JPH0441504A - Production of new copolymer latex - Google Patents

Abstract

PURPOSE:To produce the title latex improved in adhesiveness and being useful for paper coating, pressure-sensitive adhesives or the like by emulsion- copolymerizing a conjugated diene with an ethylenically unsaturated carboxylic acid and another comonomer, in the presence of a specified chain transfer agent. CONSTITUTION:40-60wt.% monomer mixture of a particle diameter of 0.05-1mum comprising 20-90wt.% conjugated diene (e.g. butadiene), 0.5-10wt.% ethylenically unsaturated carboxylic acid (e.g. itaconic acid) and another comonomer (e.g. styrene) is emulsion-copolymerized at 60-90'C in a solvent, in the presence of 0.2-20 pts. wt., per 100 pts.wt. this mixture, chain transfer agent which comprises a naphthalene derivative of the formula (wherein X and Y are each H, OH, OR, O-R-OH or halogen; and R is 1-6C alkyl), e.g. 1-naphthol, and which may optionally contain another known chain transfer agent, a surfactant and a polymerization initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel copolymer latex which can be used for paper coating, carpet backing, fiber bonding or adhesives.

[Conventional technology]

Conventionally, synthetic copolymer latexes have been widely used, for example, as binders for paper coating, binders for carpet back sizing, binders for binding fibers such as nonwoven fabrics and artificial leather, and adhesives for various materials. When copolymer latex is used for such purposes, it is required that the copolymer latex has high adhesive strength and is excellent in 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 the paper's printability and optical properties such as gloss. These coatings are coated with copolymer latex as a binder and paints containing water-soluble polymers such as starch, polyvinyl alcohol, and carboxymethyl cellulose as water-retaining agents or auxiliary binders, and conventionally styrene A styrene-butadiene copolymer latex obtained by emulsion polymerization of and butadiene as main monomer components, so-called SB latex, is commonly used as a binder.

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 towards 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 is not related to other print properties, namely wet pick strength,
Since there is a negative correlation with blister resistance, halftone dot reproducibility, etc., there is a growing need for improvements that balance these physical properties to a high level.

Since these properties of coated paper are particularly strongly dependent on the design 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 solvents such as benzene, toluene, and tetrahydrofuran is the controlling factor for pick strength and blister resistance. Studies have been carried out, and specifically, it has been proposed that excellent performance can be achieved by adjusting the composition and gel fraction of the copolymer in latex within a specific range (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 adding a chain transfer agent is a common and convenient method for adjusting it to a desired level.

Conventionally, halogenated hydrocarbons such as carbon tetrachloride, alkyl mercaptans such as n- or n-dodecyl mercaptan, sulfides, and the like have been used as chain transfer agents.

However, in general, the pick strength of coated paper is highest in SB latex with a gel fraction in the range of 75 to 95% by weight, while the blister resistance is better as the gel fraction is lower. It is recognized that
None of the above-mentioned techniques is fully satisfactory in order to simultaneously improve both pick strength and blister resistance to a high level.

In addition, the optimal butadiene unit fraction for wet pick strength in offset printing is 34% by weight or less, which is different from the optimal butadiene unit fraction for pick strength.
It was difficult to achieve high levels of both physical properties at the same time.

In addition, for gravure printing paper, good halftone dot reproducibility and resistance to supercalendar staining during the production of coated paper are particularly important. A binder is disclosed, which is designed to have a high butadiene unit fraction, so that halftone dot reproducibility is sufficiently improved without impairing supercalendar stain resistance. has not yet been reached.

Additionally, carpet pack sizing adhesives are generally compositions in which copolymer latex is blended 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 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.

Furthermore, adhesives have traditionally been manufactured by dissolving natural rubber, synthetic rubber, etc. in an organic solvent, coating it on a base material, and evaporating the organic solvent. Due to sanitary issues, there is increasing momentum to use polymer aqueous dispersions (latex) that use water as a dispersion medium, and aqueous dispersions of rubber-tackifying resin combinations are being developed (Japanese Patent Publication No. 57-28545). , Japanese Patent Publication No. 55-48270
No. 58-160378, Japanese Patent Application Laid-open No. 1982-160378
-183771).

The aqueous dispersion containing the synthetic rubber latex and the tackifying resin is generally a composition in which 50 to 100 parts by weight of the tackifying resin is added to 100 parts by weight of the solid content of the latex, and the composition is generally 20 to 23 parts by weight. Although it exhibits good adhesive properties at a measurement temperature of 0°C, a satisfactory value for adhesive strength at a temperature of 0°C has not been obtained. In addition, it has been proposed that adhesive properties can be obtained only with a rubber latex polymer without the presence of a tackifying resin (JP-A-5
6-145909, JP-A-57-57707).

However, this material has the drawback of extremely low adhesion to polyethylene.

[Problem to be solved by the invention]

As described above, future technologies will not be able to cope with even higher printing speeds for coated paper, and there is a strong need for the emergence of copolymer latex as a binder that will enable the production of high-quality coated paper. The current situation is that Furthermore, copolymer latexes with high adhesive strength are similarly desired for carpets and adhesives.

[Means to solve the problem]

Under these circumstances, the present invention has been developed to develop a high-performance joint for improving the balance between pick strength and other properties in coated printing papers, as well as the adhesive strength in carpet back sizing and adhesives. As a result of various studies aimed at providing polymer latex, we found that conjugated diene,
A copolymer latex obtained by using a naphthalene derivative as a chain transfer agent in the emulsion polymerization of ethylenically unsaturated carboxylic acids and other monomers copolymerizable with these has surprisingly achieved the above objectives. This discovery led to the completion of the present invention.

That is, the present invention uses a naphthalene derivative Y represented by the following general formula as a chain transfer agent in emulsion polymerization of a conjugated diene, an ethylenically unsaturated carboxylic acid, and other monomers copolymerizable with these. y, respectively )-H,-
This is a method for producing a copolymer latex characterized by using OH, -OR, -07R=OH, i↑.

The present invention will be explained in detail below.

A feature of the present invention is that a naphthalene derivative represented by the following general formula is used as a chain transfer agent in producing a copolymer latex by emulsion polymerization.

As the chain transfer agent, naphthalene, 1-naphthol,
Examples include 2-naphthol, methquinonaphthalene, (hydroxymethyl)naphthalene, (hydroxyethyl)naphthalene, and the like.

The preferred amount of the chain transfer agent used is 0.2 to 20 parts by weight, more preferably 0.3 to 10 parts by weight, based on 100 parts by weight of the monomer.

Moreover, the chain transfer agent can also be used in combination with other well-known chain transfer agents. Examples of other well-known chain transfer agents include: thioalkanes such as t-dodecyl mercaptan, n-dodecyl mercaptan; thioalcohols such as mercaptoethanol, mercaptrobanol; dimethyl thioalkyl carboxylates such as thioglycolic acid, thiopropionic acid. Examples include sulfides such as sulfide and diethyl sulfite; 710-genated hydrocarbons such as carbon tetrachloride and bromoform.

Furthermore, any known method can be used for using the chain transfer agent. Namely, these include a pre-batch addition method, a continuous addition addition method, an intermittent addition addition method, and a concentration gradient addition method in which the addition rate is sequentially changed.

The copolymer latex is obtained by emulsion copolymerization of monomers composed of a conjugated diene, an ethylenically unsaturated carboxylic acid, and other monomers copolymerizable with these.

Conjugated dienes used in the present invention include butadiene, isoprene, 2-chloro-1,3-butadiene, and the like.

The amount used is preferably in the range of 20 to 90% by weight based on the total monomers. Furthermore, in the case of a copolymer latex for coated paper, a more preferable range of this conjugated diene is 20 to
It is 70% by weight.

Examples of ethylenically unsaturated carboxylic acids used in the present invention include monobasic carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, dibasic carboxylic acids such as itaconic acid, maleic acid, and fumaric acid, and monoesters thereof. etc. can be mentioned.

The amount of the ethylenically unsaturated carboxylic acid used is preferably in the range of 0.5 to 10% by weight based on the total monomers.

Among the other monomers used in the present invention, aromatic (di)vinyl compounds are most typically and effectively used, followed by (meth)acrylic acid esters, vinyl cyanide compounds, and ethylenic amides. Monomers, etc. Aromatic (di)vinyl compounds include styrene, α
- Examples include methylstyrene, chlorostyrene, alkylstyrene, and divinylbenzene. Examples of (meth)acrylic esters include methyl (meth)acrylate,
Ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate
Acrylates include glycidyl (meth)acrylate, ethylene glycol di(meth)acrylate, and the like. Examples of vinyl cyanide compounds include acrylonitrile and methacrylonitrile.

Examples of the ethylenic amide monomer include (meth)acrylamide and N-methylol (meth)acrylamide. In addition, vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides such as vinylidene chloride, ethylenic amine monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and styrene Examples include sodium sulfonate.

The production method of the present invention is produced by a conventionally known normal emulsion polymerization method. - For boat fishing, the polymer concentration ranges from 40 to 60% by weight. The particle size of the copolymer latex can be adjusted by the proportion of surfactant and/or seed latex used, and generally speaking, the higher the proportion used, the smaller the particles of the copolymer latex produced.

Here, the preferred range of particle diameter is 0.05 to 1 μm, more preferably 0.07 to 0.5 μm.

Examples of surfactants include fatty acid soaps, rosin acid soaps, alkyl sulfonates, dialkylaryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkylaryl sulfates, and anionic surfactants: There are nonionic surfactants and cationic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxypropylene block copolymer. The surfactant is usually used as an anionic surfactant alone or as a mixed anionic/nonionic surfactant, and its usage ratio based on the total monomers is generally in the range of 0.05 to 2% by weight.

Polymerization initiators necessary to initiate polymerization are those that initiate addition polymerization of monomers by radical decomposition in the presence of heat or reducing substances, such as water-soluble or oil-soluble beroxonisulfate, peroxide, etc. , azobis compounds, etc. are commonly used. Examples include potassium peroxonisulfate, sodium peroxonisulfate, ammonium peroxonisulfate, hydrogen peroxide, t-butyl hydroperoxide,
Examples include benzoyl peroxide, 2,2-azobisisobutyronitrile, and cumene hydroperoxide, and beroxonisulfate is most preferably used. The proportion of the polymerization initiator used is usually 0.2 to 1.5% by weight based on the total monomers. The polymerization temperature is generally in the range of 60 to 90°C, but when it is desired to accelerate the polymerization rate or polymerize at a lower temperature, sodium bisulfite, ascorbic acid or its salts, erythorbic acid or its salts, longat, etc. A so-called redox polymerization method can be used in which a reducing agent is used in combination with a polymerizing agent.

Furthermore, various polymerization modifiers are often added as desired. For example, sodium hydroxide,
These include pH adjusters such as potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, and disodium hydrogen phosphate, and various acid salt agents such as sodium ethylenediaminetetraacetate.

The copolymerized latex produced according to the present invention can be used as a binder for paper coating compositions in a conventional manner. That is, the copolymer latex is mixed with an inorganic pigment and/or organic pigment, a water-soluble polymer, and various additives in water in which a dispersant is dissolved to form a uniform dispersion. This paint can be applied to the base paper using a conventional method such as various blade coaters or roll coaters.

〔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.

(a) Blister resistance Using an RI printing tester (manufactured by Mei Seisakusho), 0.37 nl of printing ink (Webb Zett yellow, manufactured by Inu Nippon Ink Co., Ltd.) is printed on both sides of the coated paper. 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 changing the temperature of the thermostatic chamber, and the degree of blistering is compared.

The evaluation was carried out using a 10-point scale, and the better the blister resistance, the higher the score.

(b) Dry Pick Strength Using a RI printing tester, printing ink (SD Susu--Deluxe 50 Beni B; tack value 18, manufactured by Shuso Shiki Co., Ltd.) was measured to be 0.
Overprint 4m 15 times, trace the picking state that appears on the rubber roll onto another mount, and observe the degree of picking. The evaluation was performed using a 10-point evaluation method, and the fewer the picking phenomenon, the higher the score.

Examples and Comparative Examples 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, and 70 parts by weight of water was added. parts, 0.2 parts of sodium lauryl sulfate,
2.5 parts by weight of itaconic acid was charged, the internal temperature was raised to 80°C, and then an oily mixture consisting of the monomers and chain transfer agent shown in Table 1, 15 parts by weight of water, 1 part by weight of sodium beroxonisulfate, An aqueous solution consisting of 0.2 part by weight of sodium hydroxide and 0.1 part by weight of sodium lauryl sulfate was added at a constant flow rate over 4 hours and 5 hours, respectively. After maintaining the temperature at 80℃ for one hour, it was cooled, and the resulting copolymer latex was adjusted to pH 7 with sodium hydroxide, and unreacted monomers were removed using the steam stock pink method. and mesh 75μ
It was filtered through a filter cloth of m. Note that all copolymer latexes were prepared so that the final solid content concentration was 50% by weight.

Application Examples The copolymer latexes prepared in Examples and Comparative Examples 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 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.

〔Effect of the invention〕

According to the present invention, it is possible to easily obtain a high-performance copolymerization-resistant latex that can further improve the balance between pick strength and other properties in coated printing paper, and the adhesive strength in carpet back sizing and adhesives. .

Claims (1)

[Claims] In the emulsion copolymerization of conjugated dienes, ethylenically unsaturated carboxylic acids, and other monomers copolymerizable with these, a naphthalene derivative represented by the following general formula is used as a chain transfer agent ▲ Numerical formula, chemical formula, There are tables, etc. ▼ [However, X and Y represent -H, -OH, -OR, -O-R-OH, and halogen elements, respectively. Here, R represents an alkyl group having 1 to 6 carbon atoms. ] A method for producing a copolymer latex, characterized by using the following.