JP3160400B2 - Composition for coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper composition having excellent viscosity under high shearing force. More particularly, the present invention relates to a coated paper composition containing a binder and a pigment, the pH of which is adjusted using lithium hydroxide in a carboxy-modified latex.

[0002]

2. Description of the Related Art In recent years, the demand for pigment-coated paper (coat paper) has been remarkably increased.
Further, in accordance with the improvement of the quality of coated paper by increasing the density, the composition of the coated paper composition (color) has been increased for the purpose of cost reduction by saving drying energy at the time of coating and binder reduction. Is underway. With these high-speed coating and high concentration,
A variety of properties are also required for coated paper compositions. For example, in high-speed coating and high concentration,
A high shear stress acts on the coated paper composition (color), and as a result, not only the coating workability is lowered but also the quality of the obtained coated paper is lowered. Conventionally, in order to reduce the stress under high shear (reducing the viscosity under high shear), a large amount of heavy calcium carbonate is used from the pigment surface, and the natural binder is a star binder from the binder surface. Methods for reducing the particle size, reducing the particle size, and polymerizing ethylenically unsaturated carboxylic acids have been proposed for carboxy-modified latex as a synthetic binder. Ammonia water, which is an organic amine, or potassium hydroxide or sodium hydroxide, which is an inorganic alkali, is used as a pH adjuster for this synthetic binder. However, viscosity reduction under high shear is not sufficient, and further, coated paper The mechanical stability of the composition for use deteriorates. Thus, there has been a demand for a composition for coated paper which has sufficient mechanical stability and further reduces the viscosity under high shear.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a coated paper composition which has a low viscosity under the above-mentioned high shear and also has good mechanical stability.

[0004]

The inventors of the present invention have conducted various studies to achieve the above object, and as a result, have found that the use of lithium hydroxide as a pH adjuster during the production of a carboxy-modified latex results in the use of this binder. It has been found that the performance of a coated paper composition containing-can be improved, and the present invention has been completed.

That is, the present invention relates to (a) 1 to 10% by weight based on the weight of all monomers of an ethylenically unsaturated carboxylic acid. (B) 90 to 99% of another monomer copolymerizable with a. 1% by weight of an emulsion polymerization reaction product, wherein the pH is adjusted to 5 to 10 using lithium hydroxide. .

[0006] By using lithium hydroxide as a pH adjuster for an ethylenically unsaturated carboxylic acid copolymer latex, ammonia water, potassium hydroxide and sodium hydroxide can be obtained with other organic amines as pH adjusters. The effect of suppressing the expansion of the particles by adjusting the pH of the carboxy-modified latex, that is, the same effect as reducing the particle size of the latex is obtained. In addition, there is no adverse effect such as poor mechanical stability of the composition for coated paper, which is observed when the particle size is reduced.

Hereinafter, the present invention will be described in detail.

In the present invention, the ethylenically unsaturated carboxylic acid is an essential component for mainly improving the mechanical stability of the emulsion polymerization reaction product, and its use amount is 1 to 10% by weight based on the weight of all monomers. , Preferably in the range of 2 to 5% by weight. If this amount is less than 1% by weight, the mechanical stability becomes insufficient when used in a composition for coated paper. On the other hand, if the content exceeds 10% by weight, the viscosity of the carboxy-modified latex and the composition for coated paper becomes extremely high, making it difficult to handle. In addition, the wet pick strength of the coated paper decreases due to the decrease in water resistance of the latex film. Is not preferred.

Preferred examples of (a) ethylenically unsaturated carboxylic acids include monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, itaconic acid, maleic acid,
Dicarboxylic acids such as fumaric acid, or acid anhydrides thereof,
Monoalkyl esters and the like. These ethylenically unsaturated carboxylic acid monomers may be used alone or in combination of two or more.

(B) The other monomer copolymerizable with a is
1,3-butadiene, 2-methyl-1,
Aliphatic conjugated diene monomers such as 3-butadiene, 2-chloro-1,3-butadiene and chloroprene; acrylic acids such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and 2-ethyl acrylate Esters, methacrylates such as ethyl methacrylate, butyl methacrylate, propyl methacrylate, 2-ethylhexyl methacrylate, and the hard component include methyl methacrylate and styrene, α-methylstyrene, 4-methylstyrene, and 4-ethyl Styrene, 4-
Other than aromatic styrene derivatives such as ethoxystyrene, 3,4-dimethylstyrene, 2-chloro-3-methylstyrene and 2,4 dichlorostyrene, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, and carboxylic acids Acrylamide, methacrylamide, N-methylolacrylamide, N-
Methylol methacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, glycidyl acrylate and the like. Depending on the quality of the coated paper, two or more kinds of (b) may be used alone. It may be used in combination.

In the present invention, it is essential to use lithium hydroxide as a pH adjuster. The pH adjustment with lithium hydroxide may be performed during or after the polymerization of the carboxy-modified latex. The pH of the carboxy-modified latex is adjusted to 5 to 10, preferably 6 to 9, and used in the coated paper composition. If the pH is less than 5, no satisfactory decrease in viscosity under high shear is observed, and if it exceeds 10, the wet pick strength of the coated paper is undesirably reduced.

The qualitative and quantitative determination of lithium hydroxide used for adjusting the pH of the carboxy-modified latex can be easily carried out by emission analysis or the like.

Next, the composition for coated paper of the present invention will be described. The carboxy-modified latex of the present invention contains an ethylenically unsaturated carboxylic acid monomer, except that it is produced using lithium hydroxide as a pH regulator. The polymerization method may be a seed polymerization method or a known emulsion polymerization method, and the present invention is not limited by the polymerization method. As the emulsifier at this time, a known anionic surfactant or nonionic surfactant alone or a mixture of two known surfactants is used. The polymerization initiator may be any of known hydrogen peroxide, ammonium peroxide, potassium peroxide, sodium peroxide, or a redox type, or may be a mixture of two or more. The method of adding the initiator is not particularly limited, and can be arbitrarily selected from methods such as initial batch addition, divided addition, and continuous addition. In addition, as various other additives conventionally used in emulsion polymerization, inorganic salts, chelating agents, chain transfer agents and the like can be optionally selected and used as needed.

The method of adding the monomer in the polymerization reaction is not particularly limited, and it may be carried out alone or in combination of batch addition, divided addition and continuous addition. The temperature is generally about 30 to 90 ° C., and preferably 50 to 90 ° C.
８０80 ° C. The particle size of the particles formed by the emulsion polymerization is not limited.

The pH is adjusted with lithium hydroxide at the beginning, during and / or after the polymerization.
Is 5-10.

The composition for coated paper using the carboxy-modified latex as a binder is used in combination with oxidized starch, enzymatic starch, esterified starch or the like as a binder. -), Calcium carbonate, titanium oxide, aluminum hydroxide, satin white, aene oxide, barium hydroxide, talc, and plastic pigment are used. As other auxiliaries,
A dispersing agent, a lubricant, an antifoaming agent, a preservative, a water-proofing agent, a bluing agent, a fluorescent dye, a pH adjuster, and the like are blended as required, and coated paper (for sheet offset printing, web offset) Printing, gravure printing, cast coated paper, coated paperboard)
Coated on.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0018]

【Example】

Example 1 Ion-exchanged water 3 was added to an autoclave equipped with a 100 L stirrer.
3.2 kg, 45 g of sodium lauryl sulfate, and 0.215 kg of carboxy-modified polystyrene latex (average particle diameter 50 NM, solid content concentration 28% by weight) were charged as seed particles, and the system was replaced with nitrogen.
The internal temperature was raised to 75 ° C. while stirring at 80 rpm, and (A) butadiene 11.
A mixed solution of 4 kg, 12.6 kg of styrene, 4.2 kg of methyl methacrylate, 1.5 kg of acrylonitrile, 240 g of tert-dodecyl mercaptan, (B) 3.78 kg of ion-exchanged water, and sodium lauryl sulfate 60
g, 300 g of sodium persulfate, and an initiator aqueous solution obtained by mixing and dissolving each over 7 hours.
The reaction was continued for 4 hours as residual monomer polymerization, and the reaction was terminated by cooling to room temperature. The polymerization conversion of the monomer, determined by the weight method, was 96%. Further, the remaining monomer in the copolymer latex was removed by steam distillation, and this copolymer latex was designated as latex A. Next, the pH was adjusted to 9 using lithium hydroxide to obtain the latex of the present invention.

Examples 2 to 4 and Comparative Examples 1 to 7 Latexes B, C and latex were prepared in the same manner as in Example 1 except that the monomers used and their proportions were changed as shown in Table 1.
D and E were obtained.

[0020]

[Table 1] Further, latexes B to E were pH-adjusted using the pH adjusters shown in Table 2 to obtain latexes of Examples 2 to 4 and Comparative Examples 1 to 7.

[0021]

[Table 2] * LiOH → lithium hydroxide NH ₄ OH → aqueous ammonia KOH → potassium hydroxide NaOH → sodium hydroxide Next, the composition for coated paper containing these latexes and the composition for coated paper are coated. The physical properties of the coated paper are exemplified.

Using Examples 1 to 4 and Comparative Examples 1 to 7, a composition for coated paper was prepared in the following manner by a conventional method.

[0023] Coating paper composition (color) compounded by weight (solid content) Primary Clay UW-90 30 Secondary Clay HT 20 Heavy Calcium Carbonate Cavital 90 50 Dispersant Aron T-400 .2 Oxidized starch cone base C3 latex 10, manufactured by Engelhard Co., Ltd. manufactured by Fuji Kaolin Co., Ltd. manufactured by Toa Gosei Chemical Co., Ltd. manufactured by Oji Constarch Co., Ltd. The pH was adjusted to 9.5 using aqueous sodium hydroxide solution. Then, water was added to adjust the solid concentration to 66% by weight.

The composition for coated paper thus obtained is coated on a high-quality paper by a blade-type continuous winding coating machine (manufactured by Nippon Seiki Co., Ltd.) so that the coating amount on one side is 16 g / m ^2. did. Coating speed: 10m / min, drying: hot air 150 ° C, 6 seconds, drum 95
C., 6 seconds. The coated paper was conditioned for 20 hours in a constant temperature and humidity room at a temperature of 20 ° C. and a humidity of 65 RH, and the temperature was adjusted to 60 ° C.
It was passed twice through a super calender under the conditions of a temperature of 120 ° C. and a linear pressure of 120 kg / cm to obtain a coated paper sample.

The physical properties of the coated paper composition and the coated paper sample were measured by the following methods, and the results are shown in Table 3 collectively.

(Physical Properties of Coated Paper) 1) Viscosity Using a Brookfield viscometer with a No. 4 rotor, 60
The viscosity at rpm was measured. 2) Viscosity at High Shear Force The viscosity was measured under the condition of 5 × 10 ⁶ 1 / S using a capillary viscometer (manufactured by Anton PAAR). 3) Mechanical stability The resulting aggregate was filtered through a 300-mesh wire gauze using a Maron tester, and the dry weight was calculated as a percentage by weight based on the solid content of the sample. (Measurement conditions were as follows: 100 g of a coated paper composition diluted to 50% was heated to 50 ° C., and the load was kept at 15 kg for 25 minutes while keeping the temperature constant.) (Coated paper properties) 4) Dry pick strength Using an RI printing suitability tester (manufactured by Akira Seisakusho), overprinting was performed with the test ink of the ink tack 20 until paper peeling occurred, and the degree of paper peeling was determined according to the following criteria.

◎ Very good ○ Good △ Normal × Poor 5) Wet pick strength First, using a RI printing suitability tester, apply dampening water with Molton Roll, and then use the test ink of Ink Tack 15 Solid printing was performed, and the degree of paper peeling was determined based on the same standard as the dry pick strength.

[0028]

[Table 3] As is clear from Table 3, the carboxy-modified latex of the present invention has a pH of 5 using lithium hydroxide as a pH adjuster.
The composition for coated paper containing a latex adjusted to 10 to 10 as a binder has a low viscosity under high shearing force, good mechanical stability, and a wet pick strength of coated paper physical properties. There is no decline. Comparative Example 1 as compared to Example 2
When the pH adjuster of No. 3 is used, the viscosity under a high shearing force of the coated paper composition is clearly high. When the pH of Comparative Example 4 is less than 5, that is, at 4, no decrease in viscosity under high shearing force is observed.
When the pH of Comparative Example 5 exceeds 10, ie, at 11, the viscosity under high shearing force is reduced, but the wet pick strength is reduced. When the amount of the ethylenically unsaturated carboxylic acid of Comparative Example 6 is less than 1% by weight, that is, 0.5% by weight, the mechanical stability decreases. If the amount of the ethylenically unsaturated carboxylic acid in Comparative Example 7 exceeds 10% by weight, that is, if the weight is 11% by weight, the viscosity of the composition for coated paper will increase and the wet pick strength of the coated paper will decrease. From these, it is apparent that the present invention is a useful and unprecedented composition for coated paper.

[0029]

As described above, in the composition for coated paper of the present invention, the pH of the emulsion polymerization reaction product of the limited monomer is adjusted to 5 to 10 using lithium hydroxide. By adding the composition to the composition, the viscosity and mechanical stability of the composition can be made suitable.

Continuation of the front page (56) References JP-A-48-34224 (JP, A) JP-A-49-41612 (JP, A) JP-A-3-227302 (JP, A) JP-A-4-327298 (JP) , A) JP-B-44-30739 (JP, B1) JP-B-45-18722 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (1)

(57) [Claims] (1) 1 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (b) a
90 to 99% by weight of an emulsion polymerization reaction product copolymerizable with another monomer, and having a pH of 5 using lithium hydroxide.
A composition for coated paper comprising a latex as a binder, the latex being adjusted to 10 to 10.