JPS6021628B2 - Method for manufacturing plastic with high hardness coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a technique for improving the surface properties of plastics, such as surface hardness, abrasion resistance, antistatic properties, and dyeability.

[Conventional technology]

Conventionally, transparent plastic molded bodies, such as amorphous molded bodies of thermoplastic resins such as polymethyl methacrylate, polycarbonate, polystyrene, cellulose acetate butyrate, and polyvinyl chloride, are known for their transparency, light weight, easy processability, and impact resistance. Although it is used for a variety of purposes due to its characteristics such as hardness, it has drawbacks such as insufficient hardness, being easily scratched, and easily swelling and dissolving when it comes in contact with solvents.

As a means to improve these drawbacks, applying a coating containing polysiloxane is effective, and many proposals have been made. For example, there are U.S. Pat. No. 3,390,203, U.S. Pat. However, these coating materials do not reach the same level as the electric properties of the base plastic, and although they have improved scratch resistance due to surface friction, they have the disadvantage of being easily charged with static electricity and attracting dust, etc. in the air. is not improved. On the other hand, methods for imparting antistatic properties to the surface of plastics have been proposed, for example, in Japanese Patent Publication No. 36-474, Samurai Publication No. 32-5946, and Japanese Patent Publication No. 52-26578. .

However, these conventional methods have the disadvantage that even if temporary antistatic properties are imparted, they are poor in durability and lack long-lasting performance. For example, when a cast polymer plate of polymethyl methacrylate is treated with the antistatic agent described in Samurai Publication No. 32-5946, the coating film can be easily peeled off from the base plate by simply immersing it in warm water at 40°C for 10 minutes. However, it is observed that the antistatic properties are completely lost. Furthermore, the biggest drawback of these conventional antistatic agents for plastics is that the surface hardness of the coating film is low, and therefore the surface hardness of plastics cannot be improved. Publicly known examples similar to the method of the present invention include Japanese Patent Publication No. 37-16836,
Hakama Publication No. 47-47081, Special Publication No. 52-8913
No. 2 Publication and Special Publication No. 48-84878 exist, but both of these have a short pot life of the coating composition, and it is difficult to obtain a stable and uniform coating film for a long period of time. Ta.

[Problem that the invention seeks to solve]

In order to improve the above-mentioned known technology, the present invention uses an alkoxysilane or a hydrolyzate thereof containing an epoxy group, and a hydrolyzate of an alkoxysilane having an amino group and/or an imino group blocked by a volatile organic acid. By using organic solvents and organic solvents as a paint, it is possible to extend the pot life of the paint and achieve stable coating over a long period of time. The purpose is to have the properties of permanent antistatic properties and the ability to dye deep colors with acid dyes.

[Structure of the invention]

In order to achieve the above object, the present invention consists of the following configuration.

"In a method for producing plastics having a coating film on the surface, A is a polyfunctional epoxy compound having two or more epoxy groups in the molecule, or a hydrolyzate of an alkoxysilane having an epoxy group in the molecule, and B is the general formula RmRnSi(OR'')4-(m+n) (wherein R is a monovalent organic group containing an amino group and/or imino group, R', R'' is a monovalent hydrocarbon group having 1 to 4 carbon atoms, m is 1 or 2, n is an integer of 0 to 2, m and n are integers of 3 or less), a hydrolyzate of an alkoxysilane having an ami/group and/or an imino group, and a volatile organic acid. is added in an amount of 0.5 to 10 mol per 1 mol of the total of amino groups and imino groups, and the compound stabilized in the form of an organic acid salt is mixed with an organic solvent to form a paint, and the paint is applied to a plastic surface. 1. A method for producing a plastic having a high hardness coating film, which comprises coating the plastic with a coating film and then heating the organic acid and organic solvent to volatilize the organic acid and the organic solvent and heat-cure the coating film.

Next, the present invention will be explained in detail.

Examples of the polyfunctional epoxy compound of component A include polyglycidyl ether compounds obtained by reacting epichlorohydrin with polyols and glycols.
Ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol diglycidyl ether, diglycerol triglycidyl ether, solpitol Examples include tetraglycidyl ether, trimethylolpropane, triglycidyl ether, bentaerythritol, bentaglycidyl ether, and bisphenol A type epoxy resin, bisphenol F type epoxy resin, etc. can also be used.

Examples of hydrolysates of alkoxysilanes having an epoxy group in the molecule include y-glycidoxypropyltrimethoxysilane y-glycidoxypropylmethyldimethoxysilane y-glycidoxypropyltriethoxysilane 81 (3, These include hydrolyzed epoxyalkoxysilanes such as 4-epoxycyclohexylethyltrimethoxysilane and 8-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane.

During this hydrolysis, an inorganic acid such as hydrochloric acid, sulfuric acid, or phosphoric acid can be added to accelerate the hydrolysis, or a carboxylic acid such as acetic acid or formic acid can be added to the silane in advance. It is also possible to stabilize the hydrolyzate and prevent gelation due to condensation of silanol groups.
As the organic acid salt of a hydrolyzate of an alkoxysilane having either or both of an amino group and an imino group as component B, for example, N-(8-aminoethyl)y-aminopropyltrimethoxysilane QN-C2day4NHC3
6Si(OC)3N-(8-aminoethyl)y-aminopropylmethyldimethoxysilane -Aminopropyltrimethoxysilane is NC36Si(OCH3)3y-aminopropylmethyldimethoxysilaneN-(8-aminoethyl)y-aminopropyl Triethoxysilane ratio N-C 2 days 4 NHC 3 days 6 Si (OC2 ratio) 3N-(
Water is mixed with an alkoxysilane such as 3-aminoethyl)y-aminopropylmethyltriethoxysilane, and after hydrolysis, an organic acid with a relatively low boiling point such as formic acid, glacial acetic acid, propionic acid, or butyric acid is added to form an amino group. , an organic acid salt of the silane hydrolyzate that has undergone a neutralization reaction with the imino group is used.

At this time, the alkoxysilane having either an amino group or an imino group, or both, tends to gel by hydrolysis, so before adding water, use an alcoholic solvent such as methyl alcohol, ethyl alcohol, n-butyl alcohol, etc. It is preferable to dilute the solution to a concentration of about 50% and add water for hydrolysis dropwise to gradually carry out the hydrolysis reaction.

In addition, the neutralization reaction of amino groups and imino groups with organic acids after hydrolysis is accompanied by heat generation, so
It is preferable to carry out the reaction gradually by dropping an organic acid onto the hydrolyzate of the alkoxysilane while maintaining the temperature at a low temperature of about 100 yen. The amount of this organic acid added is 0.5 to 10 per mole of the total amino groups and imino groups of the silane hydrolyzate.
The molar amount ranges preferably from 1.0 to 5.0 moles; if this amount is less than 0.5 moles, the margin life of the paint to be prepared will be shortened and gelation will occur within a few days. On the other hand, if the amount is more than 10 moles, the curing of the coating material will be insufficient, and the resulting coating film will have an unsatisfactory hardness. The blending ratio of component A and component B affects the performance of the resulting coating film, and (epoxy group)/(sum of amine/imino group) is 2/1 to 1/4 in terms of molar equivalent ratio. Sometimes it shows the highest hardness, and as either component A or B becomes excessive relative to the other and deviates from the above range, the hardness of the coating decreases.

The paint containing the above A component and B component is methanol,
Ethanol, butanol, benzyl alcohol, alcoholic solvents, methyl cellosolve, ethyl cellosolve,
Cellosolve solvents such as phenyl cellosolve, aromatic solvents such as toluene, xylene, and benzene, carbon tetrachloride, trichloroethane, trichloromethane, tetrachloroethane,
The coating thickness can be freely adjusted by diluting it to an appropriate concentration and viscosity with chlorinated solvents such as 7-trachloroethylene, dichloromethane, dichloroethane, and ethylene chlorohydrin.

The appropriate thickness of the coating film is in the range of 0.5 to 10 mm; if it becomes thinner than this range, the hardness will decrease, and on the other hand, if it becomes thicker, the coating film may crack or its adhesion to the substrate may decrease. I don't like it. Additionally, additives such as surfactants can be used to improve the staining properties, adhesion properties, etc. of the paint.

Furthermore, in order to promote the silanol group condensation reaction, various catalysts used for promoting the isokinetic condensation reaction of sodium acetate and silanol can also be used in combination. When actually applying a paint consisting of the above composition to various plastic molded products, the roll coating method, dipping method, spray method, flow coating method, which has been conventionally adopted for painting this type of paint, is necessary.
After painting using various methods such as brush coating, curtain flow, and spin coating, the coating is heated and cured to form a coating.

In order to improve the adhesion with the coating film, the plastic molded article to be painted can be treated with a primer in advance and then the paint of the present invention can be applied thereto. The coating composition of the present invention comprises a hydrolyzate of an alkoxysilane containing either an amino group, an imino group, or both stabilized in the form of an organic acid salt, and a polyfunctional epoxy compound, or an epoxy group in the molecule. A stable solvent solution containing a hydrolyzate of an alkoxysilane having the following properties is applied to the plastic surface and heat-treated to volatilize the organic solvent and compound acid, resulting in a condensation reaction between silanol and epoxy. Crosslinking due to the reaction between the group and the amine/group or imino group promotes curing and provides a highly hard coating film.

The coating composition according to the present invention can be applied to plastic products to which the surface hardening agent for plastics is applied, such as sunglass lenses, watch lenses, various camera lenses, window materials for buildings, and windows for transportation facilities. It is used for materials, plastic instrument panels, etc., and has a high hardness and a resistance of 1 pi~ when measured in 65% relative humidity.
Provides an antistatic coating film with a surface resistivity value of 1 to 30.

This coating film has excellent durability compared to conventional antistatic agents, such as exposure to a Sunshine Weather-Ometer for 50 hours, immersion in hot water at 80°C for 4 hours, heat treatment in a 90qo dry heat oven for 2 hours, It withstood all durability tests after 2 years of outdoor exposure, maintained the same paint film performance immediately after painting, and showed almost no change in the appearance of the paint film, adhesion to the substrate, hardness of the paint film, and antistatic properties. In good condition. Furthermore, the coating film obtained from the coating material of the present invention is highly flexible, follows the deformation of the substrate, and can be easily aged without causing cracks in the coating film after being softened by heating.

Furthermore, this coating film can be dyed with acid dyes, which was previously considered difficult with this type of highly hard coating film, and it stains purulent. Next, the content of the present invention will be specifically explained with reference to Examples.

Example 1 Chemical formula General 2NCH2C ratio NH (C France) Bui (OCH3)
Trimethoxysilane SH6020 (manufactured by Toray Silicone) containing an amino group and an immi/group represented by 3 was collected and mixed with 222 parts of ethanol, and 54 parts of water was added dropwise thereto to carry out a hydrolysis reaction.

This reaction is slightly exothermic, so the reactants are
The lantern was worshiped while being ice-cooled to a temperature of 0°C, and the rope azusa was continued for 3 minutes even after the water drop was finished. While the hydrolyzate thus obtained was cooled to 20° C. in the presence of a fly, 346 ml of acetic acid was added dropwise and mixed to obtain an acetate.

In addition to this, a tetrafunctional epoxy resin “Denacol EX-6” represented by the chemical formula
12'' (manufactured by Nagase Sangyo ■) was mixed and dissolved, and further mixed with 100 liters of ethanol and 25 liters of xylene.
Got the paint.

The pot life of this paint was 2 weeks or more when used at room temperature, and gelatin did not occur even when stored at 40 qo for more than 1 month. This paint was applied to an extruded polycarbonate sheet by a brush coating method, and dried and cured for 2 hours in a 12-0 hot air circulation dryer. The performance of the resulting coating film was as shown in Table 1. Table 1 Example 2 Epoxy group-containing trimethoxysilane SH6 represented by the chemical formula
040 (manufactured by Toray Silicone Co., Ltd.) 236 pieces of 0.01 N hydrochloric acid solution were added dropwise to the mixture at 20° C. to perform hydrolysis.

In addition to this, SH602 was prepared separately in the same manner as in Example 1.
Solution of acetate of hydrolyzate of 0.997 ml, ethanol 5.0
55 days, xylene 1119 and sodium acetate 6.2 times were mixed and melted to obtain a paint having a solid content concentration of 21.3% and a viscosity of 8.5 centipoise. The pot life of this paint is Example 1
It was the same aircraft. This paint was spin coated onto an injection molded polycarbonate instrument panel and processed in a 12000 hot air circulation dryer for 2 hours to create a hard antistatic coating on the surface.

The coated instrument panel obtained in this way can withstand two years of practical use with instruments, has fewer scratches than uncoated products, has no static electricity on the instrument panel surface, is free from dust, and has no smudges on the pointers. , did not occur. Example 3 Acrylic polymer prepared by mixing 80 parts by weight of methyl methacrylate, 1 part by weight of methacrylic acid, 3 parts by weight of glycidyl methacrylate, 0.4 parts by weight of penzoyl peroxide, and 10 parts by weight of toluene, and solution polymerizing the mixture at 80 qo for 8 hours. The solution was further diluted to 1M with ethyl cellosolve, and a primer with a field concentration of 5% was applied in advance to a cast board made of polymethyl methacrylate and dried for 30 minutes in an 8-inch hot air circulation dryer.

The primer-coated polymethyl methacrylate board was flow-coated with the paint prepared in Example 2, and then cured in an 8000 dryer for 2 hours. The performance of the resulting coating film was second to none.
As shown in the table. Table 2 Table 3 also shows the test results for the durability of the coating film. Table 3 Comparative Example 1 A coating material was obtained in the same manner as in Example 1 except that the amino group- and imino group-containing trimethoxysilane of Example 1 was used without being hydrolyzed.

However, this paint had a very short pot life and gelled within one day. Furthermore, the strength of the coating after painting was low, making it impractical. Comparative Example 2 A paint was prepared in the same manner as in Example 1 except that acetic acid was not added in Example 2.

The pot life of this paint was several hours, and it gelled within one day. Therefore, it was not possible to obtain a stable coating film for a long time. [Effects of the Invention] Since the paint used in the method of the present invention is blocked by a volatile organic acid, it can exist extremely stably before application, and therefore has a long pot life, allowing stable painting work for a long time.

Claims (1)

[Claims] 1. A method for producing plastics having a coating film on the surface, A. Hydrolysis of a polyfunctional epoxy compound having two or more epoxy groups in one molecule, or an alkoxysilane having an epoxy group in the molecule. and B General formula R_mR'_nSi(OR〃)_4_-_(_m_+
_n_) (In the formula, R is a monovalent organic group containing an amino group and/or an imino group, R', R'' is a monovalent hydrocarbon group having 1 to 4 carbon atoms, m is 1 or 2, and n is A hydrolyzate of an alkoxysilane having an amino group and/or an imino group (an integer of 0 to 2, m+n is an integer of 3 or less), and the volatile organic acid is a total of 1 mol of the amino group and the imino group. A compound stabilized in the form of an organic acid salt, added in an amount of 0.5 to 10 moles, and an organic solvent are mixed together to form a paint, and the paint is applied to a plastic surface and then heated to combine with the organic acid. A method for producing plastics having a highly hard coating film, which comprises volatilizing an organic solvent and curing the coating film thermally.