JP2005290565A - Method for making semibleached kraft paper containing semibleached pulp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve yield of a product by effectively suppressing occurrence of defect by a resin pitch resulting from a semibleached kraft pulp while using the semibleached kraft pulp in a method for making semibleached kraft paper. <P>SOLUTION: In the method for making the semibleached kraft paper containing the semibleached pulp, an inlet raw material of a papermaking machine 10 is prepared by adding a coagulant 4 and a flocculating agent 6 to pulp slurry containing the semibleached kraft pulp so that cation requirement of the inlet raw material is controlled to +0.001 to +0.015 meq/L and the turbidity is controlled to 5-20 FAU. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for making semi-bleached kraft paper, and more particularly to a method for making semi-bleached kraft paper containing unbleached kraft pulp.

  Traditionally, kraft paper was made using highly bleached bleached kraft pulp, and semi-bleached kraft paper was made using semi-bleached kraft pulp. However, even a semi-bleached kraft pulp for making semi-bleached kraft paper is expensive to manufacture, and a method of making a paper by mixing bleached kraft pulp with unbleached kraft pulp has been used.

  In addition, after washing unbleached kraft pulp, when making kraft paper by passing through a selection process and a multi-stage bleaching process to make kraft paper, if the unbleached kraft pulp is not sufficiently washed, the bleached pulp has a pitch. Since it occurs, it is necessary to perform sufficient cleaning. Accordingly, it is known that the filtrate discharged from the final stage of the washing process is washed so that the transparency of the filtrate is in a range of 30 to 100%, and the pitch component accompanying the pulp is reduced (for example, Patent Documents). 1).

In addition, to improve papermaking and reduce the number of paper defects by adding inorganic substances and cationic polymers in combination with thermomechanical pulp to reduce cation requirements and turbidity. This is also known (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 5-9883 JP 2003-55895 A

  However, in the conventional method of making semi-bleached kraft paper using unbleached kraft pulp, defects due to resin pitch caused by unbleached pulp are likely to occur on the paper surface, and the product value is lost because the appearance is impaired. There is a problem that decreases. For this reason, when a defect occurs, it is necessary to stop the machine, replace white water, and remove the defect-generating substance by cleaning in the process, resulting in a problem of significantly reducing productivity.

  In this regard, as disclosed in Patent Document 1, it is conceivable to wash the unbleached pulp so that the filtrate has a transparency of 30 to 100%. Although the resin pitch causing the defects can be reduced to some extent by performing the cleaning, the effect of preventing the defects in the semi-bleached kraft paper is not sufficient.

  Further, the technical means disclosed in Patent Document 2 relates to papermaking using thermomechanical pulp, and the above problem is solved immediately even when inorganic materials and cationic polymers are used together in papermaking of semi-bleached kraft paper. is not.

  In view of the above-described conventional problems, the present invention includes an unbleached pulp that can improve the yield of products by effectively suppressing the occurrence of defects due to the resin pitch caused by using unbleached kraft pulp. It is an object to provide a method for producing semi-bleached kraft paper.

  In the method for producing semi-bleached kraft paper containing unbleached pulp of the present invention, an inlet raw material is prepared by adding a coagulant and a flocculant to a pulp slurry containing unbleached kraft pulp. Papermaking is performed by controlling 001 to +0.015 meq / L and turbidity to 5 to 20 FAU.

  The present inventor has intensively studied, and even if unbleached kraft pulp is contained in the inlet raw material of the paper machine, a coagulant is added to control anionic substances such as resin pitch, and the required amount of cation is +0.001. It was found that by controlling to ˜ + 0.015 meq / L and adding a flocculant to control the turbidity to 5 to 20 FAU, the occurrence of defects due to resin pitch or the like can be suppressed. Although the detailed mechanism is unknown, the anionic charge of fine fibers, chemicals, and anion trash is neutralized by a coagulant to form small flocs, and then the flocs are formed to form large flocs. This is considered to be caused by reducing the generation of foreign matter by adsorption.

  Thus, according to the papermaking method, it is possible to improve the product yield by suppressing the occurrence of defects while using unbleached kraft pulp for papermaking of semi-bleached kraft paper. In addition, by suppressing the occurrence of pitch in the wire part and press part of the paper machine, the frequency of cleaning of the machine process and replacement of white water can be reduced, productivity can be improved, and product cost can be further reduced. be able to.

  In recent years, it has been required to use deinked pulp even for semi-bleached kraft paper due to environmental considerations, but using deinked pulp makes it difficult to reduce the occurrence of defects due to anion trash caused by waste paper materials. To do. However, it has been found that by controlling the cation requirement and turbidity as described above, the occurrence of defects can be suppressed even when 40% or less of deinked pulp is included in the pulp slurry. Thus, semi-bleached kraft paper can be made with unbleached kraft pulp and deinked pulp, which contributes to suppression of environmental deterioration. In addition, when the compounding quantity of deinked pulp exceeds 40%, the defect suppression effect will become inadequate.

  Moreover, it is preferable to control the addition amount of the coagulant and the coagulant so that the concentration of white water discharged from the wire part of the paper machine is 0.01 to 0.08%. By managing in this way, it is possible to more effectively suppress the occurrence of defects. If it is attempted to control the white water concentration to be less than 0.01%, the effect is not improved for the increase in the chemical cost due to an increase in the amount of chemical added. Conversely, if the concentration exceeds 0.08%, the resin pitch, etc. Anion trash accumulates in raw material piping, chests, and tanks, and flocking progresses, causing paper defects.

  Further, when the degree of cleaning of unbleached kraft pulp is 1000 μs / cm or less, the required amount of cation can be reliably and stably controlled within the above range by adding an appropriate amount of a coagulant. Higher cleanliness (lower numerical value) is desirable, but the cost increases. If it exceeds 1000 μs / cm, it becomes difficult or impossible to keep the required cation amount and turbidity within the above ranges.

  Further, by controlling the papermaking PH to 6 to 8.5, the required cation amount can be reliably and stably controlled within the above range by adding an appropriate amount of the coagulant.

  According to the present invention, in the making of semi-bleached kraft paper, even if unbleached kraft pulp is included in the inlet raw material, a coagulant and a flocculant are added to appropriately control the cation requirement and turbidity. Further, the yield of products can be improved by suppressing the occurrence of defects due to resin pitch and the like.

  Hereinafter, an embodiment of a method for producing semi-bleached kraft paper containing unbleached pulp of the present invention will be described in detail with reference to FIG.

  In FIG. 1 showing the papermaking process of semi-bleached kraft paper, deinked pulp 2 is blended in a blending amount of 40% or less in pulp slurry containing unbleached kraft pulp 1 as a main material. To control PH 6 to 8.5.

  Next, the coagulant 4 is added to the pulp slurry, and the required amount of cation of the inlet raw material of the paper machine 10 is controlled to be +0.001 to +0.015 meq / L. Therefore, a cation requirement measuring / controlling device 5 for measuring the cation requirement of the pulp slurry after adding the coagulant 4 online and controlling the addition valve 4a of the coagulant 4 according to the measurement result is provided. ing. As the coagulant 4, a cationic polymer coagulant such as PAM (polymer acrylamide), PDADMAC (polydadomac), PEI (polyethyleneimine) or polyamine is preferably used.

  As the cation requirement measurement / control device 5, for example, “PCT15” (manufactured by Mutek) can be used. This “PCT15” utilizes the fact that the colloidal dissolved substance particles in the pulp slurry are charged with ions, and the pulp slurry is introduced into the cell of the measuring instrument. A sample liquid flow is generated between the pistons, electricity is generated by the distortion of the surface charge of the colloidal particles, and the charge requirement is measured by polyelectrolyte measurement.

  Next, the flocculant 6 is added to the pulp slurry to which the coagulant 4 is added, and the turbidity of the inlet raw material of the paper machine 10 is controlled to be 5 to 20 FAU. Therefore, a turbidity measuring device 7 for measuring the turbidity of the inlet raw material after adding the flocculant 6 online and a controller 8 for controlling the addition valve 6a of the flocculant 6 according to the measurement result are provided. ing. In addition, the measurement result is also input to the cation requirement measurement / control device 5 as necessary to control the addition amount of the coagulant 4 so as to fall within this turbidity range.

  As the aggregating agent 6, those obtained by introducing a carboxyl group into polyacrylamide as an anionic functional group are generally used, those obtained by introducing a sulfone group are also preferably used, and anionic acrylic amide and anion-modified starch are also used. be able to. Furthermore, a cationic flocculant such as a cationic polyamine resin, a cationic polyamine polyamide resin, a cationic polyacrylamide, a cation-modified starch, or a styrene acrylic resin may be used.

  As the turbidity measuring device 7, “DR-2010” (manufactured by HACH) can be used. This “DR-2010” is a method in which a pulp sample is filtered through a filter paper, the light transmittance at 860 nm is measured, and the turbidity value is compared with the transmittance of formazine, which is a standard reagent for turbidity. .

  Moreover, the white water density | concentration discharged | emitted from the wire part of the paper machine 10 is measured with the white water density | concentration measuring device 9, and the measurement result is input into the controller 8, and white water density | concentration will be 0.01-0.08%. Thus, the controller 8 is configured to control the addition amount of the flocculant 6. In addition, the measurement result is also input to the cation requirement measurement / control device 5 as necessary to control the addition amount of the coagulant 4 so as to fall within this white water concentration range.

  As the white water concentration measuring device 9, a Kajaani retention sensor “RM-i” (manufactured by Metso Automation) can be used. This Kajaani retention sensor “RM-i” measures the raw material concentration in white water filtered under the wire in order to measure the ratio of the raw material injected to the wire part remaining on the wire.

  By supplying the raw material slurry prepared as described above to the inlet of the paper machine 10, the paper machine 10 is made up of unbleached kraft pulp 1 and 40% or less deinked pulp 2, and is made into a resin pitch or the like. Unbleached kraft paper with few defects is produced.

  Next, some examples and comparative examples of the present invention will be described.

  In the process of making semi-bleached kraft paper using unbleached kraft pulp and deinked pulp (DIP), as shown in Table 1, as Example 1, the required cation amount of the inlet raw material is 0.003 meq / L, turbidity 10 FAU, white water concentration 0.03%, cleanness of unbleached pulp 300μs / cm, blending amount of deinked pulp (DIP) 30%, PH adjusted to PH6 to 8.5, half bleached craft Paper was made. Moreover, as Examples 2-10 and Comparative Examples 1-8, the required amount of cation of the inlet raw material is in the range of 0.0005 to 0.03 meq / L, the turbidity is in the range of 3 to 25 FAU, and the white water concentration is 0.00. In the range of 005 to 0.60%, the washing degree of unbleached pulp is changed to 600, 1000, 1100 μs / cm, and the amount of deinked pulp (DIP) is changed to 10, 20, 40, 50%, Moreover, what did not adjust PH to PH6-8.5 was set to Example 10, and each half bleached kraft paper was made.

And about each Example 1-10 and Comparative Examples 1-8, the defect generation number was measured. The number of defects was measured as follows. Using an online defect detector “KP22W3-DF” (manufactured by OMRON), the number of defects of 9.3 mm ² or more was measured, and less than 0.6 in 2000 m ^{2 of} paper was evaluated as good. The thing was judged as bad. The results are shown in Table 1.

表１において、実施例１〜１０から、インレット原料のカチオン要求量が０．００１〜０．０１５ｍｅｑ／Ｌ、かつ濁度が５〜２０ＦＡＵ、かつ白水濃度が０．０１〜０．０８％で、未晒パルプの洗浄度が１０００μｓ／ｃｍ以下のものを使用し、ＤＩＰの配合率がが４０％以下で抄造した半晒クラフト紙は、９．５ｍｍ² 以上の欠陥の発生が２０００ｍ² 当たり０．６個未満であり、良好な結果が得られることが分かる。

In Table 1, from Examples 1 to 10, the required amount of cation of the inlet raw material is 0.001 to 0.015 meq / L, the turbidity is 5 to 20 FAU, and the white water concentration is 0.01 to 0.08%. Semi-bleached kraft paper made using unbleached pulp with a cleanliness of 1000 μs / cm or less and a DIP blending ratio of 40% or less has a defect generation of 9.5 mm ² or more of 0.000 per 2000 m ² . It can be seen that the number is less than 6 and good results are obtained.

  On the other hand, in Comparative Examples 1 to 8, when the required cation amount of the inlet raw material of Comparative Example 1 is 0.0005 meq / L, the turbidity of Comparative Example 3 is 3 FAU, and the white water concentration of Comparative Example 5 is 0. In the case of 005%, the defect detector detects the deterioration of formation due to pulp flock as an abnormality (defect), and the number of defects generated is 0.6 or more. Moreover, when the required amount of the cation of the inlet raw material of Comparative Example 2 is 0.016 meq / L exceeding 0.016 meq / L, when the turbidity of Comparative Example 4 is 25 FAU exceeding 20 FAU, the white water of Comparative Example 6 When the concentration is 0.60% exceeding 0.08%, when the cleanness of the unbleached pulp of Comparative Example 7 is 1100 μs / cm exceeding 1000 μs / cm, the DIP blending amount of Comparative Example 8 is 40%. In the case of exceeding 50%, the number of occurrence of defects is 0.6 or more in each case, which is defective.

  The papermaking method of the semi-bleached kraft paper of the present invention is to add a coagulant and a flocculant to a pulp slurry containing unbleached kraft pulp to appropriately control the cation requirement and turbidity of the inlet raw material, Since the yield of products can be improved by suppressing the occurrence of defects due to resin pitch and the like in paper, it is useful for making semi-bleached kraft paper using unbleached kraft pulp.

It is explanatory drawing of the semi-bleached kraft paper papermaking process in one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Unbleached kraft pulp 2 Deinked pulp 3 PH adjustment part 4 Coagulant 5 Cation requirement measurement / control device 6 Flocculant 7 Turbidity measuring device 9 White water concentration measuring device 10 Paper machine

Claims (5)

  An inlet raw material is prepared by adding a coagulant and a flocculant to pulp slurry containing unbleached kraft pulp, and the cation requirement of the inlet raw material is controlled to +0.001 to +0.015 meq / L, and the turbidity is controlled to 5 to 20 FAU. A method of making semi-bleached kraft paper containing unbleached pulp, characterized by   The method for producing semi-bleached kraft paper containing unbleached pulp according to claim 1, wherein the pulp slurry contains 40% or less of deinked pulp.   The method for making semi-bleached kraft paper containing unbleached pulp according to claim 1 or 2, wherein the addition amount of the coagulant and the flocculant is controlled so that the white water concentration is 0.01 to 0.08%. .   The papermaking method for semi-bleached kraft paper containing unbleached pulp according to any one of claims 1 to 3, wherein the degree of cleaning of unbleached kraft pulp is 1000 µs / cm or less. Papermaking PH is controlled to 6-8.5, The papermaking method of the semi-bleached kraft paper containing the unbleached pulp as described in any one of Claims 1-4 characterized by the above-mentioned.

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