JP3285478B2 - Manufacturing method for paperboard - Google Patents

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 paperboard and the like using an aqueous mixture type coating agent composed of two specific acrylamide polymers. More specifically, the present invention is an aqueous mixture system coating consisting of a specific amphoteric crosslinkable acrylamide polymer and a cation-modified acrylamide polymer on the surface of the wet paper layer before combining in the manufacturing process of paperboard and the like. The present invention relates to a method for manufacturing a paperboard or the like for applying the agent.

[0002]

2. Description of the Related Art Paperboard and the like are usually produced in the production process by combining several wet paper layers, pressing and drying them. In such paperboard and the like (hereinafter collectively referred to as paperboard), when the adhesive strength between the paper layers is low, a phenomenon may occur in which the paper layers are separated during printing or the like. In the art, this is called delamination, and its strength is called interlaminar adhesive strength.

Recently, as the papermaking speed is increased to improve the productivity of paperboard, the decrease in the interlayer adhesive strength has become a serious problem. Furthermore, as printing speed increases and multi-color printing is performed, blistering phenomenon during printing and delamination phenomenon during processing due to increase in processing speed are regarded as problems, and the demand for paperboard quality is further increasing. ..

As a method for preventing the above-mentioned delamination, for example, there is a method in which a non-gelatinized starch liquid is spray-coated on the surface of the wet paper layer immediately before making the paper. In this method, the applied starch is gelatinized by heating in the dryer section of the paper machine to bond the paper layers. However, this method is greatly affected by the drying temperature and drying speed of the dryer. Also, a considerable amount of starch applied by this method is
Since it penetrates into the paper layer, it requires a very large amount of starch to completely bond the paper layers. Furthermore,
Since the non-gelatinized starch dispersion liquid is applied by spraying, the spray nozzle is likely to be clogged, and there are problems in stable operation such as uneven spraying due to sedimentation of the dispersion liquid.

As a method for preventing the above-mentioned delamination,
A method using an interlayer adhesive has been proposed. A method using various acrylamide-based water-soluble or water-dispersible polymers as shown below, for example, has been proposed in the art as the above-mentioned interlayer adhesive. (1) Japanese Patent Publication No. 54-32843 proposes a method of applying a dispersion of starch mixed with a water-soluble thermosetting cationic resin on the surface of a wet paper layer before being combined. (2) Japanese Patent Publication No. 55-35518 discloses a method of applying a Hoffmann degradation product of epoxidized polyamide polyamine and/or polyacrylamide. (3) Japanese Patent Publication No. 6-43679 discloses that a cation-modified starch and an anionic polymer which is a vinyl-bonded polymer having 10 to 100 mol% anionic groups are blended as an interlayer adhesive and the polymerization ratio is 99.5/0. A method of spray coating a liquid containing 5 to 70/30 is disclosed. (4) In JP-A-4-157999, an ionic water-soluble or water-dispersible polymer obtained by copolymerizing (meth)acrylamide, an ionic monomer and a crosslinking monomer is used as an interlayer adhesive. A method of doing so is disclosed. (5) In JP-A-7-189193, an ionic water-soluble or water-dispersible polymer obtained by copolymerizing (meth)acrylamide, an ionic monomer and a hydrophobic monomer is used as an interlayer adhesive. A method is disclosed. (6) JP-A-7-189194 discloses an anionic (meth)acrylamide-based water-soluble or water-dispersible polymer or an amphoteric (meth)acrylamide-based water-soluble or water-dispersible polymer as an interlayer adhesive. A method of mixing and using a water-soluble polyvalent metal salt is disclosed. (7) JP-A-7-189195 discloses that, as an interlayer adhesive, an amphoteric (meth)acrylamide-based water-soluble or water-dispersible polymer is clouded at a concentration of 0.1 to 5.0% by weight. The method of use is disclosed.

However, in the above-mentioned interlayer adhesives using various acrylamide-based water-soluble or water-dispersible polymers, another effect is obtained, and one having further higher interlayer adhesive strength is desired. There is.

[0007]

As described above, with respect to paperboard, problems such as an increase in printing speed, a blistering phenomenon during printing accompanying multicolor printing, and a delamination phenomenon during processing accompanying an increase in processing speed are problematic. Has been done. The interlayer adhesive strength is roughly classified into two adhesive strengths, and the first adhesive strength is the interlayer strength which is most peeled off during the printing process.
The second adhesive strength is the adhesive strength between the layers against the shear stress generated during high-speed processing. Regarding the adhesive strength between the first and third layers of Table 3, it is said that delamination easily occurs due to the fact that the raw material pulp and papermaking conditions of these three layers are generally different.
When the adhesive strength between the layers of Table 3 is weak, peeling occurs between layers and a blistering phenomenon occurs in a printing process, particularly in recent solid printing and multicolor printing.

Conventionally, for example, spray coating of starch has been carried out as a measure for improving the above-mentioned interlayer adhesive strength, but it has the drawbacks as described above. Further, as mentioned above, a method using an acrylamide polymer has been proposed, but the effect is another.

The present invention uses a specific interlayer adhesive which has a strong fixing force for the fibers between the layers of the paperboard, has the effect of strengthening the interfiber bond, and has good sprayability.
The present invention provides a method for producing paperboard having excellent interlaminar strength.

[0010]

Means for Solving the Problems The present invention can be summarized as follows. In the present invention , a crosslinkable vinyl monomer is added to the surface of a wet paper layer before papermaking in a manufacturing process of paperboard or the like which requires papermaking of paper layers. Characteristically, after applying an aqueous mixture type coating agent obtained by previously mixing a zwitterionic cross-linking type acrylamide polymer prepared as an essential constituent monomer and a cation-modified acrylamide type polymer, performing papermaking in accordance with a conventional method The present invention relates to a method for manufacturing paperboard and the like.

The technical constitution of the present invention will be described in detail below.

First, the interionic crosslinkable acrylamide polymer, which is one of the essential components of the agent for improving the interlayer adhesion strength of the present invention, that is, one of the aqueous mixture type coating agents, will be described. The amphoteric cross-linking acrylamide polymer prepared by using the above-mentioned cross-linkable vinyl monomer of the present invention as an essential constituent monomer (hereinafter, simply referred to as zwitterionic cross-linking acrylamide polymer) is obtained by copolymerizing the following monomers. It was prepared. That is, the amphoteric crosslinkable acrylamide polymer of the present invention is (a) a crosslinkable vinyl monomer,
It is composed of a copolymer prepared by copolymerizing a monomer mixture of (b) an anionic vinyl monomer, (c) a cationic vinyl monomer, and (d) acrylamide and/or methacrylamide.

In the present invention, it is used to prepare the above-mentioned zwitterionic crosslinked acrylamide polymer (a).
Examples of the crosslinkable vinyl monomer as a component include bis(meth)acrylamides such as methylolacrylamide, methylenebis(meth)acrylamide, and ethylenebis(meth)acrylamide; diglycols such as ethylene glycol di(meth)acrylate and diethylene glycol di(meth)acrylate. (Meth)acrylates; divinyl adipate,
Divinyl esters such as divinyl sebacate; epoxy acrylates; urethane acrylates; divinylbenzene, 1,3,5 - triacryloylhexahydro-
S-triazine, triallyl isocyanurate, triallyl trimellitate, triallyl amine, N,N-diallyl acrylamide, tetramethylolmethane tetraacrylate, tetraallyl pyromellilate, N,N-dimethyl acrylamide having N-substituted amide group, etc. Is mentioned.

In the above-mentioned (a) crosslinkable vinyl monomer, methylol acrylamide, methylene bis acrylamide, diethylene glycol dimethacrylate,
1,3,5 - triacryloylhexahydro--S- triazine, tetramethylolmethane tetraacrylate,
N,N-dimethylacrylamide is preferred, especially methylolacrylamide, methylenebisacrylamide, 1,3,5 - triacryloylhexahydro-S-.
Triazine and N,N-dimethylacrylamide are suitable. In the present invention, the above-mentioned (a) crosslinkable vinyl monomer may be used alone or in combination of two or more.

In the present invention, it is used to prepare the above-mentioned zwitterionic crosslinked acrylamide polymer (b).
As the anionic vinyl monomer as a component, acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, styrene sulfonic acid, (meth)allyl sulfonic acid, 2-
Examples thereof include acrylamido-2-methylpropanesulfonic acid or vinyl monomers such as sodium, potassium and ammonium salts thereof.

In the present invention, it is used to prepare the above-mentioned zwitterionic crosslinked acrylamide polymer (c).
As the component cationic vinyl monomer, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide, diethylaminopropyl acrylamide, diethylaminopropyl methacrylamide, acrylamine, Vinyl monomers having a tertiary amine group such as diallylamine or their inorganic or organic acid salts such as hydrochloric acid, sulfuric acid, nitric acid or sulfamic acid, or
Grade amine group-containing vinyl monomer and methyl chloride, benzyl chloride Lai de, dimethyl sulfate, epichlorohydrin,
Fourth obtained by reaction with a quaternizing agent such as glycidyl trimethyl ammonium chloride, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride
Examples thereof include vinyl monomers containing a graded ammonium salt.

In the present invention, the anionic vinyl monomer (b) and the cationic vinyl monomer (c) described above are used.
Can be used alone or in combination of two or more in each category.

[0018] In the zwitterionic crosslinked Akurirua <br/> Mi de polymers of the present invention, (a) the molar ratio of ~ (d) component, (a) component 0.005 to 5 mol%, ( component (b) is 1 to 20 mol %, component (c) is 0.5 to 10 mol %,
The component (d) is preferably in the range of 65 to 98 mol %. When the component (a) is less than 0.005 mol %, the effect of the present invention is not improved, and when it exceeds 5 mol %, a gelation phenomenon occurs.

The characteristic feature of the present invention is that when the use ratio (molar ratio) of each of the above-mentioned components (a) to (d) is deviated (out of the above range), the interlayer adhesive strength aimed at by the present invention is obtained. Is that you can not get enough.

In the present invention, in addition to the above essential constituent monomers, the effects of the present invention are not substantially impaired,
A monomer copolymerizable with the above-mentioned constituent monomers can be used. As the above-mentioned copolymerizable monomer,
(Meth) can be used acrylic acid esters, vinyl acetate, and the like nonionic vinyl monomer such as acryloxypropyl two <br/> tolyl.

The amphoteric crosslinked acrylamide polymer of the present invention can be produced by various conventionally known methods. For example, a reaction vessel equipped with a stirrer and a nitrogen gas introduction tube is charged with the constituent monomers (a), (b), (c) and (d) of the present invention and water.
As a polymerization initiator, hydrogen peroxide, ammonium persulfate,
Potassium persulfate, peroxides such as ammonium hydroperoxide, or a redox initiator in combination with a reducing agent such as those peroxide and bisulfite, or 2,2' - azo <br/> bis - (2-amidinopropane) was added a water-soluble azo polymerization initiators such as hydrochloride, also isopropyl alcohol if necessary, allyl alcohol, sodium hypophosphite, mercaptoethanol, modifiers such as thioglycolic acid Alternatively, a chain transfer agent is appropriately used, and the reaction temperature is 40 to 8
The desired amphoteric crosslinked acrylamide polymer may be prepared by reacting at 0° C. for 1 to 5 hours. In the above-mentioned polymerization method, when N,N-dimethylacrylamide having an N-substituted amide group is used as the crosslinkable vinyl monomer as the component (a), a copolymer containing N,N-dimethylacrylamide obtained by the above-mentioned polymerization method is used. It is necessary to add an oxidizing radical catalyst to the polymer and to carry out a crosslinking reaction at a temperature of 60 to 80° C. for 1 to 5 hours. Examples of the oxidizing radical catalyst include inorganic peroxides such as hydrogen peroxide and persulfates (ammonium persulfate, potassium persulfate, etc.).

Next, the cation-modified acrylamide polymer which is the other essential component of the aqueous mixture type coating agent of the present invention will be explained. Examples of the cation-modified acrylamide polymer of the present invention include a cation-modified acrylamide polymer by a Hoffmann decomposition reaction and a cation-modified acrylamide polymer by a Mannich reaction. For the preparation of the cation-modified acrylamide polymer by the former Hoffman decomposition reaction, a method similar to the conventional method may be adopted. For example, by adding a hypohalite and an alkali catalyst to an aqueous solution of an acrylamide polymer, the acrylamide polymer and the hypohalite are reacted in an alkaline region, and then an acid is added to adjust the pH to 3 It may be adjusted to 0.5 to 5.5.

In the present invention, the cation-modified acrylamide polymer is not limited to the above-mentioned Hoffman decomposition reaction, and may be one prepared by utilizing the Hoffman decomposition reaction of the following modes. That is, a cation-modified product prepared by Hofmann decomposition reaction of polyacrylamide in the presence of choline chloride (JP-A-53-109594),
A cation-modified product prepared by adding a quaternization reaction product of a tertiary amine having a hydroxyl group and benzyl chloride or its derivative in the Hoffman decomposition reaction (Japanese Patent Publication No. 58-86).
82), a cation-modified product prepared by adding an organic polyvalent amine as a stabilizer in the Hoffman decomposition reaction (Japanese Patent Publication No. 60-17322), or by adding a specific cationic compound as a stabilizer in the Hoffman decomposition reaction. The prepared cation-modified product (Japanese Patent Publication No. 62-45884) can be used. The polymer prepared by the Hoffmann decomposition reaction generally has a cationic monomer unit of about 5
Those containing 40 mol% and about 60 to 95 mol% of acrylamide units are preferable. The average molecular weight of the cation-modified acrylamide polymer prepared by the Hoffmann decomposition reaction is preferably about 5 to 1,000,000.

In the present invention, the cation-modified acrylamide polymer may be one obtained by the Mannich reaction. For the preparation of the cation-modified acrylamide polymer by the Mannich reaction, a method similar to the conventional method may be adopted. For example, conditions may be adopted in which a secondary amine such as formalin and dimethylamine is added to an aqueous solution of an acrylamide polymer, and the reaction is performed at a temperature of about 40 to 60° C. for about 1 to 5 hours. The polymer prepared by the Mannich reaction generally contains about 10 to 60 mol% of cationic monomer units and about 4 units of acrylamide units.
It is preferably contained in an amount of 0 to 90 mol %.

In the present invention, when a cation-modified acrylamide polymer prepared by a Hoffmann decomposition reaction is used as the cation-modified acrylamide polymer, there is a peculiarity that an extremely excellent interlayer adhesive strength can be obtained.

In the paperboard manufacturing method of the present invention, an aqueous mixture type coating agent comprising the above-mentioned specific zwitterionic cross-linking type acrylamide polymer and cation-modified acrylamide type polymer is used as an agent for improving the interlayer adhesion strength. Is mandatory. The aspect of use of the aqueous mixture-based coating agent of the present invention is that the surface of the wet paper sheet layer prior to combining in the paperboard manufacturing process is applied in the form of an aqueous mixture prepared by previously mixing the above-mentioned essential components. Thereby, the interlayer adhesive strength can be remarkably improved.

The proportion of each component of the aqueous mixture based coating agent in the production method of the paperboard of the present invention, i.e., the mixing ratio of the zwitterionic crosslinked acrylamide polymers and cation-modified acrylamide polymer, the raw material Pulp, papermaking pH,
It can be selected from a wide range depending on the papermaking conditions such as the amount of band added, but in the solid content weight ratio, the former:the latter=95:5.
It may be about 5:95. The preferable mixing ratio is the former:the latter=80:20 to 20:80. The above-mentioned specific zwitterionic cross-linking type acrylamide polymer and cation-modified acrylamide polymer of the present invention can provide a stable and uniform colloidal mixed aqueous solution in an aqueous mixture thereof. Incidentally, the above-mentioned amphoteric acrylamide other than the specific zwitterionic crosslinked acrylamide polymers of the present invention
When used in combination of a polymer and cation-modified acrylamide polymer is diluted solution immediately after mixing, it clouded insolubilized,
Aggregates may precipitate over time.

The amount of the aqueous mixture coating agent used as the agent for improving the interlayer adhesive strength of the present invention may be appropriately determined. Generally, the amount of the aqueous mixture-based coating agent used is 0.1 to 5 g in terms of solid content with respect to the surface of the wet paper layer before combining.
It is sufficient to apply an amount corresponding to /m ² .

Under the above aqueous mixture type coating agent of the present invention, the above-mentioned excellent effect of interlayer adhesive strength is exhibited.
The present inventors have inferred the following about the mechanism of expression of the above-mentioned excellent effect. The zwitterionic crosslinkable acrylamide polymer containing the crosslinkable vinyl monomer of the present invention as an essential component has a relatively high molecular weight and has a highly branched structure. It is presumed that it forms a very stable complex with an acrylamide polymer. It is considered that the stable water-soluble composite is an important factor in exerting the excellent effect in the interlayer adhesive strength property.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to Preparation Examples, Examples and Comparative Examples.

[0031]

[Preparation example of zwitterionic cross-linked acrylamide polymer]
(Preparation Example R-1) Acrylamide (d component) 62.3 in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube.
g, itaconic acid (b component) 5.9 g, trimethyl methacryloyl oxyethylene ammonium chloride (c component) 3.8g, 1% 1, 3 , 5- triacryloylhexahydro--S- triazine (a component) 2.2 g , Soft water 4
After charging 30 g, the pH was adjusted to 3.5, the temperature was raised to 50° C. while passing nitrogen gas, and 5% ammonium persulfate 1.
Add 5 ml, 1.5% sodium bisulfite 1.5 ml, 50
Allowed to react for 3 hours at to 80 ° C., to obtain a zwitterionic crosslinked acrylic <br/> Ami de polymer. The properties are shown in Table 1.

(Preparation Example R-2/R-3/R-4/R-6
/R-7) In Preparation Example R-1, components (a) to (d).
Table 1 shows the types of ingredients or the amount used.
The same procedure as in Preparation Example R-1 was carried out except that the modification was performed as shown in to obtain a zwitterionic crosslinked acrylamide polymer. The properties are shown in Table 1.

Preparation Example R-5 In Preparation Example R-1,
A copolymer is prepared by performing the same operation as in Preparation Example R-1, except that any one of the types of the components (a) to (d) or the amount thereof is changed as shown in Table 1. did. Ammonium persulfate and dimethylacrylamide were added to the copolymer in an amount equivalent to this mole, and the mixture was reacted at 70 to 80° C. for 1 hour to obtain a zwitterionic crosslinked acrylamide polymer. The properties are shown in Table 1.

In Table 1, each symbol means the following. a-1: TAF (1, 3, 5 - triacryloylhexahydro--S- triazine) a-2: MBA (methylene bisacrylamide) a-3: DMAA (dimethyl acrylamide) a-4: MAA (methylolacrylamide) b -1: itaconic acid b-2: acrylic acid b-3: maleic anhydride c-1: DMC (trimethylmethacryloyloxyethyl ammonium chloride) c-2: DM (dimethylaminoethyl methacrylate) c-3: DMAPAA (dimethylamino) Propyl acrylamide) d: acrylamide

[0035]

[Table 1]

[0036]

[Preparation example of cation-modified acrylamide polymer by Hoffmann degradation]

(Preparation Example H-8) Effective chlorine concentration of 12% with respect to 300 g of an acrylamide polymer having an average molecular weight of 100,000 and a concentration of 15%
Sodium hypochlorite 37.5g and 48% caustic potash 15g
An alkaline aqueous solution of sodium hypochlorite containing water is added dropwise while cooling and stirring, and after completion of the addition, the temperature is kept at 25°C for another 60 minutes.
Hold at ℃ to carry out the reaction. After completion of the reaction, the reaction solution was adjusted to pH 4.5 with dilute hydrochloric acid to obtain a cation-modified acrylamide polymer by Hofmann decomposition reaction with a polymer concentration of 10%. The properties are shown in Table 2.

(Preparation Example H-9/H-10) Preparation Example H-8
In the same manner as in Preparation Example H-8, except that the acrylamide polymer was replaced with that having an average molecular weight of 500,000, and sodium hypochlorite and caustic potash were used in an amount corresponding to the cation modification rate shown in Table 2. Thus, a cation-modified acrylamide polymer was obtained by the Hoffman decomposition reaction. The properties are shown in Table 2. In Table 2, the cation modification rate mol%
(Cationic monomer unit) is an actual measurement value quantified by the colloid titration method. In addition, the values in parentheses in the same column indicate theoretical values.

[0038]

[Table 2]

[Preparation Example of Cation-Modified Acrylamide Polymer by Mannich Reaction] (Preparation Example M-11) For 400 g of anionic acrylamide polymer aqueous solution having an average molecular weight of 200,000 and a concentration of 7%, 9.6 g of 37% formalin. , 50% dimethylamine aqueous solution (12.5 g) was added, and the mixture was reacted at a temperature of 50 to 60° C. for 3 hours to obtain a cation-modified acrylamide polymer by a Mannich reaction. The properties are as follows: cation modification rate (cation monomer unit) 28.6 mol%, concentration 10%, viscosity 850 cps/
It was 25.degree. C. and pH (10-fold solution) 10.2.

[0040]

[Example] (Example 1 to 10) handsheet paper production 2% pulp slurry (newspaper old paper, C.S.F 175m
l) with TAPPI standard sheet machine 1 basis weight
A wet paper of 00 g/m ² was obtained. Preparation Example R-
1 to R-6 amphoteric cross-linking type acrylamide polymers and the cation-modified acrylamide polymers of Preparation Examples H-8, H-9, H-10 and M-11 at respective mixing ratios shown in Table 4. The admixed amount of the mixed aqueous mixture was about 0.3 g/
Spray coating was applied so that m ² (solid content) was obtained.
The spray coating concentration of the aqueous mixture was 0.5% aqueous dispersion). Apart from 2% pulp slurry (newspaper old paper C.S.
F175 ml) was placed on a wet paper having a basis weight of 100 g/m ² obtained by a TAPPI standard sheet machine, press dehydrated, and then dried at 105° C. for 5 minutes to obtain a basis weight of 200 g/m ^2.
m ² of the combined paper was obtained. Interlayer adhesion strength is TAPPI T
It was measured according to 506-su68. The results are also shown in Table 3.

Comparative Examples 1 to 6 Preparation Examples R-7, H-9 and M were used in place of the water-soluble mixture of the zwitterionic crosslinked acrylamide polymer and the cation-modified acrylamide polymer used in the Examples. -11 and the combination shown in Table 4, the aqueous mixture prepared by mixing at a mixing ratio, or each of Preparative Examples R-1, H- 9 and potato starch solution was used alone, except that each of them was used in the same manner as in the above Examples. A composite paper was obtained. Table 3 also shows the measurement results of the interlayer adhesive strength of this laminated paper.

[0042]

[Table 3]

(Examples 11 to 12) Production of handmade paper 2% pulp slurry (L-BKP C.S.F. 400 m
l) with TAPPI standard sheet machine 1 basis weight
A wet paper of 00 g/m ² was obtained. Preparation Example R-
1 and Preparation Example H-9 were mixed at a ratio of 50:50, and the aqueous mixture and potato starch. 20:80
The amount of the water dispersion mixed at a ratio of about 0.5 g/m
² (solid content) was spray-coated (spray coating concentration was 1% dispersion liquid). Apart from TAPPI 2% pulp slurry (newspaper old paper C.S.F170ml)
100 g/m ² basis weight obtained with a standard sheet machine
It was superposed on the wet paper of No. 3, press-dehydrated, and dried at a temperature of 105° C. for 5 minutes to obtain a paper having a basis weight of 200 g/m ² . The interlayer adhesive strength was measured according to TAPPI T506 - su68. The results are shown in Table 4.

(Comparative Examples 7 to 9) Instead of the aqueous mixture used in Example 11, Stargum A-15 (manufactured by Hoshiko Kagaku Kogyo KK; anionic polyacrylamide, concentration 15)
%), Preparation Example R-7, an aqueous dispersion obtained by mixing potato starch with each combination mixing ratio shown in Table 4, and the same procedure as in Example 11 except that potato starch and water were used alone. A laminated paper was obtained. The potato starch was applied in the form of a cold water dispersion. Table 4 shows the measurement results of the interlayer strength of this composite paper.
Shown together with.

[0045]

[Table 4]

[0046]

EFFECTS OF THE INVENTION The method for producing a paperboard or the like of the present invention is an aqueous mixture type coating agent in which two specific acrylamide polymers are mixed as an interlaminar adhesive strength improving agent, specifically, (1) crosslinkability Zwitterionic cross-linked acrylamide polymer prepared by using vinyl monomer as an essential constituent monomer, and (2)
It is characterized by using an aqueous mixture type coating agent in which a Hofmann decomposition reaction or a Mannich reaction, especially a cation-modified acrylamide polymer by the former reaction is used in combination.

In particular, in the method for producing a paperboard or the like of the present invention, in the step of producing a paperboard or the like that requires the paper layers to be combined, the aqueous mixture-based coating agent is applied to the surface of the wet paper layer before the combination. Is characterized in that it exhibits an excellent effect on interlayer adhesive strength characteristics.

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-7-157999 (JP, A) JP-A-48-10306 (JP, A) JP-A-3-227491 (JP, A) JP-A-59- 189102 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (3)

(57) [Claims] 1. A zwitterionic crosslinkable acrylamide polymer prepared by using a crosslinkable vinyl monomer as an essential constituent monomer on the surface of a wet paper layer before the papermaking in a manufacturing process of a paperboard or the like which requires papermaking of the paper layer. And a cation-modified acrylamide polymer are mixed in advance to obtain an aqueous mixture-based coating agent, and then a papermaking process is carried out according to a conventional method. 2. An amphoteric crosslinkable acrylamide polymer prepared by using a crosslinkable vinyl monomer as an essential constituent monomer, comprising: (a) a crosslinkable vinyl monomer, (b) an anionic vinyl monomer, and (c) a cationic vinyl monomer. And (d) acrylamide and/or methacrylamide, which are copolymers obtained by copolymerization. 3. The method for producing paperboard or the like according to claim 1, wherein the cation-modified acrylamide polymer is a cation-modified acrylamide polymer by a Hoffmann decomposition reaction.