JPS6349696B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a coated polycarbonate resin product with excellent abrasion resistance, which is obtained by coating the surface of a polycarbonate resin molded article with an undercoat paint that has good adhesion to the polycarbonate resin, baking it, and then applying a silicone top coat paint and baking it. This invention relates to resin molded articles. Generally, polycarbonate resin has impact resistance,
Although it has excellent transparency, it has the disadvantage that it has poor abrasion resistance and solvent resistance, the surface is easily scratched, and it is easily attacked by organic solvents. As a method to improve these drawbacks, a method of coating the surface with various thermosetting resins has been conventionally used. Surface hardening coating agents used for this purpose include melamine resins, thermosetting acrylic resins, polyester resins, polyurethane resins, and silicone resins, but they have properties such as abrasion resistance, adhesion, hot water resistance, heat resistance, weather resistance, etc. Currently, it is not possible to obtain a material with good physical properties. The object of the present invention is to eliminate such conventional drawbacks and provide a polycarbonate resin molded article with improved abrasion resistance, adhesion, hot water resistance, heat resistance, and weather resistance. The present inventor has developed a polycarbonate resin base material,
A top coat containing a hydrolyzate of methacryloxyalkyltrialkoxysilane, a radical initiator, and a condensation reaction catalyst as the main components is applied and baked in a nitrogen atmosphere to improve wear resistance. An undercoat treatment is applied between the film layer and the polycarbonate resin base material to improve the adhesion of the top coat layer to the base material, thereby improving the abrasion resistance, adhesion, hot water resistance, and weather resistance of the polycarbonate resin molded article. Succeeded in improving sex etc. That is, in the present invention, a coating composition containing a hydrolyzate of methacryloxyalkyltrialkoxysilane, a radical initiator, and a condensation reaction catalyst is coated and cured to form an overcoat layer, and the coating composition is formed by the general formula (1). (In the formula, R ¹ represents a hydrogen atom, R ² represents a hydrogen atom or a lower alkyl group, and X represents a hydroxyl group-containing side chain.) and general formula (2) (In the formula, R ³ represents a hydrogen atom, R ⁴ represents a hydrogen atom or a lower alkyl group, and Y is a side chain having a carboxyl group, an alkoxycarbonyl group, an amino group, a substituted amino group, an epoxy group, or a tetrahydrofuryl group. This is a coated polycarbonate resin molded article with improved abrasion resistance, which has an undercoat layer formed by coating and curing a composition containing a polymer having each of the repeating structural units shown in (1) and alkyl etherified methylol melamine. The methacryloxyalkyltrialkoxysilane used in the present invention includes methacryloxymethyltrimethoxysilane, methacryloxy, methyltriethoxysilane, β-methacryoxyethyltrimethoxysilane, β-methacryoxyethyltriethoxysilane, and γ-methacryloxyethyltriethoxysilane. Examples include roxypropyltrimethoxysilane and γ-methacryloxypropyltriethoxysilane. In the present invention, the hydrolyzate of methacryloxyalkyltrialkoxysilane used in the top coating composition refers to methacryloxyalkyltrialkoxysilane in which part or all of the alkoxy groups have been substituted with hydroxyl groups, and Contains some naturally condensed hydroxyl groups. These methacryloxyalkyltrialkoxysilane hydrolysates can be obtained, as is known, by hydrolysis in a mixed solvent such as water and alcohol in the presence of an acid. During hydrolysis, the amount of water added is at least 3/2 times the mole of methacryloxyalkyltrialkoxysilane, more preferably at least 2 times the mole of methacryloxyalkyltrialkoxysilane. If the amount is less than 3/2 times by mole, hydrolysis will not proceed sufficiently and the curing reaction will not proceed sufficiently during bake hardening. In the present invention, an overcoat composition containing a hydrolyzate of methacryloxyalkyltrialkoxysilane, a radical initiator, and a condensation reaction catalyst is applied to the surface of a polycarbonate resin molded article that has been undercoated as described below, and then baked in a nitrogen atmosphere. By applying this coating, a coating film with good abrasion resistance, hot water resistance, heat resistance, and weather resistance can be obtained, and the abrasion resistance does not deteriorate even after a hot water resistance test. This topcoat composition may contain tetraalkoxysilane, alkyltrialkoxysilane, alkyl acrylate, alkyl methacrylate, vinyl acetate, vinyl chloride, styrene, N-methylolacrylamide, acrylonitrile, and the like. However, if these amounts are too large, the abrasion resistance of the top coat will decrease.
It is preferable to use one or more of these in equal weight or less to the hydrolyzate of methacryloxyalkyltrialkoxysilane. The details of the baking-hardening reaction mechanism of the topcoat composition in the present invention in a nitrogen atmosphere are unknown, but in order to have good wear resistance and prevent cracks from occurring in heat resistance tests, etc.
Both the addition polymerization reaction of the unsaturated double bond (radical polymerization of the vinyl group in the methacryloxy group) and the condensation polymerization reaction of the silanol group must proceed simultaneously and efficiently. Therefore, the hydrolyzate of methacryloxyalkyltrialkoxysilane must be a monomer or oligomer and not a prepolymer. For example, if the methacryloxyalkyltrialkoxysilane before or after hydrolysis is made into a prepolymer by radical polymerization of vinyl groups, and then a radical initiator and a condensation reaction catalyst are added to the prepolymer and then applied, it is possible to Even when baked and hardened in an atmosphere, the radical polymerization reaction and the condensation polymerization reaction do not occur simultaneously, so the hardness of the film is poor and cracks are likely to occur in the film. In addition, organoalkoxysilane hydrolysates having vinyl groups and silanol groups other than hydrolysates of methacryloxyalkyltrialkoxysilanes, such as vinyltrialkoxysilanes, vinyltris(alkoxyalkoxy)silanes, and vinyltriacetoxysilanes, may also be used. The same is true when using a hydrolyzate of , which tends to cause poor hardness and cracks. The radical initiators contained in the top coating composition of the present invention include benzoyl peroxide, 2,4 dichlorobenzoyl peroxide, azobisisobutyronitrile, cumene hydroperoxide, tert-butyl hydroperoxide, benzoyl peroxide-dimethylaniline. etc. can be given. In addition, as the condensation reaction catalyst in the present invention, hydrochloric acid, sulfuric acid,
Acids such as phosphoric acid and perchloric acid and their ammonium salts, bases such as potassium hydroxide and sodium hydroxide, metal salts of naphthenate, metal salts of octoate, metal salts of organic carboxylic acids, metal salts of thiocyanate, nitrous acid Examples include metal salts, boric acid metal salts, organic amines, and organic tin compounds. More preferred condensation reaction catalysts include acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and perchloric acid, and their ammonium salts. If there is a substance that has both the functions of a radical initiator and a condensation reaction catalyst, this one substance can serve as both a radical initiator and a condensation reaction catalyst. The amount of the radical initiator and condensation reaction catalyst added is 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on the solid content of the composition.
Weight%. In order to obtain a coating film with good abrasion resistance, hot water resistance, heat resistance, and weather resistance, it is necessary to use a hydrolyzate of methacryloxyalkyltrialkoxysilane, a radical initiator, and a condensation reaction catalyst, and to bake it in a nitrogen atmosphere. be. Solvents that may be included in the top coating composition include alcohols, ketones, esters, ethers, cellosolves, halides,
Examples include carboxylic acids and aromatic compounds, and one or more of these can be used as a mixed solvent. Especially methanol,
ethanol, propanol, isopropanol,
Lower alcohols such as butanol; Cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; Lower alkyl carboxylic acids such as formic acid, acetic acid, and propionic acid; Aromatic compounds such as toluene and xylene; and esters such as ethyl acetate and butyl acetate It is preferable to use these solvents alone or as a mixed solvent. Furthermore, if necessary, in order to obtain a smooth coating film, a flow control agent made of a block copolymer of alkylene oxide and dimethyl siloxane, such as NUC Silicone Y-7006 manufactured by Nippon Unicar Co., Ltd.
(Product name) etc. can be added. A small amount of these flow control agents is sufficient, and the amount is preferably 0.01 to 5% by weight, more preferably 0.03 to 3% by weight, based on the entire coating composition. Coating with the top coat is done by coating the polycarbonate substrate which has been coated with the base coat described below in advance using the commonly used coating methods such as dipping, spraying, roller coating, or flow coating, and then coating the baked polycarbonate base material in a nitrogen atmosphere. The deformation temperature of the base material at temperatures above 70℃ (e.g.
By baking and hardening at a temperature below 130℃ for 20 minutes to 5 hours, it improves wear resistance, adhesion, hot water resistance,
A good coating film with good heat resistance and weather resistance, and whose abrasion resistance does not deteriorate even after a hot water test is obtained. The preferred thickness of this top coat is 2 to 30 microns.
More preferably, it is 5 to 15 microns. If it is less than 2 microns, the wear resistance will not be sufficient, and if it is more than 30 microns, cracks will tend to occur. Next, the undercoat layer for increasing the adhesion between the top coat and the polycarbonate base material will be explained. As an undercoat paint particularly suitable for polycarbonate resin base materials, general formula (1) (In the formula, R ₁ and R ₂ are each independently a hydrogen atom,
It represents a lower alkyl group or a carboxyl group, and X represents a hydroxyl group-containing side chain. ) Repeating structural unit and general formula (2) (In the formula, R ₃ and R ₄ are each independently a hydrogen atom,
It represents a lower alkyl group or a carboxyl group, and Y is a side chain having a carboxyl group, an amino group, a substituted amino group, an epoxy group, a tetrahydrofuryl group or an alkoxycarbonyl group. ) is a coating consisting of a polymer having each of the repeating structural units shown in (a) and an alkyl etherified methylolmelamine. The above polymer has at least each of the repeating structural units represented by the above formulas (1) and (2).
It contains 2.5 mol%, more preferably 5 to 95 mol%, even more preferably 10 to 90 mol%, and the following monomers are suitable as this polymer.
It can be produced by copolymerizing (1) and monomer (2). Examples of the monomer (1) include allyl alcohol, N-hydroxymethylacrylamide, N-hydroxymethylmethacrylamide, N-hydroxymethylacrylamide, and N-hydroxymethylmethacrylamide.
-(2-hydroxyethyl)acrylamide,
N,N-dihydroxymethylacrylamide,
N,N-di(2-hydroxyethyl)methacrylamide, 2-hydroxyethyl acrylate, 2
-Hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 1,4-butylene glycol monoacrylate, 1,4-butylene glycol monomethacrylate, glycerol monomethacrylate, hydroxyallyl methacrylate, hydroxymethylaminomethyl acrylate, hydroxy Methylaminomethyl methacrylate, 2-
Hydroxyethylaminomethyl acrylate, 2
-(2'-hydroxyethylamino)ethyl methacrylate, N,N-di(hydroxymethyl)aminomethyl acrylate, N,N-di(hydroxymethyl)aminomethyl methacrylate, N,N-
di(2-hydroxyethyl)aminomethyl acrylate, etc., and these monomers (1) may be used alone or in combination of two or more. Examples of the monomer (2) include acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid,
Maleic acid, itaconic acid, acrylamide, methacrylamide, crotonamide, N-methylacrylamide, N-methylmethacrylamide, N-
Ethylacrylamide, N-ethylmethacrylamide, N-propylacrylamide, N-propylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide,
N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N-dipropylacrylamide, N,N-dipropylmethacrylamide, N-butoxymethylacrylamide, N-
iso-butoxymethyl methacramide, 2-(N
-methylamino)ethyl acrylate, 2-(N
-Methylamino)ethyl methacrylate, 2-
(N,N-dimethylamino)ethyl acrylate,
2-(N,N-dimethylmino)ethyl methacrylate, 2-(N,N-diethylamino)ethyl acrylate, 2-(N,N-diethylamino)ethyl methacrylate, 3-(N,N-diethylamino)propyl acrylate, 3- (N,N-diethylamino)propyl methacrylate, acrylic glycidyl ether, allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, etc. These monomers (2)
may be used alone or in combination of two or more. Examples of the alkyl etherified methylol melamine include hexakis methoxymethyl melamine, hexamethylol melamine pentamethyl ether, hexamethylol melamine tetramethyl ether, tetramethylol melamine trimethyl ether, hexakis butoxymethyl melamine, and tetramethylol melamine tributyl ether. These alkyl etherified methylol melamines may be used alone or in combination of two or more. The amount used is generally 0.05 to 0.7 equivalents, more preferably 0.08 to 0.4 equivalents per equivalent of functional groups (hydroxyl group, carboxyl group, amine group, substituted amino group, epoxy group, or tetrahydrofurfuryl group) in the polymer. used in Catalysts used with the polymer and alkyl etherified methylol melamine include hydrochloric acid, ammonium chloride, ammonium nitrate, ammonium thiocyanate, etc., and the amount used is generally 0.05 to 1 g equivalent of alkyl etherified methylol melamine. Suitably, it is used in a proportion of 0.8 g equivalent. When used, the primer paint is diluted to a concentration suitable for the application process, if necessary. Examples of solvents that can be used include methanol and other alcohols, methyl cellosolve and other ethers, methyl ethyl ketone and other ketones, methyl acetate and other esters, and these may be used alone or in the form of a mixed solvent. . The degree of dilution is preferably such that the total amount of the polymer and alkyl etherified methylolmelamine is 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. The undercoat may also contain small amounts of conventional paint additives, such as flow control agents, if necessary. An undercoat consisting of the above polymer, alkyl etherified methylol melamine, a catalyst, and a solvent and flow control agent added as necessary is applied to the surface of the polycarbonate resin base material, the resulting coating is dried, and further coated as necessary. depending on
The heat distortion temperature of the resin base material at 50℃ or higher (for example, 130℃)
The base coat film is obtained by baking at a temperature lower than 100°C (°C), more preferably in the range of 100°C to the heat distortion temperature of the base material, for 10 to 100 minutes. The preferred thickness of this undercoat film after drying or baking is 0.05 to 1 micron. By providing this undercoat film, the hydroxyl group, carboxyl group, amino group, etc. in the paint film react with the silicon component in the topcoat film, so that the topcoat film reacts with the polycarbonate through the undercoat film. This results in strong adhesion to the resin base material. Examples of polycarbonate resins to which the present invention can be applied include bisphenol polycarbonates, aliphatic polycarbonates, and diethylene glycol bisallyl carbonate (for example, CR-39, a product of PPG). The present invention will be explained in more detail with reference to Examples below, but is not limited thereto. The performance of the coating film was evaluated using the following method. That is,
Abrasion resistance: Resistance to scratches was examined by rubbing with #0000 steel wool and judged as follows. A: No damage occurs even if strongly rubbed. B: Slight scratches occur when rubbed strongly. C: Even weak friction causes scratches. Adhesion: In the so-called cross-cut tape test, 11 parallel lines were placed vertically and horizontally at 1 mm intervals on the surface of the coating film, and 100 squares were cross-cut, and cellophane adhesive tape was attached on top of the cross-cuts. The number of squares that did not peel off among 100 squares after peeling off the tape was indicated. Hot water resistance: The state of the coating film was examined after being immersed in boiling water for 1 hour. Heat resistance: The state of the coating film was examined after being stored in a hot air drying oven at 130°C for 100 hours. Example 1 Topcoat layer and undercoat layer solutions were prepared as follows. (1) Preparation of topcoat layer solution: Dissolve 100 g of γ-methacryloxypropyltrimethoxysilane in 70 g of isopropyl alcohol, add 30 g of 0.1N hydrochloric acid aqueous solution, stir at room temperature to perform hydrolysis, and then stir at room temperature for 20 hours. It has matured more than that. The obtained solution is CH ₂ = C・CH ₃・COO・C ₃ H ₆ -
It contained 36.1% of γ-methacryloxypropyltrimethoxysilane hydrolyzate calculated as SiO _3/2 . Add and dissolve 40 g of ethyl cellosolve, 0.7 g of benzoyl peroxide, 0.3 g of perchloric acid, and a small amount of flow control agent to 100 g of the hydrolyzate solution of γ-methacryloxypropyltrimethoxysilane obtained in this manner, and dissolve the top coat solution. And so. (2) Preparation of undercoat layer solution; Ethyl cellosolve 320
2-hydroxyethyl methacrylate in g76
g, dimethylaminoethyl methacrylate 4g
Dissolve 0.4g of azobisisobutyronitrile and
Copolymerization was carried out by heating and stirring at 90°C for 4 hours in a nitrogen atmosphere. 100g of the solution thus obtained
2.8g of hexa(methoxymethyl)melamine,
Ammonium chloride 0.18g, ethyl cellosolve
900g and a little flow control agent were added to make an undercoat paint solution. onto a pre-cleaned polycarbonate base material.
First, the undercoat layer solution prepared in (2) above was applied and dried by heating at 130° C. for 20 minutes in a hot air drying oven. Next, the topcoat layer solution prepared in (1) above was applied to the polycarbonate coated with the undercoat layer (thickness: 0.3 microns) obtained in this way, and heated in a hot air drying oven at 130°C in a nitrogen atmosphere for 2 hours. Dry and cure. The thickness of the topcoat layer after curing was 5 microns. The coated polycarbonate molded article thus obtained is transparent, has an abrasion resistance of A, an adhesion of 100/100,
The hot water resistance and heat resistance are good, and the abrasion resistance and adhesion after the hot water resistance test are A and 100/10, respectively.
It was good at 0. Comparative Example 1 An overcoat layer solution was prepared as follows.
γ-methacryloxypropyltrimethoxysilane
Dissolve 0.5g of benzoyl peroxide in 100g and heat at 60℃.
Prepolymerization was carried out in a nitrogen atmosphere for 30 minutes. To 40 g of the obtained γ-methacryloxypropyltrimethoxysilane prepolymer solution, 56 g of ethyl cellosolve, 0.3 g of perchloric acid, and a small amount of a flow control agent were added and dissolved to prepare a top coating solution. Example 1
It was coated in a similar manner to the above, and dried and cured by heating at 130°C in a nitrogen atmosphere for 2 hours in a hot air drying oven.
The coated polycarbonate molded article thus obtained is transparent, has an abrasion resistance of A, and an adhesion of 100/10.
0, but the heat resistance was poor and cracks were observed. The above-mentioned top coating solution was applied in the same manner, and dried and cured by heating in air at 130°C for 2 hours in a hot air drying oven.
The abrasion resistance of the resulting coating film was C. Examples 2 to 7 and Comparative Examples 2 to 3 The same procedure as in Example 1 was carried out except that the type of catalyst was changed as shown in Table 1 in the preparation of the top coat solution, and the undercoat layer and top coat layer were formed by polycarbonate molding. applied to the item. When the performance of the coated polycarbonate molded article thus obtained was evaluated, the results are shown in Table 1.

[Table] Example 8 Copolymers were synthesized using comonomers, solvents, and initiators as shown in Table 2, and 8 types were synthesized by adding crosslinking agents, curing accelerators, and solvents as shown in Table 3. An undercoat paint was prepared. The undercoat paint prepared above was applied to each of the polycarbonate substrates that had been washed in advance, and then heated and dried for 20 minutes in a hot air drying oven at 130°C. The top coat of Example 1 was applied to the polycarbonate base material that had been subjected to each of the undercoating treatments described above, and the adhesiveness of each sample was dried and cured by heating in a nitrogen atmosphere at 130°C for 2 hours in a hot air drying oven before and after the hot water test. It was also good.

【table】

【table】

[Table] Comparative Example 4 The top coat solution described in Example 1 was applied except that the undercoat solution was not applied, and the coating was dried and cured by heating at 130° C. for 2 hours in a nitrogen atmosphere in a hot air drying oven. The adhesion of the coated polycarbonate molded article thus obtained was poor at 0/100. Comparative Example 5 100 g of vinyltriethoxysilane was dissolved in 70 g of isopropyl alcohol, and 30 g of a 0.1N aqueous hydrochloric acid solution was added, stirred at room temperature for hydrolysis, and then aged at room temperature for 20 hours. the resulting solution
It contained 20.8% vinyltriethoxysilane hydrolyzate calculated as _CH2 =CH-SiO3 _/2 .
0.4 g of benzoyl peroxide was added to 100 g of the vinyltriethoxysilane hydrolyzate solution obtained in this way.
g, 0.2 g of perchloric acid and a small amount of flow control agent were added and dissolved to prepare a top coat solution. The above-mentioned top coat paint was applied to a polycarbonate base material which had been subjected to the same undercoat treatment as in Example 1, and was dried and cured by heating in a nitrogen atmosphere at 130°C for 2 hours in a hot air drying oven. The abrasion resistance of the coated polycarbonate molded article thus obtained was C.

Claims (1)

[Scope of Claims] 1 A coating composition containing a hydrolyzate of methacryloxyalkyltrialkoxysilane, a radical initiator, and a condensation reaction catalyst is used as a coating hardening top coat, and the general formula (1) (In the formula, R ₁ represents a hydrogen atom, R ₂ represents a hydrogen atom or a lower alkyl group, and X represents a hydroxyl group-containing side chain.) and general formula (2) (In the formula, R ₃ represents a hydrogen atom, R ₄ represents a hydrogen atom or a lower alkyl group, and Y is a side chain having a carboxyl group, an amino group, a substituted amino group, an epoxy group, a tetrahydrofuryl group, or an alkoxycarbonyl group. 1. A coated polycarbonate resin molded article having improved abrasion resistance, which is formed by coating and curing a composition containing a polymer having each of the repeating structural units shown in the following formulas and an alkyl etherified methylol melamine as an undercoat layer.