U.S. patent number 3,858,585 [Application Number 05/323,598] was granted by the patent office on 1975-01-07 for fluid absorption and retention products and methods of making the same.
This patent grant is currently assigned to Personal Products Company. Invention is credited to Pronoy Kumar Chatterjee.
United States Patent |
3,858,585 |
Chatterjee |
January 7, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
FLUID ABSORPTION AND RETENTION PRODUCTS AND METHODS OF MAKING THE
SAME
Abstract
An absorbent dressing is provided having improved fluid
absorptive properties by including therein a substantially
uncompressed body comprising absorbent fibers of an alkali metal
salt of carboxyalkyl cellulose. The absorbent carboxyalkyl
cellulose fibers are heat-treated so as to become insoluble but
swellable in water at room temperatures and by virtue of this heat
treatment, derive the improved fluid absorptive properties of this
invention.
Inventors: |
Chatterjee; Pronoy Kumar
(Spotswood, NJ) |
Assignee: |
Personal Products Company
(Milltown, NJ)
|
Family
ID: |
27257221 |
Appl.
No.: |
05/323,598 |
Filed: |
January 15, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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126743 |
Mar 22, 1971 |
3731686 |
|
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|
797791 |
Feb 10, 1969 |
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Current U.S.
Class: |
604/376; 604/371;
604/375; 604/381 |
Current CPC
Class: |
A61F
13/533 (20130101); A61F 13/53708 (20130101); A61F
13/536 (20130101); A61F 2013/53721 (20130101); A61F
2013/530131 (20130101); A61F 13/202 (20130101); A61F
13/534 (20130101); A61F 2013/8488 (20130101); A61F
2013/53778 (20130101); A61F 2013/53445 (20130101); A61F
13/53409 (20130101); A61F 13/53704 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61F 13/20 (20060101); A61f
013/16 () |
Field of
Search: |
;128/284,287,29R,296,284R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Medbery; Aldrich F.
Attorney, Agent or Firm: Lipow; Jason
Parent Case Text
This application is a continuation-in-part of my copending U.S.
application, Ser. No. 126,743, filed on Mar. 22, 1971, now U.S.
Pat. No. 3,731,686, which is a continuation-in-part of U.S.
application, Ser. No. 797,791, filed on Feb. 10, 1969 and now
abandoned.
Claims
What is claimed is:
1. In an absorbent dressing including an uncompressed body
comprised of absorbent fibers of an alkali metal salt of
carboxyalkyl cellulose having an average degree of substitution
greater than about 0.35 carboxyalkyl radicals per anhydroglucose
residue in the cellulose, the improvement wherein said fibers have
crosslinkages, said crosslinkages consisting of adjacent chains of
repeating anhydrglucose units linked directly to each other by heat
treating without the use of crosslinking agents.
2. The dressing of claim 1 wherein said linkages consist of
internal esterification between adjacent chains of the repeating
anhydroglucose units.
3. An absorbent dressing as defined in claim 1 wherein said
uncompressed body includes portions having a density of less than
90 grains per cubic inch.
4. An absorbent dressing as described in claim 1 wherein said
absorbent fibers of the alkali metal salt of carboxyalkyl cellulose
and sodium carboxymethyl cellulose fibers.
5. An absorbent dressing as defined in claim 4 wherein said
absorbent fibers of the alkali metal salt of the carboxyalkyl
cellulose have an average degree of substitution in the range of
greater than 0.35 and up to about 1.4.
6. An absorbent dressing as defined in claim 1 wherein the
absorbent dressing is a catamenial device.
Description
BACKGROUND OF THE INVENTION
The present invention relates to absorbent products and more
particularly to absorbent dressings and articles of manufacture
having improved fluid absorption and retention properties and
methods of making the same. More specifically, the present
invention relates to such articles of manufacture as sanitary
napkins, diapers, surgical dressings, hospital underpads, sponges
and bandages as well as other intra- and extra-corporeal body
exudate and fluid absorption and retention materials.
Cotton, rayon, wood pulp and similar natural and synthetic
cellulosic materials have long been used extensively in the
preparation of absorbent dressings and similar products and they
have been found satisfactory for many purposes. However, many other
materials have long been studied and have been considered as
possible replacements or improvements for such cellulosic
materials. Various carboxyalkyl ethers of cellulose, notably
carboxymethyl cellulose, have been considered and in some areas
have been suggested for fluid absorption and retention purposes.
For example, U.S. Pat. No. 3,005,456 which issued Oct. 24, 1961,
discloses the use of carboxyalkyl cellulose, notably carboxymethyl
cellulose and carboxyethyl cellulose, particularly for catamenial
tampons. However, it is to be noted that the use of such
carboxyalkyl ethers of cellulose is normally limited to those
having a maximum average degree of substitution (D.S.) of about
0.35 carboxyalkyl radicals per anhydroglucose unit in the
cellulose. Beyond that degree of substitution, the carboxymethyl
cellulose tends to become too water-soluble in its properties which
is now believed to cause the fluid absorption and retention
properties to fall off to an extremely low, undesirable value. It
is believed that water-soluble carboxymethyl cellulose, having an
average D.S. greater than 0.35, upon being contacted by fluid,
quickly becomes surface-wetted, swells rapidly and agglomerates or
cakes into a gel-like mass. This gelling is at the outermost
surface portions of the carboxymethyl cellulose and delays or
perhaps completely blocks further access of fluid to the innermost
portions of the carboxymethyl cellulose whereby very little
additional fluid absorption is accomplished in a reasonable period
of time.
In my above referenced co-pending application, it was disclosed
that if a water-soluble, carboxyalkyl ether of cellulose in fibrous
form, such as carboxymethyl cellulose, is given a controlled heat
treatment at selected elevated temperatures and for a specified
duration of time, the carboxymethyl cellulose fiber is modified and
becomes water-insoluble. It was also disclosed that when such
heat-treated carboxymethyl cellulose fibers are used in a
compressed state, as for example, in a compressed absorbent body
which includes portions compressed to a density ranging from about
90 grains per cubic inch to about 215 grains per cubic inch, the
resulting compressed body exhibits excellent fluid absorption and
retention properties for all degrees of substitution without
showing any tendency toward agglomerates, caking, gelling or
blockage of wicking. Thus, the heat-treated fibers in compressed
form are particularly useful in, for example, catamenial tampons,
and compressed portions of sanitary napkins and other absorbent
dressings.
SUMMARY OF THE INVENTION
The present invention is directed toward the use of heat treated
fibers in uncompressed products. In accordance with this instant
invention, it has been discovered that an absorbent dressing having
improved fluid absorptive properties may be provided by including
therein a substantially uncompressed body comprising absorbent
fibers of an alkali metal salt of carboxyalkyl cellulose having an
average degree of substitution greater than about 0.35 carboxyalkyl
radicals per anhydroglucose residue in the cellulose, the absorbent
alkali carboxyalkyl cellulose fibers being heat treated so as to
become insoluble but swellable in water at room temperature. Thus,
for example, the heat treated fibers of this invention may be used
in the uncompressed portions of sanitary napkins, diapers and other
absorbent products having both compressed and uncompressed portions
of these products, as well as in such products which are entirely
uncompressed. When so utilized, the heat treated fibers will
provide such products with improved fluid absorptive properties.
Stated in other words, an improvement in the absorptive properties
of absorbent products may be realized by incorporating the fibers
of this invention into bodies of absorbent fibers less dense than,
for example, the 90 to 215 grain per cubic inch densities typical
for catamenial tampons. The invention will be more clearly
understood by reference to the accompanying drawings taken together
with the detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
With reference to the accompanying drawings:
FIG. 1 is a perspective view of a sanitary napkin having an
uncompressed absorbent body incorporating the present invention and
partially cut away to reveal a representative inner
construction;
FIG. 2 is a cross-sectional view of the napkin of FIG. 1 taken
along line 2--2;
FIG. 3 is a schematic cross-sectional view of a partially
compressed absorbent body incorporating the present invention and
useful in a sanitary napkin such as that of FIG. 1;
FIG. 4 is a planar view of a single sheet of absorbent material
which may be folded to result in the absorbent body of FIG. 3;
and
FIG. 5 is a cross-sectional view of the sheet of absorbent material
shown in FIG. 4 and taken along line 5--5.
DETAILED DESCRIPTION OF THE INVENTION
The invention will be herein described with special emphasis on
carboxymethyl cellulose fibers as the fluid absorption and
retention material in a specific product; namely, a sanitary
napkin. It should be understood, however, that this is done for
illustrative purposes and that the broader aspects of the invention
are not to be construed as limited thereto but are to be considered
equally applicable to other articles of manufacture such as those
mentioned herein, as well as to fibers of other ethers of
cellulose, such as carboxyethyl cellulose, carboxymethyl
hydroxyethyl, or other cellulose ethers containing the carboxyalkyl
radical or, more precisely, as will be pointed out hereinafter, the
sodium salts thereof.
Referring now to FIGS. 1 and 2, there is shown a sanitary napkin 10
comprising an upper fluid absorption and retention pad 12 and a
lower fluid absorption and retention pad 14 between which is
positioned a sheet of fluid pervious tissue paper 16 provided to
control the flow of liquid between the pads. The upper face of the
napkin, i.e., the face used away from the body, is provided with a
fluid impervious barrier sheet 18, e.g., a sheet of polyethylene
film, to preclude body fluid from wetting this face, i.e., to
preclude fluid "strike through." As illustrated in the drawings,
the barrier sheet 18 may be extended to protect the sides of the
napkin as well. The entire construction is wrapped within an
extended cover 20 made of a non-woven fabric or of a woven fabric,
such as gauze, or even of a knitted fabric and, as is conventional,
the cover extends beyond the ends of the pads to form the usual
attachment tabs 21. Such structure is exemplary of a form of
sanitary napkin and is primarily employed to illustrate the
incorporation of the invention in a sanitary napkin. It must be
realized, however, that such structure is not limitative but is
merely illustrative of one form of a napkin incorporating the
present invention. For example, many napkins and other absorptive
pads are formed without the usual attachment tabs. In some cases,
the barrier sheet 18 or the tissue sheet 16 is dispensed with. In
other variations, more or less than two pads are used or the cover
20 does not completely enclose the pads and the barrier sheet 18 is
used to enclose the remaining portion. In any event, these
variations are all susceptible to improvement by the present
invention.
At least one of the pads 12 or 14 is comprised of fibers of this
invention and is in the essentially uncompressed state. That is to
say, unlike the absorbent bodies used in compressed catamenial
tampons wherein the density is generally in the range of about 90
grains per cubic inch or higher, the fibers in the absorbent body,
e.g., pad 12, of the illustrated sanitary napkin are in the
uncompressed state and are less than 90 grains per cubic inch.
Typical uncompressed densities of such pads are, for example, about
2.5 to about 25 grains per cubic inch and more generally are about
5 to about 13 grains per cubic inch.
Referring now to FIGS. 3-5, illustrated therein, is a second
embodiment of an absorbent body utilizing the fibers of this
invention and suitable as a substitute for one or both of the pads
12 or 14 illustrated in FIGS. 1 and 2. FIG. 3 depicts, in
schematical cross section, an absorbent body 22 folded, from the
single sheet of absorbent material 24 shown in FIGS. 4 and 5, to
create a three plied pad. The sheet 24 is shown as being divided
into three sections 26, 28 and 30, respectively, by indicia lines
X-X and Y-Y, said sections then corresponding to each of the three
plies in the folded pad shown in FIG. 3. Section 26 is provided
with transverse embossed portions 32 and section 28 is provided
with longitudinal embossed portions 34. These embossed portions
represent compressed areas of the absorbent material of sheet 24
and are useful, as is more fully described in U.S. Pat. No.
2,952,259 issued to Alfred A. Burgeni on Sept. 13, 1960, to control
the flow of fluid through the pad 22 and to provide the pad with
desirable structural stability and springiness. The pad 22 is thus
comprised of portions of both high and low density, the embossed
areas 26 and 28 having a density of the range of about 75 to about
126 grains per cubic inch and the unembossed areas such as
unembossed section 30 or side section 31 having densities of about
2.5 to about 13 grains per cubic inch. As specific examples herein
will more clearly show, the heat treated fibers of this invention,
when incorporated in an uncompressed body of fibers, such as, for
example, sections 30 and 31 of pad 22, will result in improved
fluid absorptive properties.
The absorbent fibers in the fluid absorption and retention bodies
12, 14 and 22 comprise fibrous carboxyalkyl cellulosic materials,
preferably carboxymethyl cellulose, which have been heat-treated,
modified, and improved by the methods of the present invention. The
carboxymethyl cellulose is in fibrous form, such as is described in
U.S. Pat. No. 3,005,456 issued on Oct. 24, 1961.
Although carboxymethyl cellulose is generally available
commercially in degrees of substitution up to only about 1.4,
methods are disclosed in the scientific literature for making
carboxymethyl cellulose in fibrous form from cotton linters in a
multi-stage carboxymethylation with degrees of substitution up to
2.50 and 2.77. Reference is made to Carbohydrate Chemistry, Vol.
III (Cellulose), (1963) pages 322-327 for a disclosure of such
methods.
The above literature reference describes the use of cotton linters
as the basic starting raw material for making carboxymethyl
cellulose. it is to be appreciated that other basic starting raw
materials, notably rayon fibers and wood pulp, can always be
used.
The idealized structural formula for carboxymethyl cellulose is as
follows, showing a degree of 1.0: ##SPC1##
The idealized structural formula for carboxyethyl cellulose is as
follows, showing a degree of substitution of 1.0: ##SPC2##
Carboxyethyl cellulose is obtained by basically the same mechanism
as is used for carboxymethyl cellulose except that
monochloropropionic acid and sodium hydroxide are used rather than
monochloroacetic acid and sodium hydroxide.
The structural formula for carboxymethyl hydroxyethyl cellulose is
as follows, showing a degree of substitution of 0.5 for
carboxymethyl and 0.5 for hydroxyethyl: ##SPC3##
Carboxymethyl hydroxyethyl cellulose is prepared by carrying out
the hydroxyethylation reaction first and then following with the
carboxymethylation reaction second.
Consideration of the above structural formulas will indicate that,
although the terms "carboxymethyl cellulose," "carboxyethyl
cellulose" and "carboxymethyl hydroxyethyl cellulose" are used
herein, a more precise but lengthier term should include a
reference to the fact that they are commercially available and are
normally used as the sodium salt of such chemical compounds. Other
alkali metal salts which are not as commercially available but
which are equally applicable are the potassium, lithium, rubidium
and cesium salts.
The fibers of carboxymethyl, cellulose are modified according to
the present invention by being heated at a temperature preferably
of from about 120.degree.C. (248.degree.F.) to about 270.degree.C.
(338.degree.F.) for a period of from about one hour to about 20
hours. The reaction is exothermic. Lower temperatures down to about
110.degree.C. (230.degree.F.) may be used but the duration of the
heat treatment must then be prolonged to about 30 hours or more
which is economically undesirable. In the same way, higher
temperatures of about 200.degree.C. (392.degree.F.) or even
approaching the browning temperature of about 226.degree.C.
(438.degree.F.) may be employed for durations of heat treatments of
only about 10 `or 15 minutes or even less but such is a more
delicate process, requiring much closer controls to avoid localized
overheating or other damaging influences.
Pressure may be employed during the heat treatment whereby the
temperature and time factors are decreased accordingly, as is well
known in the art.
The most notable change is that the carboxymethyl cellulose fibers,
subsequent to the heat treatment, become water-insoluble, and
although they do swell in water several hundred per cent, they do
so without developing the characteristic slippery feeling of
wetted, untreated carboxymethyl cellulose. Both the untreated and
heat-treated carboxymethyl cellulose fibers are soluble in six
percent sodium hydroxide solution. The browning temperature of the
heat-treated carboxymethyl cellulose fiber remains in the range of
about 226.degree.-228.degree.C. and the charring temperature also
is not materially changed from the original range of about
252.degree.-253.degree.C. for the untreated form. The specific
gravity of the heat-treated carboxymethyl cellulose is about 1.59
grams/milliliter.
The resulting heat-treated fibers, in the uncompressed state, when
treated with water at room temperature show tremendous water
absorption and retention, along with excellent swelling, but are
able to maintain their fibrous structural integrity. For example,
when a heat treated fibrous carboxymethyl cellulose sample having a
D.S. of 0.7 is used in the uncompressed state and treated with
water at room temperature, both the quantity of water held at
saturation and the quantity of water retained after water held in
the interfiber capillaries is removed are both substantially higher
than when an equivalent wood pulp sample is used. In contrast to
this result, equivalent samples utilizing untreated 0.7 D.S.
carboxymethyl cellulose fiber are soluble in water at room
temperature, lose their fibrous structure, and are entirely
unsuitable for use in an absorbent product as herein
contemplated.
Although the exact mechanism of the modification of the
carboxymethyl cellulose has not been completely proved beyond
doubt, it is believed that there is some degree of internal
esterification taking place between the carboxylic radicals of the
carboxyalkyl group and the remaining unreacted hydroxyl groups of
the main cellulose unit or anhydroglucose unit. As such, it may be
generally classified as a crosslinking, internal esterification
between adjacent chains of the repeating cellulose units or
anhydroglucose units.
The structural formula for a typical unit of such a crosslinked
internally esterified carboxymethyl cellulose (average D.S. = 1.0)
is believed to be as follows, with each anhydroglucose unit
illustrated being derived from separate chains. ##SPC4##
Not to be ignored, however, is the lesser possiblity that there is
an anhydride formation between adjacent carboxylic groups, leading
to a crosslinking condensation reaction between adjacent chains.
This however, is a less likely possiblity.
The invention will be described in greater detail by reference to
the following examples and tables wherein specific embodiments of
the invention are set forth for illustrative but not for limitative
purposes.
EXAMPLE I
Three parts of uncompressed absorbent cellulosic fibers are
prepared. The fibers of the first sample are southern pine,
bleached kraft wood pulp fibers such as are conventionally used in
absorbent products. The fibers of the second sample are
conventional, unmodified sodium carboxymethyl cellulose fibers
derived from wood pulp) having an average D.S. of 0.7. The fibers
of the third sample are the same sodium carboxymethyl cellulose
fibers having an average D.S. of 0.7 as those of the second sample
but are, in accordance with this invention, heat-treated in an oven
at 160.degree.C. for four hours and then conditioned at room
temperature and at a relative humidity of 50 percent for 18 hours.
The three samples are then saturated with a solution of ersatz
menstrual fluid by placing each of the samples in a beaker and
covering them with excess fluid. The excess fluid is then drained
off and the undissolved, saturated samples are weighed immediately
to determine the weight of fluid absorbed. Each undissolved sample
is then squeezed to remove fluid held in the interfiber capillaries
and then reweighed to determine the fluid retained. The results are
reported in Table I below.
TABLE I
__________________________________________________________________________
SATURATION RETENTION DRY DENSITY CAPACITY CAPACITY WEIGHT GRAIN/
(cc of fluid/ (cc of fluid/ SAMPLE GM. in.sup.3 gm of fibers) gm of
fibers)
__________________________________________________________________________
Wood Pulp 5 2.5 16 2 Unmodified Sodium Car- boxymethyl 5 2.5
soluble -- Cellulose Heat-treated Sodium Car- boxymethyl 5 2.5 45
18 Cellulose
__________________________________________________________________________
As is evident from Table I, the unmodified sodium carboxymethyl
cellulose fibers (Sample 2) are entirely unsuitable as a substitute
for the conventional absorbent wood pulp in that, these fibers,
having a D.S. of 0.7 are soluble in the ersatz menstrual fluid and
lose their fibrous structural integrity. In contrast thereto, the
heat-treated fibers of this invention (Sample 3) not only maintain
their fibrous structure but in fact significantly surpass the
absorbency and retention capacities of wood pulp.
EXAMPLE II
As in the previous examples, three pads of uncompressed absorbent
cellulose fibers are prepared; the first sample consisting of
southern pine bleached kraft wood pulp fibers, the second sample
consisting of conventional, unmodified sodium carboxymethyl
cellulose fibers derived from cotton and having an average D.S. of
0.7, and the third sample consisting of the same sodium
carboxymethyl cellulose fibers as used in the second sample,
however, these fibers being heat treated in an oven at
160.degree.C. for 4 hours and then conditioned, at room temperature
and at a relative humidity of 50 percent of 12 hours. The three
samples were then tester in a Porous Plate Testing Apparatus for
both maximum fluid capacity and for fluid retention. The Porous
Plate test is described in detail in (Textile Res. J., 37, 356-366,
1967). Briefly, this test involves placing the sample in what is
essentially a Buckner funnel having a porous bottom plate and
holding the sample in place by applying a standard weight thereto
to standardize the confining pressure. The porous plate is placed
in contact with a reservoir of fluid and the sample is allowed to
absorb fluid through the porous plate. The sample being essential
at the level of the reservoir, the fluid absorbed is subjected to
essentially a zero hydraulic level with respect to the reservoir.
The apparatus is provided with means for directly measuring the
volume of fluid absorbed from which the maximum capacity absorbed
is calculated. To determine fluid retention values, the saturated
sample is elevated with respect to the fluid reservoir, thereby
imposing a hydraulic head upon the fluid absorbed which, in the
case of the examples herein, is 36 inches of fluid The apparatus is
provided with means for directly measuring the volume of fluid
retained under this hydraulic head, from which the retention values
are calculated. Portions of each sample are tested in three
different water solutions of varying sodium chloride concentrations
representing the range of sodium chloride concentrations of body
fluids and exudates. The results are reported in Table II below.
Table II clearly indicates that, at the lower saline composition
there is a substantial difference in the total capacity and the
retention values of the heat-treated sample (Sample 3) of this
invention as compared to the conventional wood pulp fibers (Sample
1). As the saline concentration increases, the difference between
total capacity values diminishes, however, there is still a large
difference in the values obtained for retention. The unmodified
sodium carboxymethyl cellulose (Sample 2) is clearly unsuitable
because of its solubility in the test fluids. As the following
examples will serve to illustrate, the performance of the fibers in
an absorbent product, such as a sanitary napkin, is a complex
function of both the capacity and the retention.
TABLE II
__________________________________________________________________________
ABSORBENCY (CC FLUID/GM FIBERS)
__________________________________________________________________________
WATER 0.5% AQUEOUS Na Cl 1% AQUEOUS Na Cl DENSITY Maximum* Maximum*
Maximum* SAMPLE (grains/Ca in) Capacity Retention** Capacity
Retention** Capacity Retention
__________________________________________________________________________
1. Pulp 25 14 2 14 2 14 2 2. Unmodified Sodium Carboxymethyl
Cellulose 25 Soluble -- Soluble -- Soluble -- 3. Heat-Treated
Sodium Carboxymethyl Cellulose 25 33 20 16 10 15 9
__________________________________________________________________________
* Measured at zero hydraulic head and 1 gm/cm.sup.2 confining
pressure ** Measured at 36 inch hydraulic head and 1 gm/cm.sup.2
confining pressur
EXAMPLE III
Two sanitary napkins were prepared having the construction shown in
FIGS. 1 and 2 and utilizing a polyethylene barrier film and a
tissue insert. The pads of the first napkin both consisted of 100
percent southern pine, bleached kraft wood pulp fibers. The pads of
the second napkin both consisted of a uniformly distributed mixture
of southern pine, bleached kraft wood pulp fibers and sodium
carboxymethyl cellulose fibers (wood pulp derived) having a D.S. of
0.7 and having been heat treated in an oven at 160.degree.C. for 4
hours and then conditioned for 12 hours at room temperature and 50
percent relative humidity. The fibers are in a weight ratio of wood
pulp to heat-treated sodium methylcellulose of 90:10. Dynamic Form
tests are performed by suspending each of the sample napkins across
a rubber mold which simulates the female form. The form is set into
motion by means of a set of gears, cans and rods and an ersatz
menstrual fluid containing one percent NaCl, by weight, is allowed
to drip onto the napkin to simulate in-use conditions. The fluid is
applied at a rate of 0.2 c.c. per minute and the form is operated
at a speed of 60 cycles per minute. The fluid capacity of the
napkin under dynamic conditions is measured by the total volume of
fluid applied at the time of failure, i.e., the time at which
spotting is noted on the underside of the napkin. The results of
this test is shown in Table III.
TABLE III
__________________________________________________________________________
SAMPLE PAD FLUID CAPACITY AT FAILURE
__________________________________________________________________________
Weight Density Grains Grain/ cu.in.
__________________________________________________________________________
1. 100% Wood Pulp 200 10 12.2 2. 90:10 Wood Pulp: 200 10 20.5
Modified CMC
__________________________________________________________________________
EXAMPLE IV
Two sanitary napkins were prepared having the construction shown in
FIGS. 1 and 2 but substituting for the pads and tissue insert of
that construction, the embossed pad shown in FIGS. 3-5. The first
napkin pad consisted of 100 percent solution pine, bleached kraft
wood pulp fibers. In the second napkin pad, a portion of the
unembossed section 30 weighing 15 percent of the total weight of
the filler was removed and replaced by fibers of sodium
carboxymethyl cellulose having a D.S. of 0.7 and having been heat
treated in an oven at 160.degree.C. for four hours and then
conditioned at room temperature and 50 percent relative humidity
for twelve hours. In both napkins, the density of the unembossed
portions of the pad was approximately ten and the density of the
embossed portions was about 108 grains/cu. in.
The two napkins were tested for absorbency by utilizing a Burette
Drip Test and the Dynamic Form Test, the latter test being
described in the previous example. In the Burette Drip Test, the
napkin to be tested is placed on a glass plate attached to ring
stand and a 50 ml burette is positioned two inches above the napkin
so as to release fluid dropwise onto the center of that face of the
napkin normally used against the body. A mirror is placed below the
glass plate to allow observation of the opposite face. The quantity
of fluid released upon the napkin from the burette, at the time
that napkin failure is observed, is recorded as the total
absorbency. For this example, an ersatz menstrual fluid having a
one percent, by weight, sodium chloride concentration was allowed
to fall dropwise at a rate of 4 cc/min. The results of these tests
are tabulated in Table IV below.
TABLE IV ______________________________________ Total Absorbency
(cc) SAMPLE Burette Dynamic Drip Test Form Test
______________________________________ 1. 100% Wood Pulp 10.4*
10.7** 2. 15% Heat-Treated Na CMC 19.0* 23.6** 85% Wood Pulp
______________________________________ * Polyethylene Barrier Film
Removed ** Polyethylene Barrier Film Included
EXAMPLE V
Two sample napkins were prepared in accordance with Example IV,
with the exception, in that both samples, transverse embossing was
provided on that portion of the pad designated for FIG. 3 as
section 30 so that those portions embossed amounted to 15 percent
of the total weight of one filler and the density of the embossed
area was equal to 108 gr./cu. in. The unembossed area had a density
of 10 gr./cu. in. The napkins are tested using the Burette Drip
Test described above. The results are reported below in Table
V.
TABLE V ______________________________________ Napkin Total
Absorbency Burette Drip Test ______________________________________
1. 100% Wood Pulp 21.2 2 15% Heat-Treated Na CMC 39.2
______________________________________
EXAMPLE VI
Two sanitary napkins, identical to the first sample of the previous
example was prepared. A quantity of sodium carboxymethyl cellulose
fibers having a D.S. of 0.7 and heat-treated and conditioned as in
the previous examples, was added to the first sample. The sodium
carboxymethyl cellulose fibers were distributed on that portion of
the pad designated in FIG. 3 by the numeral 31. The density of this
section was 10 gr./cu. in. A quantity equivalent to five percent by
weight of the total pad weight was so distributed. In the second
napkin, a quantity of additional wood pulp equivalent to five
percent by weight was similarly distributed. The napkins were
treated for total absorbency, using the Dynamic Form Test described
above and using an ersatz menstrual fluid containing one percent Na
Cl.
TABLE VI ______________________________________ SAMPLE ABSORBENCY
(cc) DYNAMIC FORM TEST ______________________________________ 1.
100% Wood Pulp 11.9** 2. 5% Heat-Treated Na CMC 20.5** 95% Wood
Pulp ______________________________________ ** Polyethylene
Barrier
As the above examples indicate, the heat-treated carboxyalkyl
cellulose fibers of this invention may be used wherein or in
combination in the uncompressed state to improve the properties of
absorbent products. In blending the fibers of this invention with
other absorbent materials and fibers, a wide variety of such other
materials and fibers may be included in percentages as low as about
one percent by weight or as high as about 98 percent by weight,
with preferred ranges from about 5 to about 50. Such other fibers
may, for example, include cotton, rayon, wood pulp, comminuted
tissue or other paper, etc.
If desired, other materials and other fibers, not necessarily fluid
absorbent, may be added in similar percentages by weight (as noted
in the preceding paragraph) to obtain special characteristics and
properties. Such other materials and other fibers include, for
example, untreated carboxymethyl cellulose fibers, cellulose esters
such as cellulose acetate, polyamide fibers such as nylon 6, nylon
6/6, nylon 12, etc., polyester fibers scuh as "Dacron," "Kodel,"
etc., acrylic fibers such as "Dynel," "Orlon," etc.
Although the present invention has been described with several
examples and embodiments showing specific materials and specific
products in specific arrangements and conformations, such is not to
be considered limitative of the invention but merely illustrative
thereof.
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