MXPA98005025A - Better absorbent body - Google Patents

Abstract

An absorbent body formed of an absorbent network having a combination of multi-branched regenerated cellulosic fibers and unbranched cellulosic fibers has improved specific absorption capacity. This absorbent body can have the shape of toilet paper, tampons, diapers and incontinence devices for adult

Description

IMPROVED ABSORBENT BODY FIELD OF THE INVENTION This invention relates to an absorbent body having improved absorption characteristics. The body has a mixture of short fibers having a highly cross-sectionalized cross section having at least three branches and unbranched fibers. The fiber combination provides enhanced specific absorption capacity over an absorbent body formed of single-branched fibers or unbranched fibers alone.

BACKGROUND OF THE INVENTION Absorbent bodies are limited in their absorbent or absorption capacity. So. they can not continue to absorb fluids once their absorption capacity has been reached. Therefore, the researchers continue to look for improved absorption characteristics in absorbent bodies. One solution has been to use superabsorbent materials in absorbent bodies. These materials absorb liquids and swell by a substance similar to gel. Although these materials have been accepted for some uses in absorbent articles, they still have to be accepted by all users. The development of cellulosic fiber technology has helped to increase the absorption capacities of absorbent bodies based on these fibers. For example, "Courtaulds PLC" EP 0 301 874 Bl discloses that regenerated cellulosic fibers having a greatly cross section have also improved absorbency. Although this technology is a well-accepted improvement, researchers are still looking for even more improvements in absorption capacity. Therefore, what is needed is an absorbent fibrous body having improved absorption characteristics.

BRIEF DESCRIPTION OF THE INVENTION It has been found that improvements in absorbency of absorbent bodies can be achieved by adding unbranched cellulosic fibers to regenerated or irrafied cellulosic fibers having at least three branches to form an absorbent body. These unbranched cellulosic fibers generally provide a low specific absorptive capacity compared to highly branched fibers. As used herein in the specifications and claims, the term "specific absorption capacity" denotes the mass of fluid absorbed by an absorbent fibrous body per unit mass of the absorbent body in a dry state. As used herein in the specifications and claims, the term "cellulosic fiber" means that fiber contains or is derived from cellulose "v. gr. »Natural fibers containing cellulose» with cotton, and manmade fibers derived from cellulose »such as cellulose acetate. What is not expected is that the addition of the less absorbent and unbranched fibers increases the specific absorptive capacity of the absorbent bodies consisting of multifilated fibers. Then the fibers are added in an effective amount to increase the specific absorption capacity of the absorbent body. Preferably, the unbranched fibers are present in a certain amount to increase the specific absorption capacity of the absorbent body to about 10,554 of the absorption capacity of a similar absorption body of 10054 by weight of highly-branched fibers.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a graphical representation of the data of example 1. Figure 2 illustrates a graphical representation of the data of example 2.

DETAILED DESCRIPTION OF THE INVENTION This invention takes advantage of the regenerated and multi-branched cellulosic fibers and improves their absorbency by adding an effective amount of specific absorption enhancement capacity of unbranched cellulosic fibers. The multi-branched regenerated cellulosic fibers have been commercially available for several years. It is known that these fibers have increased specific absorbency compared to unbranched fibers. A commercial example of these fibers are Galaxy ™ viscose rayon fibers available from Courtaulds PLC »London» England. These fibers are described in detail in Courtaulds PLC »EP 0 301 874 Bl» which is mentioned here by way of reference. It is disclosed that these fibers are a solid filament of regenerated cellulosic material having a decitex of less than 5.0 and a multi-branched cross-section, each branch having a length-to-width ratio of at least 2: 1. The fibers are preferably fibers of short length having three or four branches and generally a transverse-sectional symmetric shape »v. gr. >; Y-shape »X» H or T. A preferred cross-sectional shape is the Y-shape having an angle between the branches of about 120. A preferred regenerated cellulosic material is viscose having a cellulose content of 5 to 125% by weight and a caustic soda content of 4 to 10% by weight. The fibers are preferably spun by having a salt amount of 4.O to 12.0. It is expected that any commercially available multi-fiber fiber or even other fibers "not commercially available today" will be useful in the practice of this invention. It is merely required that the fibers provide an absorbent body having a relatively high specific absorption capacity that is increased by the addition of a less absorbent non-branched fiber to form a fibrous absorbent body. The specific absorption capacity of an absorbent fibrous body including the multi-branched regenerated cellulosic fibers described above is increased by adding a quantity of unbranched cellulosic fibers. A non-limiting representative list of cellulosic fibers includes natural fibers such as cotton »wood pulp» jute, bagasse »silk» wool and the like »and processed fibers such as regenerated cellulose» cellulose acetate »cellulose nitrate. rayon and the like. Preferably the unbranched cellulosic fibers are rayon or cotton, and more preferably the fibers are of rayon. These unbranched fibers are less absorbent, that is to say they have a lower specific absorption capacity, than the fibers which have been branched. of regenerated cellulose fibers. However, by adding an effective amount of unbranched cellulosic fibers with improved specific absorption capacity, the specific absorption capacity of the resulting absorbent body is surprisingly increased. This increase is preferably at least 102J-de of the specific absorption capacity of a similar absorbent body made only of highly branched fibers. More preferably, the specific absorption capacity increases to at least almost 10554. It has been found that adding an amount of up to. almost 6054 by weight of unbranched cellulosic fibers can improve the specific absorption capacity of an absorbent body by having the multi-branched cellulosic fibers. Preferably the unbranched fibers are present at about 5 to about 50% by weight of the absorbent body, and more preferably about 10 to about 30% by weight of the absorbent body. Then preferred fiber blends include about 1 to about 10% by weight of unbranched fibers and about 99 to about 40% by weight of multi-branched fibers; more preferred mixtures include about 5 to about 5054 by weight of multimerized fibers and more preferred mixtures include about 10 to about 3054 by weight of unbranched fibers and about 9054 to about 7054 by weight of multiracerated fibers. . Additional fibers can also be included in the absorbent body. These additional fibers may include synthetic fibers such as polyesters, polyvinyl alcohols, polyolefins, polyamines. polyamides »pol iacri loni tri los and similars. These fibers can be included to add desirable characteristics to the absorbent body. For example »hydrophobic fibers can be used on external surfaces of the body to reduce surface moisture and hydrophilic fibers can be used to increase the speed of fluid transport within and throughout the body. The unbranched fibers and the fibers are preferably mixed with a substantial mixture of the uniform fiber. These fiber blending operations are known to those skilled in the art. For example, the fibers can be measured continuously in a serrated tooth opener. The mixed fibers can be transported, v. gr. »By air through a conduit to a carding station to form a fibrous network. The fibrous network is preferably satinated to impart a lower amount of compression. This network can then be processed to form the absorbent body. For example, the net can be used to form an absorbent layer in a sanitary paper »diaper or adult incontinence device. In addition »the network can be formed inside a buffer. In a tampon forming process, the network can be formed into a narrow, fibrous, spiral wound wick to form a tampon pattern. Further »a liquid permeable cover material may be wrapped around the buffer pattern to substantially contain the fibrous absorbent portion of the tampon. This buffer pattern can then be compressed into a buffer. That buffer pattern compression is known to those skilled in the art. For example, the buffer may be formed in accordance with Messing and others. US Patent No. 3,422,496 or its commonly assigned solids, Friese et al. E.U.A. Serial No. 07 / 596,454, and Schoelling »E.U.A. Serial No. 08 / 196,664 »each is mentioned here for reference.

EXAMPLES The improved absorbency characteristics of this invention can be further illustrated in accordance with the following examples.

EXAMPLES 1 A series of fibrous webs were formed by adding a measured amount of regenerated, multi-branched cellulosic fibers (Galaxy ™ rayon fibers with 3.3 diner having a length of about 30 mm available from Courtaulds Fibres, London, England) and short fibers. unbranched regenerated cellulosics (Danufil ™ rayon fibers »3.6" diner with a fiber length of approximately 30 mm available from Hoechst Kehlheim, Kehlheim, Germany) the compositions are identified in Table 1 below. For each network »the fibers were deeply mixed and carded to form the fibrous network. This network was carded later, TABLE 1 Product Weight Size 54 in weight 54 in test weight the average Galaxy sample of rayon (n) (q) (54) (54) Comp. Ex. A 5 2., 5 lOO 0 Comp. Ex. B 5 2. .5 0 100 Ex. C 5 2. .5 75 25 Ex. D 5 2. .5 50 50 Ex. E 5 2. .5 25 75 The specific absorption capacity of these networks was measured after compliance with the following procedure: The fibrous network was cut to provide a fibrous sample strip with a weight of 2.5 g. The sample strip was then saturated with water and left to drain the excess water for a period of five minutes. The sample strip was then weighed, and the amount of water absorbed was calculated. The results of these measurements are shown below in Table 2.

MADRO? Product Absorption Disp. Specific Absorption Test < a > Est. (Q) (q / a) Comp. Ex. A 33.69 0.35 13.48 Com. E. B 29.24 0.73 11.69 Ex. C 33.99 0.55 13.60 Ex. D 32.31 0.77 12.92 Ex. E 29.43 0.53 11.77 lO These data are also shown in Figure 1. It can be seen that an absorbent network of 10054 single-rayon rayon fibers has an absorption capacity that is greater than that of an absorbent network of 10054 unbranched rayon fibers. Unexpectedly, a combination of fibers that have been harvested and even approved. 3054 by weight of unbranched rayon fibers appear to increase the specific absorption compared to that of an absorbent body of 10054 by weight of more absorbent fibers. Then, these data illustrate that the incorporation of unbranched rayon fibers into the multiplied rayon fibers provides a synergistic increase in the specific absorption capacity of the absorption networks.

E LO 2 A second series of fiber webs were formed in accordance with the following procedure: the fiber components were weighed using a component scale and mixed together in a bale separator and subsequently opened in a serrated tooth opener. The resulting combination was carded to obtain the fibrous network. The composition of these networks is identified later in Table 3. The multifilamed and unbranched fibers used in this Example 2 were the same as those used in Example 1 above. The cotton used in this example was cotton carder »provided by Edward Hall» Stockport »England» having a fiber length of about 9mm to 13mm.

TABLE 3 Product Size of Weight 54 in weight 54 in weight 54 in test weight the average Qalaxy sample of cotton rayon (n) < S > (54) (54) < 54) Comp. Ex. F 25 2.6 100 0 0 Comp. E. T 25 2.6 0 lOO 0 Eg H 25 2.6 75 25 0 Ex. I 25 2.6 50 50 0 Eg J 25 2.6 25 75 0 Ex. K 25 2.6 75 0 25 These networks were then used to manufacture compressed tampons radially expandable and generally cylindrical in accordance with the procedure of the commonly assigned applications to Friese et al. E.U.A. series No. 07 / 596,454"and Schoell ng, E.U.A. series No. 08 / 196,664. These buffers were conditioned at 21 ° C »6554 relative humidity for at least 24 hours and pre-weighed. The conditioned tampons were then tested in accordance with the procedure for the Syngi a tests of the Food and Drug Admixture of the USA, using an aqueous test solution, modifying it by rapidly adding test fluid until the saturation of the buffer and carrying out the procedure. Approximately 20 ° C (at room temperature). The results of these tests are illustrated below in Table 4.

TABLE 4 Product Absorption of Dev. Specific Absorption of test Syngina Studied of Syngi na (q) (a) (q / q) Comp. Ex. F 12.50 0.26 4.81 Comp. Ex. < 3 11.83 0.19 4.55 Ex. H 13.48 0.27 5.18 Ex. I 12.73 0.17 4.90 Ex. J 12.09 0.20 4.65 Ex. K 13.12 0.24 4.86 Again, these data illustrate that the incorporation of fibers does not Branches of rayon to the highly distilled fibers of rayon increases the specific absorption capacity of compressed absorbent tampons compared to what would be expected from the single addition of less absorbent fibers. These data are also shown in Figure 2. This effect can be observed up to about 50 to 6054 by weight of the addition of unbranched rayon fibers or cotton fibers. The specification and the foregoing examples are presented to assist in the complete and non-limiting understanding of the invention described herein. Since many variations and modalities of this invention can be realized without departing from its essence and scope, the invention resides in the claims listed here.

Claims (14)

NQVEDAP FROM A I V? NC? Q CLAIMS

1. - An absorbent body having improved absorption capacity consisting of the mixture of about 40 to about 9954 by weight of regenerated cellulosic fibers having a multirraded cross section having at least three branches and about 60 to approximately 154 weight per cent. non-branched cellulose fibers.

2. The absorbent body of the rei indication 1 further characterized in that said regenerated cellulosic fibers consist of short viscose rayon fibers.

3. The absorbent body of the rei indication 1 further characterized in that said unbranched cellulosic fibers consist of regenerated cellulosic fibers.

4. The absorbent body of the rei indication 1 further characterized in that the unbranched cellulosic fibers consist of cotton fibers.

5. The absorbent body of the rei indication 1, which consists approximately of 50 to about 9554 by weight of said highly drawn fibers and approximately 50 to about 554 by weight of said unbranched fibers.

6. The absorbent body of claim 5 comprising approximately 65 to about 8554 by weight of said fibers and about 35 to about 1554 by weight of said unbranched fibers.

7. The absorbent body of claim 1 further characterized in that said fiber mixture is compressed.

8. An absorbent body having an improved absorption capacity consisting of a mixture of regenerated cellulose fibers having three branches and an effective amount of unbranched cellulosic fibers to increase the specific absorption capacity of the absorbent body.

9. The absorbent body of claim 8 consisting of an effective amount of said unbranched fibers to increase the specific absorption capacity to at least about 10554 of the specific absorption capacity of a similar absorbent body of 10054 by weight of multi-branded fibers.

10. A method for increasing the absorption capacity of an absorbent body by having regenerated and multilayered cellulosic short fibers consisting of the steps of: combining an effective amount of unbranched cellulosic short fibers to increase the absorption capacity of the absorbent body with said unsterile cellulosic short fibers characterized by having said at least three branched fibers and forming a network consisting of a substantially deep mixture of said fiber combination.

11. The method of claim 10 further comprising compressing the network.

12. A method for forming a tampon consisting of the steps of: - Approximately combining 1 to about 6054 by weight of unbranched cellulosic short fibers with about 99 to about 4054 by weight of regenerated cellulose short fibers. »Further characterized in that said multi-branched fibers have at least three branches» - forming said fibers in a "buffer pattern" - compressing said buffer pattern to form said buffer.

13. The method of claim 12 further comprising covering said tampon pattern with a cover material. 14.- The method of rei indication 12 characterized diner because the steps of compressing the tampon pattern consists of a fibrous core substantially surrounding the central axis »the core having a first average density» and several ribs that are radially inclined from the core »further characterized in that each rib is separated from the adjacent ribs to which it is added to the core and each rib contacts adjacent ribs proximal to the circumferential surface of the tampon.