JPH09169946A - Surface coating agent and its utilization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface coating agent, comprising an aqueous solution of an acrylamide-based polymer prepared by copolymerizing specific compounds and capable of manifesting an improvement in paper strength to a conventionally unrecognizable extent. SOLUTION: This surface coating agent comprises an aqueous solution of an acrylamide-based polymer prepared by copolymerizing (A) >=50mol% (meth) acrylamide with (B) 0.005-30mol% vinyl compound of the formula [R1 is H or a lower alkyl; (n) is 1-8] or its salt (e.g. sodium methallylsulfonate), (C) 0.01-5mol% cross-linking vinyl compound (e.g. methylenebisacrylamide) and (D) 0.1-20mol% unsaturated dicarboxylic acid or its salt (e.g. itaconic acid) as monomers. Furthermore, monomers containing (E) 0.1-49mol% vinyl cyanide compound (e.g. acrylonitrile) and (F) 0.01-49mol% other monomers copolymerizable with the component (A) are preferably used as the monomers.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a surface coating agent and its use. More specifically, it relates to a surface coating agent composed of an aqueous solution of an acrylamide polymer, which exhibits an unprecedented improvement in paper strength by polymerizing with a specific compound.

[0002]

2. Description of the Related Art In recent years, in the paper manufacturing industry, from the standpoint of environmental protection, the utilization rate of used paper has been improved, or the use of inexpensive and fast-growing Nanyo wood has been advanced. Since these contain fine fibers and have vessels and soft cells, the bond between pulps is weak and the paper strength is low. Therefore, in the production of papers made of pulp raw materials that have not been used in the past, surface coating agents have been used more than before in addition to the internal paper strength agent.

The surface coating agent is a modification of the surface physical properties of corrugated cardboard exterior liners and other paperboards, high-quality papers, medium-quality papers, coated base papers, newsprints, and the like, such as surface abrasion, fluffing, lubricity and moisture absorption. As a means for improving the properties, gloss, paper powder, picking at the time of printing, and further improving the internal paper strength, calender coating, size press impregnation, gate roll coating, spray atomization, etc. It is used.

As surface coating agents that have been conventionally used, in addition to acrylamide-based polymers, (oxidized) starch and its modified products (hereinafter referred to as starch-based), cellulose derivatives such as carboxymethyl cellulose, and natural substances such as guar gum are used. Products or semi-synthetic products, polyvinyl alcohol and its derivatives (hereinafter referred to as PVA-based), and urea resin,
There are various substances such as styrene-maleic acid copolymer, polyvinyl acetate, vinyl acetate-maleic acid copolymer, latex type and emulsion type. When actually used, they are generally coated or impregnated with one kind or a combination of two or more kinds.

It is difficult to obtain a sufficient surface strength with a conventional surface coating agent using an acrylamide polymer, and in order to achieve it, it is necessary to increase the coating amount, which results in a decrease in ink set and blocking. However, this is not a preferable method because it causes new problems.

On the other hand, starch-based and PVA-based are powders,
After dispersion in water, it is necessary to dissolve by heating, and workability is difficult. In addition, there are problems in operability such as foamability and viscosity during coating, and it is difficult to say that the coating agent is satisfactory. On the other hand, it is said that a polymer having a branched crosslinked structure can have a high molecular weight while having a low viscosity. Lowering the viscosity of the polymer improves the suitability for high-speed coating, and increasing the molecular weight contributes to the improvement of paper strength. However, in order to satisfy both of these, it is necessary to uniformly control the cross-linking structure, and it is considered that this structure control is impossible with the prior art.

The acrylamide polymer aqueous solution produced in the prior art has a molecular weight of 3 at a concentration of 15%.
Although a production method of about 1,000,000 has been proposed, a high concentration and high molecular weight one has not been known at all. Because,
If the concentration is higher than this, the high-molecular weight expected in the linear polymer will not be obtained, or the viscosity will be extremely high. In addition, when trying to introduce a branched crosslinked structure into the polymer, the crosslinking reaction partially proceeds abnormally,
This is because a gel insoluble in water is formed, or the whole gels and cannot be obtained in the state of an aqueous solution, so that it cannot be used as a surface coating agent.

Although the improvement of the polymer concentration has an advantage in terms of transportation cost, the concentration of 20% is increased due to the above reasons.
Up to now, no surface coating agent comprising an aqueous solution of a high-molecular-weight acrylamide-based polymer in an amount of 1% or more has been known.

[0009]

An object of the present invention is to produce an aqueous solution of an acrylamide polymer having a high concentration, a high molecular weight and a low viscosity, and apply it to paper to obtain a high paper strength which has never been seen before. It is an object of the present invention to provide a surface coating agent capable of obtaining strength.

[0010]

In view of the above circumstances, the present inventors have been investigating a surface coating agent composed of an aqueous solution of an acrylamide polymer. As a result, we succeeded in developing a surface coating agent that exhibits extremely excellent paper strength. That is, the present invention relates to (meth) acrylamide as a monomer and one or more vinyl compounds selected from vinyl compounds represented by the following general formula (1) and (2) and / or their salts. A surface coating agent comprising an aqueous solution of an acrylamide polymer obtained by polymerizing a crosslinkable vinyl compound and an unsaturated dicarboxylic acid or a salt thereof, and a paper coated with the surface coating agent.

[0011]

Embedded image (In the formula, R ₁ represents a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 to 8, preferably 1 to 4)

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Although the amount of acrylamide and / or methacrylamide in the surface coating agent of the present invention varies depending on the type or amount of other copolymerization components, in order to exert the effect as a surface coating agent. Is
It may be about 50 mol% or more, but is preferably 60 to 99.5 mol%.

In the present invention, specific examples of the compound represented by the general formula (1) include allyl sulfonic acid, methallyl sulfonic acid or their alkali metal salts such as sodium salt or potassium salt, ammonium salt and the like. can do. As the amount of these compounds,
It is 0.005 to 30 mol% with respect to the total amount of all the monomers constituting the acrylamide polymer, but preferably 0.01 to 2 from the viewpoint of the uniformity of the branched and crosslinked structure of the polymer.
It is 0 mol%, and more preferably 0.05 to 10 mol%. These compounds may be used alone or in combination of two or more.

In the present invention, a surface coating agent having a high concentration, a high molecular weight and a low viscosity can be easily obtained by using a crosslinkable vinyl monomer in addition to the compound represented by the general formula (1). be able to. When the crosslinkable vinyl monomer in the present invention is specifically listed, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate,
Bifunctional cross-linking monomers such as triethylene glycol di (meth) acrylate and divinylbenzene, or polyfunctional such as 1,3,5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, and pentaerythritol triacrylate. Examples of the type crosslinkable monomer can be given. The amount of these crosslinkable monomers is 0.01 to 5 mol% with respect to the total amount of all monomers constituting the acrylamide polymer, but 0.01 from the viewpoint of uniformity of the branched crosslinked structure of the polymer. It is preferably ˜2 mol%. These compounds may be used alone or in combination of two or more.

By using an unsaturated dicarboxylic acid or a salt thereof in addition to the above compounds as the surface coating agent in the present invention, a surface coating agent exhibiting high paper strength can be obtained. Specific examples of the unsaturated dicarboxylic acid or salt thereof in the present invention include itaconic acid, maleic acid, fumaric acid, citraconic acid, and their sodium salts, potassium salts, ammonium salts and the like. The amount of these unsaturated dicarboxylic acids is preferably 0.1 to 20 mol% with respect to the total monomers constituting the acrylamide polymer, and is 0.1% from the copolymerizability with acrylamide.
It is more preferably 1 to 10 mol%. These compounds can be used alone or in combination of two or more.

By using a vinyl cyanide compound in addition to the above compounds as the surface coating agent in the present invention, a surface coating agent having good viscosity can be obtained during coating. Specific examples of the vinyl cyanide compound in the present invention include ethylene-based nitrile compounds such as acrylonitrile and methacrylonitrile. The amount of these vinyl cyanide compounds is 0.1 to 49 mol% with respect to all the monomers constituting the acrylamide polymer, and more preferably 0.1 from the copolymerizability with acrylamide.
Is about 40 mol%.

As the surface coating agent in the present invention, in addition to the above compounds, it is possible to use a monomer copolymerizable therewith. Examples thereof include ionic, hydrophilic, and hydrophobic monomers, and one or more kinds of those monomers can be applied. Examples of the anionic monomer among the ionic monomers include acrylic acid, methacrylic acid, crotonic acid, 3-butene-1,2,3-tricarboxylic acid, 4-pentene-1,2,4- Unsaturated mono- and tricarboxylic acids such as tricarboxylic acid and aconitic acid and salts thereof, vinyl sulfonic acid, styrene sulfonic acid, acrylamidomethylpropane sulfonic acid, acrylamido-tert-butyl sulfonic acid and salts thereof are cationic monomers. As, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N , N-dimethylaminoethyl (meth) acrylamide, N, N-diethyl Amine such as aminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide and salts thereof (4
And the like).

Examples of the hydrophilic monomer include acetone acrylamide, N, N-dimethyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-
Diethyl (meth) acrylamide, N-propylacrylamide, N-acryloylpyrrolidine, N-acryloylpiperidine, N-acryloylmorpholine, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, various methoxypolyethylene glycol (meth) acrylates, Examples thereof include N-vinyl-2-pyrrolidone.

Examples of the hydrophobic monomer include N, N-
Di-n-propyl (meth) acrylamide, Nn-butyl (meth) acrylamide, Nn-hexyl (meth) acrylamide, Nn-octyl (meth) acrylamide, N-tert-octyl (meth) acrylamide, N-alkyl (meth) acrylamide derivatives such as N-dodecylacrylamide, Nn-dodecylmethacrylamide, N, N-diglycidyl (meth) acrylamide, N- (4-glycidoxybutyl) (meth) acrylamide, N- N- (ω-glycidoxyalkyl) (meth) acrylamide derivatives such as (5-glycidoxypentyl) acrylamide, N- (6-glycidoxyhexyl) acrylamide, methyl (meth) acrylate, ethyl (meth) acrylate , Butyl (meth) acrylate, lauryl (meth) acrylate Rate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate and other (meth) acrylate derivatives, vinyl acetate, vinyl chloride, vinylidene chloride, olefins such as ethylene, propylene and butene, styrene, α-methylstyrene, butadiene , Isoprene and the like.

Among these monomers used for copolymerization,
Particularly good copolymerizability with acrylamide and / or methacrylamide, and in consideration of performance and stability as a surface coating agent, acrylic acid, methacrylic acid, acrylamidomethylpropanesulfonic acid, and the like are preferably used.
Examples thereof include N, N-dimethylaminoethyl (meth) acrylate. Of course, the monomers used are not limited to these exemplified compounds. The amount of these copolymerizable monomers is generally 0.01 to 49 mol%, preferably 0.1 to 40 mol%.

Radical polymerization is preferred as the method for polymerizing the surface coating agent in the present invention. Water is preferable as the polymerization solvent, but it is possible to use an organic solvent such as an alcohol in combination as long as the polymer is precipitated and settled in an aqueous solution of the above concentration and the dispersibility is not impaired.

The production method may be batch (batch) polymerization in which all monomers are charged in a batch in a reaction vessel and polymerized, but a semi-batch (semi-batch) polymerization in which a part or all of the monomers are dropped into the reaction vessel to perform polymerization. It is more desirable to be legal. By performing the semi-batch (semi-batch) polymerization method, it is possible to control the molecular structure such as easy removal of polymerization heat in high-concentration polymerization and easy homogenization of the branched and crosslinked structure of the polymer. Become.

In the case of batch (batch) polymerization, the polymerization concentration (monomer + polymer concentration at the time of polymerization) is about 20-40.
% By weight. It is possible to polymerize at a concentration lower than 20% and to make a polymer aqueous solution having a concentration of 20% or more by concentration operation, but this is disadvantageous from the economical point of view. In the case of semi-batch (semi-batch) polymerization, the polymerization concentration in the reactor during the dropping can be arbitrarily selected by adjusting the initial monomer concentration in the reactor and the dropping rate of the monomer. However, the polymerization concentration at the end of dropping is approximately 20 to 60% by weight. In this case, batch
Similar to the polymerization, it is possible to carry out the polymerization at a concentration lower than 20% and to carry out the concentration operation to obtain a polymer aqueous solution having a concentration of 20% or more, but it cannot be said that it is an effective method as described above.

The polymerization initiator is not particularly limited, but a water-soluble initiator is preferable. The monomers may be added all at once to the reaction vessel charged, or may be continuously dropped. As a specific polymerization initiator, a persulfate system, a peroxide system, for example, ammonium persulfate, potassium persulfate,
Sodium persulfate, hydrogen peroxide, benzoyl peroxide, te
Examples include rt-butyl peroxide. in this case,
Although it is preferably used alone, it can also be used as a redox polymerization initiator in combination with a reducing agent. Examples of the reducing agent in this case include sulfite, bisulfite, iron,
Low-order ionized salts of copper, cobalt, etc., N, N, N ',
Organic amines such as N′-tetramethylethylenediamine,
Further, reducing sugars such as aldose and ketose can be mentioned. Azo compounds are also the most preferred initiators in the present invention, and are 2,2'-azobis-2-methylpropionamidine hydrochloride, 2,2'-azobis-2,
4-dimethylvaleronitrile, 2,2'-azobis-
N, N'-dimethyleneisobutylamidine hydrochloride, 2,
2'-azobis-2-methyl-N- (2-hydroxyethyl) -propionamide, 2,2'-azobis-2-
(2-Imidazolin-2-yl) -propane and its salt, 4,4'-azobis-4-cyanovaleric acid and its salt, etc. can be used. Furthermore, it is also possible to use two or more of the above-mentioned polymerization initiators in combination.

The polymerization temperature is about 3 in the case of a single polymerization initiator.
0 to 90 ° C., and in the case of a redox type polymerization initiator, the starting temperature is lower and is generally 5 to 50 ° C. Further, it is not necessary to keep the same temperature during the polymerization, and it may be changed appropriately as the polymerization progresses. However, since the polymerization reaction generally generates heat, it may be necessary to add cooling if necessary. The atmosphere in the polymerization container at that time is not particularly limited, but it is preferable to substitute an inert gas such as nitrogen gas for rapid polymerization.

The polymerization time is not particularly limited, but is generally 1 to 20 including the dropping time in the semi-batch (semi-batch) polymerization.
Time. The polymerization pH is not particularly limited, but the pH may be adjusted to carry out the polymerization if necessary. In that case, sodium hydroxide, potassium hydroxide, etc. can be used as pH adjusters.
Examples thereof include alkalizing agents such as ammonia, mineral acids such as phosphoric acid, sulfuric acid and hydrochloric acid, and organic acids such as formic acid and acetic acid.

The viscosity of the surface coating agent of the present invention is 50,000 cps.
(Centipoise) or less, but preferably during distribution,
From the viewpoint of workability during use, 30,000 cps (centipoise)
Hereafter, it is more preferable that the pressure is 20,000 cps (centipoise) or less. Further, the weight average molecular weight is 500,000 to 10,000,000, but from the viewpoint of the uniformity of the branched and crosslinked structure, the concentration and the molecular weight within a range that does not hinder the surface coating agent are about 500,000 at 20% concentration. ~ 8 million, 500,000-6 million at 30% concentration, 500,000-400 at 40% concentration
It is preferable that the concentration is 500,000 to 3,000,000 at a 50% concentration.

The weight average molecular weight referred to in the present invention can be determined by the static light scattering method. Specifically, the value can be obtained by using a multi-angle light scattering detector and creating a Jim plot. Alternatively, it can be obtained by creating a Debye plot by the GPC-MALLS method in which a multi-angle light scattering detector is connected to the GPC.

Generally, for measuring the molecular weight by the light scattering method,
The following basic formula for light scattering Kc / R (θ) = 1 / MwP (θ) + 2A ₂ c + ... R (θ) = scattered light at angle (θ) (Rayleigh coefficient)
Reduction intensity c = sample concentration Mw = weight average molecular weight A ₂ = second virial coefficient K = optical parameter P (θ) = angular scattering function. The weight average molecular weight referred to in the present invention is G
GPC-LALL with low angle light scattering detector connected to PC
Similar to the S method, it means a value that ignores the second and subsequent terms that are the second virial coefficient.

The value of the weight average molecular weight of the polymer by the light scattering method can be measured by using N / 10 phosphate buffer (pH 7) containing N / 10 sodium nitrate as a solvent (eluent). The polymer concentration in the present invention can be obtained by measuring the absolute dry polymer concentration of the polymer aqueous solution. Examples of the measuring method include a hot air drying method and a ket method.

As described above, an aqueous solution of an acrylamide polymer having a Brookfield viscosity at 25 ° C. of not more than 50,000 cps and a weight average molecular weight of 500,000 to 10,000,000 in a concentration range of 22 to 60%, particularly 30 to 60%. It becomes possible to provide a surface coating agent comprising, and the obtained surface coating agent exhibits various effects, and since it has a high concentration, it is possible to reduce the transportation cost per solid content and it is economical.

It is unclear at present why the surface coating agent obtained by the method of the present invention exerts various excellent effects. However, since it has a high molecular weight as compared with the conventional product, it is It is considered to have excellent ability to strengthen the binding force of. Therefore, it is presumed that the conventional surface coating agent can suppress the vessels and fine fibers that are peeled off at the time of printing, and exhibit excellent surface strength and other improving effects.

Further, the reason why the aqueous polymer solution has a high viscosity at a high concentration and a low viscosity is that a polymer molecule incorporating the compound represented by the general formula (1) is being polymerized while another polymer molecule is being polymerized. It is considered that this is because the branched cross-linking proceeds efficiently by specifically reacting with the radical of 1 or the pendant double bond derived from the cross-linking monomer. As a result, it is presumed that an acrylamide polymer having a branched cross-linking structure with a more uniform layer than that of a conventionally known one is obtained, and a high molecular weight polymer aqueous solution with a relatively low viscosity can be obtained even at a high concentration. .

When the surface coating agent of the present invention is used, the coating amount varies depending on the type of paper or the degree of physical properties required, but the solid content is diluted to 0.1 to 10% before use. It is appropriate to adjust the coating amount. As a coating method, a commonly used method, that is, a size press, a gate roll coater, a calender, a blade coater, a champion coater, a spray or the like can be used.

The surface coating agent of the present invention can be used in combination with various agents. For example, surface coating agents such as starch-based, PVA-based, carboxymethylcellulose-based, polyacrylamide-based, etc., which have been conventionally used,
Furthermore, it is a rosin-based or synthetic-based sizing agent, or a water-proofing agent, a release agent, an antifoaming agent, a rust preventive agent, and the like. By combining these agents, a more functional surface coating can be obtained. Excellent effect as an agent.

The surface coating agent for the paper of the present invention is a surface abradable material such as a corrugated cardboard exterior liner or other paperboard, or high quality paper, medium quality paper, coated base paper, fluffing, lubricity, gloss, Vessel pick, paper. It is effective and extremely excellent not only in improving the physical properties necessary for modifying the paper surface such as powder, but also in improving the internal strength of the paper.

[0037]

The present invention will be described below in more detail with reference to examples. The present invention is not limited to these examples. In addition, in the following, what is shown by% means% by weight unless otherwise specified. Shodex ^(R) GPC SYSTE manufactured by Showa Denko KK was used to measure the weight average molecular weight.
A Sho-dexOHpak SB80M was connected to M-11, and a differential refractometer and a multi-angle light scattering detector manufactured by WYATT TECHNOLOGY were used together as a detector.

Example 1 A five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port was charged with 129 g of pure water while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 678 g of a 60% acrylamide aqueous solution, 17 g of itaconic acid, acrylonitrile 17.
4 g, 2.02 g of methylenebisacrylamide, and 57 g of sodium methallylsulfonate were mixed and dissolved. Separately, 1.3 g of potassium persulfate was dissolved in 100 g of pure water.

Next, both of the above aqueous solutions are placed in a reaction vessel,
The solution was evenly dropped over 0 minute. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C. Further, the temperatures of the monomer mixed solution and the initiator solution were kept at 20 to 25 ° C., and care was taken so that polymerization did not occur before dropping and that the monomer and the initiator did not precipitate. Presence or absence of polymerization of the monomer mixed solution before dropping was confirmed by allowing the mixed solution under the same conditions to stand for 7 hours and adding it to methanol.

After the completion of dropping, polymerization was continued at 80 ° C. for 3 hours,
By cooling and terminating the reaction, an aqueous acrylamide polymer solution having a Brookfield viscosity at 25 ° C. of 46900 cps was obtained. This product is designated as A. Product A
Was precisely weighed in an aluminum cup of known weight so that the solid content was about 0.1 g, diluted with about 1 g of pure water, and dried in a hot air dryer at 105 ° C. for 3 hours to obtain the absolute dry polymer concentration. It was 52.1%. The weight average molecular weight of the product A was 530,000 as measured by the above method.

Example 2 162 g of pure water was charged into a five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 676 g of 50% acrylamide aqueous solution, 33.8 g of itaconic acid, 0.8 g of methylenebisacrylamide, and 27.6 g of sodium methallylsulfonate were mixed and dissolved, and p was added with 20% sodium hydroxide.
H was adjusted to 6. Apart from this, potassium persulfate 0.
63 g was dissolved in 100 g of pure water.

Next, both of the above aqueous solutions were uniformly dropped into the reaction vessel over 300 minutes. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C. After the completion of the dropping, the polymerization was continued at 80 ° C. for 3 hours, and the reaction was terminated by cooling to give a Brookfield viscosity of 7060 c at 25 ° C.
An aqueous solution of ps acrylamide polymer was obtained. This product is designated as B. Various physical properties of the product B were measured in the same manner as the product A.

Example 3 A five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port was charged with 129 g of pure water, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 741 g of 50% acrylamide aqueous solution, 6.4 g of maleic acid, acrylonitrile 8.
8 g, methylenebisacrylamide 0.85 g, and sodium methallylsulfonate 13.1 g are mixed and dissolved,
The pH was adjusted to 6 with 20% sodium hydroxide. Separately, 0.53 g of potassium persulfate was dissolved in 100 g of pure water.

Next, both of the above aqueous solutions were uniformly dropped into the reaction vessel over 300 minutes. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C. After the completion of the dropping, the polymerization was continued at 80 ° C. for 3 hours, and the reaction was terminated by cooling to give a Brookfield viscosity of 12300 at 25 ° C.
An acrylamide polymer aqueous solution of cps was obtained. This product is designated as C. Various physical properties of the product C were measured in the same manner as the product A.

Example 4 A five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port was charged with 327 g of pure water, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 490 g of 50% acrylamide aqueous solution, 15.6 g of itaconic acid, acrylonitrile 2
1.3 g, methylenebisacrylamide 0.62 g, and sodium methallylsulfonate 5.55 g were mixed and dissolved, and the pH was adjusted to 6 with 20% sodium hydroxide. Separately, 3.4 g of potassium persulfate was dissolved in 100 g of pure water.

Next, both of the above aqueous solutions were uniformly dropped into the reaction vessel over 300 minutes. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C. After the completion of the dropping, the polymerization was continued at 80 ° C. for 3 hours, and the reaction was terminated by cooling to give a Brookfield viscosity of 4350c at 25 ° C.
An aqueous solution of ps acrylamide polymer was obtained. This product is D. Various physical properties of the product D were measured in the same manner as the product A.

Example 5 A five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port was charged with 377 g of pure water, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 447 g of 50% acrylamide aqueous solution, 10.8 g of itaconic acid, acrylonitrile 3
9.5 g, methylenebisacrylamide 2.55 g, and sodium methallylsulfonate 23.7 g were mixed and dissolved. Separately, 4.1 g of potassium persulfate was added to 1 part of pure water.
00g. Then, the monomer solution and the initiator solution were uniformly dropped into the reaction vessel over 300 minutes. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C.

After the dropping, the polymerization was continued at 80 ° C. for 3 hours,
By cooling and terminating the reaction, an aqueous acrylamide polymer solution having a Brookfield viscosity of 3640 cps at 25 ° C. was obtained. This product is designated as E. Product E
Was measured in the same manner as for the product A.

Example 6 Pure water (433 g) was charged into a five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 434 g of 50% acrylamide aqueous solution, 6.6 g of itaconic acid, acrylonitrile 9
g, 1.04 g of methylenebisacrylamide, 10.6 g of dimethylaminoethyl methacrylate, and 5.9 g of sodium methallylsulfonate were mixed and dissolved. Separately, 2.37 g of potassium persulfate was dissolved in 100 g of pure water. Next, each of the above two aqueous solutions is placed in a reaction vessel,
It was added dropwise over 300 minutes. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C.

After the completion of dropping, polymerization was continued at 80 ° C. for 3 hours,
By cooling and terminating the reaction, an aqueous acrylamide polymer solution having a Brookfield viscosity of 9300 cps at 25 ° C. was obtained. This product is designated as F. Product F
Was measured in the same manner as for the product A.

Comparative Example 1 136 g of pure water was charged into a five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 728 g of 50% acrylamide aqueous solution, 35.1 g of itaconic acid, and 0.83 g of methylenebisacrylamide were mixed and dissolved, and the pH was adjusted to 6 with 20% sodium hydroxide. Further, 3.1 g of potassium persulfate was dissolved in 100 g of pure water.

Next, both of the above aqueous solutions were uniformly dropped into the reaction vessel over 300 minutes. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C. However, during the dropping, the reaction product became highly viscous, lost its fluidity and gelled.
This gelled polymer did not disperse and dissolve even when diluted with water, and various physical properties could not be measured.

Comparative Example 2 123 g of pure water was charged into a five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. Meanwhile, 50% acrylamide aqueous solution 739 g, itaconic acid 14.6 g, acrylonitrile 1
4.9 g, 0.86 g of methylenebisacrylamide, and 10.2 g of allyl alcohol as a molecular weight adjusting agent were mixed, and a solution in which the pH was adjusted to 6 with 20% sodium hydroxide and 0.7 g of potassium persulfate were dissolved. Aqueous solution 1
00 g was evenly dropped into each reaction container over 300 minutes. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C.

After completion of dropping, polymerization was continued at 80 ° C. for 3 hours,
By cooling and terminating the reaction, an aqueous solution of polyacrylamide polymer having a Brookfield viscosity of 14400 cps at 25 ° C. was obtained. This product is designated as G. Various physical properties of the product G were measured in the same manner as the product A.

Comparative Example 3 451 g of pure water was charged into a five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 498 g of a 50% acrylamide aqueous solution, 16.7 g of itaconic acid, and 34.0 g of acrylonitrile were mixed, and p was added with 20% sodium hydroxide.
H adjusted to 6 and potassium persulfate 1.53g
100 g of an aqueous solution prepared by dissolving
It was added dropwise over 300 minutes. During this period, the temperature inside the reaction vessel was kept constant at 80 ° C.

After completion of dropping, polymerization was continued at 80 ° C. for 3 hours,
By cooling and terminating the reaction, an aqueous solution of polyacrylamide polymer having a Brookfield viscosity of 5870 cps at 25 ° C. was obtained. This product is designated as H. Various physical properties of the product H were measured in the same manner as the product A.

Comparative Example 4 A five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a dropping port was charged with 362 g of pure water, while blowing nitrogen gas. The internal temperature was adjusted to 80 ° C. On the other hand, 468 g of 50% acrylamide aqueous solution, 19.6 g of 80% acrylic acid, 41.5 g of acrylonitrile, and 0.67 of methylenebisacrylamide.
g and sodium methallylsulfonate 8.25 g were mixed, and 100 g of an aqueous solution in which 3.48 g of potassium persulfate was dissolved were evenly dropped into the reaction vessel over 150 minutes. During this time, the temperature in the reaction vessel is kept at 80 ° C.
Kept constant.

After completion of dropping, polymerization was continued at 80 ° C. for 3 hours,
By cooling and terminating the reaction, an aqueous polyacrylamide polymer solution having a Brookfield viscosity of 4070 cps at 25 ° C. was obtained. This product is designated as I. Various physical properties of the product I were measured in the same manner as the product A.

Comparative Example 5 Pure water 629 was placed in a four-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube.
g, 50% acrylamide aqueous solution 289 g, itaconic acid 7.8 g, and acrylonitrile 47.6 g were charged into a reaction vessel and mixed while performing nitrogen substitution, and the vessel was heated to an internal temperature of 30 ° C. 10% as a polymerization initiator
Ammonium persulfate and 10% sodium hydrogen sulfite were added, and the polymerization reaction was performed for 180 minutes, followed by cooling to terminate the reaction, thereby obtaining an aqueous acrylamide polymer solution having a Brookfield viscosity of 3220 cps at 25 ° C. This product is J. Various physical properties of the product J were measured in the same manner as the product A. Various physical properties of the products A to F obtained in Examples 1 to 6 and the products G to J obtained in Comparative Examples 2 to 5 are summarized in Table 1.

[0060]

[Table 1]

Coating Example 1 A jut liner having a basis weight of 180 g / m ² was cut into 4 lengths.
Adjust to 0 cm and 30 cm in width. This is called paper (a). Next, the product A obtained in Production Example 1 was mixed with solid content of 4% and 2%.
Each was diluted with water to obtain a diluted solution.

Next, the upper part of the paper (a) was fixed on a flat glass plate with cellophane tape, and the above diluted solution was added with NO. 4 times each using the coating roll bar of 4,
The amount of liquid absorbed was measured and found to be 10 g / m ² . That is,
In terms of solid content was coated amount of 0.2 g / m ² at 0.4g / m ^{2, 2%} dilution in 4% dilution. Immediately after the weighing, it was dried in a drum dryer adjusted to 110 ° C. for 50 seconds to obtain a paper sample.

The paper sample thus obtained was seasoned in a constant temperature and humidity chamber (temperature 20 ° C., humidity 65%) for one day and night,
The following physical properties were evaluated in the same room. Wax pick: JIS-P-8129 The evaluation results are shown in Table 2 and Table-3. , And NO. Indicates that the surface strength is high.・ Abrasion resistance: JIS-P-8136 Gakushin type dyeing fastness tester

Coating Examples 2 to 6 Products B to F obtained in Examples 2 to 6 are the same as in Coating Example 1.
The diluted solution of was used to coat the paper (a), and the physical properties were tested.

Coating Comparative Examples 1 to 4 As in Coating Example 1, products G to J obtained in Comparative Examples 2 to 5 were obtained.
The diluted solution of was used to coat the paper (a), and the physical properties were tested.

Coating Comparative Example 5 A 1-liter 4-neck separable flask equipped with a stirrer, a reflux condenser, and a thermometer and a heating device (water bath) were prepared, and 889 g of water was charged in the separable flask. To this, 111 g of commercially available oxidized starch (Ace A: Oji Corn Starch Co., Ltd.) was added, and they were sufficiently stirred and mixed. While continuing to stir this, heat it from room temperature to 90 ° C with a heating device (water bath).
Hold for 0 minutes. Cooling was started after 30 minutes and cooled to room temperature.

The concentration of this product is 10%, and this is 4
% And 2% respectively. With this diluent,
Applied to a paper (a) in the same manner as the coating Example 1, were obtained, respectively coating amount 0.4 g / m ^2, and the paper sample of 0.2 g / m ^2. These paper samples were similarly tested for physical properties.

Coating Comparative Example 6 Coating Comparative Example 4 was the same as Coating Comparative Example 4 except that modified PVA (Gothenal T-330H: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used in place of the oxidized starch of Coating Comparative Example 4. The modified PVA was cooked by performing the procedure of 1. and further diluted to 4% and 2%.

Using this diluted solution, a paper (a) was coated in the same manner as in Coating Example 1, and the coating amount was 0.4 g / m ² respectively.
And a paper sample of 0.2 g / m ² was obtained. These paper samples were similarly tested for physical properties.

Coating Comparative Example 7 In accordance with the method performed in Coating Example 1 except that pure water instead of the resin liquid was coated on the jut liner which was the paper (a).
Paper samples were obtained and tested for physical properties. This is called a blank.

Coating Example 7 Fine coated base paper (NBKP: LB) having a basis weight of 70 g / m ²
KP = 70: 30) is cut in the same manner as in the jut liner of Coating Example 1 to adjust the length to 40 cm and the width to 30 cm. This is called paper (b).

Next, using the diluent used in Coating Example 1,
The paper (b) was coated. As the coating method, the paper (b) was dipped in the diluting solution for 1 second and then squeezed with two rolls to measure the amount of resin adhered. Immediately after weighing, it was dried for 50 seconds with a drum dryer adjusted to 110 ° C. to obtain a paper sample. The coating amount at this time, if in the case of 4% dilution in terms of solid content 2g / m ^2, 2% dilution was 1 g / m ^2.

The paper sample thus obtained was seasoned in a constant temperature and constant humidity chamber (temperature 20 ° C., humidity 65%) for one day in the same manner as in Coating Example 1, and then the following physical properties were evaluated in the same chamber. .・ RI pick: RI-3 type Toyo Ink manufactured by Ming Seisakusho,
Ink tack 25, ink amount 0.4ml, rotation speed 70r
pm-Z-axis strength: Internal bond tester manufactured by Kumagai Riki Kogyo Co., Ltd.

Coating Examples 8 to 12 Products B to F obtained in Examples 2 to 6 as in Coating Example 7
The diluted liquid of (1) was used to coat paper (B), and a test on physical properties was performed.

Coating Comparative Examples 8 to 11 Products G to J obtained in Comparative Examples 2 to 5 were prepared in the same manner as in Coating Example 7.
The diluted liquid of (1) was used to coat paper (B), and a test on physical properties was performed.

Coating Comparative Example 12 The diluted solution of oxidized starch used in Coating Comparative Example 5 was used to coat paper (b) in the same manner as in Coating Example 7, and the physical properties were similarly tested. went.

Coating Comparative Example 13 Using the modified PVA diluent used in Coating Comparative Example 6,
The paper (b) was coated in the same manner as in Coating Example 7, and the tests on the physical properties were conducted in the same manner.

Coating Comparative Example 14 A paper sample was coated on a paper (b) according to the method of Coating Example 7 except that pure water was used instead of the resin liquid as in Coating Example 7. Then, the test on the physical properties was conducted.
This is called a blank.

As described above, Coating Examples 1 to 6 and Coating Comparative Example 1
Table 2 collectively shows the test results for the paper (a) conducted in Nos. 7 to 7, that is, the results in the jut liner. Similarly, the results for paper (b), that is, high quality coated base paper are shown in Table 3.

[0080]

[Table 2]

[0081]

[Table 3]

[0082]

The surface coating agent of the present invention is extremely superior in paper strength as compared with the conventional surface coating agent.
And Table 3 are clear. That is, in Table 2, the conventional polyacrylamide surface coating agents shown in Coating Comparative Examples 1 to 4, oxidized starch of Coating Comparative Example 5, and PV of Coating Comparative Example 6 were used.
A has a higher wax pick and a higher abrasion resistance than the blank of Coating Comparative Example 7, and is an excellent result as a surface strength improver. Further, in the comparison between the PAM and PVA, the result that PVA was slightly superior was obtained. On the other hand, when the surface coating agent of the present invention is applied to paper, that is, Coating Examples 1 to 6 show a surface strength improving effect superior to that of the conventional polyacrylamide surface coating agent or oxidized starch. It was
Further, the result is that the PVA, which is generally said to have an excellent effect of improving the surface strength, exhibits a considerably excellent effect.

Further, from the results in Table 3, since excellent results were obtained in Z-axis strength as well, the surface coating agent of the present invention is effective not only for modifying the surface of the paper but also for modifying the inside of the paper. is there.
From the above, it is clear that the surface coating agent of the present invention is positioned as a further improvement of the excellent agents such as polyacrylamide type and PVA type that have been conventionally used and is excellent as a paper strength improving agent. Is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuguo Matsubara 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (6)

[Claims] 1. 50 mol% or more of (meth) as a monomer
Acrylamide, a vinyl compound represented by the following general formula (1) (Chemical Formula 1) or a salt thereof 0.005 to 30 mol%, a crosslinkable vinyl compound 0.01 to 5 mol%, and an unsaturated dicarboxylic acid or a salt thereof 0 A surface coating agent comprising an acrylamide polymer aqueous solution obtained by polymerization using 1 to 20 mol%. Embedded image (In the formula, R ₁ represents a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 to 8) 2. The surface coating agent according to claim 1, wherein a monomer containing a vinyl cyanide compound in an amount of 0.1 to 49 mol% is used as a monomer in addition to the monomer according to claim 1. 3. The monomer as claimed in claim 1 or 2 is used, and the monomer further contains 0.01 to 49 mol% of another monomer copolymerizable with acrylamide.
Alternatively, the surface coating agent according to 2. 4. The polymer concentration is in the range of 22-60% and the Brookfield viscosity at 25 ° C. is 50,000 c.
ps (centipoise) or less and a weight average molecular weight of 5
The surface coating agent comprising the aqueous solution of the acrylamide polymer according to any one of claims 1 to 3, which is 0,000 to 10,000,000. 5. The surface coating agent according to claim 1, which comprises an aqueous solution of an acrylamide polymer obtained by semi-batch polymerization in which a monomer is continuously added dropwise. 6. A paper obtained by applying the surface coating agent according to any one of claims 1 to 5.