JPH059336A - Production of copolymer latex for paper coating - Google Patents

Abstract

PURPOSE:To obtain the title latex suppressed in occurrence of solidified product and having excellent surface strength, etc., by adding specific water-insoluble hydrocarbons and water-soluble hydrocarbons in specific amounts and carrying out polymerization when an aliphatic conjugated diene based monomer is subjected to emulsion polymerization with other monomer. CONSTITUTION:(B) 1-70 pts.wt. 5-12C water-insoluble hydrocarbons (e.g. benzene or cyclopentane) and (C) 0.5-30 pts.wt. uncopolymerizable and water-soluble hydrocarbons (e.g. methanol or acetonitrile) having >=5wt.% solubility to water and having hydroxyl, oxo and nitrile as substituent groups are added to (A) 100 pts.wt. monomer mixture consisting of an aliphatic conjugated diene based monomer (e.g. 1,3-butadiene) and other monomer (e.g. ethylene-based unsaturated carboxylic acid monomer) copolymerizable with the above-mentioned monomer and the composition A is subjected to emulsion polymerization with the component B to provide the objective latex.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a copolymer latex for paper coating, which is preferably used as a binder for paper coating. More specifically, in particular, the production of a copolymer latex for paper coating, which gives a coated paper excellent in surface strength and printing gloss and blister resistance in the physical properties of coated paper, and which significantly suppresses the generation of coagulation during polymerization. It is about the method.

[0002]

2. Description of the Related Art It is well known that a so-called butadiene-based copolymer latex containing butadiene as a main component is used as a binder in the field of paper processing.

In recent years, a large amount of pigment-coated paper has been used for publication or packaging, and along with this, there is an increasing tendency to increase printing speed and diversify printing methods.

Therefore, the butadiene copolymer latex used as a binder for paper coating is required to have more severe physical property improvements.

For example, it has been attempted to improve the printing gloss of coated paper by introducing a vinyl cyanide-based monomer. However, if the proportion of the vinyl cyanide-based monomer is increased, the coating will be improved. The problem arises that the adhesive strength of the layers is reduced. Picking of the coating layer is likely to occur in proportion to an increase in printing speed, and this decrease in adhesive strength tends to be unfavorable especially in high-speed printing.

Further, in recent years, there has been a remarkable spread of offset rotary printing. In the case of this offset rotary printing, high temperature drying is required due to the nature of the printing method. Moisture contained therein vaporizes and expands, and blisters (blister) are likely to occur on the surface of the paper, and if this blister occurs, the commercial value is significantly impaired.

To solve these problems, Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 3-235593 proposes to use, as a binder, a copolymer latex obtained by emulsion polymerization in an aqueous medium in which a water-soluble organic solvent inert to the polymerization reaction is dissolved.

However, when emulsion polymerization is carried out using the water-soluble organic solvent, there arises a problem that fine coagulation products are generated in the copolymer latex. This finely solidified matter not only deteriorates the mechanical stability of the coating color, but also causes streak troubles during blade coating and stains during calendar processing.

Therefore, there is a demand for a copolymer latex which is excellent in the physical properties of coated paper and which is used as a binder for paper coating, in which coagulation during polymerization is remarkably suppressed.

[0010]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As a result of diligent studies on the above-mentioned problems, the present inventors have found that copolymerization reactivity with non-water-soluble hydrocarbons having 5 to 12 carbon atoms and having no copolymerization reactivity. Paper which is excellent in coated paper physical properties and remarkably suppresses generation of fine coagulation by polymerizing by adding a specific amount of specific water-soluble hydrocarbons having a solubility in water of 5% by weight or more The present invention has been accomplished by finding the fact that a copolymer latex used as a binder for coating can be obtained.

[0011]

[Means for Solving the Problems] That is, the present invention is
In emulsion-polymerizing the aliphatic conjugated diene monomer and another monomer copolymerizable therewith, the monomer mixture 10
5 to 12 carbon atoms with no copolymerization reactivity to 0 parts by weight
1 to 70 parts by weight of water-insoluble hydrocarbons and water-soluble hydrocarbons having no copolymerization reactivity, solubility in water of 5% by weight or more, and having a hydroxyl group, an oxo group or a nitrile group as a substituent The present invention provides a method for producing a copolymer latex for paper coating, which comprises adding 0.5 to 30 parts by weight and polymerizing. Hereinafter, the present invention will be described in more detail.

Examples of the aliphatic conjugated diene-based monomer in the present invention include 1,3-butadiene and 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3-butadiene,
2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes and the like can be mentioned, and one kind or two or more kinds can be used.

Other monomers copolymerizable with the above aliphatic conjugated diene-based monomer include ethylenically unsaturated carboxylic acid monomer, alkenyl aromatic monomer, unsaturated carboxylic acid alkyl ester monomer And unsaturated monomers containing a hydroxyalkyl group, vinyl cyanide monomers, unsaturated carboxylic acid amide monomers, and the like.

Examples of the ethylenically unsaturated carboxylic acid monomer include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid.

As the alkenyl aromatic monomer, styrene, α-methylstyrene, methyl α-methylstyrene,
Examples include vinyltoluene and divinylbenzene.

Examples of the unsaturated carboxylic acid alkyl ester monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl. Itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like can be mentioned.

Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethyl acrylate and β-hydroxyethyl acrylate.
-Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,
Hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate,
Di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl)
Maleate, 2-hydroxyethylmethyl fumarate and the like can be mentioned.

Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and α-ethylacrylonitrile.

As the unsaturated carboxylic acid amide monomer,
Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,
N-dimethyl acrylamide etc. are mentioned. These monomers may be used either individually or in combination of two or more.

The composition of the above-mentioned monomers is not particularly limited, but it is 10 to 80% by weight of the aliphatic conjugated diene monomer, 0 to 10% by weight of the ethylenically unsaturated carboxylic acid monomer, and the alkenyl aromatic monomer. Body, unsaturated carboxylic acid alkyl ester, unsaturated monomer containing a hydroxyalkyl group,
The amount of the monomer selected from vinyl cyanide monomer and unsaturated carboxylic acid amide monomer is preferably 20 to 90% by weight.

Examples of the water-insoluble hydrocarbons having 5 to 12 carbon atoms and having no copolymerization reactivity used in the present invention include aromatic hydrocarbons, alicyclic hydrocarbons and chain hydrocarbons.

As the aromatic hydrocarbon, benzene, toluene, o-xylene, m-xylene, p-xylene, cumene, 1,2,3-trimethylbenzene, 1,2,4-
Examples thereof include trimethylbenzene and 1,2,5-trimethylbenzene.

Examples of the alicyclic hydrocarbon include cyclopentane, cyclohexane, cycloheptane, cyclooctane and methylcyclohexane.

Examples of the chain hydrocarbon include pentane, hexane, heptane, 2-methylpentane, 3-methylisooctane, decane and dodecane. These are 1
They can be used in one kind or two or more kinds.

The amount of the water-insoluble hydrocarbons used in the present invention is 1 to 70 parts by weight per 100 parts by weight of the monomer mixture, but if the amount is less than 1 part by weight, the above effect is not sufficiently exhibited. Further, these hydrocarbons can be easily recovered by steam distillation after the completion of the polymerization reaction and can be reused, but if the amount used exceeds 70 parts by weight, the energy required for recovery becomes large, which is not preferable. Preferably 1 to 50
Parts by weight.

The water-insoluble hydrocarbons used in the present invention have 5 to 12 carbon atoms, but the carbon number is 5
If it is less than the above, it is a gas at ordinary temperature and it is difficult to handle it.

Further, in the present invention, there is no copolymerization reactivity,
Water-soluble hydrocarbons having a solubility in water of 5% by weight or more and having a hydroxyl group, an oxo group or a nitrile group as a substituent are used. The solubility in water as used herein means water 100 at a temperature of 20 ° C. It is the weight% of a substance which is uniformly dissolved and soluble with respect to the weight%.

Examples of the water-soluble hydrocarbons include methanol, ethanol, propanol, butanol, cyclohexanol, acetone, methyl ethyl ketone, cyclohexanone, acetonitrile, propionitrile and the like.

The amount of the water-soluble hydrocarbons used is 0.5 to 30 parts by weight based on 100 parts by weight of the monomer mixture.
If it is less than 0.5 parts by weight, the above-mentioned effect cannot be exhibited, and if it exceeds 30 parts by weight, the polymerization stability is deteriorated.
It is not preferable because the yield of the copolymer latex decreases.

These water-soluble hydrocarbons can be easily recovered by steam distillation after the completion of the polymerization reaction and can be reused.

Further, the solubility of the water-soluble hydrocarbons in water is 5% by weight or more, but if it is less than 5% by weight, the above effect cannot be exhibited.

The method for adding the water-soluble hydrocarbons and the water-insoluble hydrocarbons to the polymerization system is not particularly limited, and any of an initial batch addition method, a divided addition method, and a continuous addition method may be used.

As the emulsion polymerization method of the copolymer latex in the present invention, for example, a batch polymerization method, a two-step polymerization method, and a power feed polymerization method can be adopted. Also, the method of adding various components is not particularly limited,
Any of a batch addition method, a divided addition method, and a continuous addition method can be adopted. Further, in the emulsion polymerization, a commonly used emulsifier, molecular weight modifier, polymerization initiator, electrolyte, polymerization accelerator, chelating agent and the like can be used.

As the emulsifier, for example, an amphoteric surfactant,
Anionic surfactants or nonionic surfactants can be used.

Here, as the amphoteric surfactant, one having a carboxylate, a sulfate, a sulfonate or a phosphate as an anion part and an amine salt or a quaternary ammonium salt as a cation part is used. Specifically, as the salt of alkyl betaine, each salt of lauryl betaine, stearyl betaine, cocoamidopropyl betaine, 2-undecyl-hydroxyethyl imidazolinium betaine, as the amino acid type, lauryl-β- Examples thereof include alanine, stearyl-β-alanine, lauryldi (aminoethyl) glycine, octyldi (aminoethyl) glycine, and dioctyldi (aminoethyl) glycine.

Examples of the anionic surfactant include sulfuric acid ester of higher alcohol, alkylbenzene sulfonate, and aliphatic sulfonate.

Further, as the nonionic surfactant,
Ordinary polyethylene glycol alkyl ester type,
Alkyl ether type and alkyl phenyl ether type are used.

Examples of the molecular weight modifier include halogenated hydrocarbons such as chloroform, bromoform, carbon tetrachloride and carbon tetrabromide: n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-
Stearyl mercaptans and other mercaptans: Diisopropylxanthogen disulfide, dimethylxanthogen disulfide, diethylxanthogen disulfide and other xanthogen disulfides: tetraethyl thiuram monosulfide, dipentamethylene thiuram hexasulfide, thiuram disulfide and other thiuram sulfides: ethylhexyl thioglycolate, etc. Thioglycolic acid alkyl esters: acrolein, methacrolein, terpinolene, .alpha.-terpinene, .gamma.-terpinene, dipentene, .alpha.-methylstyrene dimer, etc., all of which can be used in ordinary emulsion polymerization can be used. These molecular weight regulators can be used alone or in combination.

As the initiator, water-soluble initiators such as sodium persulfate, potassium persulfate and ammonium persulfate:
Either an oil-soluble initiator such as benzoyl peroxide: or a redox type initiator can be used. Further, as the chelating agent, the inorganic salt and the like, those known in emulsion polymerization are used.

The copolymer latex for paper coating of the present invention comprises
It is prepared as an aqueous dispersion together with an inorganic pigment or an organic pigment and, if necessary, other binder, and applied on a coated paper.

At this time, 5 to 30 parts by weight of the copolymer latex of the present invention is added to 100 parts by weight of the pigment in terms of solid content,
Preferably 9 to 20 parts by weight, 0 to 10 other binders
Parts by weight, preferably 2 to 5 parts by weight are used.

Here, as the pigment, kaolin clay,
Examples include inorganic pigments such as talc, barium sulfate, titanium oxide (rutile anatase), calcium carbonate, aluminum hydroxide, zinc oxide, and satin white, or organic pigments such as polystyrene latex, which may be used alone or in combination. It

As the other binder, a natural binder such as starch, oxidized starch, soybean protein and casein, or a synthetic latex such as polyvinyl alcohol, polyvinyl acetate latex and acrylic latex is used.

Further, when preparing a composition for paper coating using the copolymer latex of the present invention, other auxiliary agents such as a dispersant (sodium pyrophosphate, sodium hexametaphosphate, etc.), antifoaming agent, etc. Agent (polyglycol,
Fatty acid ester, phosphoric acid ester, silicone oil, etc.), leveling agent (funnel oil, dicyandiamide, urea, etc.), preservative, water resistance agent (formalin, hexamine, melamine resin, urea resin, glyoxal, etc.), release agent (stear) Calcium phosphate, paraffin emulsion, etc.), fluorescent dye, color-holding agent (carboxymethyl cellulose, sodium alginate, etc.) can be added as required.

[0045]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. In the examples, parts and percentages are based on weight.

The physical properties in the examples were measured by the following methods.

Stain inside the reactor After polymerization, the deposits on the inner wall of the reactor were visually observed. O: Very low Δ: Few ×: High These three levels are used for evaluation.

The amount of the micro-coagulated substance of several μm to 50 μm was observed by microscopic observation of the micro-solidified product. ◯: Very small Δ: Little X: Larged The evaluation is carried out in three stages.

A latex film is prepared by drying the gel content at room temperature. Thereafter, about 1.0 g of the latex film was accurately weighed, put in 400 cc of toluene, and left to dissolve for 48 hours. After filtration through a 300 mesh wire net, the toluene was scattered to measure the toluene dissolved content (sol content). Then, the gel content is calculated.

RI Dry Pick The degree of picking when printed with a RI printing machine was judged with the naked eye, and evaluated by a 5-grade method from 1 grade (the best grade) to 5 grade (the worst grade). The average value of 6 times is shown.

Printing Gloss Using a RI printing machine, printing was performed once using a fixed amount of commercially available red ink for offset printing, and the printing surface of the coated paper was incident on a Murakami gloss meter at an incident angle of 75 ° and a reflection angle of 75 °. To measure. The larger the printing gloss value, the better.

Blister-resistant double-sided coated paper was conditioned to about 6% and then placed in a heated oil bath to show the minimum temperature at which blistering occurred.

Preparation of copolymer latex 14 kinds of latex shown in Table 1 were prepared . Copolymer latex 1 to 12 are examples, copolymer latex 1
3 to 14 are comparative examples.

Each monomer shown in Table 1, t-dodecyl mercaptan, water-insoluble hydrocarbons, water-soluble hydrocarbons and 0.6 part of sodium dodecylbenzenesulfonate, 0.5 part of sodium hydrogen carbonate, 0.8 parts ammonium sulfate,
Charge a mixed solution of 100 parts of water into a 10 l autoclave,
Polymerization was carried out with stirring. The polymerization temperature was 65 ° C. The polymerization conversion rates of all the obtained latexes were 99% or more.

For latex 4, two-stage polymerization was carried out. That is, each monomer shown in parentheses in Table 1 was additionally added when the conversion in the first stage reached 80%, and the polymerization was completed. The final polymerization conversion rate was 99% or more. These latexes were added with 5% concentration of ammonia water
H was adjusted to 6.0 and unreacted monomers, water-insoluble hydrocarbons and water-soluble hydrocarbons were removed by steam distillation to obtain copolymer latexes 1-14.

Preparation of Paper Coating Composition and Evaluation of Coated Paper A paper coating composition was prepared by using the copolymer latexes 1 to 10 according to the following prescription to obtain a coated paper. The resulting coated paper was measured for RI Dry Pick, print gloss and blister resistance. The results are shown in Table-2.

(Processing) Kaolin clay 80 parts Calcium carbonate 20 parts Modified starch 8 parts Copolymer latex 12 parts (solid content)

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

As described above, by using the production method of the present invention, a copolymer used as a binder for paper coating, which is excellent in coated paper physical properties and remarkably suppresses generation of fine coagulation products. A latex is obtained, which is very useful industrially.

Claims (1)

Claims: 1. When emulsion-polymerizing an aliphatic conjugated diene-based monomer and another monomer copolymerizable with the aliphatic conjugated diene-based monomer, the copolymerization is carried out with respect to 100 parts by weight of the monomer mixture. 1 to 70 parts by weight of non-reactive water-insoluble hydrocarbons having 5 to 12 carbon atoms and no copolymerization reactivity, and solubility in water of 5% by weight
Above, water-soluble hydrocarbons having a hydroxyl group, an oxo group or a nitrile group as a substituent 0.5 to 3
A method for producing a copolymer latex for paper coating, which comprises adding 0 part by weight and polymerizing.