JPH036173B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to an adhesion method for advantageously adhering a metal and an addition type polyorganosiloxane composition by chemically treating the metal surface with a platinum compound. [Technical background of the invention] Polyorganosiloxane has excellent properties such as heat resistance, cold resistance, and electrical properties, so it is used in a wide range of industrial fields, such as electrical and electronic equipment, transportation equipment, office equipment, and food and medical equipment. In particular, polyorganosiloxane products that cure into rubber-like elastic bodies or resin-like solids are recognized for their unique properties, and demand is rapidly increasing. However, the required properties are becoming stricter year by year, and there is a growing demand for stronger adhesion and improved heat resistance at the adhesive interface in the adhesion of metals and polyorganosiloxane compositions. [Problems with Background Art] A conventional method for adhering a cured polyorganosiloxane product to a metal surface is to provide a primer layer between the metal and the cured polyorganosiloxane product, and then cure and mold the product to bond them together. is taken. Many primers used to bond addition-type polyorganosiloxane cured products to metals have already been developed and are commercially available, but they do not provide sufficient adhesive strength to meet strict requirements, or the heat resistance of the adhesive layer is insufficient. At present, there is no primer that is sufficient and completely satisfies the required properties. In recent years, the development of processing methods for polyorganosiloxane compositions has progressed, and injection molding and transfer molding of solid and liquid rubbers have become popular, but in these cases as well, a primer layer is provided. The adhesion method has the disadvantage that the primer layer may shift or be damaged due to the pressure of the rubber flow, resulting in uneven adhesion. Furthermore, the adhesiveness varies greatly depending on the surrounding atmosphere during primer treatment, the conditions of primer treatment, etc., and methods using primers have many problems. Recently, self-adhesive polyorganosiloxane compositions containing carbon-functional silanes having epoxy, acrylic, or vinyl groups, or their partial hydrolysates, have also been developed. However, in this self-adhesive polyorganosiloxane composition, the heat resistance of the polyorganosiloxane composition itself is significantly impaired due to the addition of carbon-functional silane, etc., and long-term heat treatment is required to obtain sufficient adhesion. The bonding method could not be considered to be advantageous in terms of characteristics or economy. [Object of the Invention] The present invention has been made to solve these conventional difficulties, and provides a novel method for adhering a metal and an addition-type polyorganosiloxane composition, which can be applied to adhesion of an addition-type polyorganosiloxane composition. That is. [Summary of the Invention] That is, the method of adhering a metal and an addition type polyorganosiloxane composition of the present invention is as follows: (A) Applying a solution of a platinum compound to a clean metal surface, evaporating the solvent, and coating the metal surface with a platinum compound. (B) a chemical treatment step;
This method is characterized by a step of bringing an addition type polyorganosiloxane composition that can be cured by a hydrosilylation reaction catalyzed by a platinum compound into contact with the metal surface treated in step (A) to cure it. According to the present invention, there is no need to provide a primer layer as in the conventional method, and the metal surface is simply chemically treated with a platinum compound, and this surface is brought into contact with an addition type polyorganosiloxane composition and cured.
The addition type polyorganosiloxane composition can be firmly adhered to the metal surface. The application of platinum compound solution to the metal surface and the volatilization of the solvent can be easily performed, and these steps uniformly chemically treat the metal surface, making the bonding work easier and the primer layer Since there is no need to form a polyorganosiloxane, the heat resistance of the adhesive layer is not impaired, and there is no need to specifically add silane or siloxane having a carbon functional group, so the inherent heat resistance of polyorganosiloxane can be maintained. can. The metals that can be applied to the present invention are not particularly limited, and include iron, aluminum, copper, tin, zinc, nickel, chromium, and
Elemental metals such as tungsten, gold, silver, and metallic silicon, stainless steel, brass, and other alloys can be used. The metal surface is cleaned by conventional bonding methods, such as by simply cleaning with a solvent or polishing with sandpaper, followed by washing with water, degreasing with a solvent, and drying. The solvents used here are not particularly limited, but include alcohols, ethers, ketones, esters,
Hydrocarbons or halogenated hydrocarbons are used. The platinum compound solution is uniformly applied onto the cleaned metal surface with a brush, brush, gauze, etc., or by dipping, spraying, etc. The platinum compound used in the present invention is not particularly limited, and any platinum compound can be used as long as it is soluble in a suitable solvent and can be used as a catalyst for hydrosilylation reactions well known in the art. Compounds can also be used. However, it is generally desirable to avoid compounds that severely corrode or discolor metal surfaces, as they do not exhibit sufficient adhesion. Examples of platinum compounds include chloroplatinic acid and its salts, platinum-olefin complexes as shown in Japanese Patent Publication No. 39-19259, and alcohols as shown in Reference Example 1 of Japanese Patent Publication No. 43-27853. Reaction mixture of and chloroplatinic acid hexahydrate (H ₂ PtCl _{6.6H 2} O), Special Publication 1972-
Platinum-unsaturated group-containing siloxane complexes as shown in Japanese Patent Publication No. 29731, vinylsiloxane and platinum complexes as shown in Japanese Patent Publication No. 51-8926, and complexes of vinylsiloxane and platinum as shown in Japanese Patent Publication No. 53-775. Examples include compounds chemically bonded with platinum and 1,3-divinyltetramethyldisiloxane, complexes of triorganophosphine or phosphite and platinum, acetylacetonatoplatinum chelates, and complexes of cyclic diene and platinum. can. These platinum compounds may be used alone or in combination of two or more. Among these platinum compounds, they have particularly low corrosivity to metal surfaces, high solubility in various solvents, and are easy to obtain. Mixtures are suitable for the present invention. A wide range of solvents can be used to dissolve these compounds, such as organosilanes and polyorganosiloxanes containing 1 to 8 silicon atoms, alcohols, ketones, esters, ethers, carbonized Examples include hydrogen, halogenated hydrocarbons, and water. These solvents may be used alone or as a mixed solvent. 250℃
Solvents with a boiling point above can also be used, but
Preferably 250 to facilitate volatilization of the coating solution.
Use a solvent with a boiling point below °C. The concentration of the platinum compound may be as long as it is below the concentration at which it becomes a saturated solution in the solvent, preferably 10 to 100,000 ppm as platinum atoms, and more preferably 50 to 100,000 ppm.
A concentration range of 50000 ppm is suitable. i.e.
If the concentration is less than 10 ppm, sufficient adhesion cannot be obtained with a single coating treatment, and if it exceeds 100,000 ppm, corrosion and discoloration of the metal will become severe, making it difficult to treat uniformly and making the treatment solution expensive. Moreover, the adhesiveness is reduced, which is disadvantageous. The solution of the platinum compound prepared in this way is applied to the metal surface, the solvent is volatilized at a temperature between room temperature and 250° C., and at the same time, the metal surface is chemically treated with the platinum compound. The reason for chemically treating the metal surface at a temperature between room temperature and below 250°C is to prevent the adhesion from being adversely affected by the atmosphere and coating conditions as much as possible, and to obtain stronger adhesion. be. If this process is insufficient,
When hot air curing at normal pressure is carried out, a foaming phenomenon may be observed at the adhesive interface, which is not preferable. However, when using a metal whose surface has been heat-treated in advance, the foaming phenomenon completely disappears and good adhesion can be obtained. The heat treatment temperature is
There is no problem even if the temperature exceeds 250℃, but it is not a good idea to heat it for a long time because it will cause deterioration of the metal surface, decrease in adhesion, increase in energy costs, etc.
The following temperatures are suitable. In addition, the treatment time can be arbitrarily selected depending on the heating temperature, but considering work efficiency, deterioration of the metal surface, etc., it can range from a few seconds to 24
The time range is appropriate. The solution of the platinum compound may be used by adjusting it to a processing liquid to which fine inorganic powder such as silica, coloring pigment, or dye is added so that uniform application is performed. The chemically treated metal surface is brought into contact with an addition-type polyorganosiloxane composition that can be cured by a hydrosilylation reaction, and cured by heat using a mold such as press, injection, or transfer molding, or by using steam, etc. When the polyorganosiloxane composition is cured by a method such as heat curing using a pressure cooker, heat curing using a heat medium, or hot air curing, the metal and the polyorganosiloxane composition become strongly bonded to each other. Here, the methods of contact, curing, and molding are not particularly limited, and in addition to the above-mentioned curing methods, methods such as dipping and casting can also be applied. Further, the curing temperature can be arbitrarily selected within the range of room temperature or higher and 600° C. or lower, and the heating method can be either pressure heating using an apparatus or normal pressure heating. If the curing temperature is lower than room temperature, the time required for curing will be longer, and if the temperature is higher than 600°C, deterioration of the addition type polyorganosiloxane composition, deterioration of the metal, and increase in energy costs will occur. The curing temperature is preferably in the range of room temperature to 600°C or less. In addition, after the addition type polyorganosiloxane composition is cured and adhered to the metal surface, a post-treatment process using heating, which is a common technique when processing this type of polyorganosiloxane composition, is performed to form a cured product. Properties and adhesion can be further improved. The polyorganosiloxane compositions curable by a hydrosilylation reaction catalyzed by a platinum compound used in the present invention can be cured to form gels, elastomers and resins, which are well known in the silicone industry. Includes everything that becomes solid. Among these, products that harden into rubber-like elastic bodies are widely used in a wide range of fields.
Some addition-type silicone rubbers are of the one-component type, well known as addition-type RTV or LTV, in which all components are mixed homogeneously in a single container, applied to the surface of the adherend, and then heated. and two-component type silicones, in which the base polymer, crosslinking agent, and/or catalyst are stored in separate containers and mixed homogeneously immediately before use, as well as platinum crosslinked silicones. Examples include a series of product groups such as solid rubber, also known as rubber. In principle, a polyorganosiloxane composition that can be cured by a hydrosilylation reaction has a silicon-bonded aliphatic unsaturated group-containing monovalent hydrocarbon group, such as a vinyl group, and a silicon-bonded hydrogen atom formed by a platinum compound. Polyorganosiloxane compositions that undergo an addition reaction (hydrosilylation reaction) and are cured by the catalytic action of Examples include compositions in which an organic compound known as a polymer can be cured by hydrosilylation with a platinum compound. Other organic groups bonded to silicon atoms include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, phenyl, β-phenylethyl, 3.3 Examples include 3-trifluoropropyl group, but methyl group is preferred because of its good heat resistance and ease of synthesis. In order to impart mechanical properties to the cured polyorganosiloxane composition, an inorganic filler may be further added to the addition type polyorganosiloxane composition (B) of the present invention, and if necessary, heat resistance may be improved. Agents, pigments and dyes, control agents to control addition reactions, etc. can be added. For the addition type polyorganosiloxane composition (B) of the present invention, commercially available addition type polyorganosiloxane compositions can be used as they are, and they can be easily made strong by simply treating the surface of the target metal with a platinum compound. Since adhesion can be obtained and no primer layer is required, it can be applied to adhesion in various molding methods. Particularly recently, streamlining the molding process and increasing the required performance have become major issues, and the issue of adhesion is also important to help with these issues.The bonding method of the present invention, for example, provides high-performance insulation,
Potting and sealing, composite parts with metal inserts, rolls used in copiers and laminator rolls that require good heat-resistant adhesion, flexible laminates, conductive silicone rubber using metal particles and fibers, pressure-sensitive conductive rubber,
It can be widely applied to heat dissipation rubber, radio wave shielding rubber, etc. [Examples of the Invention] The present invention will be described below with reference to Examples. In addition,
In the examples, all parts represent parts by weight. Reference Example 1 35 parts of tetramethyl-1,3,5,7- were added to a mixture of 1.9 parts of sodium chloroplatinate, 9 parts of ethyl alcohol, and 2.5 parts of sodium bicarbonate.
Tetravinylcyclotetrasiloxane was added.
The resulting mixture was heated at a temperature of 70-75°C for 1 hour, then the temperature was raised to 95°C while bubbling nitrogen through the mixture, and the volatile components were removed under reduced pressure of 25 mmHg. The thus obtained mixture of yellow liquid and solid was cooled and filtered to obtain a pale yellow transparent liquid.
Chemical analysis of this liquid showed that it contained 0.8 atoms of chlorine per atom of platinum, and 0.020 g of platinum per gram of mixture. Reference Example 2 1 part of chloroplatinic acid hexahydrate (H ₂ PtCl _{6.6H 2} O) was dissolved in 10 parts of octyl alcohol, and this solution was heated to 75 to 80°C for 20 hours at a pressure of 25 mmHg.
During this time all water and hydrogen chloride were removed. The pressure was then reduced to 5 mmHg to remove unreacted octyl alcohol. In this way, a dark reddish brown liquid was obtained which was soluble in solvents such as alcohol, acetone, benzene, hexane, xylene and toluene. Chemical analysis of this mixture showed that it contained 3.5 atoms of chlorine per atom of platinum, and 0.035 g of platinum per gram of the mixture. Reference Example 3 1 part of chloroplatinic acid hexahydrate was dissolved in 99 parts of isopropyl alcohol. 1 g of this solution contains 0.0043 g of platinum. Example 1 Aluminum plates, iron plates, stainless steel plates, galvanized iron plates, chrome-plated plates, copper plates, tin-plated plates, and nickel plates with a width of 25 mm, a length of 150 mm, and a thickness of 2 mm were prepared. One side of these metal surfaces was polished with sandpaper, and cleaned by washing with water, washing with alcohol, and air drying. Reference examples 1 and 2 are applied to 1/2 area of this metal surface.
After each platinum compound shown in No. 3 was applied uniformly with a brush, a heat treatment was performed at 150° C. for 10 minutes. On the other hand, dimethylvinylsilyl end-blocked polydimethylsiloxane with a viscosity of 10,000 cSt at 25℃
100 parts, 55 mol% SiO ₂ units, (CH ₃ ) ₃ SiO _1/2 units
5 parts of polyorganosiloxane consisting of 38 mol % and 7 mol % of CH ₂ =CH (CH ₃ ) ₂ SiO _1/2 units, 15 parts of silica prepared by treating fumed silica with dimethylpolysiloxane and having a surface area of 200 m ² /g; quartz fine powder
After thoroughly kneading 80 parts and 0.05 part of the platinum compound obtained in Reference Example 1 using a universal kneader, the temperature was cooled to 30°C or less, and then 60 mol% of methylhydrogensiloxy units and 40 mol% of dimethylsiloxy units were mixed. Become,
Dimethylhydrodiene silyl end-blocked polymethylhydrogensiloxane with average degree of polymerization of 40
1.5 parts, 3- as a control agent for the hydrosilylation reaction
0.2 part of methylbutyn-3-ol was added and uniformly kneaded while defoaming under reduced pressure to prepare a curable addition-type liquid silicone rubber composition. Next, the liquid silicone rubber composition was poured onto the eight metals described above to a thickness of about 2 mm, and heated at 150° C. for 10 minutes to harden it into a rubbery state. Table 1 shows the results of examining the adhesive properties of the test pieces thus obtained. In addition, since the part that was not treated with the platinum compound did not show any adhesiveness in any of the tests, the results for the treated part are shown. Next, for the samples that showed adhesion, another set of cured test pieces was made under exactly the same test conditions, and the adhesion test results after thermal aging at 250°C for 72 hours are also shown in Table 1.

[However, in the table, sample A shows the one after curing, and sample B shows the one after heat deterioration.]

In Table 1, symbol (a) indicates the case where the adhesive is uniformly adhered and cannot be removed without destroying the cured product, (b) is the case where the adhesive is uneven, and (c) is the case where the adhesive is uniformly adhered. However, (d) shows a case where it peels off relatively easily, and (d) shows a case where it does not adhere at all. (The same applies to each of the following Examples) Example 2 The platinum compound synthesized in Reference Example 1 was diluted with toluene to prepare 10% and 1% solutions. The platinum concentrations of this solution are 2000 ppm and 200 ppm, respectively. An aluminum plate was treated in the same manner as in Example 1 with the toluene solution of the platinum compound thus obtained. On the other hand, TSE3431RTV manufactured by Toshiba Silicone Corporation,
TLM1005, KE1204 manufactured by Shin-Etsu Chemical Co., Ltd.
KE1300RTV, KE1911, KE1920, KE1941, Toray Silicone Co., Ltd. SH1821, SE6505, SE6715
For each product, the additive-type silicone rubber materials shown by (both trade names) were prepared, and each component stored separately was mixed in a ratio that would allow curing, and defoaming was performed under reduced pressure. . In addition, platinum vulcanized silicone rubber manufactured by Toshiba Silicone Co., Ltd. is used as a solid silicone rubber material.
Prepare 100 parts of THE740-7U, catalyst TC-20A0.5
1 part and 2.0 parts of crosslinking agent TC-20B were blended using two rolls. Furthermore, SiO ₂ units and H
Polyorganohydrodiene siloxane consisting of (CH ₃ ) ₂ SiO _1/2 units and containing 0.8% by weight of hydrogen atoms bonded to silicon atoms (viscosity at 25°C
A curable composition was obtained by blending 0.6 parts of 20 cSt) using two rolls. These two types of solid silicone rubber compositions were divided into 5 mm thick sheets for press vulcanization. The silicone rubber composition thus obtained is
The liquid silicone rubber composition was cured by heating in the same manner as in Example 1, and the solid silicone rubber composition was heated in a mold at 170°C for 10 minutes using a press to a thickness of about 3 mm to form a rubber. hardened into a shape. Table 2 shows the results of examining the adhesion of the test pieces thus obtained. Note that the portion of the test piece that was not treated with the platinum compound did not show any adhesiveness, so the results for the treated portion are shown.

【table】

[Table] (Note) *: Added polyorganohydrodiene siloxane as mentioned above Next, regarding THE740−7U, JIS K6301−
A test was conducted in accordance with the test conducted in 1975 in which rubber bonded to a metal piece was peeled in a 90 degree direction, and the adhesive strength was 12 Kgf/cm. This adhesive strength was approximately 1.5 times that of adhesive bonded with a primer. Example 3 A 1% toluene solution of the platinum compound obtained in Reference Example 1 was uniformly applied to the surface of a cleaned aluminum plate using a brush. Seven types were then heat-treated at room temperature for 10 minutes and 24 hours, heat-treated at 100°C for 10 minutes and 24 hours, heat-treated at 200°C for 10 minutes and 1 hour, and 260°C for 10 seconds. An aluminum plate was prepared, brought into contact with the curable addition-type liquid silicone rubber in the same manner as in Example 1, and heated at 150° C. for 30 minutes to cure it into a rubber-like state. Table 3 shows the results of examining the adhesion of these test pieces. Among these, the test piece left for 10 minutes at room temperature was firmly adhered, but numerous foaming phenomena were observed in the hardened rubber layer near the adhesive interface.

【table】

[Table] Example 4 A 1% alcohol solution of the platinum compound obtained in Reference Example 2 was prepared, applied to 1/2 of the surface of a cleaned aluminum plate, and heated at 150°C for 10 minutes. was applied. This aluminum plate was contacted in the same manner as in Example 1 with the curable composition shown in Example 1 except that the hydrosilylation reaction controller was removed, and left at room temperature for 24 hours to form a rubbery state. hardened to.
As a result of examining the adhesion of this test piece, the part not treated with the platinum compound showed no adhesion at all, but the treated part was completely adhered, and the judgment was
It was (a). Example 5 Aluminum and stainless steel rods with a diameter of 10 mm and a length of 200 mm were prepared, and their surfaces were cleaned by a conventional method. The surface of this rod was coated with a 5% solution of the platinum compound of Reference Example 1, and heat treated at 170° C. for 10 minutes. This was set in the mold of a liquid injection molding machine (LTC-24 manufactured by Toshiba Chemical Corporation),
Injection molding was performed using TLM1005 shown in Example 2 at 170° C. for 10 minutes to obtain a rod-shaped molded product with a silicone rubber layer thickness of 1 mm. As a result of examining the adhesion of this molded article, it was found to be completely adhered, and the evaluation was (a). Example 6 135 parts of phenyltrichlorosilane, 25 parts of vinyltriethoxysilane and α, ω with an average degree of polymerization of 15
-Dissolve 40 parts of dichloropoly(dimethylsiloxane) in 100 parts of toluene, dropwise dropwise over 15 minutes into a vigorously stirred mixture of 200 parts of toluene and 300 parts of water, and continue stirring for an additional 15 minutes. Hydrolysis was carried out. After neutralization, washing with water, dehydration, and filtration according to the usual method, 0.06 part of potassium hydroxide was added,
The product was heated at the reflux temperature of toluene for 1 hour while removing the condensed water from the system. After cooling, it was neutralized with an acetic acid aqueous solution, dehydrated and filtered, and excess toluene was distilled off under reduced pressure. A toluene solution of a polyorganosiloxane having non-volatile content and substantially no hydroxyl groups was obtained, and 16 parts of the polymethylhydrodienesiloxane used in Example 1 was added thereto. Next, 20 ppm of the platinum compound obtained in Reference Example 2 was added, and 3-methylbutyne-3- was added as a control agent for the hydrosilylation reaction.
A silicone varnish was prepared by adding 0.2 parts of ol and mixing. Using the metal plate shown in Example 1, after polishing both sides with sandpaper, washing with water, washing with alcohol, and air drying, only one side was treated in the same manner as in Example 1. The above varnish was applied to the surface of the metal plate. It was applied uniformly by dipping and dried by air drying. The sample prepared in this way was heated to a temperature of 150℃.
Cured by heating in a dryer for 30 minutes. In each sample, a strongly adhered film was formed on the metal surface treated with platinum, but the film on the untreated surface was easily peeled off.

Claims (1)

[Claims] 1. (A) A step of applying a solution of a platinum compound to a clean metal surface, evaporating the solvent, and treating the metal surface with a platinum compound, and (B) a step of treating the metal surface with a platinum compound by catalyzing the platinum compound. Adhesion of an addition-type polyorganosiloxane composition to a metal, characterized by comprising a step of bringing an addition-type polyorganosiloxane composition that can be cured by a chemical reaction into contact with the metal surface treated in step (A) and curing it. Method. 2. The method of adhering a metal and an addition type polyorganosiloxane composition according to claim 1, wherein the platinum compound is a complex of an unsaturated group-containing siloxane and platinum. 3. The metal and addition type polyorganosiloxane composition according to claim 1, wherein the platinum compound is a reaction mixture of an aliphatic alcohol and chloroplatinic acid hexahydrate (H ₂ PtCl _{6.6H 2} O). Adhesion method. 4 A solution of platinum compound has 10 to 10 platinum atoms.
A method of adhering a metal according to any one of claims 1 to 3 and an addition type polyorganosiloxane composition at a concentration of 100,000 ppm. 5 Chemical treatment in step (A) is performed at room temperature to 250℃
A method for bonding a metal according to any one of claims 1 to 4 and an addition type polyorganosiloxane composition, which is carried out at a temperature of .degree. 6 Claims 1 to 5 in which the curing in step (B) is carried out at room temperature to a temperature of 600°C or less.
A method for adhering a metal according to any one of Items 1 to 1 and an addition type polyorganosiloxane composition. 7. A method for adhering a metal and an addition-type polyorganosiloxane composition according to any one of claims 1 to 6, which comprises applying a platinum compound solution in step (A) and then heat-treating.