JPH0337203A - Production of copolymer latex and latex produced thereby - Google Patents

Abstract

PURPOSE:To obtain a latex excellent in adhesiveness and useful for improving the pick strength of coated printing paper by emulsion-polymerizing a conjugated diene, an ethylenically unsaturated carboxylic acid and other monomers by using a specified ester as a chain transfer agent. CONSTITUTION:A latex is produced by emulsion-polymerizing 10-60wt.% conjugated diene, 1-15wt.% ethylenically unsaturated carboxylic acid and 25-89wt.% other monomers copolymerizable therewith by using 0.01-5.0wt.%, based on 100 pts.wt. said monomer, of an alkyl thioglycolate of the formula (wherein R is a 2-18C alkyl) as a chain transfer agent. The particle diameter of the latex can be controlled by the rate of the surfactant and/or seed latex used, and as this rate increases, the particle diameter of the latex formed generally decreases. A desirable range of the particle diameter is 0.05-1mum.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a polymer latex for use in paper coatings, carpet pack sizing, and other binders.

<Conventional technology> Coated paper uses kaolin clay, calcium carbonate, satin white, talc,
It is coated with a paint whose main components are pigments such as titanium oxide, polymer latex as a binder, starch as a water-retaining agent or auxiliary binder, and water-soluble polymers such as polyvinyl alcohol and carboxymethyl cellulose. . Here, as the polymer latex as a binder, a styrene-butadiene polymer latex, which is emulsion polymerized using styrene and butadiene as main monomer components, so-called SB latex has been commonly used.

By the way, the production of coated paper has increased significantly in recent years as the demand for color-printed 91KB, pamphlets, and advertisements has increased. On the other hand, with regard to coated paper printing, there is an increasing trend toward high-speed printing due to expanding demand, and the required level of quality is also becoming more sophisticated. Therefore, among the qualities of coated paper, there is a strong demand for improvement in ink shock resistance, so-called shock strength. However, this shock strength performance has a negative correlation with other print properties, such as wet shock strength, blister resistance, halftone dot reproducibility, etc., and it is desired to improve it while maintaining a balance.

Since such quality strongly depends on the design of the SB-based latex used as a pigment binder, various studies have been made so far.

Among these, the gel fraction of the latex, that is, the film formed by drying the latex, or the addition of isopropyl alcohol etc. to the latex to coagulate and precipitate polymer particles, which are separated, and the benzene and toluene of the dried polymer mass. Since it has been confirmed that the ratio of the insoluble portion to solvents such as tetrahydrofuran is a controlling factor for the shock strength and blister resistance, various studies have been conducted from this aspect. That is, Japanese Patent Publication No. 59-3598, Japanese Patent Publication No. 60-17879, and Japanese Patent Publication No. 58-48
No. 94 proposes that latex be made to have a specific range of polymer composition and gel fraction to exhibit excellent performance.

Furthermore, in JP-A No. 62-117897, by mixing a latex with a low gel fraction with a specific polymer composition and a latex with a high gel fraction in a specific range, it is possible to improve the shock strength and blister resistance. It is said that it can be made to have excellent properties.

The gel fraction of this latex changes depending on various polymerization factors such as monomer composition and polymerization temperature, but the common and simple method for adjusting it to the desired level is to add a chain transfer agent. Conventionally, halogenated hydrocarbons represented by carbon tetrachloride, alkyl mercaptans represented by t- or n-dodecyl mercaptan, and sulfides have been used.

By the way, the Bic strength of coated paper is highest when the gel fraction is in the range of 75 to 95% by weight in SB latex, whereas the blister resistance is better as the gel fraction is lower. Generally confirmed. Therefore, it is extremely difficult to simultaneously achieve high levels of both bulk strength and blister resistance, and in the end,
Until now, we had no choice but to compromise by adjusting the gel fraction of latex within an appropriate range.

Similarly, the optimum butadiene fraction for Bic strength is 40.
%, whereas the optimum butadiene fraction for halftone dot reproducibility is 50% or more, and it has been difficult to maintain both at a high level at the same time.

Similarly, the optimum butadiene fraction for wet big strength is 34%.
It was difficult to achieve high standards for both at the same time.

On the other hand, alkyl esters of thioglycolic acid are known as chain transfer agents in emulsion polymerization, as shown in Japanese Patent Publication No. 49-31746, but their effect on latexes containing conjugated dienes is unknown. .

<Problem to be solved by the invention> Conventional techniques such as these are unable to cope with the recent increasingly faster printing speeds, and the use of latex as a binder to enable the production of high-quality coated paper has been developed. The current situation is that there is a strong need for its emergence. In view of this situation, the present inventors have made it possible to further improve the shock strength and other performances of current coated printing papers, such as blister resistance, halftone dot reproducibility, and wet shock strength. It provides a binder that can be used to

<Means for Solving the Problems> The present invention provides a method for solving the problem by using a conjugated diene of 10 to 60% by weight, an ethylenically unsaturated carboxylic acid of 1 to 15% by weight, and 25 to 89% of other monomers copolymerizable with these. When producing latex by emulsion polymerization, 0.0% of the monomer is added to 100% of the amount of melon during the polymerization. Ol or 5.
0! By producing a copolymer latex characterized by using a thioglycolic acid alkyl ester represented by the general formula (wherein R represents an alkyl group having 2 to 18 carbon atoms) with the amount of El%, It solves problems.

The present invention will be explained in detail below.

In the emulsion polymerization for preparing the polymer latex of the present invention, 0.01 to 5.0
It is characterized in that a thioglycolic acid alkyl ester represented by the general formula % by weight (wherein R represents an alkyl group having 2 to 18 carbon atoms) is used as a chain transfer agent.

This chain transfer agent can also be used, and may be desirable, in combination with other known chain transfer agents. However, in that case, in order to exhibit the effects shown in the present invention, the amount of chain transfer agents other than the above-mentioned chain transfer agent must be equal to or less than the amount of the above-mentioned chain transfer agent if it is an alkylthiol, and if it is a halogenated hydrocarbon, the amount of the chain transfer agent other than the above-described chain transfer agent must be less than or equal to the amount of the above-mentioned chain transfer agent. It is desirable that the amount is 5 times or less that of the transfer agent.

Examples of other well-known chain transfer agents include alkyl mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, mercaptoethanol, turbinolene,
Mention may be made of halogenated hydrocarbons such as dipentene, t-terpinene and carbon tetrachloride, sulfides, and the like. Among these, t-dodecyl mercaptan is particularly desirable.

Any known method for using the chain transfer agent can be used. Namely, these include a pre-batch addition method, a continuous addition addition method, an intermittent addition addition method, and a concentration gradient addition method in which the addition rate is sequentially changed.

The latex polymer emulsifies monomers consisting of 10 to 60% by weight of conjugated dienes, 11 to 15% by weight of saturated carboxylic acid injected with ethylene, and 25 to 89% by weight of other monomers that can be copolymerized with these. Obtained by polymerization.

Conjugated dienes include butadiene, isoprene, 2-
There is chloro-1,3-butadiene, and its usage amount is essential to be 10 to 60%, more preferably 30 to 45% by weight. In this range, it is possible to exhibit the highest level of Bic strength, and it is 1o!
If it is less than 60% by weight, the polymer becomes too brittle, and if it exceeds 60% by weight, it becomes too soft, and in either case, it is impossible to provide high bulk strength.

Examples of ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Ethylenically unsaturated carboxylic acid is 1-8j! It is essential that the amount be within the range of %. If it is less than 1% by weight, the dispersion stability of the latex cannot be maintained at a high level, and paint r! Various problems occur during R manufacturing and coating. Also, the shock strength is inferior. If the content exceeds 15% by weight, the viscosity of the latex or paint will become too high, and the water resistance will also be impaired.

Among other monomers, aromatic (di)vinyl compounds are most commonly and effectively used, followed by (meth)acrylic esters, vinyl cyanide compounds, ethylenic amide monomers, etc. It is.

Styrene is an aromatic (di)vinyl compound.

Examples include α-methylstyrene, chlorostyrene, alkylstyrene, and divinylbenzene.

Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, and , glycidyl (
Examples include meth)acrylate and ethylene glycol di(meth)acrylate.

As vinyl cyanide compounds, acrylonitrile,
Examples include methacrylonitrile.

Examples of the ethylenic amide monomer include (meth)acrylamide and N-methylol(meth)acrylamide.

In addition, vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides such as vinylidene chloride, aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (
Ethylenic amine monomers such as meth)acrylates
Examples include sodium styrene sulfonate.

Next, the manufacturing method will be described. In the production method of the present invention, it is produced by a conventionally known normal emulsion polymerization method. That is, in a dispersion system whose basic composition is water, a surfactant, a monomer, a radical polymerization initiator, and other raw materials if necessary, a production method in which the monomer is an aqueous dispersion of polymer particles, - For boat fishing, the polymer concentration ranges from 40 to 60% by weight. The latex particle size can be adjusted by the proportion of surfactant and/or seed latex used.
In general, the higher the usage rate, the smaller the particle size of the latex produced.

Here, the preferred range of particle diameter is 0.05 to 1 μm, more preferably 0.07 to 0.05 μm. It is 3 μm.

Examples of surfactants include fatty acid soaps, rosin acid soaps, anionic surfactants such as alkyl sulfonates, dialkylaryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, and polyoxyethylene alkylaryl sulfates. , polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxybrobylene block copolymer. The surfactant is usually used as an anionic surfactant alone or as a mixed system of anionic/nonionic surfactants, and the ratio of the surfactant to the monomer is generally in the range of 0.005 to 2% by weight.

Polymerization initiators are those that cause addition polymerization of monomers by radical decomposition in the presence of heat or reducing substances, and include water-soluble or oil-soluble beroxonisulfates, peroxides, and azobis compounds. Potassium Beroxodisulfate, Sodium Beroxodisulfate, Beroxonia a
Examples include m-ammonium, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile, and cumene hydroperoxide, with beroxonisulfate being most preferably used. The ratio of polymerization initiator to monomer is usually 0.
．． 2-1. It is 5% by weight.

The polymerization temperature is generally in the range of 60 to 90°C, but when it is desired to accelerate the polymerization rate or polymerize at a lower temperature, sodium bisulfite, ascorbic acid or its salts, erythorbic acid or its salts, Rongalite, etc. A so-called redox polymerization method can be used in which a reducing agent is used in combination with a polymerization initiator.

In addition, various polymerization modifiers are often added as desired, such as sodium hydroxide,
These include various pH-moderating agents such as potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, and disodium hydrogen phosphate, and various chelating agents such as sodium ethylenediaminetetraacetate.

The latex of the present invention can be used as a binder for paper coatings in a conventional manner. That is, latex is mixed with pigments, water-soluble polymers, and various additives in water in which a dispersant is dissolved.
This is an embodiment in which a uniform dispersion is obtained. Then, this paint can be applied to the base paper by a conventional method such as various blade coaters or roll coaters.

<Examples and Comparative Examples> Next, the present invention will be specifically explained based on Examples and Comparative Examples, but it goes without saying that the present invention is not limited only to the following Examples. Percentages are by weight.

(1) tII of polymer latex! ! Diameter 0.04
Aqueous dispersion of μm seed particles with seed solids concentration of 25
%) was placed in a side pressure reaction vessel equipped with a stirring device and a jacket for temperature VF4N, and further charged with 70 parts of water, 0.2 parts of sodium lauryl sulfate, and 112.5 parts of fumar, and brought to an internal temperature of 80°C. The temperature was raised, and then an oily mixture consisting of the monomers and chain transfer agent shown in Table 1, 15 parts of water,
1 part sodium belloxonisulfate, 0 sodium hydroxide
．． 2 parts, sodium lauryl sulfate 0. 1 part of the aqueous solution is added at a constant flow rate over a period of 4 and 5 hours, respectively. Then, the temperature was maintained at 80°C for 1 hour and then cooled. The pH of the polymer latex thus produced was adjusted to 7 with sodium hydroxide. ! After that, unreacted monomers were removed by steam stripping and filtered through a 200 mesh filter cloth. Note that all polymer latexes were adjusted to have a final solid content concentration of 50%, and were subjected to the following tests.

The particle diameter and gel fraction of these polymer latexes were measured by the following method, and the results are listed in Table 1.

<Measurement of particle size> Light scattering particle size analyzer (Model 600 manufactured by CN Wood)
The average particle diameter of the polymer latex was measured using the following method.

<Measurement of Gel Fraction> Polymer latex was uniformly applied onto a polypropylene film using an FJa2B wire bar, and dried for 1 hour in a dryer at 50"C to form a film.

Next, peel off this latex film and check it on a chemical balance to get about 0.
．． After accurately weighing 5 g, immerse it in a container containing 300 cc of toluene, and stir at room temperature for 6 hours with a shaker. Thereafter, the contents are filtered through a 325-mesh wire mesh that has been accurately weighed in advance, and the residue remaining on the wire mesh is dried in a dryer at 50° C. for 2 hours. The gel fraction is calculated by the following formula.

Gel fraction (%) = 100 Performance evaluation as a binder was conducted. The coating material had the formulation shown in Table 2 and was prepared using a high-speed stirrer with an amount of water that gave a nonvolatile content concentration of 63%. The pH of the paint was adjusted to 9.0 with aqueous ammonia. Table 3 shows the conditions for producing FJ4 coated paper using this paint.

Various physical properties of the prepared coated paper were g-equalized using the following method.

Blister resistance: Printing ink (Dainippon Ink Co., Ltd. mW e bb) on both sides of coated paper using R1 printing tester (Mei Seisakusho m1)
Zett yellow) 0.3 cc is smeared. The printed coated paper is cut to an appropriate size, and the test piece is immersed in a silicone oil constant temperature bath heated to a predetermined temperature to observe whether or not blisters occur. This test is performed by varying the temperature of the thermostatic chamber, and the lowest temperature at which blistering is observed is determined. The higher the temperature, the better the blister resistance.

Drybic strength: Using an RI printing tester, printing ink (SD Super Deluxe 50 Beni B manufactured by Shuka Shiki Co., Ltd.; tack value 18) 0
．． Overprint 4cc 5 times, trace the picking state that appears on the rubber roll onto another mount, and observe the situation. The evaluation was carried out using the IO point evaluation method, and the fewer the picking phenomenon, the higher the score.

Wet Bic Strength: Using an R1 printing tester, moisten the surface of the coated paper with a water absorbing roll, and then print once with 0.4 cc of printing ink (SD Super Deluxe 50 Beni B manufactured by Toka Shiki Co., Ltd.; tack value 18). , The picking condition that appears on the rubber roll is traced onto another mount and the situation is observed. Evaluation was performed using a 10-point evaluation method, and the fewer the picking phenomenon, the higher the score.

Halftone dot reproducibility: Printing was performed using a Ministry of Finance gravure testing machine, and the halftone dot missing rate was counted. Evaluation was performed using a 10-point evaluation method, and the smaller the missing rate, the higher the score.

Table 4 lists the test results of Examples and Comparative Examples. According to this, it is understood that the coated paper using the latex of the present invention as a binder is highly balanced in bulk strength and other physical properties.

(3) Carpet pack sizing performance evaluation The polymer latex prepared in (1) was evaluated for its performance as a binder for carpet pack sizing. In addition,
The adhesive paint has the composition shown in Table 5 and has a non-volatile content of 70.
% of water using a high-speed stirrer. Table 6 shows the conditions for preparing carpet using this paint.

: The peel strength and thread removal force of the carpet manufactured by A were evaluated by the following methods.

Peel strength: According to JIS L-1021. The higher the average value, the better.

Suture removal strength: According to JIS L-1021. The higher the average value, the better.

Table 7 lists test results as examples and comparative examples. According to this, it is understood that the carpet using the latex of the present invention as a binder has highly improved peel strength and thread removal strength.

<Effects of the Invention> The polymer latex of the present invention exhibits excellent adhesive properties, and is particularly useful as a paper coating binder for producing coated paper that has excellent ink shock resistance in printing and other physical properties, and also for carpet pack sizing. It is useful as a binder for

Table 1-1 Composition and properties of polymer latex (1) Polymer latex classification Examples Latex Polymer Latex Monomer mixture (parts) Mercaptan 0.3 0.3 Properties of prepared latex Table 1-2 Polymer Composition and Properties of Latex (2) Polymer Latex Classification Examples Latex Polymer Latex Ethylhexyl Cathioglycolate Carbon Tetrachloride t-Dodecyl Mercaptan! I! l! 1 Properties of latex" I41 Table-3 Composition and properties of polymer latex (3) Comparative example of polymer latex classification Latex Polymer latex East! Butadiene methyl methacrylate acrylonitrile thioglycolic acid ethylhexyl carbon tetrachloride t-dodecyl mercaptan Preparation of latex Properties Table 2 Blend composition of Reiko paint (dried ffi salmon part) (Note) l〉 "Ultra White 90" manufactured by Engelhard "Ultra Coat" manufactured by Engelhard "Ultra Coat" manufactured by Sankyo Kesai
Niskaran #1500J Toagosei Kagaku Co., Ltd. “Aron T-
40""Smiritz636" manufactured by Sumitomo Chemical Co., Ltd. rMs4600 manufactured by Nippon Shokuhin Kogyo Co., Ltd.] Table 3 Coating ITl Preparation article (ki) Combined latex dry strength wet strength 7 6 6 7 5 5
9 5.0 10 10 8 8
Table 4-2 Paper coating performance evaluation results (2,) Examples and comparative examples Polymer latex Table 1-3 Paper coating performance evaluation results (3) Examples and comparative examples 1 Combined Lattepa 7x0 1 2 Table 5: Blend composition of glue cutting (parts by dry weight) Table 6: Carpet pack sizing conditions

Claims (1)

[Claims] 1) A latex is produced by emulsion polymerization from 10 to 60% by weight of a conjugated diene, 1 to 15% by weight of an ethylenically unsaturated carboxylic acid, and 25 to 89% by weight of other monomers copolymerizable with these. In manufacturing, the general formula ▲numerical formula, chemical formula, table, etc. is used in the polymerization of 0.01 to 5.0% by weight based on 100% by weight of the monomers▼ (However, R is a carbon number of 2 to 18) A method for producing a copolymer latex, characterized in that a thioglycolic acid alkyl ester represented by the following formula is used as a chain transfer agent. 2) The production method according to claim 1, wherein the alkyl group R added to thioglycolic acid is ethylhexyl. 3) The method according to claim 1 or 2, in which an alkylthiol and/or a halogenated hydrocarbon is used in combination as a chain transfer agent. Manufacturing method 4) The manufacturing method according to claim 3, wherein the chain transfer agent used in combination is t-dodecyl mercaptan. 5) The method of adding the chain transfer agent is a batch pre-addition method, a continuous addition addition method, an intermittent addition addition method, or an addition rate. 6) The method for adding monomers is a concentration gradient type addition method in which the monomers are added sequentially. Claim No. 1, which is a concentration gradient addition method in which the addition rate is sequentially changed, a multi-step addition method in which the monomer components are changed stepwise, or a power feed addition method in which the monomer components are continuously changed. 7) Copolymer latex produced by the method according to claim 1, 2, 3, 4, 5 or 6; 8) Copolymer latex according to claim 7. Coated paper using the combined latex as a binder 9) A carpet using the copolymer latex according to claim 7 as a binder for backside zinc.