JPS6029752B2 - Coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides coatings suitable for improving surface properties such as surface hardness, abrasion resistance, and chemical resistance of plastic products, wood products, metal products, or their paint-coated products. The present invention relates to a composition.

Generally, plastic molded bodies such as polycarbonate,
Polymethyl methacrylate, polystyrene, polyvinyl chloride, ABS resin, etc. are used in large quantities due to their advantages such as light weight, easy processing, and impact resistance, but their surface hardness is 4. It has drawbacks such as being easy to stick to, and easily swelling and dissolving when it comes into contact with solvents.

Although many proposals have been made to improve these drawbacks, the reality is that none of them have been fully satisfactory. In order to improve these drawbacks, the present inventors have improved surface hardness, abrasion resistance, and chemical resistance, as well as heat resistance,
In order to obtain a coating film with excellent hot water resistance, heat cycle resistance and weather resistance, a co-partial hydrolyzate of a tetraalkoxy silicon and an organosilicon compound or/and a mixture of each partial hydrolyzate, proposed a coating composition obtained by dissolving a copolymer of 'B' alkyl acrylate or alkyl methacrylate and hydroxyalkyl acrylate or hydroxyalkyl methacrylate and etherified methylolmelamine in a solvent (JP-A-51-33128; Tokuken Showa 50-11285
No. 82).

The composition has excellent adhesion to acrylic base materials, such as polymethyl methacrylate resin, but has excellent adhesion to resins other than acrylic resins, such as transparency and impact resistance, and has good surface hardness. Therefore, it tends to have slightly poor adhesion to polycarbonate resins that are expected to be used as substitutes for inorganic glass. The present inventors have arrived at the present invention as a result of intensive research aimed at developing a composition with improved adhesion not only to acrylic resins but also to other resins, especially polycarbonate resins.

That is, the present invention relates to tetraalkoxy silicon represented by the general formula Si(ORI)4 (wherein RI represents an alkyl group having 1 to 4 carbon atoms) and the general formula R2Si(OR3)3 (however, in the formula, (R2 is a hydrocarbon group having 1 to 6 carbon atoms, R3 is an alkyl group having 1 to 4 carbon atoms) and/or a mixture of partial hydrolysates and/or organic trialkoxysilicon. Then, the above partial hydrolyzate of tetraalkoxy silicon calculated as Si02 and R2Si○,
．． 100 parts by weight of a partial hydrolyzate of a fluorine compound having a weight ratio of 5/95 to 95/5 with respect to the partial hydrolyzate of the organic trialkoxy silicon calculated as 5 (However, Si02 and R are also i0, . 5) and '
B'1) N,N-dialkylaminoalkyl acrylate or/and N,N-dialkylaminoalkyl methacrylate (hereinafter referred to as N,N-dialkylaminoalkyl acrylate or/and N,N-dialkylaminoalkyl methacrylate)
abbreviated as alkyl (meth)acrylate) or N
, N-dialkyl acrylamide or/and N,N
2) hydroxyalkyl acrylate or/and hydroxyalkyl methacrylate (hereinafter referred to as hydroxyalkyl (meth)acrylate); ) or alkyl acrylate or/
and 10 to 40 parts by weight of a copolymer with alkyl methacrylate (hereinafter abbreviated as alkyl (meth)acrylate) or a mixture thereof (hereinafter abbreviated as acrylic copolymer) and etherified methylol. This is a coating composition obtained by dissolving 0 to 300 parts by weight of melamine in a solvent.

Among the wind components used in the present invention, tetraalkoxy silicon is a compound represented by the general formula Si(ORI)4,
Examples include tetramethoxy silicon, tetraethoxy silicon, tetrapropoxy silicon, and tetrabutoxy silicon.

In addition, organic trialkoxy silicon is the general formula 2Si (
A compound represented by OR3)3, where R2 is a hydrocarbon group having 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl, bentyl, hexyl, vinyl, allyl, phenyl, etc.
3 is a carbon number of 1 to methyl, ethyl, propyl, butyl, etc.
4 is an alkyl group. Preferred specific examples of such organic trialkoxy silicon include methyltrimethoxy silicon, methyltriethoxy silicon, methyltributoxy silicon, ethyltriethoxy silicon, vinyltrimethoxy silicon, vinyltriethoxy silicon, phenyltrimethoxy silicon, and phenyltriethoxy silicon. etc. can be mentioned. Partial hydrolysates of these silicon compounds can be prepared by combining one or more tetraalkoxy silicones and one or more organic trialkoxy silicones separately or in combination, for example, with lower alcohols such as ethyl alcohol and butyl alcohol. It can be obtained by hydrolyzing in alcohol in the presence of an acid catalyst, adding 1/2 or more mole amount of water based on the total mole amount of alkoxy groups in the silicon compound used.

In this case, it is known that a condensation reaction occurs simultaneously with hydrolysis. Further, partial hydrolysates of these silicon compounds can also be obtained by a method of directly hydrolyzing silicon chlorides such as SIC14 and RSiC13. Generally, it is often better to mix these silicon compounds and co-hydrolyze them simultaneously than to hydrolyze them separately. The usage ratio of the partial hydrolyzate of these silicon compounds obtained in this way is 5 to 95% by weight of the tetraalkoxy silicon partial hydrolyzate calculated as Si02.
For R2Si○, . 95 to 5% by weight of organotrialkoxy silicon calculated as 5%.

At this time, the tetraalkoxy silicon partial hydrolyzate was 95% by weight.
If this value is exceeded, the flexibility of the paint film becomes weak and cracks are likely to occur. On the other hand, if the hydrolyzate is less than 5% by weight, the wear resistance decreases. Of the 'B} components used in the present invention, the acrylic copolymer is composed of 1) N,N-dialkylaminoalkyl (meth)acrylate or N,N-dialkyl (meth)acrylamide, or a mixture thereof, and 2) hydroxyalkyl. Bulk polymerization and emulsification of (meth)acrylate, alkyl (meth)acrylate, or a mixture thereof in the presence of a radical polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide, di-tetrabutyl peroxide, etc. It can be obtained by polymerization, suspension polymerization or solution polymerization.

N,N-dialkylaminoalkyl (meth)acrylate is a compound represented by the general formula, where R4 is hydrogen or a methyl group, R5 is an alkylene group having 1 to 4 carbon atoms, and R6 and R7 are each having 1 to 4 carbon atoms. It has an alkyl group.

Specific examples include 2-N,N-dimethylaminoethyl (meth)acrylate, 2-N,N-diethylaminoethyl (meth)acrylate, 3-N,N-dimethylaminoethyl (meth)acrylate, and 3-N,N-dimethylaminoethyl (meth)acrylate. Tyraminopropyl (meth)acrylate and the like can be used. N,N dialkyl (meth)acrylamide is a compound represented by a single-pronged formula, in which R4 is hydrogen or a methyl group, and R8 and R9 are alkyl groups having 1 to 4 carbon atoms.

Specific examples include N,N-dimethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N
-Dibutyl (meth)acrylamide and the like can be used. Hydroxyalkyl (meth)acrylate is a compound represented by the general formula, where R4 is hydrogen or a methyl group, RI.

is an alkyl group having 2 to 4 carbon atoms and having a hydroxyl group. For example, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, glycerol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, etc. can be used. Furthermore, alkyl (meth)acrylate is a compound represented by the general formula, where R4 is hydrogen or a methyl group, and RII has 1 to 1 carbon atoms.
8 alkyl group.

Among these compounds, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and the like are particularly useful. In the acrylic copolymer, 1) N,N dialkylaminoalkyl (meth)acrylate or N,N-dialkyl (meth)acrylamide or a mixture thereof and 2) hydroxyalkyl (
The composition ratio of meth)acrylate, alkyl(meth)acrylate, or a mixture thereof is not particularly limited, but considering the adhesion between the final coating film and the base material, the flexibility of the coating film, etc. The weight ratio of component 1) to component 2) is preferably within the range of 95/5 to 10/90.

In addition, hydroxyalkyl (meth)acrylate and alkyl (meth)acrylate in component 2) may be individually mixed with component 1) to form a copolymer, but in order to improve the flexibility of the coating film, hydroxyalkyl (meth)acrylate ( It is preferable to use meth)acrylates and alkyl(meth)acrylates together as a copolymer with component 1), especially in the weight ratio of hydroxyalkyl(meth)acrylates to alkyl(meth)acrylates. 5/95
It is preferable that it is within the range of ~50/50. The amount of the acrylic copolymer used in the composition of the present invention is 10 parts by weight of the W component (the total weight converted to Si02 for tetraalkoxy silicon and R2Si0.5 for organic trialkoxy silicon). ~40 parts by weight, preferably 2
0 to 25 parts by weight.

If the amount of the acrylic copolymer used is less than 1 part by weight, the adhesion of the final coating film will be insufficient;
Also, due to the decrease in flexibility, there is a strong tendency for cracks to occur during heat resistance tests. If the amount is more than 40 parts by weight, the hardness of the coating film will be insufficient, and the coating film will tend to whiten due to hot water immersion. Furthermore, in the composition of the present invention, it is often particularly effective to use etherified methylolmelamine for the purpose of providing the coating film with both hardness and sacrificial properties in a well-balanced manner.

The etherified methylol melamine is a well-known one whose manufacturing method has already been described in many documents,
There are also many commercially available products. Preferred are hexamethylolmelamine, bentamethylolmelamine, tetramethylolmelamine, etc., and those obtained by methylating, ethylating, propylating or butylating some or all of the methylol groups of these. These can be used alone or in combination of two or more. The amount of the etherified methylolmelamine used is 10 parts by weight of the wind component (however, tetraalkoxy silicon is Si02, organic trialkoxy silicon is R2Si
○、． 0 to 30 parts by weight based on the total weight calculated as 5. If the amount exceeds 30 parts by weight, the hardness of the coating will be insufficient, and the adhesion after immersion in hot water and after a weather resistance test will decrease.

The above-mentioned component 'B} has a very excellent effect on improving the adhesion, flexibility and durability of the composition of the present invention. The solvent used in the production of the coating composition of the present invention is one that dissolves the legs, component [B], additives described below, etc., and does not cause significant harm to the plastic molded object to be coated. Any solvent may be used, including alcohols, ketones, esters, esters, cellosolves, etc.
Halides, carboxylic acids, aromatic compounds, etc. can be used, and are mixed with various components of the composition in a wide range of ratios.

In particular lower alcohols (e.g. methanol, ethanol, pro/gol, butanol), lower alkyl carboxylic acids (e.g. formic acid, acetic acid, propionic acid), aromatic compounds (e.g. toluene, xylene), esters (e.g. ethyl acetate, butyl acetate). ) and cellosolves (for example, methyl cellosolve, butyl cellosolve), etc. are preferably used alone or in rough combination. The amount of solvent to be used can be selected appropriately depending on the required thickness of the coating film or the coating method, but the concentration of solids in the solution should be 5 to 5.
The content is preferably 35% by weight. The composition of the present invention becomes a highly hard coating film by heating and curing it at a temperature of 70°C or higher after being coated on a substrate, but in order to further lower the curing temperature and shorten the curing time, hydrochloric acid, phosphoric acid, It is useful to use curing accelerating catalysts such as acids such as toluenesulfonic acid, organic amines, organic carboxylic acid metal salts, thiocyanate metal salts, nitrite metal salts, shelf acid metal salts, and organic tin compounds. be.

It is also possible to add surfactants to prevent defects in the surface condition of the paint film, such as peeling and shrinkage, and to prevent repellency and pinholes in the paint film, especially alkylene oxide and dimethylsiloxane. A good coating is produced by adding a block copolymer with.

A small amount of these curing accelerating catalysts and surfactants is sufficient, and the purpose of addition can be achieved at 5% by weight or less, respectively, based on the solid content of the composition.

Furthermore, it is also possible to further improve the practicality of the composition as a coating composition by dissolving or dispersing ultraviolet absorbers, antistatic agents, viscosity modifiers, dyes, pigments, and fillers in the composition of the present invention.

Coating with the composition of the present invention can be done by any of the commonly used methods such as spraying, dipping, brushing, and roll coating, and it can be applied to the surface of plastic products and then heat cured to make it transparent. A coating film with excellent hardness, scratch resistance, chemical resistance, and adhesion can be formed. The coating composition of the present invention is mainly useful as a coating agent for polycarbonate resin products, and product forms include, for example, sheets, films, injection molded products, vacuum molded products, cast molded products, etc. Specific products include, for example, windows for buildings including various public facilities and various transportation facilities, various lenses, and disaster prevention surfaces.

In addition, thermoplastic resin, thermosetting resin, paper, wood,
It can also be applied to metals, ceramics, etc. The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to these examples.

Note that % and parts in the examples indicate weight % and parts by weight. In addition,
The surface hardness was evaluated by rubbing it with #000 steel wool and examining the scratch resistance, which was evaluated as follows.

A: No scratches even if rubbed strongly.

B: Slight damage occurs when rubbed strongly.

C: Even weak friction causes scratches.

Adhesion was evaluated using a cross-hatch test, in other words, a steel knife was used to make a 10 hard cut in the goblin pattern on the coated surface, reaching the base material of one rib on each side, and then cellophane tape (manufactured by Sekisui Chemical Co., Ltd.) was firmly placed on top of the cut. After adhesion, the extent to which the coating film remains when the cellophane tape is strongly peeled off in the upward 900 direction is calculated as the number of squares remaining without peeling/
100".

Example 1 The following three types of solutions were prepared.

'1' Silicon compound partial hydrolyzate solution: 66.7 parts of isopropanol 7-ethoxy silicon and methyl IJ
A solution in which 33.3 parts of ethoxy silicon was dissolved, 3 parts of a 0.05N aqueous hydrochloric acid solution was added, and hydrolysis was carried out by stirring at room temperature. After the reaction, the solution was aged at room temperature for 2 hours or more.

The composition of the silicon compound partial hydrolyzate in this solution is Sj0
Tetraethoxy silicon partial hydrolyzate calculated as 260
．． 7%, CH3Si○,. The methyl triethoxy silicon partial hydrolyzate calculated as 5 was 39.3%. [
2} Acrylic copolymer solution: 4 parts of 2-N,N-dimethylaminoethyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, 14 parts of butyl acrylate, and 0.2 part of penzoyl peroxide in ethyl cellosolve 8
The foundation was also melted and heated at 85°C for 4 hours and then 1 hour under a nitrogen atmosphere.
A solution copolymerized by heating at 00°C for 30 minutes.

{3- Hardening accelerator solution: A solution prepared by mixing and dissolving 0.8 parts of sodium acetate, 2 parts of acetic acid, 4 parts of isopropanol, and 4 parts of ethyl cellosolve.

The obtained solutions were mixed in the order of 'Kawasu 3' to form a coating liquid.

The coating liquid was coated by dip coating on a polycarbonate sheet having a thickness of 2 layers, air-dried for 30 minutes, and then heated and cured in a 13000° hot air dryer for 1 hour. The surface-coated polycarbonate sheet obtained in this way is transparent and smooth, and does not show any sunlight even if it is strongly scratched with a fingernail, and the surface hardness is evaluated as A.
Met. The surface hardness of the hardened polycarbonate sheet was graded as C. Furthermore, regarding the coating adhesion of this surface-coated polycarbonate sheet, no peeling was observed in the crosshatch test.

This surface coated polycarbonate sheet contains xylene, ethyl acetate, methyl ethyl ketone, ethylene chloride'
Even after soaking for 30 minutes, no abnormality was observed in the appearance.
The evaluation of the surface hardness after soaking in hot water for 30 minutes at 0:00 AM was the same as before soaking, and was graded A, showing no abnormality in appearance or decrease in adhesion. Examples 2 to 5 and Comparative Example 1 A polycarbonate sheet was surface coated in the same manner as in Example 1, except that the amounts of tetraethoxy silicon and methyltriethoxy silicon used were changed as shown in Table 1.

Hot water resistance test (6) of the obtained surface coated polycarbonate
The appearance, surface hardness, and adhesion before and after (0qo, 30 minute soaking) were evaluated, and the results are shown in Table 1. Table 1 Examples 6 to 7 and Comparative Examples 2 to 3 Surface coating polymers were prepared in the same manner as in Example 1 except that the amount of acrylic copolymer solution used was changed as shown in Table 2.
A carbonate sheet was obtained and subjected to a hot water resistance test (60oo, 3
0 minute bond immersion).

The results obtained are as shown in Table 2. Table 2 Examples 8 to 12 and Comparative Example 4 In preparing the acrylic copolymer solution, the amounts of 2-N,N-dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, and methyl methacrylate were as shown in Table 3. A coating composition was prepared in exactly the same manner as in Example 1 except for changing the composition to Example 1, and the composition was applied to a polycarbonate sheet in the same manner as in Example 1.
Cured by heating.

All of the thus obtained surface-coated polycarbonate sheets, except for Comparative Example 4, were transparent and smooth, and had good surface hardness and adhesion. The evaluation results before and after the hot water resistance test (immersion from 60 pm to 30 minutes) are as shown in Table 3. Table 3 Example 13 In preparing the acrylic copolymer solution, N,N- was used instead of 2-N,N-dimethylaminoethyl methacrylate.
A coating composition was produced in exactly the same manner as in Example 1 except that dimethylacrylamide was used.

A polycarbonate sheet whose surface was coated with the composition in the same manner as in Example 1 was transparent and smooth, and had good surface hardness and adhesion, and no abnormality was observed in the appearance even after a hot water resistance test (60 qo, immersion for 30 minutes). There was no decrease in adhesion.
Examples 14 to 16 and Comparative Example 5 Etherified methylolmelamine was added and dissolved in the coating solution of Example 1 in the type and amount shown in Table 4 to produce a coating composition.

The obtained composition was applied to a polycarbonate sheet having a thickness of two legs in the same manner as in Example 1, and was cured by heating to obtain a surface coated polycarbonate sheet. The results of the physical property evaluation (water resistance test: soaking for 30 minutes at 60:00 AM) of the surface-coated polycarbonate sheet thus obtained are shown in Table 4. Table 4 {1) Mitsui Toatsu Chemical Co., Ltd., butylated methylol melamine 50 and butanol-xolene mixed solvent solution (2) Sumitomo Chemical Co., Ltd. methylated methylol melamine 70 in ethyl cellosolve solution (3) Silicon compound partial hydrolyzate 100 Parts by weight (partial force of silicon tetraethoxy and methyltriethoxy silicon, calculated as separated phosphorus, respectively SiO2 and CH3Siol.5) 393 parts of etherified methio-lumelamine Comparative Example 6 Acrylic copolymer in Example 15 A coating composition was prepared in the same manner as in Example 15 without using the coalescing solution, applied to a polycarbonate sheet with a thickness of 2 mm, air-dried, and then heated at 13°C for 1 hour to cure. I let it happen.

The thus obtained surface-coated polycarbonate sheet was transparent and smooth, had no abnormal appearance, and had good surface hardness, but its adhesion was poor at 0/100 in the crosshatch test. Example 17 The base material was changed to a polymethyl methacrylate sheet with a thickness of 2, and the coating composition of Example 8 was applied as it was to the polymethyl methacrylate sheet, and after air drying, it was heated at 8000°C for 2 hours. hardened.

The surface-coated polymethyl methacrylate sheet thus obtained was transparent, smooth and in good condition. Hot water resistance test (
The evaluation results before and after the test were as shown in Table 5. Table O The surface hardness of the polymethyl methacrylate sheet treated in this process was graded as C.

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, R^3
represents a C1-C4 alkyl group) and/or a mixture of each partial hydrolyzate and the partial hydrolysis of the tetraalkoxy silicon calculated as SiO_2. Decomposition products and R^2
The weight ratio of the organic trialkoxy silicon to the partial hydrolyzate calculated as SiO_1_._5 is 5/95 to 9.
5/5 silicon compound partial hydrolyzate 100 parts by weight (
(B) 1) N,N-dialkylaminoalkyl acrylate, N,N-dialkylaminoalkyl methacrylate, N,N-dialkylacrylamide and N, 10 to 400 parts by weight of a copolymer of one or more N-dialkylmethacrylamides and 2) one or more of hydroxyalkyl acrylate, hydroxyalkyl methacrylate, alkyl acrylate, and alkyl methacrylate, and etherified methylolmelamine. A coating composition obtained by dissolving 0 to 300 parts by weight in a solvent.