JPH0441512A - Production of diene copolymer latex - Google Patents

Abstract

PURPOSE:To produce the title latex improved in adhesiveness, etc., by adding two mixtures each comprising a mixture of a conjugated diene compound, an ethylenically unsaturated carboxylic acid and another monomer and a chain transfer agent in a specified proportion and polymerizing them. CONSTITUTION:5-90wt.% conjugated diene compound (i) is mixed with at least 0.2wt.% ethylenically unsaturated carboxylic acid (ii) and a comonomer (iii) to obtain a monomer mixture (a). Separately, 0.1-0.2 pt.wt., per 100 pts.wt. component (a), alkylthiol chain transfer agent (iv) is mixed with 0.2-10 pts.wt., per 100 pts.wt. component (a), chain transfer agent (v) other than component (iv) to obtain a chain transfer agent (b). 50-80wt.% component (a) is mixed with component (iv) to obtain a mixture (A). The remainder of component (a) is mixed with component (v) to obtain a mixture (B). A process for emulsion- polymerizing component (a) in the presence of component (b), a surfactant (c) and a polymerization initiator (d) in an aqueous medium, wherein component A is added to the reaction system and polymerized in the 1st step, and component B is added to the reaction system and polymerized in the 2nd step.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved method for producing 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 back sizing, fiber binding, etc.

Conventional technology Conventionally, synthetic copolymer latex has been used, for example, as a binder for paper coating, as a binder for carpendopa resin, and as a binder for noising.
It is widely used as a binder for binding fibers such as non-woven fabrics and artificial leather, and as an adhesive for various materials.

When copolymer latex is used for such purposes, it is required that the copolymer latex has high adhesive strength and excellent water resistance and blister resistance due to dry heating. Ru.

For example, coated paper uses kaolin clay, cal/rum carbonate, satin white,
Paints whose main components are pigments such as talc and titanium oxide, their copolymer latex as a binder, starch as a water-retaining agent or auxiliary binder, and water-soluble polymers such as casein, polyvinyl alcohol, and carboxymethylcellulose are coated. Conventionally, styrene-butadiene copolymer latex, so-called SB latex, is produced by emulsion polymerization of styrene and butadiene as main monomer components. Used for general purposes.

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. Moreover, this pick strength performance has a negative correlation with other print properties, such as wet pick strength, blister resistance, halftone dot reproducibility, etc., so improvements that balance these physical properties to a high level are required. 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 pick strength and blister resistance, and various studies have been conducted from this point of view. Specifically, by adjusting the composition and gel fraction of the copolymer in the latex to a specific range,
It has been proposed to exhibit excellent performance (Japanese Patent Publication No. 59-3598, Japanese Patent Publication No. 60-17879, Japanese Patent Application Laid-open No. 58-4894). The gel fraction of this latex varies depending on various polymerization factors such as monomer composition and polymerization temperature, but a common and simple method for adjusting it to a desired level is to add a chain transfer agent.

However, when the gel fraction is adjusted by the amount of chain transfer agent, the pink strength of coated paper for boat fishing is 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 is.In order to simultaneously improve both pick strength and blister resistance to a high level, none of the above technologies can be used. It's not completely satisfying.

On the other hand, carpet back sizing adhesives are generally compositions of copolymer latex with other additives such as fillers such as calcium carbonate or aluminum hydroxide and thickeners, and are suitable for use in tufted carpets, In the production of needle punch carpets, etc., pile (
It is used to prevent tassels from falling off and to adhere to 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.

As described above, conventional technologies 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. Furthermore, it is desired that copolymer Latinx having high adhesive strength be developed for carpets and adhesives as well.

Problems to be Solved by the Invention Under these circumstances, the present invention aims to further improve the balance between pink strength and other properties in coated printing paper, and the adhesive strength in carpet back sizing and adhesives. The purpose of this work is to provide a high-performance copolymer latex for all applications.

Means for Solving the Problems As a result of intensive research to develop a copolymer latex having the above-mentioned preferred properties, the present inventors found that when producing a diene copolymer latex by emulsion polymerization,
It was discovered that the objective could be achieved by sequentially adding two specific types of chain transfer agents into the polymerization system, and based on this knowledge, the present invention was completed.

That is, the present invention provides a method for producing a diene copolymer latex by emulsion polymerizing a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and other copolymerizable monomers in an aqueous medium. ) A mixture of 50 to 80% by weight of the total monomer mixture to be additionally added and an alkylthiol chain transfer agent is added as a first step, and then (b) a second step is performed.
The present invention provides a method for producing a diene-based copolymer latex, which is characterized in that a mixture of the remainder of the monomer mixture and a chain transfer agent other than an alkylthiol-based chain transfer agent is added as a step.

The present invention will be explained in detail below.

Examples of the alkylthiol chain transfer agent used in the present invention include alkyl mercaptans such as [-dodecylmercaptan, n-dodecylmercaptan, and mercaptoethanol, and thioglycolic acid esters such as pentaerythritol tetrathioglycolate. can.

Chain transfer agents other than the alkylthiol type used in the present invention include, for example, halogen compounds such as carbon tetrachloride, 2,4-diphenyl4-methyl-1-
Examples include nuclear-substituted α-methylstyrene dimer with pentene, aromatic compounds such as ethylbenzene, naphthol and its nuclear-substituted derivatives, and the like.

The alkylthiol-based chain transfer agent may be used alone or in combination of two or more, and the amount used is usually 0.1 parts per 10011 F parts of the total amount of monomers.
The amount is selected in the range of 1 to 0.2 parts by weight, preferably 0.1 to 1.0 parts by weight. On the other hand, one type of chain transfer agent other than the alkylthiol type may be used, or two or more types may be used in combination, and the amount used is usually 0.2 to 1
0 parts by weight, preferably in the range of 0.2 to 5 parts by weight.

In the present invention, first, (a) a mixture of 50 to 80% by weight of the total monomer mixture to be additionally added and the alkylthiol chain transfer agent is added as the first step, and then (
b) As a second step, it is necessary to add a mixture of the remainder of the additional chain transfer agent and the aforementioned chain transfer agent other than the alkylthiol type. Thus, the objects of the present invention can be achieved by sequentially adding two types of chain transfer agents to the polymerization system.

The conjugated diene compounds used in the present invention include:
For example, butadiene, isoprene, 2-chloro-1,3-
Examples include butadiene. These conjugated diene compounds may be used alone or in combination of two or more, and the amount used is 5 to 50% based on the weight of all monomers.
It is desirable that the content be in the range of 90% by weight. Furthermore, in the case of a copolymer latex for coated paper, a more preferable amount of the conjugated diene compound to be used is selected within the range of 20 to 70% by weight.

Examples of the 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; Examples include monoester. These ethylenically unsaturated carboxylic acids may be used alone or in combination of two or more, and the amount used is usually 0.2% by weight or more based on the weight of the total intermediate. , preferably 0.
It is selected in the range of 2 to 15%ffi amount.

Other copolymerizable monomers used in the present invention include aromatic monohinyl compounds, 2-vinyl compounds, acrylic acid esters, methacrylic acid esters, vinyl anhydride compounds, and ethylenic amides. Nato is mentioned.

As the aromatic monovinyl compound or divinyl compound,
Examples include styrene, α-methylstyrene, chlorostyrene, alkylstyrene, and novinylbenzene. Examples of acrylic esters and methacrylic esters include methyl, ethyl, propyl, butyl, 2-ethylhexyl, hydroquinoethyl, glycidyl ester, ethylene glycoldiacrylate, dimethacrylate, etc. of acrylic acid or methacrylic acid. can be mentioned. Examples of the noaninated vinyl compounds include acrylonitrile and metaglyconitrile, and examples of the 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, aminoethyl 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.

In the present invention, the copolymer latex is obtained by emulsion polymerization of the conjugated diene compound, ethylenically unsaturated carboxylic acid, and other copolymerizable monomers 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 conventionally known methods 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 diameter of the copolymer latex in the present invention can be adjusted by the proportion of surfactant and seed latex used, and generally, the higher the proportion used, the smaller the average particle diameter of the resulting copolymer latex tends to be. There is. The average particle size is desirably in the range of 0.05 to 1 μm, 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. Active agents, nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxypropylene block copolymer can be mentioned. This surfactant is usually used as an anionic surfactant alone or as an anionic/nonionic mixed system.
The amount used is based on the weight of all monomers, and is usually 0.05~
It is selected within the range of 2% by weight.

The radical polymerization initiator required to initiate polymerization is one that has the effect of causing addition polymerization of monomers by radical decomposition using heat or a reducing substance. Examples of such initiators include water-soluble or oil-soluble beroxodisulfate,
Peroxides, azobis compounds, etc., specifically potassium beroxonisulfate, sodium beloxonisulfate, ammonium beloxonisulfate, hydrogen peroxide, tertiary-butylhydroberoquinde, benzoyl peroxide, 2,2-azobisisobutyronitrile, Examples include cumene hydroperoxide, and among these, peroxodisulfate is particularly preferred. The amount of the polymerization initiator used is usually selected within 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 60 to 100°
C. However, when accelerating the polymerization rate or polymerizing at a lower temperature, a reducing agent such as acidic sodium sulfite, ascorbic acid or its salts, erythorbic acid or its salts, or longarinoto can be used as a polymerization initiator. A so-called redox polymerization method, which is used in combination with

In the present invention, various polymerization regulators such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, disodium hydrogen phosphate, etc. can be used as desired.
Various chelating agents such as H regulators and 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 an inorganic/organic pigment to water in which a dispersant is dissolved. The copolymer latex is added and mixed together with a polymeric compound and various additives,
A method using a homogeneous dispersion can be adopted. This paper coating paint can be applied to various blade coaters.
The base paper can be coated by a conventional method using a roll coater or 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 printing paper, and the adhesive strength in carpet thickening and adhesives is provided. can be easily obtained.

Examples Next, 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.

Paper coating performance evaluation (a) Blister resistance R [Printing ink (Webb Zett yellow, manufactured by Dainippon Ink Co., Ltd.) on both sides of coated paper using a printing tester (manufactured by Mei Seisakusho)
Print 0.3 mQ. This printed coated paper is cut to an appropriate size, and the test piece is immersed in a thermostatic oil bath adjusted to a predetermined temperature to observe whether or not blisters occur. This test is performed by changing the temperature of the constant temperature bath, and the temperature at which blisters occur is compared. Rating is 10
A point evaluation method was used, and the better the blister resistance, the higher the score.

(b) Using a dry pick strength R1 printing tester, printing ink (S
D Super Deluxe 50 Beni B; Tack value 18) 0.4
MQ is overprinted 5 times, the picking state that appears on the rubber roll is reversed onto another mount, and the situation is observed.

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

Examples, Comparative Example 1.2 4 parts by weight of an aqueous dispersion of seed particles having a diameter of 0°04 μm (seed solid content concentration 25% by weight) was placed in a pressure-resistant reaction vessel equipped with a stirring device and a temperature control jacket, and further Charge 70 parts by weight of water, 0.2 parts by weight of sodium lauryl sulfate, and 2.5 parts by weight of fumaric acid, raise the internal temperature to 80°C, and then add the monomer mixture (A) shown in Table 1. Add the monomer mixture (B) for 2 hours, and then add the monomer mixture (B) for 2 hours.
Added in time. Separately, at the same time as the addition of the monomer mixture (A) started, an aqueous solution consisting of 15 parts by weight of water, 1 part by weight of sodium beloxonisulfate, 0.2 parts by weight of sodium hydroxide, and 0.1 part by weight of sodium lauryl sulfate was added. Added after 5 hours.

After 6 hours from the start of polymerization, the copolymer latex was cooled, and the resulting copolymer latex was purified with sodium hydroxide.
Adjust H to 1:.

Application Examples The copolymer latexes prepared in Examples and Comparative Examples 1.2 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 ammonium water. Table 3 shows the conditions for preparing 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 high balance of bulk strength and other physical properties.

Table 2 Note 1) “Ultra White 90J2” manufactured by Engelhard
) “Ultracoat” manufactured by Engelhard 3) “Niscallon #1500J4” manufactured by Sanki Seifun Co., Ltd. “Aron T-40J5” manufactured by Toagosei Kagaku Co., Ltd. “Sumilets 6” manufactured by Sumitomo Chemical Co., Ltd.
Table 3

Claims (1)

[Claims] 1. In producing a diene copolymer latex by emulsion polymerizing a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and other copolymerizable monomers in an aqueous medium, (a) as the first step: A mixture of 50 to 80% by weight of the total monomer mixture to be additionally added and an alkylthiol-based chain transfer agent is then added, and then (b) the remainder of the monomer mixture to be additionally added and non-alkylthiol-based chain transfer agents are added as a second step. A method for producing a diene copolymer latex, which comprises adding a mixture of diene copolymer latex and a chain transfer agent.