JP2020019909A - Method for bonding diene rubber and silicone rubber - Google Patents

Abstract

To provide a method for satisfactorily bonding a diene rubber and a silicone rubber.SOLUTION: The method for bonding a diene rubber and a silicone rubber includes the steps of: applying a primer composition containing (A) a silane compound having an alkenyl group, (B) a silane compound having a (meth)acrylic group, and (C) an organometallic compound having silane hydrolyzability as essential components to a surface of an unvulcanized product or a cured product of the diene rubber and drying the primer composition to form a primer layer; and applying a silicone rubber composition to a surface of the primer layer and heat-curing the silicone rubber composition to form a silicone rubber layer.SELECTED DRAWING: None

Description

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

The diene rubber has a double bond in the main chain, and specific examples include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, chloroprene rubber, and acrylonitrile butadiene rubber.
Among them, both natural rubber and isoprene rubber, which is known as a substitute, are mainly composed of cis-1,4-polyisoprene. The cured product of this polyisoprene has excellent mechanical strength and abrasion resistance, and , Prices are stable. Therefore, it is widely used for automobile tires, aircraft tires, hoses, belts, footwear (shoe soles), and the like. However, it also has a disadvantage that it is inferior in heat resistance, weather resistance and oil resistance.

Silicone rubber, on the other hand, has the characteristics of being excellent in heat resistance, cold resistance, and weather resistance, being tasteless and odorless, and having an excellent texture after molding. For this reason, if the surface of the cured polyisoprene can be coated with silicone rubber or integrally molded, there is a possibility that, for example, a high-strength rubber excellent in heat resistance and weather resistance can be provided at low cost.
However, there has been no method for stably adhering a cured product of polyisoprene and silicone rubber. The first reason is that the silicone rubber is non-tacky. In addition, a sulfur-based vulcanizing agent, carbon, an anti-aging agent (amines, quinolines, phenols, etc.) may be added to the cured polyisoprene, and these additives may be added to the silicone rubber near the interface. Retarding or inhibiting the curing of

Patent Document 1 (Japanese Patent Application Laid-Open No. 62-176406) discloses that the inner and outer surfaces of a natural rubber or synthetic rubber latex sponge are previously treated with a primer or treated with a self-adhesive organopolysiloxane and then treated. 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 was immersed in a primer composition composed of a methanol solution containing 3-glycidoxypropyltrimethoxysilane, air-dried, and then dried with a toluene solution of a one-part cold curing silicone rubber composition. Soak in and air dry.
However, the latex sponge is a sponge having a large surface area with fine irregularities on the surface, and the sponge is immersed in a toluene solution containing a primer composition and an organopolysiloxane to perform a surface treatment. However, it is difficult to bond the diene rubber and the silicone rubber in a plane by such a method.

In Patent Document 2 (Japanese Patent Application Laid-Open No. H11-255926), after a silicone base material is surface-treated, a silane coupling agent is applied and dried by heating, and a polymer is further deposited on the silicone substrate and dried by heating. . In Example 1, a silicone rubber catheter was 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 and heat-treated, and then immersed in a tetrahydrofuran solution of polyurethane. Dipped, room temperature dried and heat treated.
However, a surface treatment in which sulfuric acid treatment and immersion in a tetrahydrofuran solution are repeated is performed, and it is difficult to bond the diene rubber and the silicone rubber on a flat surface as in Patent Document 1.

JP-A-62-176406 JP-A-11-255926

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

  The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a silane compound having an alkenyl group, a silane compound having a (meth) acryl group, and silane hydrolysis on the surface of an unvulcanized or cured product of a diene rubber. Apply a primer composition containing an organometallic compound having properties as an essential component, dry to form a primer layer, apply a silicone rubber composition to the surface of the primer layer, and heat cure to form a silicone rubber layer By doing so, it has been found that strong adhesion is exhibited between the diene rubber and the silicone rubber, and the present invention has been accomplished.

Accordingly, the present invention provides the following method for bonding a diene rubber and a silicone rubber.
1. A method for bonding a diene rubber and a silicone rubber, the surface of an unvulcanized or cured product of the diene rubber,
The following (A) to (C) component (A) a silane compound having an alkenyl group,
(B) a silane compound having a (meth) acrylic group,
(C) an organometallic compound having silane hydrolyzability,
Applying a primer composition containing as an essential component, drying and forming a primer layer; and applying a silicone rubber composition to the surface of the primer layer and heat curing to form a silicone rubber layer. , Bonding method between diene rubber and silicone rubber.
2. 2. The method for bonding a diene rubber and a silicone rubber according to 1, wherein the diene rubber is a natural rubber or an isoprene rubber.
3. 3. The method for bonding a diene 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. 4. The method for bonding a diene rubber and a silicone rubber according to any one of 1 to 3, wherein the component (B) is an alkoxysilane having at least one (meth) acryl group in one molecule.
5. The component (C) is a metal alkoxide compound or a metal chelate compound having silane hydrolyzability, and the metal is at least one selected from titanium, tin, zirconium, and aluminum. Bonding method of diene rubber and silicone rubber.

  According to the method of bonding the cured diene rubber and the silicone rubber of the present invention, a molded product in which the diene rubber and the silicone rubber are firmly bonded can be produced.

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, acrylonitrile butadiene rubber, and the like. Among them, natural rubber or isoprene rubber is preferred.

  Diene rubber has a diene component that forms a crosslinking point in a part of the main chain or a side chain, and is often sulfur-cured using a sulfur-based vulcanizing agent. From the viewpoint of safety, organic peroxide vulcanization using an organic peroxide-based vulcanizing agent is often used.

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

[Organic peroxide vulcanizing agent]
Examples of the organic peroxide vulcanizing agent used for the diene 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-hexyne, etc., but are not particularly limited thereto. It is not something to be done. The organic peroxide vulcanizing agent may be used alone or in combination of two or more.

  The addition amount of the sulfur-based vulcanizing agent or the organic peroxide-based vulcanizing agent may be appropriately selected according to the vulcanization speed, but usually, based on 100 parts by mass of the diene rubber, the sulfur-based vulcanizing agent or The organic peroxide-based vulcanizing agent is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass. If the amount is less than 0.1 part by mass, the 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.), anti-aging agents (amines, quinolines, phenols, etc.), vulcanization accelerators, plasticizers, etc. may be appropriately added to the diene rubber. Can be.

  Further, the diene rubber may be used after being diluted with an organic solvent. 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, it is preferable to use the diene rubber as it is without diluting it with an organic solvent for reasons such as the complexity of the process and the working environment.

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

  The vulcanization time is determined based on a 90% vulcanization time (T90) determined in accordance with JIS K 6300-2: 2001. The time is preferably set to 5 to 20 minutes longer than T90, more preferably 5 to 10 minutes, but in the step of forming a primer layer described below, when the coating is heated and cured, the primer composition is applied. If the vulcanization time of the diene rubber is set to a time shorter than T90 before processing and the heat treatment time after the application of 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) an organopolysiloxane and (E) a reinforcing silica are essential components, and an organic peroxide-based curing agent or an addition reaction-based curing agent is selected depending on a 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 type can be used alone or two or more types can be used in appropriate combination.
R ¹ _a SiO _{(4-a) / 2} (I)
(Wherein, R ¹ is the same or different and is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10, preferably 1 to 8 carbon atoms, 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 the same or different and is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, Butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, alkyl group such as decyl group, phenyl group, tolyl group, xylyl group, aryl such as naphthyl group Group, benzyl group, phenylethyl group, aralkyl group such as phenylpropyl group, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group, alkenyl group such as octenyl group, and these Those in which some or all of the hydrogen atoms of the group have been replaced with halogen atoms such as fluorine, bromine and chlorine, cyano groups, etc. Methyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, but cyanoethyl group and the like, all R ¹ of 90 mol% or more, the full R ¹ especially excluding alkenyl group, preferably a methyl group .

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

  The alkenyl group may be bonded to a silicon atom at the terminal of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain, or may be bonded to both. Preferably has an alkenyl group bonded to

  The structure of the organopolysiloxane preferably basically has a linear structure, but may have 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. The organopolysiloxane having a weight average polymerization degree of 100 to 20,000 is used. Are preferable, and those having 200 to 10,000 are more preferable. If the weight average degree of polymerization is less than 100, the silicone rubber composition will have a low viscosity, the shear will not be sufficient at the time of stirring, and the silica may not be well dispersed. If it exceeds 20,000, the silicone rubber composition will have a high viscosity. 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, the organopolysiloxane may be a mixture of two or more organopolysiloxanes having different molecular structures and different weight average polymerization degrees.

[(E) Reinforcing silica]
The reinforcing silica as the component (E) is essential for giving sufficient strength to the silicone rubber, and examples thereof include fumed silica (dry silica) and precipitated silica (wet silica).
As the component (E), one type may be used alone, or two or more types may be used in combination. BET specific surface area of silica is preferably ^{50~400m 2 / g, 100~350m 2 /} g is more preferable. When the specific surface area is less than 50 m ² / g, the mechanical strength may not be sufficiently provided. When the specific surface area exceeds 400 m ² / g, the viscosity of the silicone rubber composition may be increased, and the handleability may be deteriorated. is there.

  These reinforcing silicas may be used as they are, but may be used by previously treating with a surface hydrophobizing agent or by adding a surface treating agent when kneading with the component (D). It is preferred to use. As these surface treatment agents, any known ones such as alkylalkoxysilanes, alkylchlorosilanes, alkylsilazanes, silane coupling agents, titanate treatment agents, fatty acid esters, and the like can be used. More than one species may be used simultaneously or at different times.

  The amount of the reinforcing silica (E) in the silicone rubber composition is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, per 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 be deteriorated.

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

[(F) Organic peroxide-based curing agent]
Examples of the organic peroxide-based curing agent used in the silicone composition include, for example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl Peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 1,3-bis (t-butylperoxyisopropyl) benzene, t-butylcumyl peroxide, di-t-butyl Peroxide, 2,5-bis (t-butylperoxy) -2,5-dimethyl-3-hexyne and the like, but are not particularly limited thereto, and may be used alone or in combination of two or more. You may.

  When an organic peroxide-based curing agent is used, the amount added in the silicone rubber composition may be appropriately selected according to the curing speed, but is preferably 0.1 to 10 parts by mass per 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 addition amount of the organic peroxide-based curing agent is too small, crosslinking is insufficient and strength, rubber properties such as elongation may be inferior, and if too large, scorch or Problems such as discoloration may occur.

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

[(G) Organohydrogenpolysiloxane]
The organohydrogenpolysiloxane is an organohydrogenpolysiloxane having at least two, preferably at least three, 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)
(Wherein, R ² is the same or different and is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. B is 0.7 to 2.1, 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 and represented by

In the formula (II), R ² is the same or different and is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, specifically, an alkyl group such as a methyl group, an ethyl group, and a propyl group. , A cycloalkyl group such as a cyclohexyl group, an aryl group such as a phenyl group and a tolyl group, an aralkyl group such as a benzyl group, a 2-phenylethyl group and a 2-phenylpropyl group, and a part or all of the hydrogen atoms of these groups With a halogen atom or the like, for example, a 3,3,3-trifluoropropyl group.

  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 0.1 to 0.3. It is a positive number that satisfies 9 to 2.7.

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

Examples of the organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, and methylhydrogensiloxane / dimethylsiloxane cyclic. Copolymer, tris (dimethylhydrogensiloxy) methylsilane, tris (dimethylhydrogensiloxy) phenylsilane, trimethylsiloxy group-blocked methylhydrogenpolysiloxane at both ends, trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane at both ends Coupling, dimethylhydrogensiloxy group-blocked methyl hydrogen polysiloxane at both ends, dimethylhydrogensiloxy group-blocked dimethylpolysiloxane at both ends, Dihydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both-end trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, both-end trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, (CH _{3) 2} HSiO consisting _1/2 units and SiO _4/2 units, and copolymers thereof, (CH ₃₎ and ₂ HSiO _1/2 units and SiO _4/2 units (C ₆ H ₅₎ Copolymers composed of SiO _3/2 units and those obtained by substituting some or all of the methyl groups in these exemplified compounds with other alkyl groups or phenyl groups are exemplified.

When this organohydrogenpolysiloxane is used, the amount is preferably 0.1 to 30 parts by mass, more preferably 0.3 to 10 parts by mass, per 100 parts by mass of the organopolysiloxane (D).
Further, in this organohydrogenpolysiloxane, the molar ratio of the Si-H group to the total of the alkenyl groups of the component (D) is preferably in the range of 0.5 to 5, more preferably 0.8 to 3. , 1 to 2.5. When using an organohydrogenpolysiloxane, if the blending amount of the organohydrogenpolysiloxane is too small, the crosslinking is insufficient, and the strength, the rubber properties such as elongation may be inferior.If the amount is too large, the crosslinking point is too large. (Cross-linking density is too high), which may also result in poor rubber properties.

[(H) Hydrosilylation catalyst]
Examples of the hydrosilylation catalyst include platinum black, chloroplatinic acid, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and an olefin, a platinum-based catalyst such as platinum bisacetoacetate, Palladium-based catalysts, rhodium-based catalysts and the like can be mentioned.

  In addition, when this hydrosilylation catalyst is used, the compounding amount can be a catalytic amount, and is usually preferably 0.5 to 1,000 ppm in terms of platinum metal mass with respect to the component (D), A range of 500 ppm is more preferred.

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

  The curing temperature of the silicone rubber composition of the present invention is preferably from 100 to 200 ° C for 10 seconds to 2 hours, and more preferably from 120 to 200 ° C for 20 seconds to 30 minutes. After molding the silicone rubber composition on the primer layer (that is, after primary curing), it is preferable to perform post-curing (secondary curing) for the purpose of improving adhesiveness and compression set of the cured product. Post-curing 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) acryl group, and (C) an organometallic compound having silane hydrolyzability as essential components.
An alkenyl group expresses adhesiveness to a silicone rubber composition, and a (meth) acrylic group expresses adhesiveness to a diene rubber cured product. The strength of the primer layer itself is obtained by forming a three-dimensional network by siloxane bonds between silanes.

[(A) Silane compound having 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 an appropriate 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. It is preferable to use a vinyl group from the viewpoint of easy availability.
It is preferable to use a methoxy group or an ethoxy group from the standpoint of availability, and specifically, it is preferable to use vinyltrimethoxysilane or vinyltriethoxysilane.

  The 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 compounding amount of the component (A) is less than 0.01% by mass, sufficient adhesiveness may not be exhibited. If it exceeds 5% by mass, the primer layer may be too thick to obtain sufficient strength.

[(B) Silane compound having (meth) acrylic group]
The silane compound having a (meth) acryl group of the present invention is a silane compound having at least one (meth) acryl group in one molecule, and is preferably an alkoxysilane. A partial hydrolyzate of the alkoxysilane may be contained. The silane compounds having a (meth) acrylic group can be used alone or in an appropriate combination of two or more. The (meth) acryl group represents an acryl group and / or a methacryl group.

  Specifically, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane and the like can be mentioned.

The compounding 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 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 be too thick to obtain sufficient strength.
Further, the total amount of the components (A) and (B) occupying in the primer composition is preferably 0.02 to 10 parts by mass, more preferably 0.1 to 5 parts by mass.

[(C) Organometallic compound having silane hydrolyzability]
(C) The organometallic compound having silane hydrolyzability is a component that promotes the formation of a siloxane bond accompanying the dealkoxylation reaction of the component (A) and the component (B), and one or two or more thereof may be appropriately used. They 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 often used and suitable for hydrolyzing silane.
In addition, there are alkoxide compounds (types) and chelate compounds (types), and combinations of alkoxides and chelates, depending on the type of ligand. For example, in the case of titanium, titanium tetraisopropoxide, titanium tetrabutoxide as an alkoxide compound, bis-2,4-pentanedionato titanium diisopropoxide as a chelate compound, bisacetylacetonato titanium diisopropoxide, etc. Is mentioned.
The organometallic compound is preferably selected as appropriate depending on the use conditions (drying temperature and time) and the object to be bonded, and may be used alone or in combination of two or more.

  The amount of the component (C) is preferably such that the hydrolysis of the components (A) and (B) proceeds. Specifically, the content is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass in the primer composition. If the amount of the component (C) is less than 0.01% by mass, hydrolysis may not be sufficiently promoted. If the amount exceeds 5% by mass, the alkoxy group may be excessive and the strength of the primer layer may not be easily obtained. is there.

  With respect to the mixing ratio of each of the components (A) / (B) / (C), the component (B) is preferably 0.2 to 5 parts by mass, and more preferably 0.3 to 3 parts by mass per 1 part by mass of the component (A). Parts by mass are more preferred. By setting it in this range, the adhesion between the diene rubber and the silicone rubber becomes stronger. Further, the amount of the component (C) is preferably 0.05 to 1 part by mass, and more preferably 0.2 to 0.7 part by mass based on 1 part by mass of the total amount of the components (A) and (B). Is more preferred. By setting it in 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, for the purpose of adjusting the strength of the primer layer, the components (A) and (B) A silane compound other than the silane compound shown or a silicone resin may be added. The organic peroxide-based curing agent may be added for the purpose of improving the reactivity of the (meth) acryl group. Further, a pigment may be added for the purpose of making it easier to visually confirm the state of the primer layer.

  Further, the components (A), (B) and (C) can be diluted with a solvent. The solvent is not limited as long as it can dissolve (A), (B), (C) and other optional components, and a known organic solvent can be used. Depending on the evaporation rate at the time of application and drying of the primer composition, one kind may be used alone, or two or more kinds may be used in combination 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, ligroin, mixed aromatic / aliphatic hydrocarbons such as rubber volatile oil, trichloroethylene, Perchlorethylene, chlorinated hydrocarbons such as methylene chloride, esters such as ethyl acetate, ketones such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, ethanol, isopropanol, aliphatic alcohols such as butanol, ethers such as diethyl ether, Silicone solvents and the like can be mentioned. Among them, aliphatic hydrocarbons such as heptane and hexane are preferable.

  The compounding amount of the solvent 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 relates to a method for bonding a diene rubber and a silicone rubber, comprising applying a primer composition to the surface of an unvulcanized or cured product of the diene rubber and drying to form a primer layer. (A primer layer forming step) 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 (silicone rubber layer forming step).

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

Examples of the method for applying the primer composition include brushing and a spray device. The amount of application is adjusted by the application method, the number of applications, the concentration of the primer composition, and the like, and the amount can be estimated from the change in weight after drying. Primer composition coating amount is preferably 0.05-5 g / m ² weight, 0.1-2 g / m ² is more preferable. When the coating amount is less than 0.05 g / m ^2, there is a possibility that sufficient adhesive strength is obtained and when it exceeds 5 g / m ^2, comprising a primer layer by the external stress is likely to be destroyed.

  The primer composition coating film may be air-dried at room temperature (25 ° C.) over several hours, but is preferably heated and dried to obtain stable adhesiveness. As the heating conditions, heating is performed at 80 to 200 ° C., preferably 120 to 180 ° C., for 5 minutes to 2 hours, preferably 10 minutes to 1 hour. Thus, a primer layer is formed.

  For the purpose of further improving the adhesiveness, it is also effective to provide fine scratches and irregularities on the surface of the diene rubber cured product.

[Silicone rubber layer forming step]
The method for bonding a diene rubber and a silicone rubber according to the present invention includes a step of forming a silicone rubber layer subsequent to the step of forming a primer layer. Specifically, a method of placing a silicone rubber composition on the surface of the primer layer, such as a method of diluting the silicone rubber composition with an organic solvent and coating, or a method of uncured silicone rubber There is a method in which a composition formed into a sheet is placed on the surface of the primer layer. In any case, the silicone rubber composition is thereafter heat-cured to form a silicone rubber layer.

[Molded object]
According to the method for bonding a diene rubber cured product and silicone rubber of the present invention, an integrally molded product in which the diene rubber and silicone rubber are firmly bonded can be manufactured.
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. Moldings. The primer layer (second layer) and the silicone rubber layer (third layer) may be formed on one surface of an unvulcanized or cured product of diene rubber (first layer), or may be formed on both surfaces. May be.

  Hereinafter, the present invention will be described specifically 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 having a molecular weight of about 1.75 million and a cis content of 98% or more (Nipol IR2200 manufactured by Zeon Corporation), and 11 parts by mass of carbon black (VULCAN3 manufactured by Cabot Corporation) having a specific surface area of 76 m ² / g by the BET method. Parts, poly (1,2-dihydrotrimethylquinoline) 1 part by mass, N-phenyl-N'-isopropyl-p-phenylenediamine 1.5 parts by mass, N-phenyl-N '-(1,3-dimethylbutyl) 1.5 parts by mass of -p-phenylenediamine was kneaded with a Banbury mixer at room temperature for 10 minutes to obtain a polyisoprene compound.

[Synthesis Example 2: Silicone-based compound (I)]
It comprises 99.9 mol% of dimethylsiloxane units, 0.075 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxane units, has a weight average degree of polymerization of about 6,000, and has a vinyl group content of 1.4 × 10 ⁻⁵ mol. / G of organopolysiloxane, 25 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having 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 parts by mass of methylvinyldimethoxysilane and 1 part by mass of hydrochloric acid (pH = 3) were kneaded in a kneader and heat-treated at 180 ° C. for 1 hour to obtain a silicone base compound (I).

[Synthesis Example 3: Silicone-based compound (II)]
Same as the above silicone base compound (I) except that the fumed silica of the silicone base 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. Under the conditions, 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 easily melted and were sufficiently uniform just by shaking the container with hand, and a primer composition was obtained.

[Example 1]
100 parts by mass of the polyisoprene compound and 4 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane were mixed by a two-roll mill, and pressed at 80 ° C. and 3 MPa for 1 minute to obtain 150 × 180 mm An unvulcanized isoprene rubber sheet having a thickness of 2 mm was obtained.
The T90 (measured at 165 ° C. for 1 hour) of the vulcanizing agent-added polyisoprene compound obtained using a rheometer MDR-2000 manufactured by Alpha Technology Co., Ltd. was 28 minutes.
On the obtained unvulcanized isoprene rubber sheet, apply the primer composition once with a brush and dry at room temperature for 10 minutes, and then apply another time and dry at room temperature for 10 minutes, and then in an oven at 165 ° C. 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 application of the primer composition was carried out on only half (150 × 90 mm) of the entire sheet.
0.5 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane was mixed with 100 parts by mass of the silicone base compound (I) by a two-roll mill, and the mixture was mixed at 80 ° C. and 3 MPa for 1 minute. Pressing was performed to obtain an unvulcanized silicone rubber sheet having a size of 150 × 180 mm and a thickness of 2 mm.
An unvulcanized silicone rubber sheet was bonded 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]
100 parts by mass of the polyisoprene compound and 4 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane were mixed by a two-roll mill, and pressed at 165 ° C. and 10 MPa for 10 minutes to obtain 150 × 180 mm. Thus, a vulcanized isoprene rubber sheet having a thickness of 2 mm was obtained. The subsequent application of the primer composition and the bonding operation with the silicone rubber were performed in the same manner as in Example 1.

[Example 3]
A similar operation was carried out except that the silicone base compound (I) of Example 2 was replaced with the silicone base compound (II).

[Example 4]
0.5 parts by mass of the vulcanizing agent of Example 2, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 0.05 parts by mass of a platinum catalyst (Pt concentration 1% by mass), and reaction 0.025 parts of ethynylcyclohexanol as a control agent, and methyl hydrogen dimethylpolysiloxane having both ends blocked with trimethylsiloxy groups and having an average of 20 Si-H groups in side chains as a crosslinking agent (average degree of polymerization 40, Si-H The same operation was performed with the substitution of 0.8 parts by mass (base amount: 0.014 mol / g).

[Example 5]
The same operation was performed by replacing titanium tetrabutoxide of the primer composition used in Example 2 with bisacetylacetonatotitanium diisopropoxide.

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

[Comparative Example 1]
0.5 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane was mixed with 100 parts by mass of the silicone-based compound (I) by a two-roll mill, and pressed at 165 ° C. and 10 MPa. A 2 mm thick vulcanized silicone rubber sheet was obtained.
The primer composition is applied once on the resulting vulcanized silicone rubber sheet with a brush and dried at room temperature for 10 minutes, and then applied once more and dried at room temperature for 10 minutes, and then in an oven at 165 ° C. Heat for 30 minutes. In order to carry out the adhesion test described below, the primer was applied to only half (150 × 90 mm) of the entire sheet.
100 parts by mass of polyisoprene compound and 4 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane were mixed by a two-roll mill, and pressed at 80 ° C. and 3 MPa for 1 minute to obtain a thickness of 2 mm. To obtain an unvulcanized isoprene rubber sheet.
An unvulcanized isoprene rubber sheet was bonded to the primer-coated surface of the 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]
The same operation as in Example 2 was performed, except that the essential components were removed one by one from the primer composition used in Example 2 as shown in Table 2. The coating amount of the primer in Comparative Example 2 is 0.6 g / m ² , whereas the coating amount in Comparative Examples 3 and 4 is 0.3 g / m ² .

[Adhesion test]
A test piece was prepared by cutting out the bonded rubber sheet of isoprene rubber / silicone rubber having a thickness of 4 mm 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 TENSOMETER 2020 manufactured by Alpha Technology Co., Ltd. As a measurement method, the 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 was recorded.
The adhesion surface after the test was also observed, and the area ratio of the cohesive failure portion to the primer coated portion (2 cm × 5 cm) is shown as a cohesive failure rate (%). The results are shown in Tables 1 and 2.

Claims (5)

A method for bonding a diene rubber and a silicone rubber, the surface of an unvulcanized or cured product of the diene rubber,
The following (A) to (C) component (A) a silane compound having an alkenyl group,
(B) a silane compound having a (meth) acrylic group,
(C) an organometallic compound having silane hydrolyzability,
Applying a primer composition containing as an essential component, drying and forming a primer layer; and applying a silicone rubber composition to the surface of the primer layer and heat curing to form a silicone rubber layer. , Bonding method between diene rubber and silicone rubber.   The method according to claim 1, wherein the diene rubber is a natural rubber or an isoprene rubber.   The method for bonding a diene rubber and 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 bonding a diene rubber and a silicone rubber according to any one of claims 1 to 3, wherein the component (B) is an alkoxysilane having at least one (meth) acryl group in one molecule.   The component (C) is a silane hydrolyzable metal alkoxide compound or metal chelate compound, and the metal is at least one selected from titanium, tin, zirconium, and aluminum. 2. A method for bonding a diene rubber and a silicone rubber according to claim 1.