JP2011157655A - Method for producing recycled pulp by utilizing shock wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for peeling off foreign matters from fibers in the process of producing recycled pulp, while inhibiting the pulverization of the foreign matters. <P>SOLUTION: This method for producing the recycled pulp is provided by including peeling off the foreign matters from pulp fibers by applying a shock wave to waste paper. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing pulp, and more particularly, to a method for producing regenerated pulp that promotes the separation of foreign matters other than fiber by applying a shock wave to waste paper.

  In recent years, from the viewpoint of saving resources or protecting the environment on a global scale, the promotion of recycling of used paper has been strongly demanded, and expanding the scope of recycling has become an extremely important issue. On the other hand, the types of used paper suitable for recycling are limited, and in particular, the types of used paper that can be used for western paper are further limited. Further, in factories that manufacture regenerated pulp, so-called contraindicated products are often mixed, and problems such as deterioration in the quality of the manufactured pulp and operational troubles have occurred. In addition, the recycling of recycled pulp is increasing due to the promotion of recycling of used paper, so there is a shortage of recycled paper. In order to further promote the recycling of used paper, it has been a contraindicated product until now. Development of technology that makes it possible to recycle used paper has become necessary.

  In general, examples of contraindicated products in the production of recycled pulp include paper such as carbon paper, carbonless paper, thermal paper, and laminated paper, in addition to paper, such as stone, glass, plastic, and adhesive tape. (Recycled Paper Handbook 2006: Non-Patent Document 1). According to a report by Watanabe et al. (Non-Patent Document 2), paper that has been printed with metal ink or paper that has been processed with metal foil by vapor deposition or the like is removed without refining the metal in the recycling process. Since it cannot be exhausted, it has an adverse effect on the appearance of the product, and is therefore not suitable for recycling into recycled pulp for paper. Furthermore, according to the “Fundamental Survey on the Present State and Trends of Beverage Paper Container Recycling in 2002” (Non-patent Document 3), beverage paper packs laminated with aluminum foil have a recovery rate of 9.7% based on the amount of paper used. The fact is that most of them are discarded.

  General reclaimed pulp manufacturing methods include disaggregation processes using pulpers, ink separation processes using a kneader, etc., dust removal processes using cleaners and screens, etc. A flotation process and a deinking process by a cleaning process. In the conventional technology, in the disaggregation process and the ink peeling process, the foreign matter is peeled off from the fiber by the hydrodynamic shear force or the frictional force between the fibers. At this time, the foreign matter is excessively miniaturized. It could be difficult.

  Various methods for producing a new recycled pulp different from the prior art have been studied. For example, Patent Document 1 proposes a flotation technique in which shock waves generated by a cylindrical rotating body are used to make fine air bubbles in the paper or dissolved air to promote the floating of foreign matters. However, this method does not separate foreign matter from pulp fibers.

  Patent Document 2 proposes a technique for separating colored contaminants from fibers by irradiating ultrasonic waves. However, in this technology, the colored contaminants adhering to the fiber material are separated into fine particles and emulsified by the expansion and contraction of bubbles generated using ultrasonic waves, so that the foreign matter is not refined. In addition, the foreign matter cannot be peeled off from the fiber so as to have a size that can be removed with a screen.

  Furthermore, Non-Patent Document 4 describes that hydroxy radicals generated by high-pressure discharge in water prevent ink and toner from re-adhering to the fiber surface and facilitate the aggregation of fine adhesive foreign matter. However, this method is only a technique for facilitating the removal of contaminants already separated from pulp fibers out of the system, and this method is a technique specialized for ink, toner, and finely adhered foreign matter. A foreign material such as a metal foil cannot be peeled off from the fiber.

Japanese Patent Laid-Open No. 06-272187 JP 61-201093 A

Waste Paper Handbook 2006 (Recycled Paper Recycling Promotion Center) Atsushi Watanabe et al., Paper-Paper Technology Journal Vol. 59, No. 7, p963-978, 2005 2002 Basic survey on the current status and trends of beverage container recycling (National Milk Container Environment Council, National Institute of Policy Science) Stephen Makris et al., TAPPI Paper Summit Spring Tech. Int. Environ. Conf., 1149, 2004.

  An object of this invention is to provide the method of peeling a foreign material, suppressing that foreign materials other than a pulp fiber refine | miniaturize in manufacture of a recycled pulp.

  As a result of earnestly examining the method of peeling foreign matter while suppressing the refinement of foreign matters other than pulp fibers, the present inventors have obtained a shock wave from the pulp fibers in the recycled pulp manufacturing process. It has been found that the removal of foreign matter can be promoted, and the present invention has been completed.

Although this invention is not limited to this, the following invention is included.
(1) A method for producing recycled pulp, comprising applying shock waves to waste paper to separate foreign matter from pulp fibers.
(2) The method according to (1), wherein the shock wave is applied in a liquid.
(3) The method according to (1) or (2), wherein after the shock wave treatment, a dust removal step of removing the separated foreign matter is performed.
(4) The method according to any one of (1) to (3), wherein the pressure of the shock wave is 0.1 to 500 MPa.
(5) The method according to any one of (1) to (4), wherein the shock wave is generated by an explosive.
(6) The method according to any one of (1) to (5), wherein the used paper is used paper having a multilayer structure.

  According to the present invention, by giving a shock wave to waste paper or waste paper pulp slurry, the foreign matter can be peeled off from the pulp fiber while suppressing the fineness of the foreign matter, so that the foreign matter peeled off from the fiber can be efficiently removed in the dust removing step. Can do. Further, according to the present invention, it is possible to use a waste paper raw material that is currently difficult to use as a raw material for recycled pulp for paper as a raw material for recycled pulp.

It is a cross-sectional schematic diagram of the used paper used in Example 1 and Comparative Example 1. It is a cross-sectional schematic diagram of the used paper used in Example 2 and Comparative Example 2. 2 is a photograph of a test piece taken in Example 1. FIG. 2 is a photograph of a test piece taken in Example 2. 3 is a photograph of a test piece of Comparative Example 1. 3 is a photograph of a test piece of Comparative Example 2. It is a figure which shows the outline | summary of the shock wave processing apparatus used in the Example.

In the present invention, the foreign matter is peeled from the pulp fiber by applying a shock wave to the waste paper.
Shock wave In the present invention, a shock wave is a wave of strong pressure change that propagates at a speed exceeding the speed of sound in a transmission medium. A shock wave has a property of instantaneously and suddenly changing physical factors such as pressure, temperature, and density, and a substance to which the shock wave is applied contracts and expands instantaneously. At this time, since the degree of contraction / expansion of each substance differs at the substance interface, the action of the shock wave is increased. Furthermore, the greater the density difference between the two materials, the greater the effect.

  As a generation source of the shock wave of the present invention, chemical energy, electrical energy, mechanical energy, etc. can be used, and as chemical energy, for example, energy using explosion of explosives, etc., as electrical energy, Examples of mechanical energy such as energy using an electric pulse include energy using implantation of a metal sphere into a liquid.

  Examples of the method for generating a shock wave in the present invention include, but are not limited to, explosion of explosives, electric pulses, and driving of metal spheres into a liquid. A shock wave can also be generated using a device such as a shock tube. That is, in a shock wave tube provided with a diaphragm such as a thin film, when a high pressure medium and a low pressure medium are put on both sides of the partition wall and the partition wall is broken, a shock wave is generated because the high pressure medium rapidly expands toward the low pressure medium.

  In the present invention, the place where the shock wave is applied to the waste paper may be a gas such as air or a liquid. Preferably, the treatment is performed in a liquid because the shock wave is less attenuated, so that the treatment effect is increased. The liquid here may be water or a chemical used for pulp production.

  The pressure associated with the shock wave in the present invention is preferably in the range of 0.1 to 500 MPa, more preferably in the range of 1 to 300 MPa, further preferably in the range of 10 to 300 MPa, and 50 to 300 MPa. A range is particularly preferred. When the pressure is 0.1 MPa or less, the influence on the foreign matter is small. When the pressure is 500 MPa or more, the cost for obtaining the pressure is very high, the effect of the shock wave is strong, the fineness of the foreign matter is generated, and it cannot be removed in the dust removing process, or the pulp quality is damaged and produced. May adversely affect Although the pressure accompanying a shock wave can be measured using a well-known pressure sensor (for example, PVDF pressure sensor), it can also be measured as follows. First, the tip of a metal round bar, which is a sensor, is set at a location separated from the shock wave source by an arbitrary distance. At this time, the metal round bar is set so that the length direction thereof is parallel to the propagation direction of the shock wave. A strain gauge is attached to a position (X2) several cm from the tip (X0) of the sensor. Next, a strain gauge is also attached to the position (X1) between X0 and X2 in the sensor. Next, the propagation velocity when the stress wave passes between the two points where the strain gauge is attached is obtained. Furthermore, the pressure value can be calculated by a conventional method using a pressure conversion formula that takes into consideration the impedance between the medium (water or the like) through which the shock wave propagates and the metal.

  Methods for controlling the intensity of the shock wave include, for example, a method of adjusting the amount of explosives, the voltage of the electric pulse, the mass and driving speed of the metal sphere, and the distance from the shock wave source to the processing target. .

  In the present invention, the shock wave processing on the waste paper may be performed only once, but may be performed a plurality of times as necessary. In the present invention, depending on the waste paper to be processed and the application, for example, it can be processed once with a relatively strong shock wave, or can be processed a plurality of times with a relatively weak shock wave.

The shock wave of the present invention may be a vertical shock wave whose wave front is perpendicular to the propagation direction of the shock wave, or may be an oblique shock wave whose wave front is not perpendicular.
The details of the reason why the foreign matter can be peeled from the pulp fiber while suppressing the refinement of the foreign matter according to the present invention are not clear, and the present invention is not limited to this, but is presumed as follows. In other words, since the foreign matter and the pulp are usually firmly fixed, the conventional method gives a strong mechanical load to peel off the foreign matter, but the strong mechanical load causes not only the removal of the foreign matter but also the foreign matter. At the same time, miniaturization of the material occurred. On the other hand, since the shock wave in the present invention acts more greatly at the interface having a large density difference, the shock wave acts selectively on the interface between the foreign matter and the pulp, so that the foreign matter is efficiently removed from the fiber while suppressing the refinement of the foreign matter. It can be considered that it can be peeled off.

Waste Paper Used paper as a raw material for producing recycled pulp according to the present invention means a recovered paper / paperboard that has been produced once, and is not particularly limited as long as it is used paper. The used paper of the present invention includes, in addition to used paper once used, damaged paper generated in the paper manufacturing process. Examples of used papers include newspapers, flyers, magazines for changing papers, magazines for coats, heat-sensitive / pressure-sensitive paper, imitation / color-quality paper, copy paper, computer output paper, and mixed old paper of these types. As described above, the shock wave of the present invention has a characteristic that it acts strongly at the interface. Therefore, when the present invention is applied to used paper having a multilayer structure, foreign substances and fibers can be efficiently separated, which is particularly preferable. As used paper having a multilayer structure, for example, coated paper having a pigment coating layer in addition to a base paper layer, colored paper such as thermal paper and pressure sensitive paper having a colored layer, vapor-deposited paper and laminate having a resin layer and a metal layer Paper can be mentioned. In particular, according to the present invention, paper that has been processed with metal foil, which has been conventionally contraindicated as a raw paper raw material for the manufacture of paper, or a liquid beverage paper container that has been laminated, is recycled even if it is mixed in the raw paper raw material. Pulp can be produced.

  The waste paper to be treated according to the present invention may give a shock wave to the waste paper as it is, or may give a shock wave to the pulp slurry obtained by disaggregating the waste paper. Further, the shock wave treatment according to the present invention can be performed on the entire mixed waste paper, or the shock wave treatment of the present invention may be selectively applied to, for example, waste paper that is currently contraindicated. Moreover, in the present invention, there is no particular limitation on the pulp configuration constituting the waste paper, and the pulp fiber constituting the waste paper may be a mechanical pulp or a chemical pulp.

Foreign matter In the present invention, the foreign matter is peeled from the pulp fiber by applying a shock wave to the waste paper. In the present invention, the foreign matter refers to a substance other than pulp fibers contained in the waste paper as a raw material, for example, a pigment or an adhesive contained in a pigment coating layer, a coloring layer in coloring paper such as thermal paper or pressure sensitive paper, A resin or metal thin film attached to the base paper, or a colored component such as ink may be used as long as it is printed waste paper, but is not limited thereto. Since the shock wave of the present invention selectively acts on the interface between the fiber and the foreign matter, according to the present invention, the foreign matter can be peeled from the used paper while suppressing the refinement of the foreign matter and the damage of the fiber itself.

In one embodiment of the recycled pulp , the present invention is a method for producing a recycled pulp, which includes peeling foreign matter from pulp fibers by applying a shock wave to waste paper. The present invention only needs to include a shock wave treatment step, and may include other steps known in the paper industry. For example, a disaggregation process in which used paper used as a raw material is disaggregated in water to obtain a used paper slurry, an ink peeling process in which a mechanical shearing force is applied to the used paper to separate foreign matter such as ink, and foreign matter separated from pulp fibers Such as a dust removal process for removing water, a flotation process for removing light foreign matter such as ink peeled from the fiber, a deinking process (washing process) for washing the fiber with water to remove the foreign matter, etc. The method for producing recycled pulp of the invention can appropriately include these steps. In particular, in the present invention, the foreign matter is peeled off from the fiber while suppressing the miniaturization of the foreign matter. Therefore, the foreign matter can be efficiently removed if the foreign matter is peeled off by a shock wave process before the dust removing process using a screen or a cleaner. Therefore, it is preferable.

  In the present invention, various devices known in the paper industry can be used. For example, a pulping machine such as a pulper is used in the stripping process, a kneader such as a kneader is used in the ink peeling process, and a dust removing process. For example, a dust remover such as a centrifugal cleaner or a screen, a floatator (floating separator) for a flotation process, and various cleaning devices for a deinking process (cleaning process) can be suitably used.

  The recycled pulp produced by the method of the present invention can be used for various applications without any particular limitation. The recycled pulp obtained by the present invention can be used, for example, by making a paper by a known method and using it as coated paper, information paper, processed paper, sanitary paper, in addition to printing paper and newsprint paper. More specifically, the information paper includes electrophotographic transfer paper, ink jet recording paper, thermal paper, foam paper, and the like. More specifically, examples of processed paper include release paper base paper, laminated base paper, and base paper for molding. More specifically, sanitary paper includes tissue paper, toilet paper, paper towels, and the like. Further, it can be used as a paperboard such as a corrugated cardboard.

  In particular, the regenerated pulp obtained by the present invention is excellent as a regenerated pulp because there is little mixing of foreign matters, and shock waves tend to act on the interface between the foreign matters and the fibers, so that the fibers themselves are less damaged. Further, according to the present invention, since the recycled pulp can be produced not only from the waste paper conventionally used for the production of recycled pulp, but also from the waste paper that is currently difficult to use as a raw material for recycled pulp for western paper, the present invention It is also environmentally suitable.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples. Unless otherwise specified, parts and% are based on mass in the present specification, and numerical ranges are described as including the end points.

Example 1
As used paper, commercially available aluminum vapor-deposited paper (Toppan Prosprint, Inc .: used paper A) was used. As shown in FIG. 1, the used paper A has an adhesive layer, an aluminum vapor deposition layer, and a protective layer on the base paper. This waste paper A was cut into a size of 4 × 8 cm and subjected to the test.

This test piece was installed in a water tank equipped with a shock wave source (explosive) and subjected to shock wave treatment. The test piece of waste paper A was placed in a water tank with the metal vapor deposition surface facing the shock wave source.
Explosive explosive energy was used as a shock wave source. An explosive wire (manufactured by Nippon Carlit Co., Ltd., 8 g / m) was used as the explosive, and was detonated with a No. 6 electric detonator to generate a shock wave. The distance (about 70 cm) between the explosion line and the waste paper was adjusted so that the pressure by the shock wave was 150 MPa.

  The shock wave generated in this way was applied to the waste paper once. In addition, the time from installing the test piece in the water tank to collecting it was about 5 minutes. A photograph of the test piece after the shock wave treatment is shown in FIG.

Example 2
The waste paper was subjected to shock wave treatment in the same manner as in Example 1 except that a beverage paper pack laminated with aluminum foil (used paper B, manufactured by Nippon Paper Pack Co., Ltd.) was used as the used paper. During the shock wave treatment, the surface of the used paper B laminated with the aluminum foil was placed facing the shock wave generation source. As shown in FIG. 2, the waste paper B has a polyethylene layer, an aluminum foil layer, and a polyethylene layer on one of the base papers, and a polyethylene layer on the other side of the base paper. A photograph of the test piece after the shock wave treatment is shown in FIG.

Comparative Example 1
The test piece of waste paper A was immersed in tap water for 5 minutes without performing the shock wave treatment. The photograph of the test piece after immersion is shown in FIG.

Comparative Example 2
The used paper was immersed in tap water for 5 minutes in the same manner as in Comparative Example 2 except that the used paper B was used as the used paper. A photograph of the test piece after immersion is shown in FIG.

<Result>
As can be seen from FIG. 3, in Example 1 (used paper A), it can be seen that the aluminum layer is peeled off from the base paper without being miniaturized. Further, as can be seen from FIG. 4, in Example 2 (used paper B), it can be seen that the aluminum layer and the laminate layer are peeled off from the base paper layer without being miniaturized.

  On the other hand, as can be seen from FIG. 5, no peeling of the aluminum layer was observed in Comparative Example 1 (used paper A). As can be seen from FIG. 6, in Comparative Example 2 (used paper B), no significant change was observed even when the test piece was immersed in water.

  From this, it was found that by treating the waste paper with the shock wave according to the present invention, the foreign matter can be peeled from the base paper layer without making the foreign matter such as the aluminum layer and the laminate layer finer. That is, according to the present invention, since the separated foreign matter is difficult to be miniaturized, the foreign matter can be easily removed by a dust removing process using a screen or the like, and conventionally used waste paper that is not suitable as a raw material for recycled pulp is used. Thus, recycled pulp can be produced efficiently.

Claims (6)

  A method for producing recycled pulp, comprising applying a shock wave to waste paper to separate foreign matter from pulp fibers.   The method of claim 1, wherein the shock wave is applied in a liquid.   The method according to claim 1 or 2, wherein after the shock wave treatment, a dust removal step of removing the separated foreign matter is performed.   The method according to claim 1, wherein the pressure of the shock wave is 0.1 to 500 MPa.   The method according to claim 1, wherein the shock wave is generated by an explosive.   The method according to claim 1, wherein the waste paper is waste paper having a multilayer structure.