JP5289013B2 - Multilayer coating film forming method, multilayer coating film and coated article - Google Patents

Description

  The present invention forms a coating film with a starch-based colored base paint using plant-derived starch, and forms a coating film with a photocurable paint comprising a specific starch-based resin on the coating film, And it is related with the multilayer coating-film formation method by making it photocure. The present invention also relates to a multilayer coating film and a coated article including the multilayer coating film.

In recent years, from the perspective of reducing the impact on global warming, there has been a demand for a reduction in CO ₂ emissions at a global level, which is a renewable resource and increases CO ₂ emissions in the carbon dioxide circulation on the earth. There is a demand for positive use of plant-derived materials that are not allowed to occur.

  As typical materials derived from such natural products, polysaccharide starches or modified starches such as acetylated starch have been used in the food industry and paper industry, but these starches have been used in recent years. Is used as a raw material for plastics and has been commercialized in a wide range of fields such as food containers, packaging materials, cushioning material sheets, agricultural films, and disposable diapers.

  In order to utilize starch as a raw material for industrial products, various improvements regarding processed starch have been accumulated along with the modification of starch. The basic structure of starch is a mixture of amylose in which α-D-glucose is linearly linked by 1,4-bond and amylopectin having a branched structure, utilizing the fact that the structure has a hydroxyl group, Modification by esterification, etherification and the like has been made in the 1960s.

  Patent Documents 1 to 4 disclose a method for directly producing grafted starch obtained by radically grafting unsaturated monomers to starch or modified starch by grafting starch resin and acrylic resin indirectly via polyisocyanate. Has been.

  Patent Documents 5 to 7 disclose inventions in which a polymer blend in which starch or modified starch and a cellulose derivative are combined is used as a molding material as an example in which starch and other plant-derived resins are combined. Patent Documents 5 to 7 also disclose resin compositions such as acrylic acid to starch and a graft polymer of a photocurable resin or a thermosetting resin.

  As is apparent from these prior patents, starch-based resins that combine, bind or graft various polymers are known per se. However, all of these prior patents assume adhesives, structural materials, injection molding materials, sheets and the like as uses of starch-based resins, and do not disclose uses as paints.

  Regarding a paint using a starch-based resin, Patent Document 8 includes a mixture of the starch-based resin and a curing agent having a functional group that reacts complementarily with at least one hydroxyl group contained in the starch molecule. A reactive curable paint containing a curing agent starch composition has been disclosed, and it is also suggested that curable types such as an oxidation polymerization curable type, a normal temperature curable type, and an active energy ray curable type are possible.

  Patent Document 9 includes starch, polyisocyanate curing agent, plant-derived resin excluding starch, metal complexes and β-diketones, acetoacetates, malonic esters, ketones having a hydroxyl group at β-position, A curable starch composition comprising a blocking agent selected from aldehydes having a hydroxyl group at the β-position and esters having a hydroxyl group at the β-position is disclosed.

  However, regarding these starch-based paints, a multilayer coating film forming method and a multilayer coating film excellent in finish, pencil hardness, scratch resistance, adhesion, alkali resistance and solvent resistance are not known.

JP 54-120698 A JP-A-55-90518 JP-A-56-167746 JP-A-8-239402 JP-A-6-207047 JP-A-8-231762 JP 2002-167520 A Japanese Patent Laid-Open No. 2004-224887 JP 2006-282960 A

  An object of the present invention is to use a starch-based paint derived from a plant, and to form a multilayer coating film that is excellent in finish, pencil hardness, scratch resistance, adhesion, alkali resistance, and solvent resistance. It is to provide a layer coating film forming method and a multilayer coating film excellent in these.

  As a result of intensive studies to solve the problems of the prior art described above, the present inventors have applied a starch-based coloring base paint containing a plant-derived starch-based resin on an object to be coated, so that the starch-based coloring can be achieved. Applying a photocurable paint (A) containing an unsaturated group-containing starch-based resin (a1) and a photopolymerization initiator (a2); Forming a coating film comprising the photocurable coating (A); and irradiating the coating film comprising the photocurable coating (A) with light to cure the coating film. It has been found that such a problem can be solved by a method, and the present invention has been completed.

The multi-layer coating film forming method of the present invention has a low environmental impact because the total carbon dioxide emission associated with the product life cycle is small, and the finish, pencil hardness, scratch resistance, adhesion, alkali resistance and resistance A multilayer coating film excellent in solvent property can be formed.
Furthermore, the multilayer coating film and coated article of the present invention, such as plastic parts, have a low environmental impact due to a small amount of total carbon dioxide emission related to the product life cycle, and have finish, pencil hardness, and scratch resistance. Excellent in adhesion, adhesion, alkali resistance and solvent resistance.

  In the present invention, a coating material is formed by applying a starch-based colored base paint on an object to be coated, for example, a plastic part, and a photo-curable paint (A) containing a specific starch-based resin is applied. A method for forming a multilayer coating film comprising forming a coating film and photocuring the coating film. In particular, a coated article having a multilayer coating film by the multilayer coating film forming method of the present invention is particularly useful as a plastic product. Details will be described below.

[Photocurable paint (A)]
The photocurable coating (A) used in the method for forming a multilayer coating film of the present invention is a coating containing an unsaturated group-containing starch-based resin (a1) and a photopolymerizable initiator (a2). Furthermore, a photocurable compound (a3) can be contained in the photocurable paint (A) for the purpose of improving the coating film performance.

Unsaturated group-containing starch-based resin (a1):
The unsaturated group-containing starch resin (a1) having an unsaturated group in the starch resin is:
(1) A method of reacting a hydroxyl group of the modified starch (a10) described later with an unsaturated carboxylic acid (for example, acrylic acid, itaconic acid, maleic acid, etc.);
(2) A method of transesterifying the hydroxyl group of the modified starch (a10) with a hydroxyl group-containing component of an unsaturated carboxylic acid ester (for example, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, etc.);
(3) A method of reacting the hydroxyl group of the modified starch (a10) with an unsaturated carboxylic acid chloride (for example, acrylic acid chloride);
(4) A method of reacting the hydroxyl group of the modified starch (a10) with an isocyanate group-containing unsaturated resin;
(5) A method of reacting the hydroxyl group of the modified starch (a10) with a carboxyl group-containing unsaturated group-containing resin;
(6) A method of transesterifying the hydroxyl group of the modified starch (a10) with the hydroxyl group-containing component of the ester group-containing unsaturated group-containing resin;
It can obtain by manufacturing methods, such as.

  Specific examples of the unsaturated group-containing starch resin (a1) particularly useful in the present invention are shown below.

Unsaturated group-containing starch-based resin (20):
As the unsaturated group-containing starch-based resin (a1), an unsaturated group-containing starch-based resin (20) obtained by reacting the modified starch (a10) with a compound (a11) containing an acryloyl group and an isocyanate group. Can be suitably used.

Modified starch (a10)
Examples of the starting starch include corn starch, high amylose starch, ground starch unmodified starch such as wheat starch, rice starch, and unmodified starch such as potato starch and tapioca starch, dextrin, and degradation products thereof. . Here, as the starch decomposition product, for example, starch obtained by subjecting starch to a molecular weight reduction treatment with an enzyme, an acid or an oxidizing agent can be mentioned. The starch degradation product has a number average molecular weight of 1,000 to 2,000,000, particularly 3,000 to 500,000, more preferably 3,000 to 200,000. From the point of view, it is preferable.

  The modified starch (a10) is an organic functional group such as an aliphatic saturated hydrocarbon group, an aliphatic unsaturated hydrocarbon group, an aromatic hydrocarbon group, an ester bond and / or an ether bond in starch or a starch degradation product. Modified starch (a10) bound via The modified starch (a10) can be used alone or in combination.

In this specification, the number average molecular weight or the weight average molecular weight is determined according to the method described in JIS K 0124-83 as “TSKgel G4000HXL”, “TSKgel G3000HXL”, “TSKgel G2500HXL” and “TSKgel G2000HXL” ( Chromatograms and standard polystyrene obtained with an RI refractometer at 40 ° C. and a flow rate of 1.0 mL / min, using four of Tosoh Corporation's trade names) and GPC tetrahydrofuran as the eluent. It was obtained from the calibration curve.
In addition, as a modification | denaturation method of modified starch, esterification modification | denaturation is mentioned, for example, As a preferable modification group, a C2-C18 acyl group is mentioned. Modification | denaturation can be performed by using a C2-C18 organic acid individually or in combination of 2 or more types. The degree of modification of the modified starch is preferably in the range of 0.5 to 2.8, and more preferably in the range of 1.0 to 2.5.

  Here, the degree of substitution is the average number of hydroxyl groups substituted by a modifier per monosaccharide unit constituting the starch. For example, the degree of substitution 3 is three hydroxyl groups present in the monosaccharide unit constituting the starch. Means that all of the hydroxyl groups present in the monosaccharide units constituting the starch are substituted by the modifying agent. . If the degree of substitution is less than 0.5, the compatibility with the later-described radical polymerizable unsaturated monomer may be insufficient, and the finish of the formed coating film may be insufficient. On the other hand, when the degree of substitution exceeds 2.8, finish may be deteriorated.

  The modified starch preferably has a glass transition point below the starch decomposition temperature (about 350 ° C.), and it is desirable to adjust the degree of modification so that it has thermoplasticity and finish. When the substituent used for modification has a large number of carbon atoms, for example, when the substituent is a stearyl group having 18 carbon atoms, a low modification level, for example, the degree of ester substitution is in the range of 0.1 to 1.8. In the case where the number of carbon atoms of the substituent is small, when the substituent is an acetyl group having 2 carbon atoms, a high modification level, for example, the degree of ester substitution is 1.5 to It is preferable to be within the range of 2.8.

  Examples of modified starch include hydrophobic organisms obtained by mixing anhydrous starch having an amylose content of 50% or more with an esterification reagent in an aprotic solvent and reacting the starch and the esterification reagent. A degradable starch ester product (see JP-A-8-502552), a starch ester modified using a vinyl ester as an esterifying reagent, wherein the vinyl ester has 2 to 18 carbon atoms in the ester group Starch ester obtained by reacting with starch using an esterification catalyst in a non-aqueous organic solvent (see JP-A-8-188601), and polyvinyl ester grafting is carried out together with esterification Starch (see JP-A-8-239402 and JP-A-8-301994), having a polyester graft chain on the starch molecule, Polyester graft polymerized starch in which a part or all of hydroxyl groups directly connected to the graft chain ends and starch are blocked with ester groups, and the same component as the polyester graft chain, and part or all of the terminal hydroxyl groups are based on ester groups Examples thereof include a polyester graft polymerized starch alloy (see JP-A-9-31308) in which a closed independent polyester is uniformly mixed.

  Further, a short-long chain mixed starch ester obtained by substituting the hydrogen of the reactive hydroxyl group of the same starch molecule with a short-chain acyl group having 2 to 4 carbon atoms and a long-chain acyl group having 6 to 18 carbon atoms (Japanese Patent Application Laid-Open No. 2000-2000). No. -159801), a short chain-long chain mixture in which the reactive hydroxyl group of the same starch molecule is substituted with a short chain hydrocarbon-containing group having 2 to 4 carbon atoms and a long chain hydrocarbon-containing group having 6 to 24 carbon atoms And starch-substituted derivatives (see JP 2000-159802 A). Since these modified starches are based on starch, they are derived from plants, and are excellent in solvent solubility and compatibility.

Compound containing acryloyl group and isocyanate group (a11):
Examples of the compound (a11) containing an acryloyl group and an isocyanate group include a reaction product of a hydroxyl group-containing acrylic ester and a polyisocyanate compound, and 2-acryloyloxyethyl isocyanate.

  The reaction product of the hydroxyl group-containing acrylate ester and the polyisocyanate compound is obtained by mixing a hydroxyl group-containing acrylate ester (eg, hydroxyethyl acrylate, hydroxybutyl acrylate) little by little with the polyisocyanate compound. When the isocyanate group of the polyisocyanate compound corresponding to the amount is consumed, it can be obtained by a method of stopping the reaction. Polyisocyanate compounds include isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, tolidine diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, tris (phenylisocyanate) thiophosphate, phenylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate. , Xylylene diisocyanate, bis (isocyanatomethyl) cyclohexane, bis (isocyanato) methylcyclohexane, dicyclohexylmethane diisocyanate, isopropylidenebis (cyclohexyl isocyanate), 3- (2′-isocyanatocyclohexyl) propyl isocyanate, diani Jin diisocyanate, diphenyl ether diisocyanate, and the like.

  The unsaturated group-containing starch-based resin (20) is obtained by changing the modified starch (a10) to 50 based on the total solid mass of the modified starch (a10) and the compound (a11) containing an acryloyl group and an isocyanate group. Up to 99% by weight, preferably 60-98% by weight, and the compound (a11) containing an acryloyl group and an isocyanate group in an amount ranging from 1 to 50% by weight, preferably from 2 to 40% by weight, such as an organic solvent, for example Hydrocarbon solvents such as toluene, xylene, cyclohexane and n-hexane; ester solvents such as methyl acetate, ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl amyl ketone; or these In a mixture of the above, monobutyltin oxide, dibutyltin oxide, etc. The catalyst was added, about 50 ° C. to 200 DEG ° C. under stirring, more preferably at a temperature of 60 to 150 ° C., can be obtained 10 hours 30 minutes, more preferably about 1 to 5 hours, by addition reaction. The blending ratio of the modified starch (a10) to the compound (a11) containing an acryloyl group and an isocyanate group is within the above range, and the finish, pencil hardness, scratch resistance, adhesion, alkali resistance and It is preferable for obtaining a coating film having a good balance in solvent resistance.

  The unsaturated group-containing starch-based resin (20) has a number average molecular weight in the range of 3,000 to 2,000,000, particularly 5,000 to 100,000, and a hydroxyl value in the range of 0 to 200 mgKOH. / G, preferably 50 to 150 mgKOH / g, from the viewpoint of scratch resistance and adhesion of the coating film.

Acrylic ester (21) of saccharide and / or modified saccharide:
As the unsaturated group-containing starch-based resin (a1), a saccharide and / or an acrylic ester (21) of a modified saccharide can be preferably used. The acrylic ester (21) of saccharide and / or modified saccharide means an ester of saccharide and / or modified saccharide and acrylic acid.

  Examples of the saccharide include starch, cellulose and other polysaccharides, starch degradation products such as dextrin, oligosaccharides, disaccharides, monosaccharides, and oligosaccharide mixtures obtained by decomposing polysaccharides with acids and enzymes. Of these, maltose can be preferably used. Here, as the modified saccharides, those in which a part of the hydroxyl groups in the saccharides are esterified with at least one selected from carboxylic acids having 2 to 22 carbon atoms, carboxylic acid esters and carboxylic acid halides are preferably used. Can be used.

  Production of the acrylate and / or modified acrylate acrylic ester (21) is based on the total solid mass of acrylic acid or acrylate ester (for example, methyl acrylate) after dissolving the saccharide and / or modified saccharide in a solvent. And an organic solvent such as an organic solvent, for example, in an amount ranging from 50 to 99% by weight, preferably 60 to 98% by weight of saccharide and 1 to 50% by weight, preferably 2 to 40% by weight of acrylic acid or acrylate. Hydrocarbon solvents such as toluene, xylene, cyclohexane and n-hexane; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl amyl ketone; or a mixture of these solvents, etc. For 30 minutes to 10 hours at a temperature of about 60 ° C. to 100 ° C., more preferably 70 to 90 ° C. with stirring. Ri preferably about 1 to 5 hours, the esterification or by transesterification, can be obtained sugars and / or modified sugars acrylic acid ester (21).

  As another production method of the saccharide and / or modified acrylate acrylic ester (21), the saccharide and / or modified saccharide is dissolved in an organic solvent, and an acrylic acid halide (for example, acrylic acid chloride) is added to produce the saccharide. The acid can be neutralized and washed (by dehydrochlorination method). The thus obtained saccharide and / or modified saccharide acrylic ester (21) has a weight average molecular weight of 400 to 200,000, preferably 400 to 100,000, and a hydroxyl value of 0 to 200 mgKOH / g, preferably. Is preferably from 5 to 150 mgKOH / g from the viewpoint of resin production.

Acrylate ester of dextrin and / or modified dextrin (22):
The unsaturated group-containing starch-based resin (a1) is a dextrin having a weight average molecular weight of 400 to 4,000 and having 2 to 14 acryloyl groups per molecule and / or an acrylic ester of a modified dextrin (22 ) Can be preferably used. In addition, it is preferable from the surface of the abrasion resistance of a coating film to have a weight average molecular weight of 400 to 4,000 and 2 to 14 acryloyl groups per molecule.

  Here, as the modified dextrin, those in which a part of the hydroxyl group in the dextrin is converted to a carboxylic acid ester by at least one selected from a carboxylic acid having 2 to 22 carbon atoms, a carboxylic acid ester, and a carboxylic acid halide are suitably used. Can be used. The dextrin and / or modified dextrin acrylate ester (22) is prepared by dissolving dextrin and / or modified dextrin in a solvent, and then dextrin and / or modified dextrin and acrylic acid or acrylate ester (for example, methyl acrylate). ) Based on the total solid content of 50 to 99% by weight of dextrin and / or modified dextrin, preferably 60 to 98% by weight and 1 to 50% by weight of acrylic acid or acrylate, preferably 2 to 40%. Organic solvents such as hydrocarbon solvents such as toluene, xylene, cyclohexane, and n-hexane; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone; Mix in a mixture, etc. A basic compound is added to the mixture and subjected to esterification or transesterification with stirring at a temperature of about 60 ° C. to 100 ° C., more preferably 70 to 90 ° C. for 30 minutes to 10 hours, more preferably about 1 to 5 hours. Can be obtained.

  Acrylic ester (22) of dextrin and / or modified dextrin is prepared by dissolving dextrin and / or modified dextrin in an organic solvent, and then adding an acrylic acid halide (for example, acrylic acid chloride) to neutralize and wash the acid produced. Can also be obtained (dehydrochlorination method).

  The acrylic acid ester (22) of dextrin and / or modified dextrin is partially carboxylic acid esterified by any of carboxylic acid having 2 to 22 carbon atoms, carboxylic acid ester and carboxylic acid halide. May be. The weight average molecular weight of the acrylic acid ester (22) of dextrin and / or modified dextrin is 400 to 4,000, preferably 600 to 3,000, and the hydroxyl value is 0 to 200 mgKOH / g, preferably 5 to 150 mgKOH / g. It is preferable from the viewpoint of resin production and scratch resistance.

  It should be noted that the number of acryloyl groups per molecule of dextrin and / or modified dextrin acrylic ester (22) is in the range of 2 to 14, preferably 3 to 12, the reactivity during light irradiation, and the coating film. It is preferable from the viewpoint of adhesion. As a mixture ratio of dextrin and / or acrylic ester (22) of modified dextrin, 1 to 200 parts by mass, preferably 5 to 180 parts by mass with respect to 100 parts by mass of the photocurable compound (a3). is there.

  By using the unsaturated group-containing starch-based resin (a1) in combination with the photocurable compound (a3) described later, it is possible to obtain a multilayer coating film with even better coating film hardness.

Photopolymerization initiator (a2):
The photopolymerization initiator (a2) cures the photocurable paint (A) by radically polymerizing the radically polymerizable unsaturated groups of the unsaturated group-containing starch resin (a1) and the photocurable compound (a3). It is a compound to be made. Specific examples of the photopolymerization initiator (a2) include, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, Benzyldimethyl ketal, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl)- Butanone, 2,4,6-trimethylbenzoylphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, benzophenone, methyl o-benzoylbenzoate, hydroxybenzophenone, 2-isobutane Pyrthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 2,4,6-tris (trichloromethyl) -S-triazine, 2-methyl-4,6-bis ( And trichloro) -S-triazine and 2- (4-methoxyphenyl) -4,6-bis (trichloromethyl) -S-triazine. These photopolymerizable initiators (a2) can be used alone or in combination of two or more. The content of the photopolymerizable initiator (a2) is 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the unsaturated group-containing starch resin (a1). is there. A photosensitizer may be used in combination with the photopolymerizable initiator (a2) in order to promote the photopolymerization reaction.

  Examples of photosensitizers that can be used in combination include triethylamine, triethanolamine, methyldiethanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, benzoic acid (2 -Dimethylamino) ethyl, Michler's ketone, tertiary amines such as 4,4'-diethylaminobenzophenone, alkylphosphine such as triphenylphosphine, and thioethers such as β-thiodiglycol. These photosensitization accelerators are preferably in the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the unsaturated group-containing starch-based resin (a1).

Photocurable compound (a3):
Photocurable compound (a3) is a radical polymerizable unsaturated monomers, radical polymerizable unsaturated group-containing resin, and at least one selected from the group consisting of radical polymerizable unsaturated group and a thermosetting functional group-containing resin Compounds and / or resins are preferred. Examples of the radically polymerizable unsaturated monomer include a bifunctional polymerizable monomer, a trifunctional or higher functional polymerizable monomer, and a monofunctional polymerizable monomer.

Examples of the bifunctional polymerizable monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and polypropylene. Glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, bisphenol A ethylene oxide modified di (meth) acrylate Bisphenol A propylene oxide modified di (meth) acrylate, 2-hydroxy 1-acryloxy-3-methacryloxypropane, tricyclodecane dimethanol di (me ) Acrylate, di (meth) acryloyloxyethyl acid phosphate, and the like. In addition, as bifunctional polymerizable monomers, there are also monomers that are commercially available from Nippon Kayaku Co., Ltd. under the trade names such as “Kayarad HX-220”, “Kayarad 620”, “Kayarad R-604”, “MANDA”, etc. Can be used.
Here, (meth) acrylate means acrylate and / or methacrylate.

  Examples of the tri- or more functional polymerizable monomer include trimethylolpropane tri (meth) acrylate, trimethylolpropane ethylene oxide modified tri (meth) acrylate, trimethylolpropane propylene oxide modified tri (meth) acrylate, and glycerin tri (meth) acrylate. , Glycerin ethylene oxide modified tri (meth) acrylate, glycerin propylene oxide modified tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, isocyanuric acid ethylene oxide modified triacrylate, dipentaerythritol hexa ( And (meth) acrylate.

  Monofunctional polymerizable monomers that can be used in combination include styrene, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, Cyclohexenyl (meth) acrylate, 2-hydroxyl (meth) acrylate, hydroxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, ε-caprolactone modified tetrahydrofurfuryl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxy Polyethylene glycol (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, isobornyl (meth) ) Acrylate, benzyl (meth) acrylate, ε-caprolactone-modified hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2 -Hydroxy-3-butoxypropyl (meth) acrylate, monohydroxyethyl (meth) acrylate phthalate, paracumylphenol ethylene oxide modified (meth) acrylate, N-methylol (meth) acrylamide, N-methylol (meth) acrylamide butyl ether, Examples include acryloylmorpholine, dimethylaminoethyl (meth) acrylate, and N-vinyl-2-pyrrolidone. As the radically polymerizable unsaturated monomer, it is preferable to use a bifunctional or higher functional polymerizable monomer in view of curability, adhesion, scratch resistance and the like.

The radical polymerizable unsaturated group- containing resin is a resin having two or more radical polymerizable unsaturated groups in one molecule. For example, unsaturated acrylic resin, unsaturated urethane resin, unsaturated epoxy resin, polyester (meta ) Acrylates, unsaturated silicone resins, urethane acrylates, epoxy acrylates, polyester acrylates and the like, and one or more selected from these may be used.

  The radical polymerizable unsaturated group and thermosetting functional group-containing resin is a resin having one or more radical polymerizable unsaturated groups and one or more thermosetting functional groups in one molecule. From the viewpoint of curability of the coating film, it is preferable to have a plurality of the unsaturated group and the functional group. As the thermosetting functional group, a functional group such as a hydroxyl group, an acid group, an epoxy group, or an isocyanate group can be used. Examples of the acid group include a carboxyl group and a phosphate group.

  Specific examples of the above-mentioned radical polymerizable unsaturated group and thermosetting functional group-containing resin include, for example, radical polymerizable unsaturated group and epoxy group-containing acrylic resin, radical polymerizable unsaturated group and isocyanate group-containing acrylic resin, radical Examples thereof include a polymerizable unsaturated group-containing polyester resin and a radical polymerizable unsaturated group-containing epoxy group-containing cresol novolac type epoxy resin.

  Moreover, when a photocurable compound (a3) has a thermosetting functional group, an amino resin, a polyisocyanate compound, an epoxy group containing compound, etc. can be used together, for example. As said amino resin, a melamine resin, a guanamine resin, a urea resin etc. can be used, for example.

  The blending ratio of the photocurable compound (a3) to the unsaturated group-containing starch resin (a1) is 0 to 900 parts by mass, preferably 50 to 100 parts by mass with respect to 100 parts by mass of the unsaturated group-containing starch resin (a1). 400 parts by mass is preferred from the viewpoints of finish and scratch resistance.

  Furthermore, the photo-curable paint (A) may include a crosslinking agent such as a polyisocyanate compound, a matting material, and a surface shape adjusting material, as necessary, to such an extent that the coating film formed by the starch-based colored base paint as a base can be recognized. Surface energy adjusting agents, hardness adjusting agents, ultraviolet absorbers, light stabilizers, antifoaming agents, organic colorants, natural dyes, inorganic pigments, and the like can be used. A cross-linking agent such as a polyisocyanate compound is preferable from the viewpoint of improving the coating film hardness.

  Examples of the organic colorant include those specified in Ordinance No. 37 of the Ministry of Health and Welfare. For example, Red 202 (Risor Rubin BCA), Red 203 (Rake Red C), Red 204 (Rake Red CBA), Red 205 (Risor Red), Red 206 (Risor Red CA), Red 207 (Risole) Red BA), Red 208 (Risor Red SR), Red 219 (Brilliant Lake Red R), Red 220 (Deep Maroon), Red 221 (Toluidine Red), Red 228 (Parmaton Red), orange No. 203 (Permanent Orange), Orange No. 204 (Bench Gin Orange G), Yellow 205 (Bench Gin Yellow G), Red No. 404 (Brilliant Fast Scarlet), Red No. 405 (Permanent Red F5R), Orange No. 401 ( Hansa Orange), Yellow No. 401 ( Nzaero), and the like Blue No. 404 (phthalocyanine blue).

  Specific examples of natural pigments include carotenoids such as carotene, carotenal, capsanthin, lycopene, bixin, crocin, canthaxanthin, and anato. , Chalcones such as safflower, flavonols such as rutin and quercetin, flavones such as cocoa pigment, flavin, riboflavin, quinone, lacaic acid, carminic acid (cochineal), kermesic acid , Anthraquinones such as alizarin, naphthoquinones such as shikonin, alkanine, echinochrome, etc., chlorophyll, hemoglobin, etc. for polyphyllins, curcumin (turmeric), for diketones Etc., in the Betashianijin system, and the like betanin.

  Inorganic pigments include silicic anhydride, magnesium silicate, talc, kaolin, bentonite, mica, titanium mica, bismuth oxychloride, zirconium oxide, magnesium oxide, zinc oxide, titanium oxide, light calcium carbonate, heavy calcium carbonate, light Examples include magnesium carbonate, heavy magnesium carbonate, barium sulfate, yellow iron oxide, bengara, black iron oxide, gunjou, chromium oxide, chromium hydroxide, carbon black, and calamine. The blending ratio of organic pigments, natural pigments, and inorganic pigments can vary depending on the intended use and required performance.

[Starch-based colored base paint]
The starch-based colored base paint is applied as a base layer of the photocurable paint (A) and imparts design properties to the multilayer coating film. It is preferable to use at least one of the following starch-based resin (1), starch-based resin (2) and starch-based resin (3) for the starch-based colored base paint.

Starch-based resin (1)
The starch-based resin (1) is a resin obtained by reacting the modified starch (a10) with a product (I) having an isocyanate group described later.

Modified starch (a10)
The modified starch (a10) is as described in the section “ Unsaturated group-containing starch-based resin (20) ”.

Products having isocyanate groups (I)
The product (I) having an isocyanate group can be obtained by reacting the polyisocyanate compound (a31) with the polyhydric alcohol (a32).

  Examples of the polyisocyanate compound (a31) include isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, tolidine diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, tris (phenylisocyanate) thiophosphate, phenylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene. Diisocyanate, lysine diisocyanate, xylylene diisocyanate, bis (isocyanatomethyl) cyclohexane, bis (isocyanato) methylcyclohexane, dicyclohexylmethane diisocyanate, isopropylidenebis (cyclohexyl isocyanate), 3- (2′-isocyanatocyclohexyl) propylisocyanate Door, dianisidine diisocyanate, diphenyl ether diisocyanate, and the like. Among these, isophorone diisocyanate and hexamethylene diisocyanate are preferably used from the viewpoints of hardness, adhesion, and impact resistance.

  Examples of commercially available products of the polyisocyanate compound (a31) are “Bernock D-750, -800, DN-950, -970 or 15-455” (above, Dainippon Ink and Chemicals, Inc.), “Desmodur. "L, N, HL, or N3390" (product of Bayer, Germany), "Takenate D-102, Takenate D-170HN, Takenate D-202, Takenate D-110 or Takenate D-123N" (Takeda Pharmaceutical Co., Ltd.) Product), “Coronate EH, L, HL or 203” (Nippon Polyurethane Industry Co., Ltd. product) or “Duranate 24A-90CX” (Asahi Kasei Kogyo Co., Ltd. product).

  Specific examples of the polyhydric alcohol (a32) include alkylene diols, trivalent or higher alkylene polyols, ether polyols and polyester polyols, acrylic polyols, and other polyols.

  Examples of the alkylene diol include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, and cyclohexane-1,4. -Diols such as dimethylol, methylpentanediol, hydrogenated bisphenol A;

  Examples of the trihydric or higher alkylene polyol include triols such as glycerin, trimethylolethane, and trimethylolpropane; and tetrahydric or higher alkylene polyols such as pentaerythritol, α-methylglycoside, and sorbitol. As the ether polyol, for example, polyethylene glycol, polypropylene glycol produced by a ring-opening addition reaction of alkylene oxide (specifically, ethylene oxide, diethylene glycol, propylene oxide, dipropylene glycol, butylene oxide, tetrahydrofuran, etc.) Hexols such as polytetramethylene glycol, triethylene glycol, poly (oxyethylene / oxypropylene) glycol, bisphenol A polyethylene glycol ether, bisphenol A polypropylene glycol ether, sucrose, dipentaerythritol, and the like.

  Examples of the polyester polyol include those obtained by a polycondensation reaction between an organic dicarboxylic acid or an anhydride thereof and an organic diol component under an excess of organic diol. Specific examples include a polyester polyol which is a condensate of adipic acid and ethylene glycol and a condensate of adipic acid and neopentyl glycol. The organic dicarboxylic acid used here is an aliphatic, alicyclic or aromatic dicarboxylic acid having 2 to 44 carbon atoms, particularly 4 to 36, such as succinic acid, adipic acid, azelaic acid, sebacic acid. Maleic acid, fumaric acid, glutaric acid, hexachloroheptanedicarboxylic acid, cyclohexanedicarboxylic acid, o-phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrachlorophthalic acid and the like. In addition to these dicarboxylic acids, a small amount of polycarboxylic acid anhydrides or unsaturated fatty acid adducts having three or more carboxyl groups can be used in combination. Examples of the organic diol component include alkylene glycol such as ethylene glycol, propylene glycol, butylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol, dimethylolcyclohexane, butylethylpentyl glycol, and the like. Methylpentanediol and the like. In some cases, a trivalent or higher polyol such as trimethylolpropane, glycerin or pentaerythritol may be used in a small amount.

  Among the polyhydric alcohols (a32), in particular, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, hydrogenated bisphenol A, glycerin, trimethylolethane, trimethylol What is selected from the group consisting of propane, pentaerythritol, dipentaerythritol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (oxyethylene / oxypropylene) glycol, bisphenol A ethylene glycol ether, bisphenol A polypropylene glycol ether, Suitable for impact resistance and bending resistance.

  The reaction of the polyisocyanate compound (a31) and the polyhydric alcohol (a32) is carried out using an organic solvent (for example, a hydrocarbon system such as toluene, xylene, cyclohexane or n-hexane; an ester system such as methyl acetate, ethyl acetate or butyl acetate; Acetone, methyl ethyl ketone, methyl isobutyl ketone, ketone series such as methyl amyl ketone; or a mixture thereof). As the reaction ratio of the polyisocyanate compound (a31) and the polyhydric alcohol (a32), the number of moles of OH groups based on the polyhydric alcohol (a32) relative to the number of moles of NCO groups based on the polyisocyanate compound (a31) is NCO. Group / OH group = 1 / 0.4 to 1 / 0.95, preferably 1 / 0.5 to 1 / 0.9, so that the free isocyanate remains, the polyisocyanate compound (a31) and the polyvalent Alcohol (a32) is mixed and, for example, a catalyst such as monobutyltin oxide or dibutyltin oxide is appropriately added, and at a temperature of about 50 ° C. to about 200 ° C., preferably about 60 to 150 ° C. under stirring, By reacting for 30 minutes to 10 hours, preferably about 1 to 5 hours, a product (I) solution having an isocyanate group can be produced. The NCO value of the obtained product (I) having an isocyanate group is preferably in the range of 5 to 250 mg NCO / g, particularly 7 to 200 mg NCO / g.

  Here, the blending ratio of the modified starch (a10) and the product (I) having an isocyanate group can be appropriately adjusted according to the required coating film performance. Preferably, the modified starch (a10) is 50 to 99% by mass, preferably 60 to 98%, based on the total solid mass of the starch and / or modified starch (a10) and the product (I) having an isocyanate group. And carbonization of an organic solvent such as toluene, xylene, cyclohexane, n-hexane, etc. in an amount ranging from 1 to 50% by weight, preferably from 2 to 40% by weight, of the product (I) having an isocyanate group. Hydrogen solvents; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone; or a mixture thereof in a monobutyl tin oxide as appropriate. Then, a catalyst such as dibutyltin oxide is added, and is stirred at about 50 to 200 ° C., more preferably 60 to 15 At ℃ temperature, it can be obtained 10 hours 30 minutes, more preferably about 1 to 5 hours, starch-based resin by addition reaction of (1).

  Here, the blending ratio of the modified starch (a10) and the product (I) having an isocyanate group is within the above range, and it is finished, pencil hardness, scratch resistance, adhesion, alkali resistance and solvent resistance. It is preferable in order to obtain a coating film having a good balance in properties. The number average molecular weight of the obtained starch-based resin (1) is preferably in the range of 3,000 to 200,000, more preferably in the range of 5,000 to 100,000. The resin composition produced in this manner can be suitably used as a binder for starch-based paints by dissolving or dispersing it in an organic solvent-based solvent.

Starch-based resin (2)
The starch-based resin (2) is a resin obtained by reacting the modified starch (a10), the product (I) having an isocyanate group, and the vinyl copolymer resin (a33). The modified starch (a10) is as described in the section of “Unsaturated group-containing starch-based resin (20)”, and the product (I) having an isocyanate group is the section of “starch-based resin (1)”. As explained in. The vinyl copolymer resin (a33) can be obtained by subjecting a mixture of radically polymerizable unsaturated monomers to a radical polymerization reaction in the presence of an organic solvent and a polymerization initiator.

  The mixture of the radical polymerizable unsaturated monomers is 1 to 90% by weight, preferably 5 to 80% by weight, more preferably 10 to 85% by weight based on the total weight of the mixture. % By weight, hydroxyl group-containing radically polymerizable unsaturated monomer 1 to 50% by weight, preferably 2 to 40% by weight, more preferably 5 to 30% by weight and other radically polymerizable unsaturated monomers 0 to 98% by weight, preferably A multi-layer excellent in finish, adhesion, scratch resistance, solvent resistance and weather resistance, being a mixture of radically polymerizable unsaturated monomers comprising 2 to 95% by mass, more preferably 5 to 90% by mass It is preferable for forming a coating film.

  Examples of the aromatic radical polymerizable unsaturated monomer include styrene, vinyl toluene, 2-methyl styrene, t-butyl styrene, chlorostyrene, vinyl naphthalene, and the like.

  Hydroxyl group-containing radical polymerizable unsaturated monomers include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, methacrylic acid. Hydroxyalkyl esters of acrylic acid or methacrylic acid having 2 to 8 carbon atoms in the alkyl group, such as 2-hydroxypropyl acid and 3-hydroxypropyl methacrylate, and (meth) acrylic acid hydroxyalkyl ester lactone modified products (Daicel Chemistry) Product name "PLAXEL F" series). Among these, modified starch (a10) contains at least one selected from 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and 4-hydroxybutyl acrylate. And from the viewpoint of improving the compatibility with the product (I) having an isocyanate group and ensuring the stability of the paint.

  Other radical polymerizable unsaturated monomers include carboxyl group-containing polymerizable unsaturated monomers such as (meth) acrylic acid, maleic acid, crotonic acid, itaconic acid, fumaric acid, such as methyl acrylate, ethyl acrylate, acrylic N-propyl acid, isopropyl acrylate, n-, i- or t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, lauryl acrylate, cyclohexyl acrylate, methacryl Acid methyl, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-, i- or t-butyl methacrylate, hexyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate C1-C18 alkyl ester or cycloalkyl ester of acrylic acid or methacrylic acid such as N; methyl-acrylamide, N-butoxymethylacrylamide, N-methoxymethylacrylamide, N-methylolmethacrylamide, N-butoxymethylmethacrylate Mention may be made of N-substituted acrylamide-based or N-substituted methacrylamide-based monomers such as amides, and these polymerizable unsaturated monomers may also include fatty acid-modified polymerizable unsaturated monomers.

  The fatty acid-modified polymerizable unsaturated monomer includes a polymerizable unsaturated monomer having a polymerizable unsaturated group at the end of a fatty acid-derived hydrocarbon chain. Examples of the fatty acid-modified polymerizable unsaturated monomer include those obtained by reacting a fatty acid with an epoxy group-containing polymerizable unsaturated monomer and / or a hydroxyl group-containing polymerizable unsaturated monomer.

  Examples of fatty acids include dry oil fatty acids, semi-dry oil fatty acids and non-dry oil fatty acids. Examples of dry oil fatty acids and semi-dry oil fatty acids include fish oil fatty acids, dehydrated castor oil fatty acids, safflower oil fatty acids, and linseed oil fatty acids. , Soybean oil fatty acid, sesame oil fatty acid, poppy oil fatty acid, eno oil fatty acid, hemp oil fatty acid, grape kernel oil fatty acid, corn oil fatty acid, tall oil fatty acid, sunflower oil fatty acid, cottonseed oil fatty acid, walnut oil fatty acid, rubber seed oil fatty acid, hygiene Examples include acid fatty acids, and non-drying oil fatty acids include, for example, coconut oil fatty acids, hydrogenated coconut oil fatty acids, and palm oil fatty acids. These can be used alone or in combination of two or more. Furthermore, these fatty acids can be used in combination with caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and the like.

  As the monomer that can be reacted with the above fatty acid in order to produce a fatty acid-modified polymerizable unsaturated monomer, a polymerizable unsaturated monomer containing an epoxy group is suitable, for example, glycidyl (meth) acrylate, β-methyl Examples include glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether.

  The vinyl copolymer resin (a33) can be easily prepared, for example, by subjecting a mixture of the above radical polymerizable unsaturated monomers to a radical polymerization reaction in an organic solvent in the presence of a polymerization initiator. A mixture of a polymerizable unsaturated monomer and a mixture of a polymerization initiator are uniformly added dropwise, for example, at a reaction temperature of 60 to 200 ° C., preferably 80 to 180 ° C., for about 30 minutes to 6 hours, preferably 1 to 5 The desired product can be obtained by reacting for a period of time.

  Examples of the organic solvent include hydrocarbon solvents such as toluene, xylene, cyclohexane, and n-hexane; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone. A ketone solvent; or a mixture thereof.

  The vinyl copolymer resin (a33) preferably has a hydroxyl value of 5 to 400 mgKOH / g and a weight average molecular weight of 3,000 to 100,000, particularly 5,000 to 20,000. The vinyl copolymer resin (a33) produced as described above can be used by dissolving or dispersing in an organic solvent solvent. The starch-based resin (2) is a resin obtained by reacting the modified starch (a10), the product (I) having an isocyanate group, and the vinyl copolymer resin (a33). Here, the blending ratio of the modified starch (a10), the product (I) having an isocyanate group, and the vinyl copolymer resin (a33) can be appropriately adjusted according to the required coating film performance. .

  The starch-based resin (2) is a modified starch (a10) based on the total solid weight of the modified starch (a10), the product (I) having an isocyanate group and the vinyl copolymer resin (a33). 99% by mass, more preferably 65 to 95% by mass, 1 to 39% by mass of the product (I) having an isocyanate group, more preferably 2 to 33% by mass and 1 to 39% of the vinyl copolymer resin (a33). Mixed in an organic solvent similar to that described above with respect to the production of the starch-based resin (1) in an amount in the range of mass%, more preferably in the range of 2 to 33 mass%, such as monobutyltin oxide, dibutyltin oxide, etc. It is obtained by adding a tin catalyst and reacting with stirring at a temperature of about 50 ° C. to about 200 ° C., more preferably about 60 to 150 ° C. for 30 minutes to 10 hours, more preferably about 1 to 5 hours. Door can be.

  The blending ratio of the modified starch (a10), the product (I) having an isocyanate group and the vinyl copolymer resin (a33) is within the above range, and the finish, pencil hardness, scratch resistance, adhesion, It is preferable for obtaining a coating film having a good balance between alkali resistance and solvent resistance.

  The number average molecular weight of the starch-based resin (2) is preferably in the range of 3,000 to 200,000, more preferably in the range of 5,000 to 100,000. The starch-based resin (2) produced as described above can be suitably used by dissolving or dispersing in an organic solvent-based solvent.

Starch-based resin (3)
The starch-based resin (3) is a resin containing a product (II) obtained by binding the vinyl copolymer resin (a33) to the modified starch (a10) by graft polymerization. Further, the resin obtained by reacting the product (II) with the product (I) having an isocyanate group obtained by reacting the polyisocyanate compound (a31) with the polyhydric alcohol (a32) is also used. You can also The modified starch (a10) is as described in the section of “Starch Resin (1)”, and the product (II) is produced by graft polymerization of the vinyl copolymer resin (a33).

  Conventionally, in US Pat. Nos. 3,425,971 and 3,981,100 and JP-A-56-167746, a cerium salt is used as a radical polymerization initiation catalyst in water-dispersed or slurry-like starch or modified starch. A graft polymerization of vinyl monomers is disclosed. JP-A Nos. 54-120698 and 55-90518 disclose graft polymerization of styrene and acrylic monomers on starch modified with maleic acid, which is a compound containing an unsaturated group. JP-A-8-239402 discloses graft polymerization of (vinyl) esterified starch and vinyl monomer in an organic solvent. JP-A-55-133472 and JP-A-56-157463 disclose graft polymerization of vinyl monomers onto cellulose acetate butyrate in a solution using a radical initiator. If the nitrocellulose acetate is replaced with starch and / or modified starch, it is easy to bond the vinyl polymer to the modified starch (a10) by graft polymerization.

  As mentioned above, some known examples have been described regarding the graft polymerization of the vinyl polymer, but the target starch resin (3) can be produced by these known methods.

  Here, the vinyl copolymer resin (a33) is a resin obtained by subjecting a radical polymerizable unsaturated monomer or a mixture thereof to a radical polymerization reaction in the presence of an organic solvent and a polymerization initiator.

  Here, the ratio of the modified starch (a10) and the vinyl copolymer resin (a33) is not particularly limited, but it is preferable to use a mixture of monomers having different properties as the radical polymerizable unsaturated monomer, This is preferable from the viewpoint of forming a coating film excellent in adhesion, scratch resistance, solvent resistance and weather resistance.

  The radically polymerizable unsaturated monomer is 1 to 90% by mass, preferably 5 to 80% by mass of the radically polymerizable unsaturated monomer 1 to 1% by mass, based on the total mass of the mixture. It is desirable to be a mixture of radically polymerizable unsaturated monomers comprising 50% by weight, preferably 2 to 40% by weight and other radically polymerizable unsaturated monomers 0 to 98% by weight, preferably 47 to 95% by weight. In addition, 1-50 mass% of aromatic radically polymerizable unsaturated monomers, hydroxyl group-containing radically polymerizable unsaturated monomers, and other radically polymerizable unsaturated monomers are the radically polymerizable unsaturated listed in the starch-based resin (2). Same as monomer.

  Graft polymerization of these radically polymerizable unsaturated monomers is simplified by, for example, dropping a mixture of the above radically polymerizable unsaturated monomers and a polymerization initiator into an organic solvent solution containing modified starch and causing radical polymerization reaction. Can be done. A mixture of a radically polymerizable unsaturated monomer and a mixture of a polymerization initiator are uniformly dropped, for example, at a reaction temperature of 60 to 200 ° C., preferably 80 to 180 ° C., for about 30 minutes to 6 hours, preferably 1 to It can be obtained by reacting for 5 hours.

  Here, as a polymerization initiator, a known radical polymerization initiator can be used, but when a method of dropping a monomer mixture and a polymerization initiator in an organic solvent solution of modified starch and performing graft polymerization, It is preferable to use a peroxide-based initiator. Examples of such peroxide-based initiators include hydroperoxides such as t-butyl hydroperoxide, p-menthane hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide; Peroxyesters such as oxylaurate, t-butylperoxybenzoate, t-butylperoxydecanoate; peroxy such as 1,5-di-t-butylperoxy-3,3,5-trimethylcyclohexane Ketals; ketone peroxides such as ethyl acetoacetate; and diacyl peroxides such as benzoyl peroxide.

  Examples of the organic solvent include hydrocarbon solvents such as toluene, xylene, cyclohexane and n-hexane; ester solvents such as methyl acetate, ethyl acetate and butyl acetate; acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl amyl ketone. Ketone solvents such as, or a mixture thereof. The product (I) having an isocyanate group is as described in the section of “Starch Resin (1)”.

  The starch-based resin (3) is 50 to 99% by mass, preferably 60 to 98% of the product (II), based on the total solid mass of the product (II) and the product (I) having an isocyanate group. % By weight of the product (I) having an isocyanate group in an amount of 1 to 50% by weight, preferably 2 to 40% by weight, and an organic solvent (for example, hydrocarbon such as toluene, xylene, cyclohexane, n-hexane) Solvent, ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone; or a mixture thereof), and monobutyltin oxide as appropriate. Then, a catalyst such as dibutyltin oxide is added and stirred at a temperature of about 50 ° C. to about 200 ° C., preferably 60 to 150 ° C. Minutes to 10 hours, preferably obtained by 1-5 hours the addition reaction.

Proportion of the isocyanate group-containing compound (I)及Beauty raw Narubutsu (II), it is within the above range, finishing property, pencil hardness, mar resistance, adhesion, alkali resistance and solvent resistance It is preferable for obtaining a balanced coating film.

  The starch-based resin (3) preferably has a number average molecular weight in the range of 3,000 to 2,000,000, particularly 5,000 to 100,000, from the viewpoint of film forming properties. In addition, a starch resin (1), a starch resin (2), and a starch resin (3) can also be used in combination of 2 or more types.

  Moreover, you may mix | blend other natural product origin resin with a starch-type coloring base coating material as needed. Examples of natural-derived resins other than starch-based resins include vegetable fibers (cellulose resins), polyhydroxycarboxylic acids typified by polylactic acid, polycaprolactam, and modified polyvinyl alcohol. In addition, aliphatic polyesters typified by polycaprolactone are also derived from plants. Besides those listed here, plant-derived resins are known. In the present invention, any natural-derived resin that is soluble in a solvent can be used, and among these, a cellulose-derived resin is preferred.

  The inventor of the present invention adds a small amount of nitrocellulose and / or cellulose acetate butyrate in the present invention, so that the drying property of the coating film when used as a one-component lacquer coating is improved and the surface hardness is increased. I found. In addition, polyhydroxycarboxylic acid, particularly polylactic acid, has an effect of increasing the surface hardness, but the coating film tends to become brittle, and a resin derived from cellulose has a better balance of coating film performance and is easy to use.

  As nitrocellulose that can be suitably used for the starch-based colored base paint, industrial nitrified cotton BNC-HIG-2 (trade name, manufactured by France Bergerac NC), industrial nitrified cotton RS1-4 (trade name, Korean CNC), Swancell HM1-4 (trade name, manufactured by Kyosei Yoko Co., Ltd.), Selnova BTH1-4 (trade name, manufactured by Asahi Kasei Chemicals Co., Ltd.), and the like. As cellulose acetate butyrate, CAB381- 0.1, CAB381-0.5, CAB381-2, CAB531-1, CAB551-0.01, CAB551-0.2 (all trade names, manufactured by Eastman Chemical Products) and the like. Moreover, an organic coloring agent, a natural pigment | dye, and an inorganic pigment can be used for a starch-type coloring base coating material as needed.

  As the organic colorant, natural coloring matter and inorganic pigment, those exemplified in the photocurable coating (A) can be used. The blending ratio of the organic pigment, natural pigment and inorganic pigment may vary depending on the application used and required performance, but is usually 0.001 to 100 parts by mass of the resin component of the starch-based colored base paint. It is 10 mass parts, Preferably it is the range of 0.01-5 mass parts. Furthermore, a conventionally known crosslinking agent, for example, a compound exemplified as the polyisocyanate compound (a31), a melamine resin, a guanamine resin, a urea resin, or the like is added to the starch-based colored base paint for the purpose of improving curability. be able to.

  Also, plasticizers, UV stabilizers, metal dryers, fluidity modifiers, anti-repellent agents, anti-sagging agents, antioxidants, matting agents, glossing agents, preservatives, curing accelerators, anti-scratch agents, antifoaming agents An agent or the like can be appropriately added. The starch-based colored base paint is, for example, a paint such as roller painting, brush painting, immersion painting, spray painting (non-electrostatic painting, electrostatic painting, etc.), curtain flow painting, screen printing, letterpress printing, or the like. It can be applied by printing techniques.

[Method for forming multilayer coating film]
In the method for forming a multilayer coating film of the present invention, there is no particular limitation on the object to be coated, and metals, plastics, wood and the like can be used. Among these, the plastic product which provided the designability, hardness, and abrasion resistance can be obtained by forming the multilayer coating film of this invention especially using a to-be-coated article and a plastic. Examples of such plastic include acrylic resin, polyester resin, polyamide resin, polycarbonate resin, ABS resin, polypropylene resin, and polyethylene resin.

Examples of the method for forming a coating film of the present invention include the following three steps.
On the object selected from the above,
(Step 1) The starch-based colored base paint is applied so as to have a dry film thickness of 0.1 to 30 μm, preferably 0.5 to 10 μm, and more preferably 1 to 5 μm. Next, the coating film after coating is dried at a temperature lower than 100 ° C., preferably 40 ° C. or higher and 90 ° C. or lower for 1 to 40 minutes. Or set at room temperature (less than 40 ° C) for 10 minutes or more.
(Step 2) The photocurable paint (A) is applied in a dry film thickness of 0.1 to 30 μm, preferably 1 to 25 μm, more preferably 5 to 20 μm.
(Step 3) A multilayer coating film can be obtained by irradiating the coating film with light.

  Examples of the coating method for the starch-based colored base paint and the photocurable paint (A) include a spray coating method, an electrostatic coating method, a curtain coat coating method, a spin coat coating method, and a dipping coating method. Although a coating film can be formed by the said coating method, the spray coating method is preferable among these.

  In the coating method, an organic solvent can be used as necessary. The solid content concentration of the photocurable paint (A) is not particularly limited as long as it is a paintable range, but is preferably in the range of 10 to 50% by mass. In order to volatilize the organic solvent remaining in the coating material after spray coating, heat at 40 ° C or higher and 90 ° C or lower for 1 to 40 minutes, or set at room temperature (less than 40 ° C) for 10 minutes or longer. Good to do.

  In addition, in order to harden the coating film of a photocurable coating material (A), the combined use system of light irradiation or light irradiation and a heating can be used. Note that in the combined system of light irradiation and heating, light irradiation and heating can be applied simultaneously, heating can be applied after light irradiation, or light irradiation can be performed after heating.

In the present invention, light irradiation means irradiation with radiation. Although there is no restriction | limiting in particular as the said radiation, An electron beam, an ultraviolet-ray, visible light, an alpha ray, a beta ray, a gamma ray etc. can be used. The range of ultraviolet rays having a wavelength of 150 to 450 nm is preferable. Depending on the type of photopolymerization initiator, an irradiation source having a highly sensitive wavelength can be appropriately selected and used.
Examples of the ultraviolet irradiation source include a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a carbon arc, a metal halide lamp, and sunlight. UV irradiation conditions to the coating film is usually integrated light quantity 100~2,000mJ / cm ^2, preferably is suitable range of the 200~1,500mJ / cm ^2. When irradiating with ultraviolet rays, the irradiation time is preferably about 1 second to 5 minutes.

  The heating means is not particularly limited, and for example, drying equipment such as a hot air furnace, an electric furnace, and infrared induction heating can be applied. The heating temperature is usually in the range of about 35 to 100 ° C., and preferably in the range of 40 to 90 ° C., particularly when the article to be coated is plastic. The heating time is not particularly limited, but usually a range of 1 to 30 minutes is preferable. When applying a photocurable coating (A) containing a solvent, it is desirable that the solvent is volatilized by heating or setting after coating, and then irradiating with light.

  Articles by the coating film forming method of the present invention are, for example, materials such as electric parts, mobile phones, lighting, electric elements, semiconductors, and vending (for example, paint materials, adhesive materials, printing materials, sheet materials, laminated materials, and molding materials). Material etc.).

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited only to this. “Parts” and “%” are “parts by mass” and “% by mass” unless otherwise specified.

[Production Example 1] Modified starch No. 1 1 production example (corresponding to modified starch (a10))
25 parts of high amylose corn starch (hydroxyl value 500 mg KOH / g) is suspended in 200 parts of dimethyl sulfoxide (DMSO), heated to 90 ° C. with stirring, and held at that temperature for 20 minutes for gelatinization. To this solution, 20 parts of sodium bicarbonate was added as a catalyst, 17 parts of vinyl laurate was added while maintaining 90 ° C., and reacted at that temperature for 1 hour. Next, 37 parts of vinyl acetate was further added and reacted at 80 ° C. for 1 hour. Thereafter, the reaction solution was poured into tap water, stirred at high speed, pulverized, filtered, dehydrated and dried. 1 was prepared.

[Production Example 2] Polyurethane resin solution No. Example 1 (corresponding to product (I))
Into a 1 L reaction vessel equipped with a thermometer, thermostat, stirrer, condenser, and dropping device, 125 parts of toluene and 377 parts of isophorone diisocyanate (corresponding to polyisocyanate compound (a31)) are charged and stirred under a nitrogen atmosphere. The temperature was raised to 80 ° C.
Next, 123 parts of 1,4-butanediol (corresponding to polyhydric alcohol (a32)) was added dropwise over 3 hours. After completion of the addition, the mixture was aged at 80 ° C. for 30 minutes to obtain a resin solid content of 80% and a polyurethane resin solution. No. 1 was prepared. The polyurethane resin solution No. The NCO value of the resin solid content of No. 1 was 55 mg NCO / g.

[Production Example 3] Acrylic resin solution No. 1 production example (corresponding to vinyl copolymer resin (a33))
Into a 1 L reaction vessel equipped with a thermometer, a thermostat, a stirrer, a cooling tube and a dropping device, 333 parts of toluene was charged, stirred and mixed in a nitrogen atmosphere, and heated to 100 ° C. Subsequently, the following “mixture No. 1” solution was added dropwise over 4 hours, and after completion of the addition, the solution was aged at 100 ° C. for 1 hour to obtain acrylic resin solution No. 1 having a resin solid content of 60%. 1 was obtained. The obtained acrylic resin solution No. The hydroxyl value of 1 resin solids was 86 mgKOH / g.
[Mixture No. 1]
Styrene 200 parts Methyl methacrylate 150 parts N-butyl acrylate 50 parts 2-hydroxyethyl methacrylate 100 parts 2,2'-azobis-2-methylbutyronitrile 25 parts

[Production Example 4] Acrylic resin solution No. 2 production examples (for comparative production examples)
Into a 1 L reaction vessel equipped with a thermometer, a thermostat, a stirrer, a cooling tube and a dropping device, 333 parts of toluene was charged, stirred and mixed in a nitrogen atmosphere, and heated to 100 ° C. Next, the following “mixture No. 2” solution was added dropwise over 4 hours. After completion of the addition, the mixture was aged at 100 ° C. for 1 hour to obtain an acrylic resin solution No. 2 having a resin solid content of 60%. 2 was obtained. The obtained acrylic resin solution No. The hydroxyl value of the resin solid content of No. 2 was 86 mgKOH / g.
[Mixture No. 2]
Methyl methacrylate 350 parts N-butyl acrylate 50 parts 2-hydroxyethyl methacrylate 100 parts 2,2'-azobis-2-methylbutyronitrile 25 parts

[Production example of starch-based resin]
[Production Example 5] Starch-based resin solution No. Production Example 1 595 parts of butyl acetate was charged in a 1 L reaction vessel equipped with a thermometer, thermostat, stirrer, cooling tube and cooling tube, and the temperature was raised to 50 ° C. while stirring in a nitrogen atmosphere. Next, modified starch No. 1 obtained in Production Example 1 while maintaining 50 ° C. 1 Charge 180 parts in a reaction vessel, then heat up to 100 ° C. Stir until 1 is completely dissolved.
Next, the polyurethane resin solution No. obtained in Production Example 2 was used. 25 parts of 1 was added and stirred until uniform, then 0.02 part of dibutyltin dilaurate was added as a catalyst, and the reaction was carried out at 100 ° C. for 6 hours with stirring in a nitrogen atmosphere. Resin solution no. 1 was obtained. Starch-based resin solution No. The NCO value of 1 resin solids was 0.4 mg NCO / g.

[Production Example 6] Production example of graft product solution (for colored base paint)
Into a 1 L reaction vessel equipped with a thermometer, thermostat, stirrer, condenser and dropping device, 466 parts of butyl acetate was charged and heated to 50 ° C. with stirring in a nitrogen atmosphere. Subsequently, the modified starch No. obtained in Production Example 1 was maintained at 50 ° C. 1 was charged into a 160-part reaction vessel, and then heated to 100 ° C., and the modified starch No. 1 charged was charged. Stir until 1 is completely dissolved. Next, a “mixture No. 3” solution having the following composition was added dropwise over 1 hour. After completion of the addition, the mixture was aged at 100 ° C. for 1 hour to obtain a graft product solution having a resin solid content of 30%.

[Mixture No. 3]
Styrene 28 parts Methyl methacrylate 4 parts N-butyl acrylate 4 parts 2-hydroxyethyl methacrylate 4 parts Percadox CH-50L (Note 1) 4 parts (Note 1) Percadox CH-50L: Diacyl peroxide 50% contained , Kayaku Akzo Co., Ltd., polymerization initiator

[Production Example 7] Starch-based resin solution No. Example 2 (for colored base paint)
In a 1 L reaction vessel equipped with a thermometer, thermostat, stirrer, cooling tube and cooling tube, 581.6 parts of butyl acetate and the acrylic resin solution No. obtained in Production Example 3 were used. 13.4 was charged, and the temperature was raised to 50 ° C. while stirring under a nitrogen atmosphere. Next, modified starch No. 1 obtained in Production Example 1 while maintaining 50 ° C. 1 160 parts are charged into a reaction vessel, and then heated to 100 ° C., and the charged modified starch No. 1 is charged. Stir until 1 is completely dissolved.
Next, the polyurethane resin solution No. obtained in Production Example 2 was used. 25 parts of 1 was added and stirred until uniform, then 0.02 part of dibutyltin dilaurate was added as a catalyst, and the reaction was carried out at 100 ° C. for 6 hours with stirring in a nitrogen atmosphere. Resin solution no. 2 was obtained. Starch-based resin solution No. The NCO value of resin solids of No. 2 was 0.4 mg NCO / g.

[Production Example 8] Starch-based resin solution No. Example 3 (for colored base paint)
125 L of toluene and 292 parts of hexamethylene diisocyanate were charged in a 1 L reaction vessel equipped with a thermometer, thermostat, stirrer, condenser and dropping device, and the mixture was stirred and mixed in a nitrogen atmosphere and heated to 80 ° C. Next, 208 parts of triethylene glycol was added dropwise over 3 hours, and after completion of the addition, the mixture was aged at 80 ° C. for 30 minutes to give a polyurethane resin solution No. 80 having a resin solid content of 80%. 2 was obtained. The NCO value of this polyurethane resin was 58 mg NCO / g.
Next, 41 parts of butyl acetate and 600 parts of the graft product solution obtained in Production Example 6 were charged into another 1 L reaction vessel equipped with a thermometer, a thermostat, a stirrer, and a condenser, and stirred in a nitrogen atmosphere. The temperature was raised to 100 ° C. Next, the polyurethane resin solution No. obtained above. 2 was added and stirred until homogeneous, then 0.04 part of dibutyltin dilaurate was added as a catalyst, reacted at 100 ° C. for 6 hours with stirring in a nitrogen atmosphere, diluted with butyl acetate to obtain a solid content of 25 % Of the starch-based resin solution No. 3 was obtained.

[Production of starch-based colored base paint]
[Production Example 9] Colored base paint No. Production Example 1 Starch Resin Solution No. 1 obtained in Production Example 5 1 400 parts (solid content 100 parts), Alpaste FX-7640NS (note 2) 46 parts (solid content 23 parts), high concrete black (note 3) 3 parts (solid content 3 parts), silicia 446 (note 4) 1.5 parts (1.5 parts of solid content) and 59.5 parts of methyl ethyl ketone were added and mixed well with a stirrer. 1 was obtained.

(Note 2) Al paste-7640NS: Toyo Aluminum Co., Ltd., trade name, aluminum paste.
(Note 3) High-conc black: A colorant for solvent-type paints manufactured by Yokohama Chemical Co., Ltd.
(Note 4) Silicia 446: Water-containing amorphous silicon dioxide (matting agent) manufactured by Fuji Silysia Chemical Ltd.

[Production Example 10] Colored base paint No. Production Example 2 Starch Resin Solution No. obtained in Production Example 7 2, 400 parts (solid content 100 parts), Alpaste FX-7640NS 46 parts (solid content 23 parts), High Conk Black 3 parts (solid content 3 parts), Silicia 446 1.5 parts (solid content 1.5 parts) And 59.5 parts of methyl ethyl ketone were added and mixed thoroughly with a stirrer. 2 was obtained.

[Production Example 11] Colored base paint No. Production Example 3 The colored base paint No. 3 obtained in Production Example 9 was used. 1, 5 parts of Takenate D-170HN (Note 5) was added and stirred, and the solid content was adjusted with methyl ethyl ketone. 3 was obtained.

(Note 5) Takenate D-170HN: Takeda Pharmaceutical Company, trade name, isocyanurate of hexamethylene diisocyanate.

[Production Example 12] Colored base paint No. Production Example 4 Starch-based resin solution No. obtained in Production Example 8 3, 400 parts (solid content 100 parts), Alpaste FX-7640NS 46 parts (solid content 23 parts), High Conk Black 3 parts (solid content 3 parts), Silicia 446 1.5 parts (solid content 1.5 parts) And 59.5 parts of methyl ethyl ketone were added and mixed thoroughly with a stirrer. 4 was obtained.

Production Example of Unsaturated Group-Containing Starch Resin (20) [Production Example 13] Unsaturated group-containing starch resin solution No. Example 1 (2-acryloyloxyethyl isocyanate addition type)
In a 1 L reaction vessel equipped with a thermometer, thermostat, stirrer, condenser, and dropping device, 300 parts of dehydrated butyl acetate was charged, and the temperature was raised to 50 ° C. while stirring in a nitrogen atmosphere. Subsequently, the modified starch No. obtained in Production Example 1 was maintained at 50 ° C. 1 180 parts was charged into a reaction vessel, and then heated to 110 ° C. Stir until 1 is completely dissolved.
20 parts of 2-acryloyloxyethyl isocyanate and 0.04 part of dibutyltin dilaurate were added and reacted at 110 ° C. for 3 hours. Then, 300 parts of butyl acetate was added and cooled, and an unsaturated group-containing starch having a solid content concentration of 25%. Resin solution no. 1 was obtained.

[Production Example 14] Unsaturated group-containing starch-based resin solution No. Example 2 (isophorone diisocyanate-hydroxyethyl acrylate addition type)
Into a 1 L reaction vessel equipped with a thermometer, thermostat, stirrer, condenser, and dropping device, 300 parts of dehydrated butyl acetate and 31 parts of isophorone diisocyanate were charged, and the temperature was raised to 110 ° C. Subsequently, it hold | maintained at 110 degreeC and 16 parts of hydroxyethyl acrylates were dripped over 1 hour. After reacting for 1 hour while maintaining at 110 ° C., the modified starch No. 1 obtained in Production Example 1 was used. 1 180 parts and 0.04 part of dibutyltin dilaurate are charged into a reaction vessel and reacted at 110 ° C. for 3 hours. Then, 381 parts of butyl acetate is charged and cooled to obtain an unsaturated group-containing starch system having a solid content concentration of 25%. Resin solution No. 2 was obtained.

Production Example of Acrylic Ester (21) of Sugar and / or Modified Sugar [Production Example 15] Unsaturated group-containing starch resin solution No. Production Example 3 3 parts of maltose was dissolved in 50 mL of dimethylformamide, and 10 mL of triethylamine was added at 0 ° C. Furthermore, acryloyl chloride 4.5mL was dripped at 0 degreeC, and it returned to room temperature under stirring. After stirring for 4 hours, the reaction solution was filtered with suction through filter paper. Acetone 300 mL was added to cause precipitation, and the precipitate was collected by suction filtration and dried well under reduced pressure to obtain 8 parts of a crude product. Then, after collecting fractions with a purified elution solvent (ethyl acetate / methanol / water = 7: 2: 1), the organic solvent is concentrated under reduced pressure, and the residue is lyophilized to obtain 5 parts of a white powder. It was. Next, the white powder was diluted with butyl acetate, and the unsaturated group-containing starch resin solution No. 3 was obtained.

  Unsaturated group-containing starch resin No. When the number of acryloyl groups introduced into 3 was confirmed by NMR measurement (Note 6), acryloyl groups were introduced into 4 of the 8 hydroxyl groups of maltose.

(Note 6) NMR measurement: using heavy water as a measurement solvent, proton NMR of 200 MHz was used. It was determined from the ratio of the integral value of protons derived from an acryloyl group (δ value of 5.9 to 6.6 ppm) and the integral value of protons at the anomeric position of the glucose unit skeleton (δ value of 4.7 to 5.5 ppm). .

Example of production of acrylic acid ester (22) of dextrin and / or modified dextrin [Production Example 16] Unsaturated group-containing starch-based resin solution No. Production Example 4 In a reaction vessel equipped with a distillation apparatus, a thermometer, and a stirrer, 80 parts of dextrin (glucose polymer having an average polymerization number of 3 and 11 average hydroxyl groups), 100 parts of methyl isobutyl ketone, 0.16 of methyl hydroquinone Part, 5.9 parts of lithium hydroxide monohydrate and 506.2 parts of methyl acrylate were charged.
Next, the solution was heated and stirred at 90 ° C. while blowing nitrogen into the solution, and methyl acrylate, methanol and methyl isobutyl ketone were gradually distilled out of the system. Methyl acrylate and methyl isobutyl ketone, which decrease with distillation, were added to the reaction vessel. From the amount of methanol removal accompanying the distillation, the reaction was cooled when the hydroxyl group of four functional groups was converted to an acrylate ester. The reaction solution was concentrated under reduced pressure, ethyl acetate was added to the residue, the target product was separated, and an unsaturated group-containing starch-based resin solution no. 4 was obtained.

[Production Example 17] Unsaturated group-containing starch-based resin solution No. Production Example 5 5 Instead of the dextrin (glucose polymer having an average polymerization number of 3) in Production Example 16, a glucose polymer dextrin having an average polymerization number of 4 was used, and an acryloyl group was formed on 10 of the 14 average hydroxyl groups of the dextrin. In the same manner as in Production Example 16, except that the reaction time was extended until the unsaturated group-containing starch-based resin solution No. 1 was introduced. 5 was obtained.

[Production Example 18] Unsaturated group-containing starch-based resin solution No. Production Example 6 In the same manner as in Production Example 16, except that the reaction time was shortened until an acryloyl group was introduced into one of 11 average hydroxyl groups of dextrin (one functional hydroxyl group was converted to an acrylate ester). Unsaturated group-containing starch-based resin solution No. 6 was obtained.

[Production Example 19] Unsaturated group-containing starch resin solution No. 7 Production Example Instead of the dextrin in Production Example 16 (glucose polymer having an average polymerization number of 3 and having an average of 11 hydroxyl groups), glucose polymer dextrin (average polymerization number of 5 and average of 17 hydroxyl groups) was used. In the same manner as in Production Example 16, except that the reaction time was extended until acryloyl groups were introduced into 15 of the 17 average hydroxyl groups of the polymer dextrin (15 functional hydroxyl groups were converted to acrylate esters). Saturated group-containing starch-based resin solution No. 7 was obtained.

[Production Example 20] Photocurable Compound Solution No. Example 1 (corresponding to photocurable compound (a3))
A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and an air blowing device was charged with 888 parts of isophorone diisocyanate, 464 parts of 2-hydroxyethyl acrylate and 0.7 part of hydroquinone monomethyl ether, and air was introduced into the reaction container. The mixture was heated to 80 ° C. and kept at that temperature for 5 hours, and it was confirmed that substantially all of the added 2-hydroxyethyl acrylate had reacted, then 136 parts of pentaerythritol, 372 parts of butyl acetate and dibutyltin 0.2 parts of dilaurate was added, and the temperature was further maintained at 80 ° C. After confirming that all of the isophorone diisocyanate had reacted, the photocurable compound solution No. 80 having a resin solid content of 80% was cooled. 1 was obtained. The number average molecular weight of this resin was about 1,500.

[Production Example of Photocurable Paint (A)]
[Production Example 21] Photocurable paint No. Production of unsaturated group-containing starch-based resin solution No. 1 obtained in Production Example 13 1 100 parts (solid content), Irgacure 184 (Note 7) 6 parts, photocurable compound solution No. obtained in Production Example 20 1 200 parts (solid content) was added and dissolved, and then diluted with butyl acetate to a solid content concentration of 30%. 1 was obtained.

(Note 7) Irgacure 184: Photo radical polymerization initiator manufactured by Ciba Specialty Chemicals.

[Production Examples 22 to 31] Photocurable paint No. 2-No. 11 Production of Photocurable Paint No. 11 was the same as Production Example 21 except that the composition shown in Table 1 was used. 2-No. 11 was obtained.

[Comparative Production Example 1] Colored base paint No. 1 Production of Acrylic Resin Solution No. 5 obtained in Production Example 4 2 400 parts (solid content 100 parts), Alpaste FX-7640NS 46 parts (solid content 23 parts), High Conc Black 3 parts (solid content 3 parts), Cylicia 446 1.5 parts (solid content 1.5 parts) and 59.5 parts of methyl ethyl ketone was added and mixed well with a stirrer. 5 was obtained.

[Comparative Production Example 2] Photocurable paint No. Production of Photocurable Compound Solution No. 1 obtained in Production Example 20 1 was added and dissolved in 100 parts (solid content) of Irgacure 184, and then diluted with butyl acetate to a solid content concentration of 30%. 12 was obtained.

[About the test material board]
As a test plate, 2.0 mm × 100 mm × 150 mm of Psycolac Y665C-450 (manufactured by GE Plastics, trade name, ABS resin) was used.

[Example 1]
Step 1: After degreasing the test plate with isopropanol, the colored base paint No. obtained in Production Example 9 was used. 1 was applied by air spray so that the dried coating film was 8 μm, and dried at 60 ° C. for 15 minutes to form a coating film.
Step 2: The photocurable paint No. obtained in Production Example 21. 1 was applied by air spray so that the dry coating film became 12 μm, and dried at 60 ° C. for 5 minutes to form a coating film.
Step 3: UV curing at 600 mJ / cm ^{2 with} a high-pressure mercury lamp and photocuring is performed. 1 was formed.

[Examples 2 to 15]
A multilayer coating film No. 1 was prepared in the same manner as in Example 1 except that the paint and steps shown in Table 2 were taken. 2-No. 15 was formed.

[Comparative Examples 1-3]
A multilayer coating film No. 1 was prepared in the same manner as in Example 1 except that the paint and steps shown in Table 3 were taken. 16-No. 18 was formed.

  The multilayer coating film No. 1-No. A test plate having 18 was used for the test according to the following test conditions. The results of Examples are shown in Table 2, and the results of Comparative Examples are shown in Table 3.

[Test method]
(Note 8) Biological component composition: Each colored base paint and photo-curable paint were evaluated according to the following criteria.
○: Resin obtained by reacting starch-based resin or starch-based resin (biological component) is blended in the paint. ×: Resin obtained by reacting starch-based resin or starch-based resin (biological Origin component) is not blended in the paint

(Note 9) Finishing property: The appearance of each multilayer coating film was visually evaluated.
◎: Good finish ○: Slight swell but good finish △: At least one kind of finish on swell, gloss, and chili skin is observed ×: Swell, gloss, and chile There is a significant decrease in the finish of at least one kind of skin

(Note 10) Pencil hardness: According to JIS K 5600-5-4 (1999), a pencil core is applied at an angle of about 45 degrees to each multi-layer coating film surface, and the test coating plate is strong enough to prevent the core from breaking. It was moved about 10 mm forward at a uniform speed while pressing against the surface. This operation was repeated 5 times while changing the test location, and the hardness symbol of the hardest pencil when the coating film was not torn was defined as pencil hardness.

(Note 11) Scratch resistance: Each multi-layer coating film surface was judged according to how much scratches were made after pressing a commercially available business card against the coating film and rubbing 20 times.
◎: Not scratched at all ○: Scratch is hardly scratched, and the scratches are not recognized unless approached (about 5 cm) △: Slightly scratched ×: Scratch level is severe

(Note 12) Adhesion: On each multi-layer coating film surface, 100 1 mm × 1 mm gobangs were made on the coating film according to JIS K 5600-5-6 (1990), and adhesive tape was applied to that surface. And after peeling off rapidly, the number of the Gobang eyes coating film which remained on the coating surface was evaluated.
○: Remaining number / total number = 100/100 Δ: Remaining number / total number = 99 to 90/100 ×: Remaining number / total number = 89 or less / 100

(Note 13) Alkali resistance: 0.5 mL of a 1% aqueous sodium hydroxide solution was dropped on each multilayer coating film surface and allowed to stand in an atmosphere at a temperature of 20 ° C. and a relative humidity of 65% for 24 hours. The appearance was wiped off with gauze and visually evaluated.
○: No abnormality on coating film surface Δ: Discoloration (whitening) of coating film surface is observed ×: Discoloration (whitening) of coating film surface is remarkable

(Note 14) Solvent resistance: Two filter papers were placed side by side on each multilayer coating film surface, and 78% ethanol and 2% formalin were dropped onto each filter paper with a dropper to wet the filter paper. The dropping with the dropper was performed 5 times at 1 hour intervals, and the coating film surface excluding the filter paper was visually evaluated after 2 hours.
○: No abnormalities such as bulges and peelings △: Mild abnormalities such as bulges and peelings are found visually: The coating film melts

  The coating film forming method of the present invention uses a starch-based paint derived from a plant and forms a multilayer coating film excellent in finish, pencil hardness, scratch resistance, adhesion, alkali resistance, and solvent resistance. This is industrially useful. The multilayer coating film of the present invention is industrially useful because it uses a plant-derived starch-based paint and is excellent in finish, pencil hardness, scratch resistance, adhesion, alkali resistance, and solvent resistance. .

Claims (11)

Applying a starch-based colored base paint containing a starch-based resin on an article to form a coating film comprising the starch-based colored base paint;
A coating film comprising the photocurable paint (A) by coating a photocurable paint (A) containing the unsaturated group-containing starch-based resin (a1) and the photopolymerization initiator (a2) on the coated film. And a step of irradiating the coating film made of the photocurable coating (A) with light to cure the coating film:
A method for forming a multilayer coating film comprising:   The method for forming a multilayer coating film according to claim 1, wherein the photocurable paint (A) further contains a photocurable compound (a3).   The method for forming a multilayer coating film according to claim 1 or 2, wherein the unsaturated group-containing starch-based resin (a1) is an acrylic ester (21) of a saccharide and / or a modified saccharide.   Dextrin and / or modified dextrin acrylate having a saccharide and / or modified saccharide acrylate (21) having a weight average molecular weight of 400 to 4,000 and 2 to 14 acryloyl groups per molecule The method for forming a multilayer coating film according to claim 3, which is (22). The unsaturated group-containing starch-based resin (a1) is:
Modified starch (a10); and Compound (a11) containing acryloyl group and isocyanate group:
The method for forming a multilayer coating film according to claim 1 or 2, which is an unsaturated group-containing starch-based resin (20) obtained by reacting the above. Unsaturated-group-containing starch-based resin (20) is modified starch (a10) 50 to 99 based on the total solid mass of modified starch (a10) and compound containing acryloyl group and isocyanate group (a11). The method for forming a multilayer coating film according to claim 5, obtained by addition reaction of 1 to 50 mass% of a compound (a11) containing an acryloyl group and an isocyanate group to mass%. A coating layer comprising a starch-based colored base paint containing a starch-based resin;
A coating layer obtained by photocuring a layer made of the photocurable paint (A) containing the unsaturated group-containing starch-based resin (a1) and the photopolymerization initiator (a2) on the coating layer:
A multilayer coating film comprising The unsaturated group-containing starch-based resin (a1) is:
Modified starch (a10); and
Compound containing acryloyl group and isocyanate group (a11):
The multilayer coating film according to claim 7, which is an unsaturated group-containing starch-based resin (20) obtained by reacting. Unsaturated-group-containing starch-based resin (20) is modified starch (a10) 50 to 99 based on the total solid mass of modified starch (a10) and compound containing acryloyl group and isocyanate group (a11). The multilayer coating film of Claim 8 obtained by carrying out addition reaction of 1-50 mass% of compounds (a11) containing an acryloyl group and an isocyanate group to mass%. The coated article which has a multilayer coating film as described in any one of Claims 7-9 on a to-be-coated article. The coated article according to claim 10 , wherein the article to be coated is plastic.