Fluff mat, absorbent article, pulp sheet for fluff pulp, and method for manufacturing a fluff mat

Abstract

The present invention aims to provide a fluff mat that has a good feel to the touch and a sufficiently reduced rate of liquid backflow. [Solution] The present invention relates to a fluff mat containing hardwood pulp, wherein the hardwood pulp content relative to the total pulp components in the fluff mat is 20% by mass or more, and the TS7 of the fluff mat surface measured by measurement method (A) is 6.1 dBV. 2 Regarding fluff mats that are less than RMS.

Description

Technical Field

[0001] The present invention relates to a fluff mat, an absorbent article, a pulp sheet for fluff pulp, and a method for manufacturing a fluff mat.

Background Art

[0002] Fluff pulp is obtained by defibrating wood pulp until it becomes cotton-like. Fluff pulp is used as a water-absorbing material in absorbent articles such as disposable diapers and sanitary napkins.

[0003] Conventionally, fluff pulp used in absorbent articles has been produced from softwood pulp with good defibratability (for example, Patent Document 1). In Patent Document 1, fluff pulp is obtained by mechanically defibrating raw pulp (softwood kraft pulp) with a moisture content of 35% or less.

[0004] Also, Patent Document 2 discloses a pulp sheet for fluff pulp containing hardwood kraft pulp and softwood kraft pulp. Here, it has been studied to obtain a pulp sheet for fluff pulp that can reduce the amount of backflow of the absorbed liquid and suppress skin swelling by setting the content ratio of hardwood kraft pulp and softwood kraft pulp within a predetermined range.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] As mentioned above, pulp sheets for fluff pulp containing bleached hardwood kraft pulp and bleached softwood kraft pulp are known, but when fluff mats are manufactured from conventional fluff pulp sheets, the texture can deteriorate, which has been a problem. In addition, the rate of liquid backflow in fluff mats manufactured from conventional fluff pulp sheets is not sufficiently low, and improvement is needed.

[0007] Therefore, in order to solve the problems of the prior art, the inventors of this invention proceeded with research with the aim of providing a fluff mat that has a good feel to the touch and a sufficiently reduced rate of liquid backflow. [Means for solving the problem]

[0008] Examples of specific embodiments of the present invention are shown below.

[0009] [1] A fluff mat containing hardwood pulp, The hardwood pulp content in the fluff mat is 20% by mass or more of the total pulp components. The TS7 of the fluff mat surface measured using the measurement method (A) below was 6.1 dBV. 2 Fluff mat that is less than rms; Measurement method (A): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25g / m²) are placed on the top and bottom of the fluff mat. 2 ) are stacked; a circular stainless steel plate is placed on the surface of the fluff mat with the center sheet stacked on top, and the fluff mat with the center sheet is pressed with a manual press machine while adjusting the press pressure so that the thickness of the fluff mat is 4.2 mm; the fluff mat with the center sheet is placed on the sample stage of the tissue softness measuring device TSA, and a rotor with blades is pressed down on the fluff mat with the center sheet with a pressing pressure of 100 mN, and then rotated at a rotation speed of 2.0 rpm, and the intensity of the maximum peak of the spectrum including the frequency 6500 Hz obtained when the vibration of the sample stage is measured with a vibration sensor (TS7 value) is taken as the TS7 of the fluff mat surface. [2] The TS750 on the surface of the fluff mat measured by the measurement method (B) below was 7.0 dBV. 2 Fluff mat as described in [1], which is rms or greater; Measurement method (B): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25g / m²) are placed on the top and bottom of the fluff mat. 2 ) are stacked; a circular stainless steel plate is placed on the surface of the fluff mat with the center sheet stacked on top, and the fluff mat with the center sheet is pressed with a manual press machine while adjusting the press pressure so that the thickness of the fluff mat is 4.2 mm; the fluff mat with the center sheet is placed on the sample stage of the tissue softness measuring device TSA, and a rotor with blades is pressed down on the fluff mat with the center sheet with a pressing pressure of 100 mN, and then rotated at a rotation speed of 2.0 rpm, and the intensity of the first maximum peak of the spectrum viewed from the low frequency side obtained when the vibration of the sample stage is measured with a vibration sensor (TS750 value) is taken as the TS750 of the fluff mat surface. [3] A fluff mat as described in [1] or [2], wherein the HF value of the fluff mat surface measured by the measurement method (D) below is 93.0 or higher; Measurement method (D): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25g / m²) are placed on the top and bottom of the fluff mat. 2 The center sheets are stacked on top of each other; a circular stainless steel plate is placed on the surface of the fluffy mat with the center sheets stacked on top of it, and the fluffy mat with the center sheets is pressed using a manual press machine while adjusting the press pressure so that the thickness of the fluffy mat becomes 4.2 mm; the fluffy mat with the center sheets is placed on the sample stage of the tissue softness measuring device TSA, and the three parameters of the fluffy mat with the center sheets, TS7 value, TS750 value, and D value, are quantified by vibration measurement and deformation measurement. Based on these obtained parameters, the basis weight, thickness, and number of plies of the sample, the hand feel (HF) value is calculated by performing an analysis using the facial II algorithm. [4] A fluff mat according to any one of [1] to [3], wherein the content of hardwood pulp relative to the total pulp components in the fluff mat is 50% by mass or more. [5] An absorbent article comprising a fluff mat as described in any of [1] to [4]. [6] A pulp sheet for fluff pulp used in the manufacture of fluff mat as described in any of [1] to [4]. [7] A process of obtaining fluff pulp by defibrating a pulp sheet for fluff pulp containing hardwood pulp, The process includes a step of forming fluff pulp into a sheet, The hardwood pulp content in the pulp sheet for fluff pulp is 20% by mass or more of the total pulp components. A method for manufacturing a fluff mat, wherein the process of forming it into a sheet is carried out so that the compression ratio is 65% or less. [8] The method for producing a fluff mat according to [7], wherein in the step of obtaining fluff pulp, the defibration treatment is performed under conditions of a defibration rotation speed of 21,000 rpm or higher. A pulp sheet for fluff pulp used in the method for manufacturing fluff mats described in [9] [7] or [8]. [Effects of the Invention]

[0010] According to the present invention, a fluff mat can be obtained that has a good tactile feel and a sufficiently reduced rate of liquid backflow. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram illustrating the configuration of the fluff mat manufacturing apparatus used to produce the fluff mat. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below. The following descriptions of constituent elements may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, numerical ranges represented by "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits.

[0013] (Fluff mat) This embodiment relates to a fluff mat containing hardwood pulp, wherein the hardwood pulp content relative to the total pulp components in the fluff mat is 20% by mass or more, and the TS7 of the fluff mat surface measured by the following measurement method (A) is 6.1 dBV. 2 Regarding fluff mats that are less than RMS. Measurement method (A): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25g / m²) are placed on the top and bottom of the fluff mat. 2 ) are stacked; a circular stainless steel plate is placed on the surface of the fluff mat with the center sheet stacked on top, and the fluff mat with the center sheet is pressed with a manual press machine while adjusting the press pressure so that the thickness of the fluff mat is 4.2 mm; the fluff mat with the center sheet is placed on the sample stage of the tissue softness measuring device TSA, and a rotor with blades is pressed down on the fluff mat with the center sheet with a pressing pressure of 100 mN, and then rotated at a rotation speed of 2.0 rpm, and the intensity of the maximum peak of the spectrum including the frequency 6500 Hz obtained when the vibration of the sample stage is measured with a vibration sensor (TS7 value) is taken as the TS7 of the fluff mat surface.

[0014] In this specification, "fluff mat" refers to a sheet formed from fluff pulp obtained by defibrating a pulp sheet for fluff pulp, as described later. In this specification, "fluff pulp" means defibrated pulp, which is pulp that has been fibrousized or shredded. "Pulp sheet for fluff pulp" refers to a pulp sheet used to manufacture fluff pulp before defibration. In other words, "fluff pulp" is obtained by defibrating a "pulp sheet for fluff pulp," and the sheet formed from this "fluff pulp" is called a "fluff mat."

[0015] In the measurement method (A) described above, a nonwoven fabric is used on both surfaces of the fluff mat as a center sheet (manufactured by Oji Nepia Co., Ltd., basis weight 25 g / m²). 2) are measured by overlapping, and the TS7 value is an index reflecting the properties of the fluff mat. That is, the softer the touch of the fluff mat, the smaller the TS7 value. The TS7 value of the fluff mat measured by the above measurement method (A) is 6.1 dBV 2 rms or less is acceptable, and 6.0 dBV 2 rms or less is more preferable, and 5.5 dBV 2 rms or less is even more preferable, and 5.0 dBV 2 rms or less is particularly preferable. The lower limit value of the TS7 value of the fluff mat measured by the above measurement method (A) is not particularly limited, but the TS7 value is preferably 2.5 dBV 2 rms or more.

[0016] In this embodiment, for example, by appropriately adjusting the raw materials of the pulp, the manufacturing conditions of the pulp, the defibrillation conditions of the pulp sheet for fluff pulp, the forming conditions at the time of forming the fluff mat sheet, etc., the TS7 value of the fluff mat can be controlled within the above range. For example, by blending a predetermined amount or more of hardwood pulp as the pulp constituting the fluff mat, or setting the sheet forming conditions when producing the fluff mat from the fluff pulp to predetermined conditions, it becomes easy to control the TS7 value of the fluff mat within the above range.

[0017] The TS750 measured by the following measurement method (B) of the fluff mat of this embodiment is preferably 7.0 dBV from the viewpoint of improving the reverse return rate suppression effect 2 rms or more, and 10.0 dBV 2 rms or more is more preferable, and 12.0 dBV 2 rms or more is even more preferable, and 15.0 dBV 2 rms or more is still more preferable, and 17.1 dBV 2 rms or more is particularly preferable. The lower limit value of the TS750 value of the fluff mat measured by the following measurement method (B) is not particularly limited, but the TS750 value is preferably 30.0 dBV 2 rms or less. Measurement method (B): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25g / m²) are placed on the top and bottom of the fluff mat. 2 ) are stacked; a circular stainless steel plate is placed on the surface of the fluff mat with the center sheet stacked on top, and the fluff mat with the center sheet is pressed with a manual press machine while adjusting the press pressure so that the thickness of the fluff mat is 4.2 mm; the fluff mat with the center sheet is placed on the sample stage of the tissue softness measuring device TSA, and a rotor with blades is pressed down on the fluff mat with the center sheet with a pressing pressure of 100 mN, and then rotated at a rotation speed of 2.0 rpm, and the intensity of the first maximum peak of the spectrum viewed from the low frequency side obtained when the vibration of the sample stage is measured with a vibration sensor (TS750 value) is taken as the TS750 of the fluff mat surface.

[0018] The D value of the fluff mat of this embodiment, measured by the following measurement method (C), is preferably 2.0 or higher. There is no particular upper limit to the D value of the fluff mat measured by the following measurement method (C), but the D value is preferably 5.0 or lower. Measurement method (C): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25g / m²) are placed on the top and bottom of the fluff mat. 2 ) are stacked; a circular stainless steel plate is placed on the surface of the fluff mat with the center sheet stacked on top, and the fluff mat with the center sheet is pressed with a manual press machine while adjusting the press pressure so that the thickness of the fluff mat is 4.2 mm; the fluff mat with the center sheet is placed on the sample stage of the tissue softness measuring device TSA, and the D value representing "rigidity" is calculated by measuring the amount of vertical deformation displacement when a rotor with blades is pressed down from above with pressing pressures of 100 mN and 600 mN.

[0019] The tactile sensation of a fluff mat is influenced by three characteristics: "softness (TS7)," "smoothness / roughness (TS750)," and "rigidity (D)," with particular reliance on the "softness (TS7)" characteristic. The TSA measuring device is capable of quantifying the parameters that serve as indicators of these three characteristics (referred to as TS7 values, TS750 values, and D values, respectively) through vibration and deformation measurements.

[0020] The HF value of the fluff mat of this embodiment measured by the following measurement method (D) is preferably 93.0 or higher, more preferably 94.0 or higher, even more preferably 95.0 or higher, and particularly preferably 97.4 or higher. The upper limit of the HF value of the fluff mat measured by the following measurement method (D) is not particularly limited and may be 100. Measurement method (D): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25g / m²) are placed on the top and bottom of the fluff mat. 2 The center sheets are stacked on top of each other; a circular stainless steel plate is placed on the surface of the fluffy mat with the center sheets stacked on top of it, and the fluffy mat with the center sheets is pressed using a manual press machine while adjusting the press pressure so that the thickness of the fluffy mat becomes 4.2 mm; the fluffy mat with the center sheets is placed on the sample stage of the tissue softness measuring device TSA, and the three parameters of the fluffy mat with the center sheets, TS7 value, TS750 value, and D value, are quantified by vibration measurement and deformation measurement. Based on these obtained parameters, the basis weight, thickness, and number of plies of the sample, the hand feel (HF) value is calculated by performing an analysis using the facial II algorithm.

[0021] In the above measurement methods (B) to (D), a nonwoven fabric is used on both surfaces of the fluff mat as a center sheet (manufactured by Oji Nepia Co., Ltd., basis weight 25 g / m²). 2Although the measurements are taken in combination, each value is an indicator that reflects the properties of the fluff mat. Each of the above values ​​can be controlled to a desired range by appropriately adjusting, for example, the raw materials for the pulp, the manufacturing conditions for the pulp, the defibration conditions for the pulp sheet for fluff pulp, and the molding conditions when forming the fluff mat into a sheet.

[0022] Because the fluff mat of this embodiment has the above configuration, it has a good feel to the touch and provides a soft touch during use. Furthermore, the fluff mat of this embodiment has excellent water absorption and can retain liquid after absorbing it. As a result, the rate of liquid backflow is reduced in the fluff mat of this embodiment.

[0023] In the fluff mat of this embodiment, the liquid backflow rate is the backflow rate of the fluff mat with a center sheet obtained by the measurement method (A) described above, and can be calculated by the following formula. Here, the liquid backflow rate in the fluff mat with a center sheet can be calculated by measuring the weight absorbed by the filter paper when 10 sheets of filter paper (manufactured by ADVANTEC Co., Ltd., No. 1640) are placed on the fluff mat with a center sheet under pressure under the conditions described in the example, after 20g of artificial urine has been absorbed by the fluff mat with a center sheet.

[0024]

number

[0025] Specifically, the liquid backflow rate in the fluff mat is preferably 85% or less, more preferably 82% or less, even more preferably 80% or less, even more preferably 79% or less, and particularly preferably 70% or less. The lower limit of the liquid backflow rate in the fluff mat is not particularly limited, but the backflow rate is preferably 30% or more.

[0026] The thickness of the fluff mat in this embodiment is the thickness of the fluff mat with a center sheet obtained by the measurement method (A) described above, and is a value measured with a paper thickness measuring machine (PEACOCK, model number FFA-12, 0.4N). The thickness of the fluff mat is preferably 2 mm or more, more preferably 3 mm or more, and even more preferably 4 mm or more. Furthermore, the thickness of the fluff mat is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 4.5 mm or less. By setting the thickness of the fluff mat within the above range, it becomes easier to obtain a fluff mat with a superior tactile feel.

[0027] The fluff mat of this embodiment is obtained by forming a sheet of fluff pulp, which is obtained by defibrating a pulp sheet for fluff pulp. The compression ratio during sheet formation is preferably 65% ​​or less, and preferably 62% or less. The compression ratio during sheet formation may be 0% or 5% or more. By setting the compression ratio within the above range, it becomes easier to obtain a fluff mat with a good feel. The compression ratio is a value calculated using the thickness before and after sheet formation by the following formula. Compression ratio (%) = (Thickness of fluff pulp before sheeting (mm) - Thickness of fluff mat after sheeting (mm)) / Thickness of fluff pulp before sheeting (mm) × 100

[0028] The basis weight of the fluff mat in this embodiment is the basis weight of the fluff mat with a center sheet obtained by the measurement method (A) described above. The weight of the fluff mat with the center sheet attached is measured, and the basis weight is calculated. The basis weight of the fluff mat is 70 g / m². 2 Preferably, it is 80 g / m 2 It is more preferably 90 g / m² or more. 2 It is even more preferable that the above conditions are met. Furthermore, the basis weight of the fluff mat should be 300 g / m². 2The following is preferable. By keeping the basis weight of the fluff mat within the above range, it becomes easier to obtain a fluff mat with a superior feel. When measuring the basis weight of the fluff mat, the weight of the fluff mat with the center sheet attached is measured, and the basis weight is calculated from the weight of the fluff mat after subtracting the weight of the center sheet.

[0029] The density of the fluff mat in this embodiment is the density of the fluff mat with a center sheet obtained by the measurement method (A) described above, and is a value calculated by the following formula. Density (g / cm 3 ) = Weight of the fluff mat (g) / Area of ​​the fluff mat with a diameter of 10 cm (cm²) 2 ) × Mat thickness after sheeting (cm) The density of the fluff mat is 0.01 g / cm³. 3 Preferably, it is 0.015 g / cm³ or more. 3 It is more preferable that the concentration be greater than or equal to 0.02 g / cm³. 3 It is even more preferable that the above conditions are met. Furthermore, the density of the fluff mat should be 0.05 g / cm³. 3 Preferably, it is 0.04 g / cm³. 3 It is more preferable that the following is the case: 0.03 g / cm³ 3 The following is even more preferable: By setting the density of the fluff mat within the above range, it becomes easier to obtain a fluff mat with a superior tactile feel.

[0030] The content of hardwood pulp relative to the total pulp components in the fluff mat is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, even more preferably 40% by mass or more, even more preferably 45% by mass or more, and particularly preferably 50% by mass or more. The upper limit of the content of hardwood pulp relative to the total pulp components in the fluff mat is not particularly limited and may be, for example, 100% by mass. By setting the content of hardwood pulp relative to the total pulp components in the fluff mat within the above range, a fluff mat with a good feel and suppressed backflow rate can be obtained.

[0031] (Raw pulp) The fluff mat of this embodiment contains hardwood pulp. The hardwood pulp is preferably bleached hardwood kraft pulp. The raw material for the bleached hardwood kraft pulp preferably contains at least one species selected from the group consisting of Acacia, Eucalyptus, Quercus, Fagus, and Castanopsis, and more preferably contains at least one species selected from the group consisting of Acacia and Eucalyptus. In addition, in this embodiment, it is preferable to use Acacia and Eucalyptus in combination as raw materials for the bleached hardwood kraft pulp. In particular, by including bleached hardwood kraft pulp made from Acacia in the fluff mat, the liquid absorbency of the fluff mat can be more effectively increased and the rate of liquid backflow can be more effectively reduced when the fluff mat is made fluffy.

[0032] The content of hardwood pulp relative to the total pulp components in the fluff mat is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, even more preferably 40% by mass or more, even more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more. The upper limit of the content of hardwood pulp relative to the total pulp components in the fluff mat is not particularly limited and may be, for example, 100% by mass. By setting the content of hardwood pulp relative to the total pulp components in the fluff mat within the above range, the tactile feel of the fluff mat can be improved and the rate of backflow can be reduced.

[0033] The copper number of the hardwood pulp used as raw material is preferably 0.5 or higher, more preferably 0.75 or higher, and even more preferably 1.0 or higher. Furthermore, the copper number of the hardwood pulp is preferably 2.0 or lower, more preferably 1.8 or lower, even more preferably 1.6 or lower, and particularly preferably 1.5 or lower. In this embodiment, by setting the copper number of the hardwood pulp within the above range, the rate of liquid backflow from the fluff mat can be more effectively reduced. In addition, by setting the copper number of the hardwood pulp above the lower limit, not only can the bleaching chemicals used during pulp production be reduced, but rigid fibers with less damage can be formed, thereby improving the defibrillability when manufacturing the fluff mat.

[0034] The Canadian standard water-saturation fluid (CSF) of hardwood pulp, measured in accordance with JIS P 8121-2:2012, is preferably 370 ml or higher, more preferably 400 ml or higher, and even more preferably 430 ml or higher. However, this Canadian standard water-saturation fluid (CSF) of hardwood pulp is the value measured for hardwood pulp before papermaking.

[0035] The fluff mat of this embodiment may contain other raw material pulps in addition to hardwood pulp. Examples of other raw material pulps include softwood pulp, non-wood pulp, and deinked pulp. Examples of hardwood pulp and softwood pulp include chemical pulps such as sulfite pulp (SP), soda pulp (AP), unbleached kraft pulp (UKP), and oxygen-bleached kraft pulp (OKP); semi-chemical pulps such as semi-chemical pulp (SCP) and chemical groundwood pulp (CGP); and mechanical pulps such as crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP). Dissolved pulp (DP) may also be used. Examples of non-wood pulps include cotton pulps such as cotton linters and cotton lint, and non-wood pulps such as bamboo pulp, hemp, straw, and bagasse. Examples of deinked pulp include deinked pulp made from recycled paper. In particular, it is preferable to use a combination of bleached hardwood kraft pulp and bleached softwood kraft pulp as raw material pulp. By including both bleached hardwood kraft pulp and bleached softwood kraft pulp in the fluff mat, the rate of liquid backflow from the fluff mat can be reduced more effectively.

[0036] The content of softwood pulp relative to the total pulp components in the fluff mat is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 30% by mass or less. Furthermore, the lower limit of the content of hardwood pulp relative to the total pulp components in the fluff mat is not particularly limited; for example, it may be 0% by mass, preferably 5% by mass or more, and more preferably 10% by mass or more.

[0037] If the fluff mat contains softwood pulp, the softwood pulp is preferably bleached softwood kraft pulp. The raw material for the bleached softwood kraft pulp preferably contains at least one species selected from the group consisting of pine, fir, and cedar, and more preferably contains at least one species selected from the group consisting of pine and fir. In this embodiment, it is also preferable to use pine and fir in combination.

[0038] The Canadian standard filtration efficiency (CSF) of softwood pulp, measured in accordance with JIS P 8121-2:2012, is preferably 600 ml or higher, more preferably 640 ml or higher, and even more preferably 670 ml or higher. However, this Canadian standard filtration efficiency (CSF) of softwood pulp is the value measured for softwood pulp before papermaking.

[0039] The fluff mat may contain other pulps in addition to hardwood pulp and softwood pulp. Examples of other pulps include the various pulps mentioned above. In this case, the content of the other pulps is preferably 10% by mass or less relative to the total pulp components in the fluff mat.

[0040] The length-weighted average fiber length of the hardwood pulp used as raw material is preferably 0.50 mm or more, more preferably 0.60 mm or more, and even more preferably 0.65 mm or more. Furthermore, the length-weighted average fiber length of the hardwood pulp is preferably 1.20 mm or less, more preferably 1.10 mm or less, and even more preferably 1.0 mm or less. Furthermore, when softwood pulp is further included as a raw material pulp, the length-weighted average fiber length of the softwood pulp is preferably 1.50 mm or more, more preferably 1.75 mm or more, and even more preferably 2.00 mm or more. Also, the length-weighted average fiber length of the softwood pulp is preferably 3.50 mm or less, more preferably 3.20 mm or less, and even more preferably 3.00 mm or less. By keeping the fiber lengths of the various pulps contained in the fluff mat within the above range, it becomes easier to control the thickness and density of the fluff mat within an appropriate range. Furthermore, by keeping the fiber lengths of the various pulps contained in the fluff mat within the above range, the rate of liquid backflow from the fluff mat during the fluffing process can be more effectively reduced. The length-weighted average fiber length of the various pulps contained in the fluff mat is measured in accordance with JIS P 8226-2:2011.

[0041] (optional ingredient) The fluff mat may contain additives as needed. Examples of additives include softeners, fillers, pigments, sizing agents, coagulants, oil resistant agents, aluminum sulfate, yield enhancers, water drainage enhancers, dry strength enhancers, wet strength enhancers, coloring pigments, water resistant agents, antistatic agents, sodium sulfate, surfactants, pH adjusting chemicals (such as sodium hydroxide), etc. The fluff mat of this embodiment may contain a softener. By including a softener in the fluff mat, it is possible to more effectively enhance its defibrillability.

[0042] (Pulp sheet for fluff pulp) This embodiment may also relate to a pulp sheet for fluff pulp used in the manufacture of the fluff mat described above. The pulp sheet for fluff pulp of this embodiment is a pulp sheet for fluff pulp containing hardwood pulp, wherein the content of hardwood pulp relative to the total pulp components in the pulp sheet for fluff pulp is 20% by mass or more.

[0043] The basis weight of the pulp sheet for fluff pulp in this embodiment is not particularly limited and should be manufactured at a basis weight that can be produced in the papermaking apparatus used for papermaking. For example, the basis weight of the pulp sheet for fluff pulp may be 100 g / m². 2 Preferably, it should be 150 g / m² or more. 2 It is more preferable that the amount be greater than or equal to 200 g / m². 2 It is even more preferable that the above conditions are met. Furthermore, the basis weight of the pulp sheet for fluff pulp should be 1500 g / m².2 Preferably, it is 1400g / m² 2 It is more preferable that the following conditions apply: 1300 g / m² 2 The following is even more preferable: The basis weight of the pulp sheet for fluff pulp shall be measured in accordance with JIS P 8124:2011.

[0044] The density of the pulp sheet for fluff pulp in this embodiment is not particularly limited, but is 0.3 g / cm³. 3 Preferably, it is 0.4 g / cm³ or more. 3 It is more preferable that the amount be greater than or equal to 0.5 g / cm³. 3 It is even more preferable that the above conditions are met. Furthermore, the density of the pulp sheet for fluff pulp is 0.95 g / cm³. 3 Preferably, it is 0.90 g / cm³. 3 It is more preferable that the following is the case: 0.85 g / cm³ 3 The following is even more preferable: The density of the pulp sheet for fluff pulp shall be measured in accordance with JIS P 8118:2014.

[0045] The specific burst strength of the pulp sheet for fluff pulp in this embodiment, measured in accordance with JIS P 8131:2009, is 0.5 kPa·m. 2 Preferably 0.7 kPa·m or more. 2 More preferably 0.9 kPa·m² or higher. 2 A value of 1 / g or higher is even more preferable. Furthermore, the specific bursting strength of the pulp sheet for fluff pulp is 5.0 kPa·m. 2 It is preferable that it be less than or equal to / g, and 4.5kPa·m 2 It is more preferable that it be less than or equal to / g, and 4.0kPa·m 2 It is even more preferable that the amount be less than or equal to / g.

[0046] The pulp sheet for fluff pulp of this embodiment exhibits good defibration properties when fluffed. In this specification, defibration properties can be evaluated by the defibration time (seconds) required until there is no undefibrated material left. Specifically, the shorter the defibration time, the better the defibration properties are judged to be, and good defibration properties can increase the production efficiency of fluff mats. Furthermore, good defibration properties make it easier to obtain fluff mats with a reduced rate of liquid backflow. In addition, good defibration properties reduce the amount of undefibrated material in the fluff mat, which not only improves the appearance of the fluff mat but also improves the ability of the fluff mat to maintain its shape. When used as an absorbent layer in sanitary materials such as disposable diapers, it reduces the possibility that the shape of the absorbent layer will collapse due to movement during use, thereby reducing the absorbent performance of the disposable diaper.

[0047] The content of hardwood pulp relative to the total pulp components in the pulp sheet for fluff pulp is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, even more preferably 40% by mass or more, even more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more. The upper limit of the content of hardwood pulp relative to the total pulp components in the pulp sheet for fluff pulp is not particularly limited and may be, for example, 100% by mass.

[0048] In this embodiment, it is preferable to use bleached hardwood kraft pulp and bleached softwood kraft pulp in combination as raw material pulp for the pulp sheet for fluff pulp. By including bleached hardwood kraft pulp and bleached softwood kraft pulp in the pulp sheet for fluff pulp, the rate of liquid backflow from the fluff mat can be more effectively reduced when the pulp sheet for fluff pulp is made into fluff.

[0049] The content of softwood pulp relative to the total pulp components in the pulp sheet for fluff pulp is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 30% by mass or less. Furthermore, the lower limit of the content of hardwood pulp relative to the total pulp components in the pulp sheet for fluff pulp is not particularly limited; for example, it may be 0% by mass, preferably 5% by mass or more, and more preferably 10% by mass or more.

[0050] (Method for manufacturing pulp sheets for fluff pulp) The method for producing a pulp sheet for fluff pulp according to this embodiment preferably includes a digestion step of digesting hardwood to produce unbleached pulp, an oxygen delignin step, a bleaching step, and a sheeting step. A dewatering and washing step may be appropriately provided between the above steps, a pre-hydrolysis step may be provided before the digestion step, and a cold alkali step may be provided after the bleaching step. Furthermore, a beating step may be provided before the sheeting step to beat the bleached pulp to achieve a desired freeness.

[0051] (Cooking process) In the digestion process, hardwoods and / or softwoods are digested to obtain unbleached pulp. Known methods can be used for digestion. The digestion conditions in the digestion process are not particularly limited, but for example, when using the Kraft digestion method, the degree of sulfurization of the digested liquid is preferably 15-45%, the digestion temperature is preferably 130-170°C, the effective alkali addition rate is preferably 5-30% by mass per oven-dry wood mass, and the digestion time is preferably 45-500 minutes. The copper number of the unbleached pulp obtained through the digestion process is preferably 10-70.

[0052] (Oxygen delignin process) In the oxygen delignin process, an alkaline chemical and oxygen are added to unbleached pulp, and the lignin is decomposed under high temperature and pressure, then eluted by the alkaline chemical. By deligninizing in the oxygen delignin process, the amount of bleaching chemicals used in subsequent multi-stage bleaching processes can be reduced, minimizing the deterioration of pulp quality. As for the oxygen delignin method, known medium-concentration methods or high-concentration methods can be applied as they are, but the medium-concentration method, which is currently commonly used and is performed with a pulp concentration of 8 to 15% by mass, is preferred.

[0053] In the oxygen delignin process using the medium-concentration method, caustic soda or oxidized Kraft white liquor can be used as the alkali, and oxygen from cryogenic separation, PSA (Pressure Swing Adsorption), or VSA (Vacuum Swing Adsorption) can be used as the oxygen gas. The oxygen gas and alkali are added to a medium-concentration pulp slurry in a medium-concentration mixer, and after thorough mixing, the mixture of pulp, oxygen, and alkali is sent to a reaction tower capable of holding it under pressure for a certain period of time for deligninization. The oxygen gas addition rate is preferably 0.5 to 3% by mass per oven-dry pulp mass, the alkali addition rate is preferably 0.5 to 4% by mass, the reaction temperature is preferably 80 to 120°C, the reaction time is preferably 15 to 100 minutes, and the pulp concentration is preferably 8 to 15% by mass. Other known conditions can be applied.

[0054] (bleaching process) In the bleaching process, the pulp that has undergone oxygen delignin is bleached to obtain bleached pulp. The bleaching method is not particularly limited and can be bleached using known bleaching methods. Examples of bleaching methods include an ozone bleaching stage (Z), a chlorine dioxide bleaching stage (D), an alkaline extraction stage (E), an oxygen bleaching stage (O), a hydrogen peroxide bleaching stage (E / P), a peracid bleaching stage (PA), an acid washing stage (a), or an acid treatment stage (A). In this embodiment, for example, it is preferable to perform the steps in the order of D0-E / P-D1. Note that the Z stage is preferable to avoid because it causes significant damage to the pulp fibers, resulting in a loss of fiber rigidity and thus worsening the defibrillability of the pulp sheet for fluff pulp.

[0055] The bleaching conditions in stages D0 and D1 are not particularly limited, but the addition rate of chlorine dioxide is preferably 0.05 to 5.0% by mass, the bleaching temperature is preferably 30 to 90°C, the bleaching time is preferably 1 to 240 minutes, the pulp concentration is preferably 5 to 15% by mass, and the pH at the end of the reaction is preferably 2 to 6. Similarly, the bleaching conditions in stages E / P are not particularly limited, but the addition rate of hydrogen peroxide is preferably 0.05 to 5.0% by mass, the bleaching temperature is preferably 30 to 90°C, the bleaching time is preferably 1 to 240 minutes, the pulp concentration is preferably 5 to 15% by mass, and the pH at the end of the reaction is preferably 10 to 12.

[0056] (Pre-hydrolysis step) A pre-hydrolysis step can be provided before the pulping step. In the pre-hydrolysis step, hardwoods or conifers are heated in the presence of water to perform pre-hydrolysis treatment. Here, the amount of water relative to the hardwoods and conifers (liquid ratio: amount of water (parts by mass) / amount of hardwoods and conifers (parts by mass)) is preferably 1.0 to 10, more preferably 1.5 to 8.0, even more preferably 2.0 to 7.0, and even more preferably 2.7 to 5.0. A liquid ratio of 1.0 or higher is preferable because it allows hydrolysis to proceed sufficiently and the reaction to become uniform. A liquid ratio of 10 or lower is preferable because it reduces the amount of heat required to heat to the desired temperature, making it more economical. The method of adding water is not particularly limited; water may be added from an external source, water originally contained in the hardwoods or conifers may be used, or if steam is used during heating, water contained in the steam may be used. In addition, chemicals that directly or indirectly assist in the hydrolysis of polysaccharides, such as alkalis, acids, and chelating agents, may be added along with water.

[0057] (Cold alkali process) Bleached pulp can be further treated with alkali to obtain bleached pulp after cold alkali treatment. The treatment method is not particularly limited, but caustic soda can be used as the alkali. The addition rate of caustic soda is preferably 5.0 to 20.0%, the bleaching temperature is preferably 20 to 50°C, the bleaching time is preferably 1 to 240 minutes, and the pulp concentration is preferably 5 to 15% by mass.

[0058] (Sheet formation process) In the sheet-forming process, first, the bleached pulp obtained through the bleaching process is dispersed in water to prepare a slurry. The pulp concentration in the slurry is preferably 0.01 to 10% by mass. Furthermore, if additives are to be added as needed, it is preferable to add the additives to the slurry.

[0059] The sheet-forming process includes the step of forming the slurry into paper using a paper machine. The paper machine used in the paper-making process is not particularly limited, but for example, a wire screen paper machine, a cylinder screen paper machine, a hybrid former, a gap former, etc., can be used. Furthermore, when forming the paper, it may be formed into a single layer, or multiple layers may be formed by combining them.

[0060] (Dehydration and washing process) Dehydration and washing steps may be appropriately included between the various processes described above. In the dehydration and washing step, the raw pulp is diluted and washed by combining dehydration. The washing method is not particularly limited, and known washing machines can be used. For example, displacement washing, dilution and dehydration, press washing, or a combination of these methods can be used.

[0061] (Method of manufacturing a fluff mat) This embodiment relates to a method for manufacturing a fluff mat, comprising the steps of obtaining fluff pulp by defibrating a pulp sheet for fluff pulp containing the hardwood pulp described above, and forming the fluff pulp into a sheet. In the method for manufacturing a fluff mat according to this embodiment, it is preferable that the content of hardwood pulp relative to the total pulp components in the pulp sheet for fluff pulp is 20% by mass or more, and that the forming process is carried out so that the compression ratio is 65% or less.

[0062] In the process of forming the fluff pulp into a sheet, it is preferable to adjust the sheeting conditions so that the thickness of the fluff pulp is a predetermined value. More specifically, in the process of forming the sheet, it is preferable to perform the forming so that the compression ratio is 65% or less, more preferably 62% or less. In this embodiment, since the content of hardwood pulp relative to the total pulp components in the fluff mat is above a predetermined amount, the density of the fluff mat after defibration treatment can be increased. As a result, the compression ratio in the process of forming the fluff pulp into a sheet can be reduced, making it easier to manufacture a fluff mat with a superior feel. The compression ratio is a value calculated using the thickness before and after sheeting by the following formula. Compression ratio (%) = (Thickness of fluff pulp before sheeting (mm) - Thickness of fluff mat after sheeting (mm)) / Thickness of fluff pulp before sheeting (mm) × 100 In the process of forming the material into a sheet, methods such as pressing the fluff pulp or forming the fluff pulp into a sheet by suction can be employed. It is preferable to appropriately control the compression ratio by adjusting the pressing pressure or suction force.

[0063] In the process of obtaining fluff pulp, known defibrators and pulverizers can be used, but in this embodiment, it is preferable to use a defibrator. In this case, the defibration rotation speed in the defibration process is preferably 21,000 rpm or higher, preferably 22,000 rpm or higher, and more preferably 23,000 rpm or higher. There is no particular upper limit to the defibration rotation speed in the defibration process, but it is preferable that the defibration rotation speed is 50,000 rpm or lower.

[0064] The defibration time in the process of obtaining fluff pulp is preferably 15 seconds or more, and more preferably 20 seconds or more. Furthermore, the defibration time is preferably 45 seconds or less, more preferably 40 seconds or less, even more preferably 35 seconds or less, and particularly preferably 30 seconds or less.

[0065] (Analytical items) This embodiment may also relate to an absorbent article having the fluff mat described above. Examples of absorbent articles include disposable diapers, urine pads, light incontinence pads, and sanitary napkins. The fluff mat in this embodiment has a superior feel and suppresses the rate of backflow, thus providing an absorbent article that can suppress the occurrence of skin irritation. [Examples]

[0066] The features of the present invention will be further described below with reference to examples and comparative examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following specific examples.

[0067] [Preparation of coniferous pulp] [Cooking] Chips of pine and fir trees were mixed in an oven-dry mass ratio of 30:70. 200g of the mixture was taken (oven-dry mass) and placed in a 2.5-liter autoclave. Kraft pulping was performed under the following conditions: liquid ratio of 5, sulfurization degree of the pulp 28%, alkali addition rate of 22%, pulping temperature of 165°C, and pulping time of 120 minutes. The black liquor and pulp were then separated, and the pulp was refined using a flat screen with a 10-cut screen plate to obtain unbleached pulp with a copper number of approximately 30.

[0068] [Oxygen delignin] 70.0 g of unbleached pulp was taken by oven-dry weight, and caustic soda was added to the oven-dry pulp mass to a concentration of 2.0% by mass. The mixture was then diluted with deionized water to adjust the pulp concentration to 10% by mass. This was placed in a heated autoclave, and 99.9% commercially available compressed oxygen gas was injected to set the gauge pressure to 0.5 MPa. Delignin was performed at 95°C for 60 minutes. The resulting pulp was diluted to 3% by mass with deionized water, then dehydrated and washed using a Buchner funnel.

[0069] [bleaching] 60g of kraft pulp, after alkaline oxygen deligninization, was collected by its oven-dry mass, placed in a plastic bag, and the pulp concentration was adjusted to 10% by mass using deionized water. Then, chlorine dioxide was added to a concentration of 2.0% by mass relative to the oven-dry mass of pulp. This was immersed in a constant temperature water bath at 70°C for 60 minutes to perform the D0 stage treatment. The resulting pulp was diluted to 3% by mass with deionized water, then dehydrated and washed using a Buchner funnel. The pulp after the D0 stage was placed in a plastic bag, and deionized water was added to adjust the pulp concentration to 10% by mass. Then, caustic soda was added in an amount of 1.0% by mass and hydrogen peroxide in an amount of 0.2% by mass relative to the mass of the oven-dried pulp, and the mixture was thoroughly mixed. After that, the E / P stage treatment was performed by immersion in a constant temperature water bath at 70°C for 90 minutes. The obtained pulp was diluted to 3% by mass with deionized water, and then dehydrated and washed using a Buchner funnel. The pulp after the E / P stage was placed in a plastic bag, and the pulp concentration was adjusted to 10% by mass using deionized water. Then, 1.0% by mass of caustic soda and 0.3% by mass of hydrogen peroxide were added relative to the weight of the oven-dried pulp, and the mixture was thoroughly mixed. After that, the P stage treatment was performed by immersion in a constant temperature water bath at 70°C for 90 minutes. The resulting pulp was diluted to 3% by mass with deionized water, and then dehydrated and washed using a Buchner funnel. The pulp after stage P was placed in a plastic bag, and the pulp concentration was adjusted to 10% by mass using deionized water. Then, chlorine dioxide was added so that it was 0.2% relative to the mass of the oven-dried pulp, and the pulp was immersed in a constant temperature water bath at 70°C for 60 minutes to perform bleaching in stage D1. The resulting bleached softwood pulp was diluted to 3% by mass with deionized water, and then dehydrated and washed using a Buchner funnel.

[0070] [Preparation of hardwood pulp] [Cooking] Eucalyptus and acacia (acacia mangium) chips were mixed in an oven-dry mass ratio of 30:70. 200g of the mixture was taken (oven-dry mass) and placed in a 2.5-liter autoclave. Kraft pulping was performed under the following conditions: liquid ratio of 5, pulp sulfurization degree of 28%, alkali addition rate of 20%, pulping temperature of 155°C, and pulping time of 120 minutes. The black liquor and pulp were then separated, and the pulp was refined using a flat screen with an 8-cut screen plate to obtain unbleached pulp with a copper number of approximately 18.

[0071] [Oxygen delignin] 70.0 g of unbleached pulp was taken by oven-dry weight, and caustic soda was added to the oven-dry pulp mass to a concentration of 2.0% by mass. The mixture was then diluted with deionized water to adjust the pulp concentration to 10% by mass. This was placed in a heated autoclave, and 99.9% commercially available compressed oxygen gas was injected to set the gauge pressure to 0.5 MPa. Delignin was performed at 95°C for 60 minutes. The resulting pulp was diluted to 3% by mass with deionized water, then dehydrated and washed using a Buchner funnel.

[0072] [bleaching] 60g of kraft pulp, after alkaline oxygen deligninization, was collected by its oven-dry mass, placed in a plastic bag, and the pulp concentration was adjusted to 10% by mass using deionized water. Then, chlorine dioxide was added to a concentration of 1.0% by mass relative to the oven-dry mass of pulp. This was immersed in a constant temperature water bath at 70°C for 60 minutes to perform the D0 stage treatment. The resulting pulp was diluted to 3% by mass with deionized water, then dehydrated and washed using a Buchner funnel. The pulp after the D0 stage was placed in a plastic bag, and deionized water was added to adjust the pulp concentration to 10% by mass. Then, caustic soda was added in an amount of 1.0% by mass and hydrogen peroxide in an amount of 0.2% by mass relative to the mass of the oven-dried pulp, and the mixture was thoroughly mixed. After that, the E / P stage treatment was performed by immersion in a constant temperature water bath at 70°C for 90 minutes. The obtained pulp was diluted to 3% by mass with deionized water, and then dehydrated and washed using a Buchner funnel. The pulp after the E / P stage was placed in a plastic bag, and the pulp concentration was adjusted to 10% by mass using deionized water. Then, chlorine dioxide was added so that it was 0.2% by mass relative to the mass of the oven-dried pulp, and the bag was immersed in a constant temperature water bath at 70°C for 60 minutes to perform bleaching in the D1 stage. The resulting bleached hardwood pulp was diluted to 3% by mass with deionized water, and then dehydrated and washed using a Buchner funnel.

[0073] (Examples 1-15) <Preparation of pulp sheets for fluff pulp> After the D1 stage, bleached softwood pulp and bleached hardwood pulp are mixed in the proportions shown in Table 1 by oven-dry mass ratio. After diluting with deionized water to a concentration of approximately 0.5% by mass, a basis weight of 270 g / m² is produced using a circular standard hand-formed pulp mill (manufactured by Kumagai Riki Kogyo Co., Ltd.).2 The papermaking process was carried out to obtain a pulp sheet (1 ply) for fluff pulp.

[0074] <Fibranching of pulp sheets for fluff pulp> The defibration properties of pulp sheets for fluff pulp were evaluated under conditions of 23°C and 50% relative humidity. Pulp sheets for fluff pulp, which had been conditioned under conditions of 23°C and 50% relative humidity, were cut into 10mm x 10mm pieces, and the basis weight of a 10cm diameter fluff mat was 100g / m². 2 The required amount was measured and evenly placed into a Wonder Blender (manufactured by Osaka Chemical Co., Ltd., model WB-1, rotation speed 25,000 rpm). The pulp was defibrated for the time indicated in Table 1, and the pulp was made into a cotton-like consistency. Next, the fluff pulp was immersed in water and gently stirred with a stick, and then processed using a standard circular hand-operated papermaking machine to a basis weight of 25 g / m². 2 Handmade paper for evaluating fibrillation properties was prepared. The handmade paper for fibrillation evaluation was observed visually, and the time (in seconds) required for the unfibrillated material to disappear was used as an indicator of fibrillation properties.

[0075] <Making a Fluff Mat> The fluff mat was prepared under conditions of 23°C and 50% relative humidity using the fluff mat preparation apparatus 100 shown in Figure 1. The fluff mat preparation apparatus 100 was assembled as shown in Figure 1 using a pulp defibrator 5 (manufactured by Maruto Seiki Co., Ltd.), a stainless steel sieve 24 with a mesh size of 180 μm (manufactured by Nonaka Rikaki Seisakusho Co., Ltd., inner diameter 100 mm x inner height 45 mm), a column 20 made from a PET resin sheet cut to 70 cm x 40 cm (manufactured by AcrySunday Co., Ltd., Sunday PET, thickness 0.5 mm), a polypropylene powder funnel 30 (manufactured by AS ONE Corporation, model No. 169, mouth diameter 120 mm, leg outer diameter 30 mm, leg length 27 mm), and a household vacuum cleaner 40 (manufactured by Hitachi Home & Life Solutions Co., Ltd., model No. CV-CF4). First, the pulp defibrator and the household vacuum cleaner were started. The household vacuum cleaner was set to a low suction power setting (approximately 80W), and small amounts of the un-fibrillated fluff pulp obtained during the fibrillation evaluation described above were added from the top of the fluff mat production device. This was continued until the entire amount of fibrillated pulp had been added, forming the fluff mat. Once the entire amount had been discharged, the pulp fibrillator and the household vacuum cleaner were stopped. After removing the column, the fluff mat (10cm in diameter) was carefully removed from a sieve with a mesh size of 180μm to avoid damaging its shape. The side that had been in contact with the stainless steel mesh was designated as the wire side of the fluff mat. Center sheets cut into 10cm diameter circles (manufactured by Oji Nepia Co., Ltd., basis weight 25g / m²) were placed above and below the removed fluff mat. 2 A center sheet was placed on top of the surface of the fluffy mat, and a circular stainless steel plate was placed on top of the center sheet. The fluffy mat was then pressed with a manual press (vise press, manufactured by AS ONE Corporation, model number MP-001) at the press pressure indicated in Table 1 so that the thickness of the fluffy mat was 4.2 mm, thereby obtaining a fluffy mat with a center sheet. It was removed from the press without damaging its shape and used for subsequent measurements.

[0076] (Comparative Examples 1-8) <Preparation of pulp sheets for fluff pulp> A pulp sheet for fluff pulp was obtained in the same manner as in Example 1, except that the ratio of bleached softwood pulp and bleached hardwood pulp after the D1 stage was changed to the ratio shown in Table 1 in terms of oven-dry mass.

[0077] <Fibranching of pulp sheets for fluff pulp> The defibration properties of pulp sheets for fluff pulp were evaluated under conditions of 23°C and 50% relative humidity. Pulp sheets for fluff pulp, which had been conditioned under conditions of 23°C and 50% relative humidity, were cut into 10mm x 10mm pieces, and the basis weight of a 10cm diameter fluff mat was 100g / m². 2 (Other than Comparative Example 3) or 80g / m 2 The amount was measured to match (Comparative Example 3) and evenly distributed into a Wonder Blender (manufactured by Osaka Chemical Co., Ltd., model WB-1, rotation speed 25,000 rpm) (Comparative Examples 2-4, 6) or a Classic Millser (manufactured by Iwatani Corporation, IFM-800DGM, rotation speed 20,000 rpm) (Comparative Examples 1, 5). The pulp was defibrated for the time indicated in Table 1 to make it cotton-like. Subsequently, the fluff pulp was immersed in water and gently stirred with a stick, and then processed using a circular standard hand-operated papermaking machine to a basis weight of 25 g / m². 2 Handmade paper for evaluating fibrillation properties was prepared. The handmade paper for fibrillation evaluation was observed visually, and the time (in seconds) required for the unfibrillated material to disappear was used as an indicator of fibrillation properties.

[0078] <Making a Fluff Mat> Fluff mats with center sheets were obtained in the same manner as the examples, except that the fluff mats were pressed with the press pressures listed in Table 1 so that their thickness was 4.2 mm (Comparative Examples 1-3, 5, 6) or 3.0 mm (Comparative Examples 7, 8). In Comparative Example 4, pressing was not performed, and only the shape was adjusted to obtain a fluff mat with a center sheet.

[0079] (Measurement and evaluation) <Basic weight> The weight of the entire fluff mat, including the center sheet, was measured, and the weight of the center sheet was subtracted to calculate the area per square foot.

[0080] <thickness> The thickness of the fluff mat with a center sheet was measured before and after pressing using a paper thickness measuring machine (PEACOCK, model FFA-12, 0.4N).

[0081] <density> The density of the fluff mat with a center sheet was calculated using the following formula. Density (g / cm 3 ) = Weight of the fluff mat (g) / Area of ​​the fluff mat with a diameter of 10 cm (cm²) 2 ) × Mat thickness after sheeting (cm)

[0082] <TS7、TS750、D、HF> A fluffy mat with a center sheet was placed on the sample stage of a tissue softness measuring device (TSA) manufactured by Emtec Electronic GmbH. A bladed rotor was pressed down onto the fluffy mat sample with a center sheet attached, applying a pressing pressure of 100 mN, and then rotated at a rotation speed of 2.0 rpm. The intensity of the maximum peak in the spectrum containing a frequency of 6500 Hz, obtained by measuring the vibration of the sample stage with a vibration sensor, was defined as the TS7 value of the fluffy mat surface. The softer the material, the smaller the TS7 value. Furthermore, the intensity of the first maximum peak in the spectrum obtained from the low-frequency side when the vibration of the sample stage is measured with a vibration sensor (TS750 value) is defined as the TS750 of the fluff mat surface. The smoother the surface, the smaller the TS750 value. Furthermore, the D value, which represents "rigidity," was obtained by measuring the vertical deformation displacement when the bladed rotor was pressed down from above with pressing pressures of 100 mN and 600 mN. The higher the rigidity (the stiffer it is), the smaller the D value. These measurements were taken at three different locations on the same sample, and the average value of each measurement was calculated. Based on these obtained parameters, along with the sample's basis weight, thickness, and ply count, an algorithmic analysis was performed to calculate a value called the Hand Feel (HF) value. A higher HF value indicates a better tactile feel. The facial II algorithm can be used for this calculation.

[0083] <Tactile sensation (sensory evaluation)> Participants were asked to touch the surface of a fluffy mat with a center sheet and rate its texture on a three-point scale: A, B, and C. A: It feels very nice to the touch. B: It feels nice to the touch. C: The texture isn't good.

[0084] <Reverse rate> The backflow rate of the fluff mat with a center sheet was measured under conditions of 23°C and 50% relative humidity. 2 A fluff mat was placed on a 5mm thick acrylic plate with the wire side facing up. After inserting a 2mm thick spacer, another 5mm thick acrylic plate was placed on top, and it was pressed for 10 minutes using a tabletop press. After pressing, the top acrylic plate was removed, and it was left to stand for 30 minutes. A stainless steel base plate (5mm thick, 11cm x 11cm) was placed on a horizontal laboratory table, and two fluff mats were placed on top of it with the wire side facing up (total basis weight of fluff mat: 200g / m²). 2 ). On top of that, a stainless steel strike-through plate (10cm x 10cm, 85mm thick, weighing 665g) with a 25mm diameter hole in the center was placed, and after 10 seconds, 20g of artificial urine was poured into the hole of the strike-through plate. After the artificial urine was completely absorbed, the strike-through plate was immediately removed. Next, an 11cm x 11cm polyethylene sheet was placed on top of the center sheet, and an 11cm x 11cm chloroprene rubber sponge sheet (manufactured by AS ONE Corporation, 10mm thick, hardness (Asker C hardness meter): 45 degrees) was placed on top of that, and an 11cm x 11cm 5mm thick acrylic plate was placed on top of that, and a 2.2kg weight was placed on top of that. The total weight of the polyethylene sheet, sponge rubber sheet, two acrylic plates, and 2.2kg weight was 2.31kg, and the area of ​​the fluff mat was 0.00785m² 2Therefore, the pressure applied to the fluff mat was 2.9 kPa. The mat was pressurized at 2.9 kPa for 3 minutes. Next, the polyethylene sheet, sponge rubber sheet, two acrylic plates, and 2.2 kg weight were removed, and 10 sheets of 11 cm x 11 cm square filter paper (manufactured by ADVANTEC Co., Ltd., No. 1640), which were humidity-controlled and of known weight in an environment of 23°C and 50% relative humidity, were placed so that the front side was in contact with the center sheet of the fluff mat with a center sheet. The clear file, urethane rubber sheet, two acrylic plates, and 2.2 kg weight were placed back on top, and artificial urine was absorbed into the filter paper while pressurizing for 2 minutes. After 2 minutes, the 10 sheets of filter paper were removed and their weight was measured, and the return rate was measured using the following formula. The artificial urine used here was prepared by the following procedure. First, methylene blue (manufactured by Kanto Chemical Co., Ltd.) was dissolved in deionized water to prepare a methylene blue aqueous solution with a concentration of 0.50 mass%. Next, 19.40 g of urea (manufactured by Kanto Chemical Co., Ltd.), 8.040 g of sodium chloride (manufactured by Kanto Chemical Co., Ltd.), 2.045 g of magnesium sulfate heptahydrate (manufactured by Kanto Chemical Co., Ltd.), and 0.835 g of calcium chloride dihydrate were weighed out in order into a 500 ml beaker. An appropriate amount of deionized water was added, and then 1.50 g of 0.50% by mass methylene blue aqueous solution was added dropwise. Then, the solution was transferred to a 1 L volumetric flask and diluted to 1 L to obtain artificial urine.

[0085]

number

[0086] [Table 1]

[0087] Compared to the comparative example, the example obtained a fluff mat with superior tactile feel and suppressed backflow rate. [Explanation of Symbols]

[0088] 5. Pulp defibrating machine 20 columns 24 Stainless steel sieves 30 Polypropylene Powder Funnels 40 Vacuum cleaner (suction machine) 100 Fluff Mat Manufacturing Apparatus

Claims

1. A fluff mat containing hardwood pulp, The content of the hardwood pulp relative to the total pulp components in the fluff mat is 20% by mass or more. The TS7 of the fluff mat surface measured by the measurement method (A) below was 6.1 dBV. ２ Fluff mats that are less than RMS; Measurement method (A): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25 g / m²) are placed on the top and bottom of the fluff mat. ２ ) Stack the center sheets; Place a circular stainless steel plate on the surface of the fluff mat with the center sheets stacked on top, and press the fluff mat with the center sheets using a manual press machine while adjusting the press pressure so that the thickness of the fluff mat becomes 4.2 mm; Place the fluff mat with the center sheets on the sample stage of the tissue softness measuring device TSA, press a rotor with blades onto the fluff mat with the center sheets from above with a pressing pressure of 100 mN, and then rotate it at a rotation speed of 2.0 rpm, and measure the vibration of the sample stage with a vibration sensor, and the intensity of the maximum peak of the spectrum including the frequency 6500 Hz (TS7 value) obtained is taken as the TS7 of the fluff mat surface.

2. The TS750 of the fluff mat surface measured by the measurement method (B) below was 7.0 dBV. ２ A fluff mat according to claim 1, having a strength of rms or greater; Measurement method (B): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25 g / m²) are placed on the top and bottom of the fluff mat. ２ ) Stack the center sheets; Place a circular stainless steel plate on the surface of the fluff mat with the center sheets stacked on top, and press the fluff mat with the center sheets using a manual press machine while adjusting the press pressure so that the thickness of the fluff mat becomes 4.2 mm; Place the fluff mat with the center sheets on the sample stage of the tissue softness measuring device TSA, press a bladed rotor onto the fluff mat with the center sheets from above with a pressing pressure of 100 mN, and then rotate it at a rotation speed of 2.0 rpm, and measure the vibration of the sample stage with a vibration sensor, and the intensity of the first maximum peak of the spectrum viewed from the low frequency side (TS750 value) obtained is taken as the TS750 of the fluff mat surface.

3. A fluff mat according to claim 1, wherein the HF value of the fluff mat surface measured by the measurement method (D) below is 93.0 or higher; Measurement method (D): Center sheets (manufactured by Oji Nepia Co., Ltd., basis weight 25 g / m²) are placed on the top and bottom of the fluff mat. ２ The center sheets are stacked on top of each other; a circular stainless steel plate is placed on the surface of the fluffy mat with the center sheets stacked on top of it, and the fluffy mat with the center sheets is pressed using a manual press machine while adjusting the press pressure so that the thickness of the fluffy mat becomes 4.2 mm; the fluffy mat with the center sheets is placed on the sample stage of the tissue softness measuring device TSA, and the three parameters of the fluffy mat with the center sheets, TS7 value, TS750 value, and D value, are quantified by vibration measurement and deformation measurement. Based on these obtained parameters, the basis weight, thickness, and number of plies of the sample, the hand feel (HF) value is calculated by performing an analysis using the facial II algorithm.

4. The fluff mat according to claim 1, wherein the content of hardwood pulp relative to the total pulp components in the fluff mat is 50% by mass or more.

5. An absorbent article comprising a fluff mat according to any one of claims 1 to 4.

6. A pulp sheet for fluff pulp used in the manufacture of a fluff mat according to any one of claims 1 to 4.

7. A process to obtain fluff pulp by defibrating a pulp sheet for fluff pulp containing hardwood pulp, The process includes forming the aforementioned fluff pulp into a sheet, The content of the hardwood pulp relative to the total pulp components in the pulp sheet for fluff pulp is 20% by mass or more. A method for manufacturing a fluff mat, wherein the process of forming it into a sheet is carried out so that the compression ratio is 65% or less.

8. The method for producing a fluff mat according to claim 7, wherein the step of obtaining the fluff pulp is to perform the defibration treatment under conditions of a defibration rotation speed of 21,000 rpm or more.

9. A pulp sheet for fluff pulp used in the method for manufacturing a fluff mat according to claim 7 or 8.

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