Polypropylene resin and silicone rubber bonded material and manufacturing method thereof

Abstract

To provide a joined article in which a polypropylene resin and an addition curable type silicone rubber are strongly joined to each other, and a production method of the same.SOLUTION: There is provided a joined article in which a polypropylene resin subjected to dry treatment and an addition curable type silicone rubber are joined to each other by two kinds of primer compositions, and the polypropylene resin subjected to the dry treatment, a first primer layer, a second primer layer and an addition curable type silicone rubber are joined to each other in this order. First primer layer: a first primer composition containing a silane compound in which a 3-aminopropyl group is bonded to a silicon atom, and a silane compound having one or more epoxy group-containing organic groups in one molecule. Second primer layer: a second primer composition containing organopolysiloxane having two or more alkenyl groups bonded to a silicon atom in one molecule, organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule, and a platinum group metal catalyst.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a bonded material of polypropylene resin and silicone rubber and a method for producing the same. [Background technology]

[0002] Silicone rubber is used in many fields due to its excellent heat resistance, cold resistance, weather resistance, electrical insulation, safety, etc., and is often used as a part combined with organic resins, metals, etc. In addition, polypropylene resin, a type of polyolefin resin, is the second most produced synthetic resin after polyethylene resin, has a low specific gravity, and has excellent mechanical strength, processability, and scratch resistance. However, polypropylene resin is known as a difficult-to-adhere material, and a method for developing strong adhesion between polypropylene resin and silicone rubber that will reliably cause cohesive failure has yet to be found.

[0003] As an example of the adhesion between polypropylene resin and silicone rubber, Japanese Patent Laid-Open No. 60-084335 (Patent Document 1) describes providing a silane coupling agent layer containing aminosilane and vinylsilane on vulcanized silicone rubber, and then simultaneously heating and vulcanizing a silicone / polyolefin copolymer and a thermoplastic resin on top of the layer; however, this method makes it difficult to mold silicone rubber onto polypropylene resin.

[0004] Furthermore, polypropylene resins generally contain additives such as antioxidants, UV absorbers, lubricants, plasticizers, surfactants, etc. Among these additives, organic compounds containing nitrogen, sulfur, phosphorus, etc., and ionic compounds of heavy metals can also cause curing inhibition in addition-cured silicone rubbers that use platinum group metal catalysts. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-open No. 60-084335 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present invention is to provide a bonded article in which polypropylene resin and addition-curing silicone rubber are firmly bonded together, and a method for producing a bonded article in which polypropylene resin and addition-curing silicone rubber can be firmly bonded together even during a hot molding process in a mold, such as compression molding, press molding, or injection molding. [Means for solving the problem]

[0007] As a result of intensive research by the inventors in order to achieve the above-mentioned object, they have discovered that strong adhesion can be obtained between polypropylene resin and silicone rubber even in a mold by coating a polypropylene resin substrate that has been subjected to plasma treatment or silicon oxide film treatment with a primer composition containing a silane compound in which a γ-aminopropyl group is bonded to a silicon atom, and a silane compound containing an epoxy group, and drying the substrate to form a first primer layer, and then coating the substrate with a primer composition containing an organopolysiloxane having two or more alkenyl groups bonded to a silicon atom in each molecule, an organohydrogenpolysiloxane having two or more hydrosilyl groups in each molecule, and a platinum group metal catalyst, and drying the primer composition to form a second primer layer, and then heat-curing an addition-curing silicone rubber composition thereon. This discovery led to the completion of the present invention.

[0008] Accordingly, the present invention provides the following bonded article of polypropylene resin and silicone rubber and a method for producing the same.

[0009] <1> A bonded structure in which a dry-processed polypropylene resin and an addition-curing type silicone rubber are bonded with two types of primer compositions, the bonded structure being in the following order: dry-processed polypropylene resin / first primer layer / second primer layer / addition-curing type silicone rubber. First primer layer: A first primer composition containing a silane compound having a 3-aminopropyl group bonded to a silicon atom, and a silane compound having one or more epoxy group-containing organic groups in one molecule. Second primer layer: A second primer composition containing an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule, an organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule, and a platinum group metal catalyst. <2> A first step of performing a dry treatment on a surface of a polypropylene resin substrate; After the first step, A second step of applying a first primer composition to the substrate surface dry-treated in the first step and drying the composition to form a first primer layer; After the second step, a third step of applying a second primer composition onto the first primer layer and drying to form a second primer layer; a fourth step of applying an addition-curing silicone rubber composition to the surface of the second primer layer and curing the composition by heating to form an addition-curing silicone rubber layer; A method for producing a bonded article comprising the steps of: The first primer composition comprises: (A) a silane compound having a 3-aminopropyl group bonded to a silicon atom, and (B) A silane compound having one or more epoxy-containing organic groups in one molecule. Contains The second primer composition comprises: (C) Organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule (D) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule, and (E) Platinum group metal catalyst A method for producing a bonded article comprising the steps of: <3> The dry treatment is a plasma treatment or a silicon oxide film treatment. <2> 2. A method for producing a bonded article of the polypropylene resin and silicone rubber according to claim 1. <4> The component (A) is at least one selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, and 3-aminopropylmethyldiethoxysilane. <2> or <3> 2. A method for producing a bonded article of the polypropylene resin and silicone rubber according to claim 1. <5> The amount of the first primer layer formed by applying and drying the first primer composition after drying is 0.05 to 5 g / m 2 characterized in that <2> ~ <4> 13. A method for producing a bonded article of polypropylene resin and silicone rubber according to any one of claims 1 to 12. <6> The amount of the second primer layer formed by applying and drying the second primer composition after drying is 0.05 to 100 g / m 2 characterized in that <2> ~ <5> 13. A method for producing a bonded article of polypropylene resin and silicone rubber according to any one of claims 1 to 12. <7> The addition curable silicone rubber composition contains the following components (F) to (I): <2> ~ <6> 13. A method for producing a bonded article of polypropylene resin and silicone rubber according to any one of claims 1 to 12. (F) Organopolysiloxane having a degree of polymerization of 100 to 10,000 and having two or more alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass (G) Specific surface area measured by the BET method is 50 to 500 m 2 / g: 10 to 100 parts by mass per 100 parts by mass of the (F) component (H) Organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the number of hydrosilyl groups in component (H) is 0.5 to 5 moles per mole of alkenyl groups in component (F). (I) Platinum group metal catalyst: 0.5 to 1,000 ppm by mass of platinum group metal relative to the component (F) <8> In a fourth step of applying an addition-curing silicone rubber composition to the surface of the second primer layer and heat-curing the composition to form an addition-curing silicone rubber layer, the addition-curing silicone rubber composition is heat-molded by any method selected from compression molding, press molding, and injection molding. <2> ~ <7> 13. A method for producing a bonded article of polypropylene resin and silicone rubber according to any one of claims 1 to 12. Effect of the Invention

[0010] By using the manufacturing method of the present invention, a bonded product in which dry-processed polypropylene resin and addition-curing silicone rubber are firmly bonded can be stably obtained even in a hot molding process in a mold such as compression molding, press molding, injection molding, etc. Polypropylene resin is used for various purposes such as home appliances, stationery, automobile parts, toys, sporting goods, tableware, etc., and if silicone rubber of different hardness and color can be firmly bonded to it, it is useful for adjusting the texture (anti-slip, etc.) and imparting design properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will now be described in more detail.

[0012] The present invention relates to a bonded article in which a polypropylene resin and an addition-curable silicone rubber are bonded with the below-described first primer composition and the below-described second primer composition. (A) a silane compound having a 3-aminopropyl group bonded to a silicon atom, and (B) A silane compound having one or more epoxy-containing organic groups in one molecule. A first primer composition comprising: (C) an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in each molecule; (D) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule, and (E) Platinum group metal catalyst A second primer composition comprising: The method for producing a bonded article of the present invention further comprises the steps of: A first step of performing a dry treatment on a surface of a polypropylene resin substrate; After the first step, A second step of applying a first primer composition to the substrate surface dry-treated in the first step and drying the composition to form a first primer layer; After the second step, a third step of applying a second primer composition onto the first primer layer and drying to form a second primer layer; a fourth step of applying an addition-curing silicone rubber composition to the surface of the second primer layer and curing the composition by heating to form an addition-curing silicone rubber layer; having The first primer composition comprises: (A) a silane compound having a 3-aminopropyl group bonded to a silicon atom, and (B) A silane compound having one or more epoxy-containing organic groups in one molecule. Contains The second primer composition comprises: (C) Organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule (D) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule, and (E) Platinum group metal catalyst The present invention relates to a method for producing a bonded article, comprising the steps of:

[0013] Polypropylene Resin The polypropylene resin substrate used in the present invention is not particularly limited, and polypropylene resins with various melting points and molecular weights can be used. Generally, polypropylene resins are classified into three types according to the form of copolymerization: homopolymers, which are single polymers of propylene only; random copolymers containing ethylene at a ratio of 4.5% by weight or less; and block copolymers containing ethylene-propylene copolymers in which ethylene is copolymerized after polymerization of homopolymers, and any of these can be used.

[0014] Addition cure silicone rubber The addition-curing silicone rubber used in the present invention contains an alkenyl-containing organopolysiloxane, reinforcing silica, an organohydrogenpolysiloxane, and a platinum group metal catalyst. Either a millable silicone rubber composition that can be plasticized and mixed using a kneading roll or internal mixer, or a liquid silicone rubber composition that is liquid or paste-like before curing can be used.

[0015] [Method of manufacturing the bonded article of the present invention] The first step is to dry treat the surface of the polypropylene resin substrate. Dry Processing In the present invention, a dry treatment of the polypropylene resin surface before forming a primer layer is an essential step. In general, examples of dry treatments include plasma treatment, corona treatment, flame treatment, silicon oxide film treatment (Itro treatment), UV treatment, and excimer treatment. When the dry treatment is performed, hydrophilicity is expressed, for example, by generating a hydrophilic group having an oxygen atom. This can improve the reactivity between the propylene resin and the primer composition. In the present invention, among these dry treatments, plasma treatment or silicon oxide film treatment is particularly preferred because strong adhesion can be stably obtained.

[0016] The plasma treatment used in the present invention is a method of treating the surface of a substrate under reduced pressure using argon or oxygen plasma, and it is possible to adjust the plasma output, gas flow rate, degree of vacuum, treatment time, etc. The treatment conditions can be adjusted based on the wettability and spreading property of the primer composition, and the contact angle of liquid such as water.

[0017] The silicon oxide film treatment used in the present invention is also called ITORO treatment, and is a method of introducing a silane compound or the like into a fuel gas for forming a flame and using the flame to treat the surface of a substrate. After the treatment, a large number of fine particles mainly composed of silicon dioxide are formed on the surface of the substrate, improving the reactivity with the primer composition. The degree of treatment of the surface treatment can be adjusted by the size and shape of the flame, the distance between the burner and the substrate, the moving speed of the burner, the treatment time, etc. The treatment conditions can be adjusted based on the wettability and spreading of the primer composition, and the contact angle of liquids such as water. In addition, the effective procedure of this silicon oxide film treatment is described in detail in JP-A-2003-238710.

[0018] A second step of forming a first primer layer on the surface of the substrate dry-treated in the first step. The first primer composition used in the second step of the present invention for forming a first primer layer on the substrate surface dry-treated in the first step is (A) a silane compound having a 3-aminopropyl group bonded to a silicon atom, and (B) A silane compound having one or more epoxy-containing organic groups in one molecule. A primer composition comprising: Each component is described in detail below.

[0019] (A) Silane compound with a 3-aminopropyl group bonded to a silicon atom The silane compound in which a 3-aminopropyl group is bonded to a silicon atom of component (A) is a compound having one or more 3-aminopropyl groups bonded to a silicon atom in each molecule, preferably one or two, and more preferably one. Furthermore, groups bonded to silicon atoms other than the 3-aminopropyl group include groups selected from alkyl groups having 1 to 10 carbon atoms and alkoxy groups having 1 to 6 carbon atoms, and those having one or more alkoxy groups per molecule are preferred. Specific examples of the silane compound of component (A) include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, di(3-aminopropyl)dimethoxysilane, and di(3-aminopropyl)diethoxysilane. The component (A) can be used alone or in appropriate combination of two or more. Known aminosilanes include silane compounds in which an N-2-(aminoethyl)-3-aminopropyl group, an N-(1,3-dimethyl-butylidene)propylamino group, or an N-phenyl-3-aminopropyl group is bonded to a silicon atom, but none of these compounds provide strong adhesion.

[0020] (B) Silane compound having an epoxy group-containing organic group As the silane compound having an epoxy group-containing organic group of component (B), a known compound can be used. The silane compound has one or more epoxy group-containing organic groups bonded to silicon atoms in one molecule, preferably one or two, more preferably one. Furthermore, groups bonded to silicon atoms other than the epoxy group-containing organic group include groups selected from alkyl groups having 1 to 10 carbon atoms and alkoxy groups having 1 to 6 carbon atoms, and those having one or more alkoxy groups per molecule are preferred. Specific examples of the silane compound of component (B) that are easily available and have high reactivity include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The component (B) can be used alone or in appropriate combination of two or more.

[0021] The mixing ratio of components (A) and (B) in the first primer composition is preferably such that the molar ratio of amino groups to epoxy groups is 2:8 to 8:2, more preferably 3:7 to 7:3, and even more preferably 4:6 to 6:4.

[0022] The (A) component and the (B) component can be used by diluting with a solvent. The solvent is not limited as long as it dissolves the (A) component, the (B) component and other optional components, and a known solvent can be used. The solvent may be used alone or in combination of two or more depending on the evaporation rate during application and drying of the primer composition. 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; chlorinated hydrocarbons such as trichloroethylene, perchloroethylene, and methylene chloride; esters such as ethyl acetate; ketones such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; aliphatic alcohols such as ethanol, isopropanol, and butanol; ethers such as diethyl ether; and silicone-based solvents. Among them, aliphatic alcohols are preferred, and aliphatic alcohols having 1 to 6 carbon atoms, which are easy to dry, are particularly preferred. The reason for this is that in the primer composition, the amino group and the epoxy group in the silane compound react to open the epoxy group and generate a hydroxyl group, but in the aliphatic alcohol, the reaction between this hydroxyl group and the silicon atom in the silane compound is suppressed, thereby improving the storage stability of the primer solution.

[0023] The amount of the solvent is preferably such that the components (A), (B) and other optional components account for 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass, of the primer composition.

[0024] Examples of the method for applying the first primer composition include brush application and spraying. The amount of application is adjusted by the application method, the number of applications, the concentration of the first primer composition, etc., and can be estimated from the change in weight after drying. The amount of the first primer composition after drying is 0.05 to 5 g / m 2 The amount is preferably 0.1 to 3 g / m 2 The amount of coating is preferably 0.05 g / m 2 If it is less than 5g / m, sufficient adhesive strength may not be obtained. 2 If it exceeds this value, the first primer layer may be easily destroyed by external stress.

[0025] The first primer composition may be dried and cured by leaving it at room temperature or by placing it in an incubator or thermo-hygrostat. In consideration of the heat resistance of polypropylene resin, the incubator is preferably set at a temperature of 160° C. or less, more preferably 130° C. or less.

[0026] A third step of forming a second primer layer on the first primer layer formed in the second step. The second primer composition used in the third step of the present invention for forming a second primer layer on the surface of the first primer layer formed in the second step is (C) an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in each molecule; (D) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule, and (E) Platinum group metal catalyst The second primer composition comprises: Each component will be described in detail below.

[0027] (C) Alkenyl-containing organopolysiloxane The component (C) preferably used in the second primer composition is an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule. This component (C) is used as the main component (base polymer) of this composition. Representative examples of the alkenyl-containing organopolysiloxane of component (C) include those represented by the following average composition formula (I). [ka] (In formula (I), R represents the same or different monovalent hydrocarbon groups having 1 to 12 carbon atoms, and a is a number from 1.95 to 2.05.)

[0028] In the above average composition formula (I), R represents the same or different monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, specifically, alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, etc.; cycloalkyl groups such as cyclopentyl group, cyclohexyl group, etc.; fluoroalkyl groups such as 3,3,3-trifluoropropyl group, etc.; alkenyl groups such as vinyl group, allyl group, propenyl group, etc.; aryl groups such as cycloalkenyl group, phenyl group, tolyl group, etc.; aralkyl groups such as benzyl group, 2-phenylethyl group, etc., and methyl group, vinyl group, phenyl group, trifluoropropyl group, etc. are preferred, and methyl group, vinyl group are particularly preferred. Methyl group is preferably 80% or more, particularly 90% or more of R, and more preferably all R groups except alkenyl group are methyl group.

[0029] Specifically, the alkenyl-containing organopolysiloxane of component (C) is preferably an organopolysiloxane whose main chain is composed of dimethylsiloxane units, or a dimethylpolysiloxane whose main chain has, in part, a diphenylsiloxane unit having a phenyl group, a vinyl group, or a 3,3,3-trifluoropropyl group, such as a methylvinylsiloxane unit, or a methyl-3,3,3-trifluoropropylsiloxane unit, etc.

[0030] The organopolysiloxane of component (C) must have two or more (usually 2 to 50, particularly 2 to 20) alkenyl groups, preferably vinyl groups, in one molecule. For example, in the above average composition formula (I), -5 ~1×10 -3 mol / g, specifically 5×10 -5 ~5×10 -4 It is preferred that mol / g is an alkenyl group. The alkenyl group may be bonded to a silicon atom at the molecular chain terminal, or may be bonded to a silicon atom in the middle of the molecular chain (non-terminal), or may be both, but it is preferable that the alkenyl group contains at least an alkenyl group bonded to a silicon atom at both molecular chain terminals.Specifically, it is preferable that the molecular chain terminals are blocked with a dimethylvinylsilyl group, a methyldivinylsilyl group, a trivinylsilyl group, or the like.

[0031] In the above average composition formula (I), a is a number from 1.95 to 2.05, preferably from 1.98 to 2.02, and more preferably from 1.99 to 2.01. The molecular structure of the alkenyl-containing organopolysiloxane of component (C) is basically such that the main chain is made up of diorganosiloxane units (R 2 SiO 2 / 2 ) repeating units, and both ends of the molecular chain are triorganosiloxy groups (R 3 SiO 1 / 2 Generally, the main chain has a linear structure blocked with branch units (RSiO 3 / 2 ) may be contained in a branched structure (R is the same as above).

[0032] The degree of polymerization of the organopolysiloxane of component (C) is preferably 50 to 1,500, more preferably 100 to 1,000, and even more preferably 300 to 1,000. If the degree of polymerization is less than 50, sufficient rubber strength may not be obtained. When diluting with a solvent, the solubility may be improved by using an organopolysiloxane with a low degree of polymerization. In this specification, the degree of polymerization is a value calculated as the weight-average degree of polymerization from the weight-average molecular weight converted into polystyrene in gel permeation chromatography (GPC) analysis measured under the following conditions.

[0033] [GPC measurement conditions] Developing solvent: toluene Flow rate: 0.6mL / min Detector: Refractive index detector (RI) Column: TSK Guardcolumn SuperH-H TSKgel SuperH5000(6.0mmI.D.×15cm×1) TSKgel SuperH4000(6.0mmI.D.×15cm×1) TSKgel SuperH3000(6.0mmI.D.×15cm×1) (All manufactured by Tosoh Corporation) Column temperature: 40℃ Sample injection volume: 50 μL (toluene solution with a concentration of 0.5% by mass)

[0034] The alkenyl-containing organopolysiloxane of the component (C) may use either a single type, or a combination of two or more types having different molecular structures or degrees of polymerization.

[0035] The alkenyl group-containing organopolysiloxane of component (C) can be obtained by known methods, such as (co)hydrolyzing and condensing one or more organohalogenosilanes, or by ring-opening polymerization of a cyclic polysiloxane using an alkaline or acidic catalyst.

[0036] (D) Organohydrogenpolysiloxane Component (D) that is preferably used in the above addition-curable silicone rubber composition is an organohydrogenpolysiloxane having at least two, and preferably three or more, hydrogen atoms (hydrosilyl groups) bonded to silicon atoms in each molecule, and is preferably an organohydrogenpolysiloxane that is liquid at room temperature and is represented by the following average composition formula (II): [ka] (In formula (II), R 2 are each independently the same or different monovalent hydrocarbon groups having 1 to 10 carbon atoms; b is a number that satisfies 0.7 to 2.1, c is a number that satisfies 0.001 to 1, and b+c is a number that satisfies 0.8 to 3.

[0037] In formula (II), R 2 are each independently the same or different monovalent hydrocarbon group having 1 to 10 carbon atoms, and specific examples thereof include alkyl groups such as a methyl group, an ethyl group, and a propyl group.

[0038] In addition, in formula (II), b is a number that satisfies 0.7 to 2.1, preferably 0.8 to 2, c is a number that satisfies 0.001 to 1, preferably 0.01 to 1, and b+c is a number that satisfies 0.8 to 3, preferably 0.9 to 2.7.

[0039] The organohydrogenpolysiloxane of component (D) has at least two hydrosilyl groups (2 to 300), preferably three or more (e.g., 3 to 200), and more preferably four or more (e.g., 4 to 100) in one molecule, and these may be at the molecular chain terminals, in the middle of the molecular chain (non-terminal), or both. The organohydrogenpolysiloxane may have a silicon atom number (or degree of polymerization) of usually 2 to 300, preferably 3 to 200, and more preferably 4 to 100 in one molecule, and preferably has a viscosity at 25°C of 0.5 to 1,000 mPa·s, more preferably 1 to 500 mPa·s, and particularly preferably 5 to 300 mPa·s. The viscosity refers to a value measured at 25°C using a rotational viscometer described in JIS K 7117-1:1999.

[0040] The amount of the organohydrogenpolysiloxane blended is preferably 0.1 to 30 parts by mass, and more preferably 0.3 to 10 parts by mass, per 100 parts by mass of the organopolysiloxane of the component (C). The organohydrogenpolysiloxane is preferably blended so that the molar ratio of hydrosilyl groups to the total alkenyl groups in component (C) is in the range of 0.5 to 10, more preferably 0.8 to 8, and can also be blended in the range of 1 to 5. When using an organohydrogenpolysiloxane, if the blending amount of the organohydrogenpolysiloxane is too small, there is a risk of a decrease in strength due to insufficient crosslinking, and a decrease in adhesive strength with the first primer layer or silicone rubber layer. If the blending amount is too large, there is a risk of the second primer layer becoming brittle due to too many crosslinking points (too high crosslinking density).

[0041] (E) Platinum group metal catalyst Examples of the component (E) that is preferably used in the above silicone rubber composition include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts.

[0042] The amount of component (E) added can be a catalytic amount, and is usually preferably 0.5 to 1,000 ppm, and more preferably 1 to 500 ppm, calculated as platinum metal mass relative to component (C).

[0043] The second primer composition can be applied without a solvent, particularly when the degree of polymerization of the (C) component is set low, but it can also be diluted with a solvent. The solvent is not limited as long as it dissolves the (C), (D), and (E) components and other optional components, and any known solvent can be used. The solvent may be used alone or in combination of two or more types depending on the evaporation rate during application and drying of the second primer composition. 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; chlorinated hydrocarbons such as trichloroethylene, perchloroethylene, and methylene chloride; esters such as ethyl acetate; ketones such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; aliphatic alcohols such as ethanol, isopropanol, and butanol; ethers such as diethyl ether; and silicone-based solvents. Of these, it is preferable to select from aromatic hydrocarbons, aliphatic hydrocarbons, mixed aromatic / aliphatic hydrocarbons, and silicone solvents, which have excellent solubility in the component (C).

[0044] The method of applying the second primer composition includes brush application and spraying, as in the case of the first primer composition. The amount of application is adjusted by the application method, the number of applications, the concentration of the second primer composition, etc., and can be estimated from the change in weight after drying. The amount of the second primer composition after drying is 0.05 to 100 g / m 2 The amount is preferably 0.1 to 10 g / m 2 The amount of coating is preferably 0.05 g / m 2 If it is less than 100g / m, sufficient adhesive strength may not be obtained. 2 If it exceeds this value, it becomes difficult to apply the second primer composition with a uniform thickness.

[0045] The second primer composition is cured preferably at 80 to 160° C. for 10 seconds to 30 minutes, and more preferably at 90 to 150° C. for 20 seconds to 20 minutes.

[0046] The fourth step is to form an addition-curing silicone rubber layer on the surface of the second primer layer. The addition-curable silicone rubber composition used in the present invention for forming an addition-curable silicone rubber layer on the surface of the second primer layer is not particularly limited, but preferred examples include those containing the following components (F) to (I): (F) Organopolysiloxane having a degree of polymerization of 100 to 10,000 and having two or more alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass (G) Specific surface area measured by the BET method is 50 to 500 m 2 / g: 10 to 100 parts by mass per 100 parts by mass of the (F) component (H) Organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the amount of hydrosilyl groups in component (E) is 0.5 to 5 moles per mole of alkenyl groups in component (F) (I) Platinum group metal catalyst: 0.5 to 1,000 ppm by mass of platinum metal relative to the component (F) Each component will be described in detail below.

[0047] (F) Alkenyl group-containing organopolysiloxane The alkenyl-containing organopolysiloxane of the component (F) used in the addition curing silicone rubber composition is defined in the same way as the component (C) of the second primer composition. However, since the silicone rubber composition is required to have sufficient rubber strength, the degree of polymerization of the organopolysiloxane of the component (F) is 100 to 10,000, preferably 1,000 to 10,000, more preferably 2,000 to 10,000, even more preferably 3,000 to 8,000, and particularly preferably 5,000 to 8,000. If the degree of polymerization is less than 100, sufficient rubber strength may not be obtained.

[0048] (G) Reinforcing Silica The reinforcing silica of component (G), which is preferably used in the above-mentioned addition curing silicone rubber composition, may be a reinforcing silica fine powder that is usually used in silicone rubber compositions. Examples of the reinforcing silica of component (G) include fumed silica, dry silica such as calcined silica, and wet silica such as precipitated silica, and among these, fumed silica is preferred from the viewpoint of heat resistance. The specific surface area measured by the BET method is 50 to 500 m 2 / g, preferably 100 to 400m 2 / g, more preferably 100 to 300m 2 / g. The specific surface area is 50m 2 If it is less than 500m / g, the mechanical strength may be insufficient. 2 / g or more may make industrial production difficult.

[0049] If necessary, the surface of this reinforcing silica may be subjected to a hydrophobic treatment with a known treating agent such as chlorosilane or hexamethyldisilazane.

[0050] The amount of reinforcing silica (G) added to the addition curable silicone rubber composition is 10 to 100 parts by mass, preferably 20 to 70 parts by mass, and more preferably 30 to 60 parts by mass, per 100 parts by mass of the alkenyl-containing organopolysiloxane (F). If the amount is less than 10 parts by mass, the amount is too small to obtain a sufficient reinforcing effect, whereas if the amount exceeds 100 parts by mass, the processability may deteriorate and the mechanical strength may decrease.

[0051] (H) Organohydrogenpolysiloxane The organohydrogenpolysiloxane (H) used in the addition curing silicone rubber composition is defined in the same way as the component (D) in the second primer composition. The preferred amount of the alkenyl-containing organopolysiloxane (F) and the preferred molar ratio of hydrosilyl groups to the total alkenyl groups in (F) are also the same. Within these ranges, an addition curing silicone rubber composition with sufficient mechanical strength can be obtained.

[0052] (I) Platinum group metal catalyst The platinum group metal catalyst of component (I) used in the above addition-curable silicone rubber composition is defined in the same manner as component (E) of the above second primer composition.

[0053] The addition-curable silicone rubber composition is applied to the surface of the second primer layer and cured by heating to form an addition-curable silicone rubber layer (fourth step). The curing conditions for the addition curing silicone rubber composition are preferably 80 to 180°C for 10 seconds to 30 minutes, and more preferably 100 to 160°C for 20 seconds to 20 minutes. After the addition curing silicone rubber composition is molded onto the second primer layer (i.e., after the first curing), it is preferable to perform a post-cure (secondary curing) for the purpose of improving adhesion and compression set of the cured product. The post-cure conditions are preferably 80 to 160°C for 30 minutes to 100 hours, and more preferably 100 to 150°C for 1 to 8 hours, taking into consideration the heat resistance and melting point of the polypropylene resin.

[0054] The addition-curing silicone rubber composition may be molded by any method, including compression molding, pressure molding, injection molding, and extrusion molding. However, the present invention exhibits excellent adhesive properties particularly in molding within a mold, such as compression molding, pressure molding, and injection molding. EXAMPLES

[0055] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0056] [First primer composition] 3-Aminopropyltriethoxysilane (KBE-903, Shin-Etsu Chemical Co., Ltd.) and 3-glycidoxypropyltrimethoxysilane (KBM-403, Shin-Etsu Chemical Co., Ltd.) were added to isopropyl alcohol to prepare a concentration of 5 mass% each. After preparation of the primer composition, the composition was stirred for 1 hour with a shaker, and the primer composition was applied and dried on the following day or later. The primer was applied to the polypropylene resin substrate by brush coating, and the substrate was left to dry for 1 hour at room temperature. The amount after drying was 1.0 g / m 2 It was.

[0057] [Second primer composition] It is composed of 98.9 mol% dimethylsiloxane units and 1.1 mol% dimethylvinylsiloxane units, with a weight-average degree of polymerization of approximately 180 and a vinyl group content of 1.5×10 -4 mol / g, 100 parts by mass of an organopolysiloxane having an a value of 2.01 in the above composition formula (I), 10 parts by mass of a methylhydrogendimethylpolysiloxane (weight average degree of polymerization 40, amount of hydrosilyl groups 0.014 mol / g, viscosity 17 mPa·s, b value of 1.55, c value of 0.50, b+c value of 2.05 in the above composition formula (II)) blocked at both ends, 2 parts by mass of ethynylcyclohexanol, and 50 parts by mass of n-heptane were mixed and stirred for 1 hour with a shaker, after which 1 part by mass of a platinum catalyst (Pt concentration 1% by mass) was added, and the mixture was further stirred for 10 minutes, followed by coating and drying. The primer was applied to the polypropylene resin substrate to which the first primer composition had been applied by brush coating, and the mixture was left to dry at room temperature for 30 minutes, followed by heat treatment at 120°C for 30 minutes. Dry weight is 2.2g / m 2 It was.

[0058] [Base silicone rubber compound] It is composed of 99.9 mol% dimethylsiloxane units, 0.075 mol% methylvinylsiloxane units, and 0.025 mol% dimethylvinylsiloxane units, and has a weight-average degree of polymerization of approximately 6,000 and a vinyl group content of 1.4 × 10 -5 100 parts by mass of organopolysiloxane having a specific surface area of ​​200 m2 as measured by the BET method2 25 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a molecular weight of 1 / g, 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-based compound.

[0059] [Silicone rubber composition (addition crosslinking)] To 100 parts by mass of the base silicone rubber compound, 0.05 parts by mass of platinum catalyst (Pt concentration 1% by mass), 0.025 parts by mass of ethynylcyclohexanol, and 0.8 parts by mass of methylhydrogendimethylpolysiloxane (weight average degree of polymerization 40, hydrosilyl group amount 0.014 mol / g) capped at both ends with trimethylsiloxy groups and having an average of 20 hydrosilyl groups on the side chains were mixed using a two-roll mill.

[0060] [Silicone rubber composition (peroxide crosslinking)] 100 parts by mass of the base silicone rubber compound was mixed with 0.6 parts by mass of bis(4-methylbenzoyl) peroxide using a two-roll mill.

[0061] [Adhesive base material] A polypropylene resin substrate with a width of 25 mm, length of 100 mm and thickness of 2 mm was used.

[0062] [Plasma treatment] The surface of the polypropylene resin substrate was washed with ethanol, dried, and then subjected to surface treatment using a plasma dry cleaner (ODC210, manufactured by Yamato Scientific Co., Ltd.) The surface treatment was performed for 1 minute under the conditions of a high-frequency output of 100 W, an oxygen flow rate of 100 mL / min, and a vacuum degree of 60 Pa.

[0063] [Silicon oxide coating] The surface of the polypropylene resin substrate was washed with ethanol, dried, and then surface treatment was performed using a silicon oxide film treatment device (Flamebond FB-5, manufactured by Soft99 Corporation). The flame size was adjusted to about 4 cm, the distance between the nozzle and the substrate was 3 cm, and the burner travel speed was set to 40 cm / sec, and the burner was moved back and forth over the substrate three times. The loss of gloss on the substrate surface confirmed that the treatment had been performed.

[0064] [Test piece (open molding)] A first primer composition was applied to the surface of a plasma-treated or silicon oxide-coated polypropylene resin substrate, dried to form a first primer layer, and a second primer composition was applied to the first primer layer and dried to form a second primer layer, thus carrying out primer treatment. The silicone rubber composition was milled to a thickness of 2 mm using a two-roll mill, cut to a size of 25 mm x 12.5 mm, sandwiched between the primer-coated surfaces of two substrates, and placed in a 120°C oven to heat for 1 hour. [Test piece (press molding)] The edge of a plasma-treated or silicon oxide-coated polypropylene resin substrate was treated with a primer over an area of ​​25 mm x 12.5 mm. The primer-treated substrate was placed on the bottom of a 50 mm x 70 mm x 2 mm mold, 10 g of silicone rubber composition was placed on top, and press molding was performed at 120°C and 10 minutes under a pressure of 10 MPa. The test piece in which the polypropylene resin substrate and silicone rubber composition were integrated was removed from the mold and placed in an oven at 120°C and heated for an additional hour.

[0065] [Adhesion test] The adhesion test was carried out the day after the silicone rubber was molded. Test pieces in which the silicone rubber composition was sandwiched between two substrates (open molding) were evaluated in a bending test in which force was applied until the two substrates were joined. Test pieces obtained by press molding the silicone rubber composition and substrate (mold molding) were evaluated by a 180° peel test in which the rubber and substrate were pulled, and were evaluated according to the following criteria. A: The adhesive surface does not peel off at all (or the rubber breaks in other areas) B: A mixture of rubber fracture and interfacial peeling C: 100% interfacial peeling

[0066] The test results are shown in Table 1. It was shown that when two primer layers were provided on a polypropylene resin substrate that had been subjected to a dry surface treatment, strong adhesive strength was obtained regardless of the molding method used for the silicone rubber composition. [Table 1]

Claims

1. A bonded structure in which polypropylene resin that has been dry-treated by plasma treatment or silicon oxide film treatment and addition-curing silicone rubber are bonded together with two types of primer compositions, the bonded structure being bonded in the following order: dry-treated polypropylene resin / first primer layer / second primer layer / addition-curing silicone rubber. First primer layer: a first primer composition containing a silane compound having a 3-aminopropyl group bonded to a silicon atom, and a silane compound having one or more epoxy group-containing organic groups in one molecule. Second primer layer: A second primer composition containing an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule, an organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule, and a platinum group metal catalyst.

2. A first step of performing a dry treatment on the surface of a polypropylene resin substrate by plasma treatment or silicon oxide film treatment; After the first step, A second step of applying a first primer composition to the substrate surface dry-treated in the first step and drying the composition to form a first primer layer; After the second step, a third step of applying a second primer composition onto the first primer layer and drying to form a second primer layer; a fourth step of applying an addition-curing silicone rubber composition to the surface of the second primer layer and curing the composition by heating to form an addition-curing silicone rubber layer; A method for producing a bonded article comprising the steps of: The first primer composition comprises: (A) a silane compound having a 3-aminopropyl group bonded to a silicon atom, and (B) A silane compound having one or more epoxy group-containing organic groups in one molecule. Contains The second primer composition comprises: (C) Organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in each molecule (D) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule, and (E) Platinum group metal catalyst A method for producing a bonded article comprising the steps of:

3. 3. The method for producing a bonded article of polypropylene resin and silicone rubber according to claim 2, wherein component (A) is at least one selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, and 3-aminopropylmethyldiethoxysilane.

4. The amount of the first primer layer formed by applying and drying the first primer composition after drying is 0.05 to 5 g / m 2 3. The method for producing a bonded article of polypropylene resin and silicone rubber according to claim 2, wherein

5. The amount of the second primer layer formed by applying and drying the second primer composition after drying is 0.05 to 100 g / m 2 3. The method for producing a bonded article of polypropylene resin and silicone rubber according to claim 2, wherein

6. 3. The method for producing a bonded article of polypropylene resin and silicone rubber according to claim 2, wherein the addition curing type silicone rubber composition contains the following components (F) to (I): (F) Organopolysiloxane having a degree of polymerization of 100 to 10,000 and having two or more alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass (G) A specific surface area measured by the BET method is 50 to 500 m 2 / g: 10 to 100 parts by mass of reinforcing silica per 100 parts by mass of component (F) (H) Organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the amount of hydrosilyl groups in component (H) is 0.5 to 5 moles per mole of alkenyl groups in component (F) (I) Platinum group metal catalyst: 0.5 to 1,000 ppm by mass of platinum group metal relative to component (F).

7. 3. The method for producing a bonded article of polypropylene resin and silicone rubber according to claim 2, wherein in a fourth step of applying an addition-curing silicone rubber composition to the surface of the second primer layer and heat-curing it to form an addition-curing silicone rubber layer, the addition-curing silicone rubber composition is heat-molded by any method selected from compression molding, press molding, and injection molding.

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