JP2005194487A - Pigment dispersing resin and coating composition containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a block copolymer useful for producing a pigment paste and excellent in pigment dispersibility. <P>SOLUTION: The block copolymer comprises a solvent-soluble block (A) and a pigment-adsorbing block (B) containing a carboxy group or an acid anhydride group as a functional group. The block copolymer, for example, comprises the solvent-soluble block (A) having a halogen atom on its terminal and the pigment-adsorbing block (B) obtained by block-polymerizing a polymerizable unsaturated monomer having the carboxy group or the block-protected carboxy group, and the mass ratio of the block (A) to the block (B) is (40-99.5):(60-0.5). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel block copolymer comprising a block copolymer excellent in pigment dispersibility, a pigment dispersing resin comprising the block copolymer, a pigment paste containing the pigment dispersing resin, and a colored coating composition containing the pigment paste Related to things.

Today, acrylic copolymers are widely used as paint binders. If an acrylic copolymer having a narrow molecular weight distribution is obtained, it is considered that the acrylic copolymer exhibits excellent properties different from conventional ones in terms of viscoelasticity, thermal properties, mechanical properties, weather resistance, and the like.
However, since acrylic copolymers have been produced by general radical polymerization so far, recombination of growing radicals, disproportionation reaction, etc. occur, and it is difficult to control the molecular weight distribution, A narrow molecular weight distribution could not be obtained.

  Generally, a block copolymer has a plurality of blocks in which two or more different monomers are polymerized, respectively. Accordingly, a single polymer having different properties derived from the respective blocks or a composite property in which these properties are fused can be obtained. For example, by combining two blocks that are inherently incompatible with each other, it is possible to produce a useful polymer that is compatible with two or more different materials, for example, two or more different resins. . Such block copolymers are widely used as compatibilizers, surfactants, surface modifiers, elastomers and the like.

Until now, the “living polymerization method” has been a common method for synthesizing block copolymers. For example, SBR and the like are synthesized by living anionic polymerization of styrene and butadiene. The block copolymer can also be synthesized by living cationic polymerization or “living radical polymerization” which has recently attracted attention.
However, living anions and living cationic polymerizations are 1) side reactions when reaction is carried out at a high temperature to shorten the reaction time, and it is difficult to obtain the target product. 2) reaction times are carried out at a very low temperature to suppress side reactions. 3) Inappropriate for monomers having functional groups, which are prolonged, and 4) The versatility is low because the living property is lowered due to the influence of impurities in the system.

On the other hand, in recent years, a new synthesis method called atom transfer radical polymerization (hereinafter simply referred to as “ATRP method”) has been developed (see Patent Document 1). This ATRP method is a method of polymerizing a monomer using, for example, an initiator having a carbon-halogen bond and a catalyst composed of a transition metal complex. In this method, the transition metal complex acts on the carbon-halogen bond of the initiator, and the halogen atom moves on the metal through the redox cycle of the transition metal. It is characterized in that the growth reaction is continued while maintaining a dynamic equilibrium state between an active species that participates in and a dormant species that does not participate (dormant species).
In this method, the dynamic equilibrium is greatly biased toward the dormant species side, and the concentration of active species that can cause a bimolecular termination reaction is very low. Generally, in dynamic equilibrium, the concentration of active species is about one millionth of the concentration of dormant species. For this reason, dynamic equilibrium is a state in which the interconversion speed is very high, and all dormant species can be dissociated into active species with almost the same probability and can be involved in the growth reaction. Therefore, the obtained polymers have almost the same molecular weight, and a polymer having a very narrow molecular weight distribution can be obtained.
For this reason, the ATRP method is highly versatile compared to living ion polymerization in that 1) it can be polymerized at an appropriate temperature above room temperature, 2) it is not easily affected by the functional group of the monomer, and impurities in the system. Have.

In general, organic or inorganic pigments are widely used in paints, inks, and the like for the purpose of coloring, shading, aesthetics, rust prevention, and the like. When these pigments are dispersed in paint, ink, etc., the dispersion stability of the pigment is insufficient and re-aggregation, fluidity is poor, the hue when it is made into a coating film, gloss is insufficient, etc. Various proposals have been made so far to solve these problems.
For example, in order to improve pigment dispersibility, proposals have been made to add pigment derivatives having the same skeleton as the pigment dispersed at the time of pigment dispersion, or to use pigments treated with these pigment derivatives (for example, And Patent Documents 2 to 4). However, the methods according to these proposals have problems that not only the pigment dispersion effect is still insufficient, but also many kinds of pigment derivatives are required, the versatility is inferior, and the production is very expensive. .
Further, in the block copolymer having a functional group containing a nitrogen atom, a sufficient pigment dispersion effect can be obtained when the surface of the pigment is acidic or polar. However, when the surface of the pigment is basic, sufficient pigment is obtained. A dispersion effect may not be obtained (see, for example, Patent Document 5).

In addition, various pigment dispersants such as acrylic resin, polyester resin, urethane resin, and polyester-modified urethane resin are commercially available and widely used. It also contains substances with compositional balances that are not necessary due to compositional and molecular weight non-uniformity, etc., and the problem that proper fluidity, hue, gloss, etc. cannot be obtained unless they are blended in a certain amount in the paint. Is not always satisfactory.
Furthermore, in recent years, it has become an urgent task in the paint industry to reduce the amount of organic solvents in paints and to achieve high solid differentiation from the viewpoint of global environmental conservation. As a method for high solidification, studies are generally being conducted in the direction of lowering the viscosity by lowering the molecular weight of a coating resin. However, when the molecular weight of the resin is lowered, problems such as lowering of curability and lowering of coating film performance occur.
In addition to lowering the molecular weight of the coating resin, techniques for achieving high solidification of the coating include increasing the pigment concentration of the coating (reducing the amount of resin used to disperse the same amount of pigment). However, in general, when trying to increase the pigment concentration of the paint, the viscosity of the pigment paste, the pigment paste, the aggregation of the pigments in the paint, and the lack of let-down stability when forming the paint are likely to occur. There is a problem that it is difficult to obtain a stable pigment paste or paint unless the resin ratio in the paint is increased to some extent.

  Japanese National Patent Publication No. 10-509475   JP 59-96175   Japanese Patent Laid-Open No. 02-36252   Japanese Patent Laid-Open No. 10-81849   JP 2003-64139 A

An object of this invention is to provide the block copolymer excellent in pigment dispersibility.
Another object of the present invention is to provide a pigment paste composition having good letdown stability and dispersion stability over time.

As a result of intensive studies to achieve the above-mentioned problems, the present inventor has found that a block having a solvent-soluble block (A) and a pigment-adsorbing block (B) containing a carboxyl group or an acid anhydride group as a functional group. The inventors have found that the above-mentioned problems can be achieved by using a copolymer, and have reached the present invention.
By using the block copolymer for pigment dispersion of the present invention, a pigment dispersion paste composition having a pigment dispersion that is significantly stable over time can be obtained.
In addition, by using the pigment dispersion paste composition of the present invention, a colored coating composition having improved letdown stability can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
First, the pigment dispersion block copolymer of the present invention will be described.
The block copolymer of the present invention contains a solvent-soluble block (A) and a pigment-adsorbing block (B) containing a carboxyl group or an acid anhydride group as a functional group.
The solvent-soluble block (A) used in the present invention can be synthesized, for example, by polymerizing a polymerizable unsaturated monomer or resin that is not hydrolyzed.
Examples of such polymerizable unsaturated monomers include styrene monomers such as styrene, vinyltoluene, α-methylstyrene, and chlorostyrene; fluorine-containing vinyl monomers such as vinylidene fluoride; alkenes such as ethylene and propylene; Examples thereof include conjugated dienes such as butadiene and isoprene.

Examples of such monomers and resins include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) ) Acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (Meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, phenyl (meth) acrylate, toluyl (meth) acrylate, benzyl ( ) Acrylate, 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, ethoxyethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl ( (Meth) acrylic acid monomers such as meth) acrylate and glycidyl (meth) acrylate; styrene monomers such as styrene, vinyltoluene, α-methylstyrene and chlorostyrene; vinyl such as vinyl acetate, vinyl benzoate and vinyl propionate Fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, and vinylidene fluoride; silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; maleic anhydride, Dialkyl ester of maleic acid; Dialkyl ester of fumaric acid; Polyester resin containing maleic acid and fumaric acid; Alkyd resin containing unsaturated fatty acid; Alkenes such as ethylene and propylene; Conjugated dienes such as butadiene and isobrene; Preferred examples include vinyl, vinylidene chloride, allyl chloride, allyl alcohol and the like.
These polymerizable unsaturated monomers may be used alone or in combination of two or more. Among these polymerizable unsaturated monomers, a styrene monomer is particularly preferable from the viewpoint of copolymerizability, and a combination having good reactivity in normal radical polymerization is preferable.

Various solvents are used as solvents used in pigment pastes and paints. The above-mentioned various polymerizable unsaturated monomers and polymerizable resins are basically the following polymerizable unsaturated monomers, polymerizable resins, or combinations thereof with respect to various solvents on the basis of solubility in the solvent. It is preferable to use it.
Moreover, those skilled in the art can easily understand such selection criteria experimentally.
When the polarity of the solvent used in the pigment paste or paint is high, for example, a monomer having a relatively high polarity such as methyl (meth) acrylate or ethyl (meth) acrylate, and when the polarity of the solvent is low, for example, , A monomer having a relatively low polarity such as dodecyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate. The resulting block is highly soluble in the solvent used in the pigment paste or paint, and becomes a solvent-soluble block (A).

The pigment-adsorbing block (B) can be obtained by polymerizing a polymerizable unsaturated monomer containing a carboxyl group or a precursor monomer thereof. As such a polymerizable unsaturated monomer or a precursor monomer thereof (hereinafter collectively referred to as “polymerizable unsaturated monomer”), preferably, (meth) acrylic acid alkyl ester and the like are preferably used.
Formed by block polymerization of the above-mentioned solvent-soluble block (A) and the polymerizable unsaturated monomer constituting the block B, or by previously polymerizing a polymerizable unsaturated monomer having a carboxyl group blocked by an ester bond or the like The block B can be obtained by reacting with the block (B ′) and then hydrolyzing the blocked carboxyl group of the block (B ′).
Examples of the (meth) acrylic acid alkyl ester monomer as the polymerizable unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl. Examples include (meth) acrylic acid monomers such as (meth) acrylate, tert-butyl (meth) acrylate, and isobutyl (meth) acrylate. Preferred examples of the monomer include tert-butyl (meth) acrylate.
These (meth) acrylic acid alkyl ester monomers may be used alone or in combination. Moreover, you may mix and use some examples of the polymerizable unsaturated monomer quoted above by the solvent soluble block (A). At this time, the amount of (meth) acrylic acid alkyl ester monomer to be hydrolyzed is, for example, 25 to 100% by mass, preferably 40 to 100% by mass, based on the mass of the pigment-adsorbing block (B). Is appropriate.
If the alkyl ester group such as tert-butyl group is not hydrolyzed without hydrolyzing the alkyl ester group of the block (B ′), the pigment adsorptivity is low and the effect as a pigment dispersing resin cannot be obtained. Those skilled in the art can easily understand experimentally.

The alkyl ester of the block (B ′) is, for example, a carboxyl group represented by the following formula 1 under treatment with hydrochloric acid, for example, at a reaction temperature of 70 to 100 ° C., for example, for 20 to 30 hours. The conversion rate reaches about 100%.
(Formula 1)
Carboxyl group conversion rate = number of moles of carboxyl group after hydrolysis / number of moles of alkyl ester group before hydrolysis × 100
In the block copolymer of the present invention, the solvent-soluble block (A) and the pigment-adsorbing block (B) include, for example, AB, ABA, (AB) nA, and the like. It can be included in various forms. Here, n is, for example, 1 to 10, preferably 1 to 3.
The solvent-soluble block (A) is preferably contained in an amount of 40 to 99.5% by mass, preferably 50 to 96% by mass, based on the mass of the block copolymer. Accordingly, the pigment adsorbing block (B) is, for example, 0.5 to 60% by mass, preferably 4 to 50% by mass, based on the mass of the block copolymer.

If the content of the block (A) and the block (B) constituting the block copolymer of the present invention is within the above range, it is preferable from the viewpoints of dispersion stability of pigments, physical properties of the coating film, finished appearance, and the like. .
Here, the amount of the block (A) can be appropriately selected within the above range according to the polarity of the dispersion solvent, the hardness of the coating film, the curability of the coating film, the weather resistance, and the physical properties. As the block (A) is closer to the polarity of the dispersion solvent and has a three-dimensional bulk, the block copolymer after the pigment adsorption forms a three-dimensional repulsive layer, preventing aggregation of the pigments, It is considered that good dispersion stability and excellent let-down stability are exhibited.
On the other hand, the amount of the pigment-adsorptive block (B) can be appropriately selected within the above range depending mainly on the acidic-basic or polar-nonpolar nature of the pigment surface.

Various pigments are used as pigments used in pigment pastes and paints. Since the carboxyl group contained in the pigment-adsorptive block (B) works as an acidity or polarity with respect to the pigment surface, it is basically preferable to use the following combinations for various pigments. Moreover, those skilled in the art can easily understand such selection criteria experimentally.
When the pigment surface is basic or polar, the amount of the block (B) may be small, but when the pigment surface is neutral, acidic, or nonpolar, the amount of the block (B). Increasing the amount indicates good affinity with the pigment and adsorption stability.
The acidity and basicity of the pigment surface can be roughly grasped by the hydrogen ion concentration eluted in water. In general, it can be confirmed by adding water to the pigment and boiling, and after allowing to cool, the supernatant or filtrate is measured with a pH meter.
Various synthesis methods conventionally used for the synthesis of block copolymers can be appropriately employed for the block copolymer of the present invention. Examples of such a synthesis method include radical polymerization, anionic polymerization, and cationic polymerization. However, the block copolymer of the present invention is very suitable to be synthesized by the ATRP method described above.
First, the ATRP method will be described. In this method, an organic halogen compound (a) having at least one halogen selected from chlorine, bromine and iodine is used as a polymerization initiator, and groups 4 to 12 of the periodic table are used. And a ligand (c) capable of coordinating to the metal halide (b) and a metal halide (b) comprising a halogen selected from chlorine, bromine and iodine as a constituent element A polymerization method using the reaction product (d) obtained in this way in combination is appropriate.

  As the organic halogen compound (a), various organic compounds having one or more carbon-halogen bonds (halogen is, for example, chlorine, bromine or iodine) can be used. Two or more halogen atoms may be bonded to the same carbon atom, or may be bonded to different carbon atoms. Preferably, two or more halogen atoms are bonded to different carbon atoms. The number of halogen atoms bonded to carbon atoms in one molecule of the organic halogen compound (a) is not particularly limited, but is preferably 6 or less, and more preferably 1 or 2.

Examples of the organic halogen compound (a) include organic halogen compounds such as aliphatic hydrocarbon halogen compounds, alicyclic hydrocarbon halogen compounds, aromatic hydrocarbon halogen compounds, and heterocyclic halogen compounds, and fluorine. Preferable examples include organic halogen compound derivatives containing a substituent or bond having an atom, oxygen atom, nitrogen atom, or the like.
Specific examples of the organic halogen compound (a) include, for example, alkyl halides, aralkyl halides, acid halides, and the like. For example, methyl chloride, methylene chloride, chloroform, carbon tetrachloride, methyl bromide, methyl iodide, 1-phenylethyl chloride, benzyl chloride, 1-phenylethyl bromide, benzyl bromide, 1-phenylethyl iodide, benzyl iodide Preferred examples include perfluoroalkyl iodide having 1 to 20 carbon atoms in the alkyl group, perfluoroalkyl bromide, and the like.

The metal species in the metal halide (b) is a transition metal selected from Groups 4 to 12 of the periodic table, and a transition metal selected from Groups 8 to 11 of the periodic table is particularly preferable. Among them, metals from Ti with atomic number 22 to Zn with 30 are suitable, and among them, Fe, Co, Ni, and Cu are preferable. The most preferred metal is Cu. Particularly preferred metal halides (b) are cuprous halides, that is, cuprous chloride, cuprous bromide, and cuprous iodide.
The ligand (c) capable of coordination is not particularly limited as long as it can be coordinated to the metal halide (b). Examples of such a ligand (c) include pyridine, 2,2′-bipyridyl, 4,4′-bipyridyl, 1,10-phenanthroline, ethylenediamine, 4-vinylpyridine, dimethylglyoxime, terpyridine, Examples thereof include nitrogen-containing compounds such as porphyrins, and phosphorus-containing compounds such as triphenylphosphine. In particular, 2,2′-bipyridyl is preferred.
In the ATRP method, an organic halogen compound (a) is used as a polymerization initiator, and a reaction product (d) obtained by reacting a metal halide (b) and a ligand (c) is used in combination. These reaction temperatures are preferably, for example, 80 to 150 ° C.

The reaction ratio of the metal halide (b) to the organic halogen compound (a) is as follows. When the number of halogen atoms in the organic halogen compound (a) is m, halogenation is performed with respect to 1 mole of the organic halogen compound (a). The metal (b) is preferably about mmol. As the reaction ratio of the ligand (c), it is preferable to use at least the ratio of the number of molecules that can coordinate to one metal atom in the metal halide (b). For example, when the metal halide (b) is cuprous bromide, two molecules of 2,2′-bipyridyl are coordinated to one copper atom. Suitably 3 moles of 2'-bipyridyl are used.
Polymerization of the polymerizable unsaturated monomer (or the prepolymer obtained by preliminarily polymerizing the polymerizable unsaturated monomer) constituting the solvent-soluble block (A) may be performed without a solvent or in a solvent. May be. Examples of the solvent include hydrocarbon solvents such as benzene, toluene, xylene, and mineral spirits, halogenated hydrocarbon solvents such as chloroform, carbonate solvents such as ethylene carbonate and propylene carbonate, ethyl acetate, butyl acetate, and the like. Examples thereof include ester solvents, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ether solvents such as diethyl ether, tetrahydrofuran and anisole, and alcohol solvents such as methanol, ethanol and propanol. These organic solvents can be used alone or in combination of two or more.

The synthesis of the solvent-soluble block (A) may be carried out at a temperature at which the polymerizable unsaturated monomer and the like constituting it can be polymerized, but from the reaction rate, the polymerizable property of the polymerizable unsaturated monomer, the boiling point of the reaction solvent, etc. For example, 80-130 degreeC is preferable.
A solvent-soluble block (A) obtained by polymerizing a polymerizable unsaturated monomer in the coexistence of an organic halogen compound (a), a metal halide (b) and a ligand (c) has a block terminal. It is a halogen-containing block (macroinitiator A1) having at least one carbon-halogen bond.
The number average molecular weight of the block (A) is, for example, 400 to 99,850, preferably 1000 to 30,000.
Into the mixture of the generated macroinitiator (A1) and the remaining organic halogen compound (a), metal halide (b) and ligand (c), the (meth) acrylic acid alkyl ester is used as a constituent. By adding a polymerizable unsaturated monomer or the like constituting the contained block (B ′) and restarting the polymerization, the macroinitiator (A1) has a block (B1) via the halogen atom of the macroinitiator (A1). A polymerizable unsaturated monomer constituting ') is copolymerized to obtain a block copolymer having an AB structure.
The number average molecular weight of the block (B ′) added to the block (A) is, for example, 150 to 60,000, preferably 300 to 45,000.

In the preparation of the block copolymer of the present invention, the organic halogen compound (a), the metal halide (b) and the ligand ( c) can be used again as it is, and when the polymerizable unsaturated monomer of the block (B ′) is polymerized, the polymerization can be resumed without purifying the block (A).
The resulting block copolymer is subjected to a hydrolysis treatment of the alkyl ester group or the like of the block (B ′) as described above, thereby generating a pigment-adsorbing carboxyl group, and the solvent-soluble block (A), A block copolymer having a pigment adsorbing block (B) is obtained.
In the obtained block copolymer, an acid anhydride group is generated in the pigment-adsorbing block (B) by heat-treating the block (B ′) as described above, and the solvent-soluble block (A) and A block copolymer having a pigment adsorbing block (B) containing an acid anhydride group as a functional group is obtained.
When the block copolymer of the present invention is used as a pigment dispersing resin, the number average molecular weight is, for example, in the range of 1000 to 100,000, preferably 5000 to 50,000. If the number average molecular weight is too low, the pigment dispersion stability and letdown stability with time will be poor, and if the number average molecular weight is too high, problems will arise in the ease of handling of the resin, the finished appearance of the coating film, and the like.
In addition, the block copolymer of the present invention has a molecular weight distribution (Mw / Mn) of 1.1 to 1.9, preferably 1.1 to 1.7. .

Next, the pigment dispersion paste composition of the present invention will be described.
The pigment dispersion paste composition of the present invention contains the above pigment dispersion resin (block copolymer), a pigment, and, if necessary, an organic solvent.
The block copolymer as the resin for dispersing pigment is, for example, 0.1 to 40.0% by mass, preferably 0.5 to 20% by mass based on the mass of the pigment dispersion paste composition. It is.
Examples of the pigment include bright pigments such as aluminum powder, copper powder, nickel powder, stainless steel powder, chromium powder, mica-like iron oxide, acid value titanium-coated mica powder, iron oxide-coated mica powder, and bright graphite; Pink EB, cyanine blue, cyanine green, organic red pigments such as azo and quinacridone, organic yellow pigments such as benzimidazolone, isoindolinone, isoindoline and quinophthalone; titanium white, titanium yellow, bengara Preferred examples include inorganic pigments such as carbon black, chrome lead, and various calcined pigments, and extender pigments such as precipitated barium sulfate, calcium carbonate, and silica.
The pigment is suitably blended in an amount of, for example, 2 to 90% by mass, preferably 5 to 80% by mass, based on the mass of the pigment dispersion paste composition.

The organic solvent used as necessary can be used without particular limitation as long as it is an organic solvent that can dissolve the pigment-dispersing block copolymer. Specific examples thereof include hydrocarbons such as toluene, xylene, and mineral spirits. Solvent: Ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, butyl carbitol acetate, ethers such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol Solvents, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and diisobutyl ketone, alcohol solvents such as methanol, ethanol, isopropanol, n-butanol and isobutanol Cosmo Oil Co. Swasol 310, Swasol 1000, and aromatic petroleum solvent system such as Swasol 1500. These organic solvents can be used alone or as a mixture of two or more.
When these organic solvents are used, for example, 0 to 98% by mass, preferably 5 to 95% by mass is appropriate based on the mass of the pigment dispersion paste composition.

The pigment dispersion paste composition comprises a coating binder resin and, if necessary, an organic solvent, polymer fine particles, a curing catalyst, an ultraviolet absorber, an ultraviolet stabilizer, a coating surface conditioner, an antioxidant, a fluidity conditioner, A colored coating composition can be obtained by blending with an additive such as a silane coupling agent.
The pigment-dispersed paste composition is suitably used in an amount of, for example, 0.1 to 80% by mass, preferably 0.1 to 50% by mass, based on the mass of the colored coating composition.
Examples of the binder resin for paint include a base resin and a curing agent that can be used for paint. Examples of the base resin include a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, an epoxy resin, an epoxy group-containing acrylic resin, an amino resin, an optionally blocked polyisocyanate compound, a carboxyl group-containing high acid value polyester resin, and a carboxyl group. Examples thereof include a group-containing high acid value acrylic resin. These base resins can be used alone or as a mixture of two or more. The polyisocyanate compound which may be blocked includes both a blocked polyisocyanate compound in which an isocyanato group is blocked and a non-blocked polyisocyanate compound.
The binder resin is used in an amount of, for example, 10 to 90% by mass, preferably 20 to 80% by mass in terms of solid content based on the mass of the colored coating composition.

As the organic solvent used as necessary, various organic solvents similar to those exemplified as the organic solvent that can be contained in the pigment dispersion paste composition can be used.
The organic solvent is suitably used in an amount of, for example, 0 to 80% by mass, preferably 10 to 60% by mass, based on the mass of the colored coating composition.
The polymer fine particles are polymers that do not dissolve in the colored coating composition and are dispersed as fine particles, and those having an average particle diameter in the range of, for example, 0.01 to 1 μm are preferable. The fine polymer particles may or may not be crosslinked inside the particles, but those crosslinked internally are desirable. The polymer fine particles are known per se and can be appropriately selected and used.
The polymer fine particles are suitably used in an amount of, for example, 0 to 20% by mass, preferably 1 to 10% by mass, based on the colored coating composition.

Examples of the curing catalyst include dibutyltin diacetate, dibutyltin dioctate, dibutyltin dilaurate, triethylamine, diethanolamine and the like when the curing agent is a polyisocyanate compound which may be blocked. In the case of an amino resin such as a resin, sulfonic acid compounds such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid and dinonylnaphthalenesulfonic acid, and amine neutralized products of these sulfonic acid compounds should be preferably mentioned. Can do.
The curing catalyst is suitably used in an amount of, for example, 0 to 2% by mass, preferably 0.02 to 1% by mass, based on the mass of the colored coating composition.
Preferred examples of the ultraviolet absorber include benzophenone-based compounds, benzotriazole-based compounds, cyanoacrylate-based compounds, salicylate-based compounds, oxalic acid anilide-based compounds, and the like. As said ultraviolet stabilizer, a hindered amine compound can be mentioned suitably.
The ultraviolet absorber is suitably used in an amount of, for example, 0 to 10% by mass, preferably 0.1 to 5% by mass, based on the mass of the colored coating composition.

(Example)
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, the scope of the present invention is not limited at all by these Examples and comparative examples. Unless otherwise specified, “part” and “%” mean “part by mass” and “% by mass”, respectively.
First, a method for synthesizing a block copolymer for pigment dispersion of the present invention and a comparative polymer (random polymer) will be described. In each synthesis example, the monomers constituting the blocks A and B were each simply distilled. Other raw materials were used as they were, respectively. The finally obtained block copolymer is precipitated in methanol to remove the metal halide (b), the ligand (c), the unreacted polymerization initiator, and the unreacted monomer, and then filtered and decompressed. Drying was performed for 24 hours. The obtained block copolymer was measured by GPC, 1H-NMR, and IR to determine the structure.

The number average molecular weight (Mn) and the molecular weight distribution (Mw / Mn) were measured using a TSKgel column (manufactured by Tosoh Corporation) and a GPC equipped with an RI detector (manufactured by Tosoh Corporation, HLC-8120GPC). Determined by As GPC measurement conditions, tetrahydrofuran was used as a developing solvent, and measurement was performed at a flow rate of 1.0 ml / min and a temperature of 40 ° C.
1H-NMR was measured at room temperature using CDCl3 as a deuterated solvent and using UNITY 400 INOVA manufactured by Varian as an apparatus.
The IR analysis was performed by the KBr method and measured at room temperature using an infrared spectrophotometer (manufactured by Shimadzu Corporation, FTIR-8300) as an apparatus.

Synthesis example 1
1-phenylethyl bromide (hereinafter abbreviated as 1-PEBr) 3.4 g (18.2 mmol), cuprous bromide (hereinafter abbreviated as CuBr) 2.6 g (18.2 mmol), 2,2′-bipyridyl (Hereinafter abbreviated as Bpy) 8.5 g (54.5 mmol), styrene (hereinafter abbreviated as ST) 90.9 g (873 mmol) and anisole 100 ml were charged into a 500 ml three-necked flask equipped with a condenser. After deaeration, the system was purged with nitrogen, then heated to 110 ° C. and stirred for 12 hours, the flask was cooled, and the polymerization was stopped (end of the first stage reaction).
This reaction product was dissolved in 400 ml of tetrahydrofuran (hereinafter abbreviated as THF), further purified by precipitation with 8000 ml of methanol (hereinafter abbreviated as MeOH), and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 Torr) to obtain a polystyrene macroinitiator (PS1). The number average molecular weight (Mn) of PS1 was 5800, and the molecular weight distribution (Mw / Mn) was 1.20.

35.69 g (6.15 mmol) of the obtained PS1, 1.05 g (7.38 mmol) of tert-butyl methacrylate (hereinafter abbreviated as TBMA), 0.61 g (6 of cuprous chloride (hereinafter abbreviated as CuCl)) .15 mmol), 2.88 g (18.46 mmol) of Bpy, and 70 ml of anisole were charged into a 300 ml three-necked flask equipped with a condenser, and after deaeration, the system was purged with nitrogen and heated to 90 ° C. The stirring was continued for 12 hours, the flask was cooled, and the polymerization was stopped.
This reaction product was dissolved in 100 ml of THF, further purified by precipitation with 2000 ml of MeOH, and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 torr) to obtain a block copolymer BA-1. The number average molecular weight (Mn) of the block copolymer BA-1 was 7100, and the molecular weight distribution (Mw / Mn) was 1.12.
The obtained block copolymer BA-1 is put into a 100 ml eggplant flask, 90 ml of dioxane and 10 ml of hydrochloric acid are added, hydrolyzed in an oil bath at 80 ° C. for 24 hours to generate free carboxyl groups, and pigment dispersing resin B -1 was obtained. The mass ratio of the solvent-soluble block (A) and the block (B) containing a carboxyl group was 87:13.

Synthesis example 2
35.69 g (6.15 mmol) of PS1 obtained above, 3.15 g (22.15 mmol) of TBMA, 0.61 g (6.15 mmol) of CuCl, 2.88 g (18.46 mmol) of Bpy, and 70 ml of anisole were placed in a condenser tube. After deaeration, the system was purged with nitrogen, heated to 90 ° C., stirred for 12 hours, cooled, and the polymerization was stopped.
This reaction product was dissolved in 100 ml of THF, further purified by precipitation with 2000 ml of MeOH, and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 torr) to obtain a block copolymer BA-2. The number average molecular weight (Mn) of the block copolymer BA-2 was 8900, and the molecular weight distribution (Mw / Mn) was 1.12.
The obtained block copolymer BA-2 is put into a 100 ml eggplant flask, 90 ml of dioxane and 10 ml of hydrochloric acid are added, hydrolyzed in an oil bath at 80 ° C. for 24 hours to generate free carboxyl groups, and pigment dispersing resin B -2 was obtained.
The mass ratio of the solvent-soluble block (A) and the block (B) containing a carboxyl group was 69:31.

Comparative Synthesis Example 1
1-PEBr 0.32 g (1.7 mmol), ST 8.24 g (79.2 mmol), TBMA 1.44 g (10.1 mmol), CuBr 0.24 g (1.7 mmol), Bpy 0.79 g (5.1 mmol), and anisole 70 ml was charged into a 300 ml three-necked flask equipped with a condenser, and after deaeration, the inside of the system was purged with nitrogen, heated to 90 ° C., continued stirring for 12 hours, the flask was cooled, and the polymerization was stopped. did.
This reaction product was dissolved in 100 ml of THF, further purified by precipitation with 2000 ml of MeOH, and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 torr) to obtain random polymer RA-1. The number average molecular weight (Mn) of the random polymer RA-1 was 6200, and the molecular weight distribution (Mw / Mn) was 1.20.
The obtained random polymer RA-1 is put into a 100 ml eggplant flask, 90 ml of dioxane and 10 ml of hydrochloric acid are added, hydrolyzed in an oil bath at 80 ° C. for 24 hours, free carboxyl groups are generated, and pigment dispersion resin R -1 was obtained.

Comparative Synthesis Example 2
1-PEBr 0.32 g (1.7 mmol), ST 8.24 g (79.2 mmol), TBMA 4.32 g (30.3 mmol), CuBr 0.24 g (1.7 mmol), Bpy 0.79 g (5.1 mmol), and 70 ml of anisole was charged into a 300 ml three-necked flask equipped with a condenser, and after deaeration, the inside of the system was purged with nitrogen, and then heated to 90 ° C. and stirred for 12 hours, the flask was cooled, and polymerization was carried out. Stopped.
This reaction product was dissolved in 100 ml of THF, further purified by precipitation with 2000 ml of MeOH, and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 torr) to obtain random polymer RA-2. The number average molecular weight (Mn) of the random polymer RA-2 was 7500, and the molecular weight distribution (Mw / Mn) was 1.18.

The obtained random polymer RA-2 is put into a 100 ml eggplant flask, 90 ml of dioxane and 10 ml of hydrochloric acid are added, hydrolyzed in an oil bath at 80 ° C. for 24 hours to generate free carboxyl groups, and the resin R for pigment dispersion R -2 was obtained.
Each of the obtained copolymers was qualitatively determined by 1H-NMR and IR, and each single peak was confirmed by a GPC chart.
Next, an example of producing a pigment dispersion paste composition using the block copolymer of the present invention and the copolymer of the comparative example (random copolymer) is shown.

Production Example 1 of Pigment Dispersion Paste Composition
0.5 parts of the pigment dispersion resin (B-1) obtained in Synthesis Example 1, 15 parts of Bengala pigment (130ED manufactured by Toda Kogyo Co., Ltd., acidic pigment pH 6), and 10 parts of toluene are dispersed in a paint shaker for 2 hours. (Using a wide-mouth glass bottle with a capacity of 50 cc and a titania bead with a diameter of 1.3 mm), a pigment dispersion paste composition (PP-1) was obtained.
Production Examples 2 to 8 of Pigment Dispersed Paste Composition
In the same manner as in Production Example 1, pigment dispersion paste compositions (PP-2 to PP-8) of Production Examples 2 to 8 were prepared based on the compositions shown in Table 1 below. In addition, toluene used industrial supplies, and quinacridone red pigment used Daisatsu Ink Chemical Co., Ltd. Fastogen Super Red 5B (neutral pigment pH 7).

About each obtained pigment paste composition PP-1-8, the performance test was done based on the following test method. The test results are shown in Table 2 below.
Test method <Viscosity measurement>
The shear rate dependence of each pigment paste composition at the initial stage of dispersion was measured with a viscoelasticity measuring device (ARES manufactured by Rheometric Co., Ltd.). Measurement conditions were as follows: measurement temperature 20 ° C., pre-treatment applied for 1 minute × 100 / s, then placed for 3 minutes, and then changed the displacement rate from 0.01 / s to 1000 / s at 20 ° C. Viscosity measurement was performed. In addition, each pigment paste composition was subjected to accelerated storage at 50 ° C. for 14 days, and the viscosity was measured after aging under the same conditions as described above.

T.A. I. The value (thixotropic index) was calculated by dividing the viscosity obtained on the low shear side at the shear rate of the rheometer by the viscosity obtained on the high shear side. T. T. I. It can be judged that the lower the value is, the less the pigment is aggregated and the better dispersion state is maintained.
<Microscope observation>
The initial dispersion of each pigment paste composition and the state after accelerated storage at 50 ° C. for 14 days were observed with an optical microscope and evaluated according to the following evaluation criteria. Each pigment paste composition was diluted 5 times with toluene, and observed with a transmission phase contrast optical microscope (Nikon Corporation, MICROPHOTO-FXA). Observation was performed with an eyepiece lens 1 × and an objective lens 20 ×.
<Evaluation criteria>
○: Uniformly dispersed Δ: Partial aggregation of the pigment is observed x: Overall aggregation of the pigment is observed

Next, the manufacture example of binder resin for coating materials is shown.
Production Example 1 of Binder Resin for Paint
Acrylic resin reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc. was charged with 30 parts of xylene and 5 parts of isobutanol, heated and stirred, and after reaching 110 ° C., a mixture of the following monomers, etc. It was added dropwise over time.
A mixture of 15 parts of styrene, 10 parts of methyl methacrylate, 15 parts of n-butyl acrylate, 10 parts of hydroxyethyl methacrylate, 1 part of acrylic acid, and 0.3 part of 2,2′-azobisisobutyronitrile.
After completion of the dropwise addition of the mixture of monomers and the like, an additional catalyst solution that is a mixture of 0.2 part of 2,2′-azobisisobutyronitrile and 5 parts of xylene is maintained for 2 hours while maintaining 110 ° C. It was dripped over. Further, stirring was continued at 110 ° C. for 1 hour, followed by cooling. The resulting reaction solution was diluted by adding 5 parts of xylene and 5 parts of isobutanol to obtain an acrylic resin solution (AC-1) having a solid concentration of 50%. The obtained acrylic resin had a mass average molecular weight (Mw) of 50,000, a solid content acid value of 17 mg KOH / g (phenolphthalein), and a viscosity of 11 Stokes / 20 ° C. (Gardner method).

Next, the manufacture example of a coloring coating composition is shown.
Production Example 1 of Colored Paint Composition
10 parts of the pigment dispersion paste composition (PP-1) obtained in Production Example 1, 30 parts of the acrylic resin solution (AC-1), Uban 20SE60 (trade name, manufactured by Mitsui Toatsu Chemical Co., Ltd., butyl etherified melamine) Resin, NV 60%) 4 parts and butyl carbitol 1 part were mixed using a disper by a let-down method to obtain a colored coating composition (CP-1).

Production Examples 2 to 16 of Colored Paint Composition
Colored paint compositions (CP-2 to CP-8) were obtained using the pigment dispersion paste compositions (PP-2 to PP-8) in the same manner as in Production Example 1 of the above colored paint composition. Table 3 below shows the composition of the colored coating compositions of CP-1 to CP-8 containing CP-1 of Production Example 1 of the colored coating composition as Production Examples 9-16.

Using each of the colored coating compositions CP-1 to CP-8 obtained in Production Examples 9 to 16, each test coated plate was produced based on the following test coated plate production method.
Preparation Method of Test Coating Plate Each of the colored coating compositions CP-1 to CP-8 was applied undiluted to SPTE (tin plate, dimensions 0.3 × 150 × 70 mm) using a 4 mil applicator. Two minutes after the coating, the same colored coating compositions CP-1 to CP-8 were flow-coated on the lower half of the coating surface, and setting was performed while standing for 10 minutes. Then, baking drying was performed for 20 minutes at 130 degreeC, and the following evaluation method evaluated. The evaluation results are shown in Table 4 below.

Evaluation method <Appearance of coating film>
The applicator part of the coating film and the coating surface state of the flow coating part were observed with respect to color tone, gloss, and roughness, and evaluated according to the following criteria.
<Evaluation criteria>
○: All are good △: Any one of the color tone, glossiness, or irregularity is bad ×: Any two or more of the color tone, glossiness, or irregularity is defective

From these facts, it can be seen that the block copolymer of the present invention is superior in pigment dispersibility than a random polymer having a similar composition, and is excellent in storage stability of the pigment paste composition and color tone stability of the colored coating composition. It was.
Synthesis example 3
1-phenylethyl bromide (hereinafter abbreviated as 1-PEBr) 3.4 g (18.2 mmol), cuprous bromide (hereinafter abbreviated as CuBr) 2.6 g (18.2 mmol), 2,2′-bipyridyl (Hereinafter abbreviated as Bpy) 8.5 g (54.5 mmol), styrene (hereinafter abbreviated as ST) 90.9 g (873 mmol) and anisole 100 ml were charged into a 500 ml three-necked flask equipped with a condenser. After deaeration, the system was purged with nitrogen, then heated to 110 ° C. and stirred for 12 hours, the flask was cooled, and the polymerization was stopped (end of the first stage reaction).
This reaction product was dissolved in 400 ml of tetrahydrofuran (hereinafter abbreviated as THF), further purified by precipitation with 8000 ml of methanol (hereinafter abbreviated as MeOH), and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 Torr) to obtain a polystyrene macroinitiator (PS1). The number average molecular weight (Mn) of PS1 was 5800, and the molecular weight distribution (Mw / Mn) was 1.20.

35.69 g (6.15 mmol) of PS1, 1.05 g (7.38 mmol) of tert-butyl methacrylate (hereinafter abbreviated as TBMA), 0.61 g (6.15 mmol) of cuprous chloride (hereinafter abbreviated as CuCl) , 2.88 g (18.46 mmol) of Bpy and 70 ml of anisole were charged into a 300 ml three-necked flask equipped with a condenser, and after deaeration, the system was purged with nitrogen and heated to 90 ° C. for 12 hours. Stirring was continued, the flask was cooled, and the polymerization was stopped.
This reaction product was dissolved in 100 ml of THF, further purified by precipitation with 2000 ml of MeOH, and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 torr) to obtain a block copolymer BA-1. The number average molecular weight (Mn) of the block copolymer BA-1 was 7100, and the molecular weight distribution (Mw / Mn) was 1.12.
The obtained block copolymer BA-3 was subjected to heat treatment at 190 ° C. for 3 hours under 2.7 hPa (2 torr), and a functional group of an acid anhydride was generated by thermal decomposition to obtain a resin B-1 for pigment dispersion. It was. The mass ratio of the solvent-soluble block (A) and the block (B) containing an acid anhydride group was 88:12.

Synthesis example 4
35.69 g (6.15 mmol) of PS1 obtained above, 3.15 g (22.15 mmol) of TBMA, 0.61 g (6.15 mmol) of CuCl, 2.88 g (18.46 mmol) of Bpy, and 70 ml of anisole were added to a condenser tube. After charging the equipped 300 ml three-necked flask and deaeration, the inside of the system was purged with nitrogen, and then heated to 90 ° C., stirring was continued for 12 hours, the flask was cooled, and the polymerization was stopped.
This reaction product was dissolved in 100 ml of THF, further purified by precipitation with 2000 ml of MeOH, and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 torr) to obtain a block copolymer BA-4. The number average molecular weight (Mn) of the block copolymer BA-2 was 8900, and the molecular weight distribution (Mw / Mn) was 1.12.
The obtained block copolymer BA-2 was heat-treated at 190 ° C. for 3 hours under 2.7 hPa (2 torr), and a functional group of an acid anhydride was generated by thermal decomposition to obtain a pigment dispersion resin B-2. It was. The mass ratio of the solvent-soluble block (A) and the block (B) containing an acid anhydride group was 70:30.

Comparative Synthesis Example 3
1-PEBr 0.32 g (1.7 mmol), ST 8.24 g (79.2 mmol), TBMA 1.44 g (10.1 mmol), CuBr 0.24 g (1.7 mmol), Bpy 0.79 g (5.1 mmol), and 70 ml of anisole was charged into a 300 ml three-necked flask equipped with a cooling tube, and after deaeration, the inside of the system was purged with nitrogen, heated to 90 ° C., and stirred for 12 hours, the flask was cooled, and polymerization was performed. Stopped.
This reaction product was dissolved in 100 ml of THF, further purified by precipitation with 2000 ml of MeOH, and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 torr) to obtain random polymer RA-1. The number average molecular weight (Mn) of the random polymer RA-1 was 6200, and the molecular weight distribution (Mw / Mn) was 1.20. The obtained random polymer RA-1 was subjected to a heat treatment at 190 ° C. for 3 hours under 2.7 hPa (2 Torr) to obtain a pigment dispersion resin R-1.

Comparative Synthesis Example 4
1-PEBr 0.32 g (1.7 mmol), ST 8.24 g (79.2 mmol), TBMA 4.32 g (30.3 mmol), CuBr 0.24 g (1.7 mmol), Bpy 0.79 g (5.1 mmol), and anisole 70 ml was charged into a 300 ml three-necked flask equipped with a condenser, and after deaeration, the inside of the system was purged with nitrogen, heated to 90 ° C., continued stirring for 12 hours, the flask was cooled, and the polymerization was stopped. did.
This reaction product was dissolved in 100 ml of THF, further purified by precipitation with 2000 ml of MeOH, and suction filtered using a filter. The purified product on the filter was dried at 80 ° C. under 2.7 hPa (2 torr) to obtain random polymer RA-2. The number average molecular weight (Mn) of the random polymer RA-2 was 7500, and the molecular weight distribution (Mw / Mn) was 1.18.
The obtained random polymer RA-2 was heat-treated at 190 ° C. under 2 torr for 3 hours to obtain a resin R-2 for pigment dispersion. Each of the obtained polymers was qualitatively determined by 1H-NMR and IR, and each was confirmed by a single peak by a GPC chart.

Next, a production example of a pigment dispersion paste composition using the block copolymer of the present invention and the polymer of the comparative example (random polymer) is shown.
Production Example 9 of Pigment Dispersion Paste Composition
0.5 parts of the resin B-3 for pigment dispersion obtained in Synthesis Example 3, 15 parts of Bengala pigment (130ED manufactured by Toda Kogyo Co., Ltd., acidic pigment pH 6), and 10 parts of toluene were dispersed in a paint shaker for 2 hours. (A wide-mouth glass bottle with a capacity of 50 cc and a diameter of 1.3 mmφ titania beads was used), and a pigment dispersion paste composition (PP-9) was obtained.
Production Examples 10 to 16 for Pigment Dispersion Paste Composition
In the same manner as in Production Example 9, pigment dispersion paste compositions (PP-10 to PP-16) of Production Examples 10 to 16 were prepared based on the compositions shown in Table 1 below. In addition, toluene used industrial goods, and the quinacridone red pigment used Daigen Ink Chemical Industry Co., Ltd. Fastogen Super Red 5B (neutral pigment pH7).

About each obtained pigment paste composition PP-5-12, the performance test was done based on the following test method. The test results are shown in Table 2 below.
Test method <Viscosity measurement>
The shear rate dependence of each pigment paste composition at the initial stage of dispersion was measured with a viscoelasticity measuring device (ARES manufactured by Rheometric Co., Ltd.). Measurement conditions were as follows: measurement temperature 20 ° C., pre-treatment applied for 1 minute × 100 / s, then placed for 3 minutes, and then changed the displacement rate from 0.01 / s to 1000 / s at 20 ° C. Viscosity measurement was performed. In addition, each pigment paste composition was subjected to accelerated storage at 50 ° C. for 14 days, and the viscosity was measured after aging under the same conditions as described above.
T.A. I. The value (thixotropic index) was calculated by dividing the viscosity obtained on the low shear side at the shear rate of the rheometer by the viscosity obtained on the high shear side. T. T. I. It can be judged that the lower the value is, the less the pigment is aggregated and the better dispersion state is maintained.

<Microscope observation>
The initial dispersion of each pigment paste composition and the state after accelerated storage at 50 ° C. for 14 days were observed with an optical microscope and evaluated according to the following evaluation criteria. Each pigment paste composition was diluted 5 times with toluene, and observed with a transmission phase contrast optical microscope (Nikon Corporation, MICROPHOTO-FXA). Observation was performed with an eyepiece lens 1 × and an objective lens 20 ×.
<Evaluation criteria>
○: Uniformly dispersed Δ: Partial aggregation of the pigment is observed x: Overall aggregation of the pigment is observed

Next, the manufacture example of binder resin for coating materials is shown.
Production Example 2 of Binder Resin for Paint
Acrylic resin reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc. was charged with 30 parts of xylene and 5 parts of isobutanol, heated and stirred, and after reaching 110 ° C., a mixture of the following monomers, etc. It was added dropwise over time.
A mixture of 15 parts of styrene, 10 parts of methyl methacrylate, 15 parts of n-butyl acrylate, 10 parts of hydroxyethyl methacrylate, 1 part of acrylic acid, and 0.3 part of 2,2′-azobisisobutyronitrile.

After completion of the dropwise addition of the mixture of monomers and the like, an additional catalyst solution that is a mixture of 0.2 part of 2,2′-azobisisobutyronitrile and 5 parts of xylene is maintained for 2 hours while maintaining 110 ° C. It was dripped over. Further, stirring was continued at 110 ° C. for 1 hour, followed by cooling. The resulting reaction solution was diluted by adding 5 parts of xylene and 5 parts of isobutanol to obtain an acrylic resin solution (AC-1) having a solid concentration of 50%. The obtained acrylic resin has a mass average molecular weight (Mw) of 50,000, a solid content acid value of 17 mg KOH / g (phenolphthalein), and a viscosity of 11 st. / 20 ° C. (Gardner method).
Next, the manufacture example of a coloring coating composition is shown.

Production Example 17 of Colored Paint Composition
10 parts of the pigment dispersion paste composition (PP-1) obtained in Production Example 1, 30 parts of the acrylic resin solution (AC-1), Uban 20SE60 (trade name, manufactured by Mitsui Toatsu Chemical Co., Ltd., butyl etherified melamine) Resin, NV 60%) 4 parts and butyl carbitol 1 part were mixed using a disper by a letdown method to obtain a colored coating composition (CP-9).

Production Examples 18-23 of Colored Paint Composition
Colored paint compositions (CP-9 to CP-16) were obtained using the pigment dispersion paste compositions (PP-9 to PP-16) in the same manner as in Production Example 1 of the above colored paint composition. The composition of the colored coating composition of CP-9 to CP-16 including Production Example 1 (CP-9) of the above colored coating composition is shown in Table 3 below as Production Examples 9 to 16.

Using each of the colored coating compositions CP-9 to CP-16 obtained in Production Examples 9 to 16, each test coated plate was produced based on the following test coated plate production method.
Preparation Method of Test Coating Plate Each of the colored coating compositions CP-9 to CP-16 was applied undiluted to SPTE (tinplate, dimensions 0.3 × 150 × 70 mm) using a 4 mil applicator. Two minutes after the coating, the same colored coating compositions CP-9 to CP-16 were cast on the lower half of the coating surface, and setting was performed while standing for 10 minutes. Then, baking drying was performed for 20 minutes at 130 degreeC, and the following evaluation method evaluated. The evaluation results are shown in Table 4 below.

Evaluation method <Appearance of coating film>
The applicator part of the coating film and the coating surface state of the flow coating part were observed with respect to color tone, gloss, and roughness, and evaluated according to the following criteria.
<Evaluation criteria>
○: All are good △: Any one of the color tone, glossiness, or irregularity is bad ×: Any two or more of the color tone, glossiness, or irregularity is defective

  From these facts, it can be seen that the block copolymer of the present invention is superior in pigment dispersibility than a random polymer having a similar composition, and is excellent in storage stability of the pigment paste composition and color tone stability of the colored coating composition. It was.

  The pigment dispersion resin comprising the block copolymer of the present invention is useful as a pigment paste containing the pigment dispersion resin and a colored coating composition containing the pigment paste.

Claims (7)

  A block copolymer comprising a solvent-soluble block (A) and a pigment-adsorbing block (B) containing a carboxyl group or an acid anhydride group.   The solvent-soluble block (A) having a halogen atom at the terminal has a block (B) obtained by block polymerization of an alkyl (meth) acrylate and then hydrolyzing the alkyl ester group. The block copolymer described in 1.   An acid anhydride obtained by subjecting a solvent-soluble block (A) having a halogen atom at the terminal to block polymerization of a (meth) acrylic acid alkyl ester which is easily thermally decomposed by heat treatment, and then dealkylating by heat treatment. 2. The block copolymer according to claim 1, having a block (B) containing groups.   A resin for pigment dispersion comprising the block copolymer according to any one of claims 1 to 3.   The number average molecular weight of the block copolymer is 1000 to 100,000, and the mass ratio of the block (A) to the block (B) is (40 to 99.5): (60 to 0.00). The resin for pigment dispersion according to claim 4, which is 5).   A pigment paste comprising the pigment-dispersing resin according to claim 4 and a pigment.   A paint composition comprising the pigment paste according to claim 6 and a binder resin.