JP2620806B2 - Papermaking additives and papermaking methods - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a papermaking additive and a papermaking method, and more specifically to tear strength as well as various strengths such as tensile strength and internal strength of paper when dried. The present invention also relates to a papermaking additive capable of obtaining sufficiently satisfactory results, and a papermaking method using the additive.

[Prior Art] In the papermaking process, various papermaking additives have conventionally been used for the purpose of improving paper quality. Examples thereof include water-soluble natural polymer substances such as starch and modified starch, polyacrylamide and derivatives thereof, polyamide polyamine-epichlorohydrin resins, melamine and urea formaldehyde resins, and other various aqueous synthetic polymer substances.

Starch-based additives are inexpensive, but need to be used in large quantities because of poor paper-strengthening effect per amount used. Along with that, a decrease in water repellency in the papermaking process, generation of slime,
In addition to problems such as adhesion of dirt to a paper machine, the starch-based additive must be dissolved by steaming before use. For this reason, synthetic polymer-based additives have recently become mainstream from the viewpoint of workability.

A typical synthetic polymer-based additive is polyacrylamide, and various kinds of polyacrylamide-based additives modified by anion, cation or amphoteric are used. Although polyacrylamide-based additives have excellent performance as a dry paper strength enhancer, they are expensive and therefore have economical restrictions on their use. In addition, polyamide polyamine-epichlorohydrin resin, melamine and urea formaldehyde resin are effective in enhancing paper strength when dry and wet.

A graft starch polymer has been proposed as an additive having both characteristics of an acrylamide-based additive and a starch-based additive. For example, Japanese Patent Publication No. 38-17051 teaches a papermaking additive obtained by polymerizing an unsaturated amide and an unsaturated carboxylic acid in the presence of a water-dispersible polysaccharide. Japanese Patent Publication No. 50-12481 discloses a graft starch polymer obtained by polymerizing acrylamide and an unsaturated carboxylic acid in the presence of at least one of a water-soluble polysaccharide, a water-dispersible polysaccharide and a derivative thereof, and acrylamide. A paper strength agent comprising a mixture with a specific copolymer as a main monomer component is described. In Japanese Patent Application No. 62-47078, a monomer mixture comprising dialkylaminoalkyl (meth) acrylamide, (meth) acrylic acid and (meth) acrylamide is polymerized in an aqueous solution containing starch. Papermaking additives have been proposed.

[Problems to be Solved by the Invention] Needless to say, paper is required to have various strengths, but tear strength is also an important requirement of paper, and is used for kraft paper, kraft adhesive tape and the like. Paper
Particularly high tear strength is required.

The conventional various paper strength enhancers as described above are effective in improving various strengths such as tensile strength and internal strength of the paper when dried, but have a drawback of lowering the tear strength. In particular, the tendency is remarkable for acrylamide-based paper strength enhancers. Although starch-based paper strength enhancers do not reduce the tear strength as much as acrylamide-based ones, they generally have a poor effect of increasing various strengths, so they must be used in large amounts, and as a result, various adverse effects may occur. As described above. Also, polyamide polyamine-epichlorohydrin resin,
Melamine and urea-formaldehyde resins have the disadvantage that the tear strength is reduced, and that the broken paper is difficult to disintegrate.

On the other hand, the paper-strengthening agent of the grafted starch polymer system can improve the general strength of the paper and also can improve the tear strength to some extent. However, the conventional graft starch polymer-based paper-strengthening agents have room for improvement in that general strength and tear strength cannot be simultaneously increased to a satisfactory level.

Accordingly, an object of the present invention is to provide a novel grafted starch polymer-based papermaking additive capable of obtaining a paper which is sufficiently satisfactory in not only general strength but also tear strength, and a papermaking method using the additive. Is to do.

[Means for Solving the Problems] The present inventors have conducted intensive studies with the aim of improving a graft starch polymer-based papermaking additive, and as a result, using a cationic polysaccharide as one component of a polymer, In an aqueous solution containing the cationic polysaccharide, a specific vinyl monomer is graft-polymerized, and the obtained polymer is added to a raw pulp slurry for papermaking, papermaking and drying are performed in a usual manner, and then drying is performed. It has been found that papers having excellent strength and tear strength at the same time can be obtained.

Therefore, the first papermaking additive of the present invention comprises: (A) 50-95 mol% of (meth) acrylamide (B) α, in an aqueous solution containing 40 to 90 parts by weight of a cationic polysaccharide; β-unsaturated carboxylic acids and / or salts thereof
It is characterized in that a graft polymer obtained by polymerizing 10 to 60 parts by weight of a monomer mixture consisting of 50 mol% is contained as an active ingredient.

Further, the second papermaking additive of the present invention can be used in an aqueous solution containing 40 to 90 parts by weight of a cationic polysaccharide, when the (meth)
After polymerizing 10 to 60 parts by weight of acrylamide, 5 to 50 mol% of the amide group is modified into a carboxyl group with an alkali, and the resulting modified graft polymer is contained as an active ingredient. .

In the present invention, cationic polysaccharides include, for example, corn, wheat, potato, rice, raw starch such as capioca, guar gum, locust bingham, galactomannan and the like,
It contains at least one basic nitrogen selected from the group consisting of primary, secondary, and tertiary amino groups and quaternary ammonium groups. The content of basic nitrogen is
It is preferably at least 0.3% by weight, and the basic nitrogen is preferably a quaternary ammonium group. By the way, the fourth
A cationic polysaccharide containing a quaternary ammonium group is obtained by reacting a polycation with a cationizing agent comprising a reaction product of dialkylamine or trialkylamine and epichlorohydrin in an aqueous medium in the presence of an alkali. Can be manufactured by Among the cationic polysaccharides that can be used in the present invention, cationic starch, especially cationic tapioca starch, is particularly preferred. A solution having a viscosity of 20 to 200 centipoise (at 25 ° C., 10% aqueous solution) obtained by cooking a cationic starch at 90 to 100 ° C. is most suitable as an aqueous solution containing a cationic polysaccharide.

As the α, β-unsaturated carboxylic acid, (meth) acrylic acid, itaconic acid, maleic anhydride, maleic acid, fumaric acid, citraconic acid and the like can be used, and among them, (meth) acrylic acid is preferable. As salts of these acids, alkali metal salts such as sodium salts and potassium salts and ammonium salts can be used.

The first papermaking additive of the present invention comprises, in an aqueous solution containing the above-mentioned cationic polysaccharide, (A) 50 to 95 mol% of (meth) acrylamide and (B) α, β- It can be produced by reacting a monomer mixture consisting of a saturated carboxylic acid and / or a salt thereof in an amount of 5 to 50 mol% in the usual manner in the presence of a suitable polymerization initiator. Cationic polysaccharides and monomer mixtures are
It is used in the range of 40 to 90% by weight, the latter 10 to 60% by weight.

The second papermaking additive of the present invention is obtained by reacting (meth) acrylamide in an aqueous solution containing the above-mentioned cationic polysaccharide in the presence of a suitable polymerization initiator in the usual manner. It can be produced by hydrolyzing 5 to 50% by mole of an amide group with an alkali to modify it to a carboxyl group. In this case, the cationic polysaccharide and (meth) acrylamide used for the reaction are It is used in the range of 40 to 90% by weight of both, and the latter in the range of 10 to 60% by weight.

Examples of the polymerization initiator include peroxides such as hydrogen peroxide, ammonium persulfate, potassium peroxide, and ammonium hydroperoxide, or any redox initiator composed of a combination of these peroxides and a reducing agent. ,
A water-soluble azo initiator such as 2'-azobis (aminopropane) hydrochloride can be used. As the alkali for hydrolyzing the amide group, for example, sodium hydroxide, potassium hydroxide and the like can be used, and the hydrolysis temperature is suitably from 60 to 80 ° C. After the hydrolysis, an acidic substance such as hydrochloric acid, sulfuric acid or nitric acid is added to adjust the pH of the solution to 7.
It is customary to:

In any of the papermaking additives, when the amount of the cationic polysaccharide to be subjected to the reaction exceeds the upper limit of the above range, an additive having a sufficient paper strength enhancing effect cannot be obtained. Conversely, when the value falls below the lower limit of the above range, the amount of the acrylic monomer relatively increases, so that the additive cannot increase the tear strength, but rather decreases the tear strength. Invite. Further, in the first papermaking additive, the amount of the α, β-unsaturated carboxylic acid or its salt in the monomer mixture is changed to the amount of the amide group in the second papermaking additive. If the denaturation amount deviates from the above range, the paper strength enhancing effect of each additive becomes poor, resulting in a decrease in the tear strength of the paper.

The papermaking additive of the present invention is usually produced in the form of an aqueous dispersion having a solid content of about 10 to 20% by weight.
By adding an additive equivalent to 5%, preferably 0.1 to 3.0% to the raw pulp slurry, and making and drying the paper as usual, to obtain a paper having not only general strength but also excellent tear strength. Can be. The mechanism of action for obtaining such excellent results is not always fully understood at present. However, the graft polymer of the present invention is strongly adsorbed on the pulp fiber due to the balance between the cationic group of the cationic polysaccharide and the anionic group of the α, β-unsaturated carboxylic acid, and further, the hydroxyl group or (meta) It is presumed that the amide group of acrylamide forms a hydrogen bond with the hydroxyl group of the pulp fiber, so that strong adhesive strength can be obtained as a whole.

Hereinafter, preparation examples of the papermaking additive according to the present invention and examples of papermaking using the additive will be described, but these do not limit the technical scope of the present invention.

Preparation Example 1 190 g of a 26.8% aqueous cationic capioca starch (0.42% nitrogen content) aqueous solution cooked at 90-100 ° C, 25.5 g of 40% acrylamide, 3.25% of 80% acrylic acid
g, 90 g of water is adjusted to pH 4 using 10% potassium hydroxide solution. Next, at 50 ° C, 2% ammonium persulfate (APS)
2 ml of an aqueous solution and 2 ml of a 2% aqueous solution of sodium bisulfite (SBS) were added, and reacted at a temperature of 60 to 70 ° C. for 3 hours. After a while
101 g of additional water was added to obtain a graft polymer shown in Table 1.

Preparation Example 2 Cationic Capioca Starch with a Concentration of 26.8% (N.O.
42%) Aqueous solution 190g, 40% concentration acrylamide 43.8g, 8
5.5 g of 0% concentration acrylic acid, 120 g of water, 2 ml of 2% APS, 2%
Polymerization was carried out in the same manner as in Preparation Example 1 except that 2 ml of SBS and 112 g of additional water were used to obtain a graft polymer shown in Table 1.

Preparation Example 3 Cationic Capioca Starch with a Concentration of 26.8% (N.O.
42%) aqueous solution 105g, 40% concentration acrylamide 55.5g, 8
7g of 0% acrylic acid, 100g of water, 2.8ml of 2% APS, 2%
Polymerization was carried out in the same manner as in Preparation Example 1 except that 2.8 ml of SBS and 85 g of additional water were used, to obtain a graft polymer shown in Table 1.

Preparation Example 5 Cationic Capioca Starch with a Concentration of 26.8% (N.O.
42%) aqueous solution 190g, 40% concentration acrylamide 48.8g, 8
2.75 g of 0% concentration acrylic acid, 130 g of water, 2 ml of 2% APS, 2
Polymerization was carried out in the same manner as in Preparation Example 1 except that 2 ml of% SBS and 105 g of additional water were used to obtain a graft polymer shown in Table 1.

Preparation Example 6 Cationic Capioca Starch with a Concentration of 26.8% (N.O.
42%) Aqueous solution 190g, 40% concentration acrylamide 38g, 80
Acrylic acid at a concentration of 8.25 g, water 120 g, 2% APS 2 ml, 2%
Polymerization was carried out in the same manner as in Preparation Example 1 except that 2 ml of SBS and 106 g of additional water were used to obtain a graft polymer shown in Table 1.

Preparation Example 7 Cationic Capioca Starch with a Concentration of 26.8% (N.O.
42%) Aqueous solution 190g, 40% acrylamide 27g, 80
% Acrylic acid 13.7 g, water 120 g, 2% APS 2.4 ml,
Polymerization was carried out in the same manner as in Preparation Example 1 except that 2.4 ml of% SBS and 114 g of additional water were used to obtain a graft polymer shown in Table 1.

Preparation Example 8 Cationic potato starch with a concentration of 26.8% (nitrogen content 0.42
%) Aqueous solution 190g, 40% concentration acrylamide 43.8g, 80
5.5% acrylic acid, water 120g, 2% APS 2ml, 2% S
Polymerization was carried out in the same manner as in Preparation Example 1 except that 2 ml of BS and 117 g of additional water were used to obtain a graft polymer shown in Table 1.

Preparation Example 9 83.1 g of an aqueous solution of cationic capioca starch (nitrogen content 0.42%) having a concentration of 26.8% cooked at 90-100 ° C, 40%
A mixture of 24 g of acrylamide and 51.4 g of water at a concentration of 10%
Adjust to pH 7 with sulfuric acid solution. Next, 2% A at 50 ° C
1 ml of PS and 1 ml of 2% SBS were added and reacted at a temperature of 60 to 70 ° C. for 3 hours. Then, add an additional 40 g of water and add 1 more
Add 7.8 g of 0% aqueous potassium hydroxide solution and hydrolyze at 70-80 ° C for 2 hours to modify 10 mol% of amide groups to carboxyl groups, then adjust the pH of the solution to 5 using 10% sulfuric acid solution. Thus, a graft polymer shown in Table 1 was obtained.

Preparation Example 10 A graft polymer shown in Table 1 was obtained in the same manner as in Preparation Example 9, except that the amount of the 10% aqueous potassium hydroxide solution was increased to 15.7 g and the hydrolysis rate was set to 20 mol%.

Preparation Example 11 A graft polymer shown in Table 1 was obtained in the same manner as in Preparation Example 9, except that the amount of the 10% aqueous potassium hydroxide solution was increased to 30.3 g and the hydrolysis rate was set to 40 mol%.

Preparation Example 12 190 g of a 26.8% cationic corn starch (0.38% nitrogen content) aqueous solution cooked at 90-100 ° C., 40
% Acrylamide 43.8g, 80% acrylic acid
A mixture of 5.5 g and 120 g of water is prepared using a 10% potassium hydroxide solution.
Adjust to pH4. Next, at a temperature of 50 ° C, 2 ml of 2% APS and 2% SB
2 ml of S was added and reacted at a temperature of 60 to 70 ° C. for 3 hours. Thereafter, 112 g of additional water was added to obtain a graft polymer shown in Table 1.

Preparation Example 13 Cationic guar gum aqueous solution having a concentration of 26.8% (nitrogen content
0.33%) 190g, 40% concentration acrylamide 43.8g, 80%
Acrylic acid concentration 5.5g, water 12g, 2% APS 3ml, 2% SBS
Polymerization was carried out in the same manner as in Preparation Example 1 except that 3 ml and 112 g of additional water were used to obtain a graft polymer shown in Table 1.

Preparation Example 14 Cationic Capioca Starch with a Concentration of 26.8% (N.O.
42%) aqueous solution 190g, 40% concentration acrylamide 5.3g, 80
% Acrylic acid 0.66g, water 68g, 2% APS 2ml, 2% S
Polymerization was carried out in the same manner as in Preparation Example 1 except that 2 ml of BS and 86 g of additional water were used to obtain a graft polymer shown in Table 1.

Preparation Example 15 26.7% Concentration of Cationic Starch Aqueous Solution (Nitrogen Content 0.42
%) 34 g, 401.3% acrylamide 161.3 g, 80% concentration acrylic acid 20.5 g, water 248 g, 2% APS 6 ml, 2% SBS 6 m
l, Polymerization was carried out in the same manner as in Preparation Example 1 except that 150 g of additional water was used, and a graft polymer shown in Table 1 was obtained.

Preparation Example 16 Cationic starch aqueous solution having a concentration of 26.8% (nitrogen content 0.42%)
%) 190 g, 40% concentration acrylamide 16.3 g, 80% concentration acrylic acid 19.3 g, water 120 g, 2% APS 3.2 ml, 2% SBS
Polymerization was carried out in the same manner as in Preparation Example 1 except that 3.2 ml and 109 g of additional water were used, to obtain a graft polymer shown in Table 1.

Preparation Example 17 190 g of 26.8% aqueous oxidized starch solution (Amicoat NO800 manufactured by Matsutani Chemical Co., Ltd.), 43.8% acrylamide 43.8%
g, 5.5 g of 80% strength acrylic acid, 120 g of water, 2 ml of 2% APS,
Polymerization was carried out in the same manner as in Preparation Example 1 except that 2 ml of 2% SBS and 117 g of additional water were used to obtain a graft polymer shown in Table 1.

Preparation Example 18 Cationic tapioca starch having a concentration of 26.8% (nitrogen content: 0.1%)
42%) aqueous solution 67.2g, 40% concentration acrylamide 94.4g,
5.31 g of 80% acrylic acid, 130 g of water, 4.7 ml of 2% APS,
Preparation Example 1 except that 4.7 ml of 2% SBS and 103 g of additional water were used
Polymerization was carried out in the same manner as in Example 1 to obtain a graft polymer shown in Table 1.

Preparation Example 19 Cationic tapioca starch having a concentration of 26.8% (nitrogen content: 0.1%)
42%) aqueous solution 44.8g, 40% concentration acrylamide 95.7g,
80% strength acrylic acid 12.1 g, water 130 g, 2% APS 5.4 ml,
Preparation Example 1 except that 5.4 ml of 2% SBS and 136 g of additional water were used.
Polymerization was carried out in the same manner as in Example 1 to obtain a polymer shown in Table 1.

Examples 1 to 13 Copal S-40 (synthetic sizing agent, concentration 40%, Hoshiko Chemical Co., Ltd.) was added to a pulp slurry of L-UKP (CSF 570 ml).
Was added in an amount of 0.2% based on the dry weight of pulp, and the sulfuric acid band was also added in an amount of 2% based on the dry weight of pulp. % And mixed well. Each of the prepared pulp slurries was made into a paper having a basis weight of 80 g / m ² using a TAPPI standard sheet machine, and 5 kg at 3.5 kg / m ² .
After pressing at 105 ° C for 2 minutes, drying was performed at 105 ° C for 2 minutes.

Each of the handmade papers thus obtained was conditioned and subjected to a paper quality test to obtain the results shown in Table 2.

Comparative Examples 1 to 6 and Reference Examples 1 to 4 Instead of the graft polymers used in Examples 1 to 11, the graft polymers obtained in Preparation Examples 14 to 19 were used, or cationic tapioca starch (containing nitrogen) Amount 0.42%), Star Gum A-15 (anionic polyacrylamide, concentration 15%)
Product, Seiko Chemical Co., Ltd.) Urea formalin resin, concentration
Hand-made paper was obtained by performing the same operation as in the above example except that 38% was used. A paper quality test similar to that of the examples was performed on these handmade papers. The test results are also shown in Table 2.

 The paper quality test method is as follows.

Breaking length (Km): JIS P-8113 Tear strength: JIS P-8116 In-layer strength: “Paper pulp types and test methods” edited by Japan Pulp and Paper Technology Association
(Revised fourth edition) Page 248, based on paper peel strength, "Measurement method using tensile strength tester".

[Effect of the Invention] A papermaking additive containing the graft polymer of the present invention as an active ingredient is added to a raw pulp slurry for papermaking, and is then made and dried in a conventional manner. Paper having excellent tear strength as well as general strengths such as And the paper obtained by using the additive of the present invention also has a feature that it can be easily disintegrated.

Claims (9)

(57) [Claims] (1) In an aqueous solution containing 40 to 90 parts by weight of a cationic polysaccharide, (A) 50 to 95 mol% of (meth) acrylamide (B) α, β-unsaturated carboxylic acid and / or Its salt 5
A papermaking additive comprising, as an active ingredient, a graft polymer obtained by polymerizing 10 to 60 parts by weight of a monomer mixture consisting of 50 mol%. 2. The papermaking additive according to claim 1, wherein the cationic polysaccharide is a cationic starch. 3. The papermaking additive according to claim 2, wherein the cationic starch is a cationic tapioca starch. 4. The papermaking additive according to claim 1, wherein the α, β-unsaturated carboxylic acid is (meth) acrylic acid. 5. In an aqueous solution containing 40 to 90 parts by weight of a cationic polysaccharide, 10 to 60 parts by weight of (meth) acrylamide is polymerized, and 5 to 50 mol% of the amide group is converted to an alkali. A papermaking additive comprising a modified graft polymer obtained by modifying a carboxyl group with an active ingredient. 6. The papermaking additive according to claim 5, wherein the cationic polysaccharide is a cationic starch. 7. The papermaking additive according to claim 6, wherein the cationic starch is a cationic tapioca starch. 8. An aqueous solution containing 40 to 90 parts by weight of a cationic polysaccharide, (A) 50 to 95 mol% of (meth) acrylamide (B) α, β-unsaturated carboxylic acid and / or Its salt 5
A papermaking method characterized by adding a graft polymer obtained by polymerizing 10 to 60 parts by weight of a monomer mixture consisting of 50 mol% to a raw pulp slurry for papermaking, papermaking and drying. 9. In an aqueous solution containing 40 to 90 parts by weight of a cationic polysaccharide, 10 to 60 parts by weight of (meth) acrylamide is polymerized, and 5 to 50 mol% of the amide group is converted to an alkali. A papermaking method comprising modifying a carboxyl group in the above step, adding the resulting modified graft polymer to a raw pulp slurry for papermaking, papermaking and drying.