JP2007062057A - Joining method of silicone rubber cured material and composite structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for strongly joining a silicone rubber to an adherend when the silicone is used as a sealing material or the like. <P>SOLUTION: A silicone rubber cured material containing a boric acid compound is brought into contact with the surface of a primer composition, which is composed of a silane coupling agent and the boric acid compound to be bonded to the adherend under pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for bonding a cured silicone rubber to an adherend and a composite structure.

  Silicone rubber is widely used in electrical and electronic parts, automobile parts, medical instruments and the like because of its excellent weather resistance and heat resistance. It is known that by adding a boron compound to the silicone rubber, it becomes re-bondable after curing, and when the cured boron compound-containing silicone rubber is pressure-bonded, the pressure-bonding surfaces are fused and integrated. Yes. Publications disclosing these include Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, and Patent Document 7.

  When these boron compound-containing silicone rubber cured products are pressure-bonded to each other, strong adhesion at a level at which the silicone rubber cohesively breaks can be obtained. However, the reality is that there is almost no re-fusing property to other substrates. When a boron compound-containing cured silicone rubber such as boric acid ester is pressure-bonded to, for example, metal or plastic, it adheres lightly, but can be easily peeled off from the surface. Moreover, even when it is pressure-bonded to a normal cured product of silicone, it adheres lightly but easily peels off. As far as the present inventors have examined, the adhesion that is strong enough to cause cohesive failure is obtained only when the boron compound-containing cured silicone rubbers are pressure-bonded.

  On the other hand, sealing materials using silicone rubber are well known. The method of sandwiching the sealing material (gasket, O-ring) obtained by molding the silicone rubber composition into the article to be sealed is simple and clear, but the sealing material must be prepared according to the shape of the article to be sealed, There are problems such as complicated inventory management and difficulty in automation of the work process of placing the gasket on the article to be sealed. Therefore, a technique called a so-called on-site molded gasket is used in which a liquid material is applied on the site according to the shape of the article to be sealed and cured to form a gasket. In-situ molded gaskets are roughly classified into FIPG (formed in place gasket) and CIPG (cure in place gasket). FIPG applies a liquid silicone rubber composition such as moisture curable silicone or two-component mixed curable silicone to a flange that is an article to be sealed, presses the flange of the other article to be sealed, and cures and cures. . CIPG similarly applies a liquid composition to the flange, cures the silicone rubber before press-contacting it, forms a cured product, and presses the flange against it.

  Simply put, the difference between the two is the difference between whether the liquid composition is pressed before being cured or after the curing. FIPG is easy to automate, and curing curing is excellent in productivity because it can often be left with the parts combined. However, since the flanges of the parts to be sealed are bonded together when uncured, the formed sealing layer, that is, the sealing material between the flanges, becomes a thin film. This is like bonding the flanges together, which shows a very high seal pressure resistance, but on the other hand, those with severe conditions, such as those with high operating conditions and those with severe vibration, may cause the seal layer to break. There is a possibility of peeling at the interface between the sealing material and the flange, and there is a concern about use in such a place. On the other hand, since CIPG is cured before being pressed by the flange of the other member to be sealed, the thickness of the sealing material can be ensured. Because the rebound force of the thickness expresses the sealing property, even if vibration or impact is applied, it absorbs it with the elasticity of the cured silicone rubber, and the thin film sealing material like FIPG may break. There is no. However, since the CIPG is cured once, the surface is not bonded even if it is pressed against the other article to be sealed. Therefore, when there is a fine flaw on the sealing material and the surface to be sealed (flange), a fine gap is generated between them, and the possibility of contact surface leakage from there is undeniable.

  Therefore, CIPG which adheres to both flanges has also been proposed (Patent Document 8 and Patent Document 9). However, they use materials that are inferior in physical properties such as heat resistance as compared to silicone rubber, and no means for solving the above problems using silicone rubber has been proposed yet.

Japanese Patent Publication No. 34-10045 Japanese Patent Publication No. 35-18190 Japanese Patent Publication No. 35-18191 Japanese Patent Publication No. 38-26280 Japanese Patent Publication No. 40-10117 Japanese Patent Publication No.49-43699 JP-A-7-207161 Japanese Patent No. 3552237 JP-A-10-152672

  An object of the present invention is to solve the above-mentioned problems of the prior art, and in particular, by taking advantage of the characteristics of silicone rubber, a silicone rubber having a predetermined shape is firmly adhered to an adherend to cause leakage of a contact surface. It is an object of the present invention to provide a means for forming an adhesion / seal surface free from defects.

  In the present invention, first, a primer composition composed of a silane coupling agent and a boric acid compound is applied to an adherend, and a silicone rubber cured product containing the boric acid compound is brought into contact with the primer composition surface for pressure bonding. This is a method for bonding a cured silicone rubber to an adherend.

  The second aspect of the present invention is a cured product obtained by applying a silicone rubber uncured material containing a boric acid compound to an adherend other than the adherend to which the primer composition is applied. It is the above method.

  Thirdly, the present invention is the above method wherein the silane coupling agent comprises a silicon compound having an alkoxy group and a functional group other than an alkoxy group.

  Fourthly, the present invention is the above-mentioned method in which the primer composition is applied to an adherend after mixing the compound that cures the functional group of the silane coupling agent with the primer composition.

  The fifth aspect of the present invention is the above method, wherein the adherends are sealing flange surfaces, and the cured silicone rubber forms a gasket.

  Sixthly, the present invention is characterized in that a boric acid compound-containing silane coupling agent layer applied to an adherend and a boric acid compound-containing cured silicone rubber layer in contact with the silane coupling agent layer are pressure-bonded. It is a composite structure.

  According to the present invention, silicone rubber having excellent heat resistance and other excellent properties can be firmly bonded to an adherend at an arbitrary thickness, and can be effectively used as a high-performance sealing material having elasticity. It becomes possible.

  In the present invention, the primer composition is applied to the adherend to which the silicone rubber is to be bonded. The adherend includes various parts to be joined with silicone, such as metal and plastic, and is not particularly limited.

  The primer composition used in the present invention contains a silane coupling agent and a boric acid compound as essential components. As is well known, a silane coupling agent is known as a silicon compound having a plurality of different functional groups, and in the present invention, at least one functional group bonded to a silicon atom known as a typical silane coupling agent is present. A silicon compound which is an alkoxy group is used. Examples of the functional group bonded to the silicon atom together with the alkoxy group include an epoxy group, a vinyl group, a mercapto group, an amino group, and an acrylic group. Examples of the alkoxy group include ethoxy group, methoxy group, and propoxy group. Examples of such compounds are as follows. When the functional group is a vinyl group, there are vinyltrimethoxysilane (trade name: KBM1003; Shin-Etsu Chemical) and vinyltriethoxysilane (trade name: KBE1003; Shin-Etsu Chemical). In the case of an epoxy group, 3-glycidoxypropyltrimethoxysilane (trade name: KBM403; Shin-Etsu Chemical), 3-glycidoxypropyltriethoxysilane (trade name: KBE403; Shin-Etsu Chemical), and 3 in the case of an acrylic group. -Methacryloxypropyltriethoxysilane (trade name: KBE503; Shin-Etsu Chemical), 3-acryloxypropyltrimethoxysilane (trade name: KBM5103; Shin-Etsu Chemical), 3-methacryloxypropylmethyldimethoxysilane (trade name: KBM502; Shin-Etsu Chemical) In the case of an amino group, there are 3-aminopropyltrimethoxysilane (trade name: KBM903; Shin-Etsu Chemical), 3-aminopropyltriethoxysilane (trade name: KBE903; Shin-Etsu Chemical), and the like.

  As a boric acid compound which is the other essential component of the primer composition used in the present invention, boric acid or a derivative thereof may be mentioned as a typical example among the boron compounds known in Patent Document 1 to Patent Document 7 and others described above. In particular, borate esters are preferably used. Here, the borate ester is an ester compound of boric acid and a compound having a hydroxyl group, such as trimethyl borate, triethyl borate, and tributyl borate. In addition, 6-membered ring boric acid monoester ((2, (2-methoxypropyloxy) propyl) = butylene-1,3-) = borate, (2-butoxyethyl = 2-methylpentylene, 2,4-) = Borate, etc.) or an ester compound of boric acid and a polyhydric alcohol as disclosed in Patent Document 4, wherein the tetravalent boron atom forms two five-membered rings, and the five-membered ring is alkoxylated A cyclic borate ester to which a group is bonded can also be used. Such cyclic borate esters are “High Boron BC1”, “High Boron BC2”, “High Boron BC3”, “High Boron BCN” (Boron International Co., Ltd.), “Cure Duct L-07N” (Shikoku Kasei Kogyo Co., Ltd.) ) And other commercial names.

  The blending amount of the boric acid compound is preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the silane coupling agent. When the amount is less than 0.5 part, the re-bonding property is hardly exhibited, and when the amount is more than 20 parts by weight, the adhesiveness is lowered.

  There are boric acid compounds that are solid and liquid at room temperature, but if the liquid is used in an addition amount of more than 10 parts by weight, the coated surface will be completely covered even if the primer composition is applied and dried. Does not dry. When the amount of boric acid compound added is large, a sticky film is formed on the coated surface. When a cured silicone rubber containing a boric acid compound is pressure-bonded, it will be re-fused, but the cohesive failure rate will decrease and adhesion will occur. Power is reduced.

  In the primer composition used in the present invention, it is also preferable to form a dry cured coating film on the surface of the adherend by mixing a compound that reacts with the functional group of the silane coupling before coating to form a dry cured film. This primer composition is preferably used when a large amount of the liquid boric acid compound is used.

  As an example of the compound that undergoes a curing reaction, for example, when the functional group of the silane coupling agent is an epoxy group, a basic substance such as an amine compound is used, and when it is a (meth) acryloyl group, an organic peroxide or Examples include thiol compounds. In particular, a combination with a compound (such as high boron BCN) in which a functional group is an epoxy group and a basic substance is coordinated to a boric acid compound is particularly useful because the boric acid compound binds firmly to the primer film.

In addition, the boric acid compound to be used should use what is compatible in a system | strain, and it is preferable to use a boric acid ester with low polarity also from the meaning.
An organic solvent may be used for the primer composition for convenience of application. Usable organic solvents such as toluene, xylene and acetone are used.

  The primer composition can be obtained by simply mixing the components. It is preferable that the primer composition is applied to an adherend and left as it is or heated and dried.

  In this invention, after apply | coating the primer composition which consists of a silica coupling agent containing a boric acid compound in this way to a to-be-adhered body, the silicone rubber hardened | cured material containing a boric acid compound is crimped | bonded on it.

  As the silicone rubber used in the present invention, a conventionally known appropriate silicone rubber having a siloxane bond can be used. A typical example of an uncured silicone rubber is one in which an essential component has a crosslinkable reactive group at the side chain or terminal of an oligomer molecule having a repeating siloxane bond. In the present invention, a siloxane bond must be included. Don't be. For example, so-called modified silicone having a hydrolyzable silane at the terminal, such as polyoxyalkylene, polyisobutylene, and polyacrylate, does not show the effect of the present invention. Those having a siloxane bond in the molecule, such as a copolymer of bisphenol and siloxane, have the effects of the present invention.

  As a typical example of the uncured silicone rubber, a compound having a reactive functional group at the end of an oligomer in which most of the main chain in the molecule has a siloxane bond can be exemplified. Examples of the reactive functional group include a hydrolyzable group bonded to silicon, an alkenyl group, and a (meth) acryloyl group.

  Examples of hydrolyzable groups include acyloxy groups such as acetoxy group, octanoyloxy group and benzoyloxy group; ketoxime groups such as dimethyl ketoxime group, methylethyl ketoxime group and diethyl ketoxime group; methoxy group, ethoxy group and propoxy group Alkoxy groups; alkenyloxy groups such as isopropenyloxy group and 1-ethyl-2-methylvinyloxy group; amino groups such as dimethylamino group, diethylamino group, butylamino group, and cyclohexylamino group; dimethylaminoxy group, diethylaminoxy And aminoxy groups such as groups. These condense with moisture.

The alkenyl group causes crosslinking with an organic peroxide or an addition reaction with hydrogensiloxane, and is cured by two-component mixed curing or heat curing.
The (meth) acryloyl group is polymerized by radicals such as peroxides and photoinitiators.

  Any of these uncured silicone products are well known. For example, as a moisture-curing silicone compound having a hydrolyzable functional group, three bond 1216 as a deoxime type, three bond 1208 as a deacetone type, and three bond 1220 as a dealcohol type. Can be given. Three-bond 1230 is commercially available as a two-component mixed curing type addition-curing type (hydrosilylation type), and three-bond 3164 is commercially available as an ultraviolet curable silicone having a methacryloyl group at the molecular end.

Also, ALBIFLEX296, ALBIFLEX712 (manufactured by Hance Chemie) is commercially available as a bisphenol-polysiloxane copolymer.
The boric acid compound blended in the silicone rubber is the same as the boric acid compound used in the primer composition described above.

  The amount of the boric acid compound is preferably 0.5 to 20 parts by weight per 100 parts by weight of the silicone rubber component. When the amount is less than 0.5 part, the re-bonding property is hardly exhibited, and when the amount is more than 20 parts by weight, the adhesiveness is lowered.

  To the uncured silicone rubber, a curing agent corresponding to the curing mechanism of the uncured silicone rubber to be used is added, and if necessary, a filler and other various additives can be added according to a conventional method.

  The silicone rubber uncured composition containing the boric acid compound thus prepared is processed into a shape according to the purpose of use. The case of using as a sealing material will be described as an example. A silicone rubber uncured composition is applied to a flange of one sealed part to a predetermined thickness and cured to have a cured silicone rubber layer containing a boric acid compound. By preparing a flange and press-fitting it to the other flange to which the primer is applied, it is re-fused to obtain a strong bond. By pressure bonding under heating, it is fused more quickly. When it is performed at room temperature, the time required for complete re-fusion is usually about 7 days. When heated to 50 ° C., it is usually re-fused in about 24 hours. However, since the time required for re-fusion depends on the compression force, the hard-cured product tends to be re-fused more quickly when highly compressed, and when the soft-cured product is compressed, it is re-fused more slowly.

In the present invention, a cured silicone rubber having a predetermined shape is prepared in advance, and can be firmly adhered to an adherend having a fixed thin primer composition layer corresponding to a paste by simple means. The thickness can be adjusted easily and with high accuracy. For example, when using a cured silicone rubber as a sealing material, the surface of one adherend is formed with a thick band-shaped silicone rubber cured layer having a certain width and height on the other adherend. It is possible to easily prepare a sealing layer with high dimensional accuracy by press-bonding to.
The invention will now be illustrated on the basis of examples.

〔Example〕
Preparation of silicone rubber composition 1:
• 100 parts by weight of dimethylpolysiloxane having a viscosity of 20 Pa · s at 25 ° C. with both ends of the molecular chain sealed with hydroxyl groups • 8 parts by weight of methyltributanoxime silane • 0.2 parts by weight of dibutyltin octate • 100 parts of calcium carbonate Part by weight, 8 parts by weight of fumed silica, and 3 parts by weight of tributyl borate were mixed in a room temperature and anhydrous environment.

Preparation of silicone rubber composition 2:
From the above composition, only tributyl borate was changed to high boron BC3 which is a cyclic borate ester.

Preparation of silicone rubber composition 3:
・ 100 parts by weight of dimethylpolysiloxane having a viscosity of 10 Pa · s blocked at both ends of the molecular chain with dimethylvinylsiloxy groups. • Methyl hydrogensiloxane having a viscosity of 5 mPa · s blocked at both ends of the molecular chain with trimethylsiloxy groups. (Content of hydrogen atom bonded to silicon atom: 1.86% by weight) 1.5 parts ・ Chloroplatinic acid complex 0.1 part by weight ・ γ-aminopropyltrimethoxysilane 3 parts by weight ・ Calcium carbonate 70 parts by weight ・ Fume 8 parts by weight of dosilica and 3 parts by weight of tributyl borate were mixed at room temperature in an anhydrous environment.

Preparation of comparative composition 4:
・ 100 parts by weight of polypropylene oxide having a viscosity of 10 Pa · s at 25 ° C. and 12 parts by weight of γ-methacryloxypropyltrimethoxysilane with both ends of the molecular chain sealed with vinyldiisopropenoxysilyl groups. 5 parts by weight of trimethoxysilane, 1.0 part by weight of dibutyltin octate, 150 parts by weight of calcium carbonate, 8 parts by weight of fumed silica, and 3 parts by weight of tributyl borate were mixed in an ambient temperature and in an anhydrous environment.

Preparation of primer composition 1:
Silane coupling agent 3-glycidoxypropyltrimethoxysilane KBM403 (Shin-Etsu Chemical Co., Ltd.) 100 parts by weight Cyclic boric acid ester cure duct L-07N (manufactured by Shikoku Kasei Kogyo) Mixed.

Preparation of primer composition 2:
Silane coupling agent 3-glycidoxypropyltrimethoxysilane KBM403 (Shin-Etsu Chemical Co., Ltd.) 100 parts by weight Cyclic borate ester Hyboron BC3 (manufactured by Boron International Co.) 5 parts by weight was mixed in a normal temperature and anhydrous environment.

Preparation of primer composition 3:
Silane coupling agent 3-glycidoxypropyltrimethoxysilane KBM403 (Shin-Etsu Chemical Co., Ltd.) 100 parts by weight Cyclic borate ester Amine coordination bond High boron BCN (manufactured by Boron International) 5 parts by weight at room temperature and anhydrous Mixed under environment. However, it was mixed immediately before use.

1. The silicone rubber composition 1 was poured into a mold and cured in an environment of 23 ° C. × RH 55% for 7 days to obtain a sheet of cured silicone rubber having a thickness of 2 mm.
2. Primer composition 1 was applied to an aluminum plate with a brush and allowed to stand at 50 ° C. for 1 day to form a dry coating film on the aluminum plate.
3. The cured silicone rubber was sandwiched between the primer-coated surfaces of the two aluminum plate test pieces, pressed, and held at 50 ° C. for 24 hours.
4). As a result, it adhered completely. When two aluminum plates were pulled with a tensile tester, they were cohesive.

  An experiment similar to Example 1 was performed using the silicone rubber composition 2 and the primer composition 2. As a result, it was cohesive failure.

  The same experiment as in Example 1 was performed using the silicone rubber composition 3 and the primer composition 3. As a result, it was cohesive failure.

[Comparative Example 1]
The same experiment as in Example 1 was performed using a comparative silicone rubber composition which was the same composition as the silicone rubber composition 1 but did not contain tributyl borate. As a result, the aluminum plate was easily peeled off from the interface when pulled.

[Comparative Example 2]
An experiment similar to Example 1 was performed using the comparative composition 4. As a result, the aluminum plate was easily peeled off from the interface when pulled.

1. Silicone rubber composition 1 was applied to the end portion of the glass epoxy plate at a thickness of 2 mm, and cured for 7 days in an environment of 23 ° C. × RH 55% to obtain a cured silicone rubber bonded to the epoxy glass plate.
2. Primer composition 2 was applied to a glass epoxy plate with a brush and allowed to stand at 50 ° C. for 1 day to form a dry coating film on the glass epoxy plate.
The cured silicone rubber adhered to the glass epoxy plate obtained in 3.1 and the primer coated surface of the glass epoxy plate obtained in 2 were faced and pressed together, and held at 50 ° C. for 24 hours.
4). As a result, it adhered completely. When two glass epoxy plates were pulled with a tensile tester, cohesive failure occurred.
[Comparative Example 3]
As a comparative primer, only a silane coupling agent (3-glycidoxypropyltrimethoxysilane KBM403 (Shin-Etsu Chemical Co., Ltd.)) was used, and a silicone rubber composition 1 was used for the same experiment as in Example 1. As a result, the aluminum plate was easily peeled off from the interface when pulled.

Claims (6)

  A primer composition composed of a silane coupling agent and a boric acid compound is applied to an adherend, and a cured silicone rubber containing the boric acid compound is brought into contact with the primer composition surface and pressure bonded. A method of bonding cured silicone rubber to the body.   2. The method according to claim 1, wherein the cured silicone rubber is obtained by applying a silicone rubber uncured material containing a boric acid compound to an adherend different from the adherend to which the primer composition is applied, and then curing.   The method according to claim 1 or 2, wherein the silane coupling agent comprises a silicon compound having an alkoxy group and a functional group other than an alkoxy group.   The method according to any one of claims 1 to 3, wherein the primer composition is applied to an adherend after mixing the functional group of the silane coupling agent and a compound that undergoes a curing reaction with the composition.   The method according to any one of claims 2 to 4, wherein the adherends are sealing flange surfaces, and the cured silicone rubber forms a gasket.   A composite structure comprising a boric acid compound-containing silane coupling agent layer applied to an adherend and a boric acid compound-containing cured silicone rubber layer in contact with the silane coupling agent layer.