JPH10183497A - Additive for combination paper and production of combination paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an intercalation of a combination paper, capable of imparting excellent stability to a product and to produce the combination paper having sufficient adhesive strength between the layers. SOLUTION: The objective combination paper having two or more plies is produced by coating an amphoteric copolymer obtained by copolymerizing 60-95wt.% monomer mixture comprising (A) a (meth)acrylamide, (B) α,β-unsaturated carboxylic acid and/or a salt thereof, (C) a water-soluble cationic monomer and (D) a monomer having a substituting group capable of performing a chain transfer in the presence of 5-40wt.% starches, on the surface of a wet paper layer before combining paper, and combining the coated paper by papermaking to provide the combined paper having two or more layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an additive for laminated paper and a method for producing a laminated paper. The additive for laminated paper of the present invention can be used as an interlayer adhesive or a drainage improver. It is particularly useful as an interlayer adhesive.

[0002]

2. Description of the Related Art Laminated paper is produced by spraying an interlayer adhesive onto the surface of a wet paper layer before lamination. Starch is used as the interlayer adhesive at a lower cost than before. . However, since starch is used in a state of being dispersed in water at the time of use, there are operational problems such as the clogging of a spray nozzle and the addition amount fluctuating due to sedimentation of the dispersion. In addition, since starch is gelatinized and adhered in a drying process after bonding, modified starches such as oxidized starch, pregelatinized starch, and cationized starch that are easily gelatinized in the drying process are often used. Regardless, since the adhesive strength of the starch itself is weak, in order to obtain the desired interlayer adhesive strength, a large amount of starch has to be used, and therefore it cannot be sufficiently gelatinized in the drying process after lamination, It is also a problem that water that has absorbed starch during gelatinization causes a blistering phenomenon between layers. Furthermore, there are environmental problems such as the fact that the starch that has not been fixed between the layers and has escaped out of the paper causes an increase in the COD of the wastewater, and there are various problems regarding the use of starch at present.

In order to solve such a problem, there has been proposed a method using an acrylamide-based water-soluble polymer as an interlayer adhesive. In order to improve the fixation between layers with such an acrylamide-based water-soluble polymer and obtain a laminated paper having an excellent interlayer strength, the molecular weight of the acrylamide-based water-soluble polymer should be increased. Is essential. However, since the viscosity of the acrylamide-based water-soluble polymer increases as the molecular weight increases, there is a problem in workability that the spray liquid cannot be uniformly applied without being sprayed. In order to solve such a problem of workability, the present applicant has proposed an acrylamide-based interlayer adhesive using a cross-linking agent, and has solved the above-mentioned workability problem related to an increase in product viscosity due to the increase in molecular weight. doing.

[0004]

However, while acrylamide-based water-soluble polymers have excellent performance as interlayer adhesives, they are more expensive than starch and therefore have economical restrictions on their use. It is the current situation. In response to such current problems, starch and the like and acrylamide-based water-soluble polymers are blended, and copolymers of acrylamide and the like in the presence of starch and the like are also being studied.
An additive for laminated paper which can provide a laminated paper having sufficient interlayer adhesion strength has not yet been developed. Further, copolymers of acrylamide or the like in the presence of starch or the like also have a problem in terms of product stability.

Accordingly, the present invention is to provide an additive for laminated paper comprising starch and an acrylamide polymer, which can produce a laminated paper having sufficient interlayer adhesive strength. It is an object of the present invention to provide an additive for laminated paper which is also excellent in stability.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies on an additive for laminated paper comprising starch and an acrylamide polymer in order to solve the above-mentioned problems of the prior art. In an aqueous solution containing the amphoteric, an amphoteric copolymer having a branched structure obtained by copolymerizing a vinyl monomer having a specific composition shown below at a specific ratio, conforms to the above purpose, In addition, they found that the stability of the product was particularly excellent when a specific starch was used, and completed the present invention.

That is, the present invention relates to a method for preparing (A) (meth) acrylamide, (B)
α, β-unsaturated carboxylic acids and / or their salts,
Monomer mixture 60 to 9 containing (C) a water-soluble cationic monomer and (D) a monomer having a chain-transferring substituent.
After adding an interlayer adhesive to the surface of the wet paper layer before the laminating paper additive containing the amphoteric copolymer obtained by copolymerizing 5% by weight, and then laminating, In addition, the present invention relates to a method for producing a laminated paper, comprising using the additive for a laminated paper in producing a laminated paper having two or more layers.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The starches used in the present invention include raw and dextrins such as wheat, rice, corn, potato, tapioca, oxidized starch, dialdehyde starch, alkyl etherified starch, and cationized starch. ,
Various modified starches obtained by subjecting raw starch such as phosphate starch and urea phosphate starch to raw materials and subjecting them to a predetermined thermochemical treatment can be used. In the present invention, among these starches, the use of urea phosphate ester starch is preferred in view of the stability of the product comprising an amphoteric copolymer obtained by copolymerizing acrylamide or the like.

(A) (meth) acrylamide refers to acrylamide and / or methacrylamide, which can be used alone or in combination. However, from the viewpoint of economy, acrylamide is preferably used alone. Note that (meta) has the same meaning.

(B) α, β-unsaturated carboxylic acids and / or salts thereof include, for example, monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid; maleic acid, fumaric acid, itaconic acid, muconic acid, citraconic acid Dicarboxylic acids such as acids; and salts of these various organic acids such as sodium salts and potassium salts. In the present invention, among these, α, β-unsaturated dicarboxylic acids, particularly itaconic acid, are preferred in that they have excellent interlayer adhesion strength.

(C) The water-soluble cationic monomer includes:
Examples include N, N-dialkylaminoalkyl (meth) acrylamide and / or N, N-dialkylaminoalkyl (meth) acrylate. Specifically, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth)
Monomers having a tertiary amino group such as acrylamide,
Or salts of inorganic or organic acids such as hydrochloric acid, sulfuric acid, and acetic acid, and further, quaternary ammonium salts obtained by reaction with quaternizing agents such as methyl chloride, benzyl chloride, dimethyl sulfate, and epichlorohydrin. Monomers that can be used.

(D) The monomer having a chain-transferring substituent in the side chain is a monomer having a chain-transferring substituent such as a methyl group or an alkylene group which acts as a chain transfer point during polymerization.
A monomer capable of introducing many branched structures into the obtained copolymer.

Examples of such a chain transfer substituent include, for example, an allyl group, a polyalkylene glycol group or a general formula (1): -CONR ¹ R ² (wherein R ¹ represents a hydrogen atom or a methyl group; R ² is a methyl group, an isopropyl group or a general formula (2): —C (CH ₃ ) ₂ —CH ₂ —
And an N-substituted amide group represented by R ³ (R ³ represents a carboxyl group, a sulfonyl group, or an alkylester having 1 to 4 carbon atoms or an acetyl group thereof).

Specific examples of the monomer having an allyl group as a chain transfer substituent include allyl (meth) acrylate, N-allyl (meth) acrylamide, N, N-diallyl (meth) acrylamide and the like. Also,
Examples of the monomer having a polyalkylene glycol group as the chain transfer substituent include those having at least two repeating units of an oxyalkylene group. Usually, it is preferable to use one having up to about 10 oxyalkylene repeating units. As specific examples, polyethylene glycol mono (meth) acrylates such as diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, and tetraethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate similar to the above, Examples include methoxypolyethylene glycol mono (meth) acrylate, polytrimethylene glycol mono (meth) acrylate, polytetramethylene glycol mono (meth) acrylate, and polyethylene glycol propylene glycol mono (meth) acrylate. In addition, N- represented by the above general formula (1) is used as a chain transfer substituent.
Specific examples of the monomer having a substituted amide group include N, N
-Dimethylacrylamide, diacetoneacrylamide, isopropylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanecarboxylic acid, and alkyl esters having 1 to 4 carbon atoms thereof. These (D)
Among the monomers having a chain transfer substituent on the side chain, the N-substituted compound represented by the general formula (1) has good polymerizability and can introduce many branched structures into the obtained copolymer. A monomer having an amide group is preferred, and N, N-dimethylacrylamide is particularly preferred.

[0015] The amount of the starch used, the component (A),
The amounts of the components (B), (C) and (D) used are as follows:
The form of the amphoteric copolymer obtained by copolymerizing the monomers in the presence of starches has an appropriate branched structure, that is, although the molecular weight itself of the amphoteric copolymer is high,
The viscosity must be determined with due consideration so as to be low.

That is, the amount of the starch used is about 5 to 40% by weight based on the total weight of the components constituting the amphoteric copolymer of the present invention, while the copolymer is copolymerized in the presence of the starch (A ), The total weight of the monomer mixture containing the components (B), (C) and (D) is about 60 to 95% by weight. The amount of starch used is preferably as large as possible from the viewpoint of industrial utility, and the lower limit is more preferably at least 10% by weight. Further, the upper limit of the amount of the starch used is more preferably 3 from the viewpoints of interlayer adhesive strength, fixing property, stability as a product, workability, etc., of the resulting amphoteric copolymer as an interlayer adhesive.
0% by weight or less. In addition, the upper limit of the amount of starch used is 20% by weight or less, and further 15% by weight, especially considering that the stability and viscosity of the product are increased and that the workability is hindered.
It is as follows.

The amount of the component (A) is usually about 50 to 98.4 mol% based on the total mol of the monomers to be copolymerized. The lower limit is preferably 60 mol% or more, and the upper limit is preferably 95 mol% or less. If the amount is less than 50% by weight, the interlayer adhesion strength becomes insufficient, and 98.
If the content is more than 4% by weight, the ionic component tends to decrease, and the fixing tends to decrease.

The amount of component (B) used is generally about 0.5 to 20 mol%, preferably 0.5 to 15 mol%, based on the total moles of the monomers. Similarly, the amount of the component (C) to be used is generally about 1 to 20 mol%, preferably 1 to 15 mol%, based on the total mol of the monomers. The additive for laminated paper of the present invention is an amphoteric copolymer obtained by copolymerizing these ionic monomers. By using both the component (B) and the component (C), the additive of the wet paper layer is formed. The fixing property on the surface is improved. Therefore, when either the component (B) or the component (C) is not used, the fixability is insufficient, and a sufficient interlayer adhesive strength cannot be obtained. If the usage ratio is less than the above range,
The proportion of the ionic component in the resulting amphoteric copolymer is reduced, and the stability of the product is likely to be poor. If it exceeds the above range, the proportion of (meth) acrylamide is reduced and the paper strength is not sufficient.

The amount of the monomer (D) having a chain-transferring substituent is similarly about 0.1 to 10 mol%, preferably about 0.1 mol%, based on the total mol of the monomers. 1 to 5 mol%. The component (D) is used for the copolymer having acrylamide as a main component to be copolymerized in the presence of starches to have a sufficiently branched structure, and to make the resulting amphoteric copolymer high molecular weight and low viscosity. Can be The component (D) is 1
If it exceeds 0 mol%, the resulting amphoteric copolymer is insoluble in water, which is not preferable.

In the present invention, the components (A), (B),
In addition to the components (C) and (D), hydrophobic monomers such as acrylonitrile, vinyl acetate, styrene and α-olefin; sulfonic acid group-containing monomers such as vinyl sulfonic acid and styrene sulfonic acid; Di (meth) acrylates such as glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, hexamethylenebis (meth) Bis (meth) acrylamides such as acrylamide, divinyl esters such as divinyl adipate and divinyl sebacate, epoxy acrylates, urethane acrylates, N-methylol acrylamide, diallylamine, diallyldimethyl Difunctional monomers such as ammonium, diallyl phthalate, diallyl chlorendate, divinyl benzene, 1,3,5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, triallylamine, triallyl trimellitate, N, Trifunctional monomers such as N-diallylacrylamide, tetramethylolmethanetetraacrylate, tetraallyl pyromellitate, N, N, N ', N'-tetraallyl-1,4-diaminobutane, tetraallylamine salt, tetraallyloxyethane Any of the above-mentioned crosslinkable monomers can be used as needed. The use amount of these optional components is usually about 40 mol% or less based on the total moles of the monomers to be copolymerized in the presence of starches.

Various methods known in the art can be used to obtain an amphoteric copolymer by copolymerizing a monomer mixture containing the above components (A) to (D) in the presence of starches. For example,
First, starch and water are charged and gelatinized in a predetermined reaction vessel,
Next, a predetermined amount of each of the monomers was charged, potassium persulfate,
Add a persulfate such as ammonium persulfate or a usual radical polymerization initiator such as a redox polymerization initiator in which these are combined with a reducing agent such as sodium bisulfite, and then copolymerize by heating under stirring. Can be obtained.

The acrylamide-based amphoteric copolymer thus obtained is a water-soluble or water-dispersible copolymer,
(D) Since a monomer having a chain transferable substituent is used, it has a branched structure, and has a higher molecular weight than a copolymer not using the monomer. Very low viscosity. The viscosity of the amphoteric copolymer of the present invention is usually 100,000 cps in terms of a solid content of 15% by weight.
(25 ° C.) or less, preferably 20,000 cps (2
5 ° C) or less.

In the present invention, the amphoteric copolymer is used as an additive for laminated paper. Depending on the purpose, the additive for laminated paper of the present invention may be a polyamide polyamine-epichlorohydrin resin, melamine and urea. Formalin resin may be added.

The method for producing a laminated paper of the present invention can be carried out by a conventional method, and the additive for a laminated paper comprising the amphoteric copolymer is added to the surface of the wet paper layer before the lamination. After application, they are laminated, dehydrated, and dried to produce two or more layers of laminated paper.

The application of the additive for laminated paper is generally performed by spraying, and the additive for laminated paper is usually 0.1%.
At a concentration of about 1.5% by weight, 3 to 50 cps (25
° C). The additive for the laminated paper may be usually applied at a usage ratio of 0.05 to 1.5% by weight (solid content) based on the pulp solid content.

In the method for producing a laminated paper according to the present invention, when the additive for laminated paper is applied to the surface of the wet paper layer before the lamination, By applying the additive for laminated paper to the surface of the wet paper layer having the smaller amount of water, the interlayer adhesive strength and the like of the laminated paper can be further improved. That is, since the amount of moisture on the surface of the wet paper layer is different from each other, if the surface of the wet paper layer to which the additive for laminated paper is applied is selected as in the above-described coating method, during the papermaking process, the paper is moved out of the paper together with the moisture. It is possible to minimize the amount of the additive for the laminated paper flowing out, and as a result, the ratio of fixing of the additive for the laminated paper between the layers is increased, and the interlayer adhesive strength of the laminated paper is improved. Can be done.

Further, the surface of the wet paper layer before the lamination is
When applying the additive for laminated paper, the additive for laminated paper is applied to the surface of the wet paper layer on the opposite side to the dewatering direction of the paper machine among the surfaces of the wet paper layer. By doing so, the interlayer adhesive strength of the laminated paper can be further improved. That is, if the surface of the wet paper layer to be coated with the additive for the laminated paper is selected as in the above-described coating method, during the dehydration after the lamination, for the laminated paper which flows out of the paper together with the water during dehydration. Additives can be minimized, and as a result, the ratio of fixing of the additive for laminated paper between layers increases, and the interlayer adhesive strength and the like of laminated paper can be improved.

[0028]

According to the present invention, the additive for papermaking paper containing the amphoteric copolymer is a branched additive obtained by copolymerizing a monomer having a chain-transferring substituent in the presence of starch. It is a copolymer having a type structure, unlike a mere blend,
A laminated paper having both the properties of both starch and acrylamide polymer and having a branched structure based on a chain-transferring substituent can provide high interlayer adhesive strength. Moreover, the additive for laminated paper of the present invention has low viscosity and excellent workability. Further, by selecting a urea phosphate starch as a starch, a product having excellent product stability can be provided.

[0029]

The present invention will now be described more specifically with reference to examples and comparative examples. The parts and percentages in each example are based on weight. Table 1 shows the type and weight% of the starch constituting the obtained amphoteric copolymer, and the type and amount (mol%) of the monomer to be copolymerized.

(Manufacture of additive for laminated paper) Example 1 Ion exchange was carried out in a flask equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet pipe, dropping funnel for monomer and dropping funnel for catalyst. 475 parts of water and urea phosphate starch (Oji Ace P340, manufactured by Oji Cornstarch Co., Ltd.)
35 parts were added and heated to 90 ° C. with stirring. Next, 287 parts of acrylamide, 5 parts of itaconic acid, 8 parts of N, N-dimethylaminoethyl methacrylate, 0.5 part of N, N-dimethylacrylamide, and 558 parts of ion-exchanged water were charged into the dropping funnel for monomer. PH 4 using
Adjusted to ~ 5. The catalyst dropping funnel was charged with 1.4 parts of ammonium persulfate and 100 parts of ion-exchanged water as a polymerization initiator. After removing all the oxygen in the reaction system through nitrogen gas, the catalyst was continuously added dropwise over 200 minutes, while the monomer mixture was added dropwise over 120 minutes, and the polymerization was carried out under reflux to obtain a solid. An amphoteric copolymer having a concentration of 15% and a viscosity of 6900 cps (25 ° C.) was obtained.

Example 2 Into the same reactor as in Example 1, 500 parts of ion-exchanged water and 130 parts of urea phosphate starch were added, and the mixture was stirred for 9 hours.
Heated to 0 ° C. Next, 267 parts of acrylamide, 18 parts of acrylic acid, 25 parts of N, N-dimethylaminoethyl methacrylate, 1.2 parts of N, N-dimethylacrylamide and 587 parts of ion-exchanged water were charged into the dropping funnel for monomer. The catalyst dropping funnel was charged with 1.2 parts of ammonium persulfate and 100 parts of ion-exchanged water as a polymerization initiator. After removing all the oxygen in the reaction system through nitrogen gas, the catalyst was continuously added dropwise over 200 minutes, while the monomer mixture was added dropwise over 120 minutes, and the polymerization was carried out under reflux to obtain a solid. Mineral concentration 15%, viscosity 58
An amphoteric copolymer of 00 cps (25 ° C.) was obtained.

Example 3 Into the same reactor as in Example 1, 510 parts of ion-exchanged water and 80 parts of urea phosphate ester starch were added, and the mixture was stirred for 90 hours.
Heated to ° C. Next, 276 parts of acrylamide, 7 parts of itaconic acid, 10 parts of N, N-dimethylaminopropyl methacrylamide, 2.7 parts of N, N-dimethylacrylamide and 600 parts of ion-exchanged water were charged into the dropping funnel for monomer. Thereafter, the pH was adjusted to 4 to 5 using sulfuric acid.
The catalyst dropping funnel was charged with 1.4 parts of ammonium persulfate and 100 parts of ion-exchanged water as a polymerization initiator. After removing all the oxygen in the reaction system through nitrogen gas, the catalyst was continuously added dropwise over 200 minutes, while the monomer mixture was added dropwise over 120 minutes, and the polymerization was carried out under reflux to obtain a solid. Concentration 15%, viscosity 4100cps
(25 ° C.) was obtained.

EXAMPLE 4 680 parts of ion-exchanged water were added to the same reactor as in Example 1.
Urea phosphate starch 50 parts, acrylamide 200
Parts, 13 parts of itaconic acid, 30 parts of N, N-dimethylaminoethyl methacrylate, and 1.6 parts of N, N-dimethylacrylamide, and the pH was adjusted to 2-3 with sulfuric acid. Under stirring, the temperature was raised to 60 ° C., 0.9 parts of ammonium persulfate and 0.3 parts of sodium bisulfite were added as polymerization initiators, and polymerization was carried out under reflux for 120 minutes. Concentration 15%, viscosity 95
An amphoteric copolymer of 00 cps (25 ° C.) was obtained.

Example 5 The same reactor as in Example 1 was charged with 650 parts of ion-exchanged water,
Urea phosphate starch 102 parts, acrylamide 190
Parts, 13 parts of itaconic acid, 25 parts of N, N-dimethylaminopropyl methacrylamide, and 1.0 part of N, N-dimethylacrylamide, and then adjust the pH to 2 using sulfuric acid.
Adjusted to 3. Under stirring, the temperature was raised to 60 ° C., and 1.1 parts of ammonium persulfate and 0.3 part of sodium bisulfite were added as polymerization initiators, and polymerization was carried out for 120 minutes under reflux. An amphoteric copolymer having a concentration of 15% and a viscosity of 12,800 cps (25 ° C.) was obtained.

Example 6 In Example 5, the amount of urea phosphate starch was changed to 4
The same operation as in Example 5 was performed except that the amount was changed to 0 parts, to obtain an amphoteric copolymer having a solid content concentration of 15% and a viscosity of 7,700 cps (25 ° C.).

Example 7 In Example 5, the amount of urea phosphate starch used was changed to 1
The same operation as in Example 5 was performed except that the amount was changed to 6 parts, to obtain an amphoteric copolymer having a solid content of 15% and a viscosity of 3600 cps (25 ° C.).

Example 8 The same reactor as in Example 1 was charged with 617 parts of ion-exchanged water,
55 parts urea phosphate starch, 160 acrylamide
Parts, 19 parts of acrylic acid, 33 parts of N, N-dimethylaminoethyl methacrylate, 1.8 parts of N, N-dimethylacrylamide, and 42 parts of acrylonitrile, and the pH was adjusted to 2-3 with sulfuric acid. The temperature was raised to 60 ° C. with stirring, and ammonium persulfate 1.1 as a polymerization initiator was used.
And 0.3 parts of sodium hydrogen sulfite were added, polymerization was carried out for 120 minutes under reflux, and then ion-exchanged water was added to obtain an amphoteric copolymer having a solid content of 15% and a viscosity of 2500 cps (25 ° C.). .

Example 9 The same reactor as in Example 1 was charged with 500 parts of ion-exchanged water.
55.16 parts of a commercially available urea phosphate starch were added, and the mixture was stirred and heated to 90 ° C. under a nitrogen gas atmosphere. Next, 160 parts of acrylamide, 11.07 parts of methacrylic acid, 28.3 parts of N, N-dimethylaminoethyl methacrylate, 1.27 parts of N, N-dimethylacrylamide and 164. Two parts were charged, and the pH was adjusted to 4 to 5 using sulfuric acid. The catalyst dropping funnel was charged with 1.1 parts of ammonium persulfate and 100 parts of ion-exchanged water as a polymerization initiator. After removing all the oxygen in the reaction system through nitrogen gas, the catalyst was continuously added dropwise over 200 minutes, while the monomer mixture was added dropwise over 120 minutes, and the polymerization was carried out under reflux. After completion of the polymerization, a predetermined amount of ion-exchanged water was added to obtain an amphoteric copolymer having a solid content of 15% and a viscosity of 5700 cps (25 ° C.).

Example 10 An amphoteric type having a solid content of 15% and a viscosity of 4300 cps (25 ° C.) was carried out in the same manner as in Example 1, except that oxidized starch was used instead of urea phosphate starch. A copolymer was obtained.

Example 11 In Example 1, instead of urea phosphate starch,
The same operation as in Example 1 was performed except that unmodified corn starch was used, and the solid content was 15% and the viscosity was 12800 cp.
s (25 ° C.) was obtained.

Comparative Example 1 The procedure of Example 1 was repeated, except that oxidized starch was used instead of urea phosphate starch, and N, N-dimethylacrylamide was not used. % And a viscosity of 4300 cps (25 ° C.) were obtained.

Comparative Example 2 The same operation as in Example 1 was carried out except that oxidized starch was used instead of urea phosphate ester starch and N, N-dimethylaminoethyl methacrylate was not used. Concentration 15%, viscosity 5000 cps (25
° C).

Comparative Example 3 The same operation as in Example 1 was carried out except that oxidized starch was used instead of urea phosphate ester starch and that itaconic acid was not used. The solid content was 15% and the viscosity was 5%.
An amphoteric copolymer of 800 cps (25 ° C.) was obtained.

Comparative Example 4 The same operation as in Example 1 was carried out except that 245 parts of oxidized starch was used instead of urea phosphate starch, and the solid content was 15% and the viscosity was 17000 cps (2
(5 ° C.).

Comparative Example 5 In the same reactor as in Example 1, 800 parts of ion-exchanged water,
Acrylamide 190 parts, itaconic acid 13 parts, N, N-
After 25 parts of dimethylaminopropyl methacrylamide and 1.0 part of dimethylacrylamide were charged, the pH was adjusted to 2-3 using sulfuric acid. The temperature was raised to 60 ° C. with stirring, 1.1 parts of ammonium persulfate and 0.3 part of sodium hydrogen sulfite were added as polymerization initiators, and 12 parts of the mixture were refluxed.
Polymerization was performed for 0 minutes to obtain a copolymer. Separately, 45 parts of urea phosphate starch were added to 750 parts of ion-exchanged water,
A starch paste solution prepared by stirring and gelatinizing at 0 ° C. for 1 hour was mixed with the copolymer, and the solid content concentration was 15% and the viscosity was 2800 c.
A mixture of an amphoteric acrylamide polymer of ps (25 ° C.) and a urea phosphate starch paste solution was obtained.

(Product Stability) The additive for laminated paper obtained in each of the Examples and Comparative Examples was treated at 60 ° C. under the conditions of 5 ° C. and 40 ° C.
The state when left for a day was visually observed. Table 2 shows the results. In Table 2, thickening refers to an increase in viscosity of 20% or more, syneresis refers to the appearance of an aqueous layer in the upper part of the product, and separation refers to a starch paste liquid layer and amphoteric acrylamide-based resin. It means that the molecular layers are separated.

(Manufacture of laminated paper) Used cardboard paper was beaten with a Niagara beater, and 2% of a sulfuric acid band was added to pulp adjusted to 420 ml of Canadian Standard Freeness (CSF). A commercially available anionic acrylamide-based paper strength agent was added to pulp at 0.9%, and the mixture was stirred and uniformly mixed. The obtained pulp slurry was diluted to 0.5%, and the water content was adjusted to 80% with a hand paper tester.
% Wet paper was prepared. A solution obtained by diluting the additive for laminated paper obtained in Examples and Comparative Examples to 0.7% with ion-exchanged water on one side of the wet paper at a ratio of 0.7% with respect to the pulp solid content. After spray application, the paper strength agent application surface and another wet paper were overlapped and dried to obtain a laminated paper.

(Measurement of Interlaminar Adhesive Strength) The obtained laminated paper was conditioned for 24 hours, and then subjected to J-TAPPI paper pulp test method no. The interlayer adhesive strength (T-peel strength (g / in)) was measured according to 19-77. Table 2 shows the results.

[0049]

[Table 1]

In Table 1, urea is urea phosphate ester starch, oxidized is oxidized starch, corn is unmodified corn starch, AM is acrylamide, IA is itaconic acid,
AA is acrylic acid, MAA is methacrylic acid, DM is N, N-dimethylaminoethyl methacrylate, AP
DM is N, N-dimethylaminopropyl methacrylamide, DMAA is N, N-dimethylacrylamide,
AN represents acrylonitrile. The numerical values in Table 1 are rounded off.

[0051]

[Table 2]

Claims (6)

[Claims] 1. In the presence of 5 to 40% by weight of starches,
(A) (meth) acrylamide, (B) α, β-unsaturated carboxylic acid and / or a salt thereof, (C) a water-soluble cationic monomer, and (D) a monomer having a chain-transferring substituent. An additive for a laminated paper containing an amphoteric copolymer obtained by copolymerizing 60 to 95% by weight of a monomer mixture containing a polymer. 2. The additive for laminated paper according to claim 1, wherein the starch is a urea phosphate starch. 3. The additive for laminated paper according to claim 1, wherein (D) the monomer having a chain-transferring substituent is N, N-dimethylacrylamide. 4. The method according to claim 1, wherein the total molar amount of the monomers to be copolymerized is
3. The method according to claim 1, wherein (A) 50 to 98.4 mol%, (B) 0.5 to 30 mol%, (C) 1 to 20 mol% and (D) 0.1 to 10 mol%. 3. The additive for laminated paper according to 3. 5. The method according to claim 1, wherein the total molar amount of the monomers to be copolymerized is
The additive for laminated paper according to claim 4, wherein a monomer copolymerizable with the components (A) to (D) is used in a proportion of 40 mol% or less. 6. An interlayer adhesive, which is applied to the surface of the wet paper layer prior to laminating and then laminated to produce two or more layers of laminated paper. A method for producing a laminated paper, comprising using the additive for a laminated paper according to any one of 1 to 5.