JPH0441501A - 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 emulsion-polymerizing a conjugated diene compound with an ethylenically unsaturated carboxylic acid and another comonomer in an aqueous medium to a specified conversion. CONSTITUTION:At least 5wt.%, desirably 20-70wt.% conjugated diene compound (e.g. butadiene) is emulsion-polymerized with at least 0.2wt.%, desirably 0.2-15wt.% ethylenically unsaturated carboxylic acid (e.g. fumaric acid) and another comonomer (e.g. styrene) at 70-100 deg.C in an aqueous medium in the presence of a chain transfer agent, a surfactant and a radical polymerization initiator, and the polymerization is stopped when the conversion reaches 85-95%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a copolymer latex. More specifically, the present invention relates to a high-performance copolymer latex suitable as a binder for paper coating, fiber binding for carpent bank sizing, and the like.

[Prior Art] Conventionally, synthetic copolymer latex has been used as, for example, a binder for paper coating, a binder for carving, a binder for paper towels, a binder for binding fibers such as nonwoven fabrics and artificial leather, or an adhesive for various materials. It is widely used as When a 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 kaolin clay, calcium 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 retention agent or auxiliary binder, and water-soluble polymers such as casein, polyvinyl alcohol, and carboxymethyl cellulose are coated. It is something that has been done,
As the copolymer latex, styrene-butadiene copolymer latex, so-called SB latex, which is obtained by emulsion polymerization of styrene and butadiene as main monomer components, has been widely 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. 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. 593598, Japanese Patent Publication No. 60-17879,
JP-A No. 58-4894). This gel fraction is generally adjusted by the polymerization temperature and the amount of chain transfer agent.

However, when the gel fraction is adjusted by the amount of chain transfer agent, the pick strength of coated paper is generally highest when the gel fraction is in the range of 75 to 95% by weight in SB latex. It is recognized that the lower the gel fraction, the better the blister resistance is, and in order to simultaneously improve both pick strength and blister resistance to a high level, none of the above technologies is sufficiently satisfactory. It's not possible.

Furthermore, when adjusting the gel fraction by lowering the polymerization temperature, there is a drawback that the time required for polymerization becomes extremely long.

On the other hand, carpet hack sizing adhesives 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 manufacture of tufted carpets, needle bunch 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 demand for the emergence of copolymer latex as a binder that enables the production of high-quality coated paper. The current situation is that Furthermore, it is desired that a copolymer latex having high adhesive strength be developed for carpets and adhesives as well.

[Means to solve the problem]

Under these circumstances, the present inventors sought to improve the balance between pink strength and other properties in coated printing paper, and to improve adhesive strength in carpet bank sizing and adhesives. With the aim of providing a copolymer latex with high performance, as a result of intensive research to develop the above-mentioned high-performance copolymer latex, as a monomer,
Using a conjugated diene compound and at least three other monomers copolymerizable with the ethylenically unsaturated carboxylic acid, these monomers are emulsion polymerized in an aqueous medium at a temperature of 7 o'c-ioo'c. In producing a copolymer latex, the inventors have discovered that the objective can be achieved by adjusting the polymerization conversion rate of monomers within a certain range, and have completed the present invention.

That is, the present invention emulsion polymerizes a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and at least three other monomers copolymerizable in an aqueous medium at 70°C to 90"C to obtain a copolymer. This is a method for producing a copolymer latex in which polymerization is stopped when the polymerization conversion rate of monomers reaches 85% to 95%.

The present invention will be explained in detail below.

A feature of the present invention is that the polymerization conversion rate of monomers is stopped at 85% to 95% during emulsion polymerization. If the polymerization conversion rate is set outside the above range, the balance between good pick strength and other performance, which is an effect of the present invention, cannot be obtained. Methods for stopping the polymerization when a desired polymerization conversion rate is reached include a method of adding a polymerization inhibitor at that point, and a method of lowering the polymerization temperature at that point.

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 are
One type may be used, or two or more types may be used in combination,
The amount used is selected to be 5% by weight or more based on the weight of all monomers, preferably from 20 to 70% by weight from the viewpoint of cohesive force.

Examples of the ethylenically unsaturated carboxylic acid used in the present invention include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

These ethylenically unsaturated carboxylic acids may be used alone or in combination of two or more, and the amount used is 0.2% by weight or more based on the weight of all monomers, preferably,
It is selected in a range of 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, among which aromatic monovinyl compounds and divinyl compounds are particularly preferred.

As the aromatic monovinyl compound or divinyl compound,
Examples include styrene, α-methylstyrene, chlorostyrene, alkylstyrene, and divinylbenzene. Examples of acrylic esters and methacrylic esters include methyl, ethyl, propyl, butyl, 2-ethylhexyl, and hydroxyethyl glycidyl esters of acrylic acid or methacrylic acid, and ethylene glycol diacrylate or dimethacrylate. Examples of vinyl cyanide compounds include acrylonitrile and methacrylaterile, 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, 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.

Examples of the chain transfer agent used in the present invention include a/L mercaptans such as 1-)decylmercaptan, n-dodecylmercaptan, and mercaptoethanol, thioglycolic acid esters such as pentaerythster tetrathioglycolate, terpinolene, Mention may be made of halogenated hydrocarbons such as dipentene, t-terpinene and carbon tetrachloride, sulfides, and the like.

There are no particular restrictions on the method of using these chain transfer agents, and known methods such as a pre-addition method, a continuous addition method, an intermittent addition method, and a concentration gradient addition method in which the addition rate is sequentially changed are used. Can be used.

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. There are no particular restrictions on this emulsion polymerization method other than the above-mentioned termination of polymerization, and conventionally known methods such as water, the above-mentioned monomer, a chain transfer agent, a surfactant, a radical polymerization initiator, and if necessary, can be used. In a dispersion system whose basic constituents are other additive components used in the production of copolymer particles, a method is used in which the monomers are polymerized to produce an aqueous dispersion of copolymer particles, that is, a copolymer latex.

The concentration of the copolymer in this copolymer latex is usually selected in the range of 40 to 60% by weight, and the average particle size is 0.605 to 1μ, preferably 0.07 to 0.3μ.
Advantageously, it lies in the range m. The average particle size can be adjusted by adjusting the proportion of surfactant and seed latex used, and generally, the higher the proportion used, the smaller the average particle size of the resulting copolymer latex tends to be.

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. Examples include activators, nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxypropylene block copolymer. 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 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 peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, thi-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile , cumene hydroperoxide, etc. Among these, beroxonisulfate is particularly suitable. 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 70 to 100°
Selected within the range of C.

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 a paper coating material, an inorganic pigment or an inorganic/organic pigment may be added 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 water-soluble polymer and various additives to form a homogeneous dispersion. This paper coating paint can be applied to base paper by a conventional method using various blade coaters, roll coaters, etc.

[Examples] 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 CUNOD Co., Ltd.)
The average particle diameter of the polymer latex was measured using 0).

(b) Polymerization conversion rate Approximately 1 gram of the removed reaction solution was weighed accurately, and heated 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.

(Total weight of preparation) From these, the polymerization conversion rate is calculated using the following formula.

Solid content (2) Evaluation of paper coating performance (a) Blister resistance Printing on both sides of coated paper using an R1 printing tester (manufactured by Mei Seisakusho) Ink (manufactured by Dainippon Ink Co., Ltd. - ebb Zett yellow)
Print 0.3cc 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
．． 4cc Perform overprinting 5 times, trace the pinking 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 smaller the pinking phenomenon, the higher the score.

Examples 1-2 and Comparative Examples 1-2 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 placed in a pressure-resistant reaction vessel equipped with a stirring device and a temperature control jacket. Add 70 parts by weight of water, 0.2 parts by weight of sodium lauric sulfate,
2.5 parts by weight of fumaric acid was charged, the internal temperature was raised to 80°C, and then an oily mixture consisting of the monomers shown in Table 1, a chain transfer agent, and a non-polymerizable water-insoluble solvent was added to 15 parts by weight of water. Part by weight, 1 part by weight of sodium beloxonisulfate, 0.2 part by weight of sodium hydroxide, 0.1 part by weight of sodium lauric sulfate
parts by weight of the aqueous solution were added at a constant flow rate over 4 and 5 hours, respectively. After maintaining the temperature at 80°C for the time shown in Table 1, it was cooled, and the resulting copolymer latex was adjusted to pH with sodium hydroxide.
7 and then remove unreacted monomers and non-polymerizable water-insoluble solvents by steam stripping method.
It was filtered through a 00 mesh filter cloth. Note that all copolymer latexes were adjusted so that the final solid content concentration was 50% by weight.

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

The copolymer latex prepared in Examples 1 and 2 of the Margin Application Example and Comparative Examples 1 and 2 was evaluated for its performance as a binder 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 po 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 is understood that the coated paper using the copolymerized latex of the present invention as a binder has a highly balanced pick strength and other physical properties.

Margin below (note) 1) Manufactured by Engelhard, product name: Ultra White 90 2) Manufactured by Engelhard, product name: Ultra Coat 3) Manufactured by Sankyo Seifun Co., Ltd., product name: Niscalan 4) Manufactured by Toagosei Kagaku Co., Ltd., product Name: Nearon T5) Manufactured by Sumitomo Chemical Co., Ltd., product name:
Sumirenz 6366) Manufactured by Nihon Shokuhin Kako Co., Ltd., product name:
A high performance copolymer latex that can improve MS4600 Table 3 can be easily obtained.

Claims (1)

[Claims] In producing a copolymer latex by emulsion polymerizing a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and at least three other copolymerizable monomers at 70 to 100°C in an aqueous medium, A method for producing a copolymer latex, characterized in that polymerization is stopped when the polymerization conversion rate of monomers reaches 85% to 95%.