JPS61698A - Multi-layered coated paper - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention uses heavy calcium carbonate as a pigment at low cost and has excellent paint fluidity, and also has excellent printability such as white paper gloss, printing gloss, ink receptivity, and printing surface smoothness. Concerning multi-layer coated paper.

Traditionally, kaolin clay has been used as a pigment for coating compositions because of its excellent gloss and printability on coated paper, but in recent years it has become necessary to make coating compositions highly solid. Heavy calcium carbonate, which has a great effect on improving the fluidity of liquids, is used in combination with kaolin clay. In order to take advantage of the characteristics of heavy calcium carbonate such as low cost and fluidity, it is preferable to use it in a pigment as high a ratio as possible.
62296 uses finely divided ground calcium carbonate with a limited particle size distribution as the sole pigment. The use of fine particles of heavy calcium carbonate improves the gloss of white paper, which is a common drawback of calcium carbonate.
To form a dense coating layer, the unevenness of the base paper is left intact.
As a result, a sufficiently smooth coated surface is not formed, and the smoothing effect (calender effect) by calender is still small. Coated paper with a printed surface that is less smooth than when using high quality calcium carbonate. On the other hand, if heavy calcium carbonate with a large particle size is used, the smoothness of the printed surface is considerably improved, but it is inferior to kaolin clay, and the gloss of white paper becomes significantly poor.

In this way, coated paper using heavy calcium carbonate as a pigment has a poorer balance between white paper gloss and printed surface smoothness than when using kaolin clay as the main ingredient. This problem cannot be solved simply by changing the particle size of heavy calcium carbonate. This is an essential drawback of heavy calcium carbonate and is caused by the properties of heavy calcium carbonate itself.・Compared with the properties of kaolin clay, kaolin clay has a hexagonal thin plate-like shape, and it is easy to arrange the kaolin clay particles by calendering, giving it a white gloss, whereas heavy calcium carbonate has a hexagonal thin plate shape. It has a fixed shape, essentially has little calendering effect, and the expression of white paper gloss is insufficient. Also, the surface energy is 500-600 of kaolin clay.
Joule/cm, heavy calcium carbonate is 75
~80 Joule/'cm. [TAPP'I,
62N [15, 37-41 (1979):) Low surface energy means poor water retention, so using heavy calcium carbonate will improve the coating composition regardless of particle size. The immobilization point becomes high, and the unevenness of the base paper does not become smooth, making it impossible to obtain sufficient smoothness. Therefore, the smoothness of the printing surface of coated paper coated with a paper coating composition using a pigment mainly composed of a type of heavy calcium carbonate having a specified particle size or particle size distribution is determined by the fact that kaolin clay is the main component. The results are inferior compared to coated paper.

Double coating is known as a coating method that improves the coverage of base paper. Conventionally, double coating is performed using the same type of coater, or after coating with a blade coater, coating with an air knife coater,
Alternatively, different types of coaters are used in combination, such as roll coater coating followed by blade coater coating.

The present inventors have found that not only pigments mainly composed of inexpensive heavy calcium carbonate, but also even when only heavy calcium carbonate is used as the sole pigment, the fluidity of the paint is good and the coating workability is excellent.
In order to obtain coated paper with excellent white paper gloss and smoothness of the printed surface at a low cost, we focused on the combination of the double coating method and the particle size of the heavy calcium carbonate used. After various studies with the addition of latex, we decided to use heavy calcium carbonate with a large particle size for the undercoat and heavy calcium carbonate with a small particle size for the topcoat. It has been found that the objects of the invention are achieved by using it as a layer adhesive.

For coated papers with small particle sizes of heavy calcium carbonate used for both the undercoat and topcoat, the white paper has excellent gloss, but because it forms a dense coating layer structure, even with double coating, the coverage of the base paper is insufficient at a practical coating amount. It is not sufficient, and the calendering effect is still small, so the smoothness of the printed surface is poor. On the other hand, coated paper using heavy calcium carbonate with large particle sizes for both the undercoat and topcoat provides good coverage of the base paper and good smoothness of the printed surface, but poor white paper gloss. Furthermore, even if heavy calcium carbonate with a small particle size is used for the undercoat and heavy calcium carbonate with a large particle size is used for the topcoat, the coated paper will have a low white gloss. On the other hand, if heavy calcium carbonate with a large particle size is used for the undercoat and heavy calcium carbonate with a small particle size is used for the topcoat, the undercoat will cover the base paper well, and the topcoat will be applied to a fairly smooth surface. This eliminates the drawback of poor coating properties due to the small particle size of heavy calcium carbonate, and also exhibits the characteristics of excellent white paper gloss, resulting in coated paper with good white paper gloss and excellent printing surface smoothness. However, in addition to this, by using the following specific amphoteric copolymer latex as the adhesive component of the base coat paper coating composition and/or the top coat paper coating composition, further improvement of the base paper coverage can be achieved. Coated paper with improved white gloss and printed surface smoothness can be obtained.

That is, in the present invention, a paper coating composition mainly composed of a pigment containing heavy calcium carbonate and an adhesive containing 65 weight percent or less of particles of 2 μm or less is first coated, and then a paper coating composition containing 70 weight percent or more of particles of 2 μm or less is used. Amphoteric copolymer latex (4) as an adhesive component of a base coat coating composition and/or a top coat paper coating composition in a coated paper
5 parts by weight of each pigment in the primed paper coating composition and/or -F coated paper coating composition.
The object of the present invention is to provide a multilayer coated paper characterized in that the content is 30 parts by weight.

The amphoteric copolymer latex contains 1 to 10 parts by weight of at least one amphoteric surfactant as an emulsifier during polymerization, and 0.5 to 10 parts by weight of ethylenically unsaturated carboxylic acid and ethylenically unsaturated amine. This is a copolymer latex obtained by emulsion polymerization of 100 parts by weight of a monomer mixture consisting of an aliphatic conjugated diene compound 30 to 70 and a monomer 10 to 6911 copolymerizable with these in the coexistence of .

Calcylano heavy carbonate used in the undercoating paper coating composition has a particle size of 2 μm or less, with a weight ratio of 65% or less,
The content is preferably 60% by weight or less, and if it exceeds 65% by weight, the smoothness of the printed surface will decrease. The content of the heavy calcium carbonate in the pigment is preferably 50 to 100% by weight.

The heavy calcium carbonate used in the topcoat paper coating composition has a particle diameter of 2 μm or less and has a weight ratio of 70 or more, preferably 85 or more, and if it is less than 70w fd4, the gloss of the white paper decreases.

The content of the heavy calcium carbonate in the pigment is 50~
100 folds are preferred.

In the present invention, a specific amphoteric copolymer latex is used as an adhesive for the paper coating composition for either or both of the undercoat and topcoat. 5 to 3 parts per 100 parts by weight of pigment
It is essential to use 0 parts by weight to achieve excellent white paper gloss and printability. Although much of the detailed mechanism is still unknown, the amphoteric copolymer latex has a strong interaction with the pigment dispersed with an anionic dispersant in the coating liquid due to its cationic property5, resulting in bulk. This is thought to be due to the formation of a coating layer with a high structure, which further improves the coverage of the base paper.

The amphoteric copolymer latex contains 1 to 10 parts by weight of at least one amphoteric surfactant as an emulsifier during polymerization, 0.5 to 10 parts by weight of ethylenically unsaturated carboxylic acid, and 0.5 to 1 part by weight of ethylenically unsaturated amine (Lfi). It is obtained by emulsion polymerization of a monomer mixture consisting of an aliphatic conjugated diene compound of 30-70% and a monomer copolymerizable with these 10-691% in the presence of quantitative ratios.

Polymerizing the monomer mixture in the coexistence of ethylenically unsaturated carboxylic acid, which is an anionic monomer, and ethylenically unsaturated amine, which is a cationic monomer, is essential for achieving the effects of the present invention. However, in order to maintain the polymerization stability of this polymerization system, it is preferable to produce the polymer at a pH of 6 or more during polymerization.

If the amphoteric surfactant is less than 1 part by weight, it will be difficult to obtain good printing surface smoothness, and if it exceeds 10 parts by weight, it will be difficult to maintain the water resistance required as a coated paper for printing.

If the amount of ethylenically unsaturated carboxylic acid in the copolymer is less than 0.5% by weight, the adhesive strength and mechanical stability of the latex will decrease,
If it exceeds 10% by weight, the viscosity of the latex increases and the viscosity of the coating liquid increases, resulting in a decrease in coating workability.

If the amount of ethylenically unsaturated amine is less than 0.5 weight percent, it is difficult to obtain good printed surface smoothness, and if it exceeds 10 weight percent, the mechanical stability of the latex will decrease.

When the weight ratio of the aliphatic diene compound is less than 30% by weight, the adhesive force decreases, and when it exceeds 70% by weight, the rigidity becomes insufficient.

Even if this amphoteric copolymer latex is used as an adhesive component in either the undercoat or topcoat paper coating composition, a sufficient effect can be obtained for the purpose of the present invention, but it is more preferable to use it as an adhesive component in either the undercoat or topcoat paper coating composition. When this amphoteric copolymer latex is used as an adhesive component for both compositions,
Furthermore, further effects can be obtained.

In addition, the amount of the amphoteric copolymer latex is as follows: pigment 1
If it is less than 5 parts by weight to 00 parts by weight, the adhesive strength will be insufficient,
If it exceeds 30 parts by weight, the ink receptivity will decrease.

The amphoteric surfactant used here is a surfactant that has both an anionic part and a cationic part hydrophilic group in the same molecule, and the anionic part includes carboxylate, sulfate ester salt, sulfonate, and phosphate ester. Examples of salts include amine salts and quaternary tenmonium salts as cationic moieties, and specific examples include laurylbetaine, stearylbetaine, and stearylbetaine as alkylbetaine salts.
Salts of cocoamidopropyl betaine, 2-undecyl-hydroxyethylimidazolinium betaine, amino acid types such as lauryl-β-alanine, stearyl-β-alanine, lauryldi(aminoethyl)glycine, octyldi(aminoethyl)glycine and dioctyldi(aminoethyl)glycine.

Ampholytic surfactants have less deterioration in water resistance than anionic or nonionic surfactants, and can provide paper with excellent gloss and printability. The effects of the present invention can be achieved by using these amphoteric surfactants alone or in combination as emulsifiers during polymerization, and in combination with other anionic, cationic, and/or nonionic surfactants. They may be used as polymerization emulsifiers, but they may be produced using, for example, anionic and nonionic surfactants as emulsifiers during polymerization rather than amphoteric surfactants as emulsifiers during polymerization. The effects of the present invention cannot be obtained by simply adding an amphoteric surfactant to a copolymer latex.

As the ethylenically unsaturated carboxylic acid used in the present invention, mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid can be used. Anhydrides or monoalkyl esters can also be used.

Ethylenically unsaturated amine monomers include monomers represented by, for example, methylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate, dimethyl-aminoethyl (meth)acrylate, dimethylamine propyl ( meth)acrylate, diethylaminoethyl(meth)acrylate, dibutylaminoethyl(
Aminoalkyl esters of ethylenically unsaturated carboxylic acids such as meth)acrylates, aminoalkyl esters of ethylenically unsaturated carboxylic acids such as methylaminoethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, dimethylaminepropyl (meth)acrylamide, etc. amide, aminoalkyl vinyl ethers such as aminoethyl vinyl ether, methylaminoethyl vinyl ether, dimethylamine ethyl vinyl ether, monomers represented by oyohi, such as 2-vinylpyridine, 4-
Vinylpyridine, 2-methyl-5-vinylpyridine, 2
, 4-diethyl-5-vinylpyridine, and alkenylpyridines such as gropenylpyridine and impropenylpyridine.

Aliphatic conjugated diene compounds include -butadiene, isoprene, 2-chloro-1,3-butadiene, 1-chloro-
Examples include 1,3-butadiene.

Copolymerizable monomers include aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, halamethylstyrene, methyl diacrylate, ethyl acrylate,
Alkyl esters of acrylic acid or methacrylic acid such as butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, vinylisoane compounds such as acrylonitrile and methacrylonitrile, vinyl chloride, chloride Vinylidene, vinyl methyl ethyl ketone, vinyl methyl ether, vinyl acetate, vinyl formate, allyl acetate, methalyl acetate, acrylamide, methacrylamide, N-methylolacrylamide, glycidyl acrylate, glycidyl methacrylate, acrolein, allyl alcohol, and the like.

The amphoteric copolymer latex of the present invention can be polymerized by a known method in an aqueous medium using an emulsifier, a polymerization initiator, and a chain transfer agent.

As an emulsifier, anionic, cationic and/or nonionic surfactants can be used in combination with the essential amphoteric surfactant, but it is possible to use anionic, cationic and/or nonionic surfactants in combination. preferable. Examples of the anionic surfactant include higher alcohol sulfate esters, alkylbenzene sulfonates, aliphatic sulfonates, and the like. As the nonionic surfactant, ordinary polyethylene glycol alkyl ester, alkyl ether, and alkylphenyl ether types are used.

As the initiator, any of water-soluble initiators such as persulfate, potassium persulfate, ammonium persulfate, oil-soluble initiators such as benzoyl peroxide, or redox initiators can be used. As chain transfer agents, chelating agents, inorganic salts, etc., those known for emulsion polymerization are used.

In the present invention, as adhesive components that can be used in combination with the above amphoteric copolymer latex, conjugated diene polymer latex such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic ester and/or or acrylic polymer latex such as methacrylic acid ester polymer or copolymer, ethylene/
Vinyl polymer latex such as vinyl acetate copolymer, functional group-modified polymer latex with monomers containing functional groups such as carboxyl group, amine group, amide group, epoxy group, etc. of these various polymers, anionic and Cationic amphoteric copolymer latex, polyvinyl alcohol, olefinic maleic anhydride resin, synthetic resin adhesives such as melamine resin, starches such as positive starch and oxidized starch, carboxymethyl cellulose, Known adhesives for coated paper such as cellulose derivatives such as hydroxyethyl cellulose, casein, and soybean protein may be used alone or in combination.

In the paper coating composition of the present invention, various auxiliary agents such as antifoaming agents, coloring agents, flow modifiers, etc. are also used as appropriate.

In the present invention, the undercoat coating liquid is applied to a blade coater, an air knife coater, a roll coater, a flage coater, a curtain coater, a champlex coater, a percoater, a gravure coater, a size press coater, etc., which are used in general coated paper manufacturing. A coating device is installed, and the base paper is coated in one layer or in multiple layers using an on-machine or off-machine coater.

The method for forming the top coat layer formed on the undercoat layer is not particularly limited, and the coating apparatus described above may be used.

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples.

Examples 1 to 7 (1) Amphoteric copolymer latex (A) (B) Production method The raw materials shown in Table 1 were charged under nitrogen gas into a pressure-resistant container equipped with a stirrer and a temperature controller, and reacted at 50°C for 15 hours. Ta. Thereafter, 0.1 weight portion of N,N-diethylhydroxylamine was added to stop the reaction. The obtained copolymer Latinx polymer (ω) had a polymerization conversion rate of 90 or more and a pH of 8.

(2) JSII (
.

Coating compositions for top coating and undercoating having the formulations shown in Examples 1 to 7 in Table 2 were prepared using ≠0696 as an adhesive.

This coating composition was applied to high-quality base paper as an undercoat and a topcoat of 82% each.
It was double coated to a coating weight of -, and after drying, it was subjected to super calendering and its physical properties were measured.

All of these paints have good flow characteristics, and the coated paper has excellent physical properties such as white paper gloss and printed surface smoothness.

Comparative Examples 1 to 5 Comparative Example 1 is an example in which fine particles of heavy calcium carbonate used in the undercoat paper coating composition have a content of 75% by weight of particles of 2 μm or less, and although the white paper has good gloss, the printed surface Poor smoothness.

Comparative Example 2 uses JSR, which is a latex other than an amphoteric copolymer latex, as the adhesive for the coating composition for topcoat and undercoat.
This is an example using 4P0696, resulting in a coated paper with poor white paper gloss and printed surface smoothness.

Comparative Example 3 is an example in which the heavy calcium carbonate used in the topcoat coating composition was coarse particles with a content of particles of 2 μm or less of 60% by weight, and although the printed surface smoothness was good, the white paper gloss was Only coated paper with extremely poor quality can be obtained.

Comparative Examples 4 and 5 showed examples in which the content of heavy calcium carbonate in the pigment in the coating compositions for topcoat and undercoat was low, respectively, but the paints with low content of heavy calcium carbonate were Isier fluidity deteriorates significantly and coating workability deteriorates.

(Left below) Explanation of Table 2 ■ Particle size distribution measuring device manufactured by Takasugi Seisakusho (Sedegraf 50)
00).

* The amount of adhesive used is expressed in parts by weight per 100 parts by weight of pigment.

H■ Measured with a Brookfield viscometer.

Measured using a keyless Ischer viscometer manufactured by Kumagai Riki Co., Ltd., and the appearance with respect to shear rate was determined from the pattern of viscosity change.

(Good) ◎, ○, × (Poor) Chi ■ The white paper gloss is better when measured with a Murakami gloss meter and the value is higher.

Screen ■ Printed with black ink using an RI type printing tester manufactured by Mei Seisakusho was visually evaluated.

(Good) ◎, ○, △, × (Bad) Patent applicant: Japan Synthetic Rubber Co., Ltd. Kanzaki Paper Co., Ltd.

Claims (4)

[Claims] (1) Undercoating with a paper coating composition mainly consisting of a pigment and adhesive containing heavy calcium carbonate containing 65% by weight or less of particles of 2 μm or less, and then applying a paper coating composition containing 70% by weight or more of particles of 2 μm or less In multi-layer coated paper that is overcoated with a paper coating composition whose main components are a pigment containing heavy calcium carbonate and an adhesive, the adhesive component of the basecoat paper coating composition and/or the topcoat paper coating composition It is characterized by containing 5 to 30 parts by weight of the following amphoteric copolymer latex (A) per 100 parts by weight of each pigment in the undercoat paper coating composition and/or topcoat paper coating composition. Multilayer coated paper. Amphoteric copolymer latex (A): 1-10 parts by weight of at least one amphoteric surfactant used as an emulsifier during polymerization, 0.5-10% by weight of ethylenically unsaturated carboxylic acid, 0.5% by weight of ethylenically unsaturated amine A copolymer obtained by emulsion polymerization of 100 parts by weight of a monomer mixture consisting of 30 to 70% by weight of an aliphatic conjugated diene compound and 10 to 69% by weight of a monomer copolymerizable with these in the coexistence of ~10% by weight. Polymer latex. (2) The pigment of the undercoat paper coating composition contains 50 to 50% of heavy calcium carbonate containing 65% by weight or less of particles of 2 μm or less.
Claim No. 1 (1) containing 100% by weight
) Multi-layer coated paper described in section 2. (3) The pigment of the topcoat paper coating composition contains 50 to 50% of heavy calcium carbonate containing 70% by weight or more of particles of 2 μm or less.
Claim No. 1 (1) containing 100% by weight
) Multi-layer coated paper described in section 2. (4) The multilayer according to claims (1), (2), and (3), wherein the production of the amphoteric copolymer latex (A) involves emulsion polymerization of the monomer mixture at a pH of 6 or higher. Coated paper.