JPH0364597A - Coating composition for high rigidity coated paper - Google Patents

Abstract

PURPOSE:To obtain the title composition with high printing gloss, printability and mechanical strength by emulsion polymerization between an aromatic vinyl compound, conjugated diene, unsaturated carboxylic acid, etc., in the presence of a copolymer from an aromatic vinyl compound, vinyl cyanide, unsaturated carboxylic acid, conjugated diene, etc. CONSTITUTION:The objective composition can be obtained by emulsion polymerization of (A) 50-10wt.% of a monomer mixture of (1) 20-60wt.% of an aliphatic conjugated diolefin, (2) 35-79.5wt.% of an aromatic vinyl compound, (3) 0.5-5wt.% of an ethylene-based unsaturated carboxylic acid, and (4) 0-20wt.% of a comonomer in the presence of a copolymer 40-110 deg.C in glass transition point prepared by emulsion polymerization of (B) 50-90wt.% of another monomer mixture of (5) 65-98.5wt.% of an aromatic vinyl compound, (6) 1-30wt.% of a vinyl cyanide-based monomer, (7) 0.5-5wt.% of an ethylene-based unsaturated carboxylic acid, (8) 0-18wt.% of an aliphatic conjugated diene, and (9) 0-30wt.% of a comonomer. The present composition contains a synthetic copolymer latex having a minimum film-forming temperature of 30-90 deg.C and is used for coated paper to be put to hot calendering process at >=90 deg.C.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to coated paper obtained by applying a coating composition, drying it, and then heat-calendering the coating layer at a temperature of 90°C or higher. The present invention relates to a coating composition for high-stiffness coated paper that is suitably used.

More specifically, the present invention provides a coated paper for printing in publishing, advertising, packaging, etc. that has excellent stiffness (paper stiffness) even if the paper is thin, and at the same time exhibits excellent printing gloss, ink adhesion, and strength. The present invention relates to a coating composition for stiffness coated paper.

[Conventional technology]

In recent years, with the advancement of the information society, the demand for coated paper for printing has increased significantly, and the manufacturing methods and uses of the coated paper have become diverse. Therefore, there are many demands for improving the quality of coated paper for printing. For example, coated paper used for publishing, advertising, packaging, etc. is required to have a good texture, white paper gloss, and printing gloss due to the general public's preference for high-quality paper (2). Decreases the product value of paper, packaging paper, etc.

Furthermore, in industries such as publishing, paper is becoming lighter in weight in order to rationalize costs. Reducing the weight of coated paper causes the problem that the paper becomes thinner and its stiffness is extremely reduced. This decrease in paper stiffness has hindered workability such as automatic paper feeding in recent high-speed printing and paper alignment after printing.

Furthermore, in the paper manufacturing industry, paints are becoming more concentrated in order to improve productivity, rationalize costs, and improve quality of coated paper through high-speed coating. In order to increase the concentration of this paint, it is necessary to reduce casein and starch, which are water-soluble natural binders with low solubility, and to lower the molecular weight, taking into account the fluidity of the paint during high-speed coating. However, these reductions in natural binders also further reduce the stiffness of the coated paper.

On the other hand, for example, Japanese Patent Publication No. 46-6524 focused on pigments contained in water-based paints, and used styrene copolymer as a substitute for inorganic pigments with the aim of reducing the weight of coated paper (3) and improving white paper gloss. Discloses the use of coalescing latex. However, compared to inorganic pigments, styrenic copolymer latex used as organic pigments has a larger volume ratio, and thus has poorer adhesion to paper.

Furthermore, Japanese Patent Publication No. 7964/1983 discloses a method for producing high-gloss coated paper by using a polymer latex having a glass transition temperature of 38°C or higher and heating and calendering the paper to a temperature higher than the glass transition temperature. There is.

This is an effective means for developing white paper gloss, which is a characteristic of hard binders, by heat calendering.

However, compared to soft binders, hard binders have insufficient adhesion properties, so the amount of binder required is large, and ink adhesion is inferior due to heat calendering, and furthermore, the ink sets quickly. On the contrary, it has the disadvantage that printing gloss is not developed.

(4) Therefore, as a means to maintain adhesiveness and improve fluidity and stiffness, JP-A-59-179895 proposes the use of a mixture of two types of copolymer latex with different bottom film forming temperatures. ing.

By using a mixture of two different types of copolymer latex, it is possible to compensate for the shortcomings of each and improve the paper quality balance between adhesion and stiffness, but the balance between stiffness and ink adhesion is still insufficient. The reality is that satisfactory performance is not always achieved.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a coating composition for high-rigidity coated paper that simultaneously exhibits excellent printing gloss, ink adhesion, and strength compared to the coated printing papers described above.

[Means for solving problems]

In view of the current situation, in order to achieve the above object, the present inventors investigated the relationship between the treatment temperature in the heating calender treatment step (5) of coated paper and the copolymer latex used as a binder in the coating composition. As a result of careful attention and repeated studies, we have completed the present invention.

That is, the present invention provides a coating composition used for coated paper that is heated and calendered at a temperature of 90°C or higher, containing 65 to 98°5% by weight of an aromatic vinyl monomer and a vinyl cyanide monomer. 1 to 30% by weight, 0.5 to 5% by weight of ethylenically unsaturated carboxylic acid monomers, 0 to 18% by weight of aliphatic conjugated diene monomers, and 0 to 30% by weight of monomers copolymerizable with these. Monomer mixture (a) consisting of 50% to
In the presence of a copolymer (A) having a glass transition point of 40 to 110°C obtained by emulsion polymerization of 90% by weight, 20 to 60% by weight of an aliphatic conjugated diolefin monomer and an aromatic vinyl monomer. Monomer mixture (b) consisting of 35 to 795% by weight of a monomer, 0.5 to 5% by weight of an ethylenically unsaturated carboxylic acid monomer, and 0 to 20% by weight of a monomer copolymerizable with these monomers.
30 obtained by adding 50 to 10% by weight and emulsion polymerization
The present invention provides a coating composition for high-stiffness coated paper, characterized in that it contains (A) a synthetic copolymer latex having a minimum film-forming temperature of ~90°C.

The present invention will be explained in more detail below.

The glass transition point (Tl) of the copolymer (A) obtained by emulsion polymerization of the monomer mixture (a) used in the present invention is 40 to
It is in the range of 110°C. If the Tp is less than 40°C, the paper stiffness will be poor, and if it exceeds 110°C, the polymerization rate during polymerization will be slow, resulting in a decrease in productivity, which is not preferred.

The composition of the monomer mixture (a) is 65 to 985% by weight of aromatic vinyl monomers and 1 to 985% by weight of vinyl cyanide monomers.
30% by weight, ethylenically unsaturated carboxylic acid monomer 0.5
~5% by weight, aliphatic conjugated diene monomer 0-18% by weight
and 0 to 30% by weight of monomers copolymerizable with these.

If the aromatic vinyl monomer is outside this range, the balance between strength and white paper gloss will be poor, which is not preferable.

If the vinyl cyanide monomer is outside this range, the balance between printing gloss and ink adhesion will be poor, which is not preferred (7). The amount of ethylenically unsaturated carboxylic acid monomer is 0.
If it is less than 5% by weight, the strength will be poor, and if it exceeds 5% by weight, the 'PI! It is not a light that has a high degree of J and poor workability. If the content of the aliphatic conjugated diene monomer exceeds 15% by weight, the paper will have poor stiffness and is not preferred. If the copolymerizable monomer exceeds 30% by weight, the intended purpose cannot be achieved, which is not preferable.

Examples of the aromatic vinyl monomer constituting the monomer mixture (a) include styrene, α-methylstyrene, vinyltoluene, etc., and one or more of them can be used. As vinyl cyanide monomers, acrylonitrile,
Examples include methacrylate trile and the like, and one type or two or more types can be used.

Examples of the ethylenically unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, etc., and one type or two or more types can be used. Examples of aliphatic conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene, isoprene, chloroprene, etc., and one or more types can be used. (8) Polymerization Possible monomers include unsaturated carboxylic acid alkyl ester monomers such as methyl methacrylate, ethyl methacrylate, butyl acrylate, and ■-ethylhexyl acrylate; acrylamide, methacrylamide,
Examples include ethylenically unsaturated carboxylic acid amide r:lim forms such as N-methylolacrylamide; monomers containing a bitroxyalkyl group such as hydroxyethyl acrylate and hydroxypropyl acrylate, each of which may contain one or two types. The above can be used.

Monomer mixture emulsion polymerized in the presence of copolymer (2) (
The composition of b) is aliphatic conjugated diolefin monomer 20~
6ON amount%, aromatic vinyl monomer 35 to 79.5% by weight, ethylenically unsaturated carboxylic acid monomer 0.5 to 5% by weight, and monomer copolymerizable with these 0 to 20% by weight Consisting of

If the aliphatic conjugated diolefin monomer is outside this range, the balance between strength and paper stiffness will be poor, which is not preferable. If the aromatic vinyl monomer is outside this range, the balance between strength and white paper gloss will be poor, which is not preferable.

(9) If the content of the ethylenically unsaturated carboxylic acid monomer is less than 0.5% by weight, the strength will be poor, and if it exceeds 5% by weight, the viscosity of the composition will increase, resulting in poor workability, which is not preferable.

Moreover, if the copolymerizable monomer exceeds 20% by weight, the intended purpose cannot be achieved, which is not preferable.

The fatty conjugated diolefin monomer, aromatic vinyl monomer, and ethylenically unsaturated carboxylic acid monomer constituting the monomer mixture (b) include those mentioned above, and one type of each is used. Or two or more types can be used. Other copolymerizable monomers include the aforementioned vinyl cyanide monomers, unsaturated carboxylic acid alkyl ester monomers, ethylenically unsaturated carboxylic acid amide monomers, and hydroxyalkyl groups. Examples include monomers containing the following, and one type or two or more types of each can be used.

The synthetic copolymer latex of the present invention is a copolymer obtained by emulsion polymerizing the monomer mixture (a) described above (in the presence of A,
It is obtained by emulsion polymerization of monomer mixture (b), and the amount of monomer mixtures (a) and (b) used is 50 to 90 (10 )% by weight and 50-10% by weight. Monomer mixture (
If the proportion of a) is less than 50% by weight, paper stiffness decreases, and 9
If it exceeds 0% by weight, strength and print gloss will decrease, which is not preferable.

Furthermore, during emulsion polymerization, known chain transfer agents, emulsifiers, and various auxiliary agents can be used as appropriate before the start of polymerization.

Minimum film forming temperature (MF) of synthetic copolymer latex
T) is 30 to 90°C. If the MFT of the synthetic copolymer latex is less than 30°C, the paper stiffness and ink receptivity will be poor, and if it exceeds 90°C, the strength will decrease, which is undesirable.

In addition, the average particle diameter of the synthetic copolymer latex is 005~
03IL is preferable, and more preferably 0.05 to 0.15U in terms of paper stiffness and strength.

The synthetic copolymer latex of the present invention is usually prepared into a coating composition together with a pigment and applied to base paper, but in terms of solid content, it is 5 to 30 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the pigment. Used at 20 parts by weight. Further, other binders may be used as necessary, and the amount used is 0 to 8 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the pigment.
Used by weight. Further, the solid content concentration of the coating composition is adjusted to 45 to 70% by weight, preferably 50 to 65% by weight.

Examples of pigments include inorganic pigments such as kaolin clay, talc, barium sulfate, titanium oxide, carbonized calcium, aluminum hydroxide, and satin white, which may be used alone or in combination.

In addition, other binders include natural binders such as starch, oxidized starch, phosphate esterified starch, enzyme-modified starch, soybean protein, and casein, and synthetic binders such as polyvinyl alcohol, polyvinyl acetate latex, and acrylic latex. .

In order to prepare a paper coating composition containing the synthetic copolymer latex of the present invention, a dispersant, an antifoaming agent, a water resistant agent, a mold release agent, a water retention agent, a preservative, a fluorescent dye, etc. may be added as necessary. added.

The paper coating composition containing the synthetic copolymer latex of the present invention can be applied to base paper using known techniques, for example, using a coating machine such as an air knife coater, blade coater, or roll coater.

Furthermore, in order to exhibit the effects of the present invention, the coated paper must be
A process of treatment with a heating calendar of 0 or more is essential.

Conventionally, in order to improve the gloss of coated paper, the paper is passed between a steel roll under strong pressure through the roll nip of a supercalender device, etc., but normally this supercalender device has six or more multistage steel rolls. Using rolls, it is used at a relatively high nip pressure of around 200 kq/cyn and a relatively low temperature of around 70°C.

On the other hand, in the case of the heating calender treatment used in the present invention, for example, a gloss calender device or a soft calender device that can withstand high temperature conditions due to the recent development of materials for elastic rolls in place of cotton rolls is used. In this heating calender device used in the present invention, 90 k
It is used under high temperature conditions of 90'C or higher using 4 or less steel rolls at around 150 (13) °C at around q/cIn or around 200 kq/cm.

Thus, the coated paper that has been heated and calendered at 90°C or higher using the paper coating composition of the present invention has excellent paper stiffness even if the paper is thin, and has excellent strength, printing gloss, and ink receptivity. It is.

〔Example〕

The present invention will be specifically explained below with reference to Examples.
The present invention is not limited in any way by these Examples.

In addition, parts and % in Examples represent parts by weight and % by weight, respectively. In addition, measurements of various physical properties and preparation of coated paper in Examples were carried out by the following methods.

(Glass-transition temperature) Measured using a differential scanning calorimeter.

(Dry pick strength) Using an RI printing machine, printing was performed three times with sheet ink, and visual evaluation was performed based on the state of paper peeling at that time as follows.

(14) 10 (excellent) to 5.0 (poor) (wet pick strength) Using an RI printing machine, apply dampening water to coated paper and then print with sheet ink, and from the state of the paper at that time Visual evaluation was performed as follows.

1.0 (Excellent) - 5.0 (Poor) (Ink adhesion) Print using off-wheel ink with an RI printing machine and apply dampening water, and visually evaluate the ink adhesion condition as follows. went.

10 (excellent) to 50 (poor) (Print gloss) Measured with a gloss meter (incidence angle 60° C.) after printing twice using off-wheel ink using an RI printing machine.

(Paper stiffness) Measured using a Gurley style paper stiffness tester. (The larger the number, the better) Example-1 <Preparation of synthetic copolymer latex> 1.5 parts of sodium dodecylbenzenesulfonate in 100 parts of water
Add and dissolve. The first stage monomer mixture shown in Table 1 is added to this, and 02 parts of tertiary dodecyl mercaptan is further added to emulsify. Next, 05 parts of potassium persulfate was added, and the entire mixture was kept at 60°C for emulsion polymerization.

Polymerization was stopped when the polymerization conversion rate of monomer (i1) reached 97%. Unreacted monomers in the obtained latex were removed under reduced pressure.

Furthermore, after mixing the second-stage monomer mixture shown in Table 1 with the latex obtained by the first-stage polymerization, 01 part of tertiary dodecyl mercaptan and 05 parts of potassium persulfate were added, and the whole was heated to 60°C. Then, the second stage of emulsion polymerization was carried out. Polymerization was stopped when the polymerization conversion rate of the monomers reached 97%, and unreacted monomers were removed under reduced pressure to obtain a synthetic copolymer latex mead d.

<Preparation of coated paper> Using the obtained synthetic copolymer latex mee d,
After blending with pigments and auxiliary agents as shown in 2, a paper coating composition having a paint solid content concentration of 62% was prepared with pure water.

This composition was applied in a coating amount of 2 on base paper with a basis weight of 64 F/m''.
091m2, and heated this coated paper to 120℃.
The paper was dried at 140° C. and subjected to heating calender treatment at a linear pressure of 80 kq/mark to obtain coated papers ① to ②.

The performance of the obtained coated paper was evaluated and the results are shown in Table 3.

Table-2 Formulation of paper coating composition> Comparative example-1 Example-1 except that the monomer mixture shown in Table-1 was used
Perform the same operation as above to prepare a synthetic copolymer latte, a couscous e-h
I got it.

In addition, coated papers ① to ② were prepared in the same manner as in Example-1. The performance of the obtained coated paper was evaluated and the results are shown in Table 3.

(17) (18) (19) (20) Example - The same procedure as in Example 1 was carried out except that the monomer mixtures in the first and second stages were as follows. Polymer latex i was obtained.

1st row 2nd row Stitch 87 parts Stitch 62
Part acrylonitrile 10 parts Buta Diene
32 parts Acrylic acid Part I Methyl methacrylate 5 parts Fumaric acid 2 parts Acrylic acid 1 part Usage amount 70 parts Use!
80 parts T2 of copolymer 98°C MFT of the obtained synthetic copolymer latex 1 was 60°C. Thereafter, the same operations as in Example 1 were carried out to obtain coated paper (2). The performance of the obtained coated paper was evaluated and the results are presented.
4.

Comparative Example-2 5 parts of dodecylbenzenesulfonic acid Sogu was added to 100 parts of water and dissolved. This includes 79 parts of styrene and 9 parts of butadiene.
5 parts of acrylonitrile, 7 parts of methyl methacrylate, 1 part of acrylic acid, 1.5 parts of tuma(21) acid, and 0.0 parts of tertiary dodecyl mercaptan.
Add 2 parts and emulsify. Then potassium persulfate 0.5
The whole was kept at 60°C and emulsion polymerization was carried out. Polymerization was stopped when the monomer polymerization conversion rate reached 97%.

The unreacted LliQ form in the obtained latex was removed under reduced pressure to obtain a batch-polymerized synthetic copolymer latex j having an MFT of 68°C.

Thereafter, the same operation as in Example-1 was performed to obtain a coated paper [phase]. The performance of the obtained coated paper was evaluated and the results are shown in Table 4.

Comparative Example 3 A synthetic copolymer latex and 1 was obtained by carrying out the same operation as in Comparative Example 2 except that the monomer mixture was changed as follows.

(1) Steel 87 parts 66 parts Acrylonitrile 10 parts Butadiene 27 parts Methyl methacrylate 5 parts Hydroxyethyl acrylate 1 part Acrylic acid 0.5 parts 2 parts Fumaric acid
15 parts (22) of the obtained synthetic copolymer latex were mixed with 1 and 1 in a solid content ratio of 2/J=65/35. The MFT of the synthetic copolymer latex (mixture) was 84°C. Thereafter, coated paper 0 was obtained in the same manner as in Example-1. The performance of the obtained coated paper was evaluated and the results are shown in Table 4.

Table 4 <Effects of the invention> Coating in which a paper coating composition containing the synthetic copolymer latex obtained in the present invention was applied to base paper, dried, and heated and calendered at 9° 0 C or higher. Paper can exhibit paper stiffness, printing gloss, ink adhesion, and strength at the same time.

Therefore, even if the paper is thin, paper stiffness can be obtained, making it possible to manufacture coated paper, such as reducing starch and high-speed milling.
Workability during printing is improved, high-speed printing becomes possible, and the commercial value of the resulting printed coated paper is improved.

Claims (1)

[Claims] In the coating composition used for coated paper subjected to heat calendering at a temperature of 90°C or higher, 65 to 98.5% by weight of aromatic vinyl monomer, 1 part of vinyl cyanide monomer
~30% by weight, ethylenically unsaturated carboxylic acid monomer 0.
Emulsification of 50 to 90% by weight of a monomer mixture (a) consisting of 5 to 5% by weight, 0 to 18% by weight of an aliphatic conjugated diene monomer, and 0 to 30% by weight of a monomer copolymerizable with these. In the presence of a polymerized copolymer (A) having a glass transition point of 40 to 110°C, 20 to 60% by weight of an aliphatic conjugated diolefin monomer and 35 to 79% by weight of an aromatic vinyl monomer. ．．
5% by weight, ethylenically unsaturated carboxylic acid monomer 0.5~
A monomer mixture (b) consisting of 5% by weight and 0 to 20% by weight of a monomer copolymerizable with these and 50 to 10% by weight is added and emulsion polymerized to obtain a minimum film forming temperature of 30 to 90°C. A coating composition for high-stiffness coated paper, comprising a synthetic copolymer latex having the following properties.