (B) in the primer composition is preferably 0.02 to 10 parts by mass, more preferably 0.1 to 5 parts by mass.

[(C) silane hydrolyzable organometallic compound]
(C) The organometallic compound having silane hydrolyzability is a component that promotes the formation of a siloxane bond associated with the dealkoxy reaction between the component (A) and the component (B), and one type alone or two or more types are appropriately used. Can be used in combination.

As the metal component of the organometallic compound, titanium, tin, zirconium and aluminum are preferable, and titanium and zirconium are particularly suitable because they are often used for hydrolyzing silane.
Further, depending on the type of ligand, there are an alkoxide compound (type) and a chelate compound (type), and further, a combined type of an alkoxide and a chelate. For example, in the case of titanium, the alkoxide compound is titanium tetraisopropoxide, titanium tetrabutoxide, and the chelate compound is bis-2,4-pentanetotitanium diisopropoxide, bisacetylacetonatotitanium diisopropoxide, etc. Can be mentioned.
The organometallic compound is preferably appropriately selected depending on the conditions of use (drying temperature and time) and the object to be adhered, and may be used alone or in combination of two or more.

The blending amount of the component (C) is preferably an amount that promotes the hydrolysis reaction of the components (A) and (B). Specifically, 0.01 to 5% by mass is preferable, and 0.05 to 3% by mass is more preferable in the primer composition. If the blending amount of the component (C) is less than 0.01% by mass, hydrolysis may not be sufficiently promoted, and if it exceeds 5% by mass, the alkoxy group may be excessive and it may be difficult to obtain the strength of the primer layer. be.

Regarding the mixing ratio of each component (A) / (B) / (C), the component (B) is preferably 0.2 to 5 parts by mass, and 0.3 to 3 parts by mass with respect to 1 part by mass of the component (A). Parts by mass are more preferred. Within this range, the adhesion between the diene rubber and the silicone rubber becomes stronger. Further, the blending amount of the component (C) is preferably 0.05 to 1 part by mass, and 0.2 to 0.7 parts by mass with respect to 1 part by mass of the total amount of the component (A) and the component (B). Is more preferable. Within this range, the adhesion between the diene rubber and the silicone rubber becomes stronger.

The primer composition of the present invention contains the components (A), (B), and (C) as essential components. For example, the components (A) and (B) are used for the purpose of adjusting the strength of the primer layer. A silane compound other than the indicated silane compound, a silicone resin, or the like may be added. Further, the organic peroxide-based curing agent may be added for the purpose of improving the reactivity of the (meth) acrylic group. Further, a pigment may be added for the purpose of facilitating the visual confirmation of the state of the primer layer.

Further, the components (A), (B) and (C) can be solvent-diluted. The solvent is not limited as long as it dissolves (A), (B), (C) and other optional components, and known organic solvents can be used. Depending on the evaporation rate at the time of application and drying of the primer composition, one type alone or two or more types may be used as a mixed solvent. Specific examples of the solvent include aromatic hydrocarbons such as xylene, toluene and benzene, aliphatic hydrocarbons such as heptane and hexane, aromatic / aliphatic mixed hydrocarbons such as ligroin and rubber volatile oil, and trichloroethylene. Hydrocarbons such as perchloroethylene and methylene chloride, esters such as ethyl acetate, ketones such as methylisobutylketone, methylethylketone and cyclohexanone, aliphatic alcohols such as ethanol, isopropanol and butanol, ethers such as diethyl ether, Examples include silicone-based solvents. Of these, aliphatic hydrocarbons such as heptane and hexane are preferable.

The amount of the solvent to be blended is preferably such that the above (A), (B), (C) and other optional components are 0.1 to 10% by mass in the primer composition, and 0.5 to 5% by mass. Is more preferable.

The present invention is a method for adhering a diene rubber and a silicone rubber, in which a primer composition is applied to the surface of an unvulcanized or cured product of the diene rubber and dried to form a primer layer. It includes (a step of forming a primer layer) and a step of applying a silicone rubber composition to the surface of the primer layer and heat-curing to form a silicone rubber layer (a step of forming a silicone rubber layer).

More specifically, the step of applying the primer composition to the surface of the unvulcanized or cured product of the diene rubber and drying to form the primer layer is more specifically the unvulcanized or cured product of the diene rubber. The primer composition is applied to the surface of the material and dried to form a primer layer.

Examples of the method for applying the primer composition include brush coating or a spray device. The coating amount is adjusted by the coating method, the number of coatings, the concentration of the primer composition, and the like, and the amount can be estimated from the weight change after drying. The amount of the primer composition applied is preferably 0.05 to 5 g / m ² and more preferably 0.1 to 2 g / m ² . If the coating amount is less than 0.05 g / m ² , sufficient adhesive strength may not be obtained, and if it exceeds 5 g / m ² , the primer layer is likely to be broken by external stress.

The coating film of the primer composition may be air-dried at room temperature (25 ° C.) for several hours or longer, but it is preferably heat-dried in order to obtain stable adhesiveness. The heating conditions are 80 to 200 ° C., preferably 120 to 180 ° C. for 5 minutes to 2 hours, preferably 10 minutes to 1 hour. In this way, the primer layer is formed.

Further, for the purpose of improving the adhesiveness, it is also effective to provide fine scratches and irregularities on the surface of the diene-based rubber cured product.

[Silicone rubber layer forming process]
The method for adhering a diene-based rubber to a silicone rubber of the present invention is characterized by including a step of forming a silicone rubber layer after the primer layer forming step. Specifically, the silicone rubber composition is placed on the surface of the primer layer, and the method thereof includes a method of diluting the silicone rubber composition with an organic solvent and coating it, or an uncured silicone rubber. There is a method of placing a sheet-shaped composition on the surface of the primer layer. In either case, the silicone rubber composition is then heat-cured to form a silicone rubber layer.

[Molded product]
According to the method for adhering a cured diene rubber to a silicone rubber of the present invention, it is possible to produce an integrally molded product in which the diene rubber and the silicone rubber are firmly adhered to each other.
For example, a primer layer (second layer) was formed on the surface of an unvulcanized or cured product (first layer) of a diene rubber, and a silicone rubber layer (third layer) was formed on the surface of the primer layer. Molded products can be mentioned. The primer layer (second layer) and the silicone rubber layer (third layer) may be formed on one side of an unvulcanized or cured product (first layer) of a diene rubber, and may be formed on both sides. May be.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Synthesis Example 1: Polyisoprene compound]
100 parts by mass of polyisoprene (Nipol IR2200 manufactured by Nippon Zeon Co., Ltd.) with a molecular weight of approximately 1.75 million and a cis-form content of 98% or more, and 11 masses of carbon black (VULCAN3 manufactured by Cabot Corporation) having a specific surface area of 76 m ² / g by the BET method. Parts, 1 part by mass of poly (1,2-dihydrotrimethylquinolin), 1.5 parts by mass of N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl) -P-Phenylylene diamine 1.5 parts by mass was kneaded in a Banbury mixer at room temperature for 10 minutes to obtain a polyisoprene compound.

[Synthesis Example 2: Silicone Base Compound (I)]
It consists of 99.9 mol% of dimethylsiloxane unit, 0.075 mol% of methylvinylsiloxane unit, and 0.025 mol% of dimethylvinylsiloxane unit, and has a weight average degree of polymerization of about 6,000 and a vinyl group amount of 1.4 × 10 ^-5 mol. 100 parts by mass of organopolysiloxane at / g, 25 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) with a specific surface area of 200 m ² / g by the BET method, and 4 parts by mass of dimethyldimethoxysilane as a surface treatment agent. , 0.15 part by mass of methylvinyldimethoxysilane and 1 part by mass of hydrochloric acid (pH = 3) were kneaded with a kneader and heat-treated at 180 ° C. for 1 hour to obtain a silicone-based compound (I).

[Synthesis Example 3: Silicone Base Compound (II)]
Same as the silicone-based compound (I) except that the fumed silica of the silicone-based compound (I) was replaced with precipitated silica (Nipsil VN3, manufactured by Tosoh Silica Co., Ltd.) having a specific surface area of 200 m ² / g by the BET method. Conditionally, a silicone-based compound (II) was obtained.

[Synthesis Example 4: Primer Composition]
To 96 parts by mass of n-hexane, 2 parts by mass of vinyltrimethoxysilane, 2 parts by mass of γ-methacryloxypropyltrimethoxysilane, and 2 parts by mass of titanium tetrabutoxide were added in this order. All of them were easy to dissolve, and they became sufficiently uniform just by holding the container in the hand and shaking, and a primer composition was obtained.

[Example 1]
Mix 4 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane with 100 parts by mass of polyisoprene compound with a two-roll mill, press at 80 ° C. and 3 MPa for 1 minute, and press 150 × 180 mm. , An unvulcanized isoprene rubber sheet having a thickness of 2 mm was obtained.
For this vulcanizing agent-added polyisoprene compound, T90 (measured at 165 ° C. for 1 hour) obtained using Leometer MDR-2000 manufactured by Alpha Technology Co., Ltd. was 28 minutes.
On the obtained unvulcanized isoprene rubber sheet, the primer composition was applied once with a brush and dried at room temperature for 10 minutes, then applied once more and dried at room temperature for 10 minutes, and then in an oven at 165 ° C. Was heated for 30 minutes. The primer coating amount under this condition is 0.6 g / m ² . In order to carry out the adhesion test described later, the primer composition was applied to only half of the entire sheet (150 × 90 mm).
Mix 0.5 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane with 100 parts by mass of silicone-based compound (I) with a two-roll mill, and mix at 80 ° C. and 3 MPa for 1 minute. Pressing was performed to obtain an unvulcanized silicone rubber sheet having a thickness of 150 × 180 mm and a thickness of 2 mm.
An unvulcanized silicone rubber sheet was attached to the primer-coated surface of the isoprene rubber sheet, press-molded at 165 ° C. and 10 MPa for 10 minutes, and further heat-treated in an oven at 165 ° C. for 4 hours.

[Example 2]
Mix 4 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane with 100 parts by mass of polyisoprene compound with a two-roll mill, press at 165 ° C. and 10 MPa for 10 minutes, and press 150 × 180 mm. , A vulcanized isoprene rubber sheet having a thickness of 2 mm was obtained. Subsequent application of the primer composition and bonding operation with the silicone rubber were carried out in the same manner as in Example 1.

[Example 3]
The same operation was performed by replacing the silicone-based compound (I) of Example 2 with the silicone-based compound (II).

[Example 4]
Reaction of the vulture agent of Example 2, 0.5 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane with 0.05 parts by mass of a platinum catalyst (Pt concentration 1% by mass). 0.025 part of ethynylcyclohexanol as a control agent, and methylhydrogendimethylpolysiloxane having an average of 20 Si—H groups in the side chain with both ends sealed with trimethylsiloxy groups as a crosslinking agent (average polymerization degree 40, Si—H). The same operation was carried out by replacing with 0.8 parts by mass (base weight 0.014 mol / g).

[Example 5]
The same operation was carried out by replacing the titanium tetrabutoxide of the primer composition used in Example 2 with bisacetylacetonate titanium diisopropocide.

[Example 6]
The titanium tetrabutoxide of the primer composition used in Example 2 was replaced with zirconium tetraacetylacetonate, and the same operation was performed.

[Comparative Example 1]
Mix 0.5 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane with 100 parts by mass of silicone-based compound (I) with a two-roll mill and press at 165 ° C. and 10 MPa. A vulcanized silicone rubber sheet having a thickness of 2 mm was obtained.
The primer composition was applied once on the obtained vulcanized silicone rubber sheet with a brush and dried at room temperature for 10 minutes, then applied once more and dried at room temperature for 10 minutes, and then in an oven at 165 ° C. It was heated for 30 minutes. In order to carry out the adhesion test described later, the primer was applied only to half of the entire sheet (150 × 90 mm).
Mix 4 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane with 100 parts by mass of polyisoprene compound with a two-roll mill and press at 80 ° C. and 3 MPa for 1 minute to a thickness of 2 mm. Unvulcanized isoprene rubber sheet was obtained.
An unvulcanized isoprene rubber sheet was attached to a primer-coated surface on a vulcanized silicone rubber sheet, press-molded at 165 ° C. and 10 MPa for 10 minutes, and further heat-treated in an oven at 165 ° C. for 4 hours.

[Comparative Examples 2 to 4]
As shown in Table 2, the primer composition used in Example 2 was replaced with one from which the essential components were removed one by one, and the same operation as in Example 2 was carried out. The primer coating amount of Comparative Example 2 is 0.6 g / m ² , but the coating amount of Comparative Examples 3 and 4 is 0.3 g / m ² .

[Adhesion test]
A test piece is prepared by cutting out a 4 mm-thick isoprene rubber / silicone rubber bonded rubber sheet prepared in the above example so as to have a width of 2 cm, a primer-coated portion having a length of 5 cm, and a primer-uncoated portion having a length of 5 cm. did. The peel strength of the test piece was measured using TENCOMETER 2020 manufactured by Alpha Technology Co., Ltd. As a measuring method, the primer-uncoated portion of the bonded rubber sheet was chucked and pulled in the opposite direction at a speed of 50 mm / min, and the test force applied was tracked and recorded.
In addition, the adhesive surface after the test is also observed, and the area ratio of the agglomerated fractured portion to the primer coated portion (2 cm × 5 cm) is shown as the agglomerated fracture rate (%). The results are shown in Tables 1 and 2.

Claims (6)

A method of adhering a diene rubber and a silicone rubber to the surface of an unvulcanized or cured product of the diene rubber.
The following (A) to (C) components (A) silane compounds having an alkenyl group (excluding silane compounds having a (meth) acrylic group),
(B) A silane compound having a (meth) acrylic group,
(C) silane hydrolyzable organometallic compound,
Includes a step of applying a primer composition containing the above as an essential component and drying to form a primer layer, and a step of applying a silicone rubber composition to the surface of the primer layer and heat-curing to form a silicone rubber layer. , How to bond diene rubber and silicone rubber. The method for adhering a diene-based rubber to a silicone rubber according to claim 1, wherein the diene-based rubber is a natural rubber or an isoprene rubber. The method for adhering a diene-based rubber to a silicone rubber according to claim 1 or 2, wherein the component (A) is an alkoxysilane having at least one vinyl group in one molecule. The method for adhering a diene-based rubber to a silicone rubber according to any one of claims 1 to 3, wherein the component (B) is an alkoxysilane having at least one (meth) acrylic group in one molecule. The component (A) is vinyltrimethoxysilane or vinyltriethoxysilane, and the component (B) is γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltri. The method for adhering a diene rubber to a silicone rubber according to claim 1 or 2, which is one or more selected from methoxysilane and γ-acryloxypropyltriethoxysilane. Any of claims 1 to 5, wherein the component (C) is a metal alkoxide compound or a metal chelate compound having silane hydrolyzability, and the metal is one or more selected from titanium, tin, zirconium, and aluminum. The method for adhering a diene rubber and a silicone rubber according to item 1.