JPH09158082A - Water-absorbing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a water-absorbing sheet having excellent water- absorptivity, mechanical properties such as bending strength and dimensional stability and exhibiting good processability. SOLUTION: The objective water-absorbing sheet contains hydrophilic modified cross-section fibers having one or more continuous or discontinuous grooves on the surface and binder fibers, having a density of 0.25-0.4g/m<3> , ratio of the binder fiber to the total solid component of 15-25wt.% and a fineness of the binder fiber of >=3de. As an alternative, the objective water-absorbing sheet contains hydrophilic modified cross-section fibers having one or more continuous or discontinuous grooves on the surface, binder fibers and highly elastic fibers and has a density of 0.25-0.4g/m<3> , ratio of the binder fiber to the total solid component of 15-25wt.% and a fineness of the binder fiber of >=3de. The modified cross-section fiber is preferably a polyvinyl alcohol fiber.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a water absorbent sheet.
More specifically, it relates to a water absorbent sheet which is excellent in water absorbency, mechanical properties, processability, and dimensional stability and can be used as a water absorbent material for a humidifier, a dew condensation absorbent material, a water evaporation plate, a humidity control plate and the like.

[0002]

2. Description of the Related Art In recent years, porous sheets (water absorbent sheets in the present invention) have been widely used in the fields of water absorbent materials for humidifiers, dew condensation water absorbent materials, humidity control plates, filter materials and the like. As the porous sheet, conventionally, a sheet obtained by sintering and molding a fine particle of a thermoplastic resin such as polyolefin into a sheet, or a sheet obtained by bonding a perforated film of the resin and a porous substrate are used. . However, since the above-mentioned thermoplastic resins are generally hydrophobic, these porous sheets have poor water absorption, and have a problem that they do not function effectively as a water-absorbing material.

Japanese Patent Laid-Open No. 1-283129 discloses a porous sheet which solves the above-mentioned problems of the conventional porous sheet, is excellent in water absorption and has good mechanical properties such as bending strength. . The porous sheet of the publication is a sheet made of a reinforcing fiber, for example, a non-woven fabric of polyester fiber is impregnated with an aqueous dispersion of fine particles of a thermosetting phenolic resin, dried, and then heated under pressure to heat the phenol. It is obtained by curing a resin to form a sheet, then impregnating with an aqueous dispersion of silica-based fine particles, and drying.

JP-A-3-81349 discloses a porous sheet having flame retardancy, and JP-A-3-86529 discloses a porous sheet having surface smoothness and excellent in both water absorption and mechanical properties. However, the basic configuration is similar to that of the above publication.

However, the porous sheet obtained by the above method has a problem that phenol resin fine particles fall off during the secondary processing.

[0006]

The present invention solves these problems and is excellent in mechanical properties such as water absorbency and bending strength, dimensional stability, and good secondary workability. It is intended to provide a water absorbent sheet.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that hydrophilic modified cross-section fibers are fixed under a certain density condition by a binder fiber having a specific fineness. It has been found that an excellent water-absorbent sheet can be obtained. The present invention has been achieved based on these findings.

That is, the present invention contains hydrophilic modified cross-section fibers having one or more continuous or discontinuous grooves on the surface and binder fibers, and has a density of 0.25 to 0.4 g / m ³ and a total solid content. Content of the binder fiber is 15 to 25
It is a water-absorbent sheet having a weight% and a binder fiber fineness of 3 denier or more.

It also contains hydrophilic modified cross-section fibers having one or more continuous or discontinuous grooves on the surface, binder fibers and highly elastic fibers, and has a density of 0.25 to 0.4 g /
m ³ , the content of the binder fiber with respect to the total solid content is 1
It is a water-absorbent sheet having 5 to 25% by weight and a binder fiber fineness of 3 denier or more.

More preferably, the hydrophilic modified cross-section fiber is a polyvinyl alcohol fiber, which is a water absorbent sheet.

Hereinafter, the present invention will be described in detail. First, the role of the fibers used in the present invention will be described. The hydrophilic modified cross-section fiber (hereinafter abbreviated as modified cross-section fiber) is
Grooves formed on the surface serve as water passages and carry water. The binder fibers bond the constituent fibers together by adhesion and impart strength to the water absorbent sheet. Further, when the water-absorbent sheet absorbs water, it prevents the sheet from swelling and changing in thickness.

Further, regarding the materials used in the present invention,
It will be described in detail and specifically. The modified cross-section fiber used in the present invention is hydrophilic and has at least one continuous or discontinuous groove on the surface. The shape of the groove is not particularly limited, and if the cross-sectional shape is T-shaped, Y-shaped, U-shaped, star-shaped, etc., the concave portion can serve as the groove, or simply have a streak-shaped groove. May be

In general, the water absorption of a nonwoven fabric sheet depends strongly on the shape of the fibers and the state of aggregation of the fibers, as well as the properties of the fibers themselves. In particular, the latter two have a great effect on the water absorption of the nonwoven fabric sheet.

Fibers having a perfect circle or elliptical cross section are
Not only does the surface not have a groove-shaped water passage, but also the nonwoven fabric sheet composed of only the fibers has a high fiber filling rate and a denser sheet, so that there is a passage between the fibers in the sheet. The formation of the water path becomes insufficient, and it is difficult to obtain a nonwoven fabric sheet having excellent water absorbency.

However, continuous or discontinuous grooves existing on the fiber surface function as water passages. Furthermore, due to the special cross-sectional shape of the fibers, even when the fibers come into contact with or approach each other in the sheet, the contact area is smaller than that of the fibers having no atypical cross-section. Remaining, many pores are formed in the sheet, and a water passage between fibers is secured. It is considered that the water-absorbent sheet of the present invention exhibits excellent water absorption by combining these paths with the fibers described below by the capillary phenomenon.

However, when too flat fibers are used, the water absorbing sheet becomes dense in the pressing step,
In the fiber cross section, the flatness ratio (L / S) between the major axis diameter (L) and the minor axis diameter (S) is preferably 3 or less.

The type of modified cross-section fiber is not particularly limited as long as it has hydrophilicity, and includes polyvinyl alcohol fiber, recycled fiber, acetate fiber, polyamide fiber, ethylene vinyl alcohol fiber, and the like. Fibers that have been rendered hydrophilic by surface modification such as corona discharge treatment or plasma treatment, graft polymerization of a hydrophilic compound such as acrylic acid, and porosification can be used alone or in combination. It is one of the features of the present invention that the modified cross-section fiber itself constituting the water passage has hydrophilicity and imparts excellent water absorption to the water absorbent sheet.

Since the water-absorbent sheet of the present invention is used for applications around water such as water-absorbing plates and water-transpiration plates, it has complete resistance to fungi and mold among the above fibers. Those that are present are preferable. When the fiber having low resistance is used for a long period of time, the fiber is invaded by fungi and mold, and the water absorption performance of the sheet is deteriorated. In addition, it is not preferable in that odor is generated as the fungi and mold grow.

Among the fibers which are completely resistant to mold, the fibers usable in the present invention are preferably polyvinyl alcohol, nylon and acrylic fibers,
Although rayon fiber has a large hydrophilicity, it is not preferable because it has low resistance to fungi and mold, and a fiber having a strong hydrophobicity such as a polyolefin fiber is not preferable because it reduces the water absorption of the water absorbent sheet.

Among these fibers, the polyvinyl alcohol fiber is a particularly preferable fiber because it has a large Young's modulus and can impart good mechanical properties such as bending strength to the water absorbent sheet. Further, in the step of forming the sheet, the use of such a fiber having a high Young's modulus as the modified cross-section fiber densely improves the mechanical properties of the water absorbent sheet.

The fineness of the modified cross-section fiber is preferably 0.1 to 15 denier (hereinafter abbreviated as d). When it is less than 0.1 d, the water-absorbent sheet becomes dense and the water passage between the fibers in the water-absorbent sheet decreases, which is not preferable. On the other hand, if it is larger than 15d, voids are secured, but the fiber spacing is widened, the formation of pores by a plurality of fibers is suppressed, and the progress of water is inhibited by capillary action, so that water absorption decreases. Is not preferred.

In the present invention, the modified cross-section fiber is preferably 50% or more, more preferably 60% by weight or more of the weight of the water absorbent sheet. If it is less than 50%, the blending amount of the binder fiber is increased, the wettability of the water-absorbent sheet itself is lowered, and the water absorbency is deteriorated, which is not preferable.

Next, the binder fiber will be described.
Examples of the binder fiber used in the present invention include a hot-melt fiber and a hot-water-soluble fiber. The heat-fusible fiber is a fibrous material selected from synthetic resins such as polyester, polyolefin, and polyamide, and the synthetic resin is melted and adhered by treating at a temperature equal to or higher than the melting point of the synthetic resin, and develops strength. Things. The hot water-soluble fiber is a fibrous material selected from synthetic resins such as polyvinyl alcohol and ethylene vinyl alcohol, and is dissolved by an increase in water temperature in a step of drying a water-containing web by heating, and the web is dried. The fibers adhere to the fibers in contact with each other and exhibit strength.

The fineness of the binder fiber is preferably 3 denier or more, more preferably 3 to 15 denier. When it is less than 3 denier, not only the water-absorbent sheet becomes dense, but also the surface area of the binder fiber occupying in the sheet becomes large and the water absorbency is lowered, which is not preferable.

If it is larger than 15d, the number of binder fibers in the water absorbent sheet will be small, and the amount of binder fibers must be increased in order to compensate for the decrease in adhesive strength.
It is not preferable because the content of fibers contributing to water absorption is reduced.

The content of the binder fiber is preferably 15 to 25% of the weight of the water absorbent sheet. If it is less than 15%, the adhesive strength is insufficient, it is difficult to fix other constituent fibers, and the mechanical properties of the water-absorbent sheet are deteriorated, fuzz is generated, and dimensional stability is deteriorated. If it exceeds 25%, the adhesive strength is large, but the surface area of the binder fiber becomes large, and the water absorbency of the water absorbent sheet decreases due to melt plasticization of the binder fiber surface. Also, the binder fiber has a larger area covering the surface of the fiber that contributes to other water absorption,
Water absorption is reduced.

The density of the water absorbent sheet of the present invention is 0.25 to 0.25.
A range of 0.4 g / cm ³ is preferred. When it is less than 0.25 g / cm ³ , the water absorption is large, but the bending strength of the water absorption sheet becomes small, and wrinkles may be formed during punching, and punching may not be successful, which is not preferable. 0.4 g / c
When it exceeds m ³ , the water-absorbent sheet becomes dense, the water passage is blocked, and the water absorption is lowered, which is not preferable.

Further, in the present invention, it is more preferable to contain a highly elastic fiber. The high elastic fiber has a large rigidity and not only imparts bending strength to the water absorbent sheet, but also has a strong repulsion against compression, so that the binder fiber is excessively fused against heat and pressure during the production of the water absorbent sheet. By doing so, it is possible to prevent the water absorbent sheet from having a high density, blocking the water passage, and preventing the water absorption from decreasing.

As such a high elastic fiber, one having hydrophilicity is particularly preferable. The hydrophilic high-elasticity fiber includes a fiber having hydrophilicity itself and a high-elasticity fiber subjected to hydrophilic treatment. Specifically, glass, inorganic fibers such as carbon fibers, copper fibers, metal fibers such as stainless fibers, phenol fibers, aromatic polyamide fibers, polyimide fibers, polyphenylene sulfide fibers, engineering plastic fibers such as aromatic polyester fibers and the like. . The fiber length and fineness of the high-elasticity fiber are modified cross-section fibers used in the present invention,
The same range as the binder fiber can be used.

Next, the method for producing the water absorbent sheet of the present invention will be described.

First, the modified cross-section fibers and the binder fibers are uniformly mixed to form a web. There is no particular limitation on the method for web formation, and web formation can be carried out by methods such as wet papermaking methods and dry methods.

The web thus formed is laminated in a single layer or a plurality of layers and subjected to heat and pressure treatment using a heat press, a heat calender, etc. to melt the binder fiber,
By fusing with the fibers that are in contact with each other and adjusting the thickness to the desired value,
The water absorbent sheet of the present invention can be obtained.

The present invention is a water-absorbent sheet having a constant density, which is obtained by using binder fibers having a specific fineness in a specific ratio of modified cross-section fibers. Furthermore, it is a water-absorbent sheet containing a highly elastic fiber. The water absorbent sheet of the present invention is excellent in water absorption, mechanical properties, dimensional stability and processability,
It can be used in a wide range of fields such as water absorbents for humidifiers, water absorbents for dew condensation, humidity control plates, filter media, and water evaporation plates.

[0033]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
“Parts” and “%” in the examples mean “parts by weight” and “% by weight”, respectively. In the Examples and Comparative Examples, the basis weight, thickness, water absorption time, bending strength, workability, falling off, and dimensional stability were measured by the following methods. The samples manufactured in Examples and Comparative Examples were 20
The sample was left for 24 hours at a temperature of 65 ° C. and a relative humidity of 65%, and then used for measurement.

<Basis weight> 20 × 20 cm square was trimmed, and the weight per 1 m ² was obtained from the average value of 5 samples weighed. The unit is g / m ² .

<Thickness> 20 × 20 cm square was trimmed, and 4 points per sample and 5 samples were measured using a micrometer, and the average value was taken as the thickness. Unit is mm
It is.

<Water Absorption Time> The water absorbent sheet was cut into a width of 20 mm and a length of 150 mm in the lengthwise direction and the widthwise direction, and one end 30 mm of the test piece was immersed in pure water at 20 ° C.
The time required for the water to rise 40 mm above the water surface in the test piece was taken as the water absorption time (seconds) and used as an index of water absorption. The unit is seconds. If the water absorption time is within 25 seconds,
The water absorption was considered good.

<Bending strength> The bending strength is JIS K-7.
According to No. 203, a water absorbent sheet, width 25mm, length 12
It was cut into 5 mm and measured by a tensilon measuring machine (manufactured by Orientec, HTM-100) using a pressure wedge and a support (manufactured by Orientec). The unit is kg /
cm ² . When the bending strength was 50 kg / cm ² or more, the mechanical properties were determined to be good.

<Workability> A JIS K-6301 No. 2 dumbbell-shaped sample was punched. Good punchability as workability, × wrinkled or deformed sample during punching, × poor punching
And

<Detachability> 10 × 10 cm of the water absorbent sheet
After trimming, the sheet was lightly tapped with the trimming surface facing downward, and it was visually examined whether or not the powder and fibers would fall off. As the falling property, those that do not drop are ○,
The ones that were a little dropped were marked with Δ, and the ones that were dropped a lot were marked with x.
Only ○ was regarded as good.

<Dimensional Change> The water-absorbent sheet was sufficiently immersed in pure water at 20 ° C., and the thickness of the sheet was measured before and after the immersion. The unit is%. If the absolute value of the rate of change in thickness before and after immersion is within 10%, the dimensional stability is considered to be good.

Examples 1 to 3 and Comparative Examples 1 to 2 As the hydrophilic modified cross-section fibers, vinylon fibers having a fineness of 2d and a fiber length of 6 mm and having a Y-shaped cross section (VPY manufactured by Kuraray Co., Ltd.)
202), as a binder fiber, the sheath has a melting point of 110
A core-sheath type polyester binder fiber (Melty 4080 manufactured by Unitika Ltd.) having a fineness of 4 d at 5 ° C. and a fiber length of 5 mm was sequentially added and mixed in water at the level shown in Table 1 to prepare an aqueous slurry having a concentration of 0.3%. Next, a web having a dry weight of about 100 g / m ² was made into a paper by using the aqueous slurry, and seven webs were laminated to obtain a laminated web. Furthermore, after inserting a spacer having a thickness of 2 mm by using the laminated web with a hot press machine, it was 1 at a temperature of 140 ° C. and a surface pressure of 15 kg / cm ² .
It was heated under pressure for 5 minutes to obtain a water absorbent sheet.

Examples 4 to 5, Comparative Examples 3 to 4 Thickness 3 mm (Comparative Example 3), Thickness 2.7 mm (Example 4), Thickness 1.8 mm (Example 5), Thickness 1.7 mm
The same method as in Example 2 was carried out except that the spacer of (Comparative Example 4) was used.

Examples 6 to 8 As a hydrophilic modified cross-section fiber, a vinylon fiber having a fineness of 2d and a fiber length of 6 mm and having a Y-shaped cross section (VPY2 manufactured by Kuraray Co., Ltd.)
02), as a binder fiber, the melting point of the sheath is 110 ° C.
Cored-sheath type polyester binder fiber having a fineness of 4d and a fiber length of 5 mm (Melty 4080 manufactured by Unitika Ltd.), and glass fiber having a fiber diameter of 9 μm and a fiber length of 6 mm (Glaslon manufactured by Asahi Fiber Glass Co., Ltd.) as highly elastic fiber in water. Sequential addition and mixing were carried out at the level of Table 1 to prepare an aqueous slurry having a concentration of 0.3%. Next, a web having a dry weight of about 100 g / m ² was made into a paper by using the aqueous slurry, and seven webs were laminated to obtain a laminated web. Further, after inserting a spacer having a thickness of 2 mm by using the laminated web with a hot press machine, the temperature was 15 at 140 ° C. and a surface pressure of 20 kg / cm ² .
The water absorbent sheet of the present invention was obtained by pressure heating treatment for a minute.

[0044]

[Table 1]

Example 9 A hydrophilic modified cross-section fiber having a fineness of 2d and a fiber length of 51 mm
Vinylon fiber having a Y-shaped cross section (VPY, manufactured by Kuraray Co., Ltd.)
202) 80% by weight, as a binder fiber, a core-sheath type polyester binder fiber (manufactured by Unitika Ltd., Melty 4) having a sheath part melting point of 110 ° C., a fineness of 4 d, and a fiber length of 51 mm.
(080) 20% by weight of cotton was mixed and opened, and then made into a web with a card. Then, after laminating with a cross wrapper, the thickness was reduced with a needle punch, and the dry weight was about 700 g /
It was a laminated web of m ² . Furthermore, with a heat press device,
A spacer having a thickness of 2 mm was inserted using the laminated web, and then 1 at 140 ° C., 140 ° C. and a surface pressure of 20 kg / cm ² .
The water-absorbent sheet of the present invention was obtained by applying pressure and heat treatment for 0 minutes.

Comparative Example 5 As the binder fiber, the fineness 2 with the melting point of the sheath portion being 110 ° C.
d, The procedure was the same as in Example 2, except that a core-sheath type polyester binder fiber having a fiber length of 5 mm (Melty 4080, manufactured by Unitika Ltd.) was used.

Example 10 As the binder fiber, the fineness 3 with the melting point of the sheath portion being 110 ° C.
d, The procedure was the same as in Example 2 except that a core-sheath type polyester binder fiber (Tepils, manufactured by Teijin Limited) having a fiber length of 5 mm was used.

Comparative Example 6 A water absorbent sheet was obtained in the same manner as in Example 2 except that regular shaped vinylon fibers having a fineness of 2d and a fiber length of 6 mm were used instead of the modified cross-section fibers.

Comparative Example 7 A water absorbent sheet was obtained in the same manner as in Example 2 except that non-hydrophilic T-shaped polyester fibers having a fineness of 2d and a fiber length of 5 mm were used as the modified cross-sectional fibers.

Comparative Example 8 50% by weight of core-sheath type polyester heat fusion fiber having a fineness of 2d, a fiber length of 51 mm and a sheath melting point of 130 ° C., a fineness of 4 d, a fiber length of 51 mm and a sheath melting point of 130 ° C. A 50% by weight type polyester fiber was webbed by a carding machine to obtain a web A. On the other hand, a phenol resin (UA-100, manufactured by Unitika Ltd.) having an average particle diameter of 100 μm was dispersed in water at a concentration of 5%, and this was used as Dispersion A. Furthermore, fine powdery silicic acid anhydride having a particle size of 0.1 μm was dispersed in water at a concentration of 10%. This was designated as Dispersion B.

The web A was impregnated with the dispersion A, and the dispersion A was squeezed with a mangle so that the amount of the phenol resin adhered was 35% of the total weight of the web, followed by drying at 100 ° C. for 20 minutes. Basis weight 920 with cured phenolic resin
A web B of g / m ² was obtained. Web B was heat-treated under pressure at 160 ° C. and a surface pressure of 1.0 kg / cm ² for 5 minutes using a hot press machine. Further, the dispersion B was impregnated and dried at 100 ° C. for 20 minutes to obtain a water absorbent sheet having fine powdery silicic acid anhydride attached thereto. At this time, the amount of the fine powdered silicic acid anhydride attached was 1.5% based on the weight of the water absorbent sheet.

Comparative Example 9 100 parts of 100 μm phenol resin (UA-100, manufactured by Unitika Ltd.) having an average particle diameter, polyester fibers having an average fineness of 4 d and an average fiber length of 5 mm were mixed with a carding machine to form a web, and the mixture was heated to 150 ° C. A mat having a thickness of 10 mm and a basis weight of 800 g / m ² was obtained by passing through a set calender roll. Using a hot press device, the mat is
The phenol resin was cured by applying pressure and heat at 5 ° C. and a surface pressure of 1.0 kg / cm ² for 5 minutes. Further, after impregnating the dispersion liquid B used in Comparative Example 8 and drying at 100 ° C. for 20 minutes, a water absorbent sheet impregnated with fine powder silicic anhydride was obtained. At this time, the amount of the fine powdered silicic acid anhydride attached was 1.5% based on the weight of the water absorbent sheet.

Table 2 shows the results of various physical properties and performance evaluations of the water absorbent sheets of Examples 1 to 10 and Comparative Examples 1 to 9 as described above.

[0054]

[Table 2]

From the examples, it has been found that the water absorbent sheet of the present invention exhibits excellent water absorbency, mechanical properties, dimensional stability, and processability, and is excellent in handleability without falling of powder. .

However, it is understood that when the blending amount of the binder fiber is large, the performance such as bending strength is good, but the water absorption rate is inferior. There are many bonded parts with binder fibers,
The reason is that the surface of other fibers is covered. Conversely, when the amount of the binder fiber is small, the water absorption rate is good, but the bonding portion is small and the bonding strength is weak, so that the bending strength, the workability, the dimensional stability are inferior, and the fibers may be dropped off.

On the other hand, the low-density one has a good water absorption rate, but is inferior in bending strength, workability and dimensional stability, and fibers are also found to fall off. It is considered that the reason is that the number of intersections between the fibers is small, that is, the adhesion by the binder fibers is small. On the other hand, it can be seen that the high-density one has a good adhesive strength and covers other fiber surfaces, and thus has good performance such as bending strength, but has a poor water absorption rate.

Further, in the case of using a binder fiber having a fineness smaller than 3 denier, the water absorption is lowered. It is thought that the ratio of the surface area of hydrophilic fibers was relatively small due to the increase in the number of binder fibers, the increase in the number of bonded parts, the covering of other fiber surfaces, and the increase in specific surface area. Can be

Further, the water absorption was poor in the case where the fibers having the irregular cross-sectional shape were not used and the case where the hydrophilic fibers were not used.

Finally, in the case of using the binder fiber and the hydrophilic fine powder, the powder often falls off, and there is a problem in handling. That is, the one using the fine particles of the phenol resin was good in water absorption, bending strength, and dimensional stability,
After trimming, the phenol resin was found to have fallen off.

[0061]

From the above results, it became clear that the water absorbent sheet of the present invention is excellent in mechanical properties such as bending strength, dimensional stability and workability. A large number of pores are formed in the water-absorbent sheet by the hydrophilic modified cross-section fiber, and a small amount of binder fiber having a specific fiber diameter is used to control a specific density, thereby increasing the number of pores in the water-absorbent sheet. A water path can be secured, and a water-absorbent sheet having extremely good water absorption can be obtained. Further, the blockage of the water passage can be suppressed by the high elastic fiber. Further, unlike the conventional porous sheet using the fine particles of the thermoplastic resin, there is no problem such as dropping of the resin during the secondary processing.

Claims (3)

[Claims] 1. A hydrophilic modified cross-section fiber having one or more continuous or discontinuous grooves on the surface, a binder fiber, a density of 0.25 to 0.4 g / m ³ , and a binder based on the total solid content. A water absorbent sheet having a fiber content of 15 to 25% by weight and a fineness of the binder fiber of 3 denier or more. 2. A hydrophilic modified cross-section fiber having one or more continuous or discontinuous grooves on the surface, a binder fiber and a highly elastic fiber, and a density of 0.25 to 0.4 g / m ³ ,
The content of the binder fiber is 15 to 2 with respect to the total solid content.
A water-absorbent sheet having a binder fiber content of 5% by weight and a fineness of 3 denier or more. 3. The water absorbent sheet according to claim 1, wherein the hydrophilic modified cross-section fiber is a polyvinyl alcohol fiber.