JP2001140197A - Coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coated paper capable of preventing a calender roll stain being a defect of a conventional paper coating solution. SOLUTION: This coated paper having calender roll adhesion preventing ability has a coating film formed from a paper coating solution with >=3 mPa.s aqueous-phase viscosity on base paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a novel coated paper, and more particularly, to a method for preventing a binder component in a coating film from adhering to and contaminating a backing roll, a calender roll and a raster press during a calendering process. The present invention relates to a novel coated paper having a function to prevent such a problem.

[0002]

2. Description of the Related Art Generally, printing paper is provided with a coating layer of a coating liquid on the surface thereof in order to improve smoothness, glossiness and printability. This coating liquid is usually a slurry in which a white pigment such as clay or heavy calcium carbonate and latex or starch are dispersed in water as a binder. After dilution, the coating liquid is supplied from the adjustment tank to continuously apply the coating liquid to the running paper, and the excess is removed by a coating head such as a blade to obtain a required film thickness. .
The coating liquid removed from the paper is returned to the adjustment tank, mixed with a new coating liquid, and reused.

[0003] After the coating liquid is applied to the surface of the paper base material as described above, it is subjected to a calendering treatment to impart gloss. In order to obtain such a coated paper, various coating liquids such as a delaminated clay and a coating liquid containing talc and a soft styrene / butadiene copolymer as an adhesive (Japanese Patent Application Laid-Open No. JP-A-224895) and a coating liquid containing calcium carbonate (JP-A-2-139500) for improving the ink fixing property. However, when a coated paper is manufactured using these coating liquids, a binder component or the like adheres to a calender roll at the time of calendering treatment, which often causes contamination of the product and a reduction in productivity.

In order to prevent such calender roll contamination, a copolymer latex having a glass transition temperature of -20 to 20 ° C. is used as a solid component based on 100 parts by weight of the pigment.
Coating liquid containing 3 to 10 parts by weight (JP-A-9-2963)
No. 94) or a paper coating adhesive obtained by mixing an aqueous dispersion containing dispersed particles and a urethane prepolymer (JP-A-8-170).
No. 299), in a gravure printing coated paper provided with at least two coating layers on at least one surface of a base paper, an undercoat layer composition having a positive zeta potential is applied as an undercoat layer adjacent to the uppermost layer. The uppermost layer contains a pigment and an adhesive as main components, and the adhesive has at least 80% by weight.
Coating paper for gravure printing (Japanese Patent Laid-Open No. 5-59695) for coating an overcoat layer composition containing a carboxylated modified copolymer emulsion having the above gel content and a glass transition temperature of -30 ° C or lower. However, depending on the type of binder, it is necessary to reconsider the composition of the coating solution and the production conditions, and in addition, it is not possible to obtain a product comparable in quality to the conventional one. There are drawbacks, and the drawback is that production efficiency must be reduced because the number of coating layers must be two.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a coated paper capable of preventing a stain on a calender roll, which is a drawback of a conventional paper coating liquid.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on coated papers capable of preventing stains on calender rolls, and as a result, have adjusted the aqueous phase viscosity of the paper coating liquid to a specific range. As a result, the present inventors have found that it is possible to prevent stains on a calender roll of coated paper obtained using the same, and have completed the present invention based on this finding.

That is, according to the present invention, the aqueous phase viscosity is 3 mPa
-Containing s or more paper coating solutions, especially pigments and binders,
A coated paper having a calender roll adhesion preventing property, characterized by having a coating film formed from a paper coating liquid whose aqueous phase viscosity is adjusted to 3 mPa · s or more by a coatability modifier on a base paper. Is provided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The coated paper of the present invention has an aqueous phase viscosity of 3
It is necessary to have a coating film formed from a paper coating liquid of mPa · s or more. The basic composition of the paper coating liquid is not particularly different from that of the conventional paper coating liquid, and the same pigment and binder can be used. That is, the pigment is not particularly limited, and pigments conventionally used in paper coating liquids can be used. Examples of such a material include clay, calcium carbonate, kaolin, talc, titanium oxide, silica, zinc oxide, aluminum hydroxide, clay, lake, and synthetic plastic pigment. These may be used alone or in combination of two or more. The compounding amount is usually selected in the range of 40 to 70% by weight based on the total amount of the coating liquid.

Next, the binder used in the paper coating liquid is not particularly limited, and a latex or solution of a synthetic or natural polymer substance conventionally used in paper coating liquids can be used. Examples of such synthetic or natural polymer substances include styrene-butadiene copolymers,
Styrene-acrylic copolymer, vinyl acetate-acrylic copolymer, ethylene-vinyl acetate-based copolymer, butadiene-methyl methacrylate-based copolymer, vinyl acetate-butyl acrylate-based copolymer, styrene-anhydride Maleic acid-based copolymers, acrylic acid-methyl methacrylate-based copolymers, oxidized starch, esterified starch, etherified starch, enzyme-modified starch, casein, soy protein, and the like are included. These may be used alone or in combination of two or more. The compounding amount is usually selected in the range of 3 to 30 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of the pigment.

The paper coating liquid may contain a dispersing agent, a thickening agent, a defoaming agent, a water-proofing agent, a coloring agent, and the like, if necessary, as long as the object of the present invention is not impaired. . Examples of the dispersant include sodium polyacrylate, sodium hexametaphosphate, sodium pyrophosphate, and a sodium salt of an acrylic acid-maleic acid copolymer.

In the present invention, it is necessary to use a paper coating liquid whose aqueous phase viscosity has been adjusted to 3 mPa · s or more with a coatability modifier for the above basic composition. As the coating property improving agent, any one can be used. In particular, (A) alkyl acrylate and (B)
It is preferable to use a copolymer with methacrylic acid in which the alkyl group in component (A) has 1 to 8 carbon atoms. The alkyl group may be linear or branched. Examples of such an alkyl acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, 2-methylbutyl acrylate, and tert-butyl acrylate. , Acrylic acid 2-
Ethylhexyl, octyl acrylate, hexyl acrylate, 2-hydroxyhexyl acrylate and the like can be mentioned, but those having 1 to 4 carbon atoms are particularly preferable, and especially ethyl acrylate is the aqueous phase viscosity of the coating liquid. Is effectively increased.

When a component containing an alkyl group having 9 or more carbon atoms is used as the component (A), the viscosity of the coating liquid increases, but
The aqueous phase viscosity of the coating liquid cannot be increased, which is not preferable. This coating property modifier comprises the component (A),
(B) component, as component (C) methyl methacrylate,
It may contain an alkyl methacrylate such as ethyl methacrylate, propyl methacrylate, and octyl methacrylate. In this case, an ethyl acrylate-methyl methacrylate-methacrylic acid copolymer is particularly preferable because it effectively increases the aqueous phase viscosity in a coating solution of an offset formulation or a gravure formulation for an on-machine coater.

The content ratio of the component (A) to the component (B) is preferably in a molar ratio of 40:60 to 95: 5. If the molar ratio deviates from this range, for example,
When the component (A) is excessive, the hydrophobicity of the polymer substance becomes too high, and the interaction with water is so small that a sufficient aqueous phase viscosity cannot be obtained. When the component (B) is excessive, the aqueous phase viscosity increases. Increases, but also causes the coating liquid itself to become elastic, which causes a remarkable decrease in coating workability.

The copolymer of component (A) and component (B) has a weight average molecular weight of 100,000 to 8,000.
It is desirable to be in the range of 000. If the weight average molecular weight is less than 100,000, a sufficient increase in aqueous phase viscosity cannot be obtained, and if it exceeds 8,000,000, the coating liquid becomes elastic and coating workability deteriorates. further,
When the component (C) is contained, the content ratio of the component (C) is such that the molar ratio of the component (A): the component (B) is 95: 5 to 40:60, and the component (A) and the component (B) are mixed. Is selected within a range in which the molar ratio of the component (C) to the total amount of When the content of the component (C) exceeds this range, the interaction with water is reduced due to an increase in the glass transition temperature, and the viscosity of the aqueous phase is reduced, so that the adhesion to the calender roll cannot be prevented. The weight average molecular weight of the copolymer of component (A), component (B) and component (C) is 900,0.
Desirably, it is in the range of 00 to 8,000,000.

The copolymer of the alkyl acrylate and the methacrylic acid and the optionally used alkyl methacrylate may be mixed in a conventional manner, for example, by mixing them in a predetermined ratio, and adding the benzoyl peroxide in an inert organic solvent. And a copolymer such as acetyl peroxide or a radical catalyst such as bisazoisobutyronitrile.

The paper coating liquid used in the present invention needs to be adjusted so that the aqueous phase viscosity of the paper coating liquid is 3 mPa · s or more. When such a condition is satisfied, the migration of the binder is caused.
By reducing the amount of binder coming to the surface of the coating liquid, the occurrence of stains on the calendar roll can be prevented, but more preferably, the aqueous phase viscosity is reduced to 5 mPa · s.
By doing so, it is possible to prevent calendar roll contamination.

The aqueous phase viscosity of the paper coating liquid used in the present invention is a value obtained by centrifuging the adjusted paper coating liquid and measuring the viscosity of the supernatant liquid using an ELD type viscometer (Tokyo Keiki Co., Ltd.). is there. In order to adjust the aqueous phase viscosity of the paper coating liquid to 3 mPa · s or more, usually, a coatability modifier is blended at a ratio of 0.05 to 1.0 part by weight per 100 parts by weight of the pigment. If this amount is less than 0.05 part by weight, it is difficult to completely prevent the occurrence of stains on the calendar roll. If this amount exceeds 1.0 part by weight, the entire coating liquid becomes elastic, and Causes deterioration of the properties (generation of scratches, spitz, streaks). The preferable amount of the coatability modifier is 0.1 to 0.4 parts by weight per 100 parts by weight of the pigment from the viewpoints of preventing stains on the calender roll and coatability.

[0018]

The coated paper of the present invention can be used for calendering.
It is possible to prevent the binder component etc. from adhering to the calender roll, so it is excellent in productivity, especially high quality gloss processing can be continuously performed, and surface processed coated paper excellent in surface smoothness, glossiness etc. Can be obtained.

[0019]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The physical properties of the paper coating liquid and the coated paper in each example were determined according to the following methods.

(1) Aqueous phase viscosity of paper coating liquid A fully automatic high-speed cooling centrifuge RD-20IV
(Tomy Seiko Co., Ltd.) and centrifuged at 15000 rpm for 60 minutes.
The viscosity at ° C was measured. (2) Stain on the calendar roll Stain on the calendar roll was visually observed and evaluated according to the following criteria.・ ・ ・: No dirt adhered to the calendar roll. △: There is some adhesion of dirt on the calendar roll,
No problem in operability. ×: There is dirt on the calendar roll, and there is a problem in operability.

Example 1 60 parts by weight of clay, 40 parts by weight of heavy calcium carbonate, 11 parts by weight of styrene-butadiene copolymer latex (as solid content), 1 part by weight of oxidized starch and a dispersant (manufactured by Somar, SDA- 40K) 0.1 part by weight (as solid content) was mixed, and water was added so that the total solid content concentration was 63%. Then, the molar ratio of ethyl acrylate units to methacrylic acid units was 65.5. : Ethyl acrylate-methacrylic acid copolymer emulsion having a weight average molecular weight of 34.5 or more and a solid content of 30% by weight
By adding 0.3 parts by weight (as a solid content) based on the copolymer of the viscosity at 0 ° C. of 10 mPa · s) and uniformly mixing, the aqueous phase viscosity was adjusted to 8.0 mPa · s. A working solution was prepared. The above weight average molecular weight is a value in terms of polystyrene measured by the GPC method. Next, this paper coating solution was applied and dried on one surface of a medium-quality paper (basis weight: 60 g / m ² ) so that the solid content was 13 g / m ² , to prepare a coated paper. Table 1 shows the calender roll stains at this time.

Example 2 In Example 1, an ethyl acrylate-methyl methacrylate-methacrylic acid copolymer emulsion (ethyl acrylate unit, methyl methacrylate unit, methacrylic acid copolymer) was used instead of the ethyl acrylate-methacrylic acid copolymer emulsion. Except that the molar ratio of the acid unit was 28.0: 37.5: 34.5, the weight average molecular weight was 1,000,000 or more, the solid content was 30% by weight, and the viscosity at 20 ° C. was 9 mPa · s). The aqueous phase viscosity was 5.2 mP as in Example 1.
A paper coating solution adjusted to a · s was prepared. Table 1 shows the physical properties of this product. Next, this paper coating solution was applied to a medium paper (basis weight 6
(0 g / m ² ) was applied and dried so that the solid content was 13 g / m ² on one side to prepare a coated paper. Table 1 shows the physical properties of this product.

Example 3 In Example 1, a butyl acrylate-methacrylic acid copolymer emulsion (butyl acrylate unit, butyl acrylate unit) was used in place of the ethyl acrylate-methacrylic acid copolymer emulsion.
Example 1 except that the molar ratio of methacrylic acid units was 44.1: 55.9, the weight average molecular weight was 1,000,000 or more, the solid content was 30% by weight, and the viscosity at 20 ° C. was 10 mPa · s). The aqueous phase viscosity is 4.1 mP
A paper coating solution adjusted to a · s was prepared. Table 1 shows the physical properties of this product. Next, this paper coating solution was applied to a medium paper (basis weight 6
(0 g / m ² ) was applied and dried so that the solid content was 13 g / m ² on one side to prepare a coated paper. Table 1 shows the physical properties of this product.

Comparative Example 1 A paper coating liquid was prepared in the same manner as in Example 1, except that carboxymethylcellulose was used instead of the ethyl acrylate-methacrylic acid copolymer emulsion. Table 1 shows the physical properties of this product. Next, this paper coating solution was applied and dried on one surface of a medium-quality paper (basis weight: 60 g / m ² ) so that the solid content was 13 g / m ² , to prepare a coated paper. Table 1 shows the physical properties of this product.

[0025]

[Table 1]

Continuing from the front page (72) Inventor Shuichi Arai F-term (reference) 4J038 BA121 BA131 BA141 BA181 BA191 CA061 CB051 CC021 CC041 CC061 CF051 CG031 CG032 CG142 CH032 CH042 CH122 CJ132 MA08 MA10 MA15 NA05 PB11 PC10 4L055 AG11 AG27 AG63 AG71 AG76 AG89 AG97 AH02 AH36 AH37 AH50 AJ04 EA25 FA30 GA19

Claims (4)

[Claims] 1. A coated paper having an ability to prevent calender roll adhesion, wherein the coated paper has a coating formed from a paper coating liquid having an aqueous phase viscosity of 3 mPa · s or more on a base paper. 2. The coated paper according to claim 1, wherein the paper coating liquid contains a pigment and a binder, and the aqueous phase viscosity is adjusted to 3 mPa · s or more by a coatability modifier. 3. The coating composition according to claim 2, wherein the coatability modifier is a copolymer of an alkyl acrylate and methacrylic acid or a copolymer of an alkyl acrylate, methacrylic acid and an alkyl methacrylate. Papermaking. 4. The coating property modifier is a copolymer of ethyl acrylate and methacrylic acid or a copolymer of ethyl acrylate, methyl methacrylate and methacrylic acid.
Coated paper as described.