JP2010037454A - Aqueous dispersion and water-based coating composition containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous dispersion of an acrylic modified starch which has a high prolonged storage stability, and to provide a water-based coating composition which is obtained by using the dispersion and by which a coating film having excellent finishing properties, hardness, weatherability and so on can be formed. <P>SOLUTION: The aqueous dispersion is obtained by, in the presence of a starch and/or a modified starch containing a radical-polymerizable unsaturated group, separately graft-polymerizing a radical-polymerizable unsaturated monomer mixture for forming a hydrophobic polymer and a radical-polymerizable unsaturated monomer mixture for forming a hydrophilic polymer; if necessary, neutralizing carboxy groups in the acrylic modified starch with a basic substance; and performing dispersion in water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an aqueous dispersion excellent in storage stability using starch, which is a plant-derived raw material, and excellent in solvent resistance, chemical resistance, water resistance and the like obtained using the aqueous dispersion. It is related with the water-based coating composition excellent in the sclerosis | hardenability which can form the coating film.

  In recent years, the environmental pollution of the earth has become obvious, and the construction of a recycling-oriented society that takes into account the reduction of environmental burdens is progressing, and the paint industry is also demanding the development of products that are friendly to the global environment. In such a situation, it does not contain a large amount of volatile organic compounds (VOC) such as toluene and xylene, which cause deterioration of the indoor environment. Various coating agents using the materials they have have been proposed.

  For example, Patent Document 1 discloses a curable starch composition, which is a mixture of starch and a curing agent having a functional group that reacts complementarily with at least one hydroxyl group contained in the starch molecule. Is disclosed. It is described that the curable starch composition can be used by being dispersed in an aqueous solvent. However, it is not easy to stably disperse starch in an aqueous medium.

  Patent Document 2 discloses a release or moisture-proof coating composition containing a specific starch ester, a hydrophobic plasticizer, and water. However, since the starch ester used here is hydrophobic, there is a problem that it is difficult to disperse in water and the formed coating film is inferior in finish at room temperature.

  Furthermore, Patent Document 3 discloses a modified starch-containing resin aqueous dispersion comprising a modified starch and a (co) polymer of a polymerizable unsaturated monomer as constituent components. Although the storage stability of water dispersions is significantly improved with the help of copolymer resins, dispersion particles still thicken and dispersions thicken during long-term storage. Was limited.

Japanese Patent Laid-Open No. 2004-224887 JP 2001-40267 A JP 2006-52338 A

  An object of the present invention is to provide an acrylic-modified starch aqueous dispersion which does not cause precipitation of dispersion particles or increase in viscosity of the dispersion even during a considerably long-term storage, and the finish using the aqueous dispersion It is to provide a water-based coating composition capable of forming a film excellent in hardness, weather resistance, etc., and to provide a coated article excellent in hardness, weather resistance, etc. obtained by coating the water-based coating composition It is to be.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have previously determined that a specific amount of a carboxy group-containing radically polymerizable unsaturated group in the presence of a starch containing a radically polymerizable unsaturated group and / or a modified starch. Copolymerize a monomer and a radical polymerizable unsaturated monomer mixture containing a specific amount of a hydroxyl group-containing radical polymerizable unsaturated monomer, and then almost contain a carboxy group-containing radical polymerizable unsaturated monomer. First, copolymerize a radical polymerizable unsaturated monomer mixture containing a specific amount of a hydroxyl group-containing radical polymerizable unsaturated monomer, or contain almost no carboxy group-containing radical polymerizable unsaturated monomer, and contain a hydroxyl group. A radical polymerizable unsaturated monomer mixture containing a specific amount of a radical polymerizable unsaturated monomer is copolymerized, and then a specific amount of a carboxy group-containing radical polymerizable unsaturated monomer is copolymerized. An acrylic modified starch obtained by copolymerizing a radical polymerizable unsaturated monomer mixture containing a sum monomer and a specific amount of a hydroxyl group-containing radical polymerizable unsaturated monomer, and having an acid value within a specified range The present inventors have found that an aqueous dispersion obtained by dispersing an acrylic-modified starch that has been prepared in water can solve the above problems, and have completed the present invention.

  Thus, in the present invention, the reaction product is obtained by subjecting the radical polymerizable unsaturated monomer mixture (b1) to radical polymerization in the presence of the starch containing the radical polymerizable unsaturated group and / or the modified starch (a). An aqueous dispersion obtained by dispersing an acrylic modified starch (A) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (b2) in the presence of the reaction product in an aqueous medium. The amount of the carboxy group-containing radical polymerizable unsaturated monomer in the radical polymerizable unsaturated monomer mixture (b1) is 5 to 95% by mass and the amount of the hydroxyl group-containing radical polymerizable unsaturated monomer is 5 to 95% by mass, and the amount of the carboxy group-containing radical polymerizable unsaturated monomer in the radical polymerizable unsaturated monomer mixture (b2) is less than 5% by mass and the hydroxyl group-containing radical polymerizable unsaturated monomer Body quantity And 5 to 95 wt%, to a water dispersion, wherein the acid value of the acrylic modified starch (A) is in the range of 10~150mgKOH / g.

  In the above invention, the radical polymerizable unsaturated monomer mixture (b2) is first subjected to radical polymerization reaction in the presence of starch containing a radical polymerizable unsaturated group and / or modified starch (a). A water obtained by dispersing an acrylic modified starch (A) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (b1) in the presence of the reaction product in an aqueous medium after obtaining the product. It relates to a dispersion.

  The present invention also relates to an aqueous coating composition using the above aqueous dispersion, and to a coated article obtained by coating the aqueous coating composition.

  The acrylic modified starch aqueous dispersion of the present invention comprises a radical polymerizable unsaturated monomer mixture for forming a hydrophobic polymer in the presence of starch containing a radical polymerizable unsaturated group and / or modified starch. Graft-polymerize each radical-polymerizable unsaturated monomer mixture to form a hydrophilic polymer, and neutralize the carboxy group in acrylic-modified starch with a basic substance and disperse in water if necessary. Is obtained. By this method, the graft polymerization is reliably performed by the radically polymerizable unsaturated group of starch and / or modified starch, and the hydrophobic side chain and the hydrophilic side chain are separately formed, so that they are dispersed in water. It is assumed that the core part and the shell part of the particle are clear and solid particles are formed, and the particle size of the water is also water of acrylic modified starch in which hydrophilic side chains are simply introduced into starch. Compared with the dispersion, the storage stability of the acrylic modified starch aqueous dispersion over a considerably long period of time can be remarkably improved.

  The acrylic-modified starch aqueous dispersion contains a modified starch having biodegradability and is excellent in various properties, and is applied not only to paints but also to a wide range of fields such as inks, adhesives and molding agents. However, particularly when applied to a coating material, a film excellent in finish, hardness, weather resistance and the like can be formed, which is extremely useful.

Acrylic-modified starch aqueous dispersion The aqueous dispersion of the present invention comprises a radical-polymerizable unsaturated monomer mixture (b1) and a radical in the presence of starch containing a radical-polymerizable unsaturated group and / or modified starch (a). An acrylic modified starch (A) obtained by separately subjecting a polymerizable unsaturated monomer mixture (b2) to radical polymerization reaction is dispersed in an aqueous medium.

  The starch and / or modified starch (a) containing the radically polymerizable unsaturated group is obtained by introducing a radically polymerizable unsaturated group in advance into starch and / or modified starch, and as the starch and / or modified starch, Can be used conventionally, for example, corn starch, high amylose starch, wheat starch, unmodified starch such as rice starch, rhizome unmodified starch such as potato starch, tapioca starch, and their Examples include low-esterification starch, etherification, oxidation, acid treatment, dextrinized starch-substituted derivatives, and the like. These can be used alone or in combination. Among these, esterified starch is particularly excellent in terms of stability when producing acryl-modified starch, and is contained in a starch component in an amount of 30% by mass or more, particularly 50% by mass or more, and more particularly 70% by mass or more. It is preferable.

  A preferable modifying group for esterification of starch is an acyl group having 2 to 18 carbon atoms. 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 is preferably in the range of 0.5 to 2.8 in terms of the degree of substitution, particularly preferably in the range of 1.0 to 2.5. If the degree of substitution is less than 0.5, the solubility with the 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, the speed of biodegradability may be slow.

  Further, the modified starch preferably has a glass transition point below the decomposition temperature of starch (about 350 ° C.), it is desirable to adjust the degree of modification so as to have thermoplasticity and biodegradability, Therefore, when the number of carbon atoms of the substituent used for modification is large, a low modification level, for example, when the substituent is a stearyl group having 18 carbon atoms, the degree of ester substitution is 0.5 to 1.8. On the contrary, when the number of carbon atoms of the substituent is small, a high modification level, for example, when the substituent is an acetyl group having 2 carbon atoms, the degree of ester substitution is It is preferable to be in the range of 1.5 to 2.8.

  In the present specification, the degree of substitution is the average number of hydroxyl groups substituted by a denaturing agent per monosaccharide unit constituting the starch. For example, the degree of substitution 3 is one monosaccharide unit constituting the starch. This means that all the three hydroxyl groups present therein have been substituted by a modifying agent, and a substitution degree of 1 means that only one of the three hydroxyl groups present in one monosaccharide unit constituting starch is modified. It means being replaced by an agent.

  As a method for introducing a radically polymerizable unsaturated group into the starch and / or modified starch, a conventionally known method can be used. For example, an organic carboxylic acid anhydride having a radical polymerizable unsaturated group (for example, acrylic acid anhydride, methacrylic acid anhydride, maleic acid anhydride, itaconic acid anhydride, citraconic acid anhydride, tetrahydrophthalic acid anhydride, octenyl succinic acid) Anhydride etc.) to starch and / or modified starch, organic carboxylic acid anhydride such as phthalic anhydride is added to starch and / or modified starch to introduce acid groups, and then glycidyl (meth) acrylate is added. A method of adding, a method of adding a monomer having a radical polymerizable unsaturated group and an isocyanate group to starch and / or modified starch, a method of directly adding glycidyl (meth) acrylate to starch and / or modified starch, etc. be able to. Further, an allyl group may be introduced using a method described in JP-A No. 54-8694.

  Among them, a method of adding a monomer having a radical polymerizable unsaturated group and an isocyanate group to starch and / or modified starch is preferable from the viewpoint of production stability when producing acrylic-modified starch. As a monomer which has a radically polymerizable unsaturated group and an isocyanate group, 2-isocyanate ethyl (meth) acrylate etc. can be mentioned, for example. Moreover, an equimolar urethanization reaction product of a diisocyanate compound and a hydroxyalkyl (meth) acrylate can be used.

  Examples of diisocyanate compounds include toluylene diisocyanate, metaphenylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, α, α, α ', α'-tetramethylxylylene diisocyanate, etc. can do.

  The content of the radically polymerizable unsaturated group in the starch and / or the modified starch (a) is preferably within a range of 0.001 to 1.000 mmol / g, particularly preferably 0.005 to 0.500 mmol / g. As long as the content of the radically polymerizable unsaturated group is small, the content increases and the storage becomes longer. However, if the content is less than 0.001 mmol / g, there is almost no effect of improving the long-term storage stability of the aqueous dispersion, and if it exceeds 1.000 mmol / g, starch containing radically polymerizable unsaturated groups is contained. In addition, when the radical polymerizable unsaturated monomer mixture is polymerized in the presence of the modified starch (a), gelation tends to occur and attention is required for the polymerization.

As the radical polymerizable unsaturated monomer used for the radical polymerization reaction in the presence of the starch containing the radical polymerizable unsaturated group and / or the modified starch (a), for example,
-Contains carboxyl groups such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, 2-carboxyethyl (meth) acrylate, 2-carboxypropyl (meth) acrylate, 5-carboxypentyl (meth) acrylate Polymerizable unsaturated monomers;
C2-C8 hydroxyalkyl (meth) acrylates of acrylic acid or methacrylic acid such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (poly) ethylene Hydroxyl-containing radical polymerizable unsaturated monomers such as glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polybutylene glycol mono (meth) acrylate; and these hydroxyl group-containing radical polymerizable unsaturated monomers Reaction with lactone compounds such as β-propiolactone, dimethylpropiolactone, butyrolactone, γ-valerolactone, γ-caprolactone, γ-caprolactone, γ-lauryllactone, ε-caprolactone, δ-caprolactone object; Laxel FM-1, Plaxel FM-2, Plaxel FM-3, Plaxel FA-1, Plaxel FA-2, Plaxel FA-3 (above, trade name, manufactured by Daicel Chemical Industries, caprolactone-modified (meth) acrylic acid hydroxy esters );
・ Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl C1-C18 alkyl or cycloalkyl esters of (meth) acrylic acid such as (meth) acrylate;
-Vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, vinylpyridine;
N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N-methyl-N- (2-hydroxy Ethyl) (meth) acrylamide, N-ethyl-N- (2-hydroxyethyl) (meth) acrylamide, N-methyl-N- (2-hydroxypropyl) (meth) acrylamide, N-methyl-N- (3- Hydroxypropyl) (meth) acrylamide, N-ethyl-N- (2-hydroxypropyl) (meth) acrylamide, N-ethyl-N- (3-hydroxypropyl) (meth) acrylamide, N, N-di- (2 -Hydroxyethyl) (meth) acrylamide, N, N-di- (2-hydroxypropyl) (meth) acryl Nitrogen-containing radical-polymerizable unsaturated monomers such as amides;
-Vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane vinyldimethylethoxysilane, vinyltripropoxysilane, vinylmethyldipropoxysilane, vinyldimethylpropoxysilane, γ- ( Alkoxysilyl group-containing radical polymerizable unsaturated monomers such as (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- (meth) acryloyloxypropyldimethylmethoxysilane;
・ Divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1 , 4-butanediol diacrylate, glycerol di (meth) acrylate, glycerol tri (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol Tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, neopentyl glycol dia Lilate, 1,6-hexanediol diacrylate, glycerol allyloxydi (meth) acrylate, 1,1,1-tris (hydroxymethyl) ethanedi (meth) acrylate, 1,1,1-tris (hydroxymethyl) ethanetri ( Examples thereof include a monomer having two or more radically polymerizable unsaturated bonds in one molecule such as (meth) acrylate; a fatty acid-modified acrylic monomer, and the like.

  The acrylic modified starch (A) is produced by radical polymerization reaction of the radical polymerizable unsaturated monomer mixture (b1) in the presence of the starch containing the radical polymerizable unsaturated group and / or the modified starch (a). After obtaining the reaction product, the radical polymerizable unsaturated monomer mixture (b2) is subjected to radical polymerization reaction in the presence of the reaction product, or the radical polymerizable unsaturated monomer mixture (b2) is radicalized. After obtaining a reaction product by polymerization reaction, it is obtained by subjecting the radical polymerizable unsaturated monomer mixture (b1) to radical polymerization reaction in the presence of the reaction product.

From the viewpoint of long-term storage stability of the aqueous dispersion of the present invention, each compounding amount is a starch and / or modified starch (a) containing a radical polymerizable unsaturated group, a radical polymerizable unsaturated monomer mixture ( With respect to 100 parts by mass of the total amount of b1) and the radical polymerizable unsaturated monomer mixture (b2),
Starch and / or modified starch (a) 20-90 parts by weight,
It is preferably within the range of 5 to 40 parts by mass of the radical polymerizable unsaturated monomer mixture (b1) and 5 to 40 parts by mass of the radical polymerizable unsaturated monomer mixture (b2),
30-80 parts by weight of starch and / or modified starch (a),
It is more preferable to be within the range of 10 to 35 parts by mass of the radical polymerizable unsaturated monomer mixture (b1) and 10 to 35 parts by mass of the radical polymerizable unsaturated monomer mixture (b2).

  In the radical polymerizable unsaturated monomer mixture (b1), the amount of the carboxy group-containing radical polymerizable unsaturated monomer in the mixture is 5 to 95% by mass, particularly 7 to 70% by mass. From the viewpoint of storage stability of the acrylic modified starch aqueous dispersion, the amount of the hydroxyl-containing radically polymerizable unsaturated monomer is preferably in the range of 5 to 95% by mass, particularly 10 to 70% by mass. From the viewpoints of curability and weather resistance of the coating film to be formed.

  On the other hand, in the radical polymerizable unsaturated monomer mixture (b2), the amount of the carboxy group-containing radical polymerizable unsaturated monomer in the mixture is less than 5% by mass, particularly less than 4% by mass. It is preferable from the viewpoint of the storage stability of the modified starch aqueous dispersion, and the resulting coating is such that the amount of the hydroxyl-containing radically polymerizable unsaturated monomer is in the range of 5 to 95% by mass, particularly 10 to 70% by mass. From the viewpoints of curability, weather resistance and the like.

  The acrylic modified starch (A) is produced according to the above formulation, and the acid value of the resulting acrylic modified starch (A) is 10 to 150 mgKOH / g, particularly 12 to 120 mgKOH / g, more particularly 15 to 90 mgKOH / It is preferable from the point of long-term storage stability of the aqueous dispersion obtained to be in the range of g.

  The production of the acrylic modified starch (A) is carried out by using a radically polymerizable unsaturated monomer mixture (b1) and a radically polymerizable unsaturated in the presence of starch containing radically polymerizable unsaturated groups and / or modified starch (a). The monomer mixture (b2) is separately subjected to radical polymerization reaction. The order of polymerization is such that (b2) is polymerized after (b1) is polymerized first, and (b2) is polymerized. There is a tendency that the long-term storage stability of the acrylic-modified starch aqueous dispersion obtained after polymerization of (b1) is slightly superior, and this is preferable.

  The reaction temperature for polymerizing (b1) and (b2) is usually in the range of about 60 to about 200 ° C., preferably about 70 to about 160 ° C., and the reaction time is usually about 10 hours or less, preferably about 0. .5 to about 6 hours.

  In said reaction, it is preferable to add a polymerization initiator suitably. Examples of such a polymerization initiator include inorganic peroxide compounds such as potassium or ammonium persulfate, hydrogen peroxide, percarbonate, acyl peroxides (for example, benzoyl peroxide), alkyl hydroperoxides (for example, , Tertiary butyl hydroperoxide, p-menthane hydroperoxide), dialkyl peroxide (eg, di-tertiary butyl peroxide), percarbonate (eg, di-isopropyl peroxydicarbonate, t-butyl peroxide) Organic peroxide compounds such as oxyisopropyl carbonate) and azo compounds such as azobisisobutyronitrile are used. Two or more of these polymerization catalysts may be used in combination. Moreover, there is no problem even if the kind and amount of the polymerization initiator are different between the polymerization of the radical polymerizable unsaturated monomer mixture (b1) and the polymerization of the radical polymerizable unsaturated monomer mixture (b2).

  Among these polymerization initiators, use of benzoyl peroxide or t-butylperoxyisopropyl carbonate is preferable from the viewpoint of long-term storage stability of an aqueous dispersion obtained.

  As a compounding quantity of a polymerization initiator, 0.01-20 mass parts based on 100 mass parts of radically polymerizable unsaturated monomer mixtures, Especially 0.1-15 mass parts, More especially 0.3-10 mass parts Is preferable from the viewpoint of the stability of the resulting aqueous dispersion.

  The polymerization for producing the acrylic modified starch (A) is usually carried out in the presence of an organic solvent. The selection of the organic solvent can be appropriately performed in consideration of the polymerization temperature, the ease of handling during the production of the aqueous dispersion, and the long-term storage stability of the resulting aqueous dispersion.

  An organic solvent can also be added when the acrylic modified starch is dispersed in water.

  As the organic solvent, alcohol solvents, cellosolve solvents, carbitol solvents and the like are preferable. Specifically, for example, alcohol solvents such as n-butanol; cellosolv solvents such as ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether; diethylene glycol monobutyl ether, diethylene glycol monoethyl ether And carbitol-based solvents such as Further, as the organic solvent, an inert organic solvent that is not mixed with water other than the above can also be used as long as it does not hinder the stability of the acrylic-modified starch in the aqueous medium. Examples thereof include aromatic hydrocarbon solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, and ketone solvents such as methyl ethyl ketone and cyclohexanone. The amount of the organic solvent in the aqueous dispersion of the present invention is preferably in the range of 50% by mass or less in the aqueous medium from the viewpoint of environmental protection.

  When acrylic modified starch is dispersed in water, some or all of the carboxyl groups in acrylic modified starch are usually neutralized with a basic compound and dispersed in water. However, acrylic modified starch is dispersed in water containing a basic compound. It is also possible to add.

  The basic compound for neutralization is suitably used in an amount of 0.1 to 1.1 equivalents, preferably 0.5 to 0.9 equivalents, based on the carboxyl groups in the acrylic modified starch. Examples of the basic compound for neutralization include ammonia, diethylamine, ethylethanolamine, diethanolamine, triethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylaminoethylamine, hydroxyethylamine, triethylamine, and triethanolamine. Organic amines such as butylamine, dimethylethanolamine and diethylenetriamine; or alkali metal hydroxides such as caustic soda and caustic potash can be used.

In the present invention, the aqueous dispersion of acrylic-modified starch may be an aqueous dispersion having an average particle diameter (Note 1) of 0.05 to 1.0 μm, preferably 0.08 to 0.8 μm.
(Note 1) Average particle size: Dilute the sample with deionized water to a concentration suitable for measurement with a submicron particle analyzer N4 (trade name, manufactured by Beckman Coulter, Inc., particle size distribution measuring device). (Measured at about 20 ° C.)

Aqueous paint composition The acrylic-modified starch aqueous dispersion of the present invention forms a film by coating and drying itself, and thus can be used as a coating agent as it is, but is a group that reacts with a hydroxyl group in the acrylic-modified starch. By combining with a curing agent having, a film having excellent performance such as curability, weather resistance and chemical resistance can be formed. The curing agent is preferably an amino resin and / or a polyisocyanate compound which may be blocked.

  As the amino resin, a melamine resin is generally used. In particular, at least a part of a methylol melamine resin or a methylol group of the methylol melamine resin is fully etherified or partially etherified with a monohydric alcohol having 1 to 10 carbon atoms. An alkyl etherified melamine resin can be used, and a melamine resin having an imino group in its molecule can also be used. Their number average molecular weight is suitably 3000 or less, particularly 1500 or less. In particular, water-soluble or water-dispersible ones are suitable, but water-insoluble ones can also be used.

  The polyisocyanate compound which may be blocked includes both a polyisocyanate compound having a free isocyanate group and a blocked polyisocyanate compound in which the isocyanate group is blocked.

  Examples of the polyisocyanate compound having a free isocyanate group include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; cyclic aliphatic diisocyanates such as hydrogenated xylylene diisocyanate and isophorone diisocyanate; Aromatic diisocyanates such as 4'-diphenylmethane diisocyanate; triphenylmethane-4,4 ', 4 "-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4 Organic polyisocyanates such as polyisocyanate compounds having three or more isocyanate groups, such as 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate. Nate itself or an adduct of each of these organic polyisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water, or a cyclized polymer of each of the above organic polyisocyanates, and further an isocyanate / biuret In the case of using a polyisocyanate compound having a free isocyanate group, it is necessary to use a two-component paint mixed with an acrylic-modified starch aqueous dispersion immediately before coating, so that the storability and curing of the paint are possible. From the viewpoint of sex.

  As the polyisocyanate compound in which the isocyanate group is blocked, the isocyanate group of the polyisocyanate compound having a free isocyanate group described above is a known block such as oxime, phenol, alcohol, lactam, malonic acid diester, acetoacetate ester or mercaptan. What was blocked with an agent is mentioned.

  The polyisocyanate compound is preferably water-dispersible. For example, a polyisocyanate self-emulsified in water, a force-dispersed product with a stirrer or the like, an anionic or nonionic surfactant is used. And dispersed. Commercially available products include, for example, AQUANATE 100, AQUANATE 110, AQUANATE 200, and AQUANATE 210 (all trade names, manufactured by Nippon Polyurethane Industry Co., Ltd.); Bihijoule 3100, VPLS-2336 and VPLS-2150 / 1 (all trade names, manufactured by Sumika Bayer Urethane Co., Ltd.); Takenate WD-720, Takenate WD-725 and Takenate WD-220 (all trade names, Mitsui Chemicals Polyurethanes, Inc.) Manufactured); Rezamin D-56 (trade name, manufactured by Dainichi Seika Kogyo Co., Ltd.) and the like. These may be used alone or in combination of two or more.

  The curing agent is usually preferably blended within the range of about 10 to 50% by mass, particularly 15 to 40% by mass based on the total solid mass with the acrylic modified starch.

  Examples of the water-dispersible polyisocyanate compound (C) include those obtained by self-emulsifying polyisocyanate in water, those forcibly dispersed with a stirrer, etc., and an anionic or nonionic surfactant. Can be mentioned.

  The water-based paint composition may be any type of clear paint or enamel paint, and various resins (acrylic resin, urethane resin, polyolefin resin, polyester resin, etc.), anti-settling agent, antifoaming agent, thickening as appropriate. Agents, rust inhibitors, ultraviolet absorbers, surface conditioners, pigment dispersants, and pigments (for example, colored pigments such as titanium oxide, carbon black, bengara; glitter pigments such as scaly aluminum and mica; clay, Extender pigments such as mica, barita, calcium carbonate, silica, etc .; rust preventive pigments such as aluminum phosphomolybdate and aluminum tripolyphosphate) and the like can be blended according to the required purpose. Solid content adjustment of an aqueous coating material composition can be manufactured by adding deionized water and diluting coating material solid content to 5-70 mass%, Preferably it is 20-60 mass%.

  The water-based coating composition can be applied to the surface of various base materials. Examples of the base material include inorganic base materials such as slate plates and PC plates; organic base materials such as plastics; iron, aluminum and the like. The metal etc. are mentioned. A water-based or solvent-type undercoat material may be applied to these coated surfaces. If necessary, after applying the undercoat material, the aqueous coating composition can be applied as a topcoat material. On the other hand, after applying the aqueous coating composition of the present invention as an undercoat, it is also possible to apply a known aqueous overcoat.

  Examples of the application method of the aqueous coating composition of the present invention include air spray coating, airless spray coating, electrostatic coating, brush coating, roller coating, lysing gun, universal gun, dipping, roll coater, curtain flow coater, and roller curtain coater. A die coater and the like, and can be appropriately selected according to the use of the substrate. As an application quantity, it can be in the range of 10-100 micrometers, for example, Preferably it is 15-80 micrometers. Moreover, you may apply repeatedly several times in the range which does not impair the coating-film external appearance. As a drying method of the formed coating film, it depends on the kind of the aqueous dispersion of the acryl-modified starch in the aqueous coating composition, etc., for 10 to 120 minutes at 50 to 200 ° C., preferably 20 to 90 at 70 to 180 ° C. After baking for 1 minute or forced drying at less than 100 ° C. for 1 to 40 minutes, leave at room temperature (50 ° C. or less) for 10 hours or more, or leave at room temperature (50 ° C. or less) for 1 day to 7 days By this, the water and organic solvent in a coating film volatilize, and a coating film forms a continuous coating film.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Hereinafter, both “parts” and “%” are based on mass.

Production and production example 1 of modified starch
25 parts of high amylose corn starch (manufactured by Nippon Corn Starch Co., Ltd., hydroxyl value 500 mgKOH / g) is suspended in 200 parts of dimethyl sulfoxide (DMSO), heated to 90 ° C. with stirring, and then held at that temperature for 20 minutes to paste. Made it. To this solution, 20 parts of sodium bicarbonate was added as a catalyst, maintained at 90 ° C., 17 parts of vinyl laurate was added, and reacted at that temperature for 1 hour. Subsequently, 37 parts of vinyl acetate was 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 to obtain esterified starch P1.

Production Example 1 of Acrylic Modified Starch Water Dispersion
140 parts of toluene was put into a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, a water separator, and a nitrogen inlet, and the temperature was raised to 50 ° C. under a nitrogen stream while stirring. When the temperature reached 50 ° C., 70 parts of the esterified starch P1 obtained in Production Example 1 was added, the temperature was raised to around 110 ° C. while stirring, and water separation was performed over about 30 minutes while refluxing toluene through a water separator. went. After water separation, the temperature is kept at 105 ° C., 0.3 part of 2-isocyanate ethyl acrylate and a small amount (about 0.0004 part) of dibutyltin dilaurate are added, and the reaction is performed for about 2 hours to perform radical polymerizable unsaturated group An esterified starch solution containing was obtained.

  50 parts of ethylene glycol monobutyl ether was added to the above-mentioned radical polymerizable unsaturated group-containing esterified starch solution, the temperature was raised to 105 ° C., and then toluene was recovered while reducing the pressure. Substituted with butyl ether.

  The content of the radically polymerizable unsaturated group in the esterified starch containing the radically polymerizable unsaturated group is 0.030 mmol / g.

  Next, the radically polymerizable unsaturated group-containing esterified starch solution obtained by subjecting ethylene glycol monobutyl ether to solvent substitution was heated to 120 ° C., and 9.2 parts of methyl methacrylate and n-butyl acrylate were maintained while maintaining the temperature. A mixed solution of 2.2 parts, 4.6 parts of 2-hydroxyethyl methacrylate, 4.0 parts of acrylic acid, and 1.00 parts of benzoyl peroxide was added dropwise over 1 hour. Held for hours.

  Subsequently, while maintaining the temperature at 120 ° C., 4.6 parts of methyl methacrylate, 3.1 parts of n-butyl acrylate, 2.3 parts of 2-hydroxyethyl methacrylate and 0.50 part of benzoyl peroxide were added to the flask. The mixed solution was added dropwise over 1 hour, and further maintained at 120 ° C. for 1 hour after completion of the addition to obtain an acrylic-modified esterified starch solution.

  The acrylic modified esterified starch solution was cooled to 60 ° C., 4.94 parts of dimethylethanolamine was added and mixed and stirred for 15 minutes. Further, 178 parts of deionized water was added dropwise over 1 hour with stirring, and an acrylic modified starch aqueous dispersion No. 30 having a resin solid content of 30%, a resin acid value of 34 mgKOH / g, and an average particle size of 0.22 μm was obtained. 1 was obtained.

Examples 2-11
Each acrylic modified starch aqueous dispersion was obtained in the same manner as in Example 1 except that the raw materials, blending amounts, and reaction temperatures in Example 1 were as shown in Table 1 below.

Comparative Example 1
160 parts of toluene was put into a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, a water separator, and a nitrogen inlet, and the temperature was raised to 50 ° C. under a nitrogen stream while stirring. When the temperature reached 50 ° C., 80 parts of the esterified starch P1 obtained in Production Example 1 was added, the temperature was raised to around 110 ° C. while stirring, and water separation was performed over about 30 minutes while refluxing toluene through a water separator. went. After water separation, the temperature is kept at 105 ° C., 0.3 part of 2-isocyanate ethyl acrylate and a small amount (about 0.0004 part) of dibutyltin dilaurate are added, and the reaction is performed for about 2 hours to perform radical polymerizable unsaturated group An esterified starch solution containing was obtained.

  The content of the radically polymerizable unsaturated group in the esterified starch containing the radically polymerizable unsaturated group is 0.027 mmol / g.

  50 parts of ethylene glycol monobutyl ether was added to the above-mentioned radical polymerizable unsaturated group-containing esterified starch solution, the temperature was raised to 105 ° C., and then toluene was recovered while reducing the pressure. Substituted with butyl ether.

  Next, the radically polymerizable unsaturated group-containing esterified starch solution obtained by subjecting ethylene glycol monobutyl ether to solvent substitution was heated to 120 ° C., and 9.2 parts of methyl methacrylate and n-butyl acrylate were maintained while maintaining the temperature. A mixed solution of 2.2 parts, 4.6 parts of 2-hydroxyethyl methacrylate, 4.0 parts of acrylic acid, and 1.00 parts of benzoyl peroxide was added dropwise over 1 hour. The acrylic modified esterified starch solution was obtained by holding for a period of time.

  The acrylic modified esterified starch solution was cooled to 60 ° C., 4.94 parts of dimethylethanolamine was added and mixed and stirred for 15 minutes. Further, 178 parts of deionized water was added dropwise over 1 hour with stirring, and an acrylic modified starch water dispersion No. 30 having a resin solid content of 30%, a resin acid value of 34 mgKOH / g, and an average particle size of 0.52 μm was obtained. 12 was obtained.

Comparative Example 2
50 parts of ethylene glycol monobutyl ether was placed in a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, a water separator and a nitrogen inlet, and the temperature was raised to 50 ° C. under a nitrogen stream while stirring. When the temperature reached 50 ° C., 70 parts of the esterified starch P1 obtained in Production Example 1 was added, and the temperature was raised to around 120 ° C. while stirring. A mixed solution of 9.2 parts of methyl methacrylate, 2.2 parts of n-butyl acrylate, 4.6 parts of 2-hydroxyethyl methacrylate, 4.0 parts of acrylic acid and 1.00 part of benzoyl peroxide while maintaining the temperature. Was added dropwise over 1 hour, and further maintained at a temperature of 120 ° C. for 1 hour after the completion of the dropwise addition.

  Subsequently, while maintaining the temperature at 120 ° C., 4.6 parts of methyl methacrylate, 3.1 parts of n-butyl acrylate, 2.3 parts of 2-hydroxyethyl methacrylate and 0.50 part of benzoyl peroxide were added to the flask. The mixed solution was added dropwise over 1 hour, and further maintained at 120 ° C. for 1 hour after completion of the addition to obtain an acrylic-modified esterified starch solution.

  The acrylic modified esterified starch solution was cooled to 60 ° C., 4.94 parts of dimethylethanolamine was added and mixed and stirred for 15 minutes. Furthermore, 178 parts of deionized water was added dropwise over 1 hour with stirring, and an acrylic modified starch water dispersion No. 30 having a resin solid content of 30%, a resin acid value of 34 mgKOH / g, and an average particle size of 0.38 μm was obtained. 13 was obtained.

Storage stability Each acrylic modified starch aqueous dispersion obtained in the above Examples and Comparative Examples was tested for storage stability according to the following test method. The results are shown in Table 1.

Storage stability: 800 g of each aqueous dispersion was put in a glass bottle having a capacity of about 1 L and stored in a constant temperature room at 40 ° C. for 120 days. Then, it returned to room temperature, the state in a container was observed visually, and the following reference | standard evaluated.
○: No sedimentation or significant viscosity change is observed.
X: Generation | occurrence | production of sediment and / or remarkable viscosity change are recognized.

Production Example 12 of water-based coating composition
In a container, 227 parts (solid content 68 parts) of the acrylic-modified starch aqueous dispersion obtained in Example 1, Bihijoule VPLS-2319 (manufactured by Sumika Bayer Urethane Co., Ltd., hexamethylene diisocyanate water-dispersible polyisocyanate compound, solid 32 parts of 100%) and 27 parts of deionized water were mixed with stirring to obtain an aqueous coating composition B1 having a solid content of 35%.

Examples 13-22 and Comparative Examples 3-4
In the above Example 12, aqueous coating compositions B2 to B13 were obtained in the same manner as in Example 12 except that the blending composition was as shown in Table 2 below.

Preparation and Evaluation of Test Plate Each of the aqueous coating compositions obtained above was spray-coated on a polypropylene plate so that the dry film thickness was 50 μm. Next, it was dried at 80 ° C. for 30 minutes using an electric hot air dryer, and left to stand for 1 day to prepare a test coated plate, which was then subjected to the following test.

Finishing property The surface state of each test coated plate was visually observed and evaluated according to the following criteria.
○: Level with good smoothness and no problem.
Δ: Slightly at least one of swell, gloss, and chili skin is seen and is a slightly problematic level.
X: At least one of swell, gloss, and chili skin is remarkably problematic.

Non-adhesiveness of coating film The surface of each test coating plate was pressed with a fingertip (so that the nail touches the coating surface), and the adhesion and the degree of nail marks on the coating film were evaluated according to the following criteria.
A: Not sticky and does not have nail marks.
○: There is no stickiness and the nail mark is a little sticky and practically no problem.
Δ: A little sticky but no trace of fingerprints.
X: Adhesive and has fingerprint marks.

Gel fraction (%)
The coating film on the polypropylene plate was peeled off to make a free film. The film was placed in a separate type round bottom flask, 100 g or more of acetone was added to 1 g of the film, heated, and refluxed for 3 hours. Next, the film was taken out, dried at 105 ° C. for 1 hour, the film mass before and after reflux was measured, and calculated by applying to the following formula.
Gel fraction (%) = 100 × film mass after reflux / film mass before reflux.

Claims (8)

  The reaction product is obtained by subjecting the radical polymerizable unsaturated monomer mixture (b1) to radical polymerization reaction in the presence of the starch containing the radical polymerizable unsaturated group and / or the modified starch (a) to obtain a reaction product. An aqueous dispersion in which an acrylic modified starch (A) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (b2) in the presence of a product is dispersed in an aqueous medium, the radical polymerizable The amount of the carboxy group-containing radical polymerizable unsaturated monomer in the unsaturated monomer mixture (b1) is 5 to 95% by mass and the amount of the hydroxyl group-containing radical polymerizable unsaturated monomer is 5 to 95% by mass. Yes, the amount of the carboxy group-containing radical polymerizable unsaturated monomer in the radical polymerizable unsaturated monomer mixture (b2) is less than 5% by mass and the amount of the hydroxyl group-containing radical polymerizable unsaturated monomer is 5 to 5%. 95% by mass , Aqueous dispersion, wherein the acid value of the acrylic modified starch (A) is in the range of 10~150mgKOH / g.   The reaction product is obtained by subjecting the radical polymerizable unsaturated monomer mixture (b2) to radical polymerization in the presence of the starch containing the radical polymerizable unsaturated group and / or the modified starch (a) to obtain a reaction product. An aqueous dispersion obtained by dispersing, in an aqueous medium, an acrylic-modified starch (A) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (b1) in the presence of a product. The amount of the carboxy group-containing radical polymerizable unsaturated monomer in the unsaturated monomer mixture (b2) is less than 5% by mass and the amount of the hydroxyl group-containing radical polymerizable unsaturated monomer is 5 to 95% by mass. The amount of the carboxy group-containing radical polymerizable unsaturated monomer in the radical polymerizable unsaturated monomer mixture (b1) is 5 to 95% by mass and the amount of the hydroxyl group-containing radical polymerizable unsaturated monomer is 5 to 5%. 95% by mass , Aqueous dispersion, wherein the acid value of the acrylic modified starch (A) is in the range of 10~150mgKOH / g. Total amount of starch and / or modified starch (a) containing radical polymerizable unsaturated group (a), radical polymerizable unsaturated monomer mixture (b1) and radical polymerizable unsaturated monomer mixture (b2) 100 parts by mass Against
Starch and / or modified starch (a) 20-90 parts by weight,
The water according to claim 1 or 2, which is within a range of 5 to 40 parts by mass of the radical polymerizable unsaturated monomer mixture (b1) and 5 to 40 parts by mass of the radical polymerizable unsaturated monomer mixture (b2). Dispersion.   The aqueous dispersion according to any one of claims 1 to 3, wherein the component (a) contains 30% by mass or more of esterified starch containing a radical polymerizable unsaturated group.   The content of the radically polymerizable unsaturated group in the starch containing the radically polymerizable unsaturated group and / or the modified starch (a) is in the range of 0.001 to 1.000 mmol / g. The water dispersion according to any one of the above.   Radical polymerizable unsaturated monomer mixture (b1) and / or radical polymerizable unsaturated monomer mixture (b2) in the presence of starch containing radical polymerizable unsaturated group and / or modified starch (a) The aqueous dispersion according to any one of claims 1 to 5, wherein the radical polymerization initiator used in the radical polymerization reaction is benzoyl peroxide or t-butyl peroxyisobutyl carbonate.   The water-based coating composition containing the water dispersion as described in any one of Claims 1-6.   A coated article obtained by coating the water-based coating composition according to claim 7.