JPH0284599A - Coating composition for paper - Google Patents

Abstract

PURPOSE:To obtain the title composition providing coated paper having excellent drying picking strength, wet picking strength and ink receiving properties, containing pigment, aqueous binder and a copolymer of (meth)acrylamide and acrylonitrile. CONSTITUTION:The aimed composition containing (A) pigment (e.g. kaolin or talc), (B) an aqueous binder (e.g., oxidized starch or PVA), (C) a copolymer comprising (i) 60-99wt.%, preferably 70-97wt.% acrylamide and/or methacylamide and (ii) 1-40wt.%, preferably 3-30wt.% acrylonitrile in the based resin) in the ratio of preferably 5-50 pts.wt. component B and 0.05-5 pt.wt. component C based on 100 pts.wt. component A. A copolymer of (meth)acrylamide and acrylonitrile further copolymerized with (iii) 1-80wt.% vinyl-based unsaturated carboxylic acid is preferable as the component C.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application Field The present invention relates to a paper coating composition that provides coated paper with excellent printability and printing effects.

<Conventional technology> Coated paper, which is obtained by applying a paper coating composition mainly consisting of pigments and an aqueous binder to paper and performing necessary processes such as drying and calendaring, has excellent printing effects. Due to its characteristics, it is widely used in commercial printed matter, magazines, books, etc., but as quality requirements become more sophisticated and diversified and printing speeds increase, efforts are still being made to improve its quality.

In particular, in wet lithographic offset printing, which accounts for the majority of printing, improved coated paper has improved ink receptivity under the influence of dampening water, adhesive strength for wet picks and dry picks, and blister resistance in rotary printing. Along with improving the basic properties of whiteness, opacity, and gloss, this has become an important issue for the industry.

Conventionally, efforts have been made to address these issues by improving the quality of pigment brands and their formulations, binders, especially SB latex, and melamine-formaldehyde resins and polyamide polyurea resins.
A known method is to try to solve the problem by adding a so-called waterproofing agent such as formaldehyde resin.

<Problems to be Solved by the Present Invention> However, while all of the methods for solving the problems described above are effective in improving characteristics, they are not always satisfactory because they have important practical drawbacks and limitations. For example, with pigments, satin white, which is used to improve gloss, whiteness, ink receptivity, etc., has difficulty obtaining adhesive strength, and when improving the quality of SB latex, it is difficult to obtain blister resistance. Improvement in one property often results in deterioration in other properties, such as an inverse correlation between dry pick strength and dry pick strength. Furthermore, the addition of a so-called water-resistant agent can improve the wet pick strength, and especially for polyamide polyurea-formaldehyde resins, it can further improve ink receptivity and blister resistance, but the dry pick strength may be improved in some cases. There was also a decrease to 0.

In view of these circumstances, the present inventors first incorporated a reaction product containing acrylamide or methacrylamide and styrene as essential components into a paper coating composition mainly consisting of a pigment and an -Y aqueous binder. (Japanese Unexamined Patent Publication No. 63-120194). Although this method has useful features such as improved adhesive strength and improved ink receptivity, it increases the viscosity of the paper coating composition and deteriorates the flow characteristics of the paper coating composition. There is,
This was an obstacle to its development.

In other words, an object of the present invention is to address such a situation by providing a paper coating composition containing a specific copolymer that exhibits no or significantly less deterioration in flow characteristics (increase in viscosity), and which The aim is to use technology to provide sexuality without inhibiting it.

<Means for Solving the Problem> The present inventors have conducted extensive research to find a food composition for paper that provides coated paper with excellent printability and printing effects and does not increase viscosity. This led to the invention.

The present invention comprises a pigment (1), an aqueous binder (1), (a)
Acrylamide or methacrylamide, 80-9
9%, (b) Acrylonitrile 1-40%, (
c) A paper coating composition characterized in that it contains a copolymer (1) consisting of a vinyl unsaturated carboxylic acid in an amount of 0 to 80]i.

The present invention is characterized by using the copolymer (1) described above, and by incorporating the copolymer (III) into a paper coating composition mainly consisting of a pigment and an aqueous binder, dry Big strength, wet pick strength,
Effective improvements such as ink receptivity can be achieved without increasing the viscosity of the coating composition, and S
Utilizing its adhesive strength, which is 2 to 8 times higher than that of B latex, it is possible to reduce the total amount of binder, thereby improving ink receptivity, whiteness, opacity, blister resistance, ink setting properties, etc. You can get even more.

The content of the present invention will be explained in further detail.

The copolymer (lll) used in the present invention is (a
) acrylamide or methacrylamide, (b)
Although it contains acrylonitrile as an essential component, the reaction composition ratio is (a) acrylamide or ij and methacrylamide, 60 to 99% by weight, preferably 70 to
97%, (b) Acrylonitrile, 1-40%
, preferably 3 to 80 u = /v, and (c) vinyl unsaturated carbon 0, which is optionally copolymerized, is
If these ranges are super round and are used in the copolymer at a proportion of 80% or less by market weight, it may not be possible to obtain improvements in dry wipe strength, wet wipe strength, ink receptivity, etc. The flow properties of the coating composition may be significantly deteriorated, or it may become difficult to obtain a reaction product in a form preferred for the purposes of the present invention. For example, if the amount of acrylonitrile exceeds 40M%, the reaction product may undergo two-layer separation, while if the amount of acrylonitrile is less than IN%, wet pick strength, ink receptivity, etc. will not be improved. I can't.

The vinyl unsaturated carboxylic acid (c) mentioned here is:
Examples include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, etc., and (c) vinyl unsaturated carboxylic acid in an amount of 1 to 80% by weight, preferably 1 to 20% by weight.
A copolymer copolymerized with (IID) provides more preferable drying properties for improving the fluidity of paper coating compositions.

As mentioned above, the copolymer used in the present invention consists of (a) acrylamide or methacrylamide, (b) acrylonitrile, and (c) vinyl-based unsaturated carboxylic acid if desired, but other copolymers can also be used as a copolymer as an aqueous solution. The copolymerizable monomer of the present invention can be copolymerized with monomers that can be copolymerized to obtain a polymer to the extent that the effects of the present invention are not impaired. It is obtained as an aqueous solution by
~20,0OOCI)S-preferably ioo~10,
000 cps range. If the viscosity is less than 5 Q CpS, dry pick strength and wet pick strength may not be obtained, and if the viscosity exceeds 20.000 cps, there may be problems such as deterioration of the flow characteristics of the paper coating composition, which is not preferable.

There are no particular restrictions on the production of the copolymer (D) of the present invention, but it is usually prepared, for example, by the following method.

However, of course, it may be manufactured by other methods. That is, the polymerization reaction is carried out using water as a medium. The total monomer concentration of monomer a) component and b) component, if desired, C) component, is preferably 10 to 50 M%,
The polymerization reaction is carried out at 25-45 M@%.

Although not necessarily limited, examples are usually round, hydrogen peroxide,
Peroxides such as tertiary-butyl hydroperoxide, ammonium persulfate, and potassium persulfate are suitable, and in some cases, a redox system of this and an amine or sulfite may be used.

The amount of polymerization initiator used is usually 0 peroxide per monomer.
．． It is desirable to use about 1 to 6.0% by weight. A chain transfer agent may be used if necessary during polymerization. Examples of the chain transfer agent include isopropyl alcohol, allyl alcohol, and various mercaptans. , polymerization at room temperature to 100°C, preferably 50 to 90°C,
It is carried out over a period of 0.5 to 15 hours, preferably 2 to 8 hours.

Pigments (I) in the present invention include white inorganic pigments such as kaolin, talc, calcium carbonate, satin white, aluminum hydroxide, and titanium oxide, as well as polystyrene resins, melamine-formaldehyde resins, and urea-based pigments.
White organic synthetic pigments made of formaldehyde resin or the like can be used alone or in combination of two or more.

(fi) Water-based binders in the present invention include water-soluble binders such as oxidized starch, phosphate esterified starch, polyvinyl alcohol, casein, carboxymethyl cellulose, and styrene-butadiene resins, vinyl acetate resins, and ethylene-vinyl acetate resins. , methylmethac JLz-tobutadiene-based VA, and water-emulsifying binders such as acrylic acid ester resins can be used alone or in combination of two or more.

The blending ratio of the paper coating composition of the present invention is generally (1)
(It) 5 to 50 parts by weight of aqueous binder to 100?1iIi parts of pigment, (1) 0.01 to 1 Ota of copolymer
parts, preferably 0.05 to 5 parts to 4 parts.

The copolymer used in the present invention is added to and mixed with a pigment slurry, an aqueous binder, etc. when preparing a paper coating composition. The effects of the present invention can also be obtained by adding and mixing them.

The paper coating composition of the present invention includes, as other components, a pigment dispersant, a preservative, an antifoaming agent, a viscous fluidity regulator, a water retention agent,
Various auxiliary agents such as lubricants, colorants such as dyes and colored pigments, waterproofing agents, and ink receptivity improvers can be blended.

The paper coating composition of the present invention is applied onto a paper substrate by a conventionally known method, such as a blade coater, an air knife coater, a roll coater, a metalling rod coater, a size press coater, or a cast coater.
Coated paper can be obtained by drying in a conventional manner and then subjecting it to supercalender treatment if necessary.

<Effects of the Invention> The coated paper thus obtained using the paper coating composition of the present invention has effective properties such as excellent dry pick strength, wet pink strength, and ink receptivity. be. Furthermore, the paper coating composition of the present invention does not cause handling problems due to increased viscosity. Note that in the present invention, 1-paper" has a broad meaning, and "paper J"paperboard" has a narrow meaning.
This includes:

<Examples> Hereinafter, the present invention will be explained in more detail with reference to Examples and Reference Examples. Note that both % and parts in the text mean weighted percentages and parts by weight.

4 cases = 1 Ammonium acid 851 was charged and the temperature was raised to 60°C while stirring. When the temperature reached 60°C, a mixed solution of 486 g of 50% aqueous acrylamide solution and 27 f of Ac30 nitrile was added dropwise from the dropping funnel over a period of 5 hours, kept at the same temperature for an additional 8 hours, and then cooled. Then, P with a caustic soda aqueous solution
HeJ[L, resin content aO%, PH=7. g viscosity 100
A copolymer of 0 cps/25°C was obtained.

The monomer compositions shown in Table 1 were synthesized in the same manner as in Reference Example 1, and the resulting copolymers were designated as Samples B and M. However, in Comparative Reference Example-4, a 50% acrylamide aqueous solution and styrene were separately dropped and reacted.

Table 1 summarizes the physical properties of the copolymers obtained in each reference example and comparative reference example.

Examples 1 to 9 Using the copolymers obtained in Reference Examples 1 to 9 (Samples A to 9), paper coating compositions having the formulations shown in Table 2 were prepared in a conventional manner.

Table 2 Note: Ultra White 90 (kaolin manufactured by Engel Hard Minerals, USA) ■Brilliant 15 (calcium carbonate manufactured by Shiraishi Kogyo Co., Ltd.) ■Violet Resin DS-10 (polyacrylic acid dispersant manufactured by Sumima Kagaku Kogyo Co., Ltd.) ■5N-807 (styrene-butadiene latex manufactured by Sumitomo Naugatac) ■1vis-4600 (modified starch manufactured by Nippon Shokuhin Kako Co., Ltd.) The paper coating composition is completely solidified using water and a 10% caustic soda aqueous solution. After adjusting the concentration to 60% and the pH to about 9.0, it was coated on one side using a wire rod on a 55 f/m''' high-quality paper so that the coating amount was about 15 y/-. Immediately after coating, dry with hot air at 120"C for 80 seconds, then condition the humidity at 20°C and 165% RH for 24 hours, and then apply by passing the paper through a super calendar twice at 60°C and 160Kq/cm. Obtained paper.

The coated paper thus obtained was heated at 24° C. and 65% RH.
After conditioning the humidity for a period of time, it was subjected to measurement tests for dry pick strength, wet pick strength, ink receptivity, whiteness, and opacity. The test results are shown in Examples 1 to 9 in Table 8.

The measurement test method is as follows.

■Wet pink strength Using tack grade ink (TV=15), print after moistening the coated surface with a water supply roll using an RI tester, and determine the wet pick strength by observing the state of missing coating. did.

(Excellent) 5 to 1 (Poor) ■ Dry pick strength Using tack grade ink (TV = 15), perform overprinting several times with an RI tester, observe the state of missing bond layers, and check the dry pick strength. I judged it.

(trowel) 5 to 1 (poor) ■Ink receptivity (method A) Using an R-work tester, measure the coated surface with a water supply roll by m tW.
After printing, the ink receptivity was observed and determined.

(Excellent) 5 to 1 (Poor) (Method B) R [Trial 1 [1 was used to print while kneading water into the ink, and the acceptability of the ink was observed and judged.

(Poor) 5-1 (poor) ■Whiteness Compliant with JIS P-8128 Hunter whiteness test method for paper and pulp.

[F] Opacity Compliant with method A of JIS P-8188 paper opacity test method.

■PH Compliant with JIS, Z-8802-7.

■Viscosity Compliant with JISK-6888-6,8.

Comparative Example-1, 8, 4 Copolymer obtained in Comparative Reference Example 1.3.4 (Samples J, L
, M) was used, a paper coating composition was prepared in the same manner as in Examples 1 to 9, and a coated paper was obtained and subjected to a measurement test.

The test results are shown in Comparative Example 1.8.4 in Table 8.

Comparative Example-5 A paper coating composition was prepared in the same manner as in Example 1-9 without using the copolymer, and coated paper was obtained, which was subjected to a measurement test.

The test results are shown in Comparative Example 5 in Table-8.

Comparative Example-6 A paper coating composition was prepared in the same manner as in Examples 1 to 9, except that 12 parts of the aqueous binder SN-807 was blended and no copolymer was used, and coated paper was obtained and measured. Tested.

The test results are shown in Comparative Example 6 in Table-8.

rl’ノ, lower metal mortar)

Claims (2)

[Claims] (1) Pigment (I), aqueous binder (II) and (a
) Acrylamide or/and methacrylamide 60~
99% by weight, and (b) a copolymer (III) consisting of 1 to 40% by weight of acrylonitrile. (2) Pigment (I), aqueous binder (II) and (a
) Acrylamide or/and methacrylamide 60~
98% by weight (b) Acrylonitrile 1-40% by weight (c
) A paper coating composition comprising a copolymer (III) comprising 1 to 30% by weight of a vinyl unsaturated carboxylic acid.