JPH06279552A - Production of copolymer latex for paper coating - Google Patents

Abstract

PURPOSE:To obtain the latex which provides a coated paper excellent in resistance to blister, gloss on a white paper, ink acceptance, etc., by copolymerizing a specific monomer mixture contg. an aliph. conjugated diolefin monomer with a specific compd. CONSTITUTION:The latex is obtd. by copolymerizing 100 pts.wt. monomer mixture comprising 10-80wt.% aliph. conjugated diolefin monomer (e.g. 1,3-butadiene), 0.5-10wt.% ethylenically unsatd. carboxylic acid monomer (e.g. acrylic acid), and 10-89.5wt.% monoolefin monomer copolymerizable with the foregoing monomers (e.g. styrene) with 0. 1-10 pts.wt. compd. of the formula (wherein R1 is 4-20C alkyl; R2 is H or R1; R3, is H or propenyl; n is 1-100; and M is Na, K, or NH4).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a copolymer latex for paper coating. More specifically, operability,
The present invention relates to a method for producing a copolymer latex for paper coating, which provides a coated paper having excellent adhesive strength and excellent blister resistance, white paper gloss, ink acceptance, water resistance and the like.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable expansion of coated paper due to an increase in printed matter. In addition to this, productivity has been improved, and high-speed coating has been advanced in order to streamline and save labor. In high-speed coating, there is a problem in terms of operation that adhesion of the paper coating composition to the backing roll, so-called backing roll stain occurs.

Therefore, as a paper coating composition, there is an increasing demand for a composition which adheres to a backing roll as little as possible, and has excellent operability such that even if it adheres, it is quickly removed by washing with water.

On the other hand, due to the recent rapid increase in printed matter, high-speed printing has been promoted especially in offset printing, and the demand for performance of coated paper for offset printing has become strict.

That is, the properties include high-speed printing, overprinting, adhesive strength during printing, water resistance against dampening water in offset printing, ink acceptability, and blister resistance during high-temperature high-speed drying. These performances have been variously studied because the copolymer latex contained as the main binder component in the paper coating composition has a great influence and the degree of freedom of improvement is great.

However, if the operability in the above-mentioned coating is improved, on the contrary, there is a trade-off relationship that the above-mentioned various physical properties as offset coated paper are deteriorated, and a copolymer latex satisfying both of them is present. The current situation is that the above has not been obtained, and this improvement is desired.

[0007]

[Means for Solving the Problems] In view of the above-mentioned circumstances, the inventors of the present invention have made diligent studies to solve the current problems, and as a result, introduced a specific compound as a copolymerization component. It was found that the united latex can be a binder for paper coating which is excellent in operability and has excellent adhesive strength, water resistance, further blister resistance, white paper gloss, and ink acceptance,
The present invention has been completed.

That is, the present invention comprises 10 to 80% by weight of an aliphatic conjugated diolefin monomer, 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, and a monoolefin system copolymerizable therewith. 100 parts by weight of a monomer mixture consisting of 10 to 89.5% by weight of a monomer and 0.1 to 10 parts by weight of a compound represented by the following general formula (1) are copolymerized. A method for producing a coating copolymer latex is provided.

[0009]

[Chemical 2]

(Wherein R ₁ is an alkyl group having 4 to 20 carbon atoms, R ₂ is hydrogen or an alkyl group having 4 to 20 carbon atoms, and R _{3 is}
Is hydrogen or a propenyl group, n is an integer of 1 to 100, and M is Na, K or NH ₄ . )

The present invention will be described in more detail below.

Examples of the aliphatic conjugated diolefin-based monomer used in the copolymer latex of the present invention include 1,
3-butadiene, 2-methyl-1,3 butadiene, 2,
3-dimethyl-1,3 butadiene, 2-chloro-1,3
Butadiene etc. are mentioned, and these can be used 1 type or 2 types or more. The use of 1,3-butadiene is particularly preferable.

The aliphatic conjugated diolefin monomer is 10
Used in the range of up to 80% by weight, the amount used is 1
If it is less than 0% by weight, the adhesive strength tends to be poor, and if it exceeds 80% by weight, the water resistance tends to be inferior.

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. One kind or two or more kinds can be used.

The ethylenically unsaturated carboxylic acid monomer is
It is used in the range of 0.5 to 10% by weight. If the amount used is less than 0.5% by weight, mechanical stability is poor, and if it exceeds 10% by weight, the viscosity of the latex tends to increase. There is not preferable.

Other monomers copolymerizable with the above-mentioned aliphatic conjugated diolefin monomer and ethylenically unsaturated carboxylic acid monomer include alkenyl aromatic monomers and unsaturated carboxylic acid alkyl ester monomers. Examples thereof include a monomer, a hydroxyalkyl group-containing unsaturated monomer, a vinyl cyanide monomer, and an unsaturated carboxylic acid amide monomer.

As the alkenyl aromatic monomer, styrene, α-methylstyrene, methyl α-methylstyrene,
Vinyltoluene and divinylbenzene and the like,
One kind or two or more kinds can be used. Particularly preferred is styrene.

Examples of unsaturated carboxylic acid alkyl ester monomers 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, and one kind or two or more kinds can be used. Methyl methacrylate is particularly preferable.

Examples of the unsaturated monomer 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, etc. are mentioned, and 1 type (s) or 2 or more types can be used. Particularly, β-hydroxyethyl acrylate is preferable.

Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and α-ethylacrylonitrile.
One kind or two or more kinds can be used. Acrylonitrile is particularly preferable.

As the unsaturated carboxylic acid amide monomer,
Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,
N-dimethylacrylamide and the like can be mentioned, and one kind or two or more kinds can be used. Particularly preferred is acrylamide.

These other copolymerizable monomers are from 10 to 10.
Although it is used in the range of 89.5% by weight, if the amount used is less than 10% by weight, the water resistance strength tends to be poor, and if it exceeds 89.5% by weight, the adhesive strength tends to be poor, which is not preferable.

The copolymer latex in the present invention is obtained by further copolymerizing 0.1 to 10 parts by weight of the compound represented by the following general formula (1) with 100 parts by weight of the above monomer mixture. is there.

[0024]

[Chemical 3]

(Wherein R ₁ is an alkyl group having 4 to 20 carbon atoms, R ₂ is hydrogen or an alkyl group having 4 to 20 carbon atoms, and R _{3 is}
Is hydrogen or a propenyl group, n is an integer of 1 to 100, and M is Na, K or NH ₄ . )

When the amount of the above compound is less than 0.1 parts by weight with respect to 100 parts by weight of the monomer mixture, the workability tends to be poor, and when it exceeds 10 parts by weight, the water resistance tends to be poor.

In producing a copolymer latex using these monomers, an emulsifier, an initiator, a chain transfer agent, an electrolyte, a chelating agent and the like can be used.

As the emulsifier, a sulfuric acid ester salt of a higher alcohol, an alkylbenzene sulfonate, an alkyl diphenyl ether sulfonate, an aliphatic sulfonate, an aliphatic carboxylate, an anionic surfactant such as a sulfuric acid ester salt of a nonionic surfactant is used. Surfactants or nonionic surfactants such as alkyl ester type of polyethylene glycol, alkyl phenyl ether type, alkyl ether type and the like are used in one kind or in two or more kinds.

As the initiator, a water-soluble initiator such as potassium persulfate, ammonium persulfate or sodium persulfate, a redox initiator or an oil-soluble initiator such as benzoyl peroxide can be used.

As the chain transfer agent, alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan, dimethylxanthogen disulfide, diisopropylxanthogen. Xanthogen compounds such as disulfide, α-methylstyrene dimer, terpinolene, and thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide, 2,6-di-
Phenolic compounds such as t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, carbon tetrachloride and carbon tetrabromide, α-
Benzyloxystyrene, α-benzyloxyacrylonitrile, vinyl ethers such as α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate, and the like, One kind or two or more kinds can be used.

The amount of the chain transfer agent used is not particularly limited and can be appropriately adjusted according to the performance required of the copolymer latex, but preferably 0.05 to 100 parts by weight of the monomer mixture. 10 parts by weight.

Further, in the present invention, a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring such as cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene, benzene, toluene and cyclohexane. Etc. may be added,
In particular, it is preferable to add a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring in terms of physical property balance. The amount of such a compound used is 0.1 to 30 parts by weight based on 100 parts by weight of the monomer mixture.

The method of adding the above-mentioned various components in the present invention is not particularly limited, and any of a batch addition method, a divided addition method and a continuous addition method can be adopted. Regarding the compound represented by the general formula (1), it is preferable to add it all together at the initial stage of the polymerization in order to maximize the effects of the present invention.

Further, in the present invention, any one-step polymerization, two-step polymerization or multi-step polymerization can be adopted.

The copolymer latex for paper coating of the present invention comprises
It is prepared as a paper coating composition together with pigments and optionally other binders. At that time, the copolymer latex 2 of the present invention is added to 100 parts by weight of the pigment in terms of solid content.
100 parts by weight, preferably 5 to 30 parts by weight, and 0 to 30 parts by weight of other binders can be used.

Examples of the main pigments used in the present invention include mineral white pigments such as clay, calcined clay, deramie clay, ground calcium carbonate, precipitated calcium carbonate, titanium dioxide, aluminum hydroxide, talc and satin white. These may be used alone or in combination of two or more. However, if necessary, an organic synthetic white pigment such as a plastic pigment, a binder pigment or a hollow synthetic pigment may be used in combination.

Other binders include modified starch such as starch, oxidized starch, esterified starch, natural binder such as soybean protein and casein, or synthetic latex such as polyvinyl alcohol, polyvinyl acetate latex and acrylic latex. Is used.

In order to prepare the paper coating composition, other auxiliaries such as dispersants (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, etc.), defoaming agents (polyglycol, fatty acid ester) , Phosphate ester, silicone oil, etc.), leveling agent (funnel oil, dicyandiamide, urea, etc.), preservative, waterproofing agent (formalin, hexamine, melamine resin, urea resin, glyoxal, etc.), release agent (calcium stearate, Paraffin emulsion, etc.), fluorescent dye, color water retention improver (carboxymethyl cellulose, sodium alginate, etc.) are added as necessary.

The copolymer latex for paper coating of the present invention comprises
In particular, it is preferably used as a binder to give coated paper for rotary offset printing, but in addition, for sheet offset printing, gravure printing, cast coated paper, pressure sensitive copy paper top and bottom paper, thermal paper It is also suitably used as a binder used for.

Further, the method of applying the paper coating composition to the coated paper is known in the art, for example, an air knife coater,
It is carried out by a coating machine such as a blade coater, a roll coater or a bar coater. After coating, the surface is dried and finished by calendering.

[0041]

EXAMPLES In order to clearly show the excellent effects of the present invention, the present invention will be described in more detail below with reference to Examples and Comparative Examples. However, as long as the present invention does not exceed the gist thereof, these It is not limited in any way by the embodiment. In addition,
Parts and% showing ratios shown in Examples and Comparative Examples
Is based on weight unless otherwise specified.

Method for producing copolymer latex (1) 100 liters of pure water was placed in a pressure-resistant autoclave of 10 liters.
Part, t-dodecyl mercaptan 0.06 part, sodium hydrogen carbonate 0.4 part, ammonium persulfate 0.8 part and the first stage raw material shown in Table 1 were charged and the first stage polymerization was carried out at 65 ° C. Then, when the polymerization conversion in the first step reached 70%, the starting material in the second step and t-dodecyl mercaptan were added in an amount of 0.
6 parts were continuously added over 7 hours to carry out a second stage polymerization. Then, the polymerization was continued until the conversion of the polymerization reached 98% or more, and the polymerization was completed.

Then, the pH is adjusted to 8 with sodium hydroxide.
And unreacted monomers were removed by steam distillation to obtain copolymer latexes 1-14. In addition, the left side shows the usage amount in the first step and the right side shows the usage amount in the second step across "/" in the table.

The gel content of the copolymer latex was measured by the following method.

A latex film is prepared by drying the gel content at room temperature. afterwards,
After accurately weighing about 1.0 g of latex film, 400
It is placed in cc of toluene and left to dissolve for 48 hours, filtered through a 300-mesh wire net, dried, and the toluene insoluble component (gel) on the wire net is weighed to calculate the gel content.

Preparation of Paper Coating Composition Copolymer latices 1 to 14 were prepared according to the following formulations using pure water so as to have a solid content concentration of 60% to obtain a paper coating composition. It was The mechanical stability and workability of the obtained paper coating composition were measured. (Prescription) Kaolin clay 80 parts Calcium carbonate 20 parts Modified starch 6 parts Copolymer latex 12 parts (solid content)

Mechanical Stability The above-mentioned paper coating composition was kneaded between a metal roll and a rubber roll using a Patastabili tester, mechanically sheared, and the time (minutes) until a solidified product was generated on the rubber roll was determined. taking measurement. ○: 30 minutes or more △: 20 minutes or more and less than 30 minutes ×: less than 20 minutes

[0048] As a measure of the water washing of the deposit to the runnability backing roll, the paper coating composition onto a polyester film, coating using a coating bar so that 10 g / m ² on a dry coating weight -Drying and immersing the film in a water bath for 30 minutes, the degree of peeling of the composition from the film is visually evaluated. ◯: Very well peeled off Δ: Well peeled off ×: Not much peeled off

Preparation of coated paper Further, after coating and drying a commercial high-quality paper (64 g / m ² ) with a coating bar so that the coating amount of the above composition would be 10 g / m ^{2 on} one side, Roll temperature 50 ℃, linear pressure 7
Super calendering was performed under conditions of 0 to 80 kg / cm to obtain coated paper. RI W for the obtained coated paper
Et Pick, RI Dry Pick, blister resistance, white paper gloss, and ink acceptability were measured.

RI Wet Pick The degree of picking when printed with dampening water with a RI printing machine is judged with the naked eye, and there are 5 grades of 1st grade (the best grade) to 5th grade (the worst grade) Evaluated by law. The average value of 6 times is shown.

Evaluation was carried out in the same manner as in the above RI Wet Pick, except that RI Dry Pick dampening water was not used.

Blister resistance The following shows the minimum temperature at which blister is generated by throwing a coated double-sided coated paper into a heated oil bath after humidity conditioning (about 6%).

White paper gloss Measured at an angle of 75 ° according to JIS P8142.

Ink acceptability Using an RI printer, water was supplied by a rubber roll and a molton roll, and the acceptability of the ink at the time of printing was visually judged. The results are shown in Table 2.

[0055]

[Table 1]

[0056]

[Table 2]

Method for producing copolymer latex (2) 100 ml of pure water was placed in a pressure-resistant autoclave of 10 liters.
Parts, sodium hydrogencarbonate 0.4 part, ammonium persulfate 0.8 part and the first stage raw material shown in Table 3 were charged and the first stage polymerization was carried out at 65 ° C. Next, at the time when the polymerization conversion of the first stage reached 70%, the raw material of the second stage was continuously added for 7 hours to carry out the polymerization of the second stage. After that, the polymerization conversion rate is 97.
The polymerization was continued until the content became at least%, and the polymerization was completed.

Then, the pH was adjusted to 8 with sodium hydroxide.
And unreacted monomers were removed by steam distillation to obtain copolymer latexes 15 to 23. In addition, the left side shows the usage amount in the first step and the right side shows the usage amount in the second step across "/" in the table.

Preparation of Paper Coating Composition Copolymer latices 15 to 23 were prepared according to the following formulations using pure water so as to have a solid content concentration of 60% to obtain a paper coating composition. It was The mechanical stability and workability of the obtained paper coating composition were measured. (Prescription) Kaolin clay 80 parts Calcium carbonate 20 parts Modified starch 5 parts Copolymer latex 10 parts (solid content)

Preparation of Coated Paper A coated paper was obtained from the above composition in the same manner as in Example 1. About the obtained coated paper, RI Wet Pi
ck, RI Dry Pick, blister resistance, white paper gloss, and ink acceptability were measured. The results are shown in Table 4.

[0061]

[Table 3]

[0062]

[Table 4]

[0063]

As described above, by using the specific copolymer latex obtained in the present invention as a binder for paper coating, excellent operability and adhesive strength, and blister resistance, white paper gloss, It is possible to obtain a coated paper excellent in ink acceptability and water resistance.

Claims (2)

[Claims] 1. An aliphatic conjugated diolefin-based monomer 10 to 10.
80% by weight, ethylenically unsaturated carboxylic acid monomer 0.5
10 to 10% by weight and 100 parts by weight of a monomer mixture consisting of 10 to 89.5% by weight of a monoolefin monomer copolymerizable therewith and a compound represented by the following general formula (1):
A method for producing a copolymer latex for paper coating, which comprises copolymerizing 1 to 10 parts by weight. [Chemical 1] (In the formula, R ₁ is an alkyl group having 4 to 20 carbon atoms, R ₂ is hydrogen or an alkyl group having 4 to 20 carbon atoms, R ₃ is hydrogen or a propenyl group, n is an integer of 1 to 100, M is Na, K or NH _4. ) 2. An amount of 0. to 100 parts by weight of the monomer mixture.
The method for producing a copolymer latex for paper coating according to claim 1, wherein 1 to 30 parts by weight of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring is added and copolymerized.