JP2001248094A - Filled paper and composition for coating paper and coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-quality filled paper using hollow polymer particles making the most of lightweight properties and excellent in affinity for fibers of the filled paper as a filler and further excellent in strength, heat, chemical and solvent resistances, etc., a composition for coating using the hollow polymer particles making the most of the lightweight properties and excellent in affinity for fibers of the paper as a pigment and capable of providing the high-quality coated paper having surfaces excellent in heat resistance and the coated paper. SOLUTION: This filled paper comprises cationic hollow cross-linked polymer particles having a ζ potential measured in an aqueous medium at pH 2-9 within the range of +5 to +100 mV and comprising 5-90 wt.% of a structural unit derived from a cross-linking monomer and 95-10 wt.% of a structural unit derived from other monomers copolymerizable with the cross-linking monomer. The composition for coating a paper comprises the cationic hollow cross-linked polymer particles and a binder component. The coated paper is obtained by coating the paper with the composition for coating the paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a filled paper in which cationic hollow crosslinked polymer particles are internally added as a filler, and a paper coating containing cationic hollow crosslinked polymer particles as a pigment and a binder component. Composition and coated paper.

[0002]

2. Description of the Related Art Many of paper products require opacity and whiteness. As a means for imparting its performance, generally, talc, clay, calcium carbonate,
It is known that an inorganic pigment such as titanium oxide is internally added as a filler to obtain a filled paper. The problems with fillers made of inorganic pigments are that they have a large specific gravity, which increases the weight of the filling paper. not,
There are problems such as poor yield of the internal addition and poor uniform dispersibility of the filler. As a method for solving the above problems, a method using hollow polymer particles has been attempted.
However, although this method can prevent the weight of the filled paper from increasing, the heat resistance, solvent resistance and chemical resistance of the filled paper are not sufficient. Further, since the affinity between the hollow polymer particles and the fibers is inferior, the strength of the filled paper may be reduced.

On the other hand, printing paper is generally coated with a paper coating composition containing an inorganic pigment and a binder component in order to improve printing performance. However, the use of the inorganic pigment causes problems such as an increase in the weight of the paper and poor dispersibility of the pigment in the coating composition. As a method for solving the above problems, a method using hollow polymer particles instead of the inorganic pigment has been attempted. The use of hollow polymer particles can prevent an increase in the weight of the paper, but the affinity with the paper, the affinity with the binder component is not sufficient, and the uniform dispersibility of the hollow polymer particles in the coating composition is poor. As a result, the coated surface performance of the paper is impaired. Further, the surface of the coated paper using the hollow polymer particles as a pigment is inferior in heat resistance and causes a decrease in the quality of the coated paper in a drying step or the like.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to use, as a filler, hollow polymer particles which make use of lightweight properties and have an excellent affinity for the fibers of a filled paper, and which have strength and heat resistance. It is an object of the present invention to provide a high quality filled paper excellent in chemical resistance, solvent resistance, etc. Another object of the present invention is to
As a pigment, hollow polymer particles that make use of lightweight properties and have excellent affinity for paper fibers are used, and are used for coating that can produce high-quality coated paper that has a surface with excellent heat resistance. It is to provide a composition and a coated paper.

[0005]

According to the present invention, there is provided a filled paper having the following constitution, a paper coating composition and a coated paper, and the above object is achieved. 1. (I) the zeta potential measured in an aqueous medium having a pH of 2 to 9 is in the range of +5 to +100 mV, and (II) 5 to 90% by weight of a structural unit derived from the crosslinkable monomer is copolymerized with the crosslinkable monomer. 95 to 10% by weight of structural units derived from possible other monomers (where the total amount of both is 1
(Filled paper) of 100% by weight). 2. The cationic hollow crosslinked polymer particles are copolymerizable with (a) 5 to 100% by weight of a crosslinkable monomer, (b) 0 to 15% by weight of a cationic monomer, and (c) using a radical polymerization initiator. 0-95% by weight of a non-crosslinkable and nonionic monomer (total weight of monomers is 100% by weight) is polymerized in the presence of polymer particles swellable on at least one of these monomers And (2) the polymer particles are (b) 0 to 30% by weight of a cationic monomer and (d) copolymerizable with the cationic monomer using a radical polymerization initiator. It is a polymer particle obtained by polymerizing 70 to 100% by weight of ionic monomer (the total weight of the monomer is 100% by weight), and (3) the above (1) and (2) Filling paper according to claim 1, characterized in that one or both of the radical polymerization initiator is a radical initiator having a cationic group that. 3. (A) (I) The zeta potential measured in an aqueous medium having a pH of 2 to 9 is in a range of +5 to +100 mV, and (I)
I) 5 to 90% by weight of a structural unit derived from a crosslinkable monomer and 95 to 10% by weight of a structural unit derived from another monomer copolymerizable with the crosslinkable monomer (the total amount of both is 100% by weight) (B) a binder component, and a cationic hollow crosslinked polymer particle comprising: (B) a binder component. 4. The cationic hollow crosslinked polymer particles are copolymerizable with (a) 5 to 100% by weight of a crosslinkable monomer, (b) 0 to 15% by weight of a cationic monomer, and (c) using a radical polymerization initiator. 0-95% by weight of a non-crosslinkable and nonionic monomer (total weight of monomers is 100% by weight) is polymerized in the presence of polymer particles swellable on at least one of these monomers And (2) the polymer particles are (b) 0 to 30% by weight of a cationic monomer and (d) copolymerizable with the cationic monomer using a radical polymerization initiator. It is a polymer particle obtained by polymerizing 70 to 100% by weight of ionic monomer (the total weight of the monomer is 100% by weight), and (3) the above (1) and (2) Paper coating composition according to the above 3, wherein the one or both of the radical polymerization initiator that is a radical initiator having a cationic group. 5. A coated paper obtained by coating the paper coating composition according to 3 or 4 above.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the filled paper, the paper coating composition and the coated paper of the present invention will be described in more detail. First, the cationic hollow crosslinked polymer particles contained therein will be described.

[Cationic hollow crosslinked polymer particles] Cationic hollow crosslinked polymer particles (hereinafter simply referred to as “hollow crosslinked particles”)
Is referred to as (I) when the zeta potential measured in an aqueous medium having a pH of 2 to 9 is +5 to +100 mV, preferably +10 to +100 mV.
To +60 mV, and (II) 5 to 90% by weight, preferably 10 to 60% by weight, more preferably 15 to 50% by weight of a structural unit derived from a crosslinkable monomer, and 95 to 10% by weight, preferably 40% by weight of structural units derived from other copolymerizable monomers
To 90% by weight, more preferably 50 to 85% by weight (the total amount of both is 100% by weight). In a preferred embodiment, the hollow crosslinked particles have a volume hollow ratio of preferably 1 to 80%, more preferably 3 to 40.
% And the average particle diameter is preferably 0.0%.
3 to 10 μm, further preferably 0.05 to 7 μm, more preferably 0.1 to 5 μm, particularly preferably 0.2 to 5 μm.
Particles in the range of 3 μm.

[0008] The zeta potential is an index indicating the ionicity of the particles, and the fact that the zeta potential of the hollow crosslinked particles of the present invention is in the above range indicates that the particles have cationicity in a wide range of acidic to alkaline environments. ing. For this reason, the filler paper containing the hollow crosslinked particles as a filler,
The affinity between the hollow crosslinked particles and the fibers is improved, and the strength of the paper is increased. Further, also in the case of a paper coating composition containing hollow crosslinked particles, the affinity with the fibers of the coated paper is improved, and the affinity with the binder component is also improved, so that favorable results are obtained. Measurement of the zeta potential of hollow crosslinked particles
This is performed by the following method. (Measurement method of zeta potential) The aqueous dispersion of particles was diluted with a 0.1N aqueous potassium chloride solution so that the particle solid content concentration was 0.1% by weight, and this was diluted with hydrochloric acid or potassium hydroxide to pH 2,6. , 9 and the zeta potential at each pH is measured with a laser Doppler zeta potential meter.

As described above, the hollow crosslinked particles used in the present invention are composed of 5 to 90% by weight of a structural unit derived from a crosslinkable monomer and a structural unit derived from another monomer copolymerizable with the crosslinkable monomer. The unit consists of 95 to 10% by weight. The existence of the structure derived from the crosslinkable monomer in the hollow crosslinked particles in the above range as described above means that the hollow crosslinked particles have many crosslinked structures, and the strength and heat resistance of the hollow crosslinked particles of the present invention. Is good. If the amount of the structure derived from the crosslinkable monomer is less than 5% by weight, such a favorable result cannot be obtained. Here, the ratio of the structural unit derived from the crosslinkable monomer to the structural unit derived from another monomer is a value as an average of all the polymers constituting the hollow crosslinked particles. For example, a production method (I) to be described later, which is a preferred method for obtaining hollow crosslinked particles,
In (IV), the above ratio is calculated as an average value of the polymer of the swellable polymer particles and the polymer generated by polymerization in the presence of the swellable polymer particles.

The volume hollow ratio is a volume ratio of pores to particles. When the volume hollow ratio is less than 1%, it does not substantially function as hollow crosslinked particles. Also. When the volume hollow ratio exceeds 80%, the strength decreases, which is not preferable. In the present invention, the measurement of the volume hollow ratio is performed by the following method. (Measurement method of volume hollow ratio) An aqueous dispersion of particles was diluted with distilled water so that the particle solid content concentration was 0.1% by weight, and this was dropped on a copper mesh provided with a collodion film and dried.
The particles are photographed with a transmission electron microscope, the inner diameter and the outer diameter of 100 hollow crosslinked particles are measured from the obtained photograph, and the cube of the ratio of the obtained average inner diameter to the average outer diameter is defined as the volume hollow ratio. .

As described above, the average particle diameter of the hollow crosslinked particles is preferably in the range of 0.03 to 10 μm, and is in the form of fine particles. When the particle size is within this range, the dispersibility of the hollow crosslinked particles in the papermaking process of the filled paper is good. Further, in the paper coating composition, favorable results can be obtained in terms of dispersibility in a coating medium, coating film strength, and paint stability. Hollow crosslinked particles having an average particle diameter of less than 0.03 μm are difficult to produce, while dispersibility becomes unstable if the average particle diameter exceeds 10 μm. In the present invention, the average particle size is measured by the following method (measurement method of average particle size) An aqueous dispersion of particles is appropriately diluted with distilled water, and averaged using a dynamic light scattering particle size analyzer. Measure the particle size.

The cationic hollow crosslinked polymer particles contained in the coating composition of the present invention maintain cationicity even in an acidic to alkaline atmosphere and have sufficient strength and dispersibility. Therefore, it is excellent as a filler for filled paper and further as a white pigment for coating. The hollow crosslinked particles preferably further have the following properties. First, it is preferable to have solvent resistance to organic solvents such as toluene and alcohol. By having solvent resistance, there is an advantage that when filled paper or coated paper comes in contact with an organic solvent, whiteness is maintained. Specifically, it is preferable that the amount dissolved in toluene at 25 ° C. is 10% or less. Further, it is preferable to have heat resistance. By having heat resistance, there is an advantage that the shape of particles is maintained even in a high-temperature drying step in the process of producing coated paper. Specifically, it is preferable that the 10% reduction temperature is 240 ° C. or higher as measured by a thermobalance (TGA). Such solvent resistance and heat resistance can be developed by appropriately selecting the monomer species.

Examples of the polymer constituting the cationic hollow crosslinked polymer particles include acrylic resins, polystyrene resins, polyolefin resins, polyester resins, polycarbonate resins, polyurethane resins, phenol resins, epoxy resins, ionomers. Thermoplastic resins or thermosetting resins such as resins, vinyl chloride resins, fluororesins, and butadiene resins. It is essential that at least a part of the polymer constituting the hollow crosslinked particles has a cationic group. In the present invention, the cationic group includes a group capable of forming a cation by bonding to a proton such as an amino group, and a group in which the group reacts with an acid to form a salt and form a cation portion of the salt. . Specific examples of the cationic group include a primary amino group, a secondary amino group, and a tertiary amino group; a quaternary amino group, a secondary imino group, and a tertiary imino group;
A quaternary imino group; amidino groups, imidino groups, hydrazino groups of various grades; and cyclic groups containing a nitrogen atom such as a pyridyl group.

The concentration of the cationic group in the hollow crosslinked particles is preferably 0.05 to 300 mmol / 100 g particles, more preferably 0.1 to 200 mmol, and more preferably 1 to 100 mmol / 100 g particles.

The method for producing the cationic hollow crosslinked polymer particles of the present invention is not particularly limited, but the following production methods (I) to (IV) are preferred.

Hereinafter, these production methods (I) to (IV) will be described. First, the monomers (a) to (d) used in the production methods (I) to (IV), the radical polymerization initiator having a cationic group, and the like will be described in detail. <Monomer> (a) Crosslinkable monomer divinylbenzene, divinylbiphenyl, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, propylene glycol Di (meth) acrylate, dipropylene glycol di (meth)
Acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, 2,2′-bis [4- (meth) acryloyloxypropoxyoxyphenyl] propane, 2,2′-bis [4
-(Meth) acryloyloxydiethoxyphenyl] propane, glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and other divinyl monomers, trivinyl monomers and tetravinyl monomers Is mentioned. Among them, divinylbenzene, ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate are preferred. These can be used alone or in combination of two or more.

(B) Cationic monomer 2-dimethylaminoethyl (meth) acrylate, 2-
Aminoalkyl group-containing (meth) acrylates such as diethylaminoethyl (meth) acrylate, 2-dimethylaminopropyl (meth) acrylate, and 3-dimethylaminopropyl (meth) acrylate, and methylene chloride, dimethyl sulfate, and diethyl sulfate thereof. Quaternary salts such as 2- (dimethylaminoethoxy) ethyl (meth) acrylate, 2- (diethylaminoethoxy) ethyl (meth) acrylate, and aminoalkoxyalkyl groups such as 3- (dimethylaminoethoxy) propyl (meth) acrylate (Meth) acrylic acid esters and quaternary salts thereof with methylene chloride, dimethyl sulfate, diethyl sulfate and the like; N- (2-dimethylaminoethyl)
N-amino such as (meth) acrylamide, N- (2-diethylaminoethyl) (meth) acrylamide, N- (2-dimethylaminopropyl) (meth) acrylamide, N- (3-dimethylaminopropyl) (meth) acrylamide Alkyl group-containing (meth) acrylamides and quaternary salts thereof with methylene chloride, dimethyl sulfate, diethyl sulfate and the like can be mentioned. Among them, 2-dimethylaminoethyl (meth) acrylate, N- (2-
(Dimethylaminoethyl) (meth) acrylamide and quaternary salts thereof with methylene chloride are preferred. These can be used alone or in combination of two or more.

(C) Non-crosslinkable and nonionic monomer capable of being copolymerized Here, (c) the noncrosslinkable and nonionic monomer which can be copolymerized includes the above (a) crosslinkable monomer or (b) cation Non-crosslinkable and nonionic monomers that can be copolymerized with any of the hydrophilic monomers. Examples of such a monomer include aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, and halogenated styrene; unsaturated nitriles such as acrylonitrile; methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, and butyl. Acrylate,
Butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate,
Examples thereof include acrylic acid esters and methacrylic acid esters such as 2-hydroxyethyl methacrylate; diolefins such as butadiene and isoprene; vinyl carboxylic acid esters such as vinyl acetate; and vinylidene halides such as vinyl chloride and vinylidene chloride. Among them, styrene, α-methylstyrene, acrylonitrile, methyl methacrylate, butyl methacrylate,
2-hydroxyethyl acrylate is preferred. These monomers can be used alone or in combination of two or more.

(D) Nonionic monomer copolymerizable with the above (b) cationic monomer This monomer is the same as the above (a) crosslinked except that it satisfies the condition that it can be copolymerized with the (b) cationic monomer. The same as the nonionic monomer and (c) the copolymerizable non-crosslinkable and nonionic monomer. Specific examples thereof include the monomers exemplified as (a) a crosslinkable monomer and (c) a copolymerizable non-crosslinkable and nonionic monomer, including preferable monomers. However, the crosslinkable monomer is used as needed within a range that does not impair the achievement of the object of the present invention. These monomers can be used alone or in combination of two or more.

<Radical polymerization initiator having a cationic group> In the radical polymerization initiator, the polymer obtained by the radical polymerization using the radical polymerization initiator has a cationic group derived from the radical polymerization initiator at its terminal. Things. Preferred examples of the radical polymerization initiator having a cationic group include an azobis-type initiator having an amidino group, an imidino group or a pyridium group. Also, 1
Those having a 0-hour half-life temperature in the range of 40 to 95 ° C. are preferred because the polymerization can be carried out under mild conditions. Preferred specific examples of the radical polymerization initiator having a cationic group include the following.

2,2'-azobis (2-methyl-N-phenylpropionamidine) dihydrochloride2,2'-azobis [N- (4-chlorophenyl) -2
-Methylpropionamidine] dihydrochloride • 2,2'-azobis [N- (4-hydroxyphenyl)
-2-methylpropionamidine] dihydrochloride2,2'-azobis [2-methyl-N- (phenylmethyl) -propionamidine] dihydrochloride2,2'-azobis [2-methyl-N- (2- Propenyl) propionamidine] dihydrochloride • 2,2′-azobis (2-methylpropionamidine)
Dihydrochloride 2,2'-azobis [N- (2-hydroxyethyl) -2-methylpropionamidine] dihydrochloride 2,2'-azobis [N- (2-carboxyethyl)-
2-methylpropionamidine] hydrate

2,2'-azobis [2-methyl- (5-
Methyl-2-imidazolin-2-yl) propane] dihydrochloride2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride2,2'-azobis [2- (4 5,6,7-tetrahydro-1H-1,3-diazepin-2-yl) propane] dihydrochloride • 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) Propane] dihydrochloride2,2'-azobis [2- (5-hydroxy-3,4,
5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride. 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride. 2′-azobis [2- (2-imidazolin-2-yl) propane] Among them, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (V-50), 2,2′-azobis [N -(2-carboxyethyl) -2-methylpropionamidine] hydrate (VA-057),
The use of 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (VA-044) is preferred.

Next, the production methods (I) to (IV) for producing the cationic hollow crosslinked polymer particles will be described. <Production method (I)> In the present production method (I),
(A) 5 to 99.99% by weight, preferably 10 to 80% by weight, more preferably 15 to 70% by weight, and (b) 0.01 to 15% by weight of a cationic monomer,
Preferably it is 0.1 to 10% by weight, more preferably 0.1 to 10% by weight.
5 to 5% by weight, and (c) 0 to 94.9% by weight, preferably 10 to 89.9% by weight, more preferably 25 to 84.9% by weight of a copolymerizable non-crosslinkable and nonionic monomer.
5% by weight (total weight of monomer is 100% by weight)
Is polymerized in the presence of polymer particles swellable with respect to at least one of the monomers used in the polymerization (hereinafter, also simply referred to as “swellable polymer particles”), preferably in an aqueous medium. By doing so, hollow crosslinked particles are produced.

In the above method, the mechanism by which the hollow crosslinked particles are formed is not necessarily clear, but, for example, by coexisting a swellable polymer particle in addition to a polymerizable monomer containing a crosslinkable monomer in an aqueous medium,
During polymerization, the volume change occurs when the monomer that has infiltrated into the swellable polymer particles is polymerized and converted into a polymer, and as a result, pores are formed inside the crosslinked polymer, resulting in a hollow body formed by the crosslinked polymer. Is thought to be formed. On the other hand, when no swellable polymer particles are present, no pores are formed. This presumption is considered to apply not only to the manufacturing method (I) but also to other manufacturing methods (II) to (IV).

In the present method, if the amount of the crosslinkable monomer (a) used is too small, less than 5% by weight, the strength of the particles during polymerization becomes insufficient, so that the whole particles tend to shrink, and the inside of the particles becomes difficult. Insufficient strain due to polymerization shrinkage may make it difficult to form an inner hole, or even if polymer particles having an inner hole are formed, strength may be reduced. If the amount of (a) the crosslinkable monomer used exceeds 99.99% by weight and is excessive, the amount of (b) the cationic monomer used is reduced,
The cationic properties of the hollow crosslinked particles obtained are low. In addition,
(A) The amount of the crosslinkable monomer to be used is a pure product conversion excluding the inert solvent and the monofunctional non-crosslinkable monomer component contained in the commercially available crosslinkable monomer material. (B) If the amount of the cationic monomer used is too small as less than 0.01% by weight, the resulting hollow crosslinked particles will have reduced cationicity, and will not satisfy the above-mentioned conditions regarding the zeta potential. On the other hand, if the amount of the cationic monomer used exceeds 15% by weight and is excessive, it is not preferable because agglomerates are formed during polymerization. (C) The copolymerizable non-crosslinkable and nonionic monomer is a monomer optionally used for changing hydrophilicity or improving heat resistance as desired. If the amount used exceeds 94.9% by weight,
The amount of (a) the crosslinkable monomer or (b) the cationic monomer used is reduced, and the strength and cationicity of the obtained polymer particles are reduced.

In the present invention, "swellable in monomer"
The term means the case where the polymer particles can absorb the monomer, and includes the case where the monomer can dissolve the polymer particle.

As the polymer constituting the swellable polymer particles, at least one selected from styrene homopolymers and styrene copolymers is preferably used. Examples of the styrene copolymer include a copolymer of styrene and at least one selected from acrylates, methacrylates, and acrylonitrile. Among these, a styrene homopolymer or a styrene copolymer containing 50% by weight or more of a styrene component is particularly preferable.

The amount of the swellable polymer particles used is 100% by weight of the total amount of (a) a crosslinkable monomer, (b) a cationic monomer, and (c) a copolymerizable non-crosslinkable and nonionic monomer. 1 to 100 parts by weight per part,
Preferably it is 2 to 50 parts by weight, more preferably 5 to 20 parts by weight. If the amount of the swellable polymer particles is less than 1 part by weight, the volume hollow ratio is reduced, while if the amount of the swellable polymer particles is more than 100 parts by weight, the formation of pores tends to be suppressed. Is generated.

As a method of carrying out the polymerization by allowing the swellable polymer particles to be present in the aqueous dispersion, the swellable polymer particles are dispersed in the aqueous medium, and the above-mentioned (a), (b) and (c) are added thereto. The method of polymerizing after swelling any of the polymerizable monomers of the above) can be preferably employed. In this case, it is highly preferred that the swellable polymer particles function as seed polymer particles and that any of the polymerizable monomers swell well. For that purpose, the polymer constituting the swellable polymer particles preferably has a small molecular weight,
For example, the number average molecular weight is 20,000 or less, preferably 10,000 or less, and more preferably 700 to 7000.

Here, the number average molecular weight is a value in terms of polystyrene measured by dissolving the swellable polymer particles in a good solvent thereof and measuring the resulting solution by gel permeation chromatography (GPC). When the number average molecular weight of the swellable polymer particles is greater than 20,000, the amount of the monomer that does not swell in the swellable polymer particles increases, and this polymerizes separately from the swellable polymer particles in the aqueous dispersion, thereby resulting in polymer particles having pores. Not only will a large amount of fine particles not be formed be generated, but also the problem that the polymerization system will become unstable will occur.

The average particle diameter of the swellable polymer particles used as seed polymer particles is 30 to 8 times the average particle diameter (outer diameter) of the cationic hollow crosslinked polymer particles of the present invention.
It is preferably 0%. The particle size of the polymer particles having voids obtained by polymerization using the swellable polymer particles approximately matches the particle size when the swellable polymer particles swell the polymerizable monomer and enlarge. Therefore, by adjusting the particle size of the swellable polymer particles, the amount of the swellable polymer particles used relative to the polymerizable monomer, and the like, the particle size of the hollow crosslinked particles to be produced can be controlled. Specifically, in the production of polymer particles having pores, in order to obtain hollow crosslinked particles having a particle size of 0.06 to 0.6 μm having excellent whiteness and hiding power, 0.1% of swellable polymer particles is required. 03-0.4
A particle having a particle diameter of 0 μm may be used.

The method for preparing such swellable polymer particles is not particularly limited, and for example, a polymerization method such as emulsion polymerization or suspension polymerization using a relatively large amount of a chain transfer agent can be used.

The polymerization of the monomers (a) to (c) in the presence of the swellable polymer particles is preferably carried out in an aqueous medium by an emulsion polymerization method or a suspension polymerization method.

In the above polymerization, a surfactant used in ordinary polymerization, or an organic or inorganic suspension protective agent can be used. In general, when producing hollow crosslinked particles having an average particle diameter smaller than 1 μm, a surfactant is mainly used, and when producing hollow crosslinked particles having an average particle diameter larger than 1 μm, a suspension is used. It is good to use a protective agent mainly.

Examples of the surfactant include cationic surfactants such as alkylamines (salts), polyoxyethylene alkylamines (salts), quaternary alkylammonium salts, and alkylpyridinium salts; dodecyldimethylbetaine, alkylimidazo. Amphoteric surfactants such as rhinium betaine; polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, ethylene oxide addition derivative of alkylphenol formalin condensate, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid alkanolamide Nonionic surfactants such as polyoxyethylene fatty acid amides and reactive emulsifiers having polyoxyethylene as a hydrophilic group; and combinations thereof. Anionic surfactants are not suitable for use in the present invention because they tend to form aggregates during polymerization.

Examples of the organic suspension protective agent include hydrophilic synthetic high molecular substances such as polyvinyl alcohol, polyvinylpyrrolidone and polyethylene glycol, natural hydrophilic high molecular substances such as gelatin and water-soluble starch, and carboxymethyl cellulose. Examples include hydrophilic semi-synthetic polymer substances. Further, as the inorganic suspension protective agent, for example, magnesium, barium, phosphates such as calcium, calcium carbonate, magnesium carbonate,
Examples include zinc white, aluminum oxide, and aluminum hydroxide.

As the polymerization initiator, either an oil-soluble polymerization initiator or a water-soluble polymerization initiator can be used. When performing polymerization for producing hollow crosslinked particles having a particle diameter of 1 μm or less, it is preferable to use a water-soluble polymerization initiator, whereby monomer droplets having a large particle size that are not swollen by the hollow crosslinked particles are preferably used. Polymerization can be prevented. In the case of performing polymerization for producing hollow crosslinked particles having a particle size exceeding 1 μm, an oil-soluble polymerization initiator is used in order to prevent generation of polymer particles having no unnecessary pores. Is preferred.

Examples of the water-soluble polymerization initiator include persulfates and redox initiators such as hydrogen peroxide-ferrous chloride and cumene hydroperoxide-sodium ascorbate. Examples of the oil-soluble polymerization initiator include benzoyl peroxide, lauroyl peroxide, t-butylperoxy-2-ethylhexanoate, and azobisisobutyronitrile. Further, the above-mentioned radical polymerization initiator having a cationic group can also be used.

Depending on the combination of the monomers (a), (b) and (c), the polymerization rate may be high. In this case, the polymerization is carried out using a large polymerization vessel and all of the polymerization components are placed in the polymerization vessel. When a so-called batch polymerization method is used in which the polymerization is carried out, it is difficult to control the polymerization temperature, and there is a danger that the polymerization reaction will run away. Therefore, in order to avoid such danger, a so-called increment polymerization method, in which the monomer component is supplied to the polymerization vessel continuously or in a divided state during the polymerization in the state of the emulsion or in the form of an emulsion, is usually employed. Can also.

After the polymerization, the hollow crosslinked particles are separated from the aqueous dispersion and dried to obtain the cationic hollow crosslinked polymer particles of the present invention having pores therein.

According to the production method (I) of the present invention, for example, a hollow body having an average outer diameter (average particle diameter) of 0.03 to 10 μm and an inner diameter of 0.2 to 0.95 times the outer diameter is used. Thus, cationic hollow crosslinked polymer particles having a single void are obtained. This is the same for the production methods (II) to (IV).

Such a production method (I) is preferably used particularly for producing hollow crosslinked particles having a large amount of cationic groups.

<Production method (II)> In the production method (II),
Polymerization is carried out using a radical polymerization initiator having a cationic group to give the resulting hollow crosslinked particles cationicity. And (a) 5 to 100% by weight of the crosslinkable monomer, preferably 10 to 80% by weight, more preferably 15 to 70% by weight, and (b) 0 to 15% by weight of the cationic monomer, preferably 0 to 10% by weight , More preferably 0.1 to 10
% By weight, and (c) 0 to 95% by weight, preferably 10 to 90% by weight, more preferably 20 to 84.9% by weight of the copolymerizable non-crosslinkable and nonionic monomer (the total amount of the monomers is 100%). % By weight) is polymerized in the presence of polymer particles swellable with at least one of the monomers used for the polymerization. Therefore, the production method (I) is the same as the production method (I) except that a radical polymerization initiator having a cationic group is used and the amounts of the monomers (a), (b) and (c) are slightly different. ), And the polymerization method, operation, conditions, etc., including the method for preparing the swellable polymer particles, are the same as those described in the production method (I).

In the production method (II), the polymerizable monomer may be only (a) a crosslinkable monomer, or (b) a cationic monomer and / or (c) a copolymerizable non-crosslinkable and nonionic monomer in combination. You may. (A) when the amount of the crosslinkable monomer used is too small as less than 5% by weight, (b) when the amount of the cationic monomer used is more than 15% by weight and (c) non-crosslinkable copolymerizable Undesirable phenomena that occur when the amount of the ionic and nonionic monomer used exceeds 95% by weight are the same as those described in the production method (I).

The amount of the radical polymerization initiator having a cationic group to be used is preferably 0.1 to 10 parts by weight per 100 parts by weight of the total monomers used for the polymerization.
More preferably, it is 0.5 to 5 parts by weight. The amount used is 0.
If the amount is less than 1 part by weight, the cationic properties of the obtained hollow crosslinked particles decrease, and if it exceeds 10 parts by weight, polymerization becomes unstable, which is not preferable.

The production method (II) is characterized in that hollow crosslinked particles having less aggregates can be obtained.

<Production method (III)>
This is a method for obtaining the cationic hollow crosslinked polymer particles of the present invention by making the swellable polymer particles in the production method (I) cationic. The swellable polymer particles are
(B) 0.01 to 30% by weight, preferably 0.1 to 15% by weight, more preferably 1 to 10% by weight of cationic monomer
%, And (d) 70 to 99.99% by weight, preferably 85 to 99.9% by weight, more preferably 90 to 9% by weight of a nonionic monomer copolymerizable with the cationic monomer.
It is obtained by polymerizing 99% by weight (the total weight of the monomers is 100% by weight). The swellable polymer particles include the following monomers (a), (b),
It can swell to any of (c). And, in the presence of the cationic swellable polymer particles,
(A) 5-100% by weight, preferably 1%, of a crosslinkable monomer
0 to 80% by weight, more preferably 15 to 70% by weight,
(B) 0 to 15% by weight, preferably 0 to 10% by weight, more preferably 0.1 to 10% by weight of a cationic monomer, and (c) 0 to 95% of a copolymerizable non-crosslinkable and nonionic monomer. % By weight, preferably from 10 to 90% by weight, more preferably from 20 to 84.9% by weight (the total amount of monomers is 100% by weight). Therefore, the production method (III) uses the above-mentioned swellable polymer particles and the production method (I
It is almost the same as the production method (I) except that the amounts of the polymerization monomers (a), (b) and (c) used are slightly different from those in the case of I). What has been said in method (I) applies.

In preparing the cationic swellable polymer particles by polymerization, the method of preparing swellable polymer particles described in the production method (I) can be applied. The amount of the monomer (b) used for preparing the cationic swellable polymer particles is less than 0.01% by weight (the amount of the monomer (d) is 99.99).
In the case where the amount of the monomer (b) exceeds (by weight), the cationic hollow crosslinked polymer particles of the present invention obtained have a reduced cationicity, and the amount of the monomer (b) exceeds 30% by weight (excess of the monomer (d)). If the amount is too small (less than 70% by weight), the polymerization becomes unstable, which is not preferable.

The polymerization of the production method (III) is carried out according to the production method (I
As in the case of I), the polymerization monomer may be only (a) a crosslinking monomer, and (b) a cationic monomer and / or
Alternatively, (c) a copolymerizable non-crosslinkable and nonionic monomer may be used in combination. (A) when the amount of the crosslinkable monomer used is less than 5% by weight, and (b) when the amount of the cationic monomer used is more than 15% by weight,
(C) Undesirable phenomena that occur when the use amount of the copolymerizable non-crosslinkable and nonionic monomer exceeds 95% by weight are the same as those described in the production method (I). .

Such a production method (III) is preferably used when producing hollow crosslinked particles in which the amount of cationic groups and the small amount of aggregates are balanced.

<Production method (IV)>
(A) a method of preparing cationic hollow crosslinked polymer particles by preparing a swellable polymer particle by polymerization using a radical polymerization initiator having a cationic group and making the swellable polymer particle cationic, B) a method of polymerizing monomers (a), (b), and (c) using a radical polymerization initiator having a cationic group similarly to production method (II) to obtain cationic hollow crosslinked polymer particles; Alternatively, (c) using the above methods (a) and (b) together,
This is a method for obtaining cationic hollow crosslinked polymer particles. Especially, the method (c) is preferable.

The swellable polymer particles are prepared by using a radical polymerization initiator to form (b) a cationic monomer in an amount of 0 to 30% by weight, preferably 0 to 15% by weight, and more preferably 0.1 to 15% by weight.
1 to 10% by weight, and (d) 70 to 100% by weight of a nonionic monomer copolymerizable with the cationic monomer,
Preferably 85 to 100% by weight, more preferably 90%
-99.9% by weight (Total weight of monomer is 100% by weight
Is prepared by polymerizing The above (a)
In the methods (c) and (c), a radical initiator having a cationic group is used as the radical polymerization initiator, and the prepared swellable polymer particles are cationic. The swellable polymer particles comprise a monomer (a) used for polymerization,
Swellable in at least one of (b) and (c). Then, in the presence of the swellable polymer particles, as in the production method (III), (a) 5 to 100% by weight, preferably 10 to 80% by weight, more preferably 15 to 70% by weight of the crosslinkable monomer, ( b) 0 to 15% by weight of cationic monomer, preferably 0 to 10% by weight, more preferably 0.1 to 10% by weight, and (c) 0 to 95% by weight of copolymerizable non-crosslinkable and nonionic monomer %, Preferably 10 to 90% by weight, more preferably 2% by weight.
0 to 84.9% by weight (the total weight of the monomers is 100% by weight) is polymerized using a radical initiator to obtain hollow crosslinked particles. In the above methods (b) and (c),
A radical initiator having a cationic group is used as the radical polymerization initiator. Thus, the production method (IV)
A radical polymerization initiator having a cationic group may be used when preparing the swellable polymer particles, and a radical polymerization initiator having a cationic group may be used when polymerizing the monomers (a), (b) and (c). May be used, and a monomer (b) for obtaining swellable polymer particles
And (d), except that the use ratio is slightly different.
Almost the same as I). Thus, monomers (a),
As for the polymerization method, operation, conditions and the like of (b) and (c), those described in the production method (I) are applied.

When a radical polymerization initiator having a cationic group is used for preparing the swellable polymer particles, the amount of the radical polymerization initiator used is 0.1 to 10 parts by weight per 100 parts by weight of the total amount of the monomers (b) and (d). It is preferable to use one part by weight, more preferably 0.5 to 5 parts by weight. 0.1 used
If the amount is less than 10 parts by weight, the cationic property of the obtained hollow crosslinked particles is reduced. If the amount exceeds 10 parts by weight, the polymerization becomes unstable, which is not preferable. Monomers (a), (b),
When a radical polymerization initiator having a cationic group is used when polymerizing (c), it is preferably used in an amount of 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the total monomer. Department.

In preparing the above-mentioned swellable polymer particles by polymerization, a polymerization method (II
As in the case of I), the polymerization method for producing hollow crosslinked particles described in the production method (I) can be applied. In addition,
In preparation, a seed polymer may be used.

When the amount of the monomer (b) used to prepare the cationic swellable polymer particles is more than 30% by weight (the amount of the monomer (d) is less than 70% by weight), The polymerization becomes unstable, which is not preferable.

The polymerization of the production method (IV) is carried out by the production method (II)
As in the case of I), the polymerization monomer may be only (a) a crosslinking monomer, and (b) a cationic monomer and / or
Alternatively, (c) a copolymerizable non-crosslinkable and nonionic monomer may be used in combination. (A) when the amount of the crosslinkable monomer used is less than 5% by weight, and (b) when the amount of the cationic monomer used is more than 15% by weight,
(C) Undesirable phenomena that occur when the use amount of the copolymerizable non-crosslinkable and nonionic monomer exceeds 95% by weight is the same as described in the production method (I). In the polymerization, it is preferable to use a radical polymerization initiator having a cationic group as the polymerization initiator in view of adjusting the zeta potential and stabilizing the polymerization within the scope of the present invention. In this case, the amount of the radical polymerization initiator having a cationic group is as described above.

Such a production method (IV) is characterized in that hollow crosslinked particles having extremely few aggregates can be obtained. The cationic hollow crosslinked polymer particles have been described above.
Next, the filled paper of the present invention and subsequently the paper coating composition will be described.

[Filled Paper] The filled paper of the present invention mainly contains water-dispersible fibers and contains the above-mentioned cationic hollow crosslinked polymer particles as a filler. Cationic hollow cross-linked polymer particles,
It is usually 0.1% per 100% by weight of the total amount with the water-dispersible fiber.
It is used in a proportion of 1 to 50% by weight, preferably 0.5 to 10% by weight. The water-dispersible fiber only needs to have dispersibility in water, and those conventionally used, for example, unbleached kraft pulp, chemical pulp such as bleached kraft pulp, mechanical pulp, semi-chemical pulp, synthetic Pulp such as wood pulp and pulp obtained from recovered waste paper are preferably used. Further, together with these pulp, if desired, inorganic fibers such as glass fiber and rock wool, synthetic fibers such as polyester, nylon and polyacrylonitrile, ceramic fibers, wheat straw, cotton lint and the like can be used in combination.

The filled paper of the present invention contains these water-dispersible fibers in a proportion of usually 50 to 99% by weight, preferably 50 to 95% by weight, more preferably 70 to 95% by weight. The basis weight and thickness of the filled paper of the present invention are not particularly limited, but are usually in the range of ^{20 to} 500 g / m ² .

In the filled paper of the present invention, in addition to the water-dispersible fiber and the cationic hollow crosslinked polymer particles, a filler other than the hollow crosslinked particles can be used in combination, if desired. As a filler other than the hollow crosslinked particles, for example, titanium oxide, silica,
Examples include zinc oxide, barium sulfate, calcium carbonate, calcium oxide, aluminum silicate, diatomaceous earth, clay, magnesium hydroxide, and talc. Further, the filled paper of the present invention, latex, starch and other adhesives,
A coagulant and various additives used in a usual papermaking process can be appropriately added.

A typical example of the method for producing a filled paper of the present invention will be described below. First, after beating the water-dispersible fiber, dispersed in a predetermined amount of water, the cationic hollow cross-linked polymer particles,
A filler is prepared by adding fillers, additives, flocculants, adhesives, etc. other than the cationic hollow cross-linked polymer particles used as necessary to form a slurry, which is subjected to a paper machine known per se and dried to produce a filled paper. can do. After this, a calendar process or the like can be performed as needed. The pH of the papermaking slurry is preferably 9 or less, and a higher pH tends to lower the yield. When an inorganic filler such as talc or clay is used as the filler, the yield can be increased by using an adhesive together or by increasing the amount of the cationic hollow crosslinked polymer particles.

The filled paper of the present invention can be used as it is. It can also be used as base paper for coated paper. Next, the paper coating composition of the present invention will be described.

[Paper Coating Composition] The paper coating composition of the present invention comprises (A) a binder for binding the cationic hollow crosslinked polymer particles as a pigment component and (B) a pigment component. Contains ingredients. (B) Binder component (solid content)
Is preferably 1 to 100 parts by weight, more preferably 3 to 50 parts by weight, particularly preferably 5 to 30 parts by weight, based on 100 parts by weight of the cationic hollow crosslinked polymer particles (A). . If the blending ratio of the binder component (B) is less than 1 part by weight, the adhesive strength is remarkably reduced, and blanket stains during printing are likely to occur, which is not preferable. On the other hand, if it exceeds 100 parts by weight, blank paper gloss, whiteness,
Opacity decreases.

As the binder component (B) in the paper coating composition of the present invention, a conjugated diene, and a latex obtained by polymerizing other monomers as required, an acrylic polymer latex, a vinyl acetate polymer Combined latex, casein, modified casein, starch, modified starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, alkali thickening emulsion and the like can be used. These can be used in combination as needed.

The above-mentioned copolymer latex preferably includes (a) 5-90 (wt%) of a conjugated diene compound, (b) 0.01-50 (wt%) of a cationic monomer, and (c) other copolymers. The polymerizable monomer is a cationic copolymer latex of 0 to 94.9 (% by weight). Examples of the (a) conjugated diene-based compound include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene and the like, and preferably 1,3-butadiene. The (b) cationic monomer is as described above. Examples of the above (c) other copolymerizable monomers include aromatic vinyl compounds such as styrene and α-methylstyrene, and acryl groups such as ethyl acrylate, propyl acrylate, butyl acrylate and 2-ethylhexyl acrylate having 1 carbon atom. To 18 alkyl acrylates, such as alkyl methacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate.

In the paper coating composition of the present invention, examples of the pigment used together with the hollow crosslinked particles as needed include mineral pigments and organic pigments generally used for paper coating. . Typical examples thereof include inorganic pigments such as clay, barium sulfate, titanium oxide, calcium carbonate, and satin white; and organic pigments such as polystyrene latex and urea formalin resin.

The paper coating composition of the present invention may contain various compounding agents generally used in paper coating compositions, such as water resistance improvers, water resistance promoters, pigment dispersants, viscosity modifiers. , A color pigment, a fluorescent dye and a pH adjuster can be arbitrarily compounded. The paper coating composition of the present invention can also be used for various printings such as offset printing, letterpress printing, and gravure printing. The coated paper of the present invention uses a specific cationic hollow cross-linked polymer particle as a pigment, so that weight reduction can be achieved, and since it has excellent affinity with paper, it has high pick strength and high quality. Is obtained. Further, since the cationic hollow crosslinked polymer particles are excellent in heat resistance, they can cope with high temperatures in the drying step, so that high quality can be obtained and productivity is excellent.

[0068]

EXAMPLES The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited by the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

<Examples and Comparative Examples Related to Coated Paper Composition> [Hollow polymer particles (A-1) (cationic hollow crosslinked polymer particles)] (1) Preparation of seed particles A In an adjustable autoclave, 600 parts of water, 27% solution of dodecyltrimethylammonium chloride (Coatamine 24P, manufactured by Kao Corporation) 5
Part, 2,2'-azobis (2-methylpropionamidine) dihydrochloride (V-50, manufactured by Wako Pure Chemical Industries, Ltd.)
6 parts, styrene 75 parts, acrylonitrile 10 parts, 2
-Ethylhexyl acrylate 10 parts, dimethylaminopropylacrylamide methylene chloride quaternary salt (Co., Ltd.)
5 parts of DMAPAA-Q manufactured by Kojin Co., Ltd. and 15 parts of t-dodecyl mercaptan are charged all at once and reacted at 70 ° C. for 3 hours. After cooling, coarse aggregates are filtered and removed with a 300-mesh wire net to remove swellable polymer particles. Thus, an aqueous dispersion of the seed particles A was obtained.

(2) Preparation of Hollow Polymer Particles (A-1) (Cationically Hollow Crosslinked Polymer Particles) by Polymerization 430 parts of water 10 parts of seed particles A (solid content) 2,2′-azobis (2-methylpropion) Amidine) dihydrochloride (V-50, manufactured by Wako Pure Chemical Industries, Ltd.) 1 part 59 parts methyl methacrylate 12 parts styrene 28 parts Divinylbenzene 28 parts were charged all at once, reacted at 70 ° C. for 3 hours, cooled, and cooled.
The coarse aggregates were filtered and removed with a 300 mesh wire net to obtain an aqueous dispersion of cationic hollow crosslinked polymer particles. The cationic hollow crosslinked polymer particles are converted into hollow polymer particles (A-
1). About this hollow polymer particle (A-1), the zeta potential, the volume hollow ratio, and the average particle diameter were measured by the methods described above. As a zeta potential measuring device, BRO
Using "Zetaplus" manufactured by OKHAVENINSTRUMENTS, "JEM-100S" manufactured by JEOL Ltd. as a transmission electron microscope for measuring volumetric porosity.
"LPA-300" manufactured by Otsuka Electronics Co., Ltd. as a dynamic light scattering particle size analyzer for measuring the average particle size using "X".
0/3100 ".

(3) Measurement results of physical properties of hollow polymer particles (A-1) Zeta potential: +40 mV at pH 2 and +36 m at pH 6
V, +32 mV at pH 9 Volumetric hollow ratio: 30% Average particle diameter: 0.4 μm

[Hollow polymer particles (A-2) (anionic non-crosslinked hollow particles)] The polymer of the hollow polymer particles (A-2) is composed of 40% by weight of a styrene component, 50% by weight of a methyl methacrylate component, and a methacrylic acid component. Consists of 10% by weight. The physical properties of the particles are as follows. Zeta potential: -5 mV at pH 2, -20 mV at pH 6,
-30 mV at pH 9 Hollow polymer particles having a volume hollow ratio of 30% and an average particle size of 0.3 μm

[Binder Component: Copolymer Latex (B-1)] A first-stage component shown in Table 1 was charged into a pressure-resistant reaction vessel equipped with a stirrer and a temperature controller, and the inside of the polymerization system was replaced with nitrogen. After that, the temperature in the polymerization system was raised to 40 ° C., and polymerization was carried out for 2 hours. Then, the second stage component and 1/2 of the reducing agent aqueous solution shown in Table 2 were continuously polymerized over 5 hours. Added into the system. Then, in order to complete the polymerization,
The remaining 1/2 amount of the aqueous reducing agent solution was continuously added over a further 5 hours. The final polymerization conversion was 98%.
The obtained copolymer latex was adjusted to pH 7.
After adjusting to 5, steam was blown in to remove unreacted monomers, and the solid content concentration was 50% by heating steam distillation.
Was obtained as a copolymer latex (B-1). Table 2 shows the properties of the copolymer latex (B-1). (Measurement Method of Toluene-Insoluble Content of Copolymer Latex) A copolymer latex was adjusted to pH 8.0, coagulated with isopropanol, and the coagulated product was washed and dried, and a predetermined amount (about 0.03 g) of a sample was collected. It is immersed in a predetermined amount (100 ml) of toluene for 20 hours. Thereafter, the mixture is filtered through a 120-mesh wire gauze, and the weight% of the obtained residual solid content relative to the total solid content is determined.

[0074]

[Table 1]

[0075]

[Table 2]

Example 1, Comparative Example 1 (1) Preparation of Composition for Paper Coating Dissolve 0.05 part of dispersant in water, and stir with a Coreless disperser while stirring the amount of hollow polymer shown in Table 3. Particles (A-
1) (Example 1), (A-2) (Comparative Example 1), copolymer latex (B-1) and starch (Nippon Shokuhin Co., Ltd.)
MS-4600), and water was added so that the solid content was 62% to prepare a paper coating composition.

(2) Preparation of Coated Paper The above-prepared paper coating composition was coated on a commercially available high-quality paper (basis weight: 72 g / m ² ) with a coating amount of 3 g / m ² (one side) after drying. ) And dried in a gear oven at 150 ° C. for 5 seconds. The obtained single-side coated paper was passed twice through a Lab Super Calendar (Yuri Roll Co., Ltd.) at a roll surface temperature of 40 ° C. and a linear pressure of 10 N / m to obtain a glossy coated paper.

(3) Evaluation of Coated Paper The paper coating composition prepared above was evaluated by the following test methods, and the results are shown in Table 3. Dry pick strength The degree of picking when printed with an RI printing machine is visually judged and evaluated on a five-point scale. The lower the picking phenomenon, the higher the score. Numerical values are shown as an average value of six measurements. Wet pick strength Using a RI printing machine, the surface of the coated paper is moistened with a water-absorbing roll, and then the degree of picking when printing with the RI printing machine is visually judged and evaluated on a five-point scale. The lower the picking phenomenon, the higher the score. Numerical values are shown as an average value of six measurements. Blank glossiness Measure with a Murakami gloss meter (75 °). The larger the value, the better. Opacity is measured with a Hunter colorimeter. (Whiteness) Measured with a Hunter colorimeter. The larger the value, the better.

[0079]

[Table 3]

From the results shown in Table 3, it can be seen that the coated paper (Example 1) coated with the coating composition containing the cationic hollow crosslinked polymer particles of the present invention was anionic non-crosslinked hollow. It is clear that the dry pick strength, the wet pick strength, the white paper gloss, the opacity and the whiteness are superior to the coated paper coated with the coating composition containing the particles (Comparative Example 1).

<Examples and Comparative Examples Regarding Filled Paper> Example 2 [Preparation of Filled Paper] 100 parts of blended pulp for newspaper was diluted with warm water to obtain a 3% dispersion, and this dispersion was stirred for 4 hours.
It was kept at 0 ° C. Subsequently, 2 parts (solid content) of the hollow polymer particles (A-1) (cationic hollow cross-linked polymer particles) prepared above, 3 parts of a sulfuric acid band, 0.3 parts of an emulsion sizing agent, and 0 parts of an anionic paper strength agent .3 parts were added in this order and finally diluted with water to a pulp concentration of 1%. From this dispersion, paper was formed with a square sheet machine using an 80 mesh wire, and 3 kg at 10 kg / cm ² .
It was dried at 120 ° C. for 5 minutes with a press and a rotary drum dryer for 5 minutes. The obtained filled paper is dried at 20 ° C. and 65% humidity for 2 hours.
The temperature was adjusted for 4 hours and subjected to a paper quality test.

[Paper Quality Test] For the prepared filled paper, basis weight (JIS P8124) and whiteness (JIS P812)
3), opacity (JIS P8138), tensile strength (J
IS P8113). Table 4 shows the results.

Comparative Example 2 The procedure of Example 2 was repeated except that the hollow polymer particles (A-1) were not used. Table 4 shows the evaluation results.

Comparative Example 3 The procedure of Example 2 was repeated except that the hollow polymer particles (A-1) were replaced with white carbon. Table 4 shows the evaluation results.

Comparative Example 4 In Example 2, Example 1 of JP-A-3-74440 was used instead of the hollow polymer particles (A-1) (page 6, lower right column, line 6 to page 9, upper right column, two lines). Example 2 was carried out in the same manner as in Example 2, except that the cationic hollow polymer particles having a slightly crosslinked structure prepared by the method described in 1) were used. Table 4 shows the evaluation results.
It was shown to.

[0086]

[Table 4]

From the results shown in Table 4, the following is clear. The filled paper of Example 2 is lightweight, has excellent whiteness and opacity, and has high strength. On the other hand, Comparative Example 2 with no filler added
Is lightweight, but extremely inferior in whiteness and opacity. The filled paper of Comparative Example 3 using white carbon as a filler is extremely heavy and inferior in whiteness, opacity, and strength. The filled paper of Comparative Example 4 using hollow polymer particles having a low degree of crosslinking as a filler is inferior in whiteness and opacity.

[0088]

The filled paper of the present invention uses a specific cationic hollow crosslinked polymer particle as a filler, so that it is possible to achieve a reduction in weight, and since it is cationic, it has an affinity for the fibers of the filled paper. Excellent resistance, as a result, the yield of internal addition is improved, excellent in strength, heat resistance, chemical resistance, solvent resistance, etc.,
High quality. Further, since the paper coating composition and coated paper of the present invention use specific cationic hollow crosslinked polymer particles as a pigment, the weight of the coated paper can be reduced, and the affinity with paper can be improved. Because it is excellent, high quality coated paper with excellent pick strength can be obtained. In addition, since the cationic hollow crosslinked polymer particles have excellent heat resistance, they can cope with high temperatures in the drying step, so that high-quality coated paper can be obtained and productivity is excellent.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 101/12 C08L 101/12 C09D 7/12 C09D 7/12 A 201/00 201/00 201/00 D21H 17/38 D21H 17/38 19/42 19/42 F term (reference) 4J002 AB01W AB03Y AB04Y AC02Y AD02Y BC04X BE02Y BF02Y BG04X BG04Y 4J011 PA65 PA66 PA68 PA69 PA76 PB07 PC02 4J015 AA01 AA02 4J038 BA091 BA121 CB CB CB CG CB CB CB CG DB002 DD002 DE002 DG002 EA011 EA012 KA08 KA21 MA10 NA04 NA11 NA14 NA17 PC10 4L055 AG62 AG63 AG71 AG89 AG93 AG94 AH01 AH02 AH50 AJ04 BE08 EA35 FA12 GA15 GA19

Claims (5)

[Claims] (1) The zeta potential measured in an aqueous medium having a pH of 2 to 9 is in the range of +5 to +100 mV, and (II) 5 to 90% by weight of a structural unit derived from a crosslinking monomer and the crosslinking. Containing from 95 to 10% by weight of structural units derived from another monomer copolymerizable with the cationic monomer (the total amount of both is 100% by weight). Characterized filling paper. 2. The cationic hollow cross-linked polymer particles,
(1) Using a radical polymerization initiator, (a) 5 to 100% by weight of a crosslinkable monomer, and (b) cationic monomer 0 to 1
5% by weight, and (c) 0-95% by weight of the copolymerizable non-crosslinkable and nonionic monomers (total weight of the monomers is 100% by weight) swelling with respect to at least one of these monomers Produced by polymerizing in the presence of possible polymer particles, and (2) the polymer particles are prepared by using a radical polymerization initiator to form (b) 0 to 30% by weight of a cationic monomer and (d) )
Polymer particles obtained by polymerizing 70 to 100% by weight of a nonionic monomer copolymerizable with the cationic monomer (the total amount of the monomers is 100% by weight);
(3) The filled paper according to claim 1, wherein one or both of the radical polymerization initiators in the above (1) and (2) are a radical initiator having a cationic group. (A) (I) a zeta potential measured in an aqueous medium of pH 2 to 9 in the range of +5 to +100 mV, and (II) a structural unit 5 derived from a crosslinkable monomer.
Cationic hollow cross-linking weight consisting of about 90% by weight and 95-10% by weight of structural units derived from another monomer copolymerizable with the cross-linkable monomer (the total amount of both is 100% by weight). A paper coating composition comprising the coalesced particles and a binder component (B). 4. The cationic hollow cross-linked polymer particle,
(1) Using a radical polymerization initiator, (a) 5 to 100% by weight of a crosslinkable monomer, and (b) cationic monomer 0 to 1
5% by weight, and (c) 0-95% by weight of the copolymerizable non-crosslinkable and nonionic monomers (total weight of the monomers is 100% by weight) swelling with respect to at least one of these monomers Produced by polymerizing in the presence of possible polymer particles, and (2) the polymer particles are prepared by using a radical polymerization initiator to form (b) 0 to 30% by weight of a cationic monomer and (d) )
Polymer particles obtained by polymerizing 70 to 100% by weight of a nonionic monomer copolymerizable with the cationic monomer (the total amount of the monomers is 100% by weight);
4. The paper coating composition according to claim 3, wherein (3) one or both of the radical polymerization initiators in (1) and (2) are radical initiators having a cationic group. . 5. Coated paper obtained by applying the paper coating composition according to claim 3 or 4.