JPH0562154B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to pigment dispersion resins, particularly pigment dispersion resins that exhibit good compatibility with paint vehicle resins such as polyester and alkyd resins, pigment dispersion pastes containing the resins, and pigment dispersion pastes containing the resins. The present invention relates to a pigment-dispersed coating composition containing a pigment-dispersed paste.

Conventionally, in order to prepare a pigment-dispersed paint composition, a pigment is uniformly mixed with a pigment-dispersing resin to form a pigment-dispersed paste, and this is added to a paint vehicle.
It is common to mix them evenly. As the above pigment dispersing resin, a part of the paint vehicle itself or a resin different from the paint vehicle has been used.

However, in the latter case, it must have excellent compatibility with the vehicle resin, and it must also be able to provide good dispersion stability depending on the surface characteristics of the pigment used. In order to obtain pigment dispersion stability, it has been proposed and widely put into practice that appropriate acidic and/or basic groups be introduced into the resin depending on the surface properties of the pigment (Japanese Patent Application No. 1983-
No. 138062).

By the way, polyester paints generally have weather resistance, chemical resistance, heat resistance, and many other excellent coating properties, so they occupy an important position in the paint field, but when considering pigment dispersion resins for such paints, In addition to the compatibility with the resin vehicle, the coating performance of the dispersing resin itself is also an issue, and it is required to have weather resistance and other properties at least comparable to those of the vehicle. Therefore, it is preferable that the pigment dispersing resin be a polyester type resin as much as possible. Furthermore, it is desirable that the pigment dispersion system has a viscosity as low as possible, and therefore it is desirable that the pigment dispersion resin also have a viscosity as low as possible, but polyester resins conventionally used as paint resins have high viscosity and require a large amount of It is diluted with a solvent to create a low-viscosity dispersion system. The present inventors previously discovered that a polymer having a star-shaped structure has a characteristic of lower viscosity than a linear polymer, and succeeded in obtaining a high molecular weight polyether type star polymer. However, although this polyether type resin can be used for dispersing pigments by taking advantage of its low viscosity characteristics, it is difficult to obtain excellent weather resistance and is not suitable for polyester paints. As a result of intensive research by the present inventors in order to obtain a low-viscosity star-shaped polyester resin useful as a resin for dispersing pigments in paints using polyester resin vehicles such as polyester resins and alkyd resins,
We have arrived at the present invention.

That is, according to the present invention, a star-structured polymer obtained by reacting a polyol having at least three hydroxyl groups in one molecule with epsilon-caprolactones has a hydroxyl group having a hydroxyl group and a carboxyl group in one molecule. Carboxylic acid is subjected to a condensation reaction such that the molar amount of hydroxyl groups [OH] of the polymer and the molar amount of carboxyl groups [COOH] of the hydroxyl carboxylic acid are in a ratio of [COOH]/[OH]≦1, and then the acidic groups and A resin for pigment dispersion comprising a modified polyester obtained by introducing/or a basic group is provided. In the present invention, first, a compound having at least three hydroxyl groups in the molecule, that is, a polyol, is used as a core compound, and such polyols include, for example, tetrols such as pentaerythritol, hexols such as D-sorbitol, etc. Monosaccharides such as glucose, disaccharides such as sucrose, and polysaccharides such as starch are particularly preferably used. Compounds other than these may also be suitably used as the core compound as long as they have at least three hydroxyl groups. Prior to such polyols, epsilon-kaptons,
i.e. expression (In the formula, R ₂ is hydrogen or an alkyl group) caprolactone, or dialkyl-epsilon-caprolactone, as substituted with two alkyl groups on the same or different carbon atoms, or trialkyl-epsilon, as substituted with 2 or 3 carbon atoms. - Caprolactone etc. are normally used in the presence of catalysts (e.g. metal chelates of tin, titanium, zinc, zirconium, beryllium, magnesium, calcium, strontium, barium, manganese, iron, cobalt, nickel, copper, cadmium, lead, germanium, etc.) The star-shaped structured polymer is reacted at 130°C or higher to produce a star-shaped structured polymer.This star-shaped structured polymer has a hydroxyl group at the end of the polymer chain, but due to its structural characteristics, it is a semi-solid to solid product at room temperature, and pigment dispersion is not possible when left as is. Therefore, in the present invention, this terminal hydroxyl group is used to generate an ester bond with the carboxyl group of a compound having a carboxyl group and a hydroxyl group in the molecule, and to form an ester bond in the crystal structure. Epsilon caprolactone is reacted with a hydroxyl carboxylic acid having a different structural unit for the purpose of introducing a different type of structural unit to break the crystal structure and make it liquid, and at the same time introduce a hydroxyl group to the terminal end of the resin.

Therefore, the hydroxylcarboxylic acids used in the present invention are aliphatic or aromatic hydroxycarboxylic acids that differ in carbon number and atomic arrangement from the epsilon-caprolactones that make up the star polymer, such as 12-hydroxystearic acid and 2-hydroxyisomer. Butyric acid, 3-hydroxybutyric acid, α-hydroxylauric acid, 2-hydroxy-2-methylbutyric acid, α-hydroxy-propionic acid, hydroxycinnamic acid, 4-hydroxybenzoic acid, etc., or one or more of these It may be an oligomer obtained by condensation polymerization.

The reaction ratio between the star polymer and the hydroxycarboxylic acid compound is such that the molar amount of hydroxyl groups in the polymer [OH] and the molar amount of carboxyl groups in the hydroxycarboxylic acid compound [COOH] are such that [COOH]/[OH]≦1. It is important to react with

If [COOH]/[OH]>1 or more, the compound remains unreacted in the polymer, which causes a decrease in weather resistance when it is finally formed into a coating film.
Also, the value of [COOH]/[OH] is preferably 0.5
-1, and a range in which the star polymer (with a molecular weight of 1000 or more is solid at room temperature) and the compound becomes semi-solid to liquefied at room temperature is preferable.

Although it is possible to introduce acidic groups and/or basic groups into the polymer before reacting with the hydroxycarboxylic acid, the polymer will not liquefy as long as the introduction is carried out appropriately depending on the surface substance of the pigment. As the molecular weight of the polymer increases, it becomes a highly crystalline and extremely hard solid. It has been found that even if the polymer has a molecular weight of 1000, if it is diluted with xylene to a concentration of 60% and left at room temperature, it will crystallize and precipitate in about 2 to 3 days. This means that even if acidic groups and/or basic groups are introduced and used as a resin for pigment dispersion, the storage stability of the pigment dispersion paste is expected to deteriorate, and in fact, the above resin is used to disperse pigments. When a paste was prepared and the changes in its viscosity and yield value over time due to storage were determined, it was found that the viscosity and yield value increased. However, when the terminal OH group of the polymer was reacted with a hydroxyl carboxylic acid compound under the conditions of the formula, it was found that the resulting polymer became semisolid to liquefied. (If the molecular weight exceeds ~5000,
It tends to be semi-solid. ) This is the most important point of the present invention, and it not only prevents star-shaped polyester crystallization and therefore lowers the viscosity and yield value of the pigment dispersion paste made using this resin, but also reduces aging due to storage. Good stability is also desirable.

In the reaction between a star polymer and a hydroxycarboxylic acid, it is expected that the condensation reaction will occur only with the latter, and thus impurities due to side reactions will be mixed into the resulting polymer. However, if the hydroxyl group of the hydroxycarboxylic acid compound has a secondary structure, the carboxyl group of the compound is 1
It was confirmed from the results of various studies (for example, studies using gel permeation chromatography) of the produced polymer that the polymer reacts preferentially with the hydroxyl group of a polymer having a class structure.

The star-shaped polyester obtained in this way is used in liquid form for dispersing pigments, but since the surface substances differ depending on the type of pigment, in order to obtain a stable dispersion, it is necessary to It is necessary to introduce acidic and/or basic groups into the resin.

The acidic group referred to herein means an electron-accepting group (e.g., a carboxylic acid group, a sulfonic acid group), and the basic group means an electron-donating group (e.g., a nitrogen-containing group with a lone pair of electrons), respectively, in the polymer. It is preferably introduced by reaction with a hydroxyl group.Reagents capable of introducing carboxyl groups are commonly used as acidic group-introducing reagents, and typical examples include phthalic anhydride, isophthalic acid, terephthalic acid, succinic anhydride, and adipine. Acid, azelaic acid, sebacic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrabromo phthalic anhydride, tetrachlorophthalic anhydride, hexic anhydride, heimic anhydride, maleic anhydride, fumaric acid, itaconic acid, trimellitic anhydride, Examples include methylcyclohexcentric carboxylic anhydride, pyromellitic anhydride, etc. Among these, dibasic acid anhydrides such as phthalic anhydride and maleic anhydride are particularly preferred.

As the basicity introducing reagent, isocyanate compounds such as naphthylene diisocyanate, phenylene diisocyanate, isophorosodiisocyanate, tolyl isocyanate, diphenyl ether diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate Monomer compounds such as or compounds that have lower toxicity by increasing their molecular weight (hexamethylene diisocyanate-based “Dieranate EXPD”)
−101” (Asahi Kasei Corporation), “Desmodille TPL−
2291” (Sumitomo Bayer Co., Ltd.), “Coronate EH” (Nippon Polyurethane Co., Ltd.), xylylene diisocyanate-based “Takenate D120N” (Takeda Pharmaceutical Co., Ltd.), isophorone diisocyanate-based “Desmodyur Z-4370” ( Sumitomo Bayer Co., Ltd.), melamine compounds such as compounds obtained by condensing melamine and formaldehyde, or compounds obtained by adding alcohol to the condensation process (such as methylated melamine such as "Cymel 303" and "Cymel").
300” (Mitsui Toatsu Co., Ltd.), “Sumimar 40W (Sumitomo Chemical)
Co., Ltd.), and “Yuban” as n-butylated melamine.
20SE-60” (Mitsui Toatsu Co., Ltd.), isobutylated melamine “MF-013” (Nippon Paint Co., Ltd., etc.), hydroxylamine compounds such as monoethanolamine, diethanolamine, aminobentanol, aminobenzyl alcohol, Amino acid compounds such as 2-dimethylaminoethanol, e.g.
Examples include polyamide compounds such as -dimethylaminobenzoic acid, 2-aminoisobutyric acid, and 4-amino-n-butyric acid. Among these, it is particularly desirable to use isocyanate compounds and melamine compounds.

When reacting a star-structured polymer with these basic group-introducing reagents, the number of moles of the latter is usually equal to or less than the number of hydroxyl groups present in the former molecule (preferably the number of moles It may be used in a molar amount corresponding to 0.1 to 50% of When acidic groups and basic groups are to be introduced, the star polymer structure may be reacted with an acidic group-introducing reagent in any order. in this case,
The total number of moles of the acidic group-introducing reagent and the basic group-introducing reagent used is less than or equal to the number of moles corresponding to the number of hydroxyl groups in the star-structure polymer molecule (preferably a number of moles corresponding to 0.1 to 5% of the number of moles). ) is desirable.

The modified polymer thus obtained is a semi-solid to liquid substance (with a molecular weight of 5,000 or more, it tends to become semi-solid), and by selecting an appropriate one, uniform dispersion with various pigments can be easily achieved. Moreover, the pigment dispersion paste obtained here also has a low viscosity,
Its viscosity remains virtually unchanged even after a long period of time. In addition, the gloss (for example, 20° specular gloss) does not change over a long period of time.

There are no particular limitations on the range of pigments that can be used.
A variety of inorganic as well as organic raw materials can be used. Specific examples of inorganic pigments include zinc white, titanium oxide,
Antimony white, iron black, red iron, red lead, cadmium yellow, zinc sulfide, lithopone, barium sulfide,
Examples of organic pigments include lead sulfate, barium carbonate, lead white, and alumina white. Specific examples of organic pigments include azo pigments, polycondensation pigments, metal complex azo pigments, benzimidazolone pigments, and phthalocyanine pigments (bray, green, etc.). ), thioindigo series, anthraquinone series, flavanthrone series, indanthrene series, anthrapyridine series, pyranthrone series,
Examples include isoindolinone series, perylene series, perinone series, and quinacridone series. The amount of pigment used is usually 10 to 90% (by weight), preferably 30 to 70% (by weight), based on the total weight of the modified polymer and pigment. The pigment dispersion paste may consist only of the modified polymer and the pigment as described above, but it may also contain appropriate resins, solvents, modifiers, etc., as long as it does not have an essentially negative effect on its dispersibility. Good too. In the pigment dispersion paste of the present invention, the resin used is polyester, and therefore, the paint vehicle is particularly preferably blended with a polyester such as polyester or alkyd, but if desired, acrylic resin, melamine resin, epoxy resin, polyurethane resin is used. , polyamide resin, urea resin, polyether resin, etc. There are no particular restrictions on the blending ratio of pigment dispersion paste and paint vehicle, but it is usually 1:99 to 99:1.
(weight ratio). In addition, if necessary, use appropriate resin,
A solvent, a modifier, etc. may be added.

In the above description, specific examples of solvents that can be appropriately blended into the pigment dispersion paste or pigment dispersion coating composition include hydrocarbon solvents (e.g. toluene, xylene, Solbetsuso 100, Solbetsuso 150),
Ester solvents (e.g. ethyl acetate, butyl acetate), ketone solvents (e.g. methyl ethyl ketone,
Examples include methyl isobutyl ketone).

In addition, when preparing the above-mentioned pigment dispersion paste or pigment dispersion coating composition, it is sufficient to adopt ordinary dispersion and mixing means, for example, a dispersion machine such as a roll mill, a ball mill, a sand mill, a planetary mixer, or a high-speed dispersion machine is used. .

The pigment dispersion coating composition thus obtained can maintain a good dispersion state for a long period of time, and its coating film performance is also excellent. What is particularly noteworthy is that compared to conventional pigment dispersion compositions, the solid pigment content can be maintained much higher. That is, when performing a painting operation using a pigment-dispersed coating composition, if the viscosity of the composition is too high, the operation becomes difficult. In order to maintain a suitable viscosity for operation, significant amounts of solvent must be incorporated, resulting in a reduction in solids content. Recently, spray painting is often used in painting operations due to its efficiency, and this tendency is particularly noticeable in industrial or large-scale painting operations. Therefore, there has been a strong demand for a pigment-dispersed coating composition that has a high solids content and does not cause any trouble in working. The pigment dispersion coating composition according to the present invention meets these demands and also contributes to improving coating efficiency and reducing the amount of solvent used. The present invention will be explained in more detail with reference to Examples below.

Production Example 1 Production of Dispersion Resin 1 34 g of pentaerythritol, 228 g of epsilon-caprolactone and 0.23 g of di-n-butyltin oxide as a catalyst were placed in a 500 ml round bottom flask equipped with a stirring bar, condenser and thermometer and heated at 180°C. Heated for 3 hours. The resulting polymer was a white waxy solid.

Next, 52.5 g of this waxy solid, 60 g of 12-hydroxystearic acid and methanesulfonic acid as a catalyst.
0.12 g of xylene (50 ml) as a circulating solvent was placed in a 500 ml round bottom flask equipped with a stirring bar, a water meter with a condenser, and a thermometer, and refluxed at about 150° C. for 5 hours. (About 3.6 ml of produced water) After reflux, the solvent xylene in the reaction product was removed using an evaporator. The obtained polymer was a pale yellow transparent liquid.

Next, 100g of this liquid polymer, phthalic anhydride
1.3 g and 30 ml of the solvent xylol were placed in a 500 ml round bottom flask equipped with a stir bar condenser and thermometer and allowed to react for approximately 5 hours. The solvent xylol in the reaction product was removed by an evaporator.
The obtained polymer was a pale yellow liquid with an acid value of 5.2, a molecular weight Mn of 2178 (measured by gel permeation chromatography), and a viscosity of 56 cps (measured with a 60% xylol solution, using a cone-plate type E-type viscosity system). It was hot.

Example 1 Production of pigment dispersion paste (1) 15.0 g of dispersion resin 1 obtained in Production Example 1 85 g of white pigment CP-95 (Ishihara Sangyo Co., Ltd. titanium oxide) and 7.14 g of isobutanol and xylol as solvents
14.28 g was placed in a 250 ml mayonnaise pin and dispersed for 20 minutes in a paint shaker using 140 g of glass beads with a diameter of 1 mm as a dispersion medium to obtain a dispersed paste (1) (NV = 82.4%). The 20° specular gloss of the dispersed paste was 44, and the viscosity was 515 cps (using a cone-plate type E-type viscometer).

Production Example 2 Production of Dispersion Resin 2 17 g of pentaerythritol, 228 g of epsilon-caprolactone, and 0.23 g of di-n-butyltin oxide as a catalyst were heated under the same conditions as in Production Example 1. The resulting polymer was a white waxy solid. Next, 100 g of this waxy solid, 60 g of 12-hydroxystearic acid, 0.16 g of methanesulfonic acid as a catalyst, and 50 ml of xylene as a circulating solvent were refluxed under the same conditions as in Production Example 1. (About 3.6 ml of produced water) After reflux, the solvent xylene produced during the reaction was removed using an evaporator. The obtained polymer was a light brown transparent liquid.

Next, this polymer was subjected to a phthalic anhydride addition reaction in the same manner as in Production Example 1, and the acid value was 4.2, the molecular weight was Mn=
3128, a viscosity of 94 cps (60% xylol solution) was obtained.

Example 2 Production of Pigment Dispersion Paste (2) A dispersion paste (2) (NV=82.4%) was obtained in exactly the same manner as in Example 1 except that Dispersion Resin 2 was used instead of Dispersion Resin 1. Dispersion paste (2)
The 20° specular gloss was 45 and the viscosity was 538 cps.

Production Example 3 Production of Dispersion Resin 3 9.07 g of pentaerythritol, 191 g of epsilon-caprolactone, and oxidized di-n-
0.20 g of butyltin was heated under the same conditions as in Production Example 1. The resulting polymer was a white waxy solid.

Next, 172 g of this waxy solid, 68 g of 12-hydroxystearic acid, and 0.10 g of methanesulfonic acid as a catalyst, and 60 ml of xylene as a circulating solvent were refluxed under the same conditions as in Production Example 1. (About 4.1 ml of produced water) After reflux, the solvent xylene in the reaction product was removed using an evaporator. The obtained polymer was a light brown liquid.

Next, this polymer was subjected to a phthalic anhydride addition reaction in the same manner as in Production Example 1 to obtain an acid value of 4.8, a molecular weight of Mn 4128,
A polymer with a viscosity of 134 cps (60% xylol solution) was obtained.

Example 3 Production of pigment dispersion paste (3) Dispersion paste (3) (NV=82.4%) was obtained in exactly the same manner as in Example 1 except that dispersion resin 3 was used instead of dispersion resin 1. Dispersion paste (3)
The 20° specular gloss was 63 and the viscosity was 570 cps.

Comparative Example 1 Alkyd resin (Nippon Paint Co., Ltd., molecular weight
Mn2800, viscosity 5248cps, NV=60%, acid value 5.0)
25g (solid content 15g), white pigment CR-95 (Ishihara Sangyo)
Ltd. 85g, and isobutanol 7.14g as a solvent,
Place 4.28g of xylol in a 250ml mayonnaise bottle and add 1mm diameter glass beads as a dispersion medium.
When 140 g of the mixture was shaken in a paint shaker for 20 minutes, the beads did not move at all and a well-dispersed paste could not be obtained.

Comparative Example 2 In Comparative Example 1, oil-free polyester resin (Nippon Paint Co., Ltd. molecular weight Mn 2400, viscosity 9800 cps, NV = 60%, acid value 6.0) was used instead of alkyd resin.
A dispersion paste (NV82.4%) was obtained under exactly the same conditions except that . This dispersed paste had a 20° specular gloss of 6 and a viscosity of 1807 cps.

Claims (1)

[Scope of Claims] 1. Hydroxycarboxylic acid having a hydroxyl group and a carboxyl group in one molecule is added to a star-structured polymer obtained by reacting a polyol having at least three hydroxyl groups in one molecule with epsilon-caprolactones. The molar amount of hydroxyl groups in the polymer [OH] and the molar amount of carboxyl groups in the hydroxyl carboxylic acid [COOH]
A pigment dispersion resin made of a modified polyester obtained by carrying out a condensation reaction so that the ratio of [COOH]/[OH]≦1 is satisfied, and then introducing an acidic group and/or a basic group. 2 A hydroxycarboxylic acid having a hydroxyl group and a carboxyl group in one molecule is added to a star-structured polymer obtained by the reaction of a polyol having at least three hydroxyl groups in one molecule and epsilon-caprolactones. Molar amount of hydroxyl group [OH] and molar amount of carboxyl group of hydroxyl carboxylic acid [COOH]
Pigment dispersion consisting of a pigment uniformly dispersed in a modified polyester resin obtained by carrying out a condensation reaction so that the ratio of [COOH]/[OH]≦1 and then introducing an acidic group and/or a basic group. A coating composition comprising a paste and a polyester resin vehicle.