JPS6043876B2 - Coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition for improving surface conditions such as surface hardness and chemical resistance of plastic products, wood products, metal products, etc.

Plastic molded productsFor example, thermoplastic resins such as polycarbonate, polymethyl methacrylate, polystyrene, and polyvinyl chloride have excellent lightness, easy processability, and impact resistance.However, on the other hand, they have poor abrasion resistance and solvent resistance. It has the disadvantage that it has poor surface properties, is easily scratched, and is easily attacked by solvents.

As a method to improve these drawbacks, a method has conventionally been used in which the surface is coated with various thermosetting resins.
Surface hardening coating agents used for this purpose include melamine resins, thermosetting acrylic resins, polyester resins, polyurethane resins, and silicone resins. It is difficult to obtain a material with all good physical properties, and one that is fully satisfactory has not yet been obtained. In general, when trying to increase the hardness of a paint film, it tends to lose its flexibility, and cracks may occur in the paint film during hot water resistance tests, etc.
Furthermore, if an attempt is made to increase the flexibility of the coating film, the hardness of the coating film will decrease. The inventors have developed heat resistance,
As a result of repeated research into a coating composition that would give the final coating film both hardness and flexibility without sacrificing properties such as weather resistance, we developed an organic coating composition that reacts with silicon components. It has been found that good results can be obtained by using methylol or melamine, partially or entirely alkyl etherified, and a polyhydric alcohol (hereinafter abbreviated as polyol) as compound components.

That is, the present invention provides: (4) Tetraalkoxy silicon represented by the general formula Sl(0R1)4 (wherein R1 represents an alkyl group having 1 to 4 carbon atoms) and a tetraalkoxy silicon represented by the general formula R2Si(0R3)3( (wherein R2 is a hydrocarbon group having 1 to 6 carbon atoms, and R3 is an alkyl group having 1 to 4 carbon atoms), a copartial hydrolyzate of organotrialkoxysilicon or/and each partial hydrolyzate consisting of a mixture of tetraalkoxy silicon partial hydrolyzate calculated as SiO2 and R2SlOl. The partial hydrolyzate of the organotrialkoxy silicon calculated as 5 and the silicon compound partial hydrolyzate having a weight ratio of 5/95 to 95/5, and (B) the silicon compound partial hydrolyzate calculated as SiO2 in CA). Alkoxy silicon partial hydrolyzate and R2SlOl. For a total of 10 parts by volume of the partial hydrolyzate of organotrialkoxy silicon calculated as 5, methylolmelamine partially or completely alkyl etherified and polyol are added in a gram equivalent ratio of 1:0.5 to 1. This is a coating composition obtained by dissolving 10 to 50 parts of a precondensate mixed with .5 to 50 parts in a solvent.

It is represented by the general formula Si(0R1)4 used in the present invention.
Tetraalkoxy silicon means that the alkoxy group is methoxy,
These include ethoxy, propoxy, butoxy, etc. Further, in the organic trialkoxy silicon compound represented by the general formula R2Si(0R3)3, a hydrocarbon group R having 1 to 6 carbon atoms
2 specifically refers to methyl, ethi. The alkyl group R3 having 1 to 4 carbon atoms is an organic group such as allyl, propyl, butyl, pentyl, hexyl, vinyl, allyl, or phenyl, and the alkyl group R3 having 1 to 4 carbon atoms is a methyl group, an ethyl group, a propyl group, or a butyl group. These silicon compound partial hydrolysates can be obtained by hydrolyzing tetraalkoxy silicon and organic trialkoxy silicon separately or in a mixture in the presence of an acid in a mixed solvent such as water and alcohol. . In some cases, these silicon compound partial hydrolysates are SiCl
It can also be obtained by directly hydrolyzing a silicon chloride such as 4 or RSiCI3. In general, better results are often obtained when these silicon compounds are mixed and co-hydrolyzed at the same time than when they are hydrolyzed separately. The tetraalkoxy silicon partial hydrolyzate calculated as SiO2 obtained in this way and R2SiOl. The ratio of the partial hydrolyzate of organic trialkoxy silicon calculated as 5 is 5/95 to 95 to 5 by weight, more preferably 3
It is 0/70 to 80/20. If the content of tetraalkoxy silicon partial hydrolyzate is less than 5% by weight, the hardness of the coating will decrease,
Practical abrasion resistance is lost and when the content exceeds 95% by weight, the flexibility of the coating film decreases and cracks are likely to occur. Alkyl etherified methylol melamine used together with a silicon component has already been described in many literatures, and there are many commercially available products.

Preferred are hexa(alkoxymethyl)melamines, such as hexa(methoxymethyl)melamine, hexa(ethoxymethyl)melamine, hexa(propoxymethyl)melamine, hexa(isopropoxymethyl)melamine, hexa(butoxymethyl)melamine, Hexa (
Examples include cyclohexyloxymethyl) melamine. Polyols used in the composition of the present invention include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1◆3-propanediol, (1,3-
, 1,4-,2,3-)butanediol, 1●6-hexadiol, 1,8-octanediol, 1,10-decanediol, neopentyl glycol, pentaerythritol, glycerin, sorbitol, each with a molecular weight of 50
These include polyethylene glycol, polypropylene glycol, and ethylene glycol-propylene glycol copolymers.

Molecular weight 5001). When the above polyol is used, flexibility increases, but surface hardness and abrasion resistance tend to decrease. By using the polyol in combination with the silicon component and the alkyetherized methylose melamine in this way, a good coating film having surface hardness, abrasion resistance and flexibility can be obtained.

The desirable mixing range of the pre-condensed mixture of alkyl etherified methylose melamine and polyol in a gram equivalent ratio of 1:0.5 to 1.5 and the silicon component is 10 parts by weight of the silicon component. It is in the range of 10 to 50 saliva parts.

That is, if the mixture of alkyl etherified methylose melamine and polyol or the precondensed mixture is 10 parts by weight or less per 10 parts of the silicon component, the flexibility of the coating film decreases and cracks occur. This is because hardness tends to occur easily, and conversely, if it exceeds 500 parts by weight, the hardness decreases. In addition, in a precondensate of a mixture of alkyl etherified methylol melamine and polyol used together with a silicon component, if the polyol is in excess of the alkyl etherified methylol melamine, unreacted polyol will remain in the coating film, which will reduce the hardness and durability of the coating film. This is not desirable. On the other hand, if the amount of polyol is too small, the coating film will lose its flexibility, making it more likely to crack. The gram equivalent ratio of mixing the alkyl etherified methylol melamine and the polyol melamine is 1:0.5 to 1.5, preferably 1:0.8.
~1.2. Although it is possible to obtain some results by using a mixture of these as is, in order to provide the coating with both hardness and flexibility and to adjust the viscosity of the coating liquid, a mixture of alkyl etherified methylol melamine and polyol is used. It is more preferable to use a precondensate. It has also been found that the proportion of the tetraalkoxy silicon partial hydrolyzate in the coating composition greatly affects the hardness of the coating film.

Taper abrasion hardness (AST) is a method for evaluating the surface hardness of paint films.
MD-1044), but the haze value y after the taper abrasion test of the coating film obtained with the coating composition of the present invention
(%) and S occupying the solid content in the coating composition
There is a nearly linear relationship between the weight x (%) of the tetraalkoxy silicon partial hydrolyzate calculated as iO2, in which as x increases, y decreases. As X increases, the hardness of the film increases and the wear resistance improves, but on the other hand, the flexibility of the film decreases and cracks are more likely to occur in the film. Therefore, it is preferable to keep the value of X within the range of 6 to 45%.
As an organic compound component used together with the silicon component, a mixture of the alkyl etherified methylolmelamine and polyol or a precondensate thereof, an alkyl acrylate or/and alkyl methacrylate (hereinafter abbreviated as alkyl (meth)acrylate), and a hydroxyalkyl Copolymer of acrylate or/and hydroxyalkyl methacrylate (hereinafter abbreviated as hydroxyalkyl (meth)acrylate) or/and N◆
N-dialkylaminoalkyl acrylate, N●N-
dialkylaminoalkyl methacrylate (hereinafter abbreviated as N●base alkylaminoalkyl (meth)acrylate), N●N-dialkylacrylamide and N
-One or more types of N-dialkyl methacrylamide (hereinafter abbreviated as N-N-dialkyl (meth)acrylamide) and one or more types of hydroxyalkyl (meth)acrylate or alkyl (meth)acrylate. It is also possible to use a mixture of copolymers. As the alkyl (meth)acrylate, (meth)acrylic acid esters of alcohols having 1 to 18 carbon atoms can be selected. For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate
Acrylate etc. can be used. As the hydroxyalkyl (meth)acrylate, for example, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, glycerol mono(meth)acrylate, etc. can be used.

N◆N-dialkylaminoalkyl (meth)acrylate includes 2-N-N-dimethylaminoethyl (meth)acrylate, 2-N-N-diethylaminoethyl (
meth)acrylate, 3-N-N-diethylaminopropyl (meth)acrylate, etc. can be used.

As N-N-dialkyl (meth)acrylamide,
N-N-dimethyl (meth)acrylamide, N-N-diethyl (meth)acrylamide, N-N-dibutyl (meth)acrylamide, etc. can be used. As the solvent used for manufacturing the coating composition, alcohols, ketones, esters, ethers, cellosolves, halides, carboxylic acids, aromatic compounds, etc. may be used as one or a mixed solvent of two or more. I can do it.

Especially lower alcohols (e.g. methanol, ethanol,
propanol, butanol), cellosolves (e.g. methyl cellosolve, ethyl cellosolve, butyl cellosolve), lower alkyl carboxylic acids (e.g. formic acid, acetic acid, propionic acid), aromatic compounds (e.g. toluene, xylene) and esters (e.g. ethyl acetate, acetic acid). It is preferable to use solvents such as (butyl) alone or as a mixed solvent.
The composition of the present invention becomes a highly hard coating film by heating and curing at a temperature of 70°C or higher after being coated on a substrate.
Furthermore, in order to lower the curing temperature and shorten the curing time,
It is useful to use curing accelerating catalysts such as acids such as hydrochloric acid, phosphoric acid toluenesulfonic acid, ammonium hydrochloric acid such as ammonium chloride, ammonium nitrate, ammonium thiocyanate, etc. If necessary, a commercially available flow control agent can be added to this to obtain a smooth coating film. Even small amounts of these curing accelerating catalysts and flow control agents are sufficient, and the purpose of addition can be achieved at 5% by weight or less, respectively, based on the solid content of the composition. The coating of the composition of the present invention is coated by a commonly used coating method such as dipping, spraying, roller coating, or flow coating, and is then cured by baking at a temperature of 70°C or higher. It is possible to obtain a good coating film that has both properties of flexibility.

The composition of the present invention can be applied to plastic substrates such as polycarbonate, polymethyl methacrylate, polystyrene and polyvinyl chloride.

If adhesion is a particular problem, primer treatment can provide a coating film with sufficiently effective adhesion. The present invention will be explained in more detail below with reference to Examples.

Examples 1 to 12 and Comparative Examples 1 to 4 (1) Preparation of co-partial hydrolyzate solution of tetraethoxy silicon and methyltriethoxy silicon (component 1) Tetraethoxy silicon in isopropyl alcohol 70y, 66.7y and methyltriethoxy 33.3 da of silicon was dissolved, and 30 y of 0.05 N hydrochloric acid aqueous solution was added and stirred at room temperature to effect hydrolysis.

After the reaction, the mixture was aged at room temperature for 20 hours or more. The resulting solution is S
Tetraethoxy silicon partial hydrolyzate 9.6% calculated as iO2, CH3SiOl. It contained 6.3% of methyltriethoxy silicon partial hydrolyzate calculated as 5. ') Preparation of a co-partial hydrolyzate solution of tetraethoxy silicon and methyltriethoxy silicon (component ■) Dissolve isopropyl alcohol 68y1 tetraethoxysilicon 38y and methyltriethoxysilicon 72d in a hydrolysis container equipped with a reflux condenser. Further, 36 V of a 0.05N aqueous hydrochloric acid solution was added, and the solution was heated under reflux for 5 hours while stirring to perform hydrolysis.

After the reaction, the mixture was cooled to room temperature to obtain a copartial hydrolyzate solution.
The resulting solution contained 5.1% tetraethoxy silicon partial hydrolyzate calculated as SlO2, CH3SiOl. , methyltriethoxy silicon partial hydrolyzate 1
It contained 2.6%.

() Preparation of co-partial hydrolyzate solution of tetraethoxy silicon and methyltriethoxy silicon (Component ■) Dissolve 88 y of tetraethoxy silicon and 16 y of methyltriethoxy silicon in 60 y of isopropyl alcohol, and further dissolve 36 y of 0.05N hydrochloric acid aqueous solution.
y was added and stirred at room temperature to perform hydrolysis.

After the reaction, the mixture was aged at room temperature for 20 hours or more. The obtained solution is
Tetraethoxy silicon partial hydrolyzate, calculated as SiO2, 12.8%, CH3SiOl. Contained 3.0% methyltriethoxy silicon partial hydrolysis, calculated as 5. 1) Hexa(methoxymethyl)melamine and 1●4
Preparation of monobutanediol precondensate solution (precondensate solution, a) hexa(methoxymethyl)melamine 78y and 1
・4-butanediol 54y (y equivalent ratio 1:1) to 8
0.2 ml of 5% phosphoric acid was added and reacted at 130 to 140°C to form a prepolymer with a molecular weight of about 5000, and ethyl cellosolve was added to form a solution with a solid content of 75% by weight.

)) Preparation of hexa(methoxymethyl)melamine and 1,6-hexanediol precondensate solution (precondensate solution,
b) Hexa(methoxymethyl)melamine 78q and 1.6
-85 to hexanediol 71y (y equivalent ratio 1:1)
% phosphoric acid was added thereto, and the mixture was reacted at 130 to 140°C to form a solution having a solid content of 9 weight % and ethyl cellosolve was added as a prepolymer having a molecular weight of about 500.

(6) Preparation of hexa(methoxymethyl)melamine and diethylene glycol precondensate solution (precondensate solution, c
) A prepolymer with a molecular weight of about 30,000 was made from hexa(methoxymethyl)melamine 65y and diethylene glycol 53q (1:1 in g equivalent ratio) and ethyl cellosolve was added to make a solution with a solid content of 9% by weight.

(7) Preparation of hexa(methoxymethyl)melamine and triethylene glycol precondensate solution (precondensate solution,
d) 8 to 260 y of hexa(methoxymethyl)melamine and 300 y of triethylene glycol (1:1 in y equivalent ratio)
Added 0.2 mL of 5% phosphoric acid and reacted at 130 to 140°C until the amount of distillate reached 42.7y to form a prepolymer, and added ethyl cellosolve to form a solution with a solid content of 9% by weight. .

(8) Hexa(methoxymethyl)melamine and molecular weight, 2
Preparation of 00 polyethylene glycol precondensate solution (
Precondensate solution, e) Hexa(methoxymethyl)melamine 520y and polyethylene glycol 8 with a molecular weight of 200
Add 0.4 mL of 85% phosphoric acid to 00V (f equivalent ratio: 11), react at 130-140°C until the amount of distillate reaches 86y, form a prepolymer, and add ethyl cellosolve to solidify. A solution with a mold content of 9% saliva was prepared.

(9) Preparation of paint Add the solutions of component 1, component (2), and component (2) described above. A precondensate of hexa(methoxymethyl) melamine and polyol or hexa(methoxymethyl) melamine and polyol, and additives such as a curing accelerator and a flow control agent are added, and the solid content is 10 to 40% by weight. Ethyl cellosolve was added to prepare paints as shown in Table 1.

0 coating and performance test of coated products The above coating was applied to a polycarbonate plate having a thickness of 3T0n which had been cleaned in advance, and was heated and dried in a hot air dryer at 130° C. for 2 hours to harden it.

The painted polycarbonate plates were subjected to the following tests. (
a) Adhesion: In the so-called cross-cut tape test, 11 parallel lines were drawn vertically and horizontally at 1TrrIn intervals on the painted surface using a knife to cross-cut 10C@ squares, and cellophane adhesive tape was adhered on top of the cross-cuts. After peeling off the tape, the number of squares that did not peel off among the 10 grid squares of the coating film was indicated. (b) Abrasion Resistance Steel Wool Test The scratch resistance was examined by rubbing with #0000 steel wool and judged as follows.

A: No scratches even with strong friction B: Slight scratches with strong friction C: Scratches even with weak friction Taper wear test According to ASTM D-1044,
A CS-10F wheel was used in a taper type abrasion tester, and the haze value (%) was expressed after 5 rotations under a 500y load.

(c) Hot water resistance: The state of the coating film after immersion in boiling water was examined.

(d) Flexibility: Sample at room temperature (50T!Tm x 100 order x
Thickness 0.7? ) was evaluated based on the occurrence of cracks when bent to a radius of curvature of 15TmIfL.

(e) Heat cycle test two samples at -20℃ and 80℃
The state of the coating film was examined after 10 times of storage for 2 hours each.

The etherified methylolmelamine in the table is hexa(methoxymethyl)melamine.

The solid content of precondensate solution a was 75% by weight, and B. ．． c.
．． ．． The solid content of dNe is %wt. Example 12 Add 0.4 da of azobisisobutyronitrile to ethyl cellosolve 320y12-hydroxyethyl methacrylate 36y1 dimethylaminoethyl methacrylate 44q and react at 90°C to copolymerize 2-hydroxyethyl methacrylate and dimethylaminoethyl methacrylate. A combined solution was obtained.

Claims (1)

[Claims] 1 (A) General formula Si(OR^1)_4 (However, in the formula R^
1 represents an alkyl group having 1 to 4 carbon atoms) and the general formula R^2Si(OR^3)_3(
However, in the formula, R^2 is a hydrocarbon group having 1 to 6 carbon atoms, and R^3 is an alkyl group having 1 to 4 carbon atoms. Consisting of a mixture of partial hydrolysates, tetraalkoxy silicon partial hydrolysates calculated as SiO_2 and R^2S
iO_1_. The weight ratio of the partial hydrolyzate of organic trialkoxy silicon calculated as _5 is 5/95 to 95.
A silicon compound partial hydrolyzate consisting of /5, and (B) (A
) and the tetraalkoxy silicon partial hydrolyzate calculated as SiO_2 in R^2SiO_1_. Total of partial hydrolysates of organotrialkoxysilicon calculated as _5 1
00 parts by weight, 10 to 500 parts by weight of a precondensate of a mixture of methylolmelamine partially or completely alkyl etherified and polyhydric alcohol in a gram equivalent ratio of 1:0.5 to 1.5. A coating composition obtained by dissolving it in a solvent.