GB2061339A - Autogeneously Bonded Absorbent Pad - Google Patents

Abstract

A secretafacient unit or pad which includes an intimate mixture of nonfusible absorbent fibers and relatively easily fusible fibers. The fibers are maintained in an integral unit by fusing the heat-fusible fibers by embossment. Embossment is conducted under conditions of relatively low temperature and pressure. This creates a unit or pad which has integrity, without the use of adhesive, flexibility and which is relatively cheap to produce. The unit may be used as an absorbent material in a variety of applications e.g. sanitary napkins, diapers, wound dressings, panty liners.

Description

SPECIFICATION Improvements in and Relating to Absorbent Units or Pads This invention relates to an absorbent device and particularly a device in which an integral unit is formed by embossment under conditions of elevated heat and pressure.

Recently products designed to absorb vaginal discharges between menstrual periods and also low levels of menstrual flow have been introduced. An example of such a product is Kotex Lightdays Pantiliners. (Kotex Lightdays is a Trademark of Kimberly-Clark Corporation, Neenah, Wisconsin, United States of America.

This pad has an absorbent component made from commonly used cellulosic material such as wood pulp, and a fluid impervious backing layer. This backing layer contains adhesive strips on the underside thereof for attachment to feminine undergarments. The absorbent portion has a moisture pervious cover material deposed thereon which contacts the perineal area. The moisture permeable layer is attached to the fluff component by means of an adhesive layer added to the fluff. This pad is then subjected to embossing to give integrity to the fluff and also provide channels for fluid flow during secretion.

The backing is then adhesively attached.

While this pad has proven to be extremely popular because of its relatively thinness and small overall configuration, the presence of adhesive tends to adversely affect resiliency and softness, therefore limiting the desired degree of comfort associated with wearing such a pad. In addition, manufacturing would be substantially simpler if a moisture pervious cover layer could be avoided.

The common, relatively inexpensive, fluff materials traditionally used for these pads, other pads, diapers and the like, tend to lose their integrity when wet and, due to the desire to maximize absorbency, are generally designed to have maximum volume over the nonembossed areas. These nonembossed areas, while positively affecting absorbency, adversely affects the integrity of the absorbent batt, i.e. it allows for ease of separation of the individual fibers from the mass of the batt. This phenomenon referred to generally as sloughing, is always undesirable and particularly disadvantageous where the sloughing fibers embed themselves in the perineal area or, in the event that this absorbent type of material is used as a component of a surgical dressing, in a wound.

Ideally, if some sort of composite absorptive matrix could be designed which would eliminate sloughing and maintain integrity while still taking advantage of the traditional absorptive materials and the low cost and ready availability which have made such materials standbys over the years, a quantum advance in the area of absorptive systems would result. The subject application provides such an absorptive medium.

A secretafacient unit in accordance with the invention comprises in combination an intimate mixture of nonfusible absorbent fiber and a sufficient amount of fibers which are mildprocess-fusible to form an integral unit, the integrity of said unit being obtained primarily by embossing in selectively spaced areas.

The term "secretafacient" is meant to describe an absorbent material which absorbs a variety of biological fluids with similar efficiency. As such, the term is designed to cover materials which absorb both urinary secretions and menstrual exudate as well as fluid from surgical wounds.

Such secretafacient material has excellent integrity, good wettability, flexibility, and relatively low cost. Such a material has particular application as a panty liner but has broad applications throughout a variety of product areas requiring absorbency.

The secretafacient material is preferably formed on conventional textile forming machines and is done by intermixing fibers of similar or dissimilar lengths of, a first group of fibers including rayon, wood pulp or other traditional cellulosic-based absorbent material and, a second group of fibers which are mild-process-fusible in nature. This intermixed fibrous batt is then subjected to embossing by heat and pressure. The embossing gives integrity to the batt by the compression of the absorbent fluff material in certain areas but, in addition, fuses the fusible fibers to give a substantially greater integrity than had been present previously. Furthermore, by the interaction of heat and pressure during the embossing, the possibility of substantial sloughing of fibers is almost completely eliminated.

"Mild-process-fusible fibers" are those fibers which will fuse at temperatures between about 2250F. and 3750 F. at a lineal embossing pressure up to 300 pli. The minimum lineal embossing pressure is dependent upon the particular fusible fibers chosen with the lower melting fibers requiring less pressure. Pressures as low as 50 pli have been utilized in the practice of this invention and lower pressures may be possible but it is necessary that some positive embossing pressure be utilized to accomplish the bonding necessary for forming the secretafacient pad.

While other patents teach combinations of types of fibers for various purposes, e.g. U.S.

patent 3,976,074 which discloses hydrophilichydrophobic fiber combinations, the latter used to maintian interfiber differences, non of these references teach the concept of the subject invention.

Of course it is apparent that the amount of sloughing as well as the degree of integrity is a direct function of the proportion of the fusible fibers to the nonfusible fibers and to their length with the longer fibers providing less sloughing. It is generally preferred that the amount of fusible fibers be between about 20% to 35% by weight although amounts greater or lower than the preferred range is possible. Fusible fibers up to 50% by weight of the mixture have been tried and performed suitably although, it should be noted that there is a decrease in absorbency associated with an increase in the percentage of fusible fibers in the secretafacient of this invention.

Depending upon the absorbent fiber component, the fusible fiber component, fiber length and other factors well known in the absorbency art, the secretafacient can be virtually custom designed by proper choice and application of these same parameters.

It is apparent that a substantial contributor to both absorbency and slough in the performance of the secretafacient unit of this invention is the amount of embossing that such a unit (pad) is subjected to. Generally, a random embossing pattern which is spaced over the entire surface of the pad is preferred although, for certain specialized embodiments, locally more clustered or dense embossing patterns may be desirable. In addition, for purposes of integrity, it is desired that the individual components of the embossing pattern or, the components of the embossing lines if the pattern is comprised of a series of straight or wavy lines, is closer together in distance than the length of the individual fibers. If the majority of such embossing lines are located in this way, the integrity resulting from embossing is increased.On the other hand, if embossment occurs over greater than 25% of the area of the pad, absorbency will be seriously adversely affected and it is desired that embossment be present at a lower level than that 25% value.

One concept of uniting absorbent and nonabsorbent fibers without adhesive, is broadly described in U.S. patent 4,100,324. This patent describes forming coherent integrated fibrous structures of thermoplastic microfibers and wood pulp fibers whereiri the fibers are united by intermixing of a primary airstream containing melt blown thermoplastic microfibers and a secondary airstream containing the wood pulp fibers. The streams are merged under turbulent conditions. It should be noted that melt blowing requires substantially higher temperature conditions and the merging of the two airstreams along with melt blowing requires substantially more sophisticated equipment than that utilized to randomly merge the fusible fibers and absorbent fibers which form the secretafacient of this invention.In fact, the secretafacient of this invention may be formed by a machine such as a Rando-webber or other conventional textile forming machines.

It should be noted that while the secretafacient of this invention has broad applications, it is of particular use in the panty liner area. A panty liner according to this invention can be made without a separate fluid permeable top covering material and the panty liner per se therefore only consists of a fluid impermeable shield and adhesive bonding which had been previously necessary between the wrap and the panty liner absorbent is, quite obviously, eliminated. The stiffness and interference in absorbency associated with the adhesive is, also, eliminated and the manufacturing operation is simplified as a result Furthermore, since the fluid impermeable baffle can be a thermoplastic, the secretafacient can be fused directly to the baffle, thereby eliminating all of the structural adhesive used for the panty liner in a particularly preferred embodiment.

Examples of the secretafacient of this invention follow. In all instances the various fiber blends were weighed out in individual components and blended on a Rando-opener Blender unit to form a uniform fiber batt The batt is made on the Randoweb Processor which is a conventional piece of apparatus utilized for bath formation throughout the fiber-forming industry. The finished blended roll from the Rando-web Processor is fed to heated embossing rolls where the fibers were fused into the fibrous batt forming the basis of this invention. (All of the processing apparatus described in the preceding paragraph and throughout the examples are made by the Rando Machine Corporation, Macedon, New York).

Example 1 The first example provides a pad which was made of a mixture of 70% rayon staple and 30% Vinyon staple. Vinyon staple is made by Avtex Fibers, Inc. and is a thermoplastic vinyl resin fiber made from a copolymer of vinyl chloride and vinyl acetate. After processing in the Rando-webber, the density of the base web was 0.040 grams per cc. The web formed was then subjected to heat embossing at a temperature of 2800 F. and an embossing pressure of 90 pli. Embossing for this and all subsequent examples was done on a conventional embossing roll utilized in conjunction with a steel anvil roll. After embossing the overall density of the embossed web was 0.096 g/cc while the density of the web in the embossed area was 0.637 g/cc. The length of the fibers of the starting material was 1-9/16" for the rayon and 2" for the vinyon staple.

Example 2 The pad for Example 1 was compared with the material currently used in a Kotex Lightdays pad on a Handle-O-Meter. The samples measured were 2"x3" and the gap set on the Handle-O Meter of 1". The run of five samples produced averages showing a value of 95.7 for the material found in the Lightdays pad and 29.9 grams for the material formed according to Example 1. Handle O-Meter is well known, is a recognized testing apparatus for a standard test providing a measure of flexibility which is a perceived component of comfort as is made by Thwing Albert Instrument Company, Philadelphia, Pennsylvania. The test is set out in their Instruction Manual. The lower the number of the Handle-O-Meter generally the more comfortabe the pad. As can be seen there is a substantial order of magnitude difference both in softness and resilience as demonstrated by the Handle-OMeter test when the conventional panty liner pad is compared with that which is the subject of this invention.

Example 3 Several other blends were made as indicated in Example 1. The nature of the blends appear in the table below.

Table 1 Fiber Blend% Rayon 70/Polypropylene 30 Rayon 60/Polypropylene 40 Rayon 50/Polypropylene 50 Rayon 30/Wood Pulp 30/Polypropylene 40 Rayon 25/Cotton Fibres 50/Polypropylene 25 Rayon 75/Chisso ES 25 Rayon 60/Vinyon 40 In all instances in the table, the rayon fiber length was 1-9/16" while polypropylene was 1 1/2" and Chisso and Vinyon were 2". Wood pulp and cotton fibers were each 1-9/16". Chisso ES is a trademark of Chisso Corporation of Wyckoff, New Jersey and is a bicomponent fiber with one side being polypropylene while the other is polyethylene. These fibers fuse between 2800 and 3000 F. and this was the process temperature utilized during the heating-embossing step in its manufacture. Polypropylene melts at 3200 to 3400 F. and processing temperature was maintained in that range.

As can be seen from this table, embodied within the scope of this invention are composite thermoplastic fibers as well as mixtures of absorbent fibers. Variations on types of absorbent fibers and mixtures of fusible fibers, as long as the fusible fibers fuse within approximately the same temperature range are, in fact possible under the conditions of this invention and, may in fact be even desirable for certain specialized uses in which particular properties of a variety of thermoplastics are utilized.

Each of these absorbent pads were subject to embossing in a sine wave pattern. Repeated sine wave configurations were spaced throughout the length of the pad increment.

While Handle-O-Meter tests on each of these composites were not performed, subjective inspection indicated that they were indeed much closer to the product of Example 1 in resiliency and perceived softness than was the Kotex Lightdays pad which consisted of 100% wood pulp fibers as the absorbent component. While preliminary absorption tests revealed that absorption went down slightly when compared to the Kotex Lightdays pad and that the effect was related to the amount of thermoplastic present, the amount of absorption decrease was minimal and would logically be overcome by the introduction of a small amount of superabsorbent type material either in powder form during the forming stage or else, as an additional fiber during the forming stage. Superabsorbents are wellknown in the art and need not be discussed in detail here.

Claims (11)

Claims

1. A secretafacient unit or pad comprising in combination an intimate mixture of nonfusible absorbent fiber and a sufficient amount of fibers which are mild-process-fusible to form an integral unit, the integrity of said unit being obtained primarily by embossing in selectively spaced areas.

2. A secretafacient unit or pad according to Claim 1 wherein the major proportion of the embossment defines spaces between embossing lines which are narrower than the length of the fusible fibers.

3. A secretafaclent unit or pad according to Claim 1 or 2 in which the fusible fiber constitutes up to about 50% of the mixture.

4. A secretafacient unit or pad according to any of the preceding claims wherein the embossment constitutes less than 25% of the surface area.

5. A secretafacient unit or pad according to any of the preceding claims in which the pad contains a superabsorbent.

6. A sanitary napkin containing a unit or pad as claimed in any of the preceding claims.

7. A diaper containing a unit or pad as claimed in any of the preceding claims.

8. A wound dressing containing a unit or pad as claimed in any of the preceding claims.

9. An incontinence pad containing a unit or pad as claimed in any of the preceding claims.

10. A panty liner including a secretafaclent absorbent component, the absorbent comprising an integral embossed pad of an intimate mixture of nonfusible absorbent fiber and a sufficient amount of fibers which are mild-process-fusible and a fusible baffle fused thereto.

11. A secretafacient pad as hereinbefore described with reference to any one of the Examples.