JPH03141945A - Absorptive base material and manufacture thereof - Google Patents

Abstract

PURPOSE:To preferentially generate absorption and diffusion in the specific direction of liquid, when it is brought into contact with surfaces of a base material, by integrally connecting a fiber material, which shows absorptive liquid anisotropy, to the surface of the absorptive base material consisting of cellulose system sponge. CONSTITUTION:A mixture, which contains a cellulose component, reinforcing fiber and crystal mirabilite, is molded, and on surface of the obtained molded product, various threads, consisting of natural or synthetic fiber of predominantly generating diffusion of absorbed liquid in a specific direction, and a fiber material, showing absorptive liquid anisotropy of thin sheet paper and unwoven fabric or the like having directivity in constitution fiber, are pasted. Under this condition, the molded product is heated, solidified and brought into contact with an acid water solution, thereafter washed by water and dried with an absorptive base material manufactured. Accordingly, when liquid is brought into contact with surfaces of the base material, absorption and diffusion of the liquid can be predominantly generated in a specific direction, and a product, having efficient liquid absorbing performance, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an absorbent substrate made of cellulose sponge and a method for producing the same.

(Prior Art and its Problems) Cellulose sponges have been known as base materials with excellent liquid absorption properties. This cellulose sponge is made by adding reinforcing fibers, crystalline mirabilite, and auxiliary additives to a solution containing a cellulose component (e.g., viscose), mixing them uniformly, and molding the mixture into a desired shape. After coagulating by heating, cellulose is regenerated by contacting with an acidic aqueous solution, followed by washing with water and drying.

The cellulose sponge thus obtained is a porous material with a network structure having a large number of pores communicating with the interior on its surface, and has excellent liquid absorption properties.
Since its surface and internal structure are homogeneous, its liquid absorption properties have no anisotropy. Therefore, when a cellulose sponge formed into an IF shape is used as an absorbent material for sanitary napkins, for example, when liquid is added to one location on the surface and absorbed, the liquid absorption part in the vertical direction (longitudinal direction) Even though there is sufficient margin, the liquid absorption capacity in the lateral direction is saturated, causing a problem of liquid leakage from the lateral direction.

(Problems to be solved by the invention) The present invention provides a product and a product in which when a liquid is brought into contact with the surface of an absorbent base material made of cellulose sponge and absorbed and diffused, the absorption and diffusion occurs predominantly in a specific direction. The objective is to provide a method for producing the same.

(Means for Solving the Problems) As a result of intensive research to solve the above-mentioned problems, the present inventors found that the surface of a mixed molded product containing a cellulose component, reinforcing fibers, and crystalline mirabilite is capable of absorbing and diffusing liquid. By attaching a fiber material that exhibits anisotropy and processing the molded product in this state using a conventional method to make a cellulose sponge,
The inventors have discovered that the fiber material is integrally bonded to the surface of the sponge and that a sponge exhibiting anisotropy in liquid absorption and diffusion based on the fiber material bonded to the surface can be obtained, and the present invention has been completed.

That is, according to the present invention, there is provided an absorbent base material made of 5-cellulose sponge, characterized in that a fibrous material exhibiting liquid absorption anisotropy is integrally bonded to the surface of the absorbent base material. Ru.

Furthermore, according to the present invention, a mixture containing a cellulose component, reinforcing fibers, and crystalline mirabilite is molded, and a fiber material exhibiting liquid absorption anisotropy is adhered to the surface of the resulting molded product, and in this state, a fiber material exhibiting liquid absorption anisotropy is attached. A method for producing an absorbent substrate is provided, which comprises heating and coagulating a molded article, bringing it into contact with an acidic aqueous solution, washing with water, and drying.

In this specification, the cellulose sponge refers to a sponge made of a material having a cellulose skeleton, and includes sponges made of cellulose itself, as well as sponges made from cellulose derivatives, such as cellulose ethers and cellulose esters. There are sponges made of these materials or mixtures thereof, which are conventionally known materials.

In addition, liquid absorption anisotropy in the specification means liquid absorption in which diffusion of absorbed liquid occurs predominantly in a specific direction.

In the present invention, any fiber material can be used as long as it has liquid absorption anisotropy as the fiber material bonded to the sponge surface. Examples of such fiber materials include various yarns made of natural or synthetic fibers such as rayon filament, spun rayon yarn, cotton yarn, linen yarn, and crepe-processed yarn, as well as thin paper and nonwoven fabric whose constituent fibers have directionality. Examples include sheet-like products. As the nonwoven fabric, those obtained by the spunbond method or the wet method are particularly suitable. When using yarn as the fiber material, the thickness of the yarn is 0.5~
No. 10 is preferable, and it is preferable that the distance between the threads attached to the sponge surface be set in the range of 3 to 20 mm. If the thickness of the thread becomes too thin, the liquid absorption and diffusion effect due to capillary phenomenon will be insufficient.On the other hand, if the thread becomes too thick, the physical properties of the sponge will change significantly, causing problems such as loss of flexibility and texture. There is. Furthermore, if the distance between the attached threads is too wide, the anisotropy of liquid absorption and diffusivity by the threads will be insufficient, which is not preferable. Further, even if the thread spacing is narrower than the above range, no particular improvement is seen in the effect of making the liquid absorption/diffusivity anisotropic.

The thickness of the fiber sheet material exhibiting liquid absorption anisotropy is 0.01~
3+am, preferably in the range of 0.05 to 21. Note that the thickness of the sponge is not specified in any way from the viewpoint of liquid absorption and diffusion.

In the present invention, a material mixture containing a cellulose component, reinforcing fibers, and crystalline mirabilite is used as a raw material mixture for producing cellulose sponge.

As the cellulose component, in addition to cellulose itself, the above-mentioned cellulose derivatives are used. In this case, the cellulose component exists in a dissolved state in a solution such as viscose.

As the reinforcing fibers, for example, natural fibers such as ramie hemp, cotton, and kapok, and synthetic fibers such as rayon fibers, polyester fibers, and polypropylene fibers are used. These fibers can be used alone or in a mixture.

Furthermore, for the raw material mixture used in the present invention.

If necessary, colorants, antibacterial agents, and various auxiliary additives for the purpose of modification can be added.

The method for producing the cellulose sponge of the present invention can be carried out according to conventionally known methods.

For example, an example of production in which viscose is used as a raw material for cellulose is that cellulose is first made into alkali cellulose with an alkali, then sulfurized with carbon disulfide to make cellulose xanthate, which is then dissolved in a sodium hydroxide solution. and get viscose. Next, crystalline mirabilite, reinforcing fibers, and optional auxiliary additives are mixed with this viscose, and the resulting mixture is molded into a desired shape.

The above-mentioned liquid-absorbing anisotropic fiber material is adhered to the surface of this molded product, heated and solidified in this state, brought into contact with an acidic aqueous solution to regenerate cellulose, and then washed with water.
dry. In this way, a desired sponge can be obtained. The viscose mixture can be molded using a molding can or an extruder.

The heating temperature for solidifying the viscose mixture is:
Temperatures of 85-95°C are generally employed, and treatment times are on the order of about 2 hours. In this case, in order to shorten the heat treatment time, the viscose mixture may be treated with sulfuric acid or sulfuric acid/zinc sulfate in advance during the heat treatment. The amount of reinforcing fibers added to the viscose is such that the content in the sponge is 70% by weight or less, preferably 10 to 50% by weight. That is, the amount is 70% by weight or less, preferably 10 to 50% by weight, based on the total amount of cellulose and reinforcing fibers in the viscose. In addition, the average particle size of crystalline mirabilite added to viscose is generally 0.5-
5I, and the amount added is determined as appropriate depending on the density of the target sponge. If the addition ratio is high, the density of the sponge will decrease and the flexibility will improve, but the strength will decrease. On the other hand, if the addition ratio is small, the density of the sponge will increase and the strength will increase, but the flexibility will decrease. Generally, it is 20 to 80 times the weight of the total amount of cellulose and auxiliary ingredients in the viscose. The crystalline awn crystals added to the viscose are eluted and removed from the sponge during the subsequent regeneration process and water washing process.

In the present invention, as described above, the cellulose component,
A fiber material having liquid absorption anisotropy is attached to the surface of a molded product of a mixture containing reinforcing fibers and crystalline mirabilite. Since it has adhesive properties, it can be easily done. The surface of the molded article to which the fiber material is attached may be the upper surface and/or the lower surface of the molded article, or may be only a part of the surface of the molded article. After the fibrous material adhered to the surface of the molded article passes through the coagulation process and the contact process with the acidic aqueous solution, it becomes integrally bonded to the sponge surface via the cellulose.

The cellulose sponge according to the present invention can be used as a compressed body if necessary. By making it into a compressed body, it can be used as a compact product6 (Effects of the invention) The absorbent base material made of the cellulose sponge of the present invention is
It is characterized by having a fibrous material that exhibits liquid absorption anisotropy attached to its surface, and when a liquid comes into contact with the surface to which the fibrous material is attached, it absorbs liquid based on the fibrous material. Due to the anisotropy, absorption and diffusion of liquid can occur predominantly in a specific direction. For example, in the case of fiber materials to which yarn is attached, absorption and diffusion of liquid occurs predominantly in the length direction of the yarn, and in the case of fibers in which directional paper or nonwoven fabric is attached to the constituent fibers. In this case, liquid absorption and diffusion occur predominantly in the same direction as the fiber direction.

The absorbent substrate of the present invention can be made into a product with efficient liquid absorption performance by adjusting the direction of liquid absorption and diffusion to an appropriate direction depending on the shape of the absorbent substrate. For example, if the absorbent base material is strip-shaped, its longitudinal direction (
By attaching the fiber material so that absorption and diffusion of liquid occurs predominantly in the longitudinal direction, it is possible to obtain a product with high liquid-absorbing ability that prevents liquid from leaking in the lateral direction. In other words, in such a product, when liquid is absorbed from one place on its surface, absorption and diffusion of liquid occurs quickly in the vertical direction, and absorption and diffusion of liquid in the horizontal direction occurs at a slower rate. .

As a result, the liquid is ultimately absorbed preferentially in the vertical direction of the product, and overall efficient liquid absorption can be achieved without causing liquid leakage in the horizontal direction.

The absorbent substrate of the present invention can be advantageously used in various fields, particularly in the field of sanitary materials such as sanitary napkins and disposable diapers, by utilizing the liquid absorption anisotropy as described above.

(Example) Next, the present invention will be explained in more detail with reference to Examples.

Example To 778 parts of viscose containing 2 parts by weight of cellulose 9 and 1 part by weight of alkali 5, 30 parts of ramie hemp having a length of lon+m was added as a reinforcing fiber, and crystalline mirabilite (average particle size:
201!11) was added and mixed in an amount 30 times the weight of the total amount of cellulose and reinforcing fibers (sponge constituents) in the viscose. Pour this viscose mixture vertically:
The bottom of the molded sheet was 250+++m, width: 150mm, height: 5a+m, and Table 1 was printed on the surface of this sheet-shaped molded product.
The threads shown in are pasted at different intervals, and this is heated at 90°C for 2
After heat treatment for a period of time, the cellulose was regenerated by immersing it in 4Z sulfuric acid, washed with water, and dried to obtain a cellulose sponge.6 The performance of the cellulose sponge obtained as described above was evaluated, and the results are shown in Table 1. Shown below.

The contents of the yarn shown in Table 1 are as follows.

Rayon yarn: The leftover water from twisting 1000 rayon filament yarns with a thickness of 1 denier Cotton yarn: IO count twisted yarn Rayon spun yarn: 10 count spun yarn Also, the sponge yarn shown in Table 1 The performance evaluation method is as follows.

(1) Texture (flexibility) Evaluation was made on a three-level scale based on a sensory test conducted by five women.

0...Good Δ...Normal
A test solution (0.1 g% liquefied sodium aqueous solution colored with a trace amount of pigment) was placed in the center of a 1I test piece (a dry sponge sheet compressed to about 1/8 thickness).
was dropped, and the distance of liquid diffusion in the vertical and horizontal directions after saturated diffusion was measured. In this case, the longitudinal direction means the longitudinal direction of the attached yarn, and the transverse direction means the direction perpendicular thereto.

(3) Liquid absorption rate Using the test piece shown in item (2) above, with the side to which the thread is attached facing down, the test liquid shown in item (2) above is brought into contact with the test piece from the bottom side, and the test piece is The rate at which liquid is absorbed due to the phenomenon (-
7 minutes) was measured.

Example 2 An experiment was conducted in the same manner as in Example 1, except that tissue paper and nonwoven fabric were used instead of yarn as the fiber materials. A cellulose sponge adhered to the surface was obtained. The performance of these sponges was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

The thin paper used in this experiment was manufactured by a wet method using rayon fibers with a thickness of 5 denier and had a basis weight of 25 g/r&, and had liquid absorption anisotropy in the fiber direction. there were. The nonwoven fabric was manufactured by spunbonding using polypropylene fibers with a thickness of 5 sol, had a basis weight of 30 g/bo, and had liquid absorption anisotropy in the direction of the fibers.

Table 2 Example 3 The sponge of sample Nα1 of Example 1 has a thickness of about 17 mm.
A compressed sheet obtained by compressing to a size of 8 is used as an absorber, and 200
The laminate was laminated with a basis weight of g/rrr, the laminate was wrapped with a leak-proof sheet (polyethylene film) except for the surface portion, and the whole was wrapped with a nonwoven fabric to produce a sanitary napkin. In this case, the flow direction of the threads on the upper surface of the compressed sheet was made to match the longitudinal direction of the napkin.

The liquid absorption properties of this sanitary napkin were evaluated as follows, and the results are shown in Table 3.

For comparison, a napkin was prepared in the same manner using a normal cellulose sponge without threads attached as an absorbent material, and its liquid absorption properties were evaluated.

The results are also shown in Table 3.

(Liquid absorption properties of the napkin) 8g of physiological saline 101II2 colored with a trace amount of pigment.
The liquid is supplied to the surface of the napkin through a cylindrical container under a load of (diffusion area) was measured.

Table-3 Patent application Lion Corporation

Claims (4)

[Claims] (1) An absorbent base material made of cellulose sponge, characterized in that a fibrous material exhibiting liquid absorption anisotropy is integrally bonded to the surface of the absorbent base material. (2) The absorbent substrate according to claim 1, wherein the fibrous material is a thread made of natural or synthetic fiber. (3) The absorbent substrate according to claim 1, wherein the fibrous material is tissue paper or nonwoven fabric. (4) A mixture containing a cellulose component, reinforcing fibers, and crystalline mirabilite is molded, a fiber material exhibiting liquid absorption anisotropy is adhered to the surface of the resulting molded product, and the molded product is heated and solidified in this state. A method for producing an absorbent base material, which comprises: contacting with an acidic aqueous solution, washing with water, and drying.