JPH0354715B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a primer composition having excellent initial adhesion and adhesion durability, and particularly for adhering a thermosetting silicone rubber composition to the surface of a base material such as metal or ceramic with which it is in contact during curing. The present invention relates to a primer composition that is suitable for bonding and can provide excellent adhesive durability in various atmospheres such as air, steam, and oil even at high temperatures exceeding 200°C. In recent years, silicone rubber has been widely used in applications requiring rubber elastic bodies at high temperatures due to its excellent heat resistance. However, when these silicone rubbers are used in high-temperature environments, they are often used as composites bonded to various base materials, especially metals such as iron, aluminum, and stainless steel, and ceramics. They are often exposed to heated lubricating oils, such as various mineral oils, silicone oils, and steam. In this case, the silicone rubber deteriorates and peels off at the interface with the base material before it loses its rubber elasticity, so a primer composition that can maintain strong adhesion for a long period of time even under such high temperatures and harsh atmospheres. was expected to appear. Many primer compositions have been proposed to improve adhesion under such harsh conditions;
None of these are perfect, and various studies are still ongoing. As a result of intensive studies to develop the above primer composition, the present inventors found that a primer composition containing a specific organopolysiloxane as a main component has good initial adhesion to various metals and ceramics.
In particular, it was discovered that it maintains extremely good adhesive strength even when exposed to a high temperature atmosphere or heated mineral oil for a long period of time, leading to the present invention. Therefore, the present invention has excellent initial adhesion to various substrates,
Another object of the present invention is to provide a primer composition for a silicone rubber composition that can maintain strong adhesive strength for a long period of time even under high temperature conditions. That is, the present invention provides formula A

It consists of a siloxane unit represented by the formula and a siloxane unit represented by the formula SiO4/2 (where a is 1, 2, or 3, b is 0,
1, 2 or 3, where a+b is 1, 2 or 3, R ¹ is an alkenyl group, and R ² is an alkyl group or an aryl group. ), (R ¹ group) in 1 molecule/
(Si atom) is within the molar ratio of 0.10 to 0.98, and one molecule contains both a silanol group and a Si atom-bonded alkoxy group, or only a Si atom-bonded alkoxy group (a silanol group and a Si atom-bonded alkoxy group). Total amount of ) / (Si atom) or (Si atom-bonded alkoxy group) / (Si atom) in molar ratio
The present invention relates to a primer composition comprising: 100 parts by weight of an organopolysiloxane having a molecular weight within the range of 1.0 to 2.5, B: 0.01 to 100 parts by weight of a curing catalyst, and C: an organic solvent. To explain this in detail, component A used in the present invention is the main component of the primer composition of the present invention, and has the formula

It consists of a siloxane unit represented by the formula and a siloxane unit represented by the formula SiO4/2 (where a is 1, 2, or 3, b
is 0, 1, 2 or 3, provided that a+b is 1, 2 or 3, R ¹ is an alkenyl group, and R ² is an alkyl group or an aryl group. ). formula

Typical examples of siloxane units represented by the formula are R ¹ R ² SiO 1/2 units, R ¹ R ² SiO 2/2 units, and R ¹ SiO 3/2 units, and one to three of these siloxane units are represented by the formula It may be combined with a siloxane unit represented by SiO4/2 to constitute the organopolysiloxane of component A, or one to three of these siloxane units and R ² ₃ SiO 1/2 unit, R ² ₂ SiO 2/2 One to three types of the unit and R ² SiO3/2 may be combined with the formula SiO4/2 unit to constitute the organopolysiloxane of the A component. However, in any configuration, (R ¹ group)/(Si atom) in one molecule
is required to be within the range of 0.10 to 0.98 in terms of molar ratio. If this molar ratio is less than 0.10, the initial adhesion of the thermosetting silicone rubber composition to the cured film of the primer composition and the adhesive durability at high temperatures will be poor; if this molar ratio exceeds 0.98, the primer composition will be cured. This is because the adhesion durability of the coating to various substrates, especially under dry heat and when immersed in high-temperature mineral oil, becomes poor. R ¹ is an alkenyl group, which includes vinyl group,
Examples include allyl group and 2-butenyl group. R ² is an alkyl group or an aryl group, and examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, and an n-propyl group.
Examples include unsubstituted alkyl groups such as -hexyl group; haloalkyl groups such as 3-chloropropyl group and 3,3,3-trifluoropropyl group; and cycloalkyl groups such as cyclohexyl group. Alkyl groups are those with a small number of carbon atoms from the viewpoint of mineral oil resistance,
That is, it is preferably 6 or less. Examples of the aryl group include a phenyl group and a naphthyl group. The organopolysiloxane of component A contains both a silanol group and a Si atom-bonded alkoxy group or only a Si atom-bonded alkoxy group in one molecule, (total amount of silanol groups and Si atom-bonded alkoxy group)/(Si
atom) or (Si atom-bonded alkoxy group)/(Si
atoms) in a molar ratio of 1.0 to 2.5. If the molar ratio of (total amount of silanol groups and Si atom-bonded alkoxy groups)/(Si atoms) or (Si atom-bonded alkoxy groups)/(Si atoms) in one molecule is less than 1.0, the cured film of this primer composition will deteriorate. The initial adhesion to various substrates, especially metals, and the adhesion durability when immersed in high-temperature mineral oil will be poor.If this molar ratio exceeds 2.5, the hardness of the cured film of this primer composition will become too high, and it will be difficult to adhere to metals and This is because it cannot follow the thermal expansion of silicone rubber and cannot maintain sufficient adhesive strength. The degree of polymerization of organopolysiloxane as component A is 2.
Any above is acceptable, but dimers to octamers are preferred from the viewpoint of adhesion and coating workability. Component A may be used alone or in a mixture of different types. The organopolysiloxane of component A is produced by partial cohydrolysis of an organoalkoxysilane having an alkenyl group bonded to a Si atom and a tetraalkoxysilane.
Partial cohydrolysis of organoalkoxysilane having an atom-bonded alkenyl group, organoalkoxysilane having no Si atom-bonded alkenyl group, and tetraalkoxysilane, partial cohydrolysis of organoalkoxysilane having a Si atom-bonding alkenyl group and alkyl silicate, etc. It can be easily manufactured by In this case, it is preferred to use small amounts of organohalogenosilanes, such as organochlorosilanes, or halogen acids, such as hydrochloric acid, as hydrolysis catalysts. Component B used in the present invention is a catalyst that cures component A by a condensation reaction and imparts air-drying properties to the primer composition. Examples of such catalysts include tetraisopropyl titanate, tetra-n-butyl titanate, tetra(2-ethylhexyl) titanate, polycondensates of these organic titanate esters, dialkoxytitanium acetylacetonate, titanium bisacetylacetonate, and polytitanium acetylacetonate. Organic titanate esters, titanium complex compounds, titanium chelate compounds such as nate, titanium glycolate, titanium lactate, titanium lactate ethyl ester, titanium triethanolaminate; organic zirconate esters; organic esters such as stannath octoate, dibutyltin dilaurate Tin compounds; organohalogenosilanes such as methyltrichlorosilane and dimethyldichlorosilane are exemplified. Among these, the above-mentioned organic titanium compounds are preferred because they not only cure component A but also improve the adhesiveness of the primer composition. The blending amount of component B is based on 100 parts by weight of component A.
The amount is 0.01 to 100 parts by weight, preferably 0.05 to 60 parts by weight. If the amount is less than 0.01 part by weight, the air-drying properties of this primer composition and the adhesion to various substrates, especially metals, will decrease, and the adhesion of the silicone rubber composition to the cured film of this primer composition will decrease under high temperatures. Adhesive durability decreases. On the other hand, if the amount exceeds 100 parts by weight, the primer composition cannot form a good cured film and tends to inhibit the curing of silicone rubber compositions, particularly addition reaction-curable silicone rubber compositions. C used in the present invention
The component is an organic solvent for dissolving component A and component B, and this is selected taking into consideration the solubility of component A and the evaporability during application of the primer composition, such as toluene, xylene, etc. , benzene, heptane, hexane, trichlorethylene, perchlorethylene, methylene chloride, methanol, ethanol, isopropanol, butanol and the like. These organic solvents may be used alone or as a mixed solvent of two or more. The blending ratio of component C with component A and component B is not particularly limited, but may be appropriately selected in consideration of the solubility of component A and component B, the viscosity of the dissolved product, coating workability, etc. The primer composition of the present invention can be easily produced by simply uniformly mixing the components A to C described above. The primer composition of the present invention may optionally contain a heat resistant agent, a pigment, an inorganic filler, an organoalkoxysilane such as an alkenyltrialkoxysilane or an alkylalkenyldialkoxysilane, a tetraalkoxysilane, an alkyl polysilicate, and components other than component A. organopolysiloxane,
For example, a partial condensate of vinyltrialkoxysilane, a partial condensate of allyltrialkoxysilane,
The addition and blending of methylvinylpolysiloxane and the like is optional as long as the properties aimed at by the present invention are not impaired. When using the primer composition of the present invention, it is preferable to air dry it for 30 minutes or more after applying it to the adherend before applying the silicone rubber composition, and in some cases, the primer composition may be cured. Baking may be performed to improve adhesion to metals. When the primer composition of the present invention is used to cure a silicone rubber composition while adhering it to a substrate that is in contact with it, it can firmly adhere to various metals such as iron, stainless steel, aluminum, and ceramics. Moreover, its adhesive strength does not deteriorate even when exposed to high-temperature mineral oil or water vapor. Taking advantage of these characteristics, the primer can be used to bond oil seal housings and silicone rubber, to bond silicone rubber to copy machine roll cores, to bond silicone rubber to engine mound cores, and to bond silicone rubber to other metals. It is effectively used as Reference Examples and Examples are shown below, in which "parts" represent "parts by weight" and "%" represent "% by weight". Reference example 1 (a) Production of vinyltrimethoxysilane and tetraethoxysilane condensate In a three-necked flask with an internal volume of 1, vinyltrimethoxysilane [SZ6300 manufactured by Toray Silicone Co., Ltd.]
148 g (1 mole), 208 g (1 mole) of tetraethoxysilane [first grade ethyl silicate reagent manufactured by Wako Pure Chemical Industries, Ltd.], and 0.1 g of methyltrichlorosilane were added, and the temperature was raised to 70° C. with stirring. Then ion exchange water
The reaction was continued while adding 9 g (0.5 mol) little by little and at the same time attaching a fractionating tube to the flask to remove by-products ethyl alcohol and methyl alcohol from the system. After the addition of ion-exchanged water was completed, the reaction was continued for 1.0 hour, and the reaction was stopped when the distillation of methyl alcohol stopped. The reaction product was heated under reduced pressure to remove unreacted raw materials and by-produced alcohol, and the residue was neutralized with aqueous sodium bicarbonate and washed with water.
A composition analysis revealed that most of the material is a condensate (dimer to tetramer) of vinyltrimethoxysilane and tetraethoxysilane, and the molar ratio of (vinyl group)/(Si atom) in one molecule is 0.5. It was found that the average molar ratio of (Si atom-bonded alkoxy group)/(Si atom) was 2.25. (b) Production of a condensate of allyltriethoxysilane and tetraethoxysilane In the production method of (a) above, allyltriethoxysilane is used instead of vinyltrimethoxysilane.
Except for using 204 g (1 mol), the combination reaction and fractionation operation were carried out under the same conditions, and the majority of the residue was a condensate (dimer to tetramer) of allyltriethoxysilane and tetraethoxysilane, The molar ratio of (allyl group)/(Si atom) in one molecule is 0.5,
It was found that the average molar ratio of (Si atom-bonded alkoxy group)/(Si atom) was 2.25. Reference Example 2 (c) Production of vinyltrimethoxysilane condensate Add vinyltrimethoxysilane [SZ6300 manufactured by Toray Silicone Co., Ltd.] to a three-necked flask with an internal volume of 1.
148 g (1 mole) and 0.1 g of methylchlorosilane were charged and mixed with stirring. Next, 0.5 g (1 mol) of ion-exchanged water was added while increasing the temperature, and when the temperature reached 90° C., the reaction was continued for 1 hour while removing by-product methyl alcohol from the reaction system. When the distillation of methanol stopped, the reaction was stopped and the pressure was reduced under heating to remove unreacted vinyltrimethoxysilane and by-produced methanol from the system. The resulting reaction residue was neutralized with aqueous sodium bicarbonate, washed with water, and then analyzed, and it was found that the main component was a condensate (dimer to tetramer) of vinyltrimethoxysilane. (d) Production of a condensate of tetraethoxysilane In the production method of (c) above, 208 g of tetraethoxysilane [Ethyl silicate reagent first grade manufactured by Wako Pure Chemical Industries, Ltd.] was used instead of vinyltrimethoxysilane,
A condensate was produced under the same conditions as in (c) above.
The reaction product obtained is 2 of tetraethoxysilane.
It was found to be a mixture of ~20 mers. These reaction products were fractionally distilled to separate a tetraethoxysilane condensate (dimer to tetramer). Example 1 The condensate of vinyltriethoxysilane and tetraethoxysilane obtained in Reference Example 1(a) was dissolved in n-heptane, and tetra(n-butyl) titanate was added thereto as a curing agent. Primer compositions as shown in the table were prepared. This composition was applied to an iron plate and a stainless steel plate, each with sellotape attached to one end, and left to air dry at room temperature for 60 minutes. Next, as a vulcanizing agent, 0.5% 2,3-dimethyl-
A 4 mm thick unvulcanized molded product of a silicone rubber composition [SH-52U manufactured by Toray Silicone Co., Ltd.] containing 2,5-di(t-butylperoxy)hexane was brought into close contact with the primer-coated surface. , pressure 25Kg/
When the silicone rubber composition was cured at a temperature of 170° C. and a temperature of 170° C., a test plate in ^which the silicone rubber was firmly adhered to the metal plate was obtained. The following tests were conducted on these test plates to examine the initial adhesiveness and adhesive durability between the silicone rubber and the metal plate. () Initial adhesion test Regarding the above test plate in which the silicone rubber and metal plate were adhered, the metal part and the rubber layer covered with Sellotape were peeled off, and the rubber was strongly pulled in a 90-degree direction and peeled off. If the rubber layer did not peel off, a cutter knife was used to cut the rubber layer toward the metal plate and peel it off. The peeled metal plate was observed, and the ratio of the part that suffered cohesive failure (broken at the rubber part) is listed in Table 2 as the cohesive failure rate. () Adhesive durability test ()-1 Adhesive durability under dry heat The test plate with the silicone rubber and metal plate bonded above was placed in a heating oven set at 230°C.
After 72 hours, the sample was taken out and subjected to a peel test according to the method shown in () above, and the ratio of the cohesive failure area was reported in Table 2 as the cohesive failure rate. ()-2 Adhesion durability in mineral oil The test plate with the silicone rubber and metal plate bonded together was immersed in mineral oil kept at 180°C, removed after 72 hours, and peeled off according to the method shown in () above. A test was conducted to examine the adhesion state, and the results are shown in Table 2. For comparison, primer compositions containing as main components the raw material silane of component A or its partially hydrolyzed product (Reference Example 3) and mixtures thereof were prepared. These compositions were also examined for adhesion and adhesion durability as primer compositions under the same conditions as above, and the results are shown in Tables 1 and 2.

【table】

[Table] Example 2 Primer compositions No. 1 and No. 1 obtained in Example 1.
2 on each iron plate (SS-41), then 130
It was placed in a heated oven set at ℃ and heated to dry for 30 minutes. Next, (CH ₃ ) ₂ SiO units 98.5 mol%, CH ₃ (CH ₂ =
100 parts of organopolysiloxane raw rubber (degree of polymerization 10,000) consisting of 1.5 mol% CH) units, 50 parts of fumed silica (trade name Aerosil 200), and 10 parts of organopolysiloxane with a viscosity of 20 centistokes having hydroxyl groups at both ends as a silica dispersant. To 100 parts of the base compound thus obtained, which was mixed in a kneader mixer and treated at 150° C. for 3 hours, were added 2 parts of methylhydrodiene polysiloxane with a viscosity of 10 centistokes and end-blocked with trimethylsilyl groups at both ends, and chloroplatinic acid. After thoroughly mixing an isopropyl alcohol solution (platinum content: 200 ppm) and 0.05 part of methylbutynol as an addition reaction inhibitor using two rolls, an addition reaction curing silicone rubber composition sheet having a thickness of 2 mm was prepared. This rubber sheet was brought into close contact with the primer-coated surface and heated at 150°C for 5 minutes under a pressure of 25 kg/cm ² to cure the silicone rubber composition. Tests showed that the silicone rubber and metal plate were firmly bonded. A board was obtained. These test plates were examined for adhesiveness and adhesive durability under the same conditions as in Example 1. Similarly, for comparison, primer composition No. 3 used in Example 1
~ No. 9 was also examined for adhesiveness and adhesive durability, and the results are shown in Table 3.

[Table] Example 3 92 parts of isopropyl alcohol was added to 8 parts of the condensate of allyltriethoxysilane and tetraethoxysilane obtained in Reference Example 1(b) and mixed. 4 parts of dipropoxytitanium bisacetylacetonate was added as a curing catalyst and mixed well to prepare primer composition No. 10. This was applied to an aluminum plate (JISH4000), and then placed in a heated oven set at 150°C and dried by heating for 15 minutes. Next, 100 parts by weight of dimethylpolysiloxane (degree of polymerization 1000) with both ends (CH ₃ ) ₂ (CH ₂ =CH) capped with SiO groups, fumed silica (trade name Aerosil 200)
10 parts were mixed in a Ross mixer. To 100 parts by weight of the obtained base compound, add methylhydrodiene polysiloxane with both terminals blocked with trimethylsilyl groups, isopropyl alcohol solution of chloroplatinic acid (platinum amount 200 ppm), and 0.05 part of methylbutynol, mix well in a loss mixer, and make a paste. A similar compound was obtained. This compound was applied to the primer-coated surface using a palette knife, and heated at 170° C. for 5 minutes to cure it to obtain a silicone rubber. The initial adhesion and adhesion durability of these test plates were examined under the same conditions as in Example 1, and the initial adhesion, adhesion durability under dry heat, and adhesion durability in mineral oil were all good. . On the other hand, when we similarly investigated the primer compositions of comparative examples listed in Table 1 of Example 1 for comparison, none of them could satisfy both initial adhesion and adhesive durability under dry heat. The adhesive durability in mineral oil was 100% interfacial peeling. Example 4 Using vinyltrimethoxysilane and tetraethoxysilane as main raw materials, various condensates of vinyltrimethoxysilane and tetraethoxysilane as shown in Table 4 were prepared according to the method described in Reference Example 1(a). Next, a primer composition was prepared using this condensate under the same conditions as described in Example 1, and its adhesion was examined. The results are shown in Table 5.

【table】

【table】

Claims (1)

[Claims] 1 Consists of a siloxane unit represented by the formula A [formula] and a siloxane unit represented by the formula SiO4/2 (wherein a is 1, 2 or 3, and b is 0, 1, 2 or 3) , where a+b is 1, 2 or 3, R ¹ is an alkenyl group, R ² is an alkyl group or an aryl group), and the molar ratio of (R ¹ group)/(Si atom) in one molecule is 0.10 to 0.98, and one molecule contains both a silanol group and a Si atom-bonded alkoxy group, or only a Si atom-bonded alkoxy group, (total amount of silanol groups and Si atom-bonded alkoxy groups)/(Si
atom) or (Si atom-bonded alkoxy group)/(Si
1. A primer composition comprising: 100 parts by weight of an organopolysiloxane having a molar ratio of 1.0 to 2.5 atoms), 0.01 to 100 parts by weight of a curing catalyst, and C an organic agent. 2. The primer composition according to claim 1, wherein the organopolysiloxane is a dimer to octamer. 3. The primer composition according to claim 1, wherein the organopolysiloxane is a compound obtained by a condensation reaction of an alkenyl group-containing alkoxysilane and a tetraalkoxysilane. 4. The primer composition according to claim 1, wherein the curing catalyst is an organic titanium compound.