Note: Descriptions are shown in the official language in which they were submitted.
13~7~9~
SUPERABSORBENT THERMOPLASTIC COMPOSITIONS
AND NONWOVEN WEBS PREPARED THEREFROM
Background of the Invention
The present invention relates to superabsorbent
thermoplastic compositions, superabsorbent thermoplastic
polymer blends, and to meltblown or spunbonded webs
prepared therefrom.
10Disposable absorbent products such as diapers,
sanitary napkins, tampons, incontinence products, and the
like typically are comprised of a batt or absorbent portion
which is wrapped with a liner. The batt typically i5
comprised primarily of cellulose fibers and the liner
15usually is a nonwoven web of a polyolefin such as
polyethylene or polypropylene.
Meltblowing techniques for forming nonwoven webs or
materials from the random deposition of relatively small
diameter fibers from thermoplastic resins are well known in
20the art. For example, the production of fibers by
meltblowing is described in an article by Van A. Wente,
entitled, "Superfine Thermoplastic Fibers," which appeared
in Industrial and Engineering Chemistry, Vol. 48, No. 8,
pp. 1342-1346 (1956). The article was ~ased on work done
25at the Naval Research Laboratories in Washington, D.C. See
also Naval Research Laboratory Report 111437, dated April
15, 1954. A more recent article of a general nature is
Robert R. Butin and Dwight T. Lohkamp, "Melt Blowing - A
one-Step Web Process for New Nonwoven Products", Journal of
30the Technical Association of the Pulp and Paper Industry,
~ol.~56, No. 4,~pp. 74-77 (197i~. ~
In general; meltblowing techniques include heating a
thermoplastic, fiber-forming resin~ to a molten state and
extruding the molten~resin as threads from a die having a
35~plurality of linearly arranged small diameter capillaries.
The molten threads or ila~ents exit~the die into a high
:
176~
velocity stream of a heated gas which usually is air. The
heated gas serves to attenuate, or draw, the threads of
molten resin to form fibers having diameters which are less
than the diameter of the capillaries of the die. The
fibers thus obtained usually are deposited in a random
fashion on a moving porous collecting device, such as a
screen or wire, thereby resulting in the formation of a
nonwoven web. By way of illustration only, some specific
examples of meltblowing techniques are described in U.S.
Paten~ Nos. 3,016,599, 3,755,527, 3,704,198, 3,849,241 and
4,100,324.
In the past, significant efforts have been made to
find ways to make disposable absorbent products more
efficient or more appealing to the consumer. Much of such
efforts have focused on increasing the absorbent capacity
of the product on a unit mass basis while at the same time
increasing the ability of the product to retain absorbed
fluid. The ability of a product to remove and keep body
fluids from the skin is perceived as a desirable attribute
and is believed to be a factor in the reduction of such
skin problems as diaper rash.
Such increased absorbent capacity and fluid retention
typically have been accomplished by incorporating a
superabsorbent material into the absorbent batt. The
superabsorbent material usually is in particulate form.
Unfortunately, particulate superabsorbents often migra~e in
or fall out of the absorbent product and/or exhibit
gel-blocking, a phenomenon which prevents the migration of
fluid into the central portion of the superabsorbent
particle. Moreover, the use~of particulate superabsorbents
complicates the manufacturing process and the particulate
nature of the superabsorbents limits the applications for
the superabsorbents.
It is expected that all of the foregoing difficulties
encountered through the use of particulate superabsorbents
in disposable absorbent products can be minimized or even
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eliminated if the superabsorbent were in the form of a
nonwoven web. However, superabsorbent nonwoven webs are
believed to be unknown prior to the present invention, even
though there is a large body of literature relating to
superabsorbents and to products into which superabsorbents
have been incorporated.
Superabsorbent materials, also referred to as
hydrogels, frequently are based on acrylate and
methacrylate polymers and copolymers. Other hydrogels are
based on starch or a modified starch. Hydrogels prepared
from hydrolyzed crosslinked polyacrylamides and crosslinked
sulfonated polystyrenes or based on maleic anhydride (or
similar compounds) have been described. Finally, still
other hydrogels are based on polyoxyalkylene ~lycols and
include polyurethane hydrogels.
The known polyoxyalkylene glycol-based superabsorbents
generally tend to come within one of the following classes,
at least in so for as they are reasonably related to the
present invention:
(1) crosslinked poly(oxyalkylene) glycols;
(2) crosslinked isocyanate-capped poly(oxyalkylene)
glycols, i.e., polyurethanes or polyureas;
(3) polyurethanes prepared from polyfunctional
prepolymers or reqins and diisocyanates;
(4) polyurethanes prepared from isocyanate-capped
polyesters or poly (oxyalkylene) glycols and difunctional
extenders;
(5) polyurethanes prepared from poly(oxyalkylene)
glycols, isocyanate-capped low molecular weight
prepolymers, and polyfunctional low molecular weight
components.
:
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U.S. Patent No. 3,783,872 describes absorbent pads
cont~-ni~g insoluble hydrogels The hydrogels can be
~ ' .
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present in the pads as a powder or as a film. The
hydrogels are comprised of crosslinked poly(alkylene
oxide). Suitable materials are stated to include, by way
of illustration, a poly(alkylene oxide), such as
poly(ethylene oxide); poly(vinyl alcohol); poly(vinyl
methyl ether); copolymers of maleic anhydride and ethylene;
and copolymers of maleic anhydride and vinyl methyl ether.
The polymers are crosslinked by ioniziny radiation.
An apparently preferred group of polymers includes
poly(ethylene oxide), copolymers of ethylene oxide and
propylene oxide, and alkyl-substituted phenyl ethers of
ethylene oxide polymers in which the alkyl groups may be
methyl and/or butyl.
The polymers which can be used also are described in
terms of reduced viscosity, rather than by molecular
weight. The polymers apparently can have average molecular
weights of less than about 150,000 to more than about
10, 000, 000 .
Class 2 - Crosslinked Isocyanate-Capped Poly(oxyalkylene)
Glycols, i.e., Polyurethanes or Polyureas
U.S. Patent No. 3,939,105 describes microporous
polyurethane hydrogels. The hydrogels are the reaction
products of a poly(oxyalkylene) polyol having an average
molecular weight of up to about 25,000 and organic
diisocyanate which have been lightly crosslinked with water
or an organic amine. In practice, the polyol is reacted
with the diisocyanate to give an isocyanate-capped polyol.
Before the isocyanate-capped polyol is crosslinked, a
liquid nonsolvent is added thexeto in an amount which will
not result in precipitation. It is the addition of the
nonsolvent which result~ in the production of the
microporous hydrogel. The nonsolvent typically is an
aliphatic hydrocarbon or a dialky1 ether.
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The disclosure of U.S. Patent No. 3,939,123 is similar
to that of the foregoing patent, except that a nonsolvent
is not employed.
In a variation of the procedures disclosed in the two
S precedlng patents, U.S. Patent No. 3,940,542 describes the
extrusion of a solution of the isocyanate-capped
poly(oxyalkylene) polyol of such preceding patents into a
coagulant or crosslinking bath containing water or an
organic polyamine as a crosslinking agent to produce water
swellable, lightly crosslinked hydrogel polymer tapes or
fibers. U.S. Patent No. 4,209,605 describes another
variation in which hydrogels are produced by charging
preselected feeds containing the poly(alkyleneoxy) polyol,
diisocyanate, and catalyst to a reaction zone, ex~ruding
the resulting high viscosity polymer through a suitable
die, and allowing crosslinking to take place by exposure to
atmospheric humidity.
U.S. Patent No. 4,182,827 describes a method of
increasing the wetting rates of the hydrogels disclosed in
the above three patents. The wetting rates are enhanced by
treating the surface of the solid hydrogel with certain
ketones, alcohols, organic amines, aromatic hydrocarbons,
or aqueous alkali metal hydroxide solutions.
Class 3 - Polyurethanes Pre~ared from Polyfunctional
Prepolymers or Resins and Diisocyanates
Hydrophilic polyurethane polymers are described in
U.S, Patent No. 3,822,238. They are prepared by reacting a
diisocyanate with a poIyfunctional prepolymer or resin.
The prepolymer or resin can be, among other things, an
adduct of ethylene oxide, propylene oxide, ethylene imine,
propylene amine, dioxolane, or a mixture thereof with a
polyhydroxy compound; a hydroxy carboxylic acid; a low
moIecular weight, hydrolyzed poly(vinyl acetate),
polyacrylic acid, or polymethacrylic acid; or mixtures
- 1317~9~
thereof. ~xamples of polyhydroxy compounds include ethylene
glycol, propylene glycol, glycerol, trimethylolpropane,
erythritol, pentaerythritol, anhydroenneaheptitol, sorbitol,
mannitol, sucrose, and lactose. See also U.S. Patent No.
3,975,350 which describes a carrier system employing the
hydrophilic polyurethane polymers of the first patent.
Class 4 - Po~y~ _repared from Isocyanate-Capped
Polyesters or Poly(oxyalkylene) Glycols and
Difunctional Extenders
Segmented urethane polymers are described in U.K. Patent
Application GB 2,154,886A, of ~thicon Inc., published
September 18, 19~5, and granted July 22, 1987. Briefly, a
polyester or polyether glycol having a molecular weight of at
least about 200 is reacted with an excess of organic
diisocyanate to ~orm an isocyanate-terminated prepolymer.
The prepolymer then is reacted with a difunctional extender
and, optionally, with a very small proportion o a monofunc-
tional material which acts as a molecular weight regulator.
A polyether glycol apparently is preEerred, such as a
poly(tetramethylene ether) glycol having a molecular weight
above about 600, e.g., from about 800 to about 5000.
The diisocyanate usually is an aromatic diisocyanate
such as 4,4'-diphenylmethane diisocyanate and toluene
diisocyanate. An excess of diisocyanate is employedl e.g.,
from about 1.2 to about 1.9 moles o~ diisocyanate per mole of
glycol.
~ he difunctional extender has two groups which are
reactive witll isocyanates. The extender can be a diol, an
amine havlng at least one amino hydrogen per amino group, or
water. Examples of suitable extenders include water, 1,4-
butanediol, diethylene glycol, ethylene glycol,
ethylenediamine, diphenylmethane diamine, l,3-cyclohëxylene
diamine, 1,4-cyclohexylene diamine, and the like.
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~317694
Similar polymers are described in U.S. Patent Nos.
2,929,~00r 2,929,80~, 3,~2~,711 and 3,557,0~.
Class 5 - Polyurethanes Prepared Erom Poly(oxyalkylene)
Glycols, Isocyanate-Capped Low Molecular Wei~
Prepoly ers, and Polyfunctional Low Molecular Wei~ht
Components
A polyurethane similar to the polyurethane hydrogels
- described above is disclosed in U.K. Patent Application GB
2,157,703A, of Shirley Institute, published October 30, 1985,
granted April 29, 1987. The material is described as useful
for coating fabrics and clothing, with no mention of ~ater-
absorbing properties. According to the re~erence, the
polyurehane is ~ormed from a reaction mi~ture comprising an
isocyanate-terminated prepolymer, a polyol component contain-
ing at least 25 percent by weight o~ polyoxyethylene units
based on the total weight o~ constituents, and a low
molecular weight constituent having an active hydrogen
functionality oE at least two. I~ desired, the viscosity o~
the reaction mixture can be increased by adding one or more
additional low molecular weight constituents having a
functionality o~ at least two and preferably three; in the
pre~erred case, it is clear that the additional constituent
is functioning as a crosslinking agent.
The prepolymer is Eormed from the reaction product of a
polyisocyanate containing at leas-t two isocyanate groups per
molecule with a low molecular weight component having an
active hydrogen functionality of at least two. Such com-
ponent can be a diamine, dihydrazide, diamide, diol, dithiol,
dicarboxylic acid, disulfonic acid, or a mixture thereo~. -
Diols are pre~erred, with representatives examples including
thiodiglycol, ethylene glycol, diethylene glycol, and 1,~-
butanediol. Tri~unctional compounds can be included, such as
trimethylolpropane, diethylenetriamine, and compounds having
two or more
- 7 -
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different types of functional groups. Preferably, such low
molecular weight component has a molecular weight of not
more than 200.
The polyisocyanate used to prepare the prepolymer can
be any of those known to be useful for preparing poly-
urethanes. Examples include toluene-2,4-diisocyanate,
toluene-2,6-diisocyanate, mixtures of the foregoing two
compounds, 1,6 hexamethylenediisocyanate, l,S-naphthalene-
diisocyanate, 4,4'-diphenylmethanediisocyanate, 1,4-cyclo-
hexanediisocyanate, 1,4-phenylenediisocyanate, m- and
~-tetramethylxylyldiisocyanates and mixtures thereof,
isophoronediisocyanate, and 4,4'-dicyclohexylmethanediiso-
cyanat~.. The last two compounds are preferred.
The polyol component contains at least 25 percent
polyoxyethylene units. The preferred polyoxyethylene-
containing compound is a polyethylene glycol having a
molecular weight of from about 400 to about 2000. Other
suitable compounds include block copolymers of ethylene
oxide with other 1,2-alkylene oxides, such as propylene
oxide and butylene oxide; and copolymers formed by reaction
of ethylene oxide with polyols, polyamines, and polythiols.
The polyol component may consist in part of substances
which do not contain polyoxyethylene units, such as
polyester polyols and polyether polyols. Examples of the
former include polycaprolactone diols and polyesters
prepared from a dicarboxylic acid such as oxalic, maleic,
succinic, adipic, suberic, sebacic, and the isomeric
phthalic acids and a polyol such as ethylene glycol,
diethylene glycol, 1,4-butanediol, 1,6-hexanediol, mixtures
thereof, glycerol, trimethylolpropane, pentaerythritol,
sorbitol, and sucrose~ An example of the latter, which is
preferred, is polytetramethylene glycol.
The low molecular weight constituent in general can be
the same type of compound as the low molecular weight
component already described.
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If desired, crosslinking agents such as
triisocyanates and melamine-formaldehyde resins also can
be employed.
It now has been unexpectedly discovered that
certain compositions similar to those of Class 4, but
based on a difunctional poly(oxyethylene) having a
molecular weight greater than about 5,000, and blends of
such certain compositions with thermoplastic polymers,
can be formed into nonwoven webs or fabrics,
particularly by meltblowing or spunbonding and that
these compositions (unlike those of Class 4) are
superabsorbent.
Accordingly, the present invention provides a
superabsorbent, thermoplastic pol~meric compostion
comprising:
(A) ~rom a~out 86 to about 98 percent by weight,
based on the total weight of the composition, of a
poly(oxyethylene) soft segment having a weight
average molecular weight in the range of from about
5,000 to about 50,000; and
(B) from about 2 to about 14 percent by weight,
based on the total weight of the composition, of a
hard se~ment which has a melting point above
ambient temperature and below the temperature at
which decomposition of either the composition or
the soft segment takes place, is essentially
insoluble in water, and phase separates from the
soft segment, said hard segment being selected from
the group consisting of polyurethanes, polyamides,
polyesters, polyureas, and combinations thereof;
wherein the soft and hard segments are covalently bound
together by means of urethane, amide, ester, or
secondary urea linkages or combinations thereof.
The present invention also provides a
superabsorbent, thermoplastic polymeric composition
having the following general formula:
. g _
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1317~9~
-~S-H)n~
in which S represents
Zl-X1-(Yl-P-Y2-X2)p-Z2
and H represents
Z3 X3 ~Y3 X5 Y4 X4)m Z4
wherein P represent a poly(oxyethylene) moiety having a
weight average molecular weight of from about 5,000 to
about S0,000: each of Y1, Y2, Y3~ and Y4 independently
represents a urethane, amide, ester, or secondary urea
linkage; each of Xl, X2, X3, X4, and X5 independently
represents a divalent aliphatic, cycloaliphatic, aromatic,
or heterocyclic group; each of ~1~ Z2~ Z3~ and Z4
independently represents a monovalent functional group
which is reactive with another functional group to give a
urethane, amide, ester, or secondary urea linkage; m is an
integer of from 0 to about 50; n is an integer of from
about 1 to about 20; p is an integer of from about 1 to
about 10; S represents from about 86 to about 98 percent by
weight of the total composition; and H represents from
about 2 to about 14 percent by weight of the total
composition and has a melting point above ambient
temperature and below the temperature at which
decomposition of either the compoQition or the soft segment
takes place, is essentially insoluble in water, and phase
30 ~ sepaxates from the soft segment, said hard segment being
selected from the group consisting of polyurethanes,
polyamides:, polyesters, polyureas, and combinations
~thereof.
~ ~ ~n ~preferred embodiments,~ the hard segment is a
: 35 polyurethane. In other preferred embodiments, the hard
: segment is a polyurethane based on 1,4-butanediol.
1~
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The present invention also provides a method of
preparing a superabsorbent, thermoplastic polymeric
composition which comprises:
(A) reacting a first compound with a second
compound at a temperature of from about 50 to about
200 degrees C for a time sufficient to effect
essentially complete reaction; and
(B) reacting with the product from step A a
third compound at a temperature of from about 80 to
about 200 degrees C for a time sufficient to obtain
a melt flow rate of less than about 1,000 g per 10
minutes under the test conditions described
hereinafter;
in which said first compound is a difunctional
poly(oxyethylene) having a weight average molecular
weight of from about 5,000 to about 50,000; said second
compound is an aliphatic, cycloaliphatic, aromatic, or
heterocyclic compound having two functional groups which
are reactive with the functional groups of said first
compound; the mole ratio of said second compound to said
first compound is in the range of from about 2 to about
100; said third compound is an aliphatic,
cycloaliphatic, aromatic, heterocyclic, or polymeric
compound having two functional groups which are reactive
with the functional groups of said second compoundJ the
reaction product of said first compound with said second
compound, excluding excess second compound, is from
about 86 to about 9~ percent by weight of the final
composition; and said third compound plus the excess of
said second compound are from about 2 to about 14
percent by weight of the final composition; in which the
functional groups of said second compound and said third
compound independently are selected from the group
consisting of hydroxy, carboxy, amino, epoxy, imino, and
isocyanate groups, with the selection of all such
functional groups being such that said superabsorbent,
'`B
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1317694
, . .
thermoplastic polymeric composition contains linkages
selected from the group consisting of urethane, amide,
ester, and secondary urea linkages; and the melt flow
rate is determined at a temperature of 195 degrees C,
under a 2.16 kg load, and with an orifice diameter of
2.0955 0.0051 mm.
In preferred embodiments, said second compound is
an aliphatic or aromatic diisocyanate. In other
preferred embodiments, said third compound is an
aliphatic or aromatic diol having from 2 to about 24
carbon atoms.
In preferred embodiments, the superabsorbent,
thermoplastic polymeric composition is a polyurethane.
The present invention further provides a stable,
nonreactive, thermoplastic polymer blend comprising (a)
from about 10 to about 95 percent by weight of a
superabsorbent, thermoplastic polymeric composition
characterized by a poly(oxyethylene) group-containing,
functional group-terminated soft segment covalently
bonded to a hard segment through reaction with a third
segment which may be monomeric or polymeric, and (b)
from about 90 to about 5 percent by weight of at least
one thermoplastic polymer.
In preferred embodiments, the polymeric composition
component of the polymer blend is a superabsorbent,
thermoplastic polymeric composition of the present
invention as already described.
In other preferred embodiments, said polymeric
composition comprises from about 30 to about 90 percent
by weight of said blend. In other preferred
embodiments, said polymeric composition comprises from
about 40 to about 75 percent by weight of said blend.
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Detailed Description of the Invention
Although the term "superabsorbent" has been used
rather loosely in the prior art, the term is used herein to
mean that the composition absorbs at least about 10 g of
water per g of composition (10 g/g).
The superabsorbent articles of the present invention
have broad application in the preparation of disposable
absorbent products. The methods of the present invention
have broad application in the forming of superabsorbent
articles by any suitable method. Suitable methods include,
by way of illustration only, molding, such as injection
molding; extrusion, such as continuous melt extrusion to
form films or fibers; and the like. A particularly useful
method is the meltblowing of a thermoplastic superabsorbent
to form a superabsorbent nonwoven web.
In general, the nature of the superabsorbent,
thermoplastic polymeric composition is not known to be
critical, provided that it othe~wise meets the criteria set
forth herein. Preferred compositions are those of the
present invention described hereinafter. Especially
prefexred are the superabsorbent thermoplastic
polyurethanes described herein. Such especially preferred
polyurethanes were used in the examples of the present
disclosure.
The superabsorbent, thermoplastic polymeric
composition of the present invention comprises a soft
segment and a hard segment, each segment being described
herein in terms of segment constituents or composition and
by general formula.
The soft segment typically comprises from about 86 to
about 98 percent by weight of the total composition.
Pre~erably, the soft segment comprises from about 90 to
about ~97~ percent by weight,~ and most preferably from about
3~5 95 to about 97 percent by weight, of the total composition.
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1317694
In general, the soft segment is based on a first
compound having ~ weight average molecular weight of from
about 5,000 to about 50,000. Preferably, the molecular
weight of the first compound will be in the range of from
about 8,000 to about 50,000, more preferably from about
8,000 to about 30,000, and most preferably from about 8,000
to about 16,000.
More particularly, the first compound is a
difunctional poly(oxyethylene). The functional groups can
be any group which will react with a second compound to
give urethane, amide, ester, or secondary urea linkages,
with urethane linkages being preferred. Examples of
suitable functional groups include hydroxy, carboxy, amino,
epoxy, imino, isocyanate, and the like. Preferably, both
groups will be the same, and most preferably, both groups
will be hydroxy groups.
When both functional groups of the first compound are
hydroxy groups, the first compound will be a
poly(oxyethylene) diol which is most preferred. Other
functional groups can be present, however, either through
direct synthesis or by reacting a poly(oxyethylenel diol
with a modifier, with the latter procedure being preferred.
However, a modi~ier does not have to introduce functional
groups other than hydroxy groups. By way of illustration,
a diol will be obtained upon reacting a poly(oxyethylenel
diol with propylene oxide or a hydroxy-substituted
carboxylic acid.
The use of a modiier involves procedures already
known to those having ordinary skill in the art. To
illustrate further, reacting a poly(oxyethylene) diol with
ethylenimine will give a poly(oxyethylene) diamine. A
diamine also will be obtained upon reacting the diol with
an amino-substituted carboxylic acid. For convenience, a
first compound obtained from the use of a modifier will be
referred to herein as a modified poly(oxyethylene) diol,
even though the functional groups present may not be
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hydroxy groups. Such term also is meant to include a
poly(oxyethylene) having two functional groups other than
hydroxy which was prepared by means other than through the
use of a modifier. Similarly, the term "poly(oxyethylene)
diol" i5 not to be limited to a diol which is the
polycondensation product of ethylene oxide; rather, the
term includes any diol composed substantially of a
plurality of oxyethylene units, including a diol prepared
by covalently coupling together two or more molecules of a
poly(oxyethylene) diol by means of a coupling reagent, such
as a diisocyanate.
The soft seqment comprises the reaction product of
first compound with second compound; excess second compound
which may be present is not a part of the soft segment.
Thus, the soft segment is a second compound-terminated
poly(oxyethylene). The linkages by which the first
compound is covalently bound to the second compound will be
selected independently from the group consisting of
urethane, amide, ester, and secondary urea linkages.
Preferably, such linkages will be the same, and most
preferably such linkages will be urethane linkages.
The second compound can be any compound having two
functional groups which are reactive with the functional
groups of the first compound to give urethane, amide,
ester, and secondary urea linkages, provided only that the
properties of the resulting soft segment are not
significantly adversely affected by the choice of second
compound. Thus, the second compound can be aliphatic,
cycloaliphatic, aromatic, or heterocyclic. Moreover, for
any given first compound functional group, one having
ordinary ~kill in the art will be able to select
appropriate functional groups for the second compound.
As alr ady noted, the reaction between the first
compound and the second compound preferably will result in
the formation of urethane linkages. Since the preferred
functional groups of the first compound are hydroxy groups,
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13~7~9~
it follows that the preferred functional groups of the
second compound are isocyanate groups. Thus, the most
preferred second compounds are diisocyanates.
By way of illustration only, suitable diisocyanates
which can be employed as the preferred second compound
include toluene-2,4-diisocyanate, toluene-2,6-diisocyanate,
ethylidene diisocyanate, propylene-1,2,-diisocyanate,
cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diiso-
cyanate, m-phenylene diisocyanate, 4,4'-biphenylene
diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate,
1,4-tetramethylene diisocyanate, 1,6 hexamethylene diiso-
cyanate, 1,10-decamethylene diisocyanate, xylene diisocya-
nate, chlorophenylene diisocyanate, diphenylmethane-4,-
4'-diisocyanate, naphthalene-1,5-diisocyanate, cumene-2,4-
diisocyanate, 4-methoxy-1,3-phenylene diisocyanate,
4-chloro-1,3-phenylene diisocyanate, 4-bromo-1,3-phenylene
diisocyanate, 4-ethoxy-1,3-phenylene diisocyanate, 2,4-di-
isocyanatodiphenyl ether, 5,6-dimethyl-1,3-phenylene
diisocyanate, 2,4-dimethyl-1,3-phenylene diisocyanate,
4,4'-diisocyanatodiphenyl ether, benzidine diisocyanate,
xylene-alpha, alpha'-diisothiocyanate, 3,3'-dimethyl-4,4'-
biphenylene diisocyanate, 2,2',5,5'-tetramethyl-4,4'-bi-
phenylene diisocyanate, 4,4'-methylenebis(phenylisocya-
nate), 4,4'~sulfonylbis(phenylisocyanate), 4,4'-methylene
di-o-tolylisocyanate, 1l4-bis(2-isocyanatoisopropyl)-
benzene, ethylene diisocyanate, trimethylene diisocyanate,
mixtures thereof, and the like.
The most preferred second compounds are toluene-2,-
4-diisocyanate, toluene-2,6-diisocyanate, mixtures of
toluene-2,4- and toluene-2,6-diisocyanates, 4,4'-methylene
bis(phenylisocyanate), and 1,6-hexamethylene diisocyanate.
The hard segment generally comprises from about 2 to
about 14 percent by weight of the total co~position.
Pre~erably, the hard segment comprises from about 3 to
about 10 percent by weight and most preferably from about 3
to about 5 percent by weight, of the total composition.
/ ~ '_~_
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1317~9~
The hard segment must have a melting point abo~e
ambient temperature and below the temperature at which
decomposition of either the composition or the soft segment
takes place. In addition, the hard segment must be
essentially insoluble in water and must phase separate from
the soft segment.
The hard segment is selected from the group consisting
of polyurethanes, polyamides, polyesters, polyureas, and
combinations thereof. The hard segment can be polymeric ab
initio or prepared in situ by the reaction between second
compound and a third compound. Regardless of how the hard
segment is prepared, polyurethanes are preferred. Most
preferably, the hard segment is obtained by reacting second
compound with a third compound.
Stated differently, the third compound can be either
polymeric or monomeric. In either case, it is the reaction
between the functional groups of the third compound with
those of the second compound which results in the co~alent
linkage joining the hard and soft segments together. When
the third compound is monomeric, excess second compound
should be present in order for a condensation
polymeri~ation reaction to occur between the third compound
and the excess second compound; such polycondensation
reaction often is desired in order to obtain the
appropriate properties for the hard segment.
As already noted, monomeric third compounds are
preferred. If desired, a mixture of two or more third
compounds can be employed. In addition, mixtures of one or
more monomeric third compounds with one or more polymeric
third compounds also are contemplated and come within the
scope of the present invention.
In general, the third compound can be any compound
having two functional groups which are reactive wi~h second
compound to form urethane, amide, ester, or secondary urea
linkages. Thus, the third compound can be aliphatic,
cycloaliphatic, aromatic, or heterocyclic.
- 17 -
~ .
~-` 13~769~
The functional groups of the third compound can be any
of those listed for the first compound. Preferably, the
functional groups of the third compound will be of the same
type as those of the first compound. Thus, the preferred
functional groups of the third compound are hydroxy groups.
The most preferred third compounds are aliphatic and
aromatic diols having from 2 to about 24 carbon atoms.
Examples of suitable most preferred third compounds
include, among others, ethylene glycol, 1,3-propanediol,
1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,3-pen-
tanediol, 1,5-pentanediol, 1,6-hexanediol, 1,6-heptane-
diol, 1,4-dodecanediol, 1,16-hexadecanediol, resorcinol,
4-hydroxymethylphenol, 1,4-bi 5 ( 2-hydroxyethyl)benzene,
1,3-bis(2-hydroxyethyl)benzene, bis(2-hydroxyethyl~
terephthalate, and the like.
The superabsorbent, thermoplastic polymeric
composition of the present invention ~an be represented by
the following general formula:
-(S-H) - (1)
in which S represents
z -X ~(Y -P-y2-x2) -Z2 (2)
and H represents
Z3 X3 (Y3 x5-y4-x4)m-z4 (3)
wherein P represents a poly(oxyethylene) moiety; each of
Yl, Y2, Y3, and Y4 independently represents a urethane,
amide, ester, or secondary urea linkage; each of Xl, X2,
X3, X~, and X5 independently represents a divalent
aliphatic, cycloaliphatic, aromatic, or heterocyclic group;
each of Zl~ Z2~ Z3r and Z4 independen~ly represents a
monovalent functional group which is reactive with another
r
.
.
131769~
functional group to give a urethane, amide, ester, or
secondary urea linkage; m is an integer of from 0 to about
50; n is an integer of from about 1 to about 20; p is an
integer of from about 1 to about 10; S represents from
about 86 to about 98 percent by weight of the total
composition and has a weight average molecular weight of
from about 5,000 to about 50,000; and H represents from
about 2 to about 14 percent by weight of the total
composition and has a melting point above ambient
temperature and below the temperature at which
decomposition of either the composition or the soft segment
takes place, is essentially insoluble in water, and phase
separates from the soft se~ment, said hard segment being
selected rrom the group consisting of polyurethanes,
polyamides, polyesters, polyureas, and combinations
- thereof.
Formulas 1-3, above, necessarily represent the ideal.
For example, formula 1 does not include the terminal
moieties. In addition, because not all of the polymer
molecules have the same length (or molecular weight), the
. values for m, n, and p rarely are whole numbers; such
values typically are expressed as decimal fractions which
represent average values. Consequently, the term 'linteger"
as used herein is meant to include both whole numbers and
decimal fractions.
According to formulas 2 and 3, each of the first,
second, and third compounds can have two different
functional groups. As a practical matter, however, this
: rarely will be the case. Consequently, typically Xl = X2,
1 Y2~ Zl Z2' X3 = X4, Y3 = Y4~ and Z3 ~ Z4. Moreover,
: usually X5 = %1 and Y3 = Yl. Under these circumstances,
.
:~ ~3 / 9
,,. . ~. ., .,,,, , ~
.
.
317~9~
formulas 2 and 3 can be rewritten as formulas 4 and 5,
respectively:
1 1 (Yl P Yl Xl)p Zl (4)
~3 X3-~Yl~Xl~Yl~X3)m~Z3 (5)
It should be apparent to one having ordinary skill in
the art that the terminal moieties of the polymeric
composition can be either soft segment or hard segment.
When the terminal moieties are soft segment, formulas 4 and
5 can ~e combined to give formula 6:
Zl-Xl-[Yl-(P Yl Xl Yl)p X3 (Yl Xl Yl 3)mln 1
Similarly, formula 7 results when ~he ~erminal moieties are
hard segment:
Z3-x3-(yl-xl-yl-x3)m~[Yl-(p-yl-xl-yl)p-x3-(yl-xl~yl-
X3)m]n Z3 (7)
There necessarily is a relationship between the
molecular weight of the soft segment (or first compound)
and the amount of hard segment which is present in the
~5 composition. The amount of hard segment present in turn is
partly a function of the value of m, i.e., the number of
repeating units in the hard segment. The amount of hard
segment pre~ent in the composition also is a function of
the mole ratio of soft segment to hard segment. Thus, the
mole ratio of soft segment to hard segment can vary from 2
to 0.5. Mole ratios of 2 and 0.5 will result in
compositions represented by formulas 6 and 7, respectively.
Mole ratios greater than 2 or less than 0.5 will result in
the presence in the composition of unreacted soft segment
or unreacted hard segment, respectively.
.
~.
i ,., ~.. ~ .... . . .. . . . .
~ 1317~9~
These relationships are illustrated for compositions
based on a poly(oxyethylene) diol, 4,4'-methylenebis-
(phenylisocyanate), and 1,4-butanediol, i.e., compositions
representative of those prepared in the examples. The
5relationships are summarized in Tables 1-6, inclusive,
which show the percent hard segment present in the
composition for a soft segment of a given molecular weight
and different values of m at each of three soft segment :
hard segment (S:H) mole ratios. The soft segment and hard
segment molecular weights were calculated from formulas 2
and 3, respectively.
Table 1
Percent Hard Segment in Compositions
Based on 8,500 M.W. Soft Segment
Percent Hard Segment
-_ S:H Mole Ratio
Value o_ m 2 1 0.5
0 0.5 1.0 2.1
1 2.5 4.8 9.2
2 4~3 8.3 15.3
3 6.1 11.6 20.7
4 7.9 14.6 25.4
~ 9.5 17.4 29.6
6 11.1 20.0 33.4
7 12.7 22.5 36.8
8 14.2 24.8 39.8
~ ~ ~ ~ :
,, ~ .
1317~9~
Table 2
Percent Hard Segment in Compositions
Based on 14,500 M.W. Soft Segment
Percent Hard Segment
S:H M _e Ratio
Value of m 2 1 0.5
0 0.3 0.6 1.2
1 1.5 2.9 5.6
2 2.65.0 g.6
3 3.77.1 13.3
4 4.89.1 16.7
5.811.0 19.8
6 6.812.8 22.7
7 7.814.6 25.4
10.719.4 32.5
14 14.325.1 40.1
Table 3
Percent Hard Segment ln Compositions
Based on 16,750 M.W. Soft Seqment
Percent Hard Se~ment _ :
: S~H Mole Ratio
::~Value:of m 2 : 1 0.5
~: 0 : 0.3 ~ ~ 0.5 : 1.1
1.3~ : 2.5 4.9
: :2 : : 2.2 :~ 4.4 8.4
3 3.~ : 6.2 11.7
: :: 4 ~ 8.0 14.8
~ 9.7 17.6
`:6 :~ 6.0 ~ 11.3 20.3
B ~ ~
; J-
:
,
.
.
.
-
~ 7~
7 6.9 12.9 22.8
8 7.7 14.~ 25.1
12 ll.l 19.9 33.2
16 14.2 24.8 39.8
Table 4
-
Percent Hard Segment in Compositions
Based on 28,750 M.W. Soft Segment
Percent Hard Segment
S:H Mole Ratio
Value of m 2 1 0.5
0 0.2 0.3 0.5
1 0.7 1.5 2.9
2 1.3 206 5.1
3 1.9 3.7 7.2
4 2.5 4.8 9.2
3.0 5.9 11.1
6 3.6 6.9 12.9
7 4.1 7.9 14.7
5~7 10.8 19.5
14 7.8 14.4 25.2
24 12.5 22.3 36.5
28 14.3 25.1 40.1
: :
~ 30~
~:
: 35 ~ :
:
:
:
'
~317~94
Table 5
Percent Hard Segment in Compositions
Based on 33,250 M.W. Soft Segment
s
_ Percent Hard Segment
S:H Mole Ratio
_
Value of m 2 1 0.5
0 0.1 0.3 0.5
1 0.6 1.3 2.5
2 1.1 2.3 4.4
3 1.6 3.2 6.2
4 2.1 4.2 8.0
6 3.1 6,0 11.4
8 4.1 7.8 14,S
12 5.9 11.1 20.1
16 7.7 14.3 25.0
13.4 23.6 38.2
33 14.5 25.4 40.5
Table 6
Percent Hard Segment in Compositions
25Based on 50,500 M.W. Soft Segment_
Percent Hard Segment
S-H Mole Ratio
Value of m 2 1 0.5
:~ 30
:0 0.1 0.2 0.4
1 0.4 : ;0.8 1.7
~: ~ : 2 0.8 ~::; : 1.5 3.0
4 ~ 4 2.8 5.4
6: 2.1 4.0 7.8
8 2.7 ~ 5.3 10.0
:
!
':
'
13~7~9~
12 4.0 7.6 14.2
6.4 12.0 21.4
24 7.6 14.0 24.6
11.9 21.3 35.2
14.4 25.2 40.2
To the extent desired, similar calculations can be
made for any combination of soft segment or first compound,
second and thlrd compounds, value of m, and mole ratio of
soft segment to hard segment, thereby enabling one having
ordinary skill in the art to readily determine the mole
ratios of first, second, and third compounds, and,
consequently, the amounts of such materials necessary to
prepare a composition coming within the scope of the
present inventionO
By way of illustration, suppose m is selected to be
three; each mole of hard segment then must contain three
moles of second compound and four moles of third compound.
Suppose further that a mole ratio of soft segment to hard
segment of 1.5:1 is selected. Since each mole of soft
segment must contain two moles of second compoùnd and one
mole of first compound, the 1.5:1 S:H mole ratio requires 3
moles of second compound and 1.5 moles of first compound
per mole of hard segment. Consequently, the reaction will
require 1.5 moles of first compound, 6 moles of second
compound, and four moles of third compound. It then
becomes a simple matter to calculate the amounts of each
compound required, based on the scale desired and the
molecular weights of the compounds to be used. It may be
noted at this point that the preferred mole ratio of soft
segment to hard segment is~ about 1. Consequently, the
preferred range for m is from 0 to about 24.
~ From the discussion thus far, it should be apparent
that the mole ratio of soft segment to hard segment in the
polymeric composition cannot be greater than 2 or less than
~ 0.5. If the reaction mixture S:H mole ratio is outside of
:
.
, - --- - .
.- :
:
:
.
.
.
13~7~
this range, there necessarily must be present in the final
reaction mixture unreacted soft or hard segment. Such a
result comes withln the scope of the present invention, but
is not preferred since such unreacted segments generally
contribute to increased water solubility and decreased
absorbence of the final reaction product which typically is
not purified to remove unreacted materials and/or unwanted
by-products of the reaction.
As a practical matter, the permissible molecular
weight ranges of the first compound and the soft segment
are essentially the same since the molecular weight of the
second compound is relatively small when compared with that
of the first compound. Consequently, the same range is
used herein for both the first compound and the soft
segment as a matter of convenience, it being understood
that (1) the range is approximate only and (2) in reality,
the range of the soft segment is slightly greater than that
of the first compound as a result of the reaction between
first compound and second compound.
From the discussion thus far, it should be apparent
that Xl, X2, and X5 represent the nonfunctional group
portions of second compounds and that they typically will
be the same since only one second compound usually is
employed. Similarly, X3 and X4 represent the nonfunctional
group portions of third compounds and X3 and X4 typically
will be the same since only one third compound usually is
employed. In addition, Zl and Z2 and 23 and Z4 represent
the functional group portions of the second and third
compounds, respectively. Furthermore, Yl and Y2 and Y3 and
Y4 represent linkages which result from the reaction of the
functional groups of second compounds with ~hose of the
first and third compounds, respectively. Typically, all of
such linkages will be the same.
As already stated, the superabsorbent, thermoplastic
polymeric composition of the presen~ invention can be
prepared by the method which comprises:
~3 ~
, ... .
13~6~
(A) reacting a first compound with a second
compound at a temperature of from about S0 to about
20p degrees C for a time sufficient to effect
essentially complete reaction; and
(B) reacting with the product from step A a
third compound at a temperature of from about 80 to
about 200 degrees C for a time sufficient to obtain a
melt index of less than about 1,000 g per 10 minutes
under the test conditions described hereinafter;
in which said first compound is a difunctional
poly(oxyethylene) having a weight average molecular weight
of from abbut 5,000 to about 50~000; said second compound
is an aliphatic, cycloaliphatic, aromatic, or heterocyclic
compound having two functional groups which are reactive
with the functional groups of said first compound; the mole
ratio of said second compound to said first compound is in
the range of from about 2 to about 100; said third compound
is an aliphatic, cycloaliphatic, aromatic, heterocyclic, or
polymeric compound having two functional groups which are
reactive with the functional groups of said second
compound; the reaction product of said first compound with
said second compound, excluding excess second compound, is
from about 86 to about 98 percent by weight of the final
composition; and said third compound plus the excess of
said second compound are from about 2 to about 14 percent
by weight of the final composition.
In the first step of the above method, first compound
is reacted with second compound at a temperature in the
~ range of from about 50 to about 200 degrees C for a time
sufficient to effect essentially complete reaction. The
reaction temperature preferably will be in the range of
from about 80 to about 150 degrees C and most preferably
will be in the range of from about 95 to about 120 degrees
C.: While reaction time is not critical, typically the
reaction time will be in the range of from about 20 minutes
''''' ~ .' . `
:' '
~.
.,
1317~
to about 3 hours when the reaction is carried out in the
most preferred temperature range.
The mole ratio of second compound to first compound
should be in the range of from about 2 to about 100.
Because the hard segment must be polymeric, a larger excess
of second compound relative to first compound is requirPd
when the third compound is a monomer; in such cases, the
polymeric hard segment is formed in situ. If desired,
however, the third compound can be a polymer. All that is
required in this case is to provide sufficient second
compound to covalently link first compound with third
compound to give the composition of the present invention.
Thus, when the third compound is a monomer, the preferred
mole ratio of second compound to first compound is from
about 2.5 to about 50; the most preferred mole ratio is
from about 2.5 to about 26. When the third compound is
polymeric, the preferred mole ratio of second compound to
first compound is from about 2 to about 5.
Preferably, the first compound will have a weight
average molecular weight of from about 8,000 to about
50,000, more preferably from about 8,000 to about 30,000,
and most preferably from about 8,000 to about 16, 000.
As already noted, the first compound most preferably
is a poly(oxyethylene) diol. When such a compound is
employed, the second compound most preferably is a
diisocyanate and the third compound most preferably is a
diol. In preferred embodiments, he first compound is a
poly(oxyethylene) diol having a weight average molecular
weight of from about 8,000 to about 16,000, the second
compound is 4,4'-methylenebis(phenylisocyanats), the third
compound is 1,4-butanediol, and the percent hard seqm nt in
the composition is in the range of from about 3 to about 5
percent by weight of the total composition.
The second step of the method of the present invention
involves reacting the product from the first step with a
third compound at a temperature of from about 80 to about
~.
.. ~, . . . .
1 3~769~
200 degrees C for a time sufficient to obtain a melt flow
rate of less than about 1,000 g per 10 minutes.
Preferably, the reaction temperature will be from about 90
to about 150 degrees C, and most preferably from about 110
to about 130 degrees C.
Although the use of a solvent usually is not
necessary, one or more solvents may be employed in either
or both steps, if desired. For example, the use of a
solvent may be convenient if the viscosity of the reaction
mixture in the first step is too high to allow satisfactory
mixing.
In general, any solvent can be used which is not
reactive with any of the components of the reaction mixture
and in which the reactants are sufficiently soluble.
Examples of suitable solvents include, by way of
illustration only, aliphatic ketones, such as acetone,
methyl ethyl ketone, methyl propyl ketone, and the like;
aliphatic esters of the lower aliphatic carboxylic acids,
such as ethyl acetate, methyl propionate, butyl acetate,
and the like; aliphatic ethers, such as diethyl ether,
methyl propyl ether, and the like; aromatic hydrocarbons,
such as benzene, toluene, the xylenes, and the like;
halogenated aliphatic hydrocarbons, such as methylene
chloride and the like; dioxane; tetrahydrofuran;
dimethylformamide; N-methylpyrrolidone; and the like. The
amount of solvent used is not known to be critical.
However~ a substantial amount of solvent preferably will
not be present in the reaction mixture at the conclusion of
the second step.
As already stated, the melt flow rate of the reaction
mixture at the end of the second step should be less than
about 1,000 g per 10 minutes. The melt flow r~te value is
for a solvent-free reaction mixture. The target value for
the malt flow rate is largely dependent upon the use
intended for the resulting composition. For example, if
the composition is to be converted into a nonwoven web or
B ~9
_ g~_
,,
,, ~ .
. -, ~
..
~31769~
fabric, the melt flow rate should be from about 20 to about
500 g per 10 minutes, preferably from about 50 to about
400 g per l0 minutes, and most preferably from about 80 to
about 300 g per l0 minutes. On the other hand, if the
composition is to be extruded as a film, the melt ~low rate
of the final reaction mixture probably should be from about
10 to about 30 g per 10 minutes.
The melt flow rate was determined in accordance with a
slightly modified version of ASTM Test Method D1238-82,
"Standard Test Method for Flow Rates of Thermoplastics by
Extrusion Plastometer," using a Model VE 4-78 Extrusion
Plastometer (Tinius Olsen Testing Machine Co., Willow
Grove, Pennsylvania). The modifications were as follows:
(l) the sample was predried at ambient temperature under
reduced pressure prior to loading; (2) the piston was not
preheated; (3) the sample was loaded in 2-3 minutes; and
(4~ the loaded sample was preheated for 5 minutes. In
every case, a 2.16 kg load was employed and the orifice
diameter was 2.0955 + 0.0051 mm.
As already noted, the stable, nonreactive,
thermoplastic polymer blend comprises from about l0 to
about 95 percent by weight of a superabsorbent,
thermoplastic polymeric composition and from about 90 to
about 5 percent by weight of at least one thermoplastic
polymer. The level of polymeric composition present in the
blend preferably will be in the range of from about 30 to
about 90 percent by weight, and most preferably will be in
the range of from about 40 to about 75 percent by weight.
As used herein, the phrase "stable, nonreactive
thermoplastic polymer blend" means that: (l) the blend is
stable at temperatures rang1ng from ambient temperature to
the maximum temperature at which the blend may be melt
processed; (2) the components of the blend do not react to
a significant extent with each other; and (3) the blend is
capable of beiny melt processed without significant
decomposition or other deleterious effects. The term
,
~3~7~94
~st~ble~ has refer~nce prim~ri~y to chemica1 stability; it
excludes phase s~para~ion in so ~ar as ~ny phase separation
which may occur does not have a significant deleterious
effect on the melt processability of the blend.
Stated differently, phase separation is permissible i
it does not have a signiicant deleterious effect on the
melt processability of the blend. Phase separation can
occur at the melt processing temperature or at lower
temperatures. In act, the components of the blend need
not form a homogeneous mixture at any stage o~ melt
processing.
In addition to a superabsorbent, the~moplastic
polymeric composition, the blend also contains at least one
thermoplastic polymer. The thermoplastic polymer can be
any thermoplastic polymer which ~ill result in a stable,
nonreactive, thermoplastic polymer blend.
Examples o~ thermoplastic polymers include, ~y way of
illustration only, end capped polyacetals, s~ch as poly-
(oxymethylene~ or polyformaldehyde, poly(trichloroacetal-
dehyde), poly(_-~aleraldehydej, poly(acetaldehyde),
poly(propionaldehyde), and the like; acrylic polymers, such
as polyacrylamide, poly(acrylic acid), poly(methacrylic
acid), poly~ethyl acrylate), poly(methyl methacrylate), and
the like; fluorocar~on polymers, such as poly(tetrafluoro-
ethylene), per~luo~inated ethylene-propylene copolymer,
ethylene-tetrafluoroethylene copolymer, poly(chlorotri-
fluoroe~hylene), ethylene chlorotrifluoroe~hylene
copolymer, poly(vinylidene fluoride), poly(vinyl fluoride),
and the liXe; polyamides, such as poly(6- aminocaproic acid)
or poly ( ~ -caprolactam), poly(hexamethylene adipamide),
poly(hexamethylene sebacamide), poly(ll-aminoundecanoic
acid), and the like; polyaramides, subh a~ poly(imino-1,3-
phenyleneiminoisophthaloyl) or poly(m-phenylene isophthala-
mide), and the like; parylenes, such as poly-~-xylylene,
poly(chloro-~-xylylene), and the like; polyàryl ethers,
such as poly(oxy-2,6-dimethyl-1,4-phenylene) or poly(p-
- 31 -
E
~3~7~9~
phenylene oxide~, and the like; polyaryl sulfones, such as
poly(oxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenyl-
ene-isopropylidene-1,4-phenylene), poly(sulfonyl-1,4-
phenyleneoxy-1,4-phenylenesulfonyl-4,4'-biphenylene), and
the like; polycarbonates, such as poly(bisphenol A) or
poly(carbonyldioxy-1,4-phenyleneisopropylidene-1,4-phenyle-
ne), and the like; polyesters, such as poly(ethylene
terephthalate), poly(tetramethylene terephthalate),
poly(cyclohexylene-1,4-dimethylene terephthalate) or
poly(oxymethylene-1,4-cyclohexylenemethyleneoxyterephthal-
oyl), and the like; polyaryl sulfides, such as poly(~-
phenylene sulfide) or poly(thio-1,4-phenylene), and the
like; polyimides, such as poly(pyromellitimido-1,4-
phenylene~, and the like; polyolefins, such as poly-
ethylene, polypropylene, poly(l-butene), poly(2-butene),
poly(l-pentene), poly(2-pentene), poly(3-methyl-1-pentene),
poly(4-methyl-1-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-
1,3-butadiene, polyisoprene, polychloroprene, polyacrylo-
nitrile, poly(vinyl acetate), poly(vinylidene chloride),
polystyrene, and the like; copolymers of the foregoing,
such as acrylonitrile-butadiene-styrene (ABS) copolymers,
and the like; and the like.
The preferred thermoplastic polymers are polyolefins,
with polyethylene and polypropylene being most preferred.
It should be apparent to those having ordinary skill
in the art that the present invention contemplates blends
containing two or more superabsorbent, thermoplastic
polymeric compositions and/or two or more thermoplastic
polymers. Furthermore, the blends of the present invention
are readily obtained by known procedures.
While the blends contain at least one superabsorbent,
thermoplastic polymeric composition, such blends may or may
not be superabsorbent, depending upon the level and
absorb~ncy of the superabsorben , thermoplastic polymeric
composition in the blend and the availability of the
polymeric composition to aqueous media.
~ ~ '
.:
.,
7~
~ecause the composition and blend of the present
invention are thermoplastic, they can be melt processed to
give films, fibers, nonwoven webs, molded articles,
powders, particles, rods, tubes, and the like. Such
compositions are especially useful for the preparation of
nonwoven webs by meltblowing and spunbonding processes,
such as those described in U.S. Patent Nos. 3,016,599,
3,755,527, 3,704,198, 3,849,241, 3,341,394, 3,692,618, and
4,340,563. Such compositions also can be used in
variations thereo~. For example, the compositions can be
used to prepare a coformed nonwoven material as described
generally in U.S. Patent No. 4,100,324.
Thus, the formation of fibers from the compositions of
the present invention by melt spinning techniques
represents the area of greatest interest. As used herein,
however, the term "fiber" includes not only fibers which
consist solely of a composition of the present invention,
but also polycomponent fibers, at least one component of
which is a composition of the present invention.
Polycomponent fibers are, of course, well known in the
art, the two most common examples being sheath-core fibers
and side-by-side bicomponent fibers. By way of
illustration, a sheath-core fiber could have a
polypropylene core and a sheath of a composition of the
present invention. Alternatively, the sheath and core
polymers could be two different compositions of the present
invention. In the alternative case, the core perhaps would
be a higher molecular weight polymer having an absorbency
lower than that of the sheath composition. Similar polymer
selections also are possible with a side-by-side
bicomponent fiber.
Tricomponent, and higher polycomponent, fibers are
known. In such cases, one or more of the components can be
a composition of the present invention.
B -~-
'~dA,''
. . :.
1317~9~
Although the compositions of the present invention are
particularly well-suited for the formation of nonwoven webs
by meltblowing and coforming, the preparation of nonwovens
by other methods is contemplated and comes within the scope
of the present inventionO For example, continuous
filaments can be produced by melt spinning techniques,
collected as a tow, and converted to staple fibers.
Nonwovens then can be prepared by carding, air forming, or
the like. Variations in the production of the staple
fibers, such as false twisting, crimping, and the like, can
be practiced, if desired.
The present invention is further described by the
following examples which illustrate specific em~odiments.
Such e~amples are not to be construed as in any way
limiting either the spirit or scope of the present
invention. In the examples, all temperatures are in
degrees Celsius and all amounts are in parts by weight,
unless specified otherwise. In every case, the
poly(oxyethylene) diol was dried overnight at 95 degrees C
under reduced pressure in order to reduce water content to
0.01 percent by weight or less and the assembled resin
kettle was heat-dried by passing a portable butane burner
flame over the external kettle surfaces while purging the
vessel with nitrogen.
A. Preparation of Therm~plastic Superabsorbent.
Example 1
A 500-ml, wide mouth, two piece resin kettle with
ground glass flanges and a four-necked cover was charged
with 203 g (0.025 mole) of a poly(oxyethylene) dio~ having
a molecular weight of 8,000 (CARBOWAX~ PEG-8,000, Union
Carbide Corporation, South Charleston, West Virginia) and
19.5 g (0.078 mole) of 4,4'-methylenebis(phenylisocyanate)
(Eastman Kodak Co., Rochester, New York~. The cover ~as
~ 3 ~
_ ~ _
.
r
'
~ rl~9~;
attached and fitted with a nitrogen inlet, thermometer,
condenser, and high torque mechanical stirrer (Caframa,
Type RZR50, CSA3 Wiarton, Ontario, Canada; Fisher Catalog
No. 14-500, Fisher Scientific, Pittsburgh, Pennsylvania).
The kettle was flushed with nitrogen and maintained under a
nitrogen atmosphere. The reaction mixture was heated to
100 degrees over a one-hour period and maintained at that
temperature with stirring for one hour. The kettle then
was charged with 4.8 g (0.053 mole) of 1,4-butanediol
(J. T. Baker Chemical Co., Phillipsburg, New Jersey).
Stirring and heating at 100 degrees were continued for
about 15 minutes, during which time the viscosity of the
reaction mixture increased to the point where the mixture
began to climb up the shaft of the stirrer. The reaction
mixture was cooled, removed from the kettle, and stored.
The resulting composition consisted of 94.8 percent by
weight soft segment and 5.2 percent by weight hard segment,
calculated as follows: from formula (2), it is seen that
the weight of soft segment is approximately equal to the
amount of first compound or poly(oxyethylene) diol plus an
amount of second compound or diisocyanate which is equal to
twice the molar amount of first compound. The remaining
amount of second compound plus third compound or
1,4-butanediol constitutes the weight of hard segment.
Since 0.025 mole of first compound was employed, the weight
of second compound which must be added to the weight of
first compound is 0.05 mole x 250 g/mole or 12.5 g. Thus,
the weight of soft segment is 203 g plus 12.5 g, or 215.5
g, while the weight of the composition must equal the sum
of the weights of the components, or 227.3 g.
Consequently, the percent of soft segment present in the
composition is equal to (215.5 x 100)/227.3, or 94.8
percent. The remainder, of course, is hard segment.
~ ~ 5
.
.
. . ~
.. ' .
1317~9~
Example 2
The procedure of Example 1 was repeated, except that
the second stage or step B reaction time was 240 minutes.
The final reaction mixture viscosity was comparable to that
of Example 1. As with Example 1, the composition consisted
of 94.8 percent by weight soft segment and 5.2 percent by
weight hard segment.
Example 3
The procedure of Example 1 was repeated, except that
the initial kettle charge consisted of 214 g (0.015 mole)
of a poly(oxyethylene) diol having a molecular weight of
14,000 (CARBOWAX~ PEG-14,000, Union Carbide Corporation,
South Charleston, West Virginia) and 10.5 g (0.042 mole) of
the diisocyanate, the amount of 1,4-butanediol was 2.43 g
(0.027 mole), and the second stage or step B reaction time
was 83 minutes. The composition obtained consisted of 97.3
percent by weight soft segment and 2.7 percent by weight
hard segment.
Example 4
The procedure o Example 3 was repeated, except that
the amount of the poly(oxyethylene) diol was decreased
slightly to 196 g (0.014 mole), the amount of diisocyanate
was increased to 14.5 g (0.058 mole), the amount of
1,4-butanediol was increased to 4.21 g tO.044 mole), and
the second stage or step B reaction time was 96 minutes.
The composition thus obtained consisted of 94.7 percent by
weight soft segment and 5.3 percent by weight hard segment.
,." ,, ~ . , ~- ~
~ ` - ` ` .
,
,
1~17~9~
Example 5
The procedure of Example 3 was repeated eleven times,
except that a 2-1 resin kettle was employed and the amounts
S of poly(oxyethylene) diol, diisocyanate, and 1,4-butanediol
were increased four-fold to 857 g (0.061 mole), 42 g (0.168
mole), and 9.6 g (0.107 mole), respectively. In addition,
the second stage or step B reaction was continued until the
torque on the stirrer reached about 3.2 lb-in, at which
time 10.5 g (0.14 mole) of n-butanol was added as a
molecular weight limiter. The eleven batches were labeled
5A-5K, respectively. As with Example 3, the compositions
consisted of 97.3 percent by weight soft segment and 2.7
parcent by weight hard segment.
Because higher molecular weight polytoxyethylene)
diols were not available in sufficiently pure form, lower
molecular weight poly(oxyethylene) diols were coupled by
means of urethane linkages, the extent of coupling being
controlled by the ratio of diol and diisocyanate. The
coupling reaction in effect yields a soft segment.
Consequently, the preparation of the final superabsorbent
thermoplastic composition requires the addition of both
second compound and third compound for the second stage or
step B reaction. This coupling reaction and the subsequent
formation of the final composition are illustrated by
Examples 6-9, inclusive.
Example 6
A 500-ml, wide mouth, two piece resin kettle with
ground glass 1anges and a four-necked cover was charged
with 211 g (0.0264 mole) of the poly(oxyethylene) diol
empIoyed in Example 1 and 9.9 g (0.0396 mole) of
4,4l-methylenebis(phenylisocyanate) (a 3:2 mole ratio of
diisocyanate to PEG). The cover was attached and fitted as
3 ~
r
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.
' "
,
, .
.
~17~9~
described in Example 1. The kettle was flushed with
nitrogen and maintained under a nitrogen atmosphere. The
reaction mixture was heated to 100 degrees over a one-hour
period -and maintained at that temperature with stirring for
one hour. The kettle then was charged with an additional
3.3 g ~0.0132 mole) of the diisocyanate and 2.4 g (0.0266
mole) of 1,4-butanediol. Stirring and heating at 100
degrees were continued for about 134 minutes, during which
time the viscosity of the reaction mixture increased to the
point where the mixture began to climb up the shaft of the
stirrer. The reaction mixture was cooled, removed from the
kettle, and stored. The resultiny composition consisted of
97.5 percent by weight soft segment and 2.5 percent by
weight hard segment.
The modified poly(oxyethylene) diol obtained from the
first staye or step A reaction, before carrying out the
next step, was composed of two molecules of the
poly~oxyethylene~ diol linked together by the diisocyanate.
Such modified poly(oxyethylene) diol can be represented
schematically as follows: MDI-PEG-MDI-PEG-MDI in which MDI
represents the diisocyanate and PEG represents the
poly(oxyethylene) diol. Such modified poly~oxyethylene)
diol or soft segment had a molecular weight of about
16,750.
Example 7
The procedure of Example 6 was repeated two times,
except that in each case a 2-1 resin kettle was employed,
the initial kettle charge consisted of 845 g (0.106 mole)
of poly(oxyethylene) diol and 39.6 g (0.158 mole) of
diisocyanate (a 3:2 mole ratio of diisocyanate to PEG), the
subsequent kettle charge consisted of 13.2 g (0.053 mole)
of diisocyanate and 9.6 g (0.107 mole) of 1,4-butanediol,
and the ~econd stage or step B reaction times for the two
procedures were 113 minutes and lS9 minutes, respectively.
-~` 131769~
The two batches of po~ymers were labeled 7h and 7B,
respectively. As with Example 6, the compositions
consisted of 97.5 percent by weight soft segment and 2.5
percent by weight hard segment.
Example 8
The procedure of Example 6 was repeated, except that
the initial kettle charge consisted of 240 g (0.017 mole)
of the poly(oxyethylene) diol employed in Example 6 and 6.4
g (0.026 mole) of the diisocyanate (a 3:2 mole ratio of
diisocyanate to PEG), the subsequent kettle charge
consisted of 5.3 g (0.021 mole) of the diisocyanate and 2.7
g (0.030 mole) of 1,4-butanediol, and the second stage or
step B reaction time was 124 minutes. The resulting
composition consisted of 96.8 percent by weight soft
segment and 3.2 percent by weight hard segment.
The modified poly(oxyethylene) diol obtained from the
first stage or step A reaction was composed of two
molecules of the poly(oxyethylene) diol linked together by
the diisocyanate. Such modified poly(oxyethylene) diol can
be represented schematically as follows: MDI-PEG-MDI-PEG-
MDI. Such modified poly(oxyethylene) diol or soft segment
had a molecular weight of about 28,750.
Example 9
The procedure of Example 6 was repeated, except that
the initial kettle charge consisted of 211 g (0.026 mole)
of the poly(oxyethylene) diol employed in Example 3 and 8.3
g (0.033 mole) of the diisocyanate (a 5:4 mole ratio of
dilsocyanate to PEG), the subsequent kettle charge
consisted of 5.0 g (0.020 molel of the diisocyanate and 2.4
g (0.027 mole) of 1,4-butanediol, and the second stage or
step~ B reaction time was 200 minutes. The resulting
'
' . ',-
.'
13~7~
composition consisted of 96.8 percent by weight soft
segment and 3.2 percent by weight hard segment.
The modified poly(oxyethylene) diol obtained from the
first stage or step A reaction was composed of four
molecules of the poly(oxyethylene) diol linked together by
the diisocyanate. Such modified poly(oxyethylene) diol can
be represented schematically as follows: MDI-PEG-MDI-PEG-
MDI-PEG-MDI-PEG-MDI. Such modified poly(oxyethylene) diol
or soft segment had a molecular weight of about 33,250.
As already noted, Examples 6-9, inclusive, detail the
preparation of soft segment followed by the in situ
preparation of hard segment with the concomitant formation
of the desired composition. It is possible, of course, to
prepare both the soft and hard segments separately and then
combine them to obtain a superabsorbent thermoplastic
composition. This procedure is illustrated by Example 10.
Example 10
Preparation of Hard Segment
A 50-m~, wide mouth, two piece resin kettle with
yround glass flanges and a three-necked cover was charged
with 9.96 g ~0.1107 mole) of 1,4-butanediol (J. T. Baker
Chemical Co., Phillipsburg, New Jersey) and 13.a3 g ~0.0553
mole) of 4,4'-methylenebis(phenylisocyanate~ (Eastman Kodak
Co., Rochester, New York). The cover was attached and
fitted with a nitrogen inlet, condenser, and mechanical
stirrer (T line Laboratory Stirrer, Model No. 134-2,
Talboys Engineering Corp., Emerson, New Jersey). The
kettle was flushed with nitrogen and maintained under a
nitrogen atmosphere. The reaction mixture was heated in an
oil bath to 72 degrees over ten minutes, after which a
solid material formed. The resulting hard segment melted
over the range 175-185 degrees.
"~, .. . . .
'
1 3 ~
The hard segment was characterized by hydroxyl number
in order to estimate the molecular weight of the hard
segment, or the extent of coupling of diol to diisocyanate.
The hydroxyl number, which is defined as the number of
milligrams of potassium hydroxide equivalent to the
hydroxyl content of 1 g of sample, was determined as
follows: Duplicate approximately 1.5 g samples were
weighed into tared single-necked round-bottomed flasks. To
each 1ask was added exactly 25 ml of phthalating reagent
which consisted of 42.0 g of phthalic anhydride in 300 ml
of freshly distilled pyridine. Each flask was fitted with
a condenser and purged slowly with nitrogen. The flasks
were placed in an oil bath at 115 degrees for one hour.
Using five drops of phenoIphthalein solution as the
indicator, the reaction solution of each flask was titrated
while hot with 0.5 N aqueous sodium hydroxide to a faint
pink end-point lasting for 15 seconds. Blank samples were
run with only the phthalating reagent. The hydroxyl number
then was calculated by dividing the milliequivalents of
potassium hydroxide required (corrected for the blank) by
the weight of the sample. The average hydroxyl number from
the duplicate runs was 270. This n~mber is equivalent to
an apparent molecular weight for the hard segment of 416.
Since the theoretical hard segment molecular weight is 430,
the hydroxyl number indicates that there probably was a
slight excess of 1,4-butanediol present in the hard seqment
reaction mixture.
Preparation of Soft Segment
A 500-ml, wide mouth, two piece resin kettle with
ground glass flanges and a four-necked cover was charged
with 391.5 g tO.028 mole) of the poly(oxyethylene) diol and
13.98 g (0.056 mole) of the diisocyanate employed in
Example 3. The cover was atta~hed and fitted with a
nitrogen inlet, thermometer, condenser, and high torque
B ~l
. . ,~. ~
~3176~d
mechanical stirrer (Caframa, Type RZR50, CSA~, Wiarton,
Ontario, Canada; Fisher Catalog No. 14-500, Fisher
Scientific, Pittsburgh, Pennsylvania). The kettle was
flushed with nitrogen and maintained under a nitrogen
atmosphere. The reaction mixture was heated to 100 degrees
over a one-hour period and maintained at that temperature
with stirring for 231 minutes.
Preparation of 5u~erabsorbsnt Thermoplastic Composition
To the resulting soft segment was added 11.63 g (0.027
mole) of hard segment dissolved in about 40 ml of dry
N-methyl-2 pyrrolidinone~ The resulting mixture was heated
at 72-82 degrees for 158 minutes to give the desired
composition, the last 15 minutes being under reduced
pressure to remove the solvent. The resulting composition
consisted of 97.2 percent soft segment and 2.8 percent hard
segmentO
The compositions prepared in the preceding examples
all are polyether urethanes based on a poly(oxyethylene)
diol and an aliphatic third compound, 1,4-butanediol.
Moreover, in cases where the poly(oxyethylene) diol was
coupled to give a modified poly(oxyethylene) diol leading
to a higher molecular weight soft segment, coupling
employed a diisocyanate which resulted in the formation of
urethane bonds. Conse~uently, all of such compositions
contain onl~ ether and urethane linkages.
As already stated, however, the compositions of the
present invention are not limited to aliphatic third
compounds or only to ether and urethane linkages, as
demonstrated by the next five examples.
:
' .
~3~769~
Example 11
Preparation of Polyether Urethane Ester
Following ~he procedure of Example 1, the resin kettle
wascharged with 212.8 g (0.0266 mole) of the
poly(oxyethylene) diol employed in Example 1. As the diol
was being heated to 95 degrees, 2.70 g (0.0133 mole) of
terephthaloyl chloride (recrystallized from hexane) was
added to the resin kettle. Unlike the use of a
diisocyanate as a coupling agent, the use of terephthaloyl
chloride does not resul~ in the formation of soft segment.
The resulting reaction mixture was heated, with stirring
and under a nitrogen atmosphere, at 95 degrees for about
1.5 hours. To the kettle then was added 10.0 g (0.040
mole) of the diisocyanate employed in Example 1; the
temperature of the reaction mixture now was 104 degrees.
After an additional hour, 2.40 g (0.0267 mole) of
1,4-butanediol was added. The reaction mixture was heated
for one more hour, at which time 2.0 g tO.027 mole) of
n-butanol was added as described in Example 5. The
resulting composition contained 97.5 percent soft segment
and 2.5 percent hard segment.
Example 12
Use o~ a Third Compound Containin~ an Aromatic Group
: The procedure of Example 1 was ~epeated, except that
the initial kettle chaxge consisted of 305.6 g 10.0382
mole) of the poly(oxyethylene) diol and 19.1 g (0.0764
mole) o~ the diisocyanate, in the second stage reaction the
1,4 butanediol was replaced with 7.56 g (0.038 mole~ of
hydroquinone ~isl2-hydroxyethyl) ether IEastman Kodak Co.,
Kingsport, Tennessee~, and the second state or step B
reaction time was 47 minutes. It may be noted that the
-" 13176~
first compound : sec~nd compound : third compound mole
ratio was 1:2:1. The resulting composition contained 97.7
percent soft segment and 2.3 percent hard segmen~.
Example 13
In order to evaluate the effect of replacing the third
compound us~d in Example 12 with the aliphatic diol
employed in Examples 1-10, inclusive, the procedure of
Example 12 was repeated with the same 1:2:1 mole ratio of
first compound : second compound : third compound. Thus,
the initial kettle charge consisted of 208 g (0.026 mole)
of the poly(oxyethylene) diol and 13O25 g (0.053 mole) of
diisocyanate, the amount of 1~4-butanediol was ~.34 g
(0.026 mole), and the second stage or step B reaction time
was 280 minutes. The resulting composition consisted of
98.8 percent soft segment and 1.2 percent hard segment.
The decrease in the percent hard segment relative to the
composition of Example 12 is a result of the lower
molecular weight of 1,4-butanediol.
Example 14
Preparation of Polyether Urethane Amide
Following the procedure of Example 11, the resin
kettle was charged with 63.81 g (0.007g8 mole) of the
poly(oxyethylene) diol employed in Example l and 250 ml of
dry N-methyl-2-pyrrolidinone. A the reaction mixture was
b ing heated and after the diol had dissolved, 3.99 g
(0.01596 mole) of the diisocyanate employed in Example l
was addea to~the Xettle. The reaction solution was heated
at 65 degrees for one hour. To the resin kettle then were
added 1.17 g (0~00798 mole) of~ adipic acid, 100 ml of
35~ ~N-methyl-2-pyrrolidinone, and a catalytic amount of sodium
hydride. The resulting solution was heated at 120 degrees
:
.
::
: '
for one hour. Films were cast from the reaction solution
~nd air dried, followed by drying under reduced pressure at
80 degrees. The composition consisted of 98.3 percent soft
segment and 1.7 percent hard segment.
Example 15
Preparation of Polyether Urethane Amide
Following the procedure of Example 14, the resin
kettle was charged with 45.02 g (0.0032 mole) of the
poly(oxyethylene) diol of Example 3, 4.89 g (0.0196 mole)
of the diisocyanate, and 300 ml of dry
~-methyl-2 pyrrolidinone. The reaction mixture was heated
to 100 degrees over a one-half hour period and maintained
at that temperature for 1.5 hours. To the kettle then were
added 2.40 g (0.016 mole) of adipic acid and a catalytic
amount of sodium hydride. Heating was continued for an
additional hour. The composition consisted of 89.1 percent
soft segment and 10.9 percent hard segment.
The next example briefly summarizes scale-up
activities with respect to certain of the compositions
prepared in the preceding examples.
Example 16
The procedure of Example 6 was repeated a number of
~times~ in 50-lb. and 200-lb. batches using appropriate
multiples of reactantsO The second step reaction was
~oarried out ~for four hours at 130 + 3n degrees. In each
case,~ zinc octoate was added with the 1,4-butanediol at a
level~o~ 8 g zinc octoate per 1,000 lbs. of polymer. Each
-
composition, of course, consisted of 97.5 percent by weight
soft segm nt and 2.5 percent by weight hard segment.
B -'~
~ : r
13~7~
The compositions obtained in the above examples were
characterized by a number of methods:
1. Infrared analysis (IR). A sample of the
composition was mulled in Nujol. The instrument was a
Perkin-Elmer Model 710B Spectrophotometer (Perkin-Elmer
Corporation, Norwalk, Connecticut).
2. Proton nuclear magnetic resonance analysis (NMR).
The sample was dissolved in chloroform at a concentration
of 10 percent by weight. The instrument was an IBM
Instruments Model NR/250AF 250 Megahertz Spectrophotometer
(I~M Corporation, Armonk, New York).
3. Elemental anal~__s (EA?. Elemental analyses were
carried out by Atlantic Microlabs, Atlanta, Georgia.
4. Inherent viscosity (IV)~ The apparatus employed
was a Schotte Gerate XPG~ Ubbelohde Viscometer (Jenaer
Glasswerk Schott & Gen., Mainz, Germany) with a suspended
level bulb. The sample was dissolved in m-cresol at a
concentration of 0.5 percent, weight per volume. The
solution was filtered through a medium frit scintered glass
funnel and equilibrated 30 min at 30 degrees in a constant
temperature bath (Canner Instrument Company, Boalsburg,
Pennsylvania) before measuring the rate of flow.
5. Melting Point (MP). The melting point range of
the sample was determined by means of a hotbench
(C. Reichert Ag., Wien, Austria).
6. Melt flow rate (MFR). The melt flow rate was
determined as described at page 31.
7. Tensile strength _ (TS) _(Ultimate Modulus).
Tensile strength was measured on film samples by means of
an Instron Model 1122 (Instron Corporation, Canton,
Massachusetts~. Films were made in a Carver Laboratory
Press, Model 2518 (Fred S. Carver, Inc., Menomonee Falls,
Wisconsin) at 175 degrees and pressure less than 100
pounds, the minimum gauge pressure reading. Since roughly
S g of polymer was employed in each case and film thickness
varied from 0 010 to 0.031 inch (0.25 to 0.79 mm), the
.., ,.~.. . . . .
.
: ' '
-
. 1317g9~
estima~ed pressure range was from about 2 to about 10 psi.
The films were equilibrated at ambient temperature and
humidity for at least one day. Rectangular film samples
measuring 0.5 x 1.5 lnch (12.7 x 38.1 mm) were cut from the
films. The ends of the samples were wrapped with masking
tape. The Instron grips had 1 x 1.5 inch (25.4 x 38.1 mm)
smooth rubber faces. Gauge length was one inch (25.4 mm)
and the crosshead speed was 2 inches (50.8 mm) per minute.
8. Thermal ~ravimetric analy~ (TGA). Thermal
gravimetric analysis employed a DuPont Model 1090 Thermal
Analyzer with a Model 1091 Disc Memory and a Model 950
Thermal Gravimetric Analyzer (DuPont Instruments,
Wilmington, Delaware). Each polymer sample (8-10 mg) was
weighed in a tared platinum sample pan and heated to 550
degrees at 10 degrees/minute.
9. Differential scanning calorimetry (DSC). Each
polymer was analyzed by differential scanning calorimetry
using a DuPont Model 1090 Thermal Analyzer with a Model
1091 Disc Memory and a Model 910 Differential Scanning
Calorimeter (DuPont Instruments, Wilmington, Delaware).
Polymer (about 4 mg) was weighed in a tared,
non-hermetically sealed aluminum pan and cooled in the
sample cell to -80 degrees with a liquid nitrogen jacket.
1'he sample then was heated at 10 degrees/minute to 550
degrees.
10. Centrifu~e Absorbency (A) and Solubility (S).
Absorbency was determined with either water ~WA) or with
synthetic urine (SUA). Briefly, a polymer sample was
melt-pressed into a film essentially as described abo~e in
method 7 (tensile strength). A film thickness of 0.0109
inch (0.28 mm) was achieved by using flat metal spacer
strips and TEFLON~-coated foil. The film was cut into l-cm
squares which were weighed. Each square was placed in
water or synthetic urine at ambient temperature and allowed
to soak for four hours. The soaked sample was placed in a
centrifuge tube adapter. The adapter had at the bottom a
.
13~7~9~
barrier to the sample which was permeable to the test
liquid under the conditions of centrifugation. The sample
then was centrifuged at 1,000 rpm (196 x G) for 30 minutes.
To the extent possible, the sample was removed from the
centrifuge tube adapter and placed in a tared aluminum
weighing dish. The sample was weighed, dried for three
hours at 90 degrees, and reweighed. The absorbency then
was calculated in accordance with the following equation
A = (wt. wet - final wt. dry)/final wt. dry
Thus, absor~ency is the number of g of test liquid absorbed
per g of sample, corrected for soluble sample. When
synthetic urine was used, the final dry weight also was
corrected for the solids present in the absorbed liquid.
The solubility of the test sample, expressed as a
percentage, was calculated from the water absorbency data
as follows:
S = lOO(initial wt. dry - final wt. dry)/initial wt. dry
The synthetic urine test liquid contained the
~ollowing compounds in the amounts shown, per liter of
liquid:
0.309 g of Ca(H2PO4)2.H2O
0.681 g of KH2PO4
0.477 g o MgSO4.7H2O
1.333 g of K2SO4
g 3 4 2
4.441 g of NaCl
3.161 g of KCl
0.400 g of NaN3
8.560 g of urea
The compounds were added in the order listed to 900 ml
of distilled water in a well rinsed, chromic acid washed,
_ ~~~ r
r
.
- ' .
1000 ml volumetric flask; each compound was dissolved
completely before the next one was added. Distilled water
then was added to the mark. The total solids content of
the synthetic urine was 20.606 g/liter which is
approximately equivalent to 2.01 percent by weight.
The IR and NMR analyses supported the structures
described herein for the compositions of the present
invention, as did the EA. The MP determinations gave broad
ranges which were indicative of wide molecular weight
distributions The thermograms obtained by DSC showed
endotherms at about 50-60 degrees and 410-430 degrees,
indicating the presence of block copolymers. Finally, TGA
demonstrated that the compositions are stable, at least in
a nitrogen atmosphere, to about 260 degrees, in that they
undergo less than one percent by weight degradation. Some
of the other characterization results are summarized in
Table 7; it perhaps should be noted that the preferred
temperature for determining the melt flow rate is 195
degrees.
Table 7
Summary of Melt Flow Rates and Absorbencies
_
Absorbency, g/g WaterMelt Flow
Ex~mple Water Syn. Urine Sol.a Rate/Temp
2 14.2 12.2 23300/190
3 40.7 44 38 65/140
4 39.2 48.2 452g4/190
5A -- -- -- 33/195
5B -- -- -- 16/195
5C ~ 20/195
SD -- -- -- 47/195
5E -- ~ 27/195
5F -- -- __ 48/195
5G -- -- -- 63/195
F
,
~3~7g~
5H 41.9 31.7 __ 103/195
5I -- -- -- 30/195
5J -- -- -- 130/195
5K -- -- -- 122/190
6 33.7 27.7 27 90/195
7A -- -- -- 64/195
7B -~ 300/195
8 39.2 31 43 116/195
9 50.6 41.3 49 119/190
20.7 19.4 28.5 --
11 10.7b 11.5b -- 200/190
12 17.7 14.6 36.291/190
13 Diss. Diss. -- 182/190
14 74.7 Diss.
31.3 72.8
16 ~ -- 43-147/190
aPercent of sample soluble in water at ambient temperature.
bMeasured with 0.5 cm or smaller chips of polymer which
20were soaked for approximately 24 hours.
CRange of values obtained for multiple batches.
Finally, the inherent viscosity and ultimate modulus
were determined for each of the polymers of Examples 3 and
254. The values obtained are summarized in Table 8.
.
Table 8
Summary of Inherent Viscosity
30and Ultimate Modulus Values
Example~Is~3llr~ 8e 35~ Ultimate Modulus -~
3~ 0.572 2200
4 0.505 4000
: ~:: :
~.
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1 3 ~
Several of the compositions prepared in Examples 1-16,
inclusive, were subjected to molecular weight
determinations by means of gel permeation chromatography.
The apparatus consisted of a Beckman Model 112 Solvent
Delivery System (Beckman Instruments, Inc., Fullerton,
California), a Beckman Model 421 System Controller, and
Waters 500, 10 , and 10 Angstrom ~Styragel columns (Waters
Chromatography Division, Millipore Corporation, Milford,
Massachusetts) in chloroform, HPLC-grade (Burdick and
Jackson Laboratories, Inc., a subsidiary of American
Hospital Supply Corporation, McGaw Park, Illinois),
equilibrated at 30 degrees.
Sample injection consisted of 50~ l of a 0.5 percent,
weight per volume, solution of the polymer in HPLC-grade
chloroform. The flow rate of eluant (chloroform) was
maintained at 1 ml per minute. Sample peaks were detected
by means of changes in the refractive index using a Waters
Model 410 Differential Refractometer. The calibration
curves were constructed through the use of narrow molecular
weight range standards coverin~ the range from 600 to
600,000; below about 18,000, the standards were
polyethylene glycols from American Polymer Standards
Corporation, Mentor, Ohio, and above about 18,000, the
standards wexe poly(ethylene oxide) standards rom Polymer
Laboratories, Inc., Stow, Ohio.
Data acquisition was performed with a Nelson
Analytical Model 760 Interface and an IBM Personal Computer
AT (IBM Corporation, Endicott, New York), in conjunction
with Nelson Analytical GPC Software, Version 3.6 (Nelson
Analytical, Cupertino, California).
In general, the manufacturers' instructions were
followed. However, the most relevant data acquisition
parameters were as follows: -
Minimum peak width 15.00 seconds
Time for one sample 1.50 seconds
Real time plot ~uIl scale for CH.O. 500 millivolts
E 51 -
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Full scale range for A.D.C. 1 volt
Area reject for reference peaks 1000.00
The results of the molecular weight determinations are
summarized in Table 9.
Table 9
Summary of Results of
Molecular Wei~ht Determinatlonsa
Ex. Peak Area % Peak MW Mwb Mnc Mw/Mn
2 MPd ~- 25,425 190,878 46,656 4.091
S -- 9,628 7,702 6,757 1.140
3 MP 59.7 28,595 117,424 41,217 2.849
S -- 16,000 ~
SH MP 91.7 34,570 108,455 33,331 3.254
S -- 16,000 -~
7A MP 80.8 37,764 307,465 44,458 6.916
S 9.3 10,621 9,206 8,534 1.079
8 MP 97.5 32,806 91,605 31,632 2.896
S -- 16,000 -- -- --
9 MP 92.4 34,570 139,135 38,201 3.642
S ---- 10,000 ---- ---- ----
13 MP 88.7 29,585 70,867 32,828 2.159
S 10.9 10,039 9,281 8,957 1.036
aIn each case, a main peak with a shoulder was obtained.
~ bWeight a~erage molecular weight.
Number average molecular weight.
dMain~peak.
eshOulder -
f
~ Approximate value.
35 ~ Since the ~tandards used to construct the calibration
curves may not be the most appropriate s~andards for the
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type of polymer studied, it can be stated only that the
shoulder represents a relatively low molecular weight
oligomer with a narrow polydispersity. The shoulder may
represent either soft segment or hard segment which was not
incorporated into the polymer. On the other hand, the main
peak apparently represents a relatively high molecular
weight polymer with moderate to broad polydispersity.
Because of the limited amount of data, correlation of
polymer properties, such as water solubility and
absorbency, with molecular weight and/or polydispersity is
not possible.
B. Preparation of Meltblown Nonw_ven Webs.
Examples 17 - 22
To determine the suitability of the compositions of
the present invention for the formation of nonwoven webs,
several of the compositions from the above examples were
extruded by means of a bench-scale apparatus having a
single orifice in the die tip. The apparatus consisted of
a cylindrical steel reservoir having a capacity of about 15
g. The reservoir was enclosed by an electrically heated
steel jacket. The temperature of the reservoir was
thermostatically controlled by means of a feedback
thermocouple mounted in the body of the reservoir. The
extrusion orifice had a diameter of 0.016 inch (0.41 mm)
and a length of 0.060 inch (1.5 mm). A second thermocouple
was mounted near the die tip. The exterior surface of the
die tip was flush with the reservoir body. Polymer
extrusion was accomplished by means of a compressed air
piston in the reservoir. The extruded filament was
surrounded and attenuated by a cylindrical air stream
exiting a circular 0.075-inch (l.9-mm) gap. The forming
distance was from 8 to 2n inches (20 to 51 cm). The
attenuated extruded filament was collected on the clear
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plastic film of an 8.5 x 11 inch loose leaf protector
having a black paper insert.
Examples 17-22, inclusive, consisted of six separate
meltblowing experiments using the above-described
bench-scale apparatus. Meltblowing conditions are
summarized in Table 10. The table identifies the polymer
employed (by reference to a previous Example), the
temperatures of the reservoir, die tip, and air stream, the
air pressure (in psig), and the forming distance in inches
(cm).
Table 10
Summary of Meltblowing Conditions
Using Bench-Scale Apparatus
Polymer Res. Die Air Air Forming
Example Example Temp. Temp. Temp. Press. Distance
17 5A 185 169 2222 10 (25.4)
18 5B 183 173 2211-2 10 (25.4)
195D~F 180 179 2161-2 10 (25.4)
7A 164 157 1921 10 (25.4)
21 11 227 209 26410-15 10 (25.4)
22 12 191 196 1577-8 17-18
(43.2-45.7)
In each case, a coherent superahsorbent nonwoven web
was obtained.
Examples 23 and 24
In a variation of the procedures described in Examples
17-22, inclusive, two of the bench scale apparatus were
oriented 90 degrees from each other. One apparatus was
oriented vertically with the die tip in the downward
direction and the other apparatus was oriented horizontally
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with the die tip facing the vertically oriented apparatus.
The straight-line distance between the two die tips was
5.75 inches (14.5 cm). Thus, the extruded filaments met at
a point 4 inches (10.2 cm) from each die tip. The
confluent filament stream was directed at a 45 degree angle
from the vertical. The forming distance was either 4 or 12
inches (10.2 or 30.5 cm), measured from the point of
con~luence to the collecting arrangement. The collecting
arrangement was a 400-openings/in2 screen attached to a
vacuum hose.
The vertical apparatus was charged with PF-011
polypropylene (Himont U.S.A., Inc. Wilmington, Delaware).
The horizontal apparatus was charged with the composition
of Example 5 (specifically, a mixture of 5D and 5F).
Two experiments were conducted. In Example 23, the
forming dist`ance was 4 inches (10.2 cm) and the weight
ratio of polypropylene to superabsorbent composition was
approximately 60:40. In Example 24, the forming distance
was 12 inches (30.5 cm) and the weight ratio of
polypropylene to superabsorbent composition was
approximately 70:30. The meltblowing conditions for these
two Examples are summarized in Tables 11 and 12,
respectively.
B ~5
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Table 11
Summary of Meltblowing Conditions
- for Example 23
Res. Die Air Air
Temp. ~ ~ Temp. Press.
Vertical apparatusa 173 178 226 20
Horizontal apparatus 156 153157,223 4,12
aThe extrusion orifice diameter was 0.010 inch (0.25 mm).
bThe air temperature initially was 157 degrees, but was
changed to 223 degrees about halfway through the
experiment.
CThe air pressure initially was 4 psig, but was changed to
12 psig about one-fifth of the way through the experiment.
Table 12
Summary of Meltblowing Conditions
for Example 24
Res. Die Air Air
Temp. Temp. Temp.Press.
Vertical apparatusa 173 177 226 20
Horizontal apparatus 156 158 207 12
:
`aThe extrusion orlfice diàmeter was 0.010 inch (0.25 mm).
;In~each case, a coherent superabsorbent nonwoven web
was~obtained.
~b
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Examples 25-41
Since the above bench-scale meltblowing trials were
successful, many of the compositions from the examples were
meltblown on a pilot-scale meltblowing apparatus, essentially
as described in U.S. Patent No. 4,663,220. Meltblowing of
various of the thermoplastic superabsorbent polymers o~
Examples 1-16 was accomplished by extruding polymer through a
0.75 inch tl9-mm) diameter Brabender extruder and through a
meltblowing die having nine extrusion capillaries per linear
inch (approximately 3.5 capillaries per linear cm) of die
tip. Each capillary had a diameter of about 0.0145 inch
(about 0.37 mm) and a length of about 0.113 inch (about 2.9
mm). The process variables in general were as follows:
calculated polymer viscosity in the capillaries (in poise),
polymer extrusion rate (g per capillary per min) and tempera-
ture, extrusion pressure (psig), die tip configuration which
was either negative (recessed) or positive (protruding),
perpendicular die tip distance, air passageway width,
attenuating air temperature and pressure (psig), and forming
distance. These meltblowing process variables are summarized
for Examples 25 41 in Tables 13-15, inclusive.
Table 13
Summary of Polymer Characteristics
Using Brabender Extruder
ExamplePolymer ExamplePolymer Viscositya
5D&5F 1960
26 SD&5F 2110
27 7A 1110
28 SJ 698
29 5J 620
~7
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1317694
5J 605
31 5J 904
32 16A 241
33 16B 301
S 34 ~ 5K 243
5H&7B 429
36 16C 738
37 16D 525
38 16E 219
39 16F 214
16G 939
41 16H 320
a In poise at the extrusion temperature.
b A mixture consisting of 25 percent by weight of 5H and
75 percent by weight of llB.
Table 14
Summary of Extrusion Variables
Uslng Brabender Extruder
Poly~_r Extrusion Die Tip
Example Rate Temp~Press. Config. Dist.
0.16186 430 - O.llO
26 0.14187 406 - 0.110
27 0.14178 214 - 0.110
28 0.47189 450 - 0.110
29~ 0.47188 ~ 400 - 0.110
~30 ~ ~ 30 0.47188 ~390 - 0.110
~31 ~ 0.22188 273 - 0.110
32 0.45190 149 - 0.110
33~ ; 0~29~ 190 ~ 120 - 0.110
34 0.49190 165 - 0.110
35~ ~35 0.49190 290 ;- 0.110
36~ ~ 0.27190 275 + 0.010
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37 0.50 190 360 + 0.010
38 0.35 193 104 + 0.010
39 0.51 193 149 + 0.010
0.27 193 350 + 0.010
41 0.36 193 160 - 0.110
a Perpendicular distance in inches from the plane of the
air plate lips, or perpendicular die tip distance.
b Or 2.8 mm.
10 c Or 0.25 mm.
Table 15
Summary of Attenuation Variables
Using Brabender Extruder
Attenuating Air
Example APWa Tem~ Press. Forming Distanceb
0.090C 412 1 38d
26 0.090 412 5 38
27 0.090 427 2 25e
28 0.090 432 1 25
29 0.090 432 2 25
0.090 420 4 25
31 0.090 430 0.5 25
32 0.090 437 0.75 25
33 0.090 435 1.5 25
34 0.090 442 1.5 25
0.090 433 1.5 25
f
~ 36 0.060 430 0.75 25
37 0.060 427 1 ~ 25
38~ 0.0~0 428~ 1.5 25
39` ~ 0.060 418 1.25 25
-:
.
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40 0.060 419 1.25 25
41 0.0g0 419 2.25 25
a Air passageway width, in inches.
In inches.
c Or 2.3 mm.
d Or 96.5 cm.
e Or 63.5 cm.
f Or 1.5 m~.
The collecting arrangement consisted of a rotating
six-inch (15.2-cm) wide drum having a diameter of 30 inches
176.2 cm). The surface of the drum was a screen which had
been coated with spunbonded polypropylene to prevent
sticking of the meltblown web to the screen. The nonwoven
webs were allowed to stay on the forming screen for at
least ten seconds to assure sufficient web integrity for
removal and subsequent handling. Well ormed, coherent,
superabsorbent nonwoven webs were obtained.
The synthetic urine absorbencies of the meltblown webs
obtained in Examples 28-39, inclusive, and Example 41 were
determined by means of a saturated capacity test. The
apparatus consisted of a stainless steel vacuum tank which
was 28 cm high, 60 cm long, and 35 cm wide. The top of the
tank was a removable stainless steel grid. The grid was
approximately 59.5 x 34 cm and contained approximately 84
4-mm diameter holes per 100 cm2. A latex rubber dam was
attached to the top edge of one of the longer sides of the
tank and was of a size to easily cover the grid without
stretching. Evacuation of the tank was accomplished by a
combination pressure/vacuum pump (Gast Manufacturing,
Fisher Catalog No. 01-094, Fisher Scientific, Pittsburgh,
Pennsylvania). The pump was gaged to provide a reading of
the achieved pressure reduction in inches of water which
was converted to pounds per square inch IPsi).
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To carry out the test, at least three 3-inch (7.6-cm)
square samples were cut from each meltblown web; the
spunbonded carrier was removed from each sample. Each
sample then was dried for at least one hour at ambient
S temperature under reduced pressure. For each sample, two
4-inch (10.2-cm) squares were cut from a polypropylene
meltblown web having a nominal basis weight of 25-34 g/m2.
Each sample and the accompanying two squares of
polypropylene meltblown web were weighed separately.
The sample was placed on one polypropylene square and
immersed~ with the sample underneath the polypropylene
square, for 30 minutes in a bath of synthetic urine at 37
degrees (98.6 degrees F). The sample was removed carefully
from the bath and placed on the second polypropylene square
which was on the vacuum tank grid, the sample being
sandwiched between the two polypropylene squares. After
draining for one minute, the sample sandwich was weighed.
The sample sandwich was placed on the grid. The grid
was covered completely with the rubber dam and the pressure
in the tank was reduced to 0.5 psi less than atmospheric
pressure; i.e., the pressure differential from one side of
the sample sandwich to the other was 0.5 psi. This
pressure differential was maintained for 5 minutes, after
which time the sample sandwich was weighed. This procedure
was repeated three additional times at pressure
differentials of 1.0, 2.0, and 3.0 psi. After the sample
sandwich weighing at the 3.0-psi differential, the sample
was removed from the sandwich and weighed separately.
In order to calculate an absorbence a~ each pressure
differential, it was necessary to correct each sandwich
weig~t for the weight of the wet polypropylene squares
(WPPS). This was done by subtracting the sample weight at
the~3.0-psi pressure differential from the sandwich weight
at the same pressure differential. The absorbence (A) for
each sample a~ each pressure differential then was
B ~/
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calculated as follows:
A = (wt. sandwich - wt. WPPS - wt. dry sample)/wt. dry
sample
Thus, the absorbence value at each pressure differential is
the number of g of synthetic urine absorbed per g of
sample.
The results of the saturated capacity test are
lQsummarized in Table 16. The absorbencies reported are
averages of at least three samples.
Table 16
15Summary of Saturated Capacity Test
on Meltblown Webs from Examples 28-39, 41
_ Absorbency, g Syn. Urine/~
Example 0.5 psi 1.0 psi2.0 psi 3.0 psi
28 19.91 17.09 15.52 14.17
29 23.00 19.36 18.06 16.46
25.65 21.42 19.02 16.86
31 25.43 22.36 19.61 17.76
32 9.56 9.40 9.14 8.92
33 11.16 10.91 10.64 10.37
34 11.16 10.94 10.54 10.13
7.68 7.60 7.45 7.33
36 15.77 13.82 12.69 11.91
~30 37 17.92 16.82 16.33 15.75
38 12.39 11.90 11.59 11.30
39 15.70 14.62 13.82 13.20
41 17.69 16.16 14.4S 13.26
.
It should be noted that the data in Tables 7 and 16,
respectively, were obtained by two different test
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procedures. Moreover, the data in Table 7 were obtained
with polymer films, whereas the data in Table 16 were
obtained with meltblown webs.
Larger scale meltblowing runs were carried out,
primarily to prepare coformed webs essentially as described
in U.S. Patent No. 4,663,220, supra. These larger scale
runs are described in Examples 42-66, inclusive, below. In
each case the superabsorbent thermoplastic composition
employed was that of Example 16.
~xample 42
A fibrous coformed nonwoven web was formed by
meltblowing a superabsorbent thermoplastic composition of
the present invention and incorporating polyester staple
fibers therein.
Meltblowing of the superabsorbent thermoplastic
composition was accomplished by extruding the composition
from a 1.5-inch (3.75-cm) Johnson extruder and through a
meltblowing die having 15 extrusion capillaries per linear
inch (about 5.9 extrusion capillaries per linear cm) of die
tip. Each capillary had a diameter of about 0.018 inch
(about 0.46 mm) and a length of about 0.14 inch (about 3.6
mm). The composition was extruded through the capillaries
at a rate of about 0.50 g per capillary per minute at a
temperature of about 184 degrees. The extrusion pressure
exerted on the composition in the die tip was in the range
of from about 180 to 200 psig. The composition viscosity
in the die tip under these conditions was about 500 poise.
The die tip configuration was adjusted to have a positive
perpendicular die tip distance of about 0.010 inch (about
O.25 mm). The air gaps of the two attenuating air
passageways were adjusted to be about 0.060 inch (about
0.15 mm). Forming air for meltblowing the composition was
supplied to the air passageways at a temperature of about
209 degrees and a pressure of about 2 psig. The fibers
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thus formed were deposited on a forming screen drum which
was approximately 18 inches (46 cm) below and 20 inches
(51 cm) back from the die tip.
Following the procedure illustrated by Figure 5 of
said U.S. Patent No. 4,663,220 and described therein,
l.S-inch (3.75-cm) long, lS denier per filament polyester
staple was incorporated into the stream of meltblown fibers
prior to deposition upon the forming drum. The polyester
fibers were first formed by a Rando Webber mat-forming
apparatus into a mat having a basis weight of about 100
gtm . The mat was fed to the picker roll by a feed roll
which was positioned about 0.007 inch (about 0.18 mm) from
the picker roll surface. The picker roll was rotating at a
rate of about 3,000 revolutions per minute and fiber
transporting air was supplied to the picker roll at a
pressure of about 3 psig. While actual measurement of the
position of the nozzle of the coform apparatus with respect
to the stream of meltblown fiber was not made, it was
estimated to be about 2 inches (about 5.1 cm) below and
about 2 inches 15.1 cm) away from the die tip of the
meltblowing die.
A coformed nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 cm)
and which was composed of about 25 percent by weight of the
meltblown fibers and about 75 percent by weight of the
polyester fibers. The web had a basis weight of about 200
glm .
Exa~ple 43
The procedure of Example 42 was repeated, except that
the coformed web was composed of about 50 percent by weight
of the meltblown fibers and about 50 percent by weight of
the polyester fibers.
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Example 44
The procedure of Example 43 was repeated, except that
the basis weight of the coformed web was about 400 g/m2.
Example 45
The procedure of Example 42 was repeated, except that
the coformed web was composed of about 75 percent by weight
of the meltblown fibers and about 25 percent by weight of
the polyester fibers.
Example 46
The procedure of Example 45 was repeated, except that
the staple was 2-inch (5.1-cm) long, 5.5 denier per
filament polyester staple.
Example 47
The procedure of Example 46 was repeated~ except that
the coformed web was composed of about 50 percent by weight
of the meltblown fibers and about 50 percent by weight of
the polyester fibers.
Example 48
The procedure of Example 46 was repeated, except that
the coformed web was composed of about 25 percent by weight
of the meltblown fibers and about 75 percent by weight of
the polyester fibers.
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Example 49
The procedure of Example 42 was repeated, except that
the polyester fiber was replaced with International Paper
Super Soft pulp fibers. The pulp mat had a basis weight of
about 200 g/m2 and the mat feed roll was about 0.030 inch
(about 0.76 mm) from the picker role surface.
~ coformed nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 cm)
and which was composed of about 50 percent by weight of the
meltblown fibers and about 50 percent by weight of the pulp
fibers. The web had a basis weight of about 200 g/m2.
15 Example 50
The procedure of Example 49 was repeated, except that
the coformed web was composed of about 25 percent by weight
of the meltblown fibers and about 75 percent by weight of the
pulp fibers and had a basis weight of about 400 g/m2.
Example 51
The procedure of Example 50 was repeated, except that
the coformed web was composed of about 50 percent by weight
of the meltblown fibers and about 50 percent by weight of the
pulp fibers.
Example 52
The procedure of Example 51 was repeated, except that
the basis weight of the coformed web was about 200 g/m2.
:
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Example 53
The procedure of Example 42 was repeated, except that
the meltblowing throughput was at a rate of about 0.25 g per
capillary per hour at a temperature of about 181 degrees, the
extrusion pressure at the die tip was 282 psig, composition
viscosity was about 1500 poise, the forming air was at a
temperature of about 197 degrees and a pressure of about 3
psig, the forming screen drum was about 7.5 inches (lg cm)
from the die tip, and secondary fibers were not added to the
meltblown stream.
A nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 cm)
and a basis weight of about 60 g/m2.
Example 54
The procedure of Example 53 was repeated, except that
the forming air for meltblowing was supplied at a pressure of
about 6 psig and the forming screen drum was about 17 inches
(about 43.2 cm) from the die tip.
Example 55
The procedure of Example 42 was repeated, except that
the meltblowing conditions of Example 53 were employed and
the mat feed roll was about 0.005 inch (about 0.13 mm) from
the picker roll surface.
A coformed nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 cm)
and which was composed of about 30 percent by weight of the
meltblown fibers and about 70 percent by weight of the
polyester fibers. The web had a basis weight of about 200
g/m2 .
- 67 -
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Example 56
The procedure of Example 55 was repeated, except that
the forming air for meltblowing was supplied at a pressure
of about 6 psig, the forming screen drum was about 17
inches (about 43.2 cm) from the die ~ip, and the fiber
transporting air was supplied to the picker roll at a
pressure of about 2 psig.
Example 57
The procedure of Example 56 was repeated, except that
the coformed web was composed of about 60 percent by weight
of meltblown fibers and about 40 percent by weight of the
polyester fibers and the basis weight of the web was about
160 g/m .
Example 58
The procedure of Example 42 was repeated, except that
the meltblowing throughput was at a rate of about 0.40 g
per capillary per minute at a temperature of about 204
degrees, the extrusion pressure at the die tip was about
288 psig, composition viscosity was about 950 poise,
forming air was at a temperature of about 231 degrees and a
pressure of about 3 psig, the forming screen drum was about
17 inches labout 43.2 m) from the die tip, and the
secondary fiber process parameters were the same as those
of Example 55, except that the fiber transporting air
pressure was 2 psig.
A coformed nonwoven web was formed which had a width
(cross-machine directionj of about 20 inches (about 51 cm)
and which was composed of about 60 percent by weight of the
meltblown fibers and about 40 percent by weight of the
polyester fibers. The web had a basis weight of about 200
g/m .
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Example 59
The procedure of Example 49 was repeated, except that
the meltblowing throughput was at a rate of about 0.35 g per
capillary per minute at a temperature of about 194 degrees,
the extrusion pressure at the die tip was about 273 psig, the
composition viscosity was about 1030 poise, and the forming
air was at a temperature of about 206 degrees.
A coformed nonwoven web was formed which had a width
~cross-machine direction) of about 20 inches (about 51 cm)
and which was composed of about 30 percent by weight of the
meltblown fibers and about 70 percent by weight of the pulp
fibers. The web had a basis weight of about 200 g/m2.
Example 60
The procedure of Example 59 was repeated, except that
the forming air for meltblowing was supplied at a pressure of
about 6 psig and the forming screen drum was about 17 inches
(about 43.2 cm) from the die tip.
Exampl.e,n,~61
The procedure of Example 59 was repeated, except that
the melt temperature was about 196 degrees, the extrusion
pressure of the die tip was about 253 psig, the composition
viscosity was about 960 poise, and the forming air pressure
was 6 psig.
A coformed nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 cm)
and which was composed of about 30 percent by weight of the
meltblown fibers and about 70 percent by weight of the pulp
fibers. The web had a basis weight of about 200 g/m2.
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Example 62
The procedure of Example 61 was repeated, except that
the forming air pressure was about 3 psig.
A coformed nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 cm)
and which was composed of about 30 percent by weight of the
meltblown fibers and about 70 percent by weight of the pulp
fibers. The web had a basis weight of about 250 g/m2.
Example 63
The procedure of Example 62 was repeated, except that
the fiber transporting air was supplied to the picker roll
at a pressure of about 2 psig, the coformed web was
composed of about 40 percent by weight of the meltblown
fibers and about 60 percent of the pulp fibers, and the web
basis weight was about 216 g/m2.
Example 64
~he pracedure of Example 62 was repeated, except that
the pulp fibers were Weyerhauser XB-309 pulp fibers and the
fiber transporting air pressure was about 2 psig.
A coformed nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 cm)
and which was composed of about 44 percent by weight of the
meltblown fibers and about 56 percent by weight of the pulp
fibers. The web had a basis weight of about 250 g/m .
The~ procedure of Example 64 was rep~ated, except that
the forming air pressure was about 6 psig.
7a
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1317~94
A coformed nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 c~)
and which was composed of about 44 percent by weight of the
meltblown fibers and about 56 percent by weigh of the pulp
fibers. The web had a basis weight of about 250 g/m .
Example 66
The procedure of Example 65 was repeated.
A coformed nonwoven web was formed which had a width
(cross-machine direction) of about 20 inches (about 51 cm)
and which was composed of about 30 percent by weight of the
meltblown fibers and about 70 percent by weight of the pulp
fibers. The web had a basis weight of about 200 g/m2.
The nonwoven webs obtained in Examples 43-50 and
53-66, inclusive, were subjected to the saturated capacity
test to determine synthetic urine absorbencies. The
results are summarized in Table 17; the absorbency values
reported are averages of at least three samples. It
perhaps should be noted that the test procedure this time
did not require the removal of a spunbonded carrier since
such carrier was not employed.
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Table 17
Summary of Saturated Capacity Test
5on Nonwoven Webs from Examples 42-50 and 53-66
Absorbency, g Syn. Urine/g
Example 0.5 psl 1.0 psi 2.0 psi 3.0 psi
42 9.0 6.8 5.9 5.3
43 11.8 9.8 8.9 8.4
44 8.9 7.7 7.4 7.2
12.8 12.0 11.7 11.5
46 11.3 10.2 9.7 9.5
47 10.5 9.0 8.6 8.3
48 9.2 8.5 7.9 7.2
49 7.3 6.0 5.0 4.8
7.4 5.8 4.8 4.7
53 9.5 9.3 9.0 8.7
54 13.8 13.1 12.3 11.3
10.4 8.1 6.9 6.2
56 9.4 800 6.5 5.6
57 10.8 8.3 7.2 6.5
58 13.7 12.5 11.7 11.1
59 9.0 7.2 5.7 4.9
7.9 6.3 5.0 4.3
61 8.3 6.5 5.3 4.8
62 8.5 7.0 6.1 5.6
63 9.0 7.4 6.2 5.7
64 8.8 7.2 6.2 5.6
8.4 7.0 6.5 6.1
66 7.7 6.2 5.7 5.2
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Exam~le 67
The procedure of Example 31 was repeated, except that
the polymeric composition of Example 5J was replaced with a
blend consisting of 67 percent by weight of the polymeric
composition of Example 5J and 33 percent by weight of low
density polyethylene (PETROTHENE TM NA 601, U.S.I.
Chemicals, National Distillers & Chemical Corporation, New
York, New York). According to the manufacturer, the
polyethylene has a density of 0.903 g/cc, a Brookfield
viscosity at 190 degrees of 3300 centipoise (ASTM D 3236),
and an equivalent melt index ~f 2000 g per 10 minutes (ASTM
D 1238).
The extrusion throughput wa~ estimated to be about
0.47 g per capillary per minute ~t a temperature of about
188 degrees. The extrusion pressure at the die tip was 220
psig. The viscosity of the blend in the capillaries was
calculated to be 340 poise.
As before, a well-formed, coherent nonwoven web was
formed. This time, though, the web exhibited considerable
wet strength in the presence of excess water. The web had
a water absorbency by the centrifuge method of 16.2 g per g
of web (average of two samples) which is equivalent to 24.3
g per g of superabsorbent, thermoplastic polymeric
composition in the blend. Two additional samples gave an
average value of 24 g per g of web, equivalent to 37 g per
g of polymeric composition. The average water absorbency
of these two samples by the centrifuge method was 52
percent by weight.
Having thus described the invention, numerous changes
and modifications thereto will be apparent to those having
ordinary skill in the art without departing from the spirit
and scope of the present invention. The above-described
nonwoven web is also described and is claimed in
applicant's copending divisional application Serial
No. 616,266 , filed on December 17, l991.
- 73 -
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