KR101561719B1 - Pigment dispersing agent - Google Patents

Abstract

An object of the present invention is to provide an acrylic acid-based pigment dispersant that satisfies the improvement of dispersibility of a pigment having a small particle size and suppression of heat generation at the time of wet pulverization, which is required for a dispersant. Further, as a dispersing agent comprising a (meth) acrylic acid-based copolymer having an alkyl (meth) acrylate monomer and an alkyl (meth) acrylate monomer having an alkyl group having 4 to 8 carbon atoms as an essential component and an alcohol having 4 to 8 carbon atoms, And a mass ratio of an alcohol having 4 to 8 carbon atoms to a (meth) acrylic acid-based copolymer is 1000 to 30000 ppm.

Description

[0001] PIGMENT DISPERSING AGENT [0002]

The present invention relates to a dispersant of a pigment such as calcium carbonate. More specifically, when the pigment is used as a dispersant for an inorganic pigment having a small particle size, it is possible to disperse the pigment with high dispersion stabilizing effect while maintaining good flowability in a fine particle form, (Meth) acrylic acid-based copolymer which can be stably dispersed over a long period of time while suppressing the occurrence of the above-mentioned problems.

In the present invention, (meth) acrylic acid or a part or all of the (meth) acrylic acid is neutralized is referred to as (meth) acrylic acid (salt).

Conventionally, as a dispersant such as an inorganic pigment, a homopolymer of acrylic acid (salt) and a copolymer of acrylic acid (salt) and another copolymerizable monomer are known. A homopolymer or copolymer of acrylic acid (salt) is adsorbed on the pigment particle, and provides a repulsive action by steric hindrance between the particles, so that a stable pigment dispersion can be obtained. In particular, the acrylic acid (salt) copolymer is superior to the acrylic acid (salt) homopolymer and has been proposed as follows.

According to Patent Document 1 (Japanese Unexamined Patent Publication (Kokai) No. 61-69872), a monomer containing a monocarboxylic acid (salt), a monomer containing a dicarboxylic acid (salt) and a monomer containing a (meth) Wet milling of calcium carbonate is carried out by a dispersant containing a copolymer.

According to Patent Document 2 (Japanese Unexamined Patent Publication (Kokai) No. 56-115630), it is known that a monomer containing a carboxylic acid (salt), a (meth) acrylic acid ester monomer having 1 to 8 carbon atoms and a sulfonic acid The pigment is dispersed with a dispersant containing a copolymer of monomers.

According to Patent Document 3 (Japanese Unexamined Patent Publication (Kokai) No. 49-130915), a dispersant comprising a copolymer of a carboxylic acid (salt) -containing monomer and a (meth) acrylic acid ester monomer having 1 to 4 carbon atoms The pigment is dispersed.

According to Patent Document 4 (Japanese Patent Application Laid-Open No. 2004-306022), a monomer containing a carboxylic acid (salt) and a (meth) acrylic acid ester monomer having 1 to 20 carbon atoms in a ratio of 97 to 99: 1 to 3 And the hard calcium carbonate is dispersed with a dispersant containing a phosphorus-containing copolymer.

According to Patent Document 5 (Japanese Unexamined Patent Publication (Kokai) No. 55-18423), a dispersant containing a copolymer of (meth) acrylic acid (salt) and (meth) acrylic acid ester monomer having 1 to 12 carbon atoms, .

However, in recent years, an inorganic pigment having a smaller particle diameter than conventional ones has been used, and it has been required to make the heat generation generated when wet pulverization is minimized as much as possible. In addition, improvement of the separation between the media and the slurry is required.

Inorganic pigments and the like having small particle diameters have an increased surface area, so that the interactions between the particles are strengthened. As a result, the particles tend to agglomerate each other and the viscosity of the dispersion tends to increase. Further, at the time of wet pulverization, since the particles repeatedly collide with each other very much, heat generation becomes large. Further, if the particle size is small, separation between the medium and the slurry tends to deteriorate, and the amount of the recovered slurry is small.

With respect to such a demand, satisfactory performance can not be obtained with the dispersing agent of the prior art as shown above.

For example, Japanese Patent Application Laid-Open No. 61-69872, Japanese Patent Application Laid-Open No. 56-115630, Japanese Patent Application Laid- 130915) and Patent Document 4 (Japanese Patent Application Laid-Open No. 2004-306022), there is a problem that the viscosity of the dispersion increases over time, and when the wet grinding is carried out, the heat generation increases. Further, there is a problem that the amount of the recovered slurry is small.

In addition, the emulsifier used in the dispersant described in Patent Document 5 (Japanese Unexamined Patent Publication (Kokai) No. 55-18423) adversely affects the dispersibility, and therefore, when the viscosity of the dispersion becomes high as in Patent Document 1, There is a problem that heat generation becomes large. Further, there is a problem that the amount of the recovered slurry is small.

Thus, even when the above-mentioned acrylic acid (salt) copolymer is used, a dispersant which can sufficiently satisfy the dispersion stability of an inorganic pigment having a small particle diameter, the suppression of heat generation during wet grinding, and the recovery of slurry can not be obtained.

Japanese Patent Laid-Open Publication No. 61-69872 Japanese Patent Application Laid-Open No. 56-115630 Japanese Patent Application Laid-Open No. 49-130915 Japanese Patent Application Laid-Open No. 2004-306022 Japanese Patent Application Laid-Open No. 55-18423

An object of the present invention is to provide a (meth) acrylic acid-based pigment dispersant that satisfies the improvement of the dispersibility of an inorganic pigment having a small particle size and the effect of suppressing heat generation upon wet pulverization,

In order to solve the above-described problems, the present inventors have found that, in the conventionally known copolymer of (meth) acrylic acid and (meth) acrylic acid alkyl ester, specific alkyl (meth) acrylates having 4 to 8 carbon atoms (Meth) acrylic acid-based copolymer obtained by selecting an ester and an alcohol having 4 to 8 carbon atoms, wherein the mass ratio of the alcohol having 4 to 8 carbon atoms to the (meth) acrylic acid-based copolymer is 1000 to 30000 ppm And that the present invention has been completed.

The invention for solving the above problems is described below.

The first invention relates to a (meth) acrylic acid-based copolymer comprising a (meth) acrylic acid monomer and a (meth) acrylic acid alkyl ester monomer having an alkyl group having 4 to 8 carbon atoms as an essential constituent and a dispersant containing an alcohol having 4 to 8 carbon atoms Wherein the mass ratio of the alcohol having 4 to 8 carbon atoms to the (meth) acrylic acid-based copolymer is 1000 to 30000 ppm.

The second invention is the pigment dispersant according to the first aspect of the present invention, wherein the mass ratio of the alcohol having 4 to 8 carbon atoms to the (meth) acrylic acid-based copolymer is 2000 to 15000 ppm.

The third aspect of the present invention is a polymerizable composition comprising 60 to 95 mass% of a (meth) acrylic acid monomer, 5 to 40 mass% of a (meth) acrylic acid alkyl ester monomer having an alkyl group of 4 to 8 carbon atoms and 0 to 10 mass% (Meth) acrylic acid-based copolymer is the pigment dispersant according to any one of the first invention and the second invention.

The fourth aspect of the present invention is directed to the pigment dispersion according to any one of the first to third inventions, wherein the (meth) acrylic acid alkyl ester monomer having 4 to 8 carbon atoms is butyl (meth) acrylate and the alcohol having 4 to 8 carbon atoms is butyl alcohol Dispersant.

The fifth invention is the pigment dispersant according to any one of the first to fourth inventions which is a dispersant for wet pulverization.

A sixth invention is a wet grinding method for a pigment characterized by using the pigment dispersant according to any one of the first to fourth inventions for the wet pulverization of a pigment.

When the pigment dispersant containing the (meth) acrylic acid (salt) -based copolymer of the present invention is used as a dispersant such as an inorganic pigment having a small particle diameter, the viscosity of the dispersion does not increase with time, Can be reduced, and the amount of slurry to be recovered is large, so that it is useful as a dispersant in various applications.

The effect of the present invention as a pigment dispersing agent is presumed to be attributable to the fact that the dispersant of the present invention is adsorbed on the particles in the dispersion and gives slip properties between the particles and between the slurry and the medium as compared with the conventional dispersant do.

Hereinafter, embodiments of the present invention will be described in detail.

The pigment dispersant of the present invention includes a (meth) acrylic acid-based copolymer having an (meth) acrylic acid monomer and an alkyl (meth) acrylate monomer having an alkyl group of 4 to 8 carbon atoms as an essential component and an alcohol having 4 to 8 carbon atoms , And the mass ratio of the alcohol having 4 to 8 carbon atoms to the (meth) acrylic acid-based copolymer is 1000 to 30000 ppm.

Examples of the (meth) acrylic acid include acrylic acid and methacrylic acid, and some or all of them may be in the form of a neutralized salt ((meth) acrylate). Among them, acrylic acid and / or acrylate are preferred from the viewpoints of polymerizability and water solubility in the production of the copolymer.

Examples of the (meth) acrylate include alkali metal salts of (meth) acrylic acid such as sodium salts, potassium salts and lithium salts, ammonium salts and organic amine salts such as diethanolamine salts and triethanolamine salts. . Among them, the form of the (meth) acrylate salt is preferably in the form of an alkali metal salt, particularly a sodium salt, in terms of balance of production cost and performance.

The (meth) acrylate salt can be produced by reacting (meth) acrylic acid with a hydroxide of an alkali metal such as sodium hydroxide or potassium hydroxide, or an organic amine such as ammonia or monoethanolamine.

The (meth) acrylic acid-based copolymer in the present invention may be a carboxyl group in which the entire carboxyl group of the (meth) acrylic acid is non-neutralized. However, 15 to 100 mol%, particularly 25 to 100 mol% (Meth) acrylic acid-based copolymer increases in water solubility and the dispersion stabilizing effect increases.

From the viewpoint of pH, the carboxyl group is neutralized by the base at a rate that the pH of the aqueous solution of the (meth) acrylic acid copolymer is in the range of 3 to 9, especially 4 to 8, And the dispersion stabilizing effect is enhanced.

(40 to 100 mol%) of the carboxyl group of the (meth) acrylic acid is in an un-neutralized state before and after the polymerization for producing the (meth) acrylic acid-based copolymer, (Meth) acrylic acid copolymer is preferably in the form of a salt in an amount of not less than 15 mol% and more preferably not less than 25 mol% of the carboxyl group of the (meth) acrylic acid copolymer in view of smooth progress of the polymerization reaction for producing the Do.

Examples of the (meth) acrylic acid alkyl ester monomers having 4 to 8 carbon atoms in the alkyl group include n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, (Meth) acrylate, isobutyl (meth) acrylate, isobutyl (meth) acrylate and t-butyl (meth) acrylate are exemplified. Butyl (meth) acrylate is preferable, and n-butyl (meth) acrylate is particularly preferable.

As the (meth) acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group is not more than 3, the dispersion tends to thicken and heat generation during wet milling tends to increase. Further, the amount of the recovered slurry is undesirably decreased. This is presumably because the slip property between the particles is small. On the other hand, as the (meth) acrylic acid alkyl ester having 9 or more carbon atoms in the alkyl group, the dispersion tends to be separated, which is not preferable.

The mass ratio of (meth) acrylic acid (salt) and (meth) acrylic acid alkyl ester having 4 to 8 carbon atoms in the alkyl group is 95: 5 to 60:40 in the (meth) acrylic acid (salt) And more preferably 90:10 to 70:30.

If the proportion of the (meth) acrylic acid (salt) is less than 60 mass%, the pigment dispersant may be separated, while if it exceeds 95 mass%, the viscosity of the dispersion tends to increase.

In the (meth) acrylic acid-based copolymer in the present invention, besides the (meth) acrylic acid (salt) and the (meth) acrylic acid alkyl ester, monomers copolymerizable therewith may be copolymerized. Examples of such monomers include unsaturated acids such as maleic acid and itaconic acid or salts thereof, unsaturated acid anhydrides such as maleic anhydride and itaconic anhydride, unsaturated sulfonic acids such as 2-acrylamide-2-methylpropane sulfonic acid and styrene sulfonic acid, (Meth) acrylic acid hydroxyalkyl esters, acrylamides, (meth) acrylic esters containing esters of polyalkylene oxide skeletons. These may be used in combination of two or more.

These monomers are preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, based on 100 parts by mass of the total monomer. If it exceeds 10 parts by mass, the dispersion may be thickened, which is not preferable.

(Meth) acrylic acid copolymer is not particularly limited and can be produced by a solution polymerization method, an aqueous solution polymerization method, a high-temperature high-pressure polymerization method, a reversed-phase suspension polymerization method, an emulsion polymerization method and the like. Among them, A polymerization method is preferable, and an aqueous solution polymerization method is particularly preferable.

According to aqueous solution polymerization, a dispersant can be obtained as a homogeneous solution. On the other hand, in the case of producing by a different polymerization method such as emulsion polymerization, a uniform solution can not be obtained, so that only a non-uniform dispersion can be performed, and the resulting dispersion also tends to increase in viscosity.

As a solvent for aqueous solution polymerization, it is preferable to use a mixture of water and an organic solvent. Use of only water as a solvent is not preferable because the (meth) acrylic acid alkyl ester is difficult to dissolve. On the other hand, if only an organic solvent is used, it is necessary to replace the organic solvent with water at the time of use as a dispersant, which is not preferable because it takes time and cost.

Preferable examples of the organic solvent include alcohols such as isopropyl alcohol and ketones such as acetone, and isopropyl alcohol is particularly preferable.

As the polymerization initiator in the polymerization reaction, a known polymerization initiator can be used without particular limitation, and a radical polymerization initiator is particularly preferably used.

As the radical polymerization initiator, for example, persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate, hydroperoxides such as t-butyl hydroperoxide, and water-soluble peroxides such as hydrogen peroxide; Ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, and dialkyl peroxides such as di-t-butyl peroxide and t-butyl quercyl peroxide.

The peroxide radical polymerization initiator may be used alone or in combination of two or more.

Of the above-mentioned peroxide radical polymerization initiators, hydrogen peroxide or persulfate-based peroxides which are easy to control molecular weight and have a low decomposition temperature are preferably used, and particularly preferred are persulfates such as sodium persulfate and ammonium persulfate .

The amount of the radical polymerization initiator to be used is not particularly limited, but is preferably 0.1 to 15 mass%, particularly 0.5 to 10 mass%, based on the total mass of the total monomers of the (meth) acrylic acid copolymer. If the amount of the radical polymerization initiator used is less than 0.1 mass%, the copolymerization ratio decreases. If the amount exceeds 15 mass%, the stability of the (meth) acrylic acid copolymer may deteriorate or adversely affect performance as a dispersant.

In some cases, the (meth) acrylic acid-based copolymer may be produced by using a water-soluble redox polymerization initiator. Examples of the oxidation-reduction polymerization initiator include a reducing agent such as an oxidizing agent (for example, the peroxide described above), sodium bisulfite, sodium sulfite, sodium hydrosulfite, and combinations of iron alum and alum.

In the production of the (meth) acrylic acid-based copolymer, a chain transfer agent may be added to the polymerization system in an appropriate amount in order to adjust the molecular weight. Examples of the chain transfer agent that can be used include sodium hypophosphite, sodium hypophosphite, Mercaptoacetic acid, mercaptopropionic acid, 2-propanethiol, 2-mercaptoethanol, thiophenol and the like.

The polymerization temperature at the time of producing the (meth) acrylic acid-based copolymer is not particularly limited and can be broadly defined, but the polymerization temperature is preferably 60 to 100 ° C.

If the polymerization temperature is lower than 60 占 폚, the polymerization reaction is delayed, which is not preferable from the viewpoint of productivity. The reaction can be carried out under pressure or under reduced pressure, but it is preferable to carry out the reaction at normal pressure because a cost is required for equipment for pressurization or decompression reaction.

The polymerization time is preferably from 2 to 20 hours, particularly from 3 to 10 hours.

The weight average molecular weight of the (meth) acrylic acid copolymer in the present invention is preferably from 2,000 to 10,000, more preferably from 3,000 to 8,000. If the weight average molecular weight is less than 2000, the dispersant tends to be thickened because the dispersant tends to be desorbed from the particles in the dispersion. If the weight average molecular weight is more than 10,000, the viscosity of the dispersion tends to increase, And therefore, it is not preferable. The weight average molecular weight is a value measured by GPC (gel permeation chromatography).

The organic solvent is removed from the solution containing the (meth) acrylic acid copolymer obtained above by distillation, vacuum distillation and drying, and if necessary, neutralized with a basic compound to give the carboxyl group of the (meth) acrylic acid as a salt form Methacrylic acid-based copolymer. As described above, the degree of neutralization is preferably 15 to 100 mol%, particularly 25 to 100 mol%, neutralized with a base to be in the form of a salt.

Examples of the basic compound used for neutralization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and organic amines such as ammonia water, diethanolamine and triethanolamine. Of these, sodium hydroxide and / or potassium hydroxide are preferable, Sodium hydroxide is preferably used.

The water-soluble (meth) acrylic acid copolymer obtained in the above is used for various dispersants by adding an alcohol having 4 to 8 carbon atoms. The content of the alcohol having 4 to 8 carbon atoms is preferably from 1,000 to 30,000 ppm, more preferably from 1,500 to 20,000 ppm, particularly preferably from 2,000 to 15,000 ppm, based on the mass of the (meth) acrylic acid copolymer.

If the ratio of the alcohol is less than 1000 ppm, the slip property imparted between the particles is small, so that the dispersion tends to thicken and heat generation during wet pulverization tends to increase. Further, the amount of the recovered slurry is undesirably decreased. On the other hand, if it exceeds 30000 ppm, aggregation of the particles tends to occur, and the dispersion tends to be thickened, which is not preferable.

Examples of the alcohol having 4 to 8 carbon atoms include n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, pentyl alcohol, n-hexyl alcohol, heptyl alcohol, octyl alcohol and 2-ethylhexyl alcohol. Of these, n-butylalcohol, isobutylalcohol and t-butylalcohol are preferable in view of the performance as a dispersant, and particularly preferable is n-butylalcohol.

As the alcohol having not more than 3 carbon atoms, the dispersion tends to be thickened, and heat generation at the time of wet pulverization tends to increase, which is not preferable. Further, the amount of the recovered slurry is undesirably decreased. On the other hand, an alcohol having 9 or more carbon atoms tends to separate the dispersant, which is not preferable.

The pigment dispersant of the present invention is usually produced in a solid content concentration of 50 to 80 mass%, preferably 60 to 78 mass%. To prepare the concentration, it is preferred to add water.

The pigment dispersant of the present invention exerts an excellent effect on the inorganic pigment. Specific examples thereof include pigment clay, heavy calcium carbonate, light calcium carbonate, titanium oxide, alumina, and satin white.

The amount of the pigment dispersant of the present invention is usually 0.01 to 10% by mass, preferably 0.05 to 5% by mass, particularly preferably 0.1 to 3% by mass with respect to the pigment. If it is less than 0.01% by mass, the dispersing effect is insufficient, and if it exceeds 10% by mass, the slurry or the like tends to thicken.

<Examples>

Hereinafter, the present invention will be described in more detail with reference to Examples. In addition, unless otherwise stated,% means mass% and part means mass part.

Example 1

170 kg of deionized water and 250 kg of isopropyl alcohol were charged into a molding reactor equipped with a stirrer and a condenser, and maintained at 80 占 폚. To the reactor were fed 330 kg of a monomer mixture of 255 kg of acrylic acid and 75 kg of n-butyl acrylate and 60 kg of a 15% aqueous solution of ammonium persulfate over 5 hours. After completion of dropwise addition, the reaction solution was kept at 80 DEG C for 1 hour. Then, isopropyl alcohol was distilled off under reduced pressure while adding deionized water. Thereafter, the reaction solution was maintained at 50 캜 and neutralized by supplying a 48% aqueous solution of sodium hydroxide over 4 hours. When the liquid was analyzed by gas chromatography, 300 ppm of n-butanol was detected. Therefore, n-butanol was added thereto to adjust it to 1500 ppm. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 6, and n-butanol of 1500 ppm was obtained.

The weight average molecular weight (Mw) of the obtained pigment dispersant was measured by gel permeation chromatography (GPC). The eluent was 0.1 MNaCl + phosphate buffer (pH7), and the elution solution was adjusted to pH 7.0 with a buffer solution of 0.1 M NaCl + phosphate buffer (pH7) , And a calibration curve was prepared using polyacrylic acid Na (manufactured by Sowa Chemical Co., Ltd.). As a result of the measurement, Mw was 6,000.

17 g of the pigment dispersant obtained above, 320 g of ion-exchanged water, and 900 g of heavy calcium carbonate (Tankal A, manufactured by Maruo Calcium Co., Ltd.) were added to the cylindrical container, and the mixture was uniformly fused by gentle stirring. Subsequently, 3000 g of the medium (sand) was introduced, and wet pulverized by stirring at 1000 rpm for 50 minutes. Here, the liquid temperature at the end of the stirring was measured with a thermometer, and it was 79 ° C. Thereafter, the dispersion was recovered through the follicles of 200 holes. The obtained amount of the recovered dispersion liquid was measured and found to be 390 g. Ion-exchanged water was added to the slurry and the solid content was adjusted to 75% to obtain a dispersion.

The fluidity of the heavy calcium carbonate slurry during the wet grinding treatment was evaluated according to the following evaluation criteria.

◎: The slurry after grinding is separated from the medium very quickly, and the fluidity of the slurry is excellent.

○: The slurry after the pulverization and the separation of the media are fast, and the fluidity of the slurry is excellent.

?: The slurry after the pulverization and the separation of the media did not rapidly proceed, and the fluidity of the slurry was low.

The viscosity of the dispersion slurry on the wet grinding day and the viscosity after standing at 25 占 폚 for 7 days were measured using a BL viscometer at 25 占 폚 and 60 rpm. The viscosity on the wet pulverization day was 250 mPa s, and the viscosity after 7 days was 2200 mPa..

The median diameter and the 1.32 μm undercoat value of the dispersion immediately after preparation were measured using a laser diffraction scattering particle size distribution analyzer LA-910 (manufactured by Horiba Seisakusho Co., Ltd.). Median diameter was 0.67 μm and 1.32 μ under was 100%.

These results are shown in Table 1.

Example 2

Polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 290 kg of acrylic acid and 40 kg of 2-ethylhexyl acrylate. Here, the liquid was analyzed. Since 2-ethylhexanol was detected at 100 ppm, 2-ethylhexanol was added thereto to adjust it to 3000 ppm. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 6, and a content of 2-ethylhexanol of 3,000 ppm was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 1.

Example 3

Polymerization and vacuum distillation were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 230 kg of acrylic acid and 100 kg of n-butyl acrylate. Thereafter, the reaction solution was maintained at 80 캜 and neutralized by supplying a 48% aqueous solution of sodium hydroxide over 4 hours. Analysis of the liquid showed that no additional alcohol was added since 800 ppm of n-butanol was detected. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 6, and n-butanol of 800 ppm was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 1.

Example 4

Polymerization and vacuum distillation were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 270 kg of acrylic acid and 60 kg of n-butyl acrylate. Thereafter, the reaction solution was maintained at 70 캜 and neutralized by supplying 48% aqueous sodium hydroxide solution over 4 hours. When the liquid was analyzed, 500 ppm of n-butanol was detected, but n-butanol was further added to adjust it to 5000 ppm. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 7, and n-butanol of 5000 ppm was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 1.

Example 5

Polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 290 kg of acrylic acid and 40 kg of isobutyl acrylate. From the analysis of the liquid, 100 ppm of isobutanol was detected, and was adjusted to 2000 ppm by adding isobutanol. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 6, and 2000 ppm of isobutanol was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 1.

Example 6

Polymerization and vacuum distillation were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 255 kg of acrylic acid and 75 kg of n-butyl acrylate. Thereafter, the reaction solution was maintained at 60 캜 and neutralized by supplying a 48% aqueous solution of sodium hydroxide over 4 hours. From the analysis of the liquid, 400 ppm of n-butanol was detected, and n-butanol was added thereto to adjust it to 500 ppm. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 6, and n-butanol of 500 ppm was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 1.

Example 7

Polymerization and vacuum distillation were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 255 kg of acrylic acid and 75 kg of n-butyl acrylate. Thereafter, the reaction solution was maintained at 60 캜 and neutralized by supplying a 48% aqueous solution of sodium hydroxide over 4 hours. When the liquid was analyzed, 400 ppm of n-butanol was detected, but n-butanol was further added to adjust it to 11000 ppm. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 7, and 11000 ppm of n-butanol was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 1.

Comparative Example 1

Polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 255 kg of acrylic acid and 75 kg of methyl acrylate. When the liquid was analyzed, 350 ppm of methanol was detected, but no alcohol having 4 to 8 carbon atoms was detected. Therefore, n-butanol was added to adjust the concentration to 1500 ppm. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 6, and n-butanol of 1500 ppm was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 2.

Comparative Example 2

Polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1 except that the monomers used in Example 1 were changed to 255 kg of acrylic acid and 75 kg of ethyl acrylate. When the liquid was analyzed, 350 ppm of ethanol was detected, but no alcohol having 4 to 8 carbon atoms was detected. Therefore, n-butanol was added to adjust the concentration to 1500 ppm. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 6, and n-butanol of 1500 ppm was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 2.

Comparative Example 3

Polymerization, vacuum distillation and neutralization were attempted in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 255 kg of acrylic acid and 75 kg of lauryl acrylate. However, since a uniform liquid could not be obtained, the evaluation was stopped.

Comparative Example 4

The polymerization, decompression distillation and neutralization were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 290 kg of acrylic acid and 40 kg of n-butyl acrylate. When the liquid was analyzed, 100 ppm of n-butanol was detected, and n-butanol was added thereto to adjust it to 300 ppm. Thus, a pigment dispersant containing a solid concentration of 40 mass%, a pH of 6, and n-butanol of 300 ppm was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 2.

Comparative Example 5

The polymerization, distillation and neutralization were carried out in the same manner as in Example 1 except that the monomer used in Example 1 was changed to 290 kg of acrylic acid and 40 kg of n-butyl acrylate. Here, the liquid was analyzed and 100 ppm of n-butanol was detected. n-butanol was added thereto, and the temperature was adjusted to 13000 ppm. Thus, a pigment dispersant having a solid concentration of 40 mass%, a pH of 6, and 13000 ppm of n-butanol was obtained. The measured values of Mw and the results of the wet pulverization are shown in Table 2.

(Meth) acrylic acid-based copolymer having an alkyl group of 4 to 8 carbon atoms and an alcohol having 4 to 8 carbon atoms, wherein the number of carbon atoms of the (meth) acrylic acid-based copolymer is 4 to 8 Examples 1 to 7 in which the mass ratio of phosphorus alcohol was in the range of 1,000 to 30,000 ppm exhibited excellent flowability during wet pulverization, that the amount of recovered slurry was large, the slurry temperature immediately after wet pulverization was low and the viscosity change of the wet pulverized dispersion slurry And it was found to be a very excellent pigment dispersant.

On the other hand, as shown in Comparative Examples 1 and 2, in the case of using a (meth) acrylic acid copolymer using a (meth) acrylic acid alkyl ester having an alkyl group of 3 or less, the flowability during wet pulverization decreased, The amount obtained was small, the slurry temperature immediately after the wet pulverization was high, and the viscosity change of the wet pulverized dispersion slurry was large. Further, in Comparative Example 3 using lauryl acrylate having a carbon number of 12, a uniform polymerization solution could not be obtained.

On the other hand, in Comparative Example 4 and Comparative Example 5 in which the mass ratio of the alcohol having 4 to 8 carbon atoms to the (meth) acrylic acid copolymer was not in the range of 1000 to 30000 ppm, the fluidity during the wet pulverization decreased, , The slurry temperature immediately after the wet pulverization is high and the viscosity change of the wet pulverized dispersion slurry is large, it is difficult to use it as a pigment dispersant.

The pigment dispersant obtained by the present invention contains acrylic acid (salt) and a polymer of acrylic acid alkyl ester having 4 to 8 carbon atoms and an alcohol having a specific amount of 4 to 8 carbon atoms, so that it is adsorbed to the particles in the dispersion, It is possible to lower the viscosity of the dispersion even when the pigment having a small particle diameter is dispersed and to increase the viscosity of the dispersion over time and to reduce the viscosity of the dispersion The amount of slurry to be obtained can be increased. Therefore, the dispersion liquid containing the pigment dispersant of the present invention can be easily handled, and the storage period can be made longer than in the past. In addition, since heat generation at the time of wet milling can be reduced, there is also an effect that the thermal load on the machine at the time of milling is reduced.

Claims (6)

(Meth) acrylic acid (salt) monomer having an alkyl group of 4 to 8 carbon atoms and an alkyl (meth) acrylic acid (salt) monomer having an alkyl group of 4 to 8 as an essential constituent, and an alcohol having 4 to 8 carbon atoms Wherein the mass ratio of the alcohol having 4 to 8 carbon atoms to the (meth) acrylic acid (salt) -based copolymer is 1000 to 30000 ppm. The dispersant for aqueous calcium carbonate according to claim 1, wherein the mass ratio of the alcohol having 4 to 8 carbon atoms to the (meth) acrylic acid (salt) based copolymer is 2000 to 15000 ppm. The positive resist composition as claimed in claim 1 or 2, which comprises 60 to 95 mass% of a (meth) acrylic acid (salt) monomer, 5 to 40 mass% of a (meth) acrylic acid alkyl ester monomer having an alkyl group having 4 to 8 carbon atoms, (Meth) acrylic acid (salt) -based copolymer containing 0 to 10% by mass of a monomer. The dispersant of claim 1 or 2, wherein the (meth) acrylic acid alkyl ester monomer having 4 to 8 carbon atoms is butyl (meth) acrylate and the alcohol having 4 to 8 carbon atoms is butyl alcohol. The aqueous dispersing agent for calcium carbonate according to claim 1 or 2, which is a dispersant for wet pulverization. A wet grinding method of calcium carbonate characterized by using the aqueous dispersing agent for calcium carbonate according to any one of claims 1 to 3 for wet grinding calcium carbonate.