Method for manufacturing surface-modified silicone rubber

Abstract

To provide a method for manufacturing silicone rubber which is a cured product of a silicone rubber composition containing a specific component, and surface-modified by a very simple method.SOLUTION: There is provided a method for manufacturing surface-modified silicone rubber which is a cured product of a silicone rubber composition containing the following component (A) within the range of 0.1 to 20 mass% in the silicone rubber composition, and in which the surface of the cured product is treated by acidic liquid. (A) partial hydrolysate of organoalkoxysilane represented by formula (1). RSi(OR1)3 (1) (In the formula, R denotes monovalent hydrocarbon group having a carbon number of 1 to 12, and R1 denotes alkyl group having a carbon number of 1 to 4.)SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a surface-modified silicone rubber.

Background Art

[0002] Silicone rubber has characteristics such as excellent weather resistance, electrical properties, low compression set, heat resistance, and cold resistance, and is widely used in various fields such as electrical equipment, automobiles, construction, medical, and food. Depending on these applications, there are cases where silicone rubbers with different physical properties are laminated and molded for use. In such cases, there is a concern about peeling due to insufficient adhesion at the interface between different silicone rubbers. In addition, there were problems such as natural peeling of the adhesive interface due to aging deterioration, complexity of the lamination process, deterioration of workability due to an increase in processes, and cost increase.

[0003] In order to solve the above problems, various surface modification methods for silicone rubber have been proposed. Typically, there are a surface modification method using light energy (Patent Document 1), a surface modification method using thermal energy (Patent Document 2), a surface modification method by chemical modification (Patent Document 3), or a surface modification method by combining them (Patent Document 4), etc. However, in the surface modification method using light or thermal energy, since a device for generating energy is always required, problems such as equipment investment costs and equipment installation space occur. In addition, in the surface modification method by chemical modification, there were problems such as a long time required for surface modification or the need for heating, resulting in a decrease in productivity and lack of simplicity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a silicone rubber surface-modified by a very simple method in a silicone rubber which is a cured product of a silicone rubber composition containing a specific component.

Means for Solving the Problems

[0006] In order to solve the above problems, in the present invention, in a silicone rubber which is a cured product of a silicone rubber composition containing the following component (A) in the range of 0.1 to 20 mass percent, a method for producing a surface-modified silicone rubber is provided, which is characterized in that the surface of the cured product is treated with an acidic liquid. (A) A partial hydrolyzate of an organoalkoxysilane represented by the following formula (1) RSi(OR 1 ) 3 (1) (In the formula, R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, and R 1 represents an alkyl group having 1 to 4 carbon atoms.)

[0007] Further, in the method for producing a surface-modified silicone rubber of the present invention (hereinafter, the production method of the present invention), it is preferable that R and R 1 in the above formula (1) are each independently any one of a methyl group, an ethyl group, and a propyl group.

[0008] According to these production methods, it is possible to provide a method for producing a surface-modified silicone rubber having different physical properties with one cured product by a very simple method of treating the surface of the silicone rubber (cured product) with an acidic liquid.

[0009] Furthermore, in the production method of the present invention, it is preferable that the acidic liquid is an acidic solution having a pH of less than 3.0 and a concentration of the acidic substance contained in the acidic liquid of 0.001 mol / L or more.

[0010] With such a production method of the present invention, a surface modification effect can be surely obtained.

Effect of the Invention

[0011] As described above, according to the production method of the present invention, in the silicone rubber which is a cured product in the silicone rubber composition containing a specific component, a very simple method of treating the surface of the cured product with an acidic liquid can provide a method for producing a surface-modified silicone rubber. In particular, it is also possible to produce surface-modified silicone rubbers having different physical properties with one cured product.

Mode for Carrying Out the Invention

[0012] As described above, there has been a demand for the development of a method for producing a surface-modified silicone rubber by a very simple method.

[0013] As a result of intensive studies on the above problems, the present inventors have found that in a cured product of a silicone rubber composition containing 0.1 to 20 mass percent of a partial hydrolyzate of an organoalkoxysilane ((component (A)) represented by the following formula (1)), when the surface of the cured product is treated with an acidic liquid, a silicone rubber can be obtained in which the rubber hardness of the treated surface is harder than the rubber hardness of the untreated surface by a short-time treatment, and thus the present invention has been completed. (A) A partial hydrolyzate of an organoalkoxysilane represented by the following formula (1) RSi(OR 1 ) 3 (1) (In the formula, R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, and R 1 represents an alkyl group having 1 to 4 carbon atoms.)

[0014] That is, the present invention is a method for producing a surface-modified silicone rubber, which is a cured product of a silicone rubber composition containing the following component (A) in the range of 0.1 to 20 mass percent in the silicone rubber composition, and treating the surface of the cured product with an acidic liquid. (A) A partial hydrolyzate of an organoalkoxysilane represented by the following formula (1) RSi(OR 1 ) 3 (1) (In the formula, R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, and R 1 represents an alkyl group having 1 to 4 carbon atoms.)

[0015] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0016] [Silicone rubber composition] In the present invention, the silicone rubber composition refers to a composition that can be cured by applying some energy such as heat, light, vibration, etc. to the composition, or a composition that can be cured by utilizing moisture or oxygen in the air.

[0017] [Component (A)] In the present invention, as the component (A), a partial hydrolyzate of an organoalkoxysilane represented by the following formula (1) is used. This component (A) is an essential component of the production method of the present invention. RSi(OR 1 ) 3 (1) In the above formula (1), R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms. Specifically, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, etc. may be mentioned. Also, R 1 represents an alkyl group having 1 to 4 carbon atoms, preferably a methyl group, an ethyl group, or a propyl group.

[0018] Specific examples of the above organoalkoxysilane include trimethoxy(methyl)silane, trimethoxy(ethyl)silane, trimethoxy(propyl)silane, trimethoxy(butyl)silane, trimethoxy(hexyl)silane, triethoxy(methyl)silane, tripropoxy(methyl)silane, tributoxy(methyl)silane, etc. Among them, trimethoxy(methyl)silane, trimethoxy(ethyl)silane, and triethoxy(methyl)silane are preferred, and trimethoxy(methyl)silane is more preferred. Partial hydrolyzates of these organoalkoxysilanes are used as the component (A). Since the component (A) is a partial hydrolyzate, in addition to the monovalent hydrocarbon group having 1 to 12 carbon atoms derived from the above R and the alkyl group having 1 to 4 carbon atoms derived from the above R 1 there is also a part of hydroxy groups (hydroxysilyl groups).

[0019] Here, the degree of polymerization of the partial hydrolyzate of the organoalkoxysilane of the component (A) is preferably 2 or more and 100 or less. Among them, those mainly composed of partial hydrolyzates having a degree of polymerization of 2 to 30 are particularly preferred. If the component (A) is not a partial hydrolyzate, that is, a monomer of organoalkoxysilane, it is likely to volatilize. Therefore, when a monomer of organoalkoxysilane is contained in the silicone rubber composition, the amount of alkoxysilane in the silicone rubber composition becomes unstable, or the remaining alkoxysilane is too little, so that the expected surface modification effect cannot be obtained. On the other hand, if the degree of polymerization of the component (A) is within 100, the molecular weight of the component (A) becomes appropriate, and the hardness of the silicone rubber surface obtained by the production method of the present invention does not become extremely high, and the silicone rubber after surface modification does not become brittle.

[0020] In addition, the kinematic viscosity of the component (A) at 25 °C is preferably in the range of 1.0 to 1,000 mm 2 / s, more preferably 1.5 to 500 mm 2 / s, and particularly preferably 1.5 to 300 mm 2 / s. This kinematic viscosity is a value measured by a Cannon-Fenske viscometer described in JIS Z8803:2011.

[0021] In addition, the partial hydrolyzate of the organoalkoxysilane of component (A) is preferably contained in the silicone rubber composition in the range of 0.1 to 20% by mass, preferably 0.5 to 15.0% by mass. When the content of component (A) is less than 0.1% by mass, the desired surface modification effect such as an increase in the hardness of the silicone rubber cannot be sufficiently obtained. On the other hand, when the content of component (A) exceeds 20% by mass, since the content of component (A) is too high, the hardness of the silicone rubber after surface modification becomes extremely high or the silicone rubber becomes brittle.

[0022] [Treatment of the cured product (silicone rubber) with an acidic liquid] In the production method of the present invention, it is essential to treat the surface of the cured product (silicone rubber) with an acidic liquid. Here, the treatment method is not particularly limited. For example, if one side of the silicone rubber is treated by spray coating, brush coating, etc., a cured product (silicone rubber) with different hardnesses on the front and back of the silicone rubber can be obtained. Further, as a treatment method, dipping, that is, immersing in an acidic liquid, can obtain a silicone rubber with different hardnesses on the surface and inside of the silicone rubber. That is, by selecting the application method of the acidic liquid, the physical properties of the obtained silicone rubber can be changed, and it becomes possible to provide a surface-modified silicone rubber suitable for its use.

[0023] The acidic liquid used in the production method of the present invention is not particularly limited, but preferably an acidic liquid with a pH of less than 3.0 is used. If it is an acidic liquid with a pH of less than 3.0, the effects of the production method of the present invention can be obtained. Specific examples of the acidic liquid with a pH of less than 3.0 include hydrochloric acid, an organic solvent solution of hydrogen chloride, an aqueous sulfuric acid solution, an organic solvent solution of sulfuric acid, an aqueous nitric acid solution, acetic acid, an aqueous acetic acid solution, lemon water, vinegar, citric acid, etc. Among them, hydrochloric acid and an organic solvent solution of hydrogen chloride are preferred, and more preferably an organic solvent solution of hydrogen chloride. Solvents used in the acidic liquid include water, cyclopentyl methyl ether, 1,4-dioxane, ethyl acetate, 2-propanol, ethanol, methanol, etc. Among them, ethyl acetate, 2-propanol, and ethanol are preferred. Among these, using a 2-propanol solution of hydrogen chloride is preferred because the surface modification of silicone rubber proceeds very smoothly.

[0024] Regarding the concentration of the acidic substance contained in the acidic liquid, it is preferably 0.001 mol / L or more. When it is 0.001 mol / L or more, the surface modification effect by the production method of the surface-modified silicone rubber of the present invention can be obtained.

[0025] The time for treating the surface of the cured product in the production method of the present invention with the acidic liquid is not particularly limited, but in order to quickly obtain the desired surface modification effect, it is preferably as short as possible. Preferably within 1 hour, more preferably 1 to 30 minutes.

[0026] Also, after treating the silicone rubber surface with the acidic liquid, it is preferably washed with water or the like so that there is almost no residue of the acidic liquid on the silicone rubber surface. Especially when using an aqueous sulfuric acid solution or a sulfuric acid organic solvent that is likely to remain, since the acidic component is likely to remain on the silicone rubber surface, it is preferable to remove the acidic component adhering to the silicone rubber surface with water or the like. In the case of an acid such as hydrochloric acid that is easily volatile, the acidic component can also be removed by heating.

Examples

[0027] Hereinafter, examples and comparative examples are shown to specifically describe the present invention, but the present invention is not limited to the following examples.

[0028] As a sample used for surface modification by the production method of the present invention, a cylindrical cured product with a diameter of 29.0 ± 0.5 mm and a height of 12.5 ± 0.5 mm was prepared, and one side thereof was subjected to surface modification. In the surface modification, an acidic liquid was applied twice to the one side with a brush and washed with water after about 5 minutes to obtain a surface-modified surface. The acidic liquid used for surface modification was a hydrogen chloride - 2-propanol solution (about 2 mol / L) [manufactured by Fujifilm Wako Pure Chemical Corporation]. The hardness [hardness (durometer A)] was measured based on the description in JIS K6249:2003 24 hours after the surface modification. The index for determining whether surface modification was achieved or not was to measure the hardness [hardness (durometer A)] of the surface-modified surface and the unmodified surface of the above sample based on the description in JIS K6249:2003, and it was judged that surface modification was possible when (hardness of the surface-modified surface) - (hardness of the unmodified surface) ≥ 3 points, and those with 3 points or less were judged as non-surface-modifiable.

[0029] [Example 1] As the silicone rubber composition, a moisture-curing one-component silicone adhesive KE-4910-T (manufactured by Shin-Etsu Chemical Co., Ltd., containing 1.8 mass percent of a partial hydrolyzate of an organoalkoxysilane (methylmethoxy oligomer) with a polymerization degree of 4 to 5 monomers and a kinematic viscosity of 5 mm 2 / s) was used. After curing this composition at 23 ± 2 °C / 50 ± 5% RH (relative humidity) for about 1 month, the hardness before and after surface modification was measured using this cured product.

[0030] [Example 2] Miracle type silicone rubber compound X-30-4895-2-U (manufactured by Shin-Etsu Chemical Co., Ltd., as the (A) component, with a polymerization degree of 4 to 5 monomers and a kinematic viscosity of 5 mm 2To 100 parts by mass of a partial hydrolyzate of organoalkoxysilane ( / s) (methylmethoxy oligomer) containing 0.5 mass percent, 0.5 part by mass of C-25A (manufactured by Shin-Etsu Chemical Co., Ltd., non-containing component (A)) and 2.0 parts by mass of C-25B (manufactured by Shin-Etsu Chemical Co., Ltd., non-containing component (A)) were uniformly kneaded using two rolls to obtain a silicone rubber composition. After press-curing this composition at 120 °C for 10 minutes, it was post-cured at 200 °C for 4 hours to obtain a cured product for evaluation. The hardness before and after surface modification was measured using this cured product.

[0031] [Example 3] Miracle type silicone rubber compound X-30-4895-10-U (manufactured by Shin-Etsu Chemical Co., Ltd., as component (A), degree of polymerization 4 to 5-mer, kinematic viscosity 5 mm 2 To 100 parts by mass of a partial hydrolyzate of organoalkoxysilane ( / s) (methylmethoxy oligomer) containing 6.0 mass percent, 0.5 part by mass of C-25A (manufactured by Shin-Etsu Chemical Co., Ltd., non-containing component (A)) and 2.0 parts by mass of C-25B (manufactured by Shin-Etsu Chemical Co., Ltd., non-containing component (A)) were uniformly kneaded using two rolls to obtain a silicone rubber composition. After press-curing this composition at 120 °C for 10 minutes, it was post-cured at 200 °C for 4 hours to obtain a cured product for evaluation. The hardness before and after surface modification was measured using this cured product.

[0032] [Comparative Example 1] As the silicone rubber composition, a moisture-curing type one-component silicone adhesive KE-4898-T (manufactured by Shin-Etsu Chemical Co., Ltd., non-containing component (A)) was used. After curing this composition at 23 ± 2 °C / 50 ± 5% RH (relative humidity) for about 1 month, the hardness before and after surface modification was measured using this cured product.

[0033] [Comparative Example 2] As the silicone rubber composition, moisture-curing one-component silicone adhesive KE-4811-W (manufactured by Shin-Etsu Chemical Co., Ltd., containing 3.2 mass percent of the monomer component of organoalkoxysilane (methyltrimethoxysilane) as component (A)) was used. After curing this composition at 23 ± 2°C / 50 ± 5% RH (relative humidity) for about one month, the hardness before and after surface modification was measured using this cured product.

[0034] [Comparative Example 3] A compound was prepared by replacing 0.5 mass percent of the partial hydrolyzate of component (A) contained in the millable silicone rubber compound X-30-4895-2-U with 0.5 mass percent of methyltrimethoxysilane. Otherwise, a cured product for evaluation was obtained in the same manner as in Example 2. The hardness before and after surface modification was measured using this cured product.

[0035] [Comparative Example 4] A compound was prepared by replacing 6.0 mass percent of the partial hydrolyzate of component (A) contained in the millable silicone rubber compound X-30-4895-10-U with 6.0 mass percent of methyltrimethoxysilane. Otherwise, a cured product for evaluation was obtained in the same manner as in Example 3. The hardness before and after surface modification was measured using this cured product.

[0036] [Comparative Example 5] In the cured product of Example 1, basic lime water (0.02 mol / L) was used as the liquid for surface modification, and the hardness before and after surface modification was measured in the same manner otherwise.

[0037] The results obtained in Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Tables 1 and 2.

[0038]

Table 1

[0039]

Table 2

[0040] [Evaluation Results] The silicone rubbers surface-modified in Examples 1 to 3 meet the requirements of the present invention. Since the hardness difference between the surface-modified surface and the non-modified surface is 3 points or more, the surface modification according to the present invention has been achieved as a result.

[0041] On the other hand, Comparative Example 1 does not contain component (A). As a result, even when surface modification was carried out using the same acidic liquid as in Example 1, no surface modification progressed at all. Further, Comparative Examples 2 to 4 use organoalkoxysilane monomers instead of partial hydrolyzates of organoalkoxysilane which is component (A). Therefore, even when surface modification was carried out using the same acidic liquid as in Example 1, almost no surface modification progressed. In Comparative Example 5, since the material used for surface modification is lime water which is a basic liquid instead of an acidic liquid, it deviates from the present invention. Therefore, the expected surface modification effect was not obtained.

[0042] From the above results, the method for producing the surface-modified silicone rubber of the present invention can obtain the desired surface treatment effect in a short time by treating the silicone rubber surface with an acidic liquid, and it can be seen that it is simpler than the conventional surface modification methods which were carried out by using bonding or other energies. [Industrial Applicability]

[0043] The method for producing the surface-modified silicone rubber of the present invention uses a silicone rubber which is a cured product of a silicone rubber composition containing a specific component, and by a very simple method of treating the surface of the cured product with an acidic liquid, it is possible to provide a surface-modified silicone rubber, particularly a silicone rubber having different cured physical properties in one cured product. Therefore, it is a technology that can completely prevent adhesion failure due to bonding and peeling over time. The method for producing the surface-modified silicone rubber of the present invention can be expected to have a wide range of applications in the fields of electrical equipment, automobiles, construction, medical treatment, food, etc.

[0044] Note that the present invention is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Claims

1. A method for producing a surface-modified silicone rubber, which is a cured product of a silicone rubber composition containing the following component (A) in the range of 0.1 to 20% by mass in the silicone rubber composition, characterized in that the surface of the cured product is treated with an acidic liquid. (A) A partial hydrolyzate of an organoalkoxysilane represented by the following formula (1) RSi(OR １ ) ３ (1) (In the formula, R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, and R １ represents an alkyl group having 1 to 4 carbon atoms.)

2. R and R in the formula (1) １ are each independently any one of a methyl group, an ethyl group, and a propyl group, and the method for producing a surface-modified silicone rubber according to claim 1.

3. The method for producing a surface-modified silicone rubber according to claim 1 or 2, wherein the acidic liquid according to claim 1 is an acidic solution having a pH of less than 3.0 and a concentration of an acidic substance contained in the acidic liquid of 0.001 mol / L or more.

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