U.S. patent number RE30,029 [Application Number 05/608,304] was granted by the patent office on 1979-06-12 for absorbent mass of alloy fibers of regenerated cellulose and polyacrylic acid salt of alkali-metals or ammonium.
This patent grant is currently assigned to Avtex Fibers Inc.. Invention is credited to Frederick R. Smith.
United States Patent |
RE30,029 |
Smith |
June 12, 1979 |
Absorbent mass of alloy fibers of regenerated cellulose and
polyacrylic acid salt of alkali-metals or ammonium
Abstract
A mass of alloy fibers of polyacrylic acid salt of alkali-metals
or ammonium and regenerated cellulose, useful for absorbing fluids,
are prepared by mixing a caustic solution of polyacrylic acid with
viscose, spinning the mixture into fibers and obtaining dry fibers
in the alkaline state. The fibers are advantageously dried with an
alkaline lubricating finish thereon and then processed into
dressings, sanitary napkins, tampons and diapers.
Inventors: |
Smith; Frederick R.
(Wilmington, DE) |
Assignee: |
Avtex Fibers Inc. (Valley
Forge, PA)
|
Family
ID: |
22987109 |
Appl.
No.: |
05/608,304 |
Filed: |
August 27, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
259944 |
Jun 5, 1972 |
03844287 |
Oct 29, 1974 |
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Current U.S.
Class: |
604/363; 523/303;
524/36; 525/54.23; 604/368; 604/371; 604/372; 604/375; 604/376;
604/904 |
Current CPC
Class: |
A61L
15/225 (20130101); A61L 15/50 (20130101); A61L
15/60 (20130101); D01D 1/02 (20130101); D01F
2/08 (20130101); D01F 6/52 (20130101); A61L
15/225 (20130101); C08L 33/02 (20130101); C08L
1/12 (20130101); A61L 15/225 (20130101); C08L
33/02 (20130101); Y10S 604/904 (20130101) |
Current International
Class: |
A61L
15/50 (20060101); A61L 15/16 (20060101); A61L
15/22 (20060101); A61L 15/60 (20060101); D01F
2/10 (20060101); D01F 2/00 (20060101); A61F
013/20 () |
Field of
Search: |
;260/17.4GC,17.4CL
;128/285,284,270,296,263 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Z Physik. Chem. A181, 249-282 (1938), Werner Kern. .
Annalen der Chemie, vol. 322, pp. 387-390, Wolff..
|
Primary Examiner: Woodberry; Edward M.
Attorney, Agent or Firm: Eglington; Arthur R.
Claims
I claim:
1. An article of manufacture comprising a highly fluid absorbent
mass of.Iadd.dry alkaline.Iaddend.alloy fibers.[.said alloy
fibers.]. comprising a matrix of regenerated cellulose and
polyacrylic acid salt of alkali-metals .[.or ammonium uniformly.].
dispersed therein,.Iadd. said salt being present in an amount
ranging from about 5 to about 35 percent, based on the weight of
the cellulose.Iaddend.. .[.2. The article of claim 1 wherein the
polyacrylic acid salt of alkali-metals or ammonium is present in
the regenerated cellulose in an amount ranging from about 5 to
about 35 percent, based on the weight of the cellulose..]. .[.3.
The article of claim 1 wherein the fibers have a lubricating finish
for
cellulose thereon..]. 4. The article of claim 1 in the form of a
pad. 5. The article of claim 1 in the form of a tampon. .Iadd.
thereon, 6. An article as in claim 3 wherein said lubricating
finish comprises a partial higher fatty acid ester of sorbitan or
mannitan or of a polyoxyethylene derivative thereof.
.Iaddend..Iadd. 7. An article as in claim 3 wherein said fibers are
carded staple fibers, said article comprising a compressed mass of
said staple fibers. .Iaddend. .Iadd. 8. An article as in claim 6,
said salt being such, and present in such proportion, that the
"fluid holding capacity" is at least 4.55 cc./g., said fluid
holding capacity being measured by taking two grams of said fiber
in staple form, carded or well opened, placing said two grams of
fiber in a 1 inch diameter die, pressing the fibers in the die to
0.127 inch thickness for one minute, removing the resulting pressed
test pellet, placing said pellet on a Buchner funnel with a 1 inch
diameter foot of a vertically movable plunger weighing 2.4 pounds
resting on said pellet, immersing said so-placed pellet in water
for two minutes and then draining the water for three minutes,
removing the resulting wet pellet and weighing it to determine the
amount of water held thereby. .Iaddend. .Iadd. 9. An article as in
claim 1 produced by a method comprising mixing a polyacrylic acid
salt of alkali-metals with a filament-forming viscose whereby the
viscose predominates in the mixture, forming the mixture into
fibers, coagulating and regenerating the fibers, applying a
lubricating finish for cellulose to said fibers, and drying the
fibers in an alkaline state with said polyacrylic acid salt in said
fiber in the form of a sodium salt, said method including the step
of cutting the fibers into staple form before drying, the
proportion of said polyacrylic acid salt added to said viscose
ranging from about 5 to about 35 percent, based on the weight of
the cellulose, said lubricating finish comprising a partial higher
fatty acid ester of sorbitan or mannitan or of a polyoxyethylene
derivative thereof, said sodium salt in said dried alkaline fibers
being such, and present in such proportion, that the "fluid holding
capacity" is at least 4.55 cc./g., said fluid holding capacity
being measured by taking two grams of said fiber in staple form,
carded or well opened, placing said two grams of fiber in a 1 inch
diameter die, pressing the fibers in the die to 0.127 inch
thickness for one minute, removing the resulting pressed test
pellet, placing said pellet on a Buchner funnel with a 1 inch
diameter foot of a vertically movable plunger weighing 2.4 pounds
resting on said pellet, immersing said so-placed pellet in water
for two minutes and then draining the water for three minutes;
removing the resulting wet pellet and weighing it to determine the
amount of water held thereby. .Iaddend. .Iadd. 10. An article as in
claim 8 in which said salt is a sodium salt. .Iaddend. .Iadd. 11. A
dry alkaline alloy fiber comprising a matrix of regenerated
cellulose and polyacrylic acid salt of alkali-metals, said fiber
having a lubricating finish for cellulose thereon, said salt being
such, and present in such proportion, within the range of about 5
to about 35 percent based on the weight of cellulose, that the
"fluid holding capacity" is at least 4.55 cc./g., said fluid
holding capacity being measured by taking two grams of said fiber
in staple form, carded or well opened, placing said two grams of
fiber in a 1 inch diameter die, pressing the fibers in the die to
0.127 inch thickness for one minute, removing the resulting pressed
test pellet, placing said pellet on a Buchner funnel with a 1 inch
diameter foot of a vertically movable plunger weighing 2.4 pounds
resting on said pellet, immersing said so-placed pellet in water
for two minutes and then draining the water for three minutes,
removing the resulting wet pellet and weighing it to determine the
amount of water held thereby. .Iaddend. .Iadd. 12. Fiber as in
claim 11, said fiber being in staple form and said alkali metal
being sodium and said salt being present in amount of at least 10%
based on weight of cellulose. .Iaddend. .Iadd. 13. Fiber produced
by a method comprising mixing a polyacrylic acid salt of
alkali-metals with a filament-forming viscose whereby the viscose
predominates in the mixture, forming the mixture into fibers,
coagulating and regenerating the fibers, applying a lubricating
finish for cellulose to said fibers, and drying the fibers in an
alkaline state with said polyacrylic acid salt in said fiber in the
form of a sodium salt, said method including the step of cutting
the fibers into staple form before drying, the proportion of said
polyacrylic acid salt added to said viscose ranging from about 5 to
about 35 percent, based on the weight of the cellulose, said sodium
salt in said dried alkaline fibers being such, and present in such
proportion, that the "fluid holding capacity" is at least 4.55
cc./g., said fluid holding capacity being measured by taking two
grams of said fiber in staple form, carded or well opened, placing
said two grams of fiber in a 1 inch diameter die, pressing the
fibers in the die to 0.127 inch thickness for one minute, removing
the resulting pressed test pellet, placing said pellet on a Buchner
funnel with a 1 inch diameter foot of a vertically movable plunger
weighing 2.4 pounds resting on said pellet, immersing said
so-placed pellet in water for two minutes and then draining the
water for three minutes, removing the resulting wet pellet and
weighing it to determine the amount of water held thereby.
.Iaddend.
Description
Alloy fibers consisting of sodium carboxymethyl cellulose and
regenerated cellulose have been used as absorbent fibers in
articles designed to absorb body fluids. While these alloy fibers
are quite useful for this purpose, they are relatively expensive.
The carboxymethyl cellulose-regenerated cellulose fiber is
difficult to dry down to cardable form from an aqueous system.
These fibers may be readily finished and dried by solvent exchange
but this adds considerably to the cost of manufacturing the
fibers.
It is an object of this invention to provide a highly fluid
absorbent mass of alloy fibers of sodium polyacrylate and
regenerated cellulose.
It is another object of this invention to provide a method of
preparing absorbent alloy fibers of sodium polyacrylate and
regenerated cellulose.
These and other objects are accomplished in accordance with this
invention which is an article of manufacture comprising a highly
fluid absorbent mass of alloy fibers, said fibers comprising a
matrix of regenerated cellulose and sodium polyacrylate uniformly
dispersed therein.
The alloy fibers are prepared by mixing an aqueous solution of
sodium polyacrylate or aqueous solution of sodium hydroxide and
polyacrylic acid with viscose at any stage of ripening, forming the
mixture into fibers, coagulating and regenerating the fibers, and
driving the fibers in the alkaline state. Advantageously, the
fibers are coagulated and regenerated in an acid bath, washed,
finished by application of an aqueous alkaline finish composition
for cellulose, and dried. These fibers are now alkaline and
cardable, and are prepared in a conventional manner into articles
for absorbing body fluids.Iadd. , such as pads.Iaddend..
Sodium polyacrylate solutions or polyacrylic acid emulsions are
readily commercially available and need not be described in detail.
The solutions which are mixed with the viscose preferably have
solids concentrations of from about 2.5 to about 13 percent. Sodium
hydroxide is added to polyacrylic acid emulsions to obtain the
sodium polyacrylate solutions.
The filament-forming viscose used herein is also well known and
need not be described in detail. In general, alkali cellulose is
reacted with carbon disulfide and the resulting sodium cellulose
xanthate is diluted with sodium hydroxide to produce the viscose
which is aged to spinning viscosity. Additives or modifiers may be
mixed with the viscose, if desired.
The alloy fiber which is formed predominantly from viscose is
coagulated and regenerated by known means and preferably in an acid
bath containing sulfuric acid and sodium sulfate. Zinc sulfate is
often incorporated in the bath as well as other coagulation
modifiers, as desired.
The sodium polyacrylate solution may be mixed with the viscose at
any stage of the viscose ripening. Conventionally, the sodium
polyacrylate solution is injected into the viscose stream of a
spinning machine by means of a metering pump. The amount of sodium
polyacrylate which is incorporated in the viscose ranges from about
5 to about 35 percent based on the weight of the cellulose in the
viscose. The cellulose in the viscose will preferably range from
about 6 to about 10 percent based on the weight of the viscose
solution.
After injection or mixing of the sodium polyacrylate into the
viscose, the mixture may be run through a blender or homogenizer to
assure a thorough mix, if desired. The mixture is then pumped to
the spinneret and extruded in the form of fibers into a coagulating
medium. After coagulation and at least partial regeneration, the
fibers are stretched, if desired, conventionally wet processed and
treated with an aqueous lubricating finish composition. The fibers
are then dried to an alkaline, cardable product.
In the preferred method of this invention, the sodium polyacrylate
containing viscose during processing into fibers is alternately in
the alkaline state, the neutralized state and the alkaline state.
During passage of the viscose solution through the acid coagulating
and regenerating bath, the sodium polyacrylate is neutralized. In
order to obtain fibers containing sodium polyacrylate as required
by the invention, the wet gel fibers are made alkaline preferably
in the finish bath. An alkaline bath preceding the finish bath may
also be used, if desired.
The aqueous alkaline lubricating finish is preferably a bath
containing an aqueous solution of sodium carbonate and sorbitan
monolaurate, however, other alkaline agents and lubricating agents
may be employed as taught in the art for ordinary rayon yarn. Some
examples of finishes for cellulose fibers include partial higher
fatty acid esters of sorbitan or mannitan and their polyoxyethylene
derivatives, sodium oleate and oleic acid. Some examples of
alkaline agents for alkalizing the fibers include dibasic ammonium
phosphate, dibasic sodium phosphate, tribasic sodium phosphate,
sodium tetraborate and the like.
The fiber is usually cut in the form of staple before drying, dried
and shipped to the manufacturer of the absorbent articles. The
absorbent articles may require carding of the fibers which is
accomplished in the usual manner without difficulty.
In tampon application, the fibers are formed into the tampon in
accordance with any desired procedure. They may be blended with any
other fibers which may or may not serve to enhance the properties
of the absorbent articles. Some fibers with which the alloy fibers
of this invention may be blended include rayon, cotton, chemically
modified rayon or cotton, cellulose acetate, nylon, polyester,
acrylic, polyolefin and similar fibers.
The fluid holding capacity of the alloy fibers in this invention
was determined in accordance with the following procedure.
Sample staple fibers are carded or well opened, conditioned and two
grams placed in a 1 inch diameter die. The fibers in the die are
then pressed to 0.127 inches thickness for one minute, removed and
placed on a porous plate (e.g., a Buchner funnel) so that the 1
inch diameter foot of a plunger weighing 2.4 pounds rests on the
test pellet. (The plunger is held in a vertical position and is
free to move vertically). The pellet is then wetted with water
which flows into the funnel from the stem which is connected by a
flexible tube to a dropping bottle, the flow of water being
controlled by the position of the dropping bottle. After two
minutes immersion, the water is drained for three minutes, the wet
pellet is removed and weighed. The fluid holding capacity of the
fibers in cc./g. is one-half the weight of water in the test
pellet.
To demonstrate this invention, the following example is set
forth.
Example
A sodium polyacrylate solution (12.5 ) percent solids having 10,000
to 20,000 cps. viscosity) was injected through a metering pump into
the viscose stream of a spinning machine. The viscose composition
was 9.0 percent cellulose, 6.0 percent sodium hydroxide and 32
percent carbon disulfide, based on the weight of the cellulose. The
viscose ball fall was 70 and its common salt test was 8.
The mixture was spun through a 720 hole spinneret into an aqueous
spinning bath consisting of 7.5 percent by weight of sulfuric acid,
18 percent by weight of sodium sulfate and 3.5 percent by weight of
zinc sulfate. The alloy fibers passed through the bath and were
washed with water, desulfurized and washed again with water. The
wet gel fibers were then passed through an alkaline finish bath
consisting of 1 percent by weight of sodium carbonate and 1 percent
by weight of sorbitan monolaurate (Span 20). The fibers were cut,
dried and carded. The fluid holding capacity was tested for fibers
having different amounts of sodium polyacrylate in the alloy fibers
in the previously described test procedure. The results are set
forth in the following table along with results for other fibers
prepared as above except that these alloy fibers were prepared with
polyacrylic acid without the formation of the sodium salt in the
dried fiber product.
Table ______________________________________ Sodium polyacrylate, %
B.O.C.* 0 10 20 Fluid held, cc./g. 2.75 4.55 6.05 Polyacrylic acid,
% B.O.C.* 0 10 20 Fluid held, cc./g. 2.50 3.25 3.85
______________________________________ *B.O.C. - Based on the
weight of the cellulose in the alloy fiber.
From the above data, it is seen that the absorbent mass of alloy
fibers, as disclosed herein, has good fluid holding capacity and
the sodium salt is necessary to provide distinctly better fluid
holding results.
While this invention has been described in terms of sodium
polyacrylate, polyacrylate salts of other alkali-metals such as
potassium and lithium, and ammonium are also included and may be
successfully used to replace sodium polyacrylate in the
example.
Various changes and modifications may be made in practicing the
invention without departing from the spirit and scope thereof and,
therefore, the invention is not to be limited except as defined in
the appended claims.
* * * * *