JPH038643B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing a copolymer latex of an aliphatic conjugated diene compound. The latex obtained by the present invention is used as a coating liquid composition when producing coated printing paper. BACKGROUND ART In recent years, as printing speeds have increased, it has become increasingly important for coated paper to have excellent printability even under severe printing conditions. In order to improve this printability, it is important to form a bulky coating layer with good coverage of the base paper, and to have a large so-called calender effect, which improves smoothness by finishing with a super calender or gloss calender. Methods to provide such a bulky coating layer include blending pigments with a large aspect ratio and increasing the concentration of the coating solution, as well as adding salt and flocculants to the coating solution. It is known to destabilize the coating to speed up the time it takes for the coating layer to become immobilized after coating. On the other hand, as a method for improving the properties of latex for coating liquids used as adhesives, it is possible to improve the coating layer by interacting with pigments during the process of losing moisture after coating until drying. It is thought that a substance that exhibits the effect of accelerating the immobilization of is preferable, and it is known that one way to achieve this is that an amphoteric latex that has both anionic and cationic properties can be expected to have this effect. (e.g. TAPPI Coating Conference
Preprints P.143−153'81). As an amphoteric latex for paper coating, for example, when manufacturing carboxy-modified latexes in JP-A-54-30910 and JP-A-58-4894, ethylenically unsaturated amine monomers are used as cationic monomers. A method has been proposed for improving the performance of coated paper by imparting amphoteric properties to coated paper. Problems to be Solved by the Invention According to the research conducted by the present inventors, it is true that the use of latex produced by this method does improve water resistance, ink receptivity, etc., but the improvements have not yet been sufficiently improved. However, it has not yet been possible to obtain coated paper with good printability. This is believed to be due to the fact that such latexes still do not interact sufficiently with pigments, so that a sufficiently bulky coating layer cannot be obtained. In particular, if a large amount of heavy calcium carbonate, which has a smaller surface energy than clay, is used in the pigment formulation, extremely insufficient printability will be obtained. The present inventors provide a paper coating composition that has excellent printability and sufficient adhesive strength. As a result of repeated studies on polymer latex as a particularly excellent adhesive, the present invention was arrived at. Means for Solving the Problems The present invention provides at least one amphoteric surfactant.
Using ~10 parts by weight as an emulsifier, aliphatic conjugated diene compound 30-70% by weight ethylenically unsaturated carboxylic acid 0.5-5% by weight ethylenically unsaturated amine 0.2-5% by weight copolymerizable containing amide bond unsaturated compounds
1% by weight or more and less than 5% by weight Unsaturated carboxylic acid ester containing a hydroxyl group
A copolymer latex characterized by emulsion polymerizing 100 parts by weight of a monomer mixture consisting of 1% by weight or more and less than 5% by weight and 10 to 67.3% by weight of a monomer copolymerizable with these at a pH of 6 or higher. This is the manufacturing method. The configuration of the present invention will be explained in detail below. (Ampholytic surfactant) The amphoteric surfactant used in the present invention is a surfactant that has both an anionic moiety and a cationic hydrophilic group in the same molecule, and the anionic moiety is a carboxylic acid salt or a sulfuric acid ester salt. , sulfonates, and phosphate ester salts, and those having amine salts and quaternary ammonium salts as the cation moiety. Specific examples of such amphoteric surfactants include salts of lauryl betaine, stearyl betaine, cocoamidopropyl betaine, and 2-undecyl-hydroxyethylimidazolinium betaine as alkyl betaine salts, and lauryl betaine as an amino acid type. Examples include salts of -β-alanine, stearyl-β-alanine, lauryldi(aminoethyl)glycine, octyldi(aminoethyl)glycine, and dioctyldi(aminoethyl)glycine. Ampholytic surfactants have less deterioration in water resistance than anionic or nonionic surfactants, and can provide white paper with excellent gloss and printability. The effects of the present invention can be achieved by using these amphoteric surfactants alone or in combination of two or more as emulsifiers during polymerization. It may be used as a polymer emulsifier. However, in this case, rather than using an amphoteric surfactant as an emulsifier during polymerization, for example, an amphoteric surfactant is added to a copolymer latex produced using an anionic and/or nonionic surfactant as an emulsifier during polymerization. The effects of the present invention cannot be obtained by simply adding . The amount of amphoteric surfactant to be used is 1 to 10 parts by weight, preferably 2 to 6 parts by weight, per 100 parts by weight of the monomer mixture; if it is less than 1 part by weight, the object of the present invention will not be achieved; If it exceeds this, it becomes difficult to maintain the water resistance required for coated paper for printing. Although there are still many unknowns about the mechanism by which the effects of using this amphoteric surfactant occur, copolymer latex produced in the presence of this amphoteric surfactant
It is thought that it forms a bulky coating layer by having an appropriate cationic property and having an appropriate interaction with the pigment in the coating composition. (Monomer) As an emulsifier containing at least one of the above amphoteric surfactants, an aliphatic conjugated diene compound that provides appropriate elasticity to the coating film of the coating composition as a monomer, and an ethylenically unsaturated carboxylic acid, By polymerizing an ethylenically unsaturated amine, a copolymerizable unsaturated compound containing an amide bond, and an unsaturated carboxylic acid ester containing a hydroxyl group, the desired effects of the present invention can be further expressed, and particularly good adhesive strength can be achieved. The above monomers are essential components in order to obtain. (Aliphatic conjugated diene compound) Examples of the aliphatic conjugated diene compound used in the present invention include butadiene, isoprene, 2-chloro-1,
Examples include 3-butadiene, 1-chloro-1,3-butadiene, and butadiene is preferably used. The aliphatic conjugated diene compound is used in an amount of 30 to 70% by weight, preferably 35 to 65% by weight. usage is 30
If it is less than % by weight, sufficient elasticity and adhesive strength cannot be obtained.
If it exceeds 70% by weight, the stickiness will become too large. (Ethylenically Unsaturated Carboxylic Acid) As the ethylenically unsaturated carboxylic acid, mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid can be used. Anhydrides or monoalkyl esters of dicarboxylic acids can also be used. The amount of ethylenically unsaturated carboxylic acid used is 0.5~
5% by weight, preferably 1-3% by weight. 0.5
If it is less than 5% by weight, adhesive strength and mechanical stability will be reduced, and if it exceeds 5% by weight, water resistance will be reduced. (Ethylenically unsaturated amine) Ethylenically unsaturated amines include aminoalkyl esters of ethylenically unsaturated carboxylic acids such as methylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and dimethylaminoethyl (meth)acrylate. , methylaminoethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, and aminoalkydamides of ethylenically unsaturated carboxylic acids such as 2-vinylpyridine, 4-vinylpyridine, 2-methyl Examples include alkenylpyridines such as -5-vinylpyridine. The amount of ethylenically unsaturated amine used is 0.2 to 5% by weight, preferably 0.5 to 3% by weight. If it is less than 0.2% by weight, printability will be reduced, and if it exceeds 5% by weight, adhesive strength will be reduced. In this specification, "(meth)acrylate" refers to "acrylate" and "methacrylate".
It should be understood that the term "(meth)acrylamide" and "methacrylamide" are collectively expressed. (Copolymerizable unsaturated compound containing an amide bond) As a copolymerizable unsaturated compound containing an amide bond, acrylamide, methacrylamide, N-
Examples include methylol acrylamide, N-butoxyacrylamide, diacetone acrylamide, and the like. The amount of the copolymerizable unsaturated compound containing an amide bond used is 1% by weight or more and less than 5% by weight, preferably 1.5 to 3% by weight. If it is less than 1% by weight, printability decreases, and if it is less than 5% by weight.
If the viscosity of the latex is exceeded, the viscosity of the latex increases significantly, making handling difficult. (Unsaturated carboxylic acid ester containing a hydroxyl group) Examples of the unsaturated carboxylic acid ester containing a hydroxyl group include 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate,
Hydroxybutyl (meth)acrylate, di-
(ethylene glycol) itaconate, di-(ethylene glycol) maleate, 2-hydroxyethyl maleate, and 2-hydroxyethylmethyl fumarate. The unsaturated carboxylic acid ester containing a hydroxyl group is 1% by weight or more and less than 5% by weight, preferably 1.5 to 5% by weight.
Use 3% by weight. If it is less than 1% by weight, dispersion stability and adhesive strength will be reduced, and if it exceeds 5% by weight, water resistance will be reduced. (Other monomers that can be copolymerized) Other monomers that can be copolymerized with these include styrene, α-methylstyrene, vinyltoluene,
Aromatic vinyl compounds such as paramethylstyrene:
Alkyl esters of acrylic acid or methacrylic acid such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate, unsaturated fatty acid glycidyl esters such as glycidyl (meth)acrylate, acrylonitrile, and methacrylate. Examples include vinyl cyanide compounds such as nitrile, vinyl chloride, vinylidene chloride, vinyl methyl ethyl ketone, vinyl methyl ether, vinyl acetate, vinyl formate, allyl acetate, methacrylic acetate, acrolein, and allyl alcohol. The amount of other copolymerizable monomers used is 10 to 67.3% by weight, preferably 23 to 61.5% by weight. If the amount used is less than 10% by weight, it will become too sticky,
If it exceeds 67.3% by weight, sufficient elasticity and adhesive strength cannot be obtained. (Polymerization method) When polymerizing the copolymer latex of the present invention, an ethylenically unsaturated carboxylic acid and an ethylenically unsaturated amine are allowed to coexist, and an emulsifier, a polymerization initiator, and a chain transfer agent are used in an aqueous medium by a known method. However, during polymerization, it is necessary to maintain the pH in the polymerization system at 6 or higher, preferably 7.5 or higher. If polymerization is carried out at a pH lower than 6, the polymerization stability of the polymerization system will be significantly deteriorated. (Auxiliary substance for polymerization) As an emulsifier, anionic, cationic, and/or nonionic surfactants can be used in combination with the essential amphoteric surfactant; It is preferable to use a surfactant in combination. Examples of anionic surfactants include sulfate esters of higher alcohols,
Examples include alkylbenzene sulfonates and aliphatic sulfonates. As the nonionic surfactant, common alkyl ester type, alkyl ether type, alkyl phenyl ether type, etc. of preethylene glycol are used. As the initiator, any of water-soluble initiators such as sodium persulfate, potassium persulfate, and ammonium persulfate, oil-soluble initiators such as benzene peroxide, and redox-based initiators can be used. Known chain auxiliaries, chelating agents, inorganic salts, etc. for emulsion polymerization can also be used. (Polymerization operation) The copolymer latex of the present invention has a polymerization temperature of 5
It is produced by ordinary emulsion polymerization at ~100°C, and batch, semi-batch, or continuous polymerization can be employed. (Uses of latex) The copolymer latex thus obtained can be used alone or in combination with a known copolymer latex for blending in a pigment composition for paper coating. In this case, 3 to 50 parts by weight of solid content per 100 parts by weight of mineral pigments such as various clays, aluminum hydroxide, titanium dioxide, satin white, calcium carbonate, etc., especially heavy calcium carbonate,
It is preferably used in an amount of 5 to 30 parts by weight, and can be used in combination with other binders such as starch, casein, and polyvinyl alcohol. The use of such copolymer latex improves adhesive strength, printing gloss,
To provide a paper coating composition which is significantly improved in printability such as ink receptivity, which is not seen in conventional paper coating latexes. In particular, in combination with a pigment containing calcium carbonate at a blending ratio of 10% by weight or more, the excellent effects aimed at by the present invention are exhibited. Examples Examples are shown below to explain the present invention in more detail, but the present invention is not limited to the following examples in any way. Note that parts and % in the examples mean parts by weight and % by weight, respectively. Example 1 Method for producing copolymer latexes (A) to (E) In an autoclave with an internal volume of 100 ml under nitrogen gas Butadiene 10000 g (40 parts) Styrene 7500 g (30 parts) Methyl methacrylate 5750 g (23 parts) Itaconic acid 500 g ( 2 parts) Diethylaminoethyl methacrylate
250g (1 part) Acrylamide 500g (2 parts) Hydroxyethyl methacrylate
500 g (2 parts) per 100 parts of monomer Sodium salt of lauryl betaine (amphoteric surfactant) 625 g (2.5 parts) tert-dodecyl mercaptan 50 g (0.2 parts) Sodium carbonate 125 g (0.5 parts) Sodium hydroxide 100 g (0.4 parts) Sodium sulfate 250g (1.0 parts) Tetrasodium salt of ethylenediaminetetraacetic acid
12.5 g (0.05 parts) and 50000 g (200 parts) of water were charged and reacted at 50°C for 15 hours. Then N,N-diethylhydroxylamine 25
g was added to stop the reaction. The obtained copolymer latex had a polymerization conversion rate of 96%, a pH of 7.8, and an average particle size of 0.18 microns, and was concentrated to a solid content of 45% by vacuum distillation to obtain a copolymer latex (A). Emulsion polymerization was carried out using the monomer mixture having the composition shown in Table 1 in the same manner as for copolymer latex (A).
Copolymer latexes (B) to (E) were obtained. Comparative Example 1 Copolymer latexes (a) to (h) were obtained by polymerizing in the same manner as in Example 1 using the monomer components, emulsifier components, and pH during polymerization of (a) to (li) in Table-1. Ta. Table 1 (i) shows a copolymer latex in which an amphoteric surfactant was not used as an emulsifier during polymerization but was added after polymerization. Example 2 and Comparative Example 2 A paper coating paint was prepared using the copolymer latexes (A) to (E) and (a) to (i) obtained in Example 1 and Comparative Example 1 according to the following formulation. did. Table 2 shows the white paper properties and printing test results of the coated paper. (Composition) Clay 50 parts Heavy calcium carbonate 50 parts Dispersant 0.5 parts Copolymer latex 10 parts Oxidized starch 4 parts Water Added in an amount equivalent to 60% total solids The latex of the present invention has white paper properties and printing. A significant improvement in aptitude that was not seen before was observed. Comparative Example 2 uses a copolymer latex (Comparative Example 1 (a)) without using an amphoteric surfactant, and is inferior in ink receptivity, white paper gloss, and printing gloss. Comparative Example 2 uses a copolymer latex (Comparative Example 1 (b)) polymerized at a pH of less than 6, and is inferior in ink receptivity, white paper gloss, and printing gloss. Comparative Example 2 is a copolymer latex in which the amount of conjugated diene used is outside the range of the present invention (Comparative Example 1 (c),
(b)), both of which have adhesive strength and
Print gloss is poor. Comparative Example 2 is a case where a copolymer latex (Comparative Example 1 (e)) without using ethylenically unsaturated carboxylic acid was used, and the adhesive strength was significantly inferior. Comparative Example 2 is a case where a copolymer latex (Comparative Example 1 (e)) without using ethylenically unsaturated carboxylic acid was used, and the ink receptivity, white paper gloss, and printing gloss were poor. Comparative Example 2 is a copolymer latex that does not use a copolymerizable unsaturated compound containing an amide bond (Comparative Example 1 (g)), and Comparative Example 2 is a copolymer latex that does not use an unsaturated carboxylic acid ester that contains a hydroxyl group (comparison). Example 1 (h)) was used. is particularly poor in ink receptivity, and is particularly poor in adhesive strength. Comparative Example 2 is a case in which a copolymer (Comparative Example 1 (i)) in which an amphoteric surfactant was not used during polymerization and was simply added afterward, was inferior in ink receptivity and print gloss. In addition, in the examples, the evaluation test of the coated paper was conducted according to the following method. Note 1 “Dry pick” is based on RI printing tester.
The test piece is fixed to a drum and printed repeatedly at a speed of 30 rpm, stopped after a certain period of time and judged. The judgment is 5 for those that were completely printed.
The data that could hardly be printed was counted as 1 point, and the 5 data obtained from each sample were arithmetic averaged. Note 2 “Ink receptivity” is based on RI printing tester. Water was applied once to a test piece fixed on a drum, and after a certain period of time, printing was performed once, and the degree of ink adhesion was visually judged. 5 items with good ink adhesion,
An inferior score is given 1 point, and the 5 data obtained from each sample are arithmetic averaged. Note 3 White paper gloss: Based on JIS method. Print gloss: According to JIS method.

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【table】

[Table] Effects of the Invention The latex produced according to the present invention can be used to produce a coating liquid composition for producing coated paper for printing, which is excellent in printability such as printing gloss and ink receptivity, and adhesive strength. It is suitable as a raw material for

Claims (1)

[Claims] 1. Using 1 to 10 parts by weight of at least one amphoteric surfactant as an emulsifier, aliphatic conjugated diene compounds 30 to 70% by weight ethylenically unsaturated carboxylic acids 0.5 to 5% by weight ethylenically unsaturated Saturated amine 0.2-5% by weight Copolymerizable unsaturated compound containing an amide bond and no amino group in the same molecule
1% by weight or more and less than 5% by weight Unsaturated carboxylic acid ester containing a hydroxyl group
When emulsion polymerizing 100 parts by weight of a monomer mixture consisting of 1% by weight or more and less than 5% by weight and 10 to 67.3% by weight of a monomer copolymerizable with these at a pH of 6 or higher, ethylenically unsaturated carboxylic acid and ethylene A method for producing a copolymer latex characterized by the coexistence of a system unsaturated amine.