JPH0819269B2 - Diene copolymer latex - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial 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, carpent backsizing, fiber binding and the like.

[Conventional technology]

Conventionally, synthetic copolymer latex is, for example, a binder for paper coating, a binder for carpet back sizing,
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 papers are pigments such as kaolin clay, calcium carbonate, satin white, talc, and titanium oxide on the surface of the raw paper that has been made for the purpose of improving the printability of the paper and improving optical properties such as gloss. Copolymer latex as a binder and starch as a water retention agent or an auxiliary binder, casein, polyvinyl alcohol, a coating composition having a water-soluble polymer such as carboxymethyl cellulose as a main constituent is applied, Conventionally, styrene and butadiene as the main monomer component as a copolymer latex, styrene-butadiene-based copolymer latex obtained by emulsion polymerization of these,
So-called SB-based latex is commonly used.

By the way, in recent years, the production of coated paper has remarkably increased along with the increasing demand for color printed magazines, pamphlets, and advertisements. In particular, with the trend toward high-speed printing in offset printing, the required level for the quality of coated paper and pigment binders is becoming increasingly sophisticated, and therefore, among the quality of coated paper, especially ink pick resistance, so-called pick strength There is a strong demand for improvement. Moreover, this pick strength performance has other print properties, namely wet pick strength,
Blister resistance, halftone dot reproducibility, and the like are in a negative correlation, and therefore, further improvement is required to balance these various properties to a high level.

Since these properties of the coated paper are strongly preserved in the performance of the SB-based latex used as a pigment binder, various studies have been made on the performance of the SB-based latex so far.

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 and the gel fraction in the latex to specific ranges (Japanese Patent Publication No. 59-3598). Gazette, Japanese Patent Publication No. Sho 60-17879,
No. 8-4894). 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 a chain transfer agent, the pick strength of the coated paper is generally the highest in SB latex in the range of 75 to 95% by weight. It is recognized that the lower the gel fraction, the better the blister resistance. Especially, when a sulfur-containing chain transfer agent is used, it is possible to improve both pick strength and blister resistance to a high level at the same time. However, none of the above techniques are fully satisfactory.

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

On the other hand, the adhesive for carpet backsizing is generally a composition in which a filler such as calcium carbonate or aluminum hydroxide and other additives such as a thickener are blended with a copolymer latex. This adhesive composition is mainly used for the production of tufted carpets, needle punch carpets and the like, for preventing piles from dropping off and for bonding to a secondary base fabric such as jute. Therefore, in this case, the improvement of the adhesive strength, which is the most important physical property of the carpet, is one of the greatest technical problems in the industry, and therefore, the improvement of the copolymer latex and the composition from the aspect of blending has been studied. However, in reality, a copolymer latex using a sulfur-containing chain transfer agent has not yet been obtained at a satisfactory level.

[Problems to be Solved by the Invention]

As described above, the conventional technology cannot cope with a further increase in the speed of printing of coated paper, and the emergence of a copolymer latex as a binder capable of producing high quality coated paper is strongly demanded. It is the present situation. Also, the appearance of a copolymer latex having a high adhesive force has been desired for carpets and adhesives.

[Means for solving the problem]

Under the circumstances, the present inventors have made it possible to further improve the balance between the pick strength and other performance of coated paper for printing, and the adhesive strength of carpet backsizing and adhesives. The present invention has been completed as a result of earnest studies for developing the above-mentioned high-performance copolymer latex for the purpose of providing a high-performance copolymer latex.

 That is, the present invention is as follows.

1. A single amount of a sulfur-containing chain transfer agent is used in emulsion-polymerizing at least three kinds of monomers of a conjugated diene compound and another monomer copolymerizable with an ethylenically unsaturated carboxylic acid in an aqueous medium. Continuously added separately from the body mixture, a copolymer latex obtained by emulsion polymerization by setting the end point of the addition to a point where the polymerization conversion rate of the monomer is 95% or more,
A diene-based copolymer latex in which the toluene-insoluble matter X of the film and the toluene swelling degree Y of the insoluble matter are within the range of the following formula.

Y ≧ 800 ÷ X 2. The average particle diameter of the diene copolymer latex is 0.05 to 1
The diene copolymer latex according to the above-mentioned item 1, which is in the range of μm.

A feature of the present invention is a diene-based copolymer latex obtained by a specific emulsion polymerization, wherein the relationship between the toluene insoluble matter X and the swelling degree Y of the insoluble matter is within a certain range, that is, the product of X and Y. Is set to 800 or more. More preferably, the product of X and Y is 1000 or more.

The method in which the swelling degree of the toluene insoluble matter and the insoluble matter is adjusted to the above range is, in the emulsion copolymerization, the addition of the sulfur-containing chain transfer agent is continuously added to the reactor separately from the monomer mixed solution,
This is because the end time of the addition is set to a point where the polymerization conversion rate of the monomer is 95% or more.

Examples of the chain transfer agent used in the present invention include t-
Examples thereof include alkyl mercaptans such as dodecyl mercaptan, n-dodecyl mercaptan and mercaptoethanol, thioglycolic acid esters such as pentaerythritol tetrathioglycolate, and sulfides. In addition to this, it is also possible to use other conventionally known chain transfer agents in combination.

Examples of the conjugated diene compound used in the present invention include butadiene, isoprene, and 2-chloro-1,3-butadiene. These conjugated diene compounds may be used alone or in combination of two or more, and the amount used is 5% by weight or more based on the weight of all monomers, preferably from the viewpoint of cohesive force. It is selected in the range of 20 to 70% by weight.

Examples of the ethylenically unsaturated carboxylic acid used in the present invention include acrylic acid, methacrylic acid, itaconic acid,
Maleic acid, fumaric acid, crotonic acid and the like can be mentioned. These ethylenically unsaturated carboxylic acids may be used alone or in combination of two or more, and the amount thereof is 0.2% by weight or more, preferably 0.2 to 15% by weight based on the weight of all monomers. It is selected in the range of%.

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

Examples of the aromatic monovinyl compound and divinyl compound include styrene, α-methylstyrene, chlorostyrene, alkylstyrene, and divinylbenzene. Examples of acrylic acid ester and methacrylic acid ester include methyl acrylic acid or methacrylic acid,
Examples thereof include ethyl, propyl, butyl, 2-ethylhexyl, hydroxyethyl glycidyl ester, and ethylene glycol diacrylate or dimethacrylate. Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile, and examples of the ethylenic amide 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. It is possible to use ethylenic amines, sodium styrene sulfones and the like.

These other copolymerizable monomers may be used alone or in combination of two or more.

The diene copolymer latex in the present invention is obtained by emulsion-polymerizing the conjugated diene compound and another monomer copolymerizable with the ethylenically unsaturated carboxylic acid in an aqueous medium. The emulsion polymerization method is not particularly limited, and a conventionally known method, for example, water and the above-mentioned monomer, a chain transfer agent, a surfactant, a radical polymerization initiator, and other additive components used as necessary may be used. A method of producing an aqueous dispersion of copolymer particles, that is, a diene copolymer latex by polymerizing the monomer in a dispersion system as a basic constituent is used. The concentration of the copolymer in the diene copolymer latex is usually 40
~ 60% by weight, the average particle size is 0.
Advantageously, it is in the range from 05 to 1 μm, preferably from 0.07 to 0.3 μm. The average particle diameter can be adjusted by the use ratio of the surfactant or the seed latex, etc. Generally, the higher the use ratio, the smaller the average particle size of the produced copolymer latex.

Examples of the surfactant include anionic interfaces such as fatty acid soap, rosin acid soap, alkyl sulfonate, dialkyl aryl sulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate, and polyoxyethylene alkyl aryl sulfate. Examples include nonionic surfactants such as activators, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene sorbitan fatty acid esters, and oxyethyleneoxypropylene block copolymers. This surfactant is usually used alone or in a mixed system of anionic and nonionic, the amount used is usually 0.05 ~
It is selected in the range of 2% by weight.

The radical polymerization initiator has a function of radically decomposing by heat or a reducing substance to cause addition polymerization of a monomer, and examples of such a radical polymerization initiator include water-soluble or oil-soluble peroxodione Sulfates, peroxides, azobis compounds, etc., specifically potassium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t-
Butyl hydroperoxide, benzoyl peroxide, 2,2-
Examples thereof include 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 the monomers.

The polymerization temperature in this emulsion polymerization is usually selected in the range of 60 to 90 ° C., but if acceleration of the polymerization rate or polymerization at a lower temperature is desired, sodium hydrogen sulfite, ascorbic acid or a salt thereof, erythorbic acid or A reducing agent such as its salt or Rongalit is used in combination with the polymerization initiator.
A so-called redox polymerization method can be adopted.

In the production of the diene copolymer latex of the present invention, various polymerization regulators as desired, for example, sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, pH adjusting agents such as disodium hydrogen phosphate and ethylenediamine. Various chelating agents such as sodium tetraacetate can be added.

When the diene copolymer latex of the present invention is used as a binder for a coating material for paper coating, a commonly used method, for example, water in which a dispersant is dissolved, is used as an inorganic pigment or an inorganic / organic pigment, or a water-soluble pigment. It is possible to employ a method in which the copolymer latex is added together with a water-soluble polymer and various additives and mixed and used as a homogeneous dispersion. Then, this paper coating paint can be applied to the base paper by a usual method using various blade coaters, roll coaters and the like.

[Examples] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

 Each property was determined as follows.

(1) Properties of copolymer latex (a) Average particle size Light scattering particle size analyzer (Model 60 manufactured by CNN Wood Co., Ltd.)
The average particle size of the polymer latex was measured according to (00).

(B) Polymerization yield About 1 gram of the extracted reaction liquid is precisely weighed, dried at 130 ° C. for 1 hour, and then the residue is weighed. The solid content is calculated by the following method.

The charged solid content is calculated by the following method.

From these, the polymerization yield is calculated by the following formula.

(C) Copolymer gel fraction and swelling degree A polymer latex was uniformly coated on a polypropylene film with a No. 26 wire bar and dried for 2 hours in a hot air circulation dryer at 40 ° C to form a film. It was

Next, peel off this latex film, and remove it with an analytical balance to about 0.
Accurately weigh 5 g, immerse it in a container containing 300 cc of toluene, shake it with a shaker for 4 hours at room temperature,
The content is filtered through a 325-mesh wire mesh that has been precisely weighed in advance, and the residue remaining on the wire mesh is weighed. Then, it is dried in a dryer at 130 ° C. for 2 hours, and the gel fraction and the degree of swelling are determined by the following formulas.

(2) Evaluation of paper coating performance (a) Blister resistance Using a RI printing tester (Myo Seisakusho), 0.3 cc of printing ink (Dainippon Ink and Webb Zett yellow) was applied to both sides of the coated paper. To do. The printed coated paper is cut into an appropriate size, and the test piece is immersed in a silicone oil thermostatic bath adjusted to a predetermined temperature to observe whether blisters occur. This test is performed by changing the temperature of the thermostatic bath, and the lowest temperature at which blistering is observed is determined. The higher this temperature, the better the blister resistance.

(B) Dry pick strength Using an RI printing tester, 0.4cc of printing ink (SD Super Deluxe 50 Red B; Tuck value 18) manufactured by Toka Dye Co., Ltd. was overprinted 5 times, and the picking state that appeared on the rubber roll was changed. Line up on a mount and observe the situation. The evaluation was carried out by a 10-point evaluation method, and the less the picking phenomenon, the higher the score.

Examples 1-2 and Comparative Examples 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 stirrer and a temperature control jacket. , More water 70
1 part by weight, 0.2 part by weight of sodium lauric sulfate, and 2.5 parts by weight of fumaric acid were charged, the internal temperature was raised to 80 ° C., and then the monomer mixture (a), the chain transfer agent (b) shown in Table 1,
Water 15 parts by weight, sodium peroxodisulfate 1 part by weight, sodium hydroxide 0.2 parts by weight, sodium laurin sulfate 0.1
An aqueous solution (c) consisting of parts by weight was added at a constant flow rate over the time period shown in Table 1. The start time of addition is the same. After all the additions were completed, the temperature of 80 ℃ was maintained for the time shown in Table 1, and then 20
The resulting copolymer latex was cooled to 0 ° C., the pH of the resulting copolymer latex was adjusted to 7 with sodium hydroxide, unreacted monomers were removed by the steam stripping method, and the copolymer latex was filtered with a 200-mesh filter cloth. In addition, all the copolymer latexes were adjusted so that the solid content concentration was finally 50% by weight.

Table 1 shows the average particle size, polymerization yield, gel fraction and swelling degree of these copolymer latexes.

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

The coated paper has the composition shown in Table 2 and has a nonvolatile content of
It was prepared with a high speed stirrer at a water content of 63 wt%. PH of sample
Was adjusted to 9.0 with aqueous ammonia. Table 3 shows the preparation conditions of the coated paper using this paint.

It can be seen from Table 4 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.

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location D06M 15/693 D21H 19/56

Claims (2)

[Claims] 1. A sulfur-containing chain transfer agent for emulsion-polymerizing at least three kinds of monomers of a conjugated diene compound and another monomer copolymerizable with an ethylenically unsaturated carboxylic acid in an aqueous medium. Continuously added separately from the monomer mixture,
A copolymer latex obtained by emulsion polymerization with the addition conversion end point set to a point where the polymerization conversion rate of the monomer is 95% or more, the toluene insoluble content X of the film and the toluene swelling degree of the insoluble content. A diene copolymer latex in which Y is in the range of the following formula. Y ≧ 800 ÷ X 2. The diene copolymer latex has an average particle size of 0.05 to 1 μm.
The diene copolymer latex described.