JPH0292934A - Method for improving adhesion of silicone rubber - Google Patents

Abstract

PURPOSE:To improve adhesion by pretreating a substrate with a specific surface treating agent in bonding a thermosetting type silicone rubber to the substrate simultaneously with curing thereof. CONSTITUTION:A thermosetting type silicone rubber is bonded to a substrate, especially a plastic simultaneously with curing thereof. In the process, the substrate is predipped in a surface treating agent consisting of (A) 100 pts.wt. organic solvent (e.g., benzene or toluene), (B) 0.1-30 pts.wt. organopolysiloxane (e.g., dimethylhydrogenpolysiloxane) containing >=70mol% units -CH3(H)SiO- in one molecule and (C) a platinum-based catalyst in an amount of 0.001-0.5 pt.wt., preferably 0.005-0.2 pt.wt. expressed in terms of platinum metal at ambient temperature or while being heated and then dried. Alternatively, the surface of the substrate is coated with the surface treating agent and subsequently dried while being heated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for improving the adhesion of heat-curable silicone rubber. It concerns a method of improving sex.

[Prior Art] Many techniques have been proposed for adhering heat-curable silicone rubber, particularly heat-curable silicone rubber that hardens by addition reaction, to various base materials as it hardens. There are broadly two types of techniques for this; one is a method in which an adhesion promoter is added internally to a heat-curable silicone rubber composition, and the other is a method in which the base material is surface-treated in advance. . The present invention belongs to the latter technique, but most of the conventional techniques involve surface treatment with a brimer whose main components are alkoxysilanes and a titanium-based catalyst or a tin-based catalyst (Japanese Patent Publication No. 4B- No. 23659, Special Publication Show 6
1-4865 and Japanese Patent Application Laid-Open No. 57-21457).

[Problems to be Solved by the Invention] When the base material to be bonded (hereinafter referred to as the adherend) is metal or glass, heat-curable silicone rubber is preferable for surface treatment agents according to these conventional techniques. Although it exhibits adhesive properties,
When the adherend is plastic, it tends not to exhibit good adhesion. Among plastics, especially those called engineering plastics such as polybutylene terephthalate, polyamide, and polyphenylene sulfide, the adhesion of heat-curable silicone rubber has not been good.

The object of the present invention is to improve upon these drawbacks of the prior art and to provide a method by which a heat-curable silicone rubber can adhere well to plastics, especially engineering plastics, as it hardens.

[Means for Solving the Problems and Their Effects] That is, the object of the present invention is to: When curing and adhering a heat-curable silicone rubber to a base material, the base material is preliminarily treated with (A) 100 parts by weight of an organic solvent and 0.00 parts by weight of an organic solvent. 1 to 30 parts by weight, (C) 0.001 to 0.5 as platinum metal as platinum-based catalyst
The adhesion of silicone rubber is characterized by immersing it in a surface treatment agent consisting of parts by weight at room temperature or under heat and then drying, or by applying the surface treatment agent to the surface of the base material and then drying it with room salt or heat. This is accomplished by an improved method.

To explain this in detail, component (A) is component (B) and (
An organic solvent for dispersing or dissolving component (B) and (C) to facilitate surface treatment, especially if it is inert to both components. There are no restrictions on the types. For example, benzene, toluene,
Aromatics like xylene, aliphatics like pentane, hexane, heptane, octane, petroleum distillates like petroleum benzine, petroleum ether, ligroin, gasoline, kerosene etc., like tetrahydrofuran, diethyl ether, dimethoxyethane ethers, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, esters such as ethyl acetate, butyl acetate, chlorinated hydrocarbons such as carbon tetrachloride, trichloroethane, chloroform, and even dimethyl formamide. , dimethyl sulfoxide, etc. are recommended. Furthermore, two or more types of solvents may be used in combination.

Since it is necessary to dry the solvent after surface treatment, the boiling point of the component is preferably 200° C. or lower.

Component (B) is the main component of the surface treatment agent, and contains 1
It is an organopolysiloxane containing 70 mol percent or more of -Cth(H)SiO- units in the molecule. This component is generally known to those skilled in the art as organohydrodiene polysiloxane, and the method for its production is also known. It is necessary to contain 70 mole percent or more of methyl hydrogen siloxane units in one molecule;
This is because if the amount is less than the mole percent, good adhesion cannot be obtained. Most preferred is an organopolysiloxane in which all molecules other than the molecular chain ends are methylhydrogen siloxane units. This component combines active hydrogen on or near the surface of the adherend,
It is thought that it reacts under the action of component (C) to form a crosslinked product that improves adhesiveness.

The main components include methylhydrogen polysiloxane with trimethylsiloxy groups blocked on both ends, methylhydrogen polysiloxane-dimethylsiloxane copolymer with both ends blocked with trimethylsiloxy groups, methylhydrogen polysiloxane with both ends blocked with dimethylhydrogensiloxy groups, and dimethylhydrogen on both ends. An example is a siloxy group-capped methylhydrogen polysiloxane-dimethylsiloxane copolymer.

The amount of this component added is 0.1 to 30 parts by weight, but if it is less than 0.1 part by weight, good adhesion cannot be obtained, and if the amount exceeds 30 parts, it is difficult to treat the surface of the base material. This is because.

Component (C) serves as a catalyst for the reaction of component (B), and is a platinum-based catalyst. Compounds and complexes of base metals such as platinum, palladium, and rhodium are suitable for this purpose. Examples include chloroplatinic acid and its alcohol solution, platinum-asbestos, platinum-carbon, platinum-olefin complex, platinum-alkenylsiloxane complex, platinum-phosphine complex, and Wilkinson complex.

The amount of this component added is 0.001 to 0.5 parts by weight of platinum metal per 100 parts by weight of component (A), but if it is less than 0.001 parts by weight, good adhesion will not be obtained. This is because the amount exceeds 0.5 part by weight, making the scale meaningless or uneconomical. A preferable addition amount is 0.005 to 0.2 parts by weight of platinum metal. In particular, when applying a solution to the adherend without immersing it in the solution to improve adhesion, the amount of catalyst added is preferably 0.01 part by weight or more as platinum metal. When using a catalyst other than a platinum catalyst, such as a rhodium catalyst or a palladium catalyst, the amount to be added may be such that the amount of rhodium metal or palladium metal is corrected by the ratio of the atomic weight to platinum.

The method of improving the adhesion of silicone rubber according to the present invention involves first immersing an adherend in the surface treatment agent obtained above at room temperature or under heating, and then drying it, or applying the above surface treatment agent to the surface of the adherend. This is done by drying at room temperature or under heat.

First, let's talk about the case of immersion. In this, the surface of the adherend is treated by immersing it in the above-mentioned surface treatment agent under pressure, normal pressure, or reduced pressure. In this case, the temperature of the surface treatment agent is may be at room temperature or may be heated to a temperature below the boiling point of the solvent. Alternatively, the soaking may be carried out while the solvent is refluxed. In order to obtain good adhesion, the temperature of the surface treatment agent is preferably at or slightly lower than the reflux temperature of the solvent. Although there is no particular restriction on the soaking time, it is usually preferable to soak for about 10 minutes to about 3 hours from the viewpoint of workability. After taking out the adherend from the surface treatment agent, it may be dried as is, or the surface of the adherend may be washed with a solvent and then dried in order to remove unreacted substances on the surface of the adherend. Drying may be carried out at room temperature or by heating. In this case, it is preferable that the heating temperature does not exceed 250° C. in order not to melt and destroy the components that improve adhesiveness.

When applying a surface treatment agent to the surface of an adherend, there are no restrictions on the method of application. Various methods can be applied, such as brushing, tamponing, and spraying.

The coated adherend may be dried at room temperature or under heating, similar to the drying described above. However, in the case of coating, drying by heating is recommended to improve adhesion. The heating temperature in this case is preferably 250° C. or lower, as described above. Heating methods include blowing hot air, leaving on a hot plate,
Methods include leaving it in a heating furnace and irradiating it with infrared rays (including far infrared rays).

Although there are no particular restrictions on the type of heat-curing silicone rubber to be adhered to the surface-treated adherend, it is recommended to use addition reaction-curing silicone rubber, as it is highly effective.

Also, peroxide vulcanized silicone rubber is also effective.

The method for improving adhesion according to the present invention can be applied in all fields where it is necessary to bond heat-curable silicone rubber to a substrate. Utilizing this feature, we are able to support the electrical and electronic information equipment industry, machinery industry, automobile industry, rubber and plastic industry,
It is useful for bonding work in all industrial fields, including the textile and medical equipment industries.

[Example] The present invention will be described below with reference to Examples. In the example, "part"
It refers to "parts by weight."

In the formula, rMeJ represents a methyl group.

Reference Example 100 parts of dimethylpolysiloxane (average degree of polymerization 300) with dimethylvinylsiloxy groups blocked at both ends, 20 parts of dry silica with a specific surface area of 200 m2/g surface-treated with hexamethyldisilazane, divinyltetramethyldisiloxane of chloroplatinic acid 5 ppm of total siloxane complex as metal platinum weight
, dimethylsiloxane-methylhydrogensiloxane copolymer with trimethylsiloxy groups blocked at both ends (average degree of polymerization 10,
A heat-curable silicone rubber was prepared by thoroughly mixing 1.8 parts of the former and the latter (molar ratio of 3:5) and 0.004 parts of 3-methyl-1-butyn-3-ol in a planetary mixer. did. Hereinafter, it will be referred to as composition 1.

Example J In a glass container equipped with a reflux condenser, 100 parts of a sufficiently dried isoparaffin solvent (boiling point 140°C), 1 part of methylhydrogen polysiloxane (average degree of polymerization 45) with trimethylsilyl groups blocked at both ends, and divinyl chloroplatinic acid were placed in a glass container equipped with a reflux condenser. Tetramethyldisiloxane complex was added in an amount of 0.006 part based on the weight of metal platinum, and mixed under a stream of dry nitrogen. Here, polybutylene terephthalate (hereinafter referred to as PBT), polyamide-6
(hereinafter referred to as T, PA6) was immersed and heated under reflux for 1 hour. After cleaning the test plate taken out with acetone,
Air-dried at room temperature for an hour. Composition 1 obtained in Reference Example was applied onto this test plate and heated at 120° C. for 1 hour to cure Composition 1 into a rubber-like state. I tried to peel this rubber off from the test plate with a knife, but it was firmly adhered to the test plate and the rubber part broke. As a comparative example, 2 parts of dimethylsiloxane-methylhydrogensiloxane copolymer (average degree of polymerization 10, molar ratio of the former and latter 3:5) with trimethylsiloxy groups blocked at both ends was used instead of the methylhydrogen polysiloxane described above. When we conducted a similar test,
The rubber was easily peeled off from the test plate.

Example 2 100 parts of thoroughly dried hexane was placed in a glass container, and methylhydrogen polysiloxane (with trimethylsilyl group capped at both ends) was placed in a glass container.
An average degree of polymerization of 45) (3 parts) and a divinyltetramethyldisiloxane complex of chloroplatinic acid (0.05 part based on the weight of metal platinum) were added and mixed thoroughly under a stream of dry nitrogen to obtain a solution. This solution was applied with gauze onto test plates of PBT, PA6, and polyphenylene sulfide (hereinafter referred to as T: PPS), and dried at 100° C. for 5 minutes. Using this test plate and Composition 1 of Reference Example, an adhesion test specimen conforming to JIS K6301 8.2 was prepared. However, the above test plate was used instead of the metal plate.

The curing conditions were 120°C for 1 hour. ), the tensile adhesive strength was measured. As a comparative example, Me2H5iO+, 2 units and 5i
A similar adhesion test was conducted using a copolymer consisting of 2 units of Oa (molar ratio of the former and back motion: 10:6, average molecular weight: 1000).

The adhesion test results of Examples and Comparative Examples are shown in the table (
The unit in the table is "kg/cm").

Table: Adhesion test results [Effects of the invention] In the present invention, when adhering a heat-curable silicone rubber to a base material as it hardens, the base material is pre-contained with an organic solvent and methylhydrogensiloxane units of 70 mol percent or more. Because it is treated with a surface treatment agent consisting of predetermined amounts of organopolysiloxane and platinum-based catalyst, it has particularly good adhesion to plastics.

Claims (1)

[Scope of Claims] 1. When adhering heat-curable silicone rubber to a base material while curing, the base material is preliminarily treated with (A) an organic solvent of 100%
Parts by weight, (B) 70 -CH_3(H)SiO- units in one molecule
Organopolysiloxane containing 0 mole percent or more
．． 1 to 30 parts by weight, (C) 0.001 to 0.5 as platinum metal as platinum-based catalyst
Improving the adhesion of silicone rubber by immersing it in a surface treatment agent consisting of parts by weight at room temperature or under heat, and then drying it, or by applying the surface treatment agent to the surface of the base material and then drying it at room temperature or under heat. Method. 2 Claim 1, wherein the organopolysiloxane of component (B) is methylhydrogenpolysiloxane.
Adhesion improvement method described in section. 3. The adhesion improving method according to claim 1, wherein the platinum-based catalyst is 0.005 to 0.2 parts by weight as platinum metal.