US 3371666 A
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March 5, 1968 A. w. LEWING ABSORBENT DEVICE Filed Jan. 26, 1965 INVENTOR ,4: 55 97 14/. L'W/A/G ATTORNEYS fiber spacing,
United States Patent Ofltice 3,371,666 ABSORBENT DEVICE Albert W. Lewing, Monson, Mass., assignor to Tampax Incorporated, New York, N.Y. Filed Jan. 26, 1965, Ser. No. 428,025 23 Claims. (Cl. 128-285) ABSTRACT OF THE DISCLOSURE Apparatus and method having improved liquid absorption and retention properties, particularly useful as catamenial tampons, where typically a pad of cotton has water soluble, non-fibrous, carboxymethyl cellulose (CMC) having a degree of substitution above 0.35 dispersed within the pad in conjunction with an agglomeration-inhibiting means. The agglomeration inhibiting being accomplished by granulations, thin films, or the like, which maximize the total eflective CMC surface exposed for absorption.
This invention relates to devices for fluid absorption and retention, and more particularly to water-absorbent pads and tampons, and especially intra-corporeal absorbent devices such as catamenial tampons, dental rolls, surgical pads, and the like. The invention makes use of additives such as water-soluble cellulosics.
The highest quality vaginal tampons have been made, and continue to be made, from high quality staple cotton fibers. Such fibers have a natural resilience, absorbency, and length, which ideally suit them for use in such compressed tampons. The resilience ensures that the tampon expands upon being wetted, so as to open up the thereby sucking fluids into, and holding them in, spaces between inner fibers by wetting and capillary action and restoring the tampon to its full body and potential of absorbency. Tampons not employing staple fibers are very inefiicient because of their inability to wick the fluid into all the fibers, often resulting (for example in tampons made from cotton linters) in as much as 60% of the tampon being unused when, for practical purposes, the tampon has become saturated.
Much research and development have gone into attempts to find substitutes or additives for staple cotton which would make functionally superior tampons. One attempt to use cotton fiber modified to a water-insoluble carboxymethyl cellulose fiber appears in British Patent No. 848,896, published Sept. 21, 1960, and later in United States Patent No. 3,005,456, issued Oct. 24, 1961.
In both of these patents it was asserted that as the degree of substitution (i.e., degree of esterification, of carboxyniethyl radicals for the hydroxyl radicals of the cellulose molecule) was increased, the absorbency of the resulting modified-cotton tampons also increased, but only up to a point, and thereafter rapidly fell oil to very low values.
The above-mentioned US. patent explains the maximum degree of substitution is three (3), because each glucose unit in the cellulose molecular chain has three hydroxyl groups as potential points of substitution. When the degree of substitution becames about 0.30 to 0.35, the sodium carboxymethyl cellulose (NaCMC) becomes water-soluble and pretty much loses its fibrous nature.
Both the aforementioned patentees are emphatic that NaCMC (or any carboxyalkyl cellulose) having a degree of substitution above 0.35 is unsuitable for use in tampons or the like, because beyond this point the patentees found that absorbency is increased negligibly over pure cotton tampons or is even actually decreased.
Although NaCMC which has an average degree of substitution above 0.35, or which is water-soluble, has had no significant beneficial effect on the absorbency of 3,371,666 Patented Mar. 5, 1968 the tampons, applicant has made the striking discovery that NaCMC can be treated or handled so that a greater absorbency is actually realized.
Accordingly, it is an object of the present invention to make absorbent devices having absorbencies of to well over 200% when compared with ordinary commercial tampons. More specifically, it is an object of the invention to find an adjuvant or a substitute for use with or in place of staple cotton fibers in pads or tampons to increase the latters fluid absorbing capacity without significant detrimental side efiects. It is a further object to provide such pads or tampons which not only have greater absorbency for a given volume but also exhibit a greater physical retention of the fluid once absorbed.
It is another object to employ any of a number of water-soluble absorbent cellulosics, in general, and NaCMC, in particular, in pads or tampons. A collateral objects is to overcome the demonstrated inability of water-soluble NaCMC to enhance the absorbency of pads and tampons. It is still a further object to employ in catamenial tampons a material whose natural tendency to swell during absorption aids in the opening up of the tampon in use.
It has been heretofore disclosed, and up until now been accepted as an established fact, that both watersoluble and non-fibrous CMC are unsuitable for use in an absorbent device (especially when the CMC has a degree of substitution well above 0.30). However, applicant in investigating this problem has discovered how this CMC can be used in aiding the absorbency of such devices. Without being bound by theory, we may express our belief that when Water-soluble CMC is incorporated in a pad or tampon and the latter is wetted, the outer CMC takes the water up so fast, and swells so quickly, thus closing the pad so tightly against further access of water, that the inner CMC, for all practical purposes, is effectively blocked from the moisture. Thus the CMC in the prior devices does not suffer from a lack of absorbency, but rather from an excessive absorbency which results in a caking or an agglomeration rendering useless both the CMC and cotton in the interior part of the pad.
According to the present invention, superior absorbent pads and tampons can be made from water-soluble carboxyalkyl cellulosics dispersed in a wettable open supportive structure when the water-soluble cellulosic is combined with an agglomeration inhibiting means. The term wettable open supportive structure is meant to include besides tampons; sponges, pads, and the like; which are capable of wicking or otherwise drawing water-solutions therein. The purpose of the agglomeration inhibiting means is to disperse the CMC in units small enough or thin enough to readily accept water substantially throughout the unit and to keep these units sufficiently separated to ensure continuing access of water thereto, thereby to promote absorption by preventing agglomeration. This technique maximizes the total amount of effective CMC surface exposed for absorbing.
The agglomeration inhibiting means can accomplish the requisite separation and water accessibilty by forming the CMC units in granular form with water-soluble or water-permeable protective coatings, by casting the CMC in water-soluble thin fihns separated by layers of cotton, or by other techniques which will be apparent to those skilled in the art from the present disclosure.
In the ordinary uses of CMC, it is added to water and careful solution techniques are followed to prevent lump formation and to give non-agglomerated solutions. These techniques include keeping the CMC concentration low, heating the water, vigorously agitating the mixture, and adding the CMC particles at a slow enough rate to ensure wetting of all the individual particles, yet at a fast enough rate to complete the solution before the particles swell and agglomerate so as to impair access of water to the still undissolved particles.
In contrast, the agglomeration inhibiting means in the present invention assists the CMC into solution even though (1) it is now the aqueous liquid which is added to the CMC, (2) neither the aqueous liquid nor the CMC is agitated, (3) the CMC concentration is relatively high, (4) the liquid temperature is not above body temperature, and (5) the rate of mixing is quite independent of the dissolving requirements. In other words, by use of agglomeration inhibiting means, the present invention promotes a passive, yet effective, mixture of an aqueous liquid in CMC under unusually adverse conditions.
In the preferred embodiments the granules or films of treated CMC are incorporated in staple fiber cotton pads leaving channels of cotton free of the CMC. These channels are normally formed merely by alternating a layer of cotton with a layer of CMC. The channels serve as paths for conveying water quickly into the interior of the pad so that the CMC can be functioning simultaneously throughout the pad. The CMC in granular form may be distributed in intimate contact with the fibers, yet such distribution should be sparce enough so as not to close the liquid access channels by swelling of the CMC with the aqueous liquids.
In this specification and the accompanying drawings applicant has shown and described several preferred embodiments of his invention and has suggested various alternatives and modifications thereof; but it is to be understood that these are not intended to be exhaustive and that many other changes and modifications can be made within the scope of the invention. These suggestions herein are selected and included for purposes of illustration in order that others skilled in the art will more fully understand the invention and the principles thereof and will thus be enabled to modify it and embody it in a variety of forms, each as may be best suited to the conditions of a particular use.
In the accompanying drawings:
FIGURE 1 is an exploded perspective view of a pad for a catamenial tampon embodying the present invention, and
FIGURE 2 is a perspective view of a pad similar to FIGURE 1.
In the illustrated preferred embodiments, a 4-inch wide web of staple cotton fibers (whose fibers are oriented substantially longitudinally to the web) is cut into 1% inch widths to form layers 12 of the tampon pad 10. NaCMC 14, prepared in combination with additives as discussed below in granular or thin film form, is distributed between the layers 12. The whole pad is then bound together with a widthdrawal string 16 by a chain of stitching 18. The NaCMC 14 in film form (see FIGURE 1 or 2) is preferably about one to two thousandths of an inch thick, or in granular form (in FIGURE 2) it advantageously passes a sieve having openings of 20 to 40 per linear inch. The total Weight of these pads 10 averages around 3 grams with the NaCMC 14 accounting for anywhere from about a to well over a half the total, and usually about ,6 of the total.
These foregoing illustrated structures are merely exemplary of the many forms of this invention and many commercial uses to which it may be adapted.
In the following examples are illustrated several different ways of preparing a superior absorbent device having CMC whose agglomeration potential is greatly reduced or eliminated as a practical matter. In all of these examples a commercial preparation of NaCMC having an average degree of substitution of 0.7 was used (specifically Hercules Powder C0.s NaCMC identified by code #7-H). The higher the solution viscosity of the NaCMC used in these absorbent devices, the greater their potential retention of fluid. Thus, although Hercules NaCMC #7-L (low viscosity grade) could have been Cir - 4 used in the examples, it is preferred that a NaCMC such as Hercules NaCMC #7-H (high viscosity grade) be used, or even a NaCMC similar to Hercules NaCMC #7- HSP (special high viscosity grade), if the expense of the latter can be cost justified.
The percentage expressed in such example is the average absorbency (i.e., weight of liquid absorbed) of each of several tampons prepared according to the example as compared with the average absorbency of similar commercial tampons of the same size and weight and prepared in the same way except that the latter lack the NaCMC additive. This commercial tampon is the Tampax Super tampon which weighs approximately 3.0 grams and employs staple cotton fibers having a length of approximately one (1) inch. As mentioned before, the pad size is 4" by 1%" before compacting.
EXAMPLE I Grams (,1) NaCMC (H 7-H) 1.62 (2) Citric Acid, USP 0.18 (3) Cotton fibers 1.20
(1) was partially acidified by (2) in the presence of water. A granulation was prepared by drying the acidified mixture at an oven temperature of about 45 C. ot a stabilized condition. The resulting granulation was distributed between layers of the cotton (3) and the pad was then compressed into a tampon. Average absorbency, 165% EXAMPLE II Grams (1) NaCMC 0.90 (2) Citric acid 0.10 (3) Cotton fibers 2.00
Prepared as in Example I. Average absorbency,
EXAMPLE III Grams (l) NaCMC 0.45 (2) Tartaric acid 0.05 (3) Cotton fibers 2.45
Prepared as in Example I. Average absorbency, 131%.
EXAMPLE IV Grams (1) NaCMC 1.17 (2) Carbowax 400 1 2.24 (3) Cotton fibers 2. 00
(l) and (2) were heated and mixed at 105 C. The resultant granulation was sieved and distributed between layers of cotton and then compressed into a tampon. Average absorbency,
Union Carbide Corporation trademark for a polyethylene glycol of the indicated molecular weight.
Prepared as in Example IV. Average absorbency, 164%.
5 EXAMPLE v1 Grams (1) NaCMC 0.90 (2Q Polyox WSR--35 0. 10 (3) Cotton fibers 2.00
Union Carbide Corporation trademark for ethylene oxide polymer resins with molecular weights of 100,000 to several 17161611011, WSR-35 indicates a 5% solution with a viscosity of c.p.s.
Prepared as in Example IV. Average absorbency, 152%.
EXAMPLE VII Grams (l) NaCMC 0.63 (2) Cellosize 52,000 .06 (3) Cotton fibers 2.30
1) and (2) were dissolved in water. A film was cast from this solution to a thickness of about 0.0015 inch. Three 1 /8" x 4" strips of this film were individually laid between layers of the cotton. A tampon was compressed from the resulting pad. Average absorbency, 197%.
EXAMPLE VIII Grams (1) NaCMC 0.65 (2) Cellosize 52,000 0.06 (3) Voranol 0.01 (4) Cotton fibers 2. 20
3 Union Carbide Corporation trademark as used for hydroxyethyl cellulose.
Dow Chemical Company trademark as used for polypropylene sucrose (see also trademark Hyprose). (1), (2) and (3) were dissolved in water. A film cas-t from this solution had a thickness of about 0.0015 ll'lCh. Three 1%" x 4" strips of this film were individually laid between layers of the cotton. A tampon was compressed from the resulting pad. Average absorbency,
Prepared as in Example VII, except only a single 1 /2" x 4" strip was placed between the layers of cotton. Average absorbency, 135%.
EXAMPLE XI Grams (1) NaCMC 0.45 (2) Glycerine 0.21 (3) Cotton fibers 2.30
Prepared as in Example VII. Average absorbency, 160%.
Examples 1 to 3 illustrate the use of organic acids to acidify NaCMC in water down to a pH of about 5 and thereby produce NaCMC in granular form which protects against agglomeration. Of these three examples,
Example 1 with the most NaCMC (over 50%) had the greatest absorbency. The cotton fibers form the wettable open supportive structure. In spite of the greater absorbency of NaCMC, these cotton fibers are still very necessary to these examples in order to act as a carrying medium for the granules prior to use, to give the necessary body to the resulting gelatinous mass after use, and to enhance the effectiveness of the tampon by acting as interior channels for wicking the fluid in to the granules, all in addition to supplementing the absorbency of the NaCMC.
Examples 4 to 6 illustrate the use of several types of water-soluble polymers for forming granulations of agglomeration-inhibited water-soluble NaCMC. These polymers apparently disperse and coat the NaCMC with the non-'agglomerative water-soluble polymer. Thus, the coating serves, like the cotton fibers, to keep available channels for aqueous liquid to get to this CMC and to aid in absorption. For a given amount of NaCMC the polymers are more eifective than the organic acids in increasing absorbency (compare Examples 2, 5, and 6).
Many types of water-soluble cellulosics and other water-soluble components were tested (e.g., Polyox, polyvinyl alcohol, Carbopols, polyvinyl pyrolidone, etc.). None were found to equal the absorbency of water-soluble NaCMC which has been modified by combination with an agglomeration inhibitor. However, they can be used advantageously in compositions with water-soluble NaCMC. Methyl cellulose (MC) and hydroxyethyl cellulose (HEC), to cite two examples, by acting as plasticizers, so improved the film strength and film rewettability of NaCMC films that the tendencies of the delicate NaCMC films to flake and to break-up and to subsequently agglomerate upon wetting was overcome.
As can be seen in Examples 7 to 11 these film combinations give superior results with smaller amounts of NaCMC (compare Example 7 with the best of Examples 1 to 6). Such films keep the NaCMC in a form so as to be available to the aqueous liquid and are thin enough to enable water to penetrate easily into these water-soluble films. In these examples, film thicknesses above 0.003 inch begin to cause a noticeable lowering of absorbency. The lower limits of film thickness are governed by film strength requirements for handling during production. Thus, the optimum range for these examples has been found to be 0.001 to 0.002 inch. In these examples, unit weight values of 18 milligrams per square inch to 35 milligrams per square inch were found to function satisfactorily. For example, the films in Examples 7 and 8 had unit weight values of 20 mg./in. and 31 mg./in. respectively. However, film thickness was found to be a better control factor than these unit weight values.
In Example 8 the polypropylene sucrose is added to give the film more flexibility and strength thereby facilitating ease of handling during production and enhancing comfort during use for the customer. Natural gums such as starch, Karaya, and others, as well as synthetic alginates can be used to improve film properties such as shelf stability or rewettability, Additionally, surfactants can be added to some advantage, e.g., sodium lauryl sulfate.
Many geometric combinations of the films and granulations in the wettable open supportive structure can be employed to aid in the dispersion of the modified water-soluble NaCMC. In addition to the simple multilayer combination illustrated in FIGURES 1 and 2, herringbone film strips, corrugated film, or coated threads; or the like may be used to increase the channels of liquid into the pad 10 while increasing the surface area of the film, granule, or coated thread groupings. These geometric combinations may be thought of as part of the agglomeration inhibiting means, because in dispersing the NaCMC the units thereof are separated, thereby increasing the effective surface area of NaCMC actually wetted.
The aforementioned coated threads might take the form of units of water-soluble NaCMC chemically or physically bonded to an otherwise unmodified cotton fiber which would result in preventing agglomeration of the NaCMC due to the binding thereof to the cotton.
As the degree of substitution in water-soluble NaCMC increases from 0.30 to above 0.95 the absorbency of tampons prepared according to Example 7 also increases significantly. However, as the degree of substitution increases even further with these examples, countervailing factors begin to become significant and depress the ab sorbcncy. For example, the amount of the agglomeration inhibitor required to render such NaCMC effective might become so significantly large as to displace much of the potentially more absorbent NaCNC, resulting in a net lowering of absorbency. A more cfiicient agglomeration inhibiting means developed according to this invention can prevent this problem. However, the means used in Example 7 with NaCMC having a degree of substitution of 1.2 resulted in an absorbency increase to only 120% (as compared to 197% for 0.7 and l6l% for 0.4). Applicant has also theorized that steric hindrance may become a factor decreasing NaCMC absorbency at a 1.2 degree of substitution and above.
NaCMC is not commercially available with a degree of substitution above 0.7, except for a fraction of 0.95 in Hercules NaCMC #7 ESP and except at 1.2 and the latter only in experimental quantities. Thus, while it is feasible to increase significantly the absorbency of 1.2 NaCMC, it is not practical since 0.7 NaCMC is readily available and is easier to render highly absorbent.
The discussion of the present invention in this specification has been generally in terms of non-fibrous NaCMC, or water-soluble NaCMC having a degree of substitution above 0.35, as the highly absorbent, readily agglomerative composition of matter for use in absorbent pads. Nevertheless, the invention in its boarder aspects includes other known, or yet to be discovered, functionally equiva lent composition of matter. Specifically, sodium carboxyethyl cellulose, mentioned in the above-cited US. patent and other alkali metal carboxyalkyl celluloses (CAC) can be rendered useful for absorbent pads by combination with an agglomeration inhibiting means according to the above disclosure.
1. In an absorbent device for aqueous liquids the improvement comprising non-fibrous, water soluble CMC dispersed in said absorbent device and agglomeration-inhibiting means, said CMC being modified to a more absorbent form through a combination with said agglomeration inhibiting means which significantly increases the total effective surface area exposure of the CMC to aqueous liquids from the external environment of said device.
2. A device as claimed in claim 1 wherein the CMC is NaCMC.
3. A device as in claim 2 wherein the NaCMC has a degree of substitution above about 0.30.
4. A device as in claim 3 wherein the NaCMC has a maximum degree of substitution of about 0.95.
5. A device as claimed in claim 1 wherein said absorbent device is a catamenial tampon.
6. A liquid absorbent device comprising agglomeration inhibiting means, wettable open supportive structure, and water-soluble CMC having a degree of substitution above about 0.30, said CMC being modified to a more absorbent form through combination with said agglomeration inhibiting means.
7. A device as claimed in claim 6 wherein the CMC is NaCMC.
8. A device as claimed in claim 7 wherein the degree of substitution is from 0.03 to about 0.95
9. A device as in claim 7 wherein the wettable supportive structure is a fibrous cotton pad.
10. A device as claimed in claim 9 wherein said modified absorbent device is a catamenial tampon.
11. A device as claimed in claim 6 wherein said watersoluble CMC increases the average absorbency of said device to at least 135%.
12. In an absorbent device, the improvement comprising a highly absorbent, inherently agglomerative, non-fibrous, water soluble cellulosic polymer, said polymer being dispersed within said device in units sufiiciently small to readily accept the water substantially throughout the units and a Water permeable means separating said units by an amount sufficient to enable penetration of water throughout said device.
13. A device as described in claim 12 wherein the polymer is an alkali metal carboxyalkyl cellulose.
14. An absorbent device for aqueous liquids comprising a pad of cellulosic fibers having a plurality of layers, a thin film of water-soluble NaCMC having a degree of substitution of about 0.30 to about 0.95 and a maximum thickness of about 0.003 inch, hydroxyethyl cellulose present in said film as a binder and agglomerationinhibitor, said film being laid between layers of the pad.
15'. A device according to claim 14 wherein the NaCMC comprises generally about by weight of the film.
16. A device according to claim 15 for use as a catamenial tampon wherein the pad comprises cotton fibers, several strips of the film are laid individually between layers of the cotton pad, and the hydroxyethyl cellulose has a molecular weight of about 52,000.
17. An aqueous liquid absorbent device comprising a pad of cellulose fibers, a thin film of water-soluble NaCMC having a degree of substitution of about 0.30 to about 0.95, glycerine comprising about 10% by weight of said film, said film being laid between layers of the pad.
18. An aqueous liquid absorbent device comprising a wettable open supportive structure, water-soluble NaCMC in an agglomeration-inhibiting granular form having a degree of substitution of about 0.30 to about 0.95 and being dispersed within said structure.
19. A device according to claim 18 wherein said granulated NaCMC is prepared by a partial acidification with an organic acid.
20. A device according to claim 19 wherein the acidification is carried out to a pH of about 5 by an organic polycarboxylic acid, the wettable open supportive structure is a cellulosic fibrous pad having a plurality of layers, and the dispersion of NaCMC within the pad occurs substantially between layers of the pad.
21. A device according to claim 18 wherein said NaCMC attains its granular form through combination with a water permeable, non-agglomerating polymer.
22. A device according to claim 21 wherein said polymer is polyethylene glycol.
23. A device according to claim 21 wherein said polymer is polyethylene oxide.
References Cited UNITED STATES PATENTS 3,121,427 2/1964 Mosier 128-285 3,078,849 2/1963 Morse 128290 3,055,369 9/1962 Graham 128285 2,849,000 8/1958 Lewing 128285 2,808,832 10/1957 Myers et a1. 128-285 2,764,159 9/1956 Masci et a1. 128-296 2,761,449 9/1956 Bletzinger 128285 2,486,805 11/1949 Seymour et a1. 128284 RICHARD A. GAUDET, Primary Examiner.
CHARLES F. ROSENBAUM, Examiner.