JP2009235648A - Method for producing pulp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain paper which achieves both bulkiness and excellent dimensional stability by employing pulp produced by a method for manufacturing pulp which is bulk and excellent in the dimensional stability. <P>SOLUTION: In a producing process of pulp, the amount of fine fibers having a fiber length of ≤0.2 mm with respect to the whole pulp fiber is adjusted to ≤10%. Preferably, beating process is carried out before or after the adjustment of the amount of fine fibers. It is preferable that the beating process is imparting impact force of collapsed bubbles produced by cavitation, to pulp fibers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an invention of a method for producing pulp. More specifically, the present invention relates to a method for producing a pulp capable of obtaining a bulky and excellent dimensional stability pulp by adjusting the amount of fine fibers in the pulp production process.

  In recent years, there has been an increasing demand for bulky and lightweight paper from the viewpoint of resource saving, logistics cost reduction, and high added value such as luxury and volume. Up to now, various methods as described below have been tried as a study for increasing the bulk. For example, (1) a method using a crosslinked pulp (Patent Document 1), (2) a method of mixing synthetic fibers (Patent Document 2), and (3) a method of filling an inorganic substance between pulp fibers (Patent Document 3) (4) A method of adding expandable particles that cause voids (Patent Document 4), (5) a method of adding bulky chemicals (Patent Document 5), and the like have been proposed. However, new methods such as the inability to recycle pulp by the above method, the inevitable increase in cost due to the addition of other chemicals and fillers to the pulp, and increased foaming in the papermaking process. There were problems such as being unavoidable.

  In order to avoid such a risk, it has been proposed to provide bulkiness during pulp production. For example, (6) a method of blending curled fibers (Patent Document 6), and (7) a method of manufacturing a chemo-thermomechanical pulp excellent in bulkiness from hardwood (Patent Document 7) have been devised. However, curled fibers have a significant impact on paper dimensional stability, and when mechanical pulp is used, the pulp contains a large amount of fine fibers. There was a concern of worsening sex.

Japanese Patent Laid-Open No. 4-185791 JP-A-3-269199 Japanese Patent Laid-Open No. 3-124895 JP-A-5-230798 JP 58-24000 A JP-A-9-41300 JP 2002-294574 A

  In order to solve these problems, the present invention provides a method for producing a bulky and good dimensional stability pulp, and uses the obtained pulp to obtain a paper having both bulkiness and good dimensional stability. For the purpose.

  As a result of intensive studies on the pulp manufacturing process and fiber characteristics, the inventors have reduced the amount of fine fibers having a fiber length of 0.2 mm or less to 10% or less in the pulp manufacturing process. The present inventors have found that a pulp which is bulky and has good dimensional stability can be produced. In particular, the beating process is performed before or after the adjustment of the fine fiber amount, and further, the process of giving impact force generated when the bubbles generated by cavitation collapse to the pulp fiber as the beating process is performed. The present inventors have found that the effect on stability is further enhanced and completed the present invention.

  In the present invention, a bulky and good dimensional stability pulp can be produced by adjusting the amount of fine fibers having a fiber length of 0.2 mm or less relative to the total pulp fibers.

  Hereinafter, the manufacturing method of the pulp which concerns on embodiment of this invention is demonstrated.

  The raw material pulp that is the subject of the present invention is a fibrous substance mainly composed of cellulose obtained from wood, and is a chemical pulp fiber such as softwood and hardwood kraft pulp, sulfite pulp, softwood and hardwood groundwood pulp. , Refiner groundwood pulp, thermomechanical pulp, chemithermomechanical pulp, and other mechanical pulp fibers, and recycled pulp fibers derived from sheet-like substances made of waste paper or fiber. These pulps may be used alone or in combination.

  The fine fiber of the present invention refers to a fiber having a fiber length of 0.2 mm or less among all pulp fibers.

  In the present invention, the amount of fine fibers having a fiber length of 0.2 mm or less with respect to all the pulp fibers is preferably adjusted to 10% or less, more preferably 6% or less, based on the absolutely dry pulp. Further, fine fibers may not be included. When the amount of fine fibers is 10% or more, the effect of improving bulkiness and dimensional stability is reduced.

  The amount of fine fibers is determined by measuring the length-weighted average fiber length of the pulp fiber using an optical fiber length measuring device (for example, KAJAANI Fiber Bar) using the disaggregated pulp slurry. It can be measured by the ratio (percentage) of the weight of the following fibers. The lower limit value that can be detected by the optical fiber length measuring instrument is 1.5 μm.

  The method for adjusting the amount of fine fibers is not particularly limited, and can be adjusted using a known mechanical classifier and classification technique. For example, fine fibers contained in all pulp fibers can be removed by dehydrating using a machine that dehydrates the pulp using a mesh, such as a pulp washer or a cylinder press.

  The fine fiber amount is preferably adjusted before or after the beating process. This is because in the pulp manufacturing process, the amount of fine fibers is particularly likely to increase during the beating process, and the effect of the present invention can be easily obtained by adjusting the amount of fine fibers.

  Any method may be used as the beating processing method of the present invention. For example, mechanical processing such as a double disc refiner (DDR), a conifier, a cylinder type beating machine, a beater, a PFI mill, a kneader, and a disperser ( Beating plate), or a treatment (hereinafter referred to as “cavitation treatment”) that gives an impact force generated when bubbles generated by cavitation collapse to pulp fibers. Among them, a conifer, for the purpose of viscous beating, mechanical treatment by a cylinder type beating machine, etc., and performing cavitation treatment, because the generation of fine fibers can be suppressed low, the effect of the present invention is preferably obtained, It is particularly preferable to perform a cavitation treatment.

  When a beating machine or beating plate that promotes beating by normal mechanical processing, particularly cutting beating, the amount of fine fibers after the beating process is greatly increased. In such a case, it is desirable to adjust the amount of fine fibers after the beating process. On the other hand, when a beating method with less cutting such as viscous beating is used, or when the beating load is kept low, the variation in the amount of fine fibers is reduced. In particular, when a cavitation process is used as the beating process, it is estimated that the amount of fine fibers hardly increases. As described above, when a beating method is used in which the amount of fine fibers after the beating process is unlikely to increase, the amount of fine fibers may be adjusted before the beating process.

  Examples of the cavitation generating means in the present invention include a method using a liquid jet, a method using an ultrasonic vibrator, a method using an ultrasonic vibrator and a horn-shaped amplifier, and a method using laser irradiation, but are not limited thereto. It is not something. Preferably, the method using the liquid jet has a high effect on the unseparated fragments because the generation efficiency of cavitation bubbles is high and a cavitation bubble cloud having a stronger collapse impact force can be formed. The cavitation generated by the above method is clearly different from cavitation that causes uncontrollable harm that naturally occurs in conventional fluid machines.

  In the present invention, when cavitation is generated using a liquid jet, the pulp fibers and bubbles can be brought into contact with each other by jetting the pulp suspension as a liquid jet. In addition, the fluid in which the liquid jet forms a jet may be any liquid, gas, solid such as powder or pulp, or a mixture thereof as long as it is in a fluid state. Further, if necessary, another fluid can be added as a new fluid to the above fluid. The fluid and the new fluid may be uniformly mixed and ejected, but may be ejected separately.

  The liquid jet refers to a jet of fluid in which solid particles or gas are dispersed or mixed in the liquid or the liquid. The gas referred to here may include bubbles due to cavitation.

  Since cavitation occurs when a liquid is accelerated and the local pressure is lower than the vapor pressure of the liquid, flow rate and pressure are particularly important. From this, the basic dimensionless number representing the cavitation state, the cavitation number σ is defined as the following formula 1 (edited by Yoji Kato, new edition of cavitation basics and recent advances, Tsuji Shoten, 1999) ).

(P _∞: pressure general flow, U _∞: flow rate of the general flow, _{p v:} fluid vapor pressure, [rho: the density of the fluid)
Here, a large number of cavitations indicates that the flow field is in a state where cavitation is difficult to occur. In particular, when cavitation is generated through a nozzle or orifice pipe such as a cavitation jet, the cavitation number σ is calculated from the following equation (2) from the nozzle upstream pressure p ₁ , the nozzle downstream pressure p ₂ , and the saturated vapor pressure p _v of the sample water. In the cavitation jet, the pressure difference between p ₁ , p _{2, and} p _v is large and p ₁ >> p ₂ >> p _v. Therefore, the cavitation number σ is further as follows: (H. Soyama, J. Soc. Mat. Sci. Japan, 47 (4), 381 1998).

  The cavitation condition in the present invention is preferably such that the above-mentioned cavitation number σ is 0.001 or more and 0.5 or less, preferably 0.003 or more and 0.2 or less, and 0.01 or more and 0.1 or less. It is particularly preferred that If the cavitation number σ is less than 0.001, the effect is small because the pressure difference with the surroundings when the cavitation bubbles collapse is low, and if it is greater than 0.5, the flow pressure difference is low and cavitation occurs. It becomes difficult to occur.

  Further, when the jet liquid is jetted through the nozzle or the Ophiris tube to generate cavitation, the pressure of the jet liquid (upstream pressure) is desirably 0.01 MPa or more and 30 MPa or less, and 0.7 MPa or more and 20 MPa or less. Preferably, it is preferably 3 MPa or more and 15 MPa or less. When the upstream pressure is less than 0.01 MPa, it is difficult to produce a pressure difference with the downstream pressure, and the effect is small. On the other hand, when the pressure is higher than 30 MPa, a special pump and a pressure vessel are required, and energy consumption increases, which is disadvantageous in terms of cost. On the other hand, the pressure in the container (downstream pressure) is preferably 0.05 MPa to 0.3 MPa in static pressure. Moreover, the pressure ratio between the pressure in the container and the pressure of the spray liquid is preferably in the range of 0.001 to 0.5.

  Further, the jet velocity of the jet liquid is desirably in the range of 1 m / second to 200 m / second, and preferably in the range of 20 m / second to 100 m / second. When the jet velocity is less than 1 m / sec, the effect is weak because the pressure drop is low and cavitation hardly occurs. On the other hand, when it is higher than 200 m / sec, a high pressure is required and a special device is required, which is disadvantageous in terms of cost.

  In the present invention, the cavitation generation place can be selected from any container such as a tank or inside a pipe, but is not limited thereto. Further, although it is possible to perform processing in one pass, the effect can be further increased by circulating the required number of times. Furthermore, it can be processed in parallel or in permutation using a plurality of generating means.

  Injection for generating cavitation may be performed in a container open to the atmosphere, but is preferably performed in a pressure container in order to control cavitation.

  In the present invention, the cavitation generation place can be selected from any container such as a tank or inside a pipe, but is not limited thereto. Although it is possible to perform processing in one pass, the disaggregation effect can be further increased by circulating the required number of times.

  The solid content concentration of the pulp suspension to be treated when cavitation is generated by liquid jet is preferably 10% by weight or less, more preferably 0.1 to 5.0% by weight. This is preferable from the viewpoint of bubble generation efficiency. When the solid content concentration of the liquid to be jetted is 10% by weight or more and 30% by weight or less, the effect can be obtained by setting the jet liquid concentration to 10% by weight or less. Further, it is desirable that the pH of the pulp suspension is in an alkaline condition because the fiber swellability is good and the amount of OH active radicals generated is increased.

  In the present invention, by increasing the jetting pressure of the liquid, the flow velocity of the jetting liquid is increased, and the pressure is lowered accordingly, and stronger cavitation is generated. Further, by pressurizing the container for storing the liquid to be ejected, the pressure in the region where the cavitation bubbles collapse is increased, and the pressure difference between the bubbles and the surroundings is increased, so that the bubbles collapse violently and the impact force increases. Cavitation is influenced by the amount of gas in the liquid, and when there is too much gas, collision and coalescence of bubbles occur, so that a collapse impact force is absorbed by other bubbles, and the impact force is weakened. Therefore, since it is influenced by dissolved gas and vapor pressure, the treatment temperature is preferably 0 ° C. or higher and 70 ° C. or lower, and particularly preferably 10 ° C. or higher and 60 ° C. or lower. In general, since it is considered that the impact force becomes maximum at the midpoint between the melting point and the boiling point, in the case of an aqueous solution, around 50 ° C. is suitable, but even at a temperature lower than that, it is not affected by the vapor pressure. Therefore, a high effect can be obtained within the above range.

  In the present invention, the energy required to generate cavitation can be reduced by adding a surfactant. As the surfactant to be used, known or novel surfactants, for example, nonionic surfactants such as fatty acid salts, higher alkyl sulfates, alkylbenzene sulfonates, higher alcohols, alkylphenols, alkylene oxide adducts such as fatty acids, etc. , Anionic surfactants, cationic surfactants, amphoteric surfactants and the like. These may be composed of a single component or a mixture of two or more components. The addition amount may be an amount necessary for reducing the surface tension of the jet liquid and / or the liquid to be jetted.

  When paper is produced from the pulp produced according to the present invention, a known paper machine can be used, but the paper making conditions are not particularly limited. For example, as a paper machine, a long net type, an on-top twin wire type, a gap former type, a circular net type, a multi-layer type, etc. can be used, and for the purpose of improving surface strength and imparting water absorption resistance, A surface treatment agent may be applied. When applying the surface treatment agent, there are no particular limitations on the components of the surface treatment agent, and there is no limitation on the size press type, and the size of a liquid film transfer system such as a two-roll size press, a gate roll size press, or a shim sizer. A press or the like can be used as appropriate. Further, for the purpose of smoothing the surface of the paper, the treatment may be performed using a known calendar device such as a machine calendar, a soft nip calender, or a high temperature soft nip calender.

The paper obtained by the present invention is not limited to the type and basis weight of the paper, and further includes various base papers and paperboard. There is no limitation on the ash content in the paper. In addition to single-layer paper, multi-layer paper having two or more layers may be used.
[Action]

  In the present invention, the following reasons can be considered as the reason why a pulp having a high bulk and good dimensional stability can be obtained. Regarding the bulk of the paper, when the bonding strength between the fibers is high, for example, when the amount of fibrillated long fibers or fine fibers is large, the paper after the paper making tends to be high in density and low in bulk. On the other hand, although there are various factors that deteriorate the dimensional stability of paper, especially when considering the effects of changes in fiber shape, the increase in fiber curl, the amount of fine fibers, the difference in beating methods, etc. will affect dimensional stability. Has been. As described above, since fine fibers are involved in both the bulk and dimensional stability of paper, reducing the fine fibers has an effect on both bulkiness and improved dimensional stability. It is thought that it was done.

  In particular, the following reasons can be considered as the reason why the effects of the present invention can be easily obtained by the cavitation treatment. In pulp beating using cavitation processing, external fibrillation of pulp fibers is likely to occur compared to beating by mechanical action such as DDR. Many of the fine fibers contained in such a pulp are fibril-like, and the fibril-like fine fibers are strongly bonded to each other and tend to have a high density. For this reason, if the fibril-like fine fibers are removed, it is presumed that the bonds between the fibers become smaller and the density becomes smaller. In addition, since the number of internally fibrillated fibers is small, the number of fibers crushed by the beating process is small, which may have contributed to the reduction in density. Furthermore, the externally fibrillated fiber has a lower water retention than the internally fibrillated fiber, and it is presumed that the fiber is less likely to swell. Therefore, it is presumed that it contributed to the improvement of dimensional stability.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to the Example which concerns.

[Examples 1 to 3]
A high-quality raw material manufactured at the factory (DIP whose raw paper is mainly high-quality waste paper) was designated as DIP raw material A (CSF 404 ml). This was washed with running water on a 150 mesh wire (aperture 106 μm) and separated into a long fiber (150 mesh on) and a fine fiber (150 mesh pass). The long fiber content at this time was used as the raw material B (fine fiber amount 0%), and the fine fiber content was concentrated by sedimentation separation. Next, 5% by weight or 10% by weight of the fine fiber was added to the raw material B, the ash contained in each raw material before and after blending was measured, and the amount of fine fiber was calculated by the following method.
100 ppm of a yield improver (DR1500) was added to each of the above raw materials, and a handsheet was produced based on JIS P 8222. The thickness and basis weight of the handsheet were measured by the following method, and the density was calculated based on this. Furthermore, as an evaluation of dimensional stability, the water immersion elongation was measured by the following method. The results are shown in Table 1.
Thickness: According to JIS P8118: 1998.
-Basis weight: According to JIS P8124: 1998 (ISO536: 1995).
Density: Calculated from the measured values of the hand-sheet thickness and basis weight.
Ash content: It was calculated from the ratio of the weight of the ash remaining after heating the DIP raw material at a temperature of 525 ° C. for 2 hours and the original solid content.
-Fine fiber amount: Calculated by removing the proportion of ash from the value of the fine fiber amount measured with FibarLab of KAJAANI.
・ Water immersion elongation: A hand-sheet is produced in accordance with JIS P 8222: 1998 except that it is dried all day and night in the standard state specified in JIS P 8111: 1998 without using a drying plate or ring. About J. TAPPI No. According to 27A, the water immersion elongation after 60 minutes was measured.

[Comparative Example 1]
A handsheet was prepared in the same manner as in Example 1 using the raw material A, and the same evaluation was performed. The results are shown in Table 1.

[Comparative Examples 2 and 3]
Evaluation was performed in the same manner as in Examples 2 and 3 except that the raw material B was added with 15% by weight or 20% by weight of the fine fiber content. The results are shown in Table 1.

  From the results of Table 1, it can be seen that Examples 1 to 3 having a smaller amount of fine fibers compared to Comparative Examples 1 to 3 have a smaller density and a higher bulk as the amount of fine fibers is decreased. In addition, Examples 1 to 3 are excellent in dimensional stability because the water immersion elongation decreases with the decrease in the amount of fine fibers.

[Example 4]
The hardwood bleached kraft pulp sheet was disaggregated and adjusted to an arbitrary concentration, and then beaten with a Niagara beater until it reached 390 ml of CSF, thereby preparing raw material C. Thereafter, the pulp after beating the raw material C on a 150 mesh wire (mesh 106 μm) was washed with running water to remove fine fibers. Ash content was measured and the amount of fine fibers was calculated.
A yield improver (DR1500) was added to the raw material at 100 ppm, and a handsheet was prepared based on JIS P 8222. The thickness and basis weight of the handmade sheet were measured, and the density was calculated based on this. Furthermore, the water immersion elongation was measured as an evaluation of dimensional stability. The results are shown in Table 2.
-Canadian standard freeness (CSF): According to JIS P8121: 1995.

[Comparative Example 4]
About the raw material C, the handsheet was produced similarly to Example 4, and the same item was evaluated. The results are shown in Table 2.

[Example 5]
After disaggregating the hardwood bleached kraft pulp sheet and adjusting it to an arbitrary concentration, using the cavitation jet cleaning device (nozzle diameter 1.5 mm) described in Japanese Patent Application No. 2005-321231, the pressure of the jet liquid (upstream pressure) Was 7 MPa (jet flow velocity 70 m / sec), the pressure in the container to be jetted (downstream pressure) was 0.3 MPa, and the CSF reached 390 ml, and the raw material D was obtained. Note that a pulp suspension having a concentration of 1.1% by weight was used as the propellant, and the treatment was performed as a pulp suspension in the container (concentration of 1.1% by weight). Thereafter, the pulp after beating the raw material D on a 150 mesh wire (mesh 106 μm) was washed with running water to remove fine fibers. Ash content was measured and the amount of fine fibers was calculated.
A yield improver (DR1500) was added to the raw material at 100 ppm, and a handsheet was prepared based on JIS P 8222. The thickness and basis weight of the handmade sheet were measured, and the density was calculated based on this. Furthermore, the water immersion elongation was measured as an evaluation of dimensional stability. The results are shown in Table 2.

[Comparative Example 5]
About the raw material D, the handsheet was produced similarly to Example 5, and the same item was evaluated. The results are shown in Table 2.

  From the results of Table 2, the density of Example 4 with a small amount of fine fibers compared with Comparative Example 4 and Example 5 with a small amount of fine fibers compared with Comparative Example 5 are smaller than those of Comparative Example 4 and Comparative Example 5, respectively. It was bulky. Moreover, since Example 4 and Example 5 have smaller water immersion elongation than the comparative example 4 or the comparative example 5, respectively, it turns out that it is excellent in dimensional stability. In addition, since Example 5 is smaller in density and more excellent in dimensional stability than Example 4, it can be seen that the effect of the present invention is remarkably exhibited particularly when cavitation treatment is performed.

Claims (4)

  In the pulp manufacturing process, a pulp manufacturing method is characterized in that the amount of fine fibers having a fiber length of 0.2 mm or less with respect to all pulp fibers is adjusted to 10% or less.   The pulp production method according to claim 1, wherein after the pulp is beaten, the amount of fine fibers having a fiber length of 0.2 mm or less with respect to all the fibers of the pulp is adjusted to 10% or less by dehydration.   The pulp production method according to claim 1, wherein the pulp is beaten after the amount of fine fibers having a fiber length of 0.2 mm or less with respect to all the fibers of the pulp is adjusted to 10% or less by dehydration.   4. The method for producing pulp according to claim 2, wherein the beating process is a process for giving an impact force generated when bubbles generated by cavitation collapse to a pulp fiber.