JP2002227092A - Multilayer coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer coated paper having a good dry pick strength and printed surface feeling when printed, and causing no roll stain in the production process. SOLUTION: This multilayer coated paper is such that the outermost coating layer is made by the use of a copolymer latex; wherein the copolymer is composed of two kinds of copolymer segments A and B, and the segment A consists of (a1) 25-100 wt.% of aliphatic conjugated diene-based monomer unit, (b1) 0-10 wt.% of ethylenically unsaturated carboxylic acid monomer unit and (c1) another vinyl-based monomer unit copolymerizable with the unit a1 and unit b1 and has a glass transition temperature of -100 to 20 deg.C, and the segment B consists of (a2) 10-60 wt.% of aliphatic conjugated diene-based monomer unit, (b1) 0.5-30 wt.% of ethylenically unsaturated carboxylic acid monomer unit and (c1) another vinyl-based monomer unit copolymerizable with the unit a2 and unit b2 and has a glass transition temperature of -20 to 70 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multilayer coated paper using a diene copolymer latex as a binder. More specifically, it is a coated paper for printing such as coated paper or coated paperboard which is provided for offset printing, gravure printing, and is composed of two or more coating layers. By using a copolymer latex composed of two different copolymer parts (A) and (B), the surface strength, blister resistance, print gloss, print surface feeling at the time of printing are improved, and coating is performed. The present invention relates to a multi-layer coated paper having a good blank surface feeling of paper.

[0002]

2. Description of the Related Art In recent years, printing speed has been increased along with an increase in demand for magazines, brochures, and advertisements printed in color, and the required level of coated paper has become increasingly sophisticated. For example, improvement of ink pick resistance, so-called dry pick strength, and ink pick resistance after a dampening solution is applied, so-called wet pick strength, are strongly required, and at the same time, glossiness of blank paper, blank paper feeling, Quality such as blister resistance, print surface appearance, print gloss, and ink setting property are required. These qualities often conflict with each other, for example, when the dry pick strength at the time of printing is improved, the blister resistance at the time of printing is reduced. Items often deteriorate.

[0003] Conventionally, two or more coating layers are provided on a base paper, and the function of each coating layer is controlled by controlling the design of a copolymer latex which is a binder used for each coating layer. A method has been adopted in which the composition is effectively used to improve the balance between these conflicting requirements. For example, Japanese Patent Publication No. Hei 7-13360 discloses that in a pigment-coated paper having two layers, a styrene-butadiene-acrylic copolymer having a gel content of 5 to 60% is used as an undercoat layer, thereby improving the blister resistance. There is a description that a coated paper for rotary offset printing having good suitability and excellent glossiness and printability is obtained. In this method, since the gel content of the copolymer used for the undercoat is 5 to 60%, the blister resistance and the glossiness of the white paper are certainly improved, but the dry pick strength and the wet pick strength are improved. Not enough. In addition, there is no effect of improving the feeling of blank paper and the feeling of printing.

On the other hand, as a copolymer latex used as a binder, a styrene-butadiene copolymer latex obtained by emulsion polymerization of styrene and butadiene as main monomer components, a so-called SB latex is used. It is used for general purposes. Various studies have been made on the design of SB-based latex itself used as a pigment binder in order to improve the balance between conflicting performance requirements for coated paper described above. For example, an improvement in latex using a method of polymerizing with a specific monomer composition in a two-stage or multi-stage polymerization method has been proposed in order to achieve a high balance of the various physical properties described above (Japanese Patent No. 1427990, JP-A-62-11).
No. 7897, JP-A-6-240559, JP-A-7-2
58308, JP-A-7-324112, JP-A-7-324
324113, JP-A-9-25308, JP-A-9-208
31141, JP-A-9-31895, JP-A-2000
-351803). However, in this technical field in recent years, achievement of a higher degree of balance of physical properties is required, and any of the methods such as dry pick strength, wet pick strength, print gloss, print surface feeling, blank surface feeling, etc. in coated paper. It was hardly enough to improve the physical properties of coated paper.

[0005]

The problem to be solved by the present invention is that the surface strength at the time of printing, that is, the dry pick strength and the wet pick strength are high and the blister resistance is low, based on the above technical background. An object of the present invention is to provide a coated paper which is excellent, has excellent printing gloss, excellent printing surface feeling, and excellent blank surface feeling.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the present invention has two or more coating layers. By using a copolymer latex consisting of (A) and (B) polymer parts having different (co) polymer parts, the surface strength at the time of printing, that is, the dry pick strength and wet pick strength are high, and the printing gloss and printing surface feeling are improved. It has been found that a coated paper which is excellent and has excellent backing roll stain resistance represented by stickiness of the surface layer of the coated paper when wet can be provided, and the present invention has been completed.

That is, a first aspect of the present invention is to provide a coated paper having at least two coating layers on a base paper, wherein (a) an aliphatic conjugated diene-based 20 to 80% by weight of monomer units, (b) 0.5 to 10% by weight of ethylenically unsaturated carboxylic acid monomer units, and (c) copolymerizable with monomer units (a) and (b) A copolymer latex comprising 10 to 79.5% by weight of another vinyl monomer unit, wherein the copolymer is composed of two kinds of copolymer parts (A)
And (B), wherein the copolymer part (A) is (A)
With the total amount of the monomer units constituting 100% by weight,
(A-1) Aliphatic conjugated diene monomer unit 25 to 100
% By weight, (b-1) 0 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer unit, (c-1) a monomer unit (a-1)
And from 0 to 75% by weight of other vinyl monomer units copolymerizable with (b-1) and having a glass transition temperature of -1.
It is in the range of 00 to 20 ° C, and the copolymer part (B) is
Assuming that the total amount of the monomer units constituting (B) is 100% by weight, (a-2) aliphatic conjugated diene monomer units 10 to 6
0% by weight, (b-2) 0.5 to 30% by weight of an ethylenically unsaturated carboxylic acid monomer unit, and (c-2) a monomer unit (a
-2) and 10-89.5% by weight of other vinyl monomer units copolymerizable with (b-2), and having a glass transition temperature in the range of -20 to 70 ° C. Is a multi-layer coated paper containing a copolymer latex.

That is, it is essential that the outermost coating layer of the multilayer coated paper contains a copolymer latex having a portion having a different composition within the same particle, that is, a so-called hetero-layered latex, Conventional multi-layer coated paper that does not use such a different layer structure latex has high surface strength during printing, that is, high dry pick strength and wet pick strength, good blister resistance, excellent print gloss, and excellent print surface feeling. However, it is not possible to provide a coated paper excellent in blank surface feeling, and if the coating layer using the above-mentioned different layered structure latex is simply coated on the base paper in a single layer, the high level of the present invention still remains. It is impossible to obtain a coated paper having a well-balanced performance.

A second aspect of the present invention is that, in the coating layer immediately below the outermost coating layer of the multilayer coated paper according to the first aspect, at least 30 parts by weight based on 100 parts by weight of the total pigment. It is characterized by containing calcium carbonate. With this design, the effects of the present invention, particularly the effects of improving the dry pick strength and the wet pick strength, and the printing surface feeling, are improved in each step. A third aspect of the present invention is that the particle size distribution (= volume average particle diameter / number average particle diameter) of the copolymer latex used in the multilayer coated paper is in the range of 1.05 to 1.8. It is characterized by. The larger this value is, the more the particle diameter is distributed, and the smaller this value is, the more uniform the monodisperse particle diameter is. In the case of perfect uniform monodispersion, the value of the particle size distribution is 1.0. In the outermost coating layer, this particle size distribution plays an important role. That is, when the particle size distribution is extremely small (when the particle size distribution is 1.05 or less), characteristics of a blank surface appearance and a print surface appearance are hardly obtained, while when the distribution is too wide, the strength of the coating layer is reduced. At the same time, the print gloss also deteriorates. this is,
In the outermost coating layer, when the paint is applied on the undercoat layer and dried, the copolymer latex as a binder has a certain relationship with the phenomenon of moving in the coating layer (binder migration). It is presumed.

A fourth aspect of the present invention is that the number average particle diameter of the copolymer latex used in the above-mentioned multilayer coated paper is 70-11.
It is characterized by being in the range of 0 nm. When the number average particle diameter is in this range, the effects of the present invention, particularly, the printing gloss, dry pick strength, and wet pick strength are remarkably improved. Conventionally, by setting the number average particle diameter of the copolymer latex to the level of 70 to 110 nm, it can be expected that print gloss, dry pick strength and wet pick strength are improved to some extent. Feeling worse. However, when the (1) outermost layer of the multilayer coated paper satisfies the three requirements of (2) using a latex having a different layer structure and (3) adjusting the number average particle diameter to 70 to 110 nm, an undercoat layer is formed. The balance between the print surface appearance, the blank surface appearance, the print glossiness, and the dry and wet pick strengths is particularly improved by the interaction with.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The copolymer latex used in the outermost coating layer of the present invention will be described in detail. Examples of the conjugated diene monomer units (a), (a-1) and (a-2) used in the present invention include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-
Ethyl-1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene, chloroprene, 2-
Chlor-1,3-butadiene, cyclopentadiene and the like can be mentioned, and 1,3-butadiene is preferable. These conjugated diene monomers are used alone or in combination of two or more.

The amount of the conjugated diene monomer unit (a) in the copolymer latex is preferably 20 to 80% by weight, more preferably 25 to 80% by weight, based on 100% by weight of the total amount of the monomers in the copolymer latex. It is in the range of 60% by weight. If the amount is less than 20% by weight, the obtained copolymer latex will have insufficient strength, and if it exceeds 80% by weight, the wet coated paper will have poor tackiness. The amount of the (a-1) conjugated diene-based monomer unit in the copolymer part (A) is 25% based on 100% by weight of all the monomer units in the copolymer part (A).
To 100% by weight, preferably 30 to 80% by weight. If the amount is less than 25% by weight, the obtained polymer is too brittle, and the object of the present invention cannot be sufficiently achieved. The amount of the (a-2) conjugated diene-based monomer unit in the copolymer part (B) is preferably 10 to 60% by weight, preferably 100% by weight, based on 100% by weight of all monomer units in the copolymer part (B). Is selected in the range of 20 to 50% by weight. If the amount is less than 10% by weight, the obtained polymer is too brittle, and the object of the present invention cannot be sufficiently achieved. If the amount is more than 60% by weight, the coated paper has poor wet tackiness, Roll stains occur during processing, and the wet strength of the coated paper decreases.

The ethylenically unsaturated carboxylic acid monomer units (b), (b-1) and (b-2) used in the copolymer latex used in the present invention include, for example, acrylic acid and methacrylic acid. , Itaconic acid, maleic acid,
Fumaric acid, crotonic acid and the like. These ethylenically unsaturated carboxylic acid monomers may be used alone or in combination of two or more.

The amount of the (b) ethylenically unsaturated carboxylic acid monomer unit in the copolymer latex is 0.5 to 0.5% based on 100% by weight of the total monomer in the copolymer latex.
It is in the range of 10% by weight, preferably 1 to 6% by weight. If the amount used is less than 0.5% by weight, the stability of the obtained copolymer latex is insufficient, and the printed surface feel is deteriorated due to streaks or the like during coating. If it exceeds 10% by weight,
The wet pick strength decreases. In the copolymer portion (A), the ethylenically unsaturated carboxylic acid monomer unit (b-
The amount of 1) is selected from the range of 0 to 10% by weight, preferably 0 to 2% by weight, based on 100% by weight of the total monomer units of the copolymer part A. If this amount exceeds 10% by weight, the viscosity of the latex or the coating liquid tends to be too high, and the wet pick strength tends to decrease, so that the object of the present invention cannot be sufficiently achieved. When the content is 2% by weight or less, the effect of the present invention, particularly, the effect of improving the tackiness of the coated paper when wet is greater. The amount of the ethylenically unsaturated carboxylic acid monomer unit (b-2) in the copolymer portion (B) is 0.5 to 0.5% based on 100% by weight of all the monomer units in the copolymer portion B.
It is selected from the range of 30 parts by weight, preferably 2 to 20% by weight. If this amount exceeds 30% by weight, the viscosity of the latex or the coating liquid tends to be too high and the wet pick strength tends to decrease, so that the object of the present invention cannot be sufficiently achieved. On the other hand, when the content is 0.5% by weight or less, the stability of the coating material is reduced, and as a result, streaks and roughening of the coated surface are generated at the time of coating, and the coated paper has a reduced blank surface appearance and printed surface appearance.

The conjugated diene monomer units (a) and (a-
1) and (a-2), other vinyl monomers (c) copolymerizable with the ethylenically unsaturated carboxylic acid monomer units (b), (b-1) and (b-2), (C-1) and (c-2) include a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, an alkyl (meth) acrylate monomer unit, and a (meth) acrylamide monomer unit. Monomer units, carboxylic acid vinyl esters such as vinyl acetate,
Examples thereof include vinyl halides such as vinyl chloride, amino group-containing ethylenic monomers such as aminoethyl acrylate and dimethylaminoethyl acrylate, and sodium styrene sulfonate. These copolymerizable monomers are used alone or in combination of two or more.

Examples of the vinyl cyanide-based monomer unit include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and the like, and acrylonitrile is particularly preferred. These vinyl cyanide monomers may be used alone or in combination of two or more.
The amount of the (c) other copolymerizable vinyl monomer in the copolymer latex is in the range of 10 to 79.5% by weight, preferably 34 to 74% by weight. If the amount is less than 10% by weight, the coated paper has poor tackiness when wet.
If it exceeds 79.5% by weight, the strength of the obtained copolymer latex is insufficient. In the copolymer part (A), the amount of (c-1) another copolymerizable vinyl monomer is as follows:
It is selected in the range of 0 to 75% by weight, preferably 18 to 70% by weight, based on 100% by weight of the total monomer units of the copolymer portion (A). In the copolymerized moiety (B), (c-
2) The amount of the other copolymerizable vinyl monomer is 10 to 8 with respect to 100% by weight of the total monomer units of the copolymer part (B).
It is selected in the range of 9.5% by weight, preferably 30 to 78% by weight.

The amount of the vinyl cyanide-based monomer unit contained in the copolymer latex is from 5 to 60% based on 100% by weight of the total amount of the monomer units used in the copolymer latex.
% By weight, more preferably 15 to 50% by weight.
It is. The amount of the vinyl cyanide monomer unit contained in the (co) polymer portion (A) is from 0 to 60% by weight based on 100% by weight of the total monomer units contained in the copolymer portion (A). %, More preferably 5 to 50% by weight. (Both)
The amount of the vinyl cyanide monomer unit contained in the polymer part (B) is preferably from 5 to 65% by weight, based on the total amount of the monomer units contained in the copolymer part (B) being 100% by weight. ,
10 to 55% by weight is more preferred.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, vinylxylene, bromostyrene, vinylbenzyl Chloride, pt-butylstyrene, chlorostyrene, alkylstyrene, divinylbenzene, trivinylbenzene and the like can be mentioned, but styrene is particularly preferred. Examples of the alkyl (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, and isobutyl (meth) acrylate. (Meth) acrylate, n-amyl (meth) acrylate, isoamylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (Meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-ethyl-hexyl (meth) acrylate, 2-hydroxyethyl (meth)
Acrylate, glycidyl (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 5-pentanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, diethylene glycol ethoxy acrylate, triethylene glycol di (meth) acrylate , Tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate,
Polypropylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, allyl (meth) acrylate, bis (4-acryloxypolyethoxyphenyl) Propane, methoxypolyethylene glycol (meth) acrylate, stearyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, 2,2-bis [4-((meth) acryloxyethoxy) phenyl] propane 2,2-bis [4-((meth) acryloxydiethoxy) phenyl] propane,
Examples thereof include 2,2-bis [4-((meth) acryloxypolyethoxy) phenyl] propane and isobornyl (meth) acrylate.

Examples of the (meth) acrylamide-based monomer include N-monoalkyl (meth) acrylamide such as (meth) acrylamide, N-methylol (meth) acrylamide, and N-methyl (meth) acrylamide; N, N-dialkyl (meth) acrylamide such as dimethyl (meth) acrylamide, glycidyl methacrylamide, N-alkoxy (meth) acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and the like are preferable. It is at most 10% by weight, more preferably at most 7% by weight, based on 100% by weight of all monomer units contained in the polymer latex. If it is used in an amount exceeding 10% by weight, the low shear viscosity of the latex and the paper coating composition is increased, thereby deteriorating the surface condition of the coated paper and causing a reduction in the printed surface feeling.

The weight ratio of the copolymer part (A) in the copolymer latex used in the present invention is preferably 20 to 80 parts by weight, and more preferably 30 to 70 parts by weight, based on 100 parts by weight of the whole copolymer latex. Is more preferred. If the amount of (A) is not within this range, the effect of the present invention will be insufficient. In the present invention, the glass transition temperature of the copolymer part (A) is-
It is in the range of 100 to 20 ° C, preferably -70 to 1
It is 0 degreeC, More preferably, it is -60-0 degreeC. When the glass transition temperature of the copolymer part (A) is lower than -100 ° C,
If the wet strength of the coated paper decreases, and if it is higher than 20 ° C., the dry strength decreases, and the object of the present invention cannot be achieved.

The glass transition temperature of the copolymer (B) in the present invention is in the range of -20 to 70, preferably -10 to 60 ° C, more preferably 0 to 50 ° C.
When the glass transition temperature of the copolymer part (B) is lower than -20 ° C, the wet strength decreases, and when the glass transition temperature is higher than 70 ° C,
The dry strength is reduced, and the object of the present invention cannot be achieved.
The weight average molecular weight of the copolymer part (A) is preferably 100,000 or more, more preferably 150,000 or more.

In producing the copolymer latex used in the present invention, any of a multi-stage polymerization method of two or more stages and a power feed method of continuously changing the composition may be used. Emulsion polymerization is preferably carried out using a multi-stage polymerization method having at least two stages. Preferably, the copolymer part (A) is polymerized in the first step and the copolymer part (B) is polymerized in the final step. At this time, the polymerization conversion of the monomer mixture in the first step is Immediately before the monomer mixture is added, the content is preferably 30 to 90% by weight. In this case, if the polymerization conversion in the first step is less than 30% by weight, the wet stickiness and wet pick strength are not particularly sufficient, and if it exceeds 90% by weight, the dry pick strength is not sufficient, and the object of the present invention is not achieved. It cannot be achieved enough. On the other hand, in the second step, the polymerization conversion of the total monomer mixture in the system at the time when the total amount of the monomer mixture used is added is preferably 60 to 95% by weight, and 65 to 9% by weight.
0% by weight is most preferred. If it is less than 60% by weight, the coated paper will not be sufficiently sticky when wet. If it exceeds 90% by weight, the dry pick strength and the wet pick strength decrease.

The polymerization temperature at the time of producing the copolymer latex is preferably 75 ° C. or lower until the polymerization conversion with respect to all the monomers reaches 80%. If the polymerization temperature is increased above 75 ° C. before the polymerization conversion reaches 80%, the dry pick strength or wet pick strength decreases, which is not desirable. The polymerization time is usually 3 to 30 hours. As a method of adding the monomer composition, in each polymerization step, a batch addition method of the monomer composition, intermittently or continuously added according to the progress of polymerization after adding a part of the monomer composition Any of a method, a method of continuously adding the monomer composition, and the like may be used. In addition, there is no particular limitation on the addition rate when the monomer composition is continuously added.

In the method for producing a diene copolymer latex of the present invention, a known chain transfer agent used in general emulsion polymerization can be used. For example, dimers of nuclear-substituted α-methylstyrene such as α-methylstyrene dimer, mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, Disulfides such as tetramethylthiuram disulfide and tetraethylthiuram disulfide; halogenated derivatives such as carbon tetrachloride and carbon tetrabromide; 2-ethylhexylthioglycolate; terpinolene; and the like, and one or more of these may be used. Is done. As the chain transfer agent, in particular, α-methylstyrene dimer, t
-Dodecyl mercaptan and terpinolene are preferred.
The chain transfer agent is preferably used in the range of 0.1 to 10 parts by weight per 100 parts by weight of the monomer. Outside of this range, the balance between pick strength, wet pick strength, and blister resistance is reduced, making it difficult to achieve the effects of the present invention. α-Methylstyrene dimer has 2,4-diphenyl-4-methyl-1-pentene as an isomer,
There are 2,4-diphenyl-4-methyl-2-pentene and 1,1,3-trimethyl-3-phenylindane, and the α-methylstyrene dimer used in the present invention includes 2,4-diphenyl- The proportion of 4-methyl-1-pentene is preferably at least 60% by weight, particularly preferably the proportion of 2,4-diphenyl-4-methyl-1-pentene is at least 80% by weight.

As the surfactant, a known surfactant used in general emulsion polymerization can be used. For example, aliphatic soap, rosin acid soap, alkyl sulfonate, dialkylaryl sulfonate,
Anionic surfactants such as alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl aryl sulfates, and nonions such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, and polyoxyethylene oxypropylene block copolymers Amphoteric surfactants such as amphoteric surfactants, reactive surfactants having an unsaturated bond such as sodium styrenesulfonate, and, if necessary, betaine type and the like. One or more of these may be used. used. This surfactant is usually used in an anionic surfactant alone, a reactive surfactant alone, or a mixed system of anionic / reactive or anionic / nonionic, and the amount used is based on the weight of all monomers. On the other hand, it is usually selected in the range of 0.05 to 2% by weight.

In the present invention, a radical polymerization initiator generally used for emulsion polymerization can be used. These radical polymerization initiators radically decompose in the presence of heat or a reducing substance to initiate addition polymerization of monomers, and any of an inorganic initiator and an organic initiator can be used. Such compounds include, for example, water-soluble or oil-soluble persulfates, peroxides, azobis compounds and the like, specifically, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide Benzoyl peroxide, 2,2-azobisbutyronitrile, cumene hydroperoxide, etc., and POLYMER HANDBOOK (3rd ed
ition), J. et al. Brandrup and E.C. H. I
Merrygut, John Willy & Son
s (1989). Also, a so-called redox polymerization method in which a reducing agent such as sodium acid sulfite, ascorbic acid or a salt thereof, erythorbic acid or a salt thereof, or Rongalit is used in combination with a polymerization initiator can be employed. In the first step, it is particularly preferable to use an inorganic radical polymerization initiator, and it is more preferable to use an inorganic radical polymerization initiator in all steps of the polymerization. Of these, persulfates are particularly preferred as polymerization initiators. The amount of the polymerization initiator used is usually 0.1 to
It is selected from the range of 5.0% by weight, preferably from the range of 0.2 to 3.0% by weight.

In the present invention, various polymerization regulators can be added as required. For example, as a pH adjuster, a pH adjuster such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogen carbonate, sodium carbonate, disodium hydrogen phosphate, etc. can be added. It is particularly preferable in terms of enhancing the balance between strength and wet pick strength, and is suitable as a pH adjuster after polymerization. Also, various chelating agents such as sodium ethylenediaminetetraacetate, inorganic electrolytes, organic electrolytes, and polymer electrolytes such as sodium polyacrylate and ammonium polyacrylate can be added as polymerization stabilizers and viscosity polymerization regulators. Also,
If necessary, an alkali-sensitive latex may be added to the copolymer latex of the present invention.

Examples of the coating pigment used in the present invention include inorganic pigments such as kaolin clay, calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, talc, silica, zinc oxide, activated clay, acid clay, diatomaceous earth, and plastics. And organic pigments known as pigments and binder pigments. In each coating layer, in addition to the copolymer latex of the present invention, starch, casein, polyvinyl alcohol, water-soluble polymer binders such as carboxymethyl cellulose, thickeners, dyes, defoamers, preservatives, waterproofing agents Various additives such as a lubricant, a printability improver, and a water retention agent can be added.

The coating layer of the present invention is a multilayer coating layer of two or more layers, and any of the above-mentioned pigments can be optionally used in any of the coating layers. Of these pigments, in the coating layer that is the outermost layer, it is preferable to use kaolin clay in an amount of 30 parts by weight or more, based on 100 parts by weight of the total amount of the pigment in the coating constituting the coating layer, and 50 parts by weight. It is more preferable to use the above, and most preferably 70 parts by weight or more. On the other hand, in the coating layer of the innermost layer of the outermost coating layer, calcium carbonate is preferably used in an amount of 30 parts by weight or more, more preferably 50 parts by weight or more, based on 100 parts by weight of the total pigment. It is more preferred to use at least part by weight. In the coating layers other than the outermost coating layer, the binder to be used can be arbitrarily selected from the above polymer binders, but starch is preferably used. At that time, it is preferable to use 2 parts by weight or more of starch with respect to 100 parts by weight of the total amount of pigment in each layer. Further, the effect of the present invention can be further enhanced by using the copolymer latex used in the outermost coating layer of the present invention other than the outermost coating layer.

The proportion of the pigment and the copolymer latex of the present invention can be appropriately determined depending on the purpose. Preferably, the proportion of the copolymer to 100 parts by weight of the total pigment used in the outermost coating layer is used. Latex is 3 to 30 parts by weight. The multilayer coating of the present invention can be applied to base paper by a usual method using various blade coaters, roll coaters, air knife coaters, bar coaters and the like. The coated paper thus coated is a super calendar,
Processing can be performed by a finishing step such as a high-temperature soft nip calender, and any other general processing means can be applied.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by these examples. In addition, each characteristic was calculated | required as follows. (A) Dry pick strength Using a RI printing tester (Meiji Seisakusho), a base paper (30 cm) with coated paper (1.5 cm × 20 cm) stuck on the center part
cm × 25.5 cm), printing ink (manufactured by
Product Name: SD Super Deluxe 50 Beni B (Tack 18
0.5 cc) was printed on a mount with a print area of 25 cm × 21 cm, and overprinted on coated paper. The picking state that appeared on the rubber roll was backed by another mount, and the state was observed. The evaluation was performed by a five-point evaluation method, and the smaller the picking phenomenon, the higher the score.

(B) Wet pick strength Using a RI printing tester (Meiji Seisakusho), a base paper (30 c
mx 25.5 cm) with a Molton roll to supply water to the surface of the coated paper. Immediately afterwards, 0.5 cc of printing ink (trade name: SD Super Deluxe 50 red B (product of Tack 15), manufactured by Toka Pigment Co., Ltd.) is 25 cm. Printing was performed once with a printing area of × 21 cm, and the picking condition that appeared on the rubber roll was backed up on another backing paper, and the condition was observed, and the condition was evaluated by a five-point evaluation method. And

(C) Gloss of printing A backing sheet (30 cm) coated with coated paper (1.5 cm × 20 cm) at the center using an RI printing tester (Meiji Seisakusho).
cm × 25.5 cm) and 0.6 cc of printing ink (manufactured by Dainippon Ink Inc., trade name: Geos G Sumi) in 25 cm × 2 cm.
One print was performed with a 1 cm print area. After standing at 23 ° C. and a humidity of 50% for 24 hours, the print gloss value was measured at 60 ° C. using a gloss meter. A score of 60 or more was considered acceptable. (D) Printing surface feeling Using a RI printing test machine (Meiji Seisakusho), a printing ink (manufactured by Dainippon Ink, Inc., trade name: Geos) was applied to a backing paper (30 cm x 25.5 cm) with coated paper in the center. G Sumi) 0.6
The cc was printed once with a printing area of 25 cm × 21 cm. After standing at 23 ° C and 50% humidity for 24 hours, 6
The printed surface feeling was evaluated by visual observation of white light from an angle of 0 °. In a five-point evaluation, the higher the score, the better.

(E) Blank paper surface The coated paper is cut out to the size of the A4 size plate, white light is irradiated from an angle of 60 ° in front, and the blank paper surface feeling is determined by visual evaluation.
The higher the score in the five-level evaluation, the better the evaluation. (F) Measurement of particle size and particle size distribution The particle size of the copolymer latex was measured by a conventional method for 500 particles from a transmission electron micrograph of an osmate-stained copolymer latex sample, and the number average was measured. The average value of the particle diameter and the volume average particle diameter was determined.

(G) Measurement of glass transition temperature The copolymer latex was cast on a glass plate at a thickness of 0.3 mm, and was dried in an oven at 80 ° C. for 24 hours under vacuum to completely remove water, thereby forming a film. After the film was formed, the glass transition temperature of the film was measured using a differential scanning calorimeter (DSC; manufactured by Seiko Instruments Inc.). The measurement was performed under the conditions of a sample amount of 10 mg and a heating rate of 20 ° C./min. (H) Measurement method of polymerization conversion rate 2 g of the latex sampled during the polymerization was weighed, 500 ppm of a polymerization inhibitor was added, and then dried at 130 ° C. for 30 minutes to remove water and unreacted monomers. The remaining solid content (portion converted into a copolymer) was weighed, and the polymerization conversion was determined from the total amount of monomer units added to the reactor.

[0036]

Examples 1 to 8 (Copolymer latex (L-1))
(Production of (L-6)) 0.5 part by weight of sodium dodecylbenzenesulfonate and 200 parts by weight of ion-exchanged water were placed in a pressure-resistant reaction vessel equipped with a stirrer and a jacket for temperature control. Of the first step, a first step chain transfer agent and 1 part of sodium persulfate were added, and the reaction was allowed to proceed at a stirring rotation speed of 150 rpm. Six hours after the start of the initiator addition, the second step monomer and chain transfer agent in Table 1 were added to 60
C. was added over 7 hours. The rotation speed of the stirring in the second step was 200 rpm. After the completion of the second step monomer addition, the internal temperature was raised to 65 ° C. and the reaction was carried out for 6 hours. The final polymerization conversion was 98%. The produced latex was filtered through a 200 mesh wire mesh. Next, potassium hydroxide is added and p
After adjusting to H8, unreacted monomers were removed, and after further concentration,
0.5 parts by weight of sodium polyacrylate and potassium hydroxide were added, and the copolymer latex was finally adjusted to a solid concentration of 50% and pH 8. Table 1 shows the particle size, glass transition temperature, and the like of the obtained copolymer latex.

(Copolymer latex for undercoating (L-7)
Production) 0.3 parts by weight of seed latex, 0.5 parts by weight of sodium dodecylbenzenesulfonate, and 90 parts by weight of ion-exchanged water were placed in a pressure-resistant reaction vessel equipped with a stirrer and a temperature control jacket. , Butadiene 4
0 parts by weight, 50 parts by weight of styrene, acrylonitrile 10
Parts by weight, 0.8 parts by weight of α-methylstyrene dimer, t-
A mixture of 0.5 parts by weight of dodecyl mercaptan, and
After an aqueous solution in which 1.0 part by weight of potassium persulfate was dissolved in 5 parts by weight of ion-exchanged water was added over 5 hours, the temperature inside the system was raised to 100 ° C., and the reaction was carried out for 1 hour. The final polymerization conversion was 99%. The produced latex was filtered through a 200 mesh wire mesh. Next, add potassium hydroxide,
After adjusting to pH 8, unreacted monomers were removed, and 0.5 parts by weight of sodium polyacrylate and potassium hydroxide were added to adjust the solid content concentration to 50% and pH 8. The number average particle diameter of the obtained latex is 170 nm, and the glass transition temperature is
2 ° C.

[0038]

[Table 1]

(Production of multilayer coated paper) To a homomixer, 0.1 part by weight of sodium polyacrylate, 0.1 part by weight of sodium hydroxide and an appropriate amount of water were added, and pigments (clay and calcium carbonate) shown in Table 2 were added. ) Was added and stirred to prepare a pigment slurry having a solid content of 75% by weight. After adding the binder components (starch and copolymer latex) shown in Table 2 to the slurry, the solid content was adjusted to 65% by weight to obtain a coating liquid for overcoating and undercoating. Subsequently, the coating liquids for overcoating and undercoating shown in Table 2 were double-coated in the order of undercoating and overcoating using a sheet-fed blade coater. The coating speed was 50 m / min, the drying temperature was 130 ° C., and the drying time was 3 seconds. The undercoat amount was adjusted to 12 g / m ³ , and the overcoat amount was adjusted to 11 g / m ³ . After coating, constant temperature and humidity chamber (2
(3 ° C., humidity 50%) overnight, and the paper was passed twice with a calender roll under the condition of a roll temperature of 50 ° C. and a linear pressure of 147000 N / m to obtain a multilayer coated paper. Table 2 shows the results of the evaluation performed using this multilayer coated paper.
It was shown to.

[0040]

[Table 2]

[0041]

Comparative Examples 1 to 12 (Copolymer latex (L-8))
(Production of (L-11)) The copolymer latex (L) used in Examples was used except that the monomers and chain transfer agents shown in Table 3 were used.
-1), a copolymer latex (L-
8) to (L-11) were obtained. (L-8) and (L-
9) is a latex having a uniform composition in which only the copolymer portions (A) and (B) in the copolymer latex are polymerized in the same procedure as in the examples.

(Copolymer latex (L-12) to (L
-14) Production) The copolymer latex used in the Examples, except that the monomers and chain transfer agents shown in Table 3 were used, and the stirring speed in the first step was changed as shown in Table 3. Copolymer latexes (L-12) to (L-14) were obtained in the same manner as (L-1). (Production of Copolymer Latex (L-15)) Using the monomers and chain transfer agent shown in Table 3, the stirring speed and the amount of ion-exchanged water added initially were changed as shown in Table 3. Except for the above, a copolymer latex (L-15) was obtained in the same manner as in the copolymer latex (L-1) used in the examples.

[0043]

[Table 3]

(Production of Multi-Layer and Single-Layer Coated Paper) Multi-layer and single-layer coated papers were obtained in the same manner as in the Examples except that the pigments and binder components shown in Table 4 were used. Table 4 shows the results of evaluations performed using the multi-layer and single-layer coated papers.

[0045]

[Table 4]

[0046]

The multilayer coated paper of the present invention has a high dry pick strength and a high wet pick strength at the time of printing in offset printing, a high print gloss, and a good print surface feeling.
In addition, no roll contamination occurs during production of coated paper.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D21H 19/82 D21H 19/82 // (C08F 236/04 (C08F 236/04 220: 04) 220: 04 ) (C08F 236/04 (C08F 236/04 222: 02) 222: 02) F term (reference) 4J038 CQ001 CQ011 GA06 HA286 KA08 MA10 MA13 MA14 NA01 NA11 PC10 4J100 AB02R AB03R AB04R AB07R AB08R AB09R AB16R AC03R AG04AJQ A01 AL03R AL04R AL05R AL08R AL09R AL10R AL62R AL66R AL67R AL75R AM02R AM03R AM14R AM15R AM17R AM19R AM21R AR17P AS01P AS02P AS03P AS04P AS06P AS07P BA02R FA03R BA03R BA03R BC03R0130 AG47 AG63 AG70 AG71 AG74 AG76 AG89 AG94 AG97 AH02 AH37 AJ01 AJ04 BE07 BE09 EA16 EA20 EA32 FA12 FA13 FA15 FA19 GA19

Claims (4)

[Claims] In a coated paper having at least two coating layers on a base paper, (a) an aliphatic conjugated diene monomer unit of 20 to 80 is contained in the outermost coating layer. % By weight, (b) 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer unit, and (c) another vinyl monomer copolymerizable with the monomer units (a) and (b). Unit 10-7
9.5% by weight of a copolymer latex, wherein the copolymer comprises two types of copolymer parts (A) and (B), wherein the copolymer part (A) constitutes (A) (A-1) 25 to 100% by weight of an aliphatic conjugated diene-based monomer unit, and (b-1) ethylenically unsaturated carboxylic acid monomer unit of 0 to 100% by weight, 10% by weight,
(C-1) Other vinyl monomer units copolymerizable with the monomer units (a-1) and (b-1) are composed of 0 to 75% by weight, and have a glass transition temperature of -100 to 20. ° C, and the copolymer part (B) is (a-2) an aliphatic conjugated diene-based monomer unit of 10 to 60, with the total amount of the monomer units constituting (B) being 100% by weight. % By weight, (b-2) 0.5 to 30% by weight of an ethylenically unsaturated carboxylic acid monomer unit, and (c-2) a monomer unit (a-2) and (b-
Other vinyl monomer units 10 to 8 copolymerizable with 2)
Consisting of 9.5% by weight and having a glass transition temperature of -20 to 20%.
A multilayer coated paper containing a copolymer latex, which is in the range of 70 ° C. 2. The coating layer according to claim 1, wherein the innermost coating layer of the outermost coating layer contains at least 30 parts by weight of calcium carbonate with respect to 100 parts by weight of the total amount of the pigment. Multi-layer coated paper. 3. The multilayer coated paper according to claim 1, wherein the particle size distribution (= volume average particle size / number average particle size) of the copolymer latex is in the range of 1.05 to 1.8. . 4. The copolymer latex having a number average particle diameter of 7
The multilayer coated paper according to claim 1, 2 or 3, which has a thickness of 0 to 110 nm.