JP2933984B2 - Method for producing diene-based copolymer latex - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a method for producing a copolymer latex. More specifically, the present invention relates to a method for efficiently producing a high-performance copolymer latex suitable as a binder for paper coating, carpet backsizing, fiber bonding and the like.

Conventional technology Conventionally, synthetic copolymer latex is, for example, a binder for paper coating, a binder for carpet backsizing,
It is widely used as a binder for bonding fibers such as nonwoven fabric and artificial leather, or as an adhesive for various materials.
And when the copolymer latex is used for such an application, the copolymer latex has a high adhesive strength,
It is also required to be excellent in water resistance, blister resistance by drying and heating, and the like.

For example, coated paper, for the purpose of improving the printability of paper and the improvement of optical properties such as gloss, on the surface of the base paper made, kaolin clay, calcium carbonate, satin white, talc, pigments such as titanium oxide, Coated with a water-soluble polymer as a main component such as starch, casein, polyvinyl alcohol, carboxymethyl cellulose as a copolymer latex as a binder and a water retention agent or an auxiliary binder, Conventionally, styrene and butadiene are used as main monomer components as a copolymer latex, and a styrene-butadiene copolymer latex obtained by emulsion polymerization of these is used.
So-called SB latex is widely used.

By the way, in recent years, the production of coated paper has increased remarkably with the increase in demand for magazines, pamphlets and advertisements printed in color. In particular, with the tendency of high-speed printing in offset printing, the required level for the quality of coated paper and pigment binder is becoming increasingly sophisticated, and therefore, among the quality of coated paper, especially the pick resistance, the so-called pick strength Improvement is strongly demanded. Moreover, this pick strength performance is negatively correlated with other printing properties, such as wet pick strength, blister resistance, halftone dot reproducibility, etc., so further improvements to balance these various properties to a high level have been made. Has been requested.

Since these properties of the coated paper greatly depend on the performance of the SB latex used as a pigment binder, various studies have been made on the performance of the SB latex.

For example, it has been confirmed that the proportion of the insoluble portion of a copolymer latex film in a solvent such as benzene, toluene, and tetrahydrofuran is a controlling factor for pick strength and blister resistance. Specifically, it has been proposed to exhibit excellent performance by adjusting the composition of the copolymer in the latex and the gel fraction to specific ranges (Japanese Patent Publication No. 59-3598). Gazette, Japanese Patent Publication No. Sho 60-17879,
No. 8-4894). Although the gel fraction of this latex varies depending on various polymerization factors such as the monomer composition and the polymerization temperature, a method of adjusting the gel fraction to a desired level generally and simply involves adding a chain transfer agent.

However, when the gel fraction is adjusted by the amount of the chain transfer agent, the pick strength of the coated paper generally becomes the highest in the SB type latex when the gel fraction is in the range of 75 to 95% by weight. On the other hand, it has been recognized that the lower the gel fraction, the better the blister resistance is, and in order to simultaneously improve both the pick strength and the blister resistance to a high level, any of the above-described techniques is used. Not fully satisfactory.

On the other hand, a method has been proposed in which the addition rate of the chain transfer agent is changed into the polymerization system within the same range as the end point of the addition of the monomer (Japanese Patent Publication No. 62-1987).
8443, JP-A-61-63794). However, none of these methods is fully satisfactory for simultaneously increasing both pick strength and blister resistance to high levels.

On the other hand, an adhesive for carpet backsizing is generally a composition obtained by blending a filler such as calcium carbonate or aluminum hydroxide and other additives such as a thickener with a copolymer latex, and comprises a tufted carpet and a needle. In the production of punched carpets and the like, it is mainly used for preventing piles from dropping off and for bonding to a secondary base cloth such as a chute. Therefore, in this case, the improvement of the adhesive strength, which is the most important physical property of the carpet, is one of the biggest technical problems in the industry, and therefore, an improvement from the viewpoint of the blending of the copolymer latex and the composition has been studied. However, in reality, satisfactory levels have not yet been obtained.

As described above, the conventional technology cannot cope with even higher speed printing of coated paper, and there is a strong demand for the appearance of a copolymer latex as a binder capable of producing high quality coated paper. Also, the appearance of a copolymer latex having a high adhesive force has been desired for carpets and adhesives.

Problems to be Solved by the Invention Under such circumstances, the present invention is intended to improve the balance between pick strength and other performance in coated paper for printing, and the adhesive force in carpet back sizing and adhesive. The purpose of the present invention is to provide a high-performance copolymer latex for improvement.

Means for Solving the Problems The present inventors have conducted intensive studies to develop a copolymer latex having the above preferable properties, and as a result, when producing a diene copolymer latex by emulsion polymerization, a specific amount The chain transfer agent is continuously and sequentially added to the polymerization system until the polymerization rate reaches a specific value, and thereafter a specific amount of the chain transfer agent is a time after the completion of the monomer addition,
Further, it has been found that the object can be achieved by continuously and successively adding the components into the polymerization system until the polymerization rate reaches a specific value, and the present invention has been completed based on this finding.

That is, the present invention relates to a method for producing a diene-based copolymer latex by emulsion-polymerizing a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and other copolymerizable monomers in an aqueous medium. With respect to 100 parts by weight of the total amount of the body, the chain transfer agent x parts by weight until the polymerization rate becomes 70%, and further after the end of the addition of the monomer, and until the polymerization rate becomes at least 85%. A diene-based copolymer, wherein y parts by weight of a chain transfer agent is continuously and sequentially added to a polymerization system such that x and y satisfy the following relationships: 0.1 ≦ x + y ≦ 3.0 and x ≦ y / 1.1. A method for producing latex is provided.

 Hereinafter, the present invention will be described in detail.

Examples of the chain transfer agent used in the present invention include t-dodecyl mercaptan, n-dodecyl mercaptan, alkyl mercaptans such as mercaptoethanol, thioglycolic acid esters such as pentaerythritol tetrathioglycolate, sulfides, and halogen compounds. be able to. One of these chain transfer agents may be used, or two or more thereof may be used in combination.

The continuous sequential addition of the chain transfer agent in the present invention means that the chain transfer agent is continuously added to the reactor, and the addition rate should not be zero, but the change in the addition rate is continuous. It doesn't have to be, it can be intermittent.

It is important that the start of the addition of the chain transfer agent is the start of the polymerization, the end is the end of the addition of the monomer or later, and that the polymerization rate is at least 85%. The more preferable addition end point of the chain transfer agent is:
This is the time when the conversion becomes 90% or more, and more preferably the time when the polymerization rate becomes 90% or more.

Regarding the addition rate of the chain transfer agent, the total amount of the monomers was 10
With respect to 0 parts by weight, (1) x until the polymerization rate becomes 70%
Parts by weight, and (2) y parts by weight after the end of the addition of the monomer and until the polymerization rate reaches at least 85%, where x and y are represented by the formulas 0.1 ≦ x + y ≦ 3.0 and x ≦ It is necessary to continuously and sequentially add them to the polymerization system so as to satisfy the relationship of y / 1.1.

Unless the addition end time and the addition rate of the chain transfer agent are set as described above, the balance between good pick strength and other performances, which is the object of the present invention, cannot be obtained.

Examples of the method of adding the chain transfer agent include a method of adding only the chain transfer agent to the polymerization reactor alone, a method of adding the chain transfer agent by diluting it with a non-reactive solvent, and a method of emulsifying the chain transfer agent in advance and adding water. A method in which the dispersion is added after the addition is given. Alternatively, a method may be used in which a part of the chain transfer agent is previously mixed with the monomer mixture, the addition of the mixture is terminated during the polymerization, and the remaining chain transfer agent is continuously added alone.

In the present invention, as the conjugated diene compound used, for example, butadiene, isoprene, 2-chloro-1,3
-Butadiene and the like. These conjugated diene compounds may be used alone or in combination of two or more, and the amount thereof is in the range of 5 to 90% by weight based on the weight of all monomers. Is desirable. Further, in the case of a latex of a copolymer for coated paper, a more preferable use amount of the conjugated diene compound is selected in a range of 20 to 70% by weight.

As the ethylenically unsaturated carboxylic acid used in the present invention, for example, monobasic carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, dibasic carboxylic acids such as fumaric acid and monoesters thereof And the like. One of these ethylenically unsaturated carboxylic acids may be used alone, or two or more thereof may be used in combination. The amount of the ethylenically unsaturated carboxylic acid used is usually 0.2% by weight or more, preferably Is 0.2 ~
It is selected in the range of 15% by weight.

Other copolymerizable monomers used in the present invention include aromatic monovinyl compounds and divinyl compounds, acrylates and methacrylates, vinyl cyanide compounds, and ethylenic amides.

Examples of the aromatic monovinyl compound and divinyl compound include styrene, α-methylstyrene, chlorostyrene, alkylstyrene, and divinylbenzene. As the acrylate or methacrylate, for example, methyl of acrylic acid or methacrylic acid,
Ethyl, propyl, butyl, 2-ethylhexyl, hydroxyethyl, glycidyl esters, and further, ethylene glycol acrylate or dimethacrylate are exemplified. Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile, and examples of the ethylenic amide include acrylamide, methacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide.

Besides, in addition to these monomers, vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides such as vinylidene chloride, aminoethyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, etc. Of ethylenic amines, sodium styrenesulfonate and the like can also be used.

One of these copolymerizable monomers may be used,
Two or more kinds may be used in combination.

In the present invention, the copolymer latex is obtained by emulsion-polymerizing the conjugated diene compound, the ethylenically unsaturated carboxylic acid, and another copolymerizable monomer in an aqueous medium. This emulsion polymerization is not particularly limited as long as the addition of the chain transfer agent satisfies the above conditions, and a conventionally known method can be used.

The concentration of the copolymer in the copolymer latex is usually selected in the range of 40 to 60% by weight.

The average particle size of the copolymer latex in the present invention can be adjusted by the use ratio of the surfactant or the seed latex, and generally, the higher the use ratio, the smaller the average particle size of the produced copolymer latex tends to be. There is. This average particle size is 0.05 to 1 μm, preferably 0.1.
It is preferably in the range of 07 to 0.3 μm.

Examples of the surfactant include anionic surfactants such as fatty acid soap, rosin acid soap, alkyl sulfonate, dialkylaryl sulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate, and polyoxyethylene alkylaryl sulfate. Examples of the surfactant include nonionic surfactants such as an activator, polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxypropylene block copolymer. This surfactant is usually used in an anionic surfactant alone or in an anionic / nonionic mixed system, and the amount of the surfactant is usually 0.05 to 0.05% based on the weight of all monomers.
It is selected in the range of 2% by weight.

The radical polymerization initiator necessary for the initiation of polymerization is one having a function of radically decomposing by heat or a reducing substance to cause addition polymerization of a monomer, such as water-soluble or Oil-soluble peroxodisulfates, peroxides, azobis compounds, etc., specifically, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, tert-butyl hydroperoxide, benzoyl peroxide, 2, Examples thereof include 2-azobisisobutyronitrile and cumene hydroperoxide. Of these, peroxodisulfate is particularly preferred. The amount of the polymerization initiator used is usually selected in the range of 0.2 to 1.5% by weight based on the weight of all monomers.

The polymerization temperature in this emulsion polymerization is usually selected in the range of 60 to 100 ° C., but if it is desired to accelerate the polymerization rate or to carry out the polymerization at a lower temperature, sodium acid sulfite, ascorbic acid or a salt thereof, erythorbic acid or the like Salt, using a reducing agent such as Rongalit in combination with the polymerization initiator,
A so-called redox polymerization method can be employed.

In the present invention, if desired, various polymerization regulators such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, disodium hydrogen phosphate, etc.
Various chelating agents such as a pH adjuster and sodium ethylenediaminetetraacetate can be added.

When the copolymer latex produced according to the present invention is used as a binder for paper coating paint, a method generally used, for example, an inorganic pigment or an inorganic / organic content, water in a water in which a dispersant is dissolved, is used. A method can be adopted in which the copolymer latex is added and mixed together with a water-soluble polymer compound and various additives and used as a homogeneous dispersion. The coating material for paper coating can be applied to base paper by an ordinary method using various blade coaters, roll coaters and the like.

Effects of the Invention According to the present invention, a high-performance copolymer latex that can further improve the balance between pick strength and other properties in coated paper for printing and the adhesive strength in carpet backsizing and adhesives can be easily prepared. Can be obtained.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

 In addition, each characteristic was calculated | required as follows.

(1) Properties of copolymer latex (a) Polymerization rate About 1 g of the extracted reaction solution is precisely weighed, dried at 130 ° C. for 1 hour, and the residue is weighed, and the solid content is calculated by the following formula. .

The charged solid content is calculated by the following equation.

From these, the conversion is calculated by the following equation.

(2) Evaluation of paper coating performance (a) Blister resistance Using a RI printing tester (manufactured by Meiji Seisakusho), 0.3 ml of printing ink (Webb Zett yellow, manufactured by Dai Nippon Ink Co., Ltd.) is printed on both sides of the coated paper. . The printed coated paper is cut into an appropriate size, and the test piece is immersed in a silicone oil thermostat adjusted to a predetermined temperature to observe whether blisters are generated. This test is performed by changing the temperature of the thermostat, and the temperature at which blisters are generated is compared. The evaluation was performed by a 10-point evaluation method, and the higher the blister resistance, the higher the score.

(B) Dry pick strength Using a RI print tester, print ink (SD
Super Deluxe 50 crimson B; tack value 18) 0.4 ml was overprinted 5 times, and the picking condition that appeared on the rubber roll was lined up on another backing paper, and the situation was observed. The evaluation was performed by a 10-point evaluation method, and the smaller the picking phenomenon, the higher the score.

EXAMPLES, COMPARATIVE EXAMPLES 1 AND 2 4 parts by weight of an aqueous dispersion of 0.04 μm seed particles (solid content 25% by weight) were placed in a pressure-resistant reaction vessel equipped with a stirring device and a temperature control jacket. 70 parts by weight, 0.2 parts by weight of sodium lauryl sulfate and 2.5 parts by weight of fumaric acid were charged, and the internal temperature was raised to 80 ° C. Then, a monomer mixture shown in FIG. 1, 15 parts by weight of water, and sodium peroxodisulfate were added. An aqueous solution consisting of 1 part by weight, 0.2 part by weight of sodium hydroxide and 0.1 part by weight of sodium lauryl sulfate was ignited at a constant flow rate over 4 hours and 5 hours, respectively. The chain transfer agents shown in Table 1 were added at the times shown in FIG. 1 (Example), FIG. 2 (Comparative Example 1), and FIG. 3 (Comparative Example 2). After cooling for 6 hours from the start of polymerization, the copolymer latex was adjusted to pH 7 with sodium hydroxide to remove unreacted monomers and the like by steam stripping. The mixture was filtered with a mesh filter cloth. In addition, all the copolymer latexes were adjusted so that the solid content concentration was finally 50% by weight.

Application Examples The performance of the copolymer latexes prepared in Examples and Comparative Examples 1 and 2 as a binder for paper coating was evaluated. Table 4 shows the results.

The coating composition was prepared by a high-speed stirrer with the composition shown in Table 2 and an amount of water at which the nonvolatile content was 63% by weight. The pH of the paint was adjusted to 9.0 with ammonium water. Table 3 shows the preparation conditions of the coated paper using this paint.

From Table 4, it is understood that the coated paper using the copolymer latex of the present invention as a binder has a highly balanced pick strength and other physical properties.

[Brief description of the drawings]

FIGS. 1, 2 and 3 are graphs showing the relationship between the time from the start of polymerization and the amount of chain transfer agent added in Examples, Comparative Examples 1 and 2, respectively.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuyuki Nakahara 1-3-1 Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Asahi Kasei Kogyo Co., Ltd. (56) References Patent 2615249 (JP, B2) (58) Fields investigated (Int.Cl. ⁶ , DB name) C08F 2/00-2/38

Claims (1)

(57) [Claims] 1. A conjugated diene compound in an aqueous medium,
In producing a diene-based copolymer latex by emulsion-polymerizing an ethylenically unsaturated carboxylic acid and other copolymerizable monomers, the polymerization rate is 7 based on 100 parts by weight of the total amount of monomers.
0 parts by weight of the chain transfer agent until the amount reaches 0%, and y parts by weight of the chain transfer agent until the time when the polymerization rate is at least 85%.
Are continuously and sequentially added into the polymerization system such that the following formulas are satisfied: 0.1 ≦ x + y ≦ 3.0 and x ≦ y / 1.1.