JPH07189194A - Production of combination paper - Google Patents

Abstract

PURPOSE:To form combination paper having high interlaminar adhesive strength. CONSTITUTION:50-99.9mol%, preferably 60-99.5 mol% of 4 (meth)acryl amide is polymerized with <=10mol%, preferably 0.01-5mol% of a cross-linked monomer such as ethylene glycol di(meth)acrylate and <=40mol%, preferably <=35mol% of a hydrophobic monomer such as acrylonitrile or styrene to afford an anionic or amphoteric (meth)acrylamide-based water-soluble or water-dispersible polymer and then, a water-soluble polyvalent metal salt such as aluminum sulfate is mixed with the polymer in a weight ratio of (20:1) to (1:10), preferably (10:1) to (1:5) to prepare an interlaminar adhesive. The interlaminar adhesive is applied to the surface of a hygroscopic paper layer having smaller water content or the surface of a hygroscopic paper layer on the side opposite to a dehydrating direction in a paper making machine among the surfaces of the hygroscopic paper layers before combining these layers, and plural hygroscopic paper layers are combined to form the objective combination 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 a method for producing laminated paper. Specifically, as an interlayer adhesive, an anionic (meth) acrylamide water-soluble or water-dispersible polymer or an amphoteric (meth) acrylamide water-soluble or water-dispersible polymer (hereinafter, these ionic (meth)
Manufacture of laminated paper with excellent interlaminar bond strength, which is made by mixing acrylamide water-soluble or water-dispersible polymer, also called acrylamide water-soluble polymer) and water-soluble polyvalent metal salt Regarding the method.

[0002]

2. Description of the Related Art Conventionally, in the production of laminated paper, in order to improve the interlaminar adhesive strength, an interlayer adhesive is applied by spraying on the surface of the wet paper layer before laminating. As the interlayer adhesive, an ungelatinized starch dispersion liquid is mainly used. However, the adhesive strength of starch is weak, and a large amount of starch must be used in order to obtain sufficient interlayer adhesive strength. In addition to problems such as insufficient gelatinization in the drying step after combining paper, and water swelling starch during gelatinization causing blistering between layers, addition due to clogging of the spray nozzle or sedimentation of the dispersion liquid There are also operational problems such as fluctuations in the amount, and further environmental problems such as the starch that has not been fixed between the layers and has escaped to the outside of the paper, causing an increase in the COD of the wastewater.

Further, there has been proposed a method for solving the above-mentioned problems in work by using an acrylamide water-soluble polymer as an interlayer adhesive. In order to obtain a laminated paper excellent in interlaminar strength using such an acrylamide-based water-soluble polymer, it is necessary to improve the fixing property between the layers by making the acrylamide-based water-soluble polymer into a high molecular weight. However, there is a problem that the spray liquid does not become a mist and cannot be applied uniformly because the viscosity also increases as the molecular weight increases. On the other hand, there are problems such as that the concentration of the spray liquid must be reduced in order to apply it uniformly, and there is still no acrylamide-based water-soluble polymer that can produce laminated paper with excellent interlaminar strength with good workability. Has not been done.

[0004]

DISCLOSURE OF THE INVENTION The present invention uses an acrylamide-based water-soluble polymer as an interlayer adhesive, which has a good fixing property between layers and is suitable for spray coating. An object of the present invention is to provide a method for producing a laminated paper having excellent adhesive strength with good workability.

[0005]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems of the prior art, and as a result, as an interlayer adhesive, an acrylamide water-soluble polymer and a water-soluble polyvalent metal salt are used. When used as a mixture, agglomerates of acrylamide water-soluble polymer and water-soluble polyvalent metal salt are formed, which improves the fixability to pulp and enables interlayer adhesion with a low addition amount. The inventors have found that a laminated paper having excellent strength can be produced with good workability, and completed the present invention.

That is, according to the present invention, an interlayer adhesive is applied to the production of a laminated paper having two or more layers by applying the interlayer adhesive on the surface of the wet paper layer before the papermaking and then laminating the paper. As an anionic (meth) acrylamide water-soluble or water-dispersible polymer or an amphoteric (meth) acrylamide water-soluble or water-dispersible polymer mixed with a water-soluble polyvalent metal salt The present invention relates to a method for producing a laminated paper.

The anionic acrylamide water-soluble polymer used in the present invention is obtained by copolymerizing (meth) acrylamide and anionic monomer, and the amphoteric (meth) acrylamide water-soluble polymer is used. , (Meth) acrylamide, an anionic monomer and a cationic monomer. It is essential that the acrylamide-based water-soluble polymer of the present invention has an anionic group in order to form an aggregate with a water-soluble polyvalent metal salt described later.

In the present invention, (meth) acrylamide means acrylamide or methacrylamide,
These can be used alone or in combination, but from the economical viewpoint, it is preferable to use acrylamide alone.

Examples of the anionic monomer include monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, muconic acid and citraconic acid; vinylsulfonic acid and styrenesulfonic acid. , An organic sulfonic acid such as 2-acrylamido-2-methylpropanesulfonic acid; or a sodium salt or potassium salt of these various organic acids.

The cationic monomer has a tertiary amino group such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide. Reaction of vinyl monomers or salts thereof with inorganic or organic acids such as hydrochloric acid, sulfuric acid, acetic acid, or the tertiary amino group-containing vinyl monomers with quaternizing agents such as methyl chloride, benzyl chloride, dimethylsulfate and epichlorohydrin Vinyl monomers containing a quaternary ammonium salt obtained by the above.

The amount of the above-mentioned (meth) acrylamide and the ionic monomer used is such that the acrylamide water-soluble polymer obtained by copolymerizing these forms an aggregate by the action of the water-soluble polyvalent metal salt, When it is used as an adhesive, it must be determined with due consideration so that the fixing ratio between layers is good, sprayability is excellent, and stable operation is possible.

That is, the amount of (meth) acrylamide used is usually 50 to 99.9 with respect to the total molar sum of the monomers.
It is about mol%, preferably 60 to 99.5 mol%.

When an anionic acrylamide water-soluble polymer is obtained, the amount of the anionic monomer is usually about 0.1 to 30 mol%, preferably 0.2 to 15 mol% based on the total molar amount of the monomers. In the case of using an amphoteric acrylamide-based water-soluble polymer, the cationic monomer is used in an amount of usually 0.1 to 20 mol%, preferably 0.2 to 15 mol%, based on the total molar amount of the monomers. The anionic monomer is usually added in an amount of 0.1 to 2 based on the total molar amount of the monomers.
The amount used is about 0 mol%, preferably 0.2 to 15 mol%. When the proportion of these ionic monomers is less than the above range, the proportion of ionic components is small and the fixability on the surface of the wet paper layer becomes poor. When it exceeds the above range, the proportion of (meth) acrylamide is The paper strength decreases and the paper strength deteriorates. In either case, a laminated paper having sufficient interlayer strength cannot be obtained. In particular, when the ratio of the anionic monomer is less than the above range, interaction with the water-soluble polyvalent metal salt is small, aggregates cannot be formed, and desired interlayer strength cannot be obtained.

In the present invention, a crosslinkable monomer may be used in addition to the above monomers. When a crosslinkable monomer is used, a low-viscosity and high-molecular weight acrylamide water-soluble polymer can be obtained, and the fixing rate between layers can be further improved.

Examples of the crosslinkable monomer include di (meth) acrylates such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate and triethylene glycol di (meth) acrylate, methylenebis (meth) acrylamide, ethylene. Bis (meth) acrylamides such as bis (meth) acrylamide and hexamethylenebis (meth) acrylamide, divinyl adipates such as divinyl adipate and divinyl sebacate, epoxy acrylates, urethane acrylates, N-methylol acrylamide, diallyl amine, Difunctional monomers such as diallyldimethylammonium, diallyl phthalate, diallyl chlorendate and divinylbenzene, 1,3,5-triacryloylhexahydro-S- Trifunctional monomers such as lyazine, triallyl isocyanurate, triallyl amine, triallyl trimellitate, N, N-diallyl acrylamide, tetramethylol methane tetraacrylate, tetraallyl pyromellitate, N, N, N ′, N ′ -Tetraallyl-1,4-diaminobutane, tetraallylamine salt, and tetrafunctional monomers such as tetraallyloxyethane.

As the crosslinkable monomer of the present invention, a vinyl monomer having a chain transfer substituent can also be used. As the vinyl monomer having a chain transfer substituent, any vinyl monomer having a chain transfer functional group can be used without particular limitation. For example, a vinyl monomer having an allyl group, a polyalkylene glycol group, an N-substituted amide group, and itacone. Examples thereof include acid diesters. As the vinyl monomer having an allyl group, allyl (meth) acrylate, N-allyl (meth) acrylamide, N, N-
Examples thereof include diallyl (meth) acrylamide and allylamine. Further, the polyalkylene glycol group may be one having at least two repeating units of an oxyalkylene group, and usually up to about 10 repeating units can be used. Specific examples thereof include polyethylene glycol mono (meth) acrylates such as diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, tetraethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylates similar to the above, Methoxy polyethylene glycol mono (meth) acrylate, polytrimethylene glycol mono (meth) acrylate, polytetramethylene glycol mono (meth) acrylate, polyethylene glycol propylene glycol mono (meth) acrylate and the like can be mentioned. Also, N
-As the vinyl monomer having a substituted amide group or the like, dimethyl acrylamide, diacetone acrylamide,
Isopropyl acrylamide, 2-acrylamide-2
-Methylpropanesulfonic acid, 2-acrylamido-2
-Methylpropanecarboxylic acid and their carbon numbers 1 to
4 alkyl ester and the like. Examples of the itaconic acid diester include itaconic acid dialkyl esters having 1 to 4 carbon atoms. In the present invention, any of the above-mentioned crosslinkable monomers can be used, but it is preferable to use a vinyl monomer having a chain transfer substituent. Moreover, 1 type may be used for a crosslinkable monomer and 2 or more types may be used for it.

The amount of the crosslinkable monomer used is usually about 10 mol% or less, preferably 0.01 to 5 mol%, based on the total molar amount of the monomers. If it exceeds 10 mol%, the copolymer obtained is insoluble in water, which is not preferable.

Further, in the present invention, in addition to the above-mentioned monomers, acrylonitrile, vinyl acetate, styrene,
Hydrophobic monomers such as α-olefins can also be used to further improve fixability. The amount of the hydrophobic monomer used is usually about 40 mol% or less, preferably 35 mol% or less, based on the total molar amount of the monomers. Four
If it exceeds 0 mol%, the copolymer becomes water-insoluble, which is not preferable.

As a method of copolymerizing the above-mentioned monomers to obtain a water-soluble acrylamide polymer, various conventionally known methods can be adopted. For example, by charging each of the monomers and water into a predetermined reaction vessel, a persulfate such as potassium persulfate or ammonium persulfate, or a redox-based polymerization initiator in the form of a combination of these with a reducing agent such as sodium bisulfite. An acrylamide water-soluble polymer can be obtained by adding an ordinary radical polymerization initiator and heating with stirring.

The weight average molecular weight of the acrylamide water-soluble polymer thus obtained is usually about 100,000 to 10,000,000, and the viscosity is usually 2 in terms of a solid content concentration of 7% by weight.
About 00000 cps (25 ° C) or less, preferably 10
The properties are about 0000 cps (25 ° C.) or less. Among such acrylamide-based water-soluble polymers, those using a crosslinkable monomer have a high molecular weight and a relatively low viscosity as compared with the conventionally used linear acrylamide-based water-soluble polymers. In this case, the weight average molecular weight is usually about 1,500,000 to 10,000,000, and the viscosity is usually 10,000 c when converted into a solid content concentration of 15% by weight.
ps (25 ° C) or less, preferably 5000 cps
(25 ° C) or less.

In the present invention, the acrylamide water-soluble polymer and the water-soluble polyvalent metal salt are mixed and used as an interlayer adhesive.

Examples of the water-soluble polyvalent metal salt include aluminum salts such as aluminum sulfate, aluminum nitrate, aluminum chloride and polyaluminum chloride, and various metal salts such as calcium chloride, magnesium chloride, magnesium sulfate and barium chloride. Of these, aluminum salts generally used in the papermaking process are preferred.

The mixing ratio of the acrylamide water-soluble polymer and the water-soluble polyvalent metal salt varies depending on the kind of the acrylamide water-soluble polymer, the kind of the water-soluble polyvalent metal salt, the concentration of the spray solution, etc. Acrylamide water-soluble polymer: Water-soluble polyvalent metal salt (weight ratio) is 20: 1 to 1:
The range is 10, preferably 10: 1 to 1: 5. As the solution obtained by mixing the acrylamide water-soluble polymer and the water-soluble polyvalent metal salt, it is possible to use a solution that is cloudy to the extent that precipitation does not occur in a short time. In the present invention, particularly excellent interlayer adhesive strength is observed when the solution is used as an interlayer adhesive in such a cloudy state.

In the present invention, an interlayer adhesive formed by mixing the acrylamide water-soluble polymer and the water-soluble polyvalent metal salt is applied to the surface of the wet paper layer before the papermaking, and then the paper is produced by a conventional method. The sheets are combined, dehydrated and dried to produce a laminated paper having two or more layers. In the coating, as the interlayer adhesive, a mixture of a water-soluble polyvalent metal salt and a diluted solution of the acrylamide-based water-soluble polymer may be used, and the diluted solution of the acrylamide-based water-soluble polymer and the water-soluble adhesive may be used. An aqueous solution of a polyvalent metal salt may be separately applied to the paper making surface and mixed on a wet paper.

The interlayer adhesive is generally applied by spraying, and the interlayer adhesive is usually used at a concentration of about 0.1 to 5.0% by weight and a viscosity of about 3 to 50 cps (25 ° C.). . Further, the interlayer adhesive may be usually applied at a use ratio such that the acrylamide water-soluble polymer is 0.05 to 3.0% by weight (solid content) with respect to the pulp solid content.

The interlayer adhesive composed of the above-mentioned acrylamide water-soluble polymer is starch, which has been conventionally used as an interlayer adhesive, to the extent that the object of the present invention is not impaired.
It can also be used in combination with a powdered product of a natural resin such as modified starch, casein or galactomannan.

In the method for producing a laminated paper of the present invention, when the interlayer adhesive is applied to the surface of the wet paper layer before the combination, the moisture content of the surface of the wet paper layer is adjusted. By applying the interlayer adhesive to the surface of the less wet paper layer, the interlayer adhesive strength of the laminated paper can be further improved. That is, since the amount of water on the surface of the wet paper layer is different, if the surface of the wet paper layer on which the interlayer adhesive is applied is selected as in the above coating method, the interlayer adhesion that flows out of the paper together with the water during the papermaking process The agent can be minimized, and as a result, the rate of fixing the interlayer adhesive between the layers is increased, and the interlayer adhesive strength of the laminated paper can be improved.

Further, on the surface of the wet paper layer before combining,
When the interlayer adhesive is applied, the surface of the wet paper layer, of the surface of the wet paper layer on the side opposite to the dehydration direction of the paper machine, can be further coated by applying the interlayer adhesive. It is also possible to improve the interlayer adhesive strength of the laminated paper.
That is, if the surface of the wet paper layer to which the interlayer adhesive is applied is selected as in the above coating method, the interlayer adhesive that flows out together with water to the outside of the paper during dehydration after assembling is minimized. As a result, the rate of fixing the interlayer adhesive between the layers is increased, and the interlayer adhesive strength of the laminated paper can be improved.

[0029]

Industrial Applicability According to the present invention, it is possible to provide a laminated paper having a high interlayer adhesive strength. Further, in the present invention, since the interlayer adhesive in which the water-soluble polyvalent metal salt is mixed in advance forms an aggregate in a solution state, it has a low viscosity and is excellent in workability.

[0030]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples. All parts and% are based on weight.

Production Example 1 A flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube was charged with 154 parts of acrylamide, 8 parts of 80% acrylic acid aqueous solution, 7 parts of dimethylaminoethyl methacrylate and 770 parts of ion-exchanged water. Was charged, the pH was adjusted to 4 to 5 with sulfuric acid, and then oxygen in the reaction system was removed through nitrogen gas. The mixture was heated to 40 ° C. with stirring, 0.25 parts of ammonium persulfate and 0.08 part of sodium hydrogen sulfite were added as a polymerization initiator, and the mixture was refluxed at 120 ° C.
After polymerizing for a minute, add ion-exchanged water to obtain a solid content of 7
%, Viscosity 7500 cps (25 ° C.), average molecular weight 140
An amphoteric amphoteric acrylamide water-soluble polymer was obtained.

Production Example 2 11 parts of methacrylic acid and 4 parts were placed in the same reactor as in Example 1.
16 parts of 8% sodium hydroxide aqueous solution and 500 parts of ion-exchanged water were charged, and the mixture was kept at 70 ° C. for 30 minutes. 60 ° C
After cooling to 200, acrylamide 200 parts, ion-exchanged water 68
Add 0 parts, 5 parts of isopropyl alcohol, 6 parts of 60-degree sulfuric acid, add 0.6 parts of potassium persulfate, polymerize under reflux for 150 minutes, and then add ion-exchanged water to obtain solid content concentration of 7% and viscosity. An anionic acrylamide water-soluble polymer having an average molecular weight of 1,000,000 was obtained at 5000 cps (25 ° C.).

Production Example 3 475 parts of ion-exchanged water was placed in a flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen gas inlet tube, a dropping funnel for monomer and a dropping funnel for catalyst, and the mixture was heated to 90 ° C. under stirring. Heated. Next, 287 parts of acrylamide, 5 parts of itaconic acid, 6 parts of dimethylaminoethyl methacrylate, and 0.
05 parts and 558 parts of ion-exchanged water were charged, and the pH was adjusted to 4 to 5 with sulfuric acid. The dropping funnel for catalyst was charged with 1.4 parts of ammonium persulfate and 100 parts of ion-exchanged water as a polymerization initiator. After removing oxygen in all the reaction system through nitrogen gas, the catalyst was continuously added dropwise for 200 minutes, while the monomer was added dropwise for 120 minutes to carry out polymerization under reflux and then ion-exchanged water. Was added, and the solid content concentration was 15%, and the viscosity was 2800 cps (25
And an amphoteric acrylamide-based water-soluble polymer having an average molecular weight of 3.1 million was obtained.

Production Example 4 499 parts of ion-exchanged water was placed in the same reactor as in Example 3 and heated to 90 ° C. with stirring. Next, 267 parts of acrylamide and 26 parts of itaconic acid were added to the dropping funnel for monomer.
Parts, 1.2 parts of dimethylacrylamide and 587 parts of ion-exchanged water were charged. Also, the dropping funnel for catalyst,
1.2 parts of ammonium persulfate and 100 parts of ion-exchanged water were charged as a polymerization initiator. After removing all oxygen in the reaction system through nitrogen gas, the catalyst was continuously heated to 200
The monomer was added dropwise over 120 minutes, while the monomer was added over 120 minutes and polymerized under reflux, and then ion-exchanged water was added to the mixture to give a solid content concentration of 15% and a viscosity of 2100 cps (25
C.), an anionic acrylamide water-soluble polymer having an average molecular weight of 2.8 million was obtained.

Production Example 5 90 parts of ion-exchanged water was placed in the same reactor as in Example 3 and heated to 90 ° C. with stirring. Next, 92 parts of acrylamide, 7 parts of itaconic acid, 25 parts of acrylonitrile, 6 parts of 48% sodium hydroxide aqueous solution, and 250 parts of ion-exchanged water were charged into the dropping funnel for monomers. Further, 0.45 part of ammonium persulfate and 60 parts of ion-exchanged water were charged as a polymerization initiator into the dropping funnel for catalyst.
After removing oxygen in all reaction systems through nitrogen gas,
The catalyst was continuously added dropwise over 140 minutes, while the monomer was added dropwise over 120 minutes, polymerization was carried out under reflux, ion-exchanged water was added, and the solid content concentration was 7% and the viscosity was 450.
An anionic acrylamide water-soluble polymer having a cps (25 ° C.) and an average molecular weight of 600,000 was obtained.

Production Example 6 474 parts of ion-exchanged water was placed in the same reactor as in Example 3 and heated to 90 ° C. with stirring. Next, 199 parts of acrylamide and 5 parts of itaconic acid were added to the dropping funnel for monomer.
Parts, 12 parts of dimethylaminopropyl methacrylamide,
66 parts of acrylonitrile, dimethyl acrylamide 2.
After charging 1 part and 558 parts of ion-exchanged water, the pH was adjusted to 4 to 5 with sulfuric acid. The catalyst dropping funnel was charged with 1.7 parts of ammonium persulfate as a polymerization initiator and 100 parts of ion-exchanged water. After removing oxygen in all the reaction system through nitrogen gas, the catalyst was continuously added dropwise for 200 minutes, while the monomer was added dropwise for 120 minutes to carry out polymerization under reflux and then ion-exchanged water. Was added, the solid content concentration was 15%, and the viscosity was 1500 cps (2
An amphoteric acrylamide-based water-soluble polymer having an average molecular weight of 2.4 million was obtained.

Examples 1 to 6 Cardboard waste paper was beaten with a Niagara type beater to obtain Canadian Standard Freeness (CSF).
After adding 2% of a sulfuric acid band to the pulp adjusted to 420 ml, 0.9% of a commercially available anionic acrylamide type paper strengthening agent was added to the pulp, and the mixture was stirred and uniformly mixed. The obtained pulp slurry (pH 5.1) was diluted to 0.5%, and a wet paper A having a water content of 86% and a wet paper B having a water content of 96% (dry basis weight 100 g / m ² ) were diluted by a handmade paper testing machine. Was prepared. On one surface of the wet paper web B, various acrylamide-based water-soluble polymers obtained in Production Examples 1 to 6 shown in Table 1 were mixed with ion-exchanged water.
A solution prepared by diluting to 7% and further mixing aluminum sulphate with the same weight as the solid content of the acrylamide water-soluble polymer,
After spray coating at a ratio that the solid content of the solution is 1.4% with respect to the solid content of the pulp, the wet paper A and wet paper B application surfaces are overlapped and suction dehydration is performed at 150 mmHg for 1 minute in the direction of the wet paper B. Then, it was dried to obtain a laminated paper.

Example 7 In Example 2, except that the acrylamide water-soluble polymer obtained in Production Example 2 was applied to one side of wet paper A and suction dehydration was performed from the direction of wet paper A. The same procedure as in 2 was performed to obtain a laminated paper.

Example 8 A laminated paper was obtained in the same manner as in Example 2 except that the suction dehydration was performed from the direction of the wet paper A.

Example 9 A laminated paper is obtained in the same manner as in Example 2 except that the acrylamide water-soluble polymer obtained in Production Example 2 is applied to one side of wet paper A. It was

Example 10 A laminated paper was obtained in the same manner as in Example 1 except that magnesium sulfate was used instead of aluminum sulfate mixed in the spray liquid.

Example 11 A laminated paper was obtained in the same manner as in Example 1 except that the aluminum sulfate mixed in the spray liquid was replaced with calcium chloride.

Example 12 In Example 2, the acrylamide-based water-soluble polymer obtained in Production Example 2 was applied to one side of wet paper A with ion-exchanged water.
The liquid diluted to 7% was spray-applied at a ratio such that the solid content of the acrylamide-based water-soluble polymer was 0.7% based on the pulp solid content, and aluminum sulfate was ion-exchanged on one side of the wet paper B. Paper was laminated in the same manner as in Example 1 except that the liquid diluted to 0.7% with water was spray-applied at a ratio such that the solid content of aluminum sulfate was 0.7% with respect to the solid content of pulp. Got

Comparative Examples 1 and 2 In the same manner as in Example 1 or 2, except that aluminum sulfate was not added to the aqueous solution of the acrylamide water-soluble polymer obtained in Production Example 1 or 2, in Example 1 or 2. Then, a laminated paper was obtained.

Examples 13 to 18 BKP was beaten with a Niagara type beater to obtain Canadian Standard Freeness (CSF) 550.
To the pulp adjusted to ml, add the sulfuric acid band to the pulp 0.5
% And calcium carbonate 10% to pulp,
A commercially available amphoteric acrylamide-based paper-strengthening agent was added to pulp.
9% was added and stirred to mix uniformly. The obtained pulp slurry (pH 7.8) was diluted to 0.5%, and a wet paper A having a water content of 86% and a wet paper B having a water content of 96% (dry basis weight 100 g / m ² ) were measured by a handmade paper testing machine. Was prepared. On one surface of the wet paper web B, various acrylamide water-soluble polymers obtained in Production Examples 1 to 6 shown in Table 1 were diluted to 0.7% with ion-exchanged water,
Further, a solution prepared by mixing aluminum sulphate with the same weight as the solid content of the acrylamide water-soluble polymer was spray-applied at a ratio of 1.4% of the solid content of the solution to the pulp solid content. And the coated surface of the wet paper B are overlapped with each other, suction-dewatered at 150 mmHg in the direction of the wet paper B for 1 minute, and then dried.
A laminated paper was obtained.

Example 19 Example 19 was repeated except that the water-soluble acrylamide polymer obtained in Production Example 2 was applied to one surface of wet paper A and suction dehydration was performed from the direction of wet paper A. The same procedure as in 14 was performed to obtain a laminated paper.

Example 20 A laminated paper was obtained in the same manner as in Example 14, except that the suction dehydration was performed from the direction of the wet paper A.

Example 21 A laminated paper is obtained in the same manner as in Example 14 except that the water-soluble acrylamide polymer obtained in Production Example 2 is applied to one side of the wet paper A. It was

Example 22 Example 13 was repeated except that magnesium sulfate was used instead of aluminum sulfate mixed in the spray liquid.
In the same manner as above, a laminated paper was obtained.

Example 23 A laminated paper was obtained in the same manner as in Example 13, except that the aluminum sulfate mixed in the spray liquid was replaced with calcium chloride.

Example 24 In Example 14, a liquid obtained by diluting the acrylamide water-soluble polymer obtained in Production Example 2 with ion-exchanged water to 0.7% on one side of wet paper A was used as a pulp solid content. On the other hand, a liquid obtained by spray-coating the solid content of the acrylamide-based water-soluble polymer to 0.7%, and diluting aluminum sulfate to 0.7% with ion-exchanged water on one surface of the wet paper B, 0.7% aluminum sulfate solids relative to pulp solids
A laminated paper was obtained in the same manner as in Example 14 except that spray coating was carried out at the following ratio.

Comparative Examples 4 and 5 In the same manner as in Example 13 or 14, except that aluminum sulfate was not added to the aqueous solution of the acrylamide water-soluble polymer obtained in Production Example 1 or 2, in Example 13 or 14. Then, a laminated paper was obtained.

(Measurement of Interlayer Adhesive Strength) The obtained laminated paper was conditioned for 24 hours and then subjected to J-TAPPI paper pulp test method No. The interlayer adhesion strength (T-shaped peel strength (g / inch)) was measured according to 19-77. The results are shown in Table 1 or Table 2.
Shown in.

(Fixing Rate) The nitrogen content of the obtained laminated paper was measured and the fixing rate between layers was calculated. Fixing rate (%) = (B−C) / A × 100. A: Nitrogen content measurement value of applied acrylamide water-soluble polymer, B: Nitrogen content measurement value of paper obtained by applying acrylamide water-soluble polymer as an interlayer adhesive, and C: same pulp as B Nitrogen amount measurement value of the paper which was laminated without using the interlayer adhesive. The results are shown in Table 1 or Table 2.

[0055]

[Table 1]

[0056]

[Table 2]

From the results shown in Tables 1 and 2, according to the interlayer adhesive using the acrylamide-based water-soluble polymer of the present invention, the same ionic acrylamide as in the prior art which does not use the water-soluble polyvalent metal salt is used. It is recognized that a laminated paper having an excellent interlayer adhesive strength can be obtained as compared with an interlayer adhesive using a water-soluble polymer. Further, it is recognized that the specific coating method of the present invention can provide a laminated paper having further excellent interlayer adhesive strength.

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Claims (6)

[Claims] 1. An anionic adhesive is used as an interlayer adhesive in the production of a laminated paper having two or more layers by applying an interlayer adhesive to the surface of a wet paper layer before making the sheets and then making the sheets together. The (meth) acrylamide water-soluble or water-dispersible polymer or the amphoteric (meth) acrylamide water-soluble or water-dispersible polymer and a water-soluble polyvalent metal salt are used as a mixture. Method of manufacturing laminated paper. 2. The method for producing a laminated paper according to claim 1, wherein the water-soluble polyvalent metal salt is an aluminum salt. 3. The method for producing a laminated paper according to claim 1, wherein the (meth) acrylamide water-soluble or water-dispersible polymer contains a crosslinkable monomer as a constituent monomer. 4. The method for producing a laminated paper according to claim 1, 2 or 3, wherein the (meth) acrylamide water-soluble or water-dispersible polymer contains a hydrophobic monomer as a constituent monomer. 5. When applying an interlayer adhesive to the surface of a wet paper layer before assembling, an interlayer is applied to the surface of the wet paper layer having a smaller water content out of the surface of the wet paper layer. An adhesive is applied, The manufacturing method of the laminated paper of any one of Claims 1-4 characterized by the above-mentioned. 6. A wet paper layer, which is on the opposite side of the surface of the wet paper layer before application from the dehydration direction of the paper machine, when the interlayer adhesive is applied to the surface of the wet paper layer. On the surface of
The method for producing a laminated paper according to claim 1, wherein an interlayer adhesive is applied.