JP7297966B1 - Pulp sheet for fluff pulp - Google Patents

Abstract

The present invention provides a pulp sheet for fluff pulp, which has high absorption performance and good workability in the production of fluff pulp. A fluff pulp pulp sheet according to one aspect of the present invention is a pulp having a fiber length of 0.5 mm or more and less than 1.1 mm when the content of all pulp fibers is totaled at fiber length intervals of 0.02 mm. The fiber accounts for 42.6% or more, and the average content of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm at intervals of 0.02 mm in fiber length is 1.00% or more and 1.70%. below, and the standard deviation σ of the content rate is 0.58% or less, and the percentage of pulp fibers with a fiber width of 10 µm or more and less than 35 µm is 90.6% or more when the content rate is aggregated at intervals of 1 µm in fiber width. Yes, the average content of pulp fibers with a fiber width of 10 μm or more and less than 35 μm at intervals of 1 μm in fiber width is 3.1% or more and 3.9% or less, and the standard deviation σ of the content is 2.90% or less. . [Selection figure] None

Description

The present invention relates to a pulp sheet for fluff pulp.

Fluff pulp is produced by defibrating wood pulp by mechanical treatment, and is used as an absorbent member of absorbent articles such as disposable diapers.

As a fluff pulp pulp used in such absorbent articles, wood pulp derived from coniferous trees, which has good bulkiness, water absorption and fibrillating properties, is widely used (see Patent Document 1).

JP 2012-211411 A

On the other hand, wood pulp derived from hardwood trees is relatively inexpensive compared to pulp derived from softwood trees, but when wood pulp derived from hardwood trees is used as fluff pulp, the fiber length is short, so the voids in the absorbent article are reduced, resulting in water absorption. There is a risk that the amount and water absorption rate will tend to decrease. In addition, since hardwood-derived wood pulp has a shorter fiber length and a higher fiber density than softwood-derived pulp, workability such as defibration and ease of forming an absorber is not good, and productivity is low. tends to decline. In particular, among wood pulps derived from broad-leaved trees, acacia has a shorter fiber length than eucalyptus, which may greatly reduce workability.

The present invention has been made based on the above circumstances, and a fluff pulp pulp that has high absorption performance and good workability in the production of fluff pulp even when it contains wood pulp derived from broad-leaved trees. The purpose is to provide a sheet.

A pulp sheet for fluff pulp according to an aspect of the present invention contains bleached hardwood kraft pulp and bleached softwood kraft pulp, and when the content of all pulp fibers is totaled at fiber length intervals of 0.02 mm, the fiber length is 0.02 mm. The ratio of pulp fibers with a fiber length of 5 mm or more and less than 1.1 mm is 42.6% or more, and the average value of the content rate of the pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm for each interval of 0.02 mm in fiber length is 1.00% or more and 1.70% or less, the standard deviation σ of the content rate for each fiber length interval of 0.02 mm is 0.58% or less, and the content rate is determined for all pulp fibers at fiber width 1 μm intervals. When aggregated, the proportion of pulp fibers with a fiber width of 10 μm or more and less than 35 μm is 90.6% or more, and the average content of the pulp fibers with a fiber width of 10 μm or more and less than 35 μm for each interval of 1 μm in fiber width It is 3.1% or more and 3.9% or less, and the standard deviation σ of the content rate for each fiber width interval of 1 μm is 2.90% or less.

According to the present invention, it is possible to provide a fluff pulp pulp sheet that has high absorption performance even when containing wood pulp derived from a broad-leaved tree, and that has good workability in the production of fluff pulp.

FIG. 1 is a diagram showing the distribution of the average value of the content when measured at fiber length intervals of 0.02 mm in Example 1. FIG. FIG. 2 is a diagram showing the distribution of the average value of the content when measured at intervals of 1 μm in fiber width in Example 1. FIG. FIG. 3 is a diagram showing the distribution of the average value of the content when measuring at intervals of 0.02 mm in fiber length in Comparative Example 1. In FIG. FIG. 4 is a diagram showing the distribution of the average value of the content when measured at intervals of 1 μm in fiber width in Comparative Example 1. In FIG. FIG. 5 is a diagram showing the distribution of the average value of the content when measuring at intervals of 0.02 mm in fiber length in Comparative Example 2. In FIG. FIG. 6 is a diagram showing the distribution of the average value of the content when measured at intervals of 1 μm in fiber width in Comparative Example 2. In FIG.

[Description of the embodiment of the present invention]
A pulp sheet for fluff pulp according to an aspect of the present invention contains bleached hardwood kraft pulp and bleached softwood kraft pulp, and when the content of all pulp fibers is totaled at fiber length intervals of 0.02 mm, the fiber length is 0.02 mm. The ratio of pulp fibers with a fiber length of 5 mm or more and less than 1.1 mm is 42.6% or more, and the average value of the content rate of the pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm for each interval of 0.02 mm in fiber length is 1.00% or more and 1.70% or less, the standard deviation σ of the content rate for each fiber length interval of 0.02 mm is 0.58% or less, and the content rate is determined for all pulp fibers at fiber width 1 μm intervals. When aggregated, the proportion of pulp fibers with a fiber width of 10 μm or more and less than 35 μm is 90.6% or more, and the average content of the pulp fibers with a fiber width of 10 μm or more and less than 35 μm for each interval of 1 μm in fiber width It is 3.1% or more and 3.9% or less, and the standard deviation σ of the content rate for each fiber width interval of 1 μm is 2.90% or less.

The pulp sheet for fluff pulp is excellent in bulkiness of fluff pulp using the pulp sheet for fluff pulp because the pulp sheet for fluff pulp contains softwood bleached kraft pulp. In addition, since the fluff pulp pulp sheet contains hardwood bleached kraft pulp, the density of the fluff pulp surface using the fluff pulp pulp sheet is increased, and the water absorbing liquid of the absorbent article produced from the fluff pulp It is possible to improve the effect of reducing the amount of backflow and the effect of suppressing skin rashes.
In addition, in the fluff pulp pulp sheet, the proportion of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm is 42.6% when the content rate is totaled at fiber length intervals of 0.02 mm for all pulp fibers. As described above, the percentage of pulp fibers having a fiber width of 10 μm or more and less than 35 μm is 90.6% or more when the content is counted at intervals of 1 μm in fiber width. In this way, by setting the ratio of the fiber length and the fiber width in the total pulp fiber to the above range, even if the pulp sheet for fluff pulp contains wood pulp derived from broad-leaved trees, the defibration property during the manufacturing process is good. As a result, workability can be improved during production of fluff pulp. Furthermore, the effect of reducing the backflow of water-absorbing liquid in the fluff pulp pulp sheet can be improved. Therefore, even if the pulp sheet for fluff pulp contains hardwood-derived wood pulp, it has high absorption performance and good workability in producing fluff pulp.
Furthermore, in the fluff pulp pulp sheet, pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm, which account for 42.6% or more of the total pulp fibers, were counted at intervals of 0.02 mm in fiber length. The average value of the content rate for each 0.02 mm interval of the fiber length is 1.00% or more and 1.70% or less, and the standard deviation σ of the content rate for each 0.02 mm interval of the fiber length is 0.58%. It is below. In addition, for the pulp fibers with a fiber width of 10 μm or more and less than 35 μm, which account for 90.6% or more of the total pulp fibers, the average content rate for each fiber width 1 μm interval when aggregated at fiber width 1 μm intervals The value is 3.1% or more and 3.9% or less, and the standard deviation σ of the content rate for each fiber width interval of 1 μm is 2.90% or less. In this way, by reducing the variation in the distribution of the fiber length in the specific range and the distribution of the fiber width in the specific range, the pulp sheet for fluff pulp has a reduced absorption rate despite being blended with hardwood pulp. It is possible to suppress backflow of the water-absorbing liquid. Therefore, in an absorbent body using the pulp sheet for fluff pulp, rashes can be reduced.
Therefore, even if the pulp sheet for fluff pulp contains hardwood-derived wood pulp, it has high absorption performance and good workability in producing fluff pulp.

It is preferable that the mass ratio of the bleached hardwood kraft pulp to the bleached softwood kraft pulp is 25/75 or more and 38/62 or less. The pulp sheet for fluff pulp is made by blending bleached hardwood kraft pulp and bleached softwood kraft pulp in a well-balanced manner at the above mass ratio, thereby improving the water absorption amount, water absorption rate, and bulkiness required for fluff pulp pulp sheets. As it is, the effect of reducing the backflow amount of the water-absorbing liquid can be improved.

It is preferable that the content of acacia wood in the raw material wood of the bleached hardwood kraft pulp is 5% by mass or more and 95% by mass or less. When the content of acacia wood in the raw material wood of the bleached hardwood kraft pulp is within the above range, a certain amount or single acacia wood with a wide fiber width is blended, so that the gaps between uniform pulp fibers are sufficiently filled. It can be ensured, and the disentanglement property can be further improved during the fluff pulp manufacturing process. As a result, the fluff pulp used in the absorbent article can further increase the water absorption amount and the water absorption rate.

The pulp sheet for fluff pulp preferably has a density of 0.50 g/cm ³ or more and 0.65 g/cm ³ or less. When the density of the pulp sheet for fluff pulp is within the above range, even the pulp sheet for fluff pulp containing hardwood-derived wood pulp can further improve defibration properties during the manufacturing process.

The pulp sheet for fluff pulp preferably has a specific bursting strength of 1.0 kPa·m ² /g or more and 1.7 kPa·m ² /g or less. When the relative bursting strength of the fluff pulp pulp sheet is within the above range, even the fluff pulp pulp sheet containing hardwood-derived wood pulp can further improve defibration properties during the manufacturing process.

[Details of the embodiment of the present invention]
Hereinafter, a pulp sheet for fluff pulp according to one embodiment of the present invention will be described in detail. Unless otherwise specified, the amount of each material to be added to the paper base material (bone-dry internal addition amount) refers to the mass ratio to the bone-dry mass of the pulp of the paper base material.

<Pulp sheet for fluff pulp>
The pulp sheet for fluff pulp can be obtained by papermaking a slurry containing the raw material pulp.

(raw material pulp)
The raw material pulp used for the fluff pulp pulp sheet is a combination of softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP). Since the pulp sheet for fluff pulp contains the bleached softwood kraft pulp, the fluff pulp using the pulp sheet for fluff pulp is excellent in bulkiness. In addition, since the fluff pulp pulp sheet contains hardwood bleached kraft pulp, the density of the fluff pulp surface using the fluff pulp pulp sheet is increased, and the water absorbing liquid of the absorbent article produced from the fluff pulp It is possible to improve the effect of reducing the amount of backflow and the effect of suppressing skin rashes.

(Bleached hardwood kraft pulp)
The bleached hardwood kraft pulp is preferably a bleached hardwood kraft pulp made from acacia wood or eucalyptus wood.

Acacia wood shrinks less when dried, is strong against impacts, and is strong and hard. The pulp obtained from acacia wood inherits its original properties, and is a useful raw material pulp with high water absorption and drying properties. is. Eucalyptus wood belongs to the genus Eucalyptus, and Eucalyptus globulus, Eucalyptus grandis, Eucalyptus europhylla, Eucalyptus nitens, Eucalyptus regnans, etc. have been widely used as raw material pulp materials for paper manufacturing for a long time. The fiber lumen (lumen) is hard to collapse and is rigid, and by blending this pulp fiber, a bulky and low-density pulp sheet for fluff pulp can be obtained. As the bleached hardwood kraft pulp, the acacia wood is more bulky than the eucalyptus wood because of its larger fiber width, and the acacia wood is more preferable because the water absorption rate is less reduced when combined with the bleached softwood kraft pulp.

(Content of acacia wood in raw material wood for hardwood kraft pulp)
The lower limit of the acacia content in the raw material wood for the hardwood kraft pulp is preferably 5% by mass, more preferably 20% by mass, and even more preferably 50% by mass. The upper limit of the acacia material content is preferably 95% by mass, more preferably 90% by mass, and even more preferably 80% by mass. The content of acacia in the raw material wood of the hardwood kraft pulp of the pulp sheet for fluff pulp is in the above range, so that the fiber length is shorter than that of the bleached softwood kraft pulp, and the fibers tend to be tightly clogged. Even if the fiber is oriented in any direction (for example, the length direction, width direction, and thickness direction of the absorbent article manufactured from the fluff pulp pulp sheet), it is particularly good. Since uniform spaces between fibers can be ensured, it is possible to achieve both defibration property and water absorption speed required for a pulp sheet for fluff pulp. If the ratio of rigid eucalyptus wood is increased, for example, if the ratio of rigid eucalyptus wood is increased, the number of voids due to rigidity increases, but since the fiber width is lower than that of acacia wood, the voids will depend on the direction in which the fibers are oriented. Therefore, fluff pulp using the fluff pulp pulp sheet not only has low defibration properties, but also tends to have uneven water absorption speed, and as a result, the water absorption speed may be likely to decrease. be.

The pulp sheet for fluff pulp has a ratio of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm to 42.6% or more when the content rate is totaled at fiber length intervals of 0.02 mm for all pulp fibers. Yes, preferably 45.0% or more. In addition, when the content of all pulp fibers is totaled at fiber width intervals of 1 μm, the proportion of pulp fibers having a fiber width of 10 μm or more and less than 35 μm is 90.6% or more, preferably 91.0% or more. In this way, by setting the ratio of the fiber length and the fiber width in the total pulp fiber to the above range, even if the pulp sheet for fluff pulp contains wood pulp derived from broad-leaved trees, the defibration property during the manufacturing process is good. As a result, workability can be improved during production of fluff pulp. Furthermore, the effect of reducing the backflow of water-absorbing liquid in the fluff pulp pulp sheet can be improved. Therefore, even if the pulp sheet for fluff pulp contains hardwood-derived wood pulp, it has high absorption performance and good workability in producing fluff pulp.

In the fluff pulp pulp sheet, the pulp fibers having a fiber length of 0.5 mm or more and less than 1.1 mm, which account for 42.6% or more of the total pulp fibers, have a fiber length of 0 The average value of the content rate for each fiber length interval of 0.02 mm when aggregated at intervals of 0.02 mm is 1.00% or more and 1.70% or less. Here, the measurement of pulp fibers having a fiber length of 0.5 mm or more and less than 1.1 mm will be described. Softwood kraft pulp has a wide range of fiber content up to about 5 mm or more, and hardwood kraft pulp has a relatively low fiber content in the range of less than 0.50 mm and more than 1.1 mm. Regarding the sheet, the present inventors have found that the effect of the fluff pulp pulp sheet of the present invention can be obtained by using a fiber content of 0.50 mm or more and less than 1.1 mm as an index. The standard deviation σ of the content when the pulp fibers are measured at intervals of 0.02 mm is 0.58% or less, preferably 0.56% or less, more preferably 0.54% or less. If the standard deviation σ of the fiber length of all pulp fibers exceeds 0.58%, the pulp sheet for fluff pulp may be less effective in suppressing a decrease in absorption rate and backflow of water-absorbed liquid. The above fiber length is measured using a fiber length measuring machine "VALMET FS5" manufactured by Valmet, in accordance with JIS-P8226: 2011 (ISO16065-2: 2007) "Pulp - Fiber length measurement method by optical automatic analysis method". It is the measured ISO weight weighted average fiber length.

In all pulp fibers, the lower limit of the average fiber length when measuring pulp fibers having a fiber length of 0.5 mm or more and less than 1.1 mm at intervals of 0.02 mm is 0.5 mm, preferably 0.6 mm. The upper limit of the average fiber length is 0.8 mm, preferably 0.7 mm. If the average fiber length is less than 0.5 mm, the bulkiness of the pulp sheet for fluff pulp tends to be lowered, and defibration properties during the manufacturing process may be lowered. The upper limit of the average fiber length is 0.8 mm, preferably 0.7 mm. If the average fiber length exceeds 0.8 mm, the fluff pulp using the fluff pulp pulp sheet tends to vary in the direction in which the fibers are oriented, and the water absorption rate may decrease. .

In the pulp sheet for fluff pulp, the pulp fibers having a fiber width of 10 μm or more and less than 35 μm, which account for 90.6% or more of the total pulp fibers, are aggregated at intervals of 1 μm in fiber width, and the fiber width is 1 μm. The average value of the content rate for each is 3.1% or more and 3.9% or less. Here, the measurement of pulp fibers having a fiber width of 10 μm or more and less than 35 μm will be described. Softwood kraft pulp has a wide range of fiber content up to about 55 μm or more, and hardwood kraft pulp has an extremely low fiber content in the range of less than 10 μm and more than 35 μm. The inventors found that the effect of the fluff pulp pulp sheet of the present invention is obtained by using the fiber content of 10 μm or more and less than 35 μm as an index. The standard deviation σ of the content when the pulp fibers are measured at intervals of 0.02 mm is 2.9% or less, preferably 2.8% or less, and more preferably 2.6% or less. If the standard deviation σ of the fiber width of all pulp fibers exceeds 2.9%, the pulp sheet for fluff pulp may have a lower absorption speed and a lower effect of suppressing backflow of water-absorbed liquid. The above fiber width is measured using a fiber length measuring machine "VALMET FS5" manufactured by Valmet, in accordance with JIS-P8226: 2011 (ISO16065-2: 2007) "Pulp - fiber length measurement method by optical automatic analysis method". It was measured.

In all pulp fibers, the lower limit of the average fiber width when the pulp fibers having a fiber width of 10 μm or more and less than 35 μm are measured at intervals of 1 μm is 15 μm, preferably 18 μm. The upper limit of the average fiber width is 30 μm, preferably 27 μm. If the average fiber width is less than 15 μm, the fluff pulp produced from the fluff pulp pulp sheet may have dense interfiber spaces, resulting in a decrease in water absorption rate. If the average fiber width exceeds 30 μm, the contact area between the pulp fibers in the fluff pulp pulp sheet becomes too large, the binding force between the fibers increases, and the defibration property during the manufacturing process may decrease. . If the defibration property is excessively lowered, excessive defibration occurs in the production process of fluff pulp using the fluff pulp pulp sheet, and fine fibers are generated, which may reduce the water absorption rate of the fluff pulp.

The kappa number of the bleached hardwood kraft pulp is preferably 0.3 or less. If the kappa number exceeds the upper limit, the lignin in the fiber cannot be sufficiently removed, and the water absorbency of the pulp fiber becomes low, which may easily cause rashes. The kappa number is measured according to JIS-P8211 (2011).

The lower limit of the sulfidity of white liquor for cooking hardwood kraft pulp is preferably 25%, more preferably 28%. If the sulfidity is less than 25%, the pulp fibers are likely to be damaged, and the fluff pulp using the fluff pulp pulp sheet may become dense, resulting in a decrease in water absorption rate. On the other hand, the upper limit of the sulfidity is preferably 32%, more preferably 30%. If the sulfidity exceeds the above upper limit, the pulp fibers are hard to be damaged and remain rigid, and the voids of the absorbent article obtained from the pulp sheet for fluff pulp become uneven, and the amount of backflow increases, resulting in rashes. There is a risk of The above sulfidity was calculated according to the following formula as the ratio of sodium sulfide to the total of sodium sulfide and caustic soda.
Sulfidity (%) = ( _Na2S /(NaOH+ _Na2S )) x 100

(Freeness of unbeaten hardwood bleached kraft pulp)
The Canadian Standard Freeness (CSF) of the unbeaten hardwood bleached kraft pulp is preferably adjusted to 520 ml or more and 580 ml or less. If the freeness of the unbeaten pulp of the bleached hardwood kraft pulp is less than 520 ml, the dewatering property deteriorates during pulp sheet production. Not only is the bonding between the fibers stronger, but also the bulkiness of the pulp sheet is lowered, which may reduce the fibrillation property during production. On the other hand, if the Canadian standard freeness of the unbeaten pulp exceeds 580 ml, the pulp sheet may have too many voids between fibers, which may cause uneven defibration during fibrillation.

(Conifer bleached kraft pulp)
In the pulp sheet for fluff pulp, pine trees represented by radiata pine and various cedars are suitably used as raw material wood for softwood bleached kraft pulp.

(Pulp blend ratio)
The lower limit of the mass ratio of the bleached hardwood kraft pulp to the bleached softwood kraft pulp in the pulp used in the pulp sheet for fluff pulp is preferably 25/75, more preferably 28/72. When the mass ratio of the bleached hardwood kraft pulp to the bleached softwood kraft pulp is less than 25/75, the proportion of pulp fibers having a fiber length of 0.5 mm or more and less than 1.1 mm in all pulp fibers is 42.6% or more. Even if the percentage of pulp fibers with a fiber width of 10 μm or more and less than 35 μm is 90.6% or more, the voids between the fibers of the absorbent article obtained from the fluff pulp pulp sheet are likely to be uneven and easily reverted. A rash may easily occur. On the other hand, the upper limit of the mass ratio of the bleached hardwood kraft pulp to the bleached softwood kraft pulp is preferably 38/62, more preferably 35/65. When the mass ratio of the bleached hardwood kraft pulp to the bleached softwood kraft pulp exceeds 38/62, even if the fiber width of the bleached hardwood kraft pulp is within a predetermined range, the pulp sheet for fluff pulp becomes dense, Water absorption rate may decrease.

(other pulp)
The pulp sheet for fluff pulp may contain pulp other than the bleached hardwood kraft pulp and the bleached softwood kraft pulp. Examples of other pulps include soda pulp, sulfite pulp, chemithermomechanical pulp, chemrefiner mechanical pulp, and thermochemimechanical pulp. However, if the lignin in the fibers is not sufficiently removed, the water absorption amount and water absorption rate of the pulp fibers tend to decrease, so bleached pulp from which lignin has been sufficiently removed is preferable. When the other pulp is contained, the content of the other pulp is preferably 10% by mass or less with respect to the entire pulp raw material.

(Other additives)
If necessary, other additives can be added internally to the pulp sheet for fluff pulp. Additives include, for example, fillers, pigments, sizing agents, coagulants, oil resistance agents, aluminum sulfate, retention aids, drainage improvers, dry paper strength agents, wet paper strength agents, coloring pigments, and water resistance agents. etc., can be used singly or in combination.

[Physical properties of pulp sheet for fluff pulp]
(Krem water absorption)
The Kremm water absorbency is obtained by immersing the lower end of the paper vertically in water and measuring the height of water absorbed by capillary action, and is measured in accordance with JIS-P8141 (2004). Kremm water absorbency is a measurement method for water absorbency where the time after water comes into contact with the sample is relatively long, but in absorbent articles, water absorbency in a shorter time is important, Measure according to After preparing a sample using the pulp sheet for fluff pulp, in a water absorption test at room temperature, the height [mm] for 1 minute after the start of measurement and the water absorption rate [mm/min] for 1 minute to 2 minutes after the start of measurement to measure. The height 1 minute after the start of measurement is used as a measure of the water absorption of the fluff pulp pulp sheet, and the water absorption rate between 1 and 2 minutes after the start of measurement is used as a measure of the water absorption rate of the fluff pulp pulp sheet.

The lower limit of the water absorption height at 1 minute after the start of measurement when the basis weight of the fluff pulp pulp sheet is 200 g/m ² is preferably 25 mm, more preferably 27 mm, and even more preferably 29 mm. If the water absorption height is less than 25 mm one minute after the start of the measurement, fluff pulp and absorbent articles produced from the fluff pulp pulp sheet have a low water absorption amount, and skin rashes may occur. On the other hand, the upper limit of the water absorption height at 1 minute after the start of the measurement is preferably 40 mm. If the water absorption height at 1 minute after the start of the measurement exceeds 40 mm, the water absorption is too high, the water absorption rate is reduced for 1 minute to 2 minutes after the start of the measurement, and the fluff produced from the fluff pulp pulp sheet Pulp and absorbent articles may increase the amount of water-absorbing liquid flowing back and cause skin rashes. When the water absorption height at 1 minute after the start of the measurement is within the above range, the pulp sheet for fluff pulp can obtain fluff pulp with good water absorption.

The lower limit of the water absorption rate for 1 minute to 2 minutes after the start of measurement when the basis weight of the fluff pulp pulp sheet is 200 g/m ² is preferably 5 mm/minute, more preferably 7 mm/minute, and even more preferably 9 mm/minute. . When the water absorption rate is less than 5 mm/min for 1 to 2 minutes after the start of the measurement, the fluff pulp and absorbent articles produced from the fluff pulp pulp sheet have a low water absorption rate, so the amount of water-absorbing liquid returned may increase and skin rash may occur. When the water absorption rate is within the above range for 1 to 2 minutes after the start of the measurement, the fluff pulp pulp sheet can obtain fluff pulp having a good water absorption rate. In the fluff pulp pulp sheet, the water absorption height at 1 minute after the start of the measurement and the water absorption speed at 1 to 2 minutes after the start of the measurement are both within the above ranges, so that the fluff pulp is excellent in the water absorption amount and the water absorption speed. can be manufactured, and an absorbent article can be obtained that has little reversion and can suppress rashes.
Here, even if the basis weight of the pulp sheet for fluff pulp exceeds 200 g / m ² , the sample was defiberized by a standard defiberizer in accordance with JIS-P8220 (2012) "Pulp - defiberization method". After that, according to JIS-P8222 (1998) "Pulp-Preparation of test handsheet-Method using a standard handsheet", a sample having a basis weight of 200 g/m ² can be prepared and then measured.

(density)
Density is measured according to "Paper and paperboard-Testing methods for thickness, density and specific volume" described in JIS-P8118 (2014). The lower limit of the density of the pulp sheet for fluff pulp is preferably 0.50 g/cm ³ , more preferably 0.52 g/cm ³ , and still more preferably 0.55 g/cm ³ . The upper limit of the density of the pulp sheet for fluff pulp is preferably 0.65 g/cm ³ , more preferably 0.62 g/cm ³ , and still more preferably 0.60/cm ³ . When the density of the pulp sheet for fluff pulp is within the above range, it is possible to improve defibration properties during the manufacturing process, and to obtain fluff pulp in which it is easy to ensure even and uniform voids between fibers. Therefore, the water absorption amount and water absorption speed required for fluff pulp can be improved.
The density is measured in an atmosphere of 23±1° C. and 50±2% RH as described in JIS-P8111 (1998) “Paper, paperboard and pulp—standard conditions for humidity conditioning and testing”. .

(Relative burst strength)
The specific bursting strength is a value obtained by dividing the bursting strength of paper in kilopascals (kPa) measured according to JIS-P8131 (2009) by the basis weight. The lower limit of the specific burst strength is preferably 1.0 kPa·m ² /g, more preferably 1.1 kPa·m ² /g, and even more preferably 1.2 kPa·m ² /g. If the specific bursting strength of the fluff pulp pulp sheet is less than the above lower limit, the fibers are likely to be cut due to excessive defibration, so the fluff pulp becomes dense, the water absorption rate decreases, and rashes may easily occur. . On the other hand, the upper limit of the specific bursting strength of the pulp sheet for fluff pulp is preferably 1.7 kPa·m ² /g, more preferably 1.6 kPa·m ² /g, and more preferably 1.5 kPa·m ² /g. More preferred. If the above-mentioned specific bursting strength of the fluff pulp pulp sheet exceeds the above-mentioned upper limit, the defibration property during the manufacturing process is poor, and the resulting fluff pulp has many voids, which makes it easy for the water-absorbing liquid to return and causes rashes. It may occur more easily. Since the relative bursting degree of the fluff pulp sheet is within the above range, the fluff pulp pulp sheet obtained by mixing the hardwood bleached kraft pulp and the softwood bleached kraft pulp can improve defibration during the manufacturing process. In the fluff pulp, it becomes easy to ensure even and uniform voids between the fibers, so that the water absorption rate of the fluff pulp can be improved.
In addition, the relative burst rate measurement is performed under an atmosphere of 23 ± 1 ° C. and 50 ± 2% RH, as described in JIS-P8111 (1998) "Paper, paperboard and pulp - standard conditions for humidity conditioning and testing". Measured in

[Manufacturing method of pulp sheet for fluff pulp]
The method for producing the pulp sheet for fluff pulp is not particularly limited, but for example, a cooking step of cooking raw wood to obtain unbleached pulp, a delignification step of performing delignification, and bleaching to obtain bleached pulp. a beating step of beating the bleached pulp to a desired freeness; a step of preparing a pulp slurry; and a step of making paper from the pulp slurry. In addition, a dehydration washing step can be appropriately provided between the above steps.

(Cooking process)
In the cooking step, raw material wood is cooked to obtain unbleached pulp. White liquor and raw wood chips (hardwood or softwood) are placed in the digester and cooked, and the resulting (unwashed) pulp slurry mixed with black liquor is removed from the bottom of the continuous digester. The cooking method can be arbitrarily selected from commercially available kraft improvement methods such as MCC, EMCC, ITC, Lo-Solids, KobudoMari, Compact method, etc. The digester may be either a continuous digester or a batch method. Also, the cooking conditions (cooking temperature, H factor obtained by multiplying the degree of influence of the cooking temperature and cooking time and combined into one factor, the content of active alkali or effective alkali, etc.) are not particularly limited.

(Delignification process)
In the delignification step, the unbleached pulp is delignified. Alkaline chemicals and oxygen are added to unbleached pulp, and lignin is decomposed at high temperature and pressure, and lignin is eluted into the alkaline chemicals. The delignification process may be of low consistency (pulp density: 3% to 8%), medium consistency (pulp density: 8% to 15%), or high consistency (pulp density: 20% to 30%).

(Washing process)
In the washing process, the unbleached pulp is washed by a combination of displacement, dilution or dewatering. The washing method is not particularly limited, and washing can be performed using a known washing machine. For example, a displacement cleaning method, a dilution/dehydration method, a press cleaning method, or a cleaning method combining these methods is used. Diffusion washers, pressurized diffusion washers, belt-type washers, and the like are used as displacement wash-type washers. A vacuum filter washer, a pressure filter washer, and the like are used as the dilution/dehydration type washer. As the press cleaning method, a screw type press cleaning machine, a disc type press cleaning machine, a roll type press cleaning machine, or the like is used.

In the present invention, since it is preferable to remove lignin and reduce the kappa number, it is preferable to use a press washing machine that easily removes lignin. The pulp concentration after washing by the press washing method is preferably 30% or more, more preferably 32% or more, and even more preferably 35% or more. In the dehydration by the press washing method, the moisture inside the fibers can also be squeezed out and removed, so compared to other washing methods, it is easy to sufficiently remove the lignin released inside the pulp fibers.

(Bleaching process)
In the bleaching step, the delignified unbleached pulp is bleached to obtain bleached pulp. The bleaching method is not particularly limited, and can be bleached by a known bleaching method. For example, acid treatment, ozone bleaching, chlorine dioxide bleaching, hydrogen peroxide bleaching, alkali extraction with these, alkali extraction with oxygen added, alkali extraction with oxygen and hydrogen peroxide added, etc., can be performed singly or in combination. can do.

In the bleaching step, it is preferable to use ozone bleaching, which can adjust the water absorbency of pulp fibers by damaging the pulp fibers. The method of ozone bleaching is not particularly limited, and can be carried out at any of high concentration (30 to 40%), medium concentration (8 to 15%), and low concentration (1 to 3%). Concentration methods are preferred.
A known device can be used as the ozone generator. The generated ozone may be mixed with the pulp as it is, or dissolved in water and then mixed with the pulp.

In ozone bleaching, a lower pH promotes delignification and less damage to fibers, so it is preferable to adjust the pH according to the required quality of the fluff pulp pulp sheet. The pH in the ozone bleaching of the pulp sheet for fluff pulp is preferably 6 or less, more preferably 4 or less, and still more preferably 2-3. When the pH of the pulp sheet for fluff pulp in ozone bleaching is within the above range, the water absorption speed required for the pulp sheet for fluff pulp can be improved.

(Preparation process)
In the preparing step, a pulp slurry is prepared. Further, if necessary, in the preparation step, the bleached pulp is beaten to a desired freeness. After that, other additives are added as necessary to prepare a stock.

(Papermaking process)
Next, using these raw material slurries, paper is made by a paper machine in a neutral range so that the pH is 6 or more and 8 or less. In the papermaking process, the raw material pulp is made into paper using a papermaking machine that makes paper from the pulp raw material jetted onto the running wire. The paper machine is not particularly limited, and a known paper machine such as a fourdrinier paper machine, a cylinder paper machine, a hybrid former, a gap former, or the like can be used. be. The pulp sheet for fluff pulp can be produced by combining a single layer or a plurality of layers, but a single layer is preferable because the density in the layer can be easily made uniform.

According to the pulp sheet for fluff pulp, even if wood pulp derived from broad-leaved trees is contained, the absorption performance is high, and the workability in producing the fluff pulp is good.

[Fluff pulp]
The fluff pulp can be obtained by defibrating the fluff pulp pulp sheet into fibers by mechanical treatment. The fluff pulp pulp sheet used for the fluff pulp in the present invention may be in the form of a veil or a roll, but a roll is preferable because the productivity of absorbent articles using fluff pulp can be easily improved. .

In the present invention, the device used for the mechanical treatment for fibrillation is not particularly limited. A known defibrator that is used in the production of absorbent articles such as paper diapers can be used, and a defibrator that utilizes frictional force or shear force as a mechanical treatment can be preferably used. As the system of the defibrator, for example, a hammer-type defibrator, an impact-type defibrator, a roll-type defibrator, and a jet-type defibrator can be used.

[Absorbent article]
The absorbent article uses a pulp sheet for fluff pulp. By using the pulp sheet for fluff pulp in the absorbent article, the water absorption amount and the water absorption speed can be improved, and skin irritation can be suppressed. Examples of the absorbent article include, but are not particularly limited to, disposable diapers, incontinence pads, light incontinence pads, and sanitary napkins.

The manufacturing method of the absorbent article is not particularly limited, and it can be manufactured by a known method. For example, paper diapers can be manufactured by using manufacturing machines manufactured by Zuiko, Toa Kiko, and Erhardt Leimer, for example, by panel type, leg hole type, vertical flow type, horizontal flow type, and the like.

<Other embodiments>
The present invention is not limited to the above-described embodiments, and can be implemented in various modified and improved modes in addition to the above-described modes.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

[Examples 1 to 19 and Comparative Examples 1 to 5]
Pulp sheets for fluff pulp of Examples 1 to 19 and Comparative Examples 1 to 5 were produced by the following procedure. Comparative Example 1 reproduces the composition of an existing commercially available pulp sheet for fluff pulp.

(Cooking process)
(1) Hardwood Acacia and eucalyptus are mixed so that the mass ratio is as shown in Table 1, white liquor having a predetermined sulfidity is added, and the mixture is rotated at a liquor ratio of 6.0 (L / kg) and a maximum temperature of 170 ° C. Digestion was carried out by a type autoclave to obtain hardwood unbleached kraft pulp having a kappa number of about 16. In addition, "-" in Table 1 indicates that the corresponding component is not included.
(2) Conifer A white liquor having a predetermined degree of sulfidity is added to cedar, and the liquor ratio is 6.0 (L/kg), and the maximum temperature is 170°C. Got kraft pulp.

(Washing process)
After diluting the unbleached pulp to about 2% pulp consistency, the Buchner funnel was filled with a No. 2 Filter paper (manufactured by ADVANTEC) was laid and dewatered to a pulp concentration of about 12%. After that, the unbleached pulp was sandwiched between square filter papers (manufactured by ADVANTEC), pressure was applied with a press, and dewatered to a pulp concentration of 33%. This washing step was performed twice.

(Bleaching process)
(1) Hardwood (1-1) Ozone Bleaching Unbleached kraft pulp was bleached with ozone gas of 8.1% concentration at 45° C. for about 2 minutes. For ozone bleaching, ozone gas from a laboratory ozone generator of PSA Ozonizer SGA-01A-PSA4 manufactured by Sumitomo Precision Products Co., Ltd. was used.
(1-2) Chlorine Dioxide Bleaching The pulp after ozone bleaching was subjected to chlorine dioxide bleaching at 70° C. with a chlorine dioxide addition rate of 1.5% and a pulp concentration of 10% by mass to obtain broadleaf tree bleached kraft pulp.
Between each bleaching step, after diluting the pulp to a concentration of about 2%, a Buchner funnel with No. 2 Filter paper (manufactured by ADVANTEC) was laid, and a dilution washing step of dehydrating to a pulp concentration of about 12% was performed twice.
(2) Softwood Unbleached kraft pulp was subjected to chlorine dioxide bleaching at a chlorine dioxide addition rate of 1.5% and a pulp concentration of 10 mass% at 70°C for 30 minutes. Subsequently, alkaline hydrogen peroxide bleaching was carried out at 1% alkali addition rate, 0.3% hydrogen peroxide addition rate, pulp concentration 10% by mass, and 70° C. for 120 minutes. Subsequently, alkali treatment was performed at 70° C. for 120 minutes with a sodium hydroxide addition rate of 0.2% and a pulp concentration of 10% by mass. Subsequently, chlorine dioxide bleaching was performed at a chlorine dioxide addition rate of 0.3% and a pulp concentration of 10% by mass at 70° C. for 150 minutes to obtain softwood bleached kraft pulp.
Between each bleaching step, after diluting the pulp to a concentration of about 2%, a Buchner funnel with No. 2 Filter paper (manufactured by ADVANTEC) was laid, and a dilution washing step of dehydrating to a pulp concentration of about 12% was performed twice.

(Papermaking process)
The obtained hardwood bleached kraft pulp and softwood bleached kraft pulp were diluted to a concentration of about 2% without beating, and adjusted to have the blending ratio shown in Table 2. Then, using the pulp slurry after adjustment, a hand-made sheet was prepared using a semi-automatic sheet machine (manufactured by Kumagai Riki Kogyo Co., Ltd.) so as to have a basis weight of 800 g/m ² . Thus, pulp sheets for fluff pulp of Examples 1 to 19 and Comparative Examples 1 to 5 were obtained.

(Content rate of pulp fiber per interval of 0.02 mm in fiber length, content rate per interval of 1 μm in fiber width and standard deviation)
The fiber length and fiber width of the hardwood unbleached kraft pulp of Examples 1 to 19 and Comparative Examples 1 to 5 after the cooking and washing steps were measured. The fiber length and fiber width are measured using a fiber length measuring machine "VALMET FS5" manufactured by Valmet Co., Ltd., according to JIS-P8226: 2011 (ISO16065-2: 2007) "Pulp - fiber length measurement method by optical automatic analysis method". Measured according to The fiber analyzer "VALMET FS5" can measure the length and width of pulp fibers with high accuracy by image analysis when diluted pulp fibers pass through the measurement cell inside the fiber analyzer.
Using the above-mentioned fiber analyzer, the content rate of all pulp fibers was counted at fiber length intervals of 0.02 mm, and then the proportion of pulp fibers with fiber lengths in the range of 0.5 mm or more and less than 1.1 mm was determined. Then, for pulp fibers having a fiber length in the range of 0.5 mm or more and less than 1.1 mm, the average value of the content rate for each fiber length interval of 0.02 mm and the standard deviation of the content rate for each fiber length interval of 0.02 mm σ was calculated.
In addition, after totaling the content of all pulp fibers at intervals of 1 μm in fiber width, the ratio of pulp fibers having a fiber width of 10 μm or more and less than 35 μm was determined. Then, for pulp fibers having a fiber width in the range of 10 μm or more and less than 35 μm, the average value of the content rate at intervals of 1 μm in fiber width and the standard deviation σ of the content rate at intervals of 1 μm in fiber width were calculated.
The above standard deviation measurement value is a value calculated from n=10000 or more measured based on a fiber analyzer. Table 1 shows the calculation results.

In addition, the average value of the content rate for each fiber length interval of 0.02 mm when aggregated at fiber length intervals of 0.02 mm in all pulp fibers, and the content for each fiber width interval of 1 μm when aggregated at fiber width intervals of 1 μm Examples of distributions of mean values of ratios are shown in FIGS. 1 to 6. FIG. FIG. 1 shows the distribution of the average content rate for each fiber length interval of 0.02 mm in Example 1, and FIG. 2 shows the distribution of the average content rate for each fiber width interval of 1 μm in Example 1. 3 shows the distribution of the average content rate for each fiber length interval of 0.02 mm in Comparative Example 1, and FIG. 4 shows the distribution of the average content rate for each fiber width interval of 1 μm in Comparative Example 1. show. 5 shows the distribution of the average value of the content at intervals of 0.02 mm in fiber length in Comparative Example 2, and FIG. 6 shows the distribution of the average value of the content at intervals of 1 μm in fiber width in Comparative Example 2. FIG.

[evaluation]
Various evaluations were performed on the pulp sheet for fluff pulp obtained as described above.

(Density of pulp sheet for fluff pulp)
The density of each fluff pulp pulp sheet was measured according to “Paper and paperboard—Testing methods for thickness, density and specific volume” described in JIS-P8118 (2014).

(Specific bursting strength of pulp sheet for fluff pulp)
The specific bursting strength of each fluff pulp pulp sheet was obtained by dividing the paper bursting strength in kilopascals (kPa) measured according to JIS-P8131 (2009) by the basis weight.

(Fibrillation property of pulp sheet for fluff pulp)
The fibrillation property of each fluff pulp pulp sheet was evaluated based on the value of the specific bursting strength of the fluff pulp pulp sheet according to the following five-level evaluation criteria. When the evaluations are A, B, C and D, the fluff pulp pulp sheet has good defibration properties, and A is particularly excellent. Also, although D is slightly inferior, it is at a practically acceptable level.
A: The specific burst strength is 1.2 kPa·m ² /g or more and 1.5 kPa·m ² /g or less.
B: The specific burst strength is 1.6 kPa·m ² /g or 1.1 kPa·m ² /g.
C: The specific burst strength is 1.7 kPa·m ² /g or 1.0 kPa·m ² /g.
D: The specific burst strength is 1.8 kPa·m ² /g or 0.9 kPa·m ² /g.
E: The specific burst strength is 1.9 kPa·m ² /g or more or 0.8 kPa·m ² /g or less.

(Krem water absorption)
The Klemm water absorbency of each fluff pulp pulp sheet is measured in accordance with "Paper and paperboard-Water absorption test method-Klemm method" described in JIS-P8141 (2004), and the height [ mm] and the water absorption rate [mm/min] for 1 to 2 minutes after the start of measurement.
The Klemm water absorbency is a numerical value measured by preparing each fluff pulp pulp sheet having a basis weight of 200 g/m ² .

(Absorptive performance of pulp sheet for fluff pulp)
The absorption performance of the fluff pulp pulp sheet is evaluated based on the absorption amount based on the value of the height of 1 minute after the start of measurement of the Klemm water absorbency of the fluff pulp pulp sheet. The water absorption rate was evaluated based on the water absorption rate value for minutes. Evaluation criteria were as follows: 4 grades for absorption amount and 5 grades for absorption speed. When the absorption amount is evaluated as A, B or C, the absorption amount of the fluff pulp pulp sheet is good. When the absorption rate is evaluated as A, B, C or D, the absorption rate of the fluff pulp pulp sheet is good.
(1) Absorption A: The height of Kremm's water absorbency 1 minute after the start of measurement is 29 mm or more and 40 mm or less.
B: The height of 1 minute after the start of measurement of Klemm's water absorbency is 27 mm or more and 28 mm or less.
C: The height of 1 minute after the start of measurement of Klemm's water absorbency is 25 mm or more and 26 mm or less.
D: The height of 1 minute after the start of measurement of Klemm's water absorbency is 24 mm or less.
(2) Water absorption rate A: The water absorption rate is 9 mm/min or more for 1 minute to 2 minutes after the start of measurement of Klemm's water absorption.
B: The water absorption rate is 7 mm/min or more and 8 mm/min or less for 1 to 2 minutes after the start of measurement of the Klemm water absorbency.
C: The water absorption rate is 5 mm/min or more and 6 mm/min or less for 1 minute to 2 minutes after the start of measurement of the Klemm water absorbency.
D: The water absorption rate is 4 mm/min for 1 to 2 minutes after the start of measurement of Klemm's water absorbency.
E: The water absorption rate is 3 mm/min or less for 1 to 2 minutes after the start of measurement of Klemm's water absorbency.

(Workability)
The workability in the production of fluff pulp was evaluated by cutting each fluff pulp pulp sheet having a basis weight of 200 g/m into 2 cm × 2 cm pieces, pulverizing them with a commercially available mixer (manufactured by Tescom, mixer TM856), and adding paper powder during pulverization. The degree of occurrence was evaluated. The accumulated amount of pulp increases from E to A. Evaluation was carried out according to the following five stages. When the evaluations are A, B, C and D, workability is good.
A: Paper dust flew when the pulp sheet was pulverized, and there was a slight accumulation of pulp on the walls of the mixer.
B: Paper dust flutters when the pulp sheet is pulverized, and there is some accumulation of pulp on the walls of the mixer.
C: Paper dust fluttered during pulverization of the pulp sheet, and a small amount of pulp accumulated on the walls of the mixer.
D: Paper dust floats when pulverizing the pulp sheet, and some pulp deposits on the walls of the mixer, but within the range of no problem.
E: Paper dust flutters when the pulp sheet is pulverized, and a large amount of pulp accumulates on the walls of the mixer.

(Skin Rash on Absorbent Articles)
After making paper diapers using the pulp sheets for fluff pulp of Examples 1 to 19 and Comparative Examples 1 to 5, a total of 220 monitors were given Examples 1 to 19 and Comparative Examples 1 to Comparative. 10 sheets of each sample from Example 5 were used, and the number of sheets with rashes was evaluated as a percentage. Evaluation was carried out according to the following five stages. When the evaluations are A, B, C and D, the effect of suppressing skin rashes is better than that of Comparative Example 1 having the same composition as the existing product.
A: Better than Comparative Example 1 in rash occurrence rate.
B: Slightly superior to Comparative Example 1 in rash occurrence rate.
C: Slightly superior to Comparative Example 1 in rash occurrence rate.
D: Slightly superior to Comparative Example 1 in rash occurrence rate, practically usable.
E: The rash occurrence rate is equivalent to that of Comparative Example 1, and is at the same level as the existing product.

Table 2 shows the evaluation results of each example and comparative example.

As shown in Table 2, the pulp fiber containing bleached hardwood kraft pulp and bleached softwood kraft pulp and having a fiber length of 0.5 mm or more and less than 1.1 mm when totaled at fiber length intervals of 0.02 mm for all pulp fibers The ratio is 42.6% or more, and the average content of the pulp fibers having a fiber length of 0.5 mm or more and less than 1.1 mm for each interval of 0.02 mm in fiber length is 1.00% or more and 1.70% or less and the standard deviation σ is 0.58% or less, and the proportion of pulp fibers with a fiber width of 10 μm or more and less than 35 μm when aggregated at intervals of 1 μm for all pulp fibers is 90.6% or more, and the fiber width Example 1 to Example in which the average value of the content rate of pulp fibers of 10 μm or more and less than 35 μm per interval of 1 μm in fiber width is 3.1% or more and 3.9% or less, and the standard deviation σ is 2.9% or less 19 is fibrillation property and water absorption. Good results were obtained in terms of water absorption rate, workability in the production of fluff pulp, and the effect of suppressing rashes in absorbent articles.

On the other hand, Comparative Example 1, in which only the bleached softwood kraft pulp was used, was inferior in fibrillation and absorption speed, and was also inferior in the effect of suppressing rashes in absorbent articles. Comparative Example 2 containing only the bleached hardwood kraft pulp was inferior in fibrillation, absorption capacity, and absorption rate, and was also inferior in workability and rash-suppressing effect in absorbent articles. In addition, the ratio of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm when totaling the total pulp fiber at fiber length intervals of 0.02 mm is 42.6% or more, and the fiber length is 0.5 mm or more and 1.1 mm. The average value of the content of the pulp fibers at intervals of 0.02 mm in fiber length of less than 1.00% or more and 1.70% or less, and the standard deviation σ is 0.58% or less, and aggregated at intervals of 1 μm in fiber width The ratio of pulp fibers with a fiber width of 10 μm or more and less than 35 μm is 90.6% or more, and the average content of the pulp fibers with a fiber width of 10 μm or more and less than 35 μm per interval of 1 μm in fiber width is 3.1. % or more and 3.9% or less, and the standard deviation σ is 2.9% or less. The rash suppressing effect was inferior.

As a result, it was shown that the pulp sheet for fluff pulp has high absorption performance even when containing hardwood-derived wood pulp, and has good workability in the production of fluff pulp.

The pulp sheet for fluff pulp of the present invention is suitable for absorbent articles.

Claims (5)

Contains bleached hardwood kraft pulp and bleached softwood kraft pulp,
When the content rate of all pulp fibers is totaled at fiber length intervals of 0.02 mm, the proportion of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm is 42.6% or more, and the fiber length is 0.5 mm. The average value of the content rate for each interval of 0.02 mm in fiber length in pulp fibers having a length of 1.1 mm or more is 1.00% or more and 1.70% or less,
The standard deviation σ of the content rate for each 0.02 mm interval of the fiber length in the pulp fibers having a fiber length of 0.5 mm or more and less than 1.1 mm is 0.41% or more and 0.58% or less,
The ratio of pulp fibers with a fiber width of 10 μm or more and less than 35 μm is 90.6% or more when the content rate is totaled at intervals of 1 μm in fiber width for all pulp fibers, and the above-mentioned pulp fibers with a fiber width of 10 μm or more and less than 35 μm The average value of the content rate for each interval of 1 μm in fiber width is 3.1% or more and 3.9% or less,
A pulp sheet for fluff pulp, wherein the standard deviation σ of the content of the pulp fibers having a fiber width of 10 μm or more and less than 35 μm per interval of 1 μm in fiber width is 2.5% or more and 2.90% or less. The pulp sheet for fluff pulp according to claim 1, wherein the mass ratio of the bleached hardwood kraft pulp to the bleached softwood kraft pulp is 25/75 or more and 38/62 or less. 3. The pulp sheet for fluff pulp according to claim 1, wherein the content of the acacia wood in the raw material wood of the broad-leaved bleached kraft pulp is 5% by mass or more and 95% by mass or less. 4. The pulp sheet for fluff pulp according to claim 1, claim 2, or claim 3, which has a density of 0.50 g/cm ³ or more and 0.65 g/cm ³ or less. The pulp sheet for fluff pulp according to any one of claims 1 to 4, having a specific bursting strength of 1.0 kPa·m ² /g or more and 1.7 kPa·m ² /g or less.

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