Note: Descriptions are shown in the official language in which they were submitted.
The present invention is directed to alloy fibers ~ -
having high fluid-holding capacity. -
Fluid-holding capacity of fibers may be measured by
the pellet test described in Example I below or the Syngyna test
referred in Example III below. These tests use a predetermined
mass o~ fibers maintained under external pressure and indicate the
amount of water absorbed by the fibers themselves as well as the
amount of water retained within the interstices of the mass,
One aspect of this invention relates to absorbent alloy
fibers, each having a matrix of regenerated cellulose and poly-
vinylpyrrolidone uniformly dispersed therein, with the regenerated
cellulose being the major portion of the fiber mass. These alloy
fibers may be prepared by mixing an aqueous solution of polyvinyl-
pyrrolidone with a filament-forming viscose, shaping the mixture
into fibers, coagulating and regenerating the shaped fibers and
thereafter drying the same, Viscose constitutes the major portion
of the mixture and the shaped alloy fibers are coagulated and
regenerated by known means, and preferably in an acid bath con-
taining sulfuric acid and sodium sulfate, The acid bath often
contains zinc sulfate as well as other coagulation modifiers as
desired.
The present invention provides alloy rayon fibers of
higher fluid-holding capacity than non-alloy rayon, which comprises
a regenerated cellulose matrix and a water-soluble polymer dis-
persed therein--in an amount sufficient to increase the fluid-
holding capacity by more than 20%, the water-soluble polymer com-
prising an N-vinyl amide polymer.
The present invention also provides a process for making
alloy rayon fibers, of higher fluid-holding capacity than non-alloy
rayon, comprising a regenerated cellulose matrix and a water-
soluble polymer dispersed therein in an amount sufficient to in-
crease the fluid-holding capacity by more than 20%, the water-
866
soluble polymer comprising an N-vinyl amide polymer, the process
comprising spinning into an aqueous coagulating bath consisting
essent:ially of H2S04, Na2S04 and ZnS04 a blend of viscose and
the water-soluble polymer to form fibers, the proportions of the
dispersed polymer being at least about 7% of the total,
Duri~g the spinning of the viscose into the acid bath,
hydrogen ions diffuse into the stream of viscose emerging from
each spinnerette hole, The reaction of the acid with caustic soda : - -
in the viscose produces sodium sulfate and water; the acid also
decomposes xanthate groups. The presence of sodium sulfate in
the spin bath - - :
; ~ '
.. ~ r
-la-
~82~66
ZlCtS to induce coagulation of the viscose stream~ owing
l:o dehydration from the interiors of the streams. zinc
Lons in the ~pin bath act, at least at the surfaces of
the streams, to convert sodium cellulose xanthate of the
viscose to zinc cellulose xanthate which is decomposed
more slowly by the acid and thereby keeps the fiber in
more stretchable and orientable condition. Typically
the temperature of the acid bath is in the range of about
30 to 6~C (such as about 50-55C) and the fiber, after
passing through the acid bath is subjected to a bath of
water (or dilute acid) first at a high temperature such
as about 80C to the boiling point, e.g. about 85-95C,
and/or to steam, and then to water at a moderate tempera-
ture such as about 35 or 45 to 65C. Ir. the high tempera-
ture aqueous treatment the fibers may be subjected to
stretching, e.g. by about 50-75%. While for most uses
the fibers need not have high strength properties, the
alloy fibers have been found to retain to a large extent
the physical properties of non-alloy rayon, for instance,
using spinning and treatment conditions which gave a non-
alloy control having a dry (conditioned) tenacity of
about 2.9 g/d, dry elongation of about 20%, a dry modulus
of about 72 g/d, a wet tenacity of about 1.6, a wet
elongation of about 30~0, and a wet modulus of 4.8 g/d,
an alloy fiber (made from a spinning solution in which
the ratio of cellulose to polyvinylpyrrolidone was about
69:31) showed a dry tenacity of about 2.4 g/d, a dry
elongation of about 17%, a dry modulus of about 66 g/d,
a wet tenacity of about 1 g/d, a wet elongation of about
27%, and a wet modulus of about 4.1 g/d. With lower
-- 2
1082~6~; .
~proportions of polyvinylpyrrolidone these physical
properties are closer to those of the non-alloy fibers.
Typically, the alloy ibers of this invention are not
brittle and can be carded under conditions that cause
fiber breakdown of more brittle (e.g. cross-linked)
fibers. Also they swell to a greater degree in water
than the non-alloy rayon fibers.
The viscose which is employed in making the alloy
fibers of the present invention i9 desirably of a compo-
sition as is used in making conventional-regenerated
cellulose fibers, e.g. a viscose produced by reacting
alkali cellulose with carbon disulfide, with the resulting
sodium cellulo~e xanthate being diluted with aqueous
caustic to provide the resulting viscose with a desired
cellulose and alkali content. For example, the viscose
composition may contain cellulose ranging from 3 to
about 12 wt. percent (e.g. 6 to 10%), caustic from about 3
to 12 wt. percent, and carbon disulfide, based on the
weight of cellulose from about 20 to about 60%. Additives
or modifiers may be mixed in the viscose if desired.
The polyvinylpyrrolidone preferably has a high
molecular weight, such as well above 10,000. Very good
results have been attained with polyvinylpyrrolidone of
average molecular weight ranging from 100,000 to 400,000
and, more desirably, from 160~000 to 360,000, and a
preferred K-value of from 50 to 100. The procedure for
determining the K-value of such polymers is known in the
art, as disclosed in Modern Plastics, 1945, No. 3,
starting on Page 157. Polyvinylpyrrolidone of desired
character is commercially available, for example, under
- 3 -
.. . . . .
i~8~866
the designation of K~60 and K-90 from GAF Corporation.
Polyvinylpyrrolidone is described in Encyclopedia of
Polymer Science and Technology, published in 1971 by John
Wiley & Sons, in the article on "N-Vinyl Amide Polymers"
in Volume 14 pages 239-251.
The polyvinylpyrrolidone may be the sole high poly-
meric additive in the viscose or it may be used together
with other water-soluble (including aqueous alkali-
~oluble) high polymers. Preferably these are anionic
10 polymers such as polymeric acids or salts (e.g. alkali
metal salts) thereof, e.g. salts of carboxyalkyl cellu-
loses (such as sodium carboxymethyl or carboxyethyl
cellulose), salts of polyacrylic acids, (including
polyacrylic acid or polymethacrylic acid homopolymer, or
copolymers of acrylic and/or methacrylic acid with one or
more other monomers such as acrylamide or alkyl acrylates,
e.g. ethyl acrylate), salts of copolymers of maleic or
itaconic acid with other monomers such as methyl vinyl
ether, or naturally occurring polycarboxylic polymers,
such as algin. These materials are preferably dissolved
in aqueous medium before addition to the viscose, the
solution being preferably alkaLine, e.g., they may be
made with an amount of alkali, such as NaOH, stoichio-
metrically equivalent to the amount of acidic (e.g.
carboxyl) groups of the polymer or with an excess of
alkali. Less desirably, these materials may be added in
acid form (again preferably as aqueous solutions) and
be converted to salt form by the action of the alkali
present in the viscose. The anionic polymers may be
those disclosed in the art as forming complexes with
-- 4 --
1(~82~66
. . .. .
polyvinylpyrrolidone; see United States Patent
Mo. 2,901,457. Other water-soluble high polymers include
~ubstantially non-ionic polymers such as starch (which
may be added as, say an alkaline solution containing
some 2-5% of NaOH) or polyvinyl alcohol.
The proportion of polymer added to the viscose should
be such a~ to impart improved fluid holding capacity to
the rayon. Preferably it is such as to produce fibers
whose fluid holding capacity (as measured by the "Syngyna"
test described in Example III below) is at least 5 cc
per gram and more, preferabl~ at least 5.5 cc per gram.
As will be seen below, the practice of this invention has
made it possible to attain fluid holding capacities which
are well above 6 cc per gram and even above ~.5 cc per
gram. ~he fluid holding capacities at~ ined in prefer-
red forms of the invention are more than 20h better than ~-
those of fibers spun and processed under the same condi-
tions but in the absence of the added polymer material;
as can be seen from the Examples below this improvement
is often greater than 25%, such as about 30, 40, 50, 60
or even 70h. In general the total proportion of added
polyvinylpyrrolidone, alone or together with the anionic
polymer, is within the range of about 6 to 400/O based on
the weight of cellulose in the visco~e, and more
desirably in the range of about 10 or 20 to 35%, based
on the weight of cellulose. As shown below, higher
proportions, e.g. about 50 or 70% may also be used.
Expressed in terms of the total of cellulose and added
polymer (hereinafter termed "the total") the proportion
of added polymer is generally in the range of about 7
-- 5 --
1l)82866
t:o 30% such as about 10, 15 or 200/oJ although higher
~roportions may be employed. The proportion of poly-
vinylpyrroli~one, when used in combination with anionic
polymer, is advantageously above 1% of the total,
preferably above about 2 or 3% of the total such as
about 5% or more of the total. In one preferred form
the weight ratio of polyvinylpyrrolidone to anionic
polymer i8 at least about 10:90, such as about 20:80,
30:70, 50:50, 70:30 or 80:20.
The polyvinylpyrrolidone described exhibits good
colubility in water and a~ueous solutions of polyvinyl-
pyrrolidone, with or without added polymer, may be
incorporated into the visco~e at any stage, then blended
and pumped to spinneret~ for extrusion. After the
spinning, coagulation, and regeneration stages, the
shaped continuous tow of filament~ undergoes the usual
processing, which may include stretching if desired, and
is then dried by conventional means. Generally, before
drying, the continuous tow of filaments is cut into a
staple of a desired length. By the practice of the in-
vention one can prepare alloy fibers of high fluid holding
capacity which do not bond togethar during drying, even
in the absence of applied finish, and can be sub~equently
carded with no difficulty by the manufacturer of articles
incorporating such fibers. To aid in proce3sing one may
apply a lubricating finish, preferably of the hydro-
philic type, e.g. a non-ionic finish such as a Span or
Tween (partial higher fatty acid, e.g. lauric, ester of
sorbitan or mannitan or a polyoxyethylene derivative
thereof) e.g. ~pan 20 or Tween 20. Such finish may be
/f%~Je f~qrk~
- .
108;2866
applied as a dilute a~ueous dispersion thereof before
tlrying. One may also treat the fibers with alkaline
~301utions to increase the pH of the dried fiber; treat-
ments with alkaline ~olutions are described in some of
the Examples and the alkali solution may be blended with
the finish. The drying may be effected in any suitable
manner, preferably by evaporating off the water by heat,
e.g. in a hot air oven at moderate temperature (such as
about 70C) or a microwave oven. Typically drying is
effected to such degree as to bring the moisture content
of the fibers to about 8 to 200/o~ such as about 10-13%.
The alloy fibers of the present invention are adapted
for use in a variety of articles, such as sanitary
menstrual napkins and vaginal tampons, in which high fluid
retention is an essential characteristic. In the manufac-
ture of such articles, the alloy fibers necessitate no
special technique~ or equipment and they may be blended
with other fibers which may or may not enhance the
absorbent properties of the resulting articles. Fibers
with which the alloy fibers of the present invention may
be blended include, for example, rayon, cotton, chemical-
ly modified rayon or cotton, cellulose acetate, nylon,
polyester, acrylic, polyolefin, etc. Typically a tampon
is an elongated cylindrical mass of compressed fibers,
supplied within a tube which serves as an applicator;
see United States Patent~ Nos. 2,024,218; 2,587,717;
3,005,456; 3,051,177.
The following examples illustrate the invention
further.
1~82866
EXAMPLE I
Using conventional rayon spinning equipment, aqueous
Flolutlons of polyvinylpyrrolidone, designated as K-60 (GAF
C'orporation) and having an average molecular weight of
about 160,000 and K-value of 50-62~ were separately injec-
ted by a metering pump into a viscose stream during its
passage thro~gh a blender and the blend thereafter extru-
ded. During this blending, the blend was sub~ected to
high mechanical shearing. The viscose composition was
9.0% cellulose, 6~0% sodium hydroxide and 32% (based upon
the weight of the cellulose) carbon disulfide. The viscose
ball fall was 56 and its common salt test was 7.
The mixtures of viscose and polyvinylpyrrolidone
were extruded through a 720 hole spinneret into an
aqueous spinning bath consisting of 7. 5% by weight of
sulfuric acid, 18% by weight of sodium sulfate, and 3.5%
by weight of zinc sulfate. After passage through the
spinning bath, the resulting continuous tow was washed
with water, desulfurized with an aqueous solution of
sodium hydrosulfide, washed with water, acidified with
an aqueous HCl solution, and again washed with water.
The still wet multifilament tow was cut into staple
fiberx and, without any further treatment, dried.
The fluid-holding capacity of sample fibers, mads
with various approximate proportions (tabulated below~ :.
of cellulose and polyvinylpyrrolidone in the spinning :
solution, was determined using the following test
procedure.
Sample staple fibers were carded or otherwise well
opened and then conditioned at 75F and 58% relative
~ 8 ~
.
.
1~8Z86~
humidity. Two grams of such alloy fiber~ were placed in
one-inch diameter die, pressed to a thickness of 0.127
inch, and maintained in this condition for one minute.
This compressed pellet of fibers was removed from the
die and placed on a p~rous plate of a Buchner funnel~
The upper surface of the pellet wa~ then engaged with a
plunger which was mounted for free vertical movement,
the plunger having a diameter of one inch and a weight
of 2.4 pounds.
The funnel stem was connected by a flexible hose to
a dropping bottle from wh~ch water was introduced into
the funnel to wet the pellet of fibers. control over the
water flow was exercised by the position of the dropping
bottle. After an immorsion period of two minutes, the
water was permitted to drain from the fiber pellet for
three minutes, after which the still wet pellet wa3
removed from the funnel and weighed. One-half of the
weight of water in the sample pellet is a measure of
the fluid-holding capacity of the fibers, expressed in
cc/g.
The test results of ~ample fibers, as described
above, were as follows:
_ 9 _
.
108Z866
FLUID-HOLDING
POLYVINYL- CAPACITY % W~TER
SAMPLE CELLULOSE PYRROLIDONE cc/q RE~ENTION
A 100 0 3.06 105
B 95 5 3.16 112
C 90 10 3.52 121
D 80 20 4.15 145
E 70 30 4.69 186
F 65 35 4.68 178
G 60 40 4.65 190
fiWATER RETENTION is the percent water retained by the
loose mass of fibers after centrifuging the same at 1
G for 3.5 minutes.
EXAMPLE II
A 20~o aqueous solution of polyvinylpyrrolidone,
designated a~ K-90 (GAF Corporation) and having an
average molecular weight of 360,000 and a K-value
of 80-100 ~ was injected into a viscose having a
composition as de~cribed in Example I, after which
the mixture was extruded a-~ a continuous tow and
processed as described above. The relative propor-
tions of cellulose and polyvinylpyrrolidone in the
spinning solution were 83:17. The resulting fibers
had a fluid-holding capacity (tested as in Ex. I)
which was 28% higher than conventional regenerated
cellulose fibers.
EXAMPLE III
Aqueous solutions of polyvinylpyrrolidone, desig-
nated as K-90 (GAF Corporation) and having an average
molecular weight of about 160,000 and K-value of 80-100,
-- 10 - ,
i
~08Z866 : ~
were ~eparately injected into a viscose having a compo-
13ition as de~cribed in Example I. In a manner a~
described in Example I, the mixtures of vi~cose and
polyvinylpyrrolidone were shaped into a tow, treated
~ ,2~ -
with an aqueous solution containing 1.0% Span ~e and
then cut into staple fibers.
Two and one-half grams of the different fibers pre-
pared as described above were separately made into
tampons by the following procedure: The fibers were
carded into webs, each having a length of about 6 inches
and being of variable thickness and width. Each of
these webs wa~ individually rolled in the direction of
it3 width to provide a six inch roll and a string was
looped about the center thereof. Each such roll was
then folded on itself at the string loop and drawn into
a l/2 inch tube within which it was compressed by a
clamp and plunger. After compression, the resulting
tampons were removed, allowed to stand for a period of
about 30 minutes during which the tampons recovered to a
bulk density of about 0.4 g/cc. and were then evaluated
for their capacity to hold water by the Syngyna Method,
a~ described by G.W. Rapp in a June 1958 publication of
the Department of Research, Loyola University, Chicago,
Illinois. The results of such test were as follows,
for fibers made with various approximate proportions
(tabulated below) of cellulose and polyvinylpyrrolidone
in the spinning solution:
-h ~e~ tJ ~r~,/e ~4rk
-- 11 --
1~8ZB66
FLUID-HOLDING
POLYVINYL- CAPACITY
~SAMP~E CEL~UIOSE PYRROLIDONE cc/g
~ 100 0 4.36
R 90 10 4 . 84
L 85 15 5 . 3 8
M 80 2 0 5 . 46
N 75 25 5.65
~XAMPL~ IV
A conventional, non-derivatized viscose, an
aqueous solution of polyvinylpyrrolidone and a carboxy-
ethyl cellulose (specifically a cyanoethylated viscose)
were prepared separately, The compositon of the non-
derivatized vi~cose wa~ 9.0% rayon cellulose, 6~0%
sodium hydroxide and 32% carbon di~ulfide, ba~ed on the
weight of the cellulose. This viscose had a ball fall
of 56 seconds and its common salt test was 7.
The aqueous solution of polyvinylpyrrolidone was
prepared simply by dissolving, in water, polyvinyl-
pyrrolidone K-60.
Cyanoethylated viscose was prepared by premixing 8.25
lbs. of carbon disulfide and 10. 75 lbs. acrylonitrile
(34% and 45%~ respectively, based on the weight of the
cellulose), with the mixture then being charged into an
evacuated churn by gravity through a valved stainles~
steel line. The churn contained a 77 lb. batch of alkali
cellulose crumbs and was kept at a temperature of 15
to 32 C during a two hour reaction or churning period.
Sufficient water and caustic were added to the churn
after the two hour reaction period to provide a viscose
~ 12 --
' ' '
~082866
of 8.0% cellulose and 6.0% ~odium hydroxide (caustic)
ba~ed on the weight of the viscose, and 34% carbon
cli~ulide and 45% acrylonitrile based upon the weight
of the cellulose, after mixing in the churn for an
additional one and three quarter hours. The resulting
cyanoethylated viscose had a common salt test of 17-21
and a ball fall of 40-50 seconds. Its content of
cellulose derivative recoverable on spinning into, or
precipitation by, a sulfuric acid spin bath was about
90/0; tnis 9% value was used to calculate the proportions
of such cellulo~e derivative (termed "CEC", for carboxy-
ethyl-cellulose) in the table below.
Using conventional spinning equipment, the alloy-
ing materials were injected into the non-derivatized
vi~cose as hereafter set forth, with the resulting
mixture being extruded through a 720 hole spinneret into
an aqueous spinning bath consisting of 7 . 5% by weight of
sulfuric acid, 1~3% by weight of sodium sulfate, and 3.5%
by weight of zinc sulfate. After passage through the
spinning bath, the resulting continuous tow was wa~hed
with water, desulfurized, acidified, and again washed
with water in a manner as described in Example I. The
still wet tow was cut into staple fibers which were
treated with an aqueous solution containing 0.5% Span 20,
dried, carded and then conditioned at 75F and 58%
relative humidity.
The fluid-holding capacity of sample unalloyed
fibers and fibers containing the alloying components
individually and in combination was determined using
the test procedure described in Example I. The
~ id ~e ~ 13 ~
108Z8~6
approximate proportions in the spinning solutions u~ed
for the unalloyed and alloyed fibers and the results of
~uch test~ were as follow~:
POLYVINYI.- FLUID-HOIil)ING
SAMPLE CELLUIOSE CEC PYRROLIDONE CAPACITIES cc/q.
A 100 0 0 3.06: 3.07; 3.14; 3.16
B 90 10 0 2.50; 2.55
C 80 20 0 2.95;3.3
D 60 40 0 3.35; 3.5
E 90 0 10 3.52, 3.53
F 70 0 30 4.68; 4.70 -
G 75 12.5 12.5 5.03; 5.04
H 65 17.5 17.5 5.37; 5.39
It will be noted that conventional rayon fibers
(Sample A), as produced from non-derivatized visco~e,
exhibit fluid-holding capacities which are lesq than
those of alloy fibers produced from a mixture of con-
ventional vi~cose and polyvinylpyrrolidone (Samples E
and F) and that the fluid-holding capacities of fibers :
comprised of non-derivatized regenerated cellulose al~
loyed with regenerated cyanoethyl cellulose increase
directly with the regenerated cyanoethyl cellulose
content (Samples B, C and D). Significantly, notwith-
standing the detrimental effects produced when the lower
amounts of cyanoethylated viscose are employed alone as
alloying agents, as illustrated by Samples B and C, such
derivatized viscose, when combined with polyvinylpyr-
rolidone, does provide for a synergism, as exhibited by
the remarkably improved fluid-holding capacities of the
three-component alloy fibers indicated as Samples G
-- 14 --
.
:
1082866
and H.
q~he terminology "cyanoethylated viscose" as used
herein refers to a viscose to which acrylonitrile i8
added or viscose prepared by the simultaneous cyanoethy-
lation and xanthation of alkali cellulose. The latter
procedure i9 preferred from the standpoint of economy and
is described in United States Patents Nos. 3,143,116 to
A.I. Bates and 3,525,733 to I.K. Miller. Regeneration
of such cyanoethylated viscose is accomplished by use of
a conventional acidic type coagulating and regenerating
bath, as described above. Hydrolysis of the cyanoethyl
group on the cellulose during aging and processing pro-
duces predominantly carboxyethyl substituent groups on
the cellulose in place of the cyanoethyl groups in the
resulting regenerated product. The term "regenorated
cyanoethyl cellulose" as employed herein refers to a
regenerated product as produced by the cyanoethylated
viscose described.
Reference to the average degree of substitution
(D.S.) of the cyanoethyl cellulose as used herein in-
cludes products wherein the anhydroglucose units of the
cellulose molecules have an average substitution from
about 0.25 to about 0.65 of cyanoethyl groups or
chemical groups derived from said cyanoethyl groups by
hydrolysis or other chemical change which occurs during
manufacture and aging of the material. Thus, the
recitation of cyanoethyl cellulose is also meant to
include cellulose having carboxyethyl groups and some
amidoethyl substituent groups.
- 15 -
-
082866
EXAMPLE v
Example I was repeatedJ but instead of injecting
the polyvinylpyrrolidone alone there was injected a
blend of equal volumes of a ~h solution of the poly-
~inylpyrrolidone in water with a ~/0 solution of sodium
carboxymethyl cellulose ("CMC") (Hercules grade 7 MF :-~
in 6% NaOH, D.S. of 0.7). Various amounts of thi~ blend ~:
were used, specifically the proportions of cellulose;
polyvinylpyrrolidone, and carboxymethylcellulose were
varied as follaws: 100:00; 95:2 1/2: 2 1/2; 90:5:5;
85:7 1/2: 7 1/2; 80:10:10. A portion of the resulting
fibers was finished with a 1/2% water aolution of
Span 20 (sorbitan monolaurate~; and then dried; a
second portion was made somewhat alkaline by washing
in 1% aqueous solution of ~odium bicarbonateJ then
rinsed in water before finishing with the 1/2% Spa ~20
solution and drying. The presence of the additive gave
improved fluid holding capacity (measured by the Syngyna
test as in Example III above); for instanceJ the
80:10:10 blend treated with sodium bicarbonate gave a
fluid holding capacity well above 6 cc/g.
EX~MPLE VI
Example I was repeatedJ but instead of injecting
polyvinylpyrrolidone ("PVP") alone there was injected
a blend of about 450 parts of a 6.7% aqueous solution of
the polyvinylpyrrolidone K-90 and 550 parts of a 5.5%
aqueous alkaline solution of polyacrylic acid ("PAA").
The latter was made by diluting 120 gxams of Rohm &
Haas "Acrysol A-5" (a 25% aqueous solution of a poly-
acxylic acid) with 338 ml of water, then adding a
r~ rks 16
.
108Z866
13toichiometric amount of alkali, namely 92 grams of 18%
aqueou~ Na0~ solution. The K-90 solution was then
added to the polyacrylate solution with stirring and the
resulting blend was a clear solution containing about 3%
of each of the polymers. Various amounts of the blend
were used; specifically the proportions of cellulose;
polyvinylpyrrolidone; polyacrylic acid; were varied a~
follows: 100:00: 95:2 1/2: 2 1/2, 90:5:5, 85:7 1/2:
7 1/2: 80:10:10. A portion of the resulting fiber~ was
finished with a 1/2% water solution of Span 20 and then
dried. A second portion was made somewhat alkaline by
washing in a 1% aqueous solution of sodium bicarbonate,
then rin~ed in water before finishing with the 1/2%
Span 20 solution and drying. The presence of the addi-
tives gave improved fluid holding capacity (measured by
the Syngyna test as in Example 3 above); for instance,
the 90:5:5; 85:7 1/2: 7 1/2; and 80:10:10 blends each
gave a fluid holding capacity well above 6 cc/g.
When the polyacrylic acid was only partially neutra-
lized (e.g. neutralized with only 70% of the stoichio-
metric proportion of ~aOH) before blending with the
polyvinylpyrrolidone the improvement was not as marked.
Thus with 85 parts cellulose, 7 1/2 parts PVP, 7 1/2
parts PAA (or 10 PVP and 5 PAA; or 5 PVP and 10 PAA the
fluid holding capacity was about 20-25% better than the
control (100 cellulose) when such partially neutralized
PAA was used. It is therefore preferred that the amount
of alkali present in the system be at least equal to or
greater (e.g. 20-30% greater) than the amount necessary
to neutralize all the acidic groups of the added
~¢~ c/e ~7~4 - 17
~082866
anionic polymers.
EXAMPLE VII
Example I was repeated except that the solution injected
was prepared as follows: A carboxyethyl starch ("CES")
solution containing 9/0 starch was prepared (see Ex. 1 of ~ -
U.S. 3,847,636) with enough acrylonitrile added to give a
degree of substitution of 0.7. To a volume of this solu-
tion was added an equal volume of 9% aqueous solution of
PVP K-60. The resulting blend of polymer solution~ (as
tabulated below) was used for injection into viscose and --
subsequent spinning of fibers. The fibers were processed
as described in Example I. To one portion a 1/2% Spa~20
was
finish solution/applied and then the fibers were dried.
A second portion was immersed in 1% aqueous NaHC03, then
in 1/2% Span~20 and dried.
The evaluation for fluid holding by the Syngyna
test gave the following results.
FLUID HOLDING CAPACITY
CES (EXPRESSED WITHOUT WI~H
IN TERMS OF NaHC03 NaHC03 --
SAMPLE CELLULOSE STARCH CONTENT PVP TREATMENT T~EATMENT
A 100 0 0 4.3 4.0
B 90 5 5 4.8 4.2
C 80 10 10 4.7 5.2
D 70 15 15 4.9 5.2
EXAMPLE VIII
Example I was repeated with the following changes:
The solutions for injection into the viscose were
bo~
prepared as follows. A ~rbo~ starch (CES)
solution was prepared as stated in Example VII. One
solution for injection comprised equal parts of the
J e h~ 18
108Z866
above CES solution with 9/0 aqueous PVP K-90. A second
l301ution for injection comprised three parts of the above
CES ~olution with one part of a 9~/0 aqueous solution of
PVP K-90. Fibers were then spun by blending with viscose
(as tabulated below). ~he fibers were processed a~
described in Example I and finished in an aqueous solu-
tion of 1/2% Na2HP04 and 1/2% Span 20. The fibers were
dried and then evaluated.
CES
(EXPRESSED
rN TERMS OF FLUID HOLDING
SAMPLE CELLULOSE STARCH CONTENT) PVP CAPACITY
.
A 100 0 0 4.08
B B9.2 5.4 5.4 4.80
C 80 10 10 5.44
D 80 15 5 5.40
E 89.2 8.1 2.7 4.80
The more preferred fibers of this invention show a
pH (measured in a mixture of 100 parts distilled water
and one part of fibers) of well above 6 and generally at
least about 7, such as about 8, 9 or 9.5.
It is within the broader scope of this invention to
employ in place of all or part (e.g. 1/3, 1/2 or 2/3), of
the polyvinylpyrrolidone, one or more other N-vinyl
amide polymers, e.g. N-vinyl lactam polymers, N-vinyl-
2 oxazolidinone polymers or N-vinyl-3-morpholinone
polymers such as the polymers (including copolymer~)
listed in united States Patent 2,931,69~ issued April 5,
1960.
It will be noted that in the foregoing Examples,
-- 19 --
lOl~Z866 ~ ~ ~
the fibers, as spun, are unpigmented and undyed. It is
of course within the broader scope of the invention,
~lthough not at all nocessary for practicing it, to
incorporate pigments or dye into the spinning solution.
Fibers described in the above Examples had a denier
per filament of about 3. It will be understood, of
course, that the spinning may be effected to produce
other deniers such as 1.5, 4, 5.5 and 8 denier per
filament.
"
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