JPH08296162A - Water-absorbing dry type nonwoven fabric - Google Patents

Abstract

PURPOSE: To obtain a dry nonwoven fabric capable of favorably absorbing a physiological saline and having high water retention performance and suitable for hygienic materials, etc., by using a specific water-absorbing fiber and a water-absorbing polymer. CONSTITUTION: This water-absorbing dry type nonwoven fabric is obtained by uniformly spraying a mixture of >=20wt.% water-absorbing fiber such as Oasis (R) (Technical absorbent Corp., England) having >=1000wt.% water retention ratio of a physiological saline onto paper obtained by putting a mixture of a water-insoluble water-absorbing polymer such as polyethylene oxide modified material with pulp onto a sucking net and having 15g/m<2> weight by an air lay method to form a laminated web in >=30wt.% total amount of the water- absorbing fiber and the water-absorbing polymer, spraying water from above the paper of the first layer in fog-state and carrying out heat press treatment to carry out self bonding of the water-absorbing fiber. The nonwoven fabric has >=0.25g/cc density and swells to thickness of >=7 time after absorbing water, based on the thickness before water absorption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hygroscopic material such as sanitary products, disposable diapers and the like, as well as a water absorbing and swelling dry non-woven fabric used for food packaging materials, wipers, water blocking materials and the like.

[0002]

2. Description of the Related Art A water absorbent nonwoven fabric using a water absorbent polymer is described in, for example, Japanese Patent Publication No. 1-49112.
In this water absorbent nonwoven fabric, a water absorbent polymer is laminated with a porous film so as not to fall off from the nonwoven fabric. It is said that the diameter of the pores should be smaller than the particle diameter of the water-absorbing polymer so as not to fall from the pores. As described above, the water-absorbent polymer is easily removed from the nonwoven fabric, and it is difficult to retain the water-absorbent polymer in the nonwoven fabric at a high content rate. The content of water-absorbing polymer is generally at most 30
%. However, it is always the case that more is desired.

As an example of increasing the content of the water-absorbing polymer, there is a method of coating the water-absorbing polymer. However, this method has drawbacks that the water-absorbent polymer layer becomes hard and is easily peeled off and dropped due to deformation such as bending. Therefore, it is used only for special purposes.

A non-woven fabric using water-absorbent fibers is described in, for example, Japanese Patent Application Laid-Open No. 55-132754. This water absorbent nonwoven fabric is made of fibers obtained by hydrolyzing acrylic fibers. When 100% of this water-absorbent fiber is used, only a production example of a wet type nonwoven fabric is described, and a dry type nonwoven fabric is not described. Further, these non-woven fabrics focus on the amount of water absorption, but there is no description focusing on the degree of swelling. Further, there is no description of high-density nonwoven fabric. The density of a general nonwoven fabric is at most 0.2 g / cc. Usually 0.1-0.0
It is 1 g / cc.

Further, Japanese Patent Application Laid-Open No. 57-21549 discloses an example of a water-absorbent nonwoven fabric composed of fibers obtained by hydrolyzing acrylic fibers and heat-fusible binder fibers. Examples of this type of water absorbent fiber include Toyobo Co., Ltd.
There is "Lanseal" (registered trademark) manufactured by the company. This water absorbent fiber has a feature that the core of the fiber is an acrylic fiber, the fiber strength is high, and it can sufficiently withstand carding. However, since the core is an acrylic fiber, it has a drawback that the water absorption rate is inferior to that of the water absorption polymer. Especially in the case of an aqueous solution of a salt such as physiological saline, there is a drawback that the water absorption rate is inferior, and selection of water absorbing fibers is important.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a water-absorbent dry non-woven fabric which has a small thickness, is flexible, absorbs physiological saline well, and swells greatly after absorbing water, and the water-retaining performance can be understood at a glance. Is to supply.

[0007]

Means for Solving the Problems The inventors of the present invention have studied various methods of compressing a dry nonwoven fabric at a high density so that the swelling recovery is large and the original thickness is small, and the present invention has been completed. The water absorbent dry type nonwoven fabric of the present invention has a water retention rate of 1000% by weight of physiological saline.
A water-absorbent dry non-woven fabric containing 20% by weight or more of the above water-absorbing fibers and a water-absorbing polymer, swelling after absorbing water 7 times or more of the thickness before absorbing water, and the total amount of the water-absorbing polymer and the water-absorbing fibers is 30% by weight or more. Is.

The total of the above water-absorbing polymer and water-absorbing fiber is 3
If it is less than 0% by weight, the water retention of the water-absorbent dry type nonwoven fabric is insufficient. On the other hand, if the water-absorbent fiber content is less than 20% by weight, the amount of the water-absorbent polymer will increase and the texture of the water-absorbent dry nonwoven fabric will become too hard.

The water-absorbent fiber used in the present invention has a composition similar to that of the water-absorbent polymer and contains 1000% by weight of physiological saline.
As described above, "Oasis" (registered trademark) manufactured by British Technical Absorbent Co., which absorbs water and has excellent water absorption, is preferable. Judging from the patent, this fiber has a composition similar to that of the water-absorbing polymer, and as the carboxylic acid, for example, (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid,
Sorbic acid, cinnamic acid, crotonic acid, beta-acryloxypropionic acid, and their alkali metal salts can be used. Preferably (meth) acrylic acid is economically preferable.

Partly as a sulfonic acid, for example, 2- (meth) acrylamido-2-methylpropanesulfonic acid, (meth) allylsulfonic acid, ethyl (meth) acrylate sulfonate, styrenesulfonic acid, vinylsulfonic acid, 2- (meth) acryloyl propane sulfonic acid and alkali metal salts thereof can be used. The inclusion of sulfonic acid is preferable because it improves the water absorption of physiological saline.

The water-absorbent fiber may be cross-linked, and cross-linking agents therefor include 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate and its ethylene oxide and propylene oxide adducts. Used. If the amount of the cross-linking agent is too large, the water absorption rate will decrease, so it must be selected appropriately.
In the case of a water-absorbing polymer, a polyfunctional group is used, but in the case of a fiber, it is preferable that the polyfunctional group is not a polyfunctional group because gelation is less likely to occur. The above-mentioned "Lanseal" which absorbs less than 1000% by weight of physiological saline when partially used in the absorbent fiber
Can also be used. The range in which "Lanseal" can be mixed is less than 50% by weight of the water absorbent nonwoven fabric. If it exceeds 50%, the water retention performance and the swelling property deteriorate. This "Lanseal" is obtained by hydrolyzing and partially cross-linking the surface of the acrylic fiber, and the acrylic fiber remains in the core portion.
The characteristic absorption peak of the CN group can be measured with an infrared spectrophotometer.

As the water-absorbent polymer used in the present invention, an acrylic acid polymer of starch, a cross-linked product of sodium polyacrylate, a cross-linked product of polyethylene oxide, such as the water-insoluble material described in JP-A-61-26661. Polyethylene oxide modified products of An example of a commercially available water-absorbent polymer is Kuraray Co., Ltd. under the trade name K.
I-Gel 201K, Showa Denko's trade name Viscomate PX-112, Toa Gosei Kagaku's trade name Alonzap RS-2, Arakawa Chemical Co., Ltd. trade name ALASORP S-100, Sekisui Plastics Trade name of Aquamate AQ-100 of Sumitomo Chemical Co., Ltd. and Sumika Gel S of Sumitomo Chemical Co., Ltd.
There is -50 etc. There are various particle sizes of water-absorbent polymers, but 5
Particles having a particle size of about 0 to 100 μm are preferable because of cost and easy dispersion. When a water-absorbent polymer is used, it is difficult to disperse it uniformly, so that partial unevenness in swelling tends to occur.

As a method for producing the water-absorbent nonwoven fabric of the present invention, for example, there is a method in which a web is prepared by carding and crosslaying the above-mentioned water-absorbent fiber and then a water-absorbing polymer is sprayed. There are two methods for bonding webs: thermal and needling.In thermal, a water-absorbing polymer is sprayed before bonding, in needling, a water-absorbing polymer is sprayed after bonding, and when lightly needling, it is relatively evenly dispersed. It can be done. Also in the case of needling, if the needling density (the number of implants per unit area) is too high, the swelling property is lowered, which is not preferable.

For thermal bonding, heat-fusible fibers may be mixed and used, or heat-fusible powder, for example, polyethylene powder may be sprinkled and used. Examples of commercially available heat-sealing fibers are, for example, "ES" manufactured by Chisso Corporation, using polypropylene for the core and polyethylene for the sheath.
(Registered trademark), Kanebo Co., Ltd., and "Belcombi" (registered trademark) in which polyethylene or modified polyester is used for the sheath and polyester is used for the core. For thermal bonding, 5 to 20% by weight of heat-sealing fiber or heat-sealing powder may be mixed. If it is less than 5% by weight, it is preferable to use needle punching together.

When carrying out the above carding, it is preferable that the "oasis" having a small fiber strength has a large single fiber thickness. In addition, it is preferable that the single fiber of the other fibers to be mixed is thin. A web can be formed by the thin fibers sinking under the needle of the card and wrapping around the thick fiber above the needle. By selecting the thickness of the single fibers of the fibers to be mixed in this way, it is possible to reduce the loss of the fibers when forming the web. The water-absorbent fiber having a low fiber strength preferably has a thickness of 6 denier or more and 15 denier or less, and the fiber having a high fiber strength has a thickness of 5 denier or less, 2
Denier or higher is preferable. The uniformity of the web is not very important, so a woolen type roller card with one cylinder is sufficient. Roller cards are preferred over flat cards because of their higher denier. Further, it is preferable that the fiber length is 50 to 75 mm because fiber damage is small. In the same sense,
Contrary to usual, it is preferable to shorten the fiber length of thick fibers having low fiber strength.

Further, as another method for producing the above water-absorbent dry type nonwoven fabric, the air lay method can be used. In the case of thermal bonding, it is sufficient to mix 5 to 20% by weight of a binder composed of heat-sealing fibers or heat-sealing powder. If the amount is less than 5% by weight, the bonding will be insufficient, and therefore it is necessary to support it with another non-woven fabric or paper for handling. When this support is used, the water-absorbent fiber or the water-absorbent polymer can be self-bonded to each other by applying water without using the heat-meltable fiber or the heat-meltable powder. Therefore, in this case, the heat fusion fiber,
Alternatively, falling off can be prevented without using the heat-sealing powder.

In the case of thermal bonding, the swelling property is improved by using a binder having an amorphous adhesive portion having a wide heat melting temperature range. That is, strong bonding hinders the swelling property and also tends to make the texture of the water-absorbent dry nonwoven fabric extremely hard. Therefore, the binder is preferably less than 10% by weight. Further, it is preferable that the bonding is performed at a temperature lower than the temperature usually used, the bonding is performed partially, and the bonding is performed in a dot shape. For that purpose, it is preferably 5 ° C. or lower, more preferably 10 ° C. or lower than the usual bonding temperature.

In the case of the air laying method which does not use a card, it is preferable that the thickness of the water-absorbent fiber having a low fiber strength is 6 denier or more and 15 denier or less because dispersion is easy. The fiber length of the water absorbent fiber is preferably 4 to 15 mm with the same meaning. It is preferable that the other fibers used in this method have properties similar to those of the main water-absorbent fiber.

By pressing the above water-absorbent dry type nonwoven fabric, the density becomes high and the swelling property is increased. A larger pressing pressure is preferable because the water-absorbent dry type nonwoven fabric can be made thinner. Moreover, the tensile strength of the water-absorbent dry type nonwoven fabric is improved by pressing. The pressing pressure is 5 kg / cm ² or more, more preferably 10 kg / cm ² or more, and further preferably 20 kg / cm ² or more. The density of this non-woven fabric is preferably 0.25 g / cc or more, more preferably 0.3 g / cc or more, and further preferably 0.5 g / cc.
That is all. The pressing method may be a roller pressing method or a general pressing method, and may have a pattern such as embossing.

The water-absorbent dry type nonwoven fabric can be easily pressed by improving the water content by an appropriate method, and if the water content is 10% by weight or more, the water-absorbent dry nonwoven fabric can be bonded without using a usual binder. Since no binder is included, the swelling property is significantly improved. The water content is more preferably 20% by weight or more. Even if the water content is 20% by weight or more, there is no problem in use because the water-absorbent fiber having a large water absorption is used. In addition, the texture is softest, which is preferable.

In the case where a large amount of water is contained in the adhesive as described above, the other fibers constituting the water-absorbent dry nonwoven fabric are preferably cellulose fibers because of good adhesiveness. For example, pulp, rayon, acetate, tencel, cotton, hemp and the like.
On the other hand, in the case of thermal bonding, synthetic fibers such as polyester, nylon, polypropylene and polyethylene are preferable because they have good swelling properties. Among them, polyester having a large Young's modulus is more preferable.

It is also possible to mix antibacterial and deodorant fibers or particles into the nonwoven fabric of the present invention. Also, surface paper,
Alternatively, a non-woven fabric processed in the same manner can also be used. Further, a colored material as the surface material, or a material subjected to processing such as embossing when laminating can be used.

The water retention of the water-absorbent dry non-woven fabric of the present invention was determined by fully impregnating physiological saline with water, draining it with a load of 454 g applied to a square sample piece of 5 cm square and weighing it. It was calculated from the difference from the weight of the piece. The water absorption of the water-absorbent fiber and the water-absorbent polymer in physiological saline was measured by a centrifugal dehydration method according to DIN53814.

[0024]

EFFECT OF THE INVENTION The water-absorbent dry type nonwoven fabric of the present invention has less falling off of water-absorbent fibers and the like, is easy to handle, and is extremely excellent in water absorption and water retention despite having a small weight and thickness. Further details will be described in Examples.

[0025]

【Example】

Example 1 "Oasis" 9 having a physiological saline absorption rate of 1300% by weight
A mixture of d and 6 mm and a weight ratio of pulp of 1 to 3 was continuously sprinkled by an air lay method on a paper having a basis weight of 15 g / m ² on a suction net so that the weight of “Oasis” was 1000 g. / M ² was laminated. The unit weight was adjusted by continuously measuring the net speed and the amount of "Oasis" sprayed. Next, a paper having a basis weight of 15 g / m ² was laminated on the “Oasis” layer which was the second layer to form a three-layer structure.

Water is sprayed in a mist form on the first layer of paper,
Water was added to "Oasis" to prepare a water content of 20% by weight. After that, press the machine at 5 kg / cm ²
Pressed at room temperature under pressure, thickness 2.1mm, density 0.48
A water-absorbent dry type nonwoven fabric of the present invention having g / cc was produced. The water-absorbent fiber "Oasis" was self-adhesive to each other by itself and showed a soft texture. Further, the non-woven fabric was cut with scissors, but no "oasis" or fall of pulp was observed from the cut surface. The main body of the obtained non-woven fabric of the present invention was formed in the second layer. In this case, the upper and lower papers were also adhered to the second layer by "oasis". The thickness of this water-absorbent dry nonwoven fabric after swelling was 35.3 mm.

Example 2 In the same manner as in Example 1, "Oasis" 9d, 6 mm and "Aronzap RS-2" were 2 to 1, pulp and "Oasis".
And “Alon Zap” are distributed in a ratio of 2 to 1 on a suction net continuously on a paper with a basis weight of 15 g / m ² by the air laying method so that the “Oasis” and “Alon Zap” It was laminated so that the total basis weight was 1000 g / m ² . The basis weight was adjusted by continuously measuring the net speed and the amount of "Oasis" and "Alonzap" applied. Next, this second layer "Oasis" and "Alonzap"
Paper having a basis weight of 15 g / m ² was laminated on the layer to form a three-layer structure.

Water is sprayed on the first layer of paper in the form of mist,
Water was added to "Oasis" and "Alonzap", and then the sheets were pressure-bonded with a roller and dried with a hot air dryer to produce a water-absorbent dry nonwoven fabric of the present invention having a thickness of 3.5 mm and a density of 0.29 g / cc. . The water-absorbent fibers "Oasis" and "Alonzap" were self-adhesive with each other and showed a soft texture. Further, the non-woven fabric was cut with scissors, but "Oasis" and "Alonzap" were hardly removed from the cut surface. The main body of the obtained non-woven fabric of the present invention was formed in the second layer. In this case, the upper and lower papers were also adhered to the second layer by "oasis". The thickness of this water-absorbent dry nonwoven fabric after swelling was 38.3 mm.

Example 3 "Oasis" 9d, 51 mm and "Lanceir" 2d, 5
"Bell Combi 408" with 1mm and normal adhesion temperature of 110 ℃
0 ”2d, 51 mm and regular polyester SD4
The present invention having a basis weight of 100 g / m ² after being mixed with d and 51 mm at 30: 20: 10: 40% by weight, carded, cross-laid, needle punched, pressed at a press temperature of 100 ° C. and a pressure of 10 kg / cm ^2. Thickness of 0.3m
A water-absorbent dry non-woven fabric having a m and a density of 0.33 g / cc was produced. The texture of this non-woven fabric was soft, and the non-woven fabric was cut with scissors, but fibers did not fall off from the cut surface. The thickness of this water-absorbent dry type nonwoven fabric after swelling is 3.1 mm
Met.

Example 4 In the same manner as in Example 1, the pressure of the press was set to 10, 2
The thickness of the water-absorbent dry type non-woven fabric obtained after the production was changed to 0 kg / cm ² and the thickness after water absorption were measured and shown in Table 1.

[0031]

[Table 1]

Example 5 A water-absorbent dry non-woven fabric was produced in the same manner as in Example 1 except that the weight ratio of pulp to "Oasis" was changed to only 1: 1.
The thickness of the obtained water-absorbent dry nonwoven fabric was 1.7 mm, the density was 0.59 g / cc, and the thickness after water absorption was 43.9 mm.

Reference Example 1 In the same manner as in Example 1, except that “Oasis” was changed to “Lanseal”, the thickness of the produced nonwoven fabric and the thickness after water absorption were 2.7 mm and 5.9 mm, respectively.

Reference Example 2 In the same manner as in Example 1, "Oasis" was changed to "Alonzap".
The average values of the thickness of the produced nonwoven fabric and the thickness after absorbing water were 2.7 mm and 35.2 mm, respectively.
However, this non-woven fabric has a large variation in thickness after absorbing water, the thinnest part is 15 mm and the thickest part is 40 mm.
The thickness unevenness after water absorption was large.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area A61F 13/18 307G

Claims (2)

[Claims] 1. A physiological saline containing 20% by weight or more of water-absorbing fibers having a water retention rate of 1000% by weight or more and a water-absorbing polymer, and swells after absorbing water by 7 times or more of the thickness before absorbing water, thereby forming a water-absorbing polymer. A water-absorbent dry non-woven fabric in which the total amount of water-absorbent fibers is 30% by weight or more. 2. The water-absorbent dry nonwoven fabric according to claim 1, which has a density of 0.25 g / cc or more.