RU2413810C2 - Method to make paper and installation to make paper - Google Patents

Abstract

FIELD: textile, paper. ^ SUBSTANCE: method consists in addition of aqueous solution of binding agent, having concentration from 0.03 to 0.4 wt %, into suspension of cellulose material; and addition of mixed suspension of cellulose into header, and suspension contains suspension of cellulose material and aqueous solution of binding agent. Besides, addition of aqueous solution of binding agent is done between discharge box and meshy filter arranged in close proximity to discharge box. Installation comprises the following components: meshy filter to remove admixtures from suspension of cellulose material and device to add binding agent to supply aqueous solution of binding agent, having concentration from 0.03 to 0.4%, into pipe, which connects meshy filter and discharge box. ^ EFFECT: invention provides for the possibility to make well-formed paper even when using high-speed paper-making machines. ^ 4 cl, 3 dwg

Description

This invention relates to a method and apparatus for making paper using a paper machine equipped with a headbox including a collector having a cellular structure.

Typically, the papermaking process includes a pulp preparation step, in which a suspension of cellulosic material is obtained, and a papermaking step, where paper is made from this cellulose suspension. At the stage of obtaining pulp, a suspension of cellulosic material is prepared by obtaining wood chips and cooking, cleaning, plucking, bleaching, etc. In the paper preparation step, the cellulose suspension material is fed from the headbox to the wire mesh element for dewatering, and then processes such as rolling and drying are carried out to produce paper.

Various types of papermaking machines are known, such as a round-mesh (cylinder) papermaking machine, a Four-grid (Fourdrinier) machine, a tanmo machine, a two-wire machine, and a crescent-shaped casting machine.

Typically, during the papermaking process using a round-mesh machine, the material of the cellulose suspension in the headbox does not mechanically exert significant shear forces so that the cellulose is not dispersed sufficiently. Thus, to obtain paper with a relatively low base weight, such as tissue paper or toilet paper, using a round-mesh machine, a binder (viscous) pulp dispersing agent is usually used. For example, polyethylene oxide may be used as such a binding agent. Specifically, an aqueous solution of polyethylene oxide having a concentration of not more than about 0.01 wt.% And an appropriate viscosity can be added to the cellulose suspension material. Due to the dispersing effect of the binding agent added during the papermaking process, with respect to the pulp, paper is obtained in which the pulp fibers are uniformly dispersed and which is perfectly formed.

Paper machines such as the long mesh machine, the tanmo machine, the double mesh machine and the sickle casting machine (hereinafter referred to as “high speed paper machines”), which were designed to achieve higher productivity than round mesh machines and which have a production speed paper (the speed of movement of the grid) is relatively high, include a collector having a cellular structure and built into the headbox. Accordingly, in these machines, as the cellulose suspension material passes through the collector, a large shear force is applied to the cellulosic material suspension through which the suspension is mechanically dispersed. Thus, when using a high speed papermaking machine, perfectly formed paper with a low base weight is obtained without the use of a binding agent. However, compared with the paper manufacturing process using the round-mesh machine, the time required for dewatering on the wire mesh member in the paper manufacturing process using the high-speed paper machine is less due to the higher paper manufacturing speed. In addition, since no bonding agent is used, the dispersion of cellulose on a wire mesh member in a high speed paper machine is lower in quality than the dispersion of cellulose in a round-mesh machine. As a result, although the productivity of the high-speed paper machine is higher than the performance of the round-mesh machine, the quality of the resulting paper from the point of view of molding will be lower.

In recent years, competition for higher quality paper has been developing in the pulp and paper industry, and an installation is needed that can stably and easily produce perfectly formed paper. Despite ongoing improvements to paper machines, research on the addition of agents to improve the dispersion of cellulose in high-speed machines has not been very successful. A possible reason for this is the fact that even when a binding agent such as a polyethylene oxide-based binding agent, which is known to be relatively susceptible to shear failure, is used in a high-speed paper machine, this binding agent breaks down due to the high shear force exerted in the headbox . As a result, the viscosity decreases and, therefore, the action of the bonding agent decreases, so that molding improvement similar to that obtained with round-mesh machines cannot be expected.

Although Patent Document 1 (JP-A 2000-290892) describes a binder to replace polyethylene oxide, only a round-mesh machine is shown as a possible application.

The object of the present invention, which is proposed in view of the above-described problems of the prior art, is a paper making method and a paper making apparatus, making it possible to produce perfectly formable paper even when using high speed paper machines, by optimizing the concentration of the binder solution added to the cellulosic material suspension.

To solve the above problems, the authors of the present invention studied the changes in viscosity of an aqueous solution of polyethylene oxide caused by shear, and found that under the influence of shear, the viscosity decreases slightly if this aqueous solution has a concentration above a certain value. Applying these research results to the manufacture of paper, the inventors found that excellent formability of the paper is obtained even when using high-speed machines, and came to this invention.

According to a first aspect of the present invention, there is provided a method of manufacturing paper using a paper machine equipped with a headbox including a collector having a cellular structure. The method includes the steps of adding an aqueous solution of a binding agent having a concentration of 0.03 to 0.4 wt.% To a suspension of cellulosic material and introducing into the collector a mixed suspension of cellulose containing a suspension of cellulosic material and an aqueous solution of a binding agent.

When using the above-described paper manufacturing method, the effect of the binding agent on the dispersion of cellulose is manifested appropriately even in a paper machine that contains a collector with a cellular structure in the headbox. The result is paper in which the cellulose fibers are evenly distributed and which is perfectly formed. Thus, according to this paper manufacturing method, a binding agent is effectively used to improve paper quality.

In addition, when using the paper manufacturing method of the present invention, the use of a binding agent reduces defects such as tearing paper due to insufficient dispersion of cellulose fibers, and therefore, stable paper production is possible. Thus, the paper production yield is improved, and the production efficiency is improved.

Preferably, the addition of an aqueous solution of a binder is carried out between the headbox and a strainer located in close proximity to the headbox. In this case, the effect of the binding agent on the dispersion of cellulose is manifested accordingly.

Preferably, the binder is a polyethylene oxide binder. Preferably, in this case, the binding agent may contain only polyethylene oxide.

According to a second aspect of the present invention, there is provided a paper making apparatus including a strainer for removing impurities from a suspension of cellulosic material, a paper machine equipped with a headbox including a honeycomb collector located downstream of the mesh filter, and a device for adding a binder for supplying an aqueous solution of a binding agent having a concentration of from 0.03 to 0.04 wt.%, in the pipe connecting the strainer and the pressure box to each other ik.

Preferably, the coupling agent is a polyethylene oxide-based coupling agent.

Other characteristic features and advantages of the present invention will become clearer from the detailed description below, with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows a structural diagram of an example implementation of a paper machine used in the method of manufacturing paper according to this invention.

Figure 2 presents a longitudinal section schematically depicting the main part of the headbox.

Figure 3 presents an axonometric image, which shows an example of a collector.

Figure 1 schematically shows a paper machine X1 used to implement the method of manufacturing paper according to the invention. This paper machine X1, the main components of which is a pump 1, a strainer 2, a headbox 3 and a pipe connecting these components to each other, is intended for the manufacture of paper from a suspension S of cellulosic material by this paper manufacturing method.

Pump 1 delivers a suspension S of cellulosic material obtained in the cellulose preparation step and containing cellulose fibers to the strainer 2 at a predetermined pressure.

The strainer 2 removes impurities from the suspension S of the cellulosic material and makes the density of the suspension S of the cellulosic material uniform. When the slurry S of the cellulosic material is fed to the screen 2, this slurry S of the cellulosic material passes through an extremely narrow space under pressure, which creates contact with a roll not shown in the diagram. Thus, relatively high shear forces are applied to the cellulose fibers contained in the suspension S of the cellulosic material.

As shown in FIG. 2, the headbox, which is part of the paper machine, serves to push the mixed MS pulp slurry onto the wire mesh member 4 moving in the form of an endless belt. A mixed MS cellulose suspension is obtained by adding a binding agent M (which will be described later) to the cellulosic material suspension S. As shown in FIG. 3, the headbox 3 includes a collector 30 having a cellular structure composed of a plurality of pipes 31. By passing the mixed MS cellulose suspension through the collector 30, the cellulose fibers contained in this mixed MS cellulose suspension are dispersed. Each of the tubes 31 includes an inlet end 31a and an outlet end 31b, and the cross-sectional area of each tube increases stepwise from the inlet end 31a to the outlet end 31b. Examples of paper machines containing a collector similar to collector 30 include a crescent-shaped casting machine, a double-mesh machine, and a long-mesh machine, which are high-speed paper machines in which the papermaking speed is relatively high. The headbox 3 includes an outlet 3a on the side of the manifold 30 located at the outlet of the stream. The mixed MS pulp suspension exiting the collector 30 is pushed onto the element 4 from the wire mesh through the outlet 3a. In the illustrated embodiment, the outlet 3a is beveled towards the outlet of the stream.

The strainer 2 and the headbox 3 are connected to each other via a pipe 21. A pipe 22 is connected to the pipe 21 to add a solution M of a binding agent. An example of a solution M of a binding agent to be added is an aqueous solution based on polyethylene oxide.

During operation of the paper machine X1 having the above structure, the suspension S of cellulosic material is fed to the screen 2 by means of a pump 1.

On the screen 2, unnecessary components such as impurities are removed from the slurry S of the cellulosic material, and a relatively high shear is exerted on the cellulose fibers contained in the slurry S of the cellulosic material. Thus, the initially agglomerated cellulose fibers are dispersed to some extent.

The slurry S of the cellulosic material passing through the screen 2 enters the pipe 21. Through the pipe 22, an aqueous solution M of polyethylene oxide is added as a binder to the slurry S of the cellulosic material. This aqueous solution is prepared in advance, and it has a concentration of polyethylene oxide from 0.03 to 0.4 wt.%. For example, an aqueous solution of polyethylene oxide can be prepared by dissolving a powder of polyethylene oxide in water in a stainless steel bath while stirring this water using a stirrer available in this bath. The slurry S of the cellulosic material and the binder M are mixed inside the tube 21 to form a mixed slurry MS of cellulose and this mixed slurry MS of cellulose is fed to headbox 3.

In headbox 3, a mixed MS cellulose suspension is introduced into a manifold 30 (into tubes 31). Since the cross-sectional area of each pipe 31 in the part adjacent to the inlet end 31a is relatively small, the mixed cellulose suspension MS flows through this part at a relatively high speed. Since the cross-sectional area of the pipe increases stepwise as it moves toward the outlet end 31b, the flow rate of the mixed cellulose slurry MS decreases stepwise. As a result, vortices occur in the tube 31, whereby a relatively large shear is applied to the mixed MS cellulose suspension. Under this shear, the cellulose fibers contained in the mixed MS cellulose suspension are dispersed efficiently. The solution of the binding agent M is dispersed and mixed with the suspension S of the cellulosic material, without being substantially destroyed by the vortices arising in the pipe 31.

The mixed MS slurry of cellulose, in which the cellulose fibers are appropriately dispersed as they pass through the collector 30 (tubes 31), undergoes a corresponding decrease in viscosity under shear and is expelled from the outlet ends 31b onto the moving member 4 from the wire mesh through the outlet 3a. Due to the influence of the binding agent on the dispersion of the cellulose, the cellulose fibers contained in the mixed MS pulp suspension are evenly distributed on the wire mesh member 4. After that, the mixed MS pulp suspension is dehydrated and processing steps, such as rolling and drying, are carried out to obtain paper as a final product.

In the method for producing paper using the paper machine X1 according to the present invention, the use of a polyethylene oxide-based binder has a good effect even when using a high speed paper machine including a collector having a cellular structure. In particular, although a polyethylene oxide binder was usually used to make paper using a round-mesh machine, the use of a polyethylene oxide binder for paper making on high-speed paper machines was avoided due to a significant reduction in viscosity and the inability to obtain a pulp dispersion effect. Under such circumstances, the inventors of the present invention sought a method for the efficient use of polyethylene oxide, which is stably produced by the industry and used as an effective binding agent for a round-mesh machine, for high-speed paper machines. As a result, the inventors found that if a solution of a polyethylene oxide-based binding agent has a concentration of 0.03 to 0.4 wt.%, Which is significantly higher than the concentration (not higher than about 0.01 wt.%) Of the solution used for round-mesh machine, the necessary effect is shown with respect to the dispersion of the pulp and perfectly formed paper is obtained.

In the paper manufacturing method of this invention, it is preferable that the concentration of the binder agent M solution added to the suspension S of the cellulosic material is from 0.03 to 0.4 wt.%, And more preferably from 0.03 to 0.2 wt. %

If the concentration of the added solution M of the binding agent is not more than 0.03 wt.%, The effect of this solution of the binding agent on the dispersion of cellulose is reduced due to a decrease in viscosity under the action of shear in the headbox 3, and therefore, the paper forming improves only slightly. If the concentration of the added M-binding agent solution is greater than 0.4% by weight, the M-binding agent solution does not mix well in the headbox with the suspension S of cellulosic material due to the high viscosity of the M-binding agent solution. As a result, the solution of the binding agent partially agglomerates in the form of a strip or block, which makes it difficult to disperse cellulose fibers. In this case, defects such as tearing of paper may occur, and it is not possible to produce stable paper production. In addition, the resulting paper may contain defects such as spots and / or holes, resulting in reduced paper quality.

However, if the concentration of the added solution M of the binding agent is from 0.03 to 0.4 wt.%, The effect on the dispersion of cellulose is manifested properly, and defects such as spots and / or holes can be avoided. Thus, by using the paper manufacturing method of the present invention, perfectly formable paper is obtained, and thus, an improvement in quality is achieved.

In addition, when using the paper manufacturing method of the present invention, the use of a properly selected binding agent reduces defects such as tearing paper due to insufficient dispersion of cellulose fibers, and hence stable paper production is possible. In this way, paper yield is improved and production efficiency is improved.

From the point of view of the effect on the dispersion of cellulose and ease of use, it is preferable that the binding agent (polyethylene oxide) used in the papermaking process according to this invention has a viscosity average molecular weight of from 3 million to 11 million, preferably from 4 million to 9 million.

Although the amount of binding agent used depends on the type of paper and is not limited to a specific value, an amount of from 0.001 to 1.0%, preferably from 0.01 to 0.5%, relative to the dry weight of the resulting paper can be considered effective.

The binding agent solution M does not have to be added through a pipe 22 connected to the pipe 21, which connects the strainer 2 and the headbox 3 to each other. However, in order to properly effect the dispersion of cellulose with the binding agent, it is preferable to add this binding agent in the space between the mesh filter 2 and the headbox 3, that is, in a place downstream of the mesh filter 2 and upstream of the headbox 3. This is due to the fact that when adding a solution of M binding agent in a position upstream from chatogo filter 2 viscosity decreases under the effect of shear forces in the strainer 2 so that the pulp dispersion effect of the bonding agent can not be exhibited.

The paper production method of the present invention is preferably applicable to the manufacture of tissue paper, such as tissue paper or toilet paper, having a base mass of not more than about 60 g / m ² , but is not limited thereto.

The following describes examples of the implementation of the present invention, as well as comparative examples.

Example 1

Paper making

The paper was made from a slurry S of cellulosic material using a paper making machine X1 according to the embodiment described above. As a paper machine used a crescent-shaped molding machine operating at a speed of 800 m / min to obtain paper for napkins, having a base weight of 13 g / m ² . As a suspension S of cellulosic material, a suspension with a density of 0.15 wt.% Was prepared from NBKP (pulp from softwood) and LBKP (pulp from broadleaf wood) with a cage (degree of grinding) of 640 ml CSF (defined in Canadian standard CSF) mixed in a ratio of 40 to 60 (mass ratio). An aqueous solution of polyethylene oxide having a concentration of 0.07 wt.%, Which was prepared by dissolving polyethylene oxide in water with stirring (trademark REO-27, medium viscosity molecular weight 7500000, manufactured by Sumitomo Seika Chemicals Co., Ltd), was used as a solution of a binding agent. .). In the paper manufacturing process, a polyethylene oxide solution was fed into the pipe 21 between the strainer 2 and the headbox 3. The amount of binder used was 0.1% relative to the dry weight of the resulting paper.

Paper forming evaluation

Paper made as described above was examined for improved molding. The molding was checked by visual inspection, the results are shown in the table. In the table, the o indicates that the molding has been improved to a large extent, that is, the cellulose fibers are uniformly dispersed and there are almost no holes and / or clusters of cellulose fibers; the Δ sign indicates that molding improvement is almost not detectable, and the × sign indicates that the molding is poor, that is, there are holes and / or clusters of cellulose fibers or any paper production shortcomings such as tearing paper.

Example 2

In Example 2, paper was prepared under the same conditions as in Example 1, except that the aqueous polyethylene oxide solution used as the solution M of the binding agent M had a concentration of 0.03 wt.%. The results of the paper forming study obtained in this example are also shown in the table.

Example 3

In this example, a long-mesh machine was used as a paper machine. Specifically, the long-mesh machine was operating at a speed of 1100 m / min to produce tissue paper having a base weight of 17 g / m ² . As a suspension S of cellulosic material, a suspension of 0.12 wt.% Was prepared from NBKP and LBKP with a sagidity of 660 ml CSF (determined on a Canadian standard device) mixed in a ratio of 60 to 40 (mass ratio). An aqueous solution of polyethylene oxide having a concentration of 0.06 wt.%, Which was prepared by dissolving polyethylene oxide (PEO-27) in water with stirring, was used as a solution of a binding agent. In the paper manufacturing process, the polyethylene oxide solution was fed into the tube 21 between the strainer 2 and the headbox 3. The amount of binder used was 0.15% relative to the dry weight of the resulting paper. The results of the paper forming study obtained in this example are also shown in the table.

Example 4

The same paper machine as in Example 3 was operated at a speed of 1000 m / min to obtain tissue paper having a base weight of 15 g / m ² . As a suspension S of cellulosic material, a suspension of 0.12 wt.% Was prepared from NBKP and LBKP with a sagidity of 660 ml CSF (determined on a Canadian standard device) mixed in a ratio of 60 to 40 (mass ratio). An aqueous solution of polyethylene oxide having a concentration of 0.15 wt.%, Which was obtained by dissolving polyethylene oxide (PEO-27) in water with stirring, was used as a solution of a binding agent. In the paper manufacturing process, the polyethylene oxide solution was fed into the pipe 21 between the strainer 2 and the headbox 3. The amount of binder used was 0.15% with respect to the dry weight of the resulting paper. The results of the molding study obtained in this example paper are also shown in the table.

Comparative Example 1

In this comparative example, paper was prepared under the same conditions as in Example 1, except that the aqueous solution of polyethylene oxide used as the solution M of the binding agent had a concentration of 0.01% by weight. The results of the paper forming study obtained in this comparative example are also shown in the table.

Reference Example 2

In this comparative example, paper was prepared under the same conditions as in Example 3, except that the aqueous polyethylene oxide solution used as the solution M of the binding agent M had a concentration of 0.5 wt.%. The results of the paper forming study obtained in this comparative example are also shown in the table.

Reference Example 3

In this comparative example, paper was obtained under the same conditions as in comparative example 1, except that a round-mesh machine was used as a paper machine. The results of the paper forming study obtained in this comparative example are also shown in the table.

Table Example 1 Example 2 Example 3 Example 4 Comp. example 1 Comp. example 2 Comp. example 3 Paper machine Crescent Casting Machine Long mesh machine Crescent Casting Machine Long mesh machine Round mesh machine Produced paper Napkin paper Paper making speed (m / min) 800 800 1100 1000 800 1100 800 Base weight (g / m ² ) 13 13 17 fifteen 13 17 13 The concentration of the binding agent (wt.%) 0,07 0,03 0.06 0.15 0.01 0.5 0.01 The amount of binding agent
(relatively dry paper weight,%) 0.1 0.1 0.15 0.15 0.1 0.15 0.1 Molding improvement about about about about Δ × about

Since the solution M of the binding agent used in examples 1-4 has a high concentration within a predetermined range, the formation of paper proceeded better than the formation of paper obtained using a solution of M of a binding agent with a lower concentration, such as in the comparative example 1. In this case, the concentration (0.01 wt.%) Of the solution M of the binding agent used in comparative example 1 is close to the upper limit of the concentration range (not more than 0.01 wt.%) Of the polyethylene oxide solution, which is usually considered acceptable for paper making (using a round-mesh machine).

Since the solution M of the binding agent used in comparative example 2 has a concentration above a predetermined range, the solution M of the binding agent agglomerated due to its high viscosity during the papermaking process, causing defects such as tearing of paper.

Claims (4)

1. A method of manufacturing paper using a paper machine equipped with a headbox including a collector having a cellular structure; wherein the method includes the following stages:
adding an aqueous solution of a binding agent having a concentration of from 0.03 to 0.4 wt.%, in a suspension of cellulosic material; and
introducing into the collector a mixed suspension of cellulose containing a suspension of cellulosic material and an aqueous solution of a binding agent,
moreover, the addition of an aqueous solution of a binding agent is carried out between the head box and the strainer located in close proximity to the head box. 2. The paper manufacturing method of claim 1, wherein the binding agent is a polyethylene oxide-based binding agent. 3. Installation for the manufacture of paper, including:
strainer to remove impurities from the suspension of cellulosic material;
a paper machine equipped with a headbox including a collector having a honeycomb structure and located downstream of the strainer; and
a device for adding a binding agent for supplying an aqueous solution of a binding agent having a concentration of from 0.03 to 0.4 wt.%, in the pipe connecting the strainer and the headbox to each other. 4. The paper making machine according to claim 3, wherein the binding agent is a polyethylene oxide-based binding agent.

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