WO2007094076A1

WO2007094076A1 - Process for producing slurry of heavy calcium carbonate

Info

Publication number: WO2007094076A1
Application number: PCT/JP2006/302879
Authority: WO
Inventors: Takashi Nakano; Hirofumi Ohi
Original assignee: San Nopco Ltd.
Priority date: 2006-02-17
Filing date: 2006-02-17
Publication date: 2007-08-23

Abstract

A process for producing a slurry having excellent dispersion stability, by which heavy calcium carbonate can be easily reduced to fine particles. The process for producing a slurry of heavy calcium carbonate comprises a wet pulverization step in which heavy calcium carbonate having a volume-average particle diameter of Y µm is pulverized into heavy calcium carbonate having a volume-average particle diameter which is 0.0002Y-0.5Y µm and is 0.9-1.5 µm with the aid of a dispersant for the wet pulverization of heavy calcium carbonate, the dispersant comprising at least one polymer (A) selected from the group consisting of (meth)acrylic (co)polymers, (meth)acrylic acid/(meth)acrylic acid salt copolymers, and (meth)acrylic acid salt copolymers. In the polymer (A), the (meth)acrylic acid salt units contained therein comprise 49.9-99 parts by mole of alkali metal salt units, 0.1-10 parts by mole of alkaline earth metal salt units, and 0-10 parts by mole of ammonium salt units, and the (meth)acrylic acid salt units account for 50-99% by number of all monomer units constituting the polymer (A).

Description

Specification

Method for producing heavy calcium carbonate slurry

Technical field

[0001] The present invention relates to a method for producing heavy calcium carbonate slurry. More specifically, the present invention relates to a method for producing heavy calcium carbonate slurry suitable for paper coating.

Background art

[0002] Conventionally, after dry-pulverizing heavy calcium carbonate, among all carboxyl groups, 10 to 99.

Alpha 99 mole% alkali metal salt from 0.01 to 5 mole ^_0/0 constitutes an organic amine salt, beta - and wet pulverized using an unsaturated carboxylic acid salt copolymers strength becomes pigment dispersing agent, heavy A method of obtaining a calcium carbonate slurry (Patent Document 1) is known. Conventionally, using a dispersant having a (meth) acrylic acid unit of 60 to: LOO number%, the heavy calcium carbonate having a volume average particle size of Υ is changed to a heavy calcium carbonate of 0.0001Y to 0.1Y. A method of obtaining a heavy calcium carbonate slurry by wet pulverization (without dry pulverization) (Patent Document 2) is known.

Patent Document 1: Japanese Patent Laid-Open No. 11-217534

Patent Document 2: International Publication WO2004Z087574 Nonfret

Disclosure of the invention

Problems to be solved by the invention

However, in the former former method, it is necessary to perform wet pulverization after dry pulverization. Furthermore, if the slurry is pulverized to a volume average particle size of 1.5 m or less using a dry pulverization process and a wet pulverization process, and the slurry has a heavy calcium carbonate concentration of 70% by weight or more, the slurry viscosity over time There is a problem that rises (the dispersion stability is bad).

On the other hand, the conventional latter method has a problem that the pulverization time becomes long when the volume average particle diameter is pulverized to 0.9 to 1.5 m.

Therefore, an object of the present invention is to enable heavy calcium carbonate to be easily atomized (in a short time only by a wet pulverization step without requiring a dry pulverization step), and to produce a slurry with excellent dispersion stability. It is providing the manufacturing method which can be manufactured. Means for solving the problem

[0004] As a result of intensive studies to solve such problems, the present inventors have found that a specific polymer can solve the above problems, and have reached the present invention. That is, the method for producing the heavy calcium carbonate slurry of the present invention comprises (meth) acrylic acid (co) polymer (Al), (meth) acrylic acid (meth) acrylate copolymer (A2) and (meta). ) Acrylate copolymer (A3) A polymer (A) having at least one kind of force selected from the group also having strength, and (meth) acrylic acid units contained in (A) are (meth) acrylic. From 49.9 to 99 mole parts of alkali metal salt units, 0.1 to 10 mole parts of alkaline earth metal salt units of (meth) acrylate and 0 to 10 mole parts of (meth) acrylic acid ammonium salt units Based on the number of all monomer units constituting (A), a dispersant having 50 to 99% by weight of (meth) acrylate units, and a dispersant for heavy calcium carbonate wet pulverization step Using volume average particle size Y; zm heavy carbonate power Lucium volume average particle size 0.00002Y ~ 0.5Y! It is summarized as including a wet pulverization step of pulverizing to 11 to 0.9 to 1.5 m heavy calcium carbonate.

The invention's effect

[0005] The method for producing heavy calcium carbonate slurry of the present invention makes it possible to atomize heavy calcium carbonate in a very simple manner (in a short time only by a wet pulverization step without requiring a dry pulverization step). And the slurry excellent in dispersion stability can be manufactured.

That is, according to the production method of the present invention, even when pulverizing to heavy calcium carbonate having a volume average particle size of 0.9 to 1.5 m, the time required for pulverization is shortened. According to the production method of the present invention, the volume average particle diameter of 0.9 to 1. Ground to 5 m, even heavy calcium carbonate slurry concentration of 70 weight ^_0/0 or more heavy carbonate force Rushiumu, The slurry viscosity stabilizes over time.

Therefore, when the heavy calcium carbonate slurry that can be produced by the production method of the present invention is used for paper coating, not only the coating operability (high-speed coating) during paper coating is improved, but also paper coating. This is extremely effective for increasing the concentration of paint. For this reason, the heavy calcium carbonate slurry produced by the production method of the present invention can achieve improved operability and quality in the production of coated paper, and further results in reduced drying load due to higher concentration. This is particularly suitable for the production of paper-coated paper. BEST MODE FOR CARRYING OUT THE INVENTION

[0006] (Meth) acrylic acid means acrylic acid and Z or methacrylic acid, and (co) polymer means a polymer and Z or copolymer.

[0007] The (meth) acrylic acid (co) polymer (A1) includes an acrylic acid polymer, a methacrylic acid polymer, and an acrylic acid-methacrylic acid copolymer. The (meth) acrylic acid (meth) acrylate copolymer (A2) includes acrylic acid acrylate copolymer, acrylic acid-methacrylate copolymer, methacrylic acid acrylate copolymer, Methacrylic acid methacrylate copolymer, acrylic acid-methacrylic acid acrylate copolymer, acrylic acid-methacrylic acid-methacrylate copolymer and acrylic acid-methacrylic acid acrylate-methacrylate copolymer are included. Examples of the (meth) acrylate (co) polymer (A3) include an acrylate polymer, a methacrylate polymer, and an acrylate-methacrylate copolymer. Polymer (A) is composed of (meth) acrylic acid (co) polymer (Al), (meth) acrylic acid (meth) acrylate copolymer (A2) and (meth) acrylate (co) polymer. It is at least one selected from the group consisting of combined (A3) forces. In the case of a copolymer, the polymerization type may be a block, random, or a mixture thereof.

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

[0008] Examples of the alkali metal salt include salts of lithium, potassium, sodium and the like. Of these salts, sodium salts and strong rhodium salts are preferred from the viewpoint of the effect of dispersing heavy calcium carbonate, and sodium salts are particularly preferred.

[0009] Examples of alkaline earth metal salts include salts of calcium, magnesium, norlium, zinc, and the like. Of these salts, calcium salts, magnesium salts, and zinc salts are preferred from the viewpoint of the effect of dispersing heavy calcium carbonate particles, and more preferred are calcium salts and magnesium salts, and particularly preferred are magnesium salts.

[0010] Ammonium salts include ammonia (NH) salt and organic ammonium salt (aliphatic salt).

Four

A salt of an alkylene oxide adduct of an aliphatic amine, an alkanolamine salt, an alicyclic amine salt, an aromatic amine salt, and the like.

[0011] Aliphatic amin salts include primary amin salts, secondary amamine salts, tertiary amamine salts and quaternary ammo- salts. Any of um salt may be used. As the primary amine salt, a monoalkylamine salt having 1 to 12 carbon atoms is used, and examples thereof include salts such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, decylamine, and dodecylamine. Examples of the secondary amine salt include dialkylamine salts having 2 to 24 carbon atoms such as dimethylamine, jetylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dioctylamine, didecylamine, and didodecylamine. As the tertiary amine salt, a trialkylamine salt having 3 to 9 carbon atoms is used, and examples thereof include salts such as trimethylamine, triethylamine, tripropylamine, and tributylamine. As the quaternary ammonium salt, tetraalkyl ammonium salts having 4 to 16 carbon atoms are used, and examples thereof include tetramethyl ammonium, tetraethyl ammonium and tetrabutyl ammonium. .

[0012] Salts of aliphatic amine amine alkylene oxide adducts include salts of aliphatic amine amine oxide adducts (addition moles 2 to 20) or propylene oxide adducts (addition moles 2 to 20). And quaternary ammonium salts obtained by quaternizing these amines with a quaternizing agent (such as ethylene oxide, dimethyl sulfate, jetyl sulfate, dimethyl carbonate, or methyl chloride).

[0013] Examples of the alkanolamine salt include alkanolamine salts having 1 to 20 carbon atoms, such as methanolamine, ethanolamine, diethanolamine, triethanolamine, prono-V-lamine, or the like. Examples include salts of butanolamine, and quaternary ammonium salts obtained by quaternizing these alkanolamines with a quaternizing agent.

[0014] Examples of the alicyclic amine salts include cycloalkylamine salts having 5 to 8 carbon atoms, and examples include salts such as cyclopentylamine, cyclohexylamine, and cyclohexylmethylamine. In addition, quaternary ammonium salts obtained by quaternizing these cycloalkylamines with a quaternizing agent can be used.

[0015] As the aromatic amine salt, a salt of arylamine having 6 to 10 carbon atoms is used, and examples thereof include salts of aline, benzylamine, benzylmethylamine, toluidine, and the like. A quaternary ammonium salt that has been quaternized with a quaternizing agent can be used.

[0016] In the (meth) acrylic acid (co) polymer (A1), an acrylic acid-methacrylic acid copolymer In this case, the content (number%) of acrylic acid units is preferably 50 to: LO 0 force S based on the total number of acrylic acid units and methacrylic acid units, from the viewpoint of the dispersion effect of heavy calcium carbonate particles, etc. More preferably, it is 75-99.9, Most preferably, it is 90-99.9. Further, the content (number%) of the methacrylic acid unit is preferably 0 to 50 based on the total number of acrylic acid units and methacrylic acid units from the viewpoint of the dispersion effect of the heavy calcium carbonate particles. More preferably, it is 0.1 to 25, and particularly preferably 0.1 to 10.

[0017] (Meth) acrylic acid- (meth) acrylate copolymer (A2) て The content (number%) of (meth) acrylic acid units is (meth) acrylic acid units and (meth) Based on the total number of acrylate units, from the viewpoint of the dispersion effect of heavy calcium carbonate particles, etc., 1 to 50 is preferred, more preferably 1 to 40, particularly preferably 3 to 35, most preferably 5 to 30. Further, the content (number%) of (meth) acrylate units is preferably 50 to 99 intensities, more preferably, based on the total number of (meth) acrylic acid units and (meth) acrylate salts units. Is from 60 to 99, particularly preferably from 65 to 97, most preferably from 70 to 95. When methacrylic acid units are included, the content (number%) of acrylic acid units is based on the total number of acrylic acid units and methacrylic acid units from the viewpoint of the dispersion effect of heavy calcium carbonate particles. To 99.9 force S, more preferably 75 to 99, and particularly preferably 90 to 99. The content (number%) of the methacrylic acid unit is preferably 0.1 to 50 based on the total number of acrylic acid units and methacrylic acid units from the viewpoint of the dispersion effect of the heavy calcium carbonate particles. More preferably, 1 to 25, particularly preferably 1 to: LO. When the methacrylate unit is included, the content (number%) of the acrylate unit is determined based on the total number of the acrylate unit and the methacrylate unit. From the viewpoint of the effect, etc., 50 to 99.9 force S is preferable, more preferably 75 to 99, and particularly preferably 90 to 99. Further, the content (number%) of the methacrylate unit is 0.1 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. -50 is preferable, more preferably 1-25, and particularly preferably 1-10.

[0018] Te you, the (meth) acrylate (co) polymer (A3), acrylate - For methacrylate copolymer polymer, the content of the acrylate units (number ^_0/0) Based on the total number of acrylate units and methacrylate units, the viewpoint of the dispersion effect of heavy calcium carbonate particles, etc. The strength is preferably 50 to 99.9 force S, more preferably 75 to 99.9, and particularly preferably 90 to 99.9. In addition, the content (number%) of the methacrylate unit is set to 0. 0 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. 1 to 50 is preferable, more preferably 0.1 to 25, and particularly preferably 0.1 to 10.

[0019] (Meth) acrylic acid (co) polymer (A1), (meth) acrylic acid (meth) acrylate copolymer

(Α2) and (meth) acrylate (co) polymer (A3) may contain other monomers as structural units in addition to (meth) acrylic acid and (meth) acrylate.

As the other monomer, any monomer that can be copolymerized with (meth) acrylic acid and cocoon or (meth) acrylate can be used without limitation. For example, the monomer described in International Publication WO2004Z087574 (Unsaturated monocarboxylic acid ester, unsaturated dicarboxylic acid, a-hydroxy unsaturated monocarboxylic acid, hydroxylalkyl unsaturated carboxylic acid ester, polyalkylene glycol unsaturated monomer, (meth) atallyloyl group-containing amide, bull ester , Vinyl ether, sulfo group-containing unsaturated monomer, aromatic unsaturated monomer, aliphatic unsaturated monomer, alicyclic unsaturated monomer, and cyano group-containing unsaturated monomer} Can be used.

[0020] Other monomer units are not included from the viewpoint of dispersion effect, etc.! / Is preferred, but when U contains other monomer units, the content of other monomer units (number %) In the case of the (meth) acrylic acid (co) polymer (A1), preferably 0.1 to 3, more preferably 0, based on the total number of monomer units constituting the copolymer. 1 to 2, particularly preferably 0.1 to 1. In the case of (meth) acrylate (meth) acrylate copolymer (A2), 0.1 to 5 is preferable based on the total number of monomer units constituting the copolymer. More preferably, it is from 0.1 to 3, particularly preferably from 0.1 to 1. In the case of the (meth) acrylate copolymer (A3), 0.1 to 3 is preferable based on the total number of monomer units constituting the copolymer, more preferably 0.1 to 2, particularly preferably 0.1 to 1.

[0021] Polymer (A) consists of (meth) acrylic acid (co) polymer (A1), (meth) acrylic acid (meth) acrylate copolymer (A2) and Z or (meth) acrylate It is sufficient that the polymer (A) is selected from the group consisting of the (co) polymer (A3) and has at least one kind of strength. It is preferable that the acid- (meth) acrylate copolymer (A2) is composed of (A2) or (A2) and (meth) acrylate copolymer (A3), more preferably acrylic acid monoacrylic acid. Salt copolymer, acrylic acid-methacrylate copolymer, methacrylic acid acrylate copolymer, methacrylic acid-methacrylate copolymer, acrylic acid-methacrylic acid acrylate copolymer, acrylic acid-methacrylic acid-methacrylate Copolymer and Z or acrylic acid Methacrylic acid monoacrylate-methacrylate copolymer force, or these copolymer and acrylate polymer, methacrylate polymer and Z or acrylate metatalic acid And particularly preferably an acrylic acid-acrylate copolymer, an acrylic acid-methacrylate copolymer, an acrylic copolymer. Acid-methacrylic acid acrylate copolymer and Z or acrylic acid-methacrylic acid acrylate-methacrylate copolymer force, or these copolymers and acrylate polymer and Z or acrylate monomethacrylic acid It is made of a salt copolymer, and most preferably, it is made of acrylic acid monoacrylate salt or is made of this copolymer and an acrylate polymer.

[0022] The content (number%) of (meth) acrylic acid units contained in polymer (A) is preferably 1 to 50 based on the total number of monomer units constituting (A). More preferably, it is 1-40, Most preferably, it is 3-35, Most preferably, it is 5-30. Within this range, even if there is no dry pulverization process, only the wet pulverization process will achieve a better dispersion effect and stability force S of heavy calcium carbonate particles.

Further, the content (number%) of the (meth) acrylate unit contained in the polymer (A) is preferably 50 to 99 based on the total number of monomer units constituting (A). Preferably it is 60-99, Especially preferably, it is 65-97, Most preferably, it is 70-95. Within this range, even if there is no dry pulverization step, the dispersion effect and stability of the heavy calcium carbonate particles are further improved only by the wet pulverization step.

[0023] The (meth) acrylate unit contained in the polymer (A) is composed of (meth) acrylic acid alkali metal salt unit, (meth) acrylic acid alkaline earth metal salt unit and, if necessary, (meth) acrylic acid. The salt salt unit force is composed.

The (meth) acrylate unit is an alkali metal salt of (meth) acrylate 9.9 to 99 mol parts (5 5 to 90 mol parts are preferred, more preferably 60 to 80 mol parts), (meth) acrylic acid alkaline earth metal salt is 0.1 to 10 mol parts (0.5 to 8 mol parts are more preferred) Preferably 1 to 5 mole parts), and (meth) acrylic acid ammonium salt is composed of 0 to 10 mole parts (0 to 8 mole parts are preferred, more preferably 0 to 5 mole parts). . Within this range, even when there is no dry pulverization step, the dispersion effect and stability of the heavy calcium carbonate particles are further improved only by the wet pulverization step.

[0024] When the (meth) acrylic acid (co) polymer (A1) is contained in the polymer (A), the content (% by weight) is 1 to 4 based on the total weight of (A2) and (A3). 50 is preferable, more preferably 1 to 47, and particularly preferably 5 to 30. Within this range, even if there is no dry pulverization step, only the wet pulverization step will improve the dispersion effect and stability of the quality calcium carbonate particles, and realize the formation of heavy calcium carbonate fine particles with higher pulverization efficiency. be able to.

When the polymer (A) contains this (meth) acrylic acid (meth) acrylate copolymer (A2), the content (% by weight) is based on the total weight of (A2) and (A3). 1-99 is more preferable, 10-90 is more preferable, and 20-80 is particularly preferable. Within this range, even if there is no dry pulverization step, the dispersion effect and stability of the heavy calcium carbonate particles are further improved only by the wet pulverization step, and further the formation of heavy calcium carbonate fine particles with higher pulverization efficiency is realized. be able to.

When the (meth) acrylate (co) polymer (A3) is contained in the polymer (A), this content (weight%) is based on the total weight of (A2) and (A3) from 1 to 99 is preferred, more preferably 10 to 90, and particularly preferably 20 to 80. Within this range, even if there is no dry pulverization step, the dispersion effect and stability of the heavy calcium carbonate particles are further improved, and it is possible to realize heavy calcium carbonate fine particles with higher pulverization efficiency.

[0025] The weight average molecular weight (Mw) of the polymer (A) is preferably 8,000 to 50,000, more preferably <is 9,000 to 40,000, particularly preferably <is 10,000 to 20,000. Within this range, the dispersion effect and stability of the heavy calcium carbonate particles are further improved. Mw is measured by gel permeation chromatography (GPC) using polyethylene glycol as a standard substance (the same applies hereinafter). The number average molecular weight (Mn) of the polymer (A) is 4,000 to 41,000, more preferably 4,200 to 33,000, particularly preferably 4,400 to 17,000. Within this range, the dispersion effect and stability of the heavy calcium carbonate particles are further improved. Mn is measured by gel permeation chromatography (GPC) using polyethylene glycol as a standard substance (the same shall apply hereinafter).

[0026] The ratio (MwZMn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polymer (A) is preferably 1.2 to 2.0, more preferably 1.2 to 1.9, Particularly preferred is 1.2 to 1.8. Within this range, the dispersion effect and stability of the heavy calcium carbonate particles are further improved.

[0027] (Meth) acrylic acid (co) polymer (A1) and (meth) acrylic acid (meth) acrylate copolymer (A2) and (meth) acrylate (co) polymer (A3) Can be obtained by a usual polymerization method (solution polymerization method, bulk polymerization method, reverse phase suspension polymerization method and the like), and is not particularly limited, but a solution polymerization method is preferred.

In the case of (meth) acrylic acid- (meth) acrylate copolymer (A2), it may be produced by copolymerization of (meth) acrylic acid and (meth) acrylate. It can also be produced by obtaining an acrylic acid (co) polymer and then neutralizing the (co) polymer with a base or the like.

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

[0028] As a solvent that can be used in the solution polymerization method, a normal polycarboxylic acid polymerization solvent and the like can be used, and water, Z, alcohol, and the like are included. Examples of 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. Of these, water, a mixed solvent of water and alcohol are preferred, more preferably a mixed solvent of water and alcohol, particularly preferably a mixed solvent of deionized water and isopropyl alcohol.

When using a mixture of water and alcohol, the mixing weight ratio (water z alcohol) is 0.1.

~ 9.9 / 99. 9 ~ 0.1 Force to mix arbitrarily to 0.1 0.1 ~ 50/50 ~ 99.9 Force S Preferable, Furthermore, this is preferably 0.1 to 40/60 to 99.9, and particularly preferably 0.1 to 30/70 to 99.9. Within this range, the ratio of Mw to カルシウム η (MwZMn) of the polymer (Α) is adjusted to 1.2 to 2.0 and the dispersion effect and stability of the heavy calcium carbonate particles can be further improved. .

[0029] The amount of solvent used is the same as in the usual method. For example, in the case of polymer (A) force (meth) acrylic acid (co) polymer (A1), (A1)

In the case of (meth) acrylic acid- (meth) acrylate copolymer (A2), it is about 100 to 1000% by weight based on the weight of (A2). is there. In the case of the (meth) acrylate copolymer (A3), it is about 100 to 1000% by weight based on the weight of (A3).

[0030] Solvents that can be used in the case of the reverse phase suspension polymerization method include hydrocarbons having 6 to 18 carbon atoms, etc. in addition to water and Z or alcohol (same as the solution polymerization method). Lanes etc. are included.

Examples of the alkane include hexane, isohexane, octane, 2-ethyl hexane, decane, and isooctyldecane.

Examples of the arenes 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 of solvent used is the same as in ordinary methods. For example, in the case of polymer (A) force (meth) acrylic acid (co) polymer (A1), water and Z or alcohol based on the weight of (A1). In the case of (meth) acrylic acid- (meth) acrylate copolymer (A2), based on the weight of (A2), Water and Z or alcohol are about 100 to 1000% by weight and hydrocarbons are about 100 to 2000% by weight. In the case of the (meth) acrylate copolymer (A3), based on the weight of (A3), it is about 100 to 500% by weight of water and Z or alcohol, and about 100 to 2000% by weight of hydrocarbons.

[0031] For (co) polymerization, a polymerization initiator can be used. In the case of a solution polymerization method, for example, a polymerization initiator (azo compound, persulfate, perboric acid described in International Publication WO2004Z087574 Pamphlet) Salts, peroxides and redox catalysts). Of these, azo compounds and persulfates are preferred, and 2,2 'azobisisobutyl butyl-tolyl, ammonium persulfate, potassium persulfate and sodium persulfate are more preferred. These polymerization initiators can be used alone or in a mixture of two or more.

[0032] In the bulk polymerization method and the reverse phase suspension polymerization method, examples of the polymerization initiator include polymerization initiators (azo compounds, peroxides, redox catalysts, and the like described in International Publication WO2004Z087574 pamphlet). ) Is included.

Of these, azo compounds and peroxides are preferred, and azo compounds such as 2,2 ′ azobisisobutyl-tolyl. These polymerization initiators can be used alone or in a mixture of two or more.

Also in other polymerization methods, known polymerization initiators can be used.

[0033] When a polymerization initiator is used, the amount used is appropriately adjusted according to the purpose in the same manner as in normal polymerization. In the case of a solution polymerization method, the polymerization concentration, polymerization temperature, monomer Since it is greatly influenced by the charging speed, it is preferable to use a relatively small amount of a polymerization initiator of several% with respect to the polymer (A). On the other hand, in the bulk polymerization method and the reverse phase suspension polymerization method, the reaction rate is fast. In order to obtain the target weight average molecular weight and number average molecular weight, a relatively large amount of polymerization initiator is used. It is preferable. That is, the amount of the polymerization initiator used is adjusted in the same manner as in the usual method so as to obtain the target weight average molecular weight and number average molecular weight.

[0034] The polymer (A) comprises (meth) acrylic acid (co) polymers (A1) and Z, or (meth) acrylic acid (meth) acrylate copolymers (A2) and (meth) acrylates. (Co) polymer (A3) A polymer that contains at least one kind of force selected from the group that has strength (A) A polymer that only needs to contain (A) Force (meth) acrylic acid (meth) acrylate copolymer When (A2) and (meth) acrylate copolymer (A3) are prepared, (A2) and (A3) may be produced and mixed respectively, and (A1) is obtained. The force can be produced by neutralizing a part of this (A1) and (A3) can be produced, and the force can be mixed. In addition, when the polymer (A) also has (meth) acrylic acid (co) polymer (A1) and (meth) acrylate (co) polymer (A3) force, (A1) and (A3) are produced respectively. (In this case, (A2) is produced, and in this case, it is stored as a solid). If the polymer (A) also has (Al), (A2) and (A3) forces, (Al), (A2) and (A3) can be produced and mixed with force, or (A1) can be obtained and force can be produced by neutralizing a part of this (A1) and (A3) may be produced, and the strength may be mixed. Alternatively, (A1) or (A2) may be obtained and the force may be partially neutralized. In addition, when the polymer (A) also has (A2) force, (A2) may be directly produced, and (A1) may be obtained to neutralize part of the force.

[0035] The dispersant for the heavy calcium carbonate grinding step used in the production method of the present invention may contain water and Z or an additive, if necessary, in addition to the polymer (A). As this additive, those added to paper coatings, paper processing, fiber processing, emulsion coatings, etc. can be used. For example, additives (waterproofing agents, antiseptics, etc.) described in the pamphlet of International Publication WO2004Z087574 Including glazes, antifoaming agents, lubricants, dispersants, water retention agents, dyes and pigments).

[0036] When water is included, the water content can be arbitrarily adjusted according to the purpose, but it is preferable to minimize the content from the viewpoint of preventing the solid content of the heavy calcium carbonate slurry to be applied. . On the other hand, a large amount is preferable from the viewpoint of handleability. Therefore, when water is used, the water content (% by weight) is preferably 0.1 to 400, more preferably 0.2 to 150, particularly preferably 0, based on the weight of the polymer (A). 3 ~: L00. When an additive is included, the total content (% by weight) can be arbitrarily adjusted according to the purpose, but is preferably 0.1 to 5 based on the weight of the polymer (A), more preferably 0.1 to Is 3

[0037] In the case of containing no water / soot, the form of the dispersant for the heavy calcium carbonate wet pulverization step used in the production method of the present invention is added to the heavy calcium carbonate and the heavy calcium carbonate slurry. In view of the above, the form of fine powder particles is preferable. The size (mm) of the fine powder particles is 0.001 to 3 forces, more preferably 0.001 to 1. This size is the volume average particle diameter measured by the laser diffraction scattering method CFIS Z8825- 1: 2001).

[0038] Water and additives (waterproofing agents, antiseptic / antifungal agents, antifoaming agents, lubricants, dispersing agents, water retention agents, dyes, pigments, etc.) can be added at any stage, if necessary. The water used as the polymerization solvent can be used as is, and the concentration can be adjusted as necessary (heating distillation) , Vacuum distillation and z or addition).

[0039] The heavy calcium carbonate applicable to the production method of the present invention may be any of calcite crystal type heavy calcium carbonate, aragonite, or patelite crystal type heavy calcium carbonate. Calcium is preferred. The production method of the present invention can also be applied to pigments other than heavy calcium carbonate. Examples of other pigments include clay, calcite, aragonite or patelite crystal type light calcium carbonate, titanium dioxide, satin white, barium sulfate, Examples include talc, zinc oxide, gypsum, silica, ferrite and alumina.

[0040] Heavy calcium carbonate applicable to the production method of the present invention has a volume average particle diameter m) of 5 000 or less (3 to 2000, more preferably 3 to 100, particularly preferably 3 to 20). Applicable to natural limestone. If it is 5000 m or less, the dry pulverization step and the wet pulverization step are not required as in the prior art, and a heavy calcium carbonate slurry can be obtained in a short time only by the wet pulverization step in the present invention.

In addition, the production method of the present invention can also be applied to heavy calcium carbonate obtained by pulverizing natural limestone or the like in a dry pulverization process (a dispersant may not be used in the dry pulverization process). The volume average particle diameter (m) after pulverization in the dry pulverization step is preferably 3 to 2000, more preferably 3 to 100, and particularly preferably 3 to 20.

When the production method of the present invention is applied to other pigments, the particle diameters of the other pigments used are almost the same as described above.

[0041] In the production method of the present invention, heavy carbonate power having a volume average particle size (Ym) as described above is preferably from 0.0002Y to 0.5% (preferably from 0.0002% to 0.47%, Preferably, the volume average particle size is from 0.00002 mm to 0.43 mm), 0.9 to 1.5 (preferably 1.0 to 1.4, more preferably 1.1 to 1.3) m. It includes a wet process of grinding into heavy calcium carbonate.

The pulverization from the volume average particle size Y to 0.0002Y to 0.5 Υ means that the volume average particle size Υ before pulverization is pulverized to a volume average particle size of ΥΖ5,000 to ΥΖ2. Is equivalent to 1,5,000-1Ζ2. Thus, the degree of grinding is defined as the volume average particle diameter after wet grinding divided by the volume average particle diameter before wet grinding. The concentration (wt%) of heavy calcium carbonate in the heavy calcium carbonate slurry obtained in the pulverization step (slurry concentration) is preferably 70 to 85, more preferably 75 to 85, based on the weight of the slurry. Particularly preferred is 80 to 85.

The pH of the heavy calcium carbonate slurry obtained in the pulverization process is preferably 8.5 to LO.

The production method of the present invention is suitable for pulverizing heavy calcium carbonate at a high degree of pulverization to obtain fine particles in the above range and a heavy calcium carbonate slurry having a high concentration. Furthermore, it is suitable for obtaining a high-concentration fine particle slurry having a slurry concentration of 75% by weight or more and a volume average particle diameter of 0.9 to 1. Particularly, the slurry concentration is 80% by weight or more and the volume average particle. It is suitable for obtaining a high-concentration, low-viscosity heavy calcium carbonate slurry having a diameter of 0.9 to 1.5 m. According to the production method of the present invention, such a high-concentration, low-viscosity slurry can be easily produced without a dry pulverization step, and such a high-concentration fine-particle slurry can be used for particle dispersion effect, viscosity reduction effect, and stability. Excellent in properties. On the other hand, heavy calcium carbonate slurry obtained by a conventional manufacturing method (a method of manufacturing through a dry pulverization step and a wet pulverization step using a dispersant) does not have a high concentration and low viscosity, and further improves stability. It is extremely inferior. This is considered to be because the dispersant is more easily distributed more uniformly on the surface of the heavy calcium carbonate particles according to the production method of the present invention than in the case where the dry pulverization step and the wet pulverization step are performed. The production method of the present invention provides a heavy calcium carbonate slurry having a slurry concentration of less than 70% by weight and a volume average particle size of less than 0.9 μm from the viewpoints of pulverization, dispersion efficiency, and stability. It ’s suitable to be cunning.

[0042] The volume average particle size is determined by laser diffraction and scattering method according to JIS Z8825-1: 2001 {Product name: Laser, such as Microtrac UPA, manufactured by Leeds and Northerup, etc. Optical wavelength: 780 nm, measurement temperature: 25 ° C, dispersion medium: water)}.

[0043] The amount of use of the dispersant for the heavy calcium carbonate wet pulverization step (wt%) is preferably 0.01 to 4 force, more preferably as the weight of the polymer (A) based on the weight of the heavy calcium carbonate. It is preferably from 0.01 to 3, particularly preferably from 0.01 to 2. Within this range, the dispersion effect and stability of the particles are further improved. The dispersing agent for the heavy calcium carbonate wet pulverization process can be added to any part of the wet pulverization process, and divided addition by either batch addition or divided addition is preferred. More preferably, part of the dispersant Is added at the beginning of the wet pulverization process, and the rest is added during or after the wet pulverization process.

[0044] Examples of the pulverizer used in the wet pulverization step of the production method of the present invention include, for example, a general fluid stirrer (propeller mixer, turbine mixer, desolver, etc.), a high-speed rotation high shear stir disperser ( Homo mixers, attritors, sand mills, bead mills, ball mills, core mixers, disc cavity mixers and stirrer rollers, etc.), colloid mills (TK my colloiders, TK homomic line mills, TK neutral line mills, shear lot colloid mills, etc.) And pressure nozzle (jet flow) type dispersers (such as Gaurin and homogenizers), ultrasonic emulsifiers (such as Dispersonic and UltraJetter), mechanical vibration stirrers, and stirrers using electrostatic fields. Among these, a general fluid stirrer and a high-speed high shear shear stirrer are preferable, and a propeller mixer, a homomixer, an attritor, a sand mill, a bead mill, a ball mill, and a coreless mixer are more preferable. These pulverizers may be used alone or in combination of two or more (using only one type is preferable from the viewpoint of simplicity.) O Also, pulverizing conditions (temperature, etc.) The same conditions as before can be applied.

[0045] The production method of the present invention can be applied to heavy calcium carbonate slurries used for paper coating paints, paper processing, fiber treatment, emulsion coatings, etc., and heavy calcium carbonate slurries used for paper coating paints. Is particularly effective.

When applied to paper coatings, the binder content in the coatings can be reduced and the high-shear fluidity of the paper coatings is improved. Improvement in workability, etc.). Furthermore, since the heavy calcium carbonate slurry has a high concentration, it contributes to a high concentration of the paper coating itself.

[0046] When applied to paper coatings, the amount of heavy calcium carbonate slurry used (parts by weight) can be used in any proportion with respect to 100 parts by weight of pigments or fillers in paper coatings. 10-: LOO force S, more preferably 30-100, particularly preferably 50-100, most preferably 60-: L00. Within this range, the paper coating material is further reduced in viscosity and increased in viscosity. Preferable, can be in concentration.

[0047] Examples of the paper coating material include heavy calcium carbonate slurry, pigments or fillers other than heavy calcium carbonate, binders, and the like.

Pigments or fillers other than heavy calcium carbonate include inorganic pigments (clay, calcite, aragonite or patelite crystalline light calcium carbonate, titanium oxide, satin white, hydroxyaluminum hydroxide, barium sulfate, talc, zinc oxide, gypsum. , Silica and ferrite, etc.) and organic pigments (polystyrene plastic pigment, etc.).

Pigments or fillers other than heavy calcium carbonate are used in various amounts (parts by weight) based on the required performance and coating method of the coated paper, and the total amount of binder and pigment or filler is 100 parts by weight. 0 to 90 is preferable, more preferably 0 to 70, particularly preferably 0 to 50, and most preferably. ~ 40.

[0048] Examples of the binder include styrene butadiene latex (SBR), modified styrene butadiene latex, acrylic latex, and acetic acid bule latex.

The styrene-butadiene latex can be a copolymer of styrene and butadiene, and can be obtained by emulsion polymerization using an emulsifier such as sodium oleate.

As the modified styrene butadiene latex, copolymers of styrene, butadiene and other monomers can be used. Other monomers include unsaturated rubonic esters such as methyl (meth) acrylate, unsaturated carboxylic acids such as (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylic acid dimethylaminoethyl ester, (meth ) Other bur monomers such as acrylamide, glycidyl (meth) acrylate and (meth) acrylic acid hydroxyethyl ester.

As the acrylic latex, a copolymer of methacrylic acid alkyl ester and acrylic acid alkyl ester or the like can be used.

For the vinyl acetate latex, vinyl acetate, higher fatty acid vinyl ester, maleate ester, and copolymers of Z or ethylene can be used, and emulsifying dispersants that are protective colloids such as polybutyl alcohol hydroxyethyl cellulose are used. And obtained by emulsion polymerization of vinyl acetate. In addition to these, synthetic latex 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 natural binders, semi-synthetic binders, and synthetic binders can be used. Examples of natural binders include starches such as starch, mannans such as konjac, seaweeds such as alginic acid, vegetable mucilages such as soybean protein, microbial adhesives such as dextrin, and proteins 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 polybulal alcohol and sodium polyacrylate (degree of neutralization of polyacrylic acid 95 to 100%).

The amount of Roh inductor i (wt ^_0/0), based on the weight of the pigment or filler, from 0.01 to 2 0 is preferable.

[0049] Such a paper coating composition is usually used in the form of an aqueous dispersion liquid, and if necessary, other additives (for example, water retention / flow improver such as polymethacrylic acid acrylate ester, Pigment dispersants such as sodium acrylate (polyacrylic acid neutralization degree 95 ~: LOO mol%), antifoaming agents such as fatty acid esters, lubricant release agents such as calcium stearate, Darioxal® polyamide urea formaldehyde or polyamide Water resistance agents such as polyamine resins, wetting agents, preservatives, fluorescent dyes, etc.) are added.

[0050] The paper coating material can be applied to the base paper by a known method. For example, spray coater, car ten flow, ~~ "co ^ ~" ta '~ ", blur ■ ~" doco ~~ "ta' ~", mouth ■ ~ "norco ^ ~" ta '~ ", rod co ^^" ta After coating on the base paper with “~” or an air knife coater, etc., drying and calendering, super calendering or soft-calendering finishing methods can be applied as necessary. 10-60 ° C, drying temperature is usually 90-150 ° C, and calendering, supercalendering or soft-calendering temperature is usually 30-200 ° C.

Example

[0051] Hereinafter, the ability to further explain the present invention by way of examples. The present invention is not limited to these. Unless otherwise specified, parts represent parts by weight and% represents% by weight. <Example 1>

Put 200 parts of water and 300 parts of isopropyl alcohol into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer, and a thermometer. Under stirring, add 300 parts of acrylic acid and 100 parts of 40% aqueous sodium persulfate solution separately. The reaction was performed in a sealed state while dropping from the line at a constant rate over 3 hours. The reaction temperature was kept at 65-100 ° C. After completion of the dropwise addition, the temperature was maintained at 90 to 100 ° C for 3 hours, and then isopropyl alcohol was depressurized and removed while adding 150 parts of water dropwise (water addition), and then cooled to 30 ° C and the reaction product was taken out.

Thereafter, to 250 parts of the removed reaction product, while maintaining the temperature at 40 ° C. or lower with stirring, 75.6 parts of 50% sodium hydroxide aqueous solution and magnesium hydroxide (purity 94%) 0.81 parts gradually. Acrylic acid sodium acrylate acrylate-magnesium acrylate copolymer (acrylic acid unit: 30 mole parts, sodium acrylate salt unit: 68 mole parts, magnesium acrylate salt unit: 2 mole parts) A 40% aqueous solution {heavy calcium carbonate wet grinding process dispersant (1)} was obtained.

Using a Coreless mixer (Special Machine Industries Co., Ltd., TK homogenizer AM-20 type), stirring 1 part of the dispersant (1) and 33.3 parts of water at lOOOrpm, After gradually adding 1000 parts of fine calcium carbonate (Nippon Cement Co., Ltd., dry pulverized limestone raw material, volume average particle diameter 8 m), the mixture was further stirred at 20000 rpm for 10 minutes to obtain a coarse slurry. Subsequently, 1200 parts of this coarse slurry and 3600 parts of media (zirconia, volume average particle size 1.25 mm) were charged into a wet milling bead mill (Faci's Finetech Corporation, PM1RL-V) at 1,200 rpm. After wet pulverization for about 30 minutes in a sealed state, the mixture was filtered through a 38 m stainless steel mesh (JIS Z8801-1: 2000) to obtain a finely pulverized slurry. Next, water is added to this finely pulverized slurry, and the evaporation residue (slurry weight 1 to 1.5 g, 160 ° C, 20 minutes) is adjusted to 75% to obtain a heavy calcium carbonate slurry (1). Got.

Add 75.6 parts of 50% sodium hydroxide aqueous solution and 0.81 parts of magnesium magnesium hydroxide to 54.4 parts of 50% sodium hydroxide aqueous solution and 0.4 parts of magnesium hydroxide hydroxide, respectively. A heavy calcium carbonate slurry (2) was obtained in the same manner as in Example 1 except for the change. <Example 3>

Add 75.6 parts of 50% sodium hydroxide aqueous solution and 0.81 parts of magnesium magnesium hydroxide to 107.8 parts of 50% sodium hydroxide aqueous solution and 0.4 parts of magnesium hydroxide hydroxide, respectively. A heavy calcium carbonate slurry (3) was obtained in the same manner as in Example 1 except for the change.

Isopropyl alcohol 300 parts, water 200 parts, 40% aqueous sodium persulfate solution 100 parts and 50% aqueous sodium hydroxide aqueous solution 75.6 parts, isopropyl alcohol 400 parts, water 100 parts, 40% sodium persulfate A heavy calcium carbonate slurry (4) was obtained in the same manner as in Example 1 except that 200 parts of the aqueous solution and 50% aqueous solution of sodium hydroxide and sodium hydroxide 81.1 were used.

[Example 5]

300 parts of isopropyl alcohol, 100 parts of 40% sodium persulfate aqueous solution, 150 parts of water (amount of water when isopropyl alcohol is removed under reduced pressure) and 75.6 parts of 50% aqueous sodium hydroxide solution, 100 parts of isopropyl alcohol A heavy calcium carbonate slurry (5) was obtained in the same manner as in Example 1 except that 50 parts of 40% sodium persulfate aqueous solution, 200 parts of water, and 81 parts of 50% aqueous sodium hydroxide solution were used. It was.

A heavy calcium carbonate slurry (6) was obtained in the same manner as in Example 1 except that 0.81 part of magnesium hydroxide was changed to 4.1 parts of magnesium hydroxide.

A heavy calcium carbonate slurry (7) was obtained in the same manner as in Example 1, except that 0.81 part of magnesium hydroxide was changed to 0.4 part of magnesium hydroxide.

A heavy calcium carbonate slurry (8) in the same manner as in Example 1 except that 0.81 part of magnesium hydroxide was changed to 0.4 part of magnesium hydroxide and 0.8 part of a 50% aqueous solution of sodium hydroxide. Got.

0.81 part of magnesium hydroxide, 0.4 part of magnesium hydroxide and 25% aqueous ammonia Solution 3.6 A heavy calcium carbonate slurry (9) was obtained in the same manner as in Example 1 except that the amount was changed to 6 parts.

Calcite crystal type heavy calcium carbonate (Nippon Cement Co., Ltd., dry pulverized limestone raw material, volume average particle size 8 μm), heavy calcium carbonate (Nippon Cement Co., Ltd., limestone raw material dry pulverized sample) A heavy calcium carbonate slurry (10) was obtained in the same manner as in Example 1 except that the volume average particle diameter was changed to 50 μm.

Calcite crystal type heavy calcium carbonate (Nippon Cement Co., Ltd., dry pulverized limestone raw material, volume average particle size 8 μm), heavy calcium carbonate (Nippon Cement Co., Ltd., limestone raw material dry pulverized sample) A heavy calcium carbonate slurry (11) was obtained in the same manner as in Example 1 except that the volume average particle diameter was changed to 500 m).

Calcite crystal type heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., dry pulverized limestone raw material, volume average particle size 8 μm) and heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., volume average particle size 5000 μm) Except for the change to), heavy carbonate power Lucium slurry (12) was obtained in the same manner as in Example 1.

A heavy calcium carbonate slurry (13) was obtained in the same manner as in Example 1 except that 75.6 parts of 50% aqueous sodium hydroxide solution were changed to 67.2 parts of 50% aqueous sodium hydroxide solution.

A heavy calcium carbonate slurry (14) was obtained in the same manner as in Example 1 except that 75.6 parts of 50% sodium hydroxide aqueous solution was changed to 100 parts of 50% sodium hydroxide aqueous solution.

A heavy calcium carbonate slurry (15) was obtained in the same manner as in Example 1 except that 75.6 parts of the 50% aqueous sodium hydroxide solution were changed to 104.4 parts of the 50% aqueous sodium hydroxide solution.

[0066] <Comparative Example 1>

Add 75.6 parts of 50% sodium hydroxide aqueous solution and 0.81 parts of magnesium hydroxide aqueous solution, respectively. A comparative heavy calcium carbonate slurry (16) was obtained in the same manner as in Example 1 except that it was not used.

[0067] <Comparative Example 2>

Add 75.6 parts of 50% sodium hydroxide aqueous solution and 0.81 parts magnesium hydroxide to 37.8 parts of 50% sodium hydroxide aqueous solution (do not use magnesium hydroxide). A comparative heavy calcium carbonate slurry (17) was obtained in the same manner as in Example 1 except that the dispersion time of the attritor was changed to 45 minutes.

[0068] <Comparative Example 3>

Change 75.6 parts of 50% sodium hydroxide aqueous solution and 0.81 parts magnesium hydroxide to 100 parts of 50% sodium hydroxide aqueous solution (without using magnesium magnesium hydroxide). A comparative heavy calcium carbonate slurry (18) was obtained in the same manner as in Example 1 except that.

[0069] <Comparative Example 4>

Add 75.6 parts of 50% sodium hydroxide aqueous solution and 0.81 parts magnesium hydroxide, 33.3 parts of 50% aqueous sodium hydroxide solution, 0.4 parts of magnesium hydroxide and monoethanolamine 0. A comparative heavy carbonated russia slurry (19) was obtained in the same manner as in Example 1 except that the amount was changed to 9 parts.

[0070] <Comparative Example 5>

75.6 parts of 50% aqueous sodium hydroxide, 0.81 parts of magnesium hydroxide and calcite crystalline heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., dry pulverized product of limestone raw material, volume average particle size 8 m), 50% sodium hydroxide aqueous solution 33.3 parts, magnesium hydroxide 0.4 parts, monoethanolamine 0.9 parts and heavy calcium carbonate (Nippon Cement Co., Ltd., dry pulverization of limestone raw material) A comparative heavy calcium carbonate slurry (20) was obtained in the same manner as in Example 1 except that the sample was changed to a volume average particle size of 50 m).

[0071] <Comparative Example 6>

75.6 parts of 50% aqueous sodium hydroxide, 0.81 parts of magnesium hydroxide and calcite crystalline heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., dry pulverized product of limestone raw material, volume average particle size 8 m), 50% aqueous sodium hydroxide solution 33.3 parts each, Example 1 except for changing to 0.4 part magnesium, 0.9 part monoethanolamine and heavy calcium carbonate (Nippon Cement Co., Ltd., dry pulverized sample of limestone raw material, volume average particle size 500 m) In the same manner, a comparative heavy calcium carbonate slurry (21) was obtained.

[0072] <Comparative Example 7>

75.6 parts of 50% aqueous sodium hydroxide, 0.81 parts of magnesium hydroxide and calcite crystalline heavy calcium carbonate (manufactured by Nippon Cement Co., Ltd., dry pulverized product of limestone raw material, volume average particle size 8 m), 50% sodium hydroxide aqueous solution 33. 3 parts, magnesium hydroxide 0.4 parts, monoethanolamine 0.9 parts and heavy calcium carbonate (Nippon Cement Co., Ltd., volume average particle size 5000) A comparative heavy calcium carbonate slurry (22) was obtained in the same manner as in Example 1 except for changing to m).

[0073] Regarding the dispersants 1 to 22 for the heavy calcium carbonate wet pulverization step used in Examples and Comparative Examples, the composition of the copolymer, the weight average molecular weight (Mw), the weight average molecular weight (Mw) and the number average molecular weight ( The ratios (MwZMn) to Mn) are summarized in Tables 1 and 2.

[0074] [Table 1]

[0076] The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured under the following conditions. Equipment used: Model HLC-8120GPC manufactured by Tosoh Corporation

Column: Tosoh Corporation model Tskgel a 6000 and Tskgel a 3000 connected in series! / 直列

Detector: RI detector

Data processor: Tosoh Corporation Model SC-8020

Column temperature: 40 ° C

Eluent: 0.5% sodium acetate solution {Solvent: Distilled water, manufactured by Kanto Chemical Co., Ltd.> Z Methanol, made by Kanto Chemical> (Volume ratio: Distilled water, Z methanol: 1Z1)}

Eluent flow rate: 1. OmlZ min

Sample concentration: 0.25% eluent solution

Sample solution injection volume: 200 1

Reference material: TSK standard polyethylene oxide manufactured by Tosoh Corporation SE-150: (weight average molecular weight measured by light scattering method (hereinafter abbreviated as M) 885, 000, the same SE— 70: (M) 510 , 000, SE SE-30: (M) 340,000, SE SE-8: (M) 95, 000, SE SE-5: (M) 46, 00, SE-2: (M) 26, 000), Wako Pure Chemical Industries, Ltd. Reagents (Wako Standard Grade 1 Polyethylene Glycol 4000): (M) 4,000, Wako Pure Chemical Industries, Ltd. Reagents (Special Grade Polyethylene Gudicol 1000) : (M) 1,000

[0077] <Measurement of viscosity of heavy calcium carbonate slurry>

Immediately after the heavy calcium carbonate slurries 1 to 22 obtained in Examples 1 to 15 and Comparative Examples 1 to 7 were temperature-controlled at 25 ° C. and stirred for 5 minutes at lOOOrpm with a stirring motor, the B type viscosity The slurry viscosity (N1) after 60 seconds was measured at a rotational speed of 60 rpm using a meter (Tokimek Corporation, TV-20 type). The slurry viscosity (N7) was measured in the same manner after standing for 7 days in a 25 ° C incubator. Table 3 shows the measurement results.

The heavy calcium carbonate slurries 1 to 22 obtained in Examples 1 to 15 and Comparative Examples 1 to 7 were each diluted to 2.5%, and a laser light diffraction / scattering particle size distribution analyzer (trade name: MICROTO Using a rack (MICROTRAC X100, manufactured by Leeds and Northerup) (Laser wavelength: 78 Onm, measurement temperature; 25 ° C, dispersion medium; water, measurement time 6 minutes) Volume average particle diameter (after pulverization) was measured, and the measurement results are shown in Tables 3 and 4. Tables 3 and 4 show the volume average particle size (before pulverization) of the heavy calcium carbonate used and the pulverization degree calculated using this.

[0079] [Table 3]

[0080] [Table 4] Volume average grain ί 圣 (Aim)

After grinding Before grinding

1 N 1 6 7 0 2. 1 5 8 3/1 0

N 7 8 2 0

2 N 1 1 7 0 1 .6 5 8 2/1 0 it N 7 2 8 0

3 N 1 3 5 0 2. 0 0 8 3/1 0

N 7 4 7 0

4 N 1 1 9 0 1 .4 8 8 2/1 0

N 7 7 2 0

5 N 1 4 8 0 3. 5 6 δ〇 7/1 0 0 Example N 7 9 2 0

6 N 1 7 0 0 3 0 0 5 0 0 6/1 0

N 7-

7 N 1 4 0 0 0 5 0 0 0 8/1 0

N 7-

-: Exceeding measurement range (> 20000mPa's)

The heavy calcium carbonate slurry obtained in Examples 1 to 15 is extremely excellent in the dispersion effect and the viscosity reducing effect in which the viscosity (N1) is remarkably lower than the heavy calcium carbonate slurry obtained in Comparative Examples 1 to 7. It was. In the same manner, the stability of the particles with extremely low viscosity (N7) after 7 days was extremely excellent. Similarly, the dispersion effect was extremely excellent in that the volume average particle diameter after pulverization was extremely small.

Claims

The scope of the claims

[1] (Meth) acrylic acid (co) polymer (A1), (meth) acrylic acid (meth) acrylate copolymer

(A2) and (meth) acrylate copolymer (A3) comprising at least one polymer (A) selected from the group that also has strength, and (meth) acrylate contained in (A) Units are (meth) alkali metal acrylate units 49.9-9-99 mole parts, (meth) alkali earth metal salt units 0.1-10 mole parts and (meth) acrylic acid ammonium salt units Dispersant for heavy calcium carbonate wet pulverization process, comprising from 0 to 10 mole parts and having 50 to 99% by weight of meth) acrylate units based on the number of all monomer units constituting (A) Using,

It includes a wet grinding process that crushes heavy calcium carbonate with a volume average particle size Y m into heavy calcium carbonate with a volume average particle size of 0.00002Y to 0.501! 1 to 0.9 to 1.5 m. A method for producing a heavy calcium carbonate slurry.

[2] The method for producing a heavy calcium carbonate slurry according to claim 1, wherein the heavy calcium carbonate is calcite crystal type heavy calcium carbonate.

[3] (Meth) acrylic acid (co) polymer (A1), (meth) acrylic acid (meth) acrylate copolymer

Includes a wet grinding process that crushes heavy calcium carbonate with a volume average particle size of Y m into heavy calcium carbonate with a volume average particle size of 0.00002Y to 0.5 丫 1! 1 to 0.9 to 1.5 m. A heavy calcium carbonate slurry produced by the method.

[4] A paper coating composition comprising the heavy calcium carbonate slurry according to claim 3.

[5] A coated paper coated with the paper coating composition according to claim 4.