JP2000027092A - Neutralized paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a neutralized paper of high quality with increased yield of the paper-making chemicals by admixing carboxymethylcellulose and the like and chitosan to the pulp slurry to which a sizing agent and a paper- strengthening agent are internally mixed. SOLUTION: A neutral sizing agent, for example, alkyl ketene dimer or an alkenyl succinic anhydride and a paper-strengthening agent, for example, cationically modified starch, before 0.01-5.0 wt.%, preferably 0.05-3.0 wt.% of carboxymethylcellulose and/or carboxyethylcellulose and 0.01-2.0 wt.%, preferably 0.01-1.0 wt.% of chitosan based on the dry weight of pulp fibers are internally added and fixed to the pulp slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutral paper which improves the yield of papermaking chemicals such as a sizing agent and a paper strength agent, and is particularly excellent in sizing degree and strength.

[0002]

2. Description of the Related Art Conventionally, rosin sizing agents, emulsion sizing agents,
Papermaking sizing agents such as alkenyl succinate, alkyl ketene dimer and alkenyl succinic anhydride are added to pulp slurry and used. One of the major problems with these sizing agents is poor yield of sizing agents, especially in neutral papermaking. The fixing mechanism of the sizing agent to the stock varies depending on the type of the sizing agent.In particular, alkyl ketene dimer, alkenyl succinic anhydride, etc. used in neutral papermaking have a low yield and are unstable. There is a problem that the size of paper to be used is low.
Therefore, various cationic chemicals such as cation-modified starch, polyamide / epichlorohydrin resin, polyethyleneimine resin, polyacrylamide resin, and polyamide resin are added for the purpose of improving the yield of the sizing agent and the strength of the paper. . However, there are problems that the effect obtained by such treatment is not sufficient, the effect is reduced by other added chemicals or fillers, and the quality is not stable.

Further, together with the internal sizing agent, modified starch, polyacrylamide, polyamide, polyamide-epichlorohydrin resin, melamine-formaldehyde resin, urea-formaldehyde resin, etc. are used as internal paper strength enhancers for the purpose of increasing paper strength. It is used. However, even when used alone, they have various drawbacks such as a low yield, a small paper-strengthening effect, and a poor formation, and cannot be sufficiently satisfied in terms of operation and paper quality. Paper-pulp and paper technical cooperation paper issued by Japan Pulp and Paper Technology Association, Vol.
45-249 (1991) and 46: 986-
Page 996 (1992) describes a method in which anionic polyacrylamide is used in combination with Mannich-modified or Hoffman-modified cationic polyacrylamide, or a method in which these are mixed and added. However, these combined or mixed formulations can slightly improve the yield and paper strength, but the effect of the amount of the sulfate band added and the effect of other chemical auxiliary agents added are large, and the effects are satisfactory. We have not reached the level where we can do it. Carboxymethyl cellulose (hereinafter referred to as CMC)
It has long been known that cellulose derivatives such as carboxyethylcellulose (hereinafter referred to as CEC) and the like have an effect of enhancing the strength of paper. Further, if a sulfuric acid band is not added and used, it does not remain on the paper and has no effect. For example, the internal paper strength enhancer is hardly used at present.

[0004] As means for solving the problems of size and paper strength, Japanese Patent Application No. 9-43622 discloses a pulp fiber slurry obtained by adding CMC and / or CEC to a pulp slurry and then adding a mineral acid. Discloses a method of adjusting the pH of the mixture to a range of 2 to 6, converting CMC and / or CEC into an acid form, adsorbing the pulp, and making paper. However, in this method, it is necessary to use a low substitution CMC having a substitution degree in the range of 0.3 to 0.6,
In particular, there is a problem that a sufficient effect cannot be obtained in papermaking in a neutral to alkaline region.

On the other hand, chitosan is obtained by deacetylating chitin contained in shrimp and crab shells by high-concentration hot alkali treatment, and is known to have an effect of enhancing paper strength when added to pulp slurry. Have been. JP-A-60-1
Japanese Patent No. 34097 discloses that chitosan is added at 0.0 during the paper making process.
It is disclosed that drainage and yield can be improved by adding 1 to 0.1%. JP-A-2-20089
No. 4 discloses that after addition of chitosan to a pulp slurry, alkali is added, and chitosan is precipitated to form a paper, thereby improving the yield and the water resistance of the obtained paper web. Japanese Patent Application Laid-Open No. 3-16787 discloses that after adding chitosan to bast fiber and leaf fiber and then adding a water-soluble anionic polymer to paper-making, a paper sheet having excellent surface strength and printability can be obtained. Is disclosed. Further, JP-A-6-280187 discloses a papermaking method in which chitosan, a water-soluble polymer, and an acid salt that renders chitosan insoluble are added to an aqueous suspension containing cellulose fibers and a modifier to make chitosan insoluble. It is disclosed that the yield of the modifier can be improved and the antibacterial property can be obtained. However, even if these methods are used, sufficient yield improving effect and paper strength enhancing effect cannot be obtained.
Chitosan is rarely used. As described above, there is a need for a neutral papermaking that improves the yield of papermaking chemicals such as a sizing agent and a paper strength enhancer and is excellent in sizing properties and paper strength.

[0006]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the prior art and improves the yield of paper chemicals such as a sizing agent and a paper-strengthening agent. To provide neutral paper.

[0007]

In view of this background, the present inventors have found a method for improving the yield of papermaking chemicals such as a sizing agent and a paper strength agent in neutral papermaking and improving the quality of paper. We worked diligently to study. As a result, in the pulp slurry, paper chemicals such as
When MC or CEC is mixed with chitosan, paper chemicals,
CMC or CEC and chitosan form a complex, and the complex adsorbs to the pulp, thereby improving the yield of papermaking chemicals.
As a result, they have found that a neutral paper having excellent paper strength and rigidity, particularly excellent sizing properties, can be obtained, and have completed the present invention. We believe that CMC or CEC in pulp fiber slurries
As a result of studying the behavior of chitosan and chitosan in detail, CMC and / or
Alternatively, it has been found that when CEC and chitosan are mixed, carboxy ions of CMC and CEC react with ammonium ions of chitosan to form a salt, become insoluble in water, and adsorb on the surface of pulp fibers in the slurry. Also, CM
When forming C and / or CEC, chitosan complex,
When papermaking chemicals such as a neutral sizing agent and a paper strength enhancer are present, these papermaking chemicals are incorporated into the composite, the yield is improved, and the paper obtained by papermaking is the conventional paper strength enhancer described above. It has been found that the paper strength and especially the sizing properties are improved as compared with the paper obtained by using the wet strength enhancer alone. That is, the first aspect of the present invention is a neutral paper characterized by fixing a neutral internal sizing agent with carboxymethyl cellulose and / or carboxyethyl cellulose and chitosan. A second aspect of the present invention is the neutral paper according to the first aspect, wherein the neutral internal sizing agent is an alkyl ketene dimer or an alkenyl succinic anhydride. A third aspect of the present invention is the neutral paper according to the first or second aspect, further comprising an internal paper strength enhancer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION CMC or CEC used in the present invention is produced by reacting a cellulose raw material such as wood pulp, cotton pulp or linter pulp with monochloroacetic acid, chloropropionic acid or the like, and by a known production method. What is obtained by using is used. Most of the commercial products of CMC are sodium or potassium carboxylate, or more precisely, sodium carboxymethylcellulose or potassium carboxymethylcellulose.
And CEC salts, or simply CMC and CEC. In the present invention, sodium salt of CMC and CEC,
A potassium salt or an ammonium salt is used, but a sodium salt of CMC is preferred because it is inexpensive, easily available, and highly effective.

The CMC and CEC used in the present invention are:
Although various polymerization degrees can be used, the viscosity of a 1% aqueous solution is 5 to 16,000 mPa · s (0.1N-Na
Cl solvent, 25 ° C, B-type viscometer), average polymerization degree is 100
-4,500, and an average molecular weight in the range of 20,000-1,000,000. In addition, CMC and CEC used in the present invention
Can be used in various degrees of substitution.
A commercially available product in the range of 1.2 is used, but if it is water-soluble and can form a complex with chitosan, a product having a low degree of substitution or a high degree of substitution that is not available in a commercially available product may be appropriately synthesized. Can be used. Further, the respective ratios when the CMC and CEC salts are mixed and used are not particularly limited, and can be mixed at an arbitrary ratio.

The chitosan used in the present invention is generally prepared by treating the shell of crustaceans such as crabs and shrimps with an acid and an alkali to elute calcium salts and proteins, and further adding a hot concentrated alkaline solution. It is obtained by deacetylation by treatment. There is no particular limitation on the raw materials and the production method. The degree of deacetylation of commercially available chitosan produced by known methods is generally in the range of 60-100%,
If the degree of deacetylation is less than 60%, the solubility in acid is deteriorated, which is not preferable for use in the present invention.

The chitosan used in the present invention is used in the state of being dissolved in an acidic aqueous solution of acetic acid, formic acid or the like. Therefore, to be precise, chitosan acetate or chitosan formate is used. The description of formate is omitted, and it is simply expressed as chitosan. The dissolved acid of chitosan is not particularly limited as long as it has good solubility, for example, acetic acid,
Formic acid, lactic acid, oxalic acid, adipic acid, sulfamic acid,
Hydrochloric acid, L-ascorbic acid and the like can be used, but acetic acid, formic acid, lactic acid, and hydrochloric acid are preferable from the viewpoint of storage stability and economy. The molecular weight of chitosan used in the present invention is 10,000 to 100.
10,000, preferably 20,000 to 500,000. Molecular weight 100
If it exceeds 10,000, the solubility in acid is deteriorated, and the viscosity of the obtained chitosan becomes extremely large, which is not preferable in terms of work. If the molecular weight is less than 10,000, CM
The complex with C and CEC becomes brittle and a sufficient effect cannot be obtained.

The amount of CMC, CEC and chitosan used in the present invention depends on the degree of polymerization and substitution of CMC and CEC, the degree of deacetylation and degree of polymerization of chitosan, the type of paper, the application and the required performance. CMC and CEC may be 0.01 to 5.0% by weight and chitosan 0.01 to 2.0% by weight, preferably CMC and CE, based on the dry weight of the pulp fiber.
C is 0.05-3.0% by weight, chitosan is 0.01-
1.0% by weight, more preferably 0.05 to 1.
0% by weight, and chitosan is 0.05 to 0.5% by weight.
The greater the amount of these chemicals used, the more pronounced the effect. However, since they are expensive, their upper limits are appropriately selected and determined for paper applications and economic reasons.

The pulp fibers to which the method of the present invention is applied are not particularly limited, and can be applied to commonly used known paper pulp, and include chemical pulp such as sulfite pulp, kraft pulp and soda pulp, semi-chemical pulp, and the like. Wood pulp such as mechanical pulp, waste paper pulp, or non-wood pulp such as kozo, honey or hemp may be used, and either unbleached pulp or bleached pulp may be used.

In the present invention, CMC and / or CEC are added to the pulp slurry and sufficiently stirred and mixed. At this time, in order to impart desired sizing and strength to the paper web, a neutral sizing agent or paper is used. When a papermaking chemical such as a force enhancer is added, and then chitosan is added, the yield of the papermaking chemical such as a sizing agent or a paper strength enhancer is improved, and excellent sizing and strength can be obtained even with a small amount of addition. Also, by changing the order of addition,
Chitosan, papermaking chemicals, CMC and / or CEC may be added in that order.

As the sizing agent used in the present invention, alkyl ketene dimer, alkenyl succinic anhydride, and synthetic cationic sizing agent, which are neutral paper sizing agents, can be used. In this case, the amount of the individual papermaking chemicals such as a paper strength enhancer and a sizing agent varies depending on the performance required for the paper web, but is generally in the range of 0.01 to 0.01% based on the absolute dry weight of the pulp fiber.
1.0 wt%, preferably selected from the range of 0.05 to 0.5 wt%. Further, as the paper strength enhancer used in the present invention, for example, cationic modified starch, anionic starch, amphoteric starch, polyamide / epichlorohydrin resin, polyethyleneimine resin, polyacrylamide resin, cationic or anionic such as polyamide resin, And amphoteric paper strength enhancers. At this time, if necessary
In order to improve the whiteness, opacity and printability of paper,
Although calcium carbonate is added, a known papermaking filler such as titanium oxide, hydrated silica, talc, clay, and kaolin may be added. The use of the present invention is effective not only in improving papermaking chemicals such as paper strength enhancers and sizing agents, but also in improving the yield of fillers. Under conditions in which the papermaking raw material is sufficiently uniformly stirred, a complex is formed in a short time when CMC and / or CEC is mixed with chitosan. Taking into account the actual operating conditions, the formation of the composite is carried out during the transfer or storage of the stock. For example, the addition is carried out at the suction port of a fan pump.

The salts of CMC and CEC in the aqueous solution exist as carboxylate ions, that is, as polyanions. On the other hand, when chitosan is dissolved in an acid, a hydrogen ion is added to an amino group and exists as a polycation having an ammonium ion. Therefore, when mixed, a complex is formed with CMC which is a polyanion. At this time, if a cationic, amphoteric or anionic paper chemical is present, the cationic or amphoteric chemical has a high affinity with CMC or CEC, and the anionic or amphoteric chemical has a high affinity with chitosan. It is considered that the yield is improved. It is important to control the addition ratio of CMC, CEC and chitosan. When CMC, CEC and chitosan are ionically equivalent, they produce the strongest complex. Appropriate addition ratios to produce sufficient complex are CMC, CE
The degree of substitution and molecular weight of C, the degree of deacetylation and molecular weight of chitosan, the amount of added papermaking chemicals and the amount of ions, the pH of the papermaking system, and the like vary depending on the ion amount ratio, and CMC and / or CEC: chitosan are 1:10 A ratio range of 10: 1 is preferred.
The pH of the papermaking system can be favorably used in so-called neutral papermaking, in which the pH of the stock after all the chemicals have been added is 5.5 to 9.0.

The papermaking raw material thus prepared is formed in a usual papermaking process, and is subjected to an externally added size press or a calendering treatment as necessary. The paper machine used at this time is
Examples include paper machines such as long nets, round nets and short nets, but are not particularly limited. In high-speed paper machines such as hybrid formers and gap formers, it is known that the yield of chemicals generally decreases due to enhanced dewatering, and the present invention is particularly effective. Further, the paper web thus obtained can be used as it is for printing, writing paper, etc., and, on the paper web, known and publicly-known coating equipment, for example, a blade coater, an air knife coater, a roll coater, With a coating apparatus such as a reverse roll coater, a bar coater, a curtain coater, a die rod coater, a gravure coater, a chaplex coater, a size press coater, etc., a coating layer can be provided on one or both sides to be used as a coated paper. .

[0018]

As described above, the improvement in the sizing and strength of the paper in the present invention is attributable to the use of papermaking chemicals such as a sizing agent and a paper-strengthening agent when forming a composite of CMC and / or CEC and chitosan. It is taken in and adsorbed on the pulp to improve the yield.

【Example】

Hereinafter, the present invention will be described in more detail with reference to Examples, but of course, the present invention is not limited to these. In the following Examples and Comparative Examples,%
All are by weight%, and the amount of the additive added to the pulp slurry is shown by weight% based on the weight of the absolutely dried pulp.

Example 1 Hardwood bleached kraft pulp was prepared with a laboratory Niagara beater to a freeness of 480 ml CSF (Canadian standard freeness). 3% pulp slurry with three ones
While stirring at a speed of 450 rpm with a motor, the CMC was dissolved (1%
Solution viscosity 3200 mPa · s, degree of substitution 1.0, trade name:
Cellogen EP, Daiichi Kogyo Seiyaku Co., Ltd.) 0.2%, cationized starch (trade name: Kate F, manufactured by National Starch)
0.5%, 0.3% of sulfuric acid band, 0.05% of neutral papermaking sizing agent (trade name: Sizepine K903, manufactured by Arakawa Chemical Industry Co., Ltd.) containing alkyl ketene dimer, polyamide / epichlorohydrin resin 0.1% of paper strength enhancer (trade name: WS570, manufactured by PMC Japan), 10% of light calcium carbonate as a filler for paper making, and a papermaking retention improver containing polyacrylamide (trade name: Himoloc NR11L, 0.01% were added in this order, and after stirring was continued for 1 minute after completion of the addition, while stirring was further continued, a 0.5% aqueous solution of chitosan acetate (0.5% Solution viscosity 390 mPa
S, degree of deacetylation 87%, trade name: Koyo Chitosan SK-400) added to the pulp weight 0.1%,
Stirring was continued for 2 minutes. The pH of this stock was measured to be 7.2. Using this pulp stock, a TAPPI standard square sheet machine has a basis weight of 60 g / m 2.
Was dried at 120 ° C. for 3 minutes in a drum dryer. After the hand-made sheet was conditioned at a temperature of 20 ° C. and a relative humidity of 65% for 24 hours, the tensile strength, the ash content, and the degree of Stekigt sizing of the paper were evaluated by the following test methods to evaluate the quality.

Test method (1) Viscosity of CMC solution This is a value obtained by using a 0.1N-NaCl aqueous solution as a solvent and measuring at 25 ° C. with a B-type viscometer at 12 rpm. (2) Dissolution and viscosity of chitosan 1 g of chitosan was added to 199 mL of water, and the mixture was stirred at a speed of 100 rpm for 1 hour with a three-one motor. Then, 0.4 g of acetic acid was added, and stirring was continued for 1 hour. Dissolved. This chitosan acetate aqueous solution is heated at 25 ° C.
, The value obtained by measuring with a B-type viscometer at 12 rpm was defined as the viscosity. (3) Ash content The ash content was measured in accordance with JIS P8128. (4) Tensile strength Measured according to TAPPI T205, and the breaking length (k
m). (5) Degree of Sekihito size Measured according to JIS P8122.

Example 2 Example 1 was repeated except that the addition ratio of CMC was 0.7%.
A hand-made sheet was prepared in the same manner as described above, and the obtained paper was tested to evaluate the quality.

Example 3 An alkenyl succinic anhydride (trade name: Fibran-81, manufactured by Mitsubishi Petroleum Co., Ltd.) was used in place of the alkyl ketene dimer at an addition rate of CMC of 0.05% and chitosan at 0.4%. Was prepared in the same manner as in Example 1 except that) was emulsified into starch, and the obtained paper was tested to evaluate the quality.

Example 4 The procedure of Example 1 was repeated except that a 1% solution viscosity of 130 mPa · s, a degree of substitution of 0.6, and a trade name of Cellogen WS-CN, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. were used as CMC. A hand-made sheet was prepared, and the obtained paper was tested to evaluate the quality.

Example 5 Instead of CMC, CEC (1% solution viscosity 800 mPa ·
s, the degree of substitution was 0.8), except that a hand-made sheet was prepared in the same manner as in Example 1, and the obtained paper was tested to evaluate the quality.

Example 6 Example 1 was repeated except that a low-molecular-weight chitosan (trade name: Koyo Chitosan SK-10, Koyo Chemical) having a viscosity of 15 mPa · s of a 1% aqueous solution of chitosan acetate was used as chitosan. Prepare a handmade sheet in the same way,
The resulting paper was tested and evaluated for quality.

Comparative Example 1 A hand-made sheet was prepared in the same manner as in Example 1 except that the addition of CMC and chitosan was not performed, and the obtained paper was tested to evaluate the quality.

Comparative Example 2 A hand-made sheet was prepared in the same manner as in Comparative Example 1 except that the addition ratio of calcium carbonate was changed to 16%, and the obtained paper was tested to evaluate the quality.

Comparative Example 3 A handmade sheet was prepared in the same manner as in Example 1 except that chitosan was not added, and the obtained paper was tested to evaluate the quality.

Comparative Example 4 A handmade sheet was prepared in the same manner as in Example 1 except that no CMC was added, and the obtained paper was tested to evaluate the quality.

Comparative Example 5 Example 1 was repeated except that the addition rate of the retention aid was increased to 0.05% without adding CMC and chitosan.
A hand-made sheet was prepared in the same manner as described above, and the obtained paper was tested to evaluate the quality.

Comparative Example 6 A hand-made sheet was prepared in the same manner as in Example 3 except that the addition of CMC and chitosan was not performed, and the obtained paper was tested to evaluate the quality.

[0033]

[Table 1]

As is clear from the table, according to the present invention, the degree of Stekigto sizing is greatly improved, and a paper web having excellent sizing properties can be obtained. Further, the paper strength is improved despite the fact that the filler yield is improved and the ash content in the paper is increased. This is considered to be due to the effect of improving the yield of the sizing agent or the paper strength agent. Although the effects are the same between CMC and CEC (Examples 1 and 5), CMC is practically preferable in view of the fact that CMC is lower in price. Also, C
The effect of the substitution degree and viscosity of MC and the viscosity of chitosan is small,
In each case, excellent paper strength and sizing improvement were observed.
(Examples 1, 4 to 6).

[0035]

Industrial Applicability The present invention improves the yield of papermaking chemicals such as a sizing agent and a paper strength enhancer added to pulp slurry in neutral papermaking, thereby providing a high-quality paper having excellent size and strength. This has the effect of providing neutral paper.

Claims (3)

[Claims] 1. Neutral paper characterized by fixing a neutral internal sizing agent with carboxymethylcellulose and / or carboxyethylcellulose and chitosan. 2. The neutral paper according to claim 1, wherein the neutral internal sizing agent is an alkyl ketene dimer or an alkenyl succinic anhydride. 3. The neutral paper according to claim 1, further comprising an internal paper strength enhancer.