JPH09291490A - Pulp, paper and coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a coated paper for printing, imparted with strength, improved in chemical yield, excellent in gloss and having good blister resistance. SOLUTION: Salts of CMC and/or CEC which is a cellulose derivative are added to a pulp slurry as paper strengthening agents, and subsequently a mineral acid is added to the slurry to adjust the pH to 2-6. The CMC and/or CEC is converted into acid form to deposit on the surface of fibers, and subsequently paper is formed and dried. The addition ratio of the salts of the CMC and/or CEC is 0.01-5.0wt.% based on the absolute dry weight of the pulp fibers. After the adjustment of pH of the pulp fiber slurry to 2-6, a paper-making chemical and optionally a loading material are added and paper is formed at pH5-9. When the degree of substitution of the salts of CMC and/or CEC is 0.3-0.6, the pH of the slurry of the pulp fibers is adjusted to 3.5-5.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper in which the yield of fillers and paper-making chemicals is improved and the strength of the paper is remarkably increased, and a high-speed production method of the paper. The present invention also relates to a coated paper for printing having excellent gloss and a method for producing the coated paper at a high speed.
Further, the present invention relates to a coated paper for printing having excellent blister resistance and a high-speed production method for the coated paper.

[0002]

2. Description of the Related Art Conventionally, modified starch, polyacrylamide, polyamide, polyamide-epichlorohydrin resin, melamine-formaldehyde resin, urea-formaldehyde resin, etc. have been added to pulp fibers as a papermaking paper strength enhancer for the purpose of increasing the strength of paper. , Used as paper stock. However, these have various drawbacks such as a low paper-strengthening effect, a high price, or poor yield depending on the papermaking conditions, which does not give a sufficient strength-developing effect to the paper. Is not completely satisfactory.

Paper and Paper Cooperative Paper issued by Japan Pulp and Paper Technology Association, No. 4
Vol. 5, pp. 245-249 and Vol. 46, pp. 986-996 disclose a method of using anionic polyacrylamide and Mannich-modified or Hoffmann-modified cationic polyacrylamide in combination, or a method of mixing and adding them. There is. However, comparing these combined or mixed formulations with the method in which anionic polyacrylamide or cationic polyacrylamide is added alone, the strength-enhancing effect is slightly high, but it has reached a satisfactory level. However, the effect is greatly affected by the amount of the sulfuric acid band added, and there is a problem in that the effect is not constant even with other chemical auxiliaries added and used together.

Carboxymethyl cellulose (hereinafter CMC
It has been known for a long time that a cellulose derivative such as carboxy) or carboxyethyl cellulose (hereinafter referred to as CEC) also has the action of increasing the strength of paper. As an agent, there is a problem that the strength enhancing effect obtained is small, and it does not stay on the paper unless the sulfuric acid band is added and used together and the effect is not exhibited. However, the fact is that it is rarely used at present.

On the other hand, in papermaking, in addition to a paper strengthening agent, rosin sizing agent, emulsion sizing agent, alkenyl succinate, alkyl ketene dimer are used for the purpose of imparting water repellency, water resistance, sizing degree and the like to the paper. , A sizing agent for papermaking such as alkenyl succinic anhydride is added to the pulp fiber slurry and used as a paper stock. One of the major problems with these sizing agents is poor sizing agent yield. The mechanism of fixing the sizing agent to the paper stock differs depending on the type of the sizing agent, but in particular, the alkyl ketene dimer, alkenyl succinic anhydride, etc. used in neutral papermaking have poor yields and are unstable. There is a problem that the sizing degree of the paper to be used is low or it is not constant. Therefore, in order to improve the yield of the sizing agent and the strength of the paper, cationic modified starch, polyamide / epichlorohydrin resin, polyethyleneimine resin, polyacrylamide are used. Various cationic chemicals such as resin and polyamide resin are added. However, the effect still obtained is not sufficient, the chemical is expensive, or
There are problems that the effect may be reduced by other added chemicals and fillers, and that the quality may not be stable.

For the purpose of improving the whiteness, opacity or printability of the paper, known papermaking fillers such as calcium carbonate, titanium oxide, hydrous silica, talc, clay and kaolin are also added to the pulp fiber slurry as a paper stock. Used. When these fillers are used, poor yield is a big problem as in the case of the sizing agent. When the yield of the filler is low, white water stains occur, which in turn causes stains in the papermaking system, which increases the frequency with which the paper machine is stopped and repeated washings, which significantly impairs production efficiency. Along with this, problems such as paper quality deterioration occur. Therefore, in order to improve the yield of the filler, it is used by adding a filler yield improver such as polyacrylamide, polyamide, polyethyleneimine, etc. Even if these chemicals are used, the effect of improving the yield of the filler is low, and the effect is stable. There is a problem that the chemicals that are not used or expensive are used.

In recent years, the importance of printed matter as a medium for publication, advertisement, publicity, etc. has been re-recognized, and the demand for coated paper as a base thereof has been increasing. On the other hand, in order to visualize and color prints, the demand for quality of coated paper for printing, especially glossiness related to the appearance of prints, is increasing year by year. In order to meet such an increase in demand for paper, it is an essential requirement to increase the speed of the paper machine.

The revolution of the papermaking system, especially the wire part of the papermaking machine, has greatly contributed to the speeding up of the papermaking machine. That is, a top wire forming a loop is arranged above the latter half of the fourdrinier of a conventional fourdrinier paper machine (Fig. 1), and a twin wire papermaking method in which dehydration is performed on both the upper and lower sides of the machine.
A so-called on-top former or hybrid former paper machine (Fig. 2) has been put to practical use. However, even in the case of a hybrid former type paper machine, as the speed increases, jumping and disturbance of the stock material occur in the first half of the top wire, the so-called initial dehydration part, and the formation of the paper is extremely poor. There was a difficulty.

A gap former type paper machine (FIG. 3) was devised there. In the gap former type paper machine, pulp slurry is supplied from the inlet to the gap (wedge-shaped opening) formed by the top wire and the bottom wire, and the pulp slurry is sandwiched between two (upper and lower) wires from the beginning. Then, dehydration and paper layer formation are performed. For this reason, a uniform paper layer can be formed without inducing the disturbance of the raw material as in the case of the hybrid former type paper machine, and is highly evaluated.

However, in spite of such improvement of the papermaking machine, fine fibers, fillers and the like in the paper material are inevitably slipped off from the wire as the dehydrating capacity of the papermaking machine is strengthened, and the yield is deteriorated. Along with this, the yield of paper-making chemicals such as a sizing agent added to the stock suspension also becomes low, and the sizing property is not expressed, or extremely uneven size occurs. Conventionally, as a measure for improving the stock yield, it has been general to add a yield improving agent such as polyacrylamide, polyamide, or polyethyleneimine to the stock suspension. The action of these yield improvers is to suppress the detachment from the wire by aggregating the fine fibers in the stock or the filler, and although the yield improving effect is recognized by the addition of these, it is not a satisfactory effect. However, there is a problem that the drainage and the formation are rather deteriorated. In addition, the added chemicals are expensive.

The above-mentioned paper web is further coated with various starches, polyvinyl alcohol and the like in a size press or gate roll process to give the paper surface strength and sizing property, but the sizing property in the wire part is insufficient. In this case, uneven application of the applied chemicals will occur, and finally the base paper will have uneven size. When a coating layer is provided on the base paper having such a defect, there is a problem in that the coating layer has uneven penetration, so that sufficient printing gloss cannot be obtained as a coated paper for printing, and uneven gloss occurs.

As described above, as the papermaking speed increases, the quality such as the sizing degree or texture of the base paper becomes poor, and important printing gloss cannot be achieved or uneven gloss occurs on the coated paper for printing. Problems arise. Conventionally, it has been required to realize both high speed papermaking and high quality of coated paper for printing, but in papermaking of coated paper for printing, it is difficult to satisfy both of these two requirements. It has been said that there is.

On the other hand, when the base paper is produced by such a paper machine in which the dewatering ability of the paper machine is enhanced, fine fibers in the base paper are unevenly distributed in the surface layer, and the interlayer strength of the base paper is weakened. Also occurs. When a coated paper for printing is manufactured using this as a base paper, in a drying step such as offset printing, so-called "blister", which tends to cause printing defects in which the coating layer swells, and causes a serious defective product. May be. This blister is a phenomenon in which the paper is broken between layers when the moisture in the paper evaporates and escapes to the outside of the paper layer in the drying process at high temperature, and the air permeability and the interlayer strength of the base paper are important factors. Become. Generally, in order to solve this kind of problem, a method of adding or adding a paper strength enhancer such as cationized starch or polyacrylamide in the step of preparing the base paper to improve the interlaminar strength of the base paper is used. To be However, when the base paper is made into paper by increasing the addition amount of such a paper-strengthening agent, although the interlayer strength of the base paper is improved, air permeability is lowered, and in some cases, blisters are likely to occur conversely. Further, there is a problem that the texture of the base paper is deteriorated, uneven gloss is generated when the coated paper is used, and further the operability is deteriorated due to a decrease in drainage during papermaking. In addition, even when a paper strengthening agent is added externally,
As described above, since the fine fibers are localized in the surface layer of the base paper, the paper strengthening agent does not penetrate into the inside of the base paper, which is not an effective means for preventing blisters. On the other hand, when the beating degree of the pulp is increased to improve the interlaminar strength of the base paper by increasing the inter-fiber bond strength of the pulp, the blister resistance is improved, but the dimensional stability of the base paper is deteriorated, and There has been a problem that the runnability is deteriorated due to the deterioration of the drainage of the pulp.

In recent years, many techniques have been proposed in which an enzyme acts on a lignocellulosic material and fibers obtained by processing lignocellulose to modify them. For example, Japanese Examined Patent Publication No. 2-20756, Japanese Unexamined Patent Publication No. 1-92490, Japanese Examined Patent Publication No. 3-4672, and Japanese Unexamined Patent Publication No. 6-16697.
No. 8, JP-A-6-316899, JP-A-7-
No. 279078, JP-A-7-331588, etc., a method of adding cellulase to pulp fiber before beating for the purpose of improving beating property and modifying pulp fiber, and JP-A-2- Japanese Patent No. 6681, JP-A-2-
In order to improve drainage on a wire as disclosed in JP-A-229291 and JP-A-3-124891, an enzyme such as cellulase or hemicellulase is added to a stock after beating and adding a chemical. There is a way to do it. Further, JP-A-2-264087 and JP-A-2-293486.
JP-A-6-101185, JP-A-6-2
As disclosed in Japanese Patent Publication No. 07390, etc., a method of improving bleaching property by treating pulp fibers with an enzyme such as cellulase or hemicellulase before bleaching is also known. Japanese Unexamined Patent Publication (Kokai) No. 8-49187 discloses that the blister resistance and crease resistance of offset printing coated paper are improved by enzymatically treating pulp.

The inventors of the present invention have studied various enzymatic treatments of pulp with respect to a method for producing coated paper having excellent blister resistance at a high speed. As a result, by treating the pulp with an enzyme having a xylan-decomposing activity, We have found that the dimensional stability of the base paper is improved. Furthermore, if the pulp before multi-stage bleaching is treated with an enzyme having xylan-decomposing activity without filter paper-decomposing activity, and then multi-stage bleaching, the bleaching chemical required to bleach to the desired whiteness can be reduced, so the bleaching step Can minimize the damage of pulp fiber in
As a result, they have found that the dimensional stability of the base paper is improved. When the base paper using pulp treated with such an enzyme as the raw material has improved air permeability and is effective for blister resistance, but the interlayer strength is slightly inferior, so that the blister resistance is not sufficiently improved in the end. There was also.

[0016]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the prior art, obtains an excellent paper-strengthening effect, and can inexpensively produce a pulp capable of improving size property, water resistance, filler yield, and the like. To provide. The present invention also provides a paper using the pulp, which has improved sizing property, water resistance, and retention of the filler, and a high-speed production method of the paper. Further, by providing a coating layer on the paper, it is possible to provide a coated paper for printing, which has excellent surface gloss and printing gloss and has no uneven gloss.
Furthermore, the coated paper for printing excellent in blister resistance is provided.

[0017]

In view of the above background, the present inventors have made it possible to use inexpensively and easily, to obtain an excellent effect of strengthening paper strength, and further, size property, water resistance, yield of filler, etc. We have conducted intensive studies to find a way to improve the paper quality and improve the paper quality. Among them, especially CMC and CEC
Although it is water-soluble when the pH is neutral to alkaline, that is, the solubility changes depending on the dissociation state of the carboxyl group in the structure, and gelation or precipitation occurs from weakly acidic to strongly acidic regions. I focused on that. Then, an aqueous solution of such a cellulose derivative is added to the pulp fiber slurry, and a part or all of the cellulose derivative is returned to the acid form by adding an acid to make the pH of the slurry acidic. The paper that is fixed to the fiber surface, and the paper obtained by making paper with a wet paper machine using such a paper material not only has a markedly improved strength, but also improves the yield of other concomitant papermaking chemicals during papermaking. The inventors have found that the effect is remarkably enhanced and completed the present invention.

For example, in the case of CMC, the pH of the solution varies depending on the degree of substitution, the degree of polymerization, or the concentration of the solution.
Is gelled in the vicinity of 5 and precipitates when the pH is further lowered, as described in "Serogen Monogatari", page 208 (edited by Dai-ichi Kogyo Seiyaku Co., Ltd.), which is a widely recognized fact. . The present inventors are familiar with the properties of such cellulose derivatives, especially CMC and CEC salts,
Furthermore, as a result of detailed examination of the behavior in the pulp fiber slurry, the pH of the slurry in the presence of pulp fiber and a salt of CMC and / or CEC was slightly acidified by a mineral acid.
Surprisingly, adjusting to a strongly acidic region surprisingly results in CMC and CE.
It has been found that the cellulose derivative of C is uniformly adsorbed on the surface of pulp fibers in the slurry without gelation or precipitation.

Further, the CMC and / or CEC cellulose derivatives are usually on the market with a degree of substitution in the range of 0.7 to 1.2. However, these are highly acidic regions such as in the range of pH 2 to 3. In this case, it was sufficiently adsorbed to the pulp fiber, but in the weakly acidic region, it was difficult to be adsorbed to the pulp fiber. However, the handling or treatment of pulp fibers in such a strongly acidic region is extremely inconvenient in actual use, and the present inventors have made further studies to solve this problem. As a result, the degree of substitution is 0.3
The salt of CMC and / or CEC having a low degree of substitution in the range of up to 0.6 has a very good paper strength because it is well adsorbed by pulp fibers in a weak acidic region such as pH 3.5 to 5.5. It has been found that it improves the yield and improves the yield of papermaking chemicals and fillers. Moreover, such a low degree of substitution CMC and / or C
It was also found that the EC salt surprisingly improves the strength of the paper when used in combination with a paper strength enhancer or a paper wet strength enhancer comprising a conventionally used cationic chemical or resin. completed.

By the way, everyone involved in the manufacture and research of paper recognizes that the strength of paper is composed of the strength of the fibers that make up the paper and the bonding strength between the fibers. In the case of pulp fibers, it is well known that the hydrogen bond generated between cellulose molecules is the main factor in this interfiber bond, and it is possible to strengthen this interfiber bond or increase the interfiber bond area. The conventional paper-strengthening agents are factors that improve the strength of the paper, and all of the conventional paper-strengthening agents exhibit a paper-strengthening effect by forming a hydrogen bond between the pulp fiber and the paper-strengthening agent.

As a result of repeated studies based on such findings, the present inventors have added CMC and / or CEC salts to a slurry containing pulp fibers, and
It is necessary to adjust H to a strongly acidic region to a weakly acidic region, especially a low degree of substitution of 0.3 to 0.6, to convert it to an acid form by adjusting it to a weakly acidic region and to adsorb it on the pulp fiber surface. Depending on the pH
Is adjusted to weakly acidic, neutral, or alkaline, papermaking chemicals are added, and if necessary, a filler and / or a cationic chemical or a resin paper strength enhancer or wet strength enhancer is used in combination, and sulfuric acid is added. Band, acidic papermaking method using rosin sizing agent,
When a paper is manufactured by a wet paper machine by a neutral papermaking method or a neutral papermaking method using a neutral sizing agent and a fixing agent, the paper subjected to such a treatment contains the conventional paper-strengthening agent and the wet-strength enhancing agent alone. It was found that the effect of improving the strength, which is far superior to that of the paper obtained by using the above method, and the effect of improving the yield of the filler and the paper-making chemical, which are remarkable, can be obtained.

Further, by using the pulp of the present invention, the dewatering ability is enhanced at a high speed like a gap former type paper machine, and the paper can be effectively imparted with a sizing degree even in a paper machine having a low stock yield. I found it. Further, it has been found that when a coating layer is provided on the paper, a uniform coating layer can be obtained and a coated paper excellent in gloss can be obtained.

Further, according to the method of the present invention, the effect of improving the dimensional stability by the enzyme treatment described above is not diminished,
It has also been found that the interlaminar strength is remarkably improved without deterioration of the air permeability and formation of the base paper and other deterioration of operating conditions. And the coated paper provided with a coating layer on the base paper,
It was found that the blister resistance was significantly improved.

That is, the first aspect of the present invention is to add CMC and / or CEC to a slurry of pulp fibers, and then add a mineral acid to adjust the pH of the pulp fiber slurry to a range of 2 to 6, It is a pulp characterized by converting CMC and / or CEC into an acid form and adsorbing it. A second aspect of the present invention is characterized in that the substitution degree of CMC or CEC is 0.3 to 0.6, and the pH after the addition of the mineral acid is in the range of 3.5 to 5.5. It is the pulp described in the first paragraph.
A third aspect of the present invention is the pulp according to the first and second aspects of the present invention, characterized in that the pH of the pulp fiber slurry after the addition of the mineral acid is further adjusted to pH 5 to 9. A fourth aspect of the present invention is characterized in that the addition rate of CMC and / or CEC is 0.01 to 5.0% by weight based on the weight of the bone-dry pulp fiber. 2 and the pulp according to the third aspect of the present invention. A fifth aspect of the present invention is characterized in that the pulp fiber according to the first aspect of the present invention contains pulp that has been treated with an enzyme having a xylan-decomposing activity and then subjected to multi-stage bleaching. The pulp according to the third and fourth aspects of the present invention. A sixth aspect of the present invention is a paper containing the pulp according to the first aspect, the second aspect, the third aspect, the fourth aspect and the fifth aspect of the present invention. The seventh of the present invention is a paper for paper making with a wet paper machine using the pulp described in the first to sixth aspects of the present invention, a papermaking chemical containing a paper-strengthening agent, and optionally a pulp fiber slurry containing a filler. It is a manufacturing method. An eighth aspect of the present invention is the method for producing the paper according to the seventh aspect of the present invention, wherein the wet paper machine according to the seventh aspect of the present invention uses a gap former type paper machine. A ninth aspect of the present invention is the coated paper according to the seventh aspect, wherein a coating layer is provided on one side or both sides of the paper.

BEST MODE FOR CARRYING OUT THE INVENTION

The salt of CMC or CEC used in the present invention is a cellulose derivative synthesized by reacting monochloroacetic acid, chloropropionic acid, etc. from wood pulp, cotton pulp, linter pulp, etc. as raw materials.
Industrially, those obtained by a known production method such as a water medium method or a solvent method are used as they are.

The degree of substitution (degree of etherification) of the CMC and CEC salts used for the present invention is 0.3 to 1.
It is in the range of 2. However, the degree of substitution is 0.7
A salt with a high degree of substitution in the range of 1.2 to 1.2 can be sufficiently adsorbed on pulp fibers in the strongly acidic region of pH 2 to less than 3.5, but in the weakly acidic region of pH 3.5 or more. Is only partially adsorbed, the effect obtained is somewhat unsatisfactory, and as described above, the handling and treatment of pulp fibers in the strongly acidic region is a bleaching process of unbleached pulp in the paper manufacturing industry. Although it can be seen in (for example, chlorination stage), it cannot be denied that it is inconvenient in actual use. Therefore, as a result of various studies to solve this problem, the present inventors have found that CMC and / or CEC salts having a relatively low degree of substitution in the range of 0.3 to 0.6 are pulp fibers. PH of 3.5-5. With mineral acid in the presence of.
When adjusted to a weakly acidic region of 5, preferably 4 to 5, it is sufficiently adsorbed to pulp fibers even in this region, and as a result, an extremely excellent effect of improving the strength of paper and improving the yield of paper-making chemicals and fillers is obtained. He knew that he would be done. On the other hand, those with a degree of substitution of less than 0.3 are insoluble in water, and those with a degree of substitution of more than 1.2 are CMC or CEC.
It is difficult to obtain the compound by ordinary one-time reaction, and the production cost is extremely high because it is obtained only by repeating the same reaction, which is not preferable, but it can be used by the method of the present invention.

The salts of CMC and CEC used in the present invention are the properties of the pulp fiber used and the CMC as described above.
It is possible to produce various degrees of polymerization depending on the production method of CEC or CEC, but the viscosity of a 1% aqueous solution is 5 to 16,000 c.
ps (0.1N-NaCl solvent, 25 ° C., B-type viscometer), average degree of polymerization of 100 to 4,500, and average molecular weight of 20,000 to 1,000,000. Most of CMC and CEC used in the present invention are commercially available carboxylic acid sodium salt or potassium salt.
The salt of is carboxymethylcellulose sodium or carboxymethylcellulose potassium, but conventionally,
The description of sodium and potassium is omitted, and they are simply represented as CMC and CEC salts, and simply as CMC and CEC.

In the present invention, sodium salt, potassium salt or ammonium salt of CMC and CEC is used.
The sodium salt of CMC is preferable because it is inexpensive, easily available, and highly effective. or,
When the salt of CMC or CEC is added to the pulp slurry, the concentration of the salt solution is 0.01 to 5.0% by weight, preferably 0 because the viscosity becomes too high and the use becomes difficult if the concentration is too high. The range is from 0.1 to 3.0% by weight.

The solvent for dissolving the salt of CMC or CEC is water, and in the present invention, it is used as an aqueous solution of CMC or a salt of CEC or a mixed aqueous solution of CMC and a salt of CEC. If necessary, a solvent compatible with water, such as methanol and ethanol, may be mixed in any ratio within a range in which CMC is stably dissolved, and further, salts of CMC and CEC are stably dissolved. In the range, other substances may be mixed if necessary. Also, CM
The respective ratios when the C and CEC salts are mixed and used are not particularly limited, and they can be mixed in any ratio.

The amount of the CMC salt and / or CEC salt used in the present invention may be varied depending on the degree of substitution of the salt, the type of paper, the application, the required performance, etc., but the dry weight of the pulp fiber. 0.01 to 5.0% by weight, preferably 0.05 to 3.0% by weight, and more preferably 0.05 to 5.0% by weight.
1.0% by weight. The larger the amount of these salts used, the more remarkable the effect becomes, but the higher the amount used, the more rigid the paper is, and the more expensive it is. Can be decided.

When the CMC salt and / or the CEC salt is added to the pulp fiber slurry in the form of an aqueous solution, the concentration of the pulp fiber slurry is such that if the concentration is too high, stirring becomes difficult and the mixing becomes insufficient. If it is too low, a large amount of acid for adjusting the pH is required and it is uneconomical.
-5% by weight, preferably 2-4% by weight. In the present invention, the CMC salt and /
Alternatively, an aqueous solution of a salt of CEC is added, mixed with sufficient stirring, and then a mineral acid is added to adjust the pH of the slurry to a range of 2 to 6, preferably 3.5 to 5.5. Above all,
When the substitution degree of CMC and CEC is in the range of 0.3 to 0.6, the pH of the slurry is adjusted to 3.5 to 5.5, preferably 4 to 5. In this case, a cationic chemical such as known cation-modified starch, polyamide / epichlorohydrin resin, polyethyleneimine resin, polyacrylamide resin, polyamide resin, etc., or a paper-strengthening agent or wet-strength enhancing agent of the cationic resin is the above-mentioned C
When used in combination with MC salt and / or CEC salt, an excellent effect of improving dry strength or wet strength and an effect of improving yield of paper-making chemicals and filler can be obtained with an extremely small amount of addition. In this case, the amount of CMC salt and / or CEC salt added is in the range of 0.05 to 0.5% by weight, preferably 0.07 to 0.3% by weight, based on the absolute dry weight of pulp fiber. Cationic chemical or resin is 0.0 per dry weight of pulp fiber
5 to 0.5% by weight, preferably 0.07 to 0.3% by weight
Selected from the range.

The mineral acid used for pH adjustment in the present invention is not particularly limited, and examples thereof include sulfuric acid, hydrochloric acid, nitric acid, and the like, which are appropriately selected and used from these. CMC and CEC after pH adjustment within the above range are in acid form and are very easily adsorbed on the pulp fiber surface or between pulp fibers, after which pH is not further adjusted or alkali is added. The pH is adjusted, paper making chemicals, and if necessary, additives such as fillers and pigments are added, and the resulting mixture is sent to a wet paper machine as paper stock to prepare paper. PH of the pulp fiber slurry
In the adjustment, when the pH exceeds 6, the conversion of the CMC salt and the CEC salt to the acid form becomes insufficient or impossible, and the adsorption of CMC and CEC to the pulp fiber surface hardly occurs. The effect of developing the strength of the used paper is insufficient or cannot be obtained. If the pH is less than 2, C
The conversion of MC salt and CEC salt to the acid form is sufficiently completed when the pH reaches 2, so there is no point in lowering the pH above 2, and corrosion of the equipment that handles pulp fiber slurry is a problem. Therefore, it is unavoidable to use a special acid resistant material, which is uneconomical.

When the pH of the pulp fiber slurry containing the salt of CMC and / or the salt of CEC is adjusted within the above range, the dissociation of the salt of CMC and the salt of CEC to the acid form is completed in an instant. Slurry and CMC salt and /
Alternatively, under the condition that the CEC and the mineral acid are sufficiently uniformly stirred, the holding time after the pH is adjusted is extremely short, such as 0.1 second to 10 minutes. Considering the actual operating conditions, the pH may be adjusted to the range of 2 to 6 by adding mineral acid to the pulp slurry at the suction port of the mixing pump of the paper machine. You may make adjustments.

Among the papermaking chemicals containing the filler, p
Some are not convenient when added to pulp slurries with H less than 5. In such a case, an alkali such as caustic soda is added and the pH is appropriately readjusted to a range of 6 to 9, preferably 6 to 8, and then a papermaking chemical, and if necessary, a filler, a pigment and other additives are added. Preferably. pH is 5-6
Within the range, it is also possible to carry out without readjustment. Specifically, rosin sizing agents, which are mainly used in acidic papermaking, may cause cohesive sedimentation at pH of 4 or less, and calcium carbonate, which is commonly used as a filler in neutral papermaking, is Then it decomposes into carbon dioxide and calcium ions. Therefore, when using such chemicals or fillers, the pH of the pulp slurry must be adjusted as necessary.

When neutral pH or alkaline pH is adjusted by adding alkali to readjust the pH, the pH is adjusted to 6.5.
It is preferable that the content is ˜9, but if the pulp fiber slurry is kept in an alkalinity exceeding 9 for a long time, there is a possibility that part or most of CMC or CEC adsorbed on the pulp fiber surface will be desorbed. Therefore, in that case, it is preferable that the pH is 9 or less, or the pulp fiber slurry having a pH of more than 9 is quickly placed on a paper machine as a paper stock for papermaking.

The treatment for adjusting the pH of the pulp fiber slurry to the range of 2 to 6 is carried out in the process from the storage process of bleached or unbleached pulp to the papermaking process, existing containers such as chests and tanks, stirring equipment and circulation. It can be carried out by using agitation by a pump, a transfer pump, etc., but a dedicated process for carrying out the above treatment may be additionally provided. When the pH of the pulp fiber slurry is adjusted within the range of 2 to 6, as described above, the CMC salt and / or the CEC salt is partially or wholly converted to the acid form, and the pulp fiber surface can be very easily formed. It is adsorbed, which significantly improves the strength of the paper after it is made. That is, as for the pH-adjusted paper stock, if the pH is 5 to 6 as it is, or if it is less than 5, alkali is added to adjust the pH to a range above 6 again to obtain the filler and It is possible to produce a paper while adding strength to papermaking chemicals and / or significantly improving the yield of the papermaking chemicals and the filler by using a known wet paper machine to make paper after adding the papermaking chemicals and drying. it can.

The pulp fiber to which the method of the present invention is applied is not particularly limited, and it can be applied to known and commonly used papermaking pulps, such as chemical pulp such as sulfite pulp, kraft pulp and soda pulp, semi-chemical pulp, It may be wood pulp such as mechanical pulp or non-wood pulp such as groove, mitsu or hemp pulp, and may be unbleached pulp or bleached pulp. However, in the base paper for coated paper for printing, since a good formation is required, a hardwood having a short fiber length is preferably used.

When a pulp treated with an enzyme having a xylan-decomposing activity is used, the unbleached pulp obtained by a known digestion method is subjected to washing, rough selection and selective selection,
Enzyme treatment before multi-stage bleaching. However, when the optimum pH and the optimum temperature of the enzyme are taken into consideration, it is preferable to carry out the enzyme treatment after the unbleached pulp is subjected to oxygen delignification.

When the pulp is treated with an enzyme having a xylan-decomposing activity, xylan ubiquitous on the surface of the pulp or in the pulp fibers is selectively decomposed and the pulp becomes porous while retaining the cellulose skeleton. When such a pulp is used as the base paper, the air permeability of the base paper is improved, so that improvement in blister resistance can be expected. On the other hand, cellulose, which is the main skeleton of pulp, is hardly affected by the enzymatic treatment, so that the dimensional stability of the base paper is maintained.

The enzyme has a xylan-decomposing activity,
0.1-10 U / g of absolutely dry pulp, preferably 0.5-5
Add to pulp in the range of U / g of dry pulp. here,
1 U means the amount of enzyme that produces 1 μmol xylose per minute when the enzyme is allowed to act on xylan.

It is of course possible to mix and use the enzyme-treated pulp and the non-enzyme-treated pulp,
Since the higher the ratio, the higher the effect, the content of the enzyme-treated pulp is preferably in the range of 60 to 100% by weight.

As the known wet paper machine used in the present invention, a commercial-scale paper machine such as a cylinder paper machine, a short-net paper machine, or a Fourdrinier paper machine is appropriately selected and used according to the purpose. To be In addition, as described above, the gap former type paper machine is suitable for producing a base paper for printing coated paper at high speed.

In the present invention, a salt of CMC and / or C
Before or after converting the salt of EC to the acid form by adjusting the pH, the pH of the slurry containing pulp fibers and CMC and / CEC in the range of 2 to 6 is 5
In the range of 9 to 9, it is used by adding a papermaking chemical such as a papermaking sizing agent and a fixing agent, a papermaking paper strength enhancer, a filler, a pigment, a yield improving agent, a dye, an antifoaming agent, an antiseptic, and a viscosity reducing agent. However, after confirming that these papermaking chemicals are not affected by the above pH range, they are appropriately selected and used according to the purpose.

It is of course possible to subject the thus obtained base paper to a size treatment using starch, PVA or the like with various size presses or roll coaters, but in consideration of speeding up the production speed, the film meta A method of increasing the solid concentration of the paste by using a ring type size press device and performing the size press treatment is preferably used. Further, it is of course possible to carry out the preliminary coating with a roll coater, a blade coater or the like.

On the other hand, in the coated paper of the present invention, the pigment which is one of the main components of the coated composition is, for example, clay, kaolin, aluminum hydroxide, calcium carbonate,
One or more of general-purpose pigments such as talc and plastic pigment can be arbitrarily selected and blended. Examples of the adhesive include styrene-butadiene copolymer, conjugated diene-based copolymer latex such as methylmethacrylate-butadiene copolymer, acrylic acid ester and / or methacrylic acid ester polymer or copolymer, and the like. Acrylic polymer latex, vinyl polymer latex such as ethylene-vinyl acetate copolymer, or various polymer latex of these, partially soluble or not soluble in alkali modified with monomers containing functional group such as carboxyl group Polymeric latexes can be used. Examples of water-soluble adhesives used in combination with synthetic adhesives include starches such as cationized starch, oxidized starch, thermochemically modified starch, etherified starch, esterified starch, cold water soluble starch, carboxymethyl cellulose, hydroxymethyl cellulose. Cellulose derivatives such as polyvinyl alcohol, water-soluble adhesives such as olefin-maleic anhydride resin, etc. can be arbitrarily selected and used.

Various additives such as a dispersant, a water-proofing agent, a fluidity-modifying agent, a coloring agent, and a fluorescent whitening agent can be added to these pigments and adhesives as required. The coating of the coating layer is a coating device used in the production of general coated paper, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater, a die rod coater, a gravure coater, a chan. On-machine or off-machine coater provided with a coating device such as a plex coater or a size press coater is used to coat one or both sides of the base paper in a single layer or multiple layers. The solid content concentration of the coating composition at that time,
Generally, the range of 45 to 70% by weight is preferred. As a calendering method, as a gloss or mat calender, for example, a super calender, a gloss calender, a soft compact calender, or a variety of calenders made of metal and a drum and an elastic roll can be arbitrarily selected and used on-machine or off-machine. .

[0047]

As described above, the remarkable improvement in the strength of the paper in the present invention is that the hydroxyl groups of CMC and / or CEC are uniformly adsorbed and distributed on the pulp fiber surface or between the fibers,
It is considered that this is manifested by forming hydrogen bonds between these fibers during sheet formation. CMC and / or CE with a fixing agent such as a sulfuric acid band without adjusting the pH with mineral acid
When C is fixed to pulp, CMC and / or C
Since EC reacts with the sulfuric acid band and turns into a gel,
The distribution of pulp fiber surface is not uniform and does not exhibit the excellent paper-strengthening effect as in the present invention. Further, the carboxyl groups in CMC and / or CEC molecules uniformly distributed in pulp fibers adsorb fillers, pigments or various paper-making chemicals by electrostatic interaction force (Coulomb force), and as a result, the yield of paper-making chemicals is improved. At the same time, it is considered that the distribution of these chemicals on the pulp fibers is remarkably improved and the effect of each chemical is improved.

In the production of coated paper for printing, the effect of such CMC and / or CEC imparts excellent sizing property to the base paper without impairing the formation, so that the coating liquid can be made uniform. A coated paper for printing, which is coated and has excellent gloss without unevenness, is achieved. Further, the blister resistance is also improved by improving the interlayer strength, and by using a pulp treated with an enzyme having a xylan-decomposing activity, the air permeability of the base paper is increased, and printing with further excellent blister resistance is performed. It is thought that it will be possible to manufacture coated paper for use in the production.

[0049]

The present invention will be described in more detail with reference to the following examples, but of course the present invention is not limited thereto. In the following examples and comparative examples,% means% by weight, and the amount of the additive added to the pulp fiber slurry is shown as% by weight based on the weight of the absolutely dried paper material. Example 1 A freezing degree of 480 ml CSF was measured with an experimental Niagara beater.
(Canadian Standard Freeness) 100% of hardwood bleached kraft pulp and 4.9 liters of water in a pulp fiber slurry having a concentration of 2% and a solution viscosity of 1% of solid content is 160
CMC sodium salt with 0 cps and a degree of substitution of 0.6 (trade name: Serogen 4H, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) with a concentration of 1%
As an aqueous solution of 0.2% with respect to the weight of pulp, while stirring at a speed of 450 rpm with a three-one motor, 1% concentration of dilute sulfuric acid was added to adjust the pH of the pulp fiber slurry to 3. After continuing to stir for a second,
The pH of the pulp fiber slurry was adjusted to 7 by adding a 5% strength dilute caustic soda aqueous solution. TA using this pulp stock
Paper having a basis weight of 60 g / m 2 was made using a PPI standard square sheet machine, and left to dry in a room for 24 hours. The handmade sheet was conditioned at a temperature of 20 ° C. and a relative humidity of 65% for 24 hours, and then the tensile strength and the interlaminar strength of the paper were measured by the following test methods to evaluate the quality. Test method (1) Tensile strength Measured in accordance with TAPPI T205, the breaking length (K
m). (2) Interlayer strength It was measured according to TAPPI UM403. (3) Viscosity of CMC solution This is a value obtained by measuring with a B-type viscometer at 25 ° C. using 0.1N-NaCl as a solvent.

Example 2 A handmade sheet was prepared and obtained in the same manner as in Example 1 except that the sodium salt of CMC having a degree of substitution of 0.6 was 0.5% based on the weight of pulp. The paper was tested to assess quality.

Example 3 Example 1 except that the sodium salt of CEC with a degree of substitution of 0.6 (special grade reagent) was 0.2% based on the weight of the pulp.
A handmade sheet was prepared in the same manner as in 1. and the quality of the obtained paper was evaluated by testing.

Example 4 A hand-made sheet was prepared in the same manner as in Example 1 except that the sodium salt of CEC having a degree of substitution of 0.6 was 0.5% based on the weight of the pulp. Was tested to evaluate the quality.

Example 5 A handmade sheet was prepared in the same manner as in Example 1 except that the pulp fiber slurry after adding the sodium salt of CMC had a pH of 5, and the obtained paper was tested. Evaluated the quality.

Example 6 A solution having a solid content of 1% has a viscosity of 1400 cps and a degree of substitution of 0.
A handmade sheet was prepared in the same manner as in Example 1 except that the sodium salt of CMC 4 (PX01, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used, and the obtained paper was tested to evaluate the quality. .

Example 7 A solution having a solid content of 1% had a viscosity of 1400 cps and a degree of substitution of 0.
Using the sodium salt of CMC 4 (PX01, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) in the same manner as in Example 1 except that the pH of the pulp fiber slurry after addition of the sodium salt of CMC was adjusted to 5 Paper sheets were prepared and the resulting paper was tested to assess quality.

Comparative Example 1 A commercially available amphoteric polyacrylamide paper strength enhancer (trade name: Polystron 655, manufactured by Arakawa Chemical Industry Co., Ltd.) was added to the same pulp fiber slurry as used in Example 1 in an amount of 0. 2% was added and mixed well. A handmade sheet was produced using this pulp stock and the quality was evaluated.

Comparative Example 2 A handmade sheet was prepared in the same manner as Comparative Example 1 except that 0.5% of the amphoteric polyacrylamide paper strength enhancer was added to the weight of the pulp, and the obtained paper was tested. And evaluated the quality.

Comparative Example 3 The same pulp fiber slurry as used in Example 1 was mixed with C having a solution viscosity of 1% solids of 1600 cps and a degree of substitution of 0.6.
MC sodium salt (trade name: Serogen 4H, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as an aqueous solution having a concentration of 1% in an amount of 0.2% relative to the weight of the pulp, and a three-one motor was used for 450 r
Stirring was performed at a speed of pm, a pulp paper stock was prepared by adding dilute sulfuric acid without adjusting the pH, a handmade sheet was prepared in the same manner as in Example 1, and the obtained paper was tested and evaluated.

Comparative Example 4 A hand-made sheet was prepared in the same manner as in Comparative Example 3 except that CEC having a degree of substitution of 0.6 was used instead of CMC, and the quality was evaluated. The results obtained in Examples 1 to 7 and Comparative Examples 1 to 6 are shown in Table 1.

[0060]

[Table 1]

Example 8 The same pulp slurry used in Example 1 was mixed with 1% solids.
CMC with a solution viscosity of 1600 cps and a degree of substitution of 0.6
Sodium salt (trade name: Serogen 4H, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added as an aqueous solution having a concentration of 1% to the pulp weight in an amount of 0.2% and 450 rpm with a three-one motor.
1% dilute sulfuric acid was added while stirring at a speed of m.
Adjust the pH of the pulp fiber slurry to 3 and leave it at 30
After continuing stirring for 2 seconds, a 5% strength dilute caustic soda aqueous solution was added to adjust the pH of the pulp fiber slurry to 7. Further, a 2% sulfuric acid band was added and stirred for 30 seconds to prepare a papermaking sheet in the same manner as a paper material, and the obtained paper was tested and evaluated. The final pH of the pulp slurry was 4.5.

Example 9 A paper stock was prepared in the same manner as in Example 8 except that CEC having a degree of substitution of 0.6 was used instead of CMC to prepare a hand-made sheet. Tested and evaluated. The final pH of the pulp slurry was 4.5.

Example 10 A solution having a solid content of 1% had a viscosity of 1400 cps and a degree of substitution of 0.
A paper stock was prepared in the same manner as in Example 8 except that the sodium salt of CMC of No. 4 (PX01, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used to prepare a hand-made sheet, and the obtained paper was tested. Evaluated. The final pH of the pulp slurry is 4.5.
Met.

Comparative Example 5 A commercially available amphoteric polyacrylamide paper strength enhancer (trade name: Polystron 655, manufactured by Arakawa Chemical Industry Co., Ltd.) was added to the same pulp slurry as used in Example 1 in an amount of 0.
Add 2% and mix well, then add 2% sulfuric acid band
A hand-made sheet was prepared in the same manner by using the stock added and stirred for 30 seconds, and the obtained paper was tested and evaluated. The final pH of the pulp slurry was 4.5.

Comparative Example 6 The same pulp slurry used in Example 1 was mixed with 1% solids.
CMC with a solution viscosity of 1600 cps and a degree of substitution of 0.6
Sodium salt (trade name: serogen 4H, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as an aqueous solution having a concentration of 1% was added to the pulp weight in an amount of 0.2% and thoroughly mixed, and then a sulfuric acid band was further added in an amount of 2%. Stir for 30 seconds and use as stock
Similarly, a handmade sheet was prepared, and the obtained paper was tested and evaluated. The final pH of the pulp slurry was 4.5.

Comparative Example 7 Comparative Example 6 except that a CEC having a degree of substitution of 0.6 was used.
A paper stock was prepared in the same manner as above, a handmade sheet was prepared, and the obtained paper was tested and evaluated. The final pH of the pulp slurry was 4.5.

Comparative Example 8 A solution having a solid content of 1% had a viscosity of 1400 cps and a degree of substitution of 0.
A paper stock was prepared in the same manner as in Comparative Example 6 except that the sodium salt of CMC (PX01, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. 4) was used to prepare a hand-made sheet, and the obtained paper was tested. Evaluated. The final pH of the pulp slurry is 4.5.
Met.

Comparative Example 9 The same pulp slurry used in Example 1 was mixed with 1% solids.
CMC with a solution viscosity of 1600 cps and a degree of substitution of 0.6
Sodium salt (trade name: Serogen 4H, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added as an aqueous solution having a concentration of 1% to the pulp weight in an amount of 0.2% and 450 rpm with a three-one motor.
While stirring at a speed of m, a sulfuric acid band was added until the pH reached 3. Continue stirring for 30 seconds, then 5%
A handmade sheet was prepared by adding a concentrated caustic soda aqueous solution to adjust the pH of the pulp fiber slurry to 4.5, and the obtained paper was tested and evaluated.

Reference Example 1 For comparison, the same pulp fiber slurry as used in Example 1 was used as a pulp paper stock without adding any papermaking chemicals, and a handmade sheet was prepared in the same manner as in Example 1. The papers produced and tested were evaluated.

Reference Example 2 The same pulp slurry as used in Example 1 was prepared as a paper stock with only 2% of a sulfuric acid band added, and a handmade sheet was prepared. The obtained paper was tested and evaluated. The final pH of the pulp slurry was 4.5. Examples 8 to 1
Table 2 shows the results obtained in 0, Comparative Examples 5 to 9 and Reference Examples 1 and 2.

[0071]

[Table 2]

Example 11 The freeness was adjusted to 550 ml CSF with an experimental Niagara beater.
55 g of softwood bleached kraft pulp prepared to (Canadian standard freeness), 45 g of hardwood bleached kraft pulp similarly prepared to 480 ml CSF (Canadian standard freeness) and 2% concentration of pulp fiber slurry consisting of 4.9 liters of water, 1400% solids solution viscosity is 1400 cp
s, CMC sodium salt with a degree of substitution of 0.4 (PXO
1, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added as an aqueous solution having a concentration of 1% to the pulp weight by 0.1%, and a 1% concentration of dilute sulfuric acid was added while stirring with a three-one motor at a speed of 450 rpm. The pH of the pulp fiber slurry was adjusted to 4, the stirring was continued for 30 seconds as it was, and then the pH of the pulp fiber slurry was adjusted to 7 by adding a 5% concentrated dilute caustic soda aqueous solution. Furthermore, while continuing stirring, this slurry contained 0.2% of a rosin sizing agent for papermaking (trade name: Size Pine E, manufactured by Arakawa Chemical Industry Co., Ltd.) with respect to the weight of pulp, an anionic polyacrylamide-based paper-strengthening agent ( (Trade name: Polystron 194-7, manufactured by Arakawa Chemical Industry Co., Ltd.) 0.1% and sulfuric acid band 2.0% were added in the order given above to adjust the pH to 4.5 and continue stirring for 1 minute. , A TAPPI standard square sheet machine was used to prepare a hand-made sheet having a basis weight of 60 g / m 2, and the paper obtained in the same manner as in Example 1 was tested for tensile strength and interlaminar strength. Tested and evaluated for quality. In addition, the Steckigt size degree of paper is JIS
It measured based on P8122.

Comparative Example 10 The same pulp fiber slurry as used in Example 11 was added to a pulp rosin sizing agent (trade name: size) for pulp weight without adding sodium salt of CMC while stirring with a three-one motor. Pine E, Arakawa Chemical Industry Co., Ltd. 0.2%, anionic polyacrylamide paper strength enhancer (trade name: Polystron 194-7, Arakawa Chemical Industry Co., Ltd.) 0.1%, and sulfuric acid band (Al2 ( SO4) 3 ・
18H2O) 2.0% was added in this order, and stirring was continued for 1 minute to adjust the pH to 4.5. Then, a handmade sheet was prepared in the same manner as in Example 1, and the obtained paper was tested. , Evaluated the quality.

COMPARATIVE EXAMPLE 11 The chemical addition ratio in Comparative Example 10 was set to 0.5% for rosin sizing agent, 0.3% for paper strengthening agent, and 2.0% for sulfuric acid band, and the final pH of the slurry was 4.5. Other than what I did,
A handmade sheet was prepared in the same manner as in Comparative Example 10, and the obtained paper was tested to evaluate the quality. Table 3 shows the results obtained in Example 11 and Comparative Examples 10 to 11.

[0075]

[Table 3]

Example 12 Freezing degree of 450 ml CSF with an experimental Niagara beater
(Canadian standard freeness) 100% of hardwood bleached kraft pulp and 4.9 liters of water in a pulp fiber slurry having a concentration of 2% and a solution viscosity of 1% solid content of 140
Sodium salt of CMC with 0 cps and degree of substitution of 0.4 (P
(X01, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as an aqueous solution having a concentration of 1% to the pulp weight in an amount of 0.1%, and a 1% concentration of dilute sulfuric acid was added while stirring at a speed of 450 rpm with a three-one motor. The pH of the pulp fiber slurry was adjusted to 4, the stirring was continued for 30 seconds, and then a 5% strength dilute caustic soda solution was added to the pH of the pulp fiber slurry.
Was set to 7. Further, while being continuously stirred, a neutral papermaking sizing agent containing 0.5% of a cationized starch (trade name: Kate F, manufactured by National Starch Co., Ltd.) based on the weight of pulp and an alkylketene dimer as a component ( Product name: Size Pine K903, Arakawa Chemical Industry Co., Ltd.) 0.0
Paper strength agent containing 5% polyamide / epichlorohydrin resin as a component (trade name: WS570, manufactured by Nippon PMC)
0.1%, light calcium carbonate as a filler for papermaking 10
%, Sulfuric acid band 0.2%, and polyacrylamide-based retention aid for papermaking (trade name: Hymolok NR
0.01 L of 11 L, manufactured by Hymo Co., Ltd. was added in this order, and after stirring for 1 minute (final pH was 8.2), a handmade sheet was prepared in the same manner as in Example 1 and obtained. The resulting papers were tested for tensile strength, Stoecht sizing and Hunter whiteness to assess quality. Further, the ash content of the handmade sheet was measured according to JIS P 8128, and the yield (retention) of the filler was calculated using this value. The hunter whiteness of the paper is according to JIS P8123.

Comparative Example 12 CM was added to the same pulp fiber slurry as used in Example 12.
After adding the paper-making chemicals with stirring in the same manner as in Example 7 except that the sodium salt of C was not added, a handmade sheet was prepared and the quality was evaluated. The final pH of the pulp fiber slurry was 8.2.

Comparative Example 13 CM was added to the same pulp fiber slurry as used in Example 12.
Without adding the sodium salt of C, the addition ratio of paper-making chemicals was 0.7% of cationized starch to pulp weight, 0.15% of neutral papermaking sizing agent containing alkyl ketene dimer, polyamide 0.2% paper strength enhancer containing epichlorohydrin resin and 10% calcium carbonate
%, A sulfuric acid band of 0.2%, and a retention aid for papermaking of 0.
A handmade sheet was produced in the same manner as in Example 12 except that the content was 03%, and the quality of the obtained paper was evaluated. The final pH of the pulp fiber slurry was 8.2. Example 1
The results obtained in No. 2 and Comparative Examples 12 to 13 are shown in Table 4.

[0079]

[Table 4]

Example 13 (Production of Coated Paper for Printing: Preparation of Stock Material) Hardwood bleached kraft pulp having a solid content of 4% was beaten with a double disc refiner to a Canadian standard freeness of 500 ml. did. After beating, a pulp slurry having a concentration of 2% was added to a sodium salt of CMC having a solid content of 1% and a solution viscosity of 1600 cps and a substitution degree of 0.6 (trade name: serogen 4
(H, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as an aqueous solution having a concentration of 1% by 0.2% to the weight of the pulp, and then diluted sulfuric acid having a concentration of 1% was added to adjust the pH to 3. Then, the pH of the pulp slurry was adjusted to 7 by adding a 5% concentrated dilute caustic soda aqueous solution, and 0.7% of a rosin sizing agent (trade name: Size Pine E, manufactured by Arakawa Chemical Co., Ltd.) as an internally added sizing agent and 2% of a sulfuric acid band, And 20% of talc was added as a filler per weight of the absolutely dry pulp to prepare a paper material. (Papermaking) Papermaking was performed at a speed of 1300 m / min with a paper machine having a gap former using the above-mentioned stock, and further 10% concentration of oxidized starch (trade name: ace) was used with a gate roll size press machine on machine. A, manufactured by Oji Corn Starch Co., Ltd.) was applied at 2 g / m 2 and dried to produce a base paper for printing coated paper having a basis weight of 55 g / m 2. (Preparation of coating liquid) Heavy calcium carbonate (trade name: FMT
-90, made by Pharmatech Co., Ltd.) 25% and kaolin (trade name: Amazon 88, made by CADAM Co.) 75% are dispersed using a Choles disperser to obtain a solid content concentration of 72%.
A pigment slurry of was obtained. This styrene-butadiene copolymer latex (trade name: SN307, manufactured by Sumitomo Dow)
10% by solid content based on the weight of pigment, oxidized starch (trade name:
Ace A, made by Oji Corn Starch Co., Ltd.) at a solid content of 4%,
Other auxiliary agents were added and dispersed to prepare a coating liquid having a solid content concentration of 58%. (Production of Coated Paper) The above coating liquid was used for the above-mentioned base paper for printing paper for coating, and double-sided coating was carried out by a blade coater so that one side was 15 g / m 2. The obtained coated paper was passed through an off-machine super calender consisting of 6 metal rolls and 6 cotton rolls at a nip pressure of 200 kg / cm,
A coated paper for offset printing having an Oken smoothness of 1100 seconds on the front side and 1120 seconds on the back side was produced. (Quality evaluation) The quality of the obtained coated paper for printing was evaluated using the following test methods. (1) Formation of base paper The formation of the base paper was visually evaluated and evaluated according to the following three grades. ◎: Very good ○: Good
B: Slightly inferior (2) White paper gloss of coated paper It was measured according to JIS-P8142. (3) Printing gloss of coated paper Using an RI printing tester (manufactured by Meisho Seisakusho), 0.4 cc of offset ink (Graf-G ink, manufactured by Dainippon Ink & Chemicals, Inc.) was used. The surface gloss after printing was visually evaluated. In addition, gloss unevenness was also visually evaluated. ◎: Very good ○: Good
B: Slightly inferior (4) Interlayer strength Measured according to TAPPI UM403. (5) Measurement of Blister Resistance An RI rotary printing machine (manufactured by Akira Seisakusho Co., Ltd.) is used to develop 1 ml of the offset rotary printing ink and print on both sides of a coated paper sample.
Soak the printed sample in warm silicone oil,
The appearance of the generated blister was visually observed and evaluated according to the following evaluation criteria. Evaluation criteria ⊚: Almost no blister is observed. ○ ・ ・ ・ Although very slight blister generation is seen,
It does not matter in practice. B: Generation of blisters was observed and it was not practically usable. X: Severe blister formation was observed, and it cannot be practically used.

Example 14 A base paper and a coated paper for printing were produced in the same manner as in Example 13 except that the amount of the sodium salt of CMC added was 0.02% in the preparation of the stock material, and the quality was evaluated. did.

Example 15 In the preparation of a stock material, the viscosity of a 1% solids solution was 1400.
cps, CMC sodium salt with a degree of substitution of 0.4 (PX
01, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and the pH after addition of CMC
A base paper and a coated paper for printing were manufactured in the same manner as in Example 13 except that No. 4 was set, and the quality was evaluated.

Example 16 Before multi-stage bleaching of pulp, the pulp concentration was adjusted to 10% and the pH was adjusted to 8.0, and then an enzyme having a xylan-decomposing activity (trade name: Pulpzyme HC, manufactured by Novo Nordisk Ltd.)
2 U / g of absolutely dry pulp was added, and the mixture was treated at 60 ° C. for 90 minutes. After that, multi-stage bleaching was performed and enzyme-treated bleaching was performed to produce kraft pulp. A base paper and a coated paper for printing were produced in the same manner as in Example 13 except that this enzyme-treated pulp was used, and the quality was evaluated.

Example 17 A base paper and a coated paper for printing were produced in the same manner as in Example 16 except that the CMC addition rate was 0.02% in the preparation of the stock material, and the quality was evaluated.

Comparative Example 14 A base paper and a coated paper for printing were produced in the same manner as in Example 13 except that the sodium salt of CMC was not added and the pH of the pulp slurry was not adjusted in the preparation of the stock material. , Evaluated the quality.

Comparative Example 15 A base paper and a coated paper for printing were prepared in the same manner as in Example 13 except that pH adjustment with dilute sulfuric acid was not carried out after adding sodium salt of CMC to pulp slurry in the preparation of a stock material. Was manufactured and evaluated for quality.

Comparative Example 16 In the preparation of a stock, after adding a rosin sizing agent, a sulfuric acid band and talc to the same pulp slurry as used in Example 1 in the same manner, a yield improver (trade name: Hymolok NR11L) was used. (Manufactured by Hymo Co., Ltd.), a base paper and a coated paper for printing were manufactured in the same manner as in Example 13 except that 0.02% was added, and the quality was evaluated.

Comparative Example 17 The yield improver in Comparative Example 16 was added at 0.2%.
A base paper and a coated paper for printing were manufactured in the same manner as in Example 13 except that the above was performed, and the quality was evaluated.

Comparative Example 18 A base paper and a coated paper for printing were produced in the same manner as in Comparative Example 14 except that the enzyme-treated bleached kraft pulp used in Example 16 was used, and the quality was evaluated.

Comparative Example 19 Using the enzyme-treated bleached kraft pulp used in Example 16, in the preparation of a stock, the rosin sizing agent 0.7 described above was used.
%, A polyacrylamide paper strength enhancer (trade name: Polystron 194-7, manufactured by Arakawa Chemical Co., Ltd.) was added.
A base paper and a coated paper for printing were produced in the same manner as in Comparative Example 14 except that 2% was added, and the quality was evaluated.

Reference Example 3 The same stock as in Comparative Example 14 was used with a Fourdrinier paper machine to produce paper at a speed of 800 m.
The base paper was made into paper at a speed of 1 / min, and a coated paper for printing was manufactured in the same manner as in Example 13 except for the above, and the quality was evaluated. Example 13-
The results obtained in No. 17 and Comparative Examples 14 to 19 and Reference Example 3 are shown in Table 5.

[0092]

[Table 5]

As is clear from Table 1, all of the present inventions have superior paper strength-enhancing effects to the case of using a commercially available paper-strengthening agent containing polyacrylamide as a component (Example 1).
~ 7 and Comparative Examples 1-2). Also, CMC and / or CEC
Such an excellent effect was not exhibited without adjusting the pH by the mineral acid after adding (Example 1 and Example 3 and Comparative Examples 3 to 4), and the pH adjustment after adding CMC was lower. The effect is higher (Examples 1 and 5, and Examples 6 and 7). Further, in CMC and CEC, CMC is more effective (Examples 1 and 2 and Examples 3 and 4), and further CM
Considering also that C is cheaper, CMC is preferable in practice. Furthermore, the smaller the degree of CMC substitution, the greater the paper strength increasing effect (Examples 1 and 5).
Since Examples 6 to 7) and pH adjustment after addition of CMC can be reduced, CMC having a low degree of substitution is most preferable for use in the present invention.

Table 2 shows the effects of the present invention in a papermaking system containing a sulfuric acid band. Sulfuric acid band is one of the papermaking chemicals that is widely used as a sizing agent and other fixing agent, and the acidic papermaking and the neutral or alkaline papermaking are distinguished by the addition rate of the sulfuric acid band. That is, in acidic papermaking, about 1 to 3% by weight of a sulfuric acid band is added to the solid content of the stock, and therefore the pH of the stock slurry is 4 to 5%.
Becomes On the other hand, in neutral or alkaline papermaking, the addition rate of the sulfuric acid band is generally less than 0.5%, and calcium carbonate showing weak alkalinity is often added as a filler. Therefore, the pH of the stock slurry is 6%. It becomes ~ 9. Aluminum ions in the sulfuric acid band are adsorbed on the pulp fiber surface and act as a sizing agent and other fixing agent, but on the other hand, this hinders the interfiber bond, and the addition of the sulfuric acid band generally reduces the paper strength (reference example). 1 and Reference Example 2). However, in the case of neutral or alkaline papermaking,
As mentioned above, fillers such as calcium carbonate are generally blended, and these fillers also significantly reduce the paper strength.Accordingly, acid paper is inferior in paper strength to neutral paper because the addition rate of sulfuric acid band is large. Do not mean. Even when the effects of the present invention are compared under the conditions in which such a sulfuric acid band is added, the effects are superior to those of the commercially available paper strengthening agents (Examples 8 to 10 and Comparative Example 5). Further, as described in the previous paragraph, in this case as well, CMC has a higher effect than CEC (Examples 8 and 9), and CMC having a low degree of substitution also exhibits an excellent effect ( Example 8 and Example 10). Also, CMC
And / or without pH adjustment after CEC addition, even with sulfuric acid bands the final pH of the pulp slurry
Does not exhibit the high effect of the present invention even in the acidic region (Examples 8 to 10 and Comparative examples 6 to 8). Further this pH
If the adjustment is not performed with a mineral acid such as sulfuric acid, almost no effect is exhibited (Example 8 and Comparative Example 9). This is because when the pH is adjusted with a mineral acid such as dilute sulfuric acid, CMC and / or CEC are adsorbed on the pulp fiber surface with a uniform distribution, whereas when the pH is adjusted with a sulfuric acid band. Although it is adsorbed on the pulp, it is considered that CMC and / or CEC becomes a gel and the distribution on the pulp fiber is poor.
The greatest feature of the present invention is that the pH is adjusted by the mineral acid instead of the sulfuric acid band.

Table 3 shows the effect of the present invention when a sizing agent other than a paper strengthening agent is added in the acidic papermaking method. As is clear from this table, the present invention uses a conventionally used paper-strengthening agent (polyacrylamide) in a small amount (0.1% based on the weight of pulp),
Even in the above acidic papermaking, it is possible to obtain extremely excellent tensile strength and interlayer strength, and further, the yield of the sizing agent,
Also, since the distribution on the fiber is excellent, an extremely high sizing degree can be exhibited, and the amount of the sizing agent can be reduced as needed (Example 12 and Comparative Examples 12 to 12).
13).

In Table 4, calcium carbonate is added as a filler, and under the conditions of neutral papermaking in which the final pulp slurry pH is around 8, filler, sizing agent, and yield improver are used in addition to the paper strength enhancer. It shows the effect of the present invention when added. As is clear from this table, the present invention can significantly improve the yield of the filler even in the neutral papermaking method to increase the tensile strength and the sizing degree, reduce the amount of chemicals used as necessary, and reduce the manufacturing cost. Can be reduced (Example 12 and Comparative Examples 12 to 13). The high yield of the filler suggests that the stain generation in the papermaking system is small, which is also one of the remarkable effects of the present invention.

Further, as is clear from Table 5, according to the method of the present invention, it was a problem in printing the base paper of the coated paper for printing at high speed that the printing was excellent in glossiness and blister resistance. Coated paper can be produced, but the effect is higher when the amount of CMC added is larger (Examples 13 and 14), and the effect is higher when CMC having a low degree of substitution is used (Example 1).
5). Further, by using pulp treated with an enzyme having a xylan-decomposing activity, it becomes possible to produce a coated paper for printing which is further excellent in blister resistance (Example 1).
6, 17). When no CMC was added (Comparative Example 14),
Alternatively, even if CMC is added, if the pH is not adjusted (Comparative Example 15), the gloss and the blister property are unsatisfactory, and the addition of the yield improver deteriorates the formation and does not improve the blister resistance ( Comparative Examples 16 and 17).

[0098]

INDUSTRIAL APPLICABILITY The present invention not only imparts excellent strength to paper, but also a papermaking chemical added to a pulp fiber slurry,
The effect of providing a paper manufacturing method that significantly improves the yield of fillers, improves the quality of paper, and reduces the manufacturing cost is provided. In addition, when making base paper for coated paper for printing, even with high speed paper making with a gap former,
It is possible to produce a coated paper for printing which has an improved yield without deteriorating the texture and exhibits excellent sizing properties, and as a result, has excellent surface gloss and printing gloss, and which is free from uneven gloss. Further, by effectively improving the interlaminar strength, it becomes possible to produce a coated paper for printing which is also excellent in blister resistance. When the pulp treated with the enzyme having a xylan-decomposing activity is used, the air permeability of the base paper is increased, so that it becomes possible to produce a coated paper for printing which is further excellent in blister resistance.

[0099]

[Brief description of drawings]

FIG. 1 is a schematic view of a conventional Fourdrinier paper machine.

FIG. 2 is a schematic view of a normal hybrid former type paper machine.

FIG. 3 is a schematic view of a conventional gap former type paper machine.

[Explanation of symbols]

 1. Head box 2. Forming board 3. Suction foil 4. Bottom wire 5. Top wire 6. Suction box

Claims (9)

[Claims] 1. Carboxymethyl cellulose and / or carboxyethyl cellulose is added to a slurry of pulp fibers, and then mineral acid is added to adjust the pH of the pulp fiber slurry to a range of 2 to 6, to thereby obtain carboxymethyl cellulose and / or A pulp characterized in that carboxyethyl cellulose is converted to an acid form and adsorbed on the pulp. 2. The degree of substitution of carboxymethyl cellulose and / or carboxyethyl cellulose is 0.3 to 0.6.
And the pH after the addition of mineral acid is in the range of 3.5 to 5.5, The pulp according to claim 1. 3. The pulp according to claim 1 or 2, wherein the pH of the pulp fiber slurry after the addition of the mineral acid is further adjusted to pH 5-9. 4. The addition amount of carboxymethyl cellulose and / or carboxyethyl cellulose is 0.01 to 5.0% by weight based on the weight of the bone-dry pulp, wherein the addition ratio is 0.01 to 5.0% by weight. 3. The pulp according to item 3. 5. The pulp according to claim 1, wherein the pulp fiber according to claim 1 is treated with an enzyme having a xylan-decomposing activity. 6. A paper comprising the pulp according to claim 1, claim 2, claim 3, claim 4 or claim 5. 7. A method for producing a paper by a wet paper machine using a pulp fiber slurry comprising the pulp according to claim 1 and a papermaking chemical containing a paper strengthening agent and optionally a filler. . 8. The wet paper machine according to claim 7, wherein the paper is made by a gap former type paper machine.
A method for producing the described paper. 9. A coated paper, characterized in that a coated layer is provided on one side or both sides of the paper according to claim 6.