JPS6157867B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a primer composition for adhering room temperature curable silicone rubber to plastics and rubbers. Primer compositions for adhering room-temperature-curable silicone rubber to various adherends, if heat resistance is required, can be made by adding various carbon-functional silanes and other additives to silicone resin. However, all of these silicone resin-based products have the following drawbacks. (b) When using resin, the cured film becomes hard, so if the adherend is a rubber-like elastic body, when force is applied, the film cannot follow the deformation of the adherend and is destroyed, causing peeling. Become. (b) Silicone resins tend to gel due to condensation of hydroxyl groups bonded to silicon atoms, so the storage stability of the composition is poor. (c) Since the resin contains many tri- or tetrafunctional siloxane units and has a branched molecular structure, it is difficult to stabilize the composition and the properties of the composition tend to vary. Additionally, primer compositions made of carbon-functional silanes and other silane compounds without the addition of silicone resin are also known, but in this case as well, since silanes with mainly three silicon functionalities are used, the cured film is It is as hard as a resin mold, and has the disadvantage of (a) above. Also, storage stability is not good under conditions where it is affected by moisture. Instead of highly branched silicone resin, the present inventor used an essentially linear or slightly branched polyorganosiloxane containing two or more silicon-bonded hydroxyl groups in one molecule, and It has been found that all of the above problems can be solved by combining with group-containing silanes. Even if linear or slightly branched polyorganosiloxanes contain hydroxyl groups bonded to silicon atoms, they are extremely stable compared to resins, and the composition can basically be kept constant by controlling only the degree of polymerization.
Furthermore, since the cured film itself has flexibility, it can sufficiently follow the deformation of the adherend, and even if force is applied, the film will not break or peel. The present inventors have previously proposed a composition comprising a silanol group-terminated polydiorganosiloxane, an epoxy group-containing polyorganosiloxane, and an amino group-containing organosilicon compound (Patent Application No.
No. 111346). There, as the silanol group-terminated polydiorganosiloxane, as shown in the detailed description and examples of the invention of the patent application, especially at 25°C.
A material with a viscosity of 1,000 to 2,000,000 cSt is used. This composition is used primarily as a non-adhesive, but also as a primer. However, this composition has some problems with its drying properties at room temperature, and the reaction proceeds even in the solvent when the three components are mixed, so it cannot be stored as a composition in a single container. , it is necessary to mix at the time of use. On the other hand, in the present invention, the reaction does not proceed even if both of the above-mentioned components are mixed in a solvent.
To provide a composition that can be stored in a stable state and, when used, can cure and form a film in a relatively short time by applying the solution to an adherend and drying it at room temperature. It is. That is, the present invention provides (A) an average of more than 1.8 and 2.0 or less organic groups directly bonded to a silicon atom per silicon atom, and at least two hydroxyl groups directly bonded to a silicon atom in one molecule. 100 parts by weight of a polyorganosiloxane having a viscosity of 1000 cSt or less at 25°C, and (B)(1) having the formula R ¹ (CH ₂ ) ₃ Si(OR ² ) ₃ (wherein R ¹ is Q ¹ ₂ N
an amino group represented by -, and Q ² ₂ N
A nitrogen-containing group selected from the group consisting of a diamino group represented by (CH ₂ ) ₂ NH-, Q ¹ and Q ² are each a monovalent group selected from the group consisting of a hydrogen atom and an alkyl group, and R ² is a 1 to 100 parts by weight of an amino group-containing silicon trifunctional silane represented by (representing a monovalent hydrocarbon group) or (2) formula R ¹ (CH ₂ ) ₃ SiR ³ (OR ² ) ₂ (wherein R ¹ , ^R2
As mentioned above, R ³ represents a monovalent hydrocarbon group) and 1 to 100 parts by weight of an amino group-containing silicon difunctional silane and 1 to 100 parts by weight of ethyl silicate or a partial hydrolyzate thereof. The present invention relates to a primer composition. Component (A) used in the present invention is a linear or slightly branched polyorganosiloxane having two or more silicon-bonded hydroxyl groups in one molecule. The viscosity of this polyorganosiloxane is 25
Must not exceed 1000cSt at °C, 10cSt~
A range of 700 cSt is preferred. If the viscosity is too high, the adhesiveness and curability of the composition will be poor; if the viscosity is too low, it will generally be difficult to synthesize, and even if it can be synthesized, the yield will be very poor, which is industrially disadvantageous. The ratio of organic groups to silicon atoms is more than 1.8 and less than 2.0, but this is because if it is less than 1.8, the formed film will have poor flexibility, and if it exceeds 2.0, the hydroxyl groups bonded to the silicon atoms in one molecule will be reduced. The average number of
This is because it cannot crosslink and become essentially a network structure. From the viewpoint of ease of synthesis, (A) is preferably a silanol-terminated polydiorganosiloxane. Types of organic groups bonded to silicon atoms include alkyl groups such as methyl groups and ethyl groups, alkenyl groups such as vinyl groups and allyl groups, aryl groups such as phenyl groups, aralkyl groups such as styrenyl groups, and carbonized Examples include hydrogen atoms in which some of the hydrogen atoms are substituted with halogen atoms, nitrile groups, etc., but the ease of obtaining raw materials during synthesis, ease of handling the composition, and heat resistance of the cured film are important. A methyl group is preferred. Component (B) used in the present invention functions as a crosslinking agent and an adhesion improver. When the amino group-containing silane is trifunctional, it may be used alone or in combination with ethyl silicate, but when it is difunctional, it must be used because the composition hardens to form a network structure. Must be used in conjunction with ethyl silicate. Such amino group-containing silanes include H ₂ N(CH ₂ ) ₃ Si(OCH ₃ ) ₃ and H ₂ N(CH ₂ ) ₃ Si
( _OC2H5 ) ₃ , _{H2N ( CH2} ) _2NH ( _CH2 ) _3Si
( _OCH3 ) ₃ , _H2N ( _CH2 ) _2NH ( _CH2 ) _3Si
( _CO2H5 ) ₃ , _CH3NH ( _CH2 ) _{3Si ( OC2H5} ) _{3 ,}
C ₂ H ₅ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , (CH ₃ ) ₂ N
(CH ₂ ) ₃ Si (OCH ₃ ) ₃ , (CH ₃ ) ₂ N(CH ₂ ) ₃ Si
( _OC2H5 ) ₃ , ( _CH3 ) _2N ( _CH2 ) _{2NH ( CH2} ) _3Si
(OCH ₃ ) ₃ and compounds in which one of the alkoxy groups of these compounds is replaced with a methyl group or an ethyl group are exemplified, but H ₂ N(CH ₂ ) ₃ Si ( _OCH3 ) ₃ , _H2N ( _CH2 ) _3Si
( _OC2H5 ) ₃ , _{H2N ( CH2} ) _2NH ( _CH2 ) _3Si
( _OCH3 ) ₃ , _H2N ( _CH2 ) _3Si ( _CH3 )( _OCH3 ) ₃ ,
_{H2N ( CH2} ) _3Si ( _CH3 )( _OC2H5 ) ₃ , and _H2N
( _CH2 ) _2NH ( _CH2 ) _3Si ( _CH3 )( _OCH3 ) ₂ is preferred. The blending amount of amino group-containing silane is 100% of component (A).
1 to 100 parts by weight, preferably 3 to 40 parts by weight
If the amino group-containing silane is difunctional, 1 to 100 parts by weight, preferably 3 to 40 parts by weight, of ethyl silicate must be added in order to crosslink and form a network structure. Even in the case of trifunctionality, ethyl silicate may be added to adjust the hardness of the film. If the amino group-containing silane is too small, the adhesion will be extremely low, and if it is too large, the film will become too hard and the heat resistance will deteriorate. Furthermore, if the amount of ethyl silicate is too large, the film becomes too hard. Note that in place of the amino group-containing silane used in the present invention, other carbon-functional silanes such as γ-methacryloxypropyltrimethoxysilane, γ-
Even if glycidoxypropyltrimethoxysilane or the like is used, the heat resistance and adhesive properties of the present invention cannot be obtained. Significant effects can only be obtained by combining (A) and (B). When using the composition of the present invention, it is preferable to use an appropriate solvent to adjust the viscosity to a level suitable for the coating operation. Solvents suitable for this purpose include aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, n-pentane, n-hexane,
Aliphatic hydrocarbons such as n-heptane, ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, and dioxane, ketones such as acetone and methyl ethyl ketone, methyl acetate,
Examples include esters such as ethyl acetate and butyl acetate, and alcohols such as isopropyl alcohol. The composition of the present invention can be obtained by simply mixing the above components, and components (A) and (B) are easily dissolved in a solvent. Even if stored for a long time, it is stable without gelation, and if only the degree of polymerization of the polyorganosiloxane is controlled, the composition remains constant, so there is no variation in properties. In addition, the composition of the present invention can be applied to EPT, which is generally considered to be difficult to adhere to.
It strongly adheres to other organic rubbers and maintains its adhesive properties even at high temperatures of 180℃. Furthermore, since the film itself is flexible, it can fully follow the deformation of the adherend, and unlike resin-type primer compositions, deformation of the adherend will destroy the film and cause peeling. Never. Accordingly, the compositions of the present invention are particularly useful for adhering organic rubbers or plastics to room-temperature-curable silicone rubbers in various silicone rubber rolls. When used for this purpose, the plasticizer dioctyl phthalate contained in polyvinyl chloride and other plastics acts to weaken the adhesion when it comes into contact with them. It is also resistant to The composition of the present invention can also be used as a primer for sealing and encapsulating electrical parts, and generally as a primer for adhering room-temperature-curable silicone rubber to adherends such as organic rubbers and plastics. Widely used. The present invention will be explained below using examples. In the example,
All parts are by weight, and DOP is an abbreviation for dioctyl phthalate. Example 1 100 parts of silanol-terminated polydimethylsiloxane with a viscosity of 50 cSt at 25°C, H ₂ N
Primer composition 1 was obtained by mixing 20 parts of ( _CH2 ) _3Si ( _OC2H5 ) ₃ , 260 parts of toluene, and 260 parts _of isopropyl alcohol. This was applied to EPT with a hardness of 70, and after air drying for 0.5 to 1 hour, room temperature curable silicone rubber TSE3502RTV (manufactured by Toshiba Silicone Corporation) was applied.
The test piece shown in Figure 1 was made by gluing the
After curing for 30 hours, a peel test was conducted at a tensile speed of 50 mm/min. Also, cured for 30 hours in the same way.
Those left in a dryer at 180℃ for 48 hours, and
A peel test was conducted on the samples immersed in DOP at 50°C for 48 hours and at 150°C for 6 hours.
In addition, as Comparative Example 1, H ₂ N
Tests were conducted on compositions excluding (CH ₂ ) ₃ Si(OC ₂ H ₅ ) ₃ . Furthermore, as Comparative Example 2, 200 parts of a 50% xylene solution of a silicone resin consisting of 5 mol% (CH ₃ ) ₂ SiO units and 95 mol% CH ₃ SiO3/2 units, 150 parts of acetone, and 250 parts of isopropyl alcohol were added.
of H ₂ N(CH ₂ ) ₃ Si(OC ₂ H ₅ ) ₃ 10
A similar peel test was conducted using a primer composition obtained by adding 18 parts of ethyl silicate and 18 parts of ethyl silicate. The results are shown in Table 1. The adhesion force in the table indicates the force applied at the time of breakage in the case of interfacial failure, and the force applied at the time of rubber breakage in the case of cohesive failure.

[Table] When the compositions of Composition 1 and Comparative Example 2 were stored in a glass container tightly sealed at room temperature, the composition of Comparative Example 2 gelled in 14 days, but the composition of Composition 1 of the present invention
There was no change after 6 months. Furthermore, a silicone rubber roll was prepared and the following peel test was conducted. EPT was hardened to a thickness of 1.5 cm around the outer periphery of an aluminum tube with an outer diameter of 20 cm, an inner diameter of 10 cm, and a length of 50 cm. Primer composition 1 was applied to the surface of EPT, and after air drying for 1 hour, uncured room temperature curable silicone rubber TSE3502RTV (Toshiba Silicone Corporation)
(manufactured by) and the thickness of the silicone rubber layer is 0.5
Heat cure at 100℃ for 30 minutes to obtain cm
A silicone rubber roll was made. To this, the diameter
A silicone rubber roll was pressed against a 24 cm x 50 cm long aluminum tube with a linear pressure of 50 kg.
It was rotated at 1 revolution per second while being kept at ℃. A similar test was conducted using the composition of Comparative Example 2 in place of Composition 1. In the case of the composition of Comparative Example 2,
While the silicone rubber peeled off after 24 hours, in composition 1, the lower EPT rubber deteriorated and deformed after 200 hours, making it impossible to continue the test. No peeling was observed between them. Example 2 Silanol group-terminated polydimethylsiloxane whose viscosity at 25°C is as shown in Table 2
100 _parts , _H2N ( _CH2 ) _3Si ( _OC2H5 ) _3, 10 parts, toluene
260 parts of primer composition and 260 parts of isopropyl alcohol were mixed to obtain primer compositions 2 to 5 and comparative example 3. Apply this to EPT and after air drying for 0.5 to 1 hour,
The results of the same peel test as in Example 1 are shown in the second example.
Shown in the table.

[Table] These primer compositions were sealed in a glass container and left at 50°C for one month, but no change was observed. Example 3 100 parts of silanol-terminated polydimethylsiloxane having a viscosity of 80 cSt at 25°C was mixed with an amino group-containing silane and a solvent in amounts shown in Table 3 to obtain a primer composition. Also, for comparison,
A primer composition was obtained by adding a carbon-functional silane compound shown in Table 3 in place of the amino group-containing silane. This was applied to EPT, and after air drying for 1 hour, the same test as in Example 1 was conducted. The results are shown in Table 4. In addition, IPA in the table indicates isopropyl alcohol.

【table】

【table】

[Table] Primer compositions 6 to 7 were left at 50°C for one month, but no changes were observed. Example 4 The compositions used in Compositions 1 to 6 and Comparative Examples 1 to 3 were applied to each adherend, and after air drying for 1 hour, room temperature curable silicone rubber TSE3502RTV (Toshiba Silicone
Co., Ltd. product name) to prepare the specimen shown in Figure 2, and a shear adhesion test was conducted. When epoxy resin, polyester, phenolic resin, and polycarbonate were used as adherends, compositions 1 to 6 were obtained.
The compositions of Comparative Example 2 had strong adhesion with a cohesive failure rate of 100%, and the compositions of Comparative Example 1 and Comparative Example 3 had a cohesive failure rate of 0%. Example 5 Primer compositions 8 to 9 were obtained by using the following silanol group-containing polyorganosiloxane instead of the silanol group-terminated polydimethylsiloxane used in Example 1. Apply this to EPT, air dry for 1 hour, and then use room temperature curable silicone rubber.
TSE350RTV (manufactured by Toshiba Silicone Co., Ltd.) was adhered and cured at room temperature for 48 hours to produce the test specimen shown in Figure 2, and a shear adhesion test was conducted under normal conditions.
In all cases, the cohesive failure rate was 100%. Composition 8: 15 mol% diphenylsiloxy units and
Consisting of 85 mol% dimethylsiloxy units, 25
100 parts of a silanol-terminated polydiorganosiloxane having a viscosity of 250 cSt at °C Composition 9: 3 mol % trimethylsiloxy units;
100 parts of a silanol-containing polydimethylsiloxane consisting of 85 mol% dimethylsiloxy units and 12 mol% methylsiloxy units and having a viscosity of 38 cSt at 25°C Example 6 Silanol-terminated polydimethylsiloxane 100 having a viscosity of 50 cSt at 25°C 15 parts of ethyl silicate, 20 parts of _H2N ( _CH2 ) _3Si ( _OC2H5 ) _3, 300 parts _of isopropyl alcohol, and 200 parts of toluene.
A composition was prepared by mixing the two parts, and an adhesion test similar to that in Example 5 was conducted, and the cohesive failure rate was 100%. Example 7 _H2N instead of _H2N ( _CH2 ) _3Si ( _{OC2H5 ) 3}
When a test was conducted using the same composition as in Example 6 except that (CH ₂ ) ₃ Si(CH ₃ )(OCH ₃ ) ₂ was used, the cohesive failure rate was 100%.

[Brief explanation of the drawing]

FIG. 1A is a plan view and a side view of a test specimen for examining the adhesion of a primer to an adherend (EPT). Figure 1B is a side view of the test specimen, and the first
Check the adhesive strength by pulling the test piece in the direction of the arrow shown in Figure B. FIG. 2 is a side view of a specimen used to examine the adhesion of primers to various plastics. Check the adhesive force by applying force in the direction of the arrow, that is, parallel to the adhesive surface. In the figure, 1 is an adherend, 2 is a room-temperature curable silicone rubber, and 3 is a spacer.Other numbers indicate dimensions, and the units are mm.

Claims (1)

[Scope of Claims] 1 (A) An average of more than 1.8 but less than 2.0 organic groups directly bonded to a silicon atom exists per silicon atom, and 1 hydroxyl group directly bonded to a silicon atom exists.
100 parts by weight of a polyorganosiloxane having at least two molecules in the molecule and having a viscosity of 1000 cSt or less at 25°C, and (B)(1) Formula R ¹ (CH ₂ ) ₃ Si(OR ² ) ₃ (Formula Medium, R ¹ is Q ¹ ₂ N
- and an amino group represented by Q ² ₂ N
(H ₂ ) ₂ A nitrogen-containing group selected from the group consisting of diamino groups represented by NH-, Q ¹ and Q ² are each a monovalent group selected from the group consisting of a hydrogen atom and an alkyl group, and R ² is 1 to 100 parts by weight of an amino group-containing silicon trifunctional silane represented by (representing a monovalent hydrocarbon group) or (2) formula R ¹ (CH ₂ ) ₃ SiR ³ (OR ² ) ₂ (wherein R ¹ , ^R2
As mentioned above, R ³ represents a monovalent hydrocarbon group) and 1 to 100 parts by weight of an amino group-containing silicon difunctional silane and 1 to 100 parts by weight of ethyl silicate or a partial hydrolyzate thereof. A primer composition consisting of. 2. The composition of claim 1, wherein (A) is a silanol group-terminated polydiorganosiloxane. 3. The composition of claim 1, wherein (A) is a silanol group-terminated polydimethylsiloxane. 4. The composition according to claim 1, wherein (A) has a viscosity of 10 cSt to 700 cSt at 25°C. 5 (B) (1) is an amine group-containing silicon 3 selected from the group consisting of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-(β-aminoethylamino)propyltrimethoxysilane. The composition of claim 1 which is a functional silane. 6 (B) (2) is an amino group-containing silicon 2 selected from the group consisting of γ-aminopropylmonomethyldimethoxysilane, γ-aminopropylmonomethyldiethoxysilane, and γ-(β-aminoethylamino)propylmonomethyldimethoxysilane. The composition according to claim 1, which is a functional silane and ethyl silicate or a partially hydrolyzed product thereof. 7. The composition according to claim 1, wherein 3 to 40 parts by weight of the amino group-containing silicon-functional silane (B) is blended to 100 parts by weight of (A).