JPH03200872A - Adhesive silicone rubber composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. which is flowable and excellent in the adhesion to a polyolefin substrate material and gives, when cured, a silicone elastomer by compounding a silicone base polymer with a specified amt. of a specific polymer. CONSTITUTION:100 pts.wt. silicone base polymer (e.g. a polydimethylsiloxane of which both molecular terminals are blocked by silanol groups) is compounded with 0.5-20 pts.wt. polymer comprising a polyisoprene and/or an isoprene- butadiene copolymer.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention relates to an adhesive silicone rubber composition, and more specifically, to adhesive silicone rubber compositions, and more specifically, to adhesive silicone rubber compositions for adhering to polymers such as olefins, which are difficult to adhere to, such as polyethylene and polypropylene. The present invention relates to a fluid silicone rubber composition that exhibits good adhesion to bodies.

(Prior art) Silicone compositions that harden to become silicone rubber have been well known, and their excellent properties such as weather resistance, heat resistance, cold resistance, and electrical insulation properties are used to create electrical and electronic applications. It is widely used as a potting material for parts, a coating material, a molding material for molding, and a material for electric wires. It is also common practice to add various additives to this silicone rubber composition to impart properties, such as adhesion, depending on the intended use. As a technique for imparting adhesion to the above-mentioned silicone composition, generally, a functional silane or siloxane is blended as an adhesion promoter, and many techniques have been reported.

However, even with liquid silicone rubber compositions using these adhesion promoters, sufficient adhesion is not possible to polyolefin plastics such as polyethylene and polypropylene, and soft vinyl chloride resins, and in many cases, the adherend side Chemical or physical surface modification and the combined use of primers were required.

(Problems to be Solved by the Invention) As mentioned above, conventional branched silicone rubber compositions containing adhesion promoters are not sufficient on their own for polyolefin plastics and soft vinyl chloride resins, which are generally difficult to bond. Since it is not possible to obtain proper adhesion and the above-mentioned auxiliary work is required, there is a risk that not only work efficiency is poor but also deterioration of the quality of the adherend may occur.

The present invention has been made to address these issues, and provides a fluid silicone rubber composition that exhibits excellent adhesion to polyolefin plastics and soft vinyl chloride resins without any auxiliary work. is intended to provide.

[Structure of the Invention] (Means and Effects for Solving the Problems) That is, the adhesive silicone composition of the present invention is a silicone rubber composition having fluidity that becomes a silicone rubber elastic body when cured, It is characterized by containing polyisoprene and/or isoprene-butadiene copolymer in a range of 0.5 to 20 parts by weight based on 100 parts by weight of the base polymer.

The silicone rubber composition of the present invention becomes a rubber elastic body by curing at room temperature or by heating (A)
The composition is mainly composed of a polyorganosiloxane composition, to which (B) polyisoprene and/or isoprene-butadiene copolymer is blended as an adhesion promoter.

The polyorganosiloxane composition of component (A) above basically consists of (a) a polyorganosiloxane base polymer;
(silicone base polymer), (b) curing agent, and if necessary, reinforcing fillers and various additives are uniformly dispersed.

Among the various ingredients used in such compositions, (a)
The silicone base polymer (b) and the curing agent (b) are appropriately selected depending on the reaction mechanism for obtaining the rubber elastic body. Known reaction mechanisms include (1) a crosslinking method using an organic peroxide vulcanizing agent, (2) a method using a condensation reaction, and (4) a method using an addition reaction. That is, it is well known that a preferable combination with a curing catalyst or a crosslinking agent is determined.

That is, when applying the crosslinking method (2) above, the base polymer of component (a) usually contains at least one organic group bonded to a silicon atom in one molecule.
A polydiorganosiloxane having two vinyl groups is used. In addition, as the curing agent of component (b), benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butyl peroxide Various organic peroxide vulcanizing agents are used, such as hexane, di-t-butyl peroxide, and dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl- 2
, 5-di-t-butylperoxyhexane, and di-t-butylperoxide are preferred. Note that these organic peroxide vulcanizing agents may be used alone or as a mixture of two or more.

The blending amount of organic peroxide, which is the curing agent of component (b), is (
The amount is preferably in the range of 0.05 to 15 parts by weight per 100 parts by weight of the silicone base polymer of component a). If the amount of organic peroxide blended is less than 0.05 parts by weight, vulcanization will not be performed sufficiently, and if it is blended in excess of 15 parts by weight, not only will there be no particular effect, but the obtained silicone rubber will be This is because it may have an adverse effect on physical properties.

In addition, when applying the condensation reaction (■) above, (
As the base polymer for component a), a polydiorganosiloxane having hydroxyl groups at both ends is used. As the curing agent for component (b), first, as a crosslinking agent, ethyl silicate, propyl silicate, methyltrimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, methyltris(methoxyethoxy)silane, vinyltris( Alkoxy type such as methoxyethoxysilane and methyltripropenoxysilane; acetoxy type such as methyltriacetoxysilane and vinyltriacetoxysilane; methyltri(acetoneoxime)silane and vinyltri(acetoneoxime)
Silane, methyltri(methylethylketoxime)silane, vinyltri(methylethylketoxime)silane,
and its partial hydrolyzate. Also, hexamethyl-bis(diethylaminoxy)cyclotetrasiloxane, tetramethyldibutyl-bis(diethylaminoxy)cyclotetrasiloxane, heptamethyl(diethylaminoxy)cyclotetrasiloxane, pentamethyl-tris(diethylaminoxy)cyclotetrasiloxane, hexamethyl-bis(diethylaminoxy)cyclotetrasiloxane, Examples include cyclic siloxanes such as methylethylaminoxy)cyclotetrasiloxane and tetramethyl-bis(diethylaminoxy)-mono(methylethylaminoxy)cyclotetrasiloxane. Thus, the crosslinking agent may have either a silane or siloxane structure, and the siloxane structure may be linear, branched, or cyclic. Furthermore, when using these, it is not necessary to be limited to one type, and two or more types can be used in combination.

Among the curing agents of component (b), curing catalysts include carboxylic acid metal salts such as iron octoate, cobalt octoate, manganese octoate, tin naphthinate, tin caprylate, and tin oleate; dibutyltin diralate; Organotin compounds such as dimethyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin diacetate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis(triethoxysiloxy)tin, dioctyltin dilaurate are used. It will be done.

Among the curing agents of component (b), the blending amount of the crosslinking agent is (a
) component base polymer 0.1 to 100 parts by weight
20 parts by weight is preferred. If the amount of the crosslinking agent used is less than 0.1 part by weight, the cured rubber will not have sufficient strength, and if it exceeds 20 parts by weight, the resulting rubber will become brittle, and both are difficult to put into practical use. In addition, the blending amount of the curing catalyst is (a
) 0.01 to 5 parts per 100 parts by weight of the base polymer
Parts by weight are preferred.

If the amount is less than this, it will be insufficient as a curing catalyst, and curing will take a long time, and curing will be poor in areas far from the contact surface with air. On the other hand, if the amount is more than this, the storage stability will deteriorate. A more preferable blending amount range is from 0.1 to 3 parts by weight.

As the base polymer for component (a) when applying the addition reaction in (2) above, the same base polymer as in (2) above is used. In addition, as the curing agent for component (b), a platinum-based catalyst such as chloroplatinic acid, platinum olefin complex, platinum vinyl siloxane complex, platinum black, or platinum triphenylphosphine complex is used as a curing catalyst, and silicon is used as a crosslinking agent. A polydiorganosiloxane having an average number of at least two hydrogen atoms bonded to one molecule in one molecule is used.

Among the curing agents of component (b), the amount of curing catalyst blended is (
a) The amount of platinum element relative to the base polymer of component is 1-10
An amount in the range of 00 pp- is preferred.

If the amount of curing catalyst blended is less than tpp■ in terms of platinum element amount, curing will not proceed sufficiently, and even if it exceeds 11,000 pp, no improvement in the curing rate can be expected.

Further, the amount of the crosslinking agent is preferably such that the number of hydrogen atoms bonded to silicon atoms in the crosslinking agent is 0.5 to 4.0 per one alkenyl group in component (a), More preferably, the amount is 1.0 to 3.0. If the amount of hydrogen atoms is less than 0.5, the curing of the composition will not proceed sufficiently and the hardness of the cured composition will decrease, and if the amount of hydrogen atoms is less than 4.0. If it exceeds this, the physical properties and heat resistance of the cured composition will deteriorate.

(a) used in various reaction mechanisms as mentioned above
The organic group in the polyorganosiloxane as the base polymer of the component is a monovalent substituted or unsubstituted hydrocarbon group, and includes an alkyl group such as a methyl group, ethyl group, propyl group, butyl group, hexyl group, and dodecyl group. , aryl group such as phenyl group, β-phenylethyl group, β-
Examples include unsubstituted hydrocarbon groups such as an aralkyl group such as a phenylpropyl group, and substituted hydrocarbon groups such as a chloromethyl group and a 3.3.3-)lifluoroprobyl group.

Note that -numerically, a methyl group is often used due to ease of synthesis.

It should be noted that fillers, pigments, heat resistance improvers, flame retardants, etc. may be added to the polyorganosiloxane composition of component (A) as needed, as long as they do not impair the effects of the present invention. Other polyorganosiloxanes may be used in combination. These typically include reinforcing fillers such as fumed silica, precipitated silica, diatomaceous earth, titanium oxide, aluminum oxide, zinc oxide, iron oxide, cerium oxide, mica, clay, graphite, and zinc carbonate. , manganese carbonate,
Examples include cerium hydroxide, glass beads, polydimethylsiloxane, and alkenyl group-containing polysiloxane.

A characteristic feature of the adhesive silicone rubber composition of the present invention is that component (B), polyisoprene and/or isoprene-butadiene copolymer, is used as an adhesion promoter.

Among the adhesion promoters of component (B), polyisoprene includes cis-1,4-polyisoprene, trans-1
, 4-polyisoprene, l, 2-polyisoprene, 3.
There is 4-polyisoprene, and there are those that do not have functional groups or those that have functional groups such as -〇〇H group, -〇H group, epoxy group, amino group, and alkoxysilyl group. Among these, those that are liquid at 20°C are preferred from the viewpoint of blendability. Similar isoprene-butadiene copolymers also exist.

Commercially available isoprene or isoprene-butadiene copolymers include Claprene 1″IR-30,
-50, -403, -410, -501, -501f
(Isoprene), Claprene LIR-310, -3
40, -390, -290 (all of the above are isoprene-butadiene copolymers; trade names, all manufactured by Kuraray), etc., and are easily available.

The blending amount of this component (B) is (a) in the component (A) above.
0.5 parts per 100 parts by weight of silicone base polymer
-20 parts by weight. If the amount of the adhesion promoter (B) component is too small, sufficient adhesion cannot be imparted, and if it is too large, it will adversely affect crosslinking properties and the original properties of the silicone composition. This is because there is fear.

The cause of the adhesion improvement effect of the composition of the present invention is not clear, or it is difficult to achieve adhesion to polyolefins such as polyethylene and polypropylene using only a chemical adhesive mechanism such as functional silane. It is presumed that the composition of the invention improves adhesiveness due to both the adhesion mechanism and the adhesion mechanism. Above all, if the adhesive itself does not have sufficient adhesive properties, good adhesion between the adhesive and the adherend cannot be achieved in the initial stage.

(Example) Next, an example of the present invention will be described. Note that all "parts" in the following text indicate "parts by weight."

Example 1 Pulverized quartz/Crystallite VX-8 (trade name, manufactured by Ryumori) was added as a filler to 100 parts by weight of polydimethylsiloxane, which had a viscosity of 10,000 cp at 25°C and whose molecular chain ends were blocked with silanol groups. 30 parts, 8 parts of methyltri(methylethylketoxime)silane as a crosslinking agent, and 0.2 parts of dibutyltin dilaurate as a curing catalyst were mixed to prepare a base rubber composition A.

Next, liquid polyisoprene rubber Claprene LIR-30 was added to this rubber composition A as an adhesion promoter in the proportions shown in Table 1 and mixed uniformly to obtain an adhesive silicone rubber composition.

Examples 2 to 6 The liquid polyisoprene Claprene LIR used in Example 1 was added to the base rubber composition A prepared in Example 1.
-(0, carboxyl group-containing liquid polyisoprene rubber
Kuraprene LIR-410, hydroxyl group-containing liquid polyisoprene rubber Kuraprene LIR-508, isoprene-butazine copolymer liquid rubber Kuraprene LIR-840,
Adhesive silicone rubber compositions were prepared in the same manner as in Example 1 by selectively blending γ-aminopropyltrimethoxysilane as a functional silane compound in the proportions shown in Table 1.

Comparative Examples 1 to 2 The first step was carried out in the same manner as in Example 1, except that polyisoprene rubber and isoprene-butazine copolymer rubber were not used.
Adhesive silicone rubber compositions were prepared using the compounding ratios shown in the table.

Using the adhesive silicone rubber compositions of Examples 1 to 6 and Comparative Examples 1 to 2, JISK13850
Adhesive strength was measured by the method specified in (Tensile and shear bond strength test method for adhesives).

In the adhesion test, an injection molded product of polypropylene resin J700 (trade name, manufactured by Mitsui Petrochemical Industries) was used as the adherend. Also, the adhesive part has a width of 25.0 mm and a length of 12.51111 mm. The sample pieces prepared with a thickness of 1.0 mm were cured for one week at 25° C. and 65% RH to crosslink the rubber, and then subjected to measurement.

The tensile test was conducted at a tensile speed of 50 m+*/sin, and the results of the tensile test were measured on five test pieces each and are shown as the average value. The cohesive failure rate is defined as 100% when the polypropylene resin breaks with all the silicone rubber attached to the surface, and 0% when no silicone rubber remains. .

These results are also shown in Table 1.

(Leaving space below) Table [Effects of the Invention] As explained above, according to the adhesive silicone rubber composition of the present invention, by blending polyisoprene or isoprene-butadiene copolymer as an adhesion promoter, fluidity is improved. The tackiness of the silicone rubber composition is increased, the wettability to the surface to which it is applied is improved, and the adhesive strength is improved. Therefore, the composition of the present invention is extremely useful as an adhesive for polyolefin-based substrates that have conventionally been considered difficult to adhere to.

Claims (1)

[Scope of Claims] A silicone rubber composition having fluidity that becomes a silicone rubber elastic body upon curing, wherein 0 parts of polyisoprene and/or isoprene-butadiene copolymer is added to 100 parts by weight of the silicone base polymer. An adhesive silicone rubber composition characterized in that it contains in a range of 5 to 20 parts by weight.