JPH10251993A - Surface coating agent for papermaking and surface coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain surface coating agent for papermaking, having low solubility to water, excellent in paper strength and printability by compounding a specific polyamide copolymer with a water-soluble aluminum compound. SOLUTION: One to fifty mol% of a carboxyl group-vinyl monomer containing 50-99mol% acrylamide and 1-50mol% carboxyl group-containing vinyl monomer is copolymerized with 0-40mol% vinyl monomer other than the above monomer to provide a carboxyl group-containing polyacrylamide copolymer. The copolymer is compounded with at least one kind of water-soluble aluminum selected from aluminum sulfate, aluminum chloride, basic aluminum sulfate, basic aluminum chloride, aluminum sulfate silicate, etc., in 1-200 equivalent amount (as aluminum atom) based on 100 equivalent carboxyl group of the copolymer to prepare the objective coating agent having <=5wt.% solid content concentration of the acrylamide copolymer and pH2-7. The coating agent is applied to a paper substrate by a gate roll system to provide the objective coated paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a papermaking surface coating agent used for surface coating of various papers and paperboards, and a surface coated paper surface-coated with the papermaking surface coating agent.

[0002]

2. Description of the Related Art Conventionally, in the papermaking industry, the paper surface is treated with a surface coating agent such as starch, polyvinyl alcohol and polyacrylamide to improve the printability of the paper. Among the surface coating agents, polyacrylamide-based surface coating agents are superior to starch and polyvinyl alcohol-based surface coating agents in that the surface strength of paper can be improved with a small amount of coating.

[0003] However, since the surface coating agent is easily dissolved in water, in offset printing using dampening solution, the surface coating agent applied on the paper surface dissolves during printing and the adhesiveness of the paper surface is reduced. There is a problem that the increase in the surface strength or the decrease in the surface strength when wet occurs, and the blanket roll of the printing press is easily stained.

[0004] In recent years, with the increase in papermaking speed, a coating method has been used to transfer a film from a conventionally used two roll size press or the like to a paper surface such as a gate roll size press or a shim size press. Instead of this method, a surface coating agent is applied only to the paper surface layer so that the paper surface strength can be efficiently improved. However, when a polyacrylamide-based surface coating agent is applied by a film transfer method, since the surface coating agent localized in the paper surface layer is easily dissolved, when used for offset printing, blanket roll stains and the like are printed. The operability at the time is greatly affected.

Means for suppressing the solubility of such a polyacrylamide-based surface coating agent in water include, for example,
It is known to use a thermally crosslinkable resin in which glioxal is used in combination or N-methylol (meth) acrylamide is copolymerized. However, in these products, thermal crosslinking is insufficient with the amount of heat given at the time of drying after coating, and the object cannot be sufficiently achieved. Also, various zirconium-based compounds and zinc-based compounds are known as a crosslinking agent, but these are hardly used in general paper because their viscosity stability after mixing is extremely poor and expensive. .

[0006] It is known that a mixture containing polyacrylamide containing no carboxyl group and a water-soluble aluminum compound is used as a coating agent for papermaking. However, in such a coating agent for papermaking, a mixture of polyacrylamide in water is used. The solubility does not decrease and the paper strength effect is not high.
-12883 publication).

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyacrylamide-based surface coating agent and a surface-coated paper having excellent paper strength and low solubility in water.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have found that an aqueous liquid containing a carboxyl group-containing polyacrylamide and a water-soluble aluminum compound is applied to the paper surface. The present inventors have found that aluminum reacts with a carboxyl group in polyacrylamide to improve the surface strength and greatly reduce the solubility in water, thereby completing the present invention.

That is, the present invention provides a paper coating surface coating composition comprising an aqueous liquid containing a carboxyl group-containing polyacrylamide and a water-soluble aluminum compound, and a surface coating composition obtained by coating the paper coating surface coating composition on a paper surface. Regarding papermaking.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The carboxyl group-containing polyacrylamide of the present invention is a polyacrylamide containing acrylamide as a main component and can be used without any particular limitation as long as it has a carboxyl group in the molecule. Examples of the carboxyl group-containing polyacrylamide of the present invention include acrylamide, a carboxyl group-containing vinyl monomer, and a copolymer obtained by copolymerizing a vinyl monomer other than the above as required.

The proportion of acrylamide to be used is usually preferably about 50 to 99 mol% based on the total mol of vinyl monomers. The lower limit of the use ratio of acrylamide is 7
0 mol%, and more preferably 98 mol% as the upper limit. If the use ratio of acrylamide is less than 50 mol%,
Paper strength is not enough.

As the carboxyl group-containing vinyl monomer, (meth) acrylic acid ｛(meth) acrylic acid means acrylic acid and / or methacrylic acid. Hereinafter, (meta) has the same meaning.モ ノ, monocarboxylic acids such as crotonic acid and (meth) allyl carboxylic acid, dicarboxylic acids such as itaconic acid, maleic acid, fumaric acid, and muconic acid; and alkali metal salts such as sodium salts and potassium salts of these various organic acids. , Ammonium salts and the like. Among these, (meth) acrylic acid and itaconic acid are preferred.

The proportion of the carboxyl group-containing vinyl monomer to be used is usually 1 to 1 relative to the total mole of the vinyl monomer.
About 50 mol% is preferable. The lower limit of the use ratio of the carboxyl group-containing vinyl monomer is more preferably 2 mol%, and the upper limit is more preferably 10 mol%. When the use ratio of the carboxyl group-containing vinyl monomer is less than 1 mol%, the paper strength is not sufficient, and the reaction with the aluminum compound is insufficient, and the paper surface coating agent is applied to the paper surface and dried. It is difficult to sufficiently improve the solubility of the subsequent polyacrylamide in water.

As the vinyl monomer other than the above, various ones can be mentioned. For example, anionic vinyl monomers include vinyl sulfonic acid, styrene sulfonic acid,
2-acrylamido-2-methylpropanesulfonic acid,
Organic sulfonic acids such as (meth) allylsulfonic acid; and alkali metal salts such as sodium salt and potassium salt of these various organic acids, and ammonium salts. Examples of the cationic vinyl monomer include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, and diethylaminopropyl (meth)
Vinyl monomers having a tertiary amino group such as acrylamide or salts thereof of inorganic or organic acids such as hydrochloric acid, sulfuric acid and acetic acid, or the tertiary amino group-containing vinyl monomer and methyl chloride, benzyl chloride,
A vinyl monomer containing a quaternary ammonium salt obtained by a reaction with a quaternizing agent such as dimethyl sulfate or epichlorohydrin is exemplified. Examples of the nonionic vinyl monomer include a carboxyl group-containing vinyl monomer or an alkyl ester of the anionic vinyl monomer (alkyl group having 1 to 8 carbon atoms), acrylonitrile, styrenes, vinyl acetate, methyl vinyl ether,
N-vinylpyrrolidone and the like can be mentioned. Also, N, N
-Dimethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nt-butyl (meth) acrylamide, etc. N-substituted (meth) acrylamides may be mentioned.

Further, as the vinyl monomer other than the above, a polyfunctional monomer can be used. Examples of the polyfunctional monomer include di (meth) acrylates such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol di (meth) acrylate, and methylene bis (meth) acrylate.
Bis (meth) acrylamides such as acrylamide, ethylenebis (meth) acrylamide and hexamethylenebis (meth) acrylamide, divinyl esters such as divinyl adipate and divinyl sebacate, allyl methacrylate, diallylamine, diallyldimethylammonium, diallyl phthalate, Bifunctional vinyl monomers such as diallylchlorendate, divinylbenzene, N, N-diallylacrylamide, 1,3,5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, triallylamine, triallyl trimellitate Trifunctional vinyl monomers such as tetramethylolmethanetetraacrylate, tetraallyl pyromellitate, N, N, N ', N'-tetraallyl-1,4-diaminobutane, tetraa Triethanolamine salt, 4-functional vinyl monomers such as tetraallyloxyethane, other N-
Methylol acrylamide and the like can be mentioned.

The proportion of the vinyl monomer used as required is preferably about 0 to 40 mol% based on the total mole of the vinyl monomer. However, the amount of the polyfunctional monomer is preferably about 0 to 5 mol%.

The method for producing a carboxyl group-containing polyacrylamide by copolymerizing acrylamide, a carboxyl group-containing vinyl monomer and, if necessary, a vinyl monomer other than the above-mentioned ones, can employ conventional means. For example, the desired carboxyl group-containing polyacrylamide can be obtained by charging the above various monomers and water into a predetermined reaction vessel, adding a radical polymerization initiator, and heating under stirring. The reaction temperature is usually 50 to 10
The reaction time is about 0 ° C. and the reaction time is about 1 to 5 hours. Others
The monomer can be charged by various conventionally known methods such as simultaneous polymerization and continuous drop polymerization. As the radical polymerization initiator, a normal radical polymerization initiator such as a persulfate such as potassium persulfate or ammonium persulfate, or a redox polymerization initiator in the form of a combination thereof with a reducing agent such as sodium bisulfite is used. it can. Further, an azo-based initiator may be used as the radical polymerization initiator. The amount of the radical polymerization initiator used is about 0.05 to 2.0% by weight of the total weight of the vinyl monomers.

The weight average molecular weight of the carboxyl group-containing polyacrylamide is usually about 100,000 to 5,000,000, and the viscosity is usually 2,000 to 10% to 35% by weight on a solid basis.
It has a property of about 0 cps or less (25 ° C.).

As the water-soluble aluminum compound of the present invention, various compounds can be used, and any one selected from aluminum sulfate, aluminum chloride, basic aluminum sulfate, basic aluminum chloride, aluminum sulfate silicate and a polymer thereof is used. It is preferred to use at least one. Among these exemplified water-soluble aluminum compounds, aluminum sulfate is particularly preferred from the viewpoint of cost.

The water-soluble aluminum compound is reacted with a carboxyl group in the carboxyl group-containing polyacrylamide to apply a paper coating surface coating agent on the paper surface and, after drying, dissolves the polyacrylamide in water. Is to be reduced. Therefore, the amount of the water-soluble aluminum compound to be used is preferably 1 to 200 equivalents as an aluminum atom, 100 equivalents as the lower limit, and 100 equivalents as the upper limit, based on 100 equivalents of the carboxyl group of the carboxyl group-containing polyacrylamide. If the amount of the water-soluble aluminum compound is less than 1 equivalent, it is difficult to reduce the solubility of polyacrylamide in water, and if it is more than 200 equivalents, the paper strength effect per total solid content is insufficient. .

The paper coating surface coating composition of the present invention is an aqueous liquid containing the carboxyl group-containing polyacrylamide and a water-soluble aluminum compound, and is appropriately prepared so that the amounts of the respective components fall within the above ranges. Although it can be produced, if necessary, an inorganic acid, an organic acid or an alkali such as sodium hydroxide, potassium hydroxide, or ammonia is added to adjust the pH of the aqueous solution of the carboxyl group-containing polyacrylamide to 2 to 7, It is preferable to mix with a water-soluble aluminum compound to prepare a papermaking surface coating agent comprising an aqueous liquid having a pH of 2 to 7.

The concentration of the carboxyl group-containing polyacrylamide in the aqueous liquid used as the papermaking surface coating agent is usually about 40% by weight or less, but considering the storage stability of the papermaking surface coating agent. It is preferable that the content be about 5% by weight or less. At the time of use, a water-soluble aluminum compound may be mixed with the aqueous solution of the carboxyl group-containing polyacrylamide diluted to about 0.1 to 5% by weight. Further, if necessary, various additives such as a so-called surface sizing agent, an anti-slip agent, a lubricant and an antifoaming agent may be mixed. Examples of the surface sizing agent include styrene- (meth) acrylic acid copolymer, styrene-maleic acid copolymer, (di) isobutylene-maleic acid copolymer, linear α-olefin-maleic acid copolymer and the like. Alkali metal salt, ammonium salt, or styrene-acrylate copolymer, acrylonitrile-acrylate copolymer,
Emulsions such as alkyl ketene dimer and the like can be mentioned.

The surface coating agent for paper making thus obtained is used for surface treatment of paper and paperboard for producing surface coated paper. Examples of paper and paperboard include newspaper rolls, writing paper, wallpaper, PPC paper, inkjet paper, printing paper, and various types such as liners, white balls, and the like. It is particularly useful as a surface coating agent for newsprint paper because of the fact that weight reduction has progressed, color printing has increased, and strict printability has been required. Various methods can be adopted as a method of coating the paper surface. For example, a method such as an impregnation method, a bar coater method, a calendar method, a spray method, a two-roll size press, or a film transfer method such as a gate roll size press or a shim size press can be used. The coating amount of the papermaking surface coating agent is usually about 0.001 to ² g / m ² (solid content), and preferably 0.005 to 1 g / m ² .

[0024]

EFFECT OF THE INVENTION The surface coating agent for papermaking of the present invention is excellent in paper strength, and has low solubility in water after coating and drying on the paper surface. When the coated surface coated paper is used for offset printing, the printability is excellent, there is no operation trouble at the time of printing, and the quality of the printed matter is excellent. Therefore, a large amount of the surface coating agent can be applied to the paper surface by a film transfer method such as a gate roll size press.

[0025]

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. Parts and% in each example are based on weight unless otherwise specified.

Synthesis Example 1 In a four-necked flask equipped with a thermometer, a reflux condenser and a nitrogen inlet tube, 100 parts of acrylamide (95 mol% based on the total mol of monomers), 5.3 parts of acrylic acid (5 mol%) ,
5.3 parts of isopropyl alcohol and ion-exchanged water 4
Then, 00 parts were charged, and oxygen in the reaction system was removed through nitrogen gas. The temperature in the system was adjusted to 40 ° C., and 0.3 parts of ammonium persulfate and 0.2 parts of sodium bisulfite were charged as a polymerization initiator with stirring. The start of polymerization is confirmed by heat generation,
After the temperature of the reaction solution reached 90 ° C., the temperature was kept for 2 hours. After the completion of the polymerization, 15.4 parts of ion-exchanged water was added, and pH 2.8 and
Carboxyl group-containing polyacrylamide aqueous solution having a polymer concentration of 20% and a viscosity of 3500 cps (hereinafter referred to as PAM-A
).

Synthesis Example 2 65 parts of acrylamide (5 parts) were placed in the same reactor as in Synthesis Example 1.
7.2 mol%), acrylonitrile 25 parts (29.5 mol%), acrylic acid 15.3 parts (13.3 mol%), isopropyl alcohol 5.3 parts and ion-exchanged water 40
Two parts were charged and polymerization was carried out in the same manner as in Synthesis Example 1. After the completion of the polymerization, 14.1 parts of a 48% aqueous sodium hydroxide solution was added, and the pH was 5.8, the polymer concentration was 20%, and the viscosity was 3050.
An aqueous solution of cps carboxyl group-containing polyacrylamide (hereinafter referred to as PAM-B) was obtained.

Comparative Synthesis Example 1 100 parts of acrylamide (9 parts) was placed in the same reactor as in Synthesis Example 1.
6.6 mol%), 5 parts of N-methylolacrylamide (3.4 mol%), 5 parts of isopropyl alcohol, 48
% Of caustic soda and 400 parts of ion-exchanged water were charged, and polymerization was carried out in the same manner as in Synthesis Example 1. After polymerization,
14.2 parts of ion-exchanged water were added to obtain a carboxyl group-free polyacrylamide aqueous solution (hereinafter, referred to as PAM-C) having a pH of 7.8, a polymer concentration of 20%, and a viscosity of 6,800 cps.

Example 1 To 100 parts of PAM-A obtained in Synthesis Example 1, 1.45 parts of a commercially available aluminum sulfate aqueous solution (concentration: 27%, containing 1.6 mmol / g of aluminum) (the aluminum atom was PAM-A) 16. For 100 equivalents of carboxyl groups in A.
5 equivalents) and an aluminum compound-containing aqueous solution obtained by mixing 98.55 parts of water, and a polymer concentration of 10% and a pH of 10%.
A papermaking surface coating agent a of 2.4 was obtained.

Example 2 After mixing 200 parts of water with 100 parts of PAM-A obtained in Synthesis Example 1, 5.7 parts of the aluminum sulfate aqueous solution used in Example 1 (the aluminum atom is a carboxyl group in PAM-A) An aqueous solution containing an aluminum compound obtained by mixing 143.8 parts of water with 143.8 parts of water was mixed to obtain a paper coating surface coating agent b having a polymer concentration of 5% and a pH of 2.4.

Example 3 After mixing 500 parts of water with 100 parts of PAM-B obtained in Synthesis Example 2, 37.5 parts of a commercially available aluminum sulfate aqueous solution used in Example 1 (aluminum atoms in PAM-C were used). (150 equivalents to 100 equivalents of carboxyl groups) to obtain a paper coating surface coating agent c having a polymer concentration of 3.1% and a pH of 4.3.

Comparative Example 1 A commercially available aluminum compound-containing aqueous solution obtained by mixing 1.45 parts of a commercially available aqueous aluminum sulfate solution and 98.45 parts of water was mixed with 100 parts of PAM-C obtained in Comparative Synthesis Example 1 in the same manner as in Example 1. Thus, a papermaking surface coating agent d having a polymer concentration of 10% and a pH of 4.8 was obtained.

Comparative Examples 2 to 4 PAM-A,-obtained in Synthesis Examples 1 and 2 and Comparative Synthesis Example 1
B and -C were used as paper-making surface coating agents e, f, and g, respectively, without adding an aqueous solution containing an aluminum compound.

(Production of Surface Coated Paper) Using the paper surface coating agents a to c obtained in Examples 1 to 3 and the paper surface coating agents d to g obtained in Comparative Examples 1 to 4, Polymer concentration of 1.
It was diluted to 5%, coated on newspaper base paper (basis weight 43 g / m ² ) with a coating amount shown in Table 1 using a gate roll coater, and dried at 100 ° C. for 1 minute using a rotary dryer to obtain newsprint. Obtained. The obtained newsprint was evaluated by the following method. Table 1 shows the evaluation results.

(Surface Strength) Using a printability tester (manufactured by SMT), the surface strength was visually determined by the fluffing of the paper surface after printing the black ink of Tack 10 on the surface-coated newsprint. . The evaluation was made in five steps according to the degree of fluff after printing (the larger the number, the less fluff).

(Water solubility) A surface-coated newsprint (1.5 g) cut into 1 cm × 1 cm was placed in ion-exchanged water
0 g, stirred with a magnetic stirrer, and after 1 minute, water was collected and the nitrogen concentration in the water was measured to calculate the ratio (%) of the amount of the dissolved polyacrylamide to the amount of the coated polyacrylamide. did.

[0037]

[Table 1]

Claims (9)

[Claims] 1. A paper coating surface coating agent comprising an aqueous liquid containing a carboxyl group-containing polyacrylamide and a water-soluble aluminum compound. 2. A carboxyl group-containing polyacrylamide is a copolymer obtained by copolymerizing 50 to 99 mol% of acrylamide, 1 to 50 mol% of a carboxyl group-containing vinyl monomer, and 0 to 40 mol% of other vinyl monomers. The paper coating surface coating agent according to claim 1. 3. The water-soluble aluminum compound is at least one selected from the group consisting of aluminum sulfate, aluminum chloride, basic aluminum sulfate, basic aluminum chloride, aluminum sulfate silicate and a polymer thereof. The papermaking surface coating agent according to the above. 4. The use amount of the water-soluble aluminum compound is as follows:
For 100 equivalents of carboxyl groups of carboxyl group-containing polyacrylamide, 1 to 20 aluminum atoms
4. The paper coating surface coating composition according to claim 1, which has 0 equivalent. 5. The paper coating surface coating composition according to claim 1, wherein the solid content concentration of the carboxyl group-containing polyacrylamide in the aqueous liquid is 5% by weight or less. 6. The pH of the aqueous liquid is from 2 to 7.
5. The papermaking surface coating agent according to any one of 5. 7. A surface-coated paper obtained by coating the paper surface-coating agent according to claim 1 on the paper surface. 8. The surface-coated paper according to claim 7, wherein the method of coating the paper surface is a gate roll method. 9. The paper as claimed in claim 7, wherein the paper is newspaper web.
Surface coated paper as described.