JPH0456838B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a novel cyclotetrasiloxane compound, and more specifically, it is effective as an additive that can impart good adhesion to addition reaction type silicone rubber by adding it to the rubber. cyclotetrasiloxane compound. [Technical Background and Problems of the Invention] Addition-reactive silicone rubber, which is cured by the reaction of a hydrosilyl group and a vinyl group bonded to a silicon atom, has excellent heat resistance and electrical insulation properties, and is therefore used in electrical and electronic applications. Used for parts, etc. However, since such silicone rubber does not have adhesive properties, when it is used for potting electrical and electronic parts, moisture can enter through the gaps created between the parts and the silicone rubber, causing corrosion of the parts. It had the disadvantage of causing poor insulation. In order to solve this problem, methods have been proposed in which the substrate is pretreated with various primers and various adhesion imparting agents are added as a third component to the silicone rubber composition. JP-A-48-16952 uses a polysiloxane having both a hydrogen atom bonded to a silicon atom and a trialkoxysilylalkyl group as an adhesion-imparting agent, and JP-A-50-26855 uses a polysiloxane having an acryloxyalkyl group as an adhesion imparting agent. Silane or siloxane and organic peroxide
Publication No. 39345 uses a polysiloxane having an epoxy group and/or an ester group directly bonded to a silicon atom and a hydrogen atom directly bonded to a silicon atom, but both of them have sufficient properties for base materials used in electrical and electronic parts. It has not yet reached the point of imparting adhesive strength. As a result of repeated research to improve these shortcomings,
One of the inventors of the present invention previously discovered that when an unsaturated hydrocarbon compound having an oxirane group is used as an adhesion imparting agent, adhesive strength to the substrate can be imparted by heating at a relatively low temperature and for a short time. However, this method had the disadvantage that a transparent composition could not be obtained due to poor compatibility of the oxirane compound with the polyorganosiloxane. Therefore, we conducted further research and proposed the use of a polyorganosiloxane containing an oxirane group, a trialkoxysilyl group, and a hydrosilyl group as an adhesion imparting agent (Japanese Patent Application Laid-open No. 33256/1983). Although this method has extremely good adhesion when heated to 100°C, it is not possible to obtain satisfactory adhesion when heated at a low temperature of 70°C. There was a constraint on the materials that had to be used. So, as a result of further research,
As an adhesion agent, the following formula: (In the formula, Q ¹ and Q ² are linear or branched alkylene groups, and R is an alkyl group having 1 to 4 carbon atoms.) Using an organosilicon compound having both a group represented by the following and a hydrosilyl group: (Special Publication No. 58-26376). This method has sufficient adhesive strength even when heated at a low temperature of 70°C, but since the adhesion agent has a highly hydrolyzable alkoxy group, it easily hydrolyzes during storage, and furthermore, It had the disadvantage that it would peel off from the base material if it was left in high temperature, high humidity or hot water for a long time after curing. [Object of the invention] The present invention has good storage stability and can impart good adhesive properties by low-temperature heating at 70°C.
Furthermore, the object is to provide an adhesion-imparting agent that can maintain sufficient adhesive strength even when left in hot and humid conditions or in hot water for a long time. [Summary of the Invention] The present inventors synthesized various compounds in order to eliminate the conventional drawbacks, investigated their effects, and found that there was a compound among them that could fully satisfy the above object. The invention was completed. That is, the novel compound of the present invention has the following formula: (In the formula, R ¹ , R ² and R ³ may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms, and a represents an integer of 1 to 3.) It is a siloxane compound. In the above formula, the alkyl group having 1 to 3 carbon atoms represented by R ¹ , R ² and R ³ includes a methyl group,
Examples include ethyl group, n-propyl group, and isopropyl group, but ethyl group is preferred from the viewpoint of ease of synthesis. Specific examples of the novel cyclotetrasiloxane compounds of the present invention are shown in Table 1.

【table】

[Table] The compound of the present invention is produced, for example, according to the reactions shown in the following formulas (1) and (2). (In the formula, R ¹ , R ² , R ³ and a have the same meanings as above.) That is, first, intermediate A is obtained by reacting methacrylic acid allyl ester and trialkylsilane in the presence of a catalyst. Then, the obtained intermediate A
Compound B of the present invention is produced by reacting with cyclotetrasiloxane in the presence of the same catalyst as used in formula (1). The above reactions (1) and (2) may be carried out in a solvent such as benzene or n-hexane, but are preferably carried out without a solvent. Performing the reaction without a solvent is advantageous in terms of cost because there is no cost for the solvent or the cost for removing it, and the reaction can be completed in a short time. Catalysts used in the reaction include chloroplatinic acid, alcohol-modified chloroplatinic acid, complexes of platinum and olefins, complexes of platinum and ketones, complexes of platinum and vinylsiloxane, and platinum supported on a carrier such as alumina or silica. Examples include black, platinum black, etc. The reaction takes place at room temperature or higher at 100°C under normal pressure.
Proceeds smoothly at temperatures below. However, there is no particular problem even if the reaction is carried out at a temperature of 100°C or higher. The reaction time is usually 1 to 24 hours when carried out without a solvent. After the reaction is completed, it is preferable to purify the product by a conventional method such as distillation under reduced pressure. However, since this reaction necessarily involves few side reactions and proceeds almost quantitatively, it is also possible to use the target product as an adhesion imparting agent for direct addition reaction type silicone rubber without purification. The novel cyclotetrasiloxane compound of the present invention is suitable as an adhesion promoter for addition-reactive silicone rubber, and can impart good adhesion to the rubber even when heated at a low temperature of about 70°C, and Continues to provide good adhesion even after being left in water for a long time. [Examples of the Invention] The present invention will be described below with reference to Examples. In the examples, all parts indicate parts by weight. Example 1 63 parts of allyl methacrylate and an ethanol solution of chloroplatinic acid (5 ppm as platinum atoms based on allyl methacrylate) as a catalyst were placed in a reaction vessel equipped with a stirrer and a cooler. Thereafter, 58 parts of triethylsilane was added dropwise from the dropping funnel over 1 hour. After the dropwise addition was completed, the temperature of the reaction solution was raised to 50° C., and the mixture was heated and stirred for 10 hours. After the reaction, 0.7 parts of 2,5-di(t-butyl)hydroquinone was added as a polymerization inhibitor and distilled under reduced pressure to obtain 113 parts of γ-methacryloxypropyltriethylsilane (b.
p.115-118°C/7mmHg) was obtained. Next, 50 parts of 1,1,3,5,7-pentamethylcyclotetrasiloxane and an ethanol solution of chloroplatinic acid as a catalyst (platinum atoms per 1,1,3,5,7-pentamethylcyclotetrasiloxane) were added as a catalyst. (10 ppm) was placed in the same reaction vessel as above. Thereafter, 48 parts of γ-methacryloxypropyltriethylsilane obtained by the above reaction was added dropwise from the dropping funnel over a period of 10 minutes. After finishing dropping,
The mixture was heated and stirred at 110°C for 1 hour. After the reaction is completed, distillation is performed under reduced pressure to obtain a cyclotetrasiloxane compound represented by the following formula (3) (bp158-163℃/2mmHg,
100 parts of the product (purity 92.7%) were obtained. Identification was performed using infrared absorption spectroscopy and nuclear magnetic resonance spectroscopy. The infrared absorption spectrum is shown in FIG. 1, and the nuclear magnetic resonance spectrum is shown in FIG. 2. Nuclear magnetic resonance spectrum (90MHz, concentration 5 in CCl)
%): δ value a: 4.8 singlet b: 0.2 singlet c: 1.1 multiplet d: 2.6 quartet e: 0.6 multiplet f: 4.0 triplet infrared absorption spectrum: 2900cm ^-1 : CH 2100cm ^-1 : SiH 1720cm ^-1 : C=O 1250cm ^-1 : Si-CH ₃ 1050cm ^-1 : Si-O-Si Refractive index: n ²⁵ _D = 1.4398 Example 2 In a reaction vessel similar to that used in Example 1, 1,
48 parts of 3,5,7-tetramethylcyclotetrasiloxane and an ethanol solution of chloroplatinic acid (10 ppm as platinum atoms based on 1,3,5,7-tetramethylcyclotetrasiloxane) as a catalyst were added. Thereafter, 48 parts of γ-methacryloxypropyltriethylsilane was added dropwise to the intermediate obtained in Example 1 from the dropping funnel over a period of 10 minutes. After finishing dropping,
The mixture was heated and stirred at 110°C for 1 hour. After the reaction is complete,
Distilled under reduced pressure, a cyclotetrasiloxane compound represented by the following formula (4) (bp150-155℃/2mm
Hg) was obtained. The identification was performed using infrared absorption spectra and nuclear magnetic resonance spectra. Nuclear magnetic resonance spectrum (90MHz, concentration 5 in CCl)
%): δ value a: 4.8 singlet b: 0.2 singlet c: 1.1 multiplet d: 2.6 quartet e: 0.6 multiplet f: 4.0 triplet infrared absorption spectrum: 2900cm ^-1 : CH 2100cm ^-1 : SiH 1720cm ^-1 : C=O 1250cm ^-1 : Si-CH ₃ 1050cm ^-1 : Si-O-Si Refractive index: n ²⁵ _D = 1.4385 Application example 1. Polydimethylsiloxane 100
1 part, 2 parts of polymethylhydrodiene siloxane with a viscosity of 15 cSt at 25°C and blocked with trimethylsilyl groups at both ends, 50 parts of quartz powder with a particle size of 2 μ, 2 parts of titanium oxide, 1,3,5-tetramethyl-1,3,5 ，
0.2 parts of 7-tetravinylcyclotetrasiloxane,
A base composition was prepared by uniformly mixing and dispersing 0.05 part of platinum and an isopropyl alcohol solution of chloroplatinic acid. This base composition
To 100 parts, 3 parts each of the cyclotetrasiloxane compounds represented by formula (3) and formula (4) obtained in the example were added and mixed uniformly to form compositions 11 and 12 of the present invention.
I got it. As a comparative example, a composition prepared by adding and mixing 3 parts of the compound represented by the following formula to 100 parts of the base composition was prepared.
And so. These compositions were applied to an aluminum plate and 70
It was cured by heating at ℃ for 8 hours. The adhesion properties after curing and after the pressure checker test were as shown in Table 2.

[Table] (Note) ○: Good adhesion △: Partially peeled ×: Peeled

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a nuclear magnetic resonance spectrum of the compound of formula (3), and FIG. 2 is a diagram showing an infrared absorption spectrum of the same compound.

Claims (1)

[Claims] Primary formula: (In the formula, R ¹ , R ² and R ³ may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms, and a represents an integer of 1 to 3.) Siloxane compound. 2. The compound according to claim 1, wherein a is 2 or 3. 3. The compound according to claim 1, wherein R ¹ , R ² and R ³ are all ethyl groups.