RU2568218C2 - Napkin paper and methods of production of napkin paper - Google Patents

Abstract

FIELD: textiles, paper.

SUBSTANCE: invention relates to the pulp and paper industry and relates to napkin paper and a method of its production. The paper consists predominantly of a structure of two types of hydrophilic cellulosic fibres different in coarseness of fibres, and comprises a strength increasing additive. Two types of hydrophilic cellulosic fibres represent the first pulp, which has the fibre coarseness of from 0.13 to 0.16 mg/m, and the second pulp which has the fibre coarseness of from 0.17 to 0.20 mg/m. The difference in fibre coarseness between the first pulp and the second pulp is from 0.01 to 0.07 mg/m. The structure has a degree of fineness of 400 to 550 ml.

EFFECT: invention provides a napkin paper having good properties of strength and permeability.

18 cl, 8 dwg, 6 tbl, 4 ex

Description

FIELD OF TECHNOLOGY

[0001] The present invention relates, in its first and second objects, to tissue paper, in particular to tissue paper suitable as a wrapping sheet for a core wrapping an absorbent core of an absorbent article, such as a disposable diaper and a sanitary napkin. The invention also relates in its third aspect to a method for producing tissue paper with a low bulk. The invention also relates in its fourth aspect to an absorbent article, including a disposable diaper, absorbent pad and sanitary napkin.

BACKGROUND

[0002] Tissue paper is a thin paper with a relatively low bulk, which should have sufficient paper strength (eg, tensile strength) so as not to tear during use. To increase the strength of paper, the addition of a strength improver has become a practice in the art. For example, Patent Literature 1 discloses tissue paper for home hygiene that contains an additive that increases the strength of dry paper, and an additive that increases the strength of wet paper, and has a specific range of tensile strengths. The tissue paper for home hygiene described in Patent Literature 1 is intended for use requiring sensory properties such as softness and tactile properties, for example, for use as toilet paper, cosmetic wipes, and liner papers. The main method disclosed in Patent Literature 1 is aimed at achieving both sensory properties and paper strength.

[0003] A method is known in which hydrophilic cellulose fibers of two or more types that differ in the coarseness of the fiber to produce paper are used. "Fiber coarseness" is a measure used to represent the thickness of a fiber with an uneven thickness, such as wood pulp. For example, patent literature 2 discloses absorbent paper consisting primarily of two types of fibers differing in fiber coarseness (i.e. bulk cellulosic fibers and thin hydrophilic fibers), with thin hydrophilic fibers located on one side of the paper. According to patent literature 2, absorbent paper exhibits excellent absorbency; for this, it has a layer with high permeability and a layer with high diffusion of liquid in the thickness direction. In Patent Literature 2, as an example of the use of absorbent paper, an absorbent element is indicated consisting of two sheets of absorbent paper and an absorbent polymer disposed between them.

[0004] A low base tissue paper is used as a wrapping sheet for a core that wraps an absorbent core of an absorbent article, such as a disposable diaper or sanitary napkin. The tissue paper used as a wrapping sheet for the core must have a high permeability that allows fluid discharges of the body to smoothly move the absorbent core during use, and sufficient strength (e.g., tensile strength) so as not to tear during manufacture and use. Although the permeability can be effectively increased by reducing the bulk and density of tissue paper, this approach offers a reduction in the number of bonds between the fibers due to a decrease in the number of fibers constituting it, which leads to a decrease in paper strength.

[0005] Methods known for increasing paper strength (eg, tensile strength) of tissue paper with a low bulk include fibrillation of half mass and increasing the amount of additives that increase strength. With respect to the addition of a strength improver, methods from Patent Literatures 1 and 3 are known below in which a cationic polymer as a wet strength improver or an anionic polymer as a dry strength enhancer is added to the suspension half mass.

[0006] Known absorbent articles of the type described above include those having a liquid permeable top sheet, a liquid impermeable back sheet, and an elongated absorbent element located between these sheets, where the absorbent element consists of an absorbent core containing hydrophilic ( wettable by water) fibers and an absorbent polymer, and a wrapping sheet for a core that wraps the absorbent core. The wrapping sheet for the core serves as a sheet containing the absorbent core-forming material, such as an absorbent polymer, during the formation of the absorbent element, and as a sheet wrapping the absorbent core, giving it a specific shape. A water-permeable sheet, such as tissue paper and non-woven material, is standardly used as a wrapping sheet for a core.

[0007] Absorption and capacity of loose stool are of particular importance to specialists in the field of absorbent products. In particular, the problem is that loose stools tend to remain on the top sheet without being absorbed through the top sheet or after passing through the top sheet back through it without being retained in the absorbent element, which can cause a skin rash and make the skin wiping operation unpleasant. In order to improve the operational characteristics of smooth removal of loose stool from the skin and holding the loose stool in a place remote from the skin (absorption capacity for loose stool, etc.), various proposals have been made previously.

[0008] Below, patent literature 4 discloses an absorbent article having a high absorbency for liquid stool, which contains a liquid-permeable second sheet located between the top sheet and the absorbent element and in which the wrapping sheet for the core of the absorbent element contains a non-woven material having a density from 0.01 to 0.2 g / cm ^3, positioned between the second sheet and the absorbent core of the absorbent element, and crepe paper covering not facing the skin side of the absorbent cores .

[0009] Patent literature 5 discloses liquid permeable paper with a low spread of liquid for use in absorbent products, which are obtained by a wet paper production method in which the size (diameter) and pore size distribution of the tangled fibers are controlled in respective specific ranges . The liquid permeable paper with a low liquid spread according to Patent Literature 5 contains hydrophilic fibers as a constituent component and is sized to have a specific pore size distribution, thereby exhibiting low liquid spread properties and high liquid permeability. It is described as one that can be used as a sheet of a sublayer (second sheet) located between the top sheet and the absorbent element (wrapping sheet for the core).

[0010] A sheet with a low bulk, such as a wrapping sheet for a core, should have not only high liquid permeability, but also a sheet strength that is sufficient to not tear during manufacture. Methods conventionally adopted to increase the strength of a sheet include adding a strength improver. For example, patent literature 1 discloses tissue paper for home hygiene, which contains an additive that increases the strength in the dry state, and an additive that increases the strength in the wet state, and has a specific range of tensile strengths. The tissue paper for home hygiene disclosed in Patent Literature 1 is intended for use requiring sensory properties such as softness and tactile properties, including toilet paper, cosmetic wipes, and liner paper. The main method disclosed in Patent Literature 1 is aimed at achieving both sensory properties and paper strength.

LIST OF REFERENCES

Patent Literature

[0011] Patent Literature 1: JP 2005-124884A

Patent Literature 2: JP 8-291495A

Patent Literature 3: JP 2005-344274A

Patent Literature 4: JP 4390747

Patent Literature 5: JP 2009-148322A

SUMMARY OF THE INVENTION

Technical problem

[0012] Absorbent articles, such as disposable diapers and sanitary napkins, include those that have a liquid holding absorbent element. Known absorbent elements include those that have an absorbent core containing, for example, wood pulp and a super absorbent polymer, and a wrapping sheet for the core covering the outer surface of the absorbent core. The core wrapping sheet serves as a sheet containing the core-absorbent material, such as wood pulp and super absorbent polymer, during the formation of the absorbent member, and as a sheet wrapping the absorbent core, giving a certain geometric shape. Waterproof sheets, such as tissue paper and nonwoven fabric, are routinely used as a wrapping sheet for a core.

[0013] The wrapping sheet for the core must have a sheet strength that withstands the tension during transportation during manufacture, and a high liquid permeability that allows the body fluid to pass through quickly so that there is rapid absorption by the absorbent core located under the wrapping sheet for the core. Although liquid permeability can be effectively increased by lowering the bulk and density of the sheet, this approach causes a decrease in the number of bonds between the fibers due to a decrease in the number of constituent fibers, which can lead to a decrease in sheet strength. The strength of the sheet and the liquid permeability of the core wrapping sheet are conflicting properties. It is currently difficult to achieve both of them with a good balance.

[0014] The use of fibrillated pulp fiber is effective for providing tissue paper with enhanced paper strength (eg, tensile strength), but causes a decrease in permeability.

[0015] An increase in the amount of strength enhancing additive causes the additive to adhere to the wire mesh or dryer of the paper machine and to contaminate the wastewater, which may lead to a decrease in productivity. Thus, the amount of strength improver that can be added is limited. Therefore, it is difficult to sufficiently increase paper strength (for example, tensile strength) of tissue paper with a low bulk by adding an additive that increases the strength.

[0016] In Patent Literature 1, nothing is said about the procedure for adding a cationic polymer as a means for wet hardening and an anionic polymer as a means for dry hardening to a half-mass suspension. Patent Literature 3 relates to a fiber molded product obtained by a papermaking method for use as a heat generating molded product, without paying attention to the method associated with the manufacture of tissue paper with a low bulk.

[0017] A portion of the core wrapping sheet according to Patent Literature 4, which faces the skin side of the absorbent core, is formed from a synthetic fiber non-woven material in which the fibers are thermally bonded to each other. Therefore, even though the constituent fibers are hydrophilized synthetic fibers, there may be such a drawback that loose stools containing solid particles clog the core sheet when passing through it. The absorptive capacity for loose stool will be reduced if such disadvantages are not prevented, for example, by a relative increase in the distance between the fibers. However, a core wrapping sheet formed of a nonwoven material with an increased distance between the fibers will allow the absorbent core material, such as the absorbent polymer, to form absorbent core, out through it. Thus, it is difficult for a wrapping sheet for a core formed from a nonwoven material to achieve increased absorption capacity for loose stools while preventing leakage of the absorbent core material. In order to solve this problem, the absorbent article described in Patent Literature 1 has a multilayer absorbent element in which the absorbent polymer is not contained in the upper layer and thereby prevents leakage.

[0018] In order to increase the liquid permeability of the core wrapping sheet, a reduction in the bulk and density of the sheet will be effective. However, this approach causes a decrease in the number of bonds between the fibers due to a decrease in the number of constituent fibers, which can lead to a decrease in sheet strength. A core wrapping sheet having reduced sheet strength is susceptible to damage during manufacture, and the absorbent core-forming material may leak out of the damaged portion. The strength of the sheet and the liquid permeability of the core wrapping sheet are contradictory. It is currently difficult to achieve both of them with a good balance. In patent literature 1, 4 and 5, disclosure is not given regarding a means for eliminating the problems discussed above.

Solution

[0019] The inventors have conducted extensive studies of the relationship between strength and liquid permeability in paper. As a result, it has been found that improved liquid permeability is achieved while minimizing strength reduction by using pulp with a relatively large fiber diameter (thick fiber pulp) and pulp with a relatively small fiber diameter (thin fiber pulp) for making paper . As a result of further research, it was found that in order to achieve both strength and liquid permeability characteristics, it is effective to use two types of pulp (hydrophilic cellulose fibers) as fiber for making paper, in which the fiber coarseness, a measure representing the fiber diameter, is in the respective specific ranges, the differences in the coarseness of the fiber between the two pulp masses being in the specific range. This discovery is called the first discovery.

[0020] Based on the first discovery, the invention relates in its first aspect to tissue paper, advantageously containing a structure of two types of hydrophilic cellulose fibers, differing in fiber coarseness, and containing a strength improver. Two types of hydrophilic cellulosic fibers are a first pulp having a fiber coarseness of 0.13 to 0.16 mg / m and a second pulp having a fiber coarseness of 0.17 to 0.20 mg / m. The difference in the coarseness of the fiber between the first and second pulp is from 0.01 to 0.07 mg / m The structure has a grinding degree of 400 to 550 ml.

[0021] As a result of studies of the relationship between strength and liquid permeability in paper, the inventors also found that when they achieve improved liquid permeability in paper by reducing the bulk (or density), lowering the strength, which may be the result of lowering the bulk, avoided by using specific pulp (pulp that has been fibrillated) as constituent fibers and a combination of two or more additives that enhance strength. This discovery is called the second discovery.

[0022] Based on the second discovery, the invention relates, in its second aspect, to tissue paper, preferably containing bleached softwood kraft pulp having a milling degree of 400 to 550 ml, containing two or more strength improvers, and having a bulk from 10 to 14.5 g / m ² , density from 0.05 to 0.2 g / cm ³ , the degree of creping from 5% to 30%.

[0023] The invention also relates, in its third aspect, to a method for producing tissue paper with a bulk of 30 g / m ² or less, comprising the steps of forming a wet fibrous layer by making paper from raw materials obtained from a material containing bleached softwood Kraft pulp , and drying the wet fibrous layer. Raw materials are obtained by adding (a) an additive that increases the strength of wet paper containing a cationic polymer having a cationic group to a suspension of bleached kraft pulp of softwood, followed by the addition of (b) a low molecular weight additive that increases the strength of dry paper, and (c ) high-molecular additives that increase the strength of dry paper, or simultaneously or in the described order in suspension. The low molecular weight additive that increases the strength of dry paper (b) is a low molecular weight anionic polymer having an anionic group and has a weight average molecular weight of 2000 to 500,000. The high molecular weight additive that increases the strength of dry paper (c) is a high molecular weight anionic polymer having an anionic group and having a molecular weight of from 5,000,000 to 30,000,000.

[0024] The invention also relates in its fourth aspect to an absorbent article comprising an absorbent element. The absorbent element consists of an absorbent core containing hydrophilic fibers and an absorbent polymer and has an oblong shape, and a wrapping sheet for the core wraps the absorbent core. The wrapping sheet for the core contains highly liquid permeable paper located facing the skin side of the absorbent core. Highly liquid-permeable paper has a bulk of 8 to 20 g / m ² , a density of 0.05 to 0.2 g / cm ³ , a liquid travel time of 600 seconds or shorter as measured by the following method, and dry tensile strength 600 cN / 25 mm or more in machine direction during manufacture.

[0025] Method for measuring fluid transit time

Two cylinders, open at both ends and having an inner diameter of 35 mm, are vertically and concentrically mounted in a stack with a sheet to be evaluated, which is inserted between them. 10 ± 1 g of a high viscosity liquid (viscosity: 290 mPa · s) obtained by mixing glycerol and ion exchange water with a mass ratio of 94: 6 is poured into the upper cylinder. Poured viscous liquid passes through the sheet or is absorbed by it and disappears from the upper cylinder. The time from the start of pouring of a viscous liquid to the moment when the level of the liquid surface was compared with the surface of the sheet is measured in order to obtain the liquid passage time.

USEFUL EFFECTS OF THE INVENTION

[0026] The invention relates in its first and second objects to tissue paper, which has good strength characteristics and excellent liquid permeability.

[0027] The invention also relates, in its third aspect, to a method for producing tissue paper with a low bulk which has sufficient paper strength (for example tensile strength) so as not to tear during the manufacture and use of an absorbent article such as a diaper.

[0028] The invention also relates, in its fourth aspect, to an absorbent article that exhibits high absorbent performance for highly viscous fluids such as loose stools and is free from leakage problems of the absorbent core material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 illustrates a method for measuring fluid transit time.

FIG. 2 is a schematic view showing an apparatus that is preferably used to implement the method according to the third aspect of the invention.

FIG. 3 is a schematic view showing another apparatus that is preferably used to implement the method according to the third aspect of the invention.

FIG. 4 is a schematic view showing another other apparatus that is preferably used to implement the method according to the third aspect of the invention.

5 is a schematic view showing another other apparatus that is preferably used to implement the method according to the third object of the invention.

FIG. 6 is a schematic top view of a disposable diaper, an embodiment of an absorbent article according to a fourth aspect of the invention, in its open state, where each elastic member is straightened as viewed from its skin side (upper sheet side).

FIG. 7 is a schematic cross-section taken along line I-I in FIG. 6.

FIG. 8 is a schematic cross-sectional view of an absorbent member used in another embodiment of an absorbent article according to a fourth aspect of the invention.

DESCRIPTION OF EMBODIMENTS

[0030] The first and second objects of the invention relate to tissue paper having good strength characteristics and excellent liquid permeability.

[0031] A third aspect of the invention relates to a method for producing tissue paper that achieves both liquid permeability and paper strength (eg, tensile strength) that are contradictory to each other.

[0032] A fourth aspect of the invention relates to an absorbent article that exhibits high absorbency for high viscosity fluids such as loose stools and is free from the leakage problem of the absorbent core forming material.

[0033] The tissue paper according to the first object of the invention is described in detail. The tissue paper of the invention (first object) essentially contains a structure of two types of hydrophilic cellulose fibers, differing in fiber coarseness. "Fiber coarseness" is a measure used to represent the thickness of a fiber with an uneven thickness, such as wood pulp fibers, which can be measured using a commercially available fiber length analyzer, as described below. The tissue paper of the invention comprises a structure of two types of hydrophilic cellulosic fibers, varying in thickness, thereby balancing strength characteristics and liquid permeability.

[0034] The tissue paper in accordance with the invention (first object) contains a first pulp having a fiber coarseness of 0.13 to 0.16 mg / m, preferably 0.135 to 0.155 mg / m, more preferably 0.14 to 0 , 15 mg / m, and a second pulp having a fiber coarseness of from 0.17 to 0.20 mg / m, preferably from 0.175 to 0.195 mg / m, more preferably from 0.18 to 0.19 mg / m, as two types of hydrophilic cellulose fibers. The second pulp is coarser than the first pulp. The use of a relatively coarse pulp as part of the paper-forming fibers causes large formations in the paper and thereby improved liquid permeability. The term "pulp", as used herein, refers to plant fibers, such as wood fibers, bast fibers and leaf fibers, chemically or mechanically processed to the state of individual fibers.

[0035] The difference in fiber coarseness between the first and second pulp is from 0.01 to 0.07 mg / m, preferably from 0.02 to 0.06 mg / m, more preferably from 0.03 to 0.05 mg / m If the difference in fiber coarseness between the two pulp masses is less than 0.01 mg / m, then only a mild liquid permeability improvement effect can be achieved. If the difference is more than 0.07 mg / m, a significant decrease in paper strength can occur.

[0036] Each of the first and second pulp preferably has an average fiber length of 2 to 3 mm, more preferably 2.2 to 2.8 mm. With an average fiber length of two pulp pulp within this range, the fibers have a well-balanced entanglement with each other, and as a result tissue paper exhibits good formation. Two pulp masses may have the same or different average fiber lengths. The fiber coarseness and average fiber length are measured as follows.

[0037] A method for measuring fiber coarseness and average fiber length:

The average fiber length and fiber coarseness are measured using an FS-200 fiber length analyzer, which is available from Kajaani Electronics, Ltd. Non-milled fibers (pulp) were analyzed. In order to determine the true weight of the fibers to be analyzed, the fibers are dried in a vacuum dryer at 100ºC for 1 hour in order to free from water. One gram of dried fibers is accurately weighed with a weighing accuracy of ± 0.1 mg and completely disintegrated into 150 ml of water in an existing mixer, taking care to minimize fiber damage. The resulting fiber suspension is diluted with water to a volume of 5000 ml. Fifty milliliters of the diluted fiber suspension is accurately weighed to obtain a sample to be analyzed using a fiber length analyzer. The coarseness of the fiber and the average fiber length are calculated in accordance with the order of operation with the analyzer. The average fiber length is calculated according to the formula:

[0038] Mat. one

where n _i represents the number of fibers with a fiber length l _i ; and l _i represents the length of the fiber.

[0039] The mass ratio of the content of the first pulp to the content of the second pulp, namely the first pulp / second pulp, is preferably from 3/7 to 7/3, more preferably from 4/6 to 6/4, so that balance strength characteristics and fluid permeability. If the proportion of the relatively thick second pulp is too small, sufficient fluid permeability may not be achieved. Conversely, if the proportion of the second pulp is too large, the result can be a sharp decrease in paper strength.

[0040] The first and second pulp (hydrophilic cellulose fibers) are not particularly limited and may be any fibers that have a fiber coarseness falling within the range indicated above, a hydrophilic surface and the ability to form a sheet in which they have a high degree freedom of movement relative to each other. Examples of such hydrophilic cellulose fibers include natural cellulose fibers, such as wood pulp, for example, bleached softwood pulp kraft (NBKP) and bleached hardwood pulp kraft (LBKP), and non-wood pulp, for example, from cotton and straw; regenerated cellulose fibers, such as viscose and copper-ammonia fiber; synthetic hydrophilic fibers such as polyvinyl alcohol fibers and polyacrylonitrile fibers; and synthetic fibers (e.g., polyethylene terephthalate (PET) fibers, polyethylene (PE) fibers, polypropylene (PP) fibers, and polyester fibers) that are hydrophilized with a surfactant. These fibers can be used either individually or as a mixture of two or more of them.

[0041] Among the hydrophilic cellulose fibers described, NBKPs are particularly preferred. Both the first pulp and the second pulp are preferably NBKP. Any type of NBKP commonly used in this type of paper can be used in the first aspect of the invention. The bleached pulp obtained by the ECF process (ECF = no elemental chlorine) or TCF (TCF = completely chlorine free), in which the chlorine compound is not or substantially not used for bleaching, can be used as NBKP.

[0042] The tissue paper of the invention (first object) advantageously comprises a structure of two types of hydrophilic cellulosic fibers that differ in fiber coarseness (first and second pulp). As used herein, the phrase “predominantly contains” is intended to mean that the total content of the first and second pulp is at least 50% by weight. In order to balance the strength characteristics and liquid permeability, the total content is preferably from 70 to 100% by weight, more preferably from 80 to 100% by weight.

[0043] The structure of the two types of hydrophilic fibers (first and second cellulosic pulp) used in the invention (first object) has a milling degree of 400 to 550 ml. In other words, the degree of grinding of each of the first and second pulp is in the range from 400 to 550 ml. As used herein, the term "degree of milling" refers to Canadian Standard Degree of Milling (C.S.F.), as defined in JIS P8121, which is a measure representing the degree of pulp breaking (mechanical breaking and crushing of pulp in the presence of water). A lower degree of grinding indicates a higher degree of breakdown, generally indicating that the fibers have undergone more severe destruction and fibrillation due to the breakdown. Fibers in which the degree of grinding is in the range already indicated should be entangled with each other due to deeper fibrillation. Therefore, even if there is a decrease in the number of bonds between the fibers in tissue paper as a result of, for example, a decrease in the bulk (or density) aimed at increasing liquid permeability, the bond strength between the fibers is still high compared to fibers having a finer grinding ratio than 550 ml, indicating less deep fibrillation. Thus, tissue paper, which mainly contains a structure of fibers having a degree of milling from 400 to 550 ml, can exhibit satisfactory strength characteristics.

[0044] The degree of grinding of the structure of the two types of hydrophilic cellulose fibers for use in the invention (first object) is preferably from 450 to 525 ml, more preferably from 475 to 510 ml. The effect of fiber entanglement in increasing the strength reaches a maximum at a grinding degree of 400 ml. In addition, if the degree of grinding is less than 400 ml, the destruction of the fibers is accelerated, which can lead to a delay in the passage of fluid. The fiber structure can be broken by processing the raw material (suspension) of the mixed fibers of the hydrophilic cellulose fibers (first and second pulp) forming the fiber structure in a known breaking machine, such as a shredder or disk shredder, in the usual way.

[0045] The tissue paper of the invention (first object) may contain fibers other than the first and second pulp. Other fibers may not be hydrophilic cellulosic fibers, such as the first and second pulp. Other illustrative fibers include wood pulp, such as bleached hardwood kraft pulp (LBKP), bleached sulphite pulp pulp of softwood (NBSP), and thermomechanical pulp (TMP); bast fibers, for example, from paper mulberry, Edgeworthia chrysantha and Diplomorpha sikokiana; non-wood mass, for example, from straw, bamboo, kenaf and jute; and synthetic fibers, such as polyester fibers, viscose fibers and acrylic fibers. The content of other fibers is preferably not more than 20% by weight.

[0046] The tissue paper of the invention (first object) contains a strength improver in order to exhibit good strength characteristics (tensile strength). Strength enhancers include a dry paper strength improver to improve dry paper strength and a wet paper strength improver to improve wet paper strength, any of which can be used. In particular, carboxymethyl cellulose (CMC), a type of dry paper strength improver, and its salt are preferably used in the invention (first object) because of its widespread use and the weak flocculation effect on the fibers. That is, it is preferable to add at least CMC or its salt as an additive to increase the strength in the invention (first object).

[0047] The dry paper strength improver can be selected from standardly known dry paper strength improvers, such as CMC and its salts, polyacrylamide resin and its salts, cationic starch and polyvinyl alcohol (PVA). These dry paper strength improvers can be used either individually or in combination of two or more of them. The salt of CMC and the polyacrylamide resin is usually a sodium salt. The polyacrylamide resin may be, for example, cationic or anionic polyacrylamide (PAM). Preferred among these dry paper strength improvers are CMC and its salts, anionic PAM and its salts.

[0048] A wet paper strength improver can be selected from standardly known wet paper strength improvers, including epoxidized polyamide-polyamine resin (PAE), urea-formaldehyde resin, melamine-formaldehyde resin, dialdehyde starch, polyethyleneamine and hydroxymethylated polyamide. They can be used either individually or in combination of two or more of them. Among them, PAE is particularly preferred.

[0049] In the case where two or more strength improvers are used in combination in the invention (first object), a combination of two dry strength enhancers and one wet strength improver is preferred, including two enhancing enhancers the strength of dry paper is preferably a CMC salt and anionic PAM salt, and one wet strength paper additive is preferably PAE.

[0050] In the case of using a combination of CMC salt, anionic PAM salt and PAE, the anionic PAM salt preferably has a weight average molecular weight of 8000000 or more, more preferably 10000000 or more, even more preferably 15000000 or more, and the upper limit of the weight average molecular weight of the anionic PAM salt is 25000000. When using such a combination of specific three additives that increase strength, the salt of anionic PAM, which should have a weighted average molecular weight within this range (from 8000000 to 25000000), renders not only the effect of increasing the strength of tissue paper, which is ascribed to the manifestation of adhesiveness of the salts of anionic PAM per se, but also the effect of improving the strength of tissue paper, which is ascribed to improve retention of CMC salt. Two strength enhancement effects will provide additional improved strength characteristics. In addition, an anionic PAM salt with an average molecular weight of 25000000 or less has a relatively low dispersibility and viscosity in water during the manufacture of tissue paper, which is favorable from the point of view of handling and preventing contamination of the paper machine.

[0051] The amount of strength improver to be used in the tissue paper of the invention (first object) is preferably from 0.01 to 1.5% by weight, more preferably from 0.03 to 1.2% by weight, relative dry weight of all fibers forming tissue paper. Adding too little strength improver is not able to provide sufficient strength characteristics, such as tensile strength. Adding too much strength improver leads to hardening of tissue paper (reducing smoothness or softness of texture) and worsening of tissue paper formation, for example, due to sticking of paper to a Yankee dryer, sticking of strength improver to mesh screen during manufacture tissue paper.

[0052] In the case where the strength improver contains at least one dry paper strength enhancer and at least one wet paper strength enhancer, the ratio of the total weight of the dry strength improver increases the total weight of the additive , increasing the strength of wet paper, is preferably from 0.01 to 0.5, more preferably from 0.03 to 0.35.

[0053] In the case where the strength improver is a combination of CMC salt and anionic PAM salt as a dry paper strength enhancer and PAE as a wet paper strength improver, the amount of CMC salt to be added is preferably from 0.05 to 0.5% by weight, more preferably from 0.1 to 0.3% by weight relative to the dry weight of all fibers forming a tissue paper, the amount of anionic PAM salt to be added is preferably from 0.001 to 0, 1% by mass, more than expected preferably from 0.02 to 0.05% by weight relative to the dry weight of all fibers forming the tissue paper, and the amount of PAE to be added is preferably from 0.5 to 1.5% by weight, more preferably from 0.6 to 1.2% by weight of the relatively dry weight of all the fibers forming the tissue paper.

[0054] The tissue paper of the invention (first object) may contain components other than fibers containing the first and second pulp (hydrophilic cellulose fibers) and a strength improver. Other components include papermaking materials and additives commonly used in papermaking, such as fillers (e.g., talc), colorants, color pigments, antimicrobials, pH adjusters, retention aids, water resistance additives, and antifoam agents. You can use one or more than one of them.

[0055] The tissue paper of the invention (first object) can be produced by a known wet paper production method. The wet paper production method has a raw material production step, which produces paper raw materials containing an aqueous dispersion of fibers (e.g. NBKP), and a paper manufacturing step, wherein the raw materials are dried to form a fiber network and the fiber network is dried during transportation. The papermaking step is generally divided into a net part, a press part, a drying part, an size press and a calender part in the described order. The dry paper strength enhancer described above and the wet paper strength enhancer are typically added to the feed at the raw material preparation stage. Despite the fact that the strength improver is usually added in the order of a wet paper strength improver and the dry paper strength enhancer, the order of adding strength improvers to the invention (first object) is not limited to this. That is, an additive that increases the strength of dry and wet paper can be added in the reverse order or at the same time. The wet method of producing paper is carried out in the usual way using a Fourdigne paper machine, a two-wire paper machine, an on-top former, a hybrid former, a cylindrical paper machine and the like.

[0056] The tissue paper of the invention (first object) is preferably designed to have a relatively low bulk to have increased liquid permeability, in particular 10 to 20 g / m ² , more preferably 11 to 16 g / m ² , even more preferably from 12 to 14 g / m ² . Although it is alarming that a reduced bulk can lead to a decrease in paper strength, such a decrease in strength is avoided in the invention (first object) by, as indicated, (1) using a first pulp with a relatively low coarse fiber (small thickness) ) as part of the constituent fibers, (2) limiting the degree of grinding of the structure of two fibers (first and second pulp) to a specific range, and (3) using a strength improver in combination. With a bulk of less than 10 g / m ² , a significant reduction in paper strength can be obtained. With a bulk of more than 20 g / m ² , a sufficient liquid permeability improvement effect cannot be expected.

[0057] From the same point of view, the tissue paper of the invention (first object) preferably has a density of 0.05 to 0.2 g / cm ² , more preferably 0.1 to 0.2 g / cm ³ .

[0058] The bulk of tissue paper is measured as follows. Cut square samples with a side of 10 cm (area: 100 cm ² ) from a sample (tissue paper) that was conditioned under the conditions specified in JIS P8111. Each sample is weighed using weights with a minimum count of one hundredth of a gram, and the measured mass is divided by area in order to obtain the bulk of the sample. Take the average value of the thus obtained main masses of ten samples as the main mass of the sample.

[0059] The density of the tissue paper is measured as follows. A stack of ten square samples with a side of 20 cm (tissue paper) is frozen in liquid nitrogen and cut along the center with a cutter. A sample without shear on the cut surface is selected from ten samples, and the thickness of the selected sample is measured under an optical microscope. If the sample has an uneven surface (for example, crepe paper), as described later in this document, the term “thickness” does not refer to the apparent thickness measured from the deepest depression to the highest peak of the surface profile, but to the true thickness (thickness layer formed from deposited fibers). The mass W of a square sample with a side of 20 cm, the thickness of which is known, is measured using weights having a minimum reading of one hundredth of a gram. The density of the sample is the quotient obtained by dividing the mass W by the volume V of the sample, W / V, where V is calculated using the formula: V = {T × B × B × (100 + A) / 100}, where T is the thickness sample (cm); A represents the degree of creping (%) of the sample; and B is the side length of the sample (20 cm). When the tissue paper sample is not creped (crepe degree 0%), A = 0.

[0060] The tissue paper of the invention (first object) may be creped. The creped tissue paper of the invention is preferably obtained by a dry creping method in which a dry fiber network (tissue paper) adhered, for example, to a Yankee dryer in a dryer portion of a paper machine is scraped using a doctor blade or the like. The degree of creping is determined as follows.

[0061] A method for determining the degree of creping

The tissue paper is cut into rectangular samples of 200 mm in the longitudinal direction (machine direction in the manufacture of tissue paper, hereinafter MD) and 100 mm in the transverse direction (transverse to the machine direction, hereinafter CD). The sample is immersed in water for 10 minutes. Immediately after the sample is taken out of the water, measure the length C in MD, according to which the degree of creping is calculated according to the formula:

The degree of creping (%) = {(C-200) / 200} × 100

When, for example, the length C in MD after immersion for 10 minutes is 220 mm, the degree of creping of tissue paper, as calculated using the formula, is 10%.

[0062] Creped tissue paper exhibits a higher liquid permeability than uncreated tissue paper. The higher the degree of creping, the higher the liquid permeability. However, it is noted that an increase in the degree of creping tends to lead to a decrease in strength characteristics (for example, tensile strength). Based on these findings, the degree of creping of the creped tissue paper of the invention (first object) is preferably from 5 to 30%, more preferably from 5 to 20%, even more preferably from 7 to 15%, in order to balance liquid permeability and strength characteristics.

[0063] The tissue paper of the invention (first object) having the above structure has a dry tensile strength of 600 cN / 25 mm or more, preferably from 600 to 1500 cN / 25 mm, more preferably from 700 to 1200 cN / 25 mm , even more preferably from 800 to 1200 cN / 25 mm, most preferably from 900 to 1200 cN / 25 mm, in MD and 150 cN / 25 mm or more, preferably from 150 to 350 cN / 25 mm, more preferably from 180 to 300 cN / 25 mm, in CD. Tissue paper in which the dry tensile strength in MD and CD falls in the respective ranges listed, exhibits sufficient strength for practical use. For example, when applied to a core wrapping sheet that wraps an absorbent core for use in an absorbent article, such as a disposable diaper, tissue paper is less likely to tear or cause similar problems during the manufacture of the absorbent article. Dry tensile strength is determined as follows.

[0064] A method for determining dry tensile strength:

The sheet (tissue paper) to be tested is conditioned in the environment at room temperature (23 ° C ± 2 ° C) and 50% RH ± 2% for 12 hours. A rectangular specimen of 150 mm in MD and 25 mm in CD is cut from the conditioned sheet and mounted on a tensile tester (Autograph AG-1kN, Shimadzu Corp.) wherein the MD of the specimen coincides with the direction of stretching without applying tension at an initial distance between the clamps of 100 mm The sample is pulled at a speed of 300 mm / min and the maximum load at break is recorded. The measurement is carried out five times in order to obtain the average value, which is taken as the dry tensile strength in MD. The CD dry tensile strength is obtained in the same manner as for the dry tensile strength MD, except that a rectangular specimen of 150 mm in CD and 25 mm in MD are cut from the conditioned sheet and installed in a tensile tester, wherein its CD coincides with the direction of extension without applying tension.

[0065] The tissue paper of the invention (first object) has a liquid transit time of 0.2 to 3 seconds, preferably 0.3 to 2.5 seconds, more preferably 0.5 to 2 seconds, as measured by the method described below. The shorter the fluid transit time, the higher the liquid permeability (the higher the score). Tissue paper having a liquid transit time in this range exhibits excellent liquid permeability. For example, when applied to a core wrapping sheet that wraps an absorbent core for use in an absorbent article, tissue paper allows emitted bodily fluid, such as urine, to quickly pass through and absorb into the absorbent core, and thus is expected to it will provide an absorbent article with improved leakage prevention.

[0066] a method for determining the passage of fluid

As shown in FIG. 1, two cylinders 91 and 92, open at both ends and having an inner diameter of 35 mm, are vertically and concentrically mounted in a stack with square sheet S with a side of 8 cm (tissue paper) to be evaluated, which is inserted between them. The upper cylinder 91 and the lower cylinder 92 are preferably connected by means of fitting clips 93 on the annular flanges provided around the lower end of the upper cylinder 91 and the upper end of the lower cylinder 92. The elements indicated by 94 are o-rings, for example made of rubber and having through a hole in the form of a sample and an inner diameter similar to cylinders 91 and 92. Sheet S is held between the upper and lower cylinders 91 and 92 and 40 ± 1 g of physiological saline W are poured (aqueous solution of chloride n Tria 0.9% by weight) in the upper cylinder. Saline solution W passes through or is absorbed by the sheet S and disappears from the upper cylinder 91. The time from the beginning of the pouring of the physiological solution to the moment when the surface level of the liquid is compared with the surface of the sheet S (the surface on the side of the upper cylinder 91) is measured in order to obtain time fluid passage.

[0067] The tissue paper of the invention (first object) also has excellent breathability since it consists mainly of a structure of two types of hydrophilic cellulose fibers, differing in fiber coarseness. In order to investigate the relationship between breathability and the use of two types of hydrophilic cellulose fibers, differing in fiber coarseness, two types of tissue paper, designated as samples A and B, are obtained from different pulp compositions and the breathability of the samples is determined. The sample corresponds to the sample from example 1 below, and contains the first and second pulp. Sample B was prepared in the same manner as in Example 1, except for using only the first pulp (NBKP has a fiber coarseness of 0.15 mg / m) as the fibrous material forming tissue paper, i.e. without using a second pulp (NBKP has a fiber coarseness of 0.18 mg / m). Both samples A and B have a bulk of 13 g / m ² . Breathability is measured as follows.

[0068] Method for measuring breathability

Breathability is determined in accordance with JIS P8117. Get thirty-two square sheets with a side of 15 cm of tissue paper to be tested. The sheets are dried in a hot air dryer at 105 ° C. for 30 minutes and stacked on top of each other. The stack is mounted on a Gurley B-type densimeter, and the time required for a certain amount of air to pass through the stack, from 0 cm ³ to reaching 300 cm ³ , is measured five times. The average value of the five measured times is taken as the breathability of the sheet (tissue paper). The unit of air permeability so determined is s / 32P · 300 cm ³ , reflecting the time (in seconds) required for 300 cm ^{3 of} air to pass through a stack of 32 sheets. The lower the value, the easier the air passes, namely, the higher the air permeability.

[0069] Sample B containing the first pulp as the only fibrous material has a breathability of 2.1 to 2.7 s / 32P · 300 cm ³ , while Sample A containing two types of pulp (first and second), fibers differing in roughness, as a fibrous material, has a lower value of breathability from 1.6 to 2.2 s / 32P · 300 cm ³ . These results prove that the composition of tissue paper mainly from a structure of two types of hydrophilic cellulose fibers, differing in the coarseness of the fiber, is effective for providing tissue paper with improved breathability. It should be clearly understood that the tissue paper of the invention (first object) having the described structure exhibits excellent breathability.

[0070] Having good strength characteristics (tensile strength), excellent liquid permeability and high breathability, the tissue paper of the invention (first object) is suitable for various applications where such characteristics are an advantage. The tissue paper of the invention (first object) is particularly suitable as a wrapping sheet for a core that wraps a liquid-retaining absorbent core used in an absorbent article, such as a disposable diaper or sanitary napkin. Tissue paper as a wrapping sheet for the core is capable of allowing the secretion of a flowable fluid, including, to say nothing of a fluid of relatively low viscosity, such as urine, and also of relatively high viscosity, such as loose stool, to pass through and absorb into an absorbent core, thereby contributing to an improvement in preventing leakage from absorbent articles.

[0071] An absorbent article of the invention using tissue paper of the invention (first object) is illustrated with an absorbent article comprising an absorbent core and a wrapping sheet for a core that wraps an absorbent core in which the wrapping sheet for the core is a tissue paper of the invention ( first object). In particular, the absorbent article of the invention comprises a liquid-permeable topsheet forming a skin-facing surface of the absorbent article, a liquid-impervious or water-repellent backsheet forming a non-skinning surface of the absorbent article, and an absorbent member interposed between the two sheets in which the absorbent element comprises an absorbent core and a wrapping sheet for the core (tissue paper according to the first object according to the invention). The core wrapping sheet (tissue paper according to the first object of the invention) preferably covers at least the skin-facing side and the non-skin-facing side of the absorbent core. As used herein, the term “skin side” refers to the side of the absorbent article or an element of the absorbent article that faces the skin of the wearer when the absorbent article is worn, and the term “non-skin side” refers to the side an absorbent article or an element forming an absorbent article that faces away from the skin of the wearer (clothing side) when the absorbent article is worn. The top sheet, back sheet and absorbent core can be any of what is commonly used in absorbent articles of this type. Illustrative absorbent articles of the invention include flat or worn disposable diapers, sanitary napkins, and urological pads.

[0072] Next, tissue paper according to a second aspect of the invention is described. The tissue paper of the invention (second object) essentially contains bleached softwood (KKF) pulp having a milling degree of 400 to 550 ml. As used herein, the term “degree of grinding” refers to Canadian Standard Freeness (C.S.F.), which is precisely defined in JIS P8121 and which is a measure representing the degree of pulp breakdown (mechanical breaking and crushing of pulp in the presence of water). A lower degree of grinding indicates a higher degree of breakdown, generally indicating that the fibers have undergone more significant damage and fibrillation due to the breakdown. Fibers in which the degree of grinding is in the specified range are ready for tangling with each other due to deeper fibrillation. Therefore, even if the number of bonds between the fibers in the tissue paper is reduced as a result of, for example, a decrease in the bulk (or density), aimed at improving liquid permeability, the bond strength between the fibers is still high compared to fibers having a degree of grinding greater than 550 ml, which indicates less deep fibrillation. Thus, tissue paper containing NBKP as a main component, having a grinding degree of 400 to 550 ml, can exhibit satisfactory strength characteristics.

[0073] The degree of milling of NBKP for use in the invention (second object) is preferably 475 to 525 ml, more preferably 490 to 510 ml. The effect of fiber entanglement on improving strength reaches a maximum at a grinding degree of 400 ml, and if the grinding degree is less than 400 ml, fiber cutting is accelerated, which can lead to a delay in the passage of liquid. Partitioning NBKP can be accomplished by treating the NBKP paper feed (slurry) in a known breaking machine, such as a shredder or disk shredder, in the usual manner. Any type of NBKP commonly used in this type of paper can be used in a second aspect of the invention. The bleached pulp obtained by the ECF method (ECF = no elemental chlorine) or TCF (TCF = completely chlorine free), in which the chlorine compound is not or not substantially added during the process, can be used as NBKP.

[0074] The tissue paper of the invention (second object) advantageously contains NBKP, which has a milling degree of 400 to 550 ml. As used herein, the phrase “predominantly contains” is intended to mean that the content of NBKP, the degree of grinding of which is in the specified range, is at least 50% by weight. In order to obtain good strength characteristics, the NPKP content is preferably from 50 to 100% by mass, more preferably from 80 to 100% by mass.

[0075] NBKP for use in the invention (second object) preferably has a fiber coarseness of 0.1 to 0.2 mg / m, more preferably 0.12 to 0.18 mg / m. "Fiber coarseness" is a measure used to represent the thickness of a fiber with an uneven thickness, such as wood pulp. NBKP for use in the invention preferably has an average fiber length of from 1 to 4 mm, more preferably from 2 to 3 mm. The coarseness of the fiber and the average fiber length are measured by the previously described methods.

[0076] The tissue paper of the invention (second object) may contain fibers other than NBKP. Other fibers may not be hydrophilic cellulose fibers, such as NBKP. Illustrative other fibers include wood pulp, such as bleached hardwood kraft pulp (LBKP), bleached sulphite pulp pulp of softwood (NBSP), and thermomechanical pulp (TMP); bast fibers, for example, from paper mulberry, Edgeworthia chrysantha and Diplomorpha sikokiana; non-wood mass, for example, from straw, bamboo, kenaf and jute; and synthetic fibers, such as polyester fibers, viscose fibers and acrylic fibers. The content of other fibers is preferably not more than 50% by weight.

[0077] The tissue paper of the invention (second object) contains two or more strength improvers in order to exhibit good strength characteristics (tensile strength). Strength enhancing additives include dry paper strength enhancing additives to increase dry paper strength and wet paper strength enhancing additives to increase wet paper strength. All of the two or more strength additives to be used may be either dry paper strength additives or wet paper strength additives, but it is preferable to combine at least one dry paper strength enhancer and at least at least one wet strength paper additive to achieve particularly excellent strength characteristics.

[0078] The dry paper strength improver can be selected from standardly known dry paper strength improvers, including carboxymethyl cellulose (CMC) and its salts, polyacrylamide resin and its salts, cationic starch and polyvinyl alcohol (PVA). These dry paper strength improvers can be used either individually or in combination of two or more of them. The salt of CMC and the polyacrylamide resin is usually a sodium salt. The polyacrylamide resin may be, for example, cationic or anionic polyacrylamide (PAM). Preferred of these dry paper strength improvers are CMC and its salts, anionic PAM and its salts.

[0079] A wet paper strength improver can be selected from standardly known wet paper strength improvers, including epoxidized polyamide-polyamine resin (PAE), urea-formaldehyde resin, melamine-formaldehyde resin, dialdehyde starch, polyethyleneamine and hydroxymethylated polyamide. They can be used either individually or in combination of two or more of them. Of these, PAE is particularly preferred.

[0080] A particularly preferred combination of strength enhancing additives for use in the invention (second aspect) is a combination of two dry strength enhancing additives and one wet paper strength enhancing agent, of which two dry strength enhancing additives, preferably a CMC salt and anionic PAM salt, and one wet strength paper additive is preferably PAE.

[0081] In the case of using a combination of CMC salt, anionic PAM salt and PAE, the anionic PAM salt preferably has a weight average molecular weight of 8,000,000 or more, more preferably 10,000,000 or more, even more preferably 1,500,000 or more, and an upper limit of the weight average molecular weight of the anionic PAM salt is 25000000. Using this combination of specific three strength-enhancing additives, the anionic PAM salt should have a weighted average molecular weight within this range (from 8000000 to 25000000) causes not only CPC increase strength tissue paper, which is ascribed to the manifestation of adhesiveness salt anionic PAM per se, but also the effect of improving the strength of tissue paper, which is assigned to improve retention of CMC salt. Two strength enhancement effects will provide additional improved strength characteristics. In addition, an anionic PAM salt with an average molecular weight of 25000000 or less has a relatively low dispersibility and viscosity in water during the manufacture of tissue paper, which is favorable from the point of view of handling and preventing contamination of the paper machine.

[0082] The total amount of two or more strength improvers to be used in the tissue paper of the invention (second object) is preferably 0.01 to 1.5% by weight, more preferably 0.03 to 1.2 % by weight, relatively dry weight of all the fibers forming the tissue paper. Adding too little strength improver is not able to provide sufficient strength characteristics, such as tensile strength. Adding too much strength improver leads to hardening of tissue paper (reducing smoothness or softness of texture) and worsening the formation of tissue paper, for example, due to sticking of paper to a Yankee dryer, sticking of strength improver to mesh screen during manufacture tissue paper.

[0083] In the case where at least one additive that increases the strength of dry paper, and at least one additive that increases the strength of wet paper, are used in combination, the ratio of the total weight of the additive (s) that increase the strength of dry paper to the total weight additives (s) that increase the strength of wet paper, is preferably from 0.01 to 0.5, more preferably from 0.03 to 0.35.

[0084] When a combination of CMC salt and anionic PAM salt is used as additives to increase the strength of dry paper and PAE as an additive to increase the strength of wet paper, the amount of CMC salt to be added is preferably from 0.05 to 0.5% by weight, more preferably from 0.1 to 0.3% by weight relative to the dry weight of all the fibers forming the tissue paper, the amount of anionic PAM salt to be added is preferably from 0.001 to 0.1% by weight, more preferably from 0 02 to 0.05% by weight relatively dry the first mass of all fibers forming the tissue paper, and the amount of PAE to be added is preferably from 0.5 to 1.5% by weight, more preferably from 0.6 to 1.2% by weight relative to the dry weight of all fibers forming tissue paper.

[0085] The tissue paper of the invention (second object) may contain components other than fibers, such as NBKP, and strength improvers, as described above. Other components include papermaking materials and additives commonly used in papermaking, such as fillers (e.g., talc), colorants, color pigments, antimicrobials, pH adjusters, retention aids, water resistance additives and antifoam agents. You can use one or more than one of them.

[0086] The tissue paper of the invention (second object) can be produced by a known wet paper production method. A wet paper production method has a raw material production step that produces a raw material containing an aqueous dispersion of fibers (e.g., NBKP), and a paper manufacturing step, in which the raw material is dried to form a fiber network and the fiber network is dried during transportation. The papermaking step is generally divided into a net part, a press part, a drying part, an size press and a calender part in the described order. The dry paper strength enhancer described above and the wet paper strength enhancer are typically added to the feed at a raw material preparation stage. Although strength enhancing additives are typically added in order of wet paper strength increasing additive and dry paper strength increasing additive, the order of adding strength increasing additives in the invention (second aspect) is not limited to this. That is, additives that increase the strength of dry and wet paper can be added in the reverse order or at the same time. The wet method of producing paper is carried out in the usual way using a Fourdinje paper machine, a two-wire paper machine, an on-top former, a hybrid former, a cylindrical paper machine and the like.

[0087] The tissue paper of the invention (second object) is preferably designed to have a relatively low bulk and relatively low density in order to have improved liquid permeability. In particular, the bulk is from 10 to 14.5 g / m ² , preferably from 11 to 14 g / m ² , and the density is from 0.05 to 0.2 g / cm ³ , preferably from 0.1 to 0 , 2 g / cm ³ . Although it is alarming that such a low bulk and low density can lead to a decrease in paper strength, such an alarm can be eliminated in the invention (second object) by, as indicated, (1) using NBKP having a specific grinding degree range , and (2) the use of two or more strength improvers in combination. With a bulk of less than 10 g / m ² or a density of less than 0.05 g / cm ³ , a substantial decrease in paper strength can occur. With a bulk of more than 14.5 g / m ² or a density of more than 0.2 g / cm ³ , a sufficient liquid permeability improvement effect cannot be expected. The bulk and density of tissue paper is measured by the methods described above.

[0088] The tissue paper of the invention (second object) is a creped tissue paper, which has a creping degree of 5% to 30%. The creped tissue paper of the invention (second object) is preferably obtained by a dry creping method in which a dry fiber network (tissue paper) adhering, for example, to a Yankee dryer, in the dryer portion of a paper machine, is scraped using a doctor blade or the like. The degree of creping is determined by the previously described method.

[0089] Creped tissue paper exhibits a higher liquid permeability than uncreated tissue paper. The higher the degree of creping, the higher the liquid permeability becomes. However, it is noted that an increase in the degree of creping tends to lead to a decrease in strength characteristics (for example, tensile strength). Based on these findings, the crepe strength of the creped tissue paper in the invention (second object) is preferably from 5 to 30%, more preferably from 5 to 20%, even more preferably from 7 to 15%, in order to balance liquid permeability and strength characteristics.

[0090] The tissue paper of the invention (second object) having the above structure has a dry tensile strength of 600 cN / 25 mm or more, preferably from 600 to 1500 cN / 25 mm, more preferably from 700 to 1200 cN / 25 mm , even more preferably from 800 to 1200 cN / 25 mm, most preferably from 900 to 1200 cN / 25 mm, in the machine direction (MD) during the manufacture of tissue paper and 150 cN / 25 mm or more, preferably from 150 to 350 cN / 25 mm, more preferably from 180 to 300 cN / 25 mm, in a CD orthogonal to MD. Tissue paper in which the dry tensile strength in MD and CD falls within the respective indicated ranges exhibits sufficient strength for practical use. For example, when applied to a core wrapping sheet that wraps an absorbent core for use in an absorbent article such as a disposable diaper, a core wrapping sheet (tissue paper) is less likely to tear or cause a similar problem during the manufacture of the absorbent article. Dry tensile strength is determined by the previously described method.

[0091] The tissue paper of the invention (second object) has a liquid transit time of from 0.2 to 3 seconds, preferably from 0.3 to 2.5 seconds, more preferably from 0.5 to 2 seconds, as measured by the method described above. The shorter the fluid transit time, the higher the liquid permeability (higher score). Tissue paper having a liquid transit time in this range exhibits excellent liquid permeability. For example, when applied to a core wrapping sheet that wraps an absorbent core for use in an absorbent article, tissue paper allows the excreted bodily fluid, such as urine, to pass quickly through and absorbed into the absorbent core, and is thus expected to provide absorbent article with improved leakage prevention.

[0092] Having good strength characteristics (tensile strength) and excellent liquid permeability, the tissue paper of the invention (second object) is suitable for various applications where such characteristics provide an advantage. The tissue paper of the invention (second object) is particularly suitable as a wrapping sheet for a core that wraps a liquid-retaining absorbent core used in an absorbent article such as a disposable diaper or sanitary napkin. Tissue paper as a wrapping sheet for the core is capable of allowing the release of a flowable substance, including not only a relatively low viscosity fluid such as urea, but also relatively high viscosity secretions, such as loose stools, through it and soaking into the absorbent core, thereby contributing to the improvement of preventing leakage from the absorbent article.

[0093] An absorbent article of the invention using tissue paper of the invention (second object) is illustrated by an absorbent article comprising an absorbent core and a wrapping sheet for a core that wraps an absorbent core in which the wrapping sheet for the core is a tissue paper of the invention (second object) ) In particular, the absorbent article of the invention comprises a liquid-permeable topsheet forming a skin-facing surface of the absorbent article, a liquid-impervious or water-repellent backsheet forming a non-skinning surface of the absorbent article, and an absorbent member interposed between the two sheets in which the absorbent element comprises an absorbent core and a wrapping sheet for the core (tissue paper according to the second object of the invention). The wrapping sheet for the core (tissue paper according to the second object of the invention) preferably covers at least the skin-facing side and the non-skin-facing side of the absorbent core. As used herein, the term “skin side” refers to the side of the absorbent article or an element included in the absorbent article that faces the skin of the wearer when the absorbent article is worn, and the term “non-skin side” refers to the side an absorbent article or an element included in an absorbent article that faces away from the skin of the wearer (clothing side) when the absorbent article is worn. The top sheet, back sheet and absorbent core can be any of what is commonly used in absorbent articles of this type. Illustrative absorbent articles of the invention include flat or worn disposable diapers, sanitary napkins, and urological pads.

[0094] Although the second aspect of the invention is described as being independent of the first aspect of the invention, it may be an embodiment of the first aspect of the invention. That is, the second object of the invention can be (A) tissue paper, preferably containing bleached softwood Kraft pulp, which has a grinding degree of 400 to 550 ml, containing two or more strength enhancing additives, and having a bulk of from 10 up to 14.5 g / m ² , density from 0.05 to 0.2 g / cm ³ and creping degree from 5% to 30%, or (B) tissue paper, mainly containing a structure of two types of hydrophilic cellulose fibers, fibers differing in roughness, and containing an additive that increases where two types of hydrophilic cellulose fibers are the first cellulosic mass, which has a coarse fiber from 0.13 to 0.16 mg / m, and the second cellulosic mass, which has a coarse fiber from 0.17 to 0.20 mg / m , the difference in the coarseness of the fiber between the first and second pulp is from 0.01 to 0.07 mg / m, the structure has a degree of grinding from 400 to 550 ml (they are essential features for the first object of the invention), tissue paper (B) additionally has the following essential features according to the second object of the invention Niya, ie mainly contains bleached kraft pulp of soft wood species, which has a grinding degree of 400 to 550 ml, contains two or more additives that increase strength, has a bulk of 10 to 14.5 g / m ² , density of 0.05 to 0 , 2 g / cm ³ and the degree of creping from 5% to 30%. In tissue paper (B), “a structure of two types of hydrophilic cellulose fibers differing in fiber coarseness” (the structure has a degree of grinding from 400 to 550 ml), which is one of the essential features of the first object, mainly contains bleached kraft pulp from soft wood, which has a degree of grinding from 400 to 550 ml, as one of the essential features of the second object. Differently expressed, the first and second pulp, as precisely defined in relation to the first object, are bleached softwood pulp kraft pulp (NBKP).

[0095] A method for producing tissue paper according to a third aspect of the invention is described below based on its preferred embodiment with reference to the accompanying drawings.

Figure 2 schematically illustrates an example of an apparatus that can be used to implement a method for producing tissue paper in accordance with the invention (third object), which is designated as apparatus 1A. The apparatus 1A shown in FIG. 2 is mainly divided into a raw material receiving part 2 and a paper making part 7. A raw material receiving part 2 is intended to produce paper raw materials by adding softwood (a) an additive to increase the strength of wet paper in bleached kraft pulp , (b) a low molecular weight additive that increases the strength of dry paper, and (c) a high molecular weight additive that increases the strength of dry paper (c). The papermaking part 7 is intended to produce the desired tissue paper by drying the raw materials obtained in the raw material receiving part 2 to form a fibrous layer and drying the fibrous layer.

The Y direction shown in FIGS. 2-5 is a machine direction (MD) during the manufacture of tissue paper.

[0096] As shown in FIG. 2, the raw material receiving part of apparatus 1A has a cellulose breaker 21 in the process flow direction in which the crude NBKP is carefully disintegrated to obtain an aqueous suspension, and a refiner 23 in which the crude NBKP is broken, the cellulose breaker 21 and the refiner 23 is connected through a line 22 equipped with a conveying pump 24 for transporting the aqueous suspension from the pulp breaker 21 to the refiner 23.

[0097] As shown in FIG. 2, the raw material receiving part of apparatus 1A has, downstream of the refiner 23, a first raw material storage tank 32 in which a suspension is added to which a wet strength improver (a) has been added. containing a cationic polymer having a cationic group. The refiner 23 and the first raw material storage tank 32 are connected through a line 31 equipped with a wet paper strength adding unit 33 for adding a wet paper strength increasing additive (a). The first raw material storage tank 32 is designed to thoroughly mix the NBKP slurry into which a wet strength improver (a) has been added.

[0098] As shown in FIG. 2, the raw material receiving part of apparatus 1A has, downstream of the first raw material storage tank 32, a second raw material storage tank 42 in which the NBKP slurry is added to which a strength improver has been added. wet paper (a) containing a cationic polymer having a cationic group and to which a low molecular weight additive has been added to increase the strength of dry paper (b) containing a low molecular weight anionic polymer having an anionic group and having a weighted average mass (molecular weight) from 2000 to 500000. The first tank 32 for storing raw materials and the second tank 42 for storing raw materials are connected through line 41, equipped with a unit 43 for adding a low molecular weight additive that increases the strength of dry paper, to add a low molecular weight additive that increases the strength of dry paper (b), and a pump 44 for delivering the suspension from the first tank 32 for storing raw materials to the second tank 42 for storing raw materials. The second tank 42 for storing raw materials is made with the possibility of thoroughly mixing the suspension, to which was added an additive that increases the strength of wet paper (a), and a low molecular weight additive that increases the strength of dry paper (b).

[0099] As shown in FIG. 2, the raw material receiving part 2 of apparatus 1A has a mass distribution box 52 that has a variable-sized outlet in order to vary the flow rate connected to the downstream side of the second raw material storage tank 42 through the line 51. By varying the size of the outlet of the mass distribution box 52 in order to change the flow rate, the bulk of the tissue paper obtained is varied. For example, the outlet size of the distribution box 52 can be reduced in order to thereby reduce the flow rate in order to reduce the bulk of the tissue paper produced. Line 51 is equipped with a pump 53 for delivering the slurry from the second tank 42 for storing raw materials to the mass distribution box 52.

[0100] As shown, the raw material receiving part 2 of the apparatus 1A has a filter screen 62 for filtering the raw materials in order to remove fiber flakes and the like. and make the raw material uniform, which is connected to the downstream side of the mass distribution box 52 through line 61. Line 61 is equipped, in the direction of the process stream, with a dilution water supply unit for supplying dilution water in order to dilute the feed, with a mixing pump 63 which generates turbulence during delivery in line 61 in order to break down the flakes of fibers and the like, thereby making the raw material uniform, and a block 65 for adding a high molecular weight additive that increases the strength of dry paper, to add a high molecular weight anionic polymer having an anionic group and having a weighted average molecular weight (molecular weight) of from 5,000,000 to 30,000,000.

[0101] As shown in FIG. 2, the raw material receiving part 2 of apparatus 1A has a paper making part 7 connected to the downstream side of the filter screen 62 through line 66, in which the raw material obtained in the raw material receiving part 2 is dried to form the fibrous layer, and the fibrous layer is dried in order to obtain tissue paper. The papermaking part 7 may be a known papermaking machine, typically comprising a shaper, a netting part, a pressing part, a dry part and a part of a winding device. The shaper is designed to adjust the raw materials obtained in part 2 of the receipt of raw materials to a predetermined concentration and to supply the adjusted raw materials to the grid part. The mesh portion is intended to form a fibrous layer of raw materials supplied from the former to the woven mesh. The press part is designed to squeeze and remove water from the fibrous layer between the rolls of the woolen press to provide wet paper. The dry portion is intended to dry wet paper formed in the press portion in one or a plurality of dryers, which may contain a dewatering dryer. Part of the winding device is designed to wind dried paper (tissue paper) from the dry part.

[0102] A method for producing tissue paper in accordance with the invention (third object) is described based on an embodiment using apparatus 1A with reference to FIG. 2.

A method for producing tissue paper according to the invention (third object) is a method for producing tissue paper with a bulk of 30 g / m ² or less, comprising the steps of forming a wet fibrous layer from a raw material obtained from papermaking material containing bleached softwood kraft pulp, and drying the wet fibrous layer.

In the present embodiment, the feed is obtained by adding to the suspension of bleached Kraft pulp of softwood (a) a wet paper strength improver that contains a cationic polymer having a cationic group, followed by (b) a low molecular weight dry paper strength improver followed by the addition of (c) a high molecular weight additive to increase the strength of dry paper. The following describes in detail the receipt of raw materials.

[0103] Raw bleached softwood Kraft pulp is placed in a pulp breaker 21 and thoroughly disintegrated therein. The softwood bleached kraft pulp (NBKP) to be used may be any type of NBKP that is commonly used in this type of paper. The bleached pulp obtained by the ECF method (ECF = no elemental chlorine) or TCF (TCF = completely chlorine free), in which the chlorine compound is not or not substantially added during the process, can be used as NBKP. NBKP is preferably placed in a pulp breaker in such an amount as to obtain a concentration of NBKP from 0.5 to 5.0% by weight, more preferably from 1.0 to 4.0% by weight, in the resulting suspension.

[0104] NBKP for use in the present embodiment preferably has a fiber coarseness of from 0.1 to 0.3 mg / m, more preferably from 0.12 to 0.25 mg / m. "Fiber coarseness" is a measure used to represent the thickness of a fiber with an uneven thickness, such as wood pulp. NBKP for use in the invention preferably has an average fiber length of from 1 to 4 mm, more preferably from 2 to 3 mm. The coarseness of the fiber and the average fiber length are measured by the previously described methods.

[0105] A suspension of carefully disintegrated NBKP in the pulp breaker 21 is transported by pump 24 through line 22 to refiner 23, in which NBKP is broken in suspension. Partitioning is preferably carried out using a pulp breaker 21 and a refiner 23 until the NBKP has a grinding degree of 650 ml or less. As used herein, the term “degree of grinding” refers to Canadian Standard Freeness (C.S.F.), which is precisely defined in JIS P8121 and which is a measure representing the degree of pulp breakdown (mechanical breaking and crushing of pulp in the presence of water). A lower degree of grinding indicates a higher degree of breakage, generally indicating that the fibers have undergone more damage and fibrillation due to the breakage. NBKP, in which the degree of grinding is in the specified range, are ready to entangle with each other due to deep fibrillation. Therefore, even if the number of bonds between fibers in tissue paper is reduced as a result of a decrease in the bulk (or density), which is aimed at improving liquid permeability, the strength of bonds between fibers is still high compared to NBKP, which has a degree of grinding greater than 650 ml, which indicates less deep fibrillation. Thus, as long as the degree of grinding is 650 ml or less, tissue paper, consisting mainly of such NBKP, exhibits satisfactory strength characteristics.

[0106] The degree of grinding of NBKP for use in the present embodiment is preferably 300 to 650 ml, more preferably 450 to 550 ml, even more preferably 480 to 530 ml. The effect of fiber entanglement on improving strength reaches a maximum at a grinding degree of 300 ml, and if the grinding degree is less than 300 ml, fiber cutting is accelerated, which can lead to a delay in the passage of liquid.

[0107] Preferably, the tissue paper obtained using the present embodiment preferably contains NBKP having a milling degree of 300 to 650 ml. As used herein, the phrase “predominantly contains” is intended to mean that the content of NBKP, the degree of grinding of which is in the specified range, is at least 50% by weight. In order to achieve good strength characteristics, the NPKP content is preferably from 50 to 100% by mass, more preferably from 80 to 100% by mass.

[0108] The feed to be placed in the pulp breaker 21 may contain fibers other than NBKP. Other fibers may not be hydrophilic cellulose fibers, such as NBKP. Illustrative other fibers include wood pulp, such as bleached hardwood kraft pulp (LBKP), bleached sulphite pulp pulp of softwood (NBSP), and thermomechanical pulp (TMP); bast fibers, for example, from paper mulberry, Edgeworthia chrysantha and Diplomorpha sikokiana; non-wood mass, for example, from straw, bamboo, kenaf and jute; and synthetic fibers, such as polyester fibers, viscose fibers and acrylic fibers. The content of other fibers in the tissue paper obtained using the present embodiment is preferably not more than 50% by weight.

[0109] A suspension of carefully broken NBKP coming from the pulp breaker 21 and refiner 23 is delivered to the first tank 32 for storing raw materials. While the slurry is delivered to the first raw material storage tank 32, a wet paper strength improver (a) is added to it using the wet strength improver adding unit 33. The wet paper strength improver (a) and the NBKP slurry are thoroughly mixed by stirring in the first raw material storage tank 32.

[0110] Examples of a strength improver for a wet paper containing a cationic polymer that has a cationic group include a polyamide-polyamine epichlorohydrin resin (epoxidized polyamide-polyamine resin (PAE)), urea-formaldehyde resin, melamine-formaldehyde resin, dialdehyde, polyethyleneamine and oxymethylated polyamide. They can be used either individually or in combination of two or more of them. Of these, epoxidized polyamide-polyamine resin (PAE) is particularly preferred from the point of view of a wide pH range suitable for use in papermaking and the absence of formalin, which reduces the environmental load.

[0111] The wet paper strength improver (a) is preferably added in an amount of from 0.1 to 2.0% by weight, more preferably from 0.2 to 1.5% by weight, based on the dry weight of all fibers, forming tissue paper obtained using the present embodiment, due to technological contamination and the strength of wet paper. When using epoxidized polyamide-polyamine resin (PAE) as the only additive to increase the strength of wet paper (a), it is preferably added in an amount of from 0.5 to 1.5% by weight, more preferably from 0.6 to 1.2 % by weight, based on the dry weight of all the fibers forming the tissue paper obtained using the present embodiment.

[0112] The step of obtaining raw materials further includes adding a low molecular weight additive that increases the strength of dry paper (b), followed by dilution, followed by the addition of a high molecular weight additive that increases the strength of dry paper (c), followed by homogenization using a mixing pump 64 and filter mesh 62. Each operation is described specifically.

[0113] While the NBKP slurry having the wet paper strength improver (a) added and mixed by thoroughly mixing in the first raw material storage tank 32 is delivered by pump 44 through line 41 to the second raw material storage tank 42, a low molecular weight dry paper strength enhancing additive (b) is added to the slurry using a low molecular weight dry weight strength improver adding unit 43. In a second raw material storage tank 42, a low molecular weight strength improver (b), a wet strength improver (a), and NBKP slurry are mixed by thorough mixing.

[0114] The low molecular weight dry paper strength enhancing additive (b) is a low molecular weight anionic polymer that has an anionic group and has a weight average molecular weight (molecular weight) of from 2,000 to 500,000. From the viewpoint of adhering to the Yankee dryer and forming, the low molecular weight anionic a polymer having an anionic group and a molecular weight of from 5,000 to 450,000 is preferred, and a low molecular weight anionic polymer having an anionic group and a molecular weight of from 10,000 to 400,000 is more preferred. . Illustrative low molecular weight dry paper strength improvers (b) include carboxymethyl cellulose salt (CMC) and polyvinyl alcohol (PVA), which can be used either singly or in combination of two or more of them. Preferred of these low molecular weight dry paper strength additives are CMC salts from the point of view of widespread use and solubility. The degree of substitution (degree of esterification) of the CMC, which theoretically can be up to three, is preferably in the range from 0.5 to 1.5 in terms of performance. The CMC salt is usually a sodium salt.

[0115] A low molecular weight dry paper strength improver (b) is preferably added in an amount of 0.01 to 0.5% by weight, more preferably 0.1 to 0.3% by weight, based on the dry weight of all fibers forming tissue paper obtained using the present embodiment due to technological contamination and the strength of dry paper. When using CMC salt as the only low molecular weight additive to increase the strength of dry paper (b), it is preferably added in an amount of from 0.05 to 0.5% by weight, more preferably from 0.1 to 0.3% by weight, based on the dry weight of all the fibers forming the tissue paper obtained using the present embodiment.

In the manufacture of paper with a low base weight, such as tissue paper, the addition of a low molecular weight additive that increases the strength of dry paper (b), in a concentration of only 0.1 to 0.3% by weight, probably gives only insufficient paper strength, since the low molecular weight additive , increasing the strength of dry paper (b), leaves the pulp during drying. An increase in the amount (concentration) of a low molecular weight additive that increases the strength of dry paper (b) will increase the strength of the paper, but will cause concern about technological contamination. Therefore, the amount of the low molecular weight dry paper strength improver (b) to be added should be limited, so it is recommended that another dry paper strength improver be used in combination. Then, in the method for manufacturing tissue paper of the invention, a high molecular weight dry paper strength improver (c) is added as described below. The present embodiment is described in more detail.

[0116] As shown in FIG. 2, the NBKP slurry, which has a wet strength enhancing additive (a) and a low molecular weight dry weight enhancing additive (b), added and mixed by thorough mixing, are pumped through a pump 53 through a line 51 to the mass distribution box 52. The output size of the mass distribution box 52 is varied in order to adjust the flow rate so as to obtain tissue paper that has a desired bulk (30 g / m ² or less).

[0117] The NBKP suspension, which contains an additive that increases the strength of wet paper (a), and a low molecular weight additive that increases the strength of dry paper (b), and has an adjusted flow rate, is delivered via line 61 to filter mesh 62. During delivery, the suspension diluted with a dilution water supply using a dilution block water supply 63. The NBKP suspension is preferably diluted to a concentration of from 0.01 to 1.0% by weight, more preferably from 0.05 to 0.5% by weight.

[0118] The mixing pump 64 thus delivers a diluted NBKP slurry, which contains an additive that increases the strength of wet paper (a), and a low molecular weight additive that increases the strength of dry paper (b), to the filter screen 62, while creating turbulence.

[0119] Subsequently, a high molecular weight dry paper strength improver (c) is added to the NBKP slurry containing a wet paper strength improver (a) and a low molecular weight dry paper strength improver (b) is delivered with turbulence using block 65 adding high molecular weight additives that increase the strength of dry paper, and sent to the filter mesh 62. Anionic high molecular weight additives that increase the strength of dry paper (c) adheres to the fibers of the pulp, which has a cationic an additive that increases the strength of the wet paper (a) deposited on them, while the anionic low molecular weight additive is entangled, which increases the strength of the dry paper (b), on them to form inlays, which are collected by the electric charges of the anionic high molecular weight additive, which increases the strength dry paper (c) in flakes. In the present embodiment, the turbulence created by the mixing pump 64 disintegrates the flakes of inlays in order to provide uniform paper stock, which is less likely to form a poor texture. In the present embodiment, the flakes are also removed by filter mesh 62, which further prevents poor formation.

[0120] As previously established, the addition of a high molecular weight additive that increases the strength of dry paper (c) is necessary from the point of view of improving the retention of pulp, an additive that increases the strength of wet paper (a), and a low molecular weight additive that increases the strength of dry paper (b). The high molecular weight dry paper enhancer (c) is a high molecular weight polymer that has an anionic group and has a molecular weight of 5,000,000 to 30,000,000. The high molecular weight dry paper improver (c) is preferably an acrylic polyacrylamide resin (PAM), which has a molecular weight of from 8,000,000 to 2,000,000 and contains from 0.1 to 80 mol% of sodium acrylate unit, more preferably PAM, which has a molecular weight of from 6,000,000 to 20,000,000 and contains from 1 to 50 mol% of sodium acrylate unit.

[0121] A high molecular weight dry paper strength improver (c) is preferably added in an amount of from 0.001 to 0.1% by weight, more preferably from 0.01 to 0.08% by weight, based on the dry weight of all fibers forming tissue paper obtained using the present embodiment, in the interest of strength and the formation of dry paper. When PAM is used as a high molecular weight additive to increase the strength of dry paper (c), it is preferably added in an amount of from 0.001 to 0.1% by weight, more preferably from 0.02 to 0.05% by weight, based on the dry weight of all fibers forming tissue paper obtained using the present embodiment.

[0122] The ratio of the weight of the wet strength improver (a) to one type added to the total weight of the added low molecular weight dry strength improver (b) and the added high molecular weight dry strength improver (c) is preferably from 0.5 to 10, more preferably 1 to 5.

[0123] The flake-free raw material is sent through line 66 to the paper part 7, where it is dried and dried in order to make tissue paper. More specifically, the concentration of the feedstock obtained in feedstock receiving part 2 is adjusted as developed in the former in the paper part 7. Raw material from the former is fed to the wire mesh to form a fibrous layer in the net part in the paper part 7. The fibrous layer formed in the net part , squeezed and dehydrated in order to form a wet paper web in the press part of the paper part 7. The wet paper web formed in the press part is dried in a dry hour and the paper part 7 using, for example, dryers or Yankee dryers flowing air to produce tissue paper web. The canvas tissue paper is taken, for example, in the part of the winding device of the paper part 7.

[0124] A method for manufacturing tissue paper of the present embodiment is suitable for manufacturing tissue paper with a bulk of 30 g / m ² or less. In the present embodiment, the bulk of the tissue paper to be obtained is corrected to a desired value (30 g / m ² or less) by controlling the flow rate of the feed using a distribution box 52 of the feed receiving part 2 or controlling the concentration of the feed in the shaper of the paper part 7. B In the interest of improving liquid permeability, the bulk is preferably from 10 to 14.5 g / m ² , more preferably from 11 to 14 g / m ² . The density of tissue paper in the same interests is preferably from 0.05 to 0.2 g / cm ³ , more preferably from 0.1 to 0.2 g / cm ³ . Although there may be a concern that such low bulk and density can lead to a decrease in paper strength, this concern in the present embodiment is eliminated by, as indicated, (1) adding a strength improver to wet paper (a ) containing a cationic polymer that has a cationic group in the NBKP suspension, followed by the addition of a low molecular weight additive to increase the strength of dry paper (b), and (2) the addition of a low molecular weight additive to increase the strength of dry paper (b), followed by uet addition of high molecular weight enhancing additive dry strength of paper (c). With a bulk of less than 10 g / m ² or a density of less than 0.05 g / cm ³ , a substantial decrease in paper strength can occur. With a bulk of more than 30 g / m ² or a density of more than 0.2 g / cm ³ , one may not expect a sufficient effect of increasing liquid permeability. The bulk and density of tissue paper is measured by the methods described above.

[0125] The tissue paper obtained in the present embodiment is a creped tissue paper. The degree of creping is preferably 5% or more, more preferably from 5% to 30%. In the present embodiment, the creping is preferably carried out by a dry creping method in which a dry fiber network (tissue paper) adhering, for example, to a Yankee dryer in the drying part, is scraped off with a doctor blade and the like. The degree of creping is determined by the previously described method.

[0126] Creped tissue paper exhibits higher liquid permeability than uncreated tissue paper. The higher the degree of creping, the higher the liquid permeability becomes. However, it is noted that an increase in the degree of creping tends to lead to a decrease in strength characteristics (for example, tensile strength). Based on these findings, the creping rate of the creped tissue paper obtained in the present embodiment is preferably 5 to 30%, more preferably 5 to 20%, even more preferably 7 to 15%, to balance fluid permeability and strength characteristics .

[0127] The tissue paper obtained in the present embodiment has a dry tensile strength of 60 cN / g / cm ² or more, preferably 60 to 150 cN / g / cm ² , more preferably 60 to 100 cN / g / cm ² , even more preferably 60 to 90 cN / g / cm ² , in MD and 13 cN / g / cm ² or more, preferably 13 to 50 cN / g / cm ² , more preferably 13 to 40 cN / g / cm ² , even more preferably 13 to 30 cN / g / cm ² , in a CD orthogonal to MD. Tissue paper whose dry tensile strength in MD and CD falls within the respective indicated ranges exhibits sufficient strength for practical use. For example, when applied to a core wrapping sheet that wraps an absorbent core for use in an absorbent article such as a disposable diaper, the core wrapping sheet (tissue paper) is less likely to tear or cause a similar problem during the manufacture of the absorbent article. The unit "cN / g / cm ² " as used here to represent dry tensile strength is equal to the unit "cN / 25 mm" as used with reference to the first object of the invention.

[0128] The tissue paper obtained in the present embodiment has a wet tensile strength of 13 cN / g / cm ² or more, preferably from 13 to 60 cN / g / cm ² , more preferably from 13 to 50 cN / g / cm ² , even more preferably from 13 to 30 cN / g / cm ² , in MD and 5 cN / g / cm ² or more, preferably from 5 to 20 cN / g / cm ² , more preferably from 5 to 15 cN / g / cm ² , even more preferably 5 to 12 cN / g / cm ² , in CD.

Tissue paper in which the wet tensile strength in MD and CD falls within the respective indicated ranges exhibits sufficient strength for practical use. When applied, for example, to a disposable diaper, tissue paper is less likely to cause a problem. Dry tensile strength is determined by the previously described method. Wet tensile strength is determined as described below.

[0129] A method for determining wet tensile strength:

A tissue paper of the same size as that used in the method for determining dry tensile strength is immersed in a sufficient amount of water for 5 seconds and dried for 10 seconds. Wet tissue paper is tested using the same tensile tester and the same method as in the method for determining dry tensile strength to obtain maximum tensile strength.

[0130] The tissue paper obtained in the present embodiment has a liquid transit time of 3 seconds or shorter, preferably from 0.2 to 3 seconds, more preferably from 0.5 to 2 seconds, as measured by the method described above. The shorter the fluid transit time, the higher the liquid permeability (higher score). Tissue paper, which has a liquid transit time in this range, exhibits excellent liquid permeability. For example, when applied to a core wrapping sheet that wraps an absorbent core for use in an absorbent article, tissue paper allows emitted body fluid, such as urine, to quickly pass through and absorb into the absorbent core, and thus, it is expected that provides an absorbent product with improved leakage prevention.

[0131] Having good strength characteristics (tensile strength) and excellent liquid permeability, the tissue paper obtained in the present embodiment is suitable for various applications in which such characteristics give an advantage. The tissue paper obtained in the present embodiment is particularly suitable as a wrapping sheet for a core that wraps a liquid-retaining absorbent core used in an absorbent article, such as a disposable diaper or sanitary napkin. The tissue paper as a wrapping sheet for the core can allow the fluid to be released, including not only a relatively low viscosity fluid such as urea, but also relatively high viscosity secretions, such as loose stools, to pass through and absorb into the absorbent core. thereby contributing to the improvement of preventing leakage from the absorbent article.

[0132] The tissue paper obtained in the present embodiment may contain components other than fibers, such as NBKP, and strength improvers (a), (b), and (c) as described above. Other components include papermaking materials and additives commonly used in papermaking, such as fillers (e.g. calcium carbonate and talc), dyes, color pigments, perfumes, antimicrobials, pH adjusters, retention aids, water-resistant additives, and antifoam agents. You can use one or more than one of them.

[0133] A method for manufacturing tissue paper according to the invention (third object) is not limited to the embodiment described above. For example, although in the above embodiment, the addition of a low molecular weight dry paper strength improver (b) is preceded by the addition of a wet paper strength improver (a) containing a cationic polymer that has a cationic group to the NBKP slurry , you should add a high molecular weight additive that increases the strength of dry paper (c), a low molecular weight additive that increases the strength of dry paper (b), and a high molecular weight additive that increases the strength of dry paper (c), you can add simultaneously with NBKP slurry after adding the additive, the wet paper strength improver (a), which comprises a cationic polymer which has a cationic group. The simultaneous addition of a low molecular weight additive that increases the strength of dry paper (b) and a high molecular weight additive that increases the strength of dry paper (c) simplifies the step of adding additives that increase the strength, thereby making the production line more compact.

[0134] The apparatus 1A shown in FIG. 2 can be replaced by the apparatus 1B shown in FIG. 3 as an apparatus for use in the invention (third object). The apparatus 1B of FIG. 3 differs from the apparatus 1A of FIG. 2 by the position of the block 65 for adding a high molecular weight additive that increases the strength of dry paper. The apparatus 1B of FIG. 3 has, in the flow direction, a block 65 for adding a high molecular weight dry paper strength improver, a diluting water supply unit 63, and a mixing pump 64 in a line 61 connecting the distribution box 52 and the filter screen 62. An embodiment is expected using apparatus 1B shown in FIG. 3 will produce the same effects as obtained in the embodiment using apparatus 1A of FIG. 2.

[0135] The apparatus 1A shown in FIG. 2 can be replaced by the apparatus 1C shown in FIG. 4 as an apparatus for use in the invention (third object). The apparatus 1C shown in FIG. 4 differs from the apparatus 1A in FIG. 2 in that the mixing pump 64 is not provided and that the position of the block 65 for adding a high molecular weight additive to increase the strength of dry paper is changed. In particular, the apparatus 1C of FIG. 4 has a block 65 for adding a high molecular weight dry paper strength improver in line 66 connecting the filter screen 62 and the paper part 7. An embodiment using the apparatus 1C of FIG. 4 is expected. will create the same effects as obtained in the embodiment using apparatus 1A of FIG. 2. Although apparatus 1C, as shown in FIG. 4, does not have a mixing pump 64, the filter screen 62 can be replaced with a mixing pump 64.

[0136] The apparatus 1A shown in FIG. 2 can be replaced by the apparatus 1D shown in FIG. 5 as an apparatus for use in the invention (third object). The apparatus 1D shown in Fig. 5 differs from the apparatus 1A of Fig. 2 in that the second tank 42 for storing raw materials, the line 51 and the pump 53 are not provided, and that the position of the adding block 43 of the low molecular weight additive increasing the strength of the dry paper is changed. In particular, the apparatus 1D of FIG. 5 has a block 43 adding a low molecular weight additive that increases the strength of dry paper, provided along the line of the block 65 to add a high molecular weight additive that increases the strength of dry paper. In an embodiment using the 1D apparatus, a NBKP slurry having a wet paper strength improver (a) added to and mixed therein by thorough mixing in the first raw material storage tank 32 is sent to the distribution box 52 via line 41 via pump 44. Then, while the suspension, whose flow rate is adjusted by means of the mass distribution box 52, is delivered via line 61 to the filter screen 62, the suspension is first diluted using feed water y to dilute block 63 and then cause it to flow in the direction of the filter screen 62 with turbulence caused by the mixing pump 64. In apparatus 1D, when a high molecular weight dry paper strength improver (c) is added using a high molecular weight dry matter improver add block 65 paper, in NBKP slurry, having an additive that increases the strength of wet paper (a), added to it and flowing with turbulence, a low molecular weight additive that increases the strength of dry paper (b) is mixed in high omolekulyarnuyu enhancing additive dry strength of paper (a), be added using the addition block 43 low molecular weight enhancing additive dry paper strength. The embodiment using the apparatus 1D of FIG. 5 is expected to produce the same effects as those obtained in the embodiment using the apparatus 1A of FIG. 2.

[0137] The following describes an absorbent article according to a fourth aspect of the invention in relation to a disposable diaper as its preferred embodiment using the accompanying drawings. The diaper 1 according to the present embodiment is a flat disposable diaper. As shown in FIGS. 6 and 7, the diaper 1 comprises a liquid permeable topsheet 12, which forms a surface facing the skin, repellents impermeable to liquids or water (hereinafter, inclusively referred to as liquid imperviously), backsheet 13 that forms unreversed to the skin is a surface and an absorbent element 14 located between the sheets 12 and 13. The diapers 1 are essentially oblong. Each of the top sheet 12, the back sheet 13 and the absorbent element 14 is oblong and longer in the X direction. Each of the top sheet 12 and the back sheet 13 is larger than the absorbent element 14 and extends beyond the periphery of the absorbent element 14. The top sheet 12 is already than the back sheet 13 in the transverse direction Y, as shown in Fig.7.

[0138] As shown in FIG. 6, the diaper 1 has a back portion A adapted to be worn around the back of the wearer, a front portion B adapted to be worn around the front of the wearer, and a crotch portion C adapted to be worn around the wearer's crotch. The crotch part C is located in the longitudinal (in the X direction) middle part of the diaper 1. The edges of both lateral sides of the crotch part C are concave inward so that the diaper 1 has an hourglass shape and its longitudinal middle part is narrowed in a plan view, as shown in FIG. .6.

[0139] In the description of the invention, the longitudinal direction is the direction along the longer side of the absorbent article (disposable diaper) or the element forming the absorbent article, and the lateral or lateral direction is the direction perpendicular to the longitudinal direction. 6-8, the direction indicated by X is the longitudinal direction of the diaper 1 (absorbent member 140), and the direction indicated by Y is the lateral direction of the diaper 1 (absorbent member 140). The phrase “skin side” represents the side of the absorbent article (disposable diaper) or the element forming the absorbent article that faces the skin of the wearer while wearing, and the phrase “non-skin side” represents the side of the absorbent article (disposable diaper) or element forming an absorbent article that faces away from the skin (side facing the garment) while wearing.

[0140] As shown in FIGS. 6 and 7, a side sheet 162 having elastic members 161 fixed in their stretched state along one side thereof is provided along each lateral side of the diaper 1 so as to form a pair of upright cuffs while worn. Elastic elements 163 are located in the crotch portion C along each longitudinally extending leg portion adapted to be worn around the wearer's leg. While wearing the diaper 1, the elastic members 163 are contacted to form a pair of leg assemblies. As shown in FIG. 7, a pair of side sheets 162 and 162, a top sheet 12, an absorbent member 14, elastic members 163 and a back sheet 13 are joined together using known bonding means, such as hot-melt adhesive.

[0141] As shown in FIG. 6, the waist elastic member 164 is located along the edge of the waist hole of each of the rear portion A and front portion B to form a waist assembly. The waist elastic element is in the form of a tape and is fixedly located between the top sheet 12 and the back sheet 13 over substantially the entire width of the diaper 1 in the transverse direction of the diaper 1. A plurality of elastic elements forming the belted assemblies 165 are located in both lateral regions of the rear part A to form double-sided belted assemblies. The sub-belt-forming elastic members 165 are arranged in a substantially straight linear configuration extending in the transverse direction Y, and are fixedly held between the top sheet 12 and the back sheet 13.

[0142] As shown in FIG. 6, the diaper 1 has a pair of fastening tapes 18 and 18 provided along both lateral edges extending in the longitudinal direction X, the rear part A. More specifically, each of the rear part B and the front part B has a side flap 17 provided along each lateral side thereof and extending in the longitudinal direction X, each side flap 17 extending laterally outward from each longitudinally extending edge of the lateral side of the absorbent member 14. A fastening tape 18 is attached to each side flap 17 so that it la laterally outward. The fastening tape 18 has an attachable portion 181 formed on the male component of the mechanical fastener.

[0143] The diaper 1 has a seating zone 19 formed from a female component of the mechanical fastener provided on the non-skin side of the front portion B. A landing zone 19 is provided by attaching the female component of the mechanical fastener to the non-skin side of the back sheet 13 via a known connecting means (for example, adhesive bonding or heat sealing). The attachment portion 181 of the attachment tape 18 can be detachably attached to the seating area.

[0144] The absorbent element 14 is described in more detail. As shown in FIGS. 6 and 7, the absorbent member 4 consists of an absorbent core 140 and a wrapping sheet for the core that wraps the absorbent core 140. The absorbent core 140 is elongated in the longitudinal direction X of the diaper 1 and has its narrowed middle portion in the longitudinal direction.

[0145] The absorbent core 140 is made of hydrophilic fibers and an absorbent polymer. Hydrophilic fibers are not particularly limited as long as they have a hydrophilic surface and are able to form a sheet in which they have a high degree of freedom of movement from each other when wet. Illustrative examples of such hydrophilic fibers include natural cellulosic fibers, such as wood pulp, for example, softwood kraft pulp and hardwood kraft pulp, and non-wood pulp, for example, cotton pulp and straw pulp; regenerated cellulose fibers, such as viscose and copper-ammonia fiber; hydrophilic synthetic fibers such as polyvinyl alcohol fiber and polyacrylonitrile fiber; and surfactant-hydrophilized synthetic fibers, such as polyethylene terephthalate (PET) fiber, polyethylene (PE) fiber, polypropylene (PP) fiber, and polyester fiber. These fibers can be used either individually or as a mixture of two or more of them.

[0146] The absorbent polymer may be any of those commonly used in the art. Illustrative examples include sodium polyacrylate, a copolymer of acrylic acid-vinyl alcohol, a crosslinked sodium polyacrylate, a grafted polymer of starch-acrylic acid, a copolymer of isobutylene-maleic anhydride and its saponification product, potassium polyacrylate and cesium polyacrylate. These polymers can be used either individually or as a mixture of two or more of them. The absorbent polymer is usually in particulate form, but may be fibrous. Particulate absorbent polymers include, according to shape, amorphous type, lump type, bale type, spherical agglomerate type, and spherical type, any of which can be used.

[0147] The total proportion of hydrophilic fibers and absorbent polymer in the absorbent core 140 is, for example, from 70 to 100% by mass, preferably from 85 to 100% by mass, more preferably from 95 to 100% by mass. The ratio of hydrophilic fibers to the absorbent polymer is preferably from 1/9 to 9/1, more preferably from 3/7 to 7/3, to provide sufficient retention and capacity for urine, loose stool, and the like. If necessary, the absorbent core 140 may further contain components other than hydrophilic fibers and an absorbent polymer, such as pH buffers, hydrophilic powder, various additives, including deodorants, and non-hydrophilic fibers.

[0148] The absorbent core 140 preferably has a bulk of 200 to 600 g / m ² , more preferably 300 to 600 g / m ² , to provide sufficient retention and capacity for urine, loose stool, and the like. In the same interest, the density of the absorbent core 140 is preferably from 0.10 to 0.30 g / cm ³ , more preferably from 0.15 to 0.30 g / cm ³ . The thickness of the absorbent core 140 without an applied load is preferably from 1.5 to 3.5 mm, more preferably from 1.7 to 3.0 mm.

[0149] As shown in FIG. 7, the core wrapping sheet 15 comprises a sheet of highly liquid permeable paper (hereinafter referred to as high permeability paper) 151 superimposed on the skin facing side 140a of the absorbent core 140 and low permeable a liquid sheet (hereinafter referred to as a low permeability sheet) 152, which is placed on the non-skin side 140b of the absorbent core 140 and wrapped around to cover both lateral side portions 140s extending into rodolnom direction of the absorbent core 140 (this method the wrapping sheet 152 with low permeability are referred to as no location on the skin facing side 140b of the absorbent core 140). More specifically, the core wrapping sheet 15 comprises two sheets 151 and 152 that differ in size in the transverse direction Y. One of them is high permeability paper 151 that has substantially the same dimensions in the longitudinal direction X and the transverse direction Y, as the absorbent core 140, which has lengths in each direction (the lengths in the X and Y directions indicated here indicate the maximum length in the corresponding direction), and the other is a low permeability sheet 152 that is wider than paper 151 with high permeability. The high permeability paper 151 and the low permeability sheet 152 have the same length in the longitudinal direction X. The high permeability paper 151 covers substantially the entire area of the skin side 140a of the absorbent core 140. The low permeability sheet 152 covers substantially the entire area of the non-reversed to the skin of the side 140b of the absorbent core 140 and goes outward in the transverse direction Y from both side parts 140s of the absorbent core 140, the protruding parts of the low permeability sheet 152 are wrapped around and on top of the paper 1 51 with high permeability applied to the skin side 140a of the absorbent core 140 to cover both longitudinally extending lateral lateral side portions of the high permeability paper 151. The absorbent core 140 may be bonded to the high permeability paper 151 and the low permeability sheet 152 by means of a known bonding agent such as hot melt adhesive.

[0150] One of the main features of the diaper 1 of the present embodiment is that high permeability paper 151 located directly on the skin side 140a of the absorbent core 140 exhibits good strength characteristics and excellent liquid permeability without other elements between them. .

[0151] High permeability paper 151 is designed to have a relatively low bulk and density in order to achieve improved liquid permeability. In particular, the bulk of paper 151 with high permeability is from 8 to 20 g / m ² , preferably from 10 to 14.5 g / m ² , more preferably from 11 to 14 g / m ² , and the density of paper with high permeability is from 0.05 to 0.2 g / cm ³ , preferably from 0.07 to 0.20 g / cm ³ , more preferably from 0.10 to 0.20 g / cm ³ . With a bulk of less than 8 g / m ² or density less than 0.05 g / cm ³ , a substantial decrease in paper strength can occur. With a bulk of more than 20 g / m ² or a density of more than 0.2 g / cm ³ , a sufficient liquid permeability improvement effect cannot be expected. The bulk and density of high permeability paper 151 (core wrapping sheet 15) is determined as follows.

[0152] A method for determining the bulk of a wrapping sheet for a core:

Square samples with a side of 10 cm (area: 100 cm ² ) are cut out of the sample (wrapping sheet for the core), conditioned under certain conditions, precisely defined in JIS P8111. Each sample is weighed using weights having a minimum report of one hundred grams, and the measured mass is divided by area to obtain the bulk of the sample. The average of the main masses of ten samples thus obtained is taken as the main mass of the sample.

[0153] A method for determining the density of a wrapping sheet for a core:

A stack of ten square samples with a side of 20 cm (wrapping sheets for the core) is frozen in liquid nitrogen and cut along the center with a cutter. A sample that does not show a shift on the surface of the slice is selected from ten samples, and the thickness of the selected sample is measured under an optical microscope. In the case of a sample having an uneven surface (for example, crepe paper), as described later in this document, the term “thickness” does not refer to the apparent thickness measured from the deepest trough to the highest peak of the surface profile, but to the true thickness (layer thickness formed from precipitated fibers). The mass W of a square sample with a side of 20 cm, the thickness of which is known, is measured using weights having a minimum report of one hundredth of a gram. The density of the sample is the quotient obtained by dividing the mass W by the volume V of the sample, W / V, where V is calculated using the formula: V = {T × B × B × (100 + A) / 100}, where T is the thickness sample (cm); A represents the degree of creping of the sample (%); and B is the side length of the sample (20 cm). The degree of creping is determined as described above. When the core wrapping sheet sample is not creped (creping degree 0%), A = 0.

[0154] Paper 151 with a low bulk, low density and high permeability has a fluid transit time of 600 seconds or shorter, preferably 400 seconds or shorter, more preferably 300 seconds or shorter, as measured by the method described below. The shorter the fluid transit time, the higher the liquid permeability (higher score). Having excellent liquid permeability, high permeability paper having a liquid transit time in this range allows bodily fluids to be released, including not only a relatively low viscosity fluid such as urine, but also relatively high viscosity excretions such as liquid stool or menstrual blood, pass quickly through it and soak into the absorbent core 40, hardly allowing the fluid to remain on the surface of the absorbent element.

[0155] A method for determining liquid transit time:

As shown in FIG. 1, two cylinders 91 and 92, open at both ends and having an inner diameter of 35 mm, are vertically and concentrically mounted with a sheet S (high permeability paper) to be evaluated which is inserted between them. The upper cylinder 91 and the lower cylinder 92 are preferably connected by means of fitting clips 93 on the annular flanges provided around the lower end of the upper cylinder 91 and the upper end of the lower cylinder 92. The elements indicated by 94 are o-rings made, for example, of rubber and having a through hole of the same shape and inner diameter as the cylinders 91 and 92. Using a sheet S held between the upper and lower cylinders 91 and 92, approximately 10 ± 1 g of high viscosity liquid W , which has a viscosity of 290 MPa · s, is fed into the upper cylinder 91. The viscosity of the liquid W is measured by the following procedure using a CJV5000 vibrating viscometer from A & D Co., Ltd. a sample container containing approximately 10 g of a high viscosity liquid is mounted on a viscometer and the vibrator dad is inserted at the prescribed level. The measuring range is set to 50 mV. The measurement switch is pressed in order to start the measurement. The viscosity is read after 60 seconds from the start of the measurement. The measurement is carried out at 25 ° C.

High viscosity liquid passes through or is absorbed by sheet S and disappears from the upper cylinder 91. The time from the start of pouring high viscosity liquid to the moment when the surface level of the liquid is equal to the surface of sheet S (the surface on the side of the upper cylinder 91) is measured in order to obtain time fluid passage. A high viscosity liquid is obtained by mixing glycerol and ion exchange water in a weight ratio of 94: 6.

[0156] Although the high permeability paper 151 has a liquid transit time of 600 seconds or shorter and exhibits excellent liquid permeability, the low permeability sheet 152 that forms the core wrapping sheet has a time along with the high permeability paper 151 liquid passage exceeding 600 seconds and exhibits low liquid permeability. The absorbent core 140 used in the present embodiment is coated with high permeability paper 151, which has high liquid permeability, on its skin side 140a, which directly accepts emitted bodily fluids, such as loose stools, and low sheet 152 permeability, which has a low liquid permeability, on the opposite non-skin facing side 140b and both lateral side parts 140s.

[0157] The above-described configuration of the core wrapping sheet 15 causes the liquid released and passing through the top sheet 12 to be quickly absorbed into the absorbent member 14 by the action of high permeability paper 151 and absorbed and held in the absorbent core 140. Since the non-skin side 140a and both lateral side portions 140s of the absorbent core 140 are coated with a low permeability sheet 152, even if liquid already absorbed and retained in the absorbent core 140 flows out of it, pre averted its leakage from the absorbent element by means of a sheet 152 of low permeability. Lateral leakage is thus effectively limited. In order to further provide a lateral flow preventing effect of the low permeability sheet 152, the low permeability sheet 152 preferably has a fluid transit time of from 600 to 3000 seconds, more preferably from 600 to 2000 seconds.

[0158] Paper, nonwoven fabric and the like. can be used as sheet 152 with low permeability. Crepe paper is particularly preferred. In order to have a fluid transit time of more than 600 seconds, the low permeability sheet 152 preferably has a bulk of 13 to 20 g / m ² , more preferably 15 to 18 g / m ² ; a density of from 0.10 to 0.30 g / cm ³ , more preferably from 0.20 to 0.25 g / cm ³ ; and the degree of creping from 5% to 20%, more preferably from 7% to 15%. The creping can be carried out by a standard known method. The degree of creping is measured as described above. The word "tissue paper" in the description of the method is considered to be replaced by a "sheet".

[0159] High permeability paper 151 is described further. As previously established, high permeability paper 151, despite having a relatively low bulk and density to improve fluid permeability, exhibits good strength characteristics. In particular, it has a dry tensile strength of 600 cN / 25 mm or more, preferably from 600 to 1500 cN / 25 mm, more preferably from 700 to 1200 cN / 25 mm, in the machine direction (MD) during the manufacture of tissue paper. High permeability paper 151, in which the dry tensile strength in MD is in the indicated range, exhibits sufficient strength for practical use. It is less likely to break or cause a similar problem during the manufacture of the diaper 1 or allows the material forming the absorbent core to flow out.

[0160] From the same point of view, it is preferable that the high permeability paper 151 has a dry tensile strength in a CD orthogonal to MD of 150 cN / 25 mm or more, preferably from 150 to 350 cN / 25 mm, more preferably from 170 up to 300 cN / 25 mm. Dry tensile strength is determined by the method described above. The word "tissue paper" in the description of the method is considered to be replaced by "paper with high permeability."

[0161] High permeability paper 151 may be creped paper. In this case, the creping is preferably carried out by means of a dry creping method in which a dry fiber network (high permeability paper 151) adhering, for example, to a Yankee dryer in the dryer part of a paper machine, is scraped using a doctor blade or the like. Crepe paper exhibits higher liquid permeability than non-crepe paper. The higher the degree of creping, the higher the liquid permeability. However, it is noted that an increase in the degree of creping tends to lead to a decrease in strength characteristics (for example, tensile strength). Based on these findings, the creping rate of crepe paper 151 with high permeability is preferably 5% to 30%, more preferably 5% to 20%, even more preferably 7% to 15%, in order to balance the liquid permeability and the strength characteristics. The degree of creping is determined by the previously described method.

[0162] The high permeability paper 151 with good strength characteristics and high liquid permeability is preferably the paper described below, which is designated as high permeability paper A. High permeability paper A is a tissue paper, mainly consisting of a structure of two types of hydrophilic cellulosic fibers, differing in fiber coarseness, and contains a strength improver. Two types of hydrophilic cellulosic fibers include a first pulp which has a coarse fiber of 0.13 to 0.16 mg / m and a second pulp which has a coarse fiber of 0.17 to 0.20 mg / m. Differences in fiber coarseness between the first and second pulp are from 0.01 to 0.07 mg / m. The structure has a grinding degree of 400 to 550 ml. High permeability paper A is basically the same as tissue paper according to the first aspect of the invention. High permeability paper A is described mainly with reference to differences from tissue paper in the first aspect. The description of the tissue paper according to the first object is applicable accordingly to other features of paper A with high permeability.

[0163] In cases where two or more strength improvers are used in high permeability paper A, preferred combinations of strength improvers include (1) a combination of one dry strength enhancer and one wet strength improver paper, and (2) a combination of two additives that increase the strength of dry paper, and one additive that increases the strength of wet paper. Using combination (1), one dry paper strength improver is preferably an anionic PAM salt, and one dry paper strength enhancer is preferably PAE. In the case of combination (2), two dry paper strength enhancing additives are preferably CMC salt and anionic PAM salt, and one wet strength enhancing additive is preferably PAE.

[0164] A high permeability paper A is excellent not only in strength and liquid permeability, but also in breathability; for this, it consists mainly of a structure of two hydrophilic cellulose fibers, differing in fiber coarseness. In order to investigate the relationship between air permeability and the use of two types of hydrophilic cellulose fibers that differ in fiber coarseness, two types of tissue paper (samples A and B) were obtained from different pulp compositions and the air permeability of the samples was determined. Sample A is a high permeability paper II, described below, which contains the first and second pulp. Sample B is a high permeability paper I, described below, which contains only the first pulp as a fibrous material. Both samples A and B have a bulk of 13 g / m ² . Breathability is measured as described below.

[0165] A method for measuring breathability:

Breathability is determined in accordance with JIS P8117. Get thirty-two cut square sheets with a side of 15 cm, subject to evaluation (tissue paper). The sheets are dried in a hot air dryer at 105ºC for 30 minutes and stacked on top of one another. The stack is mounted on a Gurley B-type densimeter, and the time required to pass a certain amount of air through the stack, from 0 cm ³ to reaching 300 cm ³ , is measured five times. The average of the five measured times is taken as the breathability of the sheet (tissue paper). The unit of the thus determined air permeability is c / 32P · 300 cm ³ , which shows the time (in seconds) required for the passage of 300 cm ^{3 of} air through a stack of 32 sheets. The lower the value, the easier the air to pass through, that is, the higher the air permeability.

[0166] Sample B containing the first pulp as the only fibrous material (high permeability paper I) has a breathability of 2.1 to 2.7 s / 32P · 300 cm ³ , while sample A (high permeability paper II ), containing two types of pulp (first and second), differing in the coarseness of the fiber as a fibrous material, has a lower air permeability from 1.6 to 2.2 s / 32P · 300 cm ³ . These results prove that the content of tissue paper mainly from the structure of two types of hydrophilic cellulose fibers, differing in the coarseness of the fiber, is effective in order to provide tissue paper with improved breathability. It should be clearly understood that the high permeability paper A thus configured exhibits excellent breathability.

[0167] High permeability paper 151 is not limited to high permeability paper A and may be any paper whose bulk, density, liquid transit time, and dry tensile strength MD are in the respective indicated ranges. For example, high permeability paper 151 may be a creped tissue paper, preferably containing bleached softwood kraft pulp (NBKP), which has a grinding ratio of 400 to 550 ml (preferably 475 to 525 ml, more preferably 490 to 510 ml), which contains two or more strength improvers and has a creping degree of 5% to 30% (preferably 5% to 20%, more preferably 7% to 15%). As used herein, the phrase “predominantly contains” is intended to mean that the content of NBKP having a degree of grinding in the specified range is at least 50% by weight. In order to obtain good strength characteristics, the NBKP content is preferably from 50 to 100% by mass, more preferably from 80 to 100% by mass. Details of high permeability paper A, for example, illustrative examples of strength improvers, apply accordingly to creped tissue paper, unless otherwise indicated.

[0168] Describes materials that can be used to make structural members of the diaper 1. The top sheet 12 and the back sheet 13 may be of various types commonly used in the art. The top sheet 12 can be formed from a liquid permeable sheet such as a nonwoven fabric or a perforated resin film, and the back sheet 13 can be formed from various types of liquid impervious or water repellent sheets, such as a moisture impermeable resin film, a moisture permeable porous a resin film, a water-repellent non-woven material, or a laminate of such a film of resin or non-woven material and another sheet. The side sheet 162 may be of the same material as the back sheet 13.

[0169] The diaper 1 of the present embodiment is used in a similar manner as the known flat disposable diapers. Having high permeability paper 151 at the top of the core wrapping sheet 15, which is located on the skin side 140a of the absorbent core 140, the diaper 1 of the present embodiment is superior to the absorbent article disclosed in Patent Literature 4, in which this portion of the wrapping sheet for the cores are formed from a nonwoven material made of synthetic fibers, especially in relation to (1) the absorption capacity for bodily fluids, such as loose stools (absorption capacity when re-wetting), (2) less likely to cause leakage of the absorbent core forming material such as an absorbent polymer, and (3) production cost savings. With the low permeability sheet 152 as the bottom of the core wrapping sheet 15, which is located on the non-skin facing side 140b of the absorbent core 140, the diaper 1 of the present embodiment is less likely to leak laterally.

[0170] The invention (fourth aspect) is not limited to the particular embodiment described, but is intended to cover various modifications within the scope of the invention. For example, although the core wrapping sheet according to one embodiment consists of high permeability paper 151 and low permeability sheet 152, the core wrapping sheet can only be formed from high permeability paper 151, in this case a wrapping sheet for the core may consist of two sheets of paper 151 with high permeability. In this case, the low permeability sheet 152 in the embodiment shown in FIG. 7 can be replaced with high permeability paper 151.

[0171] Alternatively, the core wrapping sheet 15 can be formed from a single sheet of high permeability paper 151, as shown in FIG. The high permeability paper 151 used in the embodiment of FIG. 8 is 2-3 times larger than the absorbent core 140 in the transverse direction Y. The absorbent element 14 is made by placing the absorbent core 140 on the laterally middle portion of the high permeability paper 151, bending laterally opposite parts of high permeability paper 151 to the upper side of the absorbent core 140, attaching overlapping opposing parts of high permeability paper 151 to each other by known coupling means, such as hot-melt adhesive, to make the paper tubular, and turning it over.

[0172] The absorbent article of the invention (fourth object) can be not only a flat disposable diaper that has fastening tapes, but also a stretchable (in the form of underpants) disposable diaper, absorbent pad, sanitary napkin, and the like.

[0173] In connection with the above embodiments, the invention relates to the following aspect of the invention (including tissue paper, absorbent article, and method for producing tissue paper):

[1] Tissue paper mainly contains a structure of two types of hydrophilic cellulose fibers, differing in the coarseness of the fiber, and contains an additive that increases the strength,

two types of hydrophilic cellulose fibers are the first pulp, which has a fiber coarseness of from 0.13 to 0.16 mg / m, preferably from 0.135 to 0.155 mg / m, more preferably from 0.14 to 0.15 mg / m, and a second pulp that has a fiber coarseness of 0.17 to 0.20 mg / m, preferably 0.175 to 0.195 mg / m, more preferably 0.18 to 0.19 mg / m, a difference in fiber coarseness between the first and the second pulp mass is from 0.01 to 0.07 mg / m, preferably from 0.02 to 0.06 mg / m, more preferably from 0.03 to 0.05 mg / m, and the structure has Grinding degree from 400 to 550 ml.

[0174] [2] The tissue paper set forth in [1], wherein each of the first pulp and the second pulp has an average fiber length of 2 to 3 mm, preferably 2.2 to 2.8 mm.

[3] Tissue paper set forth in [1] or [2], wherein the ratio of the content of the first pulp to the second pulp, namely the first pulp / second pulp, is from 3/7 to 7/3, preferably from 4 / 6 to 6/4.

[4] Tissue paper set forth in any one of [1] to [3], wherein the first pulp and the second pulp are each bleached softwood pulp kraft pulp (NBKP).

[5] The tissue paper set forth in any one of [1] to [4], wherein the total content of the first and second pulp is from 70 to 100% by weight, preferably from 80 to 100% by weight.

[6] The tissue paper set forth in any one of [1] to [5], wherein the structure has a milling degree of 450 to 525 ml, preferably 475 to 510 ml.

[7] The tissue paper set forth in any one of [1] to [6], wherein the strength improver contains at least carboxymethyl cellulose or a salt thereof.

[8] The tissue paper set forth in any one of [1] to [7], which has a bulk of 10 to 20 g / m ² , preferably 11 to 16 g / m ² , more preferably 12 to 14 g / m ² .

[0175] [9] The tissue paper set forth in any one of [1] to [7] preferably contains bleached softwood kraft pulp that has a grinding ratio of 400 to 550 ml, preferably 475 to 525 ml, more preferably from 490 to 510 ml, contains two or more strength improvers, has a bulk of from 10 to 14.5 g / m ² , preferably from 11 to 14 g / m ² , density from 0.05 to 0.2 g / cm ³ , preferably from 0.1 to 0.2 g / cm ³ , and the degree of creping from 5% to 30%, preferably from 5% to 20%, more preferably from 7% to 15%.

[10] Tissue paper set forth in [9], wherein two or more strength improvers comprise a strength enhancer of dry paper and an strength enhancer of wet paper.

[11] The tissue paper set forth in [9] or [10], wherein the total content of two or more strength improvers is from 0.01 to 1.5% by weight, preferably from 0.03 to 1.2% by weight, relative to the dry weight of all the fibers forming the tissue paper.

[12] Tissue paper set forth in any one of [9] to [11], wherein two or more strength improvers are at least one dry strength enhancer and at least one strength enhancer the strength of wet paper, the ratio of the total amount of at least one additive that increases the strength of dry paper, to the total number of at least one additive that increases the strength of wet paper, is from 0.01 to 0.5, preferably from 0.03 to 0, 35.

[13] The tissue paper set forth in any one of [10] to [12], wherein the dry paper strength improver is at least one member selected from the group consisting of carboxymethyl cellulose and its salt, polyacrylamide resin, and its salts, cationic starch and polyvinyl alcohol.

[14] The tissue paper set forth in any one of [10] to [13], wherein the wet strength improver is at least one member selected from the group consisting of an epoxidized polyamide polyamine resin, urea formaldehyde resin, melamine-formaldehyde resin, dialdehyde starch, polyethyleneamine and oxymethylated polyamide.

[15] Tissue paper set forth in any one of [9] to [14], where two or more strength improvers are two dry strength enhancers and one wet strength improver.

[16] The tissue paper described in [15], where two dry paper strength improvers are carboxymethyl cellulose salt and anionic polyacrylamide salt, and one wet paper strength improver is an epoxidized polyamide-polyamine resin.

[17] The tissue paper of [16], wherein the anionic polyacrylamide resin has a weight average molecular weight of 8,000,000 or more, preferably 10,000,000 or more, more preferably 1,500,000 or more and 2,000,000 or less.

[0176] [18] The tissue paper set forth in any one of [1] to [17], which has a dry tensile strength of 600 to 1500 cN / 25 mm, preferably 700 to 1200 cN / 25 mm, more preferably from 800 to 1200 cN / 25 mm, even more preferably from 900 to 1200 cN / 25 mm, in the machine direction during the production of tissue paper and dry tensile strength from 150 to 350 cN / 25 mm, preferably from 180 to 300 cN / 25 mm in the transverse machine direction perpendicular to the machine direction.

[19] A tissue paper disclosed in any one of [1] to [18], which has a liquid transit time of from 0.2 to 3 seconds, preferably from 0.3 to 2.5 seconds, more preferably from 0.5 up to 2 seconds, as measured using a specific method, which includes:

a vertical and concentric arrangement of a stack of two cylinders open at both ends and having an inner diameter of 35 mm, with a square sample with a side of 8 cm to be tested, inserted between them, supplying 40 ± 1 g of physiological saline to the upper cylinder with the sample held between the cylinders, passing the saline solution through or absorbing it through the sample and disappearing from the upper cylinder, and measuring the time from the beginning of the pouring of the saline solution to the moment when the level overhnosti fluid is compared with the sample surface to receive the passage of fluid.

[0177] [20] An absorbent article that has tissue paper set forth in any one of [1] to [19].

[21] The absorbent article of [20], which comprises an absorbent core and a wrapping sheet for a core that wraps the absorbent core, where the wrapping sheet for the core is tissue paper.

[0178] [22] A method for producing tissue paper that has a bulk of 30 g / m ² or less, comprising the steps of forming a fibrous layer by making paper from raw materials obtained from a material containing bleached softwood Kraft pulp and drying the fibrous layer

the raw materials are obtained by adding (a) an additive that increases the strength of wet paper containing a cationic polymer that has a cationic group to a suspension of bleached kraft pulp of softwood, followed by the addition of (b) a low molecular weight additive that increases the strength of dry paper, and ( c) a high molecular weight additive that increases the strength of dry paper, simultaneously or in the manner described, into a suspension,

a low molecular weight dry paper strength improver (b) is a low molecular weight anionic polymer that has an anionic group and has a weight average molecular weight (molecular weight) of from 2,000 to 500,000, and

a high molecular weight dry paper strength improver (c) is a high molecular weight anionic polymer that has an anionic group and has a molecular weight of from 5,000,000 to 30,000,000.

[0179] [23] The method for producing tissue paper as set forth in [22], wherein the amount of low molecular weight dry-strength improver (b) to be added is from 0.01 to 0.5% by weight, preferably from 0, 1 to 0.3% by weight, relative to the dry weight of all the fibers forming the tissue paper.

[24] The method for producing tissue paper as set forth in [22] or [23], wherein the amount of a high molecular weight dry paper strength improver (c) to be added is from 0.001 to 0.1% by weight, preferably from 0.01 up to 0.08% by weight, relative to the dry weight of all the fibers forming the tissue paper.

[25] A method for producing tissue paper set forth in any one of [22] to [25], wherein the ratio of the amount of one wet strength improver (a) to be added to the total amount of a low molecular weight dry strength improver paper (b), and macromolecular additives that increase the strength of dry paper (c) to be added, namely (a) / (b) + (c), is from 0.5 to 10, preferably from 1 to 5.

[0180] [26] A method for producing tissue paper as set forth in any one of [22] to [25], wherein the raw material is obtained by adding a wet strength improver (a) to a suspension of bleached softwood kraft pulp, followed by the addition of a low molecular weight additive that increases the strength of dry paper (b), followed by the addition of a high molecular weight additive that increases the strength of dry paper (c).

[27] The method for producing tissue paper described in [26], where the addition of a low molecular weight additive that increases the strength of dry paper (b), what dilution follows, the dilution is followed by the addition of a high molecular weight additive that increases the strength of dry paper (c), and the addition of a high molecular weight dry paper strength improver (c), homogenize the slurry by using at least one of a mixing pump and a filter screen.

EXAMPLES

[0181] The invention is further illustrated in more detail with reference to examples, but it should be understood that the invention is not considered limited thereto. Unless otherwise indicated, all percentages are percentages by weight. The numbers of examples and comparative examples related to the first, second, third and fourth aspect of the invention are indicated by “A”, “B”, “C” and “D”, respectively (for example, example A1, example B1, example C1 and Example D1).

[0182] Example A1

NBKP with a fiber coarseness of 0.15 mg / m and NBKP with a fiber coarseness of 0.18 mg / m were used as the first pulp (pulp with a relatively small fiber diameter) and the second pulp (pulp with a relatively large fiber diameter), respectively. The first and second pulp were mixed in a ratio of 5/5 by weight. The resulting fibers were uniformly dispersed in water to obtain a suspension that has a fiber concentration of 2%. The suspension was processed in a breaking machine in order to provide a fiber structure that has a milling degree of 500 ml. 0.2%, relative to the dry weight of all fibers in suspension, of CMC sodium (Celogen WS-C, a dry paper strength improver available from Dai-Ichi Seiyaku Co., Ltd.) was added to the suspension as the first strength enhancer . Then, 0.78%, relative to the dry weight of all fibers in suspension, PAE (WS4030, wet paper strength improver available at Seiko PMC Corp.) was added as a second strength improver, followed by thorough mixing so that disperse all components evenly. The resulting paper feed was distributed over a paper-based metal mesh having an opening diameter of 90 μm (166 mesh) to form a paper layer on the mesh. The paper layer was dehydrated using a suction box at a speed of 6 ml / (cm ² · s) and dried in a dryer. The resulting tissue paper was used as a sample in Example A1.

[0183] Examples A2 to A6 and comparative examples A1 to A5

Samples of tissue paper were obtained in the same manner as in example A1, except for changing the type (coarseness of the fiber) or the degree of grinding of pulp, the use of additives for paper strength, etc. In Example A5, the anionic PAM sodium salt (Accofloc A95, dry paper strength improver available at MT Aquapolymer Inc .; molecular weight: 17,000,000) was used as the third strength enhancer in addition to the first and second strength improver .

[0184] The pulp (NBKP) used in examples A1 to A6 and comparative examples A1 to A5 are listed below in ascending order of fiber coarseness. These pulp products were purchased from Japan Pulp & Paper Co., Ltd. or at Itochu Corp.

Pulp list Tradename Manufacturer The coarseness of the fiber (mg / m) Cenibra Cenibra 0.09 Northwood ConFor 0.13 Cariboo Cariboo Pulp & Paper Co. 0.15 Botnia Botnia 0.16 Alabama pine Alabama Pine, Inc. 0.17 ARAUCO ARAUCO 0.18 Crofton CK Unifibra 0.2

[0185] rating

The evaluation results of the samples (tissue paper) from Examples A1 to A6 and Comparative Examples A1 to A5 are presented below in Table 1. Dry tensile strength and liquid transit time were determined using the appropriate methods described above.

[0186] Table 1 Example No. Reference Example No. A1 A2 A3 A4 A5 A6 A1 A2 A3 A4 A5 The coarseness of the fiber of the first pulp (mg / m) 0.15 0.15 0.16 0.13 0.15 0.15 0.09 0.18 0.15 0.15 0.15 The coarseness of the fiber of the second pulp (mg / m) 0.18 0.18 0.17 0.2 0.18 0.18 0.18 0.18 0.15 0.18 0.15 The difference between the coarseness of the fiber (second-first) (mg / m) 0,03 0,03 0.01 0,07 0,03 0,03 0.09 0 0 0,03 0 The mass ratio of the first pulp to the second pulp 5/5 7/3 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 The degree of grinding of the structure of the first / second pulp (ml) 500 500 500 500 500 500 500 500 350 350 650 The amount of the first additive that increases the strength (%) 0.2 0.2 0.2 0.2 0.2 - 0.2 0.2 0.2 0.2 - The amount of the second additive that increases the strength (%) 0.78 0.78 0.78 0.78 0.78 0.78 0.78 0.78 0.78 0.78 0.78 The amount of the third additive that increases the strength (%) - - - - 0,03 - - - - - - The main mass (g / m ² ) 13 13 13 13 eleven 13 13 13 13 13 13 Dry tensile strength (cN / 25 mm) MD (≥600) 923 950 935 890 950 780 458 420 1024 1205 480 CD (≥150) 247 259 236 210 250 180 120 180 265 270 110 Liquid transit time (s) 0.9 1,2 1.4 1,5 0.5 0.8 12 0.5 6.0 4,5 2 Note:
first strength enhancer: CMC sodium (dry paper strength enhancer)
second strength improver: PAE (wet strength enhancer)
third strength enhancing additive: anionic PAM sodium salt (dry strength enhancing additive)

[0187] As can be seen from the results in table 1, tissue paper samples from the examples, mainly containing a structure of two hydrophilic cellulose fibers of different fiber coarseness, the structure having a degree of grinding within the range defined above, namely, tissue paper according to the first object of the invention exhibits a dry tensile strength in MD of 600 cN / 25 mm or more, a dry tensile strength in CD of 150 cN / 25 mm or more, and a liquid transit time of 2 seconds or shorter, proving satisfactory NOSTA strength characteristics and excellent liquid permeability. In particular, the tissue paper from Example A5, which contains two additives that increase the strength of dry paper and one additive that increases the strength of wet paper, generally shows an improvement in the strength and permeability characteristics for liquids relative to other examples, clearly showing the effectiveness of such a combination of three additives increasing strength.

[0188] As can be seen from Table 1, each of the tissue paper samples of the comparative examples, in contrast, has a dry tensile strength in MD of less than 600 cN / 25 mm (comparative examples A1, A2 and A5) or transit time fluid exceeding 3 seconds (Comparative Examples A1, A3 and A4). That is, three comparative samples are not able to achieve high levels of both strength and liquid permeability characteristics. This impossibility is considered primarily due to differences in fiber coarseness between the first and second cellulosic pulp, which exceed 0.07 mg / m, in comparative example A1, using only one type of hydrophilic cellulose fiber in comparative examples A2, A3 and A5, and the degree of milling of the fiber structure beyond a well-defined range in comparative example A4

[0189] Example B1

NBKP from North America (Cariboo, available from Cariboo Pulp & Paper Co .; fiber coarseness: 0.15 mg / m; average fiber length: 2.44 mm) was uniformly dispersed in water in order to obtain a suspension that has a fiber concentration 2% The suspension was processed in a breaking machine in order to provide a fiber structure that has a milling degree of 500 ml. Although the suspension was diluted, 0.78%, relative to the dry weight of all the fibers in the suspension, PAE (WS4030, a wet paper strength improver available from Seiko PMC Corp.) was added to the suspension, and then 0.2%, relatively dry, was added thereto. the masses of all fibers in suspension, sodium CMC (Celogen WS-C, a dry paper strength improver available from Dai-Ichi Seiyaku Co., Ltd.), followed by thorough mixing in order to uniformly disperse all components in order to to get raw materials that have a concentration of 0.1%. The resulting feed was distributed on a paper-based metal mesh that has an opening diameter of 90 μm (166 mesh) in order to form a paper layer on the mesh. The paper layer was dehydrated using a suction box at a speed of 6 ml / (cm ² · s) and dried in a dryer. The dried paper layer was removed from the dryer using a wiper blade, while distinguishing between drying speed and winding speed. The resulting creped tissue paper was used as a sample from Example B1.

[0190] Examples B2 to B7 and comparative examples B1 to B7

Samples of creped tissue paper were obtained in the same manner as in Example B1, except for changes in the degree of grinding of NBKP, amounts of additives, degree of creping, and the like. In examples B4 to B7, two dry paper strength enhancing additives (additives 1 and 2) and one wet paper strength enhancing additive were used, where additive 1 increasing the dry paper strength was the same sodium CMC as used in the example B1, additive 2, increasing the strength of dry paper, was the sodium salt of anionic PAM (Accofloc A95, from MT Aquapolymer Inc .; molecular weight = 17,000,000 in examples B4 to B6 or DA4119, from Seiko PMC Corp .; molecular weight = 2,000,000 in Example B7), and the wet strength improver was the same P AE, as used in example B1.

[0191] rating

The evaluation results of tissue paper samples obtained in Examples B1 to B7 and comparative examples B1 to B7 are shown in Tables 2 and 3. The dry tensile strength and liquid transit time were determined using the corresponding methods described above.

[0192] table 2 Example No. B1 B2 B3 B4 B5 B6 B7 The degree of grinding (ml) 500 500 450 500 500 500 500 Additive 1, increasing the strength of dry paper (%) 0.20 0.20 0.20 0.20 0.20 0.20 0.20 Additive 2, increasing the strength of dry paper (%) - - - 0,03 * ¹ 0,03 * ¹ 0,03 * ¹ 0,03 * ² Additive that increases the strength of wet paper (%) 0.78 0.78 0.78 0.78 0.78 0.78 0.78 The main mass (g / m ² ) 13.0 14.5 13.0 11.0 12.0 13.0 13.0 Density (g / cm ³ ) 0.13 0.15 0.13 0.13 0.13 0.13 0.13 The degree of creping (%) 10 10 12 10 10 10 10 Dry tensile strength (cN / 25 mm) MD 1040 1182 1055 950 1110 1200 650 CD 232 274 245 250 280 300 152 Liquid transit time (s) 1,5 1.8 1,6 0.5 0.8 0.9 0.9 Additive 1, increasing the strength of dry paper: CMC sodium
Additive 2, increasing the strength of dry paper: sodium salt of anionic PAM (molecular weight; * ¹ = 17000000), * ² ; molecular weight = 2000000)
Wet paper strength improver: PAE

[0193] Table 3 Reference Example No. B1 B2 B3 B4 B5 B6 B7 The degree of grinding (ml) 650 500 500 500 500 400 650 Additive that increases the strength of dry paper (%) - - - 0.20 0.20 0.20 0.20 Additive that increases the strength of wet paper (%) 0.78 0.78 0.78 0.78 0.78 0.78 0.78 The main mass (g / m ² ) 16,0 13.0 18.0 8.0 16,0 13.0 10.0 Density (g / cm ³ ) 0.23 0.13 0.27 0.12 0.22 0.22 0.20 The degree of creping (%) 10 10 10 10 10 10 0 Dry tensile strength (cN / 25 mm) MD 934 520 1024 480 1200 1350 1284 CD 263 172 206 185 211 235 482 Liquid transit time (s) 5,0 1,5 6.3 1,2 5.2 7.0 4,5 Dry paper strength improver: CMC sodium
Wet paper strength improver: PAE

[0194] As can be seen from the results in table 2, tissue paper from each of the examples, which (1) mainly contains NBKP with a degree of grinding falling within a specific range, (2) contains two or more additives that increase strength, and (3) has a bulk, density and creping degree falling in the respective specific ranges, has a dry tensile strength in MD of 600 cN / 25 mm or more, a dry tensile strength in CD of 150 cN / 25 mm or more, and a liquid travel time of 2 seconds or in short, providing satisfactory ha akteristiki strength and excellent liquid permeability. Among examples B4 to B7 in which a combination of two additives increasing the strength of dry paper and one additive increasing the strength of wet paper is used, tissue paper samples from Examples B4 to B6, in which the anionic PAM salt added as additive 2, increasing the strength of dry paper, has a molecular weight of 17,000,000, exhibit higher dry tensile strength than tissue paper from example B7, in which the molecular weight is 2,000,000. Thus, it can be seen that in one of the embodiments and use a combination of three additives that increase strength, the use of salts of anionic PAM, having a higher molecular weight, as one of them, making the effect of increasing the strength of paper more pronounced.

[0195] As can be seen from the results in table 3, the tissue paper samples of the comparative examples, in contrast, have a dry tensile strength in MD of less than 600 cN / 25 mm (comparative examples B2 and B4) or a liquid passage time exceeding 3 seconds (comparative examples B1, B3 and from B5 to B7). That is, these comparative samples are not able to reach high levels of both strength and liquid permeability characteristics. This is considered primarily due to the inability to satisfy all the requirements from (1) to (3), which are described above in comparative example B1; the inability to satisfy requirement (2) in comparative example B2; the inability to satisfy requirements (2) and (3) in comparative example B3; the inability to satisfy requirement (3) in comparative examples B4 to B6; and the inability to satisfy requirements (1) and (3) in comparative example B7.

[0196] Example C1

The apparatus 1A shown in FIG. 2 was used (cylindrical paper machine; paper production speed: 400 m / min; width: 2000 mm). Cariboo, available at Cariboo Pulp & Paper Co. (NBKP from North America; fiber coarseness: 0.15 mg / m; average fiber length: 2.44 mm) was used as the raw material NBKP. Raw NBKP material was placed in a pulp breaker 21 and broken in refiner 23 to a grinding degree of 500 ml. An epoxidized polyamide-polyamine resin (PAE), which was a wet paper strength improver (a), was added to the pulp suspension using a wet paper strength improver adding unit 33, and the suspension was thoroughly mixed in the first raw material storage tank 32 . The amount of PAE added was 0.78% based on the dry weight of all the fibers forming the resulting tissue paper. Then, the CMC salt with a molecular weight of 100,000, which was a low molecular weight additive that increases the strength of dry paper (b), was added to the suspension using block 43 to add a low molecular weight additive that increases the strength of dry paper, and the suspension was thoroughly mixed in a second tank 42 for storing raw materials. The added amount of CMC salt was 0.2% relative to the dry weight of all the fibers forming the resulting tissue paper. Subsequently, dilution water was supplied using the dilution block feed water 63 in order to dilute the slurry of the feed to a concentration of 0.11%. Then, an acrylic polyacrylamide resin (PAM) having a molecular weight of 17,000,000, which was a high molecular weight additive that increases the strength of dry paper (c), was added using block 65 add high molecular weight additives that increase the strength of dry paper, while creating turbulence through a mixing pump 64. followed by filtering through a filter screen 62 in order to obtain paper feed. The amount of PAM added was 0.03% relative to the dry weight of all fibers forming the tissue paper to be obtained. The raw material thus obtained in part 2 of the production of raw materials was processed by means of the paper part 7, where it was dried and dried in order to make tissue paper. The bulk of tissue paper was adjusted to 11.0 g / m ² using a distribution box 52 of part 2 for the production of raw materials and a shaper of paper part 7.

[0197] Example C2

The apparatus 1A of FIG. 2 was used. Tissue paper was made in the same manner as in example C1, except for adjusting the bulk to 13.0 g / m ² by means of a distribution box 52 of part 2 for the production of raw materials and a shaper of paper part 7.

[0198] Example C3

Used the apparatus 1C shown in Fig.4. Crude NBKP from North America (Cariboo from Cariboo Pulp & Paper Co .; fiber coarseness: 0.15 mg / m; average fiber length: 2.44 mm) was broken in a pulp breaker. The degree of grinding of NBKP was adjusted to 500 ml by means of a pulp breaker 21 in combination with refiner 23. An epoxidized polyamide-polyamine resin (PAE), which was an additive to increase the strength of wet paper (a), was added to the pulp suspension using the additive adding unit 33 , increasing the strength of wet paper, followed by thorough mixing in the first tank 32 for storing raw materials. The amount of PAE added was 0.78% relative to the dry weight of the total fibers of the tissue paper to be obtained. A CMC salt with a molecular weight of 100,000, which was a low molecular weight additive that increases the strength of dry paper (b), was added to the suspension using block 43 to add a low molecular weight additive that increases the strength of dry paper, followed by thorough mixing in the second tank 42 for storing raw materials. The amount of CMC salt was 0.2% relative to the dry weight of all the fibers forming the tissue paper to be obtained. Then, the suspension was diluted with water to 0.13% using a block 63 supplying water for dilution, and the diluted suspension was applied to filter mesh 62. Subsequently, an acrylic polyacrylamide resin (PAM) with a molecular weight of 17,000,000, which was a high molecular weight additive that increases the strength of dry paper ( c), was added using block 65 adding high molecular weight additives that increase the strength of dry paper, in order to obtain paper raw materials. The amount of PAM added was 0.03% relative to the dry weight of all fibers forming the tissue paper to be obtained. The raw material thus obtained in part 2 of the production of raw materials was processed by means of the paper part 7, where it was dried and dried in order to make tissue paper. The bulk of the tissue paper was adjusted to 13.0 g / m ² using a distribution box 52 from part 2 for the production of raw materials and the former of the paper part 7.

[0199] Example C4

Used the apparatus 1D shown in Fig.5. Raw materials NBKP from North America (Cariboo from Cariboo Pulp & Paper Co .; fiber coarseness: 0.15 mg / m; average fiber length: 2.44 mm) was placed in a pulp breaker 21 and broken in refiner 23. The degree of grinding of NBKP was adjusted to 500 ml using a pulp breaker 21 and a refiner 23. An epoxidized polyamide-polyamine resin (PAE), which was a wet paper strength improver (a), was added to the pulp suspension using a wet paper strength improver adding unit 33, followed by thoroughly mixed e in the first tank 32 for storing raw materials. The added amount of PAE was 0.78% relative to the dry weight of all tissue paper fibers to be obtained. Then, the suspension was diluted with water to 0.13% using a water supplying unit for dilution of block 63. CMC salt with a molecular weight of 100,000 and acrylic polyacrylamide resin (PAM) with a molecular weight of 17,000,000 were simultaneously added to the diluted suspension using block 43 adding low molecular weight additives that increase strength dry paper, and block 65 add high molecular weight additives that increase the strength of dry paper, while creating turbulence using a mixing pump 64 in order to obtain paper cheese e. PAM connected the CMC salt along the line of block 65. The amounts of added CMC salt and added PAM were 0.2% and 0.03%, respectively, relative to the dry weight of all the fibers forming the tissue paper to be obtained. The raw material thus obtained, in the raw material receiving part 2, was processed by the paper making part 7, where it was dried and dried in order to make tissue paper. The bulk of tissue paper was adjusted to 13.0 g / m ² using a distribution box 52 of part 2 for the production of raw materials and a shaper of paper part 7.

[0200] Comparative Example C1

Tissue paper was made using apparatus 1A of FIG. 2, in a similar manner as in Example C1, with the following exceptions. Paper raw materials were obtained without the addition of additives that increase the strength of dry paper, from the block 43 add low molecular weight additives that increase the strength of dry paper, and block 65 add high molecular weight additives that increase the strength of dry paper. The raw material thus obtained was processed by means of the paper-making part 7, where it was dried and dried in order to make tissue paper, the bulk of which was adjusted to 11.5 g / m ² by means of the mass distribution box 52 of the raw-material receiving part 52 and the shaper of the paper-making part 7.

[0201] Comparative example C2

Tissue paper was made using apparatus 1A of FIG. 2 in the same manner as in Example C1, except that the paper raw material was obtained without adding an additive that increases the strength of dry paper, from the block 65 add a high molecular weight additive that increases the strength of dry paper . The raw material thus obtained was processed by means of the paper-making part 7, where it was dried and dried in order to produce tissue paper, the bulk of which was adjusted to 11.0 g / m ² by means of the mass distribution box 52 of the raw-material receiving part 52 and the shaper of the paper-making part 7.

[0202] Comparative example C3

Used the apparatus 1A, presented in figure 2. Cariboo, available at Cariboo Pulp & Paper Co. (NBKP from North America; fiber coarseness: 0.15 mg / m; average fiber length: 2.44 mm) was used as the raw material. Raw NBKP material was placed in a pulp breaker 21 and broken in refiner 23 to a grinding degree of 500 ml. An epoxidized polyamide-polyamine resin (PAE), which was a wet paper strength improver (a), was added to the pulp slurry using a wet strength improver improver adding unit 33, followed by thorough mixing in the first storage tank 32 raw materials. The amount of PAE added was 0.78% based on the dry weight of all the fibers forming the resulting tissue paper. Then, an acrylic polyacrylamide resin (PAM) having a molecular weight of 17,000,000, which was a high molecular weight additive that increases the strength of dry paper (c), was added using block 43 add high molecular weight additives that increase the strength of dry paper, followed by thorough mixing in the second tank 42 for storing raw materials. The amount of PAM added was 0.03% relative to the dry weight of all fibers forming the tissue paper to be obtained. Subsequently, dilution water was supplied using the dilution block feed water 63 in order to dilute the slurry of the feed to a concentration of 0.13%. Then, CMC with a molecular weight of 100,000, which was a low molecular weight additive that increases the strength of dry paper (b), was added to the suspension using block 65 add a low molecular weight additive that increases the strength of dry paper, while creating turbulence by means of a mixing pump 64, followed by filtration through a filter screen 62 in order to obtain paper feed. The added amount of CMC was 0.2% relative to the dry weight of all the fibers forming the resulting tissue paper. The raw material thus obtained in part 2 of the production of raw materials was processed by means of the paper part 7, where it was dried and dried in order to make tissue paper. The bulk of tissue paper was adjusted to 13.0 g / m ² using a distribution box 52 of part 2 for the production of raw materials and a shaper of paper part 7.

[0203] rating

The results of the evaluation of samples (tissue paper) from examples C1 to C4 and comparative examples C1 to C3 are shown in Table 4 below. Dry tensile strength in MD and CD, wet tensile strength in MD and CD, creping rate and liquid passage time determined by the corresponding methods described above.

[0204] Table 4 Example No. Reference Example No. C1 C2 C3 C4 C1 C2 C3 Pulp NBKP NBKP NBKP NBKP NBKP NBKP NBKP The degree of grinding (ml) 500 500 500 500 500 500 500 The main mass (g / m ² ) 11.0 13.0 13.0 13.0 11.5 11.0 13.0 Wet paper strength improver (a) (%) 0.78 0.78 0.78 0.78 0.78 0.78 0.78 Low molecular weight additive that increases the strength of dry paper (b) (%) 0.2 0.2 0.2 0.2 - 0.2 0.2 High molecular weight dry paper strength enhancer (c) (%) 0,03 0,03 0,03 0,03 - - 0,03 Dry tensile strength (cN / g / cm ² ) MD 74,4 80.8 62.5 67.0 46.5 55.6 56.0 CD 19.5 21.5 16,2 21.1 10.5 12.5 12.8 Wet tensile strength (cN / g / cm ² ) MD 18.5 20.5 13.8 19.9 9.2 10.8 11.1 CD 8.5 10.8 7.1 9.6 3,7 5.5 5.3 The degree of creping (%) 10 12 10 eleven 10 12 eleven Liquid transit time (s) 0.9 1,2 0.7 1,0 1,1 1.3 1,1

[0205] As can be seen from the results in Table 4, tissue paper samples made by the methods of Examples C1 through C4 confirm satisfactory strength characteristics and excellent liquid permeability. In contrast, tissue paper samples obtained by the methods of comparative examples C1 to C3 are lower than those obtained by the methods of examples C1 to C4 in terms of strength and liquid permeability.

[0206] A method for manufacturing high permeability paper I:

NBKP from North America (Cariboo, from Cariboo Pulp & Paper Co.) were uniformly dispersed in water in order to obtain a suspension having a fiber concentration of 2%. The suspension was broken in order to adjust the degree of grinding of NBKP to 500 ml. First, 0.2% anionic PAM sodium salt (Accofloc A95, a dry paper strength improver available from MT Aquapolymer Inc.) was added to the suspension as a first strength improver, and then 0.2% PAE (WS4030, an additive, the wet strength enhancer available at Seiko PMC Corp.) as a second strength improver, both relatively dry weights of all fibers in suspension, followed by thorough mixing to disperse each component evenly. The resulting paper raw material was distributed on a paper-based metal mesh having holes of 90 μm (166 mesh) in order to form a paper layer on the mesh. The paper layer was dehydrated using a suction box at a speed of 6 ml / (cm ² · s) and dried in a dryer. The dried paper layer was removed from the dryer using a wiper blade, while distinguishing between drying speed and winding speed. The resulting creped tissue paper was designated as high permeability paper I.

[0207] A method of manufacturing paper II and III with high permeability:

Crepe tissue paper was made in the same way as paper I with high permeability, except for a change in type (coarseness of the fiber) or degree of grinding of the pulp, etc. The resulting paper products were designated as high permeability paper II and high permeability paper III, which correspond to the above high permeability paper A.

[0208] The pulp (NBKP) used to make high permeability paper I, II, and III is listed below in ascending order of fiber coarseness. These pulp products were purchased from Japan Pulp & Paper Co., Ltd. or at Itochu Corp.

Pulp list Tradename Manufacturer The coarseness of the fiber (mg / m) Northwood ConFor 0.13 Cariboo Cariboo Pulp & Paper Co. 0.15 ARAUCO ARAUCO 0.18 Crofton CK Unifibra 0.2

[0209] rating

The results of the evaluation of paper I, II and III with high permeability are presented below in table 5. Dry tensile strength and liquid transit time were determined using the corresponding methods described above.

[0210] Table 5 High permeability paper Low permeability paper
I I II III The coarseness of the fiber of the first pulp (mg / m) 0.15 0.15 0.13 0.15 The coarseness of the fiber of the second pulp (mg / m) - 0.18 0.2 - ∆ Fiber coarseness (second-first) (mg / m) - 0,03 0,07 - The mass ratio of the first pulp to the second pulp 100/0 5/5 5/5 100/0 The degree of grinding pulp (ml) 500 500 500 650 The amount of the first additive that increases the strength (%) 0.20 0.20 0.20 - The amount of the second additive that increases the strength, (%) 0.78 0.78 0.78 0.78 The main mass (g / m ² ) 13.0 13.0 13.0 16,0 Density (g / cm ³ ) 0.13 0.13 0.15 0.23 The degree of creping (%) 10 10 10 10 Dry tensile strength (cN / 25 mm) MD 1040 923 890 934 CD 232 247 210 263 Liquid transit time (m) 175 205 295 780

Note 1: When two types of pulp were used, the degree of milling of the structure of the two pulp was obtained.
Note 2:
first strength improver A: sodium salt of anionic PAM (strength enhancer for dry paper)
second strength improver: PAE (wet strength enhancer)

[0211] Example D1

The flat disposable diaper shown in FIGS. 6 and 7 was made as an example of Example D1. The wrapping sheet for the core consisted of two sheets of paper I with high permeability without using a sheet with low permeability. The top sheet was formed from an air-permeable non-woven material with a bulk of 25 g / m ² obtained from bicomponent fibers with a shell and a core of 2.1 decitex, which have a linear polyethylene sheath and a polypropylene core (with a surface treated with a surfactant in order to to get liquid permeability). The back sheet was formed from a composite sheet consisting of a porous film with a bulk of 20 g / m ² and a polypropylene nonwoven fabric from the melt with a bulk of 20 g / m ² connected together with 1.5 g / m ^{2 of} hot-melt adhesive. The porous film of the back sheet was a film obtained by blow molding a uniform mixture of 100 parts by weight of a linear polyethylene resin having a density of 0.925 g / m ³ , 150 parts by weight of calcium carbonate and 4 parts by weight of the ester compound as the third component and stretching along a single axis obtained by extrusion with blown film in the longitudinal direction. The absorbent core was a mixed structure of air-formed fibers containing hydrophilic fibers (NB416 from Weyerhaeuser Company) and an absorbent polymer (Sunwet IM997 from Sundia Corp.) with a fiber to polymer ratio of 10/6 to 10/7 and having a bulk of 470 g / m ² . The absorbent core had a longitudinal length of 360 mm, a transverse length (maximum width) of 110 mm, a bulk of 470 g / m ² , a density of 0.17 g / cm ³ and a thickness of 2.7 mm without load.

[0212] Examples D2 to D4 and Comparative Example D1

A flat disposable diaper was made in the same way as in Example D1, except for changing the configuration of the wrapping sheet for the core (consists of two sheets, one on the skin-facing side of the absorbent core and the other on the non-skin side), as shown in the table below 6. The sheet with low permeability I, used in the examples and comparative example, was a crepe paper having a bulk of 16 g / m ² , a density of 0.23 g / cm ³ and a creping rate of 10%.

[0213] The evaluation results of the samples (disposable diapers) from Examples D2 to D4 and Comparative Example D1 are shown in Table 6. The ability to absorb loose stools and lateral leakage protection were evaluated as follows.

[0214] (1) The ability to absorb loose stools

The disposable diaper was fixed on a horizontal surface in its open configuration with the top sheet side up. Ten grams of artificial loose stool, a high viscosity fluid model, was injected at a time into the center of the absorbent element from the top of the sheet at a constant speed for 6 seconds. The sample was allowed to stand for 5 minutes with a mass of 3.5 kPa laid on it with an OHP film located between the mass and the diaper. The amount of artificial loose stool adhering to the OHP film was measured in order to obtain an amount of skin adhesion, and the amount of artificial loose stool absorbed by the absorbent core was taken as the absorption amount. Less adhesion or more absorption indicates a higher rating. The artificial loose stool consisted of 28.0 g of bentonite, 14.0 g of glycerol, 114.1 g of ion-exchange water and 14.2 g of a 0.03% aqueous solution of Emulgen 130K (from Kao Corp.). The artificial loose stool had a viscosity of 300 mPa · s, as measured as follows using a vibrating viscometer (CJV5000 from A & D Co., Ltd.). Approximately 170 g of artificial liquid stool was placed in a 300 ml beaker and stirred with a stirrer at 300 rpm for 60 seconds. Immediately, the beaker was mounted on a viscometer, and a pair of vibrators were inserted to the prescribed level. A measurement range of 50 mV was set and a measurement switch was pressed in order to start the measurement. The viscosity was read after 60 seconds from the start of the measurement. The measurement was carried out at 25 ° C.

[0215] (2) Protection against lateral leakage

The disposable diaper was fixed on a horizontal surface in its open configuration with the top sheet side up. Saline solution weighing 40 g was poured onto the center of the absorbent element through the top sheet and allowed to be absorbed, while applying a load of 2 kPa. Ten minutes after the first pouring, another portion of 40 g of physiological saline was poured and absorbed. The pouring operation was repeated until the total amount of physiological saline poured reached 160 g. During and after pouring, the diaper was visually checked for lateral saline flow from the diaper going in the longitudinal direction of the diaper. Protection against lateral leakage was classified as “A” when lateral leakage did not occur, even after total pouring reached 160 g, “B” when lateral leakage did not occur after total pouring reached 120 g, but occurred after total pouring pouring reached 160 g, or “C” when lateral leakage occurred after total pouring reached 120 g

[0216] Table 6 Example No. Comparative Example D1 D1 D2 D3 D4 Core wrapping sheet Skin side High Permeability Paper I High Permeability Paper I High Permeability Paper II High Permeability Paper III Low Permeability Sheet I Non-skin side High Permeability Paper I Low Permeability Sheet I Low Permeability Sheet I Low Permeability Sheet I Low Permeability Sheet I Ability to absorb loose stools The amount of adhesion (g) 0.3 0.3 0.4 0.4 0.7 The amount of absorption (g) 6.5 6.5 6.1 6.0 3,5 Lateral leakage protection B A A A A

[0217] As can be seen from the results in Table 6, the disposable diapers of the examples in which the wrapping sheet for the core on the skin side of the absorbent core are formed from high permeability concrete paper exhibit excellent liquid stool absorption ability (less skin adhesion and more absorption) and superior lateral flow protection compared to the disposable diaper of the comparative example in which the core wrapping sheet is completely formed from a low permeability sheet . In particular, the diapers of examples D2 to D4, in which the wrapping sheet for the core on the non-skin side of the absorbent core is formed from a sheet with low permeability, outperforms the diaper of example D1 in which the wrapping sheet for the core is completely lateral formed from concrete paper with high permeability, showing the effectiveness of such a combination of paper with high permeability and a sheet with low permeability.

Claims (18)

1. Tissue paper, which mainly contains a structure of two types of hydrophilic cellulose fibers, differing in the coarseness of the fiber and containing an additive that increases strength,
however, two types of hydrophilic cellulose fibers are the first pulp, which has a coarse fiber from 0.13 to 0.16 mg / m, and the second pulp, which has a coarse fiber from 0.17 to 0.20 mg / m, moreover, the difference in the coarseness of the fiber between the first and second pulp is from 0.01 to 0.07 mg / m, and the structure has a degree of grinding from 400 to 550 ml. 2. Tissue paper according to claim 1, where each of the first pulp and the second pulp has an average fiber length of 2 to 3 mm. 3. Tissue paper according to claim 1 or 2, where the ratio of the content of the first pulp to the second pulp, namely the first pulp / second pulp, is from 3/7 to 7/3 by weight. 4. Tissue paper according to claim 1 or 2, where the additive that increases the strength, contains at least carboxymethyl cellulose or its salt. 5. Tissue paper according to claim 1 or 2, which has a bulk of from 10 to 20 g / m ² . 6. Tissue paper according to claim 1, which mainly contains bleached kraft pulp of soft wood, having a degree of grinding from 400 to 550 ml, containing two or more additives that increase strength, and at the same time has a bulk of from 10 to 14.5 g / m ² , density from 0.05 to 0.2 g / cm ³ and the degree of creping from 5% to 30%. 7. Napkin paper according to claim 6, where two or more additives that increase the strength, contain an additive that increases the strength in the dry state, and an additive that increases the strength in the wet state. 8. The tissue paper of claim 7, wherein the dry strength improver is at least one member selected from the group consisting of carboxymethyl cellulose and its salt, polyacrylamide resin and its salt, cationic starch and polyvinyl alcohol. 9. Napkin paper according to claim 7 or 8, where the wet strength improver is at least one element selected from the group consisting of epoxidized polyamide-polyamine resin, urea-formaldehyde resin, melamine-formaldehyde resin, dialdehyde starch, polyethyleneamine and oxymethylated polyamide. 10. Tissue paper according to any one of claims 6 to 8, wherein two or more strength improvers are two dry strength enhancers and one wet strength improver. 11. Tissue paper of claim 10, where two additives that increase the strength in the dry state are a salt of carboxymethyl cellulose and a salt of anionic polyacrylamide, and one additive that increases the strength in the wet state is an epoxidized polyamide-polyamine resin. 12. Napkin paper according to claim 11, where the salt of the anionic polyacrylamide resin has a weight average molecular weight of 8000000 or more. 13. Tissue paper according to claim 1 or 2, which has a tensile strength in the dry state from 600 to 1500 cN / 25 mm in the machine direction during the manufacture of tissue paper and tensile strength in the dry state from 150 to 350 cN / 25 mm in the transverse machine direction perpendicular to the machine direction. 14. Tissue paper according to claim 1 or 2, which has a liquid passage time of from 0.2 to 3 seconds, as measured by a method that includes:
vertical and concentric stacking of two cylinders open at both ends and having an internal diameter of 35 mm, with a square sample with a side of 8 cm to be tested, which is inserted between them, supplying 40 ± 1 g of physiological saline to the upper cylinder, while the sample hold between the cylinders, passing the saline through or absorption by the sample and disappearing from the upper cylinder, and measuring the time from the beginning of the pouring of the saline to the moment when the surface level w dkosti equal to the sample surface to receive the passage of fluid. 15. An absorbent product that contains tissue paper according to any one of claims 1 or 2. 16. A method of manufacturing tissue paper, which has a bulk of 30 g / m ² or less, comprising the steps of forming a fibrous layer by making paper from raw materials obtained from a material containing bleached kraft pulp from soft wood, and drying the fibrous layer,
the feed is obtained by adding (a) a wet strength improver containing a cationic polymer that has a cationic group to a suspension of bleached softwood Kraft pulp, followed by the addition of (b) a low molecular weight dry strength improver, and (c) a macromolecular additive that increases strength in a dry state, simultaneously or in the described order in suspension,
wherein the low molecular weight dry strength improver (b) is a low molecular weight anionic polymer that has an anionic group and has a weight average molecular weight (molecular weight) of from 2,000 to 500,000, and
wherein the high molecular weight dry strength improver (c) is a high molecular weight anionic polymer that has an anionic group and has a molecular weight of from 5,000,000 to 30,000,000. 17. The method of manufacturing tissue paper according to clause 16, where the raw material is obtained by adding an additive that increases the strength in the wet state (a), in a suspension of bleached kraft pulp of softwood, and then follows the addition of a low molecular weight additive that increases the strength in the dry state ( b) followed by the addition of a high molecular weight dry strength improver (c). 18. The method of manufacturing tissue paper according to 17, where after adding a low molecular weight additive that increases the strength, (b) dilution follows, the dilution is followed by the addition of a high molecular weight additive to increase the strength, (c) and the addition of a high molecular weight additive to increase the strength, (c) followed by homogenization of the suspension using at least one of the mixing pump and filter screen.

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