JP2021159155A - Sanitary tissue paper - Google Patents

Abstract

To provide sanitary tissue paper having a nice texture and capable of securing necessary wet burst strength when being wet.SOLUTION: Sanitary tissue paper has a multi-ply configuration formed by superposing 3 or more tissue paper sheets, where at least one of outer-layer tissue paper sheets 301 forming both outer layers in the multi-ply configuration has a relatively small wet burst strength compared with at least one of inner-layer tissue paper sheets 302 forming inner layers clamped between both outer layers in the multi-ply configuration.SELECTED DRAWING: Figure 1

Description

The present invention relates to sanitary thin paper, and more particularly to sanitary thin paper having a multi-ply configuration of 3 or more plies in which a plurality of 3 or more thin papers are superposed.

Hygienic tissue paper such as toilet paper and tissue paper is required to have a good texture because it comes into direct contact with the skin. On the other hand, since these sanitary tissue papers are moistened when the nose is blown or the runny nose is wiped, it is necessary to secure sufficient wet burst strength so as not to be inadvertently torn when moistened.

JP-A-2017-202155

However, in general, when an attempt is made to increase the wet burst strength, there is a problem that the flexibility is impaired due to an increase in the wet paper strength agent for that purpose and the texture is deteriorated.

On the other hand, in Patent Document 1, for example, the toilet paper has a multi-ply structure of 2 plies or more in which two or more sheets of thin paper are laminated, and the wet burst strength of the multi-ply structure as a whole and the multi-ply structure. Focusing on the hand feel value (HF value) of the thin paper that forms both outer layers in the above, we are trying to achieve both toughness and soft texture in a wet state.

An object of the present invention is to provide a sanitary tissue paper having a structure different from that of Patent Document 1, which has a good texture and can secure the necessary wet burst strength at the time of wetting.

As a result of diligent studies, the present inventor has obtained at least one of the outer layer thin papers forming both outer layers in the multi-ply structure in the sanitary thin paper having a multi-ply structure in which three or more thin papers are superposed. It has been found that the above-mentioned problems can be solved by having a relatively small wet burst strength as compared with at least one of the inner layer tissue papers forming the inner layer sandwiched between the outer layers.

Specifically, the present invention has the following configuration.

[1] A sanitary thin paper having a multi-ply structure in which three or more thin papers are superposed.
At least one of the outer layer tissue papers forming both outer layers in the multi-ply configuration has a relatively small wet burst strength as compared to at least one of the inner layer tissue papers forming the inner layer sandwiched between the two outer layers in the multi-ply configuration. Sanitary tissue paper.

[2] The sanitary tissue paper according to [1], wherein both of the outer layer tissue papers have a relatively small wet burst strength as compared with at least one of the inner layer tissue papers.

[3] The outer layer thin paper and the inner layer thin paper have a ratio Tm / Tc of 1.30 or more when the wet tensile strength in the length direction of the thin paper is Tm and the wet tensile strength in the width direction is Tc, respectively. .. The sanitary tissue paper according to [1] or [2], which is 70 or less.

[4] Compared with the inner layer thin paper, the outer layer thin paper has a relative Tm / Tc value when the wet tensile strength in the length direction of the thin paper is Tm and the wet tensile strength in the width direction is Tc. The sanitary tissue paper according to any one of [1] to [3], which is characterized by being small in size.

According to the present invention, there is provided a sanitary thin paper having a multi-ply configuration of 3 plies or more in which a plurality of thin papers of 3 or more are superposed, which has a good texture and can secure the wet burst strength required when wet. can do. The present invention can be preferably applied to sanitary tissue paper such as toilet paper, paper towel rolls, kitchen paper, tissue paper and dust paper.

It is a schematic diagram for demonstrating the structure of the sanitary tissue paper which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments and drawings are for illustrative purposes only and are not intended to limit the invention.

(First Embodiment)
(Hygiene tissue paper)
FIG. 1 is a schematic view for explaining the configuration of sanitary tissue paper according to the embodiment of the present invention. The sanitary thin paper according to the present embodiment is a sanitary thin paper having a multi-ply configuration of 3 plies or more in which a plurality of 3 or more thin papers are superposed. FIG. 1A shows an example of a sanitary tissue paper having a three-ply structure in which three sheets of tissue paper according to the embodiment of the present invention are stacked. FIG. 1B shows an example of a sanitary tissue paper having a 4-ply structure in which four sheets of tissue paper according to the embodiment of the present invention are stacked. FIG. 1C shows an example of a sanitary tissue paper having a 5-ply structure in which five sheets of tissue paper according to the embodiment of the present invention are stacked. The embodiment of the present invention is not limited to the illustrated example, and the number of thin paper sheets to be stacked may be three, four, five, or more.

The sanitary thin paper 300 shown in FIG. 1A has a three-ply multi-ply configuration in which three thin papers 301a, 302, and 301b are stacked in this order. The thin paper 301a and the thin paper 301b are outer layer thin paper 301 forming an outer layer in this multiply configuration, respectively. Further, the thin paper 302 is an inner thin paper 302 that forms an inner layer sandwiched between both outer layers in this multi-ply configuration.

Focusing on the wet burst strength of each thin paper, the wet burst strength of both outer layers of thin paper 301 (thin paper 301a and thin paper 301b) may be the same or different. When comparing the outer layer thin paper 301 (thin paper 301a and thin paper 301b) and the inner layer thin paper 302, at least one of the outer layer thin paper 301 (thin paper 301a and thin paper 301b) has a wet burst strength smaller than that of the inner layer thin paper 302. Have.

Next, the sanitary thin paper 400 shown in FIG. 1B has a 4-ply multi-ply configuration in which four thin papers 401a, 402a, 402b, and 401b are superposed in this order. The thin paper 401a and the thin paper 401b are outer layer thin paper 401 forming an outer layer in this multiply configuration, respectively. Further, the thin paper 402a and the thin paper 402b are inner layer thin paper 402s that form an inner layer sandwiched between the outer layers in this multiply configuration, respectively.

Focusing on the wet burst strength of each thin paper, the wet burst strengths of both outer layer thin paper 401 (thin paper 401a and thin paper 401b) may be the same or different. Further, the wet burst strengths of both inner layers of thin paper 402 (thin paper 402a and thin paper 402b) may be the same or different.

When comparing the outer layer thin paper 401 (thin paper 401a and thin paper 401b) and the inner layer thin paper 402 (thin paper 402a and thin paper 402b), at least one of the outer layer thin paper 401 (thin paper 401a and thin paper 401b) is the inner layer thin paper 402. It has a wet burst strength smaller than at least one of (tissue paper 402a and tissue paper 402b). Preferably, at least one of the outer layer thin paper 401 (thin paper 401a and thin paper 401b) has a lower wet burst strength than both of the inner layer thin paper 402 (thin paper 402a and thin paper 402b).

Next, referring to FIG. 1 (c), the sanitary thin paper 500 according to the present embodiment has a 5-ply multi-ply configuration in which five thin papers 501a, 502a, 502b, 502c, and 501b are superposed in this order. .. The thin paper 501a and the thin paper 501b are outer layer thin paper 501 forming an outer layer in this multiply configuration, respectively. Further, the thin paper 502a, the thin paper 502b, and the thin paper 502c are inner layer thin paper 502 forming an inner layer sandwiched between the two outer layers in this multiply configuration, respectively.

Focusing on the wet burst strength of each thin paper, the wet burst strengths of both outer layer thin paper 501 (thin paper 501a and thin paper 501b) may be the same or different. Further, the wet burst strengths of the three inner layers of thin paper 502 (thin paper 502a, thin paper 502b and thin paper 502c) may be the same or different.

When comparing the outer layer thin paper 501 (thin paper 501a and thin paper 501b) and the inner layer thin paper 502 (thin paper 502a, thin paper 502b and thin paper 502c), at least one of the outer layer thin paper 501 (thin paper 501a and thin paper 501b) is It has a wet burst strength less than at least one of the inner layer tissue paper 502 (tissue paper 502a, tissue paper 502b and tissue paper 502c). Preferably, at least one of the outer layer thin paper 501 (thin paper 501a and thin paper 501b) has a wet burst strength less than any two of the inner layer thin paper 502 (thin paper 502a, thin paper 502b and thin paper 502c). More preferably, at least one of the outer layer thin paper 501 (thin paper 501a and thin paper 501b) has a lower wet burst strength than all of the inner layer thin paper 502 (thin paper 502a, thin paper 502b and thin paper 502c).

The same description as described above applies to a multi-ply configuration (not shown) of 6 plies or more in which a plurality of thin paper sheets of 6 or more are superposed.

That is, the sanitary thin paper according to the first embodiment of the present invention is a sanitary thin paper having a multi-ply configuration of 3 plies or more in which a plurality of 3 or more thin papers are superposed, and forms both outer layers in the multi-ply configuration. At least one of the outer layer tissue papers has a relatively small wet burst strength as compared with at least one of the inner layer tissue papers forming the inner layer sandwiched between the two outer layers in the multiply configuration. It is understood that the number of inner layer tissue papers forming the inner layer sandwiched between the two outer layers in the multi-ply configuration is one when the sanitary tissue paper has a three-ply configuration as shown in FIG. 1 (a). sea bream.

In other words, the sanitary thin paper according to the first embodiment of the present invention is a sanitary thin paper having a multi-ply configuration of 3 plies or more in which a plurality of 3 or more thin papers are superposed, and the sanitary thin paper has a multi-ply configuration. The inner layer thin paper forming the inner layer sandwiched between the two outer layers in the multiply configuration includes the thin paper having a relatively large wet burst strength as compared with at least one of the outer layer thin papers forming both outer layers.

<Wet burst strength>
The wet burst strength of tissue paper in this embodiment is measured as follows. A test piece obtained by stacking 10 sheets of thin paper cut into 5 x 5 cm is prepared, and the weight is measured. After immersing the test piece in pure water at 23 ° C., remove excess water with a filter paper (standard filter paper No. 26 of Toyo Filter Paper Co., Ltd.), and measure the weight again. After confirming that the water content of the test piece is 180% or more and 210% or less, the burst strength (kPa) is measured with a low-pressure burst tester (manufactured by Kumagai Riki Kogyo Co., Ltd., 2021-C). The average value of 6 measurements is calculated and used as the wet burst strength of thin paper (per 10 sheets). The wet burst strength is measured in an environment compliant with ISO187 (temperature 23 ° C. ± 1 ° C., relative humidity 50% ± 2%). The water content of the sample is a value calculated by the following formula (I).
Moisture content (%) = (difference in weight of test piece before and after immersion) x 100 / weight of test piece before immersion ... (I)

The wet burst strength of each layer of sanitary tissue paper (per 10 sheets) is preferably 3.0 to 25.0 kPa. If the wet burst strength is less than 3.0 kPa, tearing is likely to occur during wet use, such as when blowing the nose or wiping a runny nose. In addition, as the wet burst strength increases, the texture tends to deteriorate. The wet burst strength of the tissue paper forming the inner layer of the sanitary tissue paper is preferably 6.0 to 16.0 kPa, more preferably 8.0 to 12.0 kPa. The wet burst strength of the tissue paper forming the outer layer of the sanitary tissue paper is preferably 3.0 to 7.5 kPa, more preferably 3.0 to 6.0 kPa.

(Action effect)
According to the sanitary tissue paper according to the present embodiment, at least one of the outer layer tissue papers contained in the sanitary tissue paper has a relatively small wet burst strength as compared with at least one of the inner layer tissue papers. Therefore, by using the outer layer tissue paper having a relatively small wet burst strength as the side that comes into contact with the skin, a good texture can be obtained by the outer layer tissue paper. Moreover, the inner layer tissue paper having a relatively high wet burst strength can secure the wet burst strength required at the time of wetting.

(Tissue paper)
The thin paper, which is a component of the sanitary thin paper, is obtained by making a slurry containing a pulp component which is a fiber raw material. Since thin paper corresponds to a base paper for producing sanitary thin paper, the thin paper is also hereinafter referred to as "base paper" or "base paper sheet".

(Pulp component)
Examples of the pulp component include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include broadleaf pulp (blightwood kraft pulp (LKP)), coniferous pulp (coniferous kraft pulp (NKP)), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and unbleached craft. Examples thereof include chemical pulp such as pulp (UKP) and oxygen bleached kraft pulp (OKP). Further, semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), mechanical pulp such as crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP) can be mentioned, but are not particularly limited. Examples of the non-wood pulp include cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, and cellulose, chitin and chitosan isolated from sea squirts and seaweed, but are not particularly limited. .. Examples of the deinked pulp include deinked pulp made from used paper, but the deinking pulp is not particularly limited. As the pulp component, one of the above may be used alone, or two or more of them may be mixed and used. Since these pulp components greatly affect the quality of sanitary tissue paper, they are appropriately blended in a predetermined type and blending ratio according to the required quality.

For example, as the pulp component, at least one selected from softwood pulp and hardwood pulp can be preferably used. Softwood pulp has long fibers and strength, and can impart strength to the thin paper to be made. In addition, hardwood pulp has short fibers, and the thin paper produced can provide uniformity and texture. In the embodiment of the present invention, it is preferable to use softwood pulp and hardwood pulp in combination, and it is more preferable to use softwood kraft pulp (NKP) and hardwood kraft pulp (LKP) in combination.

When softwood pulp and hardwood pulp are used in combination as a pulp component, the L / N ratio indicating the mixing ratio (mass ratio) of softwood pulp and hardwood pulp is preferably, for example, 10/90 to 90/10. It is more preferably 20/80 or more, further preferably 30/70 or more, further preferably 80/20 or less, and further preferably 70/30 or less.

(Arbitrary ingredient)
Various chemicals may be added to the base paper sheet as optional components for the required quality and stable operation. Examples of the optional component include a dry paper strength agent, a wet paper strength agent, a softener, a bulking agent, a dye, a fragrance, a dispersant, a drainage improver, a pitch control agent, a yield improver, a sizing agent, and the like. Can be done. Examples of the dry paper strength agent include cationized starch, polyacrylamide (PAM), carboxymethyl cellulose (CMC) and the like. Examples of the wet paper force agent include polyamide epichlorohydrin, urea, melamine, and heat-crosslinkable polyacrylamide. Examples of the softener include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric ionic surfactants. The above optional components may be used alone or in combination of two or more.

The wet paper strength agent is added to improve the paper strength in a wet state, for example, wet tensile strength and wet burst strength. When the base paper sheet contains a wet paper strength agent, the content of the wet paper strength agent is 0.001 part by mass or more and 0.20 part by mass with respect to 100 parts by mass of the fiber component contained in the base paper sheet. The following is preferable.

Softeners are added to improve softness. When the base paper sheet contains a softener, the content of the softener shall be 0.01 part by mass or more and 0.50 part by mass or less with respect to 100 parts by mass of the fiber component contained in the base paper sheet. Is preferable.

The dry paper strength agent is added to improve the paper strength in a dry state, for example, dry tensile strength and dry burst strength. When the base paper sheet contains a dry paper strength agent, the content of the dry paper strength agent is 0.01 part by mass or more and 1.00 parts by mass with respect to 100 parts by mass of the fiber component contained in the base paper sheet. The following is preferable.

(Basis weight)
The basis weight of the base paper sheet can be ^{, for example, 7 to 30 g / m 2} according to the required quality of the thin paper and the sanitary thin paper. For example, the basis weight of the base paper sheet ^{can be preferably 9 g / m 2} or more, and preferably 25 g / m ² or less. Basis weight is measured according to the provisions of Japanese Industrial Standard JIS P8124.

(Paper thickness)
The thickness of the base paper sheet can be, for example, 30 to 250 μm according to the required quality of the thin paper and the sanitary thin paper. For example, the paper thickness of the base paper sheet can be preferably 50 μm or more, and preferably 200 μm or less. Paper thickness is measured according to the provisions of Japanese Industrial Standard JIS P8118 (2014).

(Production method)
The sanitary tissue paper according to the embodiment of the present invention is roughly described.
(1) A base paper manufacturing process in which a base paper roll is produced by winding a base paper sheet while making a thin paper (base paper sheet) which is a component thereof.
(2) A base paper sheet is unwound from each of three or more base paper windings, and the plurality of base paper sheets are laminated on each other to form a multi-ply laminated body (laminated sheet), and the laminated sheet is used as a winding core. Ply processing process to manufacture winding for sanitary tissue paper by winding, and (3) Laminated sheet is unwound from winding for sanitary tissue paper, and slit processing, embossing, perforation processing, folding, winding as necessary. , A product finishing process that processes into sanitary tissue paper (product) in the form of a bundle of paper or a roll of a predetermined amount and size through processes such as cutting.
It can be manufactured through such a process.

Here, the base paper manufacturing process of the above (1) will be described in more detail. The base paper manufacturing process includes a papermaking process in which papermaking is performed using a slurry containing a pulp component which is a fiber raw material. Paper machines used in the paper making process include, for example, suction breast formers (circular mesh type, long mesh type), twin wire formers, circular mesh formers (C wrap, S wrap), crescent formers, and the like. Can be mentioned.

In the papermaking process, in the wire part of the paper machine, the slurry is sprayed onto the traveling net-like wire to form a thin layer of pulp. The pulp thin layer is then dehydrated as the water in the pulp thin layer is drained under the net while being transferred towards the press part. Such a process is sometimes called a dehydration process. Generally, the wire is a ring of metal or plastic mesh.

After the dehydration process, the wet paper moves from the wire to the felt. The wet paper is further mechanically squeezed by applying pressure with a press roll through the felt. This is sometimes called a pressing process or a water pressing process.

The papermaking process includes a drying process after the water extraction process. The drying step is preferably, for example, a step of blowing hot air toward the wet paper or a step of pressing the wet paper against the outer peripheral surface of the Yankee dryer. In the drying step using a Yankee dryer, it is preferable to perform a crepe treatment for forming wrinkles on the crepe by scraping the dried paper from the Yankee dryer with a doctor blade. By the crepe treatment, the base paper sheet (thin paper) can be given a softness and a thick feeling.

After the drying step, a base paper winding step is provided. In the base paper winding step, the base paper winding is obtained by winding the base paper sheet (thin paper) finished through the above steps.

The obtained base paper winding is then subjected to the ply processing steps and product finishing steps of the above (2) and (3) to obtain sanitary tissue paper.

(Second Embodiment)
A second embodiment of the present invention will be described again with reference to FIGS. 1 (a) to 1 (c). A second embodiment of the present invention is a preferred embodiment of the first embodiment. Unless otherwise stated, the configurations applicable to the first embodiment are applicable to the present embodiment.

With reference to FIG. 1 (a), in the three-ply multi-ply configuration according to the second embodiment, both the outer layer tissue paper 301 (thin tissue paper 301a and the tissue paper 301b) have a wet burst strength smaller than that of the inner layer tissue paper 302. ..

Further, referring to FIG. 1B, in the 4-ply multi-ply configuration according to the second embodiment, both the outer layer thin paper 401 (thin paper 401a and the thin paper 401b) are the inner layer thin paper 402 (thin paper 402a and the thin paper 402b). ) Has a wet burst strength less than at least one of them. Preferably, both the outer layer thin paper 401 (thin paper 401a and thin paper 401b) have a lower wet burst strength than both of the inner layer thin paper 402 (thin paper 402a and thin paper 402b).

Further, with reference to FIG. 1 (c), in the 5-ply multi-ply configuration according to the second embodiment, both of the outer layer thin paper 501 (thin paper 501a and thin paper 501b) are inner layer thin paper 502 (thin paper 502a, It has a wet burst strength less than at least one of tissue paper 502b and tissue paper 502c). Preferably, both of the outer layer thin paper 501 (thin paper 501a and thin paper 501b) have a wet burst strength less than any two of the inner layer thin paper 502 (thin paper 502a, thin paper 502b and thin paper 502c). More preferably, both of the outer layer thin paper 501 (thin paper 501a and thin paper 501b) have a lower wet burst strength than all of the inner layer thin paper 502 (thin paper 502a, thin paper 502b and thin paper 502c).

The same description as described above applies to a multi-ply configuration (not shown) of 6 plies or more in which a plurality of thin paper sheets of 6 or more are superposed.

That is, the sanitary thin paper according to the second embodiment of the present invention is a sanitary thin paper having a multi-ply configuration of 3 plies or more in which a plurality of 3 or more thin papers are superposed, and forms both outer layers in the multi-ply configuration. Both outer tissue papers have relatively low wet burst strength compared to at least one of the inner tissue papers forming the inner layer sandwiched between the two outer layers in a multiply configuration. It is understood that the number of inner layer tissue papers forming the inner layer sandwiched between the two outer layers in the multi-ply configuration is one when the sanitary tissue paper has a three-ply configuration as shown in FIG. 1 (a). sea bream.

In other words, the sanitary thin paper according to the second embodiment of the present invention is a sanitary thin paper having a multi-ply configuration of 3 plies or more in which a plurality of 3 or more thin papers are superposed, and the sanitary thin paper has a multi-ply configuration. The inner layer thin paper forming the inner layer sandwiched between the two outer layers in the multiply configuration includes the thin paper having a relatively large wet burst strength as compared with both the outer layer thin papers forming both outer layers.

(Action effect)
According to the sanitary tissue paper according to the second embodiment, both of the outer layer tissue papers contained in the sanitary tissue paper have a relatively small wet burst strength as compared with at least one of the inner layer tissue papers. Therefore, in addition to the effects of the invention similar to the first embodiment described above, even if either side of the front and back sides of the sanitary tissue paper is used as the texture side, a good texture can be easily obtained, and the usage mode. The effect of the invention is that the degree of freedom of the invention is improved.

(Third Embodiment)
Next, a third embodiment of the present invention will be described. Unless otherwise stated, configurations applicable to the above embodiments are applicable to this embodiment.

In the sanitary tissue paper according to the third embodiment of the present invention, in the configuration of the above-described embodiment, the outer layer tissue paper and the inner layer tissue paper are further wetted with Tm in the length direction and wet tensile strength in the width direction, respectively. When the tensile strength is Tc, the ratio Tm / Tc of the two is set to 1.30 or more and 2.70 or less.

(Length direction)
The length direction of the thin paper is the papermaking direction of the thin paper, and is generally also referred to as the MD direction.

(Width direction)
The width direction of the thin paper is a direction orthogonal to the papermaking direction of the thin paper, and is generally also referred to as a CD direction.

<Wet tensile strength>
The wet tensile strength of the thin paper in the present embodiment is such that six samples obtained by cutting the thin paper into a width of 15 mm and a span length of 100 mm are stacked, 0.1 ml of water is dropped on the center of the sample, and after 1 second, the tensile speed is 50 mm / min. It is a value obtained by measuring under the conditions and calculating the average of 6 measurements. For the measurement of wet tensile strength, for example, a horizontal tensile tester (manufactured by Kumagai Riki Kogyo Co., Ltd.) can be used. The wet tensile strength is measured in an environment compliant with ISO187 (temperature 23 ° C. ± 1 ° C., relative humidity 50% ± 2%).

When measuring the wet tensile strength in the length direction of the thin paper, the sample is cut so that the length direction of the thin paper is the span direction. Similarly, when measuring the wet tensile strength in the width direction of the tissue paper, the sample is cut so that the width direction of the tissue paper is in the span direction.

In general, even if the wet tensile strength in the length direction of the thin paper is large, the wet tensile strength in the width direction of the thin paper tends to be small, that is, when the aspect ratio of the wet tensile strength is large, the wet burst strength of the thin paper tends to be small. .. In order to obtain a larger wet burst strength, the ratio Tm / Tc of both when the wet tensile strength in the length direction of the thin paper is Tm and the wet tensile strength in the width direction is Tc is 1.0 as much as possible. It is desirable to bring it closer to. When the wet tensile strength Tm in the length direction of the thin paper is the same, the wet burst strength of the thin paper tends to increase as the ratio Tm / Tc approaches 1.0. Further, even when the wet tensile strength Tm in the length direction of the thin paper is relatively small, it is possible to obtain a wet burst strength of a desired size by bringing the ratio Tm / Tc close to 1.0. obtain.

Here, in general, the pulp fibers of thin paper tend to be oriented in the papermaking direction. Therefore, the wet tensile strength in the length direction of the tissue paper tends to be larger than the wet tensile strength in the width direction, and the ratio Tm / Tc is not exactly 1.0, but generally more than 1.0. It becomes a large value. In the present embodiment, the ratio Tm / Tc of the wet tensile strength Tm in the length direction and the wet tensile strength Tc in the width direction of the thin paper is set to a value as close to 1.0 as possible, and specifically. Is 1.30 or more and 2.70 or less.

(Achievement means)
The ratio Tm / Tc of the wet tensile strength Tm in the length direction of the thin paper and the wet tensile strength Tc in the width direction can be adjusted, for example, by adjusting the J / W ratio in the papermaking process of the thin paper.

(J / W ratio)
As described above, in the thin paper making process, in the wire part of the paper machine, the slurry is sprayed onto the traveling net-like wire to form a thin layer of pulp. When the supply speed of the slurry at this time is the jet speed (J) and the traveling speed of the wire is the wire speed (W), the speed ratio between the two is called the jet wire ratio (J / W ratio).

The J / W ratio is an index for controlling the fiber orientation in thin paper. If the jet speed (J) is slow and the wire speed (W) is fast, the J / W ratio will be less than 1. On the contrary, if the jet speed (J) is high and the wire speed (W) is slow, the J / W ratio becomes larger than 1. In any of these cases, fiber orientation is likely to occur in the MD direction in the formed tissue paper. When the J / W ratio is around 1, the fiber orientation in tissue paper is relatively isotropic.

Therefore, by assuming that the thin paper is manufactured under the condition that the J / W ratio is close to 1, the ratio Tm / Tc of the wet tensile strength Tm in the length direction and the wet tensile strength Tc in the width direction of the thin paper can be determined. It can be a value close to 1, specifically 1.30 or more and 2.70 or less. The J / W ratio can be controlled by adjusting one or both of the jet speed and the wire speed.

(Action effect)
According to the sanitary tissue paper according to the present embodiment, the ratio of the outer layer tissue paper and the inner layer tissue paper to Tm / when the wet tensile strength in the length direction is Tm and the wet tensile strength in the width direction is Tc, respectively. By setting the Tc to 1.30 or more and 2.70 or less, it is possible to effectively secure the wet burst strength required at the time of wetting in each of the inner layer thin paper and the outer layer thin paper.

Further, by setting the ratio Tm / Tc within this range, even if the wet tensile strength Tm in the length direction of the thin paper is reduced, the wet burst strength of a desired size can be obtained for the thin paper as a whole. Therefore, the content of the wetting paper strength agent can be suppressed in the inner layer thin paper and the outer layer thin paper. As a result, the flexibility of the inner layer tissue paper and the outer layer tissue paper can be improved, and as a result, the texture of the hygienic tissue paper can be improved.

Therefore, according to the present embodiment, it is possible to obtain a hygienic thin paper having a good texture while effectively ensuring the wet burst strength required at the time of wetting in the outer layer thin paper and the inner layer thin paper.

(Fourth Embodiment)
Next, a fourth embodiment of the present invention will be described. Unless otherwise stated, configurations applicable to the above embodiments are applicable to this embodiment.

In the sanitary thin paper according to the fourth embodiment of the present invention, in the configuration of the above-described embodiment, the outer layer thin paper is further compared with the inner layer thin paper, and the wet tensile strength in the length direction of the thin paper is Tm and the wet tensile strength in the width direction is Tm. The value of the ratio Tm / Tc between the two is set to be relatively small when the wet tensile strength of the above is Tc.

(Action effect)
In the sanitary tissue paper according to the present embodiment, the outer layer tissue paper has a wet tensile strength in the length direction of Tm and a wet tensile strength in the width direction of Tc as compared with the inner layer tissue paper. Tc is relatively small. Here, as described above, in general, the pulp fibers of thin paper tend to be oriented in the papermaking direction. Therefore, the wet tensile strength in the length direction of the tissue paper tends to be larger than the wet tensile strength in the width direction, and the ratio Tm / Tc is not exactly 1.0, but generally more than 1.0. It becomes a large value. That is, in the present embodiment, the outer layer tissue paper has a ratio Tm / Tc closer to 1.0 as compared with the inner layer tissue paper.

As described above, when the wet tensile strength Tm in the length direction of the thin paper is the same, the wet burst strength of the thin paper tends to increase as the ratio Tm / Tc approaches 1.0. Here, in the sanitary tissue paper according to the present embodiment, at least one of the outer layer thin papers forming both outer layers in the multi-ply configuration is compared with at least one of the inner layer thin papers forming the inner layer sandwiched between the two outer layers in the multi-ply configuration. Therefore, it has a relatively small wet burst strength. On the other hand, in order to obtain a wet burst strength of a desired size, that is, a wet burst strength relatively small as compared with at least one of the inner layer thin paper, the content of the wet paper strength agent in the outer layer thin paper is suppressed. be able to. As a result, the flexibility of the outer layer tissue paper can be improved, and as a result, the texture of the hygienic tissue paper can be improved.

Therefore, according to the present embodiment, the wet burst strength of the outer layer tissue paper can be more effectively secured than that of the inner layer tissue paper, and the texture of the sanitary tissue paper can be further improved.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

(evaluation)
The evaluation used in the examples followed the following evaluation method. The methods for measuring the basis weight, paper thickness, and wet burst strength are as described above.

(sensory evaluation)
For each of the two sides of the sanitary tissue paper, the feel of the sanitary tissue paper when it was applied to the skin was sensory-evaluated on a five-point scale, and the average value of the evaluations of 50 people was calculated. In Tables 1 and 2, each number in the item of sensory evaluation (texture) has the following meaning.
5: Good 4: Somewhat good 3: Normal 2: Somewhat bad 1: Bad

(Example 1 and Comparative Example 1)
Paper was made using a twin-wire Yankee machine using pulp slurries having the same composition, and a base paper to be used as thin paper for tissue paper was wound up. The three obtained base paper winders were placed on a ply machine, and the base paper (thin paper) unwound from the base paper winding was overlapped and wound up. Next, the three-ply structure thin paper laminate obtained by ply processing is wound again to a predetermined length, and the obtained winding is cut to a predetermined width to form a surface layer, a middle layer, and a back layer. A three-ply tissue paper (roll type) product containing thin paper to be used in this order was obtained. The basis weight and thickness of each tissue paper are as shown in Table 1.

(Example 2 and Comparative Example 2)
Using pulp slurries of the same composition, papermaking was performed using a twin wire Yankee machine to obtain a roll of base paper to be thin paper for toilet rolls. The four base paper rolls obtained were placed on a ply machine, and the base paper (thin paper) unwound from the base paper winding was overlapped and wound up. Next, the laminated thin paper having a 4-ply structure obtained by ply processing is wound again to a predetermined length, and the obtained winding is cut to a predetermined width to form the surface layer, the middle layer 1, the middle layer 2, and the like. A 4-ply toilet roll product containing the thin paper forming the back layer in this order was obtained. The basis weight and thickness of each tissue paper are as shown in Table 2.

Wet burst strength was measured for each of the Examples and Comparative Examples according to the measurement method described above. Specifically, in Example 1 and Comparative Example 1, the three thin paper sheets forming the surface layer, middle layer, and back layer of the 3-ply structure were carefully peeled off so as not to be pulled and stretched, respectively. 10 samples were obtained for each of the layers, and measurements were taken. This was repeated 6 times to calculate the average. Similarly, in Example 2 and Comparative Example 2, the four thin papers forming the front layer, the middle layer 1, the middle layer 2, and the back layer of the 4-ply structure were carefully peeled off so as not to be pulled and stretched. , 10 samples were obtained for each layer and measured, and this was repeated 6 times to calculate the average.

In addition, according to the above-mentioned evaluation method, the texture when the surface layer was applied to the skin and the texture when the back layer was applied to the skin were sensory evaluated for each of the examples and the comparative examples.

The measurement results and sensory evaluation results are shown in Tables 1 and 2.

With reference to Table 1, Example 1 and Comparative Example 1 are tissue papers having a three-ply structure in which three sheets of tissue paper are laminated.

In the tissue paper of Comparative Example 1, when comparing the thin paper forming the outer layer (surface layer and back layer) of the 3-ply structure and the thin paper forming the inner layer of the 3-ply structure, the surface layer has a higher wet burst strength than the inner layer. The back layer had the same wet burst strength as the inner layer. The maximum wet burst strength in the ply configuration was 8.0 kPa (per 10 sheets) of the surface layer. In the sensory evaluation test, the texture on the surface layer side was poor (evaluation 1), and the texture on the back layer side was slightly poor (evaluation 2).

On the other hand, in the tissue paper of Example 1, when the thin paper forming the outer layer (surface layer, back layer) of the 3-ply structure and the thin paper forming the inner layer of the 3-ply structure are compared, the surface layer and the back layer are compared. Both had lower wet burst strength than the inner layer. The maximum wet burst strength in the ply configuration was 9.5 kPa (per 10 sheets) in the middle layer. In the sensory evaluation test, the texture on the surface layer side was normal (evaluation 3), and the texture on the back layer side was poor (evaluation 1).

In Example 1, the texture on the surface layer side was normal (evaluation 3), and the texture was better than that of Comparative Example 1. Further, since the wet burst strength is 9.5 kPa (per 10 sheets) as one layer of the ply structure, the wet burst strength required at the time of wetting can be secured.

Next, referring to Table 2, Example 2 and Comparative Example 2 are toilet rolls having a 4-ply configuration in which four sheets of tissue paper are stacked.

In the toilet roll of Comparative Example 2, when the thin paper forming the outer layer (surface layer, back layer) of the 4-ply structure and the thin paper forming the inner layer (middle layer 1, middle layer 2) of the 4-ply structure were compared, the surface layer was compared. Was higher in wet burst strength than any of the inner layers (middle layer 1 and middle layer 2), and the back layer was also higher in wet burst strength than any of the inner layers (middle layer 1 and middle layer 2). The maximum wet burst strength in the ply configuration was 8.3 kPa (per 10 sheets) on the surface layer. In the sensory evaluation test, the texture on the surface layer side was poor (evaluation 1), and the texture on the back layer side was slightly poor (evaluation 2).

On the other hand, in the toilet roll of Example 2, the thin paper forming the outer layer (surface layer, back layer) of the 4-ply structure and the thin paper forming the inner layer (middle layer 1, middle layer 2) of the 4-ply structure were compared. At that time, the surface layer had a lower wet burst strength than any of the inner layers (middle layer 1 and middle layer 2). In addition, the back layer had a lower wet burst strength than one of the inner layers (middle layer 1 and 2) (middle layer 2) and a higher wet burst strength than the other one (middle layer 1). The maximum wet burst strength in the ply configuration was 8.2 kPa (per 10 sheets) in the middle layer 2. In the sensory evaluation test, the texture on the surface layer side was good (evaluation 5), and the texture on the back layer side was normal (evaluation 3).

In Example 2, the surface layer side had a good texture (evaluation 5), and the back layer side had a normal texture (evaluation 3), and both sides had a better texture than Comparative Example 2. .. Further, since the wet burst strength is 8.2 kPa (per 10 sheets) as one layer of the ply structure, the wet burst strength required at the time of wetting can be secured.

(Use of the invention)
Examples of sanitary tissue paper to which the embodiment of the present invention can be applied include tissue paper, dust paper, paper towel, kitchen paper, toilet paper and the like. The sanitary tissue paper according to the embodiment of the present invention is particularly preferably used for wet applications such as blowing the nose, wiping a runny nose, wiping or absorbing water from a wet object.

300, 400, 500 Sanitary tissue paper 301, 401, 501 Outer tissue paper 302, 402, 502 Inner tissue paper

Claims (4)

A sanitary tissue paper having a multi-ply structure in which three or more tissue papers are superposed.
At least one of the outer layer tissue papers forming both outer layers in the multi-ply configuration has a relatively small wet burst strength as compared with at least one of the inner layer tissue papers forming the inner layer sandwiched between the two outer layers in the multi-ply configuration. Sanitary tissue paper characterized by having. The sanitary tissue paper according to claim 1, wherein both of the outer layer tissue papers have a relatively small wet burst strength as compared with at least one of the inner layer tissue papers. The outer layer thin paper and the inner layer thin paper have a ratio Tm / Tc of 1.30 or more when the wet tensile strength in the length direction of the thin paper is Tm and the wet tensile strength in the width direction is Tc, respectively. The sanitary tissue paper according to claim 1 or 2, characterized in that it is 70 or less. Compared with the inner layer thin paper, the outer layer thin paper has a relative value of Tm / Tc as a ratio of both when the wet tensile strength in the length direction of the thin paper is Tm and the wet tensile strength in the width direction is Tc. The sanitary tissue paper according to any one of claims 1 to 3, which is characterized by being small in size.

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