ES2861724T3 - Paper sheet and paper sheet manufacturing method - Google Patents

Abstract

A sheet of paper comprising: cellulose ester staple fibers; pulp fibers; and a binder, where a plurality of creped portions are formed on the paper sheet, so that the creped portions are arranged in a flow direction of the cellulose ester staple fibers and pulp fibers and extend in one direction orthogonal, which is orthogonal to the direction of flow.

Description

DESCRIPTION

Paper sheet and paper sheet manufacturing method

Technical field

The present invention relates to a paper sheet having excellent processability, the paper sheet achieves excellent production efficiency of processed products made with it, and also relates to a production method of the paper sheet.

Previous technique

Cellulose ester compounds typically represented by cellulose acetate are excellent natural polymeric compounds that are safe and highly processable. Cellulose ester compounds are widely used for clothing fibers, various plastics, cigarette filters, etc. For example, cellulose ester compounds are made from cellulose obtained from plant resources (biomass) that are produced in greater quantities on earth, such as wood pulp and cotton. Therefore, these environmentally friendly cellulose ester compounds are considered suitable raw materials for a recycling-oriented society, and the expansion of the use of cellulose ester compounds instead of chemical fibers and plastics made from petroleum is expected. .

For example, Patent Literature 1 discloses a technique for producing a paper sheet containing cellulose ester staple fibers, pulp fibers, and a binder. Such a sheet of paper is usable, for example, as the material of a processed product, such as a cigarette filter, as disclosed in patent literature 2 and 3.

The paper sheet is produced, for example, in the form of a continuous tape by using a wet paper machine. The tape-shaped continuous sheet of paper is cut to the required width and then wound into a roll. In a processing machine, the rolled sheet of paper is removed from the roll and undergoes continuous processing while being fed at a predetermined feed rate.

Appointment list

Patent bibliography

PTL 1: Japanese Patent No. 5225489

PTL 2: Japanese Patent No. 3606950

PTL 3: Japanese Patent Application Publication Open to Public Inspection No. 2001-120248

Document EP2862456 discloses a paper sheet comprising a cellulose ester staple fiber, a pulp and an alkali metal salt of a water soluble anionic polymer, where the paper sheet has an alkali metal content of 2 to 100 pmol per gram of sheet of paper.

EP0709037 discloses a tobacco filter material in the form of a sheet having a band structure and comprising a cellulose ester staple fiber.

Summary of the invention

Technical problem

When the rolled paper sheet is pulled out from the roll to continuously produce processed products using the paper sheet, if tension is exerted on the paper sheet in the feeding direction by a certain degree or more, the paper sheet may be damaged. As a result, the processability of the paper sheet can be reduced. Consequently, it may be difficult to improve the production efficiency of the processed products by increasing the feed rate of the paper sheet.

In view of the above, an object of the present invention is, in the case of producing processed products using a sheet of paper containing staple fibers of cellulose ester, they allow to avoid damage to the sheet of paper and improve the production efficiency of processed products.

Solution to the problem

To solve the aforementioned problems, a paper sheet according to one aspect of the present invention includes: cellulose ester staple fibers; pulp fibers; and a binder, where a plurality of creped portions are formed on the paper sheet, so that the creped portions are arranged in a flow direction of the cellulose ester staple fibers and pulp fibers and extend in one direction orthogonal, which is orthogonal to the direction of flow.

According to the above configuration, the plurality of creped parts (continuous or non-continuous wrinkles), which are arranged in the flow direction of the cellulose ester staple fibers and pulp fibers and extend in the orthogonal direction, which is orthogonal to the direction of flow, they are formed on the sheet of paper. Accordingly, when producing processed products using the paper sheet while feeding the paper sheet in the flow direction, if tension is exerted on the paper sheet in the flow direction, the paper sheet is stretched in the flow direction. flow. This makes it possible to prevent damage to the paper sheet and prevent the processability of the paper sheet from being reduced. Since the damage to the paper sheet due to the stress that is exerted on the paper sheet in the flow direction is prevented, the feeding speed of the paper sheet can be increased in a processing machine and thus Therefore, the production efficiency of the processed products can be improved.

The paper sheet can be formed in the form of a tape, so that a longitudinal direction of the paper sheet is the flow direction. Accordingly, when the sheet of paper that has been wound into a roll is pulled out from the roll and fed to be continuously processed by a processing machine, even if tension is exerted on the sheet of paper in the longitudinal direction (feeding direction ), the sheet of paper is less likely to be damaged, further improving the production efficiency of processed products.

A creping ratio of the paper sheet can be set to a value within a range of not less than 5% and not more than 35%. Since the creping ratio is set to such a value, when tension is exerted on the paper sheet in the flow direction, the paper sheet is stretched in the flow direction, and therefore damage can be adequately avoided. to the sheet of paper.

An elongation at break of the paper sheet in the flow direction can be set to a value within a range of not less than 10% and not more than 70%. Since the elongation at break is set to such a value, when stress is exerted on the paper sheet in the flow direction, damage to the paper sheet can be favorably prevented.

The tensile strength of the paper sheet in the flow direction can be set to a value within a range of not less than 1.5N / 25mm width and less than 40N / 25mm width. Accordingly, by winding the paper sheet in the flow direction, it can prevent the paper sheet from breaking due to the stress exerted on the paper sheet in the flow direction, and also the processability of the paper sheet. paper can be properly maintained.

The binder can be an alkali salt of a polysaccharide containing a carboxyl group. The use of the binder of this type makes it possible to efficiently produce a processed product having a high disintegrability in water using the paper sheet.

The paper sheet can be a filter material from a cigarette filter. Since the plurality of creped parts, which are arranged in the flow direction and extend more in the orthogonal direction than in the flow direction, are formed on the paper sheet, the paper sheet has a large area. Accordingly, by using the paper sheet as the filter material of the cigarette filter, many fine spaces can be formed uniformly within the cigarette filter. As a result of the uniform formation of the fine spaces, a cigarette filter having a beautiful cross-section without irregularities can be produced.

A method of producing a paper sheet according to another aspect of the present invention includes: a sheet body forming step to form a sheet body containing cellulose ester staple fibers, pulp fibers and a binder; and a creping step to form a plurality of creped portions in the body of the sheet, such that the creped portions are arranged in a flow direction of the cellulose ester staple fibers and the pulp fibers and spread in a orthogonal direction, which is orthogonal to the flow direction.

The sheet body forming step may include forming the sheet body in the form of a tape such that a longitudinal direction of the sheet body is the flow direction.

In the above production method, a creping ratio of the paper sheet can be set to a value within a range of not less than 5% and not more than 35%.

In the above production method, by adjusting the creping ratio to that value, a tensile elongation of the paper sheet in the flow direction can be set to a value within a range of not less than 10% and not more than 70%. %.

In the sheet body forming stage of the above production method, the tensile strength of the paper sheet in the flow direction can be set to a value within a range of not less than 1.5 N / 25mm wide and less than 40N / 25mm wide by adjusting at least one of the mixing ratios of the cellulose ester staple fibers, pulp fibers and binder, a paper sheet weight, one grade whipping rate of cellulose ester staple fibers and pulp fibers, and a creping ratio of the paper sheet.

In the above production method, an alkaline salt of a polysaccharide containing a carboxyl group can be used as a binder.

Advantageous effects of the invention

Each of the above aspects of the present invention makes it possible, in the case of producing processed products using a paper sheet containing cellulose ester staple fibers, to avoid damage to the paper sheet and to improve the production efficiency of the products. processed.

Brief description of the drawings

Figure 1 shows a sheet of paper according to one embodiment.

Figure 2 is an overview of a paper machine for producing the sheet of paper of Figure 1.

Figure 3 is a production process diagram showing processes for producing the paper sheet of Figure 1.

Figure 4 is a graph showing a relationship between the elongation at break and the tensile strength of each of the paper sheets of the Examples and Comparative Examples.

Figure 5 is a graph showing a relationship between the crepe rate and the tensile strength of each of the paper sheets of the Comparative Examples and the Examples.

Figure 6 is a graph showing a relationship between the crepe rate and the elongation at break of each of the sheets of paper of the Examples and Comparative Examples.

Figure 7 is a graph showing a relationship between the crepe rate and the air resistance of each of the paper sheets of the Examples and Comparative Examples.

Description of achievements

[Paper sheet]

Figure 1 shows a sheet of paper 1 according to an embodiment of the present invention. The paper sheet 1 contains cellulose ester staple fibers, pulp fibers and a binder. By way of example, the paper sheet 1 is produced in tape form by a paper machine 10 (see Fig. 2) and wound into a roll. Figure 1 shows schematically, in an enlarged form, creped parts 1a formed on the sheet of paper 1. For example, the roll of the sheet of paper 1 is cut to have the required width in subsequent processes, and is removed of the roll continuously to produce processed products.

By way of example, the cellulose ester is cellulose acetate, which is a typical cellulose ester. Cellulose ester staple fibers can be creped. In the case of imparting disintegrability in water to the paper sheet 1, the cellulose ester staple fibers are preferably uncreped fibers (uncreped fibers). The definition of uncreped fibers herein includes not only completely straight fibers but also slightly curved fibers.

Uncreped fibers can be made by a general man-made fiber spinning technique (eg, dry spinning, wet spinning, or melt spinning). Alternatively, the uncreped fibers can be obtained by applying tension to the creped fibers whose crimps have been previously formed in a spinning process while heating the creped fibers by heating means such as heated steam, thus completely removing the crimps and stretching the crimps. fibers.

By means of a guillotine equipment or rotary cutting equipment whose feeding interval and feeding speed are adjustable, the cellulose ester staple fibers can be obtained from a bundle of filamentous fibers obtained in the spinning process mentioned above. The process of converting the cellulose ester fibers into staple fibers by means of the guillotine equipment or rotary cutting equipment can be carried out continuously with the spinning process.

The average fiber length of the cellulose ester staple fibers (in the case of creped fibers, the average value of the end-to-end distances of the creped fibers in a natural state) can be set to, for example, a value within the range of not less than 1mm and not more than 6mm, preferably a value within the range of not less than 1.5mm and not more than 5.0mm, and more preferably a value within the range of not less than 2.0mm and not more than 4.5mm.

The average fiber diameter of the cellulose ester staple fibers can be set to, for example, a value within the range of not less than 1.5 denier and not more than 8.0 denier, preferably a value within the range of not less 2.0 denier and not more than 7.0 denier, and more preferably a value in the range of not less than 2.5 denier and not more than 6.0 denier. Each of the cellulose ester staple fibers has, for example, a Y-shaped cross section. However, the cross-sectional shape of the cellulose ester staple fibers is not limited to a Y-shape.

Creping ability, average fiber length, average fiber diameter, and cross-sectional shape of the cellulose ester staple fibers can be confirmed by disintegrating the paper sheet 1 in water and observing the disintegrated product in water. resulting under a microscope. The paper sheet 1 can also contain other fibers (synthetic fibers, recycled fibers, etc.) than cellulose ester fibers and pulp fibers.

The pulp fibers are intertwined with the cellulose ester staple fibers, and thus the pulp fibers and the cellulose ester staple fibers are bonded together. Therefore, by using the pulp fibers, the mechanical strength of the paper sheet 1 can be improved. In the case of producing a filter material, such as a cigarette filter, using the paper sheet 1, the spaces between the fibers can be adjusted by adjusting the amount of pulp fibers, the amount of cellulose ester staple fibers, and the mixing ratio of the pulp fibers and the cellulose ester staple fibers, and therefore a rate can be adjusted. required filtration of, for example, smoke components.

The pulp can be made from natural fibers, such as wood and cotton lint. In the case that the pulp is made of wood, the wood can be soft or hard. Also in the case where the pulp is made of wood, a suitable pulping process to be adopted is a chemical pulping process, such as a sulphite process or a kraft process. Among chemical pulps, kraft pulp is superior to other pulps in terms of obtaining greater strength from the sheet of paper 1 with the same composition ratio. The pulp can be any of bleached pulp, unbleached pulp, and a mixture of bleached pulp and unbleached pulp. The paste is beaten by a common mixer or blender and thus prepared for use.

The weight ratio between the weight of the cellulose ester staple fibers contained in the paper sheet 1 and the weight of the pulp fibers contained in the paper sheet 1 is suitably adjustable depending on, for example, a processed product that is produced using the paper sheet 1. In the case of producing, for example, a cigarette filter using the paper sheet 1, the weight ratio is adjusted according to the required smoke filtration performance of the cigarette filter. The weight ratio between the weight of the cellulose ester staple fibers contained in the paper sheet 1 and the weight of the pulp fibers contained in the paper sheet 1 can be adjusted so that the weight ratio M1 / M2 of the weight M1 of the cellulose ester staple fibers contained in the cigarette filter to the weight M2 of the pulp fibers contained in the cigarette filter is, for example, 30/70 to 95/5, preferably 40/60 to 80/20 and more preferably 50/50 to 70/30.

The binder makes the cellulose ester staple fibers and pulp fibers bond together. For example, a predetermined amount of the water-soluble polymer can be used as the binder of the paper sheet 1, and therefore both the strength of the paper sheet 1 in the dry state and the water disintegrability of the paper can be achieved. sheet of paper 1.

By way of example, a binder capable of imparting water disintegrability to paper sheet 1 is used as the binder of the present embodiment. The binder of the present embodiment is an alkali metal salt of a water soluble anionic polymer. Examples of the water-soluble anionic polymer include polysaccharides (for example, a polysaccharide containing a carboxyl group, for example, carboxymethyl cellulose, carboxymethyl C2-3 alkyl cellulose such as carboxymethylethyl cellulose, carboxymethyl starch or alginic acid; and a polysaccharide containing a sulfo group, eg pectin, carrageenan, hyaluronic acid or chondroitin sulfuric acid) and polyacrylic acid. The binder of the present embodiment is an alkaline salt of a polysaccharide containing a carboxyl group.

If the alkali metal salt of the water-soluble anionic polymer is contained in a predetermined amount in the paper sheet 1 as a binder, the bonding force between the cellulose ester staple fibers, the bonding force between the pulp fibers and the bonding force between these two types of fibers when the paper sheet 1 is in the dry state is increased by the binder, and therefore the strength of the paper sheet 1 can be improved.

The acid group (such as the carboxyl group or the sulfo group) of the water-soluble anionic polymer forms a salt with an alkali metal. Examples of the alkali metal include lithium, sodium, and potassium. Among these alkali metals, sodium is preferred. A single type or two or more types of alkali metals can be used.

In the alkali metal salt of the polysaccharide containing the carboxyl group (eg, carboxymethyl cellulose), the average degree of substitution of the carboxyl group (eg, carboxymethyl group) that forms the alkali metal salt (eg, average degree of substitution with respect to hydroxyl groups in the second, third and sixth positions of a glucose unit constituting the polysaccharide; the average degree of etherification; or DS) can be set to, for example, a value within the range of not less than 0.4 and not more than 2.5, preferably a value within the range of not less than 0.55 and not more than 2.0, and more preferably a value within the range of not less than 0.65 and not more than 1.5.

The alkali metal content in the sheet of paper 1 can be set to, for example, a value within the range of not less than 2 µmol and not more than 100 µmol per gram of sheet of paper 1, preferably a value within in the range of not less than 2 jmol and not more than 90 jmol, more preferably a value within the range of not less than 2 | jmol and not more than 87 jmol, and particularly preferably a value within the range of not less than 3 jm ol and not more than 75 jmol.

The alkali metal salt content of the water-soluble anionic polymer (molar amount of anionic group) in paper sheet 1 can be the same as the alkali metal content (molar amount) in paper sheet 1. In the case of producing a cigarette filter using sheet of paper 1, the alkali metal salt content of the water-soluble anionic polymer (molar amount of anionic group) in sheet of paper 1 can be set, per gram of the cigarette filter, at a value within the same range as mentioned above (for example, at a value within the range of not less than 2 jmol and not more than 100 jmol). It should be noted that the binder may be different from an alkali metal salt of a water soluble anionic polymer.

The weight of the paper sheet can be set to, for example, a value within the range of not less than 10 g / m2 and not more than 60 g / m2, and preferably a value within the range of not less than 15 g / m2 and no more than 50 g / m2. The grammage of the paper sheet 1 of the present embodiment is set to a value within the range of not less than 21 g / m2 and not more than 40 g / m2.

It should be noted that the sheet of paper 1 can contain at least one type of additive agent. The additive agent is, for example, at least one of a sizing agent, a stabilizer, a colorant, an oil solution, a retention aid, an antifoam agent, and activated carbon. The additive agent is not limited to these examples.

On the paper sheet 1, a plurality of creped parts are formed in such a way that the creped parts are arranged in a flow direction of the cellulose acetate staple fibers and pulp fibers (hereinafter, this direction may simply be referred to as "the flow direction") and extend in an orthogonal direction, which is orthogonal to the flow direction (hereinafter, this direction may simply be referred to as "the orthogonal direction"). In the present embodiment, the plurality of creped portions 1a extend parallel to the orthogonal direction.

Herein, the flow direction is the direction of substantial orientation of the cellulose acetate staple fibers and pulp fibers (ie, the grain direction). In the continuous production process of the paper sheet 1, these fibers are oriented in the orientation direction, because the flow velocity of a composition that is the raw material of the paper sheet 1 when the composition is fed to a mesh of wire 21 of the paper machine 10 is less than the feed speed of the wire mesh 21 (see Figure 2). Consequently, the fibers of the composition are deposited so that they are oriented more in the direction of flow than in the other directions. That is, the flow direction coincides with the direction in which the composition is fed to the next process. As a result of cellulose acetate staple fibers and pulp fibers being deposited so that they are oriented more in the flow direction, the strength and elongation of the paper sheet 1 in the flow direction differ from those of sheet of paper 1 in the orthogonal direction.

Generally speaking, the tensile strength of the paper sheet is higher in the flow direction. Therefore, the direction of flow of the sheet of paper 1 and the direction orthogonal to it can be confirmed by observing the difference in tensile strength in the sheet of paper 1 between two different directions, or by observing the orientation of the fibers in sheet of paper 1 with a microscope.

The paper sheet 1 is formed in the form of a tape and its longitudinal direction is the flow direction. As a result of the plurality of creped parts 1a that are formed in the paper sheet 1, elasticity is imparted to the paper sheet 1 so that the paper sheet 1 can be stretched in the flow direction, and also, the elasticity is increased. surface area of the paper sheet 1 per unit length in the flow direction.

It should be noted that the "orthogonal direction that is orthogonal to the flow direction" herein is not limited to the direction that is exactly orthogonal to the flow direction, but includes, for example, directions each of which deviates of the direction exactly orthogonal in an angular value within the interval of 10 °.

The creping ratio R of the paper sheet 1 is set to a value within the range of not less than 5% and not more than 35%. The creping ratio R is represented by the mathematical formula 1 shown below.

[Mathematical formula 1]

R = (V1-V2) / V1 x 100

In mathematical formula 1, V1 is the peripheral speed of a heating roller 26 of the paper machine 10 when the sheet of paper 1 is produced, and V2 is the peripheral speed of a winding reel 28 of the paper machine 10 when the sheet of paper 1 is produced (see Figure 2).

The elongation at break of the paper sheet 1 in the flow direction is set to a value within the range of not less than 10% and not more than 70%. The tensile strength (N / 25 mm width) of the sheet of paper 1 can be set to, for example, a value within the range of not less than 1.0 N / 25 mm width and not more than 80 N / 25mm width, and preferably a value within the range of not less than 1.5N / 25mm width and not more than 40N / 25mm width. In the present embodiment, the tensile strength of the paper sheet 1 in the flow direction is set to a value within the range of not less than 1.5 N / 25 mm in width and less than 40 N / 25 mm. wide. The tensile strength of paper sheet 1 can be measured, for example, according to the method of JIS P8113.

As described above, the plurality of creped parts 1a, which are arranged in the flow direction and extend in the orthogonal direction, which is orthogonal to the flow direction, are formed on the paper sheet 1. Accordingly, When producing processed products using sheet of paper 1 while feeding sheet of paper 1 in the direction of flow, if tension is exerted on sheet of paper 1 in the direction of flow, sheet of paper 1 is stretched in the direction flow. This makes it possible to prevent damage to the sheet of paper 1 and to prevent the processability of the sheet of paper 1 from being reduced.

Since the damage to the paper sheet 1 due to the stress exerted on the paper sheet 1 in the flow direction is prevented, the feeding speed of the paper sheet in a processing machine can be increased to improve the production efficiency of the processed products, and therefore the secondary processability of the paper sheet can be improved 1.

Specifically, since the sheet of paper 1 is less likely to break, the sheet of paper 1 can be subjected, for example, to three-dimensional processing using a mold, and thus the sheet of paper 1 can be processed to have a fine three-dimensional structure. Accordingly, for example, a mask having a three-dimensional structure can be favorably produced by using the paper sheet 1.

The paper sheet 1 is tape-shaped, so that its longitudinal direction is the flow direction. Accordingly, when the sheet of paper 1 that has been wound into a roll is taken out from the roll and fed to be continuously subjected to processing by a processing machine, even if tension is exerted on the sheet of paper 1 in the longitudinal direction (feed direction), sheet of paper 1 is less likely to be damaged, further improving the production efficiency of processed products.

The creping ratio R of the paper sheet 1 is set to a value within the range of not less than 5% and not more than 35%. Accordingly, when tension is exerted on the paper sheet 1 in the flow direction, the paper sheet 1 is stretched in the flow direction, and therefore damage to the paper sheet 1 can be suitably avoided.

The elongation at break of the paper sheet 1 in the flow direction is set to a value within the range of not less than 10% and not more than 70%. Accordingly, when tension is exerted on the paper sheet 1 in the flow direction, damage to the paper sheet 1 can be favorably prevented.

The tensile strength of the paper sheet 1 in the flow direction is set to a value within the range of not less than 1.5 N / 25 mm in width and less than 40 N / 25 mm in width. Accordingly, by winding the paper sheet 1 in the flow direction, the paper sheet 1 can be prevented from breaking due to the stress exerted on the paper sheet 1 in the flow direction, and also, the processability of sheet of paper 1 can be properly held.

The binder is an alkaline salt of a polysaccharide that contains a carboxyl group. This makes it possible to produce a processed product having a high disintegrability in water using the paper sheet 1.

An example of the processed product produced using paper sheet 1 is a make-up remover sheet (non-woven fabric). Due to the plurality of creped parts 1a, the make-up removal sheet has a larger surface area and therefore exerts a better make-up removal effect than make-up removal sheets having a flat surface.

The cellulose ester staple fibers used in the makeup remover sheet have a higher lipophilicity than, for example, rayon fibers which are an existing fiber material. Therefore, even if the make-up agents contain oily components, a high make-up removal effect can be obtained with the make-up removal sheet. Due to the plurality of creped parts 1a, the makeup remover sheet also has improved softness. Therefore, the makeup remover sheet is easily deformed on contact with the skin, thus obtaining a favorable texture and low skin irritation, and therefore an excellent wearing feeling can be expected.

Another example of the processed product produced using the paper sheet 1 is a cleaning sheet (non-woven fabric). Due to the plurality of creped parts 1a, the cleaning sheet has a larger surface area and the volume of the cleaning sheet is not easily lost. Therefore, the cleaning sheet is capable of absorbing dirt and foreign matter present on an object to be cleaned, which makes it possible to easily clean them from the object to be cleaned. On the other hand, the cleaning sheet is not easily broken since the cleaning sheet is very elastic, and furthermore, the cleaning sheet is capable of following the shape of the surface of the object to be cleaned. Therefore, the cleaning work can be done efficiently with the cleaning sheet.

If the paper sheet 1 having disintegrability in water is produced using, as a binder, an alkaline salt of a polysaccharide containing a carboxyl group, then the processed product produced using the paper sheet 1, such as a cleaning sheet, is May disintegrate in water for disposal after use.

Cellulose esters are natural compounds that contain cellulose, as a base material, which is the same cellulose as pulp. Accordingly, it is known that when said cellulose ester is dispersed in water, the cellulose ester is decomposed by microorganisms with a relatively long period of time. Therefore, the cleaning sheet produced using the paper sheet 1 is degradable in a natural environment.

Yet another example of the processed product produced using paper sheet 1 is a cigarette filter. By way of example, the cigarette filter is manufactured as follows: shaping the paper sheet 1 into a columnar shape; wrap the rolling paper around the outside of the 1 columnar sheet of paper; and cut to a predetermined length. In this case, the paper sheet 1 is used as the filter material of the cigarette filter.

Since the plurality of creped parts 1a are formed on the paper sheet 1, the paper sheet 1 has a large surface area. Accordingly, by using the paper sheet 1 as the filter material of the cigarette filter, many fine spaces can be formed uniformly within the cigarette filter. As a result of the uniform formation of the fine spaces, a columnar cigarette filter having a beautiful cross section without irregularities can be produced. Therefore, using the paper sheet 1, a cigarette filter with lower pressure drop (Pressure Drop, PD) can be obtained, which is easy to smoke and capable of efficiently capturing smoke particles, with stable quality.

Therefore, for example, even in the case of producing the cigarette filter of a cigarette having a smaller diameter than normal cigarettes, such as a "thin", "super-thin" or "micro-thin" cigarette, the cigarette filter It can be favorably produced while suppressing the increase in pressure drop and adjusting the package weight of the paper sheet 1.

As a further example, the sheet of paper 1 with the plurality of creped parts 1a formed therein can be further subjected to three-dimensional processing to form, for example, raised and recessed parts in the sheet of paper 1, so that the parts raised and lowered extend in a direction crossing the plurality of crepe portions 1a. In this way, the pressure drop of the cigarette filter can be adjusted more precisely.

Conventionally, pulp fibers and cellulose acetate fibers, which is a typical cellulose ester, have been used as cigarette filter materials. Therefore, the paper sheet 1 is very acceptable to consumers as a cigarette filter material. The cigarette filter produced using paper sheet 1 is capable of making phenols and the like which are harmful compounds contained in smoke components to be efficiently adsorbed by cellulose acetate fibers, and also, capable of making the water is efficiently adsorbed by the pulp fibers.

On the other hand, by producing the water disintegrable paper sheet 1 using a water soluble binder and then producing a cigarette filter using the paper sheet 1, the cigarette filter can be disintegrated in water in a natural environment for disposal after to smoke.

Other examples of the processed product produced using the paper sheet 1 include sanitary products such as a disposable diaper, a napkin, and a sanitary mask. In the case that the paper sheet 1 is used in any of these sanitary products, since the paper sheet 1 has high air permeability, when the user uses the sanitary product, the uncomfortable congestion and stickiness is reduced, which results in an excellent wearing feeling. Therefore, the paper sheet 1 is also suitable as a material of such a medical device.

[Paper machine]

Figure 2 is a schematic diagram of the paper machine 10 in accordance with the embodiment. By way of example, paper machine 10 is a Fourdrinier paper machine. The paper machine 10 includes a composition preparation part 11, a wire part 12, a press part 13, a drying part 14, and the winding reel 28. Each of the composition preparation part 11, the wire part 12, the press part 13 and the drying part 14 have a known configuration. It should be noted that the terms "before" and "after" in the following description mean "before something else" and "after something else" on the paper machine 10 in the feeding direction of a composition, a sheet body 30 and a sheet of paper 1.

The composition preparation part 11 is arranged, in the paper machine 10, in a position before the wire part 12, the press part 13, the drying part 14 and the winding reel 28. The winding part Composition preparation 11 prepares a liquid composition (suspension) which is the raw material of the paper sheet 1. The composition preparation part 11 includes a reservoir 20, which stores the composition.

The wire part 12 is arranged in a position posterior to the preparation part of the composition 11. The wire part 12 spreads the composition fed from the reservoir 20 in a sheet form to dehydrate the composition, and feeds the composition in the form resulting sheet in the feed direction.

The wire portion 12 includes the wire mesh 21 and a plurality of feed rollers 22. The wire mesh 21 is configured to form a wire net made of a plurality of wires in an endless belt. The plurality of feed rollers 22 rotate the wire mesh 21. In the paper machine 10, for example, at least one of the fiber concentration in the composition fed from the reservoir 20 to the wire portion 12 is adjusted, the feeding speed of the composition fed from the tank 20 to the wire part 12, and the feeding speed of the composition fed by the wire mesh 21, and therefore the grammage of the paper sheet 1 is adjusted In the description hereinafter, the composition that has been fed from the reservoir 20 to the wire portion 12 is referred to as the sheet body 30.

The press part 13 is arranged in a position posterior to the wire part 12. The press part 13 further dewaters the sheet body 30 that has passed through the wire part 12 while feeding the sheet body 30 in the feeding direction. The press part 13 includes: a plurality of felt bodies 23; a plurality of feed rollers 24; and at least one pressure roller 25. Each of the felt bodies 23 is configured to form a tape-like felt material into an endless belt. The plurality of feed rollers 24 rotate the felt bodies 23. The pressure roller 25 is pivotally supported in a position where the pressure roller 25 is oriented toward the peripheral surfaces of the feed rollers 24 through the felt bodies 23.

The drying part 14 is arranged in a position posterior to the press part 13. The drying part 14 dries the sheet body 30 that has passed through the press part 13 while feeding the sheet body 30 into feeding direction. Drying portion 14 includes at least one heating roller (such as a Yankee dryer) 26. Heating roller 26 rotates at peripheral speed V1.

The winding spool 28 is arranged at a position posterior to the drying part 14. The winding spool 28 is wound on the paper sheet 1 into a roll when the paper sheet 1 is obtained by separating it from the peripheral surface of the winding roller. heating 26. Heating roller 26 rotates at peripheral speed V2. It should be noted that the paper machine 10, of course, is not limited to a Fourdrinier paper machine, but may be a different type of machine. For example, the paper machine 10 can be a cylindrical paper machine.

[Production method of a sheet of paper]

Figure 3 is a production process diagram showing the processes for producing the paper sheet 1 according to the embodiment. As shown in Figure 3, in the paper sheet production method 1 according to the embodiment, a raw material preparation process S1, a wire process S2, a pressing process S3, a process of S4 drying, S5 creping process, S6 winding process and S7 cutting process are performed sequentially. Herein, processes S1 to S6 are performed sequentially using paper machine 10.

In the raw material preparation process S1, the cellulose ester staple fibers, pulp fibers and binder are uniformly dispersed in water, and thus the composition is prepared. The prepared composition is temporarily stored in tank 20.

It should be noted that the raw material preparation process S1 may include a whipping process to adjust the entanglement of the fibers. In the whipping process, for example, a known refiner is used to mechanically whip the fibers contained in the composition in the presence of water, thus grinding the fibers. As a result, the fibers are cut and broken into small pieces. Consequently, the fibers disintegrate and, furthermore, the fibers become highly hydrated and swollen, which results in more entanglement of the fibers after the paper is formed.

In the process of wire S2, the composition stored in the reservoir 20 is spread over the wire mesh 21 of the wire part 12, and thus the body of the sheet 30 is formed. Also, the plurality of feed rollers 22 are rotates to feed the blade body 30 in the feed direction together with the wire mesh 21. Some of the water in the blade body 30 penetrates through the gaps in the wire mesh 21 and thus , is removed from the blade body 30. In this way, the blade body 30 is dehydrated to some extent.

In the pressing process S3, the sheet body 30 that has passed through the wire portion 12 is placed on the felt bodies 23, and the plurality of feed rollers 24 rotate to feed the sheet body 30 in the feeding direction together with the felt bodies 23. Some of the water in the sheet body 30 is absorbed by the surface of the felt bodies 23. In this way, the sheet body 30 is further dehydrated. Then, the sheet body 30 is passed between the pressure roller 25 and the felt bodies 23 to press the sheet body 30 in the thickness direction, thereby further dewatering the sheet body 30 .

It should be appreciated that, in the pressing process S3, only one pair of felt bodies 23 can be used, or two or more pairs of felt bodies 23 arranged continuously in the feeding direction can be used. In the s 3 pressing process, a pressing machine can be used to press the body of the sheet 30, or a suction dewatering equipment to forcefully dehydrate the body of the sheet 30.

In the drying process S4, the sheet body 30 that has passed through the press part 13 is fed in the feeding direction while in contact with the peripheral surface of the heating roller 26. At that time, the Heat from the peripheral surface of the heating roller 26 is transferred to the body of the sheet 30, and therefore the body of the sheet 30 is heated and dried. In the S4 drying process, a heating device, such as a hot air hood, can be used in conjunction with the heating roller 26.

As shown in Figure 2, in the S5 creping process, for example, a doctor blade 27 is used to separate the body of the sheet 30 from the peripheral surface of the heating roller 26. As a result, a plurality of creped portions 1a , which are arranged in the flow direction and extend in the orthogonal direction, which is orthogonal to the flow direction, are formed in the sheet body 30 when the sheet body 30 passes through the drying part 14.

The longitudinal direction of the doctor blade 27 coincides with the axial direction of the heating roller 26. As a result, in the present embodiment, the plurality of creped portions 1a arranged in the flow direction and extending in the orthogonal direction are formed in the blade body 30.

In the creping process S5, by adjusting the peripheral speeds V1 and V2, the creping ratio R of the paper sheet 1 to be produced is set to, for example, a value within the range of not less than 5% and no more than 35%. Also, by setting the creping ratio R to such a value, the elongation at break of the paper sheet 1 to occur in the flow direction is set to a value within the range of not less than 10% and not more than 70%.

The tensile strength of the paper sheet 1 in the flow direction is set to a predetermined value by at least one of the following methods: a method for adjusting the mixing ratio of a plurality of fiber types in the process of raw material preparation S1; a method of adjusting the entanglement of the fibers by adjusting the degree of whipping; a method of adjusting the grammage (total amount of fiber) in the S2 wire process; and a method of adjusting the creping ratio R in the creping process S5. Herein, by way of example, the tensile strength of the paper sheet 1 in the flow direction is set to a value within the range of not less than 1.5 N / 25 mm in width and less than 40 N / 25 mm width.

Upon completion of the creping process S5, the sheet of paper 1 is obtained in the form of a ribbon whose longitudinal direction (feeding direction) is the flow direction. In the winding process S6, the sheet of paper 1 is wound into a roll by the winding reel 28. In the cutting process S7, the sheet of paper 1 previously wound on the roll is subjected to unwinding and slicing (cutting) to have a constant width, and then re-rolled. In this way, the paper sheet 1 is obtained as a roll-shaped product.

As described above, the production method of the paper sheet 1 according to the present embodiment includes: a sheet body forming process (sheet body forming step) to form the sheet body 30 containing the cellulose ester staple fibers, the pulp fibers and the binder; and the creping process (creping step) S5 of forming the plurality of creped parts 1a in the sheet body 30, so that the plurality of creped parts 1a are arranged in the flow direction and extend in the orthogonal direction , which is orthogonal to the flow direction. (In this example, the sheet body forming process includes the raw material preparation process S1, the wire process S2, the pressing process S3, and the drying process S4.)

In the process of forming the sheet body, the sheet body 30 is formed in the form of a tape, so that the longitudinal direction (feeding direction) of the sheet body 30 is the flow direction. In the paper sheet production method, the creping ratio R of the paper sheet 1 is set to a value within the range of not less than 5% and not more than 35%. Also, in the paper sheet production method, by adjusting the creping ratio R to the value, the tensile elongation of the paper sheet 1 in the flow direction is set to a value within the range of not less than 10%. and no more than 70%.

In the paper sheet production method, the tensile strength of the paper sheet 1 in the flow direction is set to a value within the range of not less than 1.5 N / 25 mm in width and less than 40 N / 25 mm in width by adjusting at least one of the mixing ratios of the cellulose ester staple fibers, the pulp fibers and the binder, the weight of the paper sheet 1, the degree of whipping of the cellulose ester staple fibers and the pulp fibers, and the crepe ratio of the paper sheet 1. In the method of In the production of paper sheets, an alkaline salt of a polysaccharide containing a carboxyl group is used as a binder.

It should be appreciated that, in the raw material preparation process S1, it is not essential that the binder is included in the components of the composition. That is, for example, depending on the property of the binder, the binder addition process can be carried out separately from the raw material preparation process S1. For example, in at least one of the S2 wire process, S3 pressing process, and S4 drying process, a liquid containing the binder can be sprayed or applied to the sheet body, or the sheet body can be immerse in the liquid containing the binder.

(Validation test)

[Testing method]

A paper sheet was produced using cellulose acetate staple fibers, kraft softwood pulp fibers, and sodium salt of carboxymethylcellulose (with a degree of esterification of 0.86; CMC1220 available from Daicel Corporation). The weight ratio of cellulose acetate staple fibers, softwood kraft pulp fibers and carboxymethylcellulose sodium salt was adjusted to 49.5: 49.5: 1.0.

In the creping process, creped parts were formed in each of a plurality of sheet bodies, and the creping ratio R was varied among the plurality of sheet bodies. In this way, sheets of paper of Comparative Examples 1, 2 and Examples 1 to 17 were produced, so that the weight value of each sheet of paper was adjusted to 21, 25, 35 and 40 g / m2.

An elongation at break in the flow direction (tensile elongation at break) (according to the method of JIS P8113), a tensile strength test in the flow direction (according to the method of JIS P8113), a test of disintegrability in water (according to the method of JIS P4501) and an air resistance test (permeability to air) (according to the method of JIS P8117) were carried out on each of the paper sheets of Comparative Examples 1, 2 and Examples 1 to 17.

In the elongation at break test and the tensile strength test, the width of a test piece of each sheet of paper (the width in the orthogonal direction, which is orthogonal to the flow direction) was set to 25 mm width ± 0.1 mm. Also, the maximum thickness dimension of each of the paper sheets of Comparative Examples 1, 2 and Examples 1 to 17 in a natural state (that is, a state in which no stress is applied to the paper sheet) It was measured with a thickness gauge (dial thickness gauge).

In addition, a kit including a pair of shaping rollers, a kit that simulates a cigarette filter production apparatus, was used to check the formability of each of the paper sheets of Comparative Examples 1, 2 and Examples 1 to 17 in the case of producing a cigarette filter using the paper sheet. Specifically, each of the pairs of shaping rollers used herein is provided with a plurality of raised and lowered parts formed on the peripheral surface thereof, such that the raised and lowered portions extend in the circumferential direction of each forming roll. The pair of shaping rollers was arranged such that the peripheral surfaces of the respective shaping rollers meshed with each other. Each sheet of paper was passed between the pair of forming rollers in the flow direction to subject the sheet of paper to three-dimensional processing, and at that time, it was checked whether or not cracks were formed in the sheet of paper. Also, each sheet of paper was fed at a feed rate of 100 / min, and it was checked whether the sheet of paper could be rewound without breaking.

A three-grade assessment was used to assess the formability of each sheet of paper. Specifically, in a case where no major cracks were formed on the surface of the paper sheet when the paper sheet was subjected to three-dimensional processing, and the paper sheet could be rewound without breaking frequently, the paper sheet was evaluated like". In a case where no major cracks were formed on the surface of the paper sheet when the paper sheet was subjected to three-dimensional processing, or the paper sheet could be rewound without breaking frequently, that is, in a case where If only one of these two conditions was met, the sheet of paper was evaluated as "B". In a case where major cracks were formed on the surface of the paper sheet when the paper sheet was subjected to three-dimensional processing, and the breakage of the paper sheet occurred frequently when the paper sheet was rewound, the sheet of paper was evaluated as "C". Table 1, Table 2 and Figures 4 to 7 show the results of the test.

Figure 4 is a graph showing a relationship between elongation at break and tensile strength of each of the paper sheets of Comparative Examples 1, 2 and Examples 1 to 17. Figure 5 is a graph that shows a relationship between the crepe ratio R and the tensile strength of each of the paper sheets of Comparative Examples 1, 2 and Examples 1 to 17. Figure 6 is a graph showing a relationship between the crepe ratio R and the elongation at break of each of the paper sheets of Comparative Examples 1, 2 and Examples 1 to 17. Figure 7 is a graph showing a relationship between the crepe ratio R and the air resistance of each of the paper sheets of Comparative Examples 1, 2 and Examples 1 to 17.

Test results

As shown in Table 1, Table 2 and Figure 4, it has been confirmed that the tensile strength and elongation at break of each of the paper sheets of Comparative Examples 1, 2 and Examples 1 to 17 are substantially inversely proportional to each other, and that the higher the crepe ratio R, the greater the elongation at break.

As shown in Figure 6, the higher the creping ratio R, the more the paper sheet tends to stretch in the flow direction and the elongation at break increases. Likewise, as shown in Figure 5, the tensile strength decreases as the crepe ratio R increases. The decrease in tensile strength is due to the fact that the grammage (amount of fiber) of the body of the sheet is small. in processes S2 to S4, which are the processes carried out before the creped parts are formed in the body of the sheet, that is, because the grammage (amount of fiber) of the body of the extended sheet is small.

In the creping process S5, an external force corresponding to the creping ratio R is applied to the body of the sheet in the space between the heating roller and the doctor blade. The external force loosens the bond between the fibers of the body of the blade, which is another factor that causes the decrease in tensile strength. It has been confirmed from the test results that the lower the grammage of the sheet of paper (that is, the lower the amount of fiber in the sheet of paper), the greater the decrease in the tensile strength of the paper. paper sheet.

From the data shown in Table 1, Table 2 and Figure 4, the following is considered: within the ranges adopted in the tests, for example, establishing the crepe ratio R of the sheet of paper in a value within the range of not less than 5% and not more than 35% and forming the plurality of creped parts, which are arranged in the flow direction and extend in the orthogonal direction, which is orthogonal to the flow direction, on the sheet of paper, or by setting the tensile strength of the paper sheet to a value within the range of not less than 1.5 N / 25 mm width and less than 40 N / 25 mm width and forming the plurality of creped parts, which are arranged in the flow direction and extend in the orthogonal direction, which is orthogonal to the flow direction, on the surface of the paper sheet, the breaking strength and tensile strength of the sheet of paper can be balanced.

Each of the paper sheets of Examples 1 to 17 has been found to exhibit higher elongation at break and better formability than the paper sheets of Comparative Examples 1 and 2. The reason for this is considered to be that since the plurality of creped portions extending in the orthogonal direction, which is orthogonal to the flow direction, are formed on each of the paper sheets of Examples 1 to 17, when tension in the flow direction is exerted on each From these sheets of paper, the sheet of paper can be stretched in the direction of flow and is less likely to be damaged.

The following is also considered: since each of the paper sheets of Examples 1 to 17 was subjected to the S5 creping process, the plurality of creped portions suitable for three-dimensional processing were formed on each of these paper sheets; Accordingly, when each sheet of paper was subjected to three-dimensional processing by the pair of shaping rollers, the sheet of paper was stretched; and as a result, the paper sheet was favorably formed.

Significant cracks were formed in the paper sheet of Comparative Example 1 when the paper sheet was subjected to three-dimensional processing, and also, the breakage of the paper sheet occurred frequently when it was rewound. Therefore, the formability of the paper sheet of Comparative Example 1 was found to be low. When the paper sheet of Comparative Example 2 was rewound, there were no frequent breaks of the paper sheet. However, when the paper sheet of Comparative Example 2 was subjected to three-dimensional processing, significant cracks were formed in the paper sheet. Therefore, the formability of the paper sheet of Comparative Example 2 was found to be low.

In Example 7, the creping ratio R was 35%. In Example 8, the creping ratio R was 40%. Accordingly, each of Examples 7 and 8 exhibited a high and favorable elongation at break, but their formability was relatively low. Specifically, in each of Examples 7 and 8, no significant cracks were found in the paper sheet when subjected to three-dimensional processing. However, at the time of rewinding the paper sheet, when the rotation speed of the rewinding roller was increased, a slight breakage of the paper sheet occurred.

Since the grammage of each of the sheets of paper in Examples 7 and 8 was a relatively low value of 25 g / m2, when the creped portions of each of these sheets of paper were stretched, the grammage of the sheet of paper, that is, the amount of fiber per unit area, was low, and the entanglement of the fibers with each other was low. These factors are presumed to have caused the sheet of paper to tear slightly. It is also considered that, in the case of setting the creping ratio R to a value higher than 35%, it is desirable to set the paper sheet weight to more than 25 g / m2.

It has also been found in Table 1, Table 2 and Figure 7 that, in the case of each of the sheets of paper In Examples 1 to 17, the higher the crepe ratio R, the lower the air resistance. The reason for this is considered that in the case of each of the paper sheets of Examples 1 to 17, the higher the crepe ratio R, the more the fibers are dispersed in the direction of the thickness of the paper sheet to reduce density, allowing gas to pass through the inside of the paper sheet more easily.

Accordingly, in the case of producing a filter product, such as a cigarette filter, using the paper sheet 1 of the embodiment, it is considered that, for example, by suitably increasing the crepe ratio R, the pressure drop can be reduce while maintaining adequate processability in the filter product. It is considered from the results shown in Figure 4 that, for example, by setting the creping ratio R of the sheet of paper to a value within the range of not less than 5% and not more than 35%, a cigarette filter which has excellent appearance properties, that is, it does not dent or bend easily, and which has adequate pressure drop. In Examples 1 to 17, by setting the crepe ratio R to such a value, the tensile elongation of the paper sheet in the flow direction is set to a value within the range of not less than 10% and not more than 70 %.

Through other tests carried out by the inventors of the present invention, it has been confirmed that, in the case of producing a cigarette filter using a sheet of paper whose grammage is 25 g / m2 or 35 g / m2, establishing the proportion creping R to not less than 5%, the formation of cracks in the paper sheet can be suppressed at the time of forming the paper sheet into a columnar shape, and the internal structure of the cigarette filter can be made uniform more easily and consequently, it has been found that the filtering performance of the cigarette filter can be stabilized more easily while obtaining a beautiful circular cross-section of the cigarette filter.

It has been confirmed that, in the case of the paper sheets of Examples 1 to 17, the higher the creping ratio R, the larger the thickness dimension of the paper sheet. The reason for this is that the higher the crepe ratio R, the more creped parts are formed on the sheet of paper, making the sheet of paper more voluminous.

Accordingly, it is considered that when a make-up removing non-woven fabric or a cleaning sheet is produced using the paper sheet 1 of the embodiment, by appropriately increasing the creping ratio R, the processed product can be made bulky and the effect can be increased. makeup removal or cleaning effect of the processed product.

It has been found that, in the case of using a sheet of paper whose grammage is not less than 21 g / m2 as a roll product, by setting the tensile strength of the paper sheet to be greater than 1, 5N / 25mm width, the paper sheet can be fed stably in the rewinding process even at a speed of 100m / min or higher.

Herein, if the crepe ratio R is too low, it is less likely that sufficient stretchability will be imparted to the paper sheet. On the other hand, if the creping ratio R is too high, there is a risk that the body of the sheet or the paper sheet will loosen while feeding due to excessive stretching (that is, the tension exerted on the body of the sheet or sheet of paper to feed the body of the sheet or sheet of paper cannot be held long enough) and that the resistance is reduced, causing a difficulty in stably producing the sheet of paper or the processed product.

Therefore, it is desirable to adjust the creping ratio R of the paper sheet taking into account, for example, the type of processed product that will be produced using the paper sheet, the processing conditions of the paper sheet and the tension. in the feeding direction exerted on the body of the sheet or the sheet of paper fed into the paper machine or processing machine.

Industrial applicability

As described above, each aspect of the present invention has an excellent advantageous effect of power, in the case of producing processed products using a paper sheet containing cellulose ester staple fibers, prevent damage to the paper sheet and improve the production efficiency of the processed products. Therefore, the present invention is useful when widely applied as a paper sheet and paper sheet production method, which allow to significantly exert the above advantageous effect.

Reference symbols list

1 sheet of paper

1st part crepe

30 blade body

Claims (13)

1. A sheet of paper comprising: cellulose ester staple fibers; pulp fibers; and a binder, where a plurality of creped parts is formed on the paper sheet, so that the creped parts are arranged in a flow direction of the cellulose ester staple fibers and pulp fibers and extend in an orthogonal direction, which is orthogonal to the direction of flow. 2. The sheet of paper according to claim 1, wherein the paper sheet is tape-shaped, so that a longitudinal direction of the paper sheet is the flow direction. 3. The sheet of paper according to claim 1 or 2, wherein a creping ratio of the paper sheet is set to a value within a range of not less than 5% and not more than 35%. 4. The sheet of paper according to any one of claims 1 to 3, wherein an elongation at break of the paper sheet in the flow direction is set to a value within a range of not less than 10% and not more than 70%. 5. The sheet of paper according to any one of claims 1 to 4, wherein a tensile strength of the paper sheet in the flow direction is set to a value within a range of not less than 1.5 N / 25 mm in width and less than 40 N / 25 mm in width. The sheet of paper according to any one of claims 1 to 5, wherein the binder is an alkaline salt of a polysaccharide containing a carboxyl group. The paper sheet according to any one of claims 1 to 6, wherein the paper sheet is a filter material of a cigarette filter. 8. A method of producing a sheet of paper, comprising: a sheet body forming step to form a sheet body containing cellulose ester staple fibers, pulp fibers, and a binder; and a creping step to form a plurality of creped parts in the body of the sheet, so that the creped parts are arranged in a flow direction of the cellulose ester staple fibers and pulp fibers and extend in one direction orthogonal, which is orthogonal to the direction of flow. 9. The method of producing a sheet of paper according to claim 8, wherein the step of forming the sheet body includes forming the sheet body in the form of a tape so that a longitudinal direction of the sheet body is the flow direction. 10. The method of producing a sheet of paper according to claim 8 or 9, wherein a creping ratio of the paper sheet is set to a value within a range of not less than 5% and not more than 35%. 11. The method of producing a sheet of paper according to claim 10, wherein By adjusting the creping ratio to that value, a tensile elongation of the paper sheet in the flow direction is set to a value within a range of not less than 10% and not more than 70%. 12. The method of producing a sheet of paper according to any one of claims 8 to 11, wherein the tensile strength of the paper sheet in the flow direction is set to a value within a range of not less than 1.5 N / 25 mm in width and less than 40 N / 25 mm in width by adjusting at least one of the mixing ratios of the cellulose ester staple fibers, the pulp fibers and the binder, a paper sheet grammage, one degree of whipping of the cellulose ester staple fibers and the pulp fibers, and a crepe ratio of the paper sheet. 13. The method of producing a sheet of paper according to any one of claims 8 to 12, wherein an alkali salt of a polysaccharide containing a carboxyl group is used as the binder.