Fluff pulp board

Abstract

A fluff pulp board according to one embodiment of the present invention contains hardwood bleached kraft pulp and softwood bleached kraft pulp, wherein the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp is 15 / 85 or more and 50 / 50 or less, and the content of acacia wood in the raw material wood of the hardwood bleached kraft pulp is 20% by mass or more and 100% by mass or less. The kappa number of the hardwood bleached kraft pulp is preferably 0.3 or less.

Description

Technical Field

[0001] The present invention relates to a pulp sheet for fluff pulp.

[0002] This application claims priority based on Japanese application No. 2020-215691 filed on December 24, 2020, and incorporates all the contents described in the Japanese application by reference. Background Art

[0003] Fluff pulp is produced by mechanically defibrillating wood pulp and is used as the absorbent component of absorbent articles such as disposable diapers.

[0004] As the fluff pulp used for such absorbent articles, wood pulp derived from softwood having excellent bulk (loftiness), water absorbency, and defibrillation properties is widely used (see Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2012-211411 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] On the other hand, wood pulp derived from hardwood is cheaper than pulp derived from softwood, but since the fiber length of wood pulp derived from hardwood is shorter and the fibers are densely packed than those of pulp derived from softwood, when wood pulp derived from hardwood is used in absorbent articles, the liquid absorption rate may be easily reduced. In addition, in absorbent articles, it is necessary to improve not only the water absorption performance but also the effect of suppressing contact dermatitis on the skin.

[0010] The present invention has been made based on the above circumstances, and an object of the present invention is to provide a pulp sheet for fluff pulp that can produce an absorbent article that suppresses contact dermatitis of the skin while achieving both absorption speed and rewetability.

[0011] Technical means to solve technical problems

[0012] According to one embodiment of the present invention, a pulp board for fluff pulp contains hardwood bleached kraft pulp and softwood bleached kraft pulp, wherein the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp is 15 / 85 to 50 / 50, and the content of acacia wood in the raw material wood of the hardwood bleached kraft pulp is 20% by mass to 100% by mass.

[0013] Beneficial Effects

[0014] According to the present invention, there can be provided a fluff pulp pulp sheet capable of producing an absorbent article that reduces the amount of rewetted absorbed liquid and suppresses contact dermatitis of the skin. DETAILED DESCRIPTION

[0015] [Description of Embodiments of the Invention]

[0016] According to one embodiment of the present invention, a pulp board for fluff pulp contains hardwood bleached kraft pulp and softwood bleached kraft pulp, wherein the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp is 15 / 85 to 50 / 50, and the content of acacia wood in the raw material wood of the hardwood bleached kraft pulp is 20% by mass to 100% by mass.

[0017] The fluff pulp pulp board can impart the bulk and liquid absorbency based on the softwood bleached kraft pulp to the absorbent article while imparting the surface density based on the hardwood bleached kraft pulp, the effect of reducing the amount of re-permeation of absorbed liquid, and the effect of inhibiting contact dermatitis on the skin by evenly blending the hardwood bleached kraft pulp and the softwood bleached kraft pulp in a specific mass ratio. In addition, by having the content of acacia wood in the raw material wood of the hardwood bleached kraft pulp being 20 mass % or more and 100 mass % or less, acacia wood with a thick fiber width can be blended in a certain amount or singly, so that the uniform gaps between the pulp fibers can be fully ensured, thereby further achieving a balance between the absorption speed and re-permeability of the absorbent article. Therefore, the fluff pulp pulp board can provide a fluff pulp pulp board, and the fluff pulp pulp board can manufacture an absorbent article that can inhibit contact dermatitis on the skin while reducing the amount of re-permeation of absorbed liquid.

[0018] The kappa number of the hardwood bleached kraft pulp is preferably 0.3 or less. The kappa number of the hardwood bleached kraft pulp is 0.3 or less, which can improve the inhibitory effect of contact dermatitis on the skin. The kappa number is measured according to JIS-P8211 (2011).

[0019] [Details of Embodiments of the Invention]

[0020] The fluff pulp pulp sheet according to one embodiment of the present invention is described in detail below. In addition, unless otherwise specified, the amount of each material added to the pulp sheet base material described below (absolute dry added amount) refers to the mass ratio relative to the absolute dry mass of the pulp of the pulp sheet base material.

[0021] <Pulp board for fluff pulp>

[0022] The fluff pulp pulp sheet can be obtained by making paper from a slurry containing raw material pulp.

[0023] (Raw pulp)

[0024] As the raw material pulp, for example, virgin pulp can be used. As the raw material pulp used in the fluff pulp pulp board, chemical pulp is preferred. As the chemical pulp, a combination of softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP) is preferred. By containing softwood bleached kraft pulp, the fluff pulp pulp board can improve the bulk and liquid absorbency of the absorbent article. In addition, by containing hardwood bleached kraft pulp, the fluff pulp pulp board can improve the density of the surface of the absorbent article, improve the effect of reducing the re-permeation amount of the absorbed liquid of the absorbent article, and improve the effect of inhibiting contact dermatitis on the skin.

[0025] (Bleached hardwood kraft pulp)

[0026] As the hardwood bleached kraft pulp, hardwood bleached kraft pulp produced from acacia wood or eucalyptus wood is preferred.

[0027] Acacia wood is a material that has the characteristics of little shrinkage due to drying, strong impact resistance, and strong hardness. The pulp obtained from acacia wood also inherits the original properties and is a useful raw material pulp with strong moisture absorption and drying properties. Eucalyptus wood belongs to the genus Eucalyptus, especially Eucalyptus globulus, Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus nitens, Eucalyptus regnans, etc. have been widely used as raw material pulp materials for papermaking since ancient times. The fiber lumen of the obtained pulp is rigid and not easy to collapse. By formulating the pulp fiber, a loose and thick pulp board for low-density fluff pulp can be obtained. As the hardwood bleached kraft pulp, acacia wood has a larger fiber width than eucalyptus wood and thus has a higher bulkiness. When combined with softwood bleached kraft pulp, acacia wood is more preferred because the liquid absorption rate is less reduced.

[0028] (Content of Acacia wood in the raw material wood for hardwood bleached kraft pulp)

[0029] The lower limit of the content of acacia wood in the raw material wood of the hardwood bleached kraft pulp is preferably 20% by mass, and more preferably 50% by mass. The upper limit of the content of acacia wood is preferably 100% by mass, and more preferably 80% by mass. When the content of acacia wood in the raw material wood of the hardwood bleached kraft pulp of the fluff pulp pulp board is within the above range, even the hardwood bleached kraft pulp having a shorter fiber length and easily densely packed between fibers compared with the softwood bleached kraft pulp, or regardless of the orientation of the fibers in any direction (e.g., the length direction / width direction / thickness direction of the absorbent article), the uniformity of the gaps between the fibers can be particularly well ensured, and therefore, both the absorption rate and the repermeability required for the fluff pulp pulp board can be taken into account. When the ratio exceeds the above range, for example, if the proportion of rigid eucalyptus wood increases, although the voids generated by the rigidity increase, the voids are easily deviated due to the different orientation directions of the fibers, so the absorption speed and rewetness of the absorbent article are easily uneven, resulting in a decrease in these properties, which is not preferred.

[0030] The lower limit of the average fiber width of the hardwood unbleached kraft pulp is preferably 16.7 μm, and more preferably 16.9 μm. If the average fiber width is lower than the lower limit, the spaces between the fibers in the absorbent article will become dense, the absorption rate will decrease, and contact dermatitis may be easily caused. On the other hand, the upper limit of the average fiber width is preferably 18.2 μm, and more preferably 17.7 μm. If the average fiber width exceeds the upper limit, the contact area between the pulp fibers in the pulp board for fluff pulp will become too large, the bonding force between the fibers will become high, and the crushability during the manufacturing process may be reduced. If the crushability is reduced too much, excessive crushing will occur in the manufacturing process of the absorbent article, fine fibers will be generated, and the absorption rate of the absorbent article may also be reduced. Here, the "average fiber width" refers to the weight average fiber width. The weight average fiber width was measured using a fiber length measuring instrument "FiberLab" manufactured by Metalwork Materials Co., Ltd. in accordance with JAPAN TAPPI pulp test method No. 52 "Pulp and Paper - Fiber Length Test Method - Optical Automatic Measurement" for fibers with a fiber length of 0.1 mm or more.

[0031] The lower limit of the weight average fiber length (hereinafter also referred to as the average fiber length) of hardwood unbleached kraft pulp is preferably 0.76 mm, and more preferably 0.80 mm. If the average fiber length is lower than the lower limit, the bulk of the pulp board for fluff pulp is likely to decrease, and the crushability during the manufacturing process may be reduced. On the other hand, the upper limit of the average fiber length is preferably 0.92 mm, and more preferably 0.86 mm. If the average fiber length exceeds the upper limit, the different orientation directions of the fibers in the absorbent article are likely to cause deviations in the gaps, and the absorption rate and rewetability may be reduced. Regarding the weight average fiber length, the fiber length measuring instrument "FiberLab" manufactured by Metz Ortme Shion Co., Ltd. is used to measure fibers with a fiber length of 0.1 mm or more in accordance with JAPAN TAPPI pulp test method No. 52 "Pulp and Paper-Fiber Length Test Method-Optical Automatic Measurement".

[0032] The kappa number of the hardwood bleached kraft pulp is preferably 0.3 or less. If the kappa number exceeds the upper limit, lignin in the fiber cannot be fully removed, the water absorption and rewetting of the pulp fiber are reduced, and contact dermatitis may be easily caused.

[0033] The lower limit of the sulfidation degree of the white liquor of the cooking hardwood kraft pulp is preferably 25%, and more preferably 28%. If the sulfidation degree is lower than 25%, the pulp fibers are easily damaged, and the absorbent articles become dense, which is likely to reduce the absorption rate and may cause contact dermatitis. On the other hand, the upper limit of the sulfidation degree is preferably 32%, and more preferably 30%. If the sulfidation degree exceeds the upper limit, the pulp fibers are not easily damaged and remain rigid, the unevenness in the gaps of the absorbent body increases, and the re-permeability is easily reduced, which may cause contact dermatitis. The sulfidation degree is calculated according to the following formula as the ratio of sodium sulfide to the sum of sodium sulfide and sodium hydroxide.

[0034] Sulfidation degree (%) = (Na2S / (NaOH+Na2S)) × 100

[0035] (Freeness of unbeaten hardwood bleached kraft pulp)

[0036] The Canadian Standard Freeness (CSF) of the unbeaten pulp of hardwood bleached kraft pulp is preferably adjusted to 520 ml or more and 580 ml or less. In the case where the freeness of the unbeaten pulp of hardwood bleached kraft pulp is less than 520 ml, the dewatering property during pulp board manufacturing becomes poor, and mechanically enhanced dewatering (for example, enhanced press dewatering in a paper machine) is required, which not only strengthens the bonding between pulp fibers, but also reduces the bulk of the pulp board, so that the crushing property during manufacturing may be reduced. On the other hand, if the Canadian Standard Freeness of the unbeaten pulp exceeds 580 ml, there will be too many gaps between the fibers in the pulp board, and it is easy to be unevenly crushed during crushing, and the re-permeability in absorbent articles is reduced, which may easily cause contact dermatitis.

[0037] The lower limit of the content of bleached hardwood kraft pulp in the pulp board for fluff pulp is preferably 15% by mass, and more preferably 20% by mass. On the other hand, the upper limit of the content of the bleached hardwood kraft pulp is preferably 50% by mass, and more preferably 40% by mass. The "content of bleached hardwood kraft pulp in the pulp board for fluff pulp" is also the same when it contains other pulps other than bleached hardwood kraft pulp and bleached softwood kraft pulp. By keeping the content of the bleached hardwood kraft pulp within the above range, when mixed with the bleached softwood kraft pulp, even the bleached hardwood kraft pulp with short fiber length and easy to be densely filled between fibers can ensure particularly good spaces between fibers, so that the absorption rate and re-permeability required for the pulp board for fluff pulp can be taken into account.

[0038] (softwood bleached kraft pulp)

[0039] In the fluff pulp pulp board, as the raw material wood for the softwood bleached kraft pulp, pine trees represented by radiata pine and various types of fir are preferably used.

[0040] (Pulp mixing ratio)

[0041] The lower limit of the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp in the pulp used in the fluff pulp pulp board is 15 / 85, preferably 20 / 80. If the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp is less than 15 / 85, the gaps between the fibers in the absorbent article are prone to become uneven, and back-seepage is easy, which may easily cause contact dermatitis. On the other hand, the upper limit of the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp is 50 / 50, preferably 40 / 60. If the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp exceeds 50 / 50, the absorbent article will become dense, the absorption rate will decrease, and contact dermatitis may be easily caused.

[0042] By setting the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp within the above range, even if the hardwood bleached kraft pulp, which has short fibers and is easy to be densely packed, is mixed with the softwood bleached kraft pulp, the gaps between the fibers can be uniform and not uneven regardless of the orientation of the hardwood bleached kraft pulp fibers. Therefore, the absorption speed required for the pulp board for fluff pulp and the rewet and contact dermatitis suppression effects required for absorbent articles can be well achieved.

[0043] (Other pulp)

[0044] The fluff pulp board may contain other pulps besides hardwood bleached kraft pulp and softwood bleached kraft pulp. Examples of the other pulps include soda pulp, sulfite pulp, chemical thermomechanical pulp, chemical disc mechanical pulp, thermochemical mechanical pulp, etc. However, if the lignin in the fiber is not sufficiently removed, the water absorption of the pulp fiber will decrease, the re-permeability will decrease, and contact dermatitis will be easily caused. Therefore, bleached pulp from which lignin has been sufficiently removed is preferred. When the other pulp is contained, the content of the other pulp is preferably 10% by mass or less relative to the total pulp raw material.

[0045] (Other additives)

[0046] Other additives may be added to the fluff pulp board as needed. For example, fillers, pigments, sizing agents, coagulants, oil-proofing agents, aluminum sulfate, retention aids, drainage enhancers, dry paper strength enhancers, wet paper strength enhancers, coloring pigments, water-proofing agents, etc. may be used alone or in combination.

[0047] [Physical properties of fluff pulp]

[0048] (Quantitative)

[0049] The basis weight is measured in accordance with "Paper and paperboard - Method for determination of basis weight" described in JIS-P8124 (2011). The basis weight of the fluff pulp pulp sheet can be, for example, 300.0 g / cm 2 Above 1500.0g / cm 2 the following.

[0050] (density)

[0051] The density is measured in accordance with "Paper and paperboard - Test methods for thickness, density and specific volume" described in JIS-P8118 (2014). The lower limit of the density of the fluff pulp pulp sheet is preferably 0.52 g / cm 3 , more preferably 0.53 g / cm 3The upper limit of the density of the fluff pulp pulp sheet is preferably 0.60 g / cm 3 , more preferably 0.59 g / cm 3 By setting the density of the fluff pulp sheet to be within the above range, the fluff pulp sheet obtained by mixing the hardwood bleached kraft pulp and the softwood bleached kraft pulp can improve the crushability during the manufacturing process, and can also obtain an absorbent article in which the gaps between fibers are easily ensured to be uniform and free of unevenness. Therefore, the absorption rate and the amount of re-permeation of the absorbed liquid, which are opposite properties of the absorbent article, can be balanced, and an absorbent article that can achieve good results in both can be obtained.

[0052] The density was measured in an atmosphere of 23±1° C. and 50±2% RH in accordance with “Paper, paperboard and pulp-Standard conditions for moisture conditioning and testing” described in JIS-P8111 (1998).

[0053] (Burst index (specific burst strength))

[0054] The bursting index is a value obtained by dividing the bursting strength of paper expressed in kilopascals (kPa) measured in accordance with JIS-P8131 (2009) by the quantitative value. The lower limit of the bursting index is preferably 1.20 kPa·m 2 / g, more preferably 1.22 kPa·m 2 / g. The bursting index of the fluff pulp board is lower than 1.20 kPa·m 2 / g, excessive pulverization will occur, and the fibers will be easily cut, so the absorbent article will become dense, the absorption rate will decrease, and contact dermatitis may be easily caused. On the other hand, the upper limit of the bursting index of the pulp sheet for fluff pulp is preferably 1.58 kPa·m 2 / g, more preferably 1.44 kPa·m 2 / g. The bursting index of the fluff pulp board exceeds 1.58 kPa·m 2 / g, the pulverization property during the manufacturing process is poor, and the voids in the obtained absorbent article are increased, so the absorbed liquid is easy to re-seep, and contact dermatitis may also be easily caused. When the bursting index of the fluff pulp pulp sheet is within the above range, the pulverization property during the manufacturing process of the fluff pulp pulp sheet mixed with the hardwood bleached kraft pulp and the softwood bleached kraft pulp can be improved, and the voids between the fibers in the absorbent article can be easily ensured to be uniform without unevenness, so that the opposite performances, that is, the absorption speed of the absorbent article and the amount of re-seepage of the absorbed liquid can be balanced, and both can be good.

[0055] The burst index was measured in accordance with "Paper, paperboard and pulp - Standard conditions for moisture conditioning and testing" described in JIS-P8111 (1998) in an atmosphere of 23±1°C and 50±2%RH.

[0056] [Method for manufacturing a pulp sheet for fluff pulp]

[0057] The method for producing the fluff pulp pulp sheet is not particularly limited, and for example, includes the following steps: a cooking step of cooking raw wood to produce unbleached pulp; a delignification step of delignifying; a bleaching step of bleaching to produce bleached pulp; a beating step of beating the bleached pulp to a desired freeness; and a step of making paper from the pulp slurry. In addition, a dehydration and washing step may be appropriately provided between the steps.

[0058] (Steaming process)

[0059] In the cooking process, the raw wood is cooked to produce unbleached pulp. White liquor and raw wood chips (hardwood or softwood) are put into a cooking kettle for cooking, and the pulp slurry mixed with the generated black liquor (unwashed) is taken out from the bottom of the continuous cooking kettle. The cooking method can be arbitrarily selected from MCC, EMCC, ITC, Lo-Solids, KobudoMari, Compact method, etc., which are commercial process improvement methods; the cooking kettle can be a continuous cooking kettle or an intermittent kettle method; in addition, there is no particular limitation on the cooking conditions (cooking temperature, H factor which is a factor obtained by multiplying the influence of the cooking temperature and the cooking time, the content ratio of active alkali or effective alkali, etc.).

[0060] (Delignin process)

[0061] In the delignification process, unbleached pulp is delignified. Alkaline chemicals and oxygen are added to the unbleached pulp, and lignin is decomposed under high temperature and high pressure and dissolved into the alkaline chemicals. The delignification process has no special requirements for low concentration (pulp concentration: 3% to 8%), medium concentration (pulp concentration: 8% to 15%), and high concentration (pulp concentration: 20% to 30%).

[0062] (Washing process)

[0063] In the washing process, the unbleached pulp is washed by combining displacement, dilution or dehydration. The washing method is not particularly limited, and a known washing machine can be used for washing. For example, a displacement washing method, a dilution / dehydration method, a press washing method or a washing method combining these methods can be used. As a washing machine of the displacement washing method, a diffusion washing machine, a pressurized diffusion washing machine, a belt washing machine, etc. can be used. As a washing machine of the dilution / dehydration method, a vacuum filter washing machine, a pressurized filter washing machine, etc. can be used. As a press washing method, a screw press washing machine, a disc press washing machine, a roller press washing machine, etc. can be used.

[0064] In the present invention, since it is preferred to remove lignin and reduce the kappa number, it is preferred to use a press washer that can easily remove lignin. The pulp concentration after washing by the press washing method is preferably 30% or more, more preferably 32% or more, and further preferably 35% or more. If dehydration is performed by the press washing method, since the water inside the fiber can also be removed by squeezing, it is easier to fully remove the free lignin inside the pulp fiber compared to other washing methods.

[0065] (Bleaching process)

[0066] In the bleaching step, the delignified unbleached pulp is bleached to produce bleached pulp. The bleaching method is not particularly limited, and bleaching can be carried out by a known bleaching method. For example, acid treatment, ozone bleaching, chlorine dioxide bleaching, hydrogen peroxide bleaching, or further bleaching with alkali extraction, alkali extraction with oxygen addition, alkali extraction with oxygen addition and hydrogen peroxide, etc., can be carried out alone or in combination of multiple methods.

[0067] In the bleaching step, ozone bleaching is preferably used, which can adjust the water absorption and repermeability of pulp fibers by damaging the pulp fibers. The method of ozone bleaching is not particularly limited, and it can be carried out at any of high concentrations (30% to 40%), medium concentrations (8% to 15%), and low concentrations (1% to 3%), but a high concentration method is preferred because it is more likely to damage the fibers.

[0068] A known ozone generator can be used. The generated ozone can be directly mixed with the pulp or dissolved in water and then mixed with the pulp.

[0069] In ozone bleaching, the lower the pH, the more delignification is promoted; on the other hand, the damage to the fiber becomes smaller, so it is preferable to adjust the pH according to the quality requirements of the fluff pulp pulp sheet. The pH in ozone bleaching of the fluff pulp pulp sheet is preferably 6 or less, more preferably 4 or less, and further preferably 2 to 3. When the pH in ozone bleaching of the fluff pulp pulp sheet is in the above range, it is easy to achieve both the absorption rate and the rewet property required for the fluff pulp pulp sheet, so it is preferred.

[0070] (Preparation process)

[0071] If necessary, in the pulping process, the bleached pulp is beaten to a desired freeness. Thereafter, the pulp fibers are dispersed in water to obtain a slurry, and additives corresponding to each paper layer are added to the slurry and mixed as needed to prepare paper stock for each paper layer.

[0072] (Papermaking process)

[0073] Next, these raw material slurries are used to make paper with a papermaking machine in a neutral range of pH 6 to 8. In the papermaking process, the raw material pulp is made into paper using a papermaking machine that makes paper from the pulp raw material sprayed onto the running line. The papermaking machine is not particularly limited, and known papermaking machines such as fourdrinier papermaking machines, cylinder papermaking machines, hybrid forming machines, and sandwich forming machines can be used to make paper in the form of sheets. The pulp board for fluff pulp can be manufactured by single-layer or multi-layer combined papermaking, but if it is a single layer, it is easy to make the density in the layer uniform, so it is preferred.

[0074] The fluff pulp pulp sheet can produce an absorbent article that achieves both absorption rate and rewetness and suppresses contact dermatitis of the skin.

[0075] [Fluff pulp]

[0076] Fluff pulp can be obtained by defibrillating the fluff pulp pulp sheet into fibers by mechanical treatment. The fluff pulp pulp sheet used in the fluff pulp of the present invention may be in a bundle or roll form. A roll form is preferred because it is easy to improve the productivity of absorbent articles.

[0077] In the present invention, the apparatus used for the mechanical treatment for fluffing, i.e., defibration, is not particularly limited. A known defibrator used in the manufacture of absorbent articles such as diapers can be used, and preferably a defibrator using friction or shearing force as a mechanical treatment can be used. As a defibrator for fluffing, for example, a hammer mill, an impact mill, a roller mill, a jet airflow mill, etc. can be used.

[0078] [Absorbent articles]

[0079] The absorbent article is an absorbent article using the pulp sheet for fluff pulp. Since the absorbent article uses the pulp sheet for fluff pulp, both absorption speed and repermeability can be achieved, and contact dermatitis of the skin can be suppressed. The absorbent article is not particularly limited, and examples thereof include diapers, urine pads, light incontinence pads, sanitary napkins, and the like.

[0080] The manufacturing method of the absorbent article is not particularly limited and can be manufactured by a known method. For example, in the case of diapers, the diapers can be manufactured by using manufacturing machines manufactured by Zuiko Co., Ltd., Toa Kiko Co., Ltd., or Ahaltrayma Co., Ltd., for example, by panel type, leg hole type, longitudinal flow type, cross flow type, etc.

[0081] <Other Implementation Methods>

[0082] The present invention is not limited to the above-described embodiment, and can be implemented in various modified and improved forms other than the above-described form.

[0083] Example

[0084] Hereinafter, the present invention will be further specifically described by way of examples, but the present invention is not limited to the following examples.

[0085] [Examples 1 to 14, Comparative Examples 1 to 4, Reference Example 1]

[0086] Pulp sheets for fluff pulp of Examples 1 to 14 and Comparative Examples 1 to 4 were prepared according to the following procedures.

[0087] (Steaming process)

[0088] (1) Hardwood

[0089] Acacia and eucalyptus are mixed in a specified mass ratio, white liquor with a specified sulfidation degree is added, and the mixture is cooked in a rotary autoclave at a liquid ratio of 6.0 (L / kg) and a maximum temperature of 170°C to obtain unbleached kraft pulp with a kappa number of about 16.

[0090] (2) Coniferous wood

[0091] White liquor with a specified sulfidation degree was added to fir wood, and the wood was cooked in a rotary autoclave at a liquid ratio of 6.0 (L / kg) and a maximum temperature of 170°C to obtain unbleached kraft pulp with a kappa number of about 30.

[0092] (Washing process)

[0093] After the unbleached pulp was diluted to a pulp concentration of about 2%, No. 2 filter paper (manufactured by ADVANTEC) was placed on a Buchner funnel to dehydrate the pulp to a pulp concentration of about 12%. Thereafter, in the case of press dehydration as described in Table 1, the unbleached pulp was sandwiched between square filter papers (manufactured by ADVANTEC) and pressure was applied by a press to dehydrate the pulp to a pulp concentration of 33%. This washing process was performed twice in both the case of press dehydration and the case of non-press dehydration.

[0094] (Bleaching process)

[0095] (1) Hardwood

[0096] (1-1) Acid treatment

[0097] Unbleached kraft pulp was adjusted to a pulp concentration of 10% and a pH of 3.0, and acid-treated at 90° C. for 3 hours.

[0098] (1-2) Ozone bleaching

[0099] The acid-treated pulp was subjected to ozone bleaching at 45° C. for about 2 minutes using ozone gas having a concentration of 8.1%. The ozone bleaching used ozone gas from a laboratory ozone generator such as PSA Ozonizer SGA-01A-PSA4 manufactured by Sumitomo Precision Industries, Ltd.

[0100] (1-3) Chlorine dioxide bleaching

[0101] The ozone-bleached pulp was bleached with chlorine dioxide at a chlorine dioxide addition rate of 1.5%, a pulp concentration of 10% by mass, and 70° C. to obtain hardwood bleached kraft pulp having the kappa number shown in Table 1.

[0102] In addition, between each bleaching step, the following dilution and washing step was performed twice: after diluting the pulp to a pulp concentration of about 2%, No. 2 filter paper (manufactured by ADVANTEC) was placed on a Buchner funnel to dehydrate the pulp to a pulp concentration of about 12%.

[0103] (2) Coniferous wood

[0104] The unbleached kraft pulp was subjected to chlorine dioxide bleaching at a chlorine dioxide addition rate of 1.5%, a pulp concentration of 10% by mass, and 70° C. for 30 minutes. Subsequently, alkaline hydrogen peroxide bleaching was performed at an alkali addition rate of 1%, a hydrogen peroxide addition rate of 0.3%, a pulp concentration of 10% by mass, and 70° C. for 120 minutes. Subsequently, alkali treatment was performed at a sodium hydroxide addition rate of 0.2%, a pulp concentration of 10% by mass, and 70° C. for 120 minutes. Subsequently, chlorine dioxide bleaching was performed at a chlorine dioxide addition rate of 0.3%, a pulp concentration of 10% by mass, and 70° C. for 150 minutes to obtain softwood bleached kraft pulp.

[0105] In addition, between each bleaching step, the following dilution and washing step was performed twice: after diluting the pulp to a pulp concentration of about 2%, No. 2 filter paper (manufactured by ADVANTEC) was placed on a Buchner funnel to dehydrate the pulp to a pulp concentration of about 12%.

[0106] (Papermaking process)

[0107] The obtained bleached kraft pulp was diluted to a concentration of about 2% without beating, and then a semi-automatic sheeter (manufactured by Kumagai Riki Kogyo Co., Ltd.) was used to prepare a sheet with a basis weight of 800 g / m 2In this way, the fluff pulp pulp sheets of Examples 1 to 14 and Comparative Examples 1 to 4 were obtained.

[0108] [Table 1]

[0109]

[0110] The fluff pulp pulp sheet obtained in the above manner was subjected to various evaluations.

[0111] (Weight average fiber length and weight average fiber width of pulp fibers)

[0112] The weight average fiber length and weight average fiber width of the hardwood unbleached kraft pulp (Kappa number of about 16) of Examples 1 to 14 and Comparative Examples 1 to 4 after the cooking process and the washing process were measured. The weight average fiber length and weight average fiber width were measured using a fiber length measuring instrument "FiberLab" manufactured by Metz Ort Methion Co., Ltd. in accordance with JAPAN TAPPI pulp test method No. 52 "Pulp and Paper - Fiber Length Test Method - Optical Automatic Measurement" for fibers with a fiber length of 0.1 mm or more. The fiber analyzer "FiberLab" can measure the length and width of pulp fibers with high accuracy based on image analysis when diluted pulp fibers pass through the measuring unit inside the fiber analyzer.

[0113] (Density of fluff pulp board)

[0114] The density of each fluff pulp pulp sheet was measured in accordance with "Paper and paperboard-Test methods for thickness, density and specific volume" described in JIS-P8118 (2014).

[0115] (Burst index of fluff pulp board)

[0116] The bursting index of each fluff pulp pulp sheet is obtained by dividing the bursting strength of paper expressed in kilopascals (kPa) measured in accordance with JIS-P8131 (2009) by the basis weight.

[0117] (Crushability of Fluff Pulp Board)

[0118] Regarding the crushability of each fluff pulp pulp board, 5 g of fluff pulp cut into 10 mm × 10 mm was put into a laboratory mixer to crush the pulp. Then, the pulp state was checked every 10 seconds, and the time required until the pulp lumps disappeared was measured. If the crushability is poor, the liquid absorbency and rewetness of the absorbent will be uneven, and both properties may be reduced. Based on Reference Example 1 with 100% coniferous wood, the evaluation was performed according to the following 4 levels. In the case of evaluation A and B, the crushability of the fluff pulp pulp board is good.

[0119] A: The fluff pulp can be processed with the same defibration time as that of Reference Example 1.

[0120] B: Although the time required for defibration is slightly longer than that of the fluff pulp of Reference Example 1, it can be used in practice.

[0121] C: Although it takes longer time to defibrate than the fluff pulp of Reference Example 1, it can be used in practice.

[0122] D: Compared with the fluff pulp of Reference Example 1, the time required for defibration is significantly longer and it is not practically usable.

[0123] (Absorption rate of fluff pulp)

[0124] As a procedure for measuring the absorption rate of each fluff pulp, first, 5 g of fluff pulp cut into 10 mm × 10 mm is put into a laboratory mixer and crushed. Next, 0.5 g of the crushed pulp adjusted in the crushability test is compressed into a disc shape to adjust the sample, and then thrown into the water surface, and the time required until it sinks under the water surface is measured. Based on Reference Example 1 with 100% coniferous wood, the following 4 levels are evaluated. In the case of evaluation A and B, the absorption rate of the fluff pulp is good.

[0125] A: Equivalent to the fluff pulp of Reference Example 1, and sedimented quickly.

[0126] B: Compared with the fluff pulp of Reference Example 1, it takes a little time to settle, but it can be used in practice.

[0127] C: Compared with the fluff pulp of Reference Example 1, it takes time to settle, but it can be used in practice.

[0128] D: The sedimentation time is significantly later than that of the fluff pulp of Reference Example 1, and it is not practically usable.

[0129] (Rewet amount of absorbed liquid in absorbent article)

[0130] The amount of rewetting refers to the amount of liquid that is released from the absorbent body due to pressure applied to the absorbent body. Regarding the amount of rewetting of absorbed liquid, diapers were made using the fluff pulp pulp boards of Examples 1 to 14 and Comparative Examples 1 to 4, and then artificial urine was absorbed by the absorbent body multiple times at intervals. Filter paper was placed on the absorbent body, a load was applied, and the weight of the artificial urine absorbed by the filter paper was measured. Evaluation was performed based on the following 4 levels, with reference example 1 of 100% coniferous wood as the benchmark. In the case of evaluations A, B, and C, the effect of inhibiting the rewetting of absorbed liquid in absorbent articles was good.

[0131] A: Compared with the fluff pulp of Reference Example 1, the amount of rewet is small.

[0132] B: The rewet amount is equivalent to that of the fluff pulp of Reference Example 1.

[0133] C: The amount of rewet is slightly larger than that of the fluff pulp of Reference Example 1, but it is practically usable.

[0134] D: The amount of rewet is large compared to the fluff pulp of Reference Example 1 and cannot be used practically.

[0135] (Contact dermatitis of the skin caused by absorbent articles)

[0136] After making diapers using the fluff pulp pulp sheets of Examples 1 to 14, Comparative Examples 1 to 4, and Reference Example 1, 50 monitors were asked to use 10 sheets each, and the number of sheets that developed contact dermatitis was evaluated as a percentage. Evaluation was performed based on the following four levels based on Reference Example 1. In the case of evaluation A, B, and C, the effect of suppressing contact dermatitis on the skin was good.

[0137] A: The incidence of contact dermatitis is better than that of reference example 1.

[0138] B: The incidence of contact dermatitis is slightly better than that of Reference Example 1.

[0139] C: The incidence of contact dermatitis is equivalent to that of Reference Example 1 and can be used in practice.

[0140] D: The incidence of contact dermatitis is higher than that of Reference Example 1 and cannot be used in practice.

[0141] The evaluation results of each embodiment and comparative example are shown in Table 2.

[0142] [Table 2]

[0143]

[0144] As shown in Table 2, for Examples 1 to 14 in which the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp was 15 / 85 to 50 / 50, and the content of acacia wood in the raw material wood of the hardwood bleached kraft pulp was 20% to 100% by mass, good results were obtained in terms of the crushability of the pulp board for fluff pulp, the absorption rate of the fluff pulp, the re-permeation amount of the absorbed liquid of the absorbent article, and the inhibitory effect on contact dermatitis on the skin.

[0145] On the other hand, in Comparative Example 1, in which the content of acacia wood in the raw material wood of hardwood bleached kraft pulp was less than 20% by mass, the absorption rate of fluff pulp and the suppressive effect of the absorbent article on contact dermatitis on the skin were poor. In Comparative Example 2, in which the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp was less than 15 / 85, the pulp board for fluff pulp had poor crushability, and the amount of absorbed liquid re-permeated in the absorbent article was large, and the suppressive effect on contact dermatitis on the skin was poor. It is believed that this is because when the amount of absorbed liquid re-permeated in the absorbent article is large, even after urine is absorbed, the urine returns to the surface of the absorbent article due to pressure applied by body movement and comes into contact with the skin, which easily causes contact dermatitis. In Comparative Example 3, in which the mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp exceeded 50 / 50, i.e., the mass ratio was very high, the pulp sheet for fluff pulp had poor crushability and absorption rate, and the absorbent article had poor contact dermatitis suppressing effect on the skin. It is believed that this is because the absorption rate of the fluff pulp pulp sheet slowed down, resulting in a longer contact time between the skin and excreta such as urine when the absorbent article was worn, which easily caused contact dermatitis. In addition, in Comparative Example 4, in which the mass ratio of the hardwood bleached kraft pulp slightly exceeded 50 / 50, the contact dermatitis suppressing effect on the skin was poor.

[0146] The above results show that the absorbent article using the pulp sheet for fluff pulp has a good effect of reducing the amount of rewetted absorbed liquid and a good effect of suppressing contact dermatitis on the skin.

[0147] The pulp sheet for fluff pulp of the present invention is suitable for use in absorbent articles.

Claims

1. A pulp board for fluff pulp, characterized in that: The fluff pulp pulp board contains hardwood bleached kraft pulp and softwood bleached kraft pulp. The mass ratio of the hardwood bleached kraft pulp to the softwood bleached kraft pulp is 15 / 85 or more and 50 / 50 or less, The content of acacia wood in the raw material wood of the hardwood bleached kraft pulp is 20 mass % or more and 100 mass % or less, The basis weight of the fluff pulp board is 300.0 g / cm 2 Above 1500.0g / cm 2 the following, The bursting index of the pulp board for fluff pulp is 1.22 kPa·m 2 / g or above 1.44 kPa·m 2 / g or less.

2. The pulp board for fluff pulp according to claim 1, characterized in that: The kappa number of the hardwood bleached kraft pulp is less than 0.

3.

3. An absorbent article using the pulp sheet for fluff pulp according to claim 1 or 2.

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