JPH0643679B2 - Method for producing laminated paper with excellent interlaminar strength - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a method for producing a laminated paper having excellent interlaminar strength.

(Prior art and its problems) In the past, in the production of laminated paper, in order to prevent peeling between the combined sheets, in order to improve the interlayer adhesive strength,
A method is used in which an ungelatinized starch dispersion is applied to the surface of a wet paper just before making a paper by spraying, followed by making a paper by an ordinary method, and then gelatinizing the starch by heating in a dryer section of a paper machine. There is.

However, such a production method has an uneconomical aspect in that most of the applied starch penetrates into the inside of the paper layer and the amount of starch that works effectively on the paper-making surface is a part. Further, in order to improve the interlaminar strength, it is necessary to gelatinize the ungelatinized starch remaining on the mating surface, but heating in the dryer section of the paper machine is often insufficient for gelatinization. Another problem is that it is difficult to obtain stable interlayer strength. Further, since the non-gelatinized starch dispersion liquid is applied by spraying, the spray nozzle is likely to be clogged, which causes a problem in stable operation.

(Problems of the Invention) In order to solve the above-mentioned problems in producing a conventional laminated paper, the present invention replaces a conventional non-gelatinized starch dispersion liquid with a fine colloidal form that does not cause clogging of a spray nozzle. An effective adhesive liquid that enables the active ingredients to remain without waste when applied to the wet paper surface immediately before assembling, and exerts sufficient adhesive force to perform interlayer adhesion without heating already. An object of the present invention is to provide a method for producing a laminated paper having excellent interlaminar strength.

(Means for Solving the Problems) In view of the fact that the conventional starch-based interlayer adhesive uses a non-gelatinized starch dispersion, the present invention provides a non-gelatinized starch dispersion. Instead, if a cationic modified starch that can effectively utilize the suction force with the wet paper surface charge is used as the base adhesive for the interlayer adhesive, and if an anionic polymer is used together to generate a fine colloid having cationic properties as a whole, clogging of the spray nozzle will occur. Does not occur, and because it is a cationic fine colloid,
It was completed by discovering that it can be sufficiently stopped on the surface of the wet paper and that the adhesive strength can already be exerted in the applied state. A method for producing laminated paper in which a fine colloidal liquid containing a cation-modified starch and an anionic polymer is spray-coated as an interlayer adhesive on the paper surface "
It is in.

The cation-modified starch used in the present invention contains 1 mol% to 15 mol% of a cationic group with respect to a glucose unit and has a viscosity (25 ° C.) of 2% by weight of solid content.
Is preferably 50 cps or less. Because, when the cationic group is less than 1 mol% with respect to the glucose unit, it is difficult to form a fine colloid with an anionic polymer, and it is difficult to remain even when spray-coated on a wet paper surface.
Even if it is more than mol%, the above effect cannot be expected to be improved and it is economically insignificant, because the modification cost is required.

The viscosity (25 ° C) of solid content 2% by weight is 50 cps or less, and it is necessary to use the range of 10 to 30 cps. It is necessary to prevent spraying workability and clogging of the spray nozzle. Because there is.

As a specific example of the cation-modified starch having such physical properties, those commonly used as a paper strength enhancer can be used.

On the other hand, the anionic polymer used in the present invention is 10 mol%
It is preferable to use a vinyl-bonded polymer containing -100 mol% of anionic groups and having a viscosity (25 ° C, pH 1-4) of 100-100,000 cps at a solid content of 5% by weight.

This is because if the anionic group of the anionic polymer is less than 10 mol%, a fine colloid cannot be formed with the cation-modified starch and a residual effect on the wet paper surface cannot be expected by spray coating.

Also, its viscosity (25 ° C, pH 1-4) is 5% by weight of solid content.
The reason why it is necessary to be 100 to 100,000 cps, especially 1000 to 30,000 cps is because it is necessary to prevent spraying workability and clogging of the spray nozzle.

As a specific example of the anionic polymer having such physical properties, those commonly used as a paper strength enhancer can be used.

The ratio of the cation-modified starch and the anionic polymer is 99.5 / 0.5 to 70/30 in terms of solid content weight ratio, particularly 99/1.
The range of to 90/10 is preferable. The reason is that at 99.5 / 0.5 or higher, it is not possible to expect the generation of fine colloids due to the combined use of the two, while at 70/30 or lower, the cationic colloid depletion of the fine colloids makes it impossible to stop on wet paper surfaces, and the expected effect is obtained. Because I can't get it.

(Advantageous Effects of the Invention) According to the present invention having the above-mentioned constitution, in place of the conventional non-gelatinized starch dispersion liquid, a cation-modified starch capable of effectively utilizing the suction force with the wet paper surface charge is used as the base adhesive for the interlayer, Moreover, since an anionic polymer was used together to produce a fine colloid having cationicity as a whole, the spray nozzle was not clogged, stable operation was possible, and in addition, it was a cationic fine colloid. Therefore, even if it is applied to the wet paper surface just before the assembling, it hardly penetrates into the paper surface and the active ingredient does not dissipate, and most of it remains on the wet paper surface, which is economical and
Furthermore, since it is already in a state where the adhesive force can be exerted in the applied state, it is extremely economical and efficient for the production of laminated paper.

Hereinafter, the present invention will be specifically described based on Examples.

(Example) (Preparation example 1 of cation-modified starch solution) 250 g of water and 250 g of corn starch are charged into a 1-volume separable flask equipped with a stirrer, a thermometer and a lens-shaped cooler, and stirred. Next, 20 g of a 50% aqueous solution of 3-chloro-2-hydroxy-propyltrimethylammonium chloride and 8 g of 48% sodium hydroxide are added, and the temperature is raised to 50 ° C. The reaction is carried out at 50-60 ° C for 5 hours as it is. After completion of the reaction, the mixture was neutralized with 10% hydrochloric acid, methanol was added thereto, the mixture was filtered, and the residue after filtration was washed with water-containing methanol to obtain a cation-modified starch powder. The N content of this powder was determined by the Kjeldahl method, and the cation modification rate was calculated.
Molar% was cationized. This cation-modified starch powder is referred to as cs (A) below. Next, 950 g of water and 50 g of cs (A) are charged into a 1-volume separable flask, the temperature is raised to 90 ° C., and 0.1 g of APS (ammonium persulfate) is added. Hold for 30 minutes at 90-95 ° C with stirring. The resulting cation-modified starch liquid cs (A)-(1) had a solid content of 4.6% and a viscosity at 25 ° C of 110 cp.
It was s.

(Preparation example 2 of cationically modified starch liquid) Preparation example 1 except that 0.3 g of APS (ammonium persulfate) is added
A cation-modified starch liquid cs (A)-(2) having a solid content of 4.6% and a viscosity at 25 ° C. of 30 cps was prepared in the same manner as in.

(Preparation example 3 of cation-modified starch solution) 50 g of water and 50 g of potato starch are charged into a 1-volume separable flask equipped with a stirrer, a thermometer, and a lens-shaped cooler, and stirred. Next, 10 g of a 50% aqueous solution of 3-chloro-2-hydroxy-propyltrimethylammonium chloride and 4 g of 48% sodium hydroxide are added, and the temperature is raised to 50 ° C. The reaction is continued at 50-60 ° C for 10 hours. After completion of the reaction, the mixture was neutralized with 10% hydrochloric acid, 850 g of water was added, and the mixture was heated to 98 ° C to gelatinize. The resulting cation-modified starch liquid cs (B) had glucose units of 7.8 mol% cationized, Solid content 4.9%,
The viscosity at 25 ° C was 130 cps.

(Preparation Example 1 of anionic polymer) A 1-volume glass four-necked flask equipped with a stirrer, a thermometer, and a lens-shaped cooler was charged with 94 parts by weight of 80% acrylic acid monomer and 404 parts by weight of water and heated with a mantle heater. To do. 42
At 0C, 0.2 parts by weight of sodium sulfite and 0.25 parts by weight of sodium persulfate are added. After confirming an exotherm in 2 to 3 minutes after the addition, stirring was continued until the maximum temperature was reached, and the reaction was continued for 30 minutes while maintaining the maximum temperature. Then, predetermined water is added and cooled to obtain a polyacrylic acid aqueous solution. The solid content of this polyacrylic acid aqueous solution was 15% by weight, and the viscosity at 25 ° C. was 2500 cps and PH2.2. This is PPA- (1).

(Preparation example 2 of anionic polymer) Solid content was the same as in Preparation example 1 except that 0.5 part by weight of sodium sulfite and 0.5 part by weight of sodium persulfate were added.
A polyacrylic acid aqueous solution PPA- (2) having a PH of 2.2 at 15% by weight and a viscosity of 5700 cps at 25 ° C. was obtained.

(Preparation example 3 of anionic polymer) 40% acrylic amide 50 parts by weight, 80% acrylic acid 10 parts by weight, and water 250 parts by weight in a 1-volume glass four-necked flask equipped with a stirrer, a thermometer, and a lens-shaped cooler. Is charged, and after heating to 50 ° C., 0.05 part by weight of sodium persulfate is dissolved in 5 parts by weight of water and added. Is added. After keeping the mixture for 3 hours to cause reaction, a predetermined amount of water is added to homogenize with stirring to obtain a polyacrylic acid aqueous solution having a solid content of 5.0% by weight, a viscosity (25 ° C.) of 28,000 cps and a pH of 2.4. Let this polyacrylic acid aqueous solution be PPA- (3).

(Production Example 1) Preparation of coating solution After dissolving 98 g of the above cation-modified starch cs (A)-(1) in 300 g of water, 3.3 g of the anionic polymer PPA- (1) was added, and the whole amount was added with water. It was 7,500 g. This gives a solids content of 1
%, Cation-modified starch / anionic polymer ratio 90 /
Prepare 10 microcolloid solutions.

Preparation of laminated paper Add 2% pulp slurry (LBKP 450mlcsf) with sizing agent (Harima Kasei, Harsize L-50) 0.3% (based on pulp solids content), followed by sulfuric acid band 2.0% (based on pulp A1 (8% content liquid conversion) was added and weighed with a TAPPI hand-made sheet machine.
100 g / m ² wet paper was obtained. Apply the above liquid coating solution to the surface of this wet paper
Apply 60 g / m ^{2 of} (1) by spraying. After that, weighed 100 g / m ² wet paper obtained with a TAPPI type hand-made sheet machine from 2% pulp slurry (new newspaper deinked waste paper 200 mlcsf) was layered, press-dehydrated under certain conditions, and then rotated at 105 ° C. It was dried for 3 minutes with a drum dryer to obtain laminated paper (1).

(Production Example 2) Preparation of coating solution After dissolving 76 g of the cs (A)-(2) in 300 g of water, 10 g of the anionic polymer PPA- (2) was added, and the total amount was 500 g with water.
And As a result, 1% solid content, cation-modified starch
A fine colloidal liquid with an anionic polymer ratio of 70/30 was obtained. This is designated as coating liquid (2).

Preparation of paper-making laminated paper (2) was obtained in the same manner as preparation of paper-making laminated sheet of Production Example 1 except that the coating solution (2) was sprayed onto the surface of the wet paper at 60 g / m ^2. It was

(Production Example 3) Preparation of coating liquid After dissolving 92 g of the cs (B) in 300 g of water, 10 g of the anionic polymer PPA- (3) was added, and the total amount was adjusted to 500 g with water. As a result, a fine colloidal liquid (3) having a solid content of 1% and a cation-modified starch / anionic polymer ratio of 90/10 is obtained, and this is used as a coating liquid (3).

Preparation of paper-making laminated sheet (3) was obtained in the same manner as the preparation of paper-making laminated sheet of Production Example 1 except that the coating solution (3) was sprayed onto the surface of the wet paper at 60 g / m ^2. It was

(Comparative Example 1) Preparation of coating liquid 28 g of corn starch was adjusted to a total amount of 500 g with water to obtain a corn starch coating liquid (4) having a solid content of 5%.

Preparation of paper-making paper (4) A paper-making paper (4) was obtained in the same manner as the preparation of the paper-making paper of Production Example 2 except that the coating solution (4) was sprayed onto the surface of the wet paper at 60 g / m ² .

(Comparative Example 2) Preparation of laminated paper A laminated paper (5) was obtained in the same manner as the preparation of the laminated paper of Production Example 2 except that 60 g / m ² of water was spray-coated on the surface of the wet paper.

(Test Example) Paper-making laminated paper prepared in the above production example and comparative example (1)
The interlayer strengths of (5) to (5) were measured as follows, and the test results were compared.

Affix the laminated paper (1) to (5) with a double-sided adhesive tape to a square metal block having a flat surface of 1 inch x 1 inch,
The interlaminar strength was measured by a tensile tester. This measurement is TAPP
Perform according to I T506 su68.

Test results (Table 1) Laminated paper interlaminar strength (Kgf) Production Example 1 (Paper laminated paper (1)) 22.2 2 (2) 21.0 3 (3) 24.7 Comparative Example 1 (4) 18.1 2 (5) 12.7 As is clear from the above results, according to the present invention, a laminated paper excellent in interlayer strength can be obtained.

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Claims (2)

[Claims] 1. An interlayer adhesive is sprayed onto the surface of a wet paper sheet just before making a paper, and when the paper is made, a cation-modified starch and 10 mol% to 100 mol% of an anionic group are used as the interlayer adhesive. Mixing weight ratio 99.5 / 0.5 ~ 70/3 with anionic polymer which is vinyl binding polymer
A method for producing a laminated paper having excellent interlaminar strength, which comprises spray-coating a liquid containing 0 on the surface of a wet paper sheet just before the papermaking. 2. The cation-modified starch according to claim 1, wherein the cation-modified starch contains 1 mol% to 15 mol% of a cationic group with respect to glucose unit, and the viscosity (25 ° C.) is 50 cps or less at a solid content of 2% by weight. Production method.