JPH059426A - Film former composition and prevention of staining of surface of silicone elastomer - Google Patents

Abstract

PURPOSE:To provide a film former composition excellent in an antisagging effect and giving a coating film excellent in long-term weather resistance. CONSTITUTION:A film former composition comprising 100 pts.wt. copolymer obtained by radical-polymerizing a monomer mixture essentially consisting of a fluoroolefin in the presence of a vinyl monomer containing a hydrolyzable silyl group and/or a chain transfer agent having a hydrolyzable silyl group and 10-5000 pts.wt. mixed solvent comprising a volatile organosilicon compound (i) represented by the general formula: (R<1>)4Si, (R<2>)3SiO[(R<3>)2SiO]mSi(R<2>)3, (R<4>) Si[OSi(R<5>)3]3 or [(R<6>)2SiO]n (wherein R<1> to R<6> are the same or different alkyl groups, m is 0 or a positive integer, and n is a positive integer of 3 or greater) and having an atmospheric boiling point of 70-250 deg.C and a hydrocarbon solvent (ii) and having a content of compound (i) of 5-95wt.% based on the total weight of components (i) and (ii).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention provides a coating film forming composition and a coating film of the film forming composition evenly formed on the surface of a silicone elastic body and firmly adhered to the silicone elastic body for a long period of time. The present invention relates to a method capable of preventing pollution.

[0002]

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION As a silicone composition which cures into a rubber-like elastic body, a heat-vulcanizable silicone rubber composition using an organic peroxide as a vulcanization accelerator, and a platinum-based catalyst containing Si Known are addition reaction-curable silicone rubber compositions that utilize the addition reaction between -H and Si-CH = CH ₂ groups, and condensation reaction-curable silicone rubber compositions that cure under the action of moisture in the air at room temperature. Has been. These silicone elastic bodies have excellent properties such as heat resistance, cold resistance, weather resistance, electrical insulation properties, and nontoxicity, and are therefore used in a wide range of fields such as the construction field, electric machinery industry field, food medical industry field. There is. However, although such a silicone elastic material has various excellent properties as described above, it remains slightly sticky even after the curing reaction, and since its main component, polydiorganosiloxane, is a dielectric material, it is dusty. There is a problem that it is easy to draw in. In particular,
When a non-reactive polydiorganosiloxane is added to obtain a flexible silicone elastic body while maintaining workability, polysiloxane that does not participate in such cross-linking exudes from the inside of the elastic body to dust. Since the covering dust is made water repellent, the dust is not washed off by rainwater, and it is conspicuous that it spoils the appearance. As described above, the silicone elastic body has a problem in maintaining the appearance particularly required as a building material and is restricted in use. Also, as an industrial material other than construction, there are many applications in which dust adhesion affects the appearance and use. Therefore, establishment of a technique for preventing adhesion of dust to the surface of the silicone elastic body has been desired by each industry including the construction industry. For the purpose of solving these problems, JP-A-56-157464 and JP-A-56-102343 disclose a method of forming a coating film containing a silicone resin as a main component on the surface of a silicone elastic body. However, in this method, the antifouling effect was insufficient because the component of the film was a silicone resin. Also, JP-A-59-105057 and JP-A-59-1264.
70 and JP-A-59-227955 disclose a method of forming a coating of an alkyd resin or an acrylic resin mixed or modified with a curable silicone compound on the surface of a silicone elastic body. However, these methods have a problem that the formed film has insufficient long-term weather resistance.

[0003]

It is an object of the present invention to provide a coating film forming composition which solves the above problems and has an excellent antifouling effect and a long-term weather resistance of a coating film, and a method for preventing the surface of a silicone elastomer from being soiled. With the goal.

[0004]

As a result of studies to achieve the above object, the present inventor found that a monomer mixture containing a fluoroolefin as an essential component was treated with a hydrolyzable silyl group-containing monomer and / or a hydrolyzable silyl group-containing monomer. A copolymer obtained by radical polymerization in the presence of a chain transfer agent, a film forming agent composition comprising a mixed solvent of a volatile silicon compound and an organic solvent is excellent in dustproofness, and this is applied to the surface of a silicone elastic body. By applying
The inventors have found that a coating film that does not deteriorate over a long period of time can be formed uniformly on the surface, and completed the present invention. That is, the present invention provides (A) (a) a monomer mixture containing a fluoroolefin as an essential component, (b) a hydrolyzable silyl group-containing vinyl monomer and / or a hydrolyzable silyl group-containing chain transfer. 100 parts by weight of a copolymer obtained by radical polymerization in the presence of an agent (B) (a) General formula; (R ¹ ) ₄ Si, (R ² ) ₃ SiO [(R ³ ) ₂ SiO] _m Si _{^{(R 2) 3, (R}} 4) Si [OSi (R ⁵⁾ _{3] 3} or in [(R ⁶⁾ ₂ SiO] _n (wherein, R ¹ to R ⁶ represent each the same or different alkyl group; m is 0 or a positive integer, n is a positive integer of 3 or more) and has a boiling point in the range of 70 to 250 ° C. under normal pressure, and (b) a hydrocarbon-based compound. A coating film forming composition comprising a solvent and 10 to 5000 parts by weight of a mixed solvent in which the amount of (a) is 5 to 95% by weight of the total amount of (a) and (b). And coating film forming composition Was applied to the silicone elastomer surface, to fouling prevention method of the silicone elastic layer surface, characterized in that drying curing.

The copolymer (A) is the base polymer of the composition of the present invention, which comprises (a) a monomer mixture containing a fluoroolefin as an essential component, and (b) a hydrolyzable silyl group-containing vinyl monomer. It is obtained by radical polymerization in the presence of a polymer and / or a chain transfer agent containing a hydrolyzable silyl group.

Examples of the fluoroolefin (a) include ethylene fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, trifluoromethyltrifluorovinyl ether, and heptafluoropropyl trifluorovinyl ether. Etc. are exemplified, and these may be used alone or in combination of two or more kinds. The amount of these fluoroolefins used is appropriately 10 to 70% by weight, preferably 20 to 60% by weight, based on the total amount of the monomers, and if less than 10% by weight, the weather resistance of the coating film formed is decreased, On the contrary, if it is more than 70% by weight, the solubility of (B) in the mixed solvent is lowered. Other monomers used in the present invention include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate,
Vinyl laurate, vinyl stearate such as vinyl stearate; alicyclic carboxylic acid vinyl ester such as cyclohexanecarboxylic acid vinyl ester; benzoic acid vinyl ester, pt-butyl benzoic acid vinyl ester, salicylic acid Aromatic carboxylic acid vinyl ester such as vinyl ester; methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether,
aliphatic or cycloaliphatic vinyl ethers such as n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, cyclohexyl vinyl ether;
Olefins such as ethylene, propylene and 1-butene; vinyl halides such as vinyl chloride and vinylidene chloride; aromatic vinyls such as styrene, α-methylstyrene and vinyltoluene; (meth) acrylonitrile,
Nitrogen-containing monomers such as (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide; methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylate n
-Propyl, (meth) acrylic acid esters such as n-butyl (meth) acrylate, and the like are exemplified.

The hydrolyzable silyl group-containing vinyl monomer (b) and the hydrolyzable silyl group-containing chain transfer agent have the general formula;

[0008]

[Chemical 1]

A substance having a silyl group represented by
R ⁷ is a monovalent hydrocarbon group selected from an alkyl group, an aryl group and an aralkyl group, and a methyl group is particularly preferable from the viewpoint of easy synthesis and availability of raw materials. Further, the hydrolyzable group represented by X is preferably an alkoxy group, and particularly preferably an alkoxy group having 1 to 4 carbon atoms because it has appropriate reactivity. The number a of hydrolyzable groups is required to be an integer of 1 to 3, and a is 2 for the purpose of rapidly forming a tough, insoluble and infusible cured film.
Alternatively, 3 is preferable, and 2 is particularly preferable.

As these vinyl monomers, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldimethoxysilane,
Vinylmethyldiethoxysilane, allyltrimethoxysilane, trimethoxysilylethyl vinyl ether, triethoxysilylethyl vinyl ether, methyldimethoxysilylethyl vinyl ether, methyldiethoxysilylethyl vinyl ether, trimethoxysilylpropyl vinyl ether, triethoxysilylpropyl vinyl ether, methyldimethoxy Silylpropyl vinyl ether, methyldiethoxysilylpropyl vinyl ether,
3-methacryloxypropyltrimethoxysilane, 3-
Methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-acryloxypropylmethyldimethoxy Examples thereof include silane and 3-acryloxypropylmethyldimethoxysilane. Examples of these chain transfer agents include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane. The amount of the hydrolyzable silyl group-containing monomer and the hydrolyzable silyl group-containing chain transfer agent (b) used is such that the introduction amount of the hydrolyzable silyl group per 1000 g of the copolymer (A) is from 0.05 to It is preferably in the range of 5 mol. If the amount of (b) used is less than this range, the adhesiveness to the silicone elastic body will be reduced, which is not preferable, and conversely, if it is more than this range, the crosslink density after curing will be too high and the coating will become brittle, which is not preferable.

The copolymer (A) can be obtained by polymerizing by a known method such as solution polymerization or bulk polymerization using a radical initiator in the presence of the above-mentioned monomer or chain transfer agent. it can. Radical initiators used at that time include diacyl peroxides such as acetyl peroxide and benzoyl peroxide; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; t-butyl hydroperoxide and cumene hydroperoxide. Hydroperoxides such as oxides; Dialkylperoxides such as di-t-butylperoxide and dicumylperoxide; Alkylperoxyesters such as t-butylperoxyacetate; Azobisisobutyronitrile And azo type initiators such as
A solvent may not be used in the reaction, but a hydrocarbon solvent (B) described later may be used. In this polymerization, a chain transfer agent such as lauryl mercaptan, octyl mercaptan or α-methylstyrene dimer can be used as a molecular weight modifier. The temperature during the polymerization is preferably in the range of -20 to 130 ° C, and the reaction pressure is preferably in the range of 1 to 100 kgf / cm ² . Further, the molecular weight of the obtained copolymer is preferably in the range of 1,000 to 30,000 as the number average molecular weight in order to obtain good coatability and workability.

The mixed solvent (B) dissolves the copolymer (A) to form a solution having good coating workability, and is uniformly applied to the surface of the silicone elastic body without being repelled. It is a component for forming a coating film.

The volatile organosilicon compound (B) constituting (B) is represented by the above general formula and has appropriate volatility, in other words, a boiling point of 70 to 250 ° C. Must be in range. When the boiling point is lower than this range, it does not work effectively because it volatilizes early at the time of coating, and when it is too high, the drying property deteriorates and the film formation becomes slow, which is not preferable. Specific examples of (a) include silanes such as tetraethylsilane, dimethyldiethylsilane, and trimethylbutylsilane, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane,
Chain siloxanes such as dodecamethylpentasiloxane, 3-trimethylsiloxy-1,1,1,3,7,
Branched siloxanes such as 7,7-heptamethyltrisiloxane, hexamethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, 1-ethyl-3,3,5,5,7,7.
Cyclic siloxanes such as hexamethylcyclotetrasiloxane are exemplified, but methyl-based siloxanes are preferable because of easy synthesis, and octamethylcyclotetrasiloxane is more preferable in view of appropriate volatility.

As the hydrocarbon organic solvent (b), aromatic solvents such as benzene, toluene and xylene; aliphatic solvents such as n-hexane, n-heptane, cyclohexane and gasoline, ethyl acetate and butyl acetate. Examples include ester systems such as propylene glycol monomethyl ether acetate; ketone systems such as acetone, dimethyl ketone, methyl ethyl ketone and diethyl ketone; ether systems such as diethyl ether and tetrahydrofuran.

The blending amount of (a) must be in the range of 5 to 95% by weight, and is in the range of 10 to 80% by weight, based on the total amount of (A) and (B). It is preferable.
When the amount of (a) is less than 5% by weight, the wettability of the coating film-forming agent with respect to the silicone elastic body is reduced, resulting in repellency and uneven coating, and when it is more than 95% by weight, the component (A) is separated. It is not preferable because it precipitates.

The amount of the mixed solvent (B) used is
(A) It is in the range of 10 to 5000 parts by weight with respect to 100 parts by weight. If the amount of (B) is less than this range, the viscosity of the coating film forming composition becomes high and the workability deteriorates, which is not preferable. On the contrary, if it is more than this range, it becomes necessary to repeat coating. It is not preferable because the work efficiency is reduced.

A catalyst such as an organotin compound, a titanate ester, a titanium chelate compound, and a tertiary amine may be used in the coating film forming composition of the present invention in order to accelerate the curing rate of the coating film. In addition to the above, the coating film forming composition also includes ultraviolet absorbers, antioxidants, modifiers such as viscosity / fluidity modifiers, fumed silica, pulverized quartz, fillers such as calcium carbonate, and oxidizing agents. Pigments such as titanium, iron oxide and carbon black, and water removing agents such as hydrolyzable silanes and hydrolyzable esters can also be added.

The method for preventing fouling of the surface of a silicone elastic material of the present invention comprises applying a dust-proof coating film forming agent composition comprising (A), (B) and other components to the surface of the silicone elastic material and then drying and curing. It is achieved by The method of application is not particularly limited, and any method such as brush, spray, and roller may be used. Dry curing may be accelerated at room temperature or by heating.

[0019]

According to the present invention, since an antifouling coating having excellent weather resistance can be formed on the surface of a silicone elastic body,
Contamination can be prevented for a long period of time.

[0020]

EXAMPLES The present invention will be described below with reference to examples.

Synthesis Examples 1 to 6 In a pressure-resistant tube made of stainless steel having an inner volume of 2000 ml and having a valve, methyl isobutyl ketone, di-t-butyl peroxide, vinyltrimethoxysilane, trimethoxypropyl vinyl ether and 3-mercapto shown in Table 1 were used. Propyltrimethoxysilane, n-propylmercaptan, ethyl vinyl ether and cyclohexyl vinyl ether were charged, cooled to -70 ° C in a dry ice / methanol bath, and nitrogen gas was blown thereinto to replace the air in the pressure resistant tube. Next, tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, and chlorotrifluoroethylene were sealed in a pressure tube from a cylinder. Then each pressure tube
Perform reaction for 16 hours in a rotary thermostat heated to 60 ° C,
Copolymers P-1 to P-6 shown in Table 1 were obtained.

[0022]

[Table 1]

Preparation Examples 1-9 Samples 1-9 were prepared by adding the volatile organosilicon compounds shown in Table 2 to the P-1 to P-6 synthesized in Synthesis Examples 1-6, a solvent and a curing catalyst.

[0024]

[Table 2]

Examples 1 to 6 and Comparative Examples 1 to 4 Samples 1 to 9 were prepared by curing the silicone sealant and the silicone elastic coating material into a sheet having a thickness of about 2 mm.
Was applied with a brush, and the coating properties were observed to see if it could be applied uniformly. Then, it was dried and cured at room temperature for 2 weeks. Then 50 ℃
Adhesion is tested by peel test by immersing in warm water for 7 days, and weather resistance is tested by measuring 60 degree specular reflectance before and after 6000 hours of weatherometer irradiation,
The antifouling effect was tested by observing the adhesion of dust on the coated surface after exposure to the outdoors for 6 months. These results are shown in Table 3.
Shown in. In addition, Comparative Example 1 is a comparative example using a copolymer not using a hydrolyzable silyl group-containing vinyl monomer, Comparative Example 2 is a comparative example using a copolymer not using a fluoroolefin-based monomer, Comparative Example 3 is a Comparative Example in which no volatile organosilicon compound is used as a solvent, and Comparative Example 4 is a Comparative Example in which the dustproof coating film forming agent is not applied.

[0026]

[Table 3]

Claims (2)

[Claims] 1. A monomer mixture containing (A) (a) a fluoroolefin as an essential component, and (b) a hydrolyzable silyl group-containing vinyl monomer and / or a hydrolyzable silyl group-containing chain transfer agent. 100 parts by weight of a copolymer obtained by radical polymerization in the presence of (B) (a) general formula; (R ¹ ) ₄ Si, (R ² ) ₃ SiO [(R ³ ) ₂ SiO] _m Si ( _{^{R 2) 3, (R 4}} ) Si [OSi (R ⁵⁾ _{3] 3} or in [(R ⁶⁾ ₂ SiO] _n (wherein, R ¹ to R ⁶ represent each the same or different alkyl group; m Is 0 or a positive integer, n is a positive integer of 3 or more) and has a boiling point in the range of 70 to 250 ° C. under normal pressure, and (b) a hydrocarbon solvent. A coating film forming composition comprising: 10 to 5000 parts by weight of a mixed solvent containing 5 to 95% by weight of the total amount of (A) and (B). 2. A method for preventing fouling of a silicone elastic body surface, which comprises applying the coating film forming composition according to claim 1 to the surface of the silicone elastic body, and drying and curing the composition.