JPS6163795A - 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 [Field of Industrial Application] The present invention relates to an improved paper coating composition, and more particularly, to improved operability when coating using a roll coater such as a Hasais Gres coater or a Gutro roll coater. The present invention relates to a paper coating composition suitable for use in a roll coater, which has extremely good properties and excellent quality for paper coating.

[Prior art]

Conventionally, aqueous dispersion compositions consisting of pigments, fillers, dispersants and binders have been widely used as paper coating compositions.

In recent years, on-machine roll coaters such as size press coaters and roll coaters have been used to improve the printing suitability of high-quality paper and medium-quality paper! A method of coating both sides of paper with a light weight of 1 to 15 mm and 2 mm has been implemented with high productivity without major modification of equipment.

These coating methods differ from other blade coaters, air knife coaters, etc. in that the coating is applied by pressing the paint onto the paper from both sides of the roll, so a large shearing force is applied during coating, making it difficult to inoculate during operation and due to the quality of the paper. A problem occurs. The following properties are required for roll coater paper coating compositions such as size press coaters and Gutro roll coaters.

Good mechanical stability: These roll coaters apply a high mechanical shearing force to the coating solution during coating, resulting in problems such as gum-up and roll staining during operation.

For this reason, it is necessary that the paper coating composition has good mechanical stability and tearability.

(2) Provide good leveling properties with good fluidity: In the case of size press coater, f-) roll coater,
A matte finish characteristic of roll coaters tends to occur, making it difficult to obtain a smooth coated surface. Therefore, the paper coating composition must have the ability to provide good fluidity and leveling properties.

(3) Good strength (adhesive strength and water resistance): In the case of size press coater, f-) roll coater,
Due to the high shear force applied compared to other coating methods and the low concentration of the paper coating liquid in the case of size press coaters, the pigment binder migrates into the paper substrate layer. This results in a decrease in adhesive strength and water resistance. To improve this, it is necessary to use a large amount of binder, but if a pigment binder with excellent strength is used, the amount used can be reduced.

(4) Good coverage of the coated surface: When using the roll coater mentioned above for light coating, the amount of coating is small, so it is difficult to form a dense coated surface as in the case of blade coating. Because it is brittle, the printing gloss is not good. Therefore, the paper coating composition must have the ability to provide a coated surface with good surface coverage, high air permeability, and low ink permeability.

[Problem that the invention seeks to solve]

Pigment binders in the paper coating composition include natural binders such as starch and modified starch; styrene/-butadiene copolymer latex, carboxy-modified styrene-butadiene copolymer latex, and polyvinyl acetate emulsion. , acrylic ester type (co)! Synthetic binders such as combined latex, methacrylic acid ester (co)polymer latex, polychlorogrene latex, and polyvinyl alcohol are used. However, in the case of lightweight coating, when the above-mentioned binder is used as a binder in a paper coating composition, there is a problem that mechanical stability, fluidity, and paper surface strength are poor, and it is difficult to form a dense coated surface.

An object of the present invention is to provide a paper coating composition "f" which has good mechanical stability, fluidity, adhesive strength, and water resistance, and which imparts excellent gloss to the coated surface.

[Means for solving problems]

The paper coating composition of the present invention contains, based on 100 parts by weight of the pigment, 5 to 40% by weight of ethylenically unsaturated caldicic acid, 5 to 40% by weight of aliphatic conjugated caldic acid, and ethylenically unsaturated caldic acid alkyl ester. A monomer mixture consisting of 10 to 50% by weight and 10 to 70% by weight of an alkenyl aromatic compound (
(ii) in the presence of the obtained copolymer latex, 20 to 70% by weight of aliphatic conjugated diene, 30 to 80% by weight of alkenyl aromatic compound and ethylenically unsaturated Monomer mixture (0)63 consisting of 0 to 50% by weight of one or more monomers selected from carboxylic acid alkyl ester and vinyl cyanide
(iiD) After the start of the polymerization of the monomer mixture of (ii) above and before the polymerization is substantially completed, 1.5 to 6 parts by weight of the unsaturated amide (c) is added and polymerized. Weight parts are (a), (b),
A copolymer latex obtained by adding and polymerizing (c) to a total of 100 parts by weight, which has an average particle diameter of 0.06 to 0.35 μm and a toluene insoluble content of 55 to 55 μm.
It is characterized by containing 10 to 35 parts by weight of a copolymer latex having a weight of 98% by weight as the pigment binder.

Note that the toluene-insoluble content herein refers to the toluene-insoluble content contained in the copolymer expressed as a weight percentage with respect to the total copolymer, and the method for measuring it is as described in the Examples.

Examples of pigments used in the present invention include clay, barium sulfate, titanium oxide, satin white, aluminum hydroxide, and calcium carbonate.

Ethylenically unsaturated carbon in the monomer polymerized in the first step of the present invention? Examples of the acid include acrylic acid, methacrylic acid, heptamalic acid, maleic acid, and itaconic acid. These may be used alone or in combination of two or more. Ethylenically unsaturated carboxylic acid is used in a range of 5 to 40% by weight, but if it is less than 5% by weight, the adhesive strength and stability of the latex will decrease, and if it exceeds 40% by weight, the viscosity of the latex will decrease. is too high, which is unfavorable from the viewpoint of coating properties and handling.

Examples of aliphatic conjugated diene monomers include 1,3-butadiene, isoprene, 2-methyl-1,3-butanoene, and 2-chloro-1,3-butadiene.

Aliphatic conjugated dienes are used in amounts of 5 to 40, but
If it is less than 40% by weight, the adhesive strength decreases, and if it exceeds 40% by weight, the adhesive strength and water resistance decrease.

Examples of ethylenically unsaturated carboxylic acid alkyl esters include methyl acrylate, methyl methacrylate,
Ethyl acrylate, ethyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, glycitul methacrylate, trimethyl fumarate, diethyl fumarate, trimethyl maleate, diethyl maleate,
Examples include dimethyl itaconate, monomethyl fumarate, and monoethyl fumarate. Ethylenically unsaturated carboxylic acid alkyl ester is used in an amount of 10 to 50% by weight, but if it is less than 10% by weight, the light resistance of the coated paper using the obtained copolymer latex will decrease, and if it exceeds 50% by weight, Adhesive strength and water resistance decrease.

Examples of alkenyl aromatic compounds include styrene, alpha methylstyrene, and vinyltoluene. The alkenyl aromatic compound is used in an amount of 10 to 70% by weight, but if it is less than 10% by weight, adhesive strength and water resistance decrease. If it exceeds 70% by weight, the adhesive strength decreases.

The monomer mixture (a) used in the first stage polymerization is 5-
If the amount is less than 5 parts by weight (35 parts by weight), the stability of the latex will decrease. Also 35. If the amount exceeds 1 part by weight, the water resistance of the coated paper using the obtained copolymer latex will decrease.

Of the monomers that are then polymerized in the second step, aliphatic conjugated tsene is used in an amount of 20 to 70% by weight, but if it is less than 20% by weight, the adhesive strength decreases, and if it exceeds 70% by weight, the adhesive strength and water resistance decrease. . Alkenyl aromatic compounds are 30-8
Although it is used at 0% by weight, if it is less than 30% by weight, the adhesive strength is
Water resistance decreases. If it exceeds 80 weights, the adhesive strength will decrease.

Here, one or more monomers selected from ethylenically unsaturated carenoic acid esters and vinyl cyanides such as acrylonitrile are copolymerized in an amount of 50% by weight or less, preferably 30% by weight or less, to improve adhesive strength. Although it is possible,
It is preferable not to use it when water resistance is particularly required.

The monomer mixture (b) used in the second stage is 63-94
It is used in parts by weight, but if it is less than 63 parts by weight, the stability of lattes and cookies will be reduced, and if it exceeds 94 parts by weight, the water resistance of coated paper using the obtained copolymer latex will be reduced.

Furthermore, after the start of polymerization of the monomer mixture and while the polymerization is not substantially completed (in the range of 5 to 95% in terms of polymerization conversion, preferably in the range of 10 to 70%), unsaturated acid amide 1
．． Polymerization is carried out by adding 5 to 6 parts by weight. Examples of the unsaturated acid amide include acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-butoxymethylacrylamide, and the like.

The amount of unsaturated acid amide used is 1.5 to 6 parts by weight, preferably 2 to 5 parts by weight, but if it is less than 1.5 parts by weight, the stability of the latex will decrease, and if it exceeds 6 parts by weight, the viscosity of the latex will increase. It's too cool. Further, the unsaturated acid amide may be added to the polymerization reaction system simultaneously with or without mixing with the aliphatic conjugated tsene and alkenyl aromatic compound used in the second stage polymerization. Further, the unsaturated acid amide preferably has a polymerization conversion rate of about 9 before the second stage polymerization is substantially completed.
It may be added to the polymerization reaction system all at once, in portions, or continuously before reaching 5 ml. If added after the completion of the second stage polymerization, the viscosity of the latex will increase and the water resistance and ink receptivity of the coated paper will deteriorate.

In the method for producing a copolymer latex of the present invention, the first and second stages are carried out by known bulk, divided, or continuous addition polymerization methods. Also, during polymerization, known emulsifiers,
A polymerization initiator, a chain transfer agent, etc. are used. The degree of polymerization is usually 5 to 95°C, preferably 50 to 80°C.

When the copolymer latex of the present invention has an average particle diameter in the range of 0.06 to 0.35μ, preferably 0.1 to 0.3μ, when used as a pigment binder in a paper coating composition for roll coaters. Excellent performance can be obtained in terms of , mechanical stability, fluidity 1, leveling property, etc. The average particle diameter is 0.
If it is less than 0.06μ, a satin pattern will occur and the ink drying properties will be reduced, and if it exceeds 0.35μ, the fluidity will be reduced and the adhesive strength of the coated paper will be reduced.

In the present invention, the toluene insoluble content ranges from 55 to 98%, preferably from 60 to 95%, to provide good mechanical stability and adhesive strength when used as a paper coating for roll coaters or as a pigment binder in compositions. Excellent coated paper can be obtained. If the toluene insoluble content is less than 55%, the adhesive strength and mechanical stability of the paper coating composition will decrease. On the other hand, if the toluene insoluble content exceeds 98%, adhesive strength and water resistance will decrease.

The preferred amount of the copolymer latex of the present invention varies depending on the coating method of the roll coater.

For example, in the case of a size press coater, 10 to 35 parts by weight per 100 parts by weight of pigment. - In the case of a troll coater, it is preferable to use 10 to 25 parts by weight per 100 parts by weight of pigment. In addition to the copolymer latex, there are other water-soluble binders such as starch, oxidized starch, /Ij hynyl alcohol, etc., and one or more water-soluble binders selected from these are coated with the copolymer latex on paper. They can also be blended into one composition. The amount of water-soluble binder used is preferably 10 to 30 parts by weight in the case of a size press coater, and 5 to 20 parts by weight in the case of a dirt roll coater. The test method in Examples is as follows.

(1) Method for measuring viscosity of paper coating composition: Viscosity is expressed as viscosity at 25° C. and 60 rpm using a BM type viscometer.

(2) Appearance of high-speed flowability Viscosity measurement method: Using a Vercules high shear viscometer manufactured by Kumagaya Riki Kogyo, the rotation speed was 880.
e measured under 0 rpm, &B F, torque range 20 conditions
Tmax (dyne - cm) is calculated using the following formula using f.

It is an indicator of coatability in high-speed coating, and the higher the value, the poorer the coatability.

(3) Measuring method for gum-up test: This is an indicator of roll staining property.The coating solution is kneaded with a rubber roll using a Muag tester manufactured by Kumagaya Riki, and then mechanically sheared and rolled on a 9-m roll. Time until formation of clot on top (minutes)
Measure. The longer the time, the better.

(4) Mechanical stability measurement method Using a two-mercan stability tester, the number of rotations was 1100 Orp,
The amount of aggregates generated under the conditions of pressure 1 (1?), time 10 minutes, and coating liquid temperature of 70°C is expressed as a dry weight ratio. The smaller the value, the better.

(5) Method for measuring satin pattern: After applying the coating solution to the entire paper substrate using a test size press coater manufactured by Kumagaya Riki, apply carbon powder to the coated surface and observe the condition of the coated surface. .

○ (good): Δ (slightly satin pattern occurs); × (slightly satin pattern occurs) (6) Coating and finishing method: ■For size press formulation, use Kumagaya Riki's test size press coater to coat the coating solution. is applied to a paper substrate to obtain coated paper.

Next, the coated paper was dried using a hot air dryer at a temperature of 120°C for 30 seconds, and then dried using a sous-calender at a roll temperature of 70°C, a rotation speed of 45 Orpm, and a linear pressure cuff of 0'.
q/cm, and finishing was performed by passing the paper twice.

(2) In the case of Gutrol formulation, the coating liquid is applied to the paper substrate using the coating rod 4 to obtain coated paper. The drying conditions and super calender conditions below are the same as those for size breath formulation.
~ α Additional tests were conducted. (7) R1 dry strength test: Mei Seisakusho R1-1 is an indicator of the adhesive strength of coated paper.
Printing was performed using Toyo Ink SMX TV = 15 ink using a die printing machine. Coated paper adhesive strength was evaluated using the following evaluation criteria.

○ (Good) No picking occurred Δ (Slightly poor) A small amount of picking occurred × (Poor) A large amount of picking occurred (8) R [Wet strength test: Mei Seisakusho R1-I type, which is an indicator of the water resistance of coated paper. The degree of picking when printing was performed using a Morton roll with a printing machine and applying dampening water was evaluated using the following evaluation criteria. The ink used was Toyo Ink SMX TV Tomi 15.

○ (Good) No picking occurred Δ (Slightly poor) A small amount of picking occurred × (Poor) A large amount of picking occurred (9) Ink drying test: Toyo Ink Preite Sumi ink was used using Mei Seisakusho R1-11 printing machine. After printing, g was applied to the printed matter and the degree of ink set-off was judged according to the following evaluation criteria.

O (Good) No ink set-off Δ (Slightly poor) Some ink set-off × (Poor)
There was a lot of ink set-off α1. Printing gloss development: Printed using Toyo Inkla 2ite indigo ink using Mei Seisakusho R1-11 type printing machine, and then air-dried. Measure the glossiness of the obtained printed matter using a Murakami glossmeter. The higher the number, the better.

α and air permeability test 2' This is an indicator of the density of coated paper, and measures the time (seconds) it takes for a certain amount of air to pass through the coated paper using an Oken air permeability tester. . It can be said that the longer the time, the more dense the coated surface is formed.

Method for measuring average particle size of CLa latex: Copolymer latex was treated with osmic acid and electron micrograph (3
0000 times) and measure the particle diameter of 500 particles.
It was calculated by averaging M.

Method for measuring the toluene-insoluble content of latex: Copolymer latex adjusted to pH 6-8 with sodium hydroxide is coagulated with methanol, washed and dried, and then has a pH of about 0.3. p
After the whole sample was immersed in toluene at 100 r/Ll for 20 hours, the toluene insoluble content was measured and expressed as weight % with respect to the sample.

Example 1 Production of copolymer latex> 160 parts of water, 0.5 parts of sodium alkylbenzenesulfonate, 0.6 parts of sodium bicarbonate, and 0.5 parts of potassium persulfate were charged into a container 1001 autoclave. Next, 4 parts of butadiene, 13 parts of styrene, 5 parts of methyl methacrylate,
A monomer consisting of 1 part of acrylic acid and 2 parts of fumaric acid was added all at once, mixed with 3 parts of carbon tetrachloride, and heated to 70% while stirring.
The mixture was heated to ℃ and polymerized. After 2 hours, 27 parts of butanoene,
Uniform continuous addition of a monomer mixture consisting of 4'5 parts of styrene was started, and continuous addition polymerization was continued for 15 hours. During this time, 3 hours after the start of polymerization in the second stage (conversion rate in the second stage was 18%)
3 parts of acrylamide were added all at once and polymerized.The polymerization conversion rate reached 10096 in a polymerization time of 24 hours.The obtained copolymer latex had a good polymerization mode and little generation of coagulum. A sodium hydroxide solution was added to the copolymer 2 chip to adjust the pH to 4-7, followed by concentration by monomer stripping and vacuum distillation.

Examples 2 and 3 <Manufacture of copolymer latex> Examples 2 and 3 shown in Table 1 are manufactured using the same method as Example 1, except that in Example 2, acrylamide, which is an unsaturated acid amide, is
Example 3 was polymerized using 2 parts of methacrylamide.

In both Examples 2 and 3, the average particle diameter was adjusted by varying the amount of water for polymerization and the emulsifier, and for toluene-insoluble matter, the amount of the molecular weight regulator was varied to obtain a copolymer latex.

Coating liquids for a roll coater shown below were prepared using copolymer latex obtained within the scope of the present invention with varying average particle diameters and toluene insoluble content.

Composition of coating liquid (parts by dry weight) Size press formulation (Table 2) Gutrol formulation (Table 3) Kaolin clay 70 parts 70 parts Calcium carbonate 30# 30# Oxidized starch 1
3 parts 10 parts Copolymer latex l 7
tt 15 // Coating belly 4.0%
55% Using this coating a, the test method shown above was used to determine the fluidity, coating properties, mechanical stability, and coating properties of the paper coating composition of the present invention at high speed coating. Performance was evaluated and the results are summarized in Table 2 (size press formulation) and Table 3 (f-trol formulation).

The physical properties of the coating liquid and the printing characteristics targeted by the present invention were obtained.

Comparative example 1.2 Comparative Examples 1 and 2 are produced using the same manufacturing method as Example 1.

Comparative Example 1 is an example in which the average particle diameter of the copolymer latex is smaller than the range of the present invention, while Comparative Example 2 is an example in which a copolymer latex with a larger average particle diameter is used.

The average particle size is adjusted by changing the amount of water for polymerization and emulsifier.

In Comparative Example 1, the suitability of the coating group is poor, a satin pattern occurs, and the ink drying properties are poor as printing characteristics. On the other hand, Comparative Example 2 is not preferable because the coating liquid has poor viscosity and high-speed fluidity, and printing properties such as adhesive strength and water resistance are poor.

Comparative Example 3.4 Comparative Examples 3 and 4 were produced using the same manufacturing method as Example 1, but Comparative Example 3 was an example in which the toluene insoluble content of the copolymer latex of the present invention was less than the range specified by the present invention. On the other hand, comparative example 4
On the contrary, this is an example in which a copolymer latex with a high content of toluene insolubles was used. The toluene-insoluble content is controlled by varying the molecular weight regulator. In Comparative Example 3, the mechanical stability of the coating liquid was poor, and the adhesive strength was poor in printing properties. On the other hand, Comparative Example 4 is unfavorable as it has inferior printing properties such as adhesive strength, water resistance, and ink drying properties.

Comparative Examples 5 and 6 Comparative Examples 5 and 6 were produced using the same method as Example 1, but in Comparative Example 5, the amount of unsaturated acid amide used in the copolymer latex of the present invention was less than the range specified by the present invention. On the other hand, Comparative Example 6 is an example in which a copolymer latex containing many unsaturated acid amides was used.

In Comparative Example 5, the mechanical stability, gamut, and f aptitude of the coating solution were poor, and some satiny patterns were observed. Adhesive strength as printability,
Unfavorable because of poor water resistance, ink drying properties, and printing gloss. On the other hand, Comparative Example 6 is not preferred because the viscosity of the coating liquid and high-speed fluidity are poor.

Comparative Examples 7 and 8' Comparative Examples 7 and 8 are examples in which the copolymer latex of Example 1 was used but the amount used was changed.

Comparative Example 7 is an example in which the amount of copolymer latex used was less than the range specified by the present invention, while Comparative Example 8 is an example in which a larger amount was used. Comparative Example 7 has poor adhesive strength and water resistance as printing characteristics. On the other hand, in Comparative Example 8, the coating liquid had poor muag suitability and a satin pattern also appeared. Also, as a printing property, the ink drying property is poor, which is not preferable.

〔Effect of the invention〕

As is clear from the above Examples and Comparative Examples, the roll coater paper coating composition of the present invention exhibits good mechanical stability, adhesive strength, and water resistance, and has excellent fluidity and coatability in high-speed coating. Excellent, and imparts good gloss to the coated surface.

Claims (1)

[Scope of Claims] Based on 100 parts by weight of pigment, (i) 5 to 40% by weight of ethylenically unsaturated carboxylic acid, 5 to 40% by weight of aliphatic conjugated diene, and 10 to 50% by weight of ethylenically unsaturated carboxylic acid alkyl ester. Emulsion polymerization of 5 to 35 parts by weight of a monomer mixture (a) consisting of 10 to 70 parts by weight of an alkenyl aromatic compound, and (ii) 20 parts by weight of an aliphatic conjugated diene in the presence of the obtained copolymer latex. -70% by weight, 30-80% by weight of an alkenyl aromatic compound, and 0-50% by weight of one or more monomers selected from ethylenically unsaturated carboxylic acid alkyl esters and vinyl cyanide. )63
(iii) 1.5 parts by weight of unsaturated acid amide (c) is added after the start of the polymerization of the monomer mixture in (ii) but before the polymerization is substantially completed; ~6 parts by weight (a), (b),
A copolymer latex obtained by adding and polymerizing (c) to a total of 100 parts by weight, which has an average particle diameter of 0.06 to 0.35 μm and a toluene insoluble content of 55 to 55 μm.
A paper coating composition comprising 10 to 35 parts by weight of 98% by weight copolymer latex as the pigment binder.