JPH0441503A - Production of diene copolymer latex - Google Patents

Abstract

PURPOSE:To produce a diene copolymer latex improved in adhesiveness and being useful as a paper coating binder or the like by polymerizing a conjugated diene compound with an ethylenically unsaturated carboxylic acid and another comonomer while gradually adding a chain transfer agent in a specified period. CONSTITUTION:A process for emulsion-polymerizing 40-60wt.% monomer mixture of a mean particle diameter of 0.05-17mum comprising 5-90wt.% conjugated diene compound (A) (e.g. butadiene), 0.2-15wt.% ethylenically unsaturated carboxylic acid (B), (e.g. fumaric acid) and another comonomer (C) (e.g. styrene), at 60-100 deg.C in an aqueous medium in the presence of a chain transfer agent (D) (e.g. n- dodecyl), a surfactant (E) and a radical polymerization initiator (F), wherein component D is gradually added to the reaction system until the conversion reaches 85% or above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to 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 hacksizing, fiber binding, etc.

[Conventional technology]

Conventionally, synthetic copolymer latex has been widely used, for example, as a binder for paper coating, a binder for carpet hack sizing, a binder for binding fibers such as nonwoven fabrics and artificial leather, and adhesives for various materials. When the copolymer latex is used for such purposes, the copolymer latex is required to have high adhesive strength and excellent water resistance, blistering resistance due to dry heating, and the like.

For example, coated paper uses pigments such as kaolin clay, calcium carbonate, satin white, talc, and titanium oxide on the surface of the base paper to improve printability and optical properties such as gloss. , coated with a paint containing a copolymer latex as a binder and a water-soluble polymer such as starch, casein, polyvinyl alcohol, or carboxymethyl cellulose as a water-retaining agent or auxiliary binder, The copolymer latex has traditionally been a styrene-butadiene copolymer latex obtained by emulsion polymerization of styrene and butadiene as main monomer components,
So-called SB-type R/Nx is commonly used.

Incidentally, in recent years, the production of coated paper has increased significantly as demand for color-printed magazines, pamphlets, and advertisements has increased. In particular, with the trend toward higher speed printing in offset printing, the quality requirements for coated paper and pigment binders are becoming increasingly sophisticated. There is a strong need for improvement. Furthermore, since this shock strength performance has a negative correlation with other print properties, such as wet shock strength, blister resistance, halftone dot reproducibility, etc., further improvements are needed to balance these physical properties to a high level. requested.

Since these properties of coated paper are particularly strongly dependent 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 the copolymer latex film in solvents such as benzene, toluene, and tetrahydrofuran is the controlling factor for the shock strength and blister resistance. Specifically, it has been proposed that excellent performance can be achieved by adjusting the composition and gel fraction of the copolymer in latex to a specific range (Japanese Patent Publication No. 59-3598). Publication, Japanese Patent Publication No. 60-17879, Japanese Patent Publication No. 58-4894). The gel fraction of this latex varies depending on various polymerization factors such as monomer composition and polymerization temperature, but adding a chain transfer agent is a common and convenient method for adjusting it to a desired level.

However, when the gel fraction is adjusted by the amount of the chain transfer agent, the bulk strength of coated paper is generally highest when the gel fraction is in the range of 75 to 95% by weight in SB latex. On the other hand, it is recognized that the lower the gel fraction, the better the blister resistance, and all of the above technologies are sufficient to simultaneously improve both the shock strength and the blister resistance to a high level. is not satisfactory.

Carpet bank sizing adhesives, on the other hand, are generally compositions of copolymer latex with fillers such as calcium carbonate or aluminum hydroxide and other additives such as thickeners. This adhesive composition is used in the production of tufted carpets, needle punch carpets, etc., mainly to prevent piles from falling off and to bond with secondary base fabrics such as jute. Therefore, in this case, improving adhesive strength, which is the most important physical property of carpet, is one of the biggest technical challenges in this industry, and therefore, improvements are being considered from the aspect of blending copolymer latex and compositions. However, the reality is that a satisfactory level has not been obtained so far.

[Problem to be solved by the invention]

As described above, the conventional technology cannot cope with the ever-increasing printing speed of coated paper, and there is a strong need for the emergence of copolymer latex as a binder that enables the production of high-quality coated paper. The current situation is that Furthermore, there is a desire for a copolymer latex having high adhesive strength for carvents and adhesives as well.

[Means for Solving the Problems] Under these circumstances, the present inventors have investigated the balance between big strength and other properties in coated printing paper, and the balance between carpet back sizing and adhesives. With the aim of providing a high-performance copolymer latex to further improve adhesive strength, as a result of intensive research to develop the above-mentioned high-performance copolymer latex, as a monomer,
A conjugated diene compound, an ethylenically unsaturated carboxylic acid, and at least three other copolymerizable monomers are used, and when these monomers are subjected to emulsion polymerization in an aqueous medium, the chain reaction is achieved up to a certain degree of polymerization. It was discovered that this objective could be achieved by sequentially adding and reacting a transfer agent, and based on this knowledge, the present invention was completed.

That is, the present invention provides a method for producing a copolymer latex by emulsion polymerizing at least three types of a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and another copolymerizable monomer in an aqueous medium. Polymerization rate of polymer is 85%
The present invention provides a method for producing a diene copolymer latex, which is characterized in that a chain transfer agent is successively added into the polymerization system until the above-mentioned values are reached.

The present invention will be explained in detail below.

A feature of the present invention is that a chain transfer agent is added sequentially when producing a copolymer latex by emulsion polymerization.

Examples of the chain transfer agent used in the present invention include alkyl mercaptans such as t-dodecylmercaptan, n-dodecylmercaptan, and mercaptoethanol, thioglycolic acid esters such as pentaerythritol tetrathioglycolate, sulfides, and halogen compounds. can be mentioned.

Sequential addition of the chain transfer agent in the present invention means adding the chain transfer agent to the reactor continuously or intermittently. Although the start time of addition of the chain transfer agent can be selected arbitrarily, it is important to continue adding the chain transfer agent until the polymerization yield of the monomer reaches 85% or more. Polymerization yield is 85%
If the addition of the chain transfer agent is finished before the addition of the chain transfer agent is completed, a good balance between the shock strength and other properties cannot be obtained. A more preferable timing for finishing the addition of the chain transfer agent to better exhibit the effects of the present invention is when the monomer polymerization yield is 9.
0% or more, more preferably a monomer polymerization yield of 9
It is 5% or more. When adding, the chain transfer agent is added alone, the chain transfer agent is diluted with a non-reactive solvent, and the chain transfer agent is added after being diluted with a non-reactive solvent. The chain transfer agent is emulsified in advance and made into an aqueous dispersion before being added. etc.

Another method is to mix a part of the chain transfer agent in the monomer mixture in advance, stop adding the mixture during polymerization, and then add the remaining chain transfer agent alone.

Examples of the conjugated diene compound used in the present invention include 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 used is 5 to 9 based on the weight of the total monomers.
A range of 0% by weight is desirable. Further, in the case of a copolymer latex for coated paper, a more preferable range of this conjugated diene is 20 to 70% by weight.

Ethylenically unsaturated carboxylic acids used in the present invention include monobasic carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and crotonic acid; dibasic carboxylic acids such as maleic acid and fumaric acid; and monoesters thereof. etc. can be mentioned. These ethylenically unsaturated carboxylic acids may be used alone or in combination of two or more.

The amount of the ethylenically unsaturated carboxylic acid used is preferably 0.2% by weight or more based on the total monomers.

A more preferable range is 0.2 to 15% by weight.

Other copolymerizable monomers used in the present invention include:
Examples include aromatic monovinyl compounds, divinyl compounds, acrylic esters, methacrylic esters, vinyl cyanide compounds, and ethylenic amides.

Cough aromatic monovinyl compounds and divinyl compounds include:
Examples include styrene, α-methylstyrene, chlorostyrene, alkylstyrene, divinylhensen, and the like. Examples of acrylic esters and methacrylic esters include methyl, ethyl, propyl, butyl, 2-ethylhexyl, and hydroxyethyl xericidyl esters of acrylic acid or methacrylic acid, and ethylene glycol diacrylate or dimethacrylate. Examples of vinyl cyanide compounds include acrylonitrile and methacrylonitrile, and examples of ethylenic amides include acrylamide, methacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide.

Furthermore, in addition to these monomers, vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides such as vinylidene chloride, amine ethyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, etc. Ethylenic amines, sodium styrene sulfonate, etc. can also be used.

One type of these copolymerizable monomers may be used, or two types of these copolymerizable monomers may be used.
You may use combinations of more than one species.

The method for producing a copolymer latex of the present invention is to emulsion polymerize the conjugated diene compound and another monomer copolymerizable with the ethylenically unsaturated carboxylic acid in an aqueous medium. This emulsion polymerization method is not particularly limited other than the method of adding the chain transfer agent described above, and conventionally known methods such as water, the above monomer, a chain transfer agent, a surfactant, and a radical polymerization initiator are used. In a dispersion system whose basic constituents are other additive components used depending on the method, a method is used in which the monomer is polymerized to produce an aqueous dispersion of copolymer particles, that is, a copolymer latex. . The concentration of the copolymer in the copolymer latex is usually selected in the range of 40 to 60% by weight.

The average particle diameter of the copolymer latex produced according to the present invention can be adjusted by adjusting the proportion of surfactant and seed latex used, and generally speaking, the higher the proportion of the surfactant used, the greater the average particle diameter of the copolymer latex produced. tends to become smaller.

The preferred range of the particle size is 0.05 to 1 μm, more preferably 0.07 to 0.3 μm.

Examples of the surfactants include anionic surfactants such as fatty acid soaps, rosin acid soaps, alkyl sulfonates, dialkylaryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, and polyoxyethylene alkylaryl sulfates. Nonionic surfactants such as activators, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene sorbitol, tan fatty acid esters, and oxyethylene oxypropylene block copolymers can be mentioned. This surfactant is usually used as an anionic surfactant alone or as an anionic/nonionic mixed system, and the amount used is usually 0.05% based on the weight of total monomers.
-2% by weight.

The radical polymerization initiator has the effect of causing addition polymerization of monomers by radical decomposition using heat or a reducing substance. Examples of such a radical polymerization initiator include water-soluble or oil-soluble beroxonisulfuric acid. Salts, peroxides, azobis compounds, etc., specifically potassium beroxonisulfate, sodium berooxodisulfate, ammonium beroxonisulfate, hydrogen peroxide, t-butylhydroberoxyto, benzoyl peroxide, 2,2-azobisisobutylene Examples include lonitrile, cumene hydroperoxide, and among these, beroxonisulfate is particularly preferred. The amount of this polymerization initiator used is usually in the range of 0.2 to 1.5% by weight, based on the weight of total monomers.

The polymerization temperature in this emulsion polymerization is usually 60 to 100°
C, but if it is desired to accelerate the polymerization rate or polymerize at a lower temperature, a reducing agent such as acidic sodium sulfite, ascorbic acid or its salts, erythorbic acid or its salts, or Rongalit may be used as a polymerization initiator. A so-called redox polymerization method, which is used in combination, can be employed.

The present invention may optionally include various polymerization regulators, such as pH regulators such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, and disodium hydrogen phosphate, and various chelating agents such as sodium ethylenediaminetetraacetate. can be added.

When the copolymer latex produced according to the present invention is used as a binder for paper coating materials, it is possible to use a commonly used method, for example, adding an inorganic pigment or inorganic/organic pigments to water in which a dispersant is dissolved. A method can be adopted in which the copolymer latex is added and mixed together with a polymer and various additives and used as a homogeneous dispersion. This paper coating paint can be applied to base paper by a conventional method using various blade coaters, roll coaters, etc.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

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

(1) Properties of copolymer latex (a) Average particle size Light scattering particle size analyzer (Model 600 manufactured by CN Wood)
The average particle diameter of the polymer latex was measured using 0).

(b) Polymerization yield: Accurately weigh about 1 gram of the sampled reaction solution, and heat it at 130°C for 1 hour.
After drying for a period of time, weigh the residue. Calculate the solid content using the following method.

In addition, the solid content of the charge is calculated using the following method.

Preparation solid content (%) = 100 (Total weight of preparation) From these, the polymerization yield is calculated using the following formula.

(2) Evaluation of paper coating performance (a) Blister resistance Printing ink (manufactured by Dainippon Ink Co., Ltd., WebbZett yellow) on both sides of coated paper using an RI printing tester (manufactured by Mei Seisakusho)
0.311i! to print all over. This printed coated paper is cut to an appropriate size, and the test piece is immersed in a silicone oil constant temperature bath adjusted 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.

(b) Printing ink (manufactured by Toka Shiki Co., Ltd.,
SD Susu--Deluxe 50 Beni B; Tack value 18) 0.
4d Perform overprinting 5 times, trace the picking state that appears on the rubber roll onto another mount, and observe the situation.

Evaluation was performed using a 10-point evaluation method, and the fewer the picking phenomenon, the higher the score.

Examples 1 to 2 and Comparative Examples 1 to 2 4 parts by weight of an aqueous dispersion of seed particles with a diameter of 0.04 μm (seed solid content concentration 25% by weight) was added to a pressure-resistant container equipped with a stirrer and a shaker for temperature adjustment. Add 70 parts by weight of water, 0.2 parts by weight of sodium lauric sulfate, and 2.5 parts by weight of fumaric acid to a reaction vessel, raise the internal temperature to 80°C, and then add the monomer mixture shown in Table 1. and water 15
parts by weight, 1 part by weight of sodium beloxonisulfate, 0.2 parts by weight of sodium hydroxide, 0.2 parts by weight of sodium lauric sulfate.
1 part by weight of an aqueous solution were added at a constant flow rate over 4 and 5 hours, respectively. Further, the chain transfer agent shown in Table 1 was added at the time also shown in Table 1.

After maintaining the temperature at 80°C for 1 hour, the resulting copolymer latex was adjusted to pH 7 with sodium hydroxide, and unreacted monomers and non-copolymer latex were removed by steam stripping. The polymerizable water-insoluble solvent was removed and the mixture was filtered through a 200-mesh filter cloth. In addition, all copolymer latexes have a final solid content concentration of 50
The weight percentage was adjusted accordingly.

Table 1 shows the average particle diameter and polymerization yield of these copolymer latexes.

Application Examples The copolymer latexes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated for their performance as binders for paper coating. The results are shown in Table 4.

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% by weight. The pH of the paint was adjusted to 9.0 with aqueous ammonia. Table 3 shows the conditions for preparing coated paper using this paint.

From Table 4, it can be seen that the coated paper using the copolymerized latex of the present invention as a binder has a highly balanced pink strength and other physical properties.

Table 1 [Effects of the Invention] According to the present invention, the balance between pick strength and other performance of coated printing paper, and the adhesive strength of carpet back sizing and adhesives can be improved. ) 1) Manufactured by Engelhard, product name: Ultra White a0 2) Manufactured by Engelhard, product name: Ultra Coat 3) Manufactured by Sanki Seifun Co., Ltd., product name: Niscalan 4) Manufactured by Toagosei Kagaku Co., Ltd., product name Nearon T =40 5) Manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumiretsu 6366) Manufactured by Nippon Shokuhin Kako Co., Ltd., trade name: MS4600 A high-performance copolymer latex capable of improving MS4600 can be easily obtained.

Claims (1)

[Claims] 1. In producing a diene copolymer latex by emulsion polymerizing a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and at least three other copolymerizable monomers in an aqueous medium, the monomers A method for producing a diene copolymer latex, which comprises sequentially adding a chain transfer agent into a polymerization system until the polymerization rate reaches 85% or more.