JPS60162898A - Paper coating composition - 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 relates to a paper coating composition that contains an alkali-sensitive copolymer latex as a binder and provides coated paper with extremely excellent ink gloss.

As binders for paper coating compositions, water-soluble natural polymers such as starch, casei/CMC, and synthetic styrene-butadiene copolymer latex have generally been used in combination. The biggest drawback when conventional polymer latex is used alone as a binder for pigment-coated paper is that it does not provide sufficient viscosity and water retention when applied to paper, resulting in uneven coating, streaks, etc. This means that it is likely to occur,
In order to overcome these drawbacks, water-soluble natural polymers such as casein, starch, and CMC are used in combination with polymer latex.

However, these natural polymers require labor and effort to prepare for dissolution.
It has drawbacks such as being time consuming, difficult to automatically prepare the color, and easily perishable. In order to overcome these drawbacks and provide the necessary viscosity and water retention during coating, so-called alkali-sensitive polymer latex, which is a polymer latex with alkali sensitivity, is used alone (usually called sole binder latex). ) have been considered.

The present invention exhibits optimal viscosity during coating using an alkali-sensitive copolymer latex as a binder, and provides paper coating with excellent printability, especially ink gloss, compared to when conventional polymer latex is used as a binder. The present invention provides a composition for application.

That is, the object of the present invention is to produce a mixture of 10 to 50% by weight of ethylenically unsaturated acid monomers, 10 to 80% by weight of ethylenically unsaturated cargonic acid ester monomers, and 5 to 50% by weight of lower fatty acid vinyl monomers. In the presence of copolymer latex (a) obtained by emulsion polymerization of 2 to 20 parts by weight of a monomer mixture consisting of 20 to 60 parts by weight of a conjugated diolefin monomer,
10 to 50% by weight of aromatic vinyl monomer, 5 to 30% by weight of ethylenically unsaturated acid ester monomer, 0.5 to 6% by weight of ethylenically unsaturated acid monomer, and vinyl cyanide monomer This is achieved by including as a binder in the paper coating composition an alkali-sensitive latex consisting of a monomer mixture (b) consisting of 5 to 35% by weight.

Among the monomer mixtures used in the production of the copolymer latex of the present invention, the ethylenically unsaturated acid type which is a constituent component of the copolymer latex U) is acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. acid, unsaturated carboxylic acids such as itaconic acid and crotonic acid; monoesters of unsaturated nocarboxylic acids such as itaconic acid monoethyl ester and maleic acid monobutyl ester; sulfonityl N acrylate
a1JN, the use of acids is preferred. The proportion of these used is based on the total weight of the monomer mixture used in the polymerization of copolymer latex (a) (the same applies hereinafter), and is 10 to 50.
Used within the range of % by weight. If it is less than 1% by weight, the alkali sensitivity is insufficient, and an appropriate viscosity cannot be obtained.
Also, water retention is insufficient. If it exceeds 50%, the alkali sensitivity will be excessive and the viscosity will be higher than the practical range, making handling difficult. It is preferably used in an amount of 10 to 35% by weight.

On the other hand, examples of ethylenically unsaturated carboxylic acid esters include methyl acrylate, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, and diacrylic acid.
- Ethylhexyl, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, etc. are used. The usage ratio of these is 10-8
It is used within the range of 0% by weight. If this amount is less than 10% by weight, the stability of the latex will be poor, and if it exceeds 80% by weight, adhesive strength and water resistance will decrease, and appropriate alkali sensitivity will not be obtained. It is preferably used in an amount of 25 to 65% by weight.

Further, as the lower fatty acid vinyl, vinyl acetate, vinyl propionate, vinyl dithylate, vinyl 2-ethylhexanoate, etc. can be used, but vinyl acetate and vinyl propionate are preferable. Usage ratio is 5 to 50 weight:
Il: pH is in the range of 7.5 to less than 5% by weight.
In the range of 13.0, rapid alkali thickening cannot be obtained, and if it exceeds 50 wt/f1%, the water resistance of the coated paper is significantly reduced. Preferably it is in the range of 10 to 40% by weight.

In addition, the conjugated diolefin monomers that are components of the monomer mixture (b) polymerized in the presence of the copolymer latex (a) in the second stage include 1,3-butadiene, 2-methyl- 1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, etc. are used. The proportion of these used is in the range of 20 to 60% by weight (the same applies hereinafter) based on the total weight of the monomer mixture (b).

If this amount is less than 20% by weight, the copolymer will become too hard;
Pigment binding strength decreases. Moreover, when it exceeds 60% by weight, water resistance decreases. It is preferably used in a range of 30 to 55 weight. In addition, aromatic vinyl monomers include styrene, α-methylstyrene, monochlorostyrene,
Vinyltoluene etc. are used.

These monomers are used in an amount of 10 to 50% by weight. When this amount is less than 10% by weight, water resistance decreases, and when it exceeds 50% by weight, pigment binding strength decreases. Preferably it is 25 to 40% by weight.

Further, as the ethylenically unsaturated acid monomer, the same monomers as mentioned above can be used, and if the amount of these monomers exceeds 0.510% by weight, preferred alkali sensitivity cannot be obtained.

Preferably it is 1 to 5% by weight. Further, as the ethylenically unsaturated carboxylic acid ester monomer, the same monomers as mentioned above can be used, and these monomers are used in a range of 5 to 30% by weight. If this amount is less than 5 M*%, the pigment binding strength will be reduced, and if it exceeds 30% by weight, the water resistance and printing gloss of the coated paper will be reduced. It is preferably used in an amount of 10 to 25% by weight.

Further, as the vinyl cyanide monomer, aliphatic unsaturated nitriles such as acrylonitrile, α-chloroacrylonitrile, methacrylonitrile, and α-ethyl acrylonitrile are used, and acrylonitrile is preferably used.

It gets noticeably worse. Preferably it is in the range of 5 to 25% by weight.

Further, if desired, other copolymerizable monomers may be used within a range of 20% by weight or less. Examples of copolymerizable monomers include acrylamide, methacrylamide, N-methylolacrylamide, acrolein, allyl alcohol, glycidyl acrylate, and vinylidene chloride.

The alkali-sensitive copolymer latex of the present invention is prepared by adding 80 to 98 parts by weight of the above monomer mixture (B) in the presence of 2 to 201 ft parts (solid content) of the above copolymer latex (A). obtained by emulsion polymerization. If the amount of copolymer latex (a) used is less than 2 parts by weight, the copolymer latex has insufficient thickening properties for PI-1. Moreover, if it exceeds 20 parts by weight, the alkali sensitivity is excessively lost and the viscosity increases significantly, making it difficult to handle and impractical.

The alkali-sensitive copolymer latex of the present invention can be produced by a known emulsion polymerization method except for the step of polymerizing the monomer mixture (b) in the presence of the copolymer latex (c). can. Copolymer latex (a) can be obtained by emulsion polymerization according to a known method. For example, the monomer mixture constituting the copolymer latex (a) is polymerized in the presence of water, an emulsifier, a polymerization initiator, a chain transfer agent, etc. by a polymerization method such as a patch method or a semi-continuous method. You can get it.

Moreover, the monomer mixture (b) can also be emulsion polymerized according to a known method. That is, copolymer latex (
A) is used as a seed particle to perform so-called seed polymerization. For example, seed particles [copolymer latex (a)]
, water, an emulsifier, a polymerization initiator, a chain transfer agent, etc., the monomer mixture (b) can be polymerized by a patch method, a semi-continuous method, etc.@The paper coating composition of the present invention The pigments used in the product are mineral pigments commonly used for paper coating, such as clay, calcium carbonate, aluminum hydroxide, titanium white, barium sulfate, satin white, and talc, and polystyrene as necessary. , organic pigments such as phenolic resins, and auxiliary additives such as pigment dispersants, water retention agents, water-resistant agents, dyes, fluorescent dyes, lubricants, PH regulators, antifoaming agents, and surfactants, and sodium oxide, water. It is necessary to adjust the PII to 7.5 to 13.0 using an alkaline substance such as potassium oxide.

Further, the components in the present invention can be mixed using a common mixing device.

The paper coating composition of the present invention prepared in this way is
High-quality base paper (e.g. offset or Grapure printing paper, paperboard, etc.) in the same way as for normal coated paper production.
It is possible to produce coated paper with excellent printability, especially in printing resistance.

Note that the composition of the present invention does not require the use of natural water-soluble polymer substances (natural binders) such as starch;
It is permissible to use these together if necessary.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples. Note that all parts and numbers in the examples represent parts by weight and % by weight.

Example 1 A monomer emulsion (4) was prepared by charging the following composition into a tank equipped with a stirrer.

Water 20 parts Sodium lauryl sulfate 02 parts Sodium bicarbonate 0.1 Acrylic acid 2 Methyl methacrylate 5 Vinyl acetate 3 In addition, prepare a monomer emulsion (B) by charging the following composition into a tank equipped with a separate stirrer. did.

Water 60 parts Sodium lauryl sulfate 0.2 parts Sodium bicarbonate 0.4 tt Butadiene 38 〃 Styrene 30〃 Acrylic acid 2 〃 Methyl methacrylate 15 〃 Acrylonitrile 15 〃 Carbon tetrachloride 3 〃 40 parts of water in a pressure-resistant polymerization vessel equipped with a dropping device and a stirrer, 0.1 part of sodium lauryl sulfate and 0.05 part of sodium ethylenediaminetetraacetate were charged, and the mixture was purged with nitrogen and then heated to 70°C. 011 parts of potassium persulfate was added to this, and then the monomer emulsion (4) was continuously fed over 4 hours.

During this time, the polymerization vessel was maintained at 70°C, and the temperature was maintained at 70°C for an additional 3 hours. Next, 0.5 parts of potassium persulfate was added together with 15 parts of water, followed by 5 parts of the monomer emulsion (B).
It was sent continuously over time. During this time, the autoclave was kept at 70°C, and the temperature was maintained at 70°C for an additional 3 hours. In this way, a copolymer carcinol having an average particle size of 1600X, a pH of 3.6, and a conversion rate of 99.0% was obtained.

Examples 2 to 4 Polymerization was carried out under exactly the same conditions except that the monomer compositions of monomer emulsions (4) and (B) in Example 1 were changed to those shown in Table 1. Copolymer latexes 2 to 4 were obtained.

Comparative Examples 1 to 4 Monomer emulsion in Example 1 (A), (B
) Copolymer latexes a to d were obtained by polymerizing under exactly the same conditions except that the monomer composition of (1) was changed to that shown in Table 1.

A paper coating composition with a solid content of 60% by weight was prepared using the latex of each Example and Comparative Example obtained as described above according to the formulations shown in Table 2, and the composition was adjusted to 90% with sodium hydroxide. ．．
Adjusted to 0.

Table 2 (Note) (+) ENGELHARD MI RAL
& CHEMICALS (USA) product UW-90 (2) Shiraishi Kogyo product pz (5) Takuyasei Co. product Aron T-40 The paper coating composition thus obtained was coated on one side on coated base paper. The coating amount was 159/m2), and the resulting coated paper was heated at 120°C for 30 minutes.
Dry for 0 seconds, then dry at 60°C, 100 kg, 7 cm for 2
After calendering, the temperature-controlled room (20°C, 6°C) was prepared.
54RH) for one day and night.

The physical properties of the coated paper thus obtained and the physical properties of the coating liquid were measured. The results are shown in Table 3. The following methods were used to measure each physical property.

(1) PF (measured with a knee meter (25°C)) (2)
Viscosity: Measured with BL type viscometer (60 rpm) (3)
Using a drybic = RI type printing tester (manufactured by Akashi Seisakusho), overprinting was performed four times using offset ink, and the degree of paper peeling was judged with the naked eye. →Evaluated as 1 (poor)).

(Using a Sotsu EtHick 2 RI type printing tester, water was applied onto the test piece using a Molton roll, and then the test piece was printed with offset ink, and the degree of peeling of the pigment was judged with the naked eye.

Evaluation using a 5-point system.

(5) Printing gloss: Using a gravure printing aptitude tester (Ministry of Finance Printing Bureau type), measure the 75°-75° reflectance of the portion printed with gravure ink with a gloss meter.

(6) Gravure suitability: Using a gravure printing suitability tester, judge the plate reproducibility of the printed test piece with the naked eye ◎ Excellent O Good × Poor

Claims (2)

[Claims] (1) In a paper coating composition consisting of an aqueous dispersion containing a pigment and a binder as main components, 10 to 50% by weight of an ethylenically unsaturated acid monomer and 10% by weight of an ethylenically unsaturated carpic acid ester monomer. Conjugated diolefin in the presence of a copolymer latex ff) obtained by emulsion polymerization of 2 to 20 parts by weight of a monomer mixture consisting of ~80% by weight and 5 to 50% by weight of a lower fatty acid primary vinyl monomer. Monomer 20-60% by weight,
10 to 50% by weight of aromatic vinyl monomer, 5 to 30% by weight of ethylenically unsaturated carboxylic acid ester monomer, 0.5 to 6% by weight of ethylenically unsaturated acid monomer, and vinyl cyanide. Monomer mixture (b) 8 consisting of 5 to 35% by weight of monomers
1. A paper coating composition comprising, as a binder, an alkali-sensitive copolymer latex obtained by emulsion polymerization of 0 to 98 parts by weight. (2) The paper coating composition according to claim (1), wherein the composition is made of silk having a diameter of 7.5 to 13.0.