JP2011046861A - Aqueous dispersion containing hollow polymer particles, method for producing the same and method for producing filler-containing paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous dispersion containing a hollow polymer particle, which provides filler-containing paper having high whiteness and opacity and has high dispersion stability when applied to filler-containing paper and a method for producing the aqueous dispersion. <P>SOLUTION: The method for producing an aqueous dispersion containing a hollow polymer particle includes a step for polymerizing or copolymerizing a monomer composed of 97-100 mass% of a monoethylenic unsaturated monomer and 3-0 mass% of an acidic group-containing polymer or a monomer mixture (c) in the presence of a core polymer particle (A) enclosed by an intermediate layer (B) using a specific surfactant and forming an outer layer (C) substantially enclosing the intermediate layer (B) and further performing a step for mixing the aqueous dispersion with a water-soluble cationic resin. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention provides an aqueous dispersion containing hollow polymer particles having high dispersion stability when applied to an internally-added paper and having high whiteness and opacity, and a method for producing the same, and the aqueous dispersion The present invention relates to a method for producing an internally attached paper.

  Hollow polymer particles scatter light and lower light transmission than polymer particles that are filled with a polymer in a dense and uniform manner, so that optical properties such as opacity and whiteness are improved. As an excellent organic pigment and masking agent, it is used in applications such as water-based paints and paper coating compositions. A base is added to an aqueous dispersion containing polymer particles having at least a three-layer structure to prepare an aqueous dispersion containing hollow polymer particles, and then the surface of the hollow polymer particles is cationic. An aqueous dispersion containing hollow polymer particles having a functional group introduced and exhibiting properties such as good opacity, whiteness, water absorption, and ink transferability has been studied (see, for example, Patent Document 1).

JP-A-10-279539

In recent years, when an internal additive paper is made by adding a filler containing an aqueous dispersion containing hollow polymer particles to a pulp slurry, an aqueous dispersion having high whiteness and opacity is given, and the dispersion stability is high. Liquid is sought after. However, an aqueous dispersion containing hollow polymer particles having such characteristics has not been obtained.
The problem to be solved by the present invention is to provide an aqueous dispersion containing hollow polymer particles having high dispersion stability and giving an internal paper having high whiteness and opacity when applied to an internal paper and its production The provision of a method. Furthermore, another problem to be solved by the present invention is to provide a method for producing an internal paper using the aqueous dispersion.

  In order to solve the above problems, the inventor of the present invention has intensively studied a method for producing an aqueous dispersion containing hollow polymer particles. As a result, 97 to 100% by mass of a monoethylenically unsaturated monomer and an acidic group-containing weight A monomer or a monomer mixture composed of 3 to 0% by mass of a polymer is polymerized or copolymerized using a specific surfactant in the presence of core polymer particles surrounded by the intermediate layer, And then adding a base to an aqueous dispersion containing polymer particles having at least a three-layer structure of core polymer particles, an intermediate layer and an outer layer, An aqueous dispersion in which an aqueous dispersion containing hollow polymer particles is prepared with a pH of 7 or more, and then a step of mixing a water-soluble cationic resin in a state where the pH of the aqueous dispersion is acidified This manufacturing method solves the above problems. As a result, the present invention has been completed.

In the present invention, (1) a monomer mixture (a) comprising 20 to 60% by mass of an acid group-containing monomer and 80 to 40% by mass of a monoethylenically unsaturated monomer copolymerizable therewith is copolymerized. And preparing the core polymer particles (A),
(2) A monomer or monomer mixture (b) composed of 88 to 100% by mass of a monoethylenically unsaturated monomer and 12 to 0% by mass of an acidic group-containing polymer is added to the core polymer particles (A). Polymerizing or copolymerizing in the presence to form an intermediate layer (B) substantially surrounding the core polymer particles (A);
(3) A monomer or monomer mixture (c) composed of 97 to 100% by mass of a monoethylenically unsaturated monomer and 3 to 0% by mass of an acidic group-containing polymer is surrounded by an intermediate layer (B). In the presence of the core polymer particles (A), an outer layer (C) that substantially surrounds the intermediate layer (B) by polymerization or copolymerization using a surfactant represented by the following general formula (I) Forming a process,
R—O— (CH ₂ CH ₂ O) _n —SO ₃ M (I)
(In the formula, R is an alkyl group or alkenyl group having 8 to 20 carbon atoms, M is an alkali metal ion or ammonium ion, and n is an integer of 20 to 70.)
(4) A base is added to an aqueous dispersion containing polymer particles having at least a three-layer structure of a core polymer particle (A), an intermediate layer (B), and an outer layer (C), and the pH of the aqueous dispersion A step of preparing an aqueous dispersion containing 7 or more and hollow polymer particles,
(5) Provided is a method for producing an aqueous dispersion in which a step of mixing a water-soluble cationic resin is performed in a state where the pH of the aqueous dispersion is acidified.

Moreover, this invention provides the aqueous dispersion manufactured with the manufacturing method of the said aqueous dispersion.
Furthermore, this invention provides the manufacturing method of the internal paper which implements the process which adds the filler containing the said aqueous dispersion to a pulp slurry, and carries out papermaking.

  The aqueous dispersion of the present invention gives an internal paper having high whiteness and opacity when applied to an internal paper, and its dispersion stability is high.

Core polymer particles (A)
The core polymer particle (A) prepared by the method for producing an aqueous dispersion of the present invention comprises a monomer mixture comprising an acidic group-containing monomer and a monoethylenically unsaturated monomer polymerizable with the monomer (a ) Is copolymerized.
The acidic group-containing monomer is an ethylenically unsaturated monomer having an acid group such as a carboxyl group, a sulfonic acid group, or a phosphinyl group, and is not limited to a specific monomer. Specific examples of the ethylenically unsaturated acid monomer include an ethylenically unsaturated carboxylic acid monomer, an ethylenically unsaturated sulfonic acid monomer, and an ethylenically unsaturated phosphoric acid monomer.
Specific examples of the ethylenically unsaturated carboxylic acid monomer include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; fumaric acid, maleic acid, citraconic acid, metaconic acid, glutaconic acid, itaconic acid, tetrahydrophthalate Unsaturated polyvalent carboxylic acids such as acid, crotonic acid, isocrotonic acid, nadic acid and butenetricarboxylic acid; is there.

Specific examples of the ethylenically unsaturated sulfonic acid monomer include vinyl sulfonic acid, methyl vinyl sulfonic acid, styrene sulfonic acid, (meth) acryl sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamide- Such as 2-hydroxypropanesulfonic acid.
Specific examples of the ethylenically unsaturated phosphate monomer include (meth) acrylic acid-3-chloro-2-phosphate propyl, (meth) acrylic acid-2-ethyl phosphate, 3-allyloxy-2-hydroxypropane Such as phosphoric acid.
Alkali metal salts or ammonium salts of the above acidic group-containing monomers can also be used. One or a combination of two or more acidic group-containing monomers is used.

A preferred acidic group-containing monomer is an ethylenically unsaturated carboxylic acid, and a more preferred acidic group-containing monomer is an ethylenically unsaturated monocarboxylic acid. A particularly preferred acidic group-containing monomer is methacrylic acid.
The ratio of the acidic group-containing monomer in the monomer mixture (a) is 20 to 60% by mass, preferably 25 to 50% by mass, and more preferably 30 to 40% by mass. When the said usage rate is less than 20 mass%, it becomes difficult to form a hollow part in a polymer particle. On the other hand, when the said usage rate is more than 60 mass%, an acidic group localizes on the surface of a core polymer particle, and it becomes difficult to form an intermediate | middle layer (B).

Specific examples of the monoethylenically unsaturated monomer copolymerizable with the acid group-containing monomer include aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, and halogenated styrene; acrylonitrile, Ethylenically unsaturated nitrile monomers such as methacrylonitrile; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, glycidyl (meth) Ethylenically unsaturated carboxylic acid ester monomers such as acrylate and 2-hydroxyethyl (meth) acrylate; ethylenically unsaturated such as (meth) acrylamide, N-methylol (meth) acrylamide, and N-butoxymethyl (meth) acrylamide Carboxylic acid amide monomer; butadiene Conjugated diene monomers such as isoprene; carboxylic acid vinyl ester monomers such as vinyl acetate; vinyl halide monomers such as vinyl chloride; vinylidene halide monomers such as vinylidene chloride; vinyl pyridine; . One or more monomers are used. Preferred monomers are ethylenically unsaturated carboxylic acid ester monomers, and more preferred monomers are methyl (meth) acrylate and butyl (meth) acrylate.

  Preferred core polymer particles (A) are formed from a monomer mixture comprising 35 to 77% by weight of methyl methacrylate, 3 to 15% by weight of butyl acrylate and 20 to 50% by weight of methacrylic acid. More preferable core polymer particles (A) are formed from a monomer mixture comprising 42 to 71% by mass of methyl methacrylate, 4 to 13% by mass of butyl acrylate, and 25 to 45% by mass of methacrylic acid. Further preferred core polymer particles (A) are formed from a monomer mixture comprising 50 to 65% by weight of methyl methacrylate, 5 to 10% by weight of butyl acrylate and 30 to 40% by weight of methacrylic acid.

  Crosslinkable monomers such as divinylbenzene, diallyl phthalate, allyl (meth) acrylate, and ethylene glycol di (meth) acrylate can be used during the copolymerization of the monomer mixture (a). However, when a large amount of the crosslinkable monomer is used, it becomes difficult to form voids inside the core polymer particles, and therefore the amount needs to be kept within a range in which stable void formation can be maintained.

  The copolymerization of the monomer mixture (a) is usually performed in an aqueous medium. Usually, water is used as an aqueous medium, and a water-soluble organic solvent such as methanol and ethanol can be used in combination as long as the dispersion stability of the polymer particles during production is not impaired. The usage-amount of an aqueous medium is 100-1000 mass parts normally with respect to 100 mass parts of monomer mixtures (a), Preferably it is 200-600 mass parts. If the amount of aqueous medium used is too small, the amount of aggregates generated during polymerization tends to increase, and if the amount of aqueous medium used is too large, the productivity of hollow polymer particles tends to be poor.

The copolymerization method of the monomer mixture (a) is usually an emulsion polymerization method. The polymerization method may be any of batch, semi-continuous and continuous methods. The polymerization pressure, polymerization temperature, and polymerization time are not particularly limited, and known conditions are employed.
Various additives generally used in the emulsion polymerization reaction, such as a surfactant, a polymerization initiator, a chain transfer agent, a chelating agent, an electrolyte, and an oxygen scavenger, can be used as a secondary material for polymerization.

As the surfactant used in the copolymerization of the monomer mixture (a), generally known surfactants can be used in combination. Specifically, rosinates such as potassium rosinate and sodium rosinate; fatty acid salts such as potassium oleate, potassium laurate, sodium laurate, sodium stearate and potassium stearate; aliphatic alcohols such as sodium lauryl sulfate Anionic surfactants such as sodium dodecylbenzenesulfonate; alkyl ether sulfates such as sodium polyoxyethylene alkyl ether sulfate; alkyl esters of polyethylene glycol, alkyl ethers or alkylphenyls Hydrophilic synthesis of nonionic surfactants such as ether, polyacrylic acid, polymethacrylic acid, polyvinyl sulfonic acid, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, etc. Molecular substance; like dispersion stabilizer and the like; carboxymethyl hydrophilic semi-synthetic polymeric substances such as methylcellulose; gelatin, natural hydrophilic polymeric substance, such as a water soluble starch.
These surfactants are used alone or in combination of two or more.
Of these, alkyl ether sulfates such as sodium polyoxyethylene alkyl ether sulfate are preferred because of good polymerization stability.
The usage-amount of surfactant is 0.1-5 mass% with respect to the whole quantity of the said monomer mixture (a), Preferably it is 0.5-3 mass%. If this amount is too small, aggregates are likely to be formed, and conversely if too large, the porosity of the hollow polymer particles will be low.

  The copolymerization of the monomer mixture (a) is desirably performed in the presence of seeds. Use of a seed facilitates control of the diameter of the polymer particles produced. The composition of the seed is not particularly limited. The polymerization conversion rate of the monomer mixture (a) in the polymerization reaction is usually 90% by mass or more, preferably 97% by mass or more. The composition of the produced copolymer is almost the same as that of the monomer mixture (a).

  The method for adding the surfactant is not particularly limited. The surfactant is added to the reactor in batches, in portions or continuously. A surfactant is preferably added continuously to the reaction system in that the amount of aggregates produced during production is reduced. The monomer mixture (a) and the surfactant may be mixed and added to the reaction system, or may be added separately to the reaction system. Preferably, an emulsion obtained by mixing the monomer mixture (a), the surfactant and the aqueous medium is added to the reaction system.

The monomer mixture (a) is preferably copolymerized in the presence of a small amount of inorganic salt. When the surfactant and the inorganic salt are used in combination, the formation of aggregates is suppressed, and an aqueous dispersion containing hollow polymer particles having a narrow particle size distribution is obtained.
The inorganic salt is not particularly limited. Specific examples of inorganic salts include sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium nitrate, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, sodium phosphate, sodium tripolyphosphate, and other alkali metal salts; calcium chloride, barium sulfate Alkaline earth metal salts such as aluminum sulfate and aluminum chloride. Of these, alkali metal salts are preferable, and sodium tripolyphosphate is more preferable.

  The usage-amount of an inorganic salt is 0.01-1 mass% with respect to the whole quantity of a monomer mixture (a), Preferably it is 0.05-0.5 mass%. If the amount used is too small, it is difficult to achieve the effect, while if it is too large, the generation of aggregates tends to be promoted. The method for adding the inorganic salt is not particularly limited. The inorganic salt is added to the reaction system all at once, in portions or continuously.

  The distribution in the radial direction of the acidic group-containing monomer units of the core polymer particles (A) is not particularly limited. Copolymerization can be performed while the composition of the monomer mixture (a) is sequentially changed and added to the polymerization reaction system. When a radial distribution of the content of acidic group-containing monomer units occurs in the core polymer particles (A) by such a polymerization method, the least part of the acidic group-containing monomer units is the part. The acid group-containing monomer unit is contained in an amount of 10% by mass or more, preferably 15% by mass or more, based on the total monomer units forming the. When this ratio is less than 10% by mass, small particles may be generated in the voids of the hollow polymer particles, and the porosity may be lowered.

  The volume average particle diameter of the core polymer (A) is preferably 100 to 600 nm, more preferably 250 to 500 nm. If the particle size is too small, it tends to be difficult to produce hollow polymer particles having a high porosity and a large particle size. Conversely, if the particle size is too large, the core polymer formed by the intermediate layer (B). It tends to be difficult to coat the particles (A) and to form voids in the core polymer particles (A).

Middle layer (B)
The intermediate layer (B) substantially surrounds the core polymer particle (A). A monomer or monomer mixture (b) composed of 88 to 100% by mass of a monoethylenically unsaturated monomer and 12 to 0% by mass of an acidic group-containing polymer is present in the presence of the core polymer particles (A). To form an intermediate layer (B) that substantially surrounds the core polymer particles (A).

The acidic group-containing monomer contained in the monomer mixture (b) is the same as the acidic group-containing monomer contained in the monomer mixture (a). A preferred acidic group-containing monomer contained in the monomer mixture (b) is an ethylenically unsaturated monocarboxylic acid, and more preferred acidic group-containing monomers are acrylic acid and methacrylic acid.
The monoethylenically unsaturated monomer contained in the monomer or monomer mixture (b) is the same as the monoethylenically unsaturated monomer contained in the monomer mixture (a).

  The preferred intermediate layer (B) is formed from a monomer mixture comprising methyl methacrylate 68 to 89% by mass, butyl acrylate 10 to 22% by mass, methacrylic acid and / or acrylic acid 1 to 10% by mass, and more preferred intermediate layer. (B) is formed from a monomer mixture consisting of 71 to 85% by weight of methyl methacrylate, 12 to 20% by weight of butyl acrylate, 3 to 9% by weight of methacrylic acid and / or acrylic acid, and more preferred intermediate layer (B) Is formed from a monomer mixture consisting of 74 to 81% by weight of methyl methacrylate, 14 to 18% by weight of butyl acrylate, and 5 to 8% by weight of methacrylic acid and / or acrylic acid.

  In the copolymerization of the monomer or monomer mixture (b), the chain transfer agent is preferably 0.1 to 2% by mass, more preferably, based on the total amount of the monomer or monomer mixture (b). Is carried out in the presence of 0.1 to 1.5% by mass, particularly preferably 0.2 to 1% by mass. If the amount of the chain transfer agent is too small, the void ratio of the resulting hollow polymer particles tends to be low. Conversely, if the amount of the chain transfer agent is too large, the amount of aggregates generated during polymerization tends to increase. In addition, there is a tendency for the porosity to be low.

A known chain transfer agent used in general emulsion polymerization is used. Specific examples of the chain transfer agent include mercaptans such as octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan; dimethylxanthogen disulfide, diethylxanthogen disulfide Xanthogen disulfides such as diisopropylxanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide and tetrabutylthiuram disulfide; halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide; diphenylethylene, pentaphenyl Hydrocarbons such as ethane and α-methylstyrene dimer; acrolein, methacrolein, allyl alcohol, 2-ethane Hexyl thioglycolate, terpinolene, alpha-terpinene, .gamma.-terpinene, is dipentene. One or more chain transfer agents are used. Preferred chain transfer agents are mercaptans and α-methylstyrene dimers, more preferred chain transfer agents are mercaptans, and a particularly preferred chain transfer agent is t-dodecyl mercaptan.

Outer layer (C)
The outer layer (C) substantially surrounds the intermediate layer (B). A monomer or monomer mixture (c) consisting of 97 to 100% by mass of a monoethylenically unsaturated monomer and 3 to 0% by mass of an acidic group-containing polymer is substantially surrounded by the intermediate layer (B). Polymerization or copolymerization in the presence of the core polymer particles (A) thus formed forms an outer layer (C) that substantially surrounds the intermediate layer (B).

  The acidic group-containing monomer contained in the monomer or monomer mixture (c) is the same as the acidic group-containing monomer contained in the monomer mixture (a). The monoethylenically unsaturated monomer contained in the monomer or monomer mixture (c) is the same as the monoethylenically unsaturated monomer contained in the monomer mixture (a). Preferred monomers are aromatic vinyl monomers and ethylenically unsaturated monocarboxylic acid ester monomers, and more preferred monomers are styrene. When a monomer other than the aromatic vinyl monomer is used in combination, preferably 90% by mass or more of the aromatic vinyl monomer is used with respect to the total amount of monomers contained in the monomer mixture (c). Is done.

  A preferred outer layer (C) is formed from a monomer mixture consisting of methacrylic acid and / or acrylic acid 0 to 2.2% by weight and styrene 97.8 to 100% by weight, and more preferred outer layer (C) is methacrylic acid. And / or a monomer mixture composed of 0 to 1.8% by mass of acrylic acid and 98.2 to 100% by mass of styrene, and a more preferable outer layer (C) is formed from a monomer mixture composed of 100% by mass of styrene. It is formed.

  The mass ratio (parts by mass) of the monomer mixture (a), the monomer or monomer mixture (b), and the monomer or monomer mixture (c) is preferably 1 to 25/2 to 65 / It is 40-85, More preferably, it is 3-20 / 3-55 / 44-80, More preferably, it is the range of 5-15 / 5-50 / 48-75. When the proportion of the monomer mixture (a) is too small, hollow polymer particles having a high porosity tend to be difficult to obtain. Conversely, when the proportion of the monomer mixture (a) is too large, the base treatment is performed. However, the amount of aggregates tends to increase.

  The formation of the intermediate layer (B) and the outer layer (C) is usually performed by emulsion polymerization. As the polymerization method, any of batch method, semi-continuous method, and continuous method is adopted. The polymerization pressure, polymerization temperature, and polymerization time are not particularly limited, and known conditions are employed.

  The polymerization auxiliary material exemplified in the formation of the core polymer particles (A) is used. The type of the surfactant is not particularly limited, except when forming the outer layer (C). An aqueous medium can be additionally added. The additional amount of the aqueous medium is usually in the range where the solid content concentration of the polymer particles having at least a three-layer structure is 10 to 50% by mass, preferably 20 to 40% by mass.

When the monomer or monomer mixture (c) is polymerized or copolymerized in the presence of the core polymer particle (A) substantially surrounded by the intermediate layer (B), the following general formula (I) ) Is used.
R—O— (CH ₂ CH ₂ O) _n —SO ₃ M (I)
(In the formula, R is an alkyl group or alkenyl group having 8 to 20 carbon atoms, M is an alkali metal ion or ammonium ion, and n is an integer of 20 to 70.)
The surfactant represented by the above general formula (I) is commercially available, and a specific example of the commercially available product is Ramtel (registered trademark) E-150 manufactured by Kao Corporation.

The amount of the surfactant represented by the general formula (I) used is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass with respect to the total amount of the monomer mixture (c). %. If this amount is too small, aggregates are likely to be formed, and conversely if too large, the porosity of the hollow polymer particles will be low.
Of course, as long as the effect of the present invention is not substantially inhibited, a surfactant other than the surfactant represented by the general formula (I) may be used in combination.

  The method for adding the surfactant represented by the general formula (1) is not particularly limited. The surfactant is added to the reactor in batches, in portions or continuously. A surfactant is preferably added continuously to the reaction system in that the amount of aggregates produced during production is reduced. The monomer or monomer mixture (c) and the surfactant may be mixed and added to the reaction system, or may be added separately to the reaction system. Preferably, an emulsion obtained by mixing the monomer or monomer mixture (c), the surfactant and the aqueous medium is added to the reaction system.

Base treatment A base is added to an aqueous dispersion containing polymer particles having at least a three-layer structure of a core polymer particle (A), an intermediate layer (B) and an outer layer (C), and the pH of the aqueous dispersion is The hollow polymer particles having at least one void formed by neutralizing at least a part of the acidic groups contained in the core polymer particles (A) are 7 or more. The voids are filled with an aqueous medium that forms an aqueous dispersion.

  The base is a volatile base and / or a nonvolatile base. Specific examples of the volatile base are ammonia, ammonium hydroxide, morpholine, trimethylamine, and triethylamine. Specific examples of the non-volatile base include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide; sodium carbonate, potassium bicarbonate Alkali metal (bi) carbonates such as; ammonium (bi) carbonates such as ammonium carbonate and ammonium bicarbonate. Preferred bases are volatile bases or alkali metal hydroxides, and more preferred bases are ammonia and sodium hydroxide.

The amount of the base used is an amount that neutralizes at least some of the acidic groups of the core polymer particles (A) so that the pH of the aqueous dispersion is 7 or more. The pH of the aqueous dispersion during the base treatment is preferably in the range of 7.5 to 11, more preferably 8 to 10. If the pH is too low, the void ratio of the hollow polymer particles tends to be low. On the other hand, if the pH is too high, the amount of acid added in the next acid treatment step tends to increase, and coarse aggregates tend to be generated. .
The base is preferably added in the form of an aqueous solution from the viewpoint of suppressing the generation of aggregates at the time of addition, and the concentration is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass. Furthermore, from the above viewpoint, an anionic surfactant and / or a nonionic surfactant may be added before or simultaneously with the addition of the base.
As the surfactant used here, a surfactant represented by the general formula (I) is preferably exemplified. This surfactant is preferably used in an amount of 0.1 to 5 with respect to the total amount of the monomer mixture (a), the monomer or monomer mixture (b), and the monomer or monomer mixture (c). When added in the range of mass%, more preferably in the range of 0.5 to 3 mass%, the generation of coarse aggregates can be effectively suppressed not only during the base treatment but also in the subsequent steps.

  In order for the acidic groups inside the polymer particles to be neutralized by adding the base to the aqueous dispersion, it is necessary to allow time for the bases to diffuse into the polymer particles. Thus, desirably, stirring is performed over time after the addition of the base. A preferable base treatment temperature is preferably equal to or higher than a temperature at which the polymer particles are sufficiently softened, preferably 70 ° C. or higher, and more preferably in a range of 75 to 95 ° C. If the base treatment temperature is set too high, a pressure vessel that can withstand the vapor pressure of the aqueous medium is required, resulting in excessive equipment costs. The base treatment time after the base addition is usually 5 to 180 minutes, preferably 10 to 120 minutes.

  The base can be added in the presence of an organic solvent according to the method disclosed in JP-A-3-26724. The polymer particles are softened by using an organic solvent, and the diffusion of the base is promoted. Specific examples of the organic solvent are aromatic hydrocarbons, halogenated hydrocarbons, alcohols, ethers, ketones, and saturated carboxylic acid esters. The organic solvent is usually used in the range of 0.1 to 1000 parts by mass with respect to 100 parts by mass of the polymer particles. The used organic solvent is evaporated and removed after the base treatment.

  Instead of the organic solvent, a polymerizable monomer can be used. The polymerizable monomer may contain a monomer containing an acidic group and is usually used in the range of 1 to 20 parts by mass, preferably 2 to 10 parts by mass with respect to 100 parts by mass of the polymer particles. The The polymerizable monomer can be newly added. The above-mentioned base treatment can be performed in a state where the polymerizable monomer is added excessively during the formation of the intermediate layer (B) and the outer layer (C) and the polymerization reaction is stopped by adding a polymerization inhibitor or a reducing agent. Excess polymerizable monomer is polymerized by adding a polymerization initiator after the base treatment.

Acid Treatment The base-treated aqueous dispersion is treated with an acid to adjust the pH of the aqueous dispersion to acidic. By this acid treatment, the particle diameter and porosity of the hollow polymer particles can be increased. The pH of the aqueous dispersion during the acid treatment is preferably in the range of 3 to 6.5.
The acid used for acid treatment is not particularly limited. Specific examples of the acid are mineral acids such as hydrochloric acid and sulfuric acid; organic acids such as acetic acid and malonic acid. In the acid treatment step, an acidic group-containing monomer can be used as the acid. When an acidic group-containing monomer is used as an acid, the amount of the monomer is generally 0.8% relative to 100 parts by mass of the monomers used for forming the core polymer particles (A), the intermediate layer (B), and the outer layer (C). An acidic group-containing monomer in the range of 01 to 20 parts by mass, preferably 0.05 to 10 parts by mass, and more preferably 0.2 to 5 parts by mass is used.

Examples of the acidic group-containing monomer used herein include those similar to those used in the monomer mixture (a), preferably an ethylenically unsaturated carboxylic acid, more preferably an ethylenically unsaturated monocarboxylic acid. Acid, particularly preferably methacrylic acid.
In the acid treatment step, together with the acidic group-containing monomer, a monoethylenically unsaturated monomer copolymerizable therewith may coexist. Examples of the monoethylenically unsaturated monomer include those similar to those used in the monomer mixture (a), preferably an aromatic vinyl monomer, more preferably styrene.
When using an acidic group-containing monomer and a monoethylenically unsaturated monomer copolymerizable therewith, the composition is preferably 0.5 to 10% by mass, more preferably the acidic group-containing monomer. 1 to 5% by mass, and the monoethylenically unsaturated monomer is preferably 99.5 to 90% by mass, and more preferably 99 to 95% by mass. When the content ratio of the acidic group-containing monomer is too small, it is necessary to add a large amount of the monomer mixture containing the acidic group-containing monomer for the acid treatment, and when the monomer mixture is polymerized The void ratio of the hollow polymer particles tends to decrease. In addition, if the content ratio of the acidic group-containing monomer is too large, a polymer having a high hydrophilicity is produced when the monomer mixture containing the added acidic group-containing monomer is polymerized, and the aqueous dispersion In some cases, the viscosity of the resin becomes too high, making it difficult to handle, or forming coarse aggregates.
When the monomer mixture containing an acidic group-containing monomer is added, the total amount of monomers used for forming the core polymer particles (A), the intermediate layer (B) and the outer layer (C) is 100 mass. The amount of the monomer mixture is preferably 20 to 100 parts by mass, more preferably 40 to 80 parts by mass with respect to parts.

The treatment temperature, treatment time, etc. in the acid treatment step are substantially the same as the conditions for the base treatment. In order to prevent the stability of the aqueous dispersion from decreasing due to the addition of acid, an anionic surfactant and a nonionic surfactant are added either alone or in combination before or simultaneously with the addition of acid. May be.
As the surfactant used here, a surfactant represented by the general formula (I) is preferably exemplified. This surfactant is preferably used in an amount of 0.1 to 5 with respect to the total amount of the monomer mixture (a), the monomer or monomer mixture (b), and the monomer or monomer mixture (c). When added in the range of mass%, more preferably in the range of 0.5 to 3 mass%, the generation of coarse aggregates can be effectively suppressed not only during the acid treatment but also in the subsequent steps.
When an acidic group-containing monomer is used as the acid, a method of emulsifying a monomer mixture containing the acidic group-containing monomer in an aqueous medium in the presence of a surfactant, and adding the obtained emulsion From the point that the generation of coarse aggregates can be effectively suppressed, it can be preferably employed.

Outermost layer (D)
After the acid treatment, if desired, a monoethylenically unsaturated monomer is polymerized in the presence of the polymer particles on which the outer layer (C) is formed, and the outermost layer (D) is formed on the outer periphery of the outer layer (C). Can be formed. A preferable monomer used for forming the outermost layer (D) is an aromatic vinyl monomer or 90% by weight or more of an aromatic vinyl monomer and 10% of a monoethylenically unsaturated monomer copolymerizable therewith. % Monomer mixture. The outermost layer (D) having a high glass transition temperature (Tg) is formed by polymerization of an aromatic vinyl monomer or a monomer mixture containing the aromatic vinyl monomer as a main component, thereby improving the opacifying effect of the resulting hollow polymer particles. In addition, fusion between the particles is prevented.
When a monomer mixture containing an acidic group-containing monomer is used in the acid treatment step, usually, the polymerization of the monomer mixture proceeds simultaneously, so that the polymer formed from the monomer mixture The outermost layer (D) is formed. In addition, in the acid treatment step, when the polymerization reaction is suppressed by adding a polymerization inhibitor or the like, an outermost layer (D) may be formed by additionally adding a polymerization initiator thereafter. .

  Mass ratio of polymer particles consisting of core polymer particles (A), intermediate layer (B) and outer layer (C) to outermost layer (D) [(core polymer particles (A) + intermediate layer (B) + outer layer (C)) / outermost layer (D)] is usually 100/20 to 100/100, preferably 100/40 to 100/80. If desired, a small proportion of the crosslinkable monomer can be used as part of the outermost layer (D) forming monomer mixture. The polymerization method for forming the outermost layer (D) is usually an emulsion polymerization method as in the case of the other layers, and polymerization conditions and secondary materials for polymerization are also known.

Mixing of Cationic Resin Due to the acid treatment, the pH of the aqueous dispersion becomes acidic, and in this state, the water-soluble cationic resin is mixed with the aqueous dispersion containing the hollow polymer particles.
The water-soluble cationic resin used in the present invention is not particularly limited as long as it is water-soluble and contains a cationic moiety in the molecule. For example, it is a polyacrylamide cation-modified product or acrylamide and cationic resin. Examples thereof include a monomer copolymer, polyallylamine, polyaminesulfone, polyvinylamine, polyethyleneimine, polyamide epichlorohydrin resin, and polyvinylpyridinium halide. Furthermore, copolymers of vinyl pyrrolidone monomers and other common monomers, copolymers of vinyl oxazolidone monomers and other common monomers, copolymers of vinyl imidazole monomers and other common monomers. A polymer etc. are mentioned. These water-soluble cationic resins can be used even in a quaternized state or a neutralized state with an acid. These water-soluble cationic resins may be used alone or in combination.
The weight average molecular weight of the water-soluble cationic resin is preferably in the range of 5,000 to 500,000, more preferably 10,000 to 300,000, and particularly preferably 20,000 to 200,000. If the weight average molecular weight is too low, the tensile strength of the internal paper tends to decrease. Conversely, if the weight average molecular weight is too high, the viscosity of the aqueous dispersion after mixing the water-soluble cationic resin becomes too high and handling is difficult. It may be difficult or coarse aggregates may be generated.

  The mixing amount of the water-soluble cationic resin is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass, particularly 100 parts by mass of the hollow polymer particles formed in the previous stage. Preferably it is 1-20 mass parts.

The water-soluble cationic resin is preferably mixed in the state of an aqueous solution of the water-soluble cationic resin. If it does in this way, generation | occurrence | production of the coarse aggregate in the case of mixing can be suppressed effectively. The concentration of the aqueous solution is preferably in the range of 1 to 40% by mass, more preferably 3 to 30% by mass. If this concentration is too low, the concentration of the finally obtained aqueous dispersion may decrease, and the transfer efficiency may decrease.
Further, it is preferable to add an aqueous solution of the water-soluble cationic resin to the aqueous dispersion while stirring the aqueous dispersion so that the mixing is uniform.

  By mixing the water-soluble cationic resin, the water-soluble cationic resin molecules are adsorbed on the surface of the hollow polymer particles, the surface of the hollow polymer particles is cationized, and the effect of the present invention is presumed. . This can also be seen from the fact that when the zeta potential of the finally obtained hollow polymer particles is measured, it shows a positive potential.

  Formation of core polymer particles (A), formation of intermediate layer (B), formation of outer layer (C), base treatment, acid treatment, formation of outermost layer (D) as required, and mixing of water-soluble cationic resin May be carried out stepwise in the same reactor, after the previous step, the product of the previous step is transferred to another reactor and the next step is carried out in that reactor. Also good.

  The polymerization reaction of the aqueous dispersion containing the hollow polymer particles is stopped by cooling the polymerization system, adding a polymerization inhibitor or the like. Thereafter, if desired, unreacted monomers are removed, the pH and solid content concentration of the aqueous dispersion are adjusted, and an aqueous dispersion containing the hollow polymer particles of the present invention is obtained.

  The number average particle diameter of the hollow polymer particles in the aqueous dispersion of the present invention is preferably 100 nm to 1.5 μm, more preferably 300 nm to 1.2 μm, still more preferably 500 nm to 1 μm. The number average particle diameter is a value obtained by simply averaging the maximum particle diameter of each of the 200 hollow polymer particles measured by a transmission electron microscope.

  The porosity of the hollow polymer particles is preferably 30 to 65%, more preferably 35 to 60%, and still more preferably 40 to 58%. The porosity is a value obtained by simply averaging the porosity obtained by calculation from the numerical values of the maximum particle diameter and the maximum diameter of each of the 200 hollow polymer particles measured by a transmission electron microscope.

Since the hollow polymer particles in the aqueous dispersion obtained by the production method of the present invention have cations on the surface of the particles, the dispersion is excellent in dispersion stability in a low pH region, and further to the aqueous dispersion containing the hollow polymer particles. Even if other cationic substances are mixed, aggregates are not generated, and it can be applied to various applications.
For example, organic pigments blended in coating compositions for coated paper such as coated paper for printing, ink jet recording paper, thermal paper, and pressure sensitive paper; a material for forming a heat insulating layer in thermal paper, thermal transfer paper, etc. A masking agent or pigment for water-based inks such as water-based printing inks and water-based inkjet inks; an opacity improver for internal paper; In particular, when used for internal paper, an internal paper having excellent whiteness and opacity can be produced at a high yield.

Method for Producing Internally Added Paper A filler containing an aqueous dispersion containing hollow polymer particles of the present invention can be added to pulp dispersed in water to obtain a slurry, and the slurry can be made to produce an internally added paper.

  Specific examples of the pulp include chemical pulp such as unbleached kraft pulp and bleached kraft pulp; mechanical pulp; semi-chemical pulp; synthetic wood pulp; pulp obtained from recovered recovered paper; non-wood pulp. If desired, together with these pulps, inorganic fibers such as glass fibers and rock wool; synthetic fibers such as polyester, nylon and polyacrylonitrile; ceramic fibers; wheat straw, cotton scraps and the like can be used in combination.

  In addition to the pulp and the hollow polymer particles, a desired amount of a filler, a paper strength improver, a yield improver, and other additives can be contained in the internal additive paper. The method for adding these various additives is not limited.

  Specific examples of the filler include inorganic fillers such as titanium oxide, silica, zinc oxide, barium sulfate, calcium carbonate, calcium oxide, aluminum silicate, diatomaceous earth, clay, magnesium hydroxide, and talc; hollow polymer particles, bowl-shaped heavy Organic fillers such as coalesced particles and plastic pigments.

  Specific examples of the paper strength improver include starch, oxidized starch, cationized starch, esterified starch, guar gum, modified guar gum, anionic polyacrylamide, cationic polyacrylamide, amphoteric polyacrylamide, polyamide epichlorohydrin, polyamide epoxy resin, and melamine resin. Etc.

  Specific examples of the yield improver include aluminum sulfate, alum, sodium aluminate, cationized starch, cationic polyacrylamide, and amphoteric polyacrylamide. The amount of the yield improver is not particularly limited, but is usually 3% by mass or less, preferably 2% by mass or less based on the pulp.

  Specific examples of the internal sizing agent include solution rosin sizing agent, reinforced rosin sizing agent, rosin emulsion sizing agent, alkyl ketene dimer, alkenyl succinic anhydride and the like.

  Specific examples of various additives include surfactants, antioxidants, fungicides, preservatives, bactericides, pH adjusters, water-soluble organic dyes, water-dispersible color pigments, melamine-formaldehyde resins, urea-formalins. Resins, wax emulsions, flame retardants, plasticizers and the like.

  The papermaking method of the pulp slurry containing hollow polymer particles is not particularly limited. An example of the papermaking method is shown below. The pulp is appropriately beaten if desired, then dispersed in a predetermined amount of water, and an aqueous dispersion containing hollow polymer particles or a filler containing hollow polymer particles is added to the pulp dispersion and stirred. Next, after adding desired components such as a yield improver and further stirring, the slurry concentration is adjusted to obtain a paper slurry. This can be applied to a paper machine and then dried to produce the desired internal paper. After paper making, calendar processing can be performed as necessary.

The basis weight of the internal paper is not particularly limited, but is usually selected in the range of ^{20 to} 500 g / m2. The thickness of the internal paper is not particularly limited.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. In the following examples, “part” and “%” are based on mass unless otherwise specified.
The physical properties of the aqueous dispersion, the hollow polymer particles, and the internal paper were measured as follows.

(1) Stability of aqueous dispersion The obtained aqueous dispersion was filtered using an 80-mesh filter cloth, and the residue on the filter cloth was washed with water and dried, and the mass of the residue was weighed. The ratio of the residue to the solid content in the filtered aqueous dispersion was determined as a percentage, and judged according to the following criteria. The smaller the residue, the better the stability.
Evaluation A: Residue is less than 0.1% Evaluation B: Residue is 0.1% or more and less than 1% Evaluation C: Residue is 1% or more

(2) Zeta potential The zeta potential of the hollow polymer particles in the aqueous dispersion was measured using a fully automatic electrokinetic phenomenon analyzer (PenKem System 3000, PenKem) under the conditions of 0.01 N KCl and pH 5.5. It was measured. Under this measurement condition, the movement of the hollow polymer particles due to the electric field is detected (the polymer electrolyte is not detected). Therefore, when a positive zeta potential is observed, the hollow polymer particles have a positive charge.

(3) Porosity of hollow polymer particles The maximum particle diameter and the maximum void diameter of each of the 200 hollow polymer particles were measured with a transmission electron microscope (H-7500, manufactured by Hitachi, Ltd.) and calculated according to the following equation: The value obtained by simply averaging the void ratio was the void ratio of the hollow polymer particles.

Porosity (%) = 100 × (maximum void diameter) ³ / (maximum particle diameter) ³

(4) Number average particle diameter of hollow polymer particles The number average particle diameter of the hollow polymer particles was determined by simply averaging the maximum particle diameter of each of the 200 hollow polymer particles by a transmission electron microscope.

(5) Yield rate of hollow polymer particles A calibration curve of styrene peak area versus hollow polymer particle mass was prepared using hollow polymer particles with known styrene content and pyrolysis gas chromatography. Next, about 1 g of the internal paper containing the hollow polymer particles is pulverized with a freeze pulverizer, the amount of the hollow polymer particles in the paper powder is measured by pyrolysis gas chromatography, and the hollow weight in the internal paper is measured. The content rate (% by mass) of the coalesced particles was calculated using the calibration curve. And the yield of the hollow polymer particles in the internal paper was calculated by the following formula.

Yield rate = (mass of hollow polymer particles in internal paper) / (mass of hollow polymer particles added to pulp slurry) × 100

(6) Whiteness The ISO whiteness (unit:%) of the internal paper was measured using a spectral color whiteness meter (PF10 manufactured by Nippon Denshoku Industries Co., Ltd.) based on JIS P8113-1976. The higher the value, the better the whiteness.

(7) Opacity The opacity (unit:%) of the internal paper was measured using a spectral color whiteness meter (PF10 manufactured by Nippon Denshoku Industries Co., Ltd.) based on JIS P8138-1976. The greater the number, the better the opacity.

(8) Breaking length The breaking length of the internal paper is determined by the following formula based on JIS P8113-1976.
Breaking length (km) = tensile strength / (width of test piece × basis weight of test piece) × 1000

Example 1
Preparation of monomer mixture 60 parts of methyl methacrylate, 5% butyl acrylate and 35% methacrylic acid were mixed to prepare 5 parts of the monomer mixture (a) for forming the core polymer particles (A). Methyl methacrylate 78%, butyl acrylate 16% and methacrylic acid 6% were mixed to prepare 45 parts of an intermediate layer (B) forming monomer mixture (b). The outer layer (C) forming monomer (c) 73 parts made of styrene was prepared. Styrene 97% and methyl methacrylate 3% were mixed to prepare 75 parts of a monomer mixture (d) for acid treatment and outermost layer (D) formation.

Formation of core polymer particles (A) 5 parts of monomer mixture (a), 4 parts of ion-exchanged water and 0.045 part of sodium alkyldiphenyl ether disulfonate (Perex SS-H manufactured by Kao Corporation) as an emulsifier were mixed. The emulsion of the monomer mixture (a) was prepared by stirring.
A latex (solid content) containing 13.25 parts of ion-exchanged water and 0.2 part of an acrylic polymer seed having a number average particle size of 35 nm in a reactor equipped with a stirrer, a reflux condenser, a thermometer and a separatory funnel. Concentration: 12%), and the temperature was raised to 80 ° C.
Subsequently, 0.85 part of 3% aqueous potassium persulfate solution was added, and then the emulsion of the monomer mixture (a) was continuously added to the reactor over 3 hours. After completion of the addition, a polymerization reaction was further performed at 80 ° C. for 2 hours. The polymerization conversion rate was 98%.

Formation of Intermediate Layer (B) After adding 7 parts of 3% potassium persulfate aqueous solution to the reaction solution containing the core polymer particles (A), the mixture was stirred at 80 ° C. Subsequently, 45 parts of monomer mixture (b) and sodium polyoxyethylene lauryl ether sulfate as an emulsifier (Ramtel E-150 manufactured by Kao Corporation, C ₁₂ H ₂₅ —O— (CH ₂ CH ₂ O) ₄₇ —SO _{3 Na: C 8 H 17 -O- (} CH 2 CH 2 O) 47 -SO 3 Na = 5: 1 ( molar ratio)) to the reaction mixture over a period of 2 hours 0.36 parts continuously added, the polymerization The reaction was carried out for 1 hour. The conversion rate of the monomer mixture (b) was 98%.

Formation of outer layer (C) 10 parts of a 3% potassium persulfate aqueous solution was added to the reaction solution containing the core polymer particles (A) surrounded by the intermediate layer (B), and then stirred at 80 ° C. Subsequently, 73 parts of monomer (c) and 0.584 part of Ramtel E-150 were continuously added to the reaction solution over 2 hours, and the polymerization reaction was further performed for 1 hour. The conversion rate of the monomer (c) was 98%.

Base treatment Immediately after the completion of the polymerization reaction, 15.4 parts of a 10% aqueous sodium hydroxide solution and 0.6 part of Ramtel E-150 were added from a separating funnel, and the base treatment was carried out at 85 ° C. for 2 hours. A part of the obtained aqueous dispersion was collected, and the pH of the aqueous dispersion was measured at room temperature. The pH was 9.0.

Acid Treatment and Formation of Outermost Layer (D) 75 parts of the monomer mixture (d) and 0.637 part of Ramter E-150 were continuously added to the aqueous dispersion over 2 hours. Went for hours. The conversion rate of the monomer mixture (d) was 99%. The resulting aqueous dispersion was cooled to room temperature. The pH of the aqueous dispersion was 6.0.

Mixing of water-soluble cationic resin To a 30% aqueous solution of polyethyleneimine having a weight average molecular weight of about 70,000 (manufactured by Nippon Shokubai Co., Ltd .: Epomin P-1000), a 1% hydrochloric acid aqueous solution is added, and the pH is 4. What was neutralized to 5 was used as a water-soluble cationic resin aqueous solution.
While stirring the aqueous dispersion after acid treatment, the water-soluble cationic resin aqueous solution corresponding to 1 part of the active ingredient was added thereto.
To the resulting aqueous dispersion, 0.1N hydrochloric acid was added to adjust the pH to 3.5 to obtain an aqueous dispersion containing hollow polymer particles.
The stability of the obtained aqueous dispersion, the zeta potential, the porosity, and the average particle diameter of the hollow polymer particles contained in the aqueous dispersion were measured.

Manufacture of internal paper Mixed hardwood bleached pulp beaten by Niagara Beater and softwood bleached pulp beaten by Niagara Beater at a ratio of 80:20, Canadian Freeness (CSF) JIS P811-1976) A pulp slurry was prepared. The aqueous dispersion containing the hollow polymer particles was added to the pulp slurry so as to be 5% (in terms of solid content) with respect to the absolute dry mass of the pulp, and stirred for 5 minutes. Thereafter, an aqueous aluminum sulfate solution having a concentration of 1% was added to the pulp slurry so as to be 0.5% (in terms of solid content) with respect to the absolute dry mass of the pulp, followed by stirring for 2 minutes. Next, the pulp slurry was diluted with water to a concentration of 0.02%, and stirred for 2 minutes to obtain a paper slurry. The stock slurry was transferred to a box of a square sheet paper machine that had been filled with water so that the pulp slurry concentration in the box was 0.004%, and was then sprinkled with a 100 mesh wire netting to produce a wet sheet. . The wet sheet was dehydrated with a squeeze roll having a linear pressure of 5 to 8 kg / cm, dried with a rotary drum dryer at 95 to 110 ° C. for 1 minute, and then passed through a super calender with a linear pressure of 35 to 40 kg / cm. Humidity was adjusted for 24 hours in an atmosphere of 20 ° C. and humidity 65% based on P8121-1976 to prepare an internal paper having a basis weight of 65 g / cm ² , and the yield rate of the hollow polymer particles in the internal paper, The basis weight, whiteness, opacity and tear length of the internal paper were measured. The results are shown in Table 1.

Example 2
The procedure of Example 1 was repeated except that the addition amount of the water-soluble cationic resin was changed to 5 parts.

Comparative Example 1
In the formation of the outer layer (C) and the outermost layer (D), the procedure was the same as in Example 1 except that the type and amount of the surfactant shown in Table 1 were changed.
Ramtel E-118B (manufactured by Kao Corporation) is a surfactant having the following structure.
_{C 12 H 25 -O- (CH 2} CH 2 O) 18 -SO 3 Na

The stability of the obtained aqueous dispersion was extremely low, the physical properties of the hollow polymer particles could not be measured, and the internal paper could not be produced.

Comparative Example 2
Example 1 was repeated except that no water-soluble cationic resin was added.

When forming the outer layer (C), the stability of the aqueous dispersion produced without using the surfactant defined in the present invention was low (Comparative Example 1).
The aqueous dispersion produced without adding the water-soluble cationic resin shows a negative data potential of the hollow polymer particles, and the yield of the hollow polymer particles in the internal paper obtained using the aqueous dispersion is The rate was low, the whiteness and opacity of the internal paper were low, and the tear length of the internal paper was short (Comparative Example 2).
The zeta potential of the hollow polymer particles contained in the aqueous dispersion produced by the production method of the present invention is positive, the stability of the aqueous dispersion is good, and the inner paper obtained using the aqueous dispersion The hollow polymer particles had a high yield, whiteness and opacity of the internal paper were high, and the tear length of the internal paper was long (Examples 1 and 2).

  The aqueous dispersion containing the hollow polymer particles of the present invention is a coating of paper, fiber, leather, etc .; an organic pigment, a light scattering agent or a light scattering aid in applications such as aqueous inks and paints, and an absorbent filler for inkjet paper , Internal fillers for papermaking processes, high hiding pigments for correction inks or correction ribbons, microcapsule materials, intermediate materials for toners used in electrophotography, resin, cement, concrete, etc. It can be used for applications utilizing weight reduction by air, semiconductor sealing materials, etc., and applications utilizing the low dielectric property of air. The aqueous dispersion containing the hollow polymer particles of the present invention is suitable for an internal paper filler, and enables the production of an internal paper having high whiteness and opacity.

Claims (3)

(1) A monomer mixture (a) comprising 20 to 60% by mass of an acid group-containing monomer and 80 to 40% by mass of a monoethylenically unsaturated monomer copolymerizable therewith is copolymerized to form a core weight A step of preparing coalesced particles (A),
(2) A monomer or monomer mixture (b) composed of 88 to 100% by mass of a monoethylenically unsaturated monomer and 12 to 0% by mass of an acidic group-containing polymer is added to the core polymer particles (A). Polymerizing or copolymerizing in the presence to form an intermediate layer (B) substantially surrounding the core polymer particles (A);
(3) A monomer or monomer mixture (c) composed of 97 to 100% by mass of a monoethylenically unsaturated monomer and 3 to 0% by mass of an acidic group-containing polymer is surrounded by an intermediate layer (B). In the presence of the core polymer particles (A), an outer layer (C) that substantially surrounds the intermediate layer (B) by polymerization or copolymerization using a surfactant represented by the following general formula (I) Forming a process,
R—O— (CH ₂ CH ₂ O) _n —SO ₃ M (I)
(In the formula, R is an alkyl group or alkenyl group having 8 to 20 carbon atoms, M is an alkali metal ion or ammonium ion, and n is an integer of 20 to 70.)
(4) A base is added to an aqueous dispersion containing polymer particles having at least a three-layer structure of a core polymer particle (A), an intermediate layer (B), and an outer layer (C), and the pH of the aqueous dispersion A step of preparing an aqueous dispersion containing 7 or more and hollow polymer particles,
(5) The manufacturing method of the aqueous dispersion which implements the process of mixing water-soluble cationic resin in the state which made the pH of the said aqueous dispersion acidic. An aqueous dispersion produced by the method for producing an aqueous dispersion according to claim 1. A method for producing an internally-added paper, wherein a step of making a paper by adding a filler containing the aqueous dispersion according to claim 2 to a pulp slurry.