JPS6237074B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel pigment dispersant for paints, and more specifically, the present invention relates to a novel pigment dispersant for paints, and more specifically, it contains a water-soluble salt of a copolymer of a C3 _- chain olefin and an ethylenically unsaturated dicarboxylic acid as an active ingredient, and has excellent dispersibility and storage stability. This invention relates to pigment dispersants for paints. Paints are generally composed of coloring pigments such as titanium white and red iron, extender pigments such as calcium carbonate and clay, and various resins. In such a paint, it is desirable that the pigment particles in the paint have excellent dispersibility from the viewpoints of color spreadability, hiding power, leveling property, photoselectivity, etc. of the paint film. Furthermore, during the production of paints, it is required that undesirable phenomena such as reaggregation and sedimentation of pigment particles do not occur. Therefore, dispersants are used in the production of paints to meet these requirements. As this type of dispersant, copolymer salts of diisobutylene and maleic anhydride have traditionally been used, but they are not always satisfactory in terms of pigment dispersibility, foaming during dispersion, and miscibility. Currently, sodium hexametaphosphate (HMP) is used in combination to compensate for this drawback. Therefore, as a result of intensive studies to solve these drawbacks, the present researchers found that a water-soluble salt of a copolymer of carbon water 5 chain olefin and ethylenically unsaturated dicarboxylic acid has low foaming properties during pigment dispersion. A paint that has an extremely excellent dispersion effect on various pigments without using HMP together, has good miscibility with various resins, and uses a water-soluble salt of such a copolymer as a dispersant. The present inventors discovered that the compound also has excellent storage stability, leading to the completion of the present invention. Thus, according to the present invention, there is provided a pigment dispersant for paints containing as an active ingredient a water-soluble salt of a copolymer of a chain olefin having 5 carbon atoms and an ethylenically unsaturated dicarboxylic acid. The pigment dispersant for paints of the present invention is a copolymer obtained by radical copolymerization of a mixture of a chain olefin having 5 carbon atoms and an ethylenically unsaturated dicarboxylic acid anhydride. It can be produced by hydrolysis in the presence of a base. As chain olefin, which is one of the main raw materials,
Examples include pentene-1, pentene-2,2-methyl-butene-1,2-methyl-butene-2, and mixtures thereof are used as necessary. Other main raw materials, such as ethylenically unsaturated dicarboxylic anhydrides, include maleic anhydride, itaconic anhydride, citraconic anhydride, and the like, with maleic anhydride being particularly industrially advantageous. Ethylenically unsaturated dicarboxylic anhydride where:
The charging ratio of the chain olefin can be appropriately selected depending on the desired copolymer composition. The composition of the copolymer varies depending on the reaction conditions such as the charging ratio of raw materials, the type of chain olefin, and the polymerization temperature, but the composition of the commonly used copolymer is the molar ratio of dicarboxylic acid anhydride to chain olefin. 80:20~
40:60, preferably 70:30 to 55:45. As the polymerization initiator, ordinary radical polymerization catalysts can be used, such as organic peroxides such as benzoyl peroxide and kyumene hydroperoxide, and azobisisobutyronitrile such as α,α′-azobisisobutyronitrile. Examples include, but are not limited to, compounds. Polymerization is carried out in a solvent that does not inhibit radical polymerization.
It is carried out at a temperature of about 170°C, and a solvent such as acetone, methyl ethyl ketone, benzene, toluene, ethyl acetate, or chloroform is usually used. If desired, it is also possible to carry out bulk polymerization. The molecular weight of the copolymer can be appropriately determined depending on the reaction conditions actually used, but in the present invention, the number average molecular weight measured by vapor pressure osmosis is 300 to 300.
50,000, preferably 1,000 to 20,000. This copolymer is easily hydrolyzed to form a salt in the presence of a base, and the water-soluble salts among the alkali metal salts, ammonium salts, alkaline earth metal salts, etc. are used as the pigment dispersion for paints in the present invention. The unneutralized portion may remain. The thus-obtained dispersant of the present invention is more effective for various pigments than conventionally used pigment dispersants for paints.
For example, paints that have excellent dispersion properties for titanium white, red iron, cyanine blue, calcium carbonate, clay, talc, etc., have low foaming properties, and furthermore use water-soluble salts of such copolymers as dispersants. also has excellent storage stability. The present invention will be explained in more detail with reference to Examples below. The properties of the water-soluble polymers used in the Examples are shown in Table 1.

[Table] Example 1 (Pigment dispersion test) A predetermined pigment was added to an aqueous solution containing a predetermined amount of dispersant so that the content was 70% by weight, and then a TK homomixer (Tokushu Kikaku A pigment slurry was obtained by stirring at 1,500 rpm for 3 minutes using an industrial machine (manufactured by Kogyo Co., Ltd.). This pigment slurry was measured at 25% using a B-type viscometer.
The viscosity was measured under the conditions of ℃ and 30 rpm. The results are shown in Tables 2-4. From the results in Tables 2 to 4, it can be seen that the dispersant of the present invention has a lower viscosity of the pigment slurry than conventional products, and has excellent dispersibility and miscibility.

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[Table] Example 2 (Paint formulation test) Emulsion paints using samples, samples, and HMP as dispersants were prepared using the following two types of formulations. First, a pre-prepared millbase was dispersed using a TK homo mixer at 1500 rpm, and then a letdown was added and stirred for 20 minutes using a three-one motor to prepare a paint. Next, the viscosity of the obtained paint at 25°C was measured using a Stomer viscometer and a B-type viscometer,
Furthermore, the thixotropy value was calculated from the measured value using a B-type viscometer. The results are shown in Tables 5 and 6.

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[Table] Example 3 (Paint storage stability test) The paint prepared according to Example 2 is placed in a sealed container and stored in a constant temperature bath set at 50°C. After a predetermined period of time, the paint was taken out and returned to room temperature, and its viscosity was measured using a Stormer viscometer to examine changes in paint viscosity over time. The results are shown in Table 7.

[Table] This result shows that the dispersant of the present invention has excellent storage stability.

Claims (1)

[Claims] 1. A pigment dispersant for paints containing as an active ingredient a water-soluble salt of a copolymer of a chain olefin having 5 carbon atoms and an ethylenically unsaturated dicarboxylic anhydride.