JPH0778088B2 - Dimethylpolysiloxane-vinyl polymer block copolymer and coating composition using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Applicability >> The present invention relates to a dimethylsiloxane copolymer, and more particularly to a dimethylpolysiloxane-vinyl polymer block copolymer and a coating composition using the same.

<< Prior Art >> Block polymers, graft polymers and comb polymers of organopolysiloxanes and vinyl polymers have been known in recent years as materials having excellent releasability, antifouling properties and weather resistance.

Among them, the comb-type polymer which is a copolymer of a silicone macromonomer having a radical-polymerizable group such as (meth) acrylic group and a radical-polymerizable vinyl monomer is described in JP-A-59-20360. No. 61-151272. Although these comb-type polymers show excellent performance in the above-mentioned properties, in the production aspect, when impurities having two or more polymerizable groups in one molecule are mixed even in a very small amount, Is accompanied by the great difficulty of causing gelation due to the crosslinking reaction in the radical copolymerization process with vinyl-based monomers, while the comb-type copolymer obtained when one molecule contains no impurities at all has a polymerizable group. There is a problem that the polymerized polymer is not transparent but becomes cloudy. For this reason, the radical-polymerizable silicone monomer, which is a raw material of such comb-type copolymer, is required to have an extremely high purity, but it is technically very difficult to industrially produce such a high-purity product. Therefore, there is a drawback that the raw material itself must be expensive.

On the other hand, regarding a comb-type copolymer with a vinyl monomer using mercaptosilane as a chain transfer agent, see JP-A-61
-283623 and JP-A-62-4706. According to this method, since mercaptosilane as a chain transfer agent is introduced, in the step of polymerizing the vinyl-based monomer, there is little possibility of gelation in the case of copolymerization of the radically polymerizable silicone monomer described above. In the step of co-hydrolysis / condensation of the mercaptosilane-introduced vinyl polymer and the dialkoxysilane compound, there is a drawback that three-dimensional structure and gelation are likely to occur due to a crosslinking reaction.

The present inventor is a dimethylpolysiloxane chain-containing copolymer which is excellent in mold releasability, weather resistance, water repellency, antifouling property and adhesiveness to a substrate material, and has no possibility of gelation during its production process. As a result of diligent studies on a copolymer which can be easily mass-produced and can obtain high quality, and a synthesis method thereof, an average of 1 mercaptoalkyl group and 1-
Novel dimethyl obtained by polymerizing one or more vinyl-based monomers having radical polymerizability in the presence of a radical initiator, using a dimethylpolysiloxane macromonomer having three alkoxysilyl groups as a chain transfer agent. The inventors have found that a block copolymer of a polysiloxane-vinyl-based polymer satisfies all the above requirements and completed the present invention.

<< Problems to be Solved by the Invention >> Therefore, a first object of the present invention is to contain a dimethylpolysiloxane chain which is inexpensive and excellent in mold releasability, weather resistance, water repellency, antifouling property and adhesion to a substrate material. It is to provide a copolymer.

A second object of the present invention is to provide an inexpensive coating composition which is useful as a protective coating agent for electronic parts and buildings, as a release coating, an antifouling coating, a snow accretion coating, and the like.

A third object of the present invention is to provide a method for producing a dimethylpolysiloxane chain-containing copolymer that is high in quality and easy to mass-produce.

<< Means for Solving the Problems >> The above-mentioned objects of the present invention include the general formula 1) the general formula Dimethylpolysiloxane represented by
Achieved by vinyl-based polymer block copolymers and coating compositions based on them.

In the above general formula, [A] is selected from the group consisting of (meth) acrylates, styrenes, vinyl esters, (meth) acrylic acid, (meth) acrylamide, maleic anhydride, acrylonitrile and butadiene. A (co) polymer part obtained by (co) polymerizing at least one kind of monomer, R ¹ is a divalent hydrocarbon group having 1 to 10 carbon atoms, and R ² is a monovalent carbon atom having 1 to 4 carbon atoms. Hydrogen group, n is 3-10
An integer of 0, and m is 1, 2 or 3, and the weight of the vinyl monomer spent to constitute the [A] portion and [A]
Spent to make up the other parts The weight ratio of the dimethylpolysiloxane represented by (vinyl monomer / dimethylpolysiloxane) is 95/5 to 40/60.

The dimethylpolysiloxane-vinyl polymer block copolymer of the present invention is a dimethylpolysiloxane having an average of one mercaptoalkyl group and one to three alkoxysilyl groups in one molecule, and vinyl having radical polymerizability. It is manufactured using a system monomer as a raw material.

The dimethylpolysiloxane which is one of the above raw materials is not particularly limited as long as it is a dimethylpolysiloxane having an average of one mercaptoalkyl group and one to three alkoxysilyl groups in one molecule. Such dimethylpolysiloxane is represented by, for example, the following average composition formula.

Where R ¹ is the number of carbon atoms connecting mercapto and the silicon atom
It represents a divalent hydrocarbon group of 10, as a specific example, for example, _{-CH 2 -, - CH 2 CH} 2 -, - CH 2 CH 2 CH 2 -, -CH 2 CH 2 CH 2 CH 2 -, CH _{2 5} , CH _{2 6} , CH _{2 8} , CH _{2 10} , Are exemplified.

R ₂ is a monovalent hydrocarbon group having 1 to 4 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, and the like. From the viewpoint of adhesiveness to materials, methyl group and ethyl group are preferable.

n is a number representing the chain length of dimethylsiloxane and is 3 to 10
It is preferably 0. When n is less than 3, the releasability, water repellency and antifouling property due to the dimethylpolysiloxane chain are deteriorated, whereas when n is more than 100, the releasability, water repellency and antifouling property are no longer higher. This is because the strength of the copolymer is reduced although it is not obtained.

m is the number of dimethylsiloxane blocks and is 1, 2
Or 3.

The method for synthesizing such dimethylpolysiloxane is not particularly limited, but from the viewpoint of using easily available raw materials and making it inexpensive. (Wherein R ¹ and R ² , m are the same as R ¹ , R ² and m above), and a hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane or decamethyl. A method of polymerizing a cyclic dimethylsiloxane represented by cyclopentasiloxane using a siloxane polymerization catalyst is preferable. Examples of the catalyst used in this case include trifluoromethanesulfonic acid, sulfuric acid, activated clay, acid clay, and a cation exchange resin containing a sulfonic acid group.

The reaction is usually solventless, 0 ° C to 120 ° C, preferably 20 ° C to 80 ° C.
The temperature is within the range of 3 to 10 hours.

The dimethylpolysiloxane thus obtained is Etc. are illustrated. These may be used alone or in combination of two or more.

The radical-polymerizable vinyl-based monomer, which is the second raw material component for producing the dimethylpolysiloxane-vinyl-based polymer block copolymer of the present invention, includes:
Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth)
Acrylate, cyclohexyl (meth) acrylate,
2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate,
Dodecyl (meth) acrylate, tridecyl (meth) acrylate, octadecyl (meth) acrylate, 2-
Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylate having a C1-8 perfluoroalkyl group, trimethoxysilylpropyl (meth) acrylate, dimethoxymethylsilylpropyl (meth) acrylate (Meth) acrylates such as styrene, styrenes such as styrene and α-methylenestyrene, vinyl acetates such as vinyl acetate, vinyl propionate, vinyl caproate and vinyl laurate, (meth) acrylic acid, (meth) acrylamide, Examples thereof include maleic anhydride, acrylonitrile, butadiene and the like. These vinyl-based monomers may be used alone or in combination of two or more.

The block copolymer of dimethylpolysiloxane-vinyl-based polymer of the present invention comprises one or more dimethylpolysiloxane and one or more radical-polymerizable vinyl-based monomer in the presence of a radical initiator. Obtained by copolymerization.

Weight fraction of the weight of the vinyl-type monomer spent for constituting the [A] portion and the weight of dimethylpolysiloxane spent for constituting the portion other than [A] in the block copolymer. The former is 95-40% by weight and the latter is 5%
It is preferably about 60% by weight. When the weight fraction of dimethylpolysiloxane is less than 5% by weight, properties such as releasability, antifouling property, weather resistance and water repellency when formed into a film are deteriorated. Strength and hardness decrease.

For the copolymerization of dimethylpolysiloxane and a radically polymerizable vinyl-based monomer, any method of solution polymerization, bulk polymerization, suspension polymerization and emulsion polymerization may be used without any particular limitation. Since it contains a hydrolyzable alkoxysilyl group, suspension polymerization and emulsion polymerization in the presence of water are not very preferable. A particularly preferred polymerization method is solution polymerization.

The amount of radical initiator used is 0.05 with respect to 100 parts by weight of a raw material composed of dimethylpolysiloxane and a vinyl monomer.
It is in the range of ~ 5.0. Specific examples of the radical initiator include benzoyl peroxide, perbutyl benzoate, methyl ethyl ketone peroxide, dicumyl peroxide, t-butyl hydroperoxide, 2,2'-azobisisobutyronitrile, 2,2'-azo. Examples thereof include bisisovaleronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile). Further, a redox catalyst used in the redox polymerization system, for example, a combination of a transition metal salt, amines and the like and a peroxide type radical initiator may be used.

A block copolymer of dimethylpolysiloxane-vinyl polymer can be easily produced by copolymerizing dimethylpolysiloxane and a vinyl polymerizable monomer by a conventional method using the above-mentioned polymerization method and radical initiator. .

The copolymer obtained as described above forms a low energy surface and is excellent in water repellency, oil repellency, lubrication, mold release, antifouling, weather resistance, gas permeability, etc., and also has a crosslinking group and an inorganic substance in the molecule. Since it contains an alkoxysilyl group that is a reactive group with, it is also excellent in adhesiveness to substrate materials and solvent resistance,
Electronic parts (for example, protection of circuit wiring, antifouling of electrophotographic drum, fusion prevention of thermal transfer paper or ink ribbon),
Extremely useful as a coating agent for buildings, automobiles, ships, aircrafts, etc., and as a release agent, release coating, antifouling coating, dropout, anti-papering coating, anti-icing / snow-preventing dye, weathering coating Is.

Further, the production method of the present invention in which a copolymerization polymer is obtained by carrying out a polymerization reaction in the presence of a radically polymerizable monomer and a radical generator, using the above-mentioned dimethylpolysiloxane containing a mercapto group and an alkoxysilyl group as a chain transfer agent, Compared to the conventional method of using mercaptosilane as a chain transfer agent, and the method of copolymerizing a radical-polymerizable silicone macromonomer, etc., it has a feature that gelation is less likely to occur during the reaction, so production on an industrial scale. Very suitable for.

In the composition of the present invention, in addition to the block copolymer, a solvent, a curing catalyst, a filler, a pigment, a stabilizer, a cross-linking agent, and an organic resin may be mixed and used, if necessary.

The solvent is essential for the coating composition and is not particularly limited as long as it dissolves the block copolymer. Examples of such solvents include aromatic hydrocarbons such as toluene and xylene; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, dibutyl ketone and cyclohexane; esters such as ethyl acetate, isopropyl acetate and isobutyl acetate; diethyl ether, diether -Ethers such as n-propyl ether, dibutyl ether, tetrahydrofuran, dioxane; chlorinated hydrocarbons such as dichloromethane, dichloroethane, trichloroethane, trichloroethylene, tetrachloroethane, chloroform; alcohols such as isopropanol, n-butanol, isobutanol, etc. It is illustrated. These solvents may be used alone or in combination of two or more. In particular, when solution polymerization is used as the polymerization method, it is also possible to use the block copolymer obtained by the polymerization reaction as it is as it is diluted with the solvent, without fractionation and purification.

The curing catalyst for curing the composition of the present invention after application is not particularly limited as long as it hydrolyzes and condenses the alkoxysilyl group contained in the block copolymer, and specific examples include dibutyltin dioctate and dibutyltin dioctane. Organotin compounds such as acetate and dibutyltin dilaurate;
Examples thereof include organic aluminum compounds such as aluminum acetylacetone; titanium esters such as tetraisopropyl titanate and tetrabutyl titanate; acid compounds such as phosphoric acid and p-toluenesulfonic acid; and amines such as ethylenediamine, triethylenetetramine and guanidine. These curing catalysts are usually added in the range of 0.001 to 5.0% by weight, preferably 0.01 to 3% by weight, based on the block copolymer.

<< Effects of the Invention >> Since the block copolymer of the dimethylpolysiloxane-vinyl polymer of the present invention contains a crosslinkable group and an alkoxysilyl group which is a reactive group with an inorganic substance, it has excellent adhesiveness and a low energy surface. Despite being a high-functionality copolymer capable of forming a polymer, gelation is unlikely to occur in the production process, so that the production efficiency is good and it is suitable for mass production. Further, since the coating composition of the present invention contains a copolymer having the above-mentioned characteristics as a main component, it is excellent not only in adhesiveness to a base material and solvent resistance, but also in water repellency, oil repellency, lubrication, Since it has excellent properties such as mold release, antifouling, weather resistance, gas passage, etc., it can be used as a coating agent for electronic parts, buildings, automobiles, ships, aircraft, etc. It is extremely suitable for anti-paper sticking paints, dyes for preventing ice and snow, weather resistant paints, etc.

<Example> The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto.

Reference example: Synthesis of mercapto group-containing dimethylpolysiloxane 3-mercaptopropyltrimethoxysilane was placed in a glass reaction vessel equipped with a stirrer, a reflux condenser and a thermometer.
19.6 g and octamethyl tetracyclosiloxane 222 g
After charging, trifluoromethanesulfonic acid 0.
48 g was added. Then, the internal temperature was maintained at 60 ° C. in an oil bath to carry out a polymerization reaction for 5 hours with stirring, then the reaction product was cooled to room temperature, 0.54 g of sodium hydrogen carbonate was further added, and the mixture was stirred for 2 hours, Trifluoromethanesulfonic acid was neutralized.
After neutralization, a filtration treatment was performed using diatomaceous earth, and unreacted substances were stripped under reduced pressure to obtain 228.3 g of a colorless transparent oily substance. This product has a viscosity at 25 ° C of 35.7 centistokes, a refractive index of 1.4063, a specific gravity of 0.982, a methoxy group content of 3.7% (theoretical value of 3.85%), and a mercapto group content of 1.4%.
It was (theoretical value: 1.37%), and it was confirmed from the infrared absorption spectrum and GPC that it was a compound represented by the following average composition formula.

Example 1. 100 g of toluene in a glass reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen gas introducing tube.
Also, 1 g of 2,2'-azoisobutyronitrile was charged, and the mixture was heated in a nitrogen gas stream with stirring to maintain the internal temperature at 85 to 90 ° C. Next, 50 g of methyl methacrylate, 15 g of 2-ethylhexyl acrylate, 35 g of mercapto group-containing dimethylsiloxane macromonomer synthesized in Reference Example and 2,
A mixed solution of 1 g of 2'-azoisobutyronitrile was added dropwise through the dropping funnel over 1 hour, and the aging reaction was carried out for 5 hours while maintaining the internal temperature at 85 to 90 ° C. After completion of the reaction, the reaction product was cooled to room temperature, and then dropped into 1.5 l of methanol to precipitate the produced copolymer. The copolymer was separated by filtration under reduced pressure, washed with 100 ml of methanol, and then methanol was removed under reduced pressure to obtain 83 g of the white powdery target product. The glass transition point of this white powder is 47 ° C., the weight average molecular weight in terms of polystyrene in GPC is 43,300, and from the infrared absorption spectrum, the dimethylpolysiloxane, polymethacrylate, and 2-ethylhexyl acrylate copolymer It was confirmed to be a united body.

40 g of the obtained copolymer was dissolved in 60 g of methyl isobutyl ketone, and 1 g of tetrabutyl titanate was further added to prepare a coating composition. The obtained composition was applied onto an aluminum test panel using an applicator and left at room temperature for 3 days to obtain a cured coating having a film thickness of 30μ. The coating had a critical surface tension of 22 dyn / cm, a dynamic friction coefficient of 0.22 and an adhesion of 100%. From these results, it was confirmed that the cured coating film of the coating composition of the present invention has a low critical surface tension and a small dynamic friction coefficient and has good adhesiveness to the substrate, and is excellent in water repellency, releasability and slipperiness. It was The block copolymer of the present invention also had good weather resistance and gas permeability.

The critical surface tension was determined by measuring the contact angle of a linear saturated hydrocarbon film from n-octane to n-hexadecane with respect to the film and extrapolating cos θ (θ: contact angle) to 1. For the dynamic friction coefficient, use a dynamic friction coefficient measuring device manufactured by Kyowa Interface Science Co., Ltd., friction element: SUS ball, load: 1
00g, speed: measured under the condition of 50 mm / min. Adhesion is cut into 1 mm square goggles with a goggles cutter (10 x 1
(0 = 100 pieces) was put in, and the surface was peeled off with a cellophane tape, and the residual rate (%) was evaluated.

Examples 2 to 8 and Comparative Example 1 The block copolymers shown in Table 1 were synthesized from the mercapto group-containing dimethylpolysiloxane and the radical-polymerizable monomer in the same manner as in Example 1, and this copolymer was used. Then, a coating composition was prepared in the same manner as in Example 1 to form a film, and the results of evaluating the performance of these films are also shown in Table 1.

The chemical formulas of the block copolymers of Examples 2 to 8 are shown below.

The results in Table 1 demonstrate that the copolymer of the present invention has excellent adhesiveness, a small critical surface tension and a small dynamic friction coefficient.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C09D 183/08 PMV (56) Reference JP-A-3-86775 (JP, A) JP-A-3-45680 ( JP, A) JP-A-3-88815 (JP, A)

Claims (2)

[Claims] 1. A general formula Dimethylpolysiloxane represented by
Block copolymer of vinyl polymer; in the formula [A]
Is at least one monomer selected from the group consisting of (meth) acrylates, styrenes, vinyl esters, (meth) acrylic acid, (meth) acrylamide, maleic anhydride, acrylonitrile and butadiene ( (Co) polymer portion obtained by copolymerization, R ¹ is a divalent hydrocarbon group having 1 to 10 carbon atoms, R ² is a monovalent hydrocarbon group having 1 to 4 carbon atoms, and n is 3 to 100 Is an integer and m is 1, 2 or 3
And the weight of the vinyl monomer spent to make part [A] and the weight spent to make parts other than [A]. The weight ratio of the dimethylpolysiloxane represented by (vinyl monomer / dimethylpolysiloxane) is 95/5 to 40/60. " 2. A coating composition containing the block copolymer according to claim 1 as a main component.