U.S. patent application number 11/544911 was filed with the patent office on 2007-02-08 for superabsorbent water sensitive multilayer construction.
Invention is credited to Stewart C. Anderson.
Application Number | 20070031637 11/544911 |
Document ID | / |
Family ID | 28790263 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070031637 |
Kind Code |
A1 |
Anderson; Stewart C. |
February 8, 2007 |
Superabsorbent water sensitive multilayer construction
Abstract
A multilayer construction that includes a first layer that
includes water sensitive thermoplastic polymer and a second layer
disposed on the first layer, the second layer including
superabsorbent polymer.
Inventors: |
Anderson; Stewart C.; (Eden
Prairie, MN) |
Correspondence
Address: |
H.B. FULLER COMPANY
1200 WILLOW LAKE BLVD.
P.O. BOX 64683
ST. PAUL
MN
55164-0683
US
|
Family ID: |
28790263 |
Appl. No.: |
11/544911 |
Filed: |
October 5, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10121171 |
Apr 11, 2002 |
7135135 |
|
|
11544911 |
Oct 5, 2006 |
|
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Current U.S.
Class: |
428/131 ;
428/137; 428/138; 428/373; 442/394; 604/364; 604/372 |
Current CPC
Class: |
Y10T 428/31504 20150401;
Y10T 428/24331 20150115; Y10T 442/674 20150401; B32B 27/12
20130101; Y10T 428/24 20150115; Y10T 428/2929 20150115; A61F
2013/530547 20130101; B32B 27/34 20130101; Y10T 428/31591 20150401;
Y10T 428/24273 20150115; B32B 27/08 20130101; Y10T 428/24322
20150115; Y10T 428/24091 20150115; Y10T 428/31659 20150401; A61F
13/534 20130101 |
Class at
Publication: |
428/131 ;
428/137; 428/138; 442/394; 428/373; 604/364; 604/372 |
International
Class: |
A61F 13/15 20060101
A61F013/15; B32B 3/10 20060101 B32B003/10; B32B 27/12 20060101
B32B027/12 |
Claims
1. A multilayer construction comprising: a first layer comprising
water sensitive thermoplastic polymer; and a second layer
comprising superabsorbent polymer, said second layer being disposed
on said first layer.
2. The multilayer construction of claim 1, wherein said
thermoplastic polymer comprises polyamide.
3. The multilayer construction of claim 1, wherein said water
sensitive thermoplastic polymer comprises the reaction product of
polyoxyalkylene glycol diamine and an acid selected from the group
consisting of dicarboxylic acid, dicarboxylic acid ester and
combinations thereof, said polyoxyalkylene glycol diamine having
the formula
NH.sub.2--(CH.sub.2).sub.x--(OCH.sub.2--CH.sub.2).sub.y--O--(CH.sub.2).su-
b.x--NH.sub.2, where 2.ltoreq.X.ltoreq.3, and
1.ltoreq.Y.ltoreq.2.
4. The multilayer construction of claim 1, wherein said water
sensitive thermoplastic polymer comprises the reaction product of
adipic acid and polyoxyalkylene glycol diamine.
5. The multilayer construction of claim 1, wherein said water
sensitive thermoplastic polymer is water soluble.
6. The multilayer construction of claim 1, wherein said
superabsorbent polymer comprises crosslinked polyacrylate.
7. The multilayer construction of claim 1, wherein said
superabsorbent polymer comprises crosslinked and at least partially
neutralized .alpha.,.beta.-beta ethylenically unsaturated monomers
selected from the group consisting of monocarboxylic acid monomers,
dicarboxylic acid monomers, acid anhydride monomers and
combinations thereof.
8. The multilayer construction of claim 1, wherein said
construction exhibits an absorption rate greater than the
absorption rate of the superabsorbent polymer layer in the absence
of said thermoplastic layer.
9. The multilayer construction of claim 1, further comprising
perforations.
10. A film comprising the multilayer construction of claim 1.
11. The film of claim 10, wherein said film exhibits an absorption
rate greater than the absorption rate of the superabsorbent polymer
layer in the absence of said thermoplastic layer.
12. The film of claim 10, further comprising perforations.
13. A film comprising the multilayer construction of claim 3.
14. A film comprising the multilayer construction of claim 6.
15. A fiber comprising the multilayer construction of claim 1.
16. A fiber comprising the multilayer construction of claim 3.
17. A fiber comprising the multilayer construction of claim 6.
18. An article comprising: a nonwoven web; and a multilayer
construction disposed on said web, said multilayer construction
comprising a first layer comprising a water sensitive thermoplastic
polymer; and a second layer comprising a superabsorbent polymer,
said second layer being disposed on said first layer.
19. An article comprising: an absorbent layer; and a film
comprising a first layer comprising a water sensitive thermoplastic
polymer, and a second layer comprising a superabsorbent polymer,
said second layer being disposed on said first layer.
20. A multi-component fiber comprising: a first component
comprising water sensitive thermoplastic polymer; and a second
component comprising superabsorbent polymer, said second component
being disposed on said first component.
21. The multi-component fiber of claim 20, wherein said first
component comprises a core and said second component comprises a
sheath.
22. A multi-component yarn comprising: a first component comprising
water sensitive thermoplastic polymer; and a second component
comprising superabsorbent polymer, said second component being
disposed on said first component.
23. The multi-component yarn of claim 22, wherein said first
component comprises a core comprising the water sensitive
thermoplastic polymer.
24. The multi-component yarn of claim 22, wherein the second
component comprises a sheath comprising the superabsorbent
polymer.
25. A disposable article comprising the multilayer construction of
claim 1.
26. A diaper comprising the multilayer construction of claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. Patent Application
Ser. No. 10/121,171 filed Apr. 11, 2002, now U.S. Pat. No. ______,
and incorporated herein.
BACKGROUND
[0002] The invention is directed to a superabsorbent multilayer
construction.
[0003] Superabsorbent polymers, which are available as powders,
particles, and aqueous compositions, absorb large quantities of
water and are often used in absorbent articles to increase the
absorbency of the article. Disposable diapers and feminine hygiene
products often include superabsorbent polymers to enhance body
fluid absorption. Superabsorbent polymers also have various
applications in the medical, food, and agricultural industries.
SUMMARY
[0004] In one aspect, the invention features a multilayer
construction that includes a first layer including water sensitive
thermoplastic polymer, and a second layer disposed on the first
layer, the second layer including superabsorbent polymer. In one
embodiment, the thermoplastic polymer includes polyamide. In
another embodiment the thermoplastic polymer includes the reaction
product of polyoxyalkylene glycol diamine and an acid selected from
the group consisting of dicarboxylic acid, dicarboxylic acid ester,
and combinations thereof, the polyoxyalkylene glycol diamine having
the formula
NH.sub.2--(CH.sub.2).sub.x--(OCH.sub.2--CH.sub.2).sub.y--O--(CH.sub.2).su-
b.x--NH.sub.2, where 2.ltoreq.X.ltoreq.3, and 1.ltoreq.Y.ltoreq.2.
In other embodiments, the thermoplastic polymer includes the
reaction product of adipic acid and polyoxyalkylene glycol diamine.
In another embodiment, the thermoplastic polymer is water
soluble.
[0005] In some embodiments, the superabsorbent polymer includes
crosslinked polyacrylate. In other embodiments, the superabsorbent
polymer includes crosslinked and at least partially neutralized
.alpha.,.beta.-beta ethylenically unsaturated monomers selected
from the group consisting of monocarboxylic acid monomers,
dicarboxylic acid monomers, acid anhydride monomers, and
combinations thereof.
[0006] In one embodiment, the construction exhibits an absorption
rate greater than the absorption rate of the superabsorbent polymer
layer in the absence of the thermoplastic layer.
[0007] In other embodiments, an above-described multilayer
construction is a film. In one embodiment the film exhibits an
absorption rate greater than the absorption rate of the
superabsorbent polymer layer in the absence of the thermoplastic
layer. In some embodiments, the film is flexible.
[0008] In some embodiments, an above-described multilayer
construction is a fiber.
[0009] In another aspect, the invention features an article that
includes a nonwoven web and an above-described multilayer
construction disposed on the web.
[0010] In some aspects, the invention features a multi-component
fiber that includes a first component that includes water sensitive
thermoplastic polymer, and a second component that includes
superabsorbent polymer, the second component being disposed on the
first component. In one embodiment, the first component includes a
core and the second component includes a sheath.
[0011] In other aspects the invention features a multi-component
yarn that includes a first component that includes water sensitive
thermoplastic polymer, and a second component comprising
superabsorbent polymer, the second component being disposed on the
first component. In some embodiments, the first component includes
a core that includes the water sensitive thermoplastic polymer. In
another embodiment, the second component includes a sheath that
includes the superabsorbent polymer.
[0012] In another embodiment, a disposable article (e.g., a diaper)
includes an above-described multilayer construction.
[0013] In another aspect, the invention features a method of making
a multilayer construction that includes coating an aqueous water
soluble superabsorbent polymer composition on a water sensitive
thermoplastic film.
[0014] In one embodiment, the method includes providing a molten
water sensitive thermoplastic polymer, and contacting the molten
thermoplastic polymer with an aqueous water soluble superabsorbent
polymer composition. In another embodiment, the molten
thermoplastic polymer is in a form selected from the group
consisting of fibers, filaments and combinations thereof. In some
embodiments, the molten thermoplastic polymer is in the form of a
film.
[0015] The invention features a superabsorbent self-supporting film
that is capable of degrading in water, is flushable, and degrades
in a sewer system. The multiplayer construction and can also be
constructed to include a water soluble thermoplastic polymer layer
and be capable of dissolving in water. The invention also features
a multilayer construction that can be disposed on a substrate or
incorporated into an article to render the article water soluble,
water swellable, water dispersible or a combination thereof.
[0016] The multilayer construction is well suited to use in
personal hygiene products and can be incorporated into such
products to render the products more able to degrade in sewer and
waste disposal systems.
[0017] The multilayer construction can be constructed to be
thermally bonded to a substrate.
[0018] The multilayer construction, when in the form of a
continuous or discontinuous film can allow liquid to pass through
the layers of the construction to a second layer, e.g., an
absorbent core, where it can then be stored. Storage of the liquid
in the second layer allows the liquid to be maintained away from
the skin of the user.
GLOSSARY
[0019] In reference to the invention, these terms have the meanings
set forth below:
[0020] "Water sensitive" means water soluble, water dispersible,
water swellable, and combinations thereof.
[0021] Other features and advantages will be apparent from the
following description of the preferred embodiments and from the
claims.
DETAILED DESCRIPTION
[0022] The multilayer construction (e.g., film) includes a layer of
superabsorbent polymer disposed on a layer of water sensitive
thermoplastic polymer. When the superabsorbent layer of the
multilayer construction is contacted with an aqueous composition it
forms a gel and the thermoplastic layer at the interface with the
gelling superabsorbent layer substantially maintains its integrity
as the superabsorbent layer gels. The multilayer construction can
be constructed to gel at a rate faster than the gel rate that would
be exhibited by the superabsorbent polymer layer in the absence of
the water sensitive thermoplastic layer.
[0023] The superabsorbent layer includes superabsorbent polymer
preferably in the form of a continuous or discontinuous coating or
film. The superabsorbent polymer absorbs many times its own weight
in water, preferably at least 50 times, more preferably at least
100 times, most preferably at least 150 times its weight in water.
The ability of the superabsorbent polymer to absorb water is
related to the degree of crosslinking present in the superabsorbent
polymer. Increasing the degree of crosslinking increases the
superabsorbent polymer's total fluid holding capacity under load.
The degree of crosslinking is preferably optimized to obtain a
composition in which the rate and amount of absorbency are
optimized. Preferred superabsorbent polymers are at least 10%, more
preferably from about 10% to about 50%, most preferably from about
20% to 40% crosslinked. Examples of suitable superabsorbent
polymers include crosslinked and polymerized .alpha.,.beta.-beta
ethylenically unsaturated mono- and dicarboxylic acids and acid
anhydride monomers including, e.g., acrylic acid, methacrylic acid,
crotonic acid, maleic acid/anhydride, itaconic acid, fumaric acid,
and combinations thereof.
[0024] The superabsorbent layer is preferably formed from an
aqueous composition of water soluble superabsorbent polymer (i.e.,
a polymer that exhibits superabsorbent properties when
crosslinked), and crosslinking agent. The aqueous superabsorbent
polymer composition exhibits a pH of from about 7 to about 10,
preferably a pH greater than 7, which can be achieved by adding a
pH adjusting agent (e.g., a base) to the aqueous superabsorbent
polymer composition. Examples of useful pH adjusting agents include
alkali metal hydroxide (e.g., sodium hydroxide and potassium
hydroxide), alkali metal alkoxide, alkaline earth metal hydroxide
(e.g., calcium hydroxide), and combinations thereof. The pH
adjusting agent assists in neutralizing the acid groups of the
water soluble superabsorbent polymer. Preferably alkali metal
hydroxide or alkaline earth metal hydroxide is added to neutralize
from about 50% to about 95% of the carboxyl groups, preferably from
greater than 65% to about 95% of the carboxyl groups, more
preferably from about 70% to about 95% of the carboxyl groups, more
preferably from about 70% to about 85% of the carboxyl groups, most
preferably about 75% of the carboxyl groups. The water soluble
superabsorbent polymer is then further neutralized (e.g., at least
100% neutralized) with a volatile base. The volatile base
dissipates from the aqueous water soluble superabsorbent polymer
composition as the composition dries, which allows the crosslinking
agent to crosslink the water soluble superabsorbent polymer to form
a high molecular weight polymer, i.e., the superabsorbent polymer.
Examples of suitable volatile bases include ammonia, e.g., ammonium
hydroxide, amines including, e.g., methylamine and dimethylamine,
and combinations thereof.
[0025] The viscosity of the aqueous water soluble superabsorbent
polymer composition is selected to facilitate application of the
composition on a substrate (e.g., the water soluble thermoplastic
polymer component). Useful aqueous water soluble superabsorbent
polymer compositions have a viscosity of from about 50 cPs to about
50,000 cPs, more preferably, in increasing order of preference,
from about 100 cPs to about 30,000 cPs, from abut 100 cPs to about
20,000 cPs, from about 100 cPs to abut 10,000 cPs, from about 100
cPs to about 5000 cPs, from about 100 cPs to abut 2500 cPs at room
temperature (i.e., 25.degree. C.) for a 20% by weight solids
composition. Preferably the water soluble superabsorbent polymer
has a molecular weight of from about 9000 Mw to about 4,000,000 Mw,
more preferably from about 20,000 Mw to about 1,000,000 Mw, most
preferably from about 100,000 Mw to about 200,000 Mw.
[0026] The aqueous water soluble superabsorbent polymer composition
includes from 5% by weight to about 65% by weight, preferably from
about 10% by weight to about 50% by weight, more preferably from
about 20% by weight to about 40% by weight solids.
[0027] The crosslinking agent is selected to complex with the
functional hydrophilic groups of the water soluble superabsorbent
polymer. Preferred crosslinking agents complex with the functional
groups on the water soluble superabsorbent polymer once the water
phase of the polymer composition has dissipated. Useful
crosslinking agents include, e.g., di- and trivalent crosslinking
salts including, e.g., zirconium salts, zinc salts, chromium salts,
and combinations thereof, zirconium ions, which can be mixed with
ferric aluminum ions, chromic ions, titanium ions, and aziridine,
and combinations thereof. Other useful crosslinking agents are
described in U.S. Pat. No. 4,090,013 and incorporated herein.
Useful commercially available crosslinking agents include ammonium
zirconyl carbonate available under the trade designations BACOTE 20
and ZIRMEL 1000 from Magnesium Elektron, Inc. (Flemington, N.J.),
and aziridine crosslinking agents available under the trade
designation NEOCRYL CX-100 from Zeneca Resins (Wilmington, Mass.).
Preferably the crosslinking agent is added to the aqueous
superabsorbent prepolymer composition in an amount of from about 2
parts to about 10 parts, preferably from about 2 parts to about 8
parts, most preferably from about 4 parts to 6 parts.
[0028] The crosslinking agent can also be provided separately from
the aqueous water soluble superabsorbent polymer composition. In
some applications, the aqueous water soluble superabsorbent polymer
composition is applied to the water sensitive thermoplastic layer
prior to or after application of the crosslinking agent in a
two-step process. When the aqueous water soluble superabsorbent
polymer and crosslinking agent are applied separately, the aqueous
water soluble superabsorbent polymer composition is preferably
dried prior to contact with the crosslinking agent.
[0029] Preferred superabsorbent polymers are capable of being
hydroplasticized by ambient moisture. The hydroplasticized
superabsorbent polymer provides a pliant film exhibiting
extensibility and flexibility. Preferably the superabsorbent
polymer absorbs moisture from the air at ambient temperature and
50% relative humidity in an amount of at least about 5% by weight,
more preferably at least about 10% by weight, most preferably at
least about 20% by weight of the anhydrous superabsorbent
polymer.
[0030] The aqueous water soluble superabsorbent polymer composition
may also include small amounts of water soluble monomers including,
e.g., 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, vinyl
pyrrolidone, acrylamide, methacrylamide, sodium vinyl sulfonated,
and 1-allyloxy-2-hydroxypropane sulfonate.
[0031] Useful water sensitive thermoplastic polymers include water
soluble thermoplastic polymers, water dispersible thermoplastic
polymers and water swellable thermoplastic polymers. Suitable water
sensitive thermoplastic polymers include crystalline water
sensitive thermoplastic polymers and amorphous water sensitive
thermoplastic polymers. The term "crystalline polymer" means those
polymers that retain their rubbery elastomeric or flexible
properties above the glass transition, until the melting
temperature has been surpassed. Melting of the crystalline polymer
is also accompanied by a loss of crystalline X-ray diffraction
effects. An "amorphous polymer" is a polymer that, with increasing
temperature, passes from a solid phase to a liquid phase without a
discernible transition point.
[0032] Suitable water soluble crystalline thermoplastic polymers
include the reaction product of a polyoxyalkylene glycol diamine or
a polyoxyalkylene glycol amine, and a dicarboxylic acid or
dicarboxylic acid ester. Preferred polyoxyalkylene glycol diamines
have the formula:
NH.sub.2--(CH.sub.2).sub.x--(OCH.sub.2--CH.sub.2).sub.y--O--(CH.sub.2).su-
b.x--NH.sub.2 where 2.ltoreq.X.ltoreq.3, and 1.ltoreq.Y.ltoreq.2.
Examples of suitable polyoxyalkylene glycol diamines include
triethylene glycol diamine, wherein X=2 and Y=1, and tetraethylene
glycol diamine, wherein 2.ltoreq.X.ltoreq.3 and Y=2. Useful
commercially available polyoxyalkylene glycol diamines are
available under the trade designations JEFFAMINE XTJ-504 and
JEFFAMINE EDR-192 (tetraethylene glycol diamine) from Huntsman
Chemical Co. (Houston, Tex.). A preferred diamine is
4,7,10-trioxatridecane-1,13-diamine (TTD diamine) where X=3 and
Y=2, which is available from BASF (Parsippany, N.J.).
[0033] Useful polyoxyalkylene glycol amines include JEFFAMINE
D-230, D-400, XTJ-500, XTJ-501, and XTJ-502 provided a chain
terminator acid or amine is employed during the reaction, and/or
additional ingredients such as waxes, tackifiers, crystalline
polymers, and monoacids are subsequently combined with the reacted
polyamide When adipic acid is reacted with
trioxytridecane-1,13-diamine and JEFFAMINE D-230, for example, the
resulting polyamide is relatively slow setting relative to the
reaction of adipic acid and trioxytridecane-1,13-diamine alone. The
polyoxyalkylene glycol diamine is reacted with an equal
stoichiometric ratio of a dicarboxylic acid.
[0034] Suitable dicarboxylic acids include those dicarboxylic acids
having from 5 to 36 carbon atoms including, e.g., adipic acid,
pimelic acid, azelaic acid, sebacic acid, suberic acid,
dodecanedioic acid, terephthalic acid, isophthalic acid, t-butyl
isophthalic acid, dimer acid, and mixtures thereof. The esters and
anhydrides of these acids may also be used.
[0035] Particularly useful water soluble polyether amides have a
melting point no greater than 190.degree. C. and include, e.g., the
reaction products of adipic acid and JEFFAMINE XTJ-504, adipic acid
and JEFFAMINE EDR-192, and adipic acid and TTD diamine.
[0036] Suitable crystalline water soluble polyamides are
commercially available under the trade designations NP-2126,
NP-2110, NP-2116, and NP-2068 from H.B. Fuller Company (St. Paul,
Minn.).
[0037] Suitable crystalline water dispersible polymers include,
e.g., polyethylene oxide available, e.g., from Union Carbide
(Danbury, Conn.) and crystalline polyesters.
[0038] Suitable amorphous water sensitive thermoplastic polymers
include, e.g., polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl
pyrrolidone/vinyl acetate, polyvinyl pyrrolidone/acrylic acid,
polyetheroxazoline, and linear and branched water dispersible
polyesters.
[0039] Suitable commercially available amorphous water dispersible
thermoplastic polymers include, e.g., polyvinyl alcohol available
under the trade designations GROHSERAN L-301 and GROHSERAN L-302
from Nippon Groshei (Japan), and under the trade designation
UNITIKA from Unitaka Ltd. (Japan); polyvinyl pyrrolidone available
from BASF (Mount Olive, N.J.), and International Specialty Products
(Wayne, N.J.); polyvinyl pyrrolidone/vinyl acetate copolymer and
polyvinyl pyrrolidone/acrylic acid available under the trade
designation ACRYLIDONE, both of which are available from ISP;
polyethyloxazoline available under the trade designation PEOX from
The Dow Chemical Company (Freeport, Tex.), and under the trade
designation AQUAZOL from PCI Incorporated (Tucson, Ariz.),
polyvinyl methyl ether available under the trade designation
AMOBOND from Amoco Chemical Co., linear polyesters, polyacrylamide,
and water dispersible polyesters and copolyesters available under
the trade designation EASTMAN AQ including EASTMAN AQ-14000,
EASTMAN AQ-1950, and EASTMAN AQ-1045 from Eastman Chemical Company
(Kingsport, Tenn.).
[0040] Suitable water dispersible polyesters and copolyesters are
available under the EASTMAN AQ trade designation and include linear
polyesters or branched sulfonated copolyesters. Such polymers are
saline and body fluid insoluble, yet dispersible in tap water. The
Tg of the branched water dispersible copolyesters ranges from about
-5.degree. C. to 7.degree. C., whereas the linear polyesters have a
Tg from about 30.degree. C. to about 60.degree. C. Linear
thermoplastic water dispersible polyesters are commercially
available under the EASTMAN AQ series of trade designations
including, e.g., EASTMAN AQ 35S (7,000 Mn), AQ 38S (10,000 Mw), and
AQ 55S (8,000 Mn) all from Eastman Chemical Company (Kingsport,
Tenn.). Branched thermoplastic water dispersible polyesters are
commercially available under the EASTMAN AQ series of trade
designations including, e.g., EASTMAN AQ 1045, AQ 1350, AQ 1950,
and AQ 14000 from Eastman Chemical Company.
[0041] Other useful water sensitive polymers are commercially
available under the Hydromelt trade designation from H.B. Fuller
Company (St. Paul, Minn.) and include NP 2116, NP 2055, NP 2068,
and NP 2110.
[0042] Useful water sensitive thermoplastic polymers and their
methods of manufacture are disclosed, e.g., in U.S. Pat. No.
3,882,090 (Fagerberg et al.), U.S. Pat. No. 5,053,484 (Speranza et
al.), U.S. Pat. No. 5,118,785 (Speranza et al.), U.S. Pat. No.
5,086,162 (Speranza et al.), U.S. Pat. No. 5,324,812 (Speranza et
al.), U.S. Pat. No. 5,899,675 (Ahmed et al.), U.S. Pat. No.
5,863,979 (Ahmed et al.), U.S. Pat. No. 5,663,286 (Ahmed et al.),
and U.S. Pat. No. 5,869,596 (Ahmed et al.), and incorporated
herein.
[0043] The water soluble thermoplastic polymer layer can also
include additives including, e.g., waxes, tackifying resins,
crystalline polymers, monocarboxylic acids, and mixtures thereof as
well as monocarboxylic acids and monoamines.
[0044] Preferably the multilayer construction is oriented such that
the superabsorbent polymer layer is exposed to a fluid to be
absorbed, e.g., water, body fluid, and combinations thereof.
[0045] The multilayer construction can exist in a variety of forms
including, e.g., fibers (e.g., a multicomponent fiber, e.g.,
core-sheath construction), yarn (e.g., multicomponent yarn), film
(e.g., a freestanding film), a coating on a substrate (including,
e.g., woven and nonwoven substrates, porous substrates, films,
fibers, and yarns), and combinations thereof. The multilayer
construction, itself, as well as the layers of the multilayer
construction can be continuous or discontinuous including, e.g.,
striped, dotted, and patterned.
[0046] The multilayer construction can be free standing (e.g., a
film, fiber, and yarn) or associated with, e.g., disposed on, a
substrate including, e.g., fibers, yarns, webs (woven and
nonwoven), films, release liners, and combinations thereof. Useful
fibers include cellulose fibers including, e.g., wood pulp, cotton,
silk, and wool, and synthetic fibers including, e.g., nylon, rayon,
polyesters, acrylics, polypropylenes, polyethylene, polyvinyl
chloride, polyurethane, glass, and combinations thereof. The
multilayer construction can be disposed on the substrate in various
forms including, e.g., continuous and discontinuous (e.g., striped,
dotted, and patterned) coatings, laminates, and combinations
thereof.
[0047] The layers of the construction can be applied to or formed
on the substrate simultaneously or sequentially using a variety of
techniques including, e.g., immersing, soaking, impregnating,
spraying, extruding (e.g., coextrusion), laminating, coating (e.g.,
dip coating, slot, gravure, knife, and contact coating), and
combinations thereof. Porous substrates, for example, can be
sequentially impregnated with the aqueous superabsorbent polymer
and the water sensitive thermoplastic polymer.
[0048] Preferably the aqueous water soluble superabsorbent polymer
composition is applied to the water sensitive component of the
construction while the water sensitive thermoplastic component is
at a higher temperature, e.g., in a molten state or a temperature
in the melt temperature range of the water sensitive thermoplastic
polymer, relative to the aqueous superabsorbent polymer
composition. In the case where the water sensitive component is
formed by extrusion, for example, the aqueous water soluble
superabsorbent polymer composition can be applied to the water
sensitive component as it is extruded, and, in the case of fibers
and filaments, the aqueous water soluble superabsorbent polymer
composition can be applied to the fibers or filaments at or near
the point at which the fibers or filaments are released from the
fiber or filament forming orifice. The relatively higher
temperature exhibited by the water sensitive thermoplastic
component as it is extruded from an orifice increases the rate of
dissipation of the aqueous component of the aqueous water soluble
superabsorbent polymer composition applied thereto.
[0049] The multilayer construction is suitable for use in a variety
of articles including, e.g., absorbent articles such as diapers,
sanitary napkins, bandages, wound care products, surgical pads,
drapes, and gowns as well as various paper products such as paper
towels, toilet paper, and facial tissue, cable wrap, and
packaging.
[0050] One useful article includes a fibrous nonwoven web and the
multilayer construction disposed on the web. The multilayer
construction can include perforations to allow liquid to pass
through the construction to a second layer, e.g., a nonwoven
web.
[0051] The multilayer construction also can be incorporated into an
absorbent article that includes, e.g., a body fluid pervious top
sheet, an acquisition layer, an absorbent layer (e.g., a fibrous
core), a body fluid impermeable back sheet, and combinations
thereof. The acquisition layer preferably is capable of dispersing
liquid to the surface of the absorbent layer. The absorbent layer
may include loose fibers, fibers held together through a binder,
compressed fibers, and combinations thereof. The fibers of the
absorbent layer may be natural fibers (e.g., wood pulp, jute,
cotton, silk, and wool, and combinations thereof), synthetic fibers
including (e.g., nylon, rayon polyester, acrylics, polypropylenes,
polyethylene, polyvinyl chloride, polyurethane, and combinations
thereof), and combinations thereof. The multilayer construction can
be in the form of a layer disposed between any of the
components.
[0052] In one absorbent article, the multilayer construction is
perforated and disposed between the wearer of the absorbent article
and an absorbent layer such that the thermoplastic layer is the
first layer of the multilayer construction that is available for
contact with a liquid. The perforations allow a liquid to pass
through the multilayer construction from the thermoplastic layer to
the superabsorbent layer. The superabsorbent layer then gels upon
contact with the water and the absorbent layer of the absorbent
article absorbs the water.
[0053] The invention will now be described by way of the following
examples. All ratios and percentages are by weight unless otherwise
indicated.
EXAMPLES
Example
[0054] FULATEX PD8081H aqueous polyacrylic acid solution polymer
and ammonium zirconyl carbonate composition (H.B. Fuller Company,
St. Paul, Minn.) was coated onto a 50 um thick NP 2116 polyamide
film (H.B. Fuller Company) and dried to form a film construction
that included a 15 um superabsorbent polymer coating on the 50 um
polyamide film.
[0055] Water droplets were dropped onto the superabsorbent polymer
surface of the film construction using an eye dropper. The treated
film was observed. The water was rapidly adsorbed and then absorbed
by the superabsorbent polymer and formed a gel in five seconds. The
water was then absorbed by the thermoplastic layer of the film
construction. After three minutes the film construction had
dissolved in the location of the water droplets.
[0056] Other features are present in the claims.
* * * * *