GB2144752A - Coloured base composition and paint composition containing the same - Google Patents

Abstract

A colored base composition comprises a dispersing amphoteric resin and pigment, said amphoteric resin being prepared by addition or condensation reaction of an acidic resin having an electron acceptant group and a base resin having an electron donative group by means of functional groups selected from active hydrogen and/or active alkoxyl on one of the resins and radicals which are reactive with said active hydrogen and/or active alkoxyl on the other resin, the basic resin being a melamine-formaldehyde resin having 2-6 triazine nuclei per molecule. Paints containing said colored base composition have improved properties and especially excellent optical sharpness of the film.

Description

SPECIFICATION Colored base composition and paint composition containing the same The present invention relates to a colored base composition having an excellent pigment dispersion stability and a paint composition containing the same. This paint is characterized by having improved properties and especially in regard to optical sharpness of the film.

In formulating a paint composition, has been generally practiced that a pigment is dispersed in a part of resin which will constitute a main ingredient of resinous vehicle of the final paint and thus obtained colored base composition is then diluted with the remaining amounts of said resin, together with other optional resin, and diluent(s). However, in these days, since the user's requirements are diversified, there is a trend that various grades of paints are to be manufactured each in limitted quantities. The pigments used in paint area are lacking uniformity in their surface properties, and therefore, each different dispersing resin has to be used for the respective kind of pigment and thus there is a problem of hardly striving for cost reduction by mass production thereof.If it is possible to provide beforehand for reserve stocks of various colored base compositions with a common resinous vehicle, each in larger quantities, and formulate the desired paint composition by using said stock or combination of stocks and diluting with said or other resin(s) and solvent(s) as occasion calls, inestimable benefits would be attained in the paint production. However, very unfortunately, such a multi-purpose dispersing resin has not been found yet. Optical sharpness, i.e.

distinctness of image of the film is one of the important requirements for the paint compositions, and however, many of the known paints are often deficient in that regard.

In Journal of Paint Technology 47(602) 31(1975) by P. Srensen, it is reported that when applied the concept of acid and base to the respective pigment and resin to be used, good affinity and hence excellent dispersion may be obtained with the combination of pigment and resin each having the opposing property.

The inventors, paying due regard to this S0rensen's interpretation and suspecting that if an amphoteric resin having both acidic and basic characteristics can be obtained from the conventional acidic and basic resins used in the paint compositions, it must be possesed of good compatibility with various resinous vehicles and excellent dispersing ability toward various pigments having each different surface properties, have made studies on various bonding systems between the acidic resins and basic resins, suitability as dispersing resin of the reaction product, and succeeded in providing a colored base composition fulfilling the abovesaid requirements and applied for patent on it (Japanese Patent Application No. 120866/81, filed on July 31, 1981).The base composition claimed in the aforesaid application comprises a dispersing amphoteric resin and pigment, said amphoteric resin being obtained by addition or condensation reaction of an acidic resin (A) having both of an electron acceptant group and a functional group of either active hydrogen and/or active alkoxyl group or a group which is reactive with active hydrogen and/or active alkoxyl group, and a basic resin and/or basic low molecular compound (B) having both of an electron donative group and a functional group of either a group which is reactive with active hydrogen and/or active alkoxyl group, or active hydrogen and/or active alkoxyl group per se.

A paint composition containing at least one of said colored base compositions was also a subject matter of that patent application. By the way, the term "active hydrogen" as used in that specification meant reactive hydrogen attached, for example, to oxygen, sulfur or nitrogen atom contained in primary, secondary or tertiary hydroxyl, amide bond, urethane bond, carboxyl or the like; the term "active alkoxyl" meant reactive alkoxyl as alkyl substituted active methylol; "a functional group which is reactive with active hydrogen" meant a group capable of reacting easily with active hydrogen as primary, secondary or tertiary hydroxyl, isocyanate, glycidyl group or the like; "a functional group which is reactive with active alkoxyl" meant a group capable of reacting easily with active alkoxyl as primary, secondary or tertiary hydroxyl or the like; "electron acceptant group" meant a group which will attract electron from other by the standard of hydrogen in molecule as carboxyl, sulfonic, nitro and the like; "electron donative group" meant a group which will give electron to other by the standard of hydrogen in molecule as a group having -N: (having unshared electron pair), alkyl, halogen and the like; "acidic resin" meant resin having acidic group as oil free polyester resin, long- and short- oil alkyd resin, acrylic resin, vinyl resin and the like, customarily used in the paint area; "basic resin" meant resin having basic group as urea resin, melamine resin, polyamide resin, polyurethane resin and the like customarily used in the paint area; and "basic low molecular weight compound" meant prepolymer of basic resin or such monomers as hydroxylamine compounds (e.g. mono ethanolamine, diethanolamine, aminopentanol, aminobenzyl alcohol, 2-di-methylaminoethanoi and the like), amino acids (e.g. 3-di-methylamino benzoic acid, 2-amino-isobutyric acid, 4-amino-n-butyric acid and the like), primary or secondary amine compounds (e.g. n-butylamine, n-propylamine, di-butylamine, di-(2-ethylhexyl) amine) and the like. The amphoteric resins shown in said Japanese Patent Application No.

120866/81 are very stable reaction products, compatible with various acidic and basic resins customarily used in paint industry, and have excellent affinity and hence dispersion stability toward various pigments with different surface properties because of having both acidic and basic properties. Therefore, they are indeed ideal as resinous vehicle in formulating a colored base composition. The inventors have further continued studies on the respective reaction components of said amphoteric resins and surprisingly found that melamine-formaldehyde resin did possess singular properties as compared with other basic resins used in the preparation of said amphoteric resins.As will be clear to those skilled in the art, since melamine-formaldehyde resins, in either form of methylol melamine or of alkylated methylol melamine, usually possess both -N- or - N = (as electron donative group) and > NH, -NH2, -CH2OH (as active hydrogen) and/or -CH2OR (as active alkoxyl), they are useful as basic resinous component (B) and when reacted with the acidic resinous component (A), can result amphoteric resins which are compatible with various resins and capable of forming stable dispersions with various pigments, as already stated in the aforesaid patent application.

However, this type of resin includes in its molecule a certain number of triazine nucleus and this structural feature seems to have some close connection with the final properties of the amphoteric resin. That is, according to the inventors' studies, the following have been found out. At the time when an average number of triazine nucleus per molecule of melamine-formaldehyde resin (hereinafter cailed as number average condensation degree of triazine nucleus), if the condensation degree exceeds over certain lower limit, then there is a trend that pigment dispersion stability in the formed amphoteric resin can be markedly improved, but if it exceeds over certain higher limit, then there is a trend that viscosity of the resin is undesirably increased and difficulties would be encountered with the final product in the compatibility with other resins.

Furthermore, when the abovesaid melamine-formaldehyde resin, whose number average condensation degree of triazine nucleus is within the range capable of producing markedly improved pigment dispersion stability, is used as the basic resin component, absolutely extraneous effect of optical sharpness ofthe film can be attained with thus obtained amphoteric resin as compared with those of other amphoteric resins.

On the basis of these findings, the invention has been made.

An object of the present invention is, therefore, to provide a multi-purpose dispersing resin having excellent affinity toward various pigments each having different surface properties and having good compatibility with various kinds of resins used as resinous vehicles in paint compositions. The other object is to provide a colored base composition comprising such dispersing resin and pigment. Further object of the invention is to provide a paint composition containing at least one such base composition capable of resulting the coating with excellent optical sharpness. Other objects will be apparent to those skilled in the art from the descriptions of the accompanying claims and the specification.Thus, in accordance with the invention, is provided a colored base composition having improved pigment dispersion stability and being able to give a coating with excellent optical sharpness comprising an amphoteric resin and pigment, said resin being obtained by addition or condensation reaction of an acidic resin (A) having both of electron acceptant group and a functional group selected from either active hydrogen and/or active alkoxyl per se or the group which is reactive with active hydrogen and/or active alkoxyl group, and a basic melamineformaldehyde resin having both of electron donative group and a functional group selected from either the group being reactive with active hydrogen andlor active alkoyl or an active hydrogen and/or active alkoxyl per se, and having 2-6 number average condensation degree of triazine nucleus.The dispersing resin used in the present invention is an amphoteric resin obtained by the reaction of an acidic resin bearing an electron acceptant group and a melamine-formaldehyde resin bearing an electron donative group and having a number average triazine condensation degree of 26, both resins having an active hydrogen and/or active alkoxyl on one side and functional groups or group reactive with said active hydrogen and/or active alkoxyl on other side.

Inclusion of active hydrogen and/or active alkoxyl group, or functional group being reactive with active hydrogen and/or active alkoxyl group in acidic resin and basic melamine-formaldehyde resin may be easily attained by the selection of appropriate resins bearing such groups or by copresenting in the starting materials for the respective resins an appropriate compounds bearing such groups.

The starting resins used for the preparation of the present amphoteric resin shall be explained more fully hereinunder. Oil free polyester resins to be used as an acidic resin are obtained by the condensation of polycarboxylic acid and polyhydric alcohol. Examples of poiycarboxylic acid are trimellitic acid, trimellitic anhydride, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid and the like, and examples of polyhydric alcohol are pentaerythrytol, trimethylol propane, trimethylol ethane, glycerin, polyethyleneglycol, 1 ,6-hexanediol, neopentyl glycol, propyleneglycol, ethyleneglycol and the like.Long-oil and short-oil alkyd resins are composed of said polycarboxylic acid and polyhydric alcohol components, as well as fats and oils component, as, for example, fatty acid (e.g. soybean oil fatty acid, castor oil fatty acid, tall oil fatty acid, coconut oil fatty acid, cotton seed oil fatty acid and the like), and vegetable oil (e.g. soybean oil, castor oil, tall oil, coconut oil, cotton seed oil, linseed oil and the like). Since the oil free polyester and long-oil and short-oil alkyd resins prepared by the reactions of said raw materials may thus contain primary, secondary or tertiary hydroxyl and/or carboxyl groups, they can be directly used as an acidic resin component (A) and reacted with active hydrogen as =NH, -NH2 or CH2OH and/or active alkoxyl group as -CH2OR, or a reactive functional group as isocyanate and glycidyl group of melamine-formaldehyde resin.

In the preparation of such acidic resin (oil free polyester and long- and short-oil alkyd resins), when isocyanate bearing compound or glycidyl bearing compound is presented in the reaction system as a part of raw materials or reacted with previously made active hydrogen bearing resin, free isocyanate or glycidyl groups are introduced in the resin.Thus obtained resin may be reacted with melamine-formaldehyde resin having active hydrogen capable of reacting with said isocyanate or glycidyl group As the isocyanate bearing compounds, mention is made of such diisocyanates as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and mixture thereof; aromatic diisocyanates as 4,4'-diphenylmethane diisocyanate, m-phenylene diisocyanate, 4,4'-biphenyl diisocyanate and the like; aliphatic diisocyanates as tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate and the like; aromatic aliphatic diisocyanates as xylene diisocyanate; alicyclic diisocyanates as isophorone diisocyanate; and triisocyanates as 4,4', 4"-triphenylmethane triisocyanate, 2,4,4'-biphenyltriisocyanate, 2,4,4'-diphenylmethane triisocyanate and the like.And other employable isocyanate compounds include addition products of such di- or tri-isocyanates and di- or tri-ols, bearing 2 and more isocyanate groups, and isocyanate polymeric compounds. Examples of glycidyl bearing compounds are triglycidyl isocyanurate, ethyleneglycol diglycidyl ether and the like. As the acidic resin component (A), use can also be made of acrylic or vinyl resin. Such resin may be obtained by the copolymerization of (1) neutral monomer, (2) acid monomer, and (3) monomer having a functional group reactive with active hydrogen and/or active alkoxyl group, or (3') monomer having active hydrogen and/or active alkoxyl group.Typical examples of said neutral monomer are ethylene, propylene, butadiene, isoprene, chloroprene, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, methyl vinyl ether; acrylic ester (e.g. methyl, ethyl, butyl ester and the like); methacrylic ester (e.g.

methyl, ethyl, butyl ester and the like); nitrile derivatives (e.g. acrylonitrile, methacrylonitrile and the like); styrene and styrene derivatives (e.g. a-methylstyrene) and the like.

As the acid monomer, mention is made of such carboxyl bearing monomers as acrylic acid, methacrylic acid, itaconic acid, maleic acid and the like, and such sulfonic bearing monomers as a-styrene sulfonic acid and the like.

Examples of said functional group bearing monomer (3) are glycidyl bearing monomers as glycidyl acrylate, glycidyl methacrylate and the like; isocyanate bearing monomers as vinyl isocyanate and the like; and chlorine containing monomers as vinyl chloride, vinylidene chloride and the like. Examples of said active hydrogen bearing monomer (3') are acrylamide, methacrylamide and other amide containing monomers, and examples of active alkoxyl bearing monomer are N-methoxymethylol acrylamide, N-butoxymethylol acrylamide and the like. Alternatively, as the functional group bearing monomer (3) or active hydrogen bearing monomer (3'), use can be made of hydroxyl containing monomers as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and the like, and N-methylol acrylamide and the like.

By the selection of appropriate monomer units, can be obtained acidic acrylic or vinyl resin having both of electron acceptant group and a functional group of either a group which is reactive with action hydrogen and/or active alkoxyl group or active hydrogen and/or active alkoxyl group itself. The melamineformaldehyde resin to be reacted with said acrylic or vinyl resin may be appropriately selected in consideration of the abovesaid functional group, as well as the number average condensation degree of triazine nucleus as hereinbefore mentioned. The acrylic or vinyl resin prepared by using active hydrogen bearing monomer unit may be further reacted with polyisocyanate or glycidyl bearing compound to obtain the product which is to be reacted with the melamine-formaldehyde resin having active hydrogen.As the basic resinous component (B) in the present amphoteric resin, such melamine-formaldehyde resin as having, besides an electron donative group and a reactive functional group, 2-6, in number average, of triazine nucleus per molecule is selectively used.

Such melamine-formaldehyde resins may be obtained by selecting appropriate molar quantities of melamine and formaldehyde raw materials and effecting condensation thereof. They may also be in the form of alkylated (by the introduction of methyl-, ethyl-, propyl-, butyl-, and isobutyl-alcohol and the like), methylol melamine-formaldehyde resins if desired. Alternatively, such resin may be prepared by mixing two and more melamine-formaldehyde resins together, with and without solvent, and effecting condensation until the desired number average condensation degree is obtained.

As already stated, since the resin usually contains - N - or - N = as electron donative group and > NH, -NH2, -CH2OH (as active hydrogen) and/or -CH2OR (as active alkoxy), it is possible to effect addition or condensation reaction with an acidic resin having the aforesaid functional group. When said resin is reacted with polyisocyanate or glycidyl compound, such functional group as isocyanate or glycidyl may be effectively introduced in the molecule, and the resulted resin may be reacted with an acidic resin bearing active hydrogen to obtain the present amphoteric resin. The reason why the pigment dispersion stability is markedly improved with the amphoteric resin derived from the combination of acidic resin and melamine-formaldehyde resin as above defined has not been thoroughly cleared out.However, it is so far believed that with the number average triazine condenzation degree of less than 2, the melamine-formaldehyde resin taken into the dispersing resin cannot display the ability to act as basic component in full, and hence the amphoteric resin fails to show the maximum power possessed in respect of pigment dispersing speed and storage stability.

On the other hand, if the number average condensation degree exceeds over the higher limit of 6, viscosity of the dispersing resin is markedly increased to undesirable level, which in turn will affect adversely on pigment dispersion stability and on compatibility with other resins. Though the invention cannot be limitted in any sense with the abovesaid theoretical explanation, by the selective use of such amphoteric resin, pigment dispersion stability is greatly improved and excellent coating, especially in respect of optical sharpness of the film, can be obtained without sacrificing other desirous properties as mentioned hereinbefore.

In using this type of melamine-formaldehyde resin as basic component, the amphoteric resin may preferably be composed of 99.560% by weight of acidic resin (A) (on solid basis) and 0.540% by weight of said basic resin (B), number average molecular weight (gel permeation chromatography, polystyrene reduction) being 500-100,000.

In the actual preparation of the present amphoteric resin, the selected resinous raw materials are merely combined together and heating is applied thereto to effect addition or condensation reaction therebetween.

Thus obtained amphoteric resin is, differing from the mere mixture of the acidic and basic resins, a reaction product which is excellent in stability and can never be separated into the constituting components.

The amphoteric resin is further characterized by having versatile compatibilities with various acidic and basic resins and since it is possessed of both acidic and basic properties being able to give excellent dispersions with various pigments each having different surface properties. Thus, in the present invention, is provided a novel colored base composition comprising abovesaid dispersing amphoteric resin and pigment.

In a paint industry, a huge number of inorganic and organic pigments are used, whose surface properties varying considerably with species. Viewing from the conception of acid or base, acidity or basicity of such pigments likewise varies with species. Therefore, the optimum acidity and basicity of the present amphoteric resin may, as a matter of course, vary with these pigments.

Under the circumstances, the inventors, conceiving an idea that there will probably be certain optimum ranges, from the greatest common divisory sense of view, in the acidity and basicity of the amphoteric resins which are to be used in combination with the pigments, have actually examined, after dispersing various pigments in amphoteric resins, acidity and basicity of the respective resin and their effects on dispersibility of the pigment used.

Since there are no known simple methods for the determination of acidity and basicity of amphoteric resin in nonaqueous system, the inventors have provided seif-determined method, wherein the test resin is dissolved in aniline and subjected to a quantitative determination by means of nonaqueous potentiometry with a titrant of n.tetrabutylammonium hydroxide, thereby determining the acidity of said resin from the molar quantity of said reagent required for the neutralization thereof, and the method wherein the test resin is dissolved in acetic acid and subjected to a quantitative determination by means of non-aqueous potentiometry with a titrant of perchloric acid, thereby determining the basicity of said resin from the molar quantity of said reagent required for the neutralization thereof.With these methods, actual acidities and basicities of various amphoteric resins are determined and evaluated. From the test results obtained, the inventors have come to the conclusion that excellent dispersions are obtainable, irrespect of the kind of inorganic and organic pigments, with an amphoteric resin whose acidity is 1.0-1.0x10-2m mol/g solid, and especially 0.8 -2.0x 10-2m mol/g solid and basicity is 1.0-5x10-3m mol/g solid and especially 1.0-1 x 10-2m mol/g solid. Therefore, in a preferably embodiment of the invention, there is provided a colored base composition comprising a dispersing resin and a pigment, said resin fulfilling the requirements on acidity and basicity as defined hereinabove.

Besides the abovementioned pigment dispersibility, the dispersing resin must be possessed of the properties of being compatible with various dilution resins, being soluble in various solvents and being able to give the coating with excellent film performance in respect of coloring, physical properties, chemical properties, durability and weathering properties.

As the resu Its of our extensive studies, the inventors have found that the intended objects are attained with the amphoteric resin composed of 99.560% by weight of acidic resin (A) (on solid basis) and 0.540% by weight of melamine-formaldehyde resin (B), having a number average molecular weight of 500-100,000, as hereinbefore stated. Preferably, said amphoteric resin should have a glass transition point of -30-80"C.

It was also found that the best result can be obtained with the amphoteric resin composed of 99.580% by weight (on solid basis) of resin (A) and 0.520% by weight of resin (B) having 2-6 number average triazine condensation degree, the molecular weight being 1,000-50,000 (gel permeation chromatography, polystyrene reduction) and glass transition point being -10--500C.

The present colored base composition can be obtained by using at least one of the abovesaid amphoteric dispersing resins and dispersing the coloring matter(s) therein. As the coloring matter, any of the inorganic and organic pigments customarily used in paint compositions may be satisfactorily used. Examples of inorganic pigments are carbon black, zinc white, titanium dioxide, antimony white, iron black, rouge, red lead, cadmium yellow, zinc sulfide, lithopone, barium sulfate, lead sulfate, barium carbonate, white lead, alumina white and the like, and examples of organic pigments are of azo, polycondensation azo, metal complex azo, benzimidazolone, phthalocyanine (blue, green), thioindigo, anthraquinone, flavanthrone, indanthrene, anthrapyridine, pyranthrone, isoindolinone, perylene, perynone and quinacridone series. The compounding ratio of said amphoteric resin and pigment is not critical in the present invention and may be selected in any desired range. However, from the economical and dispersion efficiency points of view, it is generally determined in the range of 10~90% by weight of resin (solid) to 90~ 10% by weight of pigment, preferably 30~70% by weight of resin (solid) to 70~30% by weight of pigment.

In formulating the present colored base composition, any of the solvents customarily used in paint industry may be used as desired, including hydrocarbons (e.g. toluene, xylene, solvesso 100, solvesso 150 and the like), esters (e.g. ethyl acetate, butyl acetate and the like), and ketones (e.g. MEK, MIBK and the like).

For mixing purpose, use may be made of roll mill, ball mill, sand grind mill, planetary mixer, high speed disper and the like. Thus obtained colored base composition is useful for the preparation of coating composition. In preparing the coating composition, at least one of the abovesaid base compositions is diluted with other resin(s) and/or solvent(s). Thus, the invention intends to include a coating composition comprising 1 ~99% by weight of at least one base composition and 99~1% by weight of other diiuting resin(s). No particular technique may be required therefor. Of course, it is possible to use the base composition per se, after dilution with solvent, for the coating purpose if desired. Invention shall be now more fully explained in the following Excamples. Unless otherwise being stated, all parts and % are by weight.

MANUFACTURING EXAMPLE 1 Preparation of high molecular weight melamine-formaldehyde resin Into a four necked flask fitted with stirrer and thermometer, were placed 200 parts of Cymei 325 (methanol modified methylol melamine resin, manufactured by Mitui Tohatsu K.K., solid 80%) and solvent was removed under reduced pressure at a temperature ranging from room temperature to 50"C. Thereafter, 35 parts of toluene, 35 parts of methanol and 0.32 parts of form ic acid were added and the mixture was refluxed for 5.5 hours, thereby effecting reaction. Then, the solvent was removed under reduced pressure and the residue was added with 65 parts of n-butanol to obtain a solution of high molecular weight.Cymel 325 (hereinafter called as MF resin 1). Number average degree of condensation of triazine nucleus per molecule based on number average molecular weight measured by gel permeation chromatography (JASCO TR 1 ROTAR-2, epoxy reduction) of Cymel 325 was 1.5, whereas the corresponding value of MF resin I was 2.9.

MANUFACTURING EXAMPLE 2 Preparation of acrylic dispersing resins land II Into a reactor fitted with stirrer, nitrogen gas inlet pipe, thermometer and dropping funnel, were placed 140 parts of toluene and 40 parts of n-butanol and the mixture was heated under nitrogen stream to 105"C. A mixture of 211 parts of methyl methacrylate, 123 parts of n-butyl acrylate, 60 parts of 2-hydroxyethyl methacrylate, 6 parts of acrylic acid and 12 parts of t-butylperoxy 2-ethylhexanoate was dropwisely added from the dropping funnel at a constant speed over 3 hours.After completion of said dropping, the mixture was maintained at 105 C for 30 minutes, added with a mixed solution of 20 parts of toluene and 2 parts of t-butylperoxy 2-ethylhexanoate dropwisely from the dropping funnel at a constant speed over 30 minutes, maintained at 105"C for 1.5 hours and the added with 210 parts of toluene to obtain a colorless clear solution of acrylic resin (acidic resin I) (solid 48%, viscosity by Gardner-Holdt bubble viscometer N).To this acrylic resinous (acidic resin I) solution (96 parts in solid), was added the high molecular weight melamineformaldehyde resinous (MF resin I) solution (4 parts in solid) obtained in Manufacturing Example 1, and the combined was heated and reacted at 110 C until the viscosity measured by bubble viscometer reached to Y, to obtain dispersing resin I (amphoteric resin of the present invention) having acidity of 2.34 x 10-1m mol/g solid and basicity of 1.39 x 10-m mol/g solid.

For comparison sake, the same acrylic resinous solution (96 parts in solid) was reacted with Cymel 325 (4 parts in solid) in a similar way, to obtain dispersing resin II (amphoteric resin outside the invention) having viscosity by bubble viscometer of Y, acidity of 2.19 x 10-m mol/g solid and basicity of 1.30 x 10-1m mol/g solid.

Example 1 To each 100 parts of acidic resin I, dispersing resin I and dispersing resin II obtained in Manufacturing Example 2 were added 22 parts of carbon black FW-200 B (manufactured by Degussa and 100 parts of toluene and the respective mixture was well dispersed in Paint shaker with 1.58 mm + glass beads for 60 minutes.

60 Specular glass (Murakami glossmeter, Type GM-3M) and viscosity (Type E viscometer, manufactured by Tokyo Keiki K.K.) of the respective dispersions were measured and the following results were obtained.

TABLE 1 Gloss viscosity acid resin 1 23 1800 cp dispersing resin 1 65 200 cp dispersing resin 11 45 250 cp As known from the above, excellent effects, i.e. increase in gloss and decrease in viscosity, were found with the amphoteric resins and especially dispersing resin I of the present invention.

The respective dispersions were then subjected to storage stability test at 60"C. Figure 1 shows the correlation between the storage duration (days) and dispersion viscosity (cp), in which 1 is the viscosity fluctuation curve for the dispersion with the acidic resin 1, 2 is for the dispersion with the dispersing resin I and 3 is for the dispersion with the dispersing resin II. As clearly known from the drawing, the present dispersing resin I showed outstanding storage stability as compared with the others.

Baking type acrylic paints were then prepared by adding to each 100 parts of the dispersions, 284 parts of the corresponding dilution resin selected from acidic resin I, amphoteric resin I and amphoteric resin 11, 28 parts of toluene, 16 parts of n-butanol and 58 parts (in solid) of a cross-linking agent of U- 20 SE (melamine-formaldehyde resin, manufactured by Mitsui Tohatsu K.K., solid 60%).

Thus obtained paints were applied by spraying onto tin plates (0.3 x 50 x 150 mm) (Nippon Test Panel Kogyo K.K.) and baked at 1400C for 30 minutes. Gloss, Jetness and optical sharpness of the film of the respective paints were determined and compared by visual observation with each other. From the test results shown in Table 2, it was apparent that the dispersing resin I surpassed others.

TABLE 2 Gloss Jetness Optical sharpness acidic resin I A X X disp. resin I 0 0 0 disp. resin II 0 A X MANUFACTURING EXAMPLE 3 Preparation of oil-free polyester dispersing resins Ill and IV 587 Parts of isophthalic acid, 60 parts of trimethylol ethane; 130 parts of neopentylglycoi and 235 parts of diethylene glycol were placed in a reactor and the mixture was heated at 220--240"C until the solid acid value reached to 6.0, while removing the formed water therefrom, and after cooling, the residue was diluted with 175 parts of cellosolve acetate and 409 parts of xylene to obtain a solution of oil-free polyester resin (acidic resin II) (viscosity by Gardner-Holdt bubble viscometer U-UV, solid 60%, color number 1).To 92 parts (in solid) of said acidic resin II, were added 8 parts (in solid) of MF resin I obtained in Manufacturing Example 1 and the mixture was heated and reacted at 90-100"C until the viscosity by Gardner-Holdt bubble viscometer reached to Y-Z, to obtain a dispersing resin Ill (the present amphoteric resin) having an acidity of 9.8 x 10-2m mol/g solid and a basicity of 2.58 x 10-m mol/g solid. Using 92 parts (in solid) of the acidic resin II and 8 parts (in solid) of Cymel 325, comparative dispersing resin IV (amphoteric resin outside the invention) was prepared in a similar way, whose viscosity by Gardner-Holdt bubble viscometer was Y, acidity was 9.6 x 10-2m mollg solid and basicitywas 2.54 x 10-m mol/g solid.

Example 2 To each 40 parts of the acidic resin II, dispersing resin Ill and dispersing resin IV, were added 130 parts of titanium dioxide CR-92 (manufactured by Ishihara Sangyo K.K.), 120 parts of Butyl Cellosolve and 150 parts of Solvesso 150, and the respective mixtures were dispersed well by means of SG mill for 30 minutes.

Storage tests conducted at a room temperature for 10 days indicated that the formation of hard cake was observed in the dispersion with acidic resin II, but not in the dispersions with the amphoteric resins and however, considerable increase in viscosity was observed in the case with dispersing resin IV, whereas no viscosity change in the case with dispersing resin lil.

To each 100 parts of the dispersions, were added each 85 parts of the corresponding resins II, Ill and IV, and then 28 parts (in solid) of melamine-formaldehyde resin (U-128, manufactured by Mitsui Tohatsu K.K., solid 60%) as a crosslinking agent, to obtain baking type oil-free polyester resin paints, respectively.

Onto JIS contrast charts for hiding power measurement (manufactured by Nippon Test Panel Kogyo K.K.), said paints were applied by using 5 mii doctor blade, respectively. After baking at 140"C for 20 minutes, color difference AE between the white and the black portions was measured by using a colorimeter (manufactured by Toyo Rika Kogyo K.K.). Next, each paint was diluted with dilution solvent to a viscosity which is suitable for spray coating, and the resulted composition was applied over tin plate (0.3 x 50 x 150 mm, manufactured by Nippon Test Panel Kogyo K.K.) by spray coating technique, and the optical sharpness of the film was visually observed. The results obtained are shown in Table 3.

TABLE 3 hE Optical sharpness acidic resin 11 0.8 X dispersing resin lil 0.1 0 dispersing resin IV 0.2 X MANUFACTURING EXAMPLE 4 Preparation ofalkyd dispersing resins Vand Vl 573 Parts of coconut oil, 218 parts of trimethylol ethane and 0.3 part of lithium naphthenate were reacted at 240 C, and then 174 parts of trimethylol ethane, 176 parts of neopentylglycol, 528 parts of phthalic anhydride and 254 parts of isophthalic acid were added thereto.The mixture was heated at 220--2300C until the solid acid value reached to 2.0, while removing the formed water, and thereafter, the mixture was cooled and diluted with 1009 parts of Solvensso 100 (manufactured by Esso Standard) and 58 parts of Ceilosolve acetate to obtain a solution of short-oil alkyd resin (acidic resin ill), having viscosity by Gardner-Holdt bubble viscometer of U-V, solid of 60% and color number of 1.To 92 parts (in solid) of the acidic resin Ill, was added 8 parts (in solid) of MF resin I obtained in Manufacturing Example 1 and the mixture was heated and reacted at 90-100"C until the viscosity by bubble viscometer reached to W-X to obtain dispersing resin V (the present amphoteric resin) having an acidity of 3.3 x 10-2m mol/g solid and a basicity of 2.58 x 10-m mol/g solid.

For comparison sake, the same acidic resin lit (92 parts in solid) was reacted with Cymel 325 (8 parts in solid) in a similar way to obtain dispersing resin VI (amphoteric resin outside the invention) having viscosity by Gardner-Holdt bubble viscometer of W-X, acidity of 3.0 x 10-2m mol/g solid and basicity of 2.55 x 10-5m mol/g solid.

Example 3 To each 40 parts of the acidic resin Ill, dispersing resin V and dispersing resin VI obtained in Manufacturing Example 4, were added 20 parts of Cynquasia Red Y (Du Pont), 40 parts of Solvesso 100 and 120 parts of steel beads respectively, and each mixture was dispersed well in SG mill for 3 hours. To each 100 parts of thus obtained dispersions, were added each 25 parts of the corresponding resins ill, V and VI, and then 22 parts (in solid) of melamine-formaldehyde resin (U - 128, manufactured by Mitsui Tohatsu K.K., solid 60%) as a crosslinking agent, to obtain baking type alkyd resin paints, respectively.

Each paint was diluted with dilution solvent to a viscosity which is suitable for spray coating and the resulted composition was applied over tin plate (0.3 x 50 x 150 mm, manufactured by Nippon Test Panel Kogyo K.K.) by spray coating technique and baked at 140"C for 30 minutes. The optical sharpness of the film and 20 specular gloss were measured and the results were shown in Table 4. From this table, it is clear that the dispersing resin V is outstandingly superior to other resins.

TABLE 4 gloss optical sharpness acidic resin lil 75 X dispersing resin V 88 0 dispersing resin VI 82 X MANUFACTURING EXAMPLE 5 96 Parts (in solid) of acrylic resin (acidic resin 1) obtained in Manufacturing Example 2 were added with 4 parts (in solid) of melamine resin (U - 20 SE, manufactured by Mitsui Tohatsu K.K., solid 60%, number average degree of condensation of triazine nucleus 2.6) and the mixture was reacted at 110 C until the viscosity by Gardner-Holdt bubble viscometer reached to Y, to obtain a solution of dispersing resin VII amphoteric resin of the present invention) having an acidity of 2.28 x 10-m mol/g solid and a basicity of 9.4 x 10-2m mol/g solid.

Example 4 To each 100 parts of dispersing resins II and VII obtained in Manufacturing Examples 2 and 5, were added 22 parts of carbon black FW - 200B (Degussa) and 100 parts of toluene. The mixture was dispersed well for 60 minutes by means of Paint Shaker with 1.58mm + glass beads. 60" Specular gloss and viscosity of each dispersions were measured, whose results were shown in Table 5.

TABLE 5 gloss viscosity dispersing resin 11 45 250 cp dispersing resin VII 60 210 By the adoption of melamine-formaldehyde resin having a number average degree of condensation of triazine nucleus of more than 2, increase in gloss and decrease in viscosity were clearly observed.

Each dispersions were then subjected to storage test at 60"C and the results obtained were shown in Figure 2, in which the perpendicular axis stands for viscosity and the horizontal axis for storage duration, days.

According to the method as stated in Example 1, baking type acrylic resin paints were prepared with said dispersions, and applied over tin plates (0.3 x 50 x 150 mm) (Nippon Test Panel Ind.) by spraying, baked at 140"C for 30 minutes and then examined the film properties by visual observation.

TABLE 6 gloss Jetness optical sharpness dispers. resin II O A X dispers. resin Vll 0 0 0 By the employment of dispersing resin VII, the designated film properties were further improved.

MANUFACTURING EXAMPLE 6 100 Parts (in solid) of alkyd resin obtained in Manufacturing Example 4 (acidic resin Liy) were added with 2 parts of isophoron diisocyanate (Hüis) and reacted at 70"C until the isophoron diisocyanate reaction rate reached to 50% (measured by infra-red spectrometer).While maintaining the reaction temperature of 70"C, 1.30 parts (equivalent to unreacted NCO) of Versamide 140 (polyamide resin having an amine value 370-400, viscosity 2-5 poise (75 C), manufactured by Henkel Japan) were added and after confirming the completion of reaction between the abovesaid unreacted isocyanate and primary or secondary amino of Versamide 140 by means of infra-red spectrometer, cooled to obtain a solution of dispersing resin VIII (resin outside the invention having an acidity of 1.43 x 10-'m mol/g solid anda basicity of 2.78 x 10-2m mol/g solid.On the other hand, to 100 parts (in solid) of said acidic resin III, were added 5 parts of melamine resin (Super Beckamine G 821, manufactured by DIC, solid 60% and number average degree of condensation of triazine nucleus 2.8) and the mixture was heated at 90-100"C until the varnish viscosity reached to U to obtain a solution of dispersing resin IX (the present resin) having an acidity of 1.4 x 10-lm mol/g solid and a basicity of 1.8 x 10-'m mol/g solid.

To each 40 parts of said dispersing resins VIII and IX, were added 130 parts of titanium dioxide CR - 92 (Ishihara Sangyo K.K.), 7 parts of Butyl celiosolve and 20 parts of Solvesso 150 (Esso Standard) and the respective mixtures was well dispersed in SG Mill for 30 minutes. 20 Specular gloss and viscosity of thus obtained compositions were measured and shown in Table 7.

TABLE 7 gloss viscosity dispersing resin VIII 40 1500 cp dispersing resin IX 50 1000 To each 100 parts of said dispersions, were added 45 parts of the corresponding dispersing resins VIII and IX, 28 parts of melamine resin (Super Beckamine G - 821) and 5 parts of isobutanol and the mixtures were stirred well to obtain baking type alkyd resin paints. These paints were applied overtin plates (0.3 x 50 x 150 mm) (Nippon Test Panel Ind.) by spraying, baked at 1 400C for 30 minutes and the resulted coatings were visually observed. Gloss and optical sharpness of the films are shown in Table 8.

TABLE 8 gloss optical sharpness dispersing resin VIII 0 A dispersing resin IX 0 0 From the test results, it is clear that the present dispersing resin IX could afford better results.

Claims (7)

1. In a colored base composition comprising a dispersing amphoteric resin and pigment, said amphoteric resin being prepared by addition or condensation reaction of an acidic resin (A) bearing both of electron acceptant group and a functional group selected from either active hydrogen and/or active alkokyl per se or a group which is reactive with active hydrogen and/or active alkoxyl group, and a basic resin (B) bearing both of electron donative group and a functional group selected from either a group which is reactive with active hydrogen andlor active alkoxyl group or an active hydrogen and/or active alkoxyl group per sue, an improvement which is characterized by that the basic resin (B) is melamine-formaidehyde resin having 2-6 triazine nucleus in number average per molecule.

2. A composition according to claim 1, wherein the amphoteric resin has the characteristics of acidity of 1.0-1.0 x 10-2m mol/g solid expressed in terms of molar concentration of titrant required for neutralization in a non-aqueous potentiometric titration with n-tetrabutylammonium hydroxide (as titrant) in anilin solution, and a basicity of 1.0-5.0 x 10-3m mollg solid expressed in terms of molar concentration of titrant required for neutralization in a non-aqueous potentiometric titration with perchloric acid (as titrant) in acetic acid solution.

3. A composition according to claim 1, wherein the compounding ratio of said amphoteric resin and pigment is, by weight %, 10-90% resin (in solid) and 90-10% pigment.

4. A composition according to claim 1, wherein the amphoteric resin is the reaction product of 99.560% by weight of resin (A) (in solid) and 0.540% by weight of melamine-formaldehyde resin (B), number average molecular weight (gel permeation chromatography, polystyrene reduction) of the resin product being 500-1000,000.

5. A coating composition comprising 199% by weight of at least one base composition comprising pigment and dispersing amphoteric resin obtained by addition or condensation reaction of an acidic resin (A) having both of electron acceptant group and a functional group selected from either active hydrogen and/or active alkoxyl group per se or a group which is reactive with active hydrogen and/or active alkoxyl, and a basic melamine-formaldehyde resin (B) having both of electron donative group and a functional group selected from either a group which is reactive with active hydrogen and/or active alkoxyl group or an active hydrogen and/or active alkoxyl group per se and having 2-6 triazine nucleus in number average per molecule, and 99~1% by weight of other resin(s).

6. A coloured base composition according to claim 1, substantially as herein described in any of the foregoing examples.

7. A coating composition according to claim 5, substantially as herein described in any of the foregoing examples.