JP2004315359A - Dispersant for calcium bicarbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersant for producing calcium bicarbonate having excellent initial flowability and flow stability. <P>SOLUTION: The dispersant contains as an essential constitutional unit a copolymer (A) composed of a vinyl group-containing monocarboxylic acid (salt) (AA) and a vinyl group-containing dicarboxylic acid (salt)(MA) and the dispersant is used in which (1) the content molar ratio (AA/MA) of an AA unit to a MA unit is 1-4, (2) the weight average molecular weight (Mw) of A is 15,000-55,000, (3) the ratio (Mw)/(Mn) of (Mw) to the number average molecular weight (Mn) is 1.3-2.8 and (4) A is composed of a copolymer (A1) having a molecular weight of ≥1,000 to ≤15,000, a copolymer (A2) having a molecular weight of ≥15,000 to ≤55,000 and a copolymer (3) having a molecular weight of ≥55,000 to ≤600,000 and (A) contains 70-20 wt.% A1, 30-50 wt.% A2 and 1-35 wt.% A3 based on the weight of A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dispersant for heavy calcium carbonate. More specifically, the present invention relates to a heavy calcium carbonate dispersant suitable for a specific heavy calcium carbonate.

  An α, β-amino group in which 10 to 99.99% by mol of a carboxy group is an alkali metal salt or an alkaline earth metal salt, 0.01 to 5% by mol is an organic amine salt, and 0 to 89.99% by mol is a carboxy group. A pigment dispersant comprising a saturated carboxylic acid copolymer has been proposed (Patent Document 1).

Japanese Patent No. 2984926

However, with the conventional dispersants, the initial fluidity and fluidity stability (long-term dispersion stability) of the slurry may be insufficient. In particular, narrow particle size distribution (in particular, be determined from the accumulated volume particle size distribution measured by a laser diffraction scattering method, a particle diameter corresponding to cumulative particle size 10% (D ₁₀₎ and the corresponding particle size cumulative particle size 90% (D ₉₀ ) grain and diameter ratio (D ₉₀ / D ₁₀₎ is like when applied to a calcium carbonate 3.0-6.0), there is an initial fluidity and flow stability of the slurry is a problem that insufficient. That is, an object of the present invention is to provide a dispersant capable of producing a heavy calcium carbonate slurry having excellent initial fluidity and flow stability even when the particle size distribution of the heavy calcium carbonate is narrow.

The present inventors have conducted intensive studies in order to solve such problems, and have found that a specific copolymer achieves the above object, and have reached the present invention. That is, the feature of the dispersant for heavy calcium carbonate of the present invention is that a copolymer comprising a vinyl group-containing monocarboxylic acid (salt) (AA) and a vinyl group-containing dicarboxylic acid (salt) (MA) as essential constituent units ( A)
(1) The molar ratio (AA / MA) of the (AA) unit and the (MA) unit is from 1 to 4,
(2) the weight average molecular weight (Mw) of (A) is 15,000 to 55,000,
(3) The ratio (Mw / Mn) of (Mw) to the number average molecular weight (Mn) of (A) is 1.3 to 2.8,
(4) (A) is a copolymer (A1) having a molecular weight of 1,000 or more and less than 15,000, a copolymer (A2) having a molecular weight of 15,000 or more and less than 55,000, and a molecular weight of 55,000 or more and 600,000. It consists of the following copolymer (A3), (A1) is 70 to 20% by weight, (A2) is 30 to 50% by weight, (A3) is 0 or 1 to 35% by weight based on the weight of (A). The point is%.

The dispersant for heavy calcium carbonate of the present invention can produce a heavy calcium carbonate slurry having excellent initial fluidity and flow stability even when the particle size distribution of heavy calcium carbonate is narrow. Further, the dispersant of the present invention exhibits excellent dispersibility to inorganic pigments other than heavy calcium carbonate, but is particularly suitable for heavy calcium carbonate among inorganic pigments. % Of the particle diameter (D ₅₀ ) corresponding to 0.3% to 0.8 μm, and the particle diameter (D ₁₀ ) corresponding to the cumulative particle diameter of 10% and the particle diameter (D ₉₀ ) corresponding to the cumulative particle diameter of 90%. the ratio (D ₉₀ / D ₁₀₎ is optimal for heavy calcium carbonate is 3.0 to 6.0.

The vinyl group-containing monocarboxylic acid (salt) (AA) means a vinyl group-containing monocarboxylic acid (AA1) and / or a vinyl group-containing monocarboxylic acid salt (AA2).
Examples of the vinyl group-containing monocarboxylic acid (AA1) include aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, and aromatic monocarboxylic acids.

  As the aliphatic monocarboxylic acid, an aliphatic monocarboxylic acid having 3 to 10 carbon atoms or the like can be used, and (meth) acrylic acid, crotonic acid, 3-butenoic acid, 2-pentenoic acid, 3-pentenoic acid, 4-pentenoic acid, Pentenoic acid, 3-methyl-2-butenoic acid, 3-methyl-3-butenoic acid, 2-methyl-3-butenoic acid, 2-methyl-2-butenoic acid, 2-ethyl-2-propenoic acid, 2- Hexenoic acid, 4-methyl-2-pentenoic acid, 2-methyl-2-pentenoic acid, 2-heptenoic acid, 4,4-dimethyl-2-pentenoic acid, 2-octenoic acid, 3-methyl-2-heptenoic acid , 2-nonenoic acid, 3-methyl-2-octenoic acid, 2-decenoic acid and 2-hydroxypropenoic acid. In addition, (meth) acryl means acryl and / or methacryl.

  As the alicyclic monocarboxylic acid, an alicyclic monocarboxylic acid having 6 to 10 carbon atoms or the like can be used, and 1-cyclopentenecarboxylic acid, 3-cyclopentenecarboxylic acid, 4-cyclopentenecarboxylic acid, 1-cyclohexenecarboxylic acid, 3-cyclohexene carboxylic acid, 4-cyclohexene carboxylic acid, 1-cycloheptene carboxylic acid, 3-cycloheptene carboxylic acid, 4-cycloheptene carboxylic acid, 5-cycloheptene carboxylic acid, 1-cyclooctene carboxylic acid 3-cyclooctenecarboxylic acid, 4-cyclooctenecarboxylic acid, 5-cyclooctenecarboxylic acid, 1-cyclononenecarboxylic acid, 3-cyclononenecarboxylic acid, 4-cyclononenecarboxylic acid, 5-cyclononenecarboxylic acid, 1-cyclodekencarboxylic acid, 3-cyclodekencarboxylic acid 4-cyclopropyl detect carboxylic acid and 5-cyclopropyl detect carboxylic acid and the like.

As the aromatic monocarboxylic acid, an aromatic monocarboxylic acid having 9 to 17 carbon atoms or the like can be used, and orthocarboxystyrene, paracarboxystyrene, cinnamic acid, atropic acid, benzyl (meth) acrylate, 5-vinyl-1 -Naphthalenecarboxylic acid, 4-vinyl-1-naphthalenecarboxylic acid and 4-vinyl-1-anthraquinonecarboxylic acid.
Among these, aliphatic monocarboxylic acids are preferable, acrylic acid, methacrylic acid and crotonic acid and 3-butenoic acid are particularly preferable, acrylic acid, methacrylic acid and crotonic acid are particularly preferable, and acrylic acid and methacrylic acid are more preferable. And most preferably acrylic acid.

Examples of the vinyl group-containing monocarboxylic acid salt (AA2) include alkali metal salts, alkaline earth metal salts, amine salts, ammonium salts and / or quaternary organic ammonium salts of vinyl group-containing monocarboxylic acids (AA1). It is.
Incidentally, the vinyl group-containing monocarboxylic acid includes the aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, and aromatic monocarboxylic acid described in the description of the vinyl group-containing monocarboxylic acid (AA1). Is the same.

Examples of the alkali metal salt include salts such as lithium, potassium and sodium.
Examples of the alkaline earth metal salt include salts such as calcium and magnesium.
As the amine salt, a salt such as an aliphatic amine having 2 to 6 carbon atoms, an alicyclic amine having 3 to 6 carbon atoms, or an aromatic amine having 6 to 8 carbon atoms can be used.
Examples of the aliphatic amine include ethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, 2-amino-2-methylpropanol, dimethylethanolamine, diethylethanolamine, and ethylenediamine.
Examples of the alicyclic amine include cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, and the like.
Examples of the aromatic amine include aniline, pyridine, piperidine, benzylamine, and phenylenediamine.
As the quaternary organic ammonium salt, an organic ammonium salt having 4 to 8 carbon atoms and the like can be used, such as a tetramethylammonium salt, a tetraethylammonium salt, a trimethylethylammonium salt, an N-methylpyridinium salt and an N-methylimidazolium salt Is mentioned.
Among these salts, alkali metal salts, amine salts and ammonium salts are preferred, and lithium salts, potassium salts, sodium salts and ammonium salts are more preferred, and sodium salts and ammonium salts are particularly preferred. That is, among the vinyl group-containing monocarboxylic acid salts (AA2), alkali metal salts, amine salts and ammonium salts of aliphatic monocarboxylic acids are preferred, and acrylic acid, methacrylic acid, crotonic acid or 3-butenoic acid is more preferred. Alkali metal salts, amine salts and ammonium salts, particularly preferably lithium, potassium, sodium and ammonium salts of acrylic acid, methacrylic acid or crotonic acid, more preferably lithium and potassium salts of acrylic acid or methacrylic acid, Sodium and ammonium salts, most preferably the sodium and ammonium salts of acrylic acid.

  Either one or both of these vinyl group-containing monocarboxylic acids (AA1) and vinyl group-containing monocarboxylic acid salts (AA2) can be used as essential constituent units. Or two or more of them may be used in combination.

The vinyl group-containing dicarboxylic acid (salt) (MA) means a vinyl group-containing dicarboxylic acid (MA1) and / or a vinyl group-containing dicarboxylic acid salt (MA2).
Examples of the vinyl group-containing dicarboxylic acid (MA1) include aliphatic dicarboxylic acids (anhydrides), alicyclic dicarboxylic acids, and aromatic dicarboxylic acids.
In addition, an aliphatic dicarboxylic acid (anhydride) means an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic anhydride.

  As the aliphatic dicarboxylic acid (anhydride), an aliphatic dicarboxylic acid (anhydride) having 4 to 11 carbon atoms can be used, and maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, butene Diacid, 2-pentenedioic acid, 3-pentenoic acid, 4-pentenoic acid, 2-methyl-2-butenedioic acid, 2-ethyl-2-propenoic acid, 2-hexenedioic acid, 2-heptenedioic acid, Examples include 2-octenoic acid, 3-methyl-2-heptenedioic acid, 2-nonenedioic acid, 2-decenedioic acid, and 2-hydroxybutenediodic acid.

  As the alicyclic dicarboxylic acid, an alicyclic dicarboxylic acid having 6 to 10 carbon atoms or the like can be used, and 1,2-cyclopentenedicarboxylic acid, 1,3-cyclopentenedicarboxylic acid, 1,4-cyclopentenedicarboxylic acid, 2-cyclohexene dicarboxylic acid, 1,3-cyclohexene dicarboxylic acid, 1,4-cyclohexene dicarboxylic acid, 1,2-cycloheptene dicarboxylic acid, 1,3-cycloheptene dicarboxylic acid, 1,4-cycloheptene dicarboxylic acid Acid, 1,5-cycloheptenedicarboxylic acid, 1,2-cyclooctenedicarboxylic acid, 1,3-cyclooctenedicarboxylic acid, 1,4-cyclooctenedicarboxylic acid, 1,5-cyclooctenedicarboxylic acid, 1, 2-cyclononene dicarboxylic acid, 1,3-cyclononene dicarboxylic acid, 1,4-cyclononene Examples include dicarboxylic acid, 1,5-cyclononenedicarboxylic acid, 1,2-cyclodekenedicarboxylic acid, 1,3-cyclodekenedicarboxylic acid, 1,4-cyclodekenedicarboxylic acid, and 1,5-cyclodekenedicarboxylic acid. Can be

As the aromatic dicarboxylic acid, an aromatic dicarboxylic acid having 9 to 17 carbon atoms and the like can be used, and o, p-dicarboxystyrene, o, p-dicarboxystyrene, 4-vinyl-1,2-naphthalenedicarboxylic acid and 4-vinyl-1,3-anthraquinone dicarboxylic acid and the like.
Of these, aliphatic dicarboxylic acids are preferred, more preferably maleic acid, maleic anhydride, itaconic acid, fumaric acid and crotonic acid, particularly preferably maleic acid, maleic anhydride, itaconic acid and crotonic acid, more particularly preferably. Maleic acid and maleic anhydride, most preferably maleic anhydride.

Examples of the vinyl group-containing dicarboxylate (MA2) include alkali metal salts, alkaline earth metal salts, amine salts, ammonium salts and / or quaternary ammonium salts of vinyl group-containing dicarboxylic acids.
The vinyl group-containing dicarboxylic acid includes the aliphatic dicarboxylic acid, alicyclic dicarboxylic acid, aromatic dicarboxylic acid, and the like described for the vinyl group-containing dicarboxylic acid unit (MA1). (Excluding anhydrides).
The alkali metal salt, alkaline earth metal salt, amine salt and ammonium salt are the same as the vinyl group-containing carboxylate (AA2), and the preferred range is also the same. That is, among the vinyl group-containing dicarboxylates (MA2), an alkali metal salt, an amine salt and an ammonium salt of an aliphatic dicarboxylic acid (excluding an aliphatic dicarboxylic anhydride) are preferable, and more preferably maleic acid, itaconic acid, or the like. Alkali metal, amine and ammonium salts of fumaric acid or crotonic acid, particularly preferably the lithium, potassium, sodium and ammonium salts of maleic acid, itaconic acid or crotonic acid, particularly preferably maleic acid, itaconic acid or crotonic acid Sodium and ammonium salts of acids, most preferably the sodium and ammonium salts of maleic acid.
Either one or both of these vinyl group-containing dicarboxylic acids (MA1) and vinyl group-containing dicarboxylic acid salts (MM2) may be used as an essential constituent unit, and only one of each may be used. Two or more types may be used in combination.

The copolymer (A) may contain, as a structural unit, other copolymerizable monomers in addition to the vinyl group-containing monocarboxylic acid (salt) (AA) and the vinyl group-containing dicarboxylic acid (salt) (MA).
The other copolymerizable monomer may be any monomer that can be copolymerized with a vinyl group-containing monocarboxylic acid (salt) (AA) and a vinyl group-containing dicarboxylic acid (salt) (MA). , Vinyl group-containing amides (such as (meth) acrylamide and N-propenylacetamide), vinyl group-containing sulfonic acids p-styrenesulfonic acid, vinylsulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid and (meth) ) Acryloxyethanesulfonic acid, etc., vinyl group-containing nitriles, such as acrylonitrile, methacrylonitrile and cyanostyrene, and vinyl group-containing esters, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid -2-ethylhexyl and polyethylene glycol (degree of polymerization 2-50) mono (meth) Acrylic acid esters and the like}.

Each constituent monomer in the copolymer (A) may be in the form of a block, a random, or a combination thereof, but from the viewpoint of productivity and the like, the random and the combination of the block and the random are preferable. And more preferably in a random form.
The content molar ratio (AA / MA) of the vinyl group-containing monocarboxylic acid (salt) (AA) unit and the vinyl group-containing dicarboxylic acid (salt) (MA) unit is preferably from 1 to 4, more preferably from 1.2 to 4. It is 3.8, particularly preferably 1.6 to 3.6, and most preferably 2.3 to 3.5. That is, the lower limit of the molar ratio (AA / MA) is preferably 1, more preferably 1.2, particularly preferably 1.6, and most preferably 2.3. Similarly, the upper limit is preferably 4. , More preferably 3.8, particularly preferably 3.6, and most preferably 3.5. Within this range, a heavy calcium carbonate slurry having more excellent initial fluidity and fluidity stability can be easily prepared.

  When a vinyl group-containing monocarboxylate (AA2) and / or a vinyl group-containing dicarboxylate (MA2) are contained, the degree of neutralization (mol%) of the copolymer (A) is determined by the carboxy group contained in (A). Is preferably from 80 to 110, more preferably from 85 to 108, particularly preferably from 90 to 105, based on the number of moles. That is, in this case, the lower limit of the degree of neutralization (mol%) of (A) is preferably 80, more preferably 85, and particularly preferably 90, based on the number of moles of the carboxy group contained in (A). Similarly, the upper limit is preferably 110, more preferably 108, and particularly preferably 105.

The degree of neutralization means the number of moles (Fn) of the carboxy group (—COOH) contained in the copolymer, the carboxylate group (—COOM; M is an alkali metal, an alkaline earth metal and / or ammonium). )) And the total number of moles (Nn) of the copolymer, the ratio of the number of moles (Cn) of the cation M (M is an alkali metal, alkaline earth metal and / or ammonium, etc.) in the copolymer 共 Cn × 100 / ( Fn + Nn)}.
The degree of neutralization is determined by using a vinyl group-containing monocarboxylic acid (AA1) and a vinyl group-containing dicarboxylic acid (MA1) and a vinyl group-containing monocarboxylic acid salt (AA2) and a vinyl group-containing dicarboxylic acid salt (MA2). The amount can be calculated from the amounts or the amounts of these constituent monomers and the neutralizing agent (such as sodium hydroxide) used. In addition, the copolymer can be determined by analyzing the copolymer as follows. That is, the number of moles of cations (Cn) in 100 g of the copolymer is determined based on ion chromatography (JIS K0102-1998) or ICP mass spectrometry (JIS K0102-1998). The total (Fn + Nn) of the carboxy group and carboxylate group contained in ( ¹ ) was determined by ¹ H-NMR method (for example, apparatus: 300 MHz superconducting NMR manufactured by VARIAN: XL-300, solvent: chloroform-d, sample concentration: 0.5% by weight). And / or ¹³ C-NMR method (e.g., apparatus: 300 MHz superconducting NMR manufactured by VARIAN: XL-300, solvent: deuterated chloroform, sample concentration: 25% by weight), and calculated from these values.

  When other comonomer is contained, the content (mol%) is based on the number of moles of vinyl group-containing monocarboxylic acid (salt) (AA) and vinyl group-containing dicarboxylic acid (salt) (MA). , 0.1 to 20, more preferably 0.3 to 15, particularly preferably 0.5 to 10.

  The weight average molecular weight (Mw) of the copolymer (A) is preferably 15,000 to 55,000, more preferably 20,000 to 50,000, and further more preferably 23,000 to 50,000, particularly Preferably from 25,000 to 50,000, then particularly preferably from 25,000 to 40,000, most preferably from 30,000 to 36,000. That is, the lower limit of (Mw) in (A) is preferably 15,000, more preferably 20,000, further more preferably 23,000, particularly preferably 25,000, and most preferably 30,000. Similarly, the upper limit is preferably 55,000, more preferably 50,000, then particularly preferably 40,000 and most preferably 36,000. Within this range, a heavy calcium carbonate slurry having more excellent initial fluidity and fluidity stability can be easily prepared.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the copolymer (A) is preferably from 1.3 to 2.8, more preferably from 1.4 to 2.6, Next, it is more preferably 1.5 to 2.6, particularly preferably 1.6 to 2.6, then particularly preferably 1.6 to 2.4, and most preferably 1.6 to 2.3. That is, the lower limit of (Mw / Mn) in (A) is preferably 1.3, more preferably 1.4, then more preferably 1.5, particularly preferably 1.6, and likewise the upper limit. Is preferably 2.8, more preferably 2.6, particularly preferably 2.4, and most preferably 2.3. Within this range, a heavy calcium carbonate slurry having more excellent initial fluidity and fluidity stability can be easily prepared.

  The weight average molecular weight (Mw) and number average molecular weight (Mn) are measured by gel permeation chromatography (GPC) using (poly) ethylene glycol of known molecular weight as a standard substance (column temperature: 40 ° C., elution Liquid: 0.1-MPB disodium hydrogen phosphate aqueous solution: 0.1-MPB sodium dihydrogen phosphate aqueous solution = 1: 1 (molar ratio), flow rate 0.8 ml / min, sample concentration: 0.4% by weight Eluent solution.).

  The copolymer (A) preferably contains a specific content of a specific molecular weight range, and the copolymer (A1) has a molecular weight of 1,000 or more and less than 15,000, and a molecular weight of 15,000 or more and less than 55,000. (A2) and a copolymer (A3) having a molecular weight of 55,000 or more and 600,000 or less.

The content (% by weight) of the copolymer (A1) is preferably from 20 to 70, more preferably from 25 to 55, and further more preferably from 26 to 50, particularly preferably based on the weight of the copolymer (A). Preferably it is 30-50. Within this range, it is easy to prepare a heavy calcium carbonate slurry having even better initial fluidity.
Further, the content (% by weight) of the copolymer (A2) is preferably 30 to 50, more preferably 40 to 50, and further more preferably 41 to 49, based on the weight of the copolymer (A). And particularly preferably 42 to 48. Within this range, it is easy to prepare a heavy calcium carbonate slurry having even better initial fluidity.
Further, the content (% by weight) of the copolymer (A3) is preferably 0 or 1 to 35, more preferably 5 to 25, and further more preferably 6 based on the weight of the copolymer (A). To 25, particularly preferably 7 to 25. Within this range, it is easy to prepare a heavy calcium carbonate slurry having even better flow stability.

That is, the lower limit of the content (% by weight) of (A1) is preferably 20, more preferably 25, then more preferably 26, and particularly preferably 30, based on the weight of (A). The upper limit is preferably 70, more preferably 55, and even more preferably 50. In addition, the lower limit of the content (% by weight) of (A2) is preferably 30 based on the weight of (A), more preferably 40, and still more preferably 41, particularly preferably 42, and the same. Is preferably 50, more preferably 49, particularly preferably 48. Further, the lower limit of the content (% by weight) of (A3) is preferably 0 or 1, more preferably 5, then more preferably 6, and particularly preferably 7, based on the weight of (A). Similarly, the upper limit is preferably 35, and more preferably 25.
If necessary, a component having a specific molecular weight range may be fractionated by a liquid separation extraction method and / or an ultrafiltration membrane method to prepare a copolymer having a specific molecular weight range.
The content of the components in each molecular weight range can be determined from the area ratio of each range using GPC results (chart) measured using (poly) ethylene glycol having a known molecular weight as a standard substance.

The copolymer (A) can be obtained by using a known polymerization method such as a solution polymerization method, a pearl polymerization method, and an inverse emulsion polymerization method, but is not particularly limited.
In the case of a solution polymerization method or the like, the copolymer (A) is obtained by mixing a vinyl group-containing monocarboxylic acid (salt) (AA), a vinyl group-containing dicarboxylic acid (salt) (MA) and, if necessary, other copolymerized monomers. It can be obtained by a method of polymerizing in water and / or a solvent at 40 to 130 ° C. for 1 to 12 hours in the presence of a polymerization initiator and / or a chain transfer agent. Then, the entire amount of the vinyl group-containing monocarboxylic acid (salt) (AA), the vinyl group-containing dicarboxylic acid (salt) (MA), and other comonomer used as needed may be charged into the polymerization tank and polymerized. Alternatively, a drop polymerization method may be appropriately employed. Further, a method of charging a part of the monomers into the polymerization tank and dropping the remaining monomers may be used. The polymerization initiator may be present in the polymerization tank in advance of the polymerization, or a method of continuously charging the polymerization initiator during the polymerization may be adopted. Further, the vinyl group-containing monocarboxylic acid (AA1), the vinyl group-containing dicarboxylic acid (MA1) and, if necessary, other copolymerized monomers are neutralized before polymerization, and the vinyl group-containing monocarboxylic acid salt (AA2), vinyl It may be in the form of a group-containing dicarboxylic acid (MA2), may be in the form of a salt after polymerization, or may be used in combination.

  In the case of a pearl polymerization method or the like, the copolymer (A) is prepared by adding a vinyl group-containing monocarboxylic acid (salt) (AA), a vinyl group-containing dicarboxylic acid (salt) (MA) and optionally a hydrophobic solvent (in a boiling state). It is obtained by, for example, a method in which a solution of a polymerization initiator is added dropwise in the presence of a polymerization retarder while gradually dropping other copolymerized monomers to carry out polymerization.

In the case of reverse phase emulsion polymerization or the like, the copolymer (A) is composed of a vinyl group-containing monocarboxylic acid (salt) (AA), a vinyl group-containing dicarboxylic acid (salt) (MA) and, if necessary, other copolymer monomers. Is obtained by emulsifying and dispersing an aqueous solution of the above in a hydrophobic solvent in the presence of a polymerization initiator and an emulsifier, and heating the reaction mixture at 40 to 130 ° C. for 1 to 20 hours with stirring. Then, the vinyl group-containing monocarboxylic acid (salt) (AA), the vinyl group-containing dicarboxylic acid (salt) (MA) and, if necessary, the total amount of the comonomer used may be charged into the polymerization tank and polymerized. Moreover, you may employ | adopt the dripping polymerization method suitably. Further, a method of charging a part of the monomers into the polymerization tank and dropping the remaining monomers may be used. The polymerization initiator may be present in the polymerization tank in advance of the polymerization, or a method of continuously charging the polymerization initiator during the polymerization may be adopted. After the polymerization, the hydrophobic solvent is preferably distilled off.
Among these polymerization methods, solution polymerization is preferred.

As the polymerization initiator, known polymerization initiators and the like can be used, and include persulfates, azo compounds, peroxides, redox initiators and the like.
Examples of the persulfate include sodium persulfate, potassium persulfate, and ammonium persulfate.
As the azo compound, 2,2′-azobis- (2-amidinopropane) dihydrochloride, 4,4′-azobis- (4-cyanovaleric acid), 2,2′-azobisisobutyronitrile and 2,2′-azobis- (4-cyanovaleric acid) 2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile) and the like.
Examples of the peroxide include benzoyl peroxide, lauroyl peroxide, peracetic acid, persuccinic acid, di-t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, hydrogen peroxide and the like.
Examples of the redox initiator include ascorbic acid-hydrogen peroxide and the like. One of these polymerization initiators may be used alone, or two or more thereof may be used in combination.
The amount (% by weight) of the polymerization initiator is preferably 0.1 to 10 based on the weight of the vinyl group-containing monocarboxylic acid (salt) (AA) and the vinyl group-containing dicarboxylic acid (salt) (MA), It is more preferably from 0.5 to 8, particularly preferably from 1 to 7.

As the chain transfer agent, known chain transfer agents and the like can be used, and include sulfur compounds, halogen compounds, alcohols and ketones.
Examples of the sulfur compound include lauryl mercaptan, dodecyl mercaptan, thioglycolic acid, mercaptoethanol, triethylene glycol dimercaptan, and tris (polyoxypropylene-2-hydroxy-3-thiolpropane) alkyl ether.
Examples of the halogen compound include chloroform, carbon tetrachloride, and methylene chloride.
Examples of the alcohol include methanol, ethanol, isopropanol and butyl alcohol.
Ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone and the like.
Of these, triethylene glycol dimercaptan, dodecyl mercaptan, tris (polyoxypropylene-2-hydroxy-3-thiolpropane) alkyl ether, carbon tetrachloride, methanol, ethanol, isopropanol and acetone are preferred, and more preferably dodecyl mercaptan , Carbon tetrachloride, methanol, ethanol, isopropanol and acetone, particularly preferably dodecyl mercaptan and isopropanol. One of these chain transfer agents may be used alone, or two or more thereof may be used in combination.
When a sulfur compound is used, the amount (% by weight) is preferably 1 to 100 based on the weight of the vinyl group-containing monocarboxylic acid (salt) (AA) and the vinyl group-containing dicarboxylic acid (salt) (MA). , More preferably 1 to 50, particularly preferably 1 to 10. The halogen compound, alcohol and ketone can be used as a reaction solvent (solvent), and may be used in the same amount as the reaction compound (solvent) in addition to the same amount as the sulfur compound.

  As the polymerization retarder, known polymerization retarders can be used, and examples thereof include allyl alcohol, α-methylstyrene, o-dinitrobenzene, vinyl acetate, triphenylchloromethane, and hexamethylparafuchsin. When a polymerization retarder is used, the amount used is preferably substantially the same as the polymerization initiator.

As the emulsifier, a known emulsifier can be used, and an anionic emulsifier, a nonionic emulsifier, and the like are used.
Examples of the anionic emulsifier include fatty acid soap having 12 to 20 carbon atoms, rosin soap, sodium alkylbenzene sulfonate (such as ABS and LAS), alkyl sulfate having 12 to 14 carbon atoms, sodium alkene sulfonate, and alkyl ether sulfonate (AES). Dialkyl sulfosuccinic acid soaps and sodium naphthalene sulfonate formalin condensates. Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, and the like. Note that two or more emulsifiers may be used in combination.
When an emulsifier is used, the amount (% by weight) is based on the weight of the vinyl group-containing monocarboxylic acid (salt) (AA) and the vinyl group-containing dicarboxylic acid (salt) (MA), and the amount of the anionic activator is 0%. 0.1 to 10, and the nonionic activator is preferably 0.1 to 4.

Solvents for the polymerization include known hydrophilic solvents and known hydrophobic solvents. For solution polymerization, hydrophilic solvents include alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, ethylene glycol, isopropyl alcohol, glycerin and diethylene glycol, and ketones having 3 to 4 carbon atoms acetone and methyl-2-chloro. Ethyl ketone and the like can be used. For reverse phase emulsion polymerization and suspension polymerization, as a hydrophobic solvent, alcohols having 4 to 8 carbon atoms (such as n-butyl alcohol, isobutyl alcohol, t-butyl alcohol and 2-ethylhexyl alcohol), and ketones having 4 to 6 carbon atoms {Methyl ethyl ketone, ethyl propyl ketone, methyl isobutyl ketone, etc.}, esters having 3 to 8 carbon atoms >> Ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, methyl hexanoate, ethyl hexanoate, hexyl acetate, etc. ｝, An aliphatic hydrocarbon having 5 to 8 carbon atoms ｛pentane, hexane, cyclohexane, ethylcyclohexane, heptane, 2-ethylhexane and the like｝, an aromatic hydrocarbon having 6 to 10 carbon atoms ｛benzene, toluene, xylene and butylbenzene Etc. can be used.
One of these solvents may be used alone, or two or more thereof may be used in combination.

  In the case of solution polymerization, as a reaction solvent, water and an alcohol having 1 to 4 carbon atoms are preferable, and water, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol and t are more preferable. -Butyl alcohol, more preferably water, methyl alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol, particularly preferably water and isopropyl alcohol.

  In the case of reverse-phase emulsion polymerization and suspension polymerization, the reaction solvent is preferably an alcohol having 4 to 8 carbon atoms, a ketone having 4 to 6 carbon atoms, or an aliphatic hydrocarbon having 5 to 8 carbon atoms, and more preferably having 5 to 8 carbon atoms. 5-8 aliphatic hydrocarbons, particularly preferably hexane, cyclohexane, ethylcyclohexane and heptane, most preferably hexane and heptane.

(1) To make the content molar ratio (AA / MA) of the vinyl group-containing monocarboxylic acid (salt) (AA) unit and the vinyl group-containing dicarboxylic acid (salt) (MA) unit from 1 to 4, i) ( What is necessary is just to make the use ratio of AA) and (MA) into the said range.

(2) To make the weight average molecular weight (Mw) of the copolymer (A) 15,000 to 55,000, ii) a vinyl group-containing monocarboxylic acid (salt) (AA), vinyl The monomer concentration at the end of the dropping of the group-containing dicarboxylic acid (salt) (MA) and, if necessary, other copolymerizable monomers (hereinafter, these are abbreviated as monomers) is 20 to 46% by weight based on the weight of the polymerization solution. Iii) a method in which the polymerization initiator is used in an amount of 0.1 to 10% by weight based on the weight of the monomer; A method of adjusting the monomer dropping time to 100 to 180 minutes by adjusting the monomer concentration to 46% by weight, and iv) a monomer concentration at the end of the monomer dropping is 20 to 46% by weight based on the weight of the polymerization solution by a solution polymerization method. Adjusting method for adjusting the dropping time of the catalyst in 100 to 180 minutes can be applied to.

(3) In order to make the ratio (Mw / Mn) of (Mw) to the number average molecular weight (Mn) of the copolymer (A) 1.3 to 2.8, v) the monomer and the polymer are obtained by the solution polymerization method. A method in which the initiator is dropped at a constant speed in 120 to 180 minutes, and a method in which the monomer concentration at the time of dropping is adjusted to 10 to 46% by weight based on the weight of the polymerization solution; and Is adjusted to 20 to 50% by weight based on the weight of the polymerization solution, and a method in which the chain transfer agent is used in an amount of 0.1 to 10 parts by weight based on the monomer can be applied.

(4) The copolymer (A) is a copolymer (A1) having a molecular weight of 1,000 or more and less than 15,000, a copolymer (A2) having a molecular weight of 15,000 or more and less than 55,000, and a molecular weight of 55,000 or more. (A1) is 70 to 20% by weight, (A2) is 30 to 50% by weight, and (A3) is 0, based on the weight of (A). Or from 1 to 35% by weight, vii) by a solution polymerization method, adjusting the monomer concentration at the end of the dropwise addition of the monomer to 15 to 40% by weight based on the weight of the polymerization solution, and adding the chain transfer agent to the monomer. Viii) by a solution polymerization method, adjusting the monomer concentration at the end of the monomer dropping to 10 to 30% by weight based on the weight of the polymerization solution, and setting the monomer dropping time to 120% by weight. Adjust to ~ 180 minutes And ix) a method of adjusting the monomer concentration at the end of the dropping of the monomer to 10 to 30% by weight based on the weight of the polymerization solution by a solution polymerization method, and charging the polymerization initiator all at once to the polymerization tank before dropping the monomer. Etc. can be applied.

  That is, as a method for satisfying all of (1) to (4), a method combining methods i), ii), v) and vii), a method combining methods i), ii), v) and viii), i ), Ii), v) and ix), a method combining methods i), ii), vi) and vii), a method combining methods i), ii), vi) and viii), a method i ), Ii), vi) and ix), methods i), iii), v) and vii), methods i), iii), v) and viii), methods i), a method combining iii), v) and ix), a method combining methods i), iii), vi) and vii), a method combining methods i), iii), vi) and viii) A method, a method combining methods i), iii), vi) and ix), a method combining methods i), iv), v) and vii), a method combining methods i), iv), v) and viii), A method combining methods i), iv), v) and ix), a method combining methods i), iv), vi) and vii), a method combining methods i), iv), vi) and viii), and a method A method of combining i), iv), vi) and ix) can be applied.

  The dispersant for heavy calcium carbonate of the present invention may contain other components in addition to the copolymer (A). Other components include an antifoaming agent ｛an emulsion mainly composed of a higher alcohol having 12 to 24 carbon atoms, an alkylene oxide of a monohydric or polyhydric alcohol such as stearyl alcohol, dipropylene glycol, glycerin and sorbitan (carbon (2-4) adducts, alkylene oxide (2-4 carbons) adducts of alkyl phenols having 7-24 carbon atoms, or those having, as main components, those obtained by esterifying terminal hydroxyl groups thereof; antioxidants {A substance containing erythorbic acid, sodium eirisorbate, ascorbic acid, sodium ascorbate, isopropyl citrate, dibutylhydroxytoluene or butylhydroxyanisole as a main component} and a preservative {5-chloro-2-methyl-4-isothiazoline- 3-one, 2-n-octyl-4-isothiazo Down-3-one or hexahydro-1,3,5-tris (2-hydroxyethyl) as the main component -s- triazine}, or the like is used.

The dispersant for heavy calcium carbonate of the present invention is dissolved in a solvent such as water (for example, a hydrophilic reaction solvent) even in a solid state comprising only the copolymer (A) and other components as necessary. It may be in a solution state or an emulsified and dispersed state in which it is emulsified and dispersed in a solvent (for example, a hydrophobic solvent among reaction solvents).
The solid state may be any of powder, granule and lump, but from the viewpoint of ease of use, powder and granule are preferred.
In the case of a solution state, the content (% by weight) of the copolymer (A) is based on the weight of the dispersant from the viewpoint of easy adjustment of the concentration of heavy calcium carbonate in the heavy calcium carbonate slurry. , Preferably from 20 to 55, more preferably from 25 to 50, particularly preferably from 30 to 45. In order to obtain a solution state, after polymerization, the solid state may be obtained by drying, and this may be dissolved in water and / or a solvent. The method is preferably a method of adjusting the concentration by adopting a solution polymerization method, if necessary.

In the case of the emulsified dispersion state, the content (% by weight) of the copolymer (A) is based on the weight of the dispersant from the viewpoint of easy adjustment of the concentration of heavy calcium carbonate in the heavy calcium carbonate slurry. Thus, it is preferably from 10 to 40, more preferably from 20 to 35, particularly preferably from 25 to 32. In order to obtain an emulsified and dispersed state, after polymerization, the solid state is obtained by drying, and this may be emulsified and dispersed in a solvent. However, it is preferable to adopt a pearl polymerization method and adjust the concentration as necessary.
Among these, a solution state and an emulsified dispersion state are preferable from the viewpoint of handleability and the like.

The dispersant for heavy calcium carbonate of the present invention is suitable for dispersing (slurrying) heavy calcium carbonate in water and / or a water-soluble solvent. % (D ₅₀ ) is 0.3 to 0.8 μm (preferably 0.4 to 0.7, particularly preferably 0.5 to 0.6), and the particle size corresponds to an integrated particle size of 10%. (D ₁₀₎ and particle diameter ratio of the particle diameter corresponding to cumulative particle size _{90% (D 90) (D} 90 / D 10) is 3.0 to 6.0 (preferably 4.0 to 5.5, particularly It is most suitable for heavy calcium carbonate which is preferably 4.5 to 5.0).
The dispersant of the present invention is used as a dispersant for other inorganic pigments (light calcium carbonate, clay, titanium oxide, calcium sulfate, barium sulfate, satin white, red iron, zinc white, ferrite, alumina, and other ceramic pigments). Also available.

The particle size (D ₅₀ ), particle size (D ₁₀ ), and particle size (D ₉₀ ) are determined from the integrated volume particle size distribution by a laser light diffraction scattering method (JIS Z8825-1: 2001).
The integrated volume particle size distribution by the laser light diffraction / scattering method can be measured by a laser light diffraction / scattering particle size distribution analyzer (for example, trade name: MICROTRAC UPA, manufactured by Leeds and Northerup), laser light wavelength: 780 nm, measurement temperature: 25 ° C. (Dispersion medium; water).

  The amount (% by weight) of the dispersant for heavy calcium carbonate of the present invention is preferably 0.01 to 5, more preferably 0.05 to 3, and particularly preferably 0, based on the weight of heavy calcium carbonate. . That is, the lower limit of the amount (% by weight) of the dispersant of the present invention is preferably 0.01, more preferably 0.05, and particularly preferably 0.1, based on the weight of the inorganic pigment. The upper limit is preferably 5, more preferably 3, and particularly preferably 2. Within this range, a heavy calcium carbonate slurry having more excellent initial fluidity and fluid stability can be obtained. The same amount is used for other inorganic pigments.

  The use amount (% by weight) of the heavy calcium carbonate is preferably 70 to 80, more preferably 71 to 78, and particularly preferably 72 to 76 based on the weight of the slurry. That is, the lower limit of the use amount (% by weight) of the heavy calcium carbonate is preferably 70, more preferably 71, and particularly preferably 72, based on the weight of the slurry, and similarly, the upper limit is preferably 80. It is preferably 78, particularly preferably 76. Within this range, a heavy calcium carbonate slurry having more excellent initial fluidity and fluid stability can be obtained.

  The dispersant for heavy calcium carbonate of the present invention can disperse heavy calcium carbonate in the same manner as a known dispersant. For example, i) a method in which a dispersant is dissolved in a prescribed amount of water, and then heavy calcium carbonate is gradually added and dispersed with stirring. Ii) The dispersant is sprayed on the heavy calcium carbonate powder and premixed. Any of the method of directly dispersing the heavy calcium carbonate in water, the method of iii) and the method of i), and the method of adding the dispersant in several portions can be employed. When used for other inorganic pigments, they can be dispersed in the same manner.

  As a disperser for dispersing the heavy calcium carbonate slurry, a known disperser or the like can be used, and examples thereof include a disperser using a medium and a disperser that disperses with a stirring blade. Examples of the disperser using a medium include an attritor, a sand mill, a rotating ball mill, a vibrating ball mill, a bead mill, and the like. Examples of the dispersing machine for dispersing with a stirring blade include a homogenizer, a disk cavitation mixer, a state roller, a Keddy mill, a colloid mill, and a Cores mixer. These dispersers may be used alone or in combination of two or more. Of these, attritors, sand mills, and coales mixers are preferred from the viewpoint of grinding efficiency.

The heavy calcium carbonate slurry using the dispersant of the present invention is applicable to applications such as a coating liquid for pigment-coated paper, a filler for papermaking, a pigment for paint paint, a reinforcing agent for rubber, a plasticizer for resin, and a toothpaste. It is particularly suitable for a coating liquid for pigment coated paper.
The coating liquid for pigment-coated paper is prepared by mixing other pigments and adhesive components with heavy calcium carbonate slurry, and if necessary, thickeners, defoamers, lubricants, wetting agents, antioxidants, and ultraviolet rays. Additives such as absorbents, waterproofing agents, coloring agents and / or preservatives can be added. Pigments blended with calcium bicarbonate slurry include light calcium carbonate, kaolin, clay, calcined clay, calcium sulfate, barium sulfate, red iron oxide, zinc white, ferrite, alumina, satin white, talc, titanium oxide, aluminum hydroxide, silica And ferrite. Examples of the adhesive component include SBR latex, NBR latex, NR latex, and polyvinyl acetate. As the thickener, sodium polycarboxylate, polycarboxylate, carboxymethylcellulose, methylcellulose, casein, oxidized starch and the like can be used. Antifoaming agents include polydimethylsiloxane, emulsions of higher alcohols, stearyl alcohol, dipropylene glycol, glycerin, sorbitan and the like, alkylene oxides added to 1-polyhydric alcohols, and alkylphenols added to alkylene oxides. Those obtained by esterifying the terminal hydroxyl groups of the above. Examples of the lubricant include emulsions such as calcium stearate, polyethylene wax, paraffin wax, and microcrystalline wax. Examples of the wetting agent include sodium sulfosuccinate, and examples of the antioxidant include erythorbic acid, sodium eirisorbate, ascorbic acid, sodium ascorbate, isopropyl citrate, dibutylhydroxytoluene, and butylhydroxyanisole. As preservatives, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, hexahydro-1,3,5 tris (2-hydroxyethyl) -s -Triazine, as a UV absorber, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, pt-butyl sylate, etc., as a water-resistant agent, an aminoaldehyde resin, glyoxal, Polyamide / epoxy resin, zirconium ammonium carbonate, zinc sulfate, satin white, etc.Colorants include phthalocyanine, organic pigments such as quinacdrine, lead white, zinc pigments and other inorganic pigments, as well as known basic dyes and acid dyes, Dyes and fluorescent dyes, and preservatives such as 5-chloro-2-methyl L-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, hexahydro-1,3,5 tris (2-hydroxyethyl) -s-triazine. Of these, only one type may be used, or two or more types may be used in combination.

  The coating liquid for pigment-coated paper is coated on a base paper mainly composed of pulp fibers on both sides or on one side, in a single layer or two or more layers, and dried to obtain a coated paper.

  Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, parts represent parts by weight and% represents% by weight. The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured as follows.

<Measurement of weight average molecular weight (Mw) and number average molecular weight (Mn)>
Equipment used: Model HLC-8120GPC manufactured by Tosoh Corporation
Column: a column in which Tosoh Corporation model G5000PWXL and model G3000PWXL are connected in series,
Detector: RI detector,
Data processor: Model SC-8020 manufactured by Tosoh Corporation
Column temperature: 40 ° C,
Eluent: A mixture of 0.1-MPB disodium hydrogen phosphate aqueous solution and 0.1-MPB sodium dihydrogen phosphate aqueous solution at a 1: 1 (molar ratio) Eluent flow rate: 0.8 ml
Sample concentration: 0.4% by weight eluent solution,
Sample solution injection volume: 50 μl,
Standard substance: Tosoh Corporation TSK standard polyethylene oxide (SE-150, weight average molecular weight (hereinafter abbreviated as M) measured by light scattering method) 885,000; SE-70, M510,000; SE-30, SE-15, M170,000; SE-8, M95,000; SE-5, M46,000; SE-2, M26,000), reagents manufactured by Wako Pure Chemical Industries, Ltd. (Wako Standard 1) Good grade polyethylene glycol 6000, M7,500; special grade ethylene glycol, molecular weight 62)

<Production Example 1>
81.4 parts of maleic anhydride and 293.9 parts of ion-exchanged water (reaction tank solution) were charged into a stainless steel reactor for polymerization equipped with a thermometer, a stirrer, a condenser, and two dropping pumps, and refluxed and stirred. Heated to 95 ° C. Then, under reflux (95 ° C.), a monomer aqueous solution obtained by previously mixing 260.0 parts of 80% acrylic acid, 173.6 parts of a 48.5% aqueous sodium hydroxide solution and 156.0 parts of ion-exchanged water was applied for 180 minutes. And the mixed catalyst solution (a mixture of 11.6 parts of sodium persulfate, 47.0 parts of 35% hydrogen peroxide solution and 11.0 parts of ion-exchanged water) was simultaneously added for 180 minutes from the other dropping pump. The polymerization was carried out while dropping at a constant speed. After the completion of the dropwise addition, reflux (95 ° C.) was maintained for another 120 minutes to complete the polymerization reaction. Next, the mixture was cooled to 40 ° C. or lower and neutralized with 152.4 parts of a 48.5% aqueous sodium hydroxide solution while maintaining the temperature at 40 ° C. or lower to obtain an aqueous solution of copolymer 1. Further, water was distilled off from the aqueous solution of the copolymer 1 by an evaporator, and the evaporation residue was adjusted to 40.5% to obtain a dispersant 1 of the present invention. The evaporation residue was measured under the condition of drying at 160 ° C. for 20 minutes in a circulating dryer (the same applies hereinafter).

<Production Example 2>
A reaction tank solution (81.4 parts of maleic anhydride and 293.9 parts of ion-exchanged water) was added to a reaction tank solution (232.0 parts of itaconic acid and 175.0 parts of ion-exchanged water) in an aqueous monomer solution (80% acrylic). 260.0 parts of an acid, 173.6 parts of a 48.5% aqueous sodium hydroxide solution, and 156.0 parts of ion-exchanged water) in a monomer aqueous solution (260.0 parts of 80% acrylic acid, 48.5% aqueous sodium hydroxide solution) A mixed catalyst solution (a mixture of 11.6 parts of sodium persulfate, 47.0 parts of 35% hydrogen peroxide and 11.0 parts of ion-exchanged water) is mixed with 230.0 and 175.0 parts of ion-exchanged water. (A mixture of 18.6 parts of sodium persulfate, 72.0 parts of 35% hydrogen peroxide solution and 60.0 parts of ion-exchanged water) and 152.4 parts of an aqueous solution of sodium hydroxide after completion of the polymerization reaction were added to 317.0 parts. Other than changed After obtaining an aqueous solution of the copolymer 2 in the same manner as in Production Example 1, the evaporation residue was adjusted to 40.5% to obtain a dispersant 2 of the present invention.

<Production Example 3>
The reaction tank solution (maleic anhydride 232.0 parts and ion-exchanged water 175.0 parts) was added to the reaction tank solution (maleic anhydride 410.0 parts and ion-exchanged water 470.0 parts) in an aqueous monomer solution (80 % Acrylic acid, 260.0 parts of a 48.5% aqueous sodium hydroxide solution, and 235.0 parts of ion-exchanged water were mixed with a monomer aqueous solution (80% acrylic acid, 260.0 parts of a 48.5% sodium hydroxide solution). A mixed catalyst solution (a mixture of 18.6 parts of sodium persulfate, 72.0 parts of 35% hydrogen peroxide and 60.0 parts of ion-exchanged water) is mixed with 261.0 parts of an aqueous solution and 261.0 parts of ion-exchanged water. To a catalyst solution (a mixture of 25.0 parts of sodium persulfate, 100.0 parts of 35% hydrogen peroxide solution and 60.0 parts of ion-exchanged water), 317.0 parts of an aqueous sodium hydroxide solution after completion of the polymerization reaction was added to 360.0 parts. Strange Except for this, an aqueous solution of the copolymer 3 was obtained in the same manner as in Production Example 1, and then the evaporation residue was adjusted to 40.5% to obtain a dispersant 3 of the present invention.

<Production Example 4>
Production Example 1 except that the reaction tank solution (maleic anhydride 81.4 parts and ion-exchanged water 293.9 parts) was changed to the reaction tank solution (maleic anhydride 81.4 parts and ion-exchanged water 900.0 parts). After obtaining an aqueous solution of the copolymer 4 in the same manner as described above, the evaporation residue was adjusted to 40.5% to obtain a dispersant 4 of the present invention.

<Production Example 5>
Production Example 1 except that the reaction tank solution (81.4 parts of maleic anhydride and 293.9 parts of ion-exchanged water) was changed to the reaction tank solution (81.3 parts of maleic anhydride and 428.0 parts of ion-exchanged water). After obtaining an aqueous solution of the copolymer 5 in the same manner as described above, the evaporation residue was adjusted to 40.5% to obtain the dispersant 5 of the present invention.

<Production Example 6>
Production Example 1 except that the reaction tank solution (81.4 parts of maleic anhydride and 293.9 parts of ion-exchanged water) was changed to the reaction tank solution (81.4 parts of maleic anhydride and 162.0 parts of ion-exchanged water). After obtaining an aqueous solution of the copolymer 6 in the same manner as described above, the evaporation residue was adjusted to 40.5% to obtain a dispersant 6 of the present invention.

<Production Example 7>
Production Example 1 except that the reaction tank solution (81.4 parts of maleic anhydride and 293.9 parts of ion-exchanged water) was changed to the reaction tank solution (81.4 parts of maleic anhydride and 136.1 parts of ion-exchanged water). After obtaining an aqueous solution of the copolymer 7 in the same manner as described above, the evaporation residue was adjusted to 40.5% to obtain the dispersant 7 of the present invention.

<Production Example 8>
500 parts of ion-exchanged water and 2,000 parts of acetone were added to 100 parts of the aqueous solution of the copolymer 1 obtained in Production Example 1, and the mixture was stirred and allowed to stand for 12 hours. After separating into two layers, the upper layer was concentrated under reduced pressure. An aqueous solution of the copolymer 8 was obtained. Water was distilled off from this aqueous solution to adjust the evaporation residue to 40.5% to obtain Dispersant 8 of the present invention.

<Production Example 9>
After obtaining an aqueous solution of the copolymer 9 in the same manner as in Production Example 1 except that the dropping time of the monomer aqueous solution and the mixed catalyst solution was changed from 180 minutes to 120 minutes, the evaporation residue was adjusted to 40.5%. Inventive dispersant 9 was obtained.

<Production Example 10>
An aqueous solution of the copolymer 10 was obtained in the same manner as in Production Example 1 except that 152.4 parts of the aqueous sodium hydroxide solution after the completion of the polymerization reaction was changed to 117.6 parts, and the evaporation residue was reduced to 40.5%. After the preparation, a dispersant 10 of the present invention was obtained.

<Production Example 11>
An aqueous solution of the copolymer 11 was obtained in the same manner as in Production Example 1 except that the aqueous sodium hydroxide solution, 152.4 parts after the completion of the polymerization reaction was changed to 190.5 parts, and the evaporation residue was reduced to 40.5%. After the preparation, a dispersant 11 of the present invention was obtained.

<Production Example 12>
After an aqueous solution of the copolymer 12 was obtained in the same manner as in Production Example 1, except that the sodium hydroxide aqueous solution 152.4 parts after the completion of the polymerization reaction was changed to 227.0 parts, the evaporation residue was reduced to 40.5%. After the preparation, a dispersant 12 of the present invention was obtained.

<Production Example 13>
A reaction tank solution (81.4 parts of maleic anhydride and 293.9 parts of ion-exchanged water) was added to a reaction tank solution (232.0 parts of maleic anhydride and 175.0 parts of ion-exchanged water) in an aqueous monomer solution (80% 260.0 parts of acrylic acid, 173.6 parts of a 48.5% aqueous sodium hydroxide solution and 156.0 parts of ion-exchanged water were converted into a monomer aqueous solution (260.0 parts of 80% acrylic acid, 48.5% potassium hydroxide) Aqueous solution (242.8 parts) and ion-exchanged water (175.0 parts) except that the polymerization reaction-completed 48.5% aqueous sodium hydroxide solution (152.4 parts) was changed to a 48.5% potassium hydroxide aqueous solution (214.0 parts). After obtaining an aqueous solution of the copolymer 13 in the same manner as in Production Example 1, the evaporation residue was adjusted to 40.5% to obtain a dispersant 13 of the present invention.

<Comparative Production Example 1>
Copolymer 14 was produced in the same manner as in Production Example 1 except that the reaction tank solution (81.4 parts of maleic anhydride and 293.9 parts of ion-exchanged water) was changed to a reaction tank solution (555.0 parts of ion-exchanged water). After obtaining an aqueous solution of the above, the evaporation residue was adjusted to 40.5% to obtain a dispersant 14 for comparison.

<Comparative Production Example 2>
An aqueous monomer solution (260.0 parts of 80% acrylic acid, 173.6 parts of a 48.5% aqueous sodium hydroxide solution, and 156.0 parts of ion-exchanged water) was mixed with an aqueous monomer solution (61.0 parts of 80% acrylic acid, After an aqueous solution of the copolymer 15 was obtained in the same manner as in Production Example 1 except that the amount was changed to 168.0 parts of a 48.5% aqueous sodium hydroxide solution and 156.0 parts of ion-exchanged water, the evaporation residue was reduced to 40.50 parts. The dispersion was adjusted to 5% to obtain a dispersant 15 for comparison.

<Comparative Production Example 3>
Same as Production Example 1 except that the reaction tank solution (maleic anhydride 81.4 parts and ion-exchanged water 293.9 parts) was changed to the reaction tank solution (maleic anhydride 232.0 parts and ion-exchanged water 1340 parts) After obtaining an aqueous solution of the copolymer 16, the evaporation residue was adjusted to 40.5% to obtain a dispersant 16 for comparison.

<Comparative Production Example 4>
Production Example 1 except that the reaction tank solution (81.4 parts of maleic anhydride and 293.9 parts of ion-exchanged water) was changed to the reaction tank solution (232.0 parts of maleic anhydride and 122.0 parts of ion-exchanged water). After obtaining an aqueous solution of the copolymer 17 in the same manner as described above, the evaporation residue was adjusted to 40.5% to obtain a dispersant 17 for comparison.

<Comparative Production Example 5>
To 100 parts of the aqueous solution of the copolymer 1 obtained in Production Example 1, 500 parts of ion-exchanged water and 2,000 parts of acetone were added, stirred, and allowed to stand for 12 hours (separated into two layers). After the lower layer was removed, 500 g of acetone was further added to the upper layer, and the mixture was allowed to stand for 12 hours. Thereafter, of the two layers separated, the lower layer was concentrated under reduced pressure to obtain an aqueous solution of the copolymer 18. Water was distilled off from this aqueous solution, and the evaporation residue was adjusted to 40.5% to obtain Comparative Dispersant 18.

<Comparative Production Example 6>
After obtaining an aqueous solution of the copolymer 19 in the same manner as in Production Example 1 except that the dropping time of the monomer aqueous solution and the mixed catalyst solution was changed to 180 minutes, the evaporation residue was adjusted to 40.5%. Thus, Comparative Dispersant 19 was obtained.

<Example 1>
A stainless steel container was charged with 280 parts of ion-exchanged water, and the mixture was stirred with a Coreless mixer having a blade diameter of 50 mm (TK homomixer-AM-20 Tokushu Kika Kogyo Co., Ltd.) having a blade diameter of 50 mm. 4.2 parts by weight of Dispersant 1 was added and uniformly dissolved. Then, 720 parts of heavy calcium carbonate described later was added over 5 minutes, and a dispersion treatment was performed at 10,000 rpm for 20 minutes to obtain a 72% heavy calcium carbonate slurry 1. The initial fluidity and fluidity stability of this heavy calcium carbonate slurry 1 were evaluated, and the results are shown in Table 2.
The heavy calcium carbonate was prepared by using Escalon 2000 (manufactured by Sankyo Flour Milling Co., Ltd.) as a table-type sieve shaker (Model VSS-50, manufactured by Tsutsui Physical and Chemical Instrument Co., Ltd.) and a 5 μm mesh sieve (Model manufactured by Tsutsui Physical and Chemical Instrument Co., Ltd., New Testing) (Sieve 5 μm). Thereby, the particle size distribution of the heavy calcium carbonate could be adjusted to (D ₅₀ ) = 0.7 μm and (D ₉₀ / D ₁₀ ) = 4.

<Examples 2 to 13>
Except that Dispersant 1 was changed to any of Dispersants 2 to 13 prepared in Production Examples 2 to 13, 72% heavy calcium carbonate slurries 2 to 13 were prepared in the same manner as in Example 1. Thereby, the particle size distribution of the heavy calcium carbonate in the heavy calcium carbonate slurry could be adjusted to (D ₅₀ ) = 0.7 μm and (D ₉₀ / D ₁₀ ) = 4. The initial fluidity and fluid stability of the slurries 2 to 13 were evaluated, and the results are shown in Table 2.

<Example 14>
A 76% heavy calcium carbonate slurry 14 was prepared in the same manner as in Example 1, except that 280 parts of ion-exchanged water was changed to 240 parts of ion-exchanged water. Thereby, the particle size distribution of the heavy calcium carbonate in the heavy calcium carbonate slurry could be adjusted to (D ₅₀ ) = 0.7 μm and (D ₉₀ / D ₁₀ ) = 4. The initial fluidity and fluidity stability of this slurry 14 were evaluated, and the results are shown in Table 2.

<Examples 15 to 26>
76% heaviness in the same manner as in Example 1 except that Dispersant 1 was changed to any of Dispersants 2 to 13 prepared in Preparation Examples 2 to 13 and 280 parts of ion-exchanged water was changed to 240 parts of ion-exchanged water. After adjusting the calcium carbonate slurries 15 to 26, their initial fluidity and fluidity stability were evaluated, and the results are shown in Table 2. Thereby, the particle size distribution of the heavy calcium carbonate in the heavy calcium carbonate slurry could be adjusted to (D ₅₀ ) = 0.7 μm and (D ₉₀ / D ₁₀ ) = 4.

<Example 27>
2000 parts of 1 mm glass beads and 1500 parts of the 76% heavy calcium carbonate slurry 14 obtained in Example 14 were put into an attritor MA-1SE (manufactured by Mitsui Miike) and pulverized at 360 rpm for 30 minutes to perform 76% heavy. A calcium carbonate slurry 27 was obtained. The initial fluidity and fluid stability of this slurry 27 were evaluated, and the results are shown in Table 2.
Thus, the particle size distribution of the heavy calcium carbonate in the heavy calcium carbonate slurry could be adjusted to (D ₅₀ ) = 0.35 μm and (D ₉₀ / D ₁₀ ) = 3.1.

<Example 28>
A 76% heavy calcium carbonate slurry 28 was obtained in the same manner as in Example 27 except that the 76% heavy calcium carbonate slurry 14 was changed to the 76% heavy calcium carbonate slurry 16 obtained in Example 16. The initial fluidity and fluid stability of this slurry 28 were evaluated, and the results are shown in Table 2.
Thus, the particle size distribution of the heavy calcium carbonate in the heavy calcium carbonate slurry could be adjusted to (D ₅₀ ) = 0.52 μm and (D ₉₀ / D ₁₀ ) = 4.8.

<Example 29>
A 76% heavy calcium carbonate slurry 29 was obtained in the same manner as in Example 27 except that the 76% heavy calcium carbonate slurry 14 was changed to the 76% heavy calcium carbonate slurry 19 obtained in Example 19. The initial fluidity and fluidity stability of this slurry 29 were evaluated, and the results are shown in Table 2.
Thus, the particle size distribution of the heavy calcium carbonate in the heavy calcium carbonate slurry could be adjusted to (D ₅₀ ) = 0.53 μm and (D ₉₀ / D ₁₀ ) = 5.

<Example 30>
A 76% heavy calcium carbonate slurry 30 was obtained in the same manner as in Example 27 except that the 76% heavy calcium carbonate slurry 14 was changed to the 76% heavy calcium carbonate slurry 20 obtained in Example 20. The initial fluidity and fluidity stability of this slurry were evaluated, and the results are shown in Table 2.
As a result, the particle size distribution of the heavy calcium carbonate in the heavy calcium carbonate slurry could be adjusted to (D ₅₀ ) = 0.70 μm and (D ₉₀ / D ₁₀ ) = 6.

<Comparative Examples 1 to 6>
Comparative 72% heavy calcium carbonate slurries 31 to 36 were prepared in the same manner as in Example 1 except that Dispersant 1 was changed to any of Dispersants 14 to 19 prepared in Comparative Production Examples 1 to 6. The initial fluidity and fluid stability of the slurries 31 to 36 were evaluated, and the results are shown in Table 3.

<Comparative Examples 7 to 12>
Dispersant 1 was replaced with any of dispersants 14 to 19 prepared in Comparative Production Examples 2 to 6, except that 280 parts of ion-exchanged water was changed to 240 parts of ion-exchanged water. After adjusting the calcium carbonate slurries 37 to 42, their initial fluidity and fluidity stability were evaluated, and the results are shown in Table 3.

<Initial fluidity of slurry>
Immediately after the preparation of the slurry, the temperature of the slurry was adjusted to 25 ° C., and the B-type viscosity (N1) and the high shear viscosity of the slurry were measured.
The B-type viscosity was measured using a B-type viscometer (TVB-20L, manufactured by Tokimec) at a rotation speed of 60 rpm. The high shear viscosity was measured using a high shear viscometer (PM-9000HV, manufactured by SMT Co.) at F Bob and a rotation speed of 4400 rpm at 25 ° C.

<Slurry flow stability>
After allowing the slurry to stand at 25 ° C. for 7 days, the B-type viscosity (N7) of the slurry was measured. The ratio (N7 / N1) between this and the B-type viscosity (N1) immediately after the preparation was determined, and this was used as an index of flow stability.

* 1) Copolymer having a molecular weight of 1,000 or more and less than 15,000 (A1)
* 2) Copolymer having a molecular weight of 15,000 or more and less than 55,000 (A2)
* 3) Copolymer having a molecular weight of 55,000 or more and 600,000 or less (A3)

As is clear from Tables 2 and 3, the slurries 1 to 30 (Examples 1 to 30) produced using the dispersants 1 to 13 (Production Examples 1 to 13) of the present invention were used for comparison. Compared to the slurries 31 to 42 (Comparative Examples 1 to 12) manufactured using No. 19 (Comparative Manufacturing Examples 1 to 6), extremely excellent initial fluidity and flow stability were exhibited.

Claims (4)

A copolymer (A) composed of a vinyl group-containing monocarboxylic acid (salt) (AA) and a vinyl group-containing dicarboxylic acid (salt) (MA) as essential structural units,
(1) The molar ratio (AA / MA) of the (AA) unit and the (MA) unit is from 1 to 4,
(2) the weight average molecular weight (Mw) of (A) is 15,000 to 55,000,
(3) The ratio (Mw / Mn) of (Mw) to the number average molecular weight (Mn) of (A) is 1.3 to 2.8,
(4) (A) is a copolymer (A1) having a molecular weight of 1,000 or more and less than 15,000, a copolymer (A2) having a molecular weight of 15,000 or more and less than 55,000, and a molecular weight of 55,000 or more and 600,000. It consists of the following copolymer (A3), (A1) is 70 to 20% by weight, (A2) is 30 to 50% by weight, (A3) is 0 or 1 to 35% by weight based on the weight of (A). % Dispersant for heavy calcium carbonate. The particle size (D ₅₀ ) corresponding to the cumulative particle size of 50% is 0.3 to 0.8 μm, the particle size (D ₁₀ ) corresponding to the cumulative particle size of 10%, and the particle size (D ₉₀ ) corresponding to the cumulative particle size of 90%. dispersing agent according to claim 1 of particle size ratio (D ₉₀ / D ₁₀₎ is for heavy calcium carbonate is 3.0 to 6.0.
In addition, the cumulative particle size is a value obtained from the cumulative volume particle size distribution by a laser diffraction scattering method (JIS Z8825-1: 2001). 3. A heavy calcium carbonate slurry containing the dispersant according to claim 1 or 2, wherein the content of heavy calcium carbonate is 70 to 80% by weight based on the weight of the slurry. A coating liquid for a pigment-coated paper, comprising the heavy calcium carbonate slurry according to claim 3.