JPH07166495A - Composition for coated paper and coated paper coated therewith - Google Patents

Abstract

PURPOSE:To obtain the composition having excellent high-speed coatability and capable of imparting coated paper with excellent bond strength (dry pick, wet pick) and ink receivability. CONSTITUTION:This composition for coated paper is characterized by using, as a binder, a copolymer latex produced by emulsion polymerization of 100 pts.wt. of a composition comprising (a) 20-60wt.% of an aliphatic conjugated diene monomer, (b) 0.5-5wt.% of an ethylene-based unsaturated acid monomer and (c) 35-75.5wt.% of a copolymerizable monoolefin monomer using chain transfer agents i.e., (d) 0.5-3 pts.wt. of alpha-methylstyrene dimer and (e) 0.2-2 pts.wt. of a 4-12C alkylmercaptan, in such a way that, at a point when the conversion rates of the components (a) and (c) reach 80-95%, the component (b) is added to the system collectively, completing the polymerization. And, the coated paper can be obtained by coating this composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for coated paper for obtaining a coated paper for offset printing, which has excellent suitability for high speed coating, and has excellent adhesive strength and ink acceptability. .

[0002]

2. Description of the Related Art Carboxy modified latex has hitherto been widely used as a binder component of a coated paper composition in view of workability at the time of coating, economical efficiency and quality of coated paper. Is used for. However, the fact is that the recent remarkable development of printing technology has not been sufficiently dealt with, and a higher-quality coated paper composition is desired. Offset printing is the mainstream of printing, and various performances such as adhesive strength (dry pick, wet pick) that can withstand the printing, and ink acceptability are required. It is known that these properties are affected by the properties of the carboxy-modified latex used as a binder in the coated paper composition. However, it is also known that the adhesive strength and the ink acceptability are in a trade-off relationship. If the adhesive strength performance is improved, there is a problem that the ink acceptability is lowered, and a composition for coated paper that satisfies the ink acceptability and the adhesive strength (dry pick, wet pick) that can withstand printing is desired. In addition, the current situation is that paper manufacturers are operating new wide machines at high speed to streamline production, and high-speed coating is also an important issue. Generally, in high-speed coating, high shear stress acts to increase blade pressure, which causes troubles such as bleeding. Therefore, in high-speed coating, it is important to reduce the viscosity of the coating under high shear rate. Conventionally, these measures have been taken, and a large amount of heavy calcium carbonate is used from the pigment side, and a star that is a natural binder from the binder side.
For example, Japanese Patent Application Laid-Open No. 3-109470 discloses a carboxy-modified latex which is a synthetic binder.
As in JP-A-5-17510, a combination of α-methylstyrene dimer and a sulfur chain transfer agent has been proposed as a chain transfer agent, and JP-A-58-60091 proposes a particle size reduction of 130 nm or less. Has been done. However, these proposals are insufficient for high-speed coating, adhesive strength to withstand printing and ink acceptability.

[0003]

[Means for Solving the Problems] Therefore, the inventors of the present invention have conducted researches to improve the offset printing suitability and the high speed coating suitability, and as a result, the adhesive strength and the ink acceptability are excellent, and the low viscosity property is obtained under the high shear rate. The present invention has been completed by finding a composition for coated paper having the above. That is, the present invention comprises (a) 20 to 60% by weight of an aliphatic conjugated diene-based monomer,
(B) 0.5 to 5 wt% of ethylenically unsaturated acid monomer,
(C) Copolymerizable monoolefin monomer 35 to 7
100 parts by weight of a composition consisting of 9.5% by weight, 0.5 to 3 parts by weight of a chain transfer agent (d) α-methylstyrene dimer and (e) 0.2 of an alkyl mercaptan having 4 to 12 carbon atoms.
When emulsion polymerization is carried out using 2 to 2 parts by weight, (a) in the monomer
And when the polymerization conversion rate of (c) reaches 80 to 95%, the component (b) is added all at once and the copolymer latex produced by completing the polymerization is used as a binder. And a coated paper obtained by applying the composition for coated paper.

The present invention will be described in more detail below. In the production of the copolymer latex used in the composition for coated paper of the present invention, among the monomers constituting the copolymer latex, (a) the aliphatic conjugated diene-based monomer is 1,3 -Butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene and the like,
They can be used alone or in combination of two or more.
These monomers impart appropriate elasticity to the copolymer, and the amount thereof is 20% based on 100% by weight of the total monomer mixture.
-60% by weight. Examples of the (b) ethylenically unsaturated acid monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid and maleic acid, and the like, which may be used alone or in combination of two or more kinds. You can do it. Generally, these impart the electrolyte stability and mechanical stability of the latex. The amount used is preferably 0.5 to 5% by weight based on 100% by weight of all the monomers. (C) Aromatic vinyl compounds such as styrene and vinyltoluene as other copolymerizable monoolefin monomers; acrylic acid esters such as methyl acrylate and ethyl acrylate, and methacrylic acid esters such as methyl methacrylate. Ethylenically unsaturated carboxylic acid alkyl ester compounds such as diethyl fumarate and dimethyl itaconate; Vinyl cyanide compounds such as acrylonitrile, α-chloroacrylonitrile and methacrylonitrile; Acrylamide, methacrylamide,
Ethylenically unsaturated carboxylic acid amides such as N-methylolacrylamide and N-substituted compounds thereof, functional alkyl ester compounds such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, and vinyl esters such as vinyl acetate And the like, which impart appropriate hardness to the copolymer and stability to the latex, and may be used alone or in combination of two or more kinds. The amount used is 35 to 79.5% by weight based on 100% by weight of all the monomers.

(D) α-methylstyrene dimer as a chain transfer agent, (e) alkyl mercaptan having 4 to 12 carbon atoms, n-butyl mercaptan, t-butyl mercaptan, n-hexyl mercaptan, n-octyl mercaptan, Examples thereof include n-dodecyl mercaptan and t-dodecyl mercaptan. Further, these compounds (e) may be used alone or in combination of two or more. The amount of α-methylstyrene dimer used as a chain transfer agent is 0.5 to 3% by weight, and the number of carbon atoms is 4 to 100 parts by weight per 100 parts by weight of the monomer.
Twelve alkyl mercaptans are used in the range of 0.2-2% by weight. Outside this range, the effect of the present invention cannot be recognized. The α-methylstyrene dimer has an action of decreasing the polymerization rate, and when it is used in an amount of 3% by weight or more, the polymerization stability is decreased, which is a great adverse effect on the production. Also, the carbon number is 4-12
Use of 2% by weight or more of the above alkyl mercaptan is not preferable because the dry strength decreases.

In the method for producing the copolymer latex used in the composition for coated paper of the present invention, a known emulsion polymerization method is particularly used except that the monomer is polymerized under the above-mentioned conditions. Not limited. As the emulsifier, higher alcohol sulfate, alkylbenzene sulfonate,
Anionic surfactants such as aliphatic sulfonates, nonionic surfactants such as alkyl ester type of polyethylene glycol, alkylphenyl ether type, alkyl ether type, and amphoteric surfactants such as betaine type, which may be used alone or in combination. The above is used in combination. Considering the water resistance of the obtained copolymer latex, the amount of these surfactants used is preferably 1% by weight or less per 100% by weight of all the monomers. As the polymerization initiator, a water-soluble initiator such as potassium persulfate, ammonium persulfate or sodium persulfate, an oil-soluble initiator such as benzoyl peroxide or azobisisobutyronitrile, or a redox initiator can be used.

The composition for coated paper of the present invention may contain various additives such as a dispersant, a water-proofing agent, a viscosity modifier and a defoaming agent, in addition to the copolymer latex and the pigment. Examples of pigments that can be used in the present invention include inorganic pigments such as clay, calcium carbonate, aluminum hydroxide, titanium oxide, satin white, and talc, and organic pigments such as polystyrene and phenol resins. Further, as the binder, in addition to the copolymer latex of the present invention, a starch, casein, a water-soluble polymer such as polyvinyl alcohol, a latex such as polyvinyl acetate, an acrylic ester copolymer may be used in combination, if necessary. You can do it. The copolymer latex used in the present invention generally has a pigment (solid content) of 5%.
Used in the range of ˜30 wt% (solid content).

[0008]

EXAMPLES The present invention will be specifically described below with reference to examples. In addition, the number of parts in Examples and Comparative Examples means% by weight unless otherwise specified. Manufacture of Copolymer Latex Manufacture Example 1 The following raw materials were placed in a reaction vessel equipped with a stirrer and having an internal volume of 100 liters, deoxidation was carried out by nitrogen substitution, and then the temperature was raised to 70 ° C while stirring. Pure water 100 parts by weight Sodium bicarbonate 0.1 parts by weight Sodium lauryl sulphate 0.15 parts by weight Sodium persulfate 2 parts by weight On the other hand, another (a) component butadiene 35 parts by weight in an autoclave with a stirrer having an internal volume of 100 liters, Component (c) 41 parts by weight of styrene, 15 parts by weight of methyl methacrylate, 6 parts by weight of acrylonitrile, 2 parts by weight of 2-hydroxyethyl methacrylate as a monomer and a chain transfer agent (e)
0.3% by weight of t-dodecyl mercaptan, 1% by weight of (d) α-methylstyrene dimer, 40 parts by weight of pure water and 0.1 part by weight of sodium lauryl sulfate are emulsified, and the emulsion is reacted at a constant rate for 6 hours. Added to the bath. The polymerization conversion rate is 8
At the time of reaching 0%, 2 parts of 1 part by weight of acrylic acid (b) is
A 0% aqueous solution was added all at once, and the polymerization was further continued, and when the polymerization conversion rate reached 98%, the reaction was terminated by cooling. The obtained latex was adjusted to pH 8.0 with an aqueous NaOH solution, and unreacted monomers and low volatile components were removed by steam stripping to obtain a copolymer latex A.

Production Examples 2 to 10 Production was carried out by the method of copolymer latex A using the monomer (a, c) components of copolymer latex A. Table 1 shows the polymerization conversion rates when the components (d, e) were used in combination and the component (b) was added. When the weight part of the component (b) was increased or decreased, the styrene component (c) was also increased or decreased accordingly. This is also shown in Table-1. Copolymer latexes B to J shown in Table 1 were produced. Latex B to E are inventive latexes, and F to J are comparative latices. However, as for J, the component (b) was uniformly added together with the components (a, c). The obtained latex was used in the following examples.

Examples 1 to 5 and Comparative Examples 6 to 10 Copolymer latices A to J were used to prepare coated paper compositions (hereinafter also referred to as color) according to the following formulation.

<Compounding Formulation> No-1 Kaolin clay 60 parts by weight Heavy carbon calcium 40 parts by weight Dispersant 0.1 parts by weight NaOH 0.1 parts by weight Oxidized starch 3 parts by weight Copolymer latex 11 parts by weight ─── ────────────────── Color density 65% One side coating amount of the above color on high quality paper is 15g / dry weight
It was coated at a speed of 10 m / min using a bench coater so as to have a surface area of m ^2, and dried at 150 ° C. The coated paper obtained was further seasoned under conditions of 20 ° C. and 65% relative humidity for one day and then subjected to a super calender treatment twice under the conditions of 60 ° C. and a linear pressure of 150 kg / cm. The coated paper was subjected to a paper quality test.

Test method High speed coating suitability (1) High shear viscosity (cps) Using a Hercules type Hibiscometer manufactured by Kumagai Riki Kogyo Co., Ltd., measurement was performed at E bob max 8800 rpm, and the shear rate was 1 The paint viscosity at 6 × 10 ⁵ sec ⁻¹ was calculated. Adhesive strength (2) Dry pick strength test Using an RI printing aptitude tester (manufactured by Akira Seisakusho), printing the ink (Toyo Ink SMX Tack 15) compares the peeled state with a standard product and visually judges 5 points. Evaluation was made by the method (5 points were excellent and 1 point was poor). (3) Wet pick strength test Using an RI printability tester (manufactured by Akira Seisakusho), moisten the surface of the paper with a molton roll, and immediately after that, ink (Toyo Ink S
Printing was performed with MX Tuck 15), the peeled state was compared with a standard product, and visually judged and evaluated by a 5-point method (5 points excellent, 1 point poor). Ink acceptability (4) Ink acceptability test Using an RI printability tester (manufactured by Ming Seisakusho), moisten the surface of the paper with a molton roll and immediately print with ink (Toyo Ink Mark Five New Indigo). The acceptance concentration of was compared with that of a standard product and visually judged, and evaluated by the ◎ ○ △ × method (◎ is excellent, × is poor). The results are shown in Table-2.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

EFFECTS OF THE INVENTION The values in Table 2 show that the coated paper compositions of the Examples within the limits of the present invention have excellent high-speed coating suitability and the coatings obtained by coating. Paper is dry pick strength
The wet pick strength and ink acceptability are excellent, and the coated paper composition of the present invention and the coated paper coated with the composition are useful as never before.

Claims (2)

[Claims] 1. (a) Aliphatic conjugated diene monomer 20 to
60% by weight, 0.5 to (b) ethylenically unsaturated acid monomer
The chain transfer agent (d) α-methylstyrene dimer 0.5 to 100 parts by weight of a composition consisting of 5% by weight and (c) 35 to 79.5% by weight of a copolymerizable monoolefin monomer.
When emulsion polymerization is performed using 3 parts by weight and (e) 0.2 to 2 parts by weight of an alkyl mercaptan having 4 to 12 carbon atoms, the polymerization conversion rate of (a) and (c) in the monomer is 80 to 95. %, The component (b) is added all at once and the copolymer latex produced by completing the polymerization is added to the binder.
A composition for coated paper, characterized by being used as. 2. A coated paper obtained by applying the composition for coated paper according to claim 1.