JPH06256717A - Matte coating composition - Google Patents

Abstract

PURPOSE:To obtain a mette coating composition composed of a polyorgano- siloxane containing a specified polymethylsilsesquioxane as the main component and a specified vinyl monomer copolymer, capable of matte finish without using fine particles and useful for a coating material, a paint, etc. CONSTITUTION:This coating composition is composed of (A) a polyorganosiloxane containing a polymethylsilsesquioxane structure of the formula [R1 and R2 are each 50 to 99mol% methyl Eroup, 1 to 40mol% crosslinkable group, a 2 to 6C alkyl and a (substituted)phenyl group in a less amount as much as possible; (n) is polymerization degreel as the main component and having 500 to 100000 (preferably 1000 to 10000) number-average molecular weigl and (B) a vinyl monomer copolymer composed of a crosslinkable vinyl monomer (e.g. hydroxyethyl acrylate) and a carboxylic acic group-containing vinyl monomer (e.g. acrylic acid or itaconic acid) as the essential constituting components and having 1000 to 100000 (preferably 3000 to 30000) number-average molecular weight and further a vinyl monomer copolymer containing a polydimethylsiloxane structure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resin composition using a polymethylsilsesquioxane-containing resin, which enables a matte surface by coating.

[0002]

2. Description of the Related Art In order to obtain a matte surface in a resin molded product, it is easily put to practical use by first matting the surface of a mold and copying the surface, but it is extremely useful in coating agents and paints. The reality is that the technology is difficult to implement.

In the conventional technology, coating agents and paints (
The fine particles of silica and plastic beads are compounded with (hereinafter collectively referred to as a coating agent) to roughen the surface, but this technique has the following problems. Viscosity increase due to addition of fine particles, instability of particle dispersion, problem of reproducibility of gloss degree, turbidity of color tone, glossy phenomenon due to surface abrasion. Further, it is pointed out that as a fatal problem, the weather resistance is significantly impaired as the amount of fine particles added increases.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop a conventional matte coating method which does not require addition of fine particles. As a result of earnest studies for the above objects, the present inventors have found that when a specific polyorganosilsesquioxane and a specific vinyl monomer copolymer are compounded, a matting phenomenon appears specifically. Found and completed the present invention.

[0005]

Means for Solving the Problems That is, the present invention provides (A) the following general formula:

[Chemical 2] (In the formula, side chain organic groups R1 and R2 are 50 to 99 mol% of a methyl group,
1 to 40 mol% of the crosslinkable reactive group or the organic group having the crosslinkable reactive group as a substituent and the remaining group has 2 carbon atoms
An alkyl group having 6 to 6 or a substituted or unsubstituted phenyl group, and n represents the degree of polymerization. ) A polyorganosiloxane having a polymethylsilsesquioxane structure as a main component and a number average molecular weight of 500 to 100,000 and (B) a number average molecular weight of 1,000 to 100,000 and at least a part of a vinyl monomer being crosslinked. Which has a reactive group on the side chain and a vinyl monomer copolymer (hereinafter, referred to as B-1) having a vinyl monomer having a carboxylic acid group on the side chain as a part of its constituents. It relates to coating compositions.

In addition to the above requirements, the present invention provides the vinyl monomer copolymer of B-1 further containing a polydimethylsiloxane structure in a part of the main chain and / or side chain ( Hereinafter, it is referred to as B-2).

The present inventors also added the same component (A) as the component B-1 or B-2 except that the vinyl monomer component having a carboxylic acid group in the component B-1 or B-2 described above was not contained. The coating composition and the coating composition of the present invention are blended in a constant ratio after three-dimensional curing with a crosslinkable reactive group and the coating film has a full gloss, and the mixture is cured to provide a matting effect. It has been found that a coating film having a desired gloss level that is in the middle of full gloss is obtained.

The polymethylsilsesquioxane in the present invention can be produced by hydrolyzing and co-condensing several corresponding trialkoxysilanes and / or trichlorosilanes. At this time, when the methyl group in the side chain is 50 mol% or less, when the coating composition of the present invention is used, the hardness and weather resistance of this composition become insufficient. On the other hand, if it is 99.9 mol% or more, the number of crosslinkable reactive groups becomes relatively small, and the crosslink density when the composition is cured becomes low, resulting in adverse effects on durability and the like. When the crosslinkable reactive group is 40 mol% or more, the hardness of the polymer increases, but it is brittle and causes a problem in terms of conformability to deformation and impact.

In the polymethylsilsesquioxane of the present invention, the remaining groups other than the side chain methyl group and the crosslinkable reactive group are an alkyl group having 2 to 6 carbon atoms or a substituted or unsubstituted phenyl group. , These are hardness,
The durability is inferior to that of the methyl group, so it is desirable to keep it as low as possible.

The number average molecular weight of the polymethylsilsesquioxane in the present invention is determined by comparison with a standard substance by GPC measurement, and is 500 to 100000, preferably 1000 to 100.
When the number average molecular weight is 10000 and the number average molecular weight is 500 or less, properties such as hardness and stain resistance, which are features of polymethylsilsesquioxane, are insufficient. On the other hand, when the number average molecular weight is 100,000 or more, the expression of the matting effect becomes unsatisfactory.

The crosslinkable reactive group in the polymethylsilsesquioxane of the present invention is a vinyl group, an alkenyl group,
Epoxy group, amino group, mercapto group, alcoholic hydroxyl group, carboxyl group, amide group, amidooxime group,
One or more selected from a sulfone group, a chlorosulfone group, an aldehyde group, and an acetylacetonate group. These are directly methyltrialkoxysilane or methyltrichlorosilane using the corresponding trialkoxysilane or trichlorosilane. And polymethylsilsesquioxane having a crosslinkable reactive group of another form may be produced by a polymer reaction.

Examples of the vinyl monomer copolymer used in the present invention include the following. Of course, the present invention is not limited to these examples. Methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate,
Propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, methacrylic acid
Number of carbon atoms and acrylic acid or methacrylic acid such as 2-ethylhexyl, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate
1 to 22 ester with monohydric alcohol; styrene, vinyltoluene, α-methylstyrene, acrylonitrile,
Copolymer of other vinyl monomers such as vinyl acetate and vinyl chloride.

In the present invention, as the vinyl monomer having a crosslinkable reactive group used as an essential component in the vinyl monomer copolymer, the following can be exemplified. Hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and other vinyl monomers containing alcoholic hydroxyl groups; glycidyl acrylate, glycidyl methacrylate, and other epoxy group-containing vinyl monomers; acrylamide, methacrylamide, N -Methylolamide, N-
Amide group-containing vinyl monomers such as methylol methacrylamide; amine vinyl monomers such as dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate and tertbutylaminoethyl methacrylate; sulfonic acid groups such as vinyl sulfonic acid and vinyl sulfonyl chloride; chlorosulfone. Acid group-containing vinyl monomer; Other mercapto group, amidoxime group, aldehyde group, acetylacetonate group-containing vinyl monomer and the like.

In the vinyl monomer copolymer used in the present invention, the vinyl monomer containing a carboxylic acid group in the side chain used as an essential component is acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, Examples thereof include maleic anhydride.

The ratio of vinyl monomers containing these carboxylic acid groups in the vinyl monomer copolymer is 1 to 35.
Mol%, preferably 5 to 25 mol%. When it is 1 mol% or less, the matting phenomenon is not sufficiently expressed, and when it is 35 mol% or more, the phase of the vinyl monomer copolymer and polymethylsilsesquioxane is Solubility becomes insufficient and the entire composition becomes cloudy.

The number average molecular weight of the copolymer of vinyl monomers in the present invention is determined by comparison with a standard substance by GPC measurement, and is preferably 1000 to 10000, preferably 3000 to 3000.
When the value is 0 and the number average molecular weight is 1,000 or less, the properties such as hardness and stain resistance, which are features of the composition of the present invention, are insufficient. On the other hand, when the number average molecular weight is 100,000 or more, the expression of the matting effect becomes unsatisfactory.

Specific examples of the vinyl monomer having a polydimethylsiloxane structure used for producing the vinyl monomer copolymer containing a polydimethylsiloxane structure at the terminal and / or side chain used in the present invention are as follows. Something like this. Shin-Etsu Chemical Co., Ltd. X-22-174D If necessary, it may be induced by polymer reaction. As an example, polydimethylsiloxane having a terminal hydroxyl group (X-22-170B manufactured by Shin-Etsu Chemical Co., Ltd.) may be reacted with an unsaturated isocyanate such as isocyanate ethyl methacrylate or isophorone diisocyanate.

In the matte coating composition of the present invention, by using the vinyl monomer copolymer containing the polydimethylsiloxane structure as described above, the matte phenomenon is more dramatically exhibited, for example, in the gloss degree. A matte area, which is difficult to achieve with conventional technology levels of 10 or less, is also possible.

In the present invention, the polymethylsilsesquioxane which is the component (A) and the component B-1 or B-2 are compounded, and the third component is further added, if necessary, so that a crosslinkable reactive group is added. By three-dimensionally curing, matte with a gloss level of about 5 to 30 can be realized. On the other hand, except that the vinyl monomer component having a carboxylic acid group in the component B-1 or B-2 is not contained, the same component as the component B-1 or B-2 and the component (A) are combined and the same operation as described above is performed. This allows for a full gloss coating with a gloss level of 80-95. It is also possible to obtain a coating film having a desired gloss level which is intermediate between matte and full gloss by blending and curing both of these coating compositions at a certain ratio.

By using the composition for matting coating of the present invention, it is possible to achieve any matting without using fine particles as a matting agent. Aiming for an effect is not meaningless.

The composition comprising the resin having the polymethylsilsesquioxane structure of the present invention can be used as a composition having excellent hardness, durability, etc., but it is a curing agent, a filler, a thickener. Further, a coloring pigment, an ultraviolet absorber, an antioxidant, an antifoaming agent, etc. can be added and used. When using the resin or resin composition as described above, various solvents or reactive diluents can be used together in order to improve workability. Examples of the solvent include alcohols such as propanol, butanol and amyl alcohol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, ethers such as cellosolve acetate and methyl cellosolve, esters such as ethyl acetate and butyl acetate, toluene and xylene. Such aromatic hydrocarbons are included. Of course, these solvents may be used as a mixture of two or more kinds.

The composition of the present invention comprising polymethylsilsesquioxane and a vinyl copolymer resin can be used as a raw material for molding materials and sheets, but it is used as a coating on the surface of articles, vehicles, buildings and the like, and paints. It is particularly useful as a base resin for use, and as the material of the base material, various materials such as metal, cementitious hardened material, wood material, plastic, and ceramics can be used.

At this time, in order to three-dimensionally cure the resin composition, an appropriate curing method and curing conditions may be selected depending on the types of the crosslinkable reactive group and the curing agent. For example, when the crosslinkable reactive group is an alcoholic hydroxyl group, when the curing agent is diisocyanate, two-part room temperature or heat curing can be selected, and when the curing agent is a melamine resin, heat curing is performed. When the crosslinkable reactive group is an acryloxy group, UV curing or peroxide curing is possible.

[0024]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following examples. In addition, each physical-property value in an Example and a comparative example was measured according to the following method.

(Glossiness) The glossiness was measured at an incident angle of 60 ° and a light receiving angle of 60 °. (Surface hardness) Using a pencil scratch tester for paint, JIS
Measured according to K5401. (Weather resistance) According to JIS B7753, a carbon arc sunshine weather meter test was performed. The surface of the test body after 2000 hours was observed and evaluated by comparing and observing the surface before the test.

(Synthesis of methacryl-reactive polymethylsilsesquioxane) In a 2 liter flask equipped with a thermometer, a stirrer and a reflux condenser, γ-methacryloxylpropyltrimethoxysilane 125 g (0.5 mol), methyl Charge 356 g (2.0 mol) of triethoxysilane, 20 g (0.1 mol) of phenyltrimethoxysilane, 200 g of acetone, 0.002 mol of hydrochloric acid, 54 g (3 mol) of water, and adjust the temperature in the flask to 60.
The temperature was raised to ℃, and kept for 3 hours with stirring. Then 70
After raising the temperature to ℃ and reacting for 1 hour, 0.004 mol of KOH was added dropwise, and after reacting for another 2 hours, it was neutralized and washed with water and toluene, and then solvent, water, etc. were added using a rotary evaporator. After removal of the above, a viscous liquid having a viscosity of 1350 cps at 20 ° C was quantitatively obtained. The GPC curve of this product was a single peak, and no residual peak derived from the monomer was observed. Therefore, it is considered that the monomers are completely co-condensed, and the molar ratio of the side chain methyl group, γ-methacryloxypropyl group, and phenyl group is derived from the raw material molar ratio.
It was 0: 5: 1. The molecular weight of this product was 2,950 as measured by GPC and Mw was 5,300. This is designated as Polymer A.

For comparison, except that the reaction molar ratio of the starting alkoxysilane in the synthesis of polymer A was changed, the molar ratio of methyl group, γ-methacryloxypropyl group and phenyl group was 12: 2:14
To obtain polymethylsilsesquioxane such that This product had a viscosity at 20 ° C of 1,350 cps and a molecular weight measured by GPC of Mn of 2,700. This is designated as Polymer B.

Further, except that the reaction molar ratio of the raw material alkoxysilane in the synthesis of the polymer A is changed, the molar ratio of the methyl group, γ-methacryloxypropyl group and phenyl group is 16: 10: 2 by the same operation and formulation as the polymer A. To obtain polymethylsilsesquioxane such that This one is 20
The viscosity at ℃ was 1,600cps, and the molecular weight measured by GPC was 3,500 in Mn. This is Polymer C.

For comparison, except that the reaction time in the synthesis of polymer A was changed, the same operation and formulation as for polymer A were used to synthesize those having molecular weights of Mn of 480 and 120,000 as measured by GPC. Let these polymers be D and E, respectively.

(Synthesis of Polyol Reactive Polymethylsilsesquioxane) 72 g (0.4 mol) of γ-hydroxypropyltrimethoxysilane and methyltriethoxy were placed in a 2 liter flask equipped with a thermometer, a stirrer and a reflux condenser. 392 g of silane (2.2 mol), 200 g of acetone, 0.002 of hydrochloric acid
Mol and 54 g (3 mol) of water were charged, and the temperature in the flask was adjusted to 60
The temperature was raised to 0 ° C., and the temperature was maintained for 3 hours with stirring. Then 70
After heating to ℃ and reacting for 1 hour, 0.004 mol of KOH was added dropwise, and after reacting for another 2 hours, it was neutralized and washed with water and toluene, and then solvent, water, etc. were added using a rotary evaporator. After removing, a viscous liquid with a viscosity of 900 cps at 25 ° C was quantitatively obtained.

The GPC curve of this product was a single peak, and no residual peak derived from the monomer was observed.
Therefore, the monomer was considered to be completely co-condensed, and the molar ratio of the side chain methyl group and γ-hydroxypropyl group was 22: 4, which was derived from the raw material molar ratio.

This product also has a molecular weight measured by vapor pressure measurement.
The (Mn) was 2,400. This is designated as Polymer F.

(Synthesis of vinyl monomer copolymer) The following composition was placed in a 2 liter flask equipped with a thermometer, a stirrer, and a reflux condenser, and refluxed (85 ° C) for 5 hours in a nitrogen stream. When reacted, the reaction rate by gel permeation chromatography (GPC) is 97%
Became. Methyl methacrylate 25 parts by weight Butyl methacrylate 20 parts by weight 2-Ethylhexyl acrylate 10 parts by weight Hydroxyethyl methacrylate 25 parts by weight Methacrylic acid 15 parts by weight Lauryl mercaptan 3.5 parts by weight Azobisisobutyronitrile 1.5 parts by weight Ethyl acetate 80 parts by weight In this way, a polymer G having a number average molecular weight of 16,000 and a weight average molecular weight of 73,000 was obtained.

For comparison, a polymer G * having a number average molecular weight of 18,000 and a weight average molecular weight of 81,000 by GPC measurement was obtained by the same operation and formulation as the polymer G except that methacrylic acid was removed from the composition during the synthesis of the polymer G. .

For comparison, the molecular weight measured by GPC was the same as that for polymer G except that the amount of lauryl mercaptan added during the synthesis of polymer G was changed.
Polymers H and I were obtained with Mn of 960 and 130,000.

Using the same apparatus as described above, 180 parts by weight of a solution of polymer G in ethyl acetate was added, 30 parts by weight of isocyanate ethyl methacrylate and 0.3 part by weight of dibutyltin dilaurate were added, and the mixture was refluxed in an air stream (85 ° C.). After reacting for 2 hours, the reaction rate by gel permeation chromatography (GPC) was 100%. Let this polymer be J.

For comparison, Polymer J *, K and L were obtained by the same operation and formulation as Polymer J except that Polymer G in the raw material during the synthesis of Polymer J was changed to Polymers G *, H and I, respectively. It was

Further, a polymer having the following composition was used in the same operation as in the synthesis of the polymer G using the same apparatus as that in the synthesis of the polymer G. Methyl methacrylate 20 parts by weight Butyl methacrylate 20 parts by weight Methacryl modified polydimethylsiloxane 15 parts by weight (X-22-174D manufactured by Shin-Etsu Chemical Co., Ltd.) Hydroxyethyl methacrylate 25 parts by weight Acrylic acid 15 parts by weight Lauryl mercaptan 3.5 parts by weight Azobisisobutyronitrile 1.5 parts by weight Ethyl acetate 80 parts by weight Thus, a polymer M having a number average molecular weight of 20,500 and a weight average molecular weight of 87,000 was obtained.

For comparison, the same operation as in Polymer M except that acrylic acid is omitted from the composition at the time of synthesis of Polymer M,
According to the formulation, a polymer M * having a number average molecular weight of 18,000 and a weight average molecular weight of 81,000 measured by GPC was obtained.

Using polymer M as a raw material, the addition reaction of isocyanate ethyl methacrylate to hydroxyl groups was carried out by the same operation and formulation as for polymer J. Let the obtained polymer be N.

Further, using the polymer M * as a raw material, the polymer I
The isocyanate ethyl methacrylate was added to the hydroxyl group by the same operation and formulation. Let the obtained polymer be N *.

Example 1 On a substrate surface obtained by integrally assembling an asbestos calcium silicate plate (thickness: 0.5 mm) with diallyl phthalate resin-impregnated paper by hot pressing,
A resin composition having the following composition was coated using a spray gun so that the coating film thickness would be 30 μm. Polymer A 35 parts by weight Polymer J 19 parts by weight Pentaerythritol tetraacrylate 40 parts by weight Benzophenone 3 parts by weight Ethyl p-dimethylbenzoate 3 parts by weight Toluene 50 parts by weight Next, using a 2 KW high pressure mercury lamp, irradiate at a distance of 10 cm for 5 seconds. To cure the composition. The physical properties of this cured film are shown in Table 1.
Shown in.

Comparative Example 1 A cured film was obtained by the same operation and formulation as in Example 1 except that the polymer A in Example 1 was changed to the polymer B. Table 1 shows the physical properties of this product.

Comparative Example 2 A cured film was obtained by the same operation and formulation as in Example 1 except that the polymer A in Example 1 was changed to the polymer C. Table 1 shows the physical properties of this product.

Comparative Example 3 A cured film was obtained by the same operation and formulation as in Example 1 except that the polymer A in Example 1 was changed to the polymer D. Table 1 shows the physical properties of this product.

Comparative Example 4 A cured coating film was obtained by the same operation and formulation as in Example 1 except that the polymer A in Example 1 was changed to the polymer E. Table 1 shows the physical properties of this product.

Comparative Example 5 A cured film was obtained by the same operation and formulation as in Example 1 except that the polymer J in Example 1 was changed to polymer J *. Table 1 shows the physical properties of this product.

Comparative Example 6 A cured film was obtained by the same operation and formulation as in Example 1 except that the polymer J in Example 1 was changed to the polymer K. Table 1 shows the physical properties of this product.

Comparative Example 7 A cured film was obtained by the same operation and formulation as in Example 1, except that the polymer A in Example 1 was changed to the polymer L. Table 1 shows the physical properties of this product.

Example 2 A resin composition having the following composition was applied to the surface of a medium-density fiberboard having a thin natural wood plate (thickness 0.2 mm) adhered to the surface thereof using a spray gun so that the coating film thickness became 30 μm. Coated. 35 parts by weight of Polymer A 19 parts by weight of Polymer N 40 parts by weight of pentaerythritol tetraacrylate 40 parts by weight of benzophenone 3 parts by weight of ethyl p-dimethylbenzoate 3 parts by weight of toluene 50 parts by weight of 2 KW High pressure mercury lamp at a distance of 10 cm for 5 seconds. To cure the composition. The physical properties of this cured film are shown in Table 1.
Shown in.

Comparative Example 8 A cured film was obtained by the same operation and formulation as in Example 1 except that the polymer N * in Example 2 was used. Table 1 shows the physical properties of this product.

Reference Example 1 Using a spray gun, a resin composition having the following composition was applied to the surface of a medium density fiberboard having a thin natural wood plate (thickness: 0.2 mm) adhered to the surface so that the coating film thickness was 30 μm. Coated. 80 parts by weight of the composition of Example 2 20 parts by weight of the composition of Comparative Example 8 Next, the composition was cured by irradiation with a 2 KW high pressure mercury lamp at a distance of 10 cm for 5 seconds. The physical properties of this cured film are shown in Table 1.
Shown in.

Example 3 A resin composition having the following composition was applied to the surface of a medium density fiberboard having a thin natural wood plate (thickness: 0.2 mm) adhered to the surface thereof using a spray gun so that the coating film thickness became 30 μm. Coated. The mixture was left at room temperature overnight and further heat-cured at 50 ° C. for 2 hours. Polymer F 32 parts by weight Polymer N 16 parts by weight Polyfunctional aliphatic isocyanate 17 parts by weight
(Sumitomo Bayer Co., Ltd., Sumidule N) Dibutyltin dilaurate 0.3 parts by weight Butyl acetate 20 parts by weight Xylene 15 parts by weight Table 1 shows data on the film thickness, surface pencil hardness, and weather resistance of this cured film.

Comparative Example 9 A cured film was obtained by the same operation and formulation as in Example 3 except that the polymer N in Example 4 was changed to the polymer N *. Table 1 shows the physical properties of this product.

Reference Example 2 A resin composition having the following composition was applied to the surface of a medium density fiberboard having a thin natural wood plate (thickness: 0.2 mm) adhered to the surface so that the coating film thickness would be 30 μm. Coated. 70 parts by weight of the composition of Example 3 30 parts by weight of the composition of Comparative Example 9 The mixture was left to stand at room temperature overnight, and further heat-cured at 50 ° C. for 2 hours. Table 1 shows the film thickness, surface pencil hardness, and weather resistance data of this cured film.

[0056]

[Table 1]

[0057]

EFFECT OF THE INVENTION By using the composition for matting coating of the present invention, matting excellent in hardness and weather resistance can be achieved, and further, any matting can be carried out without using fine particles as a matting agent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Arita 5-1 Okawamachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Sho

Claims (2)

[Claims] 1. (A) The following general formula: (In the formula, side chain organic groups R1 and R2 are 50 to 99 mol% of a methyl group,
1 to 40 mol% of the crosslinkable reactive group or the organic group having the crosslinkable reactive group as a substituent and the remaining group has 2 carbon atoms
An alkyl group having 6 to 6 or a substituted or unsubstituted phenyl group, and n represents the degree of polymerization. ) A polyorganosiloxane having a polymethylsilsesquioxane structure as a main component and having a number average molecular weight of 500 to 100,000 and (B) a number average molecular weight of 1,000 to 100,000 and at least a crosslinkable reactive group being a side chain. 1. A matte coating composition comprising a vinyl monomer having the above-mentioned and a vinyl monomer having a carboxylic acid group in a side chain as a part of its constituent components. 2. The matte coating composition according to claim 1, wherein the vinyl monomer copolymer further contains a polydimethylsiloxane structure in a part of the main chain and / or side chain.