JPS6296534A - Methacrylate resin molding - Google Patents

Abstract

PURPOSE:To provide the titled molding having a surface having excellent resistance to wear and weather, etc., by priming the outer surface of a methacrylate resin molding with an acrylic copolymer paint contg. methyl methacrylate and coating it with a specified paint compsn. CONSTITUTION:An outer surface corresponding to protrusions on the inside of a (semi)transparent acrylic resin molding is coated with a paint composed of an acrylic copolymer contg. a binder contg. 30-69wt% methyl methacrylate, and then with paint composed of 100pts.wt. (in terms of formula II) partial hydrolyzate of a compd. of formula I (wherein n is 1-3; R is a 1-6C hydrocarbon; R' is a 1-4C alkyl), 5-100pts.wt. (in terms of SiO2) partial hydrolyzate of a tetraalkoxysilicon, 5-200pts.wt. alkyl (meth)acrylate/hydroxyalkyl (meth) acrylate copolymer and 0-150pts.wt. etherified methylolmelamine. Heating is then conducted to effect curing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface-hardened methacrylic resin molded product, which has particular properties such as decorative properties, abrasion resistance, scratch resistance, dust resistance, etc. that can be used as interior and exterior parts of vehicles and the like. This relates to methacrylic resin molded products that have been surface-treated.

Conventionally, transparent synthetic resins, especially methacrylic resins, have been used as interior and exterior parts of vehicles, such as tail lamp covers, instrument covers, windshields, and reflective materials, by taking advantage of their lightness, ease of processing, and transparency. It is used in large quantities in mirrors, etc., but in recent years, the use of transparent synthetic resins in place of gold IA and glass has become popular in society, with the aim of reducing vehicle deception, improving safety, and improving decorativeness. There are many demands for this, and it is attracting a lot of interest.

Furthermore, transparent synthetic resin molded products to be used as exterior parts of vehicles are molded into complex shapes, and in order to further enhance their decorativeness, the synthetic resin is colored or the surface of the molded product is painted with paint. In addition, higher levels of surface abrasion resistance, scratch resistance, and weather resistance during use are required for these vehicle exterior parts than ever before. At present, there is no satisfactory product that can withstand practical use.

In addition, when transparent or translucent methacrylic resin molded products are used as interior and exterior parts of vehicles, etc.5, bosses and rim-shaped mounting tools are integrally molded on the back of the molded product for attachment to the vehicle body. However, such a protrusion on the back surface of a molded product is not aesthetically pleasing and requires some kind of decorative treatment.

In such a case, painting can be applied for decorative purposes to hide the protrusion on the back surface of the molded product. There is a need to subject methacrylic resin molded articles having such partially painted surfaces to the above-mentioned treatments to improve wear resistance, scratch resistance, or weather resistance. Furthermore, exterior parts for vehicles are damaged in a short period of time by sand dust, brushes and cloth during car washing, and the decorativeness of the exterior parts is greatly reduced. In order to solve these problems, it is well known that many surface treatment compositions have been proposed to prevent scratches on the surface of methacrylic resins in particular.

Among the many surface treatment compositions, the practically representative ones include JP-A No. 58-26892 and JP-A No. 50-3.
9096, JP-A-50-126038, JP-A-1I851
-83128 and Japanese Patent Publication No. 50-15118.

Such surface treatment compositions have good adhesion to the surface of methacrylic resin, but when it comes to articles that are at least partially painted, such as the exterior parts of vehicles, they do not adhere well to the surfaces of methacrylic resins, including the painted parts. It is necessary to coat the surface of the molded product with
It was not possible to use the coated parts because the adhesion was substantially poor in terms of weather resistance and heat cycle resistance. In addition, regarding the adhesion to painted surfaces,
-39096, it was said that good adhesion was maintained only to painted surfaces containing 50 or more methyl methacrylate in the paint binder.

However, paints containing 5% or more of methyl methacrylate have a decisive drawback in that the paint film, which is basically an exterior part of a vehicle, has poor resistance to thermal cycles.

Also, JP-A-55-92742, JP-A-55-94988
Once the surface treatment composition has been used, it is extremely difficult to apply it to the surface to be coated, so it is practically disadvantageous to apply a coating to create a decorative effect. There is a decisive problem in that painted parts cannot be improved to the same extent with respect to scratches.

The present inventors have conducted extensive research on the surface treatment of transparent synthetic resin molded products such as methacrylic resins that have been coated at least in part, and have found that a specific acrylic copolymer The inventors have discovered a surface-treated molded product that eliminates the above-mentioned drawbacks or problems by coating it with a specific paint and then coating it with a specific surface-treating composition, thereby creating a surface-treated molded product that is free from practical problems, and has completed the present invention. .

That is, the present invention comprises the steps of (1) coating at least a portion of a methacrylic resin molded article with a paint consisting of an acrylic copolymer containing 30 to 49 M% of methyl methacrylate in the paint binder component; 2) General formula RnS
i(OR') 4-n (wherein, n is an integer of 1 to 8,
R is a hydrocarbon group having 1 to 6 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms) and a co-partial hydrolyzate of tetraalkoxy silicon or/and each partial hydrolyzate More specifically, by a coating composition consisting mainly of a mixture, (c) RnSi-2, where n and R are as defined above, A silicon compound hydrolyzate containing 5 to 100 parts of a tetraalkoxy silicon cumulative partial hydrolyzate calculated as SiO2 for 100 parts of a partial hydrolyzate of (c) as Rn5iO□ in ■ Calculated general formula RnS 1 (OR' )4 n
5 to 2 parts by weight of a copolymer of alkyl acrylate or/and alkyl methacrylate and hydroxyalkyl acrylate or/and hydroxy methacrylate per 100 parts by weight of a partial hydrolyzate of the compound represented by
0OffiM part and etherified methylolmelamine 0
This is a methacrylic resin molded product that has been subjected to painting and surface hardening treatment, which includes the step of coating the painted area with a coating composition obtained by dissolving ~150 parts by weight in a solvent.

As mentioned above, the first step, painting, is carried out to improve the beauty of the methacrylic resin molded product. It can be applied to external surfaces and other parts.

Painted molded products reduce residual stress during molding, and can be coated and
After annealing (heat treatment) to prevent cracks and crazing during coating, and cleaning to remove chips and dirt, the first step is painting.

The paint applied in the first step is a paint using a binder that is made of at least one type of copolymer of methyl methacrylate and contains 80 to 49 times methyl methacrylate.

In general, as described in Japanese Patent Publication No. 50-89096, paints containing a large amount of methyl methacrylate in the paint binder contain a hydrolyzate of organosiloxane, which is the hardness improver (coating composition), and alkyl (methacrylate). ) Acrylate and hydroxyalkyl (meth)acrylate copolymers and compositions consisting of etherified methylolmelamine have good adhesion; If the content of methyl acrylate is 50% or more, the flexibility of the coating film will be lost if the heating and cooling cycles are repeated, and the mold film will crack and peel, which is beyond the scope of the present invention. If the content of methyl methacrylate in the paint binder is less than 80%, cracks will not occur during cooling/heating cycles, but the adhesion between the paint film and the coating composition will be significantly reduced, causing practical problems. be.

The acrylic copolymer used as a binder for a paint comprising an acrylic copolymer in the present invention is obtained from methyl methacrylate and a monomer copolymerizable with methyl methacrylate.

The monomer that can be copolymerized with methyl methacrylate is not particularly limited as long as the copolymerized polymer does not lose its transparency.

Examples of such monomers include acrylic acid esters such as methyl, ethyl, propyl, butyl, and 2-ethylhexyl; methacrylic acid esters such as ethyl, butyl, hydroxyethyl, and glycidyl; acrylic acid, methacrylic acid, Examples include acrylonitrile, acrylamide, maleic acid, fumaric acid, crotonic acid, itaconic acid, hinyl chloride, vinyl acetate, and styrene.

In addition, the binder may have a content of methyl methacrylate of 80 to 49% without losing its transparency.
Polymers other than those mentioned above can also be mixed as long as they meet the above requirements.

Examples of such polymers include resins such as nitrocellulose and melamine.

In addition, an inorganic pigment or an organic pigment is added to the binder in an amount of 10 to 60! ms, and by adding solvents and other additives one makes the paint used in the present invention.

The resulting paint is adjusted to an appropriate viscosity with thinner or the like, depending on the coating method, and then painted.

For painting, commonly used methods such as brushing and spray painting can be used without any problems.

After applying the above paint to the object to be painted, dry it in an oven at a predetermined temperature or leave it at room temperature, and after the surface is in a state where you can touch it with your fingers without getting dirty, the surface hardness is improved. However, if the coating is not dry enough.

During the second coating process, the paint film tends to discolor and blister, so please heat the coating at 40 to 80°C.
It is desirable to dry for about 20 minutes.

Furthermore, in the coating composition of the present invention, as a silicon component, the ratio of a partial hydrolyzate of an organosilicon compound to a partial hydrolyzate of alkoxy silicon is increased to improve the hot water resistance, heat cycle resistance, and weather resistance of the coating film. While trying to improve,
The ratio is set within a range that provides practical abrasion resistance of the coating film, and therefore the flexibility, which is insufficient with the silicon component alone, is improved by adding an acrylic copolymer or etherified methylolmelamine.

Furthermore, since the coating composition of the present invention uses an acrylic copolymer, it has particularly good adhesion to acrylic substrates, and moldings made of methyl methacrylate homopolymers or copolymers have particularly good adhesion to acrylic substrates. A film with good adhesion can be obtained without any pretreatment.

Furthermore, the addition of etherified methylolmelamine is often particularly effective in providing a coating with both hardness and flexibility.

The tetraalkoxy silicon used in the present invention is one in which the alkoxy group is methoxy, ethoxy, propoxy, butoxy, or the like.

In the organosilicon compound represented by the general formula Rn5i(OR)n, the hydrocarbon group R having 1 to 6 carbon atoms specifically includes methyl, ethyl, propyl, butyl, pentyl, hexyl, vinyl, allyl, phenyl, etc. The alkyl group R having 1 to 4 carbon atoms is a methyl group, an ethyl group, or a propyl group.

Butyl group, etc.

These partial hydrolysates of silicon compounds can be prepared by combining tetraalkoxysilane and the organosilicon compound of the above general formula RnS i (OR' ) 4-n, separately or in a mixture, in a mixed solvent such as water and alcohol, with an acid. obtained by hydrolysis in the presence of

In some cases, partial hydrolysates of these silicon compounds can also be obtained by directly hydrolyzing silicon chlorides such as 5iCI4 and Rn 5iCj4n. Generally, it is often better to mix these silicon compounds and co-hydrolyze them simultaneously than to hydrolyze them separately. In particular, the general formula RnSi (OR)4
-n In the case of a compound where n=2 or n=8, it is preferable to perform cohydrolysis after mixing with tetraalkoxy silicon.

The ratio of the Nishi alkoxy silicon partial hydrolyzate obtained in this way to the partial hydrolyzate of the organosilicon compound of Rn5i(OR')4n is determined by the general formula RnS i(OR')4n calculated as RnS iO□. It is preferable that at least one partial hydrolyzate of an organosilicon compound is 5 to 100 parts by weight of a tetraalkoxy silicon partial hydrolyzate calculated as SiO2 per 100 parts by weight.

If the amount of tetraalkoxy silicon partially hydrolyzed piI is less than 5 parts by weight, the hardness of the coating will decrease and the practical l1iF abrasion resistance will be lost, and if it is more than 100 parts by weight, the coating will have hot water resistance and heat resistance. Cyclability and weather resistance tend to deteriorate.

The acrylic copolymers used with the silicon component are alkyl (meth)acrylates and hydroxyalkyl (meth)acrylates.
Acrylate can be obtained by bulk polymerization, emulsion polymerization, suspension polymerization, or solution polymerization in the presence of a radical polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide, di-tert-butyl peroxide, etc. .

Alkyl (meth)acrylate has 1 to 1 carbon atoms
(meth)acrylic acid esters of alcohols consisting of 8 can be selected. Especially ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
Lauryl (meth)acrylate and the like are useful.

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.

The composition ratio of alkyl (meth)acrylate and hydroxyalkyl (meth)acrylate in the acrylic copolymer is not particularly limited, but it depends on the adhesion between the final coating film and the substrate, the flexibility of the coating film, etc. Considering that, the weight ratio is 1
It is preferably within the range of /10 to 10/l.

The amount ratio of the acrylic copolymer in the coating composition of the present invention is 100 parts by weight of the partial hydrolyzate of the compound represented by the general formula Rn5i(OR')4H calculated as Rn5iO-;-. System copolymer 5~
It is desirable that the amount is in the range of 200 melon parts. When the acrylic copolymer has a 5-tone part or less, the resulting coating film has poor heat cycle resistance and has a strong tendency to crack. If the amount of the acrylic copolymer exceeds 200 parts by weight, the hardness of the coating film will be impaired and the coating film will tend to whiten when immersed in hot water.

The production method of the etherified methylolmelamine used in the coating composition of the present invention has already been described in many documents, and there are also 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, Examples include hexa(cyclohexyloxymethyl)melamine.

The amount ratio of neethylated methylolmelamine in the coating composition of the present invention is calculated as Rn5iOT-. The amount of methylolmelamine is preferably in the range of 0 to 150 parts by weight; if it exceeds this range, the adhesion of the coating film, especially in hot water, will be adversely affected.

As the solvent used for producing the coating composition, alcohols, ketones, ester q1 ethers, cellosolves, halides, carboxylic acids, aromatic compounds, etc. can be used, but the selection depends on the use. Depending on factors such as the polymeric material substrate used and the rate of evaporation, it may be mixed with the components of the coating composition in a wide range of proportions. In particular, lower alkyl carboxylic acids such as formic acid and acetic acid are effective in increasing the adhesion between the substrate and the coating film. lower alcohols (e.g. methanol, ethanol, propatool, butanol), lower alkyl carboxylic acids (e.g. formic acid, acetic acid, propionic acid), aromatic compounds (e.g. benzene, toluene, xylene) and cellosolves (e.g. methyl cellosolve, butyl cellosolve) It is particularly useful to use them in combination. The amount of solvent used can be appropriately selected depending on the required thickness of the coating film, coating method, etc.

The above coating composition of the present invention can be coated on a substrate and then baked at a temperature of 70°C or higher to obtain a cured coating film, but in order to further reduce the curing temperature and shorten the curing time. is an acid such as hydrochloric acid or toluenesulfonic acid, or an organic amine or an organic carboxylic acid gold 1
It is useful to use curing accelerating catalysts such as g-adders, metal thiocyanates, metal nitrites, organotin compounds, and the like.

Furthermore, in order to prevent surface defects such as citrus skin and shrinkage when a thick coating film is required, and to prevent the coating film from repelling, a surfactant may be added to the composition of the present invention. It is possible, and especially when a block copolymer of alkylene oxide and dimethylsiloxane is added in small amounts, a good film is produced.

It is sufficient to add a small amount of these curing accelerating catalysts and surfactants, and the purpose of addition can be achieved at 5% or less based on the solid content of the composition.

Coating with the coating composition of the present invention can be done by any commonly used method such as spraying, dipping, brushing, etc. After coating the substrate, the coating composition can be coated at 70°C.
By baking and curing at temperatures above, it becomes transparent, hard, water resistant, hot water resistant, chemical resistant, and heat cycle resistant.

A coating film with good weather resistance and antistatic effect can be formed.

The present invention will be explained in more detail with reference to Synthesis Examples and Examples below, but the present invention is not limited thereto. In the following description, unless otherwise specified, all numbers indicate weight %.

Synthesis Example Preparation of paint (flat l-grave 4) 800 with thermometer, stirrer, cooler and dropping funnel
- Into a four-loaf flask, 60 parts of n-butanol, MIB
After adding the KIO part and replacing the air in the flask with nitrogen, keep the contents below 80°C and add 0.5 parts of azobisisobutyronitrile, 45 parts of methyl methacrylate, and 40 parts of isopropyl methacrylate. , 15 parts of 2-hydroxyethyl methacrylate was placed in a subfunnel, and while the contents of the flask were maintained at 117°C, the contents of the bottom funnel were added dropwise to react, and then 0.5 part of azoisobutylvaleronitrile and 1 part of MIBKlo were added. was added dropwise and reacted at 117°C for about 8 hours.

After the reaction was completed, it was cooled to 80°C, the solid content was adjusted to 50% with butyl acetate, and a paint (flat sheet) of acrylic copolymer with a polymerization rate of 100%, a molecular weight of about 30,000, and a glass transition point of 87°C was added. Obtained.

Similarly, acrylic copolymer paints (flats 2 to 44) were obtained with the compositions shown in Table 1.

Preparation of coating liquid (Ya 1 to Ya 5) (1) Preparation of co-partial hydrolyzate solution of tetraethoxy silicon and methyltriethoxy silicon (component 1) Add 68P% isopropyl alcohol to a hydrolysis vessel equipped with a reflux condenser. Ethoxy silicon 88F and methyltriethoxy silicon 722 were charged, mixed and dissolved, and further 86 g of 0.05N hydrochloric acid solution was added, and the solution was heated under reflux for 5 hours while stirring to perform cohydrolysis.

After the reaction, the mixture was cooled to room temperature to obtain a copartial hydrolyzate solution. The resulting solution is a tetraethoxy silicon partial hydrolyzate calculated as SiO25. lchi, C)iasiot, s
It contained 12.6% of methyltriethoxy silicon partial hydrolyzate calculated as:

(2) Preparation of co-hydrolyzate solution of tetraethoxy silicon and dimethyl jetoxy silicon (component ■) Dissolve 20 parts of tetraethoxy silicon and 69 parts of dimethyl jetoxy silicon in 89 parts of isopropyl alcohol, and further dissolve 0.0 parts of dimethyl jetoxy silicon.
A set of 5N hydrochloric acid aqueous solution 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 resulting solution contains 2.7% of the western ethoxy silicon partial hydrolyzate, calculated as 5iOz, (CHa) 2 SiO
It contained 16.1% of dimethyljethoxy silicon partial hydrolyzate calculated as .

(3) Synthesis of acrylic copolymer a. Butyl acrylate 40F, 2-hydroxyethyl methacrylate LOP, and azobisisobutyrilonitrile 0.59 are dissolved in aoop ethyl alcohol and heated at 70"C for 5 hours under a nitrogen atmosphere. The mixture was heated and stirred to polymerize. After the reaction was completed, the contents were poured into petroleum ether to remove unreacted monomers to obtain copolymer a.

b. Ethyl acrylate 50p and 3-hydroxypropyl methacrylate 102 were copolymerized in the same manner as in a to obtain a copolymer.

(4) Preparation of coating liquid Mix the aforementioned components 1 and n, copolymers a and b, and hexa(butoxymethyl)melamine in the proportions shown in Table 2, and mix n-
It was dissolved in 60 parts of butanol, 40 parts of acetic acid, and 20 parts of xylene, and 0.4 part of sodium acetate was added and dissolved to prepare coating liquids &1 to 5.

Comparative Synthesis Example 1, Preparation of Paint (O5, A6) In the same manner as in Example, the first pumping bath 5. An acrylic copolymer paint having the composition shown in Flat 6 was obtained.

2. Preparation of coating liquid (boiling 6) 60 parts of methyltrimethoxysilane, 25 fflS of tetraethoxysilane, 9 parts of trifluoropropyltrimethoxy
While stirring at room temperature, 8 parts of 2% sulfuric acid was gradually added dropwise to a mixture consisting of 9210 parts of dimethylpolysiloxane (M synthetic leather 18) and 5 parts of dimethylpolysiloxane (M synthetic leather 18), which was further aged at room temperature for 8 hours. , organopolysiloxane JI66 for coating was obtained.

8. Preparation of coating solution 7: 80 parts of hexakis (methoxymethyl) melamine, 0.08 parts of nitrified cotton with a nitrogen content of 11.9% and an average degree of polymerization of 85.
5 parts of polyethylene glycol with a molecular weight of 600, 4 parts of methanol, 49 parts of ethanol, and 46 g of methyl ethyl ketone
It was dissolved in a mixed solvent consisting of 1 s 1 part water for a total of 100 parts. Next, about 85 liters of aqueous hydrochloric acid solution was diluted with ethanol to make a 1.0N solution, and this was mixed with the above solution in a volume ratio of 1:1.
mixed with. The solvent composition of the solution thus obtained was 74 parts of Oe methanol, 2% ethanol, 191 parts of methyl ethyl ketone, and 5 parts of water.

This solution was heated at 25°C for 5 hours to form coating solution A7.
I got it.

Preparation of coating solution/I68 110 parts of tetra-n-butoxy silicon in 75 parts of ethanol
1 part was dissolved and 40 parts of a 0.1N aqueous hydrochloric acid solution was added to perform hydrolysis.

After the reaction was completed, the mixture was allowed to stand at room temperature or in a refrigerator (iooC) for 15 hours or more to obtain a tetra-n-butoxysilicone hydrolyzate.

Next, 6 parts of methyltrimethoxysilane was added to 57 parts of ethanol.
8 parts was dissolved, and while stirring while keeping the liquid temperature at 15-20C, 27 parts of a 0.01 m constant hydrochloric acid aqueous solution was gradually added dropwise.After the dropwise addition was completed, the mixture was aged at room temperature for 2 hours to form a methyltrimethoxysilane hydrolyzate. Obtained.

88.7 parts of tetra-n-butoxysilicon cumulative hydrolyzate, 100 parts of methyltrimethoxysilane hydrolyzate, 19 parts of acetic acid
．． 4 parts of sodium nitrite and 0.7 parts of sodium nitrite were mixed to prepare a coating liquid.

Preparation of coating liquid 49 40 parts of tetraethoxysilane, 42.5 m of methyltrimethoxysilane and 17.5 parts of polyvinyl acetate resin (manufactured by Saitokaji Co., Ltd.; trade name Cypinol 5A5L) were mixed,
To 100 parts of this mixture, 70 parts of an ethyl alcohol/glacial acetic acid mixture (80/20) was added, and while stirring, 30 parts of a 0.05 N aqueous hydrochloric acid solution was added. As soon as the mixture was added, an exothermic reaction started.
The liquid temperature was controlled at 20-50°C. After stirring for about 1 hour, the mixture was left to mature at 15-20°C overnight.

To 100 parts of this solution, 1,8-diazabicyclo(5
,4,0) 2 parts of undecene-7 were added and mixed well to prepare coating 711;9.

The paints &1 to 6 obtained by the above method were applied to a methacrylic resin molded article, and then a coating liquid AI=A9 was applied thereto for evaluation.

Examples and Comparative Examples Methacrylic resin (manufactured by Sumitomo Chemical, Sumipex BMH
A molded product as shown in Fig. 1 formed by injection M using O) was washed with water, mixed with metal aluminum powder (Al~6) prepared from the above-mentioned synthesis example and comparative synthesis example, and spray-painted. The back side of the molded product was painted. Furthermore, the same paint (Al~
6) Mix carbon black and paint at 60'C.
and dried for 30 minutes (Figure 8).

Next, the obtained painted methacrylic resin molded product is coated with the coating prepared by the synthesis example and the ratio synthesis example! Dip coat with L (&1 to 9) and apply 80'
It was heated and dried for 2 hours in a hot air dryer (No. 4) to harden it.
figure).

The partially painted and coated methacrylic resin molded product was subjected to the following tests.

a) Adhesion: 1w with a knife on the coating film
After making 100 cuts that reach the n-square stacked material and pasting cellophane tape (manufactured by Tanemizu Chemical) on top of the cuts, the cellophane tape was strongly peeled off in an upward direction of 90°, and the remaining eyelids were removed. I scored one song by number.

b) Mamou resistance・・・・・・・・・Steel wool g
oo.

The material was rubbed 5 times under a load of 10 and t to examine its resistance to damage.

A: No scratches B: Some scratches C: Many scratches. Polyester is completely unpainted. The methyl methacrylate plate was graded C.

C) Hot water resistance test: The state of the coating film was examined after being immersed in hot water at 80°C and left for 2 hours.

d) Heat cycle test: The sample was placed in a hot air dryer at 80°C for 2 hours and then in a cold oven at -80°C for 2 hours. After repeating this process 10 times, the state of the coating film was examined.

e) Weather resistance: Measure the sample with a Sunshine Weather Meter (WE-3CN-HC manufactured by Suga Test Instruments)
Type A'-1) Terrorism The state of film formation after 00 hours of irradiation was observed.

The results are shown in Table 8 and Section 4.

As a result of the tightness between the wall film of the third layer and the coating film, methyl methacrylate in the paint binder component was 80%
It was found that there was almost no adhesion of the coating film to coatings of less than 10% acrylic copolymer.

In addition, according to the results of the physical properties of the pond in Table 4, for coating films of acrylic copolymers containing 50 or more methyl methacrylate in the paint binder component, the difference in thermal expansion and contraction with the coating film It was found that cracks are likely to occur.

Furthermore, it was found that coating films other than the coating liquid of the present invention tend to crack when compared to the coating film of an acrylic copolymer containing 80 to 49% of methyl methacrylate in the paint binder component of the present invention. .

[Brief explanation of drawings]

FIG. 1 is a perspective view of a transparent methacrylic resin molded product used as an automobile exterior part. Figure 2 is a sectional view taken along the line A-A of the molded product shown in Figure 1. Figure 8 is the same as Figure 2 in the A-All direction, but the acrylic copolymer referred to in the present invention is applied to the surface and curved surface, respectively. The figure shown is one coated with one of the following materials. FIG. 4 shows a product coated with the acrylic copolymer paint according to the present invention and then coated with the coating agent according to the present invention. The numbers in the figure represent the following: 1; Transparent methacrylic resin 2; Mounting boss 3; Coating film of acrylic copolymer containing carbon black 4
；Contains metal aluminum powder 5；Coating film 4 3 hundred

Claims (1)

[Claims] (1) An acrylic copolymer containing 30 to 49% by weight of methyl methacrylate in the paint binder component (however, acrylic chelate (excluding resin and acrylic urethane resin), then (2) (A) general formula RnSi (OR'
)_4_-_n (wherein, n is an integer of 1 to 3, R is a hydrocarbon group having 1 to 6 carbon atoms, and R' is an alkyl group having 1 to 4 carbon atoms) and tetraalkoxy silicon or/and a mixture of their respective partial hydrolysates, calculated as RnSiO(4-n)/2, where n and R are as defined above. A silicon compound partial hydrolyzate containing 5 to 100 parts by weight of a tetraalkoxy silicon partial hydrolyzate calculated as SiO_2 based on 100 parts by weight of a partial hydrolyzate of the formula RnSi(OR')_4_-_n; ) General formula Rn calculated as RnSiO(4-n)/2 in (A)
5 to 200 parts by weight of a copolymer of alkyl acrylate or/and alkyl methacrylate and hydroxyalkyl acrylate or/and hydroxyalkyl methacrylate based on 100 parts by weight of the partial hydrolyzate of the compound represented by Si(OR')_4_-_n and methacrylic resin molding, characterized in that it has been subjected to painting and surface hardening treatment comprising the step of coating the painted area with a coating composition mainly consisting of 0 to 150 parts by weight of etherified methylolmelamine. Goods.