Note: Descriptions are shown in the official language in which they were submitted.
~l304~2
PF 50-01~1932A
EXTEL~DED Stl~LF LIFE WATE~-ABSORBING COMPOSITION
WHICH FACILITATES FIBER FORMATION
This invention relates to water-absorbing composi-
tions.
In one of its more specific aspects, this invention
relates to the incorporation of water-absorbing composi-
tions into articles of manufacture for the purpose of
improving khe absorbent properties of the articles.
Absorbent compositions are widely used in the
manufacture of products which require high absorption
capability. For example, water-absorbing compositions
are used in the manufacture o~ surgical and dental sponges,
tampons, sanitary napkins and pads, bandages, disposable
diapers, meat trays, and household pet litter. Water-
absorbing compositions are also used for the modification
of soil to improve water retention and increase air capac-
ity and for a host of other app:Lica-tions.
As used herein, the term "wa-ter" when used in the
phrases "water-absorbing" and "water-absorbent" is under-
2U stood to mean not only water but also electrolyte solutions
such as body fluids.
A number of absorbent compositions have been devel-
oped which exhibi-t water absorption capacity. For exam-
ple, U.S. Pat. Nos. 3,954,721 and 3,983,095 disclose
preparations for derivatives of copolymers of maleic anhy-
dride with at least one suitable vinyl monomer in ~ibrous
form. The fibrous copolymers are rendered hydrophilic
and water-swellable by reaction with ammonia or an alkali
metal hydroxide. U.S. Pat. No. 3,810,468 discloses lightly
cross-linked olefin-maleic anhydride copolymers prepared as
~L3~)4l!~62
substantially linear copolymers and then reacted with a
diol or a diamine to introduce cross-linking. The resul-
tant lightly cross-linked copolymers are treated with
ammonia or an aqueous or alcohol solu-tion of an alkali
metal hydroxide. U.S. Pat. No. 3,989,586 describes the
preparation of sorptive paper products by incorporating
cross-linked copolymers of styrene or olefins with maleic
anhydride in a paper web which is then treated to convert
the copolymer to a water swellable salt form. U.S. Pat.
N~. 3,980,663 describes water-swellable absorbent articles
made from carboxylic polyelectrolytes via cross-linking
with glycerine diglycidyl ether. U.S. Pat. Nos. 4,332,917
and 4,338,417 disclose blends of copolymers of styrene and
maleic anhydride with polymers derived from a monomeric
ester having vinyl unsaturation e.g., poly(vinyl acetate),
cellulose triacetate, cellulose aceto-but~rate, poly(ethyl-
acrylate) and poly(methylmethacrylate). V.S. Pat. No.
4,420,588 teaches a water absorbing rubber composition
comprising a 1,3-diene rubber and a water-absorbiny resin
dispersed in the rubber.
The desirability of having water-absorbing composi-
tions in fibrous forms is well known. For example, in
sanitary products such as disposable diapers and tampons,
fibers can be more easily confined within the product. In
this respect, the prior art water-absorbing compositions
are deficient; they do not facilitate fiber formation.
Because of the speed of their crosslinking reactions, the
prior art water-absorbing compositions possess no appreci-
able shelf life; fiber formation must be completed shortly
after the compositions are prepared. This shelf life
13~4~1~2
deficiency in the prior art compositions is discussed in
U.S. Pat. No. 3,983,095 which teaches that fiber forma-
tion should be completed within several hours and in
some cases immediately, depending upon the reactivity of
the cross linking agent used.
The water-absorbing compositions of this invention
possess excellent shelf life and have been found suitable
for forming into fibers several months after preparation.
They facilitate fiber formation over a wide range of time
and temperature. They also possess excellent integrity
in the hydrogel or water-swollen state, exhibit excellent
water and electrolyte solution absorption capacity, and
are readily incorporated into conventional water-absor-
bing products using conventional methods.
According to this invention there is provided a com-
position which is water-absorbent upon curing comprising
(a) a copolymer containing from about 25 to about 75 mole
percent of at least one CX,~ -unsaturated monomer bearing
a-t least one pendant unit selected from the group consis-
ting of carboxylic acid unlts and derivatives o~ carboxy-
lic acid units and from about 75 to about 25 mole percent
of at least one copolymerizable comonomer, wherein from
about 20 to about 80 percent of the total pendant units
introduced through the CX, ~ -unsaturated monomer are
carboxylic acid units or must be converted into carboxylic
acid units, and wherein from about 80 to about 20 percent
of the total pendant units are carboxylate metal salt
units or must be converted into carboxylate salt units;
and (b) at least one monomer containing at least two
hydroxyl groups selected from the group consisting of:
--3--
.. .. .
~3~4~S2
alkylene glycols containing 2-10 carbon atoms and their
ethers; cycloalkylene glycols; Bisphenol A; hydroxy
alkylene derivatives of Bisphenol A; hydroquinone;
phloroglucinol; hydroxy alkylene derivatives of diphenols;
glycerol; erythritol; pentaerythritol; and all natural
monosaccharides.
According to this invention there is provided a
method of producing a water-absorbing composition compris-
ing the steps of: (a) preparing a blend of i) a copoly-
mer containing from about 25 to about 75 mole percent
recurring units of at least one CY, ~ -unsaturated moncmer
which bears at least one pendant unit selected Erom the
group consisting of carboxylic acid units and derivatives
of carboxylic acid units, and from about 75 to 25 mole
percent recurring units of at least one copolymerizable
comonomer, wherein from about 20 to about 80 mole percent
of the total pendant units introduced through the recur-
ring CX ,a -unsaturated monomer units are carboxylic
acid units or must be converted into carboxylic acid
units and wherein from about ~0 to about 20 percent of
the total pendant units are carboxylate salt units or
must be converted into carbox~late salt units; and ii)
at least one monomer containing at least two hydroxyl
groups selected from the group consisting of: alkylene
glycols containing 2-10 carbon atoms and their ethers;
cycloalkylene glycols; Bisphenol A; hydroxy alkylene
derivatives of Bisphenol A; hydroquinone; phloroglucinol;
hydroxy alkylene derivatives of diphenols; glycerol;
erythritol; pentaerythritol; and all natural monosaccha-
rides; and ~b) curing the resulting blend.
--4--
, . .
130~1~36~
According to this invention there is provided a
method of absorbing water and electrolyte solutions com-
prising th~ step o:E contacting the water or electrolyte
solution to be absorbed with a cured water absorbing
composition comprising a blend of: (a) a copolymer
containing from about 25 to about 75 mole percent of at
least one CX , ~ -unsaturated monomer bearing at least
one pendant unit selected from the group consisting of
carboxylic acid units and derivatives of carboxylic acid
units and from about 75 to 25 mole percent of at least
one copolymerizable comonomer~ wherein from about 20 to
about 80 percent o the total pendant units introduced
through the CY, ~ -unsaturated monomer are carboxylic
acid units or must be converted into carboxylic acid
unitsl and wherein from about 80 to about 20 percent of
the total pendant units are carboxylate salt units or
must be converted into carboxylate salt units;
and (b) at least one monomer containing at least two
hydroxyl groups selected from the group consisting of:
: 20 alkylene glycols containing 2-10 carbon atoms and their
ethers; cycloalkylene glycols; Bisphenol A; hy~roxy
alkylene derivatives of ~isphenol A; hydroquinone;
phloroglucinol; hydroxy alkylene derivatives of diphenols;
glycerol; erythritol; pentaerythritol; and all natural
monosaccharides.
An article of manufacture comprising a cured
water-absorbing composition and a means for supporting
said composition to present said composition for absorp-
tion usage, wherein said water-absorbing composition
comprises a blend o-E: (a) a copolymer containing from
--5--
4~
about 25 to about 75 mole percent of at least one CY,
-unsaturated monomer bearing at least one pendant unit
selected Erom the group consisting of carboxylic acid
units and de.rivatives of carboxylic acid units and from
about 75 to about 25 mole percent of at least one copoly-
merizable comonomer, wherein from about 20 to 80 percent
of the total pendant units introduced through the CY,
-unsatura-ted monomer are carboxylic acid units or must
be converted in-to carboxylic acid units, and wherein
from about 80 to about 20 percent of the total pendant
units are carboxylate salt units or must be converted
into carboxylate salt units; and (b) at least one monomer
containing at least two hydroxyl groups selected from
the group consis-ting of: alkylene glycols containing
2-10 carbon atoms and their ethers; cycloalkylene glycols;
Bisphenol A; hydroxy alkylene derivatives of ~isphenol
A; hydroquinone; phloroglucinol; hydroxy alkylene deriv-
atives of diphenols; glycerol; erythritol; pentaerythritol;
and all natural monosaccharides.
According to this invention there is also provided a
method of enhancing at least one water absorbing charac-
teristic of an article which method comprises the step
of incorporating into the article a cured wateL-absorbing
composition comprlsing a blend of: (a~ a copolymer
containing from about 25 to about 75 mole percent of at
least one CX, ~ -unsaturated monomer bearing at least one
pendant unit selected from the group consisting of carboxy-
lic acid units and derivatives of carboxylic acid units
and from about 75 to about 25 mole percent of at least
one copolymerizable comonomer, wherein from about 20 to
~30~
about 80 percent of the total pendant units introduced
through the CX,~ -unsaturated monomer are carbo~ylic
acid units or must be converted into carboxylic acid
units, and wherein from about 80 to about 20 percent of
the total pendant units are carboxylate salt units or
must be converted into carboxylate metal salt units;
and (b) at least one monomer containing at least two
hydroxyl groups selected from the group consisting of:
alkylene glycols containing 2-10 carbon atoms and their
ethers; cycloalkylene glycols; Bisphenol A; hydroxy
alkylene derivatives of Bisphenol A; hydroquinone;
phloroglucinol; hydroxy alkylene derivatives of diphenols;
glycerol; erythritol; pentaerythritol; and all natural
monosaccharides, said composition being incorporated
into the article in an effective amount to enhance at
least one waterabsorbing characteristic of the article
as compared to the water-absorbing characteristics of
the article in the absence of the composition.
Copolymers suitable Eor use to produce water-
absorbing compositions of the inven-tion will contain from
about 25 to about 75 total mole percent recurring units
of at least one CY, ~ -unsaturated monomer and from-about
75 to about 25 total mole percent recurring units of at
least one copolymerizable comonomer. Preferably, the
copolymer will contain from about 35 to about 65 total
mole percent of recurring units of at least one CY, ~ -
unsaturated monomer and from about 65 to about 35 total
mole percent of at least one copolymerizable comonomer.
Most preferably, the copolymer will be an equimolar
copolymer.
Suitable CX, ~ -unsaturated monomers are those bear-
ing at least one pendant carboxylic acid unit or deriva-
tive of a carboxylic acid unit. Derivatives of carboxy-
lic acid units include carboxylic acid salt groups,
carboxylic acid amide groups, carboxylic acid illlide
groups, carboxylic acid anhydride groups and carboxylic
acid ester groups.
Suitable CX, ~ -unsaturated monomers include maleic
acid; crotonic acid; fumaric acid; mesaconic acid; the
1~ sodium salt of maleic acid; the sodium salt of 2-methyl,
2-butene dicarboxylic acid; the sodium salt of itaconic
acid; maleamic acid; maleamide; N-phenyl maleimide;
maleimide; maleic anhydride; fuameric anhydride; itaconic
anhydride; citraconic anhydride; mesaconic anhydride;
methyl itaconic anhydride; ethyl maleic anhydridei diethyl-
maleate; methylmaleate; and the like, and their mixtures.
Any suitable copolymeriæable comonomer can be
employed. Suitable copolymeri~able comonomers include
ethylene, propylene, isobutylene, Cl to C4 alkyl methacr-
ylates, vinyl acetate, methyl vinyl ether, isobutyl
vinyl ether, and styrenic compounds having the formula:
R - C--- C~2
wherein R represents hydrogen or an alkyl group having
from 1 to ~ carbon atoms and wherein the ben~ene ring may
be substituted wi-th low molecular weight alkyl or hydroxy
groups.
~3~9~
Suitable C1 to C4 alkyl acrylates include methyl
acrylate, ethyl acrylate, isopropyl acrylate, n-propyl
acrylate, n-butyl acrylate, and the like, and their mix-
tures.
Suitable Cl to C4 alkyl methacrylates include
methyl methacrylate, ethyl methacrylate, isopropyl
methacrylate, n-propylmethacrylate, n-butyl metha-
crylate, and the like, and their mixtures~
And, suitable styrenic compounds include styrenel
Cx -methylstyrene, p-methylstyrene, t-butyl styrene, and
the like, and their mixtures.
The pendant units on -the CY, a-unsaturated monomer,
will determine what, if any, additional reactions must be
carried out to obtain a copolymer having the requisite
pendant units necessary to produce the water-absorbing
compositions of this invention about 20 to about 80 per-
cent pendant carboxylic acid units and about 80 to about
20 percent pendant carboxylate salt units. Preferably,
both units are present in an amount of from about 30 to
about 70 percent.
In general, if the CX, a -unsaturated monomer bears
only carboxylic acid amide, carboxylic acid imide, carbox-
ylic acid anhydride, carboxylic acid ester groups, or
mixtures thereo~, it will be necessary to convert at
least a portion of such carboxylic acid derivative groups
to carboxylic acid groups by, or example, a hydrolysis
reaction. If the Cx~ a -unsaturated monomer bears
only carboxylic acid salt groups, acidification to form
carboxylic acid groups will be necessary.
Similarly, the final copolymer must contain from
about 80 to 20 percent pendant carboxylate salt units.
Accordingly, it may be necessary to carry out a neutral-
ization reaction. Neutral'ization of carboxylic acid
groups with a strong organic or inorganic base such as
NaO~, KOH, ammonia, ammonia~in-water solution, or organic
amines will result in the formation of carboxylate salt
units, preferably carboxylate metal salt units~
Moreover, the sequence and the number of reactions
(hydrolysis, acidification, neutralization, etc.) carried
out to obtain the desired functionality attached to copoly-
mer backbone are not critical. Any number and sequence
resulting in a final copolymer which possesses from about
20 to about 80 percent pendant carboxylic acid units and
from about 80 to about 20 percent pendant carboxylate
salt units is suitable.
One copolymer particularly suitable for use is a
copolymer of maleic anhydride and isobutylene. Another
is maleic anhydride and styrene. ~uitable copolymers
will have peak molecular wei~hts of from about 5,000 to
about 500,000 or more.
Suitable copolymers of maleic anhydride and iso-
butylene can be prepared using any suitable conventional
method. Such copolymers are also commercially available
from Kuraray Isoprene Chemical Company, Ltd., Tokyo, Japan,
under the trademark ISOBAM. ISOBAM copolymers are avail-
able in several grades which are differentia-ted by viscos-
ity molecular weight: ISOBAM-10, 160,000 to 170,000;
ISOBAM-06, 80,000 to 90,000; ISOBAM-04, 55,000 to 65,000;
and ISOBAM-600, 6,000 to 10,000.
--10--
~30~i2
To produce a water-absorbing composition of this
invention, at least one copolymer as described above and
at least one monomer bearing at least two hydroxyl groups
are blended such that the water-absorbing composition
contains in weight percent, from about 80 to about 99.5
total copolymer and from about 0.5 to about 20 total
monomer. ~referably, the composition will contain from
about 90 to about 99 weight percent total copolymer and
from about 1 to about 10 weight percent total monomer.
Any suitable monomer bearing at least two hydroxyl
groups and having a relatively low molecular weight, less
than 1,000, can be employed in -the practice of this in-
vention.
Suitable monomers include ethylene glycol, propylene
glycol, trimethylene glycol, 1,4-bu-tane diol, 2-methyl
1,3-propane diol, neopentyl glycol, 1,5-pentane diol,
diethylene glycol, dipropylene glycol, 1,4-cyclohexane
dimethanol, Bisphenol A, 1,4-bis~ hydroxyethoxy)bis-
phenol, hydroquinone, phloroglucinol, glycerol, erythritol,
pentaerythritoll 1,7-dihydroxysedoheptulose, and the
like.
Particularly suitable monomers for use in the practice
of this invention are ethylene glycol, propylene glycol,
1,4-butane diol, diethylene glycol, and glycerol.
'rhe water-absorbing composition of this invention
can be prepared using any suitable blending method such
as described in the Examples which follow. After the
water-absorbirlg composition is prepared, but typically
before it is cured but in some instances as it is curing,
it is processed into any desired form using conventional
130~8~;2
methods of fabrication. E`or example, the water-absorbing
composition can be subjected to casting; spray drying;
air-assisted spray drying; air attenuation; wet, dry or
flash spinning; and the like. The selection of the
process is typically dictated by the shape or form needed
Eor end use. Forms that the water-absorbing composition
may be fabricated into include films or sheets, powders
and granules, fibers and any ~orm into which fibers can
be processed such as for example milled fibers, chopped
fibers, fluff or bulk fibers, strands, yarns, woven
fabrics, non-woven mats and the like using a variety of
methods, including twisting, beaming, slashing, warping,
quilling, severing, texturizing, weaving, knitting,
braiding etc.
While not meaning to be limited to any theory, the
monomar bearing at least two hydroxyl groups is believed
to serve as a high temperature, slow-reacting, cross-
linking type agent for the copolymer particles resulting
in the formation of covalent cross-link type bonds upon
curingO For example, it has been found that, if a par-
tially neutralized styrene-maleic anhydride copolymer
is blended with propylene glycol to form a water-absorbing
composition according to this invention, a temperature
about 150C. or higher is typically required to achieve
cure. Similarly, if a partially neutralized ethylene-
maleic anhydride copolymer is employed, a temperature
of 140C. or higher is typically needed to achieve cure.
And, if a partially neutralized isobutylene-maleic
anhydride copolymer is employed, a temperature of 200C.
or higher is typically needed to achieve cure.
-12-
130~
Without meaning to limit -the invention, the water-
absorbing compositions of this invention are particularly
well suited for being made into fibers because of the wide
time and temperature ranges over which they can be shaped.
More specifically, the water-absorbing compositions of
this invention can be formulated to cure at te~nperatures
within the range of from about 140C to about ~50C. or
higher and possess shelf lives in excess of two months as
demonstrated in Example 7. Hence, the water-absorbing
compositions of this invention can be easily made into
fibers using conventional fiber-forming methods and
equipment. Moreover, no post-treatment (e.g., a salt-
forming reaction as taught in U~S. Patent 3,983,095) of
the cured fiber products is required.
The water-absorbing compositions of this invention
and articles of manufacture into which the compositions
are incorporated are suitable for use in a wide range of
absorptive functions. In general, the articles into which
the water-absorbing compositions are incorporated serve
the function of supporting the composition and presenting
it in a form adapted for absorptive end use. Means to
support and present the composition for absorptive use
include, but are not meant to be limited to bandages,
surgical and dental sponges, tampons, sanitary napkins
and pads, disposable diapers, meat trays, pads for absorp-
tion of perspiration, and the like.
In one embodiment, a water-absorbing composition
of this invention is incorporated into a disposable diaper,
using conventional fabrication methods to form a diaper
composite having the following typical layers: (1) an
-13-
~l305L~;2
outer layer (away from the body) oE impermeable polyeth~-
lene film; (2) a first cellulosic pulp layer superimposed
on the ~ilm; (3) a layer of (i) a cured water-absorbing
composition of this inven-tion in the form of, for example,
Eluff, a fibrous mass, a non-woven fiber mat or a woven
fabric; or (ii) a layer comprising a blend of a cured
water-absorbing composition of this invention and another
fluff conventionally employed in diapers; (4) an optional,
second cellulosic pulp layer; and (5) an inner permeable
polyethylene film layer.
Fibers made from the water-absorbing compositions
of this invention are particularly suitable for absorbent
applications. It is well known that a mass of fibers
provides a large surface area for contact with the liquid
material to be absorbed. Fibers as compared to powders
can also be more easily confined within the article in-to
which they are incorporated.
The following examples serve to further demonstrate
the invention.
EXAMPLE 1
This example demons~rates the preparation of a series
o~ water-absorbing compositions o~ the invention using
ISOBAM 10 isobutylene/maleic anhydride copolymer commer-
cially available from Kuraray Isoprene Chemical Company,
Limited. ISOBAM 10 has a molecular weight of 170,000 and
a maleic anhydride content of about 59.3 weight percent
(46.6 mole %~ as determined by titration of maleic acid.
Four water-absorbing co-mpositions (I-IV) were separately
prepared as follows.
-14-
About 1270 g oE ISOBA~ 10 isobutylene/maleic anh~-
dride copolymer and about 2007 g of demineralized water
were added to a mixing vessel with agitation and the
vessel contents were heated -to about 90C. At a tempera-
ture of about 90C about 658 g of a 50% sodium hydroxide
solution prepared from 98.9~ pure sodium hydroxide pel-
lets were slowly added to the mixing vessel over a one
hour period with agitation. After the addition of the
sodium hydroxide solution, agitation was con-tinued for
1~ about 12 hours at 90C. ~o complete the reaction.
The pH of the solution was found to be ~.5 and the
neutralization reaction was calculated to have converted
about 53~5% of -the pendant carboxylic acid units on the
46.6 mole % anhydride units into carboxylate sodium salt
units. The balance of the pendant units were converted
to carboxylic acid units.
As shown in the following Table 1, four water-absor-
bing compositions of the invention were separately pre-
pared using the above aqueous solution of partially
neutralized isobutylene/maleic anhydride copolymer.
Each of the four compositions was prepared by adding a
predetermined amount of propylene glycol to a certain
amount of copolymer solution and stirring for about 30
minutes. After stirring, each solution was separately
hea-ted to drive off excess water and to provide solutions
o~ approximately a 45~ solids content suitable for
fiber formation using a dry spinning process.
1~304~3~.2
TABLE 1
Composition I II III _ IV
Partially
neutralized
isobutylene/maleic
anhydride
copolymer
solution (g) 213.~5 203~57 198.83 222.S2
Propylene
glycol
o ~9) 2.06 3.29 4.49 7.18
o (phr) based
on copolymer 3 5 7 10
-' --- - ' -
Fibers having diameters of from about 5-25 microns
were separately produced from Compositions I-IV by dry
spinning. A sample of fibers produced from each composi-
tion was cured by heating at about 210C. for 30 minutes
and tested for absorbency. Each sample of fibers was
tested to determine Swell Index and Percent Solubility
using the ollowing test procedures.
Swell Index
This test procedure is described in U.S. 4,454,055
the teachings of which are incorporated herein by refer-
ence thereto. The test procedure and equipment used
herein were modified slightly as compared to the procedure
and equipment described in U.S. 4,454,055.
To determine the Swell Index at atmospheric (room)
pressure, about 0.2 to 0.3 9 of the water-absorbing
composition to be tested is placed in an empty W-shaped
tea bag. The tea bag containing the composition is
immersed in brine (0.9 wt,% NaCl) for 10 minutes, removed
and allowed to sit on a paper towel for 30 seconds to re-
-16-
4~
move surface brine. The Swell Index of the composition
that is, the units of liquid absorbed per each unit of
sample is calculated using the Eollowing formula:
Swell Index = Weight of Wet Composition -1
Weiyht of Dry Composition
To determine Swell Index under pressure, the follow-
ing modified procedure was used.
After the tea bag containing the sample composition
is immersed in brine and surface brine is removed, it is
immediately placed in a 16 cm ID Buchner funnel fitted
with a 2000 ml sidearm vacuum filter flask and connected
to a manometer. Then, a piece of dental dam rubber sheet-
ing is securely fixed over the mouth of the funnel such
that the sheeting just rests on the tea bag. Next, a
vacuum sufficient to create the desired pressure is
drawn on the flask for a period of five minutes, and,
the Swell Index under pressure is calculated using the
above formula.
Percent Solubility
About 0.5 g of the water-absorbing composition
sample to be tested is dispersed in about 150 y of brine
(0.9 wt.~ ~aCl) at room temperature for 20 minutes with
occasional gentle agitation. After 20 minutes, the mix-
ture is filtered through a 150 micron polypropylene
screen. ~ext, the filtrate is dried to a constant weight
in an oven and the weight of soluble composition deter-
mined by subtrac-ting the weight of the NaCl from -the
total weight of the dry filtrate. Percent solubility is
then determined using the following formula:
-17-
~3(~ .2
Percent Solubility = Wei ht of Soluble Com ositi.on x 100
The test results ~or the fiber samples o Composi-
tions I-IV are shown in Table 2.
TABLE 2
.
Composition _ I _ II _ III _ IV
Propylene
glycol (phr) 3 5 7 10
Swell Index
o Atmospheric
Pressure 46.3 39.5 28.8 27.2
o 0.5 psi 29.1 26~2 19.9 17.8
Solubility 23.9 17.9 11.7 7.9
EXAMPLE 2
This example demonstrates the preparation of a water-
absorbing composition of this invention using ISOBAM 10
isobutylene/maleic anhydride copolymer and ethylene glycol.
Fibers produced from the composition were cured at dif-
ferent temperatures and the effect of curing at the
different temperatures is shown in Table 3.
Using substantially the procedure of Example 1, about
226.13 g of -the aqueous solution of the partially neutral-
ized isobutylene/maleic anhydride copolymer produced in
Example 1 were mixed with about 2.19 g of ethylene glycol
and concentrated to give a 45% solids composition (Compo-
sition V) containing 3 phr of ethylene giycol based on
the weight of the isobutylene/maleic anhydride copolymer.
About 20-25 micron diameter fibers were prepared from the
composition as described in Example 1. The absorbency of
the fibers and the effect of three different cure tempera-
-18-
l;~O~ iZ
tures, 190C.~ ~00C., and 210C. on samples of the fibers
are shown in following Table 3.
TABLE 3
CompoSltloll V V V
Cure Temperature (C.~ 190 200 210
Swell Index
o Atmospheric Pressure 39.9 37.~ 32.5
O 0.5 psi 25.5 ~4.5 20.1
% Solubility 15.9 11.4 7.7
- ~
EXAMPLE 3
This example demonstrates the preparation of a water-
absorbing composition of this invention using ISOBAM 10
isobutylene/maleic anhydride copolymer and 1,4~butane diol.
Fibers produced from the composition were cured at dif-
ferent temperatures and the effect of curing at different
temperatures is shown in Table 4.
Using substantially the procedure of Example 1,
about 150.07 g of the aqueous solution of the partially
neutralized isobutylene/maleic anhydride copolymer
produced in Example 1 were mixed with about 3.39 g of
1,4-butane diol and concentrated to give a 45% solids
composition (Composition VI) containing 7 phr of 1,4-butane
diol based on the weight of the isobutylene/maleic anh~-
dride copolymer. About 5-10 micron diameter fibers were
prepared from the composition as described in Example 1.
The absorbency of the fibers and the effect of three
different cure temperatures, 170C., 180C., and 190C.
on samples of the fibers are shown in following Table 4.
--19-- .:
8~i2
TABLE 4
r ~
Fibers of CompoSltlOn _ VI _ _ _ VL VI
Cure Temperature (C.) 170 180 190
Swell Index
O Atmospheric Pressure 39.4 36.4 27.5
o 0.5 psi 25.923.5 16.2
% Solubility 15.18.0 5.4
. .
EXAMPLE 4
This example demonstrates the preparation oE difEer-
ent diameter fibers from a water-absorbing composition
of this invention and shows the effect of fiber diameter
on the absorbency of fibers of the same composition (Com-
position VII). Substantially the same materials and
procedures of Example 1 were employed.
About 1270 g of isobutylene/maleic anhydride copoly-
mer and about 2007 9 of demineralized water were added
to a mixing vessel with stirring and heated to about
90C. About 658.3 g of a 50~ sodium hydroxide solution
were added slowly over a one hour period. The reactor
2n
contents were stirred for about one hour, and then
abou-t 88.96 g (7 phr) of propylene glycol were added to
the reactor. The reactor contents were stirred for
about 9 hours at 90C.
A vacuum pump equipped with a cold trap was hooked
to the top of the mixing vessel and excess water was
removed to yield an aqueous solution having a solids
content of about 55%.
The 55% solids solution was charged into a holding
tank equipped with two 0.020'i nozzles located at the bot-
3()
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~3()q~ 2
tom of the tank. The solution was extruded through the
nozzles under pressure into fibers which were wound onto
a take~off roller. Fibers of different diameters were
prepared by changing the speed of the take-off rollers
and thus the speed at which ~ibers were drawn.
Four different diameter fibers were produced and
cured at 210C. for about 30 minutes. The absorbency of
the fibers and the effect of fiber diameter on the absor-
bency of the fibers are shown in Table 5.
TABLE 5
Fibers of
Composition VII _ VII VII
Fiber Diameter
(microns) 10 25 100 175
Swell Index
O Atmospheric
Pressure 33.0 33.846.5 50.8
o 0.5 psi 25.0 22.230.2 35.0
% Solubility 14.1 15.27.2 11.9
EXAMPLE 5
This example demonstrates the preparation of a water-
absorbing composition of this invention using ISOBAM 10
isobutylene/maleic anhydride copolymer and glycerol. ~ibers
produced from the composition (Composition VIII) were cured
at two different -temperatures, and the effect of the dif-
ferent cure temperatures is shown in Table 6.
Using substan-tially the procedure of Example 1, about
2869 g of the aqueous solution of the par~ially neutralized
isobuty]ene/maleic anhydride copolymer of Example 1 were
mi~ed with 64.8 g of glycerol and concentrated to give a
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62
45% solids composition containing 7 phr glycerol based on
the weight of the isobutylene/maleic anhydride copolymer.
Samples of fibers having diameters of about 10 microns
were produced by dry spinning and separately cured at
170C. and 180C. for 30 minutes and tested for absorbency.
The test results are shown in Table 6.
TABLE 6
_ _ _
Fibers of COmDOSitlOn VIII VIII
10 Cure Temperature (C.) 170 180
Swell Index
O Atmospheric Pressure 43.8 34.2
o 0.5 psi 28.3 24.9
Solubility 16.7 11.7
.
EXAMPLE 6
This example demonstrates t.he preparation of a water-
absorbing composition of this invention using IS~BAM 10
isobutylene/maleic anhydride copolymer and diethylene glycol.
Fibers produced from the composition (Composition IX) were
cured at two different temperatures, and the effec-t of
the different cure temperatures is shown in Table 7.
Using substantially the procedure of Example 1, about
109.22 g of the aqueous solution of the partially neutral-
ized isobutylene/maleic anhydride copolymer of Example 1
were mixed with 2.47 g of diethylene glycol and concen-
trated to give a 45% solids composition ~ontaining 7
phr diethylene glycol based on the weight of the isobuty-
lene/maleic anhydride copolymer. Samples of fibers
having diameters of about 10-20 microns were produced by
3~
-22-
~3~
dry spinning and separately cured at 170C. and 180C.
for 30 minutes and tested for absorbency. The test
results are shown in Table 7.
TABLE 7
_ _
_ _ . . .
Fibers of Composition IX IX
Cure Temperature (C.) 170 180
Swell Index
O Atmospheric Pressure 58.8 38.3
o 0.5 psi 41.3 32~9
10% Solubility 21.6 120 7
EXAMPLE 7
This example dernonstrates that the water-absorbing
compositions of this invention possess excellent shelf-
life in solution form.
A sample of the aqueous solution prepared according
to the procedure of Example 5 wa6 aged a-t 90C in a closed
container. Solution ViSCOSlty measurements using a BrookEield
viscometer were taken after 6, 29, 35 and 41 hours aging.
The viscosities measured are listed in Table 8, below.
After 41 hours no gel formation was observed in the solution.
TABLE 8
:;
COmDOStlOn (aaueous solution) VIII
Aging Time at 90C Viscosity (Poises)
0 hr 700
6 hrs 773
29 hrs 802
35 hrs 757
41 hrs 776
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Another sample of the aqueous solution of Example 5
was aged for ll weeks at ambient temperature. AEter ll
weeks aging, fibers were prepared from the aged solution
and the resulting fibers were cured at 180C for 30 minutes.
The absorbent property data of the resulting fibers
prepared after 11 weeks compared with the absorbent property
data of the fibers produced from the same composition
(Example 5) but in the absence of aging, the composition
is shown in Table 9.
TABLE 9
Eiber of CompositionVIII VIII
Time of Solution Aging 0 ll weeks
Swell Index:
O Atomospheric Pressure 34.2 410~
o 0.5 psi 2~1.9 30.3
.
The above data demonstrate that fibers of the inven-
tion produced after eleven weeks aging from the composi-
tion of Example 5 do not lose their absorbent properties
as compared to the absorbent properties of fibers prepared
in the absence of aging.
It will be evident from the foregoing tha-t various
modifications can be made to this invention. Such, how-
ever, are considered as being within the scope of the
inventlon.
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