JP2007314916A - Acid-free paper and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide acid-free paper excellent in sizing property and the like by increasing yield of used chemicals such as a neutral sizing agent. <P>SOLUTION: The acid-free paper uses EFC (elementary chlorine free) bleached pulp having an ISO brightness of ≥80% and a permanganate number (JIS P 8206) of ≥2 and includes a neutral sizing agent. The ECF bleached pulp is preferably is bleached pulp produced by a multistage bleaching process including a chlorine dioxide stage at ≤70°C, wherein the chlorine dioxide additive rate to absolute dry mass of the pulp is ≤0.06 mass% per 1 kappa number before bleaching (JIS P 8211) as a first bleaching step. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a neutral paper produced from ECF (elementary chlorin-free) bleached pulp. More specifically, the present invention relates to a neutral paper having a good yield of a neutral internal sizing agent and excellent in paper sizing.

  Conventionally, paper-making sizing agents such as rosin sizing agents, emulsion sizing agents, alkenyl succinates, alkyl ketene dimers, alkenyl succinic anhydrides, and the like have been added to pulp slurries for the purpose of imparting water resistance to paper during paper making. ing. One of the major problems with these sizing agents is poor sizing yield, especially in neutral papermaking. The fixing mechanism of the sizing agent on the pulp varies depending on the type of sizing agent. In particular, alkyl ketene dimers and alkenyl succinic anhydrides used in neutral paper making have poor yields and are unstable. Have problems such as low. For this reason, various cationic chemicals such as cation-modified starch, polyamide / epichlorohydrin resin, polyethyleneimine resin, polyacrylamide resin, polyamide resin, etc. are added for the purpose of improving the yield of sizing agent and the strength of paper. . However, there are problems such that the effect obtained by such treatment is not sufficient, the effect is lowered by other chemicals and fillers added, and the quality is not stable.

  Furthermore, modified starch, polyacrylamide, polyamide, polyamide-epichlorohydrin resin, melamine-formaldehyde resin, urea-formaldehyde resin, etc. are used as an internal paper strength enhancer with the purpose of increasing the strength of paper together with the internal sizing agent. However, even if these are used alone, they have various disadvantages such as poor yield, small paper strength enhancement effect, and poor formation, and are not fully satisfactory in terms of operation and paper quality. As a method for improving this, a method of using anionic polyacrylamide in combination with Mannich-modified or Hoffman-modified cationic polyacrylamide, or a method of adding a mixture of these is known. Although a slight improvement in yield and paper strength can be achieved, the amount of sulfuric acid band added is large and the influence of chemical aids used in combination with other additives is significant, and the effect has not reached a satisfactory level. .

  Cellulose derivatives such as carboxymethyl cellulose (hereinafter referred to as CMC) and carboxyethyl cellulose (hereinafter referred to as CEC) have long been known to have an effect of enhancing the strength of paper. The strength enhancement effect is small, and there is a problem that it does not stay on the paper unless the sulfuric acid band is added in combination, and the effect is not manifested. is there.

  As a means for solving these problems of size and paper strength, CMC and / or CEC is added to the pulp slurry, and then the mineral fiber is added to adjust the pH of the pulp fiber slurry to a range of 2 to 6, and CMC And / or CEC is converted into an acid form, adsorbed on pulp, and paper making is proposed (Patent Document 1). However, in this method, it is necessary to use CMC having a low substitution degree in the range of 0.3 to 0.6, and a sufficient effect cannot be obtained particularly in papermaking in a neutral to alkaline region. Have the problem.

  Chitosan, on the other hand, is obtained by deacetylating chitin contained in shrimp and crab shells with high-concentration hot alkali treatment, and is known to have a paper strength enhancing effect when added to pulp slurry. Mixing CMC or CEC and chitosan with a sizing agent, paper strength enhancer, etc. in a pulp slurry produces a composite of paper chemicals, CMC or CEC and chitosan, and the composite adsorbs to the pulp. It is disclosed that the yield is improved (Patent Document 2). However, even if this method is used, a sufficient yield improving effect and paper strength enhancing effect cannot be obtained, and chitosan is hardly used as an internal additive for papermaking. Thus, there is a need for neutral papermaking that improves the yield of papermaking chemicals such as sizing agents and paper strength enhancers and is excellent in size and paper strength.

  In addition, it is known that the degree of size is improved by using chlorous acid to oxidize the aldehyde group which is the reducing terminal of the cellulose and hemicellulose molecular chain in the bleached pulp to a carboxyl group and adding an alkyl ketene dimer ( Non-patent document 1). Further, the bleached pulp is dispersed in water to maintain the pH at 10 to 11, the catalytic amount of 2,2,6,6-tetramethylpiperidineoxy radical (TEMPO) and sodium bromide are dissolved, and hypochlorous acid is added. It is known that when added, a carboxyl group is introduced into bleached pulp and a rosin sizing agent is added to improve the sizing degree (Non-patent Document 2). However, these sizing agent fixing methods based on pulp modification have problems such as increased chemical costs and increased equipment costs, and are not practical.

  On the other hand, in recent years, it has been known that 4-O-methylglucuronic acid present in wood is converted into hexeneuronic acid in a cooking process and present in unbleached pulp (Non-patent Document 3). It has been found that this hexeneuronic acid deteriorates the fading of acidic paper if it remains in bleached pulp in large amounts without being decomposed in the multistage bleaching process (Non-Patent Document 4). Many methods for improving fading have been proposed (for example, Patent Document 3).

However, there is no known method for improving the yield of a neutral sizing agent or the like by leaving the hexeneuronic acid in bleached pulp and utilizing the carboxyl group.
JP-A-9-291490 JP 2000-27092 A Japanese National Patent Publication No. 10-508346 Akira Hatai, Pulp and Paper Technology Times 46 (7), 1-6, 2003 Takaya Kitaoka et al., Nordic Pull and Paper Research Journal, 15 (177), 2000. T.A. Vuorinen et al., 1996 Int Pull Bleaching Conf. , Vol. 1 pp. 43-52 Ayano Kawae et al., Appita Journal vol 58 (5), 378-381, 2005.

  An object of the present invention is to provide a neutral paper excellent in size and the like by overcoming the drawbacks of the prior art and improving the yield of chemicals used such as a neutral sizing agent.

  In view of such a background, the present inventors have intensively studied to find out a method for improving the yield of papermaking chemicals such as a sizing agent and a paper strength enhancer in neutral papermaking and improving the quality of paper. Of these, attention was paid to the carboxyl group of hexeneuronic acid present in bleached pulp. When acidic paper is produced using bleached pulp having a high potassium permanganate value and a large amount of hexeneuronic acid remaining, the color fading is remarkably deteriorated. However, when producing neutral paper, the color fading is not a problem.

On the other hand, when the amount of carboxyl groups in bleached pulp increases, the yield of neutral sizing agents and paper strength enhancing agents improves. From these facts, when neutral paper is produced using bleached pulp with a high potassium permanganate value and a large amount of hexeneuronic acid, neutral sizing agents and The inventors have found that the yield of the paper strength enhancer is greatly improved and that neutral paper can be produced with better size and paper strength, and the present invention has been completed.
The present invention capable of achieving the above object includes the following inventions.

(1) An ECF (elementary chlorin-free) bleached pulp having an ISO whiteness of 80% or more and a potassium permanganate value (JIS P 8206) of 2 or more is used, and neutral neutrality Neutral paper containing additive sizing agent.

(2) The neutral paper according to (1), wherein the amount of hexeneuronic acid in the bleached pulp is 15 mmol / kg or more.

(3) The bleached pulp has a temperature of 70 ° C. or less at the first stage of bleaching, and a chlorine dioxide addition rate of 0.06% by mass or less per bleached kappa number (JIS P 8211) per absolute dry pulp mass. The neutral paper according to (1) or (2), wherein the neutral paper is a pulp bleached by an ECF (elementary chlorin-free) multi-stage bleaching step.

(4) The bleached pulp is a pulp bleached by an ECF multi-stage bleaching process including at least one alkaline hydrogen peroxide stage so that the total hydrogen peroxide addition rate is 0.3% or more per mass of dry pulp. The neutral paper according to any one of (1) to (3), wherein the neutral paper is present.

(5) The neutral paper according to any one of (1) to (4), wherein the neutral internal sizing agent is an alkyl ketene dimer or an alkenyl succinic anhydride.

(6) Bleached pulp having an ISO whiteness of 80% or more, a potassium permanganate value (JIS P 8206) of 2 or more, and a hexeneuronic acid amount of 15 mmol / kg or more is used as a raw pulp. A method for producing neutral paper, which comprises making a paper with an additive sizing agent.

(7) The neutral paper manufacturing method according to (6), wherein the bleached pulp is bleached pulp manufactured according to an ECF (elementary chlorin-free) multistage bleaching step.

(8) Chlorine dioxide stage in which the ECF multi-stage bleaching step is at a temperature of 70 ° C. or less, and the chlorine dioxide addition rate is 0.06% by mass or less per bleached kappa number (JIS P 8211) per one dry pulp mass (7) The neutral paper manufacturing method according to (7), which is a multi-stage bleaching step including

(9) The ECF multi-stage bleaching process is a multi-stage bleaching process including at least one alkaline hydrogen peroxide stage so that the total amount of hydrogen peroxide added is 0.3% or more per mass of completely dried pulp (6) Or the manufacturing method of the neutral paper as described in (7).

(10) In the multistage bleaching step, the first stage is a chlorine dioxide bleaching stage (D), the second stage is a hydrogen peroxide stage (P) or an alkali extraction stage (E), and the third stage and thereafter are chlorine dioxide stages. Or the manufacturing method of the neutral paper of any one of (7)-(9) which is a bleaching process according to the bleaching sequence which is a hydrogen peroxide stage.

(11) The method for producing a neutral paper according to any one of (6) to (10), wherein the bleached pulp is bleached pulp manufactured using hardwood as a lignocellulosic material as a raw material. .

(12) The neutral paper sizing agent according to any one of (6) to (11), wherein the neutral internal sizing agent is alkyl ketene dimer or alkenyl succinic anhydride.

  When producing neutral paper by using ECF (elementary chlorin free) bleached pulp with ISO whiteness of 80% or more and potassium permanganate value (JIS P 8206) of 2 or more The yield of neutral sizing agents and paper strength enhancers can be improved, and the size and strength of paper can be greatly improved.

  The lignocellulosic material used as the raw material for the bleached pulp used in the present invention is not particularly limited. Although hardwood, softwood, and non-wood may be used, bleached pulp produced from hardwood contains a large amount of hexeneuronic acid, which is preferable because the effects of the present invention are great. Moreover, as the cooking method for obtaining the bleached pulp used in the present invention, known cooking methods such as kraft cooking, polysulfide cooking, soda cooking, alkali sulfite cooking, etc. can be used, but pulp quality, energy efficiency In view of the above, the kraft cooking method or the polysulfide cooking method is preferably used.

  For example, when kraft cooking of wood, the sulfidity of the kraft cooking solution is 5 to 75%, preferably 15 to 45%, and the effective alkali addition rate is 5 to 30% by weight, preferably 10 to 25% by weight of the absolutely dry wood. %, The cooking temperature is 130-170 ° C., and the cooking method may be either a continuous cooking method or a batch cooking method. When a continuous cooking kettle is used, a modified cooking method in which a cooking solution is added at multiple points may be used. The method is not particularly limited.

  In cooking, a known cyclic keto compound as a cooking aid in the cooking solution to be used, for example, benzoquinone, naphthoquinone, anthraquinone, anthrone, phenanthroquinone and the above-described quinone-based compounds such as alkyl and amino, or the quinone-based compounds Selected from hydroquinone compounds such as anthrahydroquinone, which is a reduced form of the compound, and 9,10-diketohydroanthracene compounds, which are stable compounds obtained as intermediates in the anthraquinone synthesis method by the Diels-Alder method 1 type (s) or 2 or more types may be added and the addition rate is 0.001-1.0 mass% per the absolute dry mass of a wood chip.

  In this invention, the unbleached pulp obtained by the well-known cooking method is delignified by the well-known alkaline oxygen bleaching method through a washing | cleaning, a rough selection, and a selection process. As the alkaline oxygen bleaching method used in the present invention, a known medium concentration method or a high concentration method can be applied as it is, but a medium concentration method which is currently used at a pulp concentration of 8 to 15% is widely used. preferable.

  In the alkali oxygen bleaching method using the medium concentration method, caustic soda or oxidized kraft white liquor can be used as the alkali. As the oxygen gas, oxygen from a cryogenic separation method, PSA (Pressure Swing Adsorption) Oxygen, oxygen from VSA (Vacuum Swing Adsorption), etc. can be used. The oxygen gas and alkali are added to a medium-concentration pulp slurry in a medium-concentration mixer. After sufficient mixing, the oxygen gas and alkali are sent to a reaction tower capable of holding a mixture of pulp, oxygen, and alkali for a certain period of time under pressure. Ligned.

  The oxygen gas addition rate is 0.5 to 3% by mass per mass of dry pulp, the alkali addition rate is 0.5 to 4% by mass, the reaction temperature is 80 to 120 ° C., the reaction time is 15 to 100 minutes, and the pulp concentration Is 8 to 15% by mass, and other known conditions can be applied. In the present invention, in the alkali oxygen bleaching step, it is a preferred embodiment that the alkali oxygen bleaching is continuously carried out a plurality of times and delignification proceeds as much as possible. The pulp that has been subjected to alkaline oxygen bleaching is then sent to a washing step. After washing, the pulp is sent to an acid treatment process or a multi-stage bleaching process.

  The multi-stage bleaching treatment for obtaining the bleached pulp of the present invention is characterized by not using elemental chlorine which has a high effect of removing hexeneuronic acid. Any combination of bleaching without using elemental chlorine (commonly referred to as ECF (Elementary Chlorine Free) bleaching) may be used, and chlorine dioxide (D), alkali (E), oxygen (O), hydrogen peroxide (P ), Ozone (Z), peracid, and the like, and known bleaching agents and bleaching assistants may be mentioned. Chlorine dioxide, alkali, oxygen, and hydrogen peroxide, which have a relatively low decomposition efficiency of hexeneuronic acid, are preferred.

  Of course, ozone, peracid, and the like can be used, but use of ozone and peracid is limited because it decomposes hexeneuronic acid relatively efficiently. Although acid treatment with sulfuric acid or the like can also be used, hexeneuronic acid is decomposed by acid treatment at a high temperature exceeding 75 ° C., and therefore, it is preferably performed at 75 ° C. or less. The first stage of the multi-stage bleaching process uses a chlorine dioxide bleaching stage (D) where the decomposition efficiency of hexeneuronic acid is relatively low, and the second stage is a hydrogen peroxide stage (P) or an alkali extraction stage where the decomposition efficiency of hexeneuronic acid is further low (E) The bleaching sequence using chlorine dioxide or hydrogen peroxide is preferably used after the second break or after the third stage. The number of bleaching stages is not particularly limited, but in consideration of energy efficiency, productivity and the like, it is preferable to finish in 3 stages or 4 stages in total.

  In the first stage chlorine dioxide stage of the multi-stage bleaching process of the present invention, when a large amount of chlorine dioxide is added, hexeneuronic acid is decomposed. Therefore, the chlorine dioxide addition ratio is 0. The amount is preferably 06% by weight or less. Moreover, since the decomposition amount of hexeneuronic acid increases when the temperature of the chlorine dioxide stage exceeds 70 ° C, the temperature is preferably 70 ° C or less. The pH of the chlorine dioxide stage is 2 to 6, and any acid or alkali can be supplementarily added to adjust the pH. As other chlorine dioxide bleaching conditions such as chlorine dioxide treatment time and pulp concentration, all known conditions can be adopted.

  In the alkaline hydrogen peroxide stage used in the multi-stage bleaching step of the present invention, it is preferable to add 0.3% or more of hydrogen peroxide which does not decompose hexeneuronic acid so much per weight of the dry pulp. This is because the addition rate of chlorine dioxide is limited in order to avoid excessive decomposition of hexeneuronic acid in the chlorine dioxide stage, so that the whiteness can be greatly improved in the alkaline hydrogen peroxide stage. In the alkaline hydrogen peroxide stage of the present invention, oxygen can be used in combination. In addition, as the conditions for the alkaline hydrogen peroxide stage of the present invention, all known conditions can be adopted.

  Examples of the multi-stage bleaching sequence in the present invention include, for example, DE / P-D, D / E / OP-D, D / E / P-P, D / E / OP-P, and D-E-P-D. , D-E / P-P-D, D-E / OP-P-D, D-E / OP-DP, and the like. Further, a chelating agent treatment stage with ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) or the like may be inserted during the multistage bleaching treatment. This multi-stage bleaching sequence does not limit the invention in any way.

  In the multi-stage bleaching treatment, in order to leave a large amount of hexeneuronic acid after bleaching, it is possible to strengthen the bleaching stage performed under alkalinity where the effect of removing hexeneuronic acid is low, and as a result, the amount of chlorine dioxide used can be reduced. There is an advantage that the load of bleaching drainage can be reduced.

  In the multi-stage bleaching treatment of the present invention, if the potassium permanganate value of the bleached pulp is set to 2 or more, details of the reason why the yield of the neutral sizing agent and paper strength enhancing agent is improved must be awaited for future research. However, it is speculated that the presence of the carboxyl group of hexeneuronic acid evaluated as the potassium permanganate value is related to the yield of the sizing agent and paper strength enhancer. Therefore, a bleaching method in which the content of hexeneuronic acid or the content of carboxyl groups is controlled to a certain level or more is very effective in improving the yield of sizing agents and paper strength enhancers.

  In the present invention, in order to impart desired size and strength to the paper web, papermaking chemicals such as a neutral sizing agent and paper strength enhancer are added to the pulp slurry, and the mixture is sufficiently stirred and mixed. In this case, as the sizing agent, an alkyl ketene dimer, an alkenyl succinic anhydride, or a synthetic cation sizing agent, which is a sizing agent for neutral papermaking, can be used. In this case, the amount of individual papermaking chemicals such as a paper strength enhancer and a sizing agent varies depending on the performance required for the paper web, but is generally 0.01 to 1 per the dry mass of pulp fiber. It is selected from the range of 0.0 mass%, preferably 0.05 to 0.5 mass%.

  Examples of the paper strength enhancer used in the present invention include cationically modified starch, anionic starch, amphoteric starch, polyamide / epichlorohydrin resin, polyethyleneimine resin, polyacrylamide resin, polyamide resin and the like, Examples include amphoteric paper strength enhancers. At this time, if necessary, calcium carbonate is added for the purpose of improving the whiteness, opacity and printability of the paper, but known paper fillers such as titanium oxide, hydrous silica, talc, clay and kaolin are added. You may do it. Use of the present invention is effective not only in papermaking chemicals such as paper strength enhancers and sizing agents, but also in improving the yield of fillers.

  The paper-making raw material prepared in this way is made in a normal paper-making process and subjected to an external size press or calendering as necessary. Examples of the paper machine used at this time include paper machines such as a long net, a round net, and a short net, but are not particularly limited. In high-speed paper machines such as hybrid formers and gap formers, since dehydration is enhanced, it is generally known that the chemical yield decreases, and the present invention is particularly effective. Further, the paper web obtained in this way can be used as it is for printing, writing paper, etc., and on the paper web, publicly known coating equipment such as a blade coater, an air knife coater, a roll coater, A coating layer such as a reverse roll coater, bar coater, curtain coater, dice rod coater, gravure coater, champlex coater, or size press coater can be used as coated paper by providing a coating layer on one or both sides. .

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Example 1 shown below was obtained by bleaching hardwood kraft pulp after factory alkaline oxygen bleaching with a D-EP-P-D sequence, and Example 2 was bleached with a D-EP-D-P sequence. In Examples 3 and 4, bleaching was performed by the D-EP-D sequence. Comparative Example 1 was bleached with a CEHD sequence, Comparative Example 2 was bleached with a ZEPD sequence, Comparative Example 3, 4 and 6 were bleached by the D-EP-D sequence, and Comparative Example 5 was bleached by the D-E-D sequence.

  Unless otherwise indicated, the following methods are used to measure the kappa number, the potassium permanganate value, the amount of hexeneuronic acid in the pulp, the ISO whiteness of the pulp, and the measurement of the steecht sizing. The results are shown. In addition, the addition rate of the chemical | medical agent in an Example and a comparative example shows the mass% per absolute dry pulp mass.

1. Measurement of Kappa number of pulp It was carried out according to JIS P 8211.

2. Measurement of potassium permanganate value of pulp It was performed according to JIS P 8206.

3. Quantification of the amount of hexeneuronic acid in the pulp 5 g of the pulp thoroughly washed with ion-exchanged water was weighed into a 500 ml SUS container and made into a total of 300 ml using a formic acid-sodium formate buffer 10 mmol / l solution. . Thereafter, the inside of the SUS container was replaced with nitrogen gas, and treated in an oil thermostat at 110 ° C. for 5 hours. After cooling the SUS container with running water, the treated pulp suspension including the washing liquid was made up to 500 ml and filtered, and the liquid was analyzed by HPLC (high performance liquid chromatography), and 2-furoicacid and 5- Carboxy-2-furaldehyde was quantified. In quantification, the following formulas and references were used.

The quantitative value of 2-furoic acid in the measurement sample was a (ng / μl), and the quantitative value of 5-carboxy-2-furaldehyde was b.
1) Amount of 2-furoic acid (mmol / kg) = a × (500/1000) / (10 × 10 ⁻³ ) /112.08
2) 5-Carboxy-2-furaldehyde value (mmol / kg) = b × (500/1000) / (10 × 10 ⁻³ ) /140.1
3) Amount of hexeneuronic acid (mmol / l) = (amount of 2-furoic acid) + (amount of 5-carboxy-2-furaldehyde)

References: Authors Vuolinen, T .; Selective hydration of hexenuronic acid groups AND it's application in ECF AND TCF bleaching of craft pulling International Pulping Conferencing 96, A43

4). Method for Producing Whiteness-Measured Pulp Sheet After bleaching the bleached pulp, a sheet having a basis weight of 60 g / m ² was produced in accordance with Tappi test method T205os-71 (JIS P 8209).

5). Measurement of Pulp Whiteness The whiteness of the pulp was measured according to JIS P 8123.

Measurement of the degree of sizing human Measured according to JIS P8122.

Example 1
Cooking Hardwood Digestion-Alkali Oxygen Bleached Kraft Pulp (ISO Whiteness 47.2%, Copper Number 9.9) Absolutely Dry Mass 80.0g was placed in a plastic bag and the pulp concentration was 10 using ion-exchanged water. %, Then 0.4% of chlorine dioxide per mass of dry pulp is added and immersed in a constant temperature water bath at 70 ° C. for 60 minutes to bleach the first stage of chlorine dioxide (hereinafter abbreviated as D stage). went. The obtained pulp was diluted to 3% with ion-exchanged water, then dehydrated and washed with a Buchner funnel. The pulp after stage D is placed in a plastic bag, and after adjusting the pulp concentration to 10% using ion exchange water, caustic soda and hydrogen peroxide are added at 1.0% and 0.3% per mass of dry pulp, respectively. The mixture was treated at a temperature of 70 ° C. for 90 minutes, and subjected to alkali extraction and hydrogen peroxide bleaching stage (hereinafter abbreviated as EP stage). The obtained pulp was diluted with ion-exchanged water to adjust the pulp concentration to 3%, and then dehydrated and washed with a Buchner funnel to obtain a post-EP stage pulp.

Subsequently, the pulp after the EP stage was put in a plastic bag, and the pulp concentration was adjusted to 10% using ion-exchanged water. %, And treated for 90 minutes at a temperature of 70 ° C. to perform a hydrogen peroxide stage (hereinafter abbreviated as P stage).
The obtained pulp was diluted with ion-exchanged water to adjust the pulp concentration to 3%, and then dehydrated and washed with a Buchner funnel to obtain P-staged pulp. After the P-stage pulp is put in a plastic bag and adjusted to a pulp concentration of 10% using ion-exchanged water, 0.2% of chlorine dioxide is added per mass of dry pulp, and the temperature is 70 ° C. as in the D-stage. The treatment was performed for 180 minutes, and the second stage D was bleached. The obtained pulp was diluted to 3% with ion-exchanged water, washed with a Buchner funnel and dehydrated to obtain a bleached pulp having an ISO whiteness of 85.4%. The obtained bleached pulp was measured for potassium permanganate value and hexeneuronic acid amount, and the results are shown in Table 1.

The resulting bleached pulp was adjusted to a freeness of 450 ml CSF (Canadian Standard Freeness) with a laboratory PFI mill. The PFI mill rotational speed at this time is shown in Table 1. Neutral paper sizing agent (trade name: Size Pine K903, Arakawa) containing 2% concentration of pulp slurry and stirring at a speed of 450 rpm with a three-one motor, 0.5% sulfuric acid band and alkyl ketene dimer. (Chemical Industry Co., Ltd.) 0.2%, light calcium carbonate 10% as a filler for papermaking was added in this order, and stirring was continued for 1 minute after completion of the addition. The measured pH of this stock was 7.2. Using this pulp stock, a paper with a basis weight of 60 g / m ² was made with a square sheet machine of TAPPI standard, treated with a drum dryer at 120 ° C. for 3 minutes, and dried. The handsheet was conditioned at a temperature of 20 ° C. and a relative humidity of 65% for 24 hours, and then the degree of sizing of the paper was measured.

Example 2
The same operation as in Example 1 was performed except that the P stage of the multistage bleaching process and the second D stage were replaced. The ISO whiteness of the pulp after multistage bleaching was 85.9%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

Example 3
The same operation as in Example 1 was performed except that the chlorine dioxide addition rate in the first stage of multistage bleaching was changed to 0.5%, the hydrogen peroxide addition ratio in the EP stage was changed to 0.5%, and the P stage was not performed. The ISO whiteness of the pulp after multistage bleaching was 86.2%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

Example 4
Multi-stage bleaching pulp is replaced with kraft pulp after factory bleaching of hardwood with ISO whiteness of 43.5% and copper number of 12.7, and the chlorine dioxide addition rate in the first stage of multi-stage bleaching is 0.7% The same operation as in Example 3 was performed except that the change was made. The ISO whiteness of the pulp after multistage bleaching was 84.5%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

Comparative Example 1
Distillation of factory hardwood-Alkali oxygen bleached kraft pulp (ISO whiteness 47.2%, copper number 9.9) is put into a plastic bag with 80.0g of dry weight, and the pulp concentration is 5 using ion-exchanged water. After adjusting to%, chlorine was added at 1.5% per mass of dry pulp and immersed in a constant temperature water bath at a temperature of 50 ° C. for 30 minutes to bleach the first stage chlorine stage (hereinafter abbreviated as C stage). . The obtained pulp was diluted to 3% with ion-exchanged water, then dehydrated and washed with a Buchner funnel. The pulp after stage C is put in a plastic bag, and after adjusting the pulp concentration to 10% using ion-exchanged water, caustic soda is added at 1.0% per mass of absolutely dry pulp, treated at 60 ° C. for 90 minutes, alkali An extraction stage (hereinafter abbreviated as E stage) was performed. The obtained pulp was diluted with ion-exchanged water to adjust the pulp concentration to 3%, and then washed and dehydrated using a Buchner funnel to obtain a pulp after stage E.

  Subsequently, the pulp after stage E is put in a plastic bag, adjusted to a pulp concentration of 10% using ion-exchanged water, then 0.2% hypochlorite per mass of dry pulp (in terms of effective chlorine), caustic soda Was added at a temperature of 70 ° C. for 90 minutes to bleach the hypochlorite stage (hereinafter abbreviated as H stage). The obtained pulp was diluted to 3% with ion exchange water, washed and dehydrated using a Buchner funnel. The pulp after the H stage is put in a plastic bag, adjusted to a pulp concentration of 10% using ion-exchanged water, 0.2% of chlorine dioxide is added per mass of completely dry pulp, treated at a temperature of 70 ° C. for 180 minutes, Chlorine stage bleaching was performed. The obtained pulp was diluted to 3% with ion-exchanged water, washed with a Buchner funnel and dehydrated to obtain a bleached pulp having an ISO whiteness of 85.6%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

Comparative Example 2
Distillation of factory hardwood-After bleaching with alkaline oxygen, kraft pulp (ISO whiteness 47.2%, copper number 9.9) is placed in a plastic bag, and the pulp concentration is adjusted to 4% using ion-exchanged water. Was added to adjust the pH to 2.5, and acid treatment was performed by immersing in a constant temperature water bath having a temperature of 35 ° C. for 10 minutes. The obtained pulp was dehydrated and washed with a Buchner funnel. Next, this pulp was dehydrated to a pulp concentration of 35% by mass, and ozone bleaching (hereinafter referred to as Z stage) was performed in an ozone reactor at an ozone addition rate of 0.5%, a reaction temperature of 30 ° C., and a reaction time of 2 minutes. After the Z stage pulp is put in a plastic bag and adjusted to a pulp concentration of 4% using ion-exchanged water, 1% of caustic soda per mass of dry pulp is added, and an alkali extraction stage for 15 minutes (hereinafter abbreviated as E stage) Went. The obtained pulp was diluted to 3% with ion exchange water, washed and dehydrated using a Buchner funnel.

  Subsequently, the pulp after stage E is put in a plastic bag, and the pulp concentration is adjusted to 10% using ion-exchanged water. %, And treated for 90 minutes at a temperature of 70 ° C. to perform a hydrogen peroxide stage (hereinafter abbreviated as P stage). The obtained pulp was diluted with ion-exchanged water to adjust the pulp concentration to 3%, and then dehydrated and washed with a Buchner funnel to obtain P-staged pulp. After the P-stage pulp is put in a plastic bag and adjusted to a pulp concentration of 10% using ion-exchanged water, 0.2% of chlorine dioxide is added per mass of dry pulp, and the temperature is 70 ° C. as in the D-stage. The treatment was carried out for 180 minutes, and the second stage D was bleached. The obtained pulp was diluted to 3% with ion-exchanged water, washed with a Buchner funnel and dehydrated to obtain a bleached pulp having an ISO whiteness of 86.7%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

Comparative Example 3
The same operation as in Example 3 was performed except that the temperature of the first stage of multistage bleaching was changed to 90 ° C. and the hydrogen peroxide addition rate of the EP stage was changed to 0.3%. The ISO whiteness of the pulp after multistage bleaching was 86.3%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

Comparative Example 4
Multi-stage bleaching pulp is replaced with kraft pulp after factory bleaching of hardwood with ISO whiteness of 43.5% and copper value of 12.7, and the chlorine dioxide addition rate in the first stage of multi-stage bleaching is 1.0% The same operation as in Example 3 was performed except that the change was made. The ISO whiteness of the pulp after multistage bleaching was 86.1%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

Comparative Example 5
The same operation as in Example 3 was performed, except that the chlorine dioxide addition rate in the first stage of multi-stage bleaching was 0.8% and hydrogen peroxide in the EP stage was not added. The ISO whiteness of the pulp after multistage bleaching was 85.3%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

Comparative Example 6
The same operation as in Example 3 was performed except that the chlorine dioxide addition rate in the first stage of multi-stage bleaching was changed to 0.7% and the hydrogen peroxide addition ratio in the EP stage was changed to 0.1%. The ISO whiteness of the pulp after multistage bleaching was 85.6%. The obtained bleached pulp was measured for potassium permanganate value, hexeneuronic acid amount, PFI mill rotation speed required to adjust the freeness to 450 ml CSF, and the squeecht sizing degree of the handsheet, and shown in Table 1. It was.

  As is apparent from comparing Examples 1 to 4 with Comparative Examples 1 and 2 in Table 1, if the multi-stage bleaching is not ECF (elementary chlorin free) bleaching without using elemental chlorine, it is also ECF bleaching. However, if the bleaching first stage is not a chlorine dioxide stage, the potassium permanganate value, the amount of hexeneuronic acid are low, and the sizing degree is also low. Further, as is clear from comparison between Examples 3 and 4 and Comparative Examples 3 and 4, even when the first bleaching stage was a chlorine dioxide stage, the temperature of the bleaching stage was too high, When the chlorine dioxide addition rate is too high relative to the kappa number before bleaching, the potassium permanganate value and the amount of hexeneuronic acid are low, and the sizing degree is also low. Further, as apparent from comparing Examples 1 to 3 with Comparative Examples 5 and 6, the multi-stage bleaching step includes at least one hydrogen peroxide stage, and the hydrogen peroxide addition rate in the bleaching stage is Unless 0.3% or more, the potassium permanganate value, the amount of hexeneuronic acid are low, and the sizing degree is also low. In addition, pulp with a higher potassium permanganate value and a larger amount of hexeneuronic acid can reduce the beating load.

As is clear from the above results, the use of ECF bleached pulp having an ISO whiteness of 80% or more and a potassium permanganate value of 2 or more can greatly improve the size of paper. I understand that

Claims (6)

  ECF (elementary chlorin-free) bleached pulp having an ISO whiteness of 80% or more and a potassium permanganate value (JIS P 8206) of 2 or more is used, and a neutral internal sizing agent Including neutral paper.   The neutral paper according to claim 1, wherein the amount of hexeneuronic acid in the bleached pulp is 15 mmol / kg or more.   The bleached pulp includes a chlorine dioxide stage in which the first stage of bleaching is at a temperature of 70 ° C. or less and the chlorine dioxide addition rate is 0.06% by mass or less per kappa number before bleaching (JIS P 8211) with respect to the mass of the absolutely dry pulp. The neutral paper according to claim 1 or 2, which is a pulp bleached by an ECF (elementary chlorin-free) multi-stage bleaching process.   The bleached pulp is bleached by an ECF multi-stage bleaching process including at least one hydrogen peroxide bleaching stage so that the total hydrogen peroxide addition rate of the hydrogen peroxide bleaching stage is 0.3% or more per mass of the dry pulp. The neutral paper according to any one of claims 1 to 3, wherein the neutral paper is fresh pulp.   The neutral paper according to any one of claims 1 to 4, wherein the neutral internal sizing agent is an alkyl ketene dimer or an alkenyl succinic anhydride. A bleached pulp having an ISO whiteness of 80% or more, a potassium permanganate value (JIS P 8206) of 2 or more, and a hexeneuronic acid amount of 15 mmol / kg or more is used as a raw material pulp, and a neutral internal sizing agent A method for producing a neutral paper, which is made by adding paper and making paper.