JPS593599B2 - tohishiyososeibutsu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coated paper composition containing a pigment and an adhesive as main components.

Conventionally, adhesives for coated paper generally use a combination of natural water-soluble polymers such as proteins and starches, and synthetic rubber or synthetic resin emulsions (latex). Kaolin, clay, sachin white, etc. are widely used.

Casein has become extremely susceptible to spoilage due to the sharp rise in price in recent years.
In addition, its use not only requires dissolution work, but also has a low dissolved concentration of about 15%, which makes it difficult to prepare high-concentration paints, which hinders the work process and rationalization.For this reason, casein is gradually used. Replacement with starch or polymer latex has been attempted. However, casein originally has various excellent properties as an adhesive for coated paper, and when casein is replaced with starch Al-powder or polymer latex, the basic properties of coated paper vary. The situation is not satisfactory due to the long-term deterioration of the situation.

For example, when casein is used as an adhesive for coated paper, the water resistance of the coated paper can be easily obtained by simply using Sachin White as a pigment, but when starch is used, the water resistance of the coated paper is Water resistance cannot be easily obtained by using water resistance agents such as glyoxal and melamine resin, and in the case of paints containing satin white, the coating layer exhibits alkalinity, so starch derivatives such as cationic starch that are easy to make water resistance are used. Even then, the water resistance of coated paper cannot be achieved. Another disadvantage is that when starch is used in place of casein, the hardness of the coated paper decreases.

Furthermore, in order to compensate for the disadvantage of starch's reduced water resistance, casein,
In order to streamline the process by eliminating the complicated dissolving action required when using starch, etc., it is easy to make coated paper water resistant when part of the adhesive is replaced with polymer latex. The hardness (stiffness) of the paper is significantly reduced, which changes the feel of the paper, which not only reduces the product value in applications such as cover paper and wrapping paper, but also increases the speed of printing operations for general printing paper. This may cause problems with automatic paper feeding or paper alignment after printing. Further, in applications such as label paper, the suitability for automatic bottle pasting is reduced, causing various problems such as frequent stoppage of the bottle pasting machine, which is undesirable. For this purpose, a method was considered to replace part of the polymer latex used in general coated paper with a synthetic resin emulsion that creates a hard coating, but in this case, the polymer latex was used as a so-called plastic pigment rather than as an adhesive. Since the properties are similar, the adhesive strength is significantly reduced and picking occurs during printing.

Furthermore, the amount of adhesive used needs to be small for economical reasons, and it is also better to use a smaller amount from the viewpoint of printing suitability such as the gloss of the coated paper and the water-absorbing ink set during offset printing. Although preferred, polymer latexes, which are hard but have weak adhesive strength, cannot be used in large quantities as adhesives in practice. Furthermore, in recent years attempts have been made to use emulsions of highly carboxylated polymers in order to use polymer latexes as adhesives and to retain the stiffness of paper.

In this case, by highly carboxylating the polymer, it is possible to make the film harder than ordinary latex without sacrificing adhesive strength, but the carboxyl groups are reactive with ions in paints such as Satin White. Due to its strong viscosity, when used in general coated paper paints containing Sachin White, it not only significantly increases the viscosity of the coated paper paints, but also
After coating and drying, the printing surface strength of the coated paper obtained is significantly reduced. Therefore, properties such as gloss, smoothness, whiteness, ink gloss, and ink receptivity of coated paper can be easily obtained.
At present, it cannot be used in paints for coated paper containing Sachin White, which is a very widely used pigment for coated paper. The present inventor has discovered that even when a polymer latex is used in a composition for coated paper containing Sachin White, which has excellent properties as a pigment for coated paper, the hardness of the paper does not decrease, and the printing strength does not decrease. As a result of continuing research on coated paper compositions that do not reduce the hardness of paper, we have found that by using a specific heterogeneous polymer latex in combination, the hardness of the paper can be maintained even without the use of casein at all, and in particular, the amount of adhesive used can be reduced. It has been found that a composition for coated paper can be obtained that enables the production of coated paper with strong printing surface strength without increasing the printing surface strength.

That is, in the present invention, as an adhesive for 100 parts by weight of a pigment for coated paper containing 1 to 50 parts by weight of Sachin White,
Contains 5 to 25 parts by weight of polymer latex as a solid content, and as the polymer latex (4) has a minimum film forming temperature of 20
25 to 90% by weight (as solid content) of one or more polymer latexes (hereinafter referred to as low-temperature film-forming latexes) with a temperature below 75 to 10% by weight (solid content) of a polymer latex (hereinafter abbreviated as high-temperature film-forming latex) is used together, and the copolymer (B) is 5 to 30% by weight of (a). (b) at least 2 weights of all monomers forming the copolymer? 2 to 15 containing methacrylic acid in an amount capable of constituting
A coated paper composition comprising an ethylenically unsaturated carboxylic acid having a weight e and (c) an ethylenically unsaturated monomer copolymerizable with (a) and (b) forming the remainder. This is what we provide. Coated paper pigments used with Sachin White in the present invention include kaolin, rosewood, hallosite, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, zinc oxide, etc., which are commonly used in coated paper compositions. In addition to the mineral pigments used, plastic pigments such as polystyrene can also be used.

In the present invention, it is necessary that 1 to 50 parts by weight, preferably 5 to 30 parts by weight, of Sachin White be contained in 100 parts by weight of the pigment. If the content of Sachin White is less than 1% by weight, the resulting coated paper will have insufficient properties such as gloss, smoothness, whiteness, ink gloss, and ink receptivity, and if the content exceeds 50 parts by weight. This is not preferable because the ink absorbency of the coating composition becomes excessive, making it difficult to produce gloss on the printed surface and further reducing the strength of the printed surface. The total amount of polymer latex used as an adhesive for the above pigment is 100% of the pigment.
Usually 5 to 25 parts by weight, preferably 10 to 1 part by weight
5 parts by weight (both as solid content) are used. The low-temperature film-forming latex constituting the polymer latex includes conjugated diene polymer latexes such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, which are used as usual latexes for coated paper; Acrylic polymer latex such as a polymer or copolymer of acrylic acid ester and/or methacrylic acid ester, vinyl acetate polymer latex such as ethylene monovinyl acetate copolymer, or carboxyl groups of these various polymers, etc. A functional group-modified polymer latex, which is not based on the functional group-containing monomer, and has a minimum film forming temperature of less than 20°C, preferably 15°C or less, is used. Of course, it is also possible to use a mixture of two or more of these polymer latexes. High-temperature production is the most characteristic six components of the present invention. Is membrane latex (a) 5 to 30 weight? Conjugated diene, (
b) 2 to 15% by weight containing at least 2% by weight (based on total monomers) of methacrylic acid? and (c) (a) and (b) forming the remainder.
A copolymer latex is used, which is composed of an ethylenically unsaturated monomer copolymerizable with the copolymer and has a minimum film forming temperature of 20° C. or higher.

The conjugated diene mentioned above includes butadiene, isoprene, chloroprene, etc., and butadiene is particularly preferably used.

As the ethylenically unsaturated carboxylic acid other than methacrylic acid, mono- or dicarboxylic acids such as acrylic acid, crotonic acid, itaconic acid, fumaric acid, and maleic acid are used.

Of course, it is also possible to use a mixture of these.
Is the amount of carboxylic acid monomer 2 to 15 weight? It can be used in a range of 2 to 10 weight e, but a range of 2 to 10 weight e is particularly suitable.

Is the amount of carboxylic acid monomer 2 weight? If the amount is less, the surface strength of the coated paper using the resulting coated paper composition will not be sufficient, and the weight will be less than 15%. A larger amount is not preferred because the viscosity of the coated paper composition increases and the surface strength of the resulting coated paper decreases. In the present invention, it is necessary to use at least a portion of the carboxylic acid monomers, ie at least 2% by weight of methacrylic acid based on the total monomers.

If the amount of methacrylic acid used is small, or if methacrylic acid is not used at all, the surface strength of the resulting coated paper will decrease, which is not preferable. The carboxylic acid monomer may be used in its entirety from the beginning of the polymerization at the same time as other monomers, or
Part or all of the amount may be used by adding 1 J (increment) during the polymerization. Examples of the ethylenically unsaturated monomer of component (c) include vinyl aromatic compounds such as styrene, α-methylstyrene, and divinylbenzene, and ethylenic compounds such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, and ethyl methacrylate. Unsaturated carboxylic esters are most preferably used.

It is of course possible to use two or more of these monomers in combination. The minimum film-forming temperature of the high-temperature film-forming latex copolymer used in the present invention is 20° C. or higher.

If the minimum film forming temperature is lower than 20℃, what is the hardness of the coated paper obtained? ) is small, making it impossible to achieve the purpose of the present invention. If the minimum film forming temperature becomes too high, the surface strength of the coated paper tends to decrease.
Polymeric latexes with minimum film forming properties of ˜50° C. are most effectively used. A high-temperature film-forming latex can be produced by conventional emulsion polymerization using each of the above-mentioned monomers.

The particle diameter of the latex is preferably about 500 to 1500λ. If the particle size is larger than 1,500λ, the adhesive force tends to decrease, and if it is smaller than 500λ, it is unfavorable from the viewpoint of latex stability and productivity. In the present invention, as an adhesive for pigments for coated paper, a low-temperature film-forming latex and a high-temperature film-forming latex are mixed in a ratio of 25 to 90:75 to 75.
They are mixed and used in a ratio of 10 to 10, particularly preferably in a ratio of 30 to 70 to 70 to 30 (both weight ratios as solid content). The effect on surface strength and hardness (firmness) is not simply an arithmetic average of each component, but the combined use of different latexes of the present invention improves the stability and workability of the coated paper composition. Coated paper with good surface strength and hardness can be obtained.

Although the coated paper composition of the present invention can exhibit sufficiently excellent effects in systems that do not use casein at all, it may be necessary to Small amounts of conventional water-soluble thickening agents such as casein or starch can also be used. In this case, casein is 20% by weight compared to latex? Hereinafter, it is preferable to use starch in an amount equal to or less than the weight of the latex. The composition for coated paper is generally applied onto base paper by a method used for coating coated paper, such as by a coater such as an air knife, blade, roll, stack, roll, size press, cast, spray, or brush. It can be coated in a single layer or in multiple layers and dried in a conventional manner to produce coated paper.

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. In addition, the parts shown in the examples and ? means parts by weight and weight %, respectively, unless otherwise specified. Example 1~
12. Control Examples 1 to 9 In an autoclave purged with nitrogen gas, a total of 100 parts of monomers having the composition ratios shown in the table below, 250 parts of water, 0.2 parts of n-dodecylmercaptan, 1.0 parts of ammonium persulfate, and When 3.0 parts of sodium dodecylbenzenesulfonate was charged and reacted at 70°C for 15 hours, the polymerization rate reached 95% or more in all cases.

All of the obtained copolymer latexes were phosphorus-treated with caustic soda.
After adjusting the temperature to 6.5, water vapor was sucked in to remove unreacted monomers.In addition, in MFT, latex is poured over a copper plate with a temperature gradient to evaporate and dry the water, forming a transparent continuous film. It is expressed as the temperature at the boundary between the part where the coating is present and the part where a continuous film does not form and becomes a white powder.

Using the obtained latexes A to D, paper coating paints were prepared according to the following formulation and subjected to the following tests.

73 parts of clay for coated paper, 2 parts of styrene plastic pigment
0 parts, Sachin White 7 parts, styrene-butadiene copolymer latex (JSRO692 manufactured by Japan Synthetic Rubber Co., Ltd., MFT 5°C or less) and netethylene-butadiene copolymer latex (Asahi Co., Ltd.) as low-temperature film-forming latexes. Tau (
Co., Ltd. Tau Latex 620sMFT (15°C) and the latex AlBlClD as a high-temperature film-forming latex.
A further 2 parts of oxidized starch were added to prepare a 47% strength paint.

Starch size press-treated 609/I base paper was coated with an air knife coater at a speed of 300 m/min to form a solid amount of 25 g.
I coated it so that it looked like this and rolled it up after drying. Table 1 shows the quality test results after Super Calendar treatment. The surface strength was measured using an RI printing tester made by Mei Seisakusho, and the ink was Super Deluxe Beni B Takku Balyu-13 (Toka Shiki Co., Ltd.). Judgments were made by dividing into five classes: = good, E = poor, N = slightly worse than A).

The hardness of the paper was measured by the JISP8l43 paper stiffness test method based on the self-weight bending method and the Clark method.

The higher the number, the harder it is, and the lower the number, the softer it is. To test the water resistance of coated paper, put 2 drops of water on the coated paper surface and apply 1 drop on the fingertip surface.
Judgment was made by a fingertip water resistance test in which the water was transferred to a black glass surface by rubbing five times and the degree of coloring was compared after drying.

Water resistance was evaluated in five grades: A-E (A=good, E=poor). The coated papers obtained in Examples 1 to 12 were printed using an offset two-color printing machine at a speed of 5,000 sheets/minute, and after being cut, a bottle sticking test was conducted, and no problems were found.

Comparative Examples 2, 3, 5, and 7 do not have paper stiffness, so automatic paper feeding is required.
Printing workability such as paper alignment after printing was poor, and the paper was soft, making it unsuitable for automatic bottle pasting. Control examples 4 and 6
Samples No. 8 and 8 had poor printing surface strength and picked, which caused printing plate stains and made it impossible to print continuously. As Control Example 9, when the same method as in Example 2 was used except that a total of 10 parts of oxidized starch was used instead of 8 parts of the high-temperature film-forming latex used in the present invention, the water resistance of the coated paper surface was inferior. . Examples 13 to 15, Control Examples 10 to 12 55 parts of kaolin, 20 parts of aluminum hydroxide, 25 parts of Sachin White as pigments, MFT 3O ℃ latex AlO part (high temperature film-forming latex) used in Example 1 as adhesive , butadiene-methyl methacrylate copolymer latex (Polylac ML7 manufactured by Mitsui Toatsu Chemical Co., Ltd.)
O7, MFT2 or less), acrylic latex (Rohm & Haas Primal E-376, MFT
8doC) or ethylene monovinyl acetate copolymer latex (Sumicaflex 100HS1M manufactured by Sumitomo Chemical Co., Ltd.)
10 parts each (low temperature film forming latex)
44 using a 55% strength paint consisting of 6 parts of modified starch.
Solids content 16 on both sides using a blade coater on g/a base paper
It was coated at a speed of 300 m/min so that the coating was 9/Trl, dried, and then wound up.

Table 2 shows the properties of the coated paper after applying Super Calendar. The coated papers obtained in Examples 13, 14, and 15 above were printed using an offset two-color machine at a speed of 5,000 sheets/minute, but there were no problems with printing workability, and the printed materials had an excellent print finish. had.

Examples 13, 14, and 1, respectively, except that 20 parts of butadiene-methyl methacrylate copolymer latex, acrylic latex, or ethylene monovinyl acetate copolymer latex were used instead of latex A.
Comparative Examples 10, 11 and 11 were obtained in the same manner as in 5.
It was shown as 12. All of the coated papers obtained in the control examples had weak paper stiffness, so automatic paper feeding and paper alignment after printing were poor at the same printing speed as in the examples, and continuous printing could not be performed. In addition, the paper curled significantly at the exit of the printing area, and as a result, ink smudges were observed on the printed surface. Examples 16-21
, Comparative Examples 13 and 14 In the same manner as in Example 1, monomers having the following composition were polymerized to obtain a latex.

65 parts of clay for coating paper, 20 parts of calcium carbonate, 15 parts of Sachin White, 2 parts of oxidized starch as an adhesive, styrene-butadiene copolymer latex (JSRO692 manufactured by Japan Synthetic Rubber Co., Ltd., MFT 5°C or less) 8 A paint having a concentration of 43% was prepared using 8 parts of each of the latex E-L.

Claims (1)

[Claims] 1 Containing 100 parts by weight of a pigment for coated paper containing 1 to 50 parts by weight of Sachin White and 5 to 25 parts by weight of a polymer latex as a solid content, as the polymer latex (A)
25-90% by weight (as solid content) of one or more polymer latexes with a minimum film-forming temperature of less than 20°C and (B) 75-10% of one or more copolymer latexes with a minimum film-forming temperature of 20°C or higher. % by weight (as solid content), and the (B
copolymer of (a) 5 to 30% by weight of a conjugated diene, (
b) 2 to 15% by weight comprising methacrylic acid in an amount capable of constituting at least 2% by weight of the total monomers forming the copolymer.
and (c) an ethylenically unsaturated monomer copolymerizable with (a) and (b) forming the remainder.