JPH04270764A - Adhesive silicone rubber composition - Google Patents

Abstract

PURPOSE:To provide an adhesive silicone rubber composition having excellent adhesivity and firmly self-adhesive to various adherend such as ethylene- propylene rubber product without using a pretreatment process. CONSTITUTION:The objective composition can be produced by compounding (A) 100 pts.wt. of an organopolysiloxane containing >=2 silanol groups in one molecule with (B) 0.5-20 pts.wt. (preferably 1-10 pts.wt.) of an organosilane (or its partial hydrolyzate) containing >=2 alkoxysilyl groups and >=1 sulfur atom bonded to silicon atom through an alkylene group in one molecule, (C) 0.1-10 pts.wt. (preferably 0.5-5 pts.wt.) of an amino group-containing silane (or its partial hydrolyzate) expressed by formula (Q is phenyl or benzyl; R<1> is 1-8C bivalent hydrocarbon group; R<2> and R<3> are 1-4C hydrocarbon group; (n) is 0 or 1) and (D) 0.01-10 pts.wt., preferably 0.1-5 pts.wt. (based on 100 pts.wt. of A+B+C) of a curing catalyst (e.g. dibutyltin dilaurate).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive silicone rubber composition which has excellent adhesive properties and is particularly useful for adhering ethylene-propylene rubber products.

0002

[Prior Art and Problems to be Solved by the Invention] Adhesive silicone rubber compositions are capable of curing at room temperature or under heating to adhere to adherends made of various materials. Appropriate primer treatment expands the range of compatible materials,
It can firmly adhere to most materials such as ceramics, metals, plastics, and rubber. Furthermore, after curing and adhesion, this adhesive silicone rubber composition becomes a cured product with excellent heat and cold resistance, weather resistance, and electrical properties, so it is used in a wide range of fields as sealants, coating agents, potting agents, etc. ing.

[0003] However, adhesive silicone rubber compositions have a problem in that they do not exhibit satisfactory adhesion to ethylene-propylene vulcanized rubber (EPDM) even after primer treatment. Therefore, various chemical and physical surface treatment methods have been proposed in the past for the purpose of improving the adhesion of such silicone rubber compositions to EPDM, but these pretreatment steps are complicated and are not practical. Ta. Therefore, the above adhesive silicone rubber composition is used as a coating agent for EPDM products used as, for example, automobile rubber, construction rubber, general industrial rubber, etc.
It has the disadvantage that its application as a lining agent, etc. is limited.

[0004] The present invention has been made in view of the above circumstances.
The object of the present invention is to provide an adhesive silicone rubber composition having excellent adhesive properties and capable of self-adhering to adherends made of various materials including EPDM without performing a pretreatment step.

[0005]

[Means and Effects for Solving the Problem] As a result of intensive studies to achieve the above object, the present inventors found that (1) an organopolysiloxane containing at least two or more silanol groups in one molecule; ) an organosilane containing at least two or more alkoxysilyl groups in one molecule and at least one sulfur atom bonded to a silicon atom via an alkylene group, or a partial hydrolyzate thereof;
(3) When an amino group-containing silane represented by the following general formula (I) or a partially hydrolyzed product thereof and (4) a curing catalyst are blended, sufficient adhesion to EPDM can be achieved by using the second and third components together. Furthermore, the adhesion can be further improved by adding an organic peroxide in addition to the above components, and therefore, it is possible to adhere EPDM and various other materials without performing a pretreatment process. It was discovered that an adhesive silicone rubber composition with excellent adhesiveness that can self-adhere well to the body can be obtained, and the present invention was completed.

[0006]

[Case 2]

Therefore, the present invention provides (1) an organopolysiloxane containing at least two silanol groups in one molecule, (2) an organopolysiloxane containing at least two or more alkoxysilyl groups in one molecule, and An organosilane containing at least one sulfur atom bonded to an atom via an alkylene group or a partial hydrolyzate thereof, (3) an amino group-containing silane represented by the above general formula (I) or a partial hydrolyzate thereof, ( 4) To provide an adhesive silicone rubber composition characterized in that it contains a curing catalyst.

The present invention will be described in more detail below. The first component of the adhesive silicone rubber composition of the present invention is the main component polymer constituting the composition of the present invention, and has at least two silanol groups in one molecule. It is an organopolysiloxane containing at least 1.

[0009] Here, as the organopolysiloxane, a compound represented by the following general formula (II) is preferably used.

0010

[Image Omitted] In the above formula (II), the substituent R has 1 to 10 carbon atoms,
Preferred are substituted or unsubstituted monovalent hydrocarbon groups or hydroxyl groups having 1 to 8 carbon atoms, such as methyl group, ethyl group, propyl group, phenyl group, vinyl group, trifluoropropyl group, cyanopropyl group, etc. (I
I) R's present in the formula may be the same or different from each other. In addition, a part of R may be a hydroxyl group, especially when necessary for characteristics. In addition, n is the viscosity of the organopolysiloxane at 25°C of 50 to 1,00.
0,000 centistokes (cs), especially 100-5
00,000 cs, more preferably 400-100,0
It is desirable that the number is 00cs. If the viscosity of this organopolysiloxane is lower than 50 cs, desired physical properties may not be obtained in the cured product.
If it is higher than 000,000 cs, workability may be poor and handling may become inconvenient. Note that the above organopolysiloxane can be produced by a conventional method.

Next, the second component used in the present invention contains at least two alkoxysilyl groups in one molecule and at least one sulfur atom bonded to a silicon atom via an alkylene group. It is an organosilane contained therein or an organopolysiloxane obtained by partially hydrolyzing the organosilane. This second component is an important component of the present invention that imparts adhesiveness to adherends such as EPDM to the silicone rubber composition when used in combination with the third component, amino group-containing silane or its partially hydrolyzed product. If the second component is not present, the adhesion will be insufficient for practical use.

In this case, the alkoxysilyl group is
Examples include methoxysilyl group, ethoxysilyl group, propoxysilyl group, and the like. In addition, in order to enhance the interaction with the sulfur crosslinked portion in the EPDM vulcanized rubber, the organosilane or its partially hydrolyzed product contains sulfur atoms that are not directly bonded to silicon atoms in one molecule but bonded through alkylene groups. Specific examples of the organosilane or organopolysiloxane include the following compounds.

[0013]

embedded image Among these, (CH3O)3Si(CH2)3
SH is preferred.

[0014] As the second component, a partial hydrolyzate of the above organosilane or organopolysiloxane or a mixture thereof may be used.

The amount of the second component to be blended is preferably 0.5 to 20 parts, particularly 1 to 10 parts, based on 100 parts (by weight, hereinafter the same) of the organopolysiloxane of the first component. If the amount is less than 0.5 parts, the curing of the composition may not progress sufficiently, resulting in poor mechanical strength or insufficient adhesion to EPDM, and if it exceeds 20 parts, the hardness of the cured product may decrease. It may become tall and brittle.

Furthermore, the third component, which is an important component of the composition of the present invention along with the second component mentioned above, is an amino group-containing silane represented by the following general formula (I) or a partially hydrolyzed product thereof.

[0017]

[C5]

Here, the substituent R1 in formula (I) includes, for example, a methylene group, an ethylene group, a propylene group, a methylethylene group, a tetramethylene group, a hexamethylene group,
-(CH2)2-NH-(CH2)3-,-(CH2)
Examples include 2-NH-(CH2)2-NH-(CH2)3-, and examples of R2 and R3 include methyl, ethyl, propyl, and butyl groups. Specific examples of such amino group-containing silanes of formula (I) include the following. C6H5NHC3H6Si(OCH3)3, C6H5C
H2NHC3H6Si(OCH3)3, C6H5CH2
NHC2H4NHC3H6Si(OCH3)3,C6H
5NHC2H4NHC3H6Si(OCH3)3,C6
H5CH2NHC2H4NHC2H4NHC3H6Si
(OCH3)3 Among these, C6H5CH2NHC3H6Si(OC
H3)3 or a partial hydrolyzate thereof or a mixture thereof is preferably used.

As the third component, a partial hydrolyzate of the above-mentioned amino group-containing silane or a mixture thereof can also be used.

The amount of the third component to be blended is preferably 0.1 to 10 parts, particularly 0.5 to 5 parts, based on 100 parts of the organopolysiloxane of the first component, and if it is less than 0.1 part, EPDM If the amount exceeds 10 parts, sufficient working time may not be obtained.

Furthermore, the composition of the present invention contains a curing catalyst as a fourth component. This curing catalyst is for accelerating the curing of the mixture of the first to third components, and those generally used in condensation type room temperature curable silicone resin compositions can be used. Specific examples of curing catalysts include metal salts of organic acids such as dibutyltin dilaurate, dibutyltin dibenzyl maleate, dibutyltin dioctoate, dibutyltin diacetate, iron stearate, lead octylate, tetrabutyl titanate, and tetraisopropyl titanate. Examples include titanate esters such as, titanium chelate compounds such as titanium acetylacetonate, and among them, tin carboxylates and titanium chelate compounds are preferred. In addition, these curing catalysts may be used alone or in combination of two types.

The amount of curing catalyst blended is preferably 0.01 to 10 parts, particularly 0.1 to 5 parts, based on 100 parts of the total amount of the first to third components, and if it is less than 0.01 part. The function as a curing catalyst may not be fully demonstrated, and the curing time of the composition may become longer, resulting in insufficient curing in the deep part of the rubber layer.If the amount exceeds 10 parts, the storage stability of the composition may deteriorate. Heat resistance after curing may decrease.

[0023] It is recommended that the composition of the present invention contain an organic peroxide as a fifth component. When this organic peroxide is blended into the composition of the present invention, it decomposes to generate radicals and acts on the radical acceptor in the second component or the adherend such as EPDM, thereby improving the adhesion of the composition to the adherend. It can improve your sexual performance.

As the organic peroxide, those commonly used for vulcanization of silicone rubber can be used, such as benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, t-
Examples include butyl peroxybenzoate, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, among others, benzoyl peroxide, bis-2,4-dichlorobenzoyl Peroxides are preferred, especially bis-2,4-dichlorobenzoyl peroxide.

The amount of organic peroxide to be added is 0 to 5 parts, preferably 0.1 to 2 parts, per 100 parts of organopolysiloxane as the first component, and even if more than 5 parts is added, adhesion will not be promoted. The effect does not improve, but instead foaming due to decomposition products,
Side effects such as siloxane decomposition are more likely to occur.

[0026] In addition to the above-mentioned components, various fillers are preferably added to the silicone rubber composition of the present invention. As fillers, for example, reinforcing fillers, anti-settling agents, and electrical conductivity imparting agents such as fumed silica, precipitated silica, hydrophobized products thereof, and carbon black are used.As reinforcing fillers, silicone resins, Organic resins etc. can also be used. In addition, quartz powder, fused silica, spherical silica, diatomaceous earth, zeolite, calcium carbonate, titanium dioxide, iron oxide, alumina, spherical alumina, aluminum hydroxide, and aluminum nitride are used as semi-reinforcing fillers, extenders, and thermally conductive fillers. , magnesium sulfate, etc., and lead compounds such as lead, lead carbonate, and lead hydroxide are preferably used as fillers used for purposes such as radiation shielding. Note that these fillers may be used alone or in combination of two or more, and the amount added is not particularly limited, but may be within a range that does not significantly reduce the physical properties of the cured product obtained. Usually, it is preferable to use 300 parts or less per 100 parts of the first component.

Furthermore, the composition of the present invention may contain various additives as optional ingredients within the range that does not impair the object of the present invention. Examples of additives include inorganic pigments,
Coloring agents such as organic dyes, heat resistance such as cerium oxide, zinc carbonate, manganese carbonate, benzotriazole, platinum compounds
Trimethoxysilane, triethoxysilane, tetramethoxysilane, tetraethoxysilane, tetra(n- Various silanes such as (propoxy) silane or their partial hydrolysates, methylhydrogenpolysiloxane, methylhydrogenpolysiloxane as a blowing agent, non-functional silicone raw rubber for the purpose of imparting lubricity to the surface of the cured product, and the like. Further, since the composition of the present invention is a condensation curing type, water and alcohols such as methanol, ethanol, propanol, and methyl cellosolve may be added for the purpose of accelerating curing or improving deep curing. Furthermore, when the composition of the present invention is used as a coating agent for EPDM weather strips, architectural gasket materials, etc., it is generally used in an organic solvent that can easily dissolve the organopolysiloxane, such as toluene, xylene, chlorinated solvent, acetic acid. It is desirable to add an ester solvent such as ethyl. Incidentally, the amount of these optional components added can be set to a normal amount within a range that does not impede the effects of the present invention.

The composition of the present invention is prepared by packaging the above-mentioned first to fifth components in three packages: (1) packaging for the first component alone, (2) packaging for a mixture of the second, third and fourth components, and (3) packaging for the fifth component alone. It is preferable to add the ingredients as appropriate, store them, and mix them at the time of use.

[0029]

Effects of the Invention The adhesive silicone rubber composition of the present invention has excellent self-adhesive properties and can strongly self-adhere to EPDM without any primer treatment, so it can be used for EPDM weather strips and construction gasket materials. It can be suitably used as a coating agent, etc. Furthermore, since the composition of the present invention can adhere well to a wide range of materials such as glass, ceramics, metals, and plastics, it can be used as a coating agent of various types in a wide range of fields such as the automobile industry, electrical/electronic industry, and construction industry. It can be used as a sealing agent, potting agent, etc.

[0030]

[Examples] The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In addition, in the following examples, all parts are parts by weight.

[Example 1] 20 parts of hydrophobic silica with a specific surface area of 120 m2/g was added to 100 parts of dimethylpolysiloxane with a viscosity of 5,000 cs at 25°C, which was blocked with hydroxyl groups at both ends, and stirred in a wing type. The mixture was kneaded in a machine for 1 hour. This mixture was passed through three rolls three times to prepare a silicone base. Furthermore, 1.1 parts of γ-mercaptopropyltrimethoxysilane, 2.7 parts of N-benzyl-γ-aminopropyltrimethoxysilane, and 0.35 parts of dibutyltin dilaurate were added to 100 parts of this silicone base, and the mixture was thoroughly mixed with a spatula. A silicone rubber composition was prepared by mixing and stirring.

Next, two EPDM rubber sheets (2 mm thick) cut out into strips (25 to 80 mm) are placed with the above composition between the two EPDM rubber sheets so that each end overlaps by 10 mm on the opposite side. The material was formed into a layer with a thickness of about 1 mm, the layers were sandwiched and overlapped, the rubber sheet was fixed so that it would not move, and it was left for 3 days at 25° C. in an atmosphere of 50% relative humidity. The obtained sample piece was tested using a tensile tester Str.
When a shear adhesion test was conducted using ograph R3 (manufactured by Toyo Seiki Co., Ltd.), cohesive failure occurred in the silicone rubber portion. The shear adhesive strength was 25 kg/cm2.

[Comparative Example 1] A silicone rubber composition was prepared in the same manner as in Example 1 except that 1.2 parts of tetraethoxysilane was used instead of 1.1 parts of γ-mercaptopropyltrimethoxysilane. When a shear adhesion test was conducted using this silicone rubber composition in the same manner as in Example 1, the shear adhesion strength was 20 kg/cm2, but the cohesive failure rate was 0%, indicating that it did not peel off at the two-phase interface. did.

[Comparative Example 2] A silicone rubber composition was prepared in the same manner as in Example 1, except that 2.2 parts of tetraethoxysilane was used instead of 2.7 parts of N-benzyl-γ-aminopropyltrimethoxysilane. Prepared. When a shear adhesion test was conducted using this silicone rubber composition in the same manner as in Example 1, the shear adhesion strength was 15 kg/cm2.
However, the cohesive failure rate was 0%, and delamination occurred at the two-phase interface.

[Example 2] 1.0 part of bis-2,4-dichlorobenzoyl peroxide paste (containing 50%) was added to a silicone rubber composition prepared in the same manner as in Example 1. Thoroughly knead with a spatula. This kneaded product was sandwiched between two EPDM rubber sheets in the same manner as in Example 1, and cured in an atmosphere of 25° C. and 50% relative humidity, and a shear adhesion test was conducted on the obtained test pieces. As a result, cohesive failure occurred in the silicone rubber portion, and the shear adhesive strength was 28 kg/cm2.

[Example 3] 15 parts of crystalline silica with an average particle size of 5 μm and 35 parts of calcium carbonate were added to 100 parts of dimethylpolysiloxane, which has a viscosity of 700 cs at 25° C. and is capped with hydroxyl groups at both ends. The mixture was then kneaded for 1 hour using a feather stirrer. This kneaded material was passed through three rolls once, and the resulting paste was used as a silicone base. Further, to 100 parts of this silicone base, 0.9 parts of γ-mercaptopropyltrimethoxysilane, 2.2 parts of N-benzyl-γ-aminopropyltrimethoxysilane,
0.25 part of dibutyltin dilaurate was added and thoroughly stirred and mixed with a spatula to obtain a silicone rubber composition.

Using the obtained silicone rubber composition, an adhesive test piece was prepared in the same manner as in Example 1, and a shear adhesion test was conducted. Cohesive failure occurred in the silicone rubber layer. The shear adhesive strength was 26 kg/cm2.

The above silicone rubber composition was applied to a thickness of 1.0 mm on test pieces of various adherends shown in Table 1, and left in an atmosphere of 25° C. and 50% relative humidity for 3 days, and then cured. The adhesion state between the object and the adherend was evaluated according to the following criteria. The results are also listed in Table 1. Judgment criteria ○: Strong adhesion and cohesive failure ×: No adhesion at all

[0039]

[Table 1]

From the results shown in Table 1, it was confirmed that the silicone rubber composition of the present invention has excellent adhesion to various adherends.

Claims (1)

[Claims] Claim 1: (1) an organopolysiloxane containing at least two or more silanol groups in one molecule;
) an organosilane containing at least two or more alkoxysilyl groups in one molecule and at least one sulfur atom bonded to a silicon atom via an alkylene group, or a partial hydrolyzate thereof; (3) the following general An amino group-containing silane represented by formula (I) or a partial hydrolyzate thereof,
(4) An adhesive silicone rubber composition comprising a curing catalyst. [Chemical formula 1]