JPS6231116B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a paper coating composition containing primarily an emulsion copolymer latex and a mineral pigment. More specifically, the first step consists of 19.5 to 60 parts by weight of an aliphatic conjugated diene monomer, 0.5 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer, and 30 parts by weight of a monoolefin monomer copolymerizable with these. ~80 parts by weight, the total amount of the first stage monomer mixture is 45
Emulsion copolymerization was carried out by using so that the amount was ~99 parts by weight,
Mainly contains an emulsion copolymer latex with a heterogeneous double structure obtained by emulsion copolymerizing the remainder of the monoolefin monomer in the presence of the emulsion copolymer in the second step, and a mineral pigment. The present invention relates to a paper coating composition characterized by: The development of paper coating technology and printing technology in recent years has been remarkable, and efforts have been made to increase the speed of coating and printing in order to cope with the increase in printed matter, rationalize it, and save labor. In particular, the spread of offset rotary presses has played a major role in increasing these speeds. Properties required of coated paper during offset rotary printing include blister resistance, adhesion, and water resistance. Among copolymer latexes conventionally used for paper coating, those with good water resistance and adhesion lack blister resistance, and those with good blister resistance lack adhesion and water resistance. This is well known in the art. As a result of intensive research into a method for comprehensively improving blister resistance, adhesion, and water resistance, the present inventors used a two-stage polymerization method, but in the second step, aliphatic conjugated diene monomer and ethylene An emulsion copolymer latex with a heterogeneous double structure was synthesized by changing the monomer composition in the first and second stages without introducing an unsaturated carboxylic acid monomer, and the resulting emulsion copolymer latex was Coated paper using coalescing latex as a binder has excellent blister resistance, adhesion,
We have discovered the surprising fact that water resistance is extremely good. That is, in the first step, the present invention comprises 19.5 to 60 parts by weight of an aliphatic conjugated diene monomer, 0.5 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer, and a monoolefin monomer copolymerizable with these. 30-80 parts by weight of the first stage monomer mixture total amount of 45
Emulsion copolymerization was carried out by using so that the amount was ~99 parts by weight,
Mainly contains an emulsion copolymer latex with a heterogeneous double structure obtained by emulsion copolymerizing the remainder of the monoolefin monomer in the presence of the emulsion copolymer in the second step, and a mineral pigment. The present invention relates to a paper coating composition characterized by: To explain the present invention in more detail, in the first step, an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer, and a part of a monoolefin monomer copolymerizable with these are used, In the second stage only monoolefin monomers are used. When an aliphatic conjugated diene monomer and an ethylenically unsaturated carboxylic acid monomer are used in the second stage emulsion copolymerization, water resistance and blister resistance decrease. The aliphatic conjugated diene monomers used in the first step include 1,3-butadiene, 2-methyl-
1,3-butadiene and 2-chloro-1,3-
Examples include butadiene. This monomer is 19.5~
60 parts by weight is used, but if it is less than 19.5 parts by weight, the adhesive strength will decrease. Moreover, if it exceeds 60 parts by weight, water resistance will decrease. Ethylenically unsaturated carboxylic acid monomers used in the first step include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and itaconic acid. The above carboxylic acids can be used alone or in combination of two or more. Ethylenically unsaturated carboxylic acid is used in an amount of 0.5 to 10 parts by weight, but if it is less than 0.5 parts by weight, the adhesive strength and mechanical stability of the latex will decrease, and if it exceeds 10 parts by weight, the viscosity of the latex will become too high. Monoolefin monomers copolymerizable with aliphatic conjugated diene monomers and ethylenically unsaturated carboxylic acid monomers include alkenyl aromatic monomers, unsaturated carboxylic acid alkyl ester monomers,
Examples include unsaturated monomers containing hydroxyalkyl groups and vinyl cyanide monomers. Examples of the alkenyl aromatic monomer include styrene, alphamethylstyrene, methylalphamethylstyrene, and vinyltoluene. Unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate. , dimethyl itaconate, monomethyl fumarate, and monoethyl fumarate. Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethyl acrylate, β
-Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2
-Hydroxybutyl methacrylate, di-(ethylene glycol) maleate, di-(ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis(2-hydroxyethyl) maleate, and 2-hydroxyethylmethyl fumarate. These monoolefin monomers can be used alone or in combination, but from the viewpoint of stability during polymerization, mechanical stability of latex, water resistance, and blister resistance, it is preferable to use monoolefin monomers. As such, it is preferable to use an alkenyl aromatic monomer, an ethylenically unsaturated carboxylic acid alkyl ester monomer, and an unsaturated monomer containing a hydroxyalkyl group in combination. These monoolefin monomers are used in an amount of 30 to 80 parts by weight, but if less than 30 parts by weight, water resistance decreases. Moreover, if it exceeds 80 parts by weight, the adhesive strength will decrease. The total amount of the aliphatic conjugated diene monomer, ethylenically unsaturated carboxylic acid monomer, and monoolefin monomer copolymerizable with these used in the first step is 45 to 99 parts by weight. However, if it is less than 45 parts by weight or exceeds 99 parts by weight, adhesive strength, blister resistance, and water resistance will decrease. Preferably, 70 to 95 parts by weight is appropriate. The emulsion copolymerization in the second stage is carried out in the presence of the emulsion copolymer in the first stage, and it is preferable that the conversion of the monomer used in the first stage is 70% or more. If it is less than 70%, the blister resistance and water resistance will be inferior to that of 70% or more. When starting the second stage of emulsion copolymerization, if the first stage reaction has been completely completed, that is, if the polymerizable radicals have completely disappeared, the process may be carried out by adding a reaction initiator, etc. It is necessary to start a new reaction. There are no particular restrictions on the method of adding the various components in the first stage of emulsion copolymerization, and any one of a batch addition method, a divided addition method, and a continuous addition method may be used. The method of adding the monoolefin monomer in the second stage emulsion copolymerization is also not particularly limited, as in the first stage, and may be any one of a batch addition method, a divided addition method, and a continuous addition method. Incidentally, ordinary emulsifiers can be used, but from the viewpoint of water resistance, it is preferable to use 2 parts by weight or less. Furthermore, during emulsion copolymerization, commonly used polymerization initiators, electrolytes, polymerization promoters, chain transfer agents, chelating agents, etc. may be used. The mineral pigments may be those commonly used in paper coating compositions, such as titanium dioxide, satin white, kaolin, and calcium carbonate, which may be used alone or in combination. In addition to the emulsion copolymer latex and mineral pigments, the paper coating composition also contains commonly used binders such as starch, casein, and PVA, as well as alkaline thickeners, crosslinking agents, alkaline stabilizers, Antifoaming agents, surfactants, etc. may be used as necessary. Examples are shown below, but the present invention is not limited to these Examples in any way. All parts in this example mean parts by weight unless otherwise specified. Example 1 As the first stage of emulsion copolymerization, butadiene, fumaric acid, styrene, and α-methylstyrene were charged in a pressure vessel in the amounts shown in Table 1, and a copolymer latex was obtained by a conventional emulsion polymerization method. In the second step, in the presence of the copolymer latex in the first step, styrene was added in the amount shown in Table 1 to complete the polymerization, resulting in copolymer latexes A, B, C, and
I got a D. In addition, in the first step, all the monomers were loaded and polymerized with the monomer composition shown in Table 1. The obtained copolymer latex is designated as E. Using the emulsion copolymer latex A to E,
A coating color was prepared based on the following coating color prescription to obtain coated paper. The results are shown in Table 1. Coating color prescription Kaolin clay 70 parts (solid content) Calcium carbonate 30 parts (solid content) Modified starch 8 parts (solid content) Emulsion copolymer latex (total solid content 62%)
12 parts (solid content)

[Table] Example 2 The first and second stages of emulsion polymerization were carried out using the monomer compositions shown in Table 2. Coated paper was obtained using the obtained copolymer latex according to Example 1, and the results are shown in Table 2.

【table】

[Table] Example 3 The first and second stages of emulsion polymerization were carried out in the same manner as in Example 1 using the monomer compositions shown in Table 3. Using the obtained copolymer latex, coated paper was prepared using the same formulation as the coating color of Example 1.
The results are shown in Table 4.

【table】

【table】

Claims (1)

[Claims] 1. An aliphatic conjugated diene monomer as the first step
19.5 to 60 parts by weight, 0.5 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer, and a portion of 30 to 80 parts by weight of a monoolefin monomer copolymerizable with these as first-stage monomers. The total amount of the mixture is at least 45 ~
A heterogeneous double structure obtained by emulsion polymerization using 99 parts by weight of the monoolefin monomer, followed by emulsion copolymerization of the remainder of the monoolefin monomer in the presence of the emulsion copolymer in the second step. 1. A paper coating composition comprising mainly an emulsion copolymer latex having the following properties and a mineral pigment. 2. The paper coating composition according to claim 1, wherein the total amount of the monomer mixture in the first stage is 70 to 95 parts by weight. 3. The paper coating composition according to claim 1 or 2, wherein the aliphatic conjugated diene monomer is 1,3-butadiene. 4. The paper coating composition according to claim 1, 2 or 3, wherein the monoolefin monomer is an alkenyl aromatic monomer and an unsaturated carboxylic acid alkyl ester monomer. 5. The paper coating composition according to claim 4, wherein the alkenyl aromatic monomer is styrene or α-methylstyrene, and the unsaturated carboxylic acid alkyl ester monomer is methyl methacrylate or n-butyl acrylate. 6. Claims 1, 2, or 6, wherein the monoolefin monomer is an alkenyl aromatic monomer, an unsaturated carboxylic acid alkyl ester monomer, and an unsaturated monomer containing a hydroxyalkyl group. 4. The paper coating composition according to item 3. 7 The alkenyl aromatic monomer is styrene, α-methylstyrene, the unsaturated carboxylic acid alkyl ester monomer is methyl methacrylate, n-butyl acrylate, and the unsaturated monomer containing a hydroxyalkyl group is β-hydroxyethyl acrylate. or β-hydroxyethyl methacrylate, the paper coating composition according to claim 6.