Absorbent Product Comprising A Fluid Impervious Barrier Of A Repellent Tissue And A Hydrocolloid

Abstract

An absorbent product for absorbing and retaining body fluids and exudates comprising a cellulosic absorbent body or core, a cellulosic covering or facing material, and a biodegradable, water imprevious barrier sheet or layer comprising a cellulosic tissue having a basis weight of from about 6 pounds to about 30 pounds, a water repellent material deposited on the cellulosic tissue in an amount equal to from about 0.1 percent by weight to about 0.5 percent by weight, based on the weight of the treated tissue, whereby the cellulosic tissue is classified as a repellent tissue, and from about 0.002 to about 0.03 gram per square inch of a hydrocolloidal material on the repellent tissue, said hydrocolloidal material being capable of swelling in body fluids and exudates and cooperating with the repellent tissue to form an impervious barrier to body fluids and exudates.

Description

This invention relates to absorbent products for absorbing and retaining body fluids and exudates and more particularly is concerned with sanitary napkins for the absorption and retention of menstrual fluids.

Although the present invention will be described with particular reference to a sanitary napkin as the preferred embodiment of the present invention, it is to be appreciated that the principles of the inventive concept are equally applicable to other absorbent products or to any product in which a water impervious barrier layer or sheet is of use. Such other products include, for example, diapers, surgical dressings, underpads, compresses, and the like.

Absorbent products such as sanitary napkins usually comprise a relatively dense, fibrous body or core of one or more layers of highly absorbent fibers conventionally in the form of carded cotton or rayon cellulosic webs, air layered cotton or rayon cellulosic webs, comminuted wood pulp bats, tissue pulp, crepe or cellulose wadding, absorbent paper, or like materials.

Such a fibrous body or core is usually wrapped within a soft, fluid permeable cover which may be a woven, nonwoven, knitted, lace, or like fabric normally made from cellulosic fibers.

Additionally, a waterproof or fluid impervious baffle or barrier sheet is often used within the wrapper whereby any fluids deposited on the top surface of the sanitary napkin and which are not completely absorbed and retained by the fibrous body or core are prevented from passing through the sanitary napkin to the bottom surface thereof. Such a waterproof or fluid impervious barrier sheet presents so-called "strike-through" of fluid and such a feature has been incorporated in the vast majority of sanitary napkins presently sold on the market today.

Unfortunately, such a waterproof or fluid impervious barrier sheet, as currently used, possesses many disadvantages. For example, practically all of these fluid impervious barrier sheets are water insoluble and not dispersible in water and are not biodegradable whereby disposal of the used sanitary napkin presents a problem. Also, many of these fluid impervious barrier sheets are crisp and noisy and undesirably call attention to the fact that a sanitary napkin is being used. Additionally, many of these fluid impervious barrier sheets are not sufficiently soft or flexible and do not satisfactorily conform to the anatomical contours of the wearer.

It is therefore a principal purpose of the present invention to provide a barrier sheet for absorbent products such as sanitary napkins, which barrier sheet will be fluid impervious in use, but which will be biodegradable, soft, flexible and conformable and not crisp or noisy.

This is accomplished by using as the barrier sheet a cellulosic tissue having a specified weight range, treating the tissue with specified amounts of water repellent materials whereby a certain degree of water repellency but not complete waterproofing is created therein, and depositing on the treated tissue a specified amount of a hydrocolloidal material which is capable of swelling in body fluids or exudates whereby it cooperates with the water repellent tissue to form an impervious barrier to body fluids and exudates.

As used herein, "tissue" is a general term indicating a class of light weight cellulosic papers of characteristic gauzy texture and in some cases translucent, made in basis weights lighter than about 30 pounds (basis 500 sheets -- 24 .times. 36 inches). Tissues used herein range in basis weights of from about 6 pounds to about 30 pounds, and preferably from about 12 pounds to about 20 pounds.

Also, as used herein, the terms "waterproof" or "water impervious" are used to describe materials which are completely impermeable to the passage of water or moisture and which will retain this property throughout their expected service life under normal use. Examples of waterproof or water impermeable materials are: polyethylene and polypropylene sheets and films; materials having knife-coated finishes comprising such ingredients as paraffins, pigments, and resin binders with add-on weights of 10 to 90 percent; rubber or vinyl coated materials; films and sheets of fluoroplastic materials and particularly chlorotrifluoroethylene resins (CTFE), polytetrafluoroethylene resins (PTFE), fluorinated ethylene-propylene resins (FEP), etc.

Water repellency, however, is a relative term, as contrasted to the term "waterproof", and is applied to materials which are not completely impermeable or impervious to the passage of water or moisture. Water repellency is usually measured in terms of the time in seconds which is required for water or a test fluid to pass from one side of a sheet material to the other side. There are various Standard Methods for determining the water resistance of fabrics (ASTM D583-63 and AATCC 22-1967) and for paper and paper board (ASTM D779-58 and TAPPI T433 m-44) but there are no industry-wide officially accepted standards for specialty paper products such as tissue.

The standard and accepted test used herein for determining the repellency or water-resistance of tissue is as follows: Two plies of highly absorbent tissue having substantially instantaneous repellency times are placed on a flat glass plate and the tissue to be tested is placed on the two highly absorbent tissues. A mirror and light source are so arranged that an observer can readily see the top and bottom surfaces of the plied tissues. A few drops of a test fluid at room temperature are placed on the top surface of the test tissue and a determination is made of the time in seconds which is required for a wet spot to appear on the bottom surface of the lowest highly absorbent tissue.

Due to the highly absorbent nature of the two lowermost tissues which have substantially instantaneous repellency times, it may be stated that the repellency time obtained for the three layers of tissue is substantially equal to the repellency time for the test tissue alone. The two lowermost tissues, however, do help the observer in noting the appearance of a wet spot.

The plies of tissue are flat and lie in a horizontal plane on the flat glass plate. No external pressure is applied and consequently the only pressure urging the drops of water to pass through the tissue material is the weight of the drops of water themselves. In order to simulate in vivo conditions to a greater degree, a small amount of a surfactant is added to the test fluid so that its surface tension approximates the surface tension of blood or of the body fluids with which the absorbent product will be used.

The test is performed on a minimum of three locations of the tissue and the results are averaged to yield the repellency time in seconds. This is necessary because of the wide variation in results obtained in different locations of a test tissue.

If it were not for the water repellent treatment, the tissue used in the application of the principles of the present invention would have an extremely short water repellency time which would range from substantially instantaneous up to as long as about 1/2 second to about 4 seconds.

Subsequent to the water repellent treatment, the treated tissue has a water repellency time which ranges from an average of about 15 seconds to an average of about 150 seconds. Such treated tissues are classified as "water repellent" within the application of the principles of the present invention. It must be kept in mind, however, that such a term is a relative term and that it is frequently loosely used in industry. Such accounts for the care taken in defining the term as used herein.

Such values are, of course, to be contrasted to the values obtained for waterproof or water impervious materials. Such materials, of which polyethylene sheets and films are outstanding examples, have water repellency times measured in weeks or longer.

The invention will be more fully understood from the description which follows, taken in conjunction with the accompanying drawing in which there are illustrated preferred designs and modes of operation embodying the invention. It is to be understood, however, that the invention is not to be considered limited to the constructions disclosed except as determined by the scope of the appended claims. In the drawings:

FIG. 1 is a perspective showing of an absorbent sanitary napkin which is shown partially cutaway to illustrate the improved fluid impervious barrier sheet of the present invention;

FIG. 2 is a cross-sectional view of the absorbent sanitary napkin of FIG. 1, taken on the line 2--2 thereof;

FIG. 3 is a partially cutaway, perspective view of the improved fluid impervious barrier sheet of the present invention, as it would appear, if removed from the absorbent sanitary napkin of FIG. 1; and

FIG. 4 is a cross-sectional view of a diaper construction utilizing the principles of the improved fluid impervious barrier sheet of the present invention.

With reference to the drawings, and particularly FIGS. 1 and 2 thereof, there is shown an absorbent sanitary napkin 10 comprising a relatively thick, elongated fibrous body or core 12, predominantly comprising cellulosic fibrous materials such as comminuted wood pulp, cotton, rayon, tissue pulp, crepe or cellulosic wadding, absorbent paper, etc.

The fibrous absorbent core 12 is enclosed within a conventional soft, fluid permeable, wrapper or cover 14 whose ends extend beyond the ends of the fibrous absorbent core 12 to provide the usual attachment tabs 16, 16. As noted in FIGS. 1 and 2, the upper facing surface and lower backing surface of the sanitary napkin 10 are soft and fluid permeable.

A fluid impervious barrier sheet 18 is positioned under the fluid absorbent core 12 and is in such a position that any body fluids or exudates which are deposited on the upper facing surface of the cover 14 and are of such volume that they pass through the absorbent core 12 will be checked and will go no farther when they contact the fluid impervious barrier sheet 18.

As shown more clearly in FIG. 3, the base or supporting layer of the fluid impervious barrier sheet 18 comprises a cellulosic tissue layer or layers 20 having properties as defined and described previously. It is to be appreciated that such tissue material is relatively thin, soft, fragile, conformable, and highly absorbent. It is of very light weight, having a basis weight of from about 6 to about 30 pounds and preferably from about 12 to about 20 pounds, is very porous, and contains very many minute openings and "pin holes". The water-repellency or water-resistance of such a tissue layer is practically negligible and the time required for a drop of test fluid to pass through a test ply of such material is less than about 4 seconds, or as little as almost substantially instantaneous.

Although one ply of tissue is used in the previously described repellency test and two plies of tissue are used in the preferred embodiment of the inventive concept, it is to be appreciated that a different number of tissues may be used in the absorbent product. For example, merely a single layer of tissue may be used, or three, four or more may be used, as desired or required. The total weight of the tissue layer or layers, however, remains in the range of from about 6 pounds to about 30 pounds, basis weight.

The tissue material 20 is treated with specified amounts of a water repellent material 22 whereby a certain degree of water repellency or water resistance but not complete waterproofing is created therein. Such water repellent treatment may be accomplished in many ways such as, for example, by inclusion of the water repellent material 22 in the beater, head box, or other part of the papermaking machine whereby it is incorporated in an "in-line" operation directly onto the cellulosic fibrous materials during their manufacture into tissue. Or, if desired, the water repellent materials 22 may be applied after the formation of the tissue sheet, in an "off-line" operation, such as by a spraying operation or by a padding or dipping treatment.

In any event, the amount of water repellent material 22 which is applied must be controlled to relatively narrow ranges of dry add-ons of from about 0.1 percent by weight to about 0.5 percent by weight, based on the dry weight of the treated tissue sheet. Within the more commercial aspects of the present invention, a range of dry add-ons of from about 0.2 percent by weight to about 0.3 percent by weight, based on the dry weight of the treated tissue material, has been found more desirable.

Many water repellent materials have been found suitable for application to the tissue material for the purpose of the present invention. Among such water repellent materials are: various fluorocarbons such as CTFE, PTFE, FEP, etc.; "Scotchgard" Repellents FC-208, FC-210, FC-212, FC-214, etc.; silicones such as Dri-Film 1040, a methyl hydrogen polysiloxane (General Electric) and Dri-Film 1042 and 1043, modified methyl hydrogen polysiloxanes (General Electric); cationic starch type water repellents such as "Cyanasize" (American Cyanamid) and "Aquapel", a ketene dimer emulsified with a cationic starch, sold by Fancourt Co.; etc.

As used herein, therefore, repellent tissue is defined as a tissue which has been so treated that its water repellency or water resistance falls in the above-defined range. The values of such range, namely, from about 15 seconds to about 150 seconds, are to be contrasted to the values obtained in testing waterproof or water impervious materials which range from many hours to days, weeks, or even longer.

The water repellent tissue is still relatively thin, soft, fragile, flexible, and conformable but is not quite as porous as it was prior to the water repellent treatment. There still remains, however, a large number of minute openings and pin holes, however, and the tissue is repellent and water resistant but not waterproof or water impervious.

After the tissue material has been treated with the water repellent material, it is then given a second treatment with a hydrocolloidal material 24 which is capable of swelling sufficiently upon contact with body fluids and exudates whereby substantially all of the minute openings and pin holes are closed and the tissue becomes substantially water-impervious or waterproof. Such a condition is reached, however, only after the hydrocolloidal material 24 has swollen sufficiently.

The amount of hydrocolloidal material 24 which is applied to the treated tissue is kept within relatively narrow ranges and is in the range of from about 0.002 to about 0.03 gram per square inch of repellent tissue. Within the more commercial ranges of the present invention, a range of from about 0.003 to about 0.02 gram per square inch of repellent tissue is preferred.

The amount of hydrocolloidal material 24 which is applied to the treated tissue may be expressed in terms of the amount which is applied per sanitary napkin. Such an amount varies as desired or required depending upon the particular hydrocolloidal material used. It also varies depending upon the size and intended use of the sanitary napkin. Expressed in this manner, it may be stated that from about 0.05 gram to about 0.4 gram of hydrocolloidal material is used per sanitary napkin. Within the preferred commercial ranges, however, it may be stated that from about 0.11 gram to about 0.2 gram is used per sanitary napkin.

The hydrocolloidal materials may be selected from a relatively large group of such materials, including both synthetic and naturally occurring hydrocolloids. Examples of such materials include cellulose ethers such as sodium carboxymethyl cellulose and methyl cellulose, guar gums, gum karaya, gum tragacanth, algin, polysaccharides, starches, gelatin, agar agar, proteins such as blood or egg albumin, etc.

If merely one tissue layer is used, the hydrocolloidal material is applied thereto in the ranges indicated. If two or more tissue layers are used, and such construction is preferred, the hydrocolloidal material is applied either merely to one tissue, or to all tissues, but the total amount applied still falls within the range of from about 0.002 to about 0.03 gram per square inch, based on the area of the absorbent product. To illustrate specifically, the total area of a sanitary napkin is in the range of from about 17 to about 25 square inches and normally from about 20 to about 22 square inches. The applied hydrocolloidal material add-on is calculated on such an area.

When two or more tissue layers are used, the hydrocolloidal material is preferably so applied and the tissues are so used that the hydrocolloidal material is located between the tissue layers, rather than being on an outer surface thereof.

In FIG. 4, there is illustrated a diaper 26 which represents another specific embodiment of the application of the principles of the present invention. The diaper 26 comprises: a soft, fluid permeable, top facing surface 34 which may be a nonwoven fabric, a nonwoven or woven scrim, a woven fabric such as gauze, or the like; a centrally-located, highly absorbent fibrous body or core 32, primarily or completely of cellulosic materials; and a waterproof or fluid impervious barrier sheet 28 comprising a repellent treated tissue and a hydrocolloidal material deposited thereon.

Such a waterproof or fluid impervious barrier sheet 28 is, of course, fundamentally similar in construction, operation and function to the waterproof or fluid impervious barrier sheet 18 which has been described previously.

If desired, an additional backing or supporting sheet 36 may be added to reinforce or strengthen the fluid impervious barrier sheet 28. Such a backing sheet 36 may be similar to the facing sheet and may also be a nonwoven fabric, a nonwoven or woven scrim, a woven fabric such as gauze, or the like.

The water repellent material and the hydrocolloidal material are preferably applied to the tissue in a finely divided particulate form. Such application may be in a liquid carrier such as an aqueous dispersion of the particulate materials wherein they are applied by spraying, padding, dipping, or other techniques. Or, if desired, the application may be dry and the particulate materials applied by spraying, dusting, brushing, sprinkling, or other techniques.

The particle size of the particulate material is not a critical consideration. Relatively small particle sizes are preferred inasmuch as such is more conducive to more uniform and more efficient and economical application and coverage.

The invention will be more specifically described by reference to the following Examples wherein particular materials and constructions are used. Such specific examples, however, are employed to illustrate selected embodiments of the inventive concept and are not to be construed as limitative of the broader aspects thereof.

EXAMPLE I

Highly absorbent, cellulosic tissue material having a basis weight of approximately 14 pounds is treated with a cationic starch water repellent material ("Aquapel" Fancourt) so as to render it water repellent. The dry add-on of the cationic starch is 0.25 percent by weight, based on the dry weight of the treated tissue. One ply of the treated tissue is tested for water repellency, using the previously described standard test. The test results are as follows:

Sample No. Time In Seconds 1 25 2 90 3 120 4 150 5 270 6 20 7 25 8 35 9 90 10 120 11 15 12 50 13 60 14 70 15 80

These values are to be compared to the water repellency time for the original, untreated tissue of one-half second.

The repellent tissue is then treated with a guar gum (Stein-Hall) hydrocolloidal material in an amount sufficient to deposit 0.11 gram (dry) on an area measuring 21/4 .times. 87/8 inches (approximately 20 square inches) for inclusion as a double thickness sandwich of two tissues in a standard napkin such as illustrated in FIG. 1. This is equivalent to a deposition of approximately 0.0055 gram of guar gum hydrocolloidal material per square inch of repellent tissue.

Upon deposition of body fluid upon the sanitary napkin and contact thereof with the guar gum, swelling of the guar gum takes place immediately and the treated repellent tissue becomes waterproof or water impervious. "Strike-through" is prevented and the sanitary napkin performs satisfactorily in use. Subsequent to use it is discarded and disposed of readily inasmuch as the absorbent cellulosic core, the cellulosic nonwoven fabric cover and the barrier sheet are biodegradable.

EXAMPLES II - III

The procedures of example I are followed substantially as set forth therein except that the add-on of the "Aquapel" water repellent material is changed from 0.25 percent by weight to 0.15 percent by weight and 0.35 percent by weight. The results are comparable.

EXAMPLES IV - V

The procedures of Example I are followed substantially as set forth herein except that the "Aquapel" water repellent material is replaced by a fluorocarbon (PTFE) and by a silicone ("Dri-Film 1042" - General Electric). The results are comparable.

EXAMPLE VI

The procedures of Example I are followed substantially as set forth therein with the exception that the "Aquapel" water repellent material is replaced by "Dri-Film 1040" (General Electric).

EXAMPLE VII

The procedures of Example I are followed substantially as set forth therein with the exception that the "Aquapel" water repellent material is replaced by "Dri-Film 1043" (General Electric).

EXAMPLES VIII - X

The procedures of Example I are followed substantially as set forth therein except that the add-on of the guar gum is changed from 0.11 gram to 0.05 gram, 0.20 gram and 0.40 gram. This is equivalent to the deposition of approximately 0.0025, 0.01, and 0.02 gram per square inch of repellent tissue, respectively. The results are comparable.

EXAMPLES XI - XIV

The procedures of Example I and II are followed substantially as set forth therein except that the guar gum is replaced by sodium carboxymethyl cellulose (DuPont - Code CS-5702-Grade P-75-H) in similar amounts of 0.05 gram, 0.11 gram, 0.20 gram, and 0.40 gram. The results are comparable.

Although the present invention has been described and illustrated with reference to preferred embodiments thereof, it is to be appreciated that such is merely for the purpose of disclosing the invention and is not to be construed as limitative of the broader aspects of the inventive concept, except as defined by the appended claims.

Claims

What is claimed is:

1. In an absorbent product for absorbing and retaining body fluids and exudates comprising a cellulosic absorbent body, a cellulosic covering material, and a fluid impervious barrier sheet when in use therebetween, the improvement wherein the fluid impervious barrier sheet is biodegradable and comprises:

a. a cellulosic tissue having a basis weight of from about 6 to about 30 pounds and a repellency time of less than 4 seconds;

b. said tissue carrying water repellent material present in an amount equal to from about 0.1 to about 0.5 percent by weight based on the weight of the tissue, thereby imparting to the water repellent carrying tissue a repellency time of about 15 to about 150 seconds; and

c. said water repellent material carrying tissue having deposited, on the surface facing said absorbent body, a hydrocolloidal material; whereby said hydrocolloidal material cooperates with said treated tissue to form a barrier, impervious to body fluids and exudates, when said barrier is in contact with said fluids and exudates.

2. An absorbent product as defined in claim 1 wherein the water repellent material is a cationic starch.

3. An absorbent product as defined in claim 1 wherein the water repellent material is a fluorocarbon.

4. An absorbent product as defined in claim 1 wherein the water repellent material is a silicone.

5. An absorbant product as defined in claim 1 wherein the hydrocolloid is present in an amount equal to from about 0.002 to about 0.03 grams per square inch.

6. An absorbent product as defined in claim 1 wherein the hydrocolloidal is a guar gum.

7. An absorbent product as defined in claim 1 wherein the hydrocolloidal is sodium carboxymethyl cellulose.

8. In a sanitary napkin for absorbing and retaining body fluids and exudates comprising a cellulosic absorbent body, a cellulosic covering material, and a fluid impervious barrier sheet when in use therebetween, the improvement wherein the fluid impervious barrier sheet is biodegradable and comprises:

a. a cellulosic tissue having a basis weight of from about 6 to about 30 pounds and a repellency time of less than 4 seconds;

b. said tissue carrying water repellent material present in an amount equal to from about 0.1 to about 0.5 percent by weight based on the weight of the tissue, thereby imparting to the water repellent carrying tissue a repellency time of about 15 to about 150 seconds; and

c. said water repellent material carrying tissue having deposited, on the surface facing said absorbent body, a hydrocolloidal material; whereby said hydrocolloidal material cooperates with said treated tissue to form a barrier, impervious to body fluids and exudates, when said barrier is in contact with said fluids and exudates.

9. In a diaper for absorbing and retaining body fluids and exudates comprising a cellulosic absorbent body, a cellulosic covering material, and a fluid impervious barrier sheet when in use therebetween, the improvement wherein the fluid impervious barrier sheet is biodegradable and comprises:

a. a cellulosic tissue having a basis weight of from about 6 to about 30 pounds and a repellency time of less than 4 seconds;

b. said tissue carrying water repellent material present in an amount equal to from about 0.1 to about 0.5 percent by weight based on the weight of the tissue, thereby imparting to the water repellent carrying tissue a repellency time of about 15 to about 150 seconds; and

c. said water repellent material carrying tissue having deposited, on the surface facing said absorbent body, a hydrocolloidal material; whereby said hydrocolloidal material cooperates with said treated tissue to form a barrier, impervious to body fluids and exudates, when said barrier is in contact with said fluids and exudates.