JP2009191130A - Coating agent composition for automotive hard surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating agent composition for automotive hard surfaces which efficiently forms a film on an automotive hard surface to impart initial water repellency, can continue the effect over a long period of time, and can suppress adhesion of dirt over time. <P>SOLUTION: The coating agent composition for automotive hard surfaces comprises (A) a hydrolytic condensation product of a mixture of alkyltrialkoxysilanes and/or alkyltrichlorosilanes different in alkyl chain length and (B) a sufficient amount of a curing agent to cure the composition, wherein 20-90 mol% of the alkyl groups in the mixture are 1C-3C alkyl groups and 10-80 mol% of the remaining alkyl groups are 4C-12C alkyl groups. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coating composition for an automotive painted surface that imparts water repellency to an automotive painted surface, reduces adhesion of dirt, and the effect lasts for a long time.

  Until now, organosilicon compounds such as silane compounds and organopolysiloxanes have been known to impart heat resistance and weather resistance to surfaces, and gloss and water repellency by applying them to various substrates as surface modifiers. ing. In particular, the hydrolysis condensate of a silane having a room temperature curing type alkoxy group can form a cured film on the surface of the substrate at room temperature, and therefore is widely used in applications where heat cannot be applied. Water repellents with wax or water-based emulsions are widely known for the purpose of giving water repellent function and gloss to the painted surface of automobiles. As a protective agent, a coating agent containing a silane compound or an organopolysiloxane has been proposed.

  For example, a polishing agent containing a room temperature curable silicone resin, isopropyl alcohol and water (see Patent Document 1), and an automotive polishing agent containing a moisture curable polysiloxane, a tin catalyst, a solvent and silicone oil (see Patent Document 2). A water repellent containing a fluoroalkyl group-containing alkoxysilane having an alkoxy group, a hydrolysis catalyst, an alcohol, a hydrocarbon solvent, and volatile silicone is known (see Patent Document 3).

JP-A-61-34081 JP-A-10-36771 JP 11-349930 A

  These compositions according to the prior art can give water repellency and gloss in the initial stage when used on automobile painted surfaces, but their effects are poor in sustainability, and further improvement is required in the persistence of the dirt adhesion reducing effect. It was done.

  In view of the above circumstances, the present invention can efficiently form a film on a painted surface of an automobile, impart initial water repellency, and at the same time maintain its effect over a long period of time, and suppress contamination due to aging. It is an object of the present invention to provide a coating agent for automobile painted surfaces.

In order to solve the above-mentioned problems, the present inventor has conducted extensive research on the structure and composition of the organosilicon compound of the coating agent for automobile painted surfaces. As a result, the alkyltrialkoxysilane or alkyltrichlorosilane having a specific alkyl chain length has been studied. The present invention finds that the problem is solved by a composition obtained by combining a curing catalyst with a hydrolytic condensate of a mixture in which the chain length of an alkyl group bonded to a silicon atom is different within a molecule or between molecules. It came to make. That is, the present invention
[1] (A) a hydrolytic condensate of a mixture of alkyltrialkoxysilanes and / or alkyltrichlorosilanes having different alkyl chain lengths, and (B) a curing catalyst in an amount sufficient to cure the composition, 20 to 90 mol% of the alkyl groups bonded to the silicon atom of the mixture are the same or different alkyl groups having 1 to 3 carbon atoms, and 10 to 80 mol% of the remaining alkyl groups are the same or different. A coating composition for automobile painted surfaces, which is an alkyl group having 4 to 12 carbon atoms.
[2] The composition according to [1], wherein the hydrolysis condensate of (A) has a viscosity of 5 to 100 mPa · s.
[3] The composition according to any one of [1] or [2], wherein 0.1 to 30 parts by weight of (C) dry silica is added to 100 parts by weight of the hydrolyzed condensate of (A).

  The composition of the present invention effectively forms a film on a painted surface of an automobile, imparts initial water repellency to the painted surface, maintains the water repellency performance over a long period of time, and enhances the durability against dirt adhesion reduction. Play.

Hereinafter, the present invention will be specifically described. The hydrolysis condensate which is the component (A) of the present invention is obtained by hydrolytic condensation of a mixture of alkyltrialkoxysilanes represented by the general formula (1) and / or alkyltrichlorosilanes having different alkyl chain lengths. is there.
R ¹ Si (X) ₃ (1)
R ¹ in Formula (1) is an alkyl group having 1 to 12 carbon atoms which may be the same or different, and X is an alkoxy group represented by OR ² or a chlorine atom.

Examples of R ¹ in formula (1) are methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, etc., and these alkyl groups are linear It may be branched or branched. As a mixture, 20 to 90 mol% of R ¹ is selected from short-chain alkyl groups having 1 to 3 carbon atoms, and the remaining 10 to 80 mol% of R ¹ is composed of long-chain alkyl groups having 4 to 12 carbon atoms. It is necessary to be selected to be. Each of the short-chain or long-chain alkyl groups may be one kind or two or more kinds. If the long chain alkyl group having 4 or more carbon atoms is not included, there is a problem that the water repellency is not sufficient, and if the long chain alkyl group has 12 or more carbon atoms, the condensation curing rate is slowed due to steric hindrance. When there is an uncured part, it is not preferable because the film strength is lowered. Further, when the mol% of the long-chain alkyl group having 4 to 12 carbon atoms contained is 10 mol% or less, sufficient water repellency cannot be expressed, and when it exceeds 80 mol%, hydrolysis is unlikely to occur. Therefore, there is a problem as a room temperature curing type coating agent for automobile painted surfaces. A preferable thing of a C1-C3 short chain alkyl group is a methyl group, and a preferable thing of a C4-C12 long-chain alkyl group is a C5-C10 alkyl group.

If X in formula (1) is an alkoxy group represented by the general formula OR ^2, examples of ^{R 2} include a methyl group, an ethyl group, n- propyl group, an isopropyl group, n- butyl group, an isobutyl group, It is a C1-C6 alkyl group such as a t-butyl group, n-pentyl group, isopentyl group, neopentyl group, t-pentyl group, n-hexyl group, and may be the same or different in the molecule. Of these, preferred R ² is an alkyl group having 1 or 2 carbon atoms. X in the general formula (1) may partially contain a hydroxyl group.

  The hydrolyzed condensate (A) of the present invention can be produced by a method known to those skilled in the art of hydrolyzing and condensing alkyl alkoxysilanes or alkylchlorosilanes in the presence of a catalyst. Hydrolysis condensation of alkylalkoxysilanes is carried out by using a hydrocarbon solvent such as toluene in the presence of methanol, alcohols such as ethanol and propanol, and water, and simultaneously performing hydrolysis and condensation using an alkali or acid catalyst. It is obtained by distilling off alcohols and solvents after neutralizing. In the case of hydrolytic condensation of alkylchlorosilanes, hydrogen chloride generated by hydrolysis serves as a catalyst and is produced in the same manner as in the case of alkylalkoxysilanes. Even if a small amount of alkyltrialkoxysilane by-produced when unreacted alkyltrialkoxysilane or alkyltrichlorosilane is used, the effect of the present invention is not particularly disturbed.

  In general, hydrolysis condensates obtained from alkylalkoxysilanes or alkylchlorosilanes having a long alkyl chain length exhibit high water repellency but promote soil adhesion, and impair soil resistance especially in the long term. On the other hand, when the alkyl chain length is short, it is known that a hard film can be formed with a high condensation rate, so that it is excellent in resistance to dirt adhesion but poor in water repellency. By using the hydrolyzed condensate of a specific alkyl chain length combination of the present invention, it exhibits higher water repellency than the midpoint of the contradictory performance effects of both short chain and long chain, and adheres to dirt. As a result, a synergistic effect of maintaining an excellent effect can be obtained. The silane used in the present invention is an alkyltrialkoxysilane or an alkyltrichlorosilane trifunctional silane, but a dialkyl dialkoxysilane or a dialkyldichlorosilane bifunctional silane cannot have a three-dimensional network structure. There is a problem that the film formed from the obtained hydrolysis condensate is weak. In addition, when a tetrafunctional silane such as tetraalkoxysilane is used, an alkyl group cannot be included, and thus water repellency is hardly exhibited. In addition, since there are four condensation reactive groups, it takes time to condense, and there is a problem that uncured alkoxy groups and hydroxyl groups after hydrolysis are likely to remain, resulting in poor water repellency. However, silanes other than trifunctional silanes can be used in small amounts as long as the object of the present invention is not impaired.

  Specific examples of such alkyltrialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltrimethoxysilane. Ethoxysilane, pentyltrimethoxysilane, pentyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, nonyltrimethoxysilane, nonyltri Ethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, undecyltrimethoxysilane, undecyltriethoxysilane, dodecylto Silane, a dodecyloxy triethoxy silane and the like. Specific examples of the alkyltrichlorosilane include methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, butyltrichlorosilane, pentyltrichlorosilane, hexyltrichlorosilane, heptyltrichlorosilane, octyltrichlorosilane, nonyltrichlorosilane, decyltrichlorosilane, Examples include undecyltrichlorosilane and dodecyltrichlorosilane. These alkyl groups may be linear or branched.

  The viscosity of the hydrolysis condensate of (A) is preferably 5 to 100 mPa · s, more preferably 5 to 50 mPa · s. When the viscosity is 5 mPa · s or less, there is a problem that the glossiness becomes poor because the coating is thin and does not become a sufficient amount to form a film. Further, when the viscosity is 100 mPa · s or more, the construction becomes heavy, and it becomes difficult to perform the uniform construction, so that there is a problem that spots are easily formed.

  In the coating composition for an automotive painted surface of the present invention, the curing catalyst of component (B) accelerates the condensation curing reaction of component (A) at room temperature to cure the film. Examples of such catalysts include metal salts of carboxylic acids such as alkyl titanates, tin octylate and dibutyltin dilaurate, dioctyltin dimaleate; amine salts such as dibutylamine-2-hexoate, dimethylamine acetate and ethanolamine acetate; acetic acid Quaternary ammonium salts of carboxylic acids such as tetramethylammonium; amines such as tetraethylpentamine; N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxy Amine-based silane coupling agents such as silane; acids such as p-toluenesulfonic acid, phthalic acid and hydrochloric acid; aluminum compounds such as aluminum alkoxide and aluminum chelate; alkali catalysts such as potassium hydroxide; tetraisopropyl titane , Tetrabutyl titanate, there are titanium compounds such as titanium tetra acetyl acetonate, as long as it is effective in promoting the condensation reaction is not particularly limited. The amount of such a curing catalyst used is an amount sufficient to promote the condensation reaction. For example, in the case of a titanium compound, the amount used is 0.5 with respect to 100 parts by weight of component (A). ~ 5 parts by weight.

  Dry silica can be further blended in the coating composition for an automotive painted surface of the present invention. A dry silica produced by a method known to those skilled in the art can be used. For example, a mixture of vaporized silicon tetrachloride and hydrogen is burned in air at 1000 to 1200 ° C. or higher, and is about 10 nm. Dry silica synthesized by a combustion method to obtain fine particles, dry silica is hydrophobized with a surface treatment agent and water vapor is heated to about 400 ° C. together with an inert carrier gas, and the dry silica surface has hydrophilic silanol groups and Examples thereof include hydrophobic dry silica synthesized by reacting a hydrophobized surface treatment agent. Examples of the hydrophobizing surface treatment agent include organopolysiloxane, organopolysilazane, chlorosilane, and alkoxysilane. In the present invention, the dry silica is particularly preferably hydrophobic dry silica. These silicas may be used alone or in combination of two or more.

  In the present invention, dry silica is a component that improves initial and persistent water repellency. In general, it is known that uniform unevenness is formed on a base material by fine particle powder and water repellency is imparted by a lotus leaf effect. However, even in the present invention, the lotus leaf effect can be achieved by adding dry silica. It is considered that the water repellency is improved by the effect formed above. In addition, even in the case where uniform unevenness is not formed and the lotus leaf effect is not formed, the water repellency is improved by relatively increasing the number of hydrophobic groups by dry silica. Conceivable.

  It is necessary that the dry silica is blended in an amount of 0.1 to 30 parts by weight with respect to 100 parts by weight of the component (A). If it is less than 0.1 parts by weight, the effect of improving water repellency is not obtained because the amount of dry silica added is not sufficient, and if it exceeds 30 parts by weight, the particles become conspicuous on the surface and the problem of deteriorating the aesthetics or the whole system Since the viscosity of the resin increases, there is a problem that workability is deteriorated.

  The dry silica can be added at the time of condensation of the alkyltrialkoxysilane or alkyltrichlorosilane, or can be added after the condensation. There is no restriction | limiting in particular in a mixing method, It can mix by a normal method.

  The coating agent composition for automobile painted surfaces of the present invention can be used by diluting with various organic solvents for ease of handling. The type of organic solvent is not particularly limited as long as it can dissolve or disperse components (A) and (B). For example, lower aliphatic alcohols such as methanol, ethanol, isopropanol, n-butanol, and isobutanol; ethylene Ethylene glycol derivatives such as glycol, ethylene glycol monobutyl ether and ethylene glycol monoethyl ether; diethylene glycol derivatives such as diethylene glycol and diethylene glycol monobutyl ether; hexane, heptane, n-octane, iso-octane, nonane, decane, undecane, dodecane, etc. Aliphatic hydrocarbons; Aromatic hydrocarbons such as toluene and xylene; Petroleum solvents such as kerosene, mineral spirits, liquid paraffin, and industrial gasoline; Cyclotetrasiloxane, cyclic methyl siloxanes such as dodecamethylcyclohexasiloxane; silicone solvents such as dimethyl polysiloxane of a low viscosity and the like.

  In the coating agent composition for automobile painted surfaces of the present invention, an ultraviolet absorber, an antioxidant, a light stabilizer, a leveling agent, a thickener, a fungicide, a fungicide, A fragrance | flavor, a rust preventive agent, a photocatalyst, an antifoamer, etc. can be added secondary.

  The coating composition for automobile painted surfaces of the present invention can be produced by stirring and mixing at room temperature using a stirrer such as a homomixer, ultradisperser, high-pressure homogenizer, or three-one motor.

  The coating composition for an automotive painted surface of the present invention may be applied directly to the painted automotive surface with a brush, cloth, sponge, nonwoven fabric, paper, or the like, or a spray or the like can be used. Moreover, as a method of drying and curing, it may be left to dry at room temperature, or may be outdoor drying or heat drying.

  The coating agent composition for automobile painted surfaces of the present invention can be used as a coating agent for hard substrates such as automobile glass, tires, side mirrors, rear mirrors, tiles and glass in addition to automobile painted surfaces.

  The present invention will be specifically described based on examples, but the present invention is not limited to the following examples. The evaluation methods performed in the examples are as follows.

<Viscosity measurement>
The viscosity of the hydrolysis condensate (A) was measured at a constant temperature of 25 ° C. Using Brookfield's BROOKFIELD DV-II + Pro cone plate type, set the sample (about 0.5 ml), and set the shear rate and cone plate (CP-40 or CP-52) so that the torque is about 50%. The value was set and the value 2 minutes after the start of rotation was taken as the viscosity measurement value.

<Application method to test piece>
An adjustment solution in which 10 parts by weight of a coating agent composition for automobile painted surfaces was diluted with 90 parts by weight of mineral spirit was used. Cationic electrodeposition-coated single-sided melamine baking coating plate (JIS G3141 (SPCC, SD) 0.8 mm x 70 mm x 150 mm) was used as a test piece (test piece initial contact angle: 82 °), and diluted adjustment liquid (about 1 ml) was used as a sponge. Apply with, lightly wipe with a towel, and leave at room temperature for 20 minutes. After standing, it was thoroughly wiped with a dry towel and allowed to stand overnight at room temperature to cure the adjustment solution. The finished test piece was used as a test piece after application.

<Initial water repellency evaluation method>
The initial water repellency of the test piece after application was determined by measuring the contact angle. Contact angle measuring device (Kyowa Interface Science Co., Ltd. Contact angle meter CA-X150 type, measurement conditions: room temperature, drop of distilled water; approx. ) Was measured and the average value was determined.
The evaluation criteria are as follows.
◎ (Excellent water repellency): Contact angle is 95 ° or more ○ (Good water repellency): Contact angle is 85 ° or more and less than 95 ° x (Inferior water repellency): Contact angle is less than 85 °

<Water repellent durability evaluation method>
The test specimen after application after the initial water repellency evaluation is attached to a stand installed outdoors so as to be perpendicular to the ground, and exposed for 6 months in a natural environment. After exposure, dust on the surface of the test piece was gently dropped under running tap water, and after the surface was dried, the water repellency was evaluated by contact angle measurement. The contact angle (°) was determined using a contact angle measuring device (Kyowa Interface Science Co., Ltd., contact angle meter CA-X150 type, measurement conditions: room temperature, drop of distilled water; approximately 1.8 μL). The average value was obtained by measurement. The evaluation criteria are the same as the initial water repellency evaluation criteria.

<Stain adhesion evaluation method>
After application, the brightness of the test piece is measured in advance with a color difference meter (Tokyo Denshoku Co., Ltd., color difference meter MODEL TC-PIII, measurement condition: room temperature). A test piece is attached to a stand installed outdoors at a right angle to the ground and exposed for 6 months in a natural environment. After exposure, the dust on the surface of the test piece is gently dropped under running tap water, and after the surface is dried, the brightness of the test piece is measured with a color difference meter. It was calculated by the calculation formula.
Dirt adhesion rate (%) = 100X ((measured value after exposure) − (measured value before exposure)) / ((measured value after exposure to untreated product) − (measured value before exposure to untreated product))
The evaluation criteria are as follows.
○: Dirt adhesion rate of less than 140% ×: Dirt adhesion rate of 140% or more
When the dirt adhesion rate exceeds 130%, a color difference starts to appear visually, and when it exceeds 150%, it can be observed that the surface is completely black.

[Example 1]
Hydrolyzed condensate (viscosity: 28 mPa · s) of alkyltrimethoxysilane (alkyl group is octyl group: 20 mol%, methyl group: 80 mol%) and curing catalyst (tetrabutyl titanate) were blended as shown in Table 1. Using the composition, a test piece after application was obtained according to the method of application to the test piece. Table 2 shows the evaluation results of evaluation according to the initial water repellency evaluation method, the water repellency persistence evaluation method, and the dirt adhesion evaluation method.

[Example 2]
Hydrolysis condensate (viscosity: 28 mPa · s) of alkyltrimethoxysilane (alkyl group is octyl group: 20 mol%, methyl group: 80 mol%), curing catalyst (tetrabutyl titanate), dry silica (surface hydrophobized silica. Using a composition having a hydrophobization rate of 99.5% or more) as shown in Table 1, a test piece after application was obtained in accordance with the method of application to the test piece. Table 2 shows the evaluation results of evaluation according to the initial water repellency evaluation method, the water repellency persistence evaluation method, and the dirt adhesion evaluation method.

[Comparative Example 1]
Using a composition in which an alkyltrimethoxysilane (alkyl group is methyl group: 100 mol%) hydrolyzed condensate (viscosity 26 mPa · s) and a curing catalyst (tetrabutyl titanate) are blended as shown in Table 1, According to the coating method, a test piece was obtained after coating. Table 2 shows the evaluation results of evaluation according to the initial water repellency evaluation method, the water repellency persistence evaluation method, and the dirt adhesion evaluation method.

  The coating agent for an automotive painted surface of the present invention is useful because it imparts initial water repellency to the painted surface, maintains its water repellency performance over a long period of time, and enhances durability against dirt adhesion reduction.

Claims (3)

  (A) a hydrolytic condensate of a mixture of alkyltrialkoxysilanes and / or alkyltrichlorosilanes having different alkyl chain lengths, and (B) a curing catalyst in an amount sufficient to cure the composition, 20 to 90 mol% of the alkyl groups bonded to the atoms are alkyl groups having 1 to 3 carbon atoms which may be the same or different, and 10 to 80 mol% of the remaining alkyl groups may be the same or different A coating composition for automobile painted surfaces, which is an alkyl group of formula 4-12.   The composition according to claim 1, wherein the hydrolysis condensate of (A) has a viscosity of 5 to 100 mPa · s.   The composition according to any one of claims 1 and 2, comprising 0.1 to 30 parts by weight of (C) dry silica with respect to 100 parts by weight of the hydrolysis condensate of (A).