JPH09108620A - Partial coating method of plastic surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form characters, images and patterns on the surface of a plastic by using a photosetting coating material. SOLUTION: The surface of a plastic is partially coated by applying the photosetting coating material curing a coating film by irradiating a fixed part of the coated surface and removing the uncured coating film of a part, which is not irradiated with light. The light irradiation only on the fixed part of the coating film is executed by using a shielding plate or a sheet, the part of which irradiated with light is cut, and the coating material is prepared by blending a photosetting composition, which consists essentially of a polymerizable unsaturated resin having the acid value of 20-300, the unsaturated equivalent of 150-3000 and the number average molecular weight of >=300 and a photopolymerization initiator, and if necessary, a coloring agent and additives.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for partially coating a plastic surface, and in particular, using a photocurable paint on the plastic surface, letters, patterns, patterns, etc.
Generically).

[0002]

2. Description of the Related Art It has been practiced to form a pattern or the like on a plastic surface with a colored paint. For example, a non-painted portion other than a pattern or the like is pasted with a masking tape or the like for masking in advance, and then a colored paint is applied to the non-masked portion, and the masking is removed before or after curing to finish.

However, when the shape and structure of plastics, patterns, etc. becomes complicated, a lot of time and labor are required for the work of attaching and removing the masking, and the plastic itself is easily deformed when heated to a high temperature of 100 ° C. or higher. A curable paint cannot be used, the applicable paint is limited, and the coating performance depending on the purpose may not be obtained. Further, it took a long time to cure the coating film, and the production efficiency was not sufficient.

[0004]

The present invention relates to a method for partially coating a plastic surface, and more particularly to a method for drawing a pattern or the like on the plastic surface, which is capable of rapidly patterning without using a masking tape and without heating. The purpose was to develop a method for forming

[0005]

The present invention relates to a method for partially coating a plastic surface, the gist of which is as follows.

A photocurable composition is applied to a plastic surface, and only a predetermined portion of the applied surface is irradiated with light to cure the coating film,
Then, a method of partially coating the plastic surface by removing the uncured coating film in the non-irradiated area, and using a shield plate or a sheet cut out in the irradiated area to cover only a prescribed portion of the coating film. The photocurable composition is exposed to light to give an acid value of 20 to 3
00, an unsaturated equivalent of 150 to 3000, and a polymerizable unsaturated resin having a number average molecular weight of 300 or more and a photopolymerization initiator as main components, and further containing a colorant and an additive as required. Partial coating method of plastic surface characterized by that.

In the plastic applicable to the present invention, the surface (coated surface) of the portion where a pattern or the like is formed is preferably a mirror surface without fine irregularities and is transparent or translucent. Suitable materials are acrylic resin, polyester resin, polyamide resin, polycarbonate resin and the like.
It may be colorless or colored.

The photocurable composition used in the present invention contains a polymerizable unsaturated resin having an acid value of 20 to 300, an unsaturated equivalent of 150 to 3000 and a number average molecular weight of 300 or more and a photopolymerization initiator as main components, Further, if necessary, a colorant or an additive is added, and these are mixed with an organic solvent and / or
It is mixed and dispersed in water.

The polymerizable unsaturated resin in the photocurable composition has an acid value of 20 to 300, an unsaturated equivalent of 150 to 3000 and a number average molecular weight of 300 or more, and specifically, the following (1) to ( It is preferable to use one selected from 5).

(1): hydroxyl group-containing unsaturated compound (1-
a) and a diisocyanate compound (1-b) partially urethanization reaction product (1-1) has an isocyanate group
Acrylic resin containing hydroxyl and carboxyl groups (1-
Polymerizable unsaturated resin added to 2). Further, the polymerizable unsaturated resin can be used in combination with an unsaturated monomer having a number average molecular weight of 300 or less and having one or more polymerizable unsaturated groups in one molecule.

The hydroxyl group-containing unsaturated compound (1-a) is a compound having one or more polymerizable unsaturated groups and one or more hydroxyl group in one molecule, for example, 2-hydroxyethyl acrylate.
, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate
, N-methyl acrylamide, N-methyl methacrylamide, allyl alcohol and methallyl alcohol. Diisocyanate compound (1-
b) is a compound having two isocyanate groups in one molecule, such as tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate and lysine diisocyanate. can give.

The hydroxyl-containing unsaturated compound (1-a) is replaced by one isocyanate in the diisocyanate compound (1-b).
The urethanization reaction product (1-1) obtained by urethanization reaction with a vinyl group has at least one free isocyanate group and at least one polymerizable unsaturated group in each molecule.

The hydroxyl group- and carboxyl group-containing acrylic resin (1-2) has at least one hydroxyl group and at least one carboxyl group in one molecule, and uses a hydroxyl group-containing unsaturated compound and a carboxyl group-containing unsaturated compound. , A polymer which is optionally combined with other unsaturated compounds. Examples of the hydroxyl group-containing unsaturated compound include those mentioned above. The carboxyl group-containing unsaturated compound is a compound having one or more polymerizable unsaturated groups and one or more carboxyl groups in one molecule, and examples thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid. The other unsaturated compound is a compound having one or more polymerizable unsaturated groups in one molecule, and examples thereof include acrylic acid ester, methacrylic acid ester, styrene, acrylonitrile, vinyl acetate and glycidyl acrylate.

The component (1) is obtained by adding the isocyanate group contained in the urethanization reaction product (1-1) to the hydroxyl group of the acrylic resin (1-2). The urethanization and polymerization can be performed by known methods.

(2): In the unsaturated bond in the fatty acid chain in the esterified product of the epoxy group-containing resin and the unsaturated fatty acid,
A polymerizable unsaturated resin obtained by adding α / β ethylenically unsaturated dibasic acid or its anhydride. Further, the polymerizable unsaturated resin can be used in combination with an unsaturated monomer having a number average molecular weight of 300 or less and having one or more polymerizable unsaturated groups in one molecule.

The unsaturated fatty acid is an unsaturated monobasic acid having 6 to 26 carbon atoms, and examples thereof include oleic acid, linoleic acid, linoleic acid, eleostearic acid, licanoic acid, ricinoic acid and arachidonic acid. can give. The α / β ethylenically unsaturated dibasic acid is a compound having one unsaturated bond and two or more carboxyl groups in one molecule, and examples thereof include maleic acid, maleic anhydride, fumaric acid and itaconic acid. The acid value can be adjusted by α / β ethylenically unsaturated dibasic acid, and the unsaturated equivalent can be adjusted by the type and amount of unsaturated fatty acid.

(3): An unsaturated fatty acid-modified carboxyl group-containing alkyd resin obtained by esterifying an unsaturated fatty acid with a hydroxyl group in an esterified product of a dibasic acid, a polybasic acid and a polyhydric alcohol. Furthermore, this unsaturated alkyd resin can be used in combination with an unsaturated monomer having a number average molecular weight of 300 or less and having one or more polymerizable unsaturated groups in one molecule.

The acid value can be adjusted by the type and amount of polybasic acid, and the unsaturated equivalent can be adjusted by the amount of unsaturated fatty acid added. The acid value can also be imparted by half-esterifying a dibasic acid to the hydroxyl group of the unsaturated fatty acid-modified alkyd resin having an excess of hydroxyl group.

The dibasic acid has two carboxyl groups in one molecule and is, for example, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, maleic acid, maleic anhydride. , Fumaric acid, succinic acid, sebacic acid and the like, polybasic acids are those having 3 or more carboxyl groups in one molecule, such as trimellitic acid, pyromellitic acid and pyromellitic dianhydride. Alcohol has two or more hydroxyl groups in one molecule, such as ethylene glycol, propylene glycol and butylene glycol.
And neopentyl glycol, glycerin, trimethylol ethane, trimethylol propane, pentaerythritol, sorbitol and diglycerol. As the unsaturated fatty acid, those exemplified in (2) above can be applied.

(4): A reaction product of an oil having a conjugated double bond or a non-conjugated double bond and maleic anhydride, which is a number having one or more polymerizable unsaturated groups in one molecule. It is also possible to use in combination with an unsaturated monomer having an average molecular weight of 300 or less.

The reaction product contains styrene, vinyltoluene, cyclopentadiene, acrylic ester,
Graft polymerization of methacrylic acid ester or the like is preferable because the curability of the coating film is improved.

In the component (4), the acid value can be adjusted by the addition amount of maleic anhydride and the unsaturated equivalent can be adjusted by the unsaturated bond contained in the oil. The oil includes linseed oil, tung oil, soybean oil, castor oil, coconut oil, cottonseed oil, hempseed oil and the like.

(5): A polymerizable unsaturated resin obtained by adding a glycidyl group-containing unsaturated compound to a carboxyl group in an acrylic resin.

The glycidyl group-containing unsaturated compound is a compound having at least one glycidyl group and a polymerizable unsaturated bond in one molecule, and examples thereof include glycidyl acrylate and glycidyl methacrylate. The carboxyl group-containing acrylic resin is obtained by polymerizing only an unsaturated acid such as acrylic acid, methacrylic acid, maleic acid or the like, or another unsaturated compound such as an acrylic acid ester or a methacrylic acid ester.

The polymerizable unsaturated resins exemplified in (1) to (5) above have an acid value of 20 to 300, preferably 30 to 15.
0, unsaturated equivalent 150-3000, preferably 250-
And those having a number average molecular weight of 300 or more, preferably 1,000 to 50,000. Unsaturated equivalent is 15
If it is less than 0, the performance of the cured coating film will decrease and 3000
If it is larger, the curability of the coating film is lowered, which is not preferable. If the number average molecular weight is less than 300, the performance of the cured coating film will deteriorate.

The photocurable composition used in the present invention may contain other resins in addition to the above polymerizable unsaturated resin. Examples of such other resins include polymerizable unsaturated bond-containing resins such as polyester acrylic resins, polyurethane resins, epoxy resins and acrylic resins; saturated resins such as polyester resins, polyurethane resins, epoxy resins and acrylic resins; and the like. To be The amount of the other resin to be added is the polymerizable unsaturated resin 10
It is preferably 100 parts by weight or less per 0 parts by weight.

The photopolymerization initiator promotes curability by light irradiation, and specifically, benzoin, benzoin methyl ether, benzoin ethyl ether, benzyl, diphenyl disulfide, tetramethyl thiuram monosulfide. , Diacetyl, eosin, thionine, mihiraketone, anthraquinone, chloranthraquinone,
Methyl anthraquinone, α-hydroxyisobutylphenone, p-isopropyl-α-hydroxyisobutylphenone, α · α′-dichloro-4-phenoxyacetophenone, 1-hydroxy1-cyclohexylacetophenone, 2.2 dimethoxy2-phenylacetophenone,
Methylbenzoyl formate, 2-methyl-1- [4
Suitable are UV-sensitive initiators such as-(methylthio) phenyl] -2.morpholino-propene, thioxanthone, benzophenone, and visible light-sensitive titaniumnocene series. One or more selected from these can be used, but it is particularly preferable to use a combination of an acetophenone type and a thioxanthone type because of excellent photocurability. The amount of the photopolymerization initiator used is 100 parts by weight of the polymerizable unsaturated resin,
0.1 to 10 parts by weight is preferable.

The photocurable composition used in the present invention contains the above-mentioned polymerizable unsaturated resin and a photopolymerization initiator as main components,
If necessary, a colorant may be added to adjust the color tone to be transparent or opaque.

As the colorant, usual coloring pigments and dyes which are mixed in the paint can be used.

As the color pigment, particularly inorganic pigments having excellent weather resistance such as titanium dioxide and carbon black, quinacridone pigments such as quinacridone red, azo pigments such as pigment red, phthalocyanine blue, and Organic color pigments such as phthalocyanine pigments such as phthalocyanine green are preferable. These color pigments can be used alone or in combination of two or more.

The dyes are excellent in light resistance and solubility in an organic solvent, for example, azo dyes such as monoazo dyes, polyazo dyes, metal complex salt azo dyes, pyrazolone azo dyes, stilbene azo dyes and thiazol azo dyes. Dyes; anthraquinone dyes such as anthraquinone derivatives and anthrone derivatives; indigoid dyes such as indigo derivatives and thioindigo derivatives; phthalocyanine dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes and acridine dyes; azine dyes, oxazines Quinone imine dyes such as dyes and thiazine dyes; methine dyes such as polymethine (or cyanine) dyes and adimethine dyes; quinoline dyes; nitro dyes; nitrone dyes; benzoquinone and na Chikinon dye; naphthalimide dyes; perinone dyes; and the like, such as. These dyes can be used alone or in combination of two or more, or in combination with the above color pigments.

The amount of these colorants to be blended is 100 parts by weight or less, and especially 0.1% by weight per 100 parts by weight of the polymerizable unsaturated resin.
1 to 80 parts by weight is preferable.

The photopolymerization initiator is used to accelerate the photocurability of the coating film of the photocurable composition, and specifically, benzoin, benzoin methyl ether, benzoin ethyl ether, benzyl, Diphenyl disulfide, tetramethyl thiuram monosulfide, diacetyl, eosin, thionine, Michler's ketone, anthraquinone, chloranthraquinone, methyl anthraquinone, α-hydroxyisobutylphenone, p-isopropyl αhydroxyisobutylphenone, α · α'dichloro-4-phenoxy Acetophenone, 1-hydroxy 1-cyclohexyl acetophenone, 2.2 dimethoxy 2-phenyl acetophenone, methylbenzoyl formate, 2-methyl-1- [4- (methylthio) phenyl] -2.morpholino-propane, thio UV-sensitive initiators such as xanthone and benzophenone and titanocene-based initiators of visible light-sensitive initiators can be applied. These can be used singly or in combination of two or more, and it is particularly preferable to use an acetophenone-based compound and a thioxanthone-based compound together because the curability is excellent. The amount of the photopolymerization initiator used is the polymerizable unsaturated resin 10
0.1 to 10 parts by weight is preferable per 0 part by weight.

As the organic solvent for dissolving or dispersing the above components of the photocurable composition, it is preferable to use a volatile solvent which does not dissolve or swell the plastic to be coated, for example, toluene or xylene. Aromatic compounds such as acetone, ketone compounds such as acetone, methyl ethyl ketone and cyclohexanone, ester compounds such as methyl acetate, ethyl acetate and butyl acetate, alcohol compounds such as ethanol, propanol and butanol, pentane and hexane Aliphatic solvents such as.

Neutralizing carboxyl groups and the like in the above-mentioned polymerizable unsaturated resin of the photocurable composition can be rendered water-dispersible or water-soluble by using triethylamine or the like, and water alone or an alcohol type solvent as a solvent, A mixed system with a hydrophilic organic solvent such as methyl ethyl ketone and cellosolve can be used.

Further, the photocurable composition contains a light stabilizer,
An ultraviolet absorber, an anti-repellent agent, a pigment dispersant, a flow regulator, an antistatic agent, and other additives can be added.

The steps of the method of the present invention are mainly: 1) coating the surface of the plastic with the photocurable composition, 2) identifying the portion of the coated surface that is to be irradiated with light, and 3) exposing only that portion to light. Irradiation is performed to cure the coating film, and 4) the uncured coating film in the non-irradiated portion is removed. Each of these steps will be described in order.

Step 1): The photocurable composition is applied to the plastic surface.

Coating (including printing) is spray coating, dip coating, roll coater, gravure coater, screen.
It can be applied by brushing or brushing, and the film thickness is suitably 5 to 15 μm based on the cured coating film.

Steps 2 and 3): A portion of the coated surface to be irradiated with light is specified, and the portion is irradiated with light to cure the coating film.

In the present invention, a pattern or the like can be formed on the plastic surface by forming a coating film of the photocurable composition only on the pattern or the like or on a portion other than the pattern or the like. That is, the coated surface on which light is irradiated does not always correspond to only a portion such as a pattern, but may be irradiated only to a portion that is not a pattern. Which of these is selected can be arbitrarily determined according to the purpose.

In the step, as a method for identifying the light-irradiated portion, 2-1) using a sheet in which the light-irradiated portion is cut out according to a shape such as a pattern, or 2-2) using a shielding plate and so on.

In 2-1), specifically, the shape and size of a pattern or the like are specified, and in accordance with this, a sheet is prepared by cutting out only the light irradiation portion. Examples of the material of the sheet include metal, paper and plastic which have a strength that does not transmit light and does not deform during use. The cut-out sheet is brought close to or in close contact with the surface of the photo-curable coating film, and then the cut-out portion of the sheet is irradiated with light to cure the coating film at that portion. The light to be applied is preferably a light having a wavelength of 3000 to 4500A, and sunlight for these light sources,
There are mercury lamps, xenon lamps and arc lamps. A suitable irradiation time is 1 second to 20 minutes. If the surface of the photocurable coating film is dry, it is preferable to bring the sheet into close contact, but if it is tacky, the sheet is irradiated with light in a state where the sheet does not come into contact with the sheet and the sheet is as close as possible. It is preferable to apply the patterns and the like formed by this method to independent individual characters, symbols, flowers and the like.

In 2-2), the shielding plate is applied to the coated surface to irradiate it with light, and the pattern and the like are relatively large on the basis of the size of the plastic to be coated, and the sharpness of the contour may be slightly inferior. is there. The material of the shielding plate and the light irradiation method can be the same as those in 2-1) above. Step 4): Removing the uncured coating film in the non-irradiated area When weak alkaline water is sprayed on the coating surface in the non-irradiated area not irradiated with light, only the uncured coating film is washed away and can be removed. As weak alkaline water, caseisode, sodium carbonate
Those capable of imparting water solubility by neutralizing with free carboxyl groups present in the coating film, such as da, causticari and aqueous ammonia, can be used. Although the concentration of these weak alkaline waters is not particularly limited, it is suitable to be about 0.1 to 5% in the caseo-soda aqueous solution. When the uncured portion is removed, only the cured coating film of the photocurable composition remains on the surface of the plastic, and a plastic having a desired pattern or the like is obtained.

[0045]

【The invention's effect】

1. It is now possible to easily paint patterns on the plastic surface with paint.

2. Since it is not necessary to perform masking beforehand with a masking tape or the like, a great deal of time and labor required for that purpose are no longer required.

3. Since it is cured by irradiation with light, deformation of plastic due to heating disappeared.

4. Since the coating film is rapidly crosslinked and cured by irradiation with light, the production efficiency is improved and the coating film performance can be improved.

[0049]

EXAMPLES Examples and comparative examples relating to the present invention will be described below. As a general rule, parts and% are based on weight.

I Reagents 1) Production Example of Polymerizable Unsaturated Resin: 40 parts of methyl methacrylate, 40 parts of butyl acrylate, 20 parts of acrylic acid and 2 parts of azobisisobutyronitrile were used to prepare propylene glycol. -Rumonomethyl ether (hydrophilic solvent) 9
Polymerization was carried out in 0 part, 1 part of azobisdimethylvaleronitrile and 10 parts of propylene glycol monomethyl ether were further added, and the mixture was aged to obtain a high acid value acrylic resin (acid value 1
55) A solution was obtained. Glycidyl methacrylate was added to this solution.
24 parts, hydroquinone 0.12 parts and tetraethylammonium bromide 0.6 parts were added and reacted to give a polymerizable unsaturated resin (acid value 50, unsaturated equivalent 740,
A solution having a number average molecular weight of 20,000) was obtained. Solid content is 56%.

2) Preparation of colored photocurable coating composition: 178 parts of the above-mentioned polymerizable unsaturated resin solution, "Cast S" (color)
Bon Black pigment, Tokai Carbon Co., Ltd., trade name) 18
Parts, isopropyl alcohol 40 parts and xylol 4
After 0 part was dispersed with a paint conditioner for 1 hour, Irgacure-907 (manufactured by Nippon Ciba-Geigy, trade name, xylol solution having a solid content of 20%) 2
5 parts, KAYACUREDETX-S (manufactured by Nippon Kayaku Co.,
Trade name, photopolymerization initiator) 10 parts, isopropyl alcohol
53 parts of xylol and 53 parts of xylol were added to obtain a colored photocurable coating composition for spray coating having a solid content of 30%.

II Example A photocurable composition of the above sample was cured and coated on the entire surface of a colorless transparent acrylic resin plate (polymethyl methacrylate, size 150 × 70 × 10 mm) having a mirror-finished surface. It was spray-coated so that the film thickness based on the film was 8 to 10 μm, and dried at room temperature for several minutes.

An opaque cardboard cut out in the shape of an airplane is placed on a dry photo-curable coating surface and brought into close contact therewith, and then the cutout portion of the cardboard is irradiated with a mercury lamp having a wavelength of 3000 to 4500 A for 1 minute to cure the coating film on the cutout portion. Let

When the cardboard was removed and a 5% aqueous solution of caseiso-da was sprayed onto the coated surface, the uncured coating film in the non-irradiated area could be washed away and removed. After washing with water and drying, the airplane-shaped colored coating film remained concave on the surface of the acrylic resin plate, and the object of the present invention was achieved.

Claims (1)

[Claims] 1. A photocurable composition is applied to a plastic surface, and only a predetermined portion of the applied surface is irradiated with light to cure the coating film,
Then, a method of partially coating the plastic surface by removing the uncured coating film in the non-irradiated area, and using a shield plate or a sheet cut out in the irradiated area to cover only a prescribed portion of the coating film. The photocurable composition is exposed to light to give an acid value of 20 to 3
00, an unsaturated equivalent of 150 to 3000, and a polymerizable unsaturated resin having a number average molecular weight of 300 or more and a photopolymerization initiator as main components, and further containing a colorant and an additive as required. Partial coating method of plastic surface characterized by that.