JP2005082893A - Paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide paper having good sizing properties similar to those of neutral paper, excellent operation efficiency and excellent preservability in spite of papermaking under acidic conditions. <P>SOLUTION: The paper is formed under the acidic conditions of papermaking pH 3.0-6.0, preferably without using elemental chlorine and contains sodium hydrogencarbonate in an amount of 0.03-1.0 g/m<SP>2</SP>expressed in terms of solids on at least one surface of paper containing aluminum sulfate and an internal sizing agent for acidic papermaking, preferably a rosin sizing agent. The paper surface pH is 6.0-8.5. The paper has excellent preservability and a wide range of uses. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a paper having good sizing properties, excellent operability, and excellent storability, similar to neutral paper, even though the paper is made under acidic conditions.

  Conventionally, sizing agents for papermaking such as rosin sizing agents, emulsion sizing agents, alkenyl succinates, alkyl ketene dimers, alkenyl succinic anhydrides, etc. have been used for the purpose of imparting water resistance to paper and preventing recording bleeding. Added to pulp slurry and used. In the case of acidic papermaking, conventionally, rosin-based sizing agent and aluminum sulfate as a fixing agent are used to impart desired sizing properties. However, acidic papermaking has problems of paper deterioration and yellowing during long-term storage, and this tendency is particularly noticeable when pulp that has been bleached without using elemental chlorine is used.

  Due to the problem of long-term storage of paper, neutral papermaking is progressing. In neutral papermaking, sizing agents for neutral paper such as alkyl ketene dimers (hereinafter referred to as AKD) and alkenyl succinic anhydrides (hereinafter referred to as ASA), cationic polymers and fillers as retention improvers. Calcium carbonate is used.

  However, the neutral sizing agent has a lower yield than the rosin sizing agent, and the resulting paper has a low sizing degree. In addition, AKD has a slow onset effect of size, and the product paper is slippery, and ASA is very easy to decompose. Therefore, emulsification is necessary just before the addition, and the paper machine becomes dirty and around the press. It causes troubles, paper dust, holes, etc. (see, for example, Non-Patent Document 1). Various cationic polymers such as cation-modified starch, polyacrylamide resin, and polyamide resin have been added to improve sizing yield and paper strength. To cause stains in the system and paper.

  Further, the pulp slurry pH at the time of papermaking is about 8.0 to 9.5, which is also a cause of deterioration in operability such as generation of pitch and slime and papermaking speed down due to deterioration of water drainage at the time of papermaking.

  In order to solve these problems, it has been proposed to improve the yield of a neutral sizing agent using carboxymethyl cellulose (for example, see Patent Document 1), but there is a problem of high cost. In addition, it has also been proposed to prevent deterioration of paper by applying an alkali metal salt of acid having a pKa of 10.0 or more to acidic paper (for example, see Patent Document 2). If applied, the paper size effect is hindered.

  On the other hand, there are also problems with products made with neutral paper using calcium carbonate. In thermal recording paper, if calcium ions are present, there is a problem that the printing density becomes insufficient due to reaction with the developer, and release paper deteriorates foaming problems at the time of lamination and adhesiveness at the time of processing. Due to problems, neutralization of these products has not progressed. In order to solve these problems, it has been proposed to neutralize the pulp slurry using a water-soluble alkali salt instead of calcium carbonate to make neutral paper (for example, see Patent Document 3). When the basic alkali salt is a strong alkali salt, the size becomes low as described above, which causes the generation of dirt.

Moreover, in order to prevent degradation of acidic paper, methods for improving papermaking pulp have been proposed (see, for example, Patent Documents 4 to 6), but these methods have problems such as remodeling of equipment and cost increase. is there.
JP 2000-27092 A Japanese Patent No. 2739918 JP 7-331593 A Japanese Patent Laid-Open No. 2002-266271 JP-A-2003-96680 Japanese Patent Laid-Open No. 2003-105684 Papa Technical Association, Vol. 44, No. 9, pp. 10-20, September 1990

  The present invention provides a neutral paper that is excellent in storage stability of paper and excellent in operability and size.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on a paper excellent in long-term storage stability and a method for producing the same while maintaining the good size effect, operability, and product quality that are the characteristics of acidic papermaking. As a result, we found that neutral paper with excellent storage stability can be obtained while maintaining the characteristics of acidic papermaking by applying sodium hydrogen carbonate to the paper made under acidic conditions and adjusting the pH of the paper surface to a neutral range. It was. The present invention includes the following inventions.

  (1) Papermaking is carried out under acidic conditions of 3.0 to 6.0, and at least one side of the paper containing aluminum sulfate and an internal sizing agent contains sodium hydrogen carbonate, and the paper surface pH is 6 Paper that is .0 to 8.5.

(2) The paper according to item (1), wherein the content of the sodium hydrogen carbonate is 0.03 to 1.0 g / m ² as a solid content.

  (3) The paper according to item (1) or (2), wherein the internal sizing agent is an acidic papermaking internal sizing agent, preferably a rosin sizing agent.

  (4) The paper containing the aluminum sulfate and the internally added sizing agent is a pulp obtained by bleaching a raw material pulp without using elemental chlorine. Paper described.

  (5) General office paper, printing paper, coating base paper, information paper base paper, release paper base paper, or label base paper using the paper according to any one of the above items (1) to (4).

(6) A step of making a pulp slurry to which aluminum sulfate and an internal sizing agent for acidic papermaking, preferably a rosin sizing agent are added, under acidic conditions of pH 3.0 to 6.0, and at least one side of the resulting paper Coating with an aqueous solution of sodium bicarbonate and drying to adjust the pH of the paper to 6.0 to 8.5, and at least one side of the paper containing aluminum sulfate and an internal sizing agent is coated with sodium bicarbonate. The manufacturing method of the paper which contains 0.03-1.0 g / m < ² > as solid content, and the paper surface pH is 6.0-8.5.

(7) The aluminum sulfate is added to the pulp slurry at a ratio of 0.5 to 3.0% by mass with respect to the dry dry pulp, at least one side of the paper containing the aluminum sulfate and the internal sizing agent according to (6) In addition, a method for producing paper having a sodium hydrogen carbonate content of 0.03 to 1.0 g / m ² and a paper surface pH of 6.0 to 8.5.

(8) The step of coating the aqueous sodium hydrogen carbonate solution and drying to adjust the paper surface pH to 6.0 to 8.5 is performed by applying 0.03 to 1.0 g / m ^{2 with} sodium hydrogen carbonate as a solid content. A method for producing a paper having a paper surface pH of 6.0 to 8.5 according to (6) or (7), which is a step of processing and drying.

  The paper of the present invention is a paper that exhibits the effect of excellent long-term storage stability while maintaining the good size effect, operability and product quality that are the characteristics of acidic papermaking.

  As the papermaking pulp used in the present invention, wood pulp such as softwood bleached kraft pulp and hardwood bleached kraft pulp, non-wood pulp such as kenaf, and waste paper pulp can be used alone or in combination. In particular, when kraft pulp bleached without using elemental chlorine is used, the effect of the present invention is great because acidic paper deteriorates more severely than pulp bleached using conventional chlorine.

  As the sizing agent used in the paper of the present invention, those for conventional acidic papermaking can be used, but a rosin sizing agent is preferable from the viewpoint of size effect and operability. As an addition rate, it is 0.05-1.0 mass% normally with respect to a pulp.

  The amount of aluminum sulfate used in the paper of the present invention is usually 0.5 to 3.0% by mass with respect to the pulp, and the pulp slurry pH becomes 3.0 to 6.0.

  In the paper of the present invention, if necessary, talc, kaolinite, illite, titanium dioxide, etc. may be used alone or in combination, but since the paper is produced under acidic conditions, the calcium carbonate used for neutral papermaking Such alkaline salts cannot be used as fillers. However, other papermaking chemicals such as known paper strength enhancers and yield improvers may be used as necessary.

  The paper of the present invention contains aluminum sulfate and an internal sizing agent, and contains sodium hydrogen carbonate (pKa 6.4) on at least one side of the paper made under acidic conditions. Sodium hydrogen carbonate is preferably contained uniformly on the paper surface, and is preferably contained by coating or impregnation. Sodium hydrogen carbonate is particularly preferred because the pH of the paper surface can be adjusted to near neutral while maintaining sizing properties, and a compound that becomes strongly alkaline, such as sodium hydroxide, has a marked decrease in sizing of the base paper when used. Therefore, it is not suitable. In addition, the value described in the Chemical Handbook Basic Edition 4th edition (Edited by Chemical Society of Japan, published by Maruzen, 1993) was used as the pKa value.

Coating or impregnating amount of sodium bicarbonate will vary depending on the pH of the base paper is 0.03 to 1.0 g / m ^2, preferably 0.05~0.7g / m ^2. If it is less than 0.03 g / m ² , the effect of adjusting the paper surface pH to near neutral cannot be obtained, and even if it is applied or impregnated in excess of 1.0 g / m ² , the effect reaches a peak, which is not preferable. The coating or impregnation method can be selected from known coating methods such as size press coating, air knife coating, blade coating, roll coating, gate roll coating, and bar coating, but size press coating is preferred from the viewpoint of operability.

  In the aqueous sodium hydrogen carbonate solution for coating, starches, surface sizing agents, water-soluble polymers, pigments, dispersants, antifoaming agents, dyes, and the like can be added as necessary.

  The paper of the present invention is used for general office paper, printing paper, coating base paper, information paper base paper, release paper base paper, label base paper, etc., and is not particularly limited. In the case of acid paper, discoloration is promoted by heating and humidification. Therefore, the paper of the present invention is effective for papers that are affected by these.

  The paper of the present invention is superior in size effect, operability and product quality because the pulp slurry at the time of papermaking is acidic, and in addition, the sheet-like paper is coated or impregnated with sodium hydrogen carbonate, among other alkali metal salts. Since the pH is adjusted to near neutrality, there is an advantage that it is excellent in long-term storage, and it is extremely useful industrially.

  EXAMPLES Next, although this invention is demonstrated in detail based on an Example, an Example does not limit this invention at all. In Examples and Comparative Examples, “parts” and percentages (%) mean parts by mass and mass% unless otherwise specified. The evaluation method is shown below.

1. Paper pH: Measured using a paper pH test solution (manufactured by Kyoritsu Riken).
2. Sizing degree: The steadiness degree was measured according to the procedure of JIS P8122.

3. Preservability: Hold for 24 hours under conditions of 80 ° C. and relative humidity 65%, and calculate the PC value as a measure of fading according to the following formula from the whiteness before and after the test to evaluate the preservability. The release paper was evaluated for the release non-coated surface.
PC value = (1−whiteness after fading) ² / (2 × whiteness after fading) − (1−whiteness before fading) ² / (2 × whiteness before fading)

Example 1
A pulp slurry consisting of 100 parts of hardwood kraft pulp bleached without using elemental chlorine (degree of beating: 450 ml CSF), 0.3 parts of reinforced rosin sizing agent (trade name: SPE, manufactured by Arakawa Chemical Industries), aluminum sulfate 1 .5 parts added to a paper obtained by paper making (paper making pH 4.5) with a long net paper machine, the following coating liquid 1 was applied at a solid content of 3.5 g / m ² (carbonic acid) was applied on both sides of sodium hydrogen using a 2-roll size press so that the 0.23 g / m ^2), to obtain a paper having a basis weight of 80 g / m ^2. The paper surface pH, sizing degree, and PC value of this paper were measured by the above methods.

<Coating liquid 1>
Oxidized starch (trade name: Ace Y, manufactured by Oji Constarch): 100 parts Surface sizing agent (trade name: Polymaron 1329, manufactured by Arakawa Chemical Industries): 4 parts Sodium bicarbonate (pKa6.35): 7 parts Water: 1500 parts

Example 2
The following coating 2 was applied in solid content to the following coating 2 on a paper obtained by papermaking under the same conditions as in Example 1 except that 1.0 part of aluminum sulfate and a papermaking pH of 5.0 were used. Double-side coating was performed using a two-roll size press so that the amount was 35 g / m ² (sodium bicarbonate was 0.08 g / m ² ), and a paper having a basis weight of 80 g / m ² was obtained. The paper surface pH, sizing degree, and PC value of this paper were measured by the methods described above.

<Coating liquid 2>
A coating solution 2 was prepared according to the same formulation as the coating solution 1 except that sodium bicarbonate was used in an amount of 2.5 parts.

Example 3
The following coating material 3 was applied in a solid content of 4 to the following coating 3 on paper obtained under the same conditions as in Example 1 except that 2.5 parts of aluminum sulfate and pH of papermaking were set to 3.5. Double-sided coating was performed using a two-roll size press so that the amount was 0 g / m ² (sodium bicarbonate was 0.7 g / m ² ) to obtain a paper having a basis weight of 80 g / m ² . The paper surface pH, sizing degree, and PC value of this paper were measured by the methods described above.

<Coating liquid 3>
A coating solution 3 was prepared according to the same formulation as the coating solution 1 except that the sodium bicarbonate was 22 parts.

Comparative Example 1
In Example 1, paper was obtained in the same process as in Example 1 except that sodium hydrogen carbonate was removed in the formulation of Coating Solution 1. The paper surface pH, sizing degree, and PC value of this paper were measured by the above methods.

Comparative Example 2
In Example 1, a base paper was obtained in the same process as in Example 1 except that sodium bicarbonate was changed to sodium hydroxide according to the formulation of Coating Solution 1. The paper surface pH, sizing degree, and PC value of this paper were measured by the above methods.

Comparative Example 3
In Example 1, a base paper was obtained in the same process as in Example 1 except that sodium bicarbonate was changed to sodium carbonate (pKa 10.33) according to the formulation of the coating liquid 1. The paper surface pH, sizing degree, and PC value of this paper were measured by the above methods.

Comparative Example 4
A sample obtained by adding 0.3 part of a neutral sizing agent (alkenyl succinic anhydride, ASA), 0.4 part of cationic starch and 0.1 part of sodium hydroxide to 100 parts of the pulp slurry used in Example 1 was obtained. Paper is made with a type paper machine (paper making pH 6.8), and the two-roll size is obtained by removing the sodium hydrogen carbonate from the coating liquid of Example 1 so that the coating amount on both sides is 3.5 g / m ^{2 in} solid content. The paper was coated on both sides using a press to obtain a paper having a basis weight of 80 g / m ² . The paper surface pH, sizing degree, and PC value of this paper were measured by the above methods.

From Example 1 and Comparative Example 1 in Table 1, it can be seen that the paper of the present invention has greatly improved storage stability while maintaining good sizing properties. Moreover, from Example 1 and Comparative Examples 2 and 3, it can be seen that when sodium hydroxide or sodium carbonate is applied, the storability is improved, but the size is significantly reduced. On the other hand, it can be seen from Example 1 and Comparative Example 4 that the present invention can obtain better sizing properties than neutral papermaking. Thus, the present invention is suitable for the production of paper having excellent paper storage stability.

Claims (7)

  Papermaking is carried out under acidic conditions of 3.0 to 6.0, and at least one side of the paper containing aluminum sulfate and an internal sizing agent contains sodium hydrogen carbonate, and the paper surface pH is 6.0 to 6.0. Paper that is 8.5. The paper according to claim 1, wherein the content of the sodium hydrogen carbonate is 0.03 to 1.0 g / m ² as a solid content.   The paper according to claim 1 or 2, wherein the internal sizing agent is an internal sizing agent for acidic papermaking, preferably a rosin sizing agent.   The paper according to any one of claims 1 to 3, wherein the paper containing the aluminum sulfate and the internal sizing agent is a pulp obtained by bleaching a pulp as a raw material without using elemental chlorine.   A general office paper, printing paper, coating base paper, information paper base paper, release paper base paper or label base paper using the paper according to any one of claims 1 to 4. A step of making a pulp slurry containing aluminum sulfate and an internal sizing agent for acidic papermaking, preferably rosin-based sizing agent, under acidic conditions of pH 3.0 to 6.0, and hydrogen carbonate on at least one side of the resulting paper Applying an aqueous solution of sodium and drying to adjust the pH of the paper to 6.0 to 8.5. On at least one side of the paper containing aluminum sulfate and an internal sizing agent, sodium bicarbonate as a solid content , 0.03 to 1.0 g / m ² , and a method for producing paper having a paper surface pH of 6.0 to 8.5. The aluminum sulfate is added to the pulp slurry at a ratio of 0.5 to 3.0% by mass with respect to the dry pulp, and at least one side of the paper containing the aluminum sulfate and the internal additive sizing agent is carbonated. The manufacturing method of the paper which contains 0.03-1.0 g / m < ² > as a solid content of sodium hydrogen, and the paper surface pH is 6.0-8.5.