WO2004087574A1 - Dispersant for the wet grinding of heavy calcium carbonate - Google Patents

Abstract

A dispersant for the wet grinding of heavy calcium carbonate which is excellent both in the effect of dispersing the particles used in the process of grinding heavy calcium carbonate (i.e., the process of producing a slurry of finely ground heavy calcium carbonate) and in the stability in the process, namely, a dispersant to be used in the process of wet -grinding heavy calcium carbonate having a volume-mean particle diameter of Yμm into one having a volume-mean particle diameter corresponding to 0.00001Y to 0.01Yμm and ranging from 0.01 to 0.7μm, which comprises at least one polymer (A) selected from the group consisting of (meth)acrylic acid (co)polymers (A1), (meth)acrylic acid/(meth)acrylic acid salt copolymers (A2), and (meth)acrylic acid salt copolymers (A3) and characterized in that the content of (meth)acrylic acid units is 60 to 100 % based on the total number of the monomer units constituting the polymer (A).

Description

 Specification

 Dispersant for heavy calcium carbonate wet grinding process

 The present invention relates to a dispersant for a heavy calcium carbonate wet grinding step. More specifically, the present invention relates to a dispersant for heavy calcium carbonate wet grinding step suitable for paper coating paint. Background art

 Conventionally, as a dispersant for pigments (such as heavy calcium carbonate and kaolin), the carboxyl groups in the dispersant are neutralized by 10 to 99.99 mol% of alkali metal or alkaline earth metal salt. A ^ -unsaturated carboxylate copolymer neutralized with organic amine at 0.01 to 5 mol% is known (for example, Japanese Patent Application Laid-Open No. H11-217754). .

 However, when a conventional dispersant for heavy calcium carbonate wet grinding process is used, dry grinding is carried out after wet grinding to prevent the dispersion effect and stability of the particles from being reduced as the fineness is advanced by grinding. It is necessary to atomize by pulverization.

 Furthermore, even when the dry grinding process and the wet grinding process are used together, when the slurry concentration is to be reduced to 70% by weight or more and the volume average particle diameter is reduced to 0.7 / m or less, the slurry viscosity increases. There is a problem that the crushing efficiency of heavy calcium carbonate is reduced and it is difficult to form fine particles.

 Accordingly, the present invention provides a dispersant for a heavy calcium carbonate wet grinding step which can easily achieve atomization in the heavy calcium carbonate wet grinding step (only the wet grinding step without the need for the dry grinding step). The purpose is to do.

 Other objects of the present invention will become apparent from the following description of the invention. Disclosure of the invention

The present inventors have conducted intensive studies to solve such problems, and as a result, have found that a specific (co) polymer achieves the above object, and have reached the present invention. That is, the dispersant for the heavy calcium carbonate wet grinding step of the present invention is obtained by converting heavy calcium carbonate having a volume average particle diameter of 111 to a volume average particle diameter of 0.000001 Y to 0.01 Ym and 0.01 μm. The dispersant used in the process of wet pulverization of (meth) acrylic acid (co) polymer (A1), (meth) acrylic acid mono (meth) acrylate copolymer ( (A2) and a (meth) acrylate (co) polymer (A3) comprising at least one polymer selected from the group consisting of (A3), wherein all the monomer units constituting (A) Based on the number, the (meth) acrylic acid units are 60 to 100% by number.

 In a preferred embodiment of the present invention, the dispersant for the heavy calcium carbonate wet milling step has a (meth) acrylic acid unit of 61 based on the total number of monomer units constituting the polymer (A). ~: It may be 100% by number.

 In a preferred embodiment of the present invention, the dispersing agent for the heavy calcium carbonate wet milling process is such that the polymer (A) is (meth) acrylic acid mono (meth) acrylate copolymer (A2) and / or Or (meth) acrylate (co) polymer (A3), and the (meth) acrylate unit is an alkali metal salt unit, an alkaline earth metal salt unit and / or an ammonium salt unit. You may.

 The method for producing a heavy calcium carbonate slurry according to the present invention is a method for producing a heavy calcium carbonate slurry, comprising: (meth) acrylic acid (co) polymer (A 1), (meth) acrylic acid mono (meth) acrylic acid. (A) comprising at least one polymer selected from the group consisting of (A 2) and (meth) acrylate copolymers (A3). Based on the number of monomer units, using a dispersant having 50 to 100% by number of (meth) acrylic acid units, heavy calcium carbonate is converted from a volume average particle diameter Y〃m to a volume average particle diameter 0.00001 Y Includes the step of wet grinding to 0.01 Ym and 0.01-0.7 / m.

In a preferred embodiment of the present invention, in the method for producing a heavy calcium carbonate slurry, the heavy calcium carbonate may be calcite crystal heavy calcium carbonate. Further, in a preferred embodiment of the present invention, the method for producing a heavy calcium carbonate slurry has a volume average particle diameter of 0.0001 Y to 0.0001 Y and 0.0. 1 to 0.4 μm, and the heavy calcium carbonate slurry may have a heavy calcium carbonate concentration of 75 to 85% by weight.

 The heavy calcium carbonate slurry of the present invention contains the dispersant for the heavy calcium carbonate wet grinding step according to the present invention.

 The paper coating composition of the present invention contains the dispersant for the heavy calcium carbonate wet grinding step according to the present invention.

 The coated paper of the present invention is one coated with the paper coating paint.

 The method for producing a paper coating composition of the present invention comprises: a heavy calcium carbonate slurry containing the dispersant for the heavy calcium carbonate wet grinding step; a pigment, a filler, a binder, and / or the heavy calcium carbonate wet grinding. And a step of mixing with a process dispersant.

 The present invention described above, the embodiments, and the components included in the embodiments can be combined as much as possible.

The dispersant for the heavy calcium carbonate wet grinding step of the present invention has a high degree of pulverization, a particle dispersing effect and stability in the heavy calcium carbonate wet grinding step (microparticulated heavy 'calcium carbonate slurry production step). Very good. Further, even when the slurry concentration is increased, a high-concentration heavy calcium carbonate slurry having excellent particle dispersing effect, stability and thinning effect, and extremely excellent fluidity, which has never existed before, can be produced. Further, even without a dry grinding step, an atomized heavy calcium carbonate slurry can be obtained only by a wet grinding step. The improvement of the fluidity of the heavy calcium carbonate slurry, when used in paper coatings, not only improves the coating operability (high-speed coating properties) when coating papers, but also improves the coating quality of paper coatings. It is very effective for concentration. That is, when the heavy calcium carbonate slurry using the dispersant for the heavy calcium carbonate wet milling process of the present invention is used as a paper coating paint component, the paper coating paint is improved in quality (fine particle formation and low viscosity). In addition to this, there is the advantage that the concentration of paper coatings can be easily increased. Therefore, the dispersant for the heavy calcium carbonate wet milling process of the present invention contributes to the improvement of operability and quality in the production of coated paper, and furthermore, the drying load by increasing the concentration of the paper coating paint. Since the cost can be reduced due to the reduction, etc., it is particularly suitable for the production of coated paper. BEST MODE FOR CARRYING OUT THE INVENTION

 (Meth) acrylic acid means acrylic acid and / or methacrylic acid, and (co) polymer means a polymer and / or a copolymer.

 The (meth) acrylic acid (co) polymer (A 1) includes an acrylic acid polymer, a methacrylic acid polymer and an acrylic acid-methacrylic acid copolymer. Examples of the (meth) acrylic acid- (meth) acrylate copolymer (A 2) include acrylic acid-acrylate copolymer, acrylic acid-methacrylic acid copolymer, and methylacrylic acid. Acid acrylate copolymer, methacrylic acid-methacrylic acid copolymer, acrylic acid-methacrylic acid monoacrylate copolymer, acrylic acid-methacrylic acid-methacrylic acid copolymer And acrylic acid-methacrylic acid-acrylic acid-methacrylic acid copolymer. The (meth) acrylate (co) polymer (A3) includes an acrylate polymer, a methacrylate polymer, and an acrylate-methacrylate copolymer. The (meth) acrylic acid (co) polymer (A1), the (meth) acrylic acid- (meth) acrylate copolymer (A2) and the (meth) acrylate (co) polymer (A 3) may be a single (co) polymer or a mixture of a plurality of (co) polymers included in (A1), (A2) or (A3). In the case of a copolymer, the polymerization may be any of block, random and mixtures thereof.

 The (meth) acrylates include alkali metal salts, alkaline earth metal salts, and ammonium salts.

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. Among these salts, from the viewpoint of the dispersion effect of the heavy calcium carbonate particles, Preference is given to alkali metal salts and ammonium salts, more preferably sodium salts, potassium salts and ammonium salts, particularly preferably the sodium salts. These salts may be used alone or in a mixture thereof.

 In addition to these salts, organic ammonium salts and the like can be used, but they are not preferred from the viewpoint of dispersing effect, odor and cost. In order to atomize only by the wet pulverization process without the dry pulverization process, the polymer (A) must contain no salt in its constituent units, or some of the constituent units in (A) must be metal salt It is preferable to use an earth metal salt and / or an ammonium salt.

 Examples of organic ammonium salts include salts of aliphatic amines, alkylene oxide adducts of aliphatic amines, alkanolamines, alicyclic amines, and aromatic amines.

 The aliphatic amine salt may be any of a primary amine salt, a secondary amine salt, a tertiary amine salt and a quaternary ammonium salt. Examples of the primary amine salt include monoalkylamine salts having 1 to 12 carbon atoms, such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, desylamine and dodecylamine. . Examples of the secondary amine salt include dialkylamine salts having 2 to 24 carbon atoms, such as dimethylamine, getylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dioctylamine, didecylamine, and didodecylamine. Salts.

 As the tertiary amine salt, a trialkylamine salt having 3 to 12 carbon atoms or the like is used, and examples thereof include salts such as trimethylamine, triethylamine, tripropylamine and tributylamine. Examples of the quaternary ammonium salt include tetraalkylammonium salts having 4 to 16 carbon atoms, such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium.

Examples of the salt of an alkylene oxide adduct of an aliphatic amamine include salts of an ethylene oxide adduct of an aliphatic amamine (2 to 20 moles added) or a salt of a propylene oxide adduct (2 to 20 moles added). , And these amines with quaternizing agents (ethylene oxide, Quaternary ammonium salts quaternized with dimethyl sulfate, getyl sulfate, dimethyl carbonate, methyl chloride, etc.).

 Examples of the alkanolamine salts include salts of alminolamine having 1 to 20 carbon atoms, such as methanolamine, ethanolamine, jetanolamine, triethanolamine, propanolamine, and busanolamine. And quaternary ammonium salts obtained by quaternizing these alkanolamines with a quaternizing agent.

 Examples of the alicyclic amine salts include salts of cycloalkylamines having 5 to 8 carbon atoms, such as cyclopentylamine, cyclohexylamine or cyclohexylmethylamine. A quaternary ammonium salt obtained by quaternizing with a quaternizing agent can also be used.

 As the aromatic amine salt, a salt of arylamine having 6 to 10 carbon atoms or the like is used, and salts of aniline, pendylamine, benzylmethylamine or toluidine are exemplified.These arylamines are further quaternized with a quaternizing agent. A quaternized quaternary ammonium salt can also be used.

 In the case of (meth) acrylic acid (co) polymer (A1), in the case of acrylic acid-methacrylic acid copolymer, the content (number%) of acrylic acid units is determined by the monomers constituting the copolymer. Based on the total number of units, from the viewpoint of the dispersion effect of the heavy calcium carbonate particles, it is preferably 50 to 100, more preferably 75 to 99.9, particularly preferably 90 to 9 9.9. Further, the content (number%) of the methacrylic acid unit is from 0 to 50 based on the total number of the monomer units constituting the copolymer and from the viewpoint of the dispersion effect of the heavy calcium carbonate particles. And more preferably 0.1 to 25, particularly preferably 0.1 to: L0.

In the (meth) acrylic acid- (meth) acrylate copolymer (A 2), the content (number%) of the (meth) acrylic acid unit is determined by the total number of the monomer units constituting the copolymer. From the viewpoint of the dispersion effect of the heavy calcium carbonate particles, it is preferably 50 to 100, more preferably 60 to 100, particularly preferably 61 to 100, Is preferably 70 to 99.9. Further, the content (number of units) of the (meth) acrylate unit is preferably from 0 to 50, more preferably from 0 to 40, based on the total number of the monomer units constituting the copolymer. It is particularly preferably from 0 to 39, most preferably from 0.1 to 30. In addition, when the acrylic acid unit is included, the content (number%) of the acrylic acid unit is determined based on the total number of the acrylic acid unit and the acrylic acid unit based on the dispersion effect of the heavy calcium carbonate particles. From the above, it is preferably 50 to 100, more preferably 75 to 99.9, particularly preferably 90 to 99.9. The content (number%) of the methacrylic acid unit is preferably from 0 to 50 based on the total number of the acrylic acid unit and the methacrylic acid unit from the viewpoint of the dispersion effect of the heavy calcium carbonate particles. More preferably, 0.1 to 25, particularly preferably 0.1 to: L 0. In addition, when a methacrylate unit is included, the content of the acrylate unit (number%) is calculated based on the total number of the acrylate unit and the methacrylate unit. From the viewpoint of the dispersing effect and the like, it is preferably from 50 to 100, more preferably from 75 to 99.9, particularly preferably from 90 to 99.9. The content (number%) of the methacrylate unit is from 0 to 5 based on the total number of the acrylate unit and the methacrylate unit from the viewpoint of the dispersion effect of the heavy calcium carbonate particles. Is preferred, more preferably 0.1 to 25, particularly preferably 0.1 to 10.

 In the case of (meth) acrylate (co) polymer (A3), in the case of acrylate-methacrylate copolymer, the content (number%) of acrylate units constitutes the copolymer From the viewpoint of the dispersion effect of the heavy calcium carbonate particles, based on the total number of monomer units to be used, it is preferably 50 to 100, more preferably 75 to 99.9, and particularly preferably 90 to 99.9. It is. The content (number%) of the methacrylate unit is from 0 to 50 based on the total number of the monomer units constituting the copolymer, from the viewpoint of the dispersion effect of the heavy calcium carbonate particles and the like. And more preferably 0.1 to 25, particularly preferably 0:! To 10.

(Meth) acrylic acid (co) polymer (Al), (meth) acrylic acid (meth) ac The acrylate copolymer (A 2) and the (meth) acrylate (co) polymer (A 3) comprise other monomers in addition to (meth) acrylic acid and (meth) acrylate. It may be included as a unit. From the viewpoint of the dispersing effect and the like, it is preferable not to include other monomer units.

 As the other monomer, any monomer can be used without limitation as long as it can be copolymerized with (meth) acrylic acid and / or (meth) acrylate. Such monomers include unsaturated monocarboxylic esters, unsaturated dicarboxylic acids, hydroxy-unsaturated monocarboxylic acids, hydroxyalkyl unsaturated carboxylic esters, polyalkylene glycol unsaturated monomers, (Meth) acryloyl group-containing amide, vinyl ester, vinyl ether, sulfo group-containing unsaturated monomer, aromatic unsaturated monomer, aliphatic unsaturated monomer, lipophilic unsaturated monomer And a cyano group-containing unsaturated monomer.

 As the unsaturated monocarboxylic acid ester, a (meth) acrylic acid ester having 4 to 50 carbon atoms is used, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (meth) acrylate. ) Butyl acrylate, heptyl (meth) acrylate, hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate and (meth) E) Eicosyl acrylate and the like.

 As the unsaturated dicarboxylic acid, an unsaturated dicarboxylic acid having 4 to 6 carbon atoms is used, and examples thereof include maleic acid, fumaric acid, and itaconic acid.

 Examples of the monohydroxy unsaturated monocarboxylic acid include monohydroxy (meth) acrylic acid.

 Examples of the hydroxyalkyl unsaturated carboxylate include hydroxyalkyl (meth) acrylate having an alkyl group of 1 to 6 carbon atoms, such as hydroxymethyl (meth) acrylate and hydroxyethyl (meth) acrylate. And hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and hydroxyisohexyl (meth) acrylate.

As the polyalkylene glycol unsaturated monomer, an alkylene group having 2 carbon atoms Polyalkylene glycol (meth) acrylate having 2 to 100 alkylenes is used, such as polyethylene glycol (10 ethylene groups) (meth) acrylate monoester, polyethylene glycol (ethylene group). 20) (Meth) acrylic acid monoester, decaoxyethylene hexoxypropylene (meth) acrylate monoester and pentacaoxyethylene pentoxy propylene (meth) acrylate monoester No.

 As the (meth) acryloyl group-containing amide, a (meth) acryloyl group-containing amide having 3 to 5 carbon atoms or the like is used, and (meth) acrylyl amide, N-methyl (meth) acryl amide, N-methylol (Meth) acrylamide and N, N-dimethylmethyl (meth) acrylamide.

 As the vinyl ester, a vinyl ester having 4 to 10 carbon atoms and the like are used, and examples thereof include vinyl acetate, vinyl propanoate, and 2-ethylhexanoate.

 Examples of the vinyl ether include vinylalkyl ethers having an alkyl carbon number of 1 to 10 and monovinyl ethers of polyalkylene glycol (ethylene and / or propylene addition mole number 1 to 100). Examples thereof include ter, vinylethyl ether, hinylbutylether, vinylhexylether, vinyldecylether, tetraethyleneglycolvinylether, and hexaethyleneglycolvinylether.

 As the sulfo group-containing unsaturated monomer, an unsaturated sulfonic acid having 2 to 8 carbon atoms or the like is used. Pinylsulfonic acid, arylsulfonic acid, vinyltoluenesulfonic acid, styrenesulfonic acid and 2-acrylamide 2-methylpropanesulfonic acid Acids and the like.

 Examples of the aromatic unsaturated monomer include an aromatic monomer having 8 to 12 carbon atoms, such as styrene, vinyl styrene, and vinyl naphthylene.

 As the aliphatic unsaturated monomer, an aliphatic unsaturated monomer having 2 to 20 carbon atoms is used, and examples thereof include ethylene, propylene, butene and butadiene.

As the alicyclic unsaturated monomer, an alicyclic unsaturated monomer having 5 to 15 carbon atoms is used. And cyclopentene, cyclopentene, bicyclopentene, and the like.

 Examples of the cyano group-containing unsaturated monomer include (meth) acrylonitrile and cyanostyrene.

 When (A l), (A2) or (A3) contains other monomer units, the content (number%) of other monomer units is as follows. In the case of the (meth) acrylic acid (co) polymer (A1), it is preferably from 0.1 to 3, more preferably from 0.1 to 2, based on the total number of the monomer units constituting the copolymer. It is particularly preferably 0.1 to 1. In the case of the (meth) acrylic acid mono (meth) acrylate copolymer (A2), it is preferably from 0.1 to 5 based on the total number of the monomer units constituting the copolymer, and more preferably from 0.1 to 5. It is preferably from 0.1 to 3, particularly preferably from 0.1 to 1. In the case of the (meth) acrylate copolymer (A3), it is preferably from 0.1 to 3, more preferably from 0.1 to 3, based on the total number of monomer units constituting the copolymer. ~ 2 ヽ Especially preferred is 0.1 ~: L.

 (Meth) acrylic acid (co) polymer (A 1), (meth) acrylic acid mono (meth) acrylate copolymer (A 2) and (meth) acrylic acid (co) polymer (A3 ) Has a weight average molecular weight (Mw) of preferably 8,000 to 50,000, more preferably 9,000 to 40,000, particularly preferably 10,000 to 20,000. That is, the Mw of (A1), (A2) or (A3) is preferably at least 8,000, more preferably at least 9,000, particularly preferably at least 10,000, and It is preferably at most 000, more preferably at most 40,000, particularly preferably at most 20,000. Within this range, the dispersion effect and stability of the particles in the heavy calcium carbonate pulverizing step are further improved, and it is possible to realize fine calcium carbonate fine particles having a higher pulverization efficiency. Mw is measured by gel permeation chromatography (GPC) using polyethylene glycol as a standard substance (the same applies hereinafter).

The polymer (A) is a (meth) acrylic acid (co) polymer (A 1), (meth) acrylic As long as it contains at least one selected from the group consisting of acid- (meth) acrylate (co) polymer (A2) and (meth) acrylate (co) polymer (A3), (meth) E) Acrylic acid (co) polymer (A1) and / or (meth) acrylic acid (meth) acrylate (co) polymer (A2), more preferably acrylic acid -Acrylic acid copolymer, acrylic acid-methacrylic acid copolymer, methacrylic acid-acrylic acid copolymer, methacrylic acid-methacrylic acid copolymer, acrylic acid-methyl methacrylate A copolymer of acrylic acid-acrylic acid, acrylic acid-methacrylic acid-methacrylic acid copolymer and / or acrylic acid-methacrylic acid-acrylic acid-methacrylic acid copolymer, or a mixture thereof Copolymer and acrylic acid polymer, Evening acrylic acid polymer and or acrylic acid - is to consist of a methacrylic acid copolymer. Further, the polymer (A) is particularly preferably an acrylic acid monoacrylate copolymer, an acrylic acid-methacrylic acid copolymer, an acrylic acid-methacrylic acid-acrylic acid copolymer and / or Acrylic acid-methacrylic acid-acrylic acid salt-methacrylic acid copolymer, or these copolymers and acrylic acid polymer and / or acrylic acid-methacrylic acid copolymer, Most preferably, it is composed of an acrylic acid monoacrylate copolymer, or is composed of this copolymer and an acrylic acid polymer.

 The content (number%) of the (meth) acrylic acid units contained in the polymer (A) is preferably 50 to 100, more preferably 55 to 100, based on the total number of the monomer units constituting (A). -100, particularly preferably 60-100, the following particularly preferred 61-100, more particularly preferred 65-100, even more particularly preferred 70-100, most preferred 75-99.9 It is. Within this range, the dispersion effect and stability of the heavy calcium carbonate particles are further improved even without the dry pulverization step, and it is possible to realize heavy calcium carbonate fine particles with higher pulverization efficiency.

The content (number%) of the (meth) acrylate unit contained in the polymer (A) is preferably from 0 to 50 based on the total number of the monomer units constituting (A). More preferably from 0 to 45, particularly preferably from 0 to 40, then particularly preferably from 0 to 39, more particularly preferably from 0 to 35, even more particularly preferably from 0 to 30, most preferably 0.1. ~ 25. Within this range, the dispersing effect and stability of the heavy calcium carbonate particles are further improved even without the dry pulverization step, and it is possible to realize the fine calcium carbonate particles having a higher pulverizing efficiency. When the polymer (A) contains (meth) acrylate units, the lower limit (number%) of this content is 0.1% based on the total number of monomer units constituting (A). It is more preferably 0.2, particularly preferably 0.5, then particularly preferably 1, and even more preferably 5. ■

 If the polymer (A) contains a (meth) acrylic acid (co) polymer (A1), its content (% by weight) is based on the total weight of (A1) and (A2). , 0.1 to 100, more preferably 0.1 to 99.9, particularly preferably 10 to 90, and most preferably 20 to 80. Within this range, the dispersing effect and stability of the heavy calcium carbonate particles are further improved even without the dry pulverization step, and it is possible to realize the heavy carbonic acid calcium fine particles having higher pulverization efficiency.

 If the polymer (A) contains (meth) acrylic acid- (meth) acrylate copolymer (A2), its content (% by weight) is the total weight of (A1) and (A2) 0.1 to 99.9, more preferably 10 to 90, particularly preferably 20 to 80, based on Within this range, the dispersing effect and stability of the heavy calcium carbonate particles are further improved even without the dry pulverization step, and it is possible to realize heavy calcium carbonate fine particles with higher pulverization efficiency.

If the polymer (A) contains (meth) acrylic acid (co) polymer (A3), its content (% by weight) is calculated based on the total weight of (A1) and (A2). It is preferably from 0.1 to 10, more preferably from 1 to 10, particularly preferably from 5 to 10. Within this range, the dispersion effect and stability of the heavy calcium carbonate particles are further improved without the dry pulverization step, and the pulverization efficiency can be further increased and the heavy calcium carbonate can be made into fine particles. The weight average molecular weight (Mw) of the polymer (A) is preferably from 8,000 to 50,000, more preferably from 9000 to 40,000, and particularly preferably from 10,000 to 20,000. . That is, Mw of (A) is preferably 8,000 or more, more preferably 9,000 or more, particularly preferably 10,000 or more, and preferably 50,000 or less, more preferably 40,000 or less. 000 or less, particularly preferably 20,000 or less. Within this range, the dispersing effect and stability of the heavy calcium carbonate particles are further improved, and it is possible to realize the heavy carbon dioxide powder with high grinding efficiency.

 The number average molecular weight (Mn) of the polymer (A) is preferably from 4,000 to 41,000, more preferably from 4,200 to 41,000, and particularly preferably from 4,400 to 41,000. Within this range, the dispersing effect and stability of the heavy calcium carbonate particles are further improved, and it is possible to realize fine particles of the heavy calcium carbonate having higher pulverization efficiency. Mn is measured by gel permeation chromatography (GPC) using polyethylene glycol as a standard substance (the same applies hereinafter).

 The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polymer (A) is preferably from 1.2 to 2.0, more preferably from 1.2 to 1.9, Particularly preferred is 1.2 to 1.8. Within this range, the dispersing effect and stability of the heavy calcium carbonate particles are further improved, and it is possible to realize fine particles of the heavy calcium carbonate having higher pulverization efficiency.

 (Meth) acrylic acid (co) polymer (A 1), (meth) acrylic acid mono (meth) acrylate copolymer (A2) and (meth) acrylate (co) polymer (A3) The polymerization method for producing is not particularly limited, and ordinary polymerization methods (such as a solution polymerization method, a bulk polymerization method, and a reversed-phase suspension polymerization method) can be used. However, it is preferable to use a solution polymerization method.

In the case of the (meth) acrylic acid- (meth) acrylate copolymer (A2), it may be produced by copolymerization of (meth) acrylic acid and (meth) acrylate. After the (meth) acrylic acid (co) polymer is obtained, the (co) polymer may be neutralized with a base or the like.

 In the case of the (meth) acrylate (co) polymer (A3), the (meth) acrylate may be produced by (co) polymerization of the (meth) acrylate, or (meth) acrylic acid (co) polymer. , The (co) polymer may be neutralized with a base or the like.

 Solvents that can be used in the case of the solution polymerization method include ordinary solvents for polycarboxylic acid polymerization, and include water and / or alcohol. Examples of the water include tap water, deionized water, and industrial water. As the alcohol, an alcohol having 1 to 4 carbon atoms is used, and examples thereof include methanol, ethanol, isopropyl alcohol, and ethylene glycol. Among these, water, a mixed solvent of water and an alcohol are preferable, a mixed solvent of water and an alcohol is more preferable, and a mixed solvent of deionized water and isopropyl alcohol is particularly preferable.

 When water and alcohol are mixed and used, the mixing weight ratio (water / alcohol)

It can be arbitrarily mixed with 0.1 to 99.9 / 0.9.1 to 99.9, preferably 0.1 to 50/5 0 to 99.9, more preferably 0.1 to 40/60 to 99.9. 9, particularly preferably 0.1 to 30/70 to 99.9. Within this range, the ratio of Mw to Mn (Mw / Mn) of the polymer (A) is easily adjusted to 1.2 to 2.0, and the dispersion effect and stability of the heavy calcium carbonate particles are further improved. Thus, it is possible to realize heavy calcium carbonate fine particles with high grinding efficiency.

 The amount (% by weight) of the solvent used is the same as in the usual method. For example, when the polymer (A) is a (meth) acrylic acid (co) polymer (A1), the amount is 100 In the case of (meth) acrylic acid mono (meth) acrylate copolymer (A2), it is about 100 to 1,000 based on the weight of (A2). In the case of the (meth) acrylate copolymer (A3), it is about 100 to 1,000 based on the weight of (A3).

Solvents that can be used in the reverse phase suspension polymerization method include water and / or alcohol (same as the solution polymerization method), as well as hydrocarbons having 6 to 18 carbon atoms, such as alkane and And arenes.

 Examples of alkanes include hexane, isohexane, octane, 2-ethylhexane, decane, and isooctyldecane.

 Examples of arene include benzene, toluene, xylene and t-butylbenzene.

 Of these, hexane, octane, toluene and xylene are preferred, hexane and toluene are more preferred, and hexane is particularly preferred.

 The amount (% by weight) of the solvent used is the same as in the usual method. For example, when the polymer (A) is a (meth) acrylic acid (co) polymer (A 1), the amount is based on the weight of (A 1). Water is about 100 to 1,000, such as hydrocarbons. In the case of (meth) acrylic acid- (meth) acrylate copolymer (A2), it is based on the weight of (A2). And water is about 100 to 1,000, and hydrocarbons are about 100 to 2,000. In the case of the (meth) acrylate copolymer (A3), the amount is about 100 to 2,000 based on the weight of (A3), such as 100 to 500 for water and hydrocarbon.

 A polymerization initiator can be used in the (co) polymerization reaction. In the case of the solution polymerization method, the polymerization initiator includes an azo compound, a persulfate, a perborate, a peroxide and a redox catalyst.

 The azo compounds include 2,2'-azobisisobutyronitrile, 4,4'-azobis-14-cyanovaleric acid, and 2,2'-azobis (4-methoxy-1,2,4-dimethylvalerodiyl). Tolyl), 2,2'-azobis (2-methylbutyronitrile), 1, -azobis (cyclohexane-1-1-bononitrile), 2,2'-azobis (2,4,4-trimethylpentane), Examples thereof include dimethyl 2,2′-azobis (2-methylpropionate), 2,2′-azobis [2- (hydroxymethyl) propionitrile], and 1,1-azobis (1-acetoxy-11-phenylethane). Examples of the persulfate include ammonium persulfate, potassium persulfate, and sodium persulfate.

Examples of perborate include ammonium perborate, potassium perborate and sodium perborate And the like.

 Examples of the peroxide include hydrogen peroxide and benzoyl peroxide.

 Examples of the redox catalyst include ascorbic acid-hydrogen peroxide.

 Of these, azo compounds and persulfates are preferred, and 2,2′-azobisisobutyronitrile, ammonium persulfate, potassium persulfate and sodium persulfate are more preferred.

 One of these polymerization initiators can be selected and used, and two or more can be selected and used as a mixture.

 When the bulk polymerization method and the reverse phase suspension polymerization method are employed, azo compounds, peroxides, redox catalysts and the like can be used as the polymerization initiator.

As the azo compound, peroxide and redox catalyst, the same ones as in the solution polymerization method can be used, and oil-soluble ones are preferred. As the azo compounds, there are 2 ₃ 2'-azobisopipyronitrile, 4,4'-azobis-14-cyanovaleric acid, 2,2 'monoazobis (4-methoxy-12,4-dimethylvaleronitrile), 2, 2 '- Azobisu (2 - methyl Petit nitrile), 1, 1' - Azobisu (hexane one 1- Aruboni tolyl cyclohexane), 2 ₃ 2 '- Azobisu (2, 4, 4-trimethylpentane), dimethyl 2 ₃ Examples include 2'-azobis (2-methylpropionate), 2,2'-azobis [2- (hydroxymethyl) propionitrile], and 1,1'-azobis (1-acetoxy-1-phenylenyl). Examples of the peroxide include hydrogen peroxide and benzoyl peroxide. Examples of redox catalysts include hydrogen ascorbate monoxide. Of these, azo compounds and peroxides are preferred, and azo compounds such as 2,2'-azobisisobutyronitrile are more preferred. One of these polymerization initiators can be selected and used, and two or more can be selected and used as a mixture.

 In other polymerization methods, known polymerization initiators can be used.

When a polymerization initiator is used, the amount of the polymerization initiator used is adjusted so that the polymer (reaction product) has the desired weight average molecular weight and number average molecular weight. solution In the case of the polymerization method, the weight average molecular weight and the number average molecular weight of the polymer are greatly affected by the polymerization concentration, the polymerization temperature, the charging speed of the monomers, and the like. And a relatively small amount of several percent. On the other hand, in the case of the bulk polymerization method and the reversed-phase suspension polymerization method, the reaction rates are both high, and a relatively large amount of the polymerization initiator is required to obtain the desired weight average molecular weight and number average molecular weight. It becomes. Polymer (A) is composed of (meth) acrylic acid (co) polymer (Al), (meth) acrylic acid- (meth) acrylate copolymer (A2) and (meth) acrylate (co) polymer It suffices if it contains at least one member selected from the group consisting of the coalescence (A3). Therefore, when the polymer (A) is composed of a (meth) acrylic acid (co) polymer (A 1) and a (meth) acrylic acid- (meth) acrylic acid copolymer (A2), (A 1) And (A2) may be prepared separately and then mixed, or (A1) may be obtained and then neutralized to produce (A1) and '(A3) May be mixed separately after production.

 When the polymer (A) is composed of (meth) acrylic acid (co) polymer (A1) and (meth) acrylic acid (co) polymer (A3), (A1) and (A3) Each of them may be manufactured and then mixed (as (A 2) is formed when converted to an aqueous solution, it is stored as a solid in this case). Further, when the polymer (A) is composed of (A 1), (A2) and (A3), (A 1), (A2) and (A3) may be mixed after producing each of them. (A 1) may be obtained and then a part thereof may be neutralized for production, (A 1) and (A3) may be produced and then mixed together, and (A 1) or (A After obtaining 2), the product may be partially neutralized for production.

 Further, when the polymer (A) is composed of (A2) and (A3), (A2) and (A3) may be separately produced and then mixed to obtain (A1) or (A2). After that, it may be manufactured by neutralizing a part.

 When the polymer (A) consists of (A2), (A2) may be directly produced, or (A1) may be obtained and then partially neutralized for production.

The dispersant for the heavy calcium carbonate wet milling process of the present invention is not a polymer (A). In addition, if necessary, additives such as water, a waterproofing agent, an antiseptic / antifungal agent, a defoaming agent, a lubricant, a dispersant, a water retaining agent, and a fluorescent dye may be contained. As these additives, known additives which are added to a paper coating material, a paper processing, a fiber treatment, an emulsion paint and the like can be used.

 Examples of the water-proofing agent include a water-proofing agent containing ammonium zirconium carbonate, polyamide urea formaldehyde, glyoxal, polyamide polyamine and / or styrene-acrylic acid ester resin. Examples of the antiseptic / antifungal agent include an antiseptic / antifungal agent containing an isothiazoline compound and / or a thiazole compound. Examples of the antifoaming agent include antifoaming agents containing a fatty acid ester, silicone oil and / or polyether. Examples of the lubricant include a lubricant containing calcium stearate and / or polyethylene wax. Examples of the dispersant include a dispersant containing naphthalene sodium sulfonate formalin condensate and / or sodium polyacrylate (degree of neutralization of polyacrylic acid: 95 to 100 mol%). . Examples of the water retention agent include carboxymethylcellulose and / or alkyl methacrylate-alkyl acrylate (in the alkyl methacrylate-alkyl acrylate copolymer, the alkyl acrylate monomer is at least 40 mol%, Water retention agents having an average molecular weight of 100,000 to 200,000). Examples of the fluorescent dye include a fluorescent dye containing a diaminostilpene or the like.

 When water is included, the content of water can be arbitrarily adjusted according to the purpose. However, from the viewpoint of preventing the solid content of the heavy calcium carbonate slurry into which the polymer (A) is mixed, it is preferable to minimize the solid content. On the other hand, from the viewpoint of handleability, the amount is preferably large. Therefore, when water is used, the content (% by weight) of water is preferably from 0.1 to 400, more preferably from 0.2 to 150; based on the weight of the polymer (A). And particularly preferably 0.3 to: L00.

When a water-proofing agent, an antiseptic / antifungal agent, an antifoaming agent, a lubricant, a dispersant, a water retention agent and / or a fluorescent dye, etc. are included, the total content (% by weight) of these can be arbitrarily adjusted according to the purpose. It is preferably from 0.1 to 5 based on the weight of the polymer (A), more preferably from 0.1 to 5. 1-3.

 When water is not contained, the form of the dispersant for the heavy calcium carbonate wet milling step of the present invention may be in the form of fine powder particles from the viewpoints of addition and solubility in the heavy calcium carbonate and the heavy calcium carbonate slurry. The form is preferred. The size (mm) of the fine powder particles is preferably from 0.001 to 3, more preferably from 0.001 to 1. This size is a volume average particle diameter determined by a laser-diffraction scattering method.

 The dispersant for the heavy calcium carbonate wet milling step of the present invention may contain the polymer (A), and may contain water, a water-proofing agent, an antiseptic / antifungal agent, an antifoaming agent, a lubricant, a dispersant if necessary. The water retention agent, the fluorescent dye and the like can be added at any stage during the production process. The water used as the polymerization solvent can be used as it is, and the concentration may be adjusted as necessary (distillation by heating, distillation under reduced pressure and / or water).

The dispersant for the heavy calcium carbonate wet milling process of the present invention has an extremely high particle dispersing effect and improves particle stability in the production of a heavy calcium carbonate slurry in which the heavy calcium carbonate is made into fine particles in the milling step. It can be applied to heavy calcium carbonate used for paper coating paint, paper processing, fiber treatment, emulsion paint and the like. In particular, its application value is high when applied to heavy calcium carbonate used in paper coatings. The dispersant for the heavy calcium carbonate wet grinding step of the present invention is particularly suitable for a wet method, but can be applied to both a wet method and a dry method. Calcite crystal-type heavy calcium carbonate is suitable as the heavy calcium carbonate to which the dispersant for the heavy calcium carbonate wet grinding step of the present invention can be applied. The calcite crystal-type heavy calcium carbonate may be a coarse-grained calcite crystal-type heavy calcium carbonate or a calcite crystal-type heavy calcium carbonate whose particle size has been adjusted. That is, it can be applied to wet crushing of natural limestone (particle diameter: lmn! ~ 7 cm) as it is, and also to wet crushing of dry limestone (heavy calcium carbonate). it can. The volume average particle size of the heavy calcium carbonate after dry grinding is usually 1 m to 2 mm, preferably 1 / π! To 100 m, more preferably 1 to 20 m. The dispersant for the heavy calcium carbonate wet grinding step of the present invention can be prepared by adding the above-mentioned heavy calcium carbonate having a volume average particle size (Y) of 0m to 0.0001 1 to 0 · 01 1 (preferably 0000 1Υ to 0.001 Υ, more preferably 0.00001 Υ to 0.001 Y) jm, and 0.01 to 0.Ί (preferably 0.01 to 0.65, more preferably 0.01 to 0.4, particularly preferably 0.01 to 0.3) Suitable for grinding to a size of 〃m.

 Pulverizing to a volume average particle size of 0.0001 Y to 0.01 Υ means that the particle size before grinding is crushed to a particle size of Y / 100,000 to Υ / 100. Is equivalent to 1 / 100,000 to 1/100. Thus, the value obtained by dividing the volume average particle diameter after wet grinding by the volume average particle diameter before wet grinding is defined as the degree of grinding.

 The concentration (weight%) (slurry concentration) of heavy calcium carbonate in the heavy calcium carbonate slurry obtained in the pulverization step is preferably 70 to 85, more preferably 75 to 85, based on the weight of the slurry. Particularly preferably, it is 80 to 85. Further, ρΗ of the heavy calcium carbonate slurry obtained in the pulverizing step is preferably 8.4 to 9.1.

That is, the dispersant for the heavy calcium carbonate wet grinding step of the present invention is suitable for grinding heavy calcium carbonate with a high degree of grinding to obtain fine particles in the above range; and a high-concentration heavy calcium carbonate slurry. . Further, it is suitable for obtaining a high-concentration ultrafine particle slurry having a slurry concentration of 75% by weight or more and a volume average particle diameter of 0.01 to 0.4 m. It is suitable for obtaining a high-concentration ultrafine particle slurry having a volume average particle diameter of 0.01 to 0.1. The use of the heavy calcium carbonate wet grinding dispersant of the present invention makes it possible to easily produce such a high-concentration ultrafine particle slurry without a dry grinding step. In such a high-concentration ultrafine particle slurry, the particles in the slurry are more uniformly dispersed, the dispersion of the particles is stable, and an increase in the viscosity of the slurry is suppressed. In addition, the dispersant for the heavy calcium carbonate wet grinding step of the present invention has a grinding degree, a dispersion efficiency and a viewpoint of stability. Therefore, it is not suitable for obtaining a heavy calcium carbonate slurry having a slurry concentration of less than 70% by weight and a volume average particle size exceeding 0.8 μm.

 In addition, the volume average particle diameter is a laser single light diffraction / scattering method based on JISZ 8825-1: 2001 (ISO 13320-1: 1999) {trade name: Microtrack (MICROTRAC UPA, manufactured by Leeds and Northerup), etc. Laser light diffraction scattering particle size distribution analyzer, laser beam wavelength: 780 nm, measurement temperature: 25 ° C, dispersion medium: water)}.

 The use amount (% by weight) of the dispersant for the heavy calcium carbonate wet grinding step of the present invention is preferably 0.01 to 4 based on the weight of the heavy calcium carbonate as the weight of the polymer (A), More preferably, it is 0.01-3, particularly preferably 0.01-2. Within this range, the dispersion effect and stability of the particles are further improved, and it is possible to realize heavy calcium carbonate fine particles with higher grinding efficiency.

 The dispersant for the heavy calcium carbonate wet milling process of the present invention can be added at any stage during the milling process. As for the addition method, the whole amount to be used may be added all at once or may be added in portions, but split addition is preferred. More preferably, a part of the dispersant is added at the beginning of the pulverizing step, and the rest is added in the middle of the pulverizing step.

The dispersant for the heavy calcium carbonate wet grinding process of the present invention can be used in the grinding process using a device capable of grinding heavy calcium carbonate irrespective of the type of the device, as long as it is a grinding process. . Examples of such a pulverizer include a stirrer for general fluids (a propeller mixer, an evening bottle mixer, a desolver, etc.), a high-speed rotating high-shear type agitator / disperser (homomixer, atrai yuichi, sand mill, bead mill, Ball mills, coil mixers, disk cavitating mixers, and stirrer mixers, colloid mills (TK Mycolloid, TK Homomic Line Mill, TK High Line Mill, Charcoal Colloid Mill, etc.) A pressure nozzle (jet flow) type disperser (gaulin and homogenizer, etc.), an ultrasonic emulsifier (dispersion, sonic and ultra-jet type, etc.), a mechanical vibration stirrer, and a stirrer using an electrostatic field can be used. Among these, general fluid stirrers and high-speed rotating high shear Preferred are a stirrer and a disperser, and more preferred are a propeller mixer, a homomixer, an atrai unit, a sand mill, a bead mill, a ball mill and a Cores mixer. In addition, these pulverizing apparatuses may be used alone, or the pulverizing step may be divided and different apparatuses may be used for the divided steps. (It is preferable to use only one type from the viewpoint of simplicity, etc.). Also, there is no limitation on the pulverizing conditions (temperature, etc.), and the same conditions as in the past can be applied.

 The dispersant for the heavy calcium carbonate wet grinding process of the present invention can be applied as a dispersant for the grinding process of pigments and the like, other than the calcite crystal type heavy calcium carbonate. Examples of such pigments include heavy calcium carbonate (crystal type: aragonite or paterite), clay, light calcium carbonate (crystal type: calcite, aragonite or paterite), titanium dioxide, sachin white, barium sulfate. , Talc, zinc oxide, stone ', silica, fluoride, alumina and the like.

 Further, in addition to the pulverization step, it can be used as a dispersant for a pigment dispersion step. For example, clay, light calcium carbonate (crystal form: calcite, aragonite or paterite), heavy calcium carbonate (crystal form: calcite, aragonite and paterite), titanium dioxide, sachin white, barium sulfate It can also be used as a dispersant for inorganic pigments such as talc, zinc oxide, gypsum, silica, graphite and alumina. When the heavy calcium carbonate slurry obtained using the dispersant for the heavy calcium carbonate wet grinding step of the present invention is applied to a paper coating paint, the coating operability at the time of coating on paper (high-speed coating property) Etc.) as well as increasing the concentration of paper coatings. Furthermore, since the content of the (meth) acrylate unit in the dispersant of the present invention is small, the use of the dispersant of the present invention improves the water resistance of coated paper. Further, when the dispersant of the present invention is used, the amount of the dispersant used can be reduced, so that the cost advantage is increased and the water resistance of the coated paper is further improved.

The heavy calcium carbonate slurry containing the dispersant for the heavy calcium carbonate wet grinding step of the present invention is contained in a paper coating paint together with a binder as a pigment or a filler. For heavy calcium carbonate wet grinding process of the present invention in the case of paper coating paint The amount (parts by weight) of the heavy calcium carbonate slurry containing a dispersing agent can be used in any proportion with respect to 100 parts by weight of the pigment or the filler of the paper coating paint. It is preferably 00, more preferably 30 to 100, particularly preferably 50 to 100, and most preferably 60 to 100. Within this range, the viscosity of the paper coating composition can be further reduced and the concentration can be increased, which is preferable.

 Pigments other than calcite crystalline heavy calcium carbonate contained in paper coating paints include inorganic pigments (heavy calcium carbonate (crystal type: aragonite or paterite), clay, light calcium carbonate (crystal type: Calcite, aragonite or paterite), titanium oxide, satin white, aluminum hydroxide, barium sulfate, talc, zinc oxide, gypsum, silica and graphite, and organic pigments (polystyrene-based plastic pigments). Can be One or more of these pigment components can be selected and used together with calcite crystal heavy calcium carbonate.

 Pigments or fillers are used as the main component of paper coatings, and the amount (parts by weight) used varies depending on the required performance of the coated paper and the coating method, and the total amount of binder and pigment or filler is used. 70 to 90 is preferable to 100 parts by weight. (When paper coating is coated by blade, it is preferably 80 to 90, and paper coating for light-weight coated paper is size-press coated.) In this case, it is preferably from 70 to 80). Within this range, the viscosity reducing effect (low viscosity) of the paper coating composition is further improved.

 Examples of the binder in these paper coating paints include styrene butadiene latex (SBR), modified styrene butadiene latex, acrylyl latex, and vinyl acetate latex.

As the styrene-butadiene latex, a copolymer of styrene and pu-jen can be used, and the modified styrene-butadiene latex obtained by emulsion polymerization using an emulsifier such as sodium oleate is a copolymer of styrene, butadiene and other monomers. Polymers and the like can be used. Other monomers include unsaturated carboxylic esters such as methyl (meth) acrylate, unsaturated carboxylic acids such as (meth) acrylic acid, (Meth) acrylonitrile, (meth) acrylic acid dimethylaminoethyl ester, (meth) acrylic amide, glycidyl (meth) acrylate, (meth) acrylic acid hydroxyethyl ester, and the like.

 As acryl latex, a copolymer of alkyl methacrylate and alkyl acrylate can be used.

 As the vinyl acetate latex, vinyl acetate, higher fatty acid vinyl ester, maleic acid diester and / or a copolymer of ethylene can be used, and an emulsifying dispersant which is a protective colloid such as polyvinyl alcohol and hydroxyethyl cellulose. It is obtained by emulsion polymerization of vinyl acetate using

 In addition to these, synthetic latexes such as vinyl acetate-acrylic copolymer latex, vinyl chloride copolymer latex, ABS latex, NBR latex, and CR latex can also be used. Examples of binders other than latex include water-soluble binders and the like, and natural binders, semi-synthetic binders, synthetic binders and the like can be used. Examples of the natural binder include starch such as starch, mannan such as konjac, seaweed such as alginic acid, vegetable mucilage such as soybean syrup, microbial adhesive such as dextrin, and protein such as casein. Examples of the semi-synthetic binder include modified cellulose such as carboxymethyl cellulose and modified starch such as carboxymethyl starch. Examples of the synthetic binder include polyvinyl alcohol and sodium polyacrylate (the degree of neutralization of polyacrylic acid is 95 to 100 mol%). When a binder other than latex is used, the amount used (% by weight) is 0.01 to 20 based on the weight of the pigment and / or filler.

Such paper coatings are usually used in the form of an aqueous dispersion liquid, and if necessary, may contain other additives (for example, a water-retaining fluidity improver such as a polyacrylic acid-acrylic acid ester, Pigment dispersants such as sodium acrylate (polyacrylic acid neutralization degree 95 to 100 mol%), antifoaming agents such as fatty acid esters, lubricants such as calcium stearate, and glioxal polyamide urea Holmaldehyde or Po Waterproofing agents such as amide polyamine resins, wetting agents, preservatives, and fluorescent dyes) are added.

 Paper coatings can be applied to the base paper in a known manner, for example, Spray Co. overnight, Power—Temploco Co., Braid Co., Co., Rico Co., G. Toro Co., Co. It can be applied to the base paper by a size press, a rodco and an air knife. After coating, dry and finish calender ring, super calender ring or soft nip calender ring as necessary. The coating temperature is usually from 10 to 60 ° C, the drying temperature is usually from 90 to 150 ° C, and the temperature of calendaring, super-calendaring or soft nip calendering is usually 30 to 2 ° C. 0 o ° c.

 The dispersant for the heavy calcium carbonate wet grinding step of the present invention has an effect (dispersion effect) of dispersing fine particles in the production of a heavy calcium carbonate slurry in which the degree of pulverization of the heavy calcium carbonate is increased during the pulverization step to produce fine particles. ), Remarkable effects of keeping finely divided particles stable without agglomeration (stability) and effect of reducing viscosity of heavy calcium carbonate slurry (thinning effect).

 However, the present dispersant can also be used as a dispersant effective for micronizing and dispersing inorganic pigments other than heavy calcium carbonate. Therefore, in the production of paper coating paints, in any step of mixing heavy calcium carbonate slurry containing a dispersant for heavy calcium carbonate wet grinding step, pigment, filler and / or binder, You may mix the dispersing agent for porous calcium carbonate wet grinding process.

(Example)

 Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, parts mean parts by weight and% means% by weight.

<Example 1>

200 parts of water and 300 parts of isopropyl alcohol are put into a pressure-resistant reaction vessel equipped with a dropping line, a distillation apparatus, a stirrer, and a thermometer, and 300 parts of acrylic acid are stirred. And 100 parts of a 40% aqueous solution of sodium persulfate are dropped from each dropping line at a constant rate over a period of 3 hours at a constant rate while sealing (the pressure in the reaction vessel is 0.03-0.

(14 M Pa Gauge). The reaction temperature was kept at 65-100 ° C. After the completion of the dropwise addition, the mixture was kept at the same temperature for 3 hours, isopropyl alcohol was distilled off under reduced pressure while adding water, and after cooling to 30 ° C, the reaction product was taken out. Then the removed reactant 2 5

Using 0 parts of the mixture, the mixture was gradually neutralized with 2.2 parts of a 50% aqueous solution of sodium hydroxide while maintaining the temperature at 40 ° C or lower while stirring, and the acrylic acid-sodium acrylic acid salt copolymer (A 2

1) A dispersant 1 for heavy calcium carbonate wet grinding step of the present invention containing 40% of (acrylic acid unit: 98% by number) was obtained.

<Example 2>

 In the same manner as in Example 1, 250 parts of the dispersant 1 for heavy calcium carbonate wet milling step was further neutralized with 50% aqueous sodium hydroxide solution (14.4 parts) to give acrylic acid-acrylic acid. A dispersant 2 for heavy calcium carbonate wet grinding step of the present invention containing 40% of a sodium salt copolymer (A22) (acrylic acid unit: 85% by number) was obtained.

<Example 3>

 In the same manner as in Example 1, 250 parts of the dispersant 1 for the heavy-calcium carbonate wet grinding step was further neutralized with 25.6 parts of a 50% aqueous sodium hydroxide solution to give acrylic acid-acrylic acid. A dispersant 3 for heavy calcium carbonate wet grinding step of the present invention containing 40% of an acid sodium salt copolymer (A23) (acrylic acid unit: 75% by number) was obtained.

<Example 4>

 In the same manner as in Example 1, 250 parts of dispersant 1 for heavy-calcium carbonate wet grinding step was further neutralized with 36.7 parts of a 50% aqueous sodium hydroxide solution to give acrylic acid-acrylic acid. A dispersant 4 for a heavy calcium carbonate wet grinding step of the present invention containing 40% of a sodium salt copolymer (A24) (acrylic acid unit: 65% by number) was obtained.

<Example 5>

In the same manner as in Example 1, 250 parts of the dispersant 1 for the heavy calcium carbonate wet grinding step was further neutralized with 42.2 parts of a 50% aqueous sodium hydroxide solution. A dispersant 5 for a heavy calcium carbonate wet grinding step of the present invention containing 40% of a luic acid-sodium acrylate copolymer (A25) (acrylic acid unit: 60% by number) was obtained.

<Example 6>

 In the same manner as in Example 1, 250 parts of the dispersant 1 for heavy calcium carbonate wet grinding step was further neutralized with 47.8 parts of a 50% aqueous sodium hydroxide solution to obtain acrylic acid-acrylic acid. A dispersant 6 for heavy calcium carbonate wet grinding step of the present invention containing 40% of a sodium acid salt copolymer (A26) (acrylic acid unit: 55% by number) was obtained.

<Example 7>

 In the same manner as in Example 1, 250 parts of the dispersant 1 for heavy calcium carbonate wet grinding step was further neutralized with 48.7 parts of an 80% aqueous potassium hydroxide solution to obtain acrylic acid-acrylic acid. Dispersant 7 for the heavy calcium carbonate wet milling step of the present invention containing 40% of a sodium salt-potassium acrylate copolymer (A27) (acrylic acid unit: 52% by number) was obtained.

<Example 8>

 Into a reaction vessel equipped with a dropping line, a reflux condenser, a distillation apparatus, a stirrer, and a thermometer, add 300 parts of water and 200 parts of isopropyl alcohol, and, with stirring, 300 parts of acrylic acid and sodium persulfate. 100 parts of a 30% aqueous solution was dropped from each of the dropping lines at a constant rate over 3 hours, and reacted at atmospheric pressure. Reaction temperature was maintained at 65-90 ° C. After maintaining the same temperature for 3 hours after the completion of the dropping, isopropyl alcohol was distilled off under reduced pressure while adding water, and the reaction product was taken out after cooling to 30 ° C. Then, using 250 parts of the reaction product taken out, the mixture was gradually neutralized with 1.6 parts of magnesium hydroxide while maintaining the temperature at 40 ° C or less while stirring, and then a 50% aqueous sodium hydroxide solution was added. Neutralized with 7 parts, 40% of acrylic acid-magnesium acrylate-sodium acrylate copolymer (A28) (acrylic acid unit: 65% by number) according to the present invention. Dispersant 8 for calcium carbonate wet grinding step was obtained.

<Example 9>

Water 200 in a pressure-resistant reaction vessel equipped with a dropping line, a distillation device, a stirrer, and a thermometer. And 300 parts of isopropyl alcohol, and under stirring, 300 parts of acrylic acid and 200 parts of a 40% aqueous solution of sodium persulfate were dripped at a constant rate over 3 hours from separate dropping lines, and sealed (reaction) The reaction was performed at a pressure in the vessel of 0.03 to 0.14 MPa Gauge. The reaction temperature was kept at 65-85 ° C. After maintaining the same temperature for 3 hours after the completion of the dropwise addition, isopropyl alcohol was distilled off under reduced pressure while adding water, and the mixture was cooled to 30 ° C, and the reaction product was taken out. Then, using 250 parts of the reaction product taken out, gradually neutralize with 0.3 parts of lithium hydroxide while maintaining the temperature at 40 ° C or less under stirring, and further add 21.1 parts of a 50% aqueous sodium hydroxide solution. Neutralized, containing 40% of acrylic acid-lithium acrylate-sodium acrylate copolymer (A29) (acrylic acid unit: 80% by number) for the wet calcium carbonate wet grinding step of the present invention. Dispersant 9 was obtained.

<Example 10>

 200 parts of water and 300 parts of isopropyl alcohol are charged into a pressure-resistant reaction vessel equipped with a dropping line, a distillation apparatus, a stirrer, and a thermometer, and while stirring, 150 parts of acrylic acid and 179.2 parts of mesylic acid are stirred. And a 100% aqueous solution of sodium persulfate was dropped at a constant rate over 3 hours from each of the separate dropping lines, and sealed (the pressure in the reaction vessel was 0.03-0.03). 14MPaGauge). The reaction temperature was kept at 65-85 ° C. After maintaining the same temperature for 2 hours after the completion of the dropwise addition, isopropyl alcohol was distilled off under reduced pressure while adding water, and the mixture was cooled to 30 ° C., and the reaction product was taken out. Then, using 250 parts of the reaction product taken out, neutralize it with 2.6 parts of 25% aqueous ammonia gradually while maintaining the temperature at 40 ° C or less in a local exhaust system (draft) while stirring, and then add another 50 parts. Neutralized with 27.3 parts of aqueous sodium hydroxide solution, acrylic acid-acrylic acid ammonium salt-acrylic acid sodium salt-methacrylic acid-methacrylic acid ammonium salt-methacrylic acid sodium salt copolymer A dispersant 10 for heavy calcium carbonate wet grinding step of the present invention containing 40% of (A30) (acrylic acid unit and methacrylic acid unit: 70% by number) was obtained.

<Example 11> Charge 300 parts of water and 200 parts of isopropyl alcohol into a reaction vessel equipped with a dropping line, reflux condenser, distillation device, stirrer, and thermometer, and stir with stirring. —100 parts of azobisisobutyronitrile 30% isopropyl alcohol solution was dropped at a constant rate over a period of 5 hours from separate dropping lines and reacted at atmospheric pressure. Reaction temperature was maintained at 65-95 ° C. After maintaining the same temperature for 3 hours after the completion of the dropwise addition, isopropyl alcohol was distilled off under reduced pressure while adding water, and the mixture was cooled to 30 ° C. Then, using 250 parts of this reaction product, gradually neutralize with 9.3 parts of a 50% aqueous solution of sodium hydroxide while maintaining the temperature at 40 ° C or less while stirring to obtain a mixture of methacrylic acid and methacrylic acid. A dispersant 11 for a heavy calcium carbonate wet milling step of the present invention containing 40% of a sodium salt copolymer (A31) (90% by number of methacrylic acid units) was obtained.

 <Example 1 2>

 200 parts of water and 300 parts of isopropyl alcohol are charged into a pressure-resistant reaction vessel equipped with a dropping line, a distillation apparatus, a stirrer, and a thermometer. Under stirring, 300 parts of acrylic acid and 200 parts of a 40% aqueous solution of sodium persulfate are separately placed. The mixture was dropped at a constant rate over 4 hours from the dropping line, and the reaction was carried out in a sealed state (pressure in the reaction vessel was 0.03 to 0.14 MPa Gauge). The reaction temperature was kept between 65 and 105 ° C. After maintaining the same temperature for 3 hours after completion of the dropwise addition, isopropyl alcohol was distilled off under reduced pressure while adding water, and the mixture was cooled to 30 ° C., and the reaction product was taken out. Then, using 50 parts of the reaction product taken out, 33.3 parts of a 50% aqueous solution of sodium hydroxide was gradually added dropwise while stirring and keeping the temperature at 40 ° C or lower, and acrylate and sodium acrylate were co-polymerized. The dispersant 12 for heavy calcium carbonate wet milling process of the present invention containing 40% of the combined (A32) (acrylic acid unit: 70% by number) was obtained.

<Example 13>

300 parts of water and 200 parts of isopropyl alcohol are charged into a reaction vessel equipped with a dropping line, a reflux condenser, a distillation apparatus, a stirrer, and a thermometer, and while stirring, 300 parts of methyric acid and 2, 2'- Azobisisobutyronitrile 30% isopropyla 100 parts of the alcohol solution was dropped at a constant rate over 3 hours from each separate dropping line, and reacted at atmospheric pressure. Reaction temperature was maintained at 65-95 ° C. After maintaining the same temperature for 3 hours after the completion of the dropwise addition, isopropyl alcohol was distilled off under reduced pressure while adding water, and the mixture was cooled to 30 ° C, and the reaction product was taken out. Then, using 250 parts of the reaction product taken out, gradually neutralize with 38.9 parts of a 50% aqueous sodium hydroxide solution while maintaining the temperature at 40 ° C or lower while stirring, and then add methacrylic acid-medium sodium methacrylate. Dispersant 13 for heavy calcium carbonate wet grinding step of the present invention containing 40% of salt copolymer (A33) (acrylic acid unit: 65% by number) was obtained.

<Example 14>

 300 parts of water and 200 parts of isopropyl alcohol are put into a reaction vessel equipped with a dropping line, a reflux condenser, a distillation apparatus, a stirrer, and a thermometer, and stirred, and 260.9 parts of acrylic acid and 30% of sodium persulfate are stirred. 100 parts of the aqueous solution was dripped at a constant rate over 3 hours from each of the dropping lines, and reacted at atmospheric pressure. The reaction temperature was kept at 65-90 ° C. After the completion of the dropwise addition, the mixture was kept at the same temperature for 3 hours, and then the isopropyl alcohol was distilled off under reduced pressure while adding water. Then, using 50 parts of the reaction product taken out, gradually neutralize with 53.3 parts of a 50% aqueous solution of sodium hydroxide while stirring at 40 ° C or lower while stirring, and mix acrylic acid-sodium acrylate with sodium salt. Dispersant 14 for heavy calcium carbonate wet grinding step of the present invention containing 40% of polymer (A34) (acrylic acid unit: 52% by number) was obtained.

<Example 15>

 In the same manner as in Example 1, 250 parts of dispersant 1 for heavy calcium carbonate wet milling step was further neutralized with 41.1 parts of a 50% aqueous sodium hydroxide solution to give acrylic acid-sodium sodium acrylate. A dispersant 15 for heavy calcium carbonate wet grinding step of the present invention containing 40% of the copolymer (A35) (acrylic acid unit: 61% by number) was obtained. Comparative Example 1>

In the same manner as in Example 1, 252.2 parts of the dispersant 1 for heavy calcium carbonate wet grinding step was further neutralized with 55.6 parts of a 50% aqueous sodium hydroxide solution. A comparative dispersant 16 for wet calcium carbonate wet grinding process containing 40% of acrylic acid-acrylic acid sodium salt copolymer (X 1) (acrylic acid unit: 48, several%) was obtained.

 <Comparative Example 2>

 In the same manner as in Example 1, 252.2 parts of dispersant 1 for heavy calcium carbonate wet grinding step was further neutralized with 70% of a 50% aqueous sodium hydroxide solution to obtain acrylic acid. One milliliter of a comparative heavy calcium carbonate wet milling dispersant containing 40% of sodium acrylate copolymer (X2) (acrylic acid unit: 35% by number) was obtained. <Comparative Example 3>

 In the same manner as in Example 1, 252.2 parts of dispersant 1 for heavy calcium carbonate wet grinding step was further neutralized with 50% aqueous sodium hydroxide solution 81.1 parts, and acrylic acid was added. A comparative heavy calcium carbonate dispersant 18 containing 40% of a sodium acrylate acrylate copolymer (X 3) (acrylic acid unit: 25 several%) was obtained.

<Comparative Example 4>

 In the same manner as in Example 1, 252.2 parts of the dispersant 1 for heavy calcium carbonate wet milling step was further neutralized with 50% sodium hydroxide aqueous solution 92.2 parts, and acrylic acid was added. A comparative dispersant 19 for heavy calcium carbonate wet milling step containing 40% of —acrylic acid sodium salt copolymer (X 4) (acrylic acid unit: 15 several%) was obtained.

 <Comparative Example 5>

 In the same manner as in Example 1, 252.2 parts of dispersant 1 for heavy calcium carbonate wet grinding step was further neutralized with 50% aqueous sodium hydroxide solution 106.7 parts, and acrylic acid A comparative dispersant 20 for the wet-milling process of heavy calcium carbonate, which contained 40% of a sodium acrylate copolymer (X5) (acrylic acid unit: 2% by several percent), was obtained.

<Comparative Example 6> According to Example 4 described in Japanese Patent Publication No. 11-214175, the dispersant 1 for the heavy calcium carbonate wet grinding step was prepared in the same manner as in Example 1 of the present invention. Further, after neutralization with a 50% aqueous sodium hydroxide solution, the mixture is neutralized with a 2-mol adduct of dodecylamine and propylene oxide, and a propylene oxide 2-mol adduct of acrylic acid / sodium acrylate / dodecylamine acrylate is added. A comparative heavy calcium carbonate wet milling dispersant 21 containing 40% of the copolymer (X 9) (acrylic acid unit: 27% by number) was obtained.

Table 1 shows the constitutions of the dispersants 1 to 20 for the heavy calcium carbonate wet grinding step of Examples 1 to 15 and Comparative Examples 1 to 6.

Composition of dispersant for heavy calcium carbonate grinding process

 S: Ratio of (meth) acrylic acid units based on the number of monomer units constituting the copolymer (number%)

 T: Counter ion of (meth) acrylate unit

 U: Weight average molecular weight (Mw) of (co) polymer

V: weight average molecular weight (Mw) / number average molecular weight (Mn) The GPC measurement conditions for weight average molecular weight (Mw) and number average molecular weight (Mn) are as follows.

 Applicable equipment: Tosoichi Co., Ltd. Model HLC-8120 GPC

 Column: Series G 5000 PWXL and model G 3000 PWXL manufactured by Tosoichi Co., Ltd. are connected in series.

 Detector: RI detector,

 Data processor: Tosoichi Co., Ltd. Model S C—8020

 Column temperature: 40 ° C,

 Eluent: 0.1 M phosphate buffer (mixing ratio ① / ②: 1/1) between aqueous sodium hydrogen phosphate solution ② and aqueous sodium dihydrogen phosphate solution ②

 Eluent flow rate: 0.6 m1,

 Sample concentration: 0.4% by weight eluent solution,

 Sample solution injection volume: 50 1 ヽ

Standard substance: TSK standard polyethylene glycol manufactured by Tosoichi Co., Ltd. (weight average molecular weight (hereinafter abbreviated as M) measured by light scattering method) SE-150: (M) 885, 000, SE- 70: (M) 5 10 ₅ 000, SE-30: (M) 340 ₃ 000, SE-15: (M) 1 70,000, SE-8: (M) 95,000, SE-5: ( M) 46,000, SE-2: (M) 26,000), reagent manufactured by Wako Pure Chemical Industries, Ltd. (polyethylene glycol that has passed Wako Standard Class 1) 6000: (M) 7,500 ヽ Wako Pure Chemical Industrial Co., Ltd. reagent (special grade ethylene glycol: molecular weight 62)

 The performances of the dispersants 1 to 20 for the heavy calcium carbonate wet milling process prepared in Examples 1 to 15 and Comparative Examples 1 to 6 were evaluated by the following methods, and the results are shown in Tables 2 to 5.

<Evaluation>

 (1) Preparation of heavy calcium carbonate slurry

① Preparation of base slurry— 1

Coreless mixer (Toki Kika Co., Ltd., TK homogenizer AM-20 1 part of the evaluation sample and 333.3 parts of water were stirred and mixed at 1, OOO rpm, and then calcite crystal heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd.) was added. Dry-milled limestone raw material, volume average particle size 8〃m) Gradually add 1,000 parts, and after adding all heavy calcium carbonate, stir at 20, OOO rpm for 20 minutes. Thus, a base slurry (A) was obtained.

② Preparation of base slurry-2

 Calcite crystal-type heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., dry-ground product of limestone, volume average particle diameter 8〃m) was replaced with heavy calcium carbonate (Nippon Cement Co., Ltd., dry-ground sample of limestone material, A base slurry (B) was obtained in accordance with the adjustment (1) of the base slurry (1) except that the volume average particle size was changed to 5 Om).

 ③ Preparation of base slurry 1

 Calcite crystal-type heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., dry-ground product of limestone, volume average particle diameter 8 m) was replaced with heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., dry-ground sample of limestone material, volume Except that the average particle diameter was changed to 500 m), a pace slurry (C) was obtained according to (1) Adjustment of base slurry (1).

 ④Preparation of base slurry— 3

 Calcite crystal-type heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., dry-ground product of limestone, volume average particle size 8 / m) was replaced with heavy calcium carbonate (Nippon Cement Co., Ltd., dry-ground sample of limestone material, A base slurry (D) was obtained in the same manner as in the preparation of the base slurry (1), except that the volume average particle diameter was changed to 5,00 O jm).

湿 Wet grinding of base slurry 1

1,000 parts of base slurry (A), 2,000 parts of media (silica sand, volume average particle diameter l mm), and attritor capable of wet grinding (Oishi Kikai Seisakusho, S MT) at 1,500 rpm for about 30 minutes, and wet-pulverize in a closed state. Then, filter through a stainless steel mesh (JISZ8801-1-1: 20000) with openings of 38 mm. A finely ground slurry was obtained. Next, a slurry (AII) was obtained by adjusting the evaporation residue (slurry weight: 1 to 1.5 g, 160 ° C., 20 minutes) of the finely ground slurry to 75%.

 湿 Wet grinding of base slurry 2

 In the same manner as in ⑤, 1,000 parts of the base slurry (A) was wet-milled in a sealed manner at 2,000 rpm and 1,500 rpm for 60 minutes with media 2,000 parts and an attritor. The mixture was filtered through a stainless steel wire mesh of 網 m to obtain a finely pulverized slurry. A slurry (AIII) was obtained by adjusting the evaporation residue of the finely ground slurry to 75%.

湿 Wet grinding of pace slurry 3

 In the same manner as in ⑤, 1,000 parts of the base slurry (A) was wet-pulverized in a closed manner at 1,500 rpm and 1,500 rpm for about 90 minutes with a media of ◦200 parts and an attritor. Filtration was performed using a 38-m-long stainless steel wire mesh to obtain a finely pulverized slurry. A slurry (AIV) was obtained by adjusting the evaporation residue of the pulverized slurry to about 5%.

湿 Wet grinding of pace slurry 4

 In the same manner as in ⑦, 1,000 parts of the pace slurry (B) is wet-milled in a sealed state at 2,000 rpm and an attritor at 1,500 rpm for about 90 minutes, and the opening is 38 m. To obtain a finely pulverized slurry. A slurry (BIV) was obtained by adjusting the evaporation residue of the finely ground slurry to 75%.

湿 Wet grinding of base slurry 5

 In the same manner as in ⑦, 1.00 part of the base slurry (C) was wet-pulverized in 2,000 parts of media and 1,500 rpm at 1,500 rpm in a sealed state for about 90 minutes. The mixture was filtered through a 38-zm stainless steel mesh to obtain a finely ground slurry. A slurry (CIV) was obtained by adjusting the evaporation residue of the finely ground slurry to 75%.

湿 Wet grinding of base slurry 4

In the same manner as in ⑦, add 1,000 parts of base slurry (D) to 2000 parts of media After wet milling at 1,500 rpm for about 90 minutes in a closed air at Atelier Yuichi, the mixture was filtered through a stainless steel mesh with openings of 38 m to obtain a finely ground slurry. A slurry (DIV) was obtained by adjusting the evaporation residue of this pulverized slurry to 75%.

 (2) Slurry viscosity measurement

The slurries (A1) to (AIV) and (BIV) to (DIV) were adjusted to a temperature of 25 ° C, and stirred immediately at 1,000 rpm for 5 minutes in a stirring mode. The slurry viscosity (N 1) after 60 seconds at a rotation speed of 60 rpm was measured using a mold viscometer (TV-20, manufactured by Tokimec Co., Ltd.). After standing in a thermostat at 25 ° C for 7 days, the slurry viscosity (N7) was measured in the same manner. Tables 2 and 3 show the measurement results.

2 Slurry viscosity

B type viscosity (mPa's)

 Slurry-(A ll) Slurry-(A III)

N 1 N 7 N 1 N 7

1 220 220 210 215

2 210 210 200 200 Actual 3 195 195 190 190

4 190 190 195 205

5 195 215 200 210 Al 6 210 225 205 225

7 220 230 220 240

8 225 230 210 225 Example 9 225 250 225 250

1 0 220 225 215 220

1 1 240 250 220 240

1 2 270 420 290 410

1 3 280 280 310 330

1 4 290 300 330 350

1 5 190 210 195 200

1 405 615 570 1450 ratio 2 440 775 645 1770 comparison 3 470 980 710 1900 Example 4 510 1120 800 1970

5 560 1500 920 2010

6 440 800 630 1850

3 Slurry viscosity

Β type viscosity (mPa • s)

 Slurry (AIV) Slurry (BIV) Slurry (CIV) Slurry (DIV)

N 1 N 7 Ν 1 Ν 7 N 1 N 7 N 1 Ν 7

1 185 185 185 185 190 195 195 195 200

2 180 180 180 185 190 190 200 205

3 185 180 190 190 195 200 205 210 Actual 4 190 195 190 190 200 205 215 220

5 195 200 210 215 225 230 235 240

6 200 220 290 295 295 295 300 295 295 Allocation 7 220 240 325 330 325 330 335 340

8 200 205 240 245 250 255 255 255

9 210 230 245 250 255 255 260 265 Example 1 0 205 210 210 215 220 225 230

 1 1 210 23ο 250 255 260 270 275

1 2 300 440 310 310 320 330 340 345

1 3 340 470 345 ύ 0 360 ^ 60 3D5

1 4 320 350 330 335 330 335 340 345

1 5 190 190 200 205 210 215 225 225

1 825 2350 840 2600 10,000 or more 10,000 or more 10,000 or more Up 10,000 2 970 2850 1060 3100 10,000 or more 10,000 or more 10,000 or more Compare 3 1050 2800 1300 3250 10,000 or more 以上 10,000 or more 10,000 More than 10,000 Ex. 4 1200 3050 1300 3100 10,000 or more 10,000 or more

5 1400 2900 1670 3460 10,000 or more 10,000 or more 10,000 or more 10,000 or more

6 1115 2770 1230 2940 10,000 or more 10,000 or more 10,000 or more 10,000 or more

The dispersant of the present invention (Examples 1 to 14) has a significantly lower viscosity (N 1) of the obtained slurry than the comparative dispersant (Comparative Examples 1 to 6), and has a dispersing effect and a reduced effect. The viscous effect was extremely excellent. Also, the viscosity (N7) after 7 days was extremely low, and the stability of the particles was extremely excellent.

 (3) Volume average particle size measurement method

 Laser light diffraction scattering particle size distribution analyzer (trade name: Micro Track)

(MICROTRAC UPAs manufactured by Leeds and Northerup) under the following conditions (laser wavelength: 780 nm, measurement temperature: 25 ° C, dispersion medium: water, calcite crystal-type heavy carbon dioxide concentration: 2.5%, measurement) At time 6 minutes), the volume average particle diameter was measured, and the measurement results are shown in Tables 4 and 5.

S-S

Dimension

Dimension

Table 5 Volume average particle size

本発明の分散剤 （実施例 1~15) は、 比較例用の分散剤 （比較例 1 6) に 比較して、 重質炭酸カルシウム粒子の体積平均粒子径が著しく小さく、 分散効果 に極めて優れていた。 産業上の利用可能性

The dispersant of the present invention (Examples 1 to 15) has a remarkably small volume average particle diameter of the heavy calcium carbonate particles and is extremely excellent in the dispersing effect as compared with the dispersant for the comparative example (Comparative Example 16). I was Industrial applicability

As described above, the dispersing agent for the heavy calcium carbonate wet grinding step of the present invention is a heavy calcium carbonate wet grinding step (microparticulated heavy calcium carbonate slurry production step). Used for The heavy calcium carbonate slurry is used, for example, as a pigment for paper coating paint.

Claims

The scope of the claims 1. A process of wet-pulverizing heavy calcium carbonate having a volume average particle diameter of Y m to a volume average particle diameter of 0.000 0 1 Y to 0.01 Y〃m and 0.01 to 0.7 μm. (Meth) acrylic acid (co) polymer (Al), (meth) acrylic acid- (meth) acrylate copolymer (A2) and (meth) acrylic acid Salt (co) polymer comprising at least one polymer (A) selected from the group consisting of polymer (A3), and based on the number of all monomer units constituting (A), (meth) A dispersant for a heavy calcium carbonate wet grinding step, wherein the acrylic acid unit content is 60 to 100% by number. 2. The dispersant according to claim 1, wherein the content of the (meth) acrylic acid unit is 61 to 100% by number based on the total number of monomer units constituting the polymer (A). 3. The polymer (A) comprises (meth) acrylic acid- (meth) acrylate copolymer (A 2) and / or (meth) acrylate (co) polymer (A 3); 2. The dispersant according to claim 1, wherein the (meth) acrylate unit is an alkali metal salt unit, an alkaline earth metal salt unit and / or an ammonium salt unit.  4. In the method for producing a heavy calcium carbonate slurry, the (meth) acrylic acid (co) polymer (A l), the (meth) acrylic acid- (meth) acrylate copolymer (A2) and (meth) ) A polymer comprising at least one polymer (A) selected from the group consisting of acrylate copolymers (A3), based on the number of all monomer units constituting (A), (Meth) Using a dispersant having an acrylic acid unit content of 50 to 100 and a few%, heavy calcium carbonate is converted from a volume average particle diameter Y m to a volume average particle diameter 0.000 00 1 Y to 0.01 A method for producing a heavy calcium carbonate slurry, comprising a step of wet pulverization into a fi m. 5. The method according to claim 4, wherein the heavy calcium carbonate is calcite crystal heavy calcium carbonate. 6. Volume average particle size after wet milling is 0.0 000 1 Y ~ 0.0 0 1 The production method according to claim 4, wherein the concentration of heavy calcium carbonate in the slurry of heavy calcium carbonate is 75 to 85% by weight. A heavy calcium carbonate slurry comprising the heavy calcium carbonate wet grinding step dispersant according to claim 1. A paper coating composition comprising the dispersant for the heavy calcium carbonate wet grinding step according to claim 1. A coated paper coated with the paper coating paint according to claim 8. 0. A heavy calcium carbonate slurry comprising the heavy calcium carbonate wet grinding step dispersant according to claim 1, a pigment, a filler, a binder and / or the heavy calcium carbonate wet grinding step according to claim 1. A method for producing a paper coating composition comprising a step of mixing a dispersing agent for paper.