U.S. patent application number 10/154607 was filed with the patent office on 2003-11-27 for meltblown absorbent fibers and composites and method for making the same.
Invention is credited to Qin, Jian, Tsai, Fu-Jya Daniel, Wang, James Hongxue, Wisneski, Anthony John.
Application Number | 20030219594 10/154607 |
Document ID | / |
Family ID | 29548915 |
Filed Date | 2003-11-27 |
United States Patent
Application |
20030219594 |
Kind Code |
A1 |
Qin, Jian ; et al. |
November 27, 2003 |
Meltblown absorbent fibers and composites and method for making the
same
Abstract
An absorbent fiber is produced from a melt processable polymer.
An absorbent composite includes the absorbent fiber in addition to
natural fibers and superabsorbent material. A method of producing
the superabsorbent fiber and absorbent composite is also
disclosed.
Inventors: |
Qin, Jian; (Appleton,
WI) ; Wang, James Hongxue; (Appleton, WI) ;
Wisneski, Anthony John; (Kimberly, WI) ; Tsai, Fu-Jya
Daniel; (Appleton, WI) |
Correspondence
Address: |
PAULEY PETERSEN KINNE & ERICKSON
2800 WEST HIGGINS ROAD
SUITE 365
HOFFMAN ESTATES
IL
60195
US
|
Family ID: |
29548915 |
Appl. No.: |
10/154607 |
Filed: |
May 23, 2002 |
Current U.S.
Class: |
428/364 |
Current CPC
Class: |
Y10T 428/2913 20150115;
A61L 15/60 20130101 |
Class at
Publication: |
428/364 |
International
Class: |
D04H 001/00; D04H
003/00; D04H 005/00; D04H 013/00; D02G 003/00 |
Claims
We claim:
1. An absorbent fiber, comprising: a melt processable, water
soluble polymer; and a cross-linking agent; wherein the absorbent
fiber has an absorbency under zero load of at least about 5
g/g.
2. The absorbent fiber of claim 1, wherein the polymer comprises a
polymer selected from polyethylene oxide, polypropylene oxide,
hydroxyl propyl cellulose, methyl cellulose, ethyl cellulose,
methylethyl cellulose, polyethylene imine, polyvinyl amine,
polyvinyl alcohol, poly(ethylene oxide-co-propylene oxide),
polyacrylic acid, polyacrylamide, and combinations thereof.
3. The absorbent fiber of claim 1, wherein the polymer comprises a
copolymer.
4. The absorbent fiber of claim 3, wherein at least one monomer of
the copolymer is sodium acrylate.
5. The absorbent fiber of claim 3, wherein at least one monomer of
the copolymer is methyl methacrylate.
6. The absorbent fiber of claim 3, wherein the copolymer includes a
ratio on a dry weight basis of a first monomer to a second monomer
of from about 30:70 to about 70:30.
7. The absorbent fiber of claim 3, wherein the copolymer comprises
sodium acrylate and methyl methacrylate.
8. The absorbent fiber of claim 1, wherein the polymer has a
molecular weight in a range of about 10,000 to about 1,000,000.
9. The absorbent fiber of claim 1, wherein the polymer has a
molecular weight in a range of about 50,000 to about 1,000,000.
10. The absorbent fiber of claim 1, wherein the polymer has a
molecular weight in a range of about 100,000 to about 500,000.
11. The absorbent fiber of claim 1, wherein the cross-linking agent
comprises at least two functional groups capable of reacting with
functional groups on the polymer.
12. The absorbent fiber of claim 11, wherein the at least two
functional groups of the cross-linking agent comprise a functional
group selected from carboxylic acid group, epoxy group, hydroxyl
group, amino group, aldehyde group, tri-valent metal ions, and
tetra-valent metal ions.
13. The absorbent fiber of claim 1, wherein the cross-linking agent
comprises a compound selected from diols, polyols, diamines,
polyamines, dicarboxylic acids, polycarboxylic acids, dialdehydes,
polyaldehydes, butandiol, diethylene triamine, ethylene glycol
diglycidyl ether, citric acid, glutaric dialdehyde, and
combinations thereof.
14. The superabsorbent fiber of claim 1, wherein a cross-linking
reaction is initiated by a treatment selected from heat treatment,
microwave radiation, e-beam radiation, UV radiation, steam
treatment, and vapor treatment.
15. An absorbent composite, comprising: a melt processable, water
soluble polymer; a superabsorbent material; hydrophilic fibers; and
a cross-linking agent; wherein the absorbent composite has an
absorbency under zero load of at least about 10 g/g.
16. The absorbent composite of claim 15, wherein the superabsorbent
material comprises superabsorbent particles.
17. The absorbent composite of claim 15, wherein the superabsorbent
material comprises superabsorbent fibers.
18. The absorbent composite of claim 15, wherein the hydrophilic
fibers comprise fibers selected from wood pulp fluff, cotton,
cotton linter, other cellulose fibers, regenerated cellulose
fibers, staple fibers, synthetic hydrophilic fibers, and
combinations thereof.
19. The absorbent composite of claim 15, wherein the polymer
comprises a polymer selected from polyethylene oxide, polypropylene
oxide, hydroxyl propyl cellulose, methyl cellulose, ethyl
cellulose, methylethyl cellulose, polyethylene imine, polyvinyl
amine, polyvinyl alcohol, poly(ethylene oxide-co-propylene oxide),
polyacrylic acid, polyacrylamide, and combinations thereof.
20. The absorbent composite of claim 15, wherein the polymer
comprises a copolymer.
21. The absorbent composite of claim 20, wherein at least one
monomer of the copolymer is sodium acrylate.
22. The absorbent composite of claim 20, wherein at least one
monomer of the copolymer is methyl methacrylate.
23. The absorbent composite of claim 20, wherein the copolymer
includes a ratio on a dry weight basis of a first monomer to a
second monomer of from about 30:70 to about 70:30.
24. The absorbent composite of claim 20, wherein the copolymer
comprises sodium acrylate and methyl methacrylate.
25. The absorbent composite of claim 15, wherein the polymer has a
molecular weight in a range of about 10,000 to about 1,000,000.
26. The absorbent composite of claim 15, wherein the polymer has a
molecular weight in a range of about 50,000 to about 1,000,000.
27. The absorbent composite of claim 15, wherein the polymer has a
molecular weight in a range of about 100,000 to about 500,000.
28. The absorbent composite of claim 15, wherein the cross-linking
agent comprises at least two functional groups capable of reacting
with functional groups on the polymer.
29. The absorbent composite of claim 28, wherein the at least two
functional groups of the cross-linking agent comprise a functional
group selected from carboxylic acid group, epoxy group, hydroxyl
group, amino group, aldehyde group, tri-valent metal ions, and
tetra-valent metal ions.
30. The absorbent composite of claim 15, wherein the cross-linking
agent comprises a compound selected from diols, polyols, diamines,
polyamines, dicarboxylic acids, polycarboxylic acids, dialdehydes,
polyaldehydes, butandiol, diethylene triamine, ethylene glycol
diglycidayl ether, citric acid, glutaric dialdehyde, and
combinations thereof.
31. The absorbent composite of claim 15, wherein a cross-linking
reaction is initiated by a treatment selected from heat treatment,
microwave, e-beam radiation, UV radiation, steam treatment, and
vapor treatment.
32. The absorbent composite of claim 15, wherein the absorbent
composite is a superabsorbent material.
33. The absorbent composite of claim 15, wherein the absorbent
composite has an absorbency under zero load of at least 15 g/g.
34. The absorbent composite of claim 15, wherein the absorbent
composite has an absorbency under zero load of up to about 50
g/g.
35. A method of producing an absorbent fiber, comprising the steps
of: melting a melt processable, water soluble polymer; extruding
the polymer; spinning the polymer to form fibers; adding a
cross-linking agent to the fibers; and curing the fibers.
36. The method of claim 35, wherein the polymer comprises a polymer
selected from polyethylene oxide, polypropylene oxide, hydroxyl
propyl cellulose, methyl cellulose, ethyl cellulose, methyethyl
cellulose, polyethylene imine, polyvinyl amine, polyvinyl alcohol,
poly(ethylene oxide-co-propylene oxide), polyacrylic acid,
polyacrylamide, and combinations thereof.
37. The method of claim 35, wherein the polymer comprises a
copolymer.
38. The method claim 37, wherein at least one monomer of the
copolymer is sodium acrylate.
39. The method of claim 37, wherein at least one monomer of the
copolymer is methyl methacrylate.
40. The method of claim 37, wherein the copolymer includes a ratio
on a dry weight basis of a first monomer to a second monomer of
from about 30:70 to about 70:30.
41. The method of claim 37, wherein the copolymer comprises sodium
polyacrylate and methyl methacrylate.
42. The method of claim 35, wherein the polymer has a molecular
weight in a range of about 10,000 to about 1,000,000.
43. The method of claim 35, wherein the polymer has a molecular
weight in a range of about 50,000 to about 1,000,000.
44. The method of claim 35, wherein the polymer has a molecular
weight in a range of about 100,000 to about 500,000.
45. The method of claim 35, wherein the cross-linking agent
comprises at least two functional groups capable of reacting with
functional groups on the polymer.
46. The method of claim 45, wherein the at least two functional
groups of the cross-linking agent comprise a functional group
selected from carboxylic acid group, epoxy group, hydroxyl group,
amino group, aldehyde group, tri-valent metal ions, and
tetra-valent metal ions.
47. The method of claim 35, wherein the cross-linking agent
comprises a compound selected from diols, polyols, diamines,
polyamines, dicarboxylic acids, polycarboxylic acids, dialdehydes,
polyaldehydes, butandiol, diethylene triamine, ethylene glycol
diglycidyl ether, citric acid, glutaric dialdehyde, and
combinations thereof.
48. The method of claim 35, wherein a cross-linking reaction is
initiated by a treatment selected from heat treatment, microwave,
e-beam radiation, UV radiation, steam treatment, and vapor
treatment.
49. A diaper comprising the absorbent fiber produced according to
the method of claim 35.
50. Training pants comprising the absorbent fiber produced
according to the method of claim 35.
51. Swim wear comprising the absorbent fiber produced according to
the method of claim 35.
52. An adult incontinence garment comprising the absorbent fiber
produced according to the method of claim 35.
53. A feminine hygiene product comprising the absorbent fiber
produced according to the method of claim 35.
54. A medical absorbent product comprising the absorbent fiber
produced according to the method of claim 35.
55. A method of producing an absorbent composite, comprising the
steps of: melting a melt processable, water soluble polymer;
extruding the polymer; spinning the polymer to form fibers; adding
hydrophilic fibers to the fibers; adding a superabsorbent material
to the fibers; adding a cross-linking agent to the fibers; and
curing the fibers.
56. The method of claim 55, wherein the hydrophilic fibers comprise
fibers selected from wood pulp fluff, cotton, cotton linter, other
cellulose fibers, regenerated cellulose fibers, staple fibers,
synthetic hydrophilic fibers, and combinations thereof.
57. The method of claim 55, wherein the polymer comprises a polymer
selected from polyethylene oxide, polypropylene oxide, hydroxyl
propyl cellulose, methyl cellulose, ethyl cellulose, methylethyl
cellulose, polyethylene imine, polyvinyl amine, polyvinyl alcohol,
poly(ethylene oxide-co-propylene oxide), polyacrylic acid,
polyacrylamide, and combinations thereof.
58. The method of claim 55, wherein the polymer comprises a
copolymer.
59. The method claim of 58, wherein at least one monomer of the
copolymer is sodium acrylate.
60. The method of claim 58, wherein at least one monomer of the
copolymer is methyl methacrylate.
61. The method of claim 58, wherein the copolymer includes a ratio
on a dry weight basis of a first monomer to a second monomer of
from about 30:70 to about 70:30.
62. The method of claim 58, wherein the copolymer comprises sodium
acrylate and methyl methacrylate.
63. The method of claim 55, wherein the polymer has a molecular
weight in a range of about 10,000 to about 1,000,000.
64. The method of claim 55, wherein the polymer has a molecular
weight in a range of about 50,000 to about 1,000,000.
65. The method of claim 55, wherein the polymer has a molecular
weight in a range of about 100,000 to 500,000.
66. The method of claim 55, wherein the cross-linking agent
comprises at least two functional groups capable of reacting with
functional groups on the polymer.
67. The method of claim 66, wherein the at least two functional
groups of the cross-linking agent comprise a functional group
selected from carboxylic acid group, epoxy group, hydroxyl group,
amino group, aldehyde group, tri-valent metal ions, and
tetra-valent metal ions.
68. The method of claim 55, wherein the cross-linking agent
comprises a compound selected from diols, polyols, diamines,
polyamines, dicarboxylic acids, polycarboxylic acids, dialdehydes,
polyaldehydes, butandiol, diethylene triamine, ethylene glycol
diglycidyl ether, citric acid, glutaric dialdehyde, and
combinations thereof.
69. The method of claim 55, wherein a cross-linking reaction is
initiated by a treatment selected from heat treatment, microwave,
e-beam radiation, UV radiation, steam treatment, and vapor
treatment.
70. A diaper comprising the absorbent composite produced according
to the method of claim 55.
71. Training pants comprising the absorbent composite produced
according to the method of claim 55.
72. Swim wear comprising the absorbent composite produced according
to the method of claim 55.
73. An adult incontinence garment comprising the absorbent
composite produced according to the method of claim 55.
74. A feminine hygiene product comprising the absorbent composite
produced according to the method of claim 55.
75. A medical absorbent product comprising the absorbent composite
produced according to the method of claim 55.
Description
FIELD OF THE INVENTION
[0001] This invention relates to absorbent materials having
improved absorbent properties. More specifically, this invention
relates to absorbent fibers produced from a melt processable
polymer and to absorbent composites containing the absorbent
fibers. This invention also relates to a method for making the
absorbent fibers and absorbent composites.
BACKGROUND OF THE INVENTION
[0002] Absorbent materials are useful in disposable personal care
absorbent products such as diapers, training pants, feminine pads,
adult incontinence products and professional health care products
for absorbing and retaining fluids. Absorbent or superabsorbent
materials are often combined with water-insoluble fibers to create
an absorbent composite for use in an absorbent core of a disposable
personal care absorbent product according to methods known in the
art.
[0003] Particulate superabsorbents are widely used as
superabsorbent material in disposable personal care absorbent
products. However, superabsorbent particles are sometimes difficult
to use because they do not remain stationary during the
manufacturing of the disposable personal care absorbent product and
may shift position in the disposable personal care absorbent
product.
[0004] The use of absorbent or superabsorbent fibers instead of
superabsorbent particles in disposable personal care absorbent
products is potentially advantageous because fibers can provide
improved product integrity, better containment, reduced product
bulkiness and improved absorbent properties, such as rapid fluid
absorption and fluid distribution properties. Furthermore, the use
of fibers may also lead to improved product attributes, such as
thinner and softer products that provide better fit, less gel
migration, and potential simplification of the manufacturing
process of the absorbent product.
[0005] Currently available commercial absorbent fibers are produced
by solution spinning processes, such as a solution dry spinning
process used for textile fiber manufacturing or a solution blowing
spinning process used for nonwoven fabric manufacturing. Solution
spinning processes start with an aqueous polymer solution. The
polymer solution is then spun into fibers and cross-linked to form
water-swellable, water-insoluble fibers. However, such solution
spinning processes have low productivity and are expensive because
of the presence of excess water in the polymer solution. For these
reasons, absorbent fibers are not widely used for the absorbent
material in disposable personal care absorbent products.
[0006] Some polymers can be processed into different shapes or
forms when the temperature is above a certain point and can be
referred to as "melt processable." Other polymers upon reaching a
certain elevated temperature will degrade, rather than melt, and
can be referred to as "non-melt processable."
[0007] Fibers produced from melt processable polymers such as
polyethylene (PE) or polypropylene (PP) are widely used in nonwoven
industries at low cost. However, they cannot be used in absorbent
composites of disposable personal care absorbent products due to
their high hydrophobicity which causes poor fluid handling
properties such as non-wetting and no wicking.
[0008] U.S. Pat. No. 5,280,079 issued Jan. 18, 1994 to Allen et
al., U.S. Pat. No. 5,147,956 issued Sep. 15, 1992 to Allen, U.S.
Pat. No. 4,962,172 issued Oct. 09, 1990 to Allen et al., U.S. Pat.
No. 5,151,465 issued Sep. 29, 1992 to Le-Khac, and U.S. Pat. No.
5,066,742 issued Nov. 19, 1991 to Gupta each describe absorbent
fibers. However, the absorbent fibers described therein are
produced by a solution spinning process. In addition, the water
soluble polymers used to form the fibers are non-melt processable.
Furthermore, superabsorbent staple fibers are commerically
available from Camelot Superabsorbent Ltd. in Calgary, Canada under
the trade designation FIBERDRI.RTM., an isobutylene-maleic
anhydride copolymer based absorbent fiber, or from Technical
Absorbents in Grimsby, United Kingdom under the trade designation
OASIS.RTM. 101, a sodium polyacrylate based absorbent fiber. These
commerically available superabsorbent fibers are also produced by
solution spinning of non-melt processable water soluble polymers.
These staple fibers are made from textile fiber dry spinning
process. They can be incorporated into absorbent cores through an
air laying process but do not form bonds with other components of
the core, such as superabsorbent particles and fluff fiber. The
absorbent core from the process is not a stabilized structure.
[0009] There is a need for absorbent fibers that can be
manufactured in high productivity and at low cost, and for
absorbent composites containing such absorbent fibers. There is
also a need for stabilized absorbent composites that can exhibit
improved dry and wet integrities. There is also a need for a high
productivity, low cost method for making the absorbent fibers and
absorbent composites.
SUMMARY OF THE INVENTION
[0010] This invention relates to absorbent fibers produced from
melt processable polymers and to absorbent composites containing
the absorbent fibers. This invention also relates to a method for
making the absorbent fibers and absorbent composites.
[0011] In one embodiment of this invention, the absorbent fibers
include a melt processable, water soluble polymer which is
meltblown and then cross-linked to form the water-swellable but
water insoluble absorbent fibers. The resulting absorbent fibers
have an absorbency under zero load value of at least about 5 grams
fluid per gram fiber (g/g). The melt processable, water soluble
polymer may be a non-ionic homopolymer, such as for example,
polyethylene oxide, polypropylene oxide, hydroxy propyl cellulose,
methyl cellulose, ethyl cellulose, methyethyl cellulose,
polyethylene imine, polyvinyl amine, polyvinyl alcohol,
poly(ethylene oxide-co-propylene oxide), polyacrylic acid,
polyacrylamide, and combinations thereof. The melt processable,
water soluble polymer may also be a copolymer of monomers of at
least one ionic and one non-ionic monomer such as sodium acrylate
(currently used in commercial superabsorbent materials) and methyl
methacrylate (currently used in commercial melt processable
polymers).
[0012] In another embodiment of this invention, an absorbent
composite includes a melt processable, water soluble polymer which
is meltblown with hydrophilic fibers (such as wood pulp fluff,
cotton, cotton linter, other cellulose fibers, regenerated
cellulose fibers, natural fibers or modified or spun staple fibers,
and hydrophilic synthetic fibers, such as those available from
Allied Corporation in Morristown, N.J., USA, under the trade
designation HYDROFIL.RTM., and combinations thereof) and
commercially available superabsorbent material. The polymer is
cross-linked to form water-swellable but water insoluble absorbent
fibers. The resulting absorbent composite has an absorbency under
zero load value of at least 5 grams fluid per gram composite (g/g)
and may also be superabsorbent, exhibiting an absorbency under zero
load of at least about 10 g/g or up to about 50 g/g. As in the
previous embodiment, the melt processable, water soluble polymer
may be a non-ionic homopolymer, such as for example, polyethylene
oxide, polypropylene oxide, hydroxy propyl cellulose, methyl
cellulose, ethyl cellulose, methylethyl cellulose, polyethylene
imine, polyvinyl amine, polyvinyl alcohol, poly(ethylene
oxide-co-propylene oxide), polyacrylic acid, polyacrylamide, and
combinations thereof, or may be a copolymer of monomers of at least
one ionic and one non-ionic monomer such as sodium acrylate and
methyl methacrylate.
[0013] In either embodiment, the cross-linking agent can be sprayed
onto the surface of the meltblown fibers. The cross-linking agent
must have at least two functional groups capable of reacting with
the functional groups on the surface of the melt processable
polymer. In order to initiate the cross-linking reaction, a post
treatment such as heat,treatment, microwave radiation, electron
beam (e-beam) radiation, ultraviolet (UV) radiation, steam
treatment or vapor treatment is required.
[0014] This invention also relates to a method for making absorbent
fibers and absorbent composites including the steps of melting a
melt processable, water soluble polymer, extruding the polymer,
spinning the polymer to form fibers, adding a cross-linking agent
and curing the resulting fibers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an exploded perspective view of a diaper with an
absorbent core containing absorbent material FIGS. 2A-2C show
photographs of an absorbent composite according to one embodiment
of the invention.
[0016] FIG. 3 is a schematic representation of a method and
apparatus for producing absorbent fibers and absorbent composites
according to one embodiment of the invention.
DEFINITIONS
[0017] Within the context of this specification, each term or
phrase below will include the following meaning or meanings.
[0018] "Polymer" includes, but is not limited to, homopolymers,
copolymers, such as for example, block, graft, random and
alternating copolymers, terpolymers, etc., and blends and
modifications thereof. Furthermore, unless otherwise specifically
limited, the term "polymer" shall include all possible geometrical
configurations of the material. These configurations include, but
are not limited to isotactic, syndiotactic and atactic
symmetries.
[0019] "Nonwoven fabric or web" means a web having a structure of
individual fibers or threads which are interlaid, but not in a
regular or identifiable manner as in a knitted fabric. Nonwoven
fabrics or webs have been formed from many processes such as, for
example, meltblowing processes, spunbonding processes, air laying
processes, and bonded carded web processes. The basis weight of
nonwoven fabrics is usually expressed in ounces of material per
square yard (osy) or grams per square meter (gsm) and the fiber
diameters useful are usually expressed in microns. (Note that to
convert from osy to gsm, multiply osy by 33.91.).
[0020] "Spunbonded fibers" refers to small diameter fibers which
are formed by extruding molten thermoplastic material as filaments
from a plurality of fine capillaries of a spinnerette having a
circular or other configuration, with the diameter of the extruded
filaments then being rapidly reduced as by, for example, in U.S.
Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to
Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S.
Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No.
3,502,763 to Hartmann, U.S. Pat. No. 3,502,538 to Petersen, and
U.S. Pat. No. 3,542,615 to Dobo et al., each of which is
incorporated herein in its entirety by reference. Spunbond fibers
are quenched and generally not tacky when they are deposited onto a
collecting surface. Spunbond fibers are generally continuous and
often have average diameters larger than about 7 microns, more
particularly, between about 10 and 30 microns.
[0021] "Meltblown fibers" means fibers formed by extruding a molten
thermoplastic material through a plurality of fine, usually
circular, die capillaries as molten threads or filaments into
converging high velocity heated gas (e.g., air) streams which
attenuate the filaments of molten thermoplastic material to reduce
their diameter, which may be to microfiber diameter. Thereafter,
the meltblown fibers are carried by the high velocity gas stream
and are deposited on a collecting surface to form a web of randomly
dispersed meltblown fibers. Such a process is disclosed for
example, in U.S. Pat. No. 3,849,241 to Butin et al. Meltblown
fibers are microfibers which may be continuous or discontinuous,
are generally smaller than 10 microns in diameter, and are
generally self bonding when deposited onto a collecting surface.
Meltblown fibers used in the present invention are preferably
substantially continuous in length.
[0022] "Coform material" refers to a product produced by combining
separate polymer and additive streams into a single deposition
stream in forming the nonwoven webs. Such a process is taught, for
example, by U.S. Pat. No. 4,100,324 to Anderson et al. which is
hereby incorporated by reference. U.S. Pat. No. 4,818,464 to Lau
discloses the introduction of superabsorbent material as well as
wood pulp fluff, cellulose, or staple fibers through a centralized
chute in an extrusion die for combination with resin fibers in a
nonwoven web. The wood pulp fluff, staple fibers, or other material
are added to vary the characteristics of the resulting web, for
example, strength and absorbency.
[0023] "Pulp fibers" refers to fibers from natural sources such as
woody and non-woody plants. Woody plants include, for example,
deciduous and coniferous trees. Non-woody plants include, for
instance, cotton, flax, esparto grass, milkweed, straw, jute hemp,
and bagasse.
[0024] "Cross-linked" refers to any means for effectively rendering
normally water-soluble materials substantially water insoluble but
swellable. Such means can include, for example, physical
entanglement, crystalline domains, covalent bonds, ionic complexes
and associations, hydrophilic associations, such as hydrogen
bonding, and hydrophobic associations or Van der Waals forces.
[0025] "Hydrophilic" describes fibers or the surfaces of fibers
which are wettable by the aqueous liquids in contact with the
fibers. The degree of wetting of the materials can, in turn, be
described in terms of the contact angles and the surface tensions
of the liquids and materials involved. Equipment and techniques
suitable for measuring the wettability of particular fiber
materials or blends of fiber materials can be provided by a Cahn
SFA-222 Surface Force Analyzer System, or a substantially
equivalent system. When measured with this system, fibers having
contact angles less than 90.degree. are designated "wettable" or
hydrophilic, while fibers having contact angles greater than
90.degree. are designated "nonwettable" or hydrophobic.
[0026] "Superabsorbent material" refers to a water-swellable,
water-insoluble organic or inorganic material capable, under the
most favorable conditions, of absorbing at least about 10 times its
weight, preferably at least about 20 times its weight in an aqueous
solution containing 0.9% by weight sodium chloride. Superabsorbent
material can comprise a form including particles, fibers,
nonwovens, films, coforms, printings, coatings, other structural
forms, and combinations thereof. "Water-swellable, water-insoluble"
refers to the ability of a material to swell to a equilibrium
volume in excess water but not dissolve into the water. The
water-swellable, water-insoluble material generally retains its
original identity or physical structure, but in a highly expanded
state upon the absorption of water.
[0027] "Absorbency Under Zero Load (AUZL)" refers to the result of
a test which measures the amount in grams of an aqueous 0.9% by
weight sodium chloride solution that a gram of material can absorb
in 1 hour under negligible applied load (about 0.01 pound per
square inch).
[0028] "Water-soluble" refers to materials which substantially
dissolve in excess water to form a solution, thereby losing its
initial form and becoming essentially molecularly dispersed
throughout the water solution. As a general rule, a water-soluble
material will be free from a substantial degree of cross-linking,
as cross-linking tends to render a material water insoluble. A
material that is "water insoluble" is one that is not water soluble
according to this definition.
[0029] "Melt processable" refers to either a crystalline or
semicrystalline polymer that has a melting point or an amorphous
polymer that has a softening point and, therefore, can be thermally
processed into different shapes or forms, for example, meltblown
fibers. In order to be considered as a melt processable polymer,
the crystalline or semicrystalline polymers have to have a melting
point as well as reasonable thermal stability and melt
processability such as adequate melt rheology. For amorphous
polymers, they have to have a softening point as well as reasonable
thermal stability and melt processability such as adequate melt
rheology.
[0030] "Solvent" refers to a substance, particularly in liquid
form, that is capable of dissolving a polymer used herein to form a
substantially uniformly dispersed mixture at the molecular
level.
[0031] The term "absorbent product" includes without limitation
diapers, training pants, swim wear, absorbent underpants, baby
wipes, adult incontinence products, feminine hygiene products,
medical garments, underpads, bandages, absorbent drapes, and
medical wipes, as well as industrial work wear garments.
[0032] These terms may be defined with additional language in the
remaining portions of the specification.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0033] This invention relates to absorbent fibers produced from a
melt processable polymer and to absorbent composites containing the
absorbent fibers. The absorbent composites can be used in absorbent
cores for disposable personal care absorbent products. The
absorbent composites are useful in absorbent articles such as
diapers, training pants, swim wear, adult incontinence articles,
feminine care products, and medical absorbent products. This
invention also relates to a method for making the absorbent fibers
and absorbent composites.
[0034] FIG. 1 illustrates an exploded perspective view of a
disposable diaper. Referring to FIG. 1, disposable diaper 10
includes outer cover 12, body-side liner 14, and absorbent core 40
located between body-side liner 14 and outer cover 12. Absorbent
core 40 can include the absorbent fibers or an absorbent composite
according to this invention. Body-side liner 14 and outer cover 12
are constructed of conventional non-absorbent materials. By
"non-absorbent" it is meant that these materials, excluding the
pockets filled with superabsorbent, have an absorptive capacity not
exceeding 5 grams of 0.9% aqueous sodium chloride solution per gram
of material.
[0035] Body-side liner 14 is constructed from highly liquid
pervious materials. This layer functions to transfer liquid from
the wearer to absorbent core 40. Suitable liquid pervious materials
include porous woven materials, porous nonwoven materials, films
with apertures, open-celled foams, and batting. Other examples of
suitable body-side liner materials include, without limitation, any
flexible porous sheets of polyolefin fibers, such as polypropylene,
polyethylene or polyester fibers; webs of spunbonded polypropylene,
polyethylene or polyester fibers; webs of rayon fibers; bonded
carded webs of synthetic or natural fibers or combinations thereof.
U.S. Pat. No. 5,904,675, issued May 18, 1999 to Laux et al. and
incorporated by reference, provides further examples of suitable
surge materials. This layer may also be an apertured plastic film.
Suitable batting includes certain air formed thermochemical and
chemithermomechanical wood pulps. The various layers of article 10
have dimensions which vary depending on the size and shape of the
wearer.
[0036] Outer cover material 12 should be breathable to water vapor.
Generally outer cover 12 will have a moisture vapor transmission
rate (MVTR) of at least about 300 grams/m.sup.2-24 hours, desirably
at least about 1000 grams/m.sup.2-24 hours, or at least about 3000
grams/m.sup.2-24 hours, measured using INDA Test Method
IST-70.4-99, herein incorporated by reference.
[0037] Attached to outer cover 12 are waist elastics 26, fastening
tapes 28 and leg elastics 30. The leg elastics 30 typically have a
carrier sheet 32 and individual elastic strands 34. The diaper of
FIG. 1 is a general representation of one basic diaper embodiment.
Various modifications can be made to the design and materials of
diaper parts.
[0038] Construction methods and materials of an embodiment of a
diaper such as illustrated in FIG. 1, are set forth in greater
detail in commonly assigned U.S. Pat. No. 5,509,915, issued Apr.
23, 1996 in the name of Hanson et al., incorporated herein by
reference. Possible modifications to the diaper illustrated in FIG.
1 are set forth in commonly assigned U.S. Pat. No. 5,509,915 and in
commonly assigned U.S. Pat. No. 5,364,382, issued Nov. 15, 1994 to
Latimer et al.
[0039] According to one embodiment of this invention, the absorbent
fibers comprise a melt processable, water soluble polymer which is
meltblown and then cross-linked to form water-swellable but water
insoluble absorbent fibers. Suitable melt processable, water
soluble polymers include non-ionic homopolymers such as
polyethylene oxide, polypropylene oxide, hydroxyl propyl cellulose,
methyl cellulose, ethyl cellulose, methylethyl cellulose,
polyethylene imine, polyvinyl amine, polyvinyl alcohol,
poly(ethylene oxide-co-propylene oxide), polyacrylic acid,
polyacrylamide and combinations of the foregoing. In order to
enhance their melt processabilities, some degree of modification
may be needed. These modifications include, but are not limited to,
additions of low percentage of additives, blends, and/or
comonomers. The modified polyvinyl alcohol used herein is available
commercially from Nippon Gohsei located in Osaka, Japan.
[0040] Although a non-ionic water soluble and melt processable
polymer is absorbent, it is not superabsorbent due to lack of ionic
charge groups on its macromolecular chains. Current commercial
particulate superabsorbent materials are made of ionic
polyacrylate. However, pure ionic water soluble polymers in general
are not melt processable.
[0041] Another melt processable, water soluble polymer may be a
copolymer of both ionic and non-ionic monomers. Suitable monomers
for the copolymer include an ionic monomer, such as sodium
acrylate, which is commerically available from Aldrich Chemical Co.
in Milwaukee, Wis., USA, and a non-ionic monomer, such as methyl
methacrylate, which is commerically available from Aldrich Chemical
Co. in Milwaukee, Wis., USA. In order to achieve both water
solubility and melt processability of the copolymer, the ratio of
the monomers on a dry weight basis is critical. Preferably, the
ratio of the monomers on a dry weight basis should be from about
30:70 to about 70:30. Polymerization to form the copolymer can be
carried out according to conventional methods known in the art.
Because of the addition of an ionic comonomer, the water soluble
and melt processable copolymers have a higher absorbency than the
non-ionic homopolymers.
[0042] Whether a homopolymer or a copolymer, the molecular weight
of the polymer is important. The molecular weight of the polymer
must be at least about 10,000 in order to have a high fluid
absorbency. However, the molecular weight of the polymer cannot
exceed about 1,000,000 because the meltblowing equipment can not
handle too high of a viscosity. Suitable polymers have a molecular
weight between about 50,000 to 1,000,000, desirably between about
100,000 to 1,000,000, or between about 100,000 and 500,000.
[0043] Following formation of the fibers, the fibers are still
water soluble. A solution containing a cross-linking agent is
sprayed onto the surface of the meltblown fibers to form
water-swellable, but water insoluble fibers instantly or after the
curing step depending on the nature of the cross-linking agent
used. The suitable cross-linking agent can be either reactive or
latent. The reactive cross-linking agent will cross-link the fibers
in the spinning process. The latent cross-linking agent does not
cross-link the fibers and normally requires some activation energy
to trigger cross-linking, such as heating. The cross-linking agent
desirably has at least two functional groups capable of reacting
with the pendant functional groups on the melt processable polymer.
Suitable cross-linking agents include diols, polyols, diamines,
polyamines, dicarboxylic acids, polycarboxylic acids, dialdehydes,
polyaldehydes, butandiol, diethylene triamine, citric acid,
glutaric dialdehyde and ethylene glycol diglycidyl ether,
tri-valent or tetra-valent metal ions, and combinations of the
foregoing.
[0044] The appropriate functional groups on the cross-linking agent
depends upon the melt processable polymer. For example, if
polyvinyl alcohol is used as the melt processable polymer, suitable
functional groups on the cross-linking agent include carboxylic
acid groups (forming ester linkages with the hydroxyl groups on the
polyvinyl alcohol), aldehyde groups (forming acetal linkages with
the hydroxyl groups on the polyvinyl alcohol), or epoxy groups
(forming ether linkages with the hydroxyl groups on the polyvinyl
alcohol). However, if the melt processable polymers have different
types of functional groups, such as amino, or carboxylic acid, or
others, the appropriate functional groups on the cross-linking
agent will be different. For example, if the polymer has carboxylic
acid functional groups, suitable functional groups on the
cross-linking agent include hydroxyl groups (forming ester linkages
with the carboxylic acid groups on the polymer), amino groups
(forming amide linkages with the carboxylic acid groups on the
polymer), or tri-valent or tetra-valent metal ions (forming ionic
bonds with the carboxylic acid groups on the polymer).
[0045] One example of a commercially available cross-linking agent
is KYMENE.RTM. available from Hercules Incorporated located in
Wilmington, Del. KYMENE.RTM. contains functional groups which are
capable of reacting with hydroxyl groups on polyvinyl alcohol.
KYMENE.RTM. is widely used to cross-link cellulose fibers. However,
the chemical composition is proprietary.
[0046] When a latent cross-linking agent is used, in order to
initiate the cross-linking reaction, a posttreatment process is
required. Such post treatment processes include heat treatment,
microwave radiation, e-beam radiation, UV radiation, steam
treatment or vapor treatment.
[0047] According to another embodiment of this invention, the
absorbent composite includes a melt processable, water soluble
polymer which is meltblown with hydrophilic fibers and commercially
available superabsorbent material to form a coform material. The
polymer is cross-linked to form water-swellable but water insoluble
absorbent fibers.
[0048] Any of the previously described homopolymers or copolymers
with a molecular weight between about 10,000 to 1,000,000 can be
suitable for the melt processable, water soluble polymer for this
embodiment of the invention.
[0049] The superabsorbent material can be any commercially
available superabsorbent material, such as superabsorbent particles
or superabsorbent fibers. Examples of commercially available
particulate superabsorbents include SANWET.RTM. IM 3900 and
SANWET.RTM. IM-5000P, available from Hoescht Celanese located in
Portsmouth, Va., DRYTECH.RTM. 2035 available from Dow Chemical Co.
located in Midland, Mich., and FAVOR.RTM. SXM 880, SXM 9543,
available from Stockhausen, located in Greensboro, N.C. Any of the
previously described commercially available superabsorbent staple
fibers can be suitable superabsorbent fibers.
[0050] The hydrophilic fibers are preferably wood pulp fluff
commerically available from US Alliance Forest Products Corporation
in Coosa Pine, Ala., USA, under the trade designation Coosa CR
1654.
[0051] The resulting absorbent composite, which is a coform
material, as shown in FIGS. 2A-2C, includes the absorbent fibers 36
made in this instance from polyvinyl alcohol, hydrophilic fibers in
this instance wood pulp fluff 38, and superabsorbent material 39 in
this instance superabsorbent particles.
[0052] The invention also includes a method for making absorbent
fibers and an absorbent composite. Referring to FIG. 3, a hopper 50
contains pellets of a melt processable, water soluble polymer. A
single or twin screw extruder 52 melts the pellets by a
conventional heating arrangement to form a molten extrudable
composition which is extruded through a melt-blowing die 54 by the
action of a turning extruder screw (not shown) located within the
extruder 52. The extrudable composition is fed through the die 54.
The die 54 and the gas supply fed therethrough are heated by a
conventional arrangement (not shown). Besides the spinning die
diameter, the air velocity can also be adjusted to control fiber
diameter.
[0053] In order to produce a nonwoven material including only the
absorbent fibers of the invention, next, a solution containing the
cross-linking agent is sprayed onto the gas borne stream of fibers
56 by a sprayer represented by stream 60. The absorbent fibers are
then directed onto a forming wire 64 including a belt 66 and
rollers 68 by vacuum 67 to air form the nonwoven material which may
then be dried and treated by a post treatment process to initiate
the cross-linking reaction. Use of the vacuum box 67 underneath the
forming wire 64 can help the fibers form a uniform web onto the
forming wire 64. The post treatment may be heat treatment,
microwave treatment, e-beam radiation, UV radiation, steam
treatment or vapor treatment. The nonwoven material is then wound
and collected onto a winder 70.
[0054] In order to produce the absorbent composite of the
invention, which is a coform material, the gas borne stream of
fibers 56 is merged with a secondary gas stream 58 containing
individualized hydrophilic fibers, preferably wood pulp fibers, so
as to integrate the different fibrous materials in a single step. A
solution containing the cross-linking agent is sprayed onto the gas
borne stream of fibers 56 by a sprayer represented by stream 60.
The superabsorbent material may be added simultaneously with the
hydrophilic fibers and cross-linking agent via an additional gas
stream 62. The integrated air stream is then directed onto a
forming wire 64 including a belt 66 and rollers 68 by vacuum 67 to
air form the coform material. The air may be supplied by any
conventional means as, for example, a blower (not shown).
[0055] Any of the previously described melt processable polymers,
superabsorbent materials, hydrophilic fibers and cross-linking
agents can be used to make the absorbent fibers and/or absorbent
composites.
[0056] Following formation of the coform material, the coform
material is dried and then treated by a post treatment process in
order to initiate the cross-linking reaction. Such post treatment
is sometimes referred to as "curing." Such treatment may be any one
of heat treatment, microwave treatment, e-beam radiation, UV
radiation treatment, steam treatment or vapor treatment. The coform
material is then wound and collected onto a winder 70.
[0057] When heat treatment is used as the post treatment process
for the coform material, undesirable discoloration of the coform
material sometimes occurs. For example, when a coform material
including wood pulp fiber is heat cured at a temperature higher
than 140.degree. C. for more than 2 hours, the cured coform
material has a dark color ranging from yellow to brown because of
the oxidation of the wood pulp fiber. Such discoloration will also
occur when the meltblown fibers are made from polyvinyl
alcohol.
[0058] Effective ways to minimize or eliminate the discoloration
include, but are not limited to: (1) reducing the curing
temperature by using catalysts or a low temperature curable
cross-linking agent; (2) curing the coform material using a
different curing method, such as microwave radiation or e-beam
radiation; (3) using different types of melt processable polymers,
such as hydroxy propyl cellulose; (4) using a self-cross-linkable
polymer, such as silane grafted polyethylene oxide, which is
capable of cross-linking itself induced by moisture; and (5) using
an antioxidant.
[0059] During the preparation of the coform material, spraying
water during the fiber spinning and in the superabsorbent
material/wood pulp fluff/superabsorbent fiber mixing zone can help
to enhance inter-fiber or inter-superabsorbent particle bonding.
Therefore, the concentration of the cross-linking agent can play a
role in controlling the structure and integrity of absorbent
composites. If more water is needed, a more dilute solution of
cross-linking agent can be prepared, or vice versa. On the other
hand, the concentration of the cross-linking agent affects the
shell thickness of the surface of the cross-linked fiber with more
dilute concentrations resulting in a thicker cross-linked surface
shell layer.
TEST METHOD--ABSORBENCY UNDER ZERO LOAD
[0060] The Absorbency Under Zero Load (AUZL) is a test which
measures the ability of an absorbent material to absorb a liquid
(such as a 0.9 weight percent solution of sodium chloride in
distilled water) while under a negligible load or restraining
force. About 0.16 g of meltblown web or coform discs (about 1 inch
in diameter) of each sample were weighed and placed into a plastic
sample cup. The sample cup consists of a plastic cylinder having a
1 inch inside diameter and an outside diameter of 1.25 inches. The
bottom of the sample cup is formed by adhering a 100 mesh metal
screen having 150 micron openings to the end of the cylinder by
heating the screen above the melting point of the plastic and
pressing the plastic cylinder against the hot screen to melt the
plastic and bond the screen to the plastic cylinder. The sample is
then covered with a plastic spacer disc, weighing 4.4 grams, which
generated a pressure of about 0.01 pound per square inch. The
sample cup is placed in a Petri dish which contains about 25 ml of
0.9% by weight sodium chloride solution. After one hour, the cup
was taken out and placed on multiple layers of paper towels to blot
the interstitial fluid of the web or coform. The blotting is
continued by moving the cup to the area with dry paper towel until
there is no fluid mark visible on the paper towel. The weight
difference of the cup between wet and dry presents total amount of
fluid absorbed by the web or coform and is used to calculate
AUZL.
EXAMPLES
Example 1
[0061] Water soluble polyvinyl alcohol Ecomaty.RTM. AX-10000,
available from Nippon Gohsei, Osaka, Japan, was melt blown into
continuous filaments through a Killion line (2" die tip, 0.35 mm
die, 20 holes/in, other parameters listed in Table 1). Air pressure
was in a range from 4 to 8 psi. Air temperature was controlled to
as close to the die temperature as possible (412.degree. F. in this
case) so that no effect of cooling off or heating up on die tip
occurred. Vacuum was about 8 inch water. The filament was collected
on a moving conveyor belt having a foraminous surface to form a
melt blown nonwoven. The nonwoven was still water soluble and
dipped into a solution of 86.5% methanol, 12.3% water, and 1.2%
ethylene glycol diglycidyl ether at a weight ratio of 1 g of fiber
to 30 g of solution. The nonwoven was then removed out of the
solution and blotted by paper towel. The wet nonwoven was dried at
80.degree. C. and then cured at 130.degree. C. for 20 hours. The
cured nonwoven was water-swellable but water-insoluble and
exhibited an Absorbency Under Zero Load (AUZL) value in 0.9% NaCl
saline of about 7.5 g/g.
1TABLE 1 Heat 1 Barrel Die Extruder Temp. Heat 2 Temp. Heat 3 Temp.
Die Temp. Pressure Pressure Screw (.degree. F.) (.degree. F.)
(.degree. F.) (.degree. F.) (psi) (psi) Speed (rpm) 269 304 410 412
1020 340 11 Note: Heat 1, Heat 2 and Heat 3 indicate the
temperatures of each of 3 zones in the extruder.
Example 2
[0062] Several solutions including different cross-linking agents
were prepared as described in Table 2. The polyvinyl alcohol
nonwoven prepared in Example 1 was treated separately by the
solution and heat cured at different temperatures for certain
times. The cured nonwovens were subjected to the AUZL test in
saline. Both the AUZL value and the color of the cured nonwoven
were recorded in Table 2 below:
2TABLE 2 Ratio of Curing Recipe # Composition Fiber/solution
T(.degree. C.)/time(hr) Discoloration AUZL (g/g) 1 98% methanol, 2%
1/50 130/15 Golden 5.5 Kymene (557LX) 2 84.5% methanol, 14% 1/25
110/70 Light Golden 6.0 water, 1.5% citric acid 3 88% methanol,
11.5% 1/15 140/20 Yellow 7.1 water, 0.5% glutaric dialdehyde 4 85%
methanol, 12.5% 1/30 130/24 White 8.2 water, 2.5% ethylene glycol
diglycidyl ether
Example 3
[0063] Polyvinyl alcohol was melt blown into continuous filaments
using the Killion line. Solutions including 1.25%, 2.5% or 5%
citric acid or KYMENE.RTM. were separately sprayed onto the surface
of the fibers at a location near the die tip. A coform material
with wood pulp fluff CR 1654 at a ratio of 50% polyvinyl alcohol
and 50% wood pulp fluff was also prepared. The polyvinyl alcohol
fiber spinning throughput was about 30 grams per minute (gpm), and
the solution spraying throughput was about 10 gpm. Process
conditions are listed in Table 3. Air pressure was in a range from
4 to 8 psi. Air temperature was controlled to as close to the die
temperature as possible so that no effect of cooling off or heating
up on die tip occurred. Vacuum was about 8 inch water. The
nonwovens obtained were heated in a 130.degree. C. oven for up to 4
days. The cured nonwovens were completely cross-linked and become
water insoluble. Again discoloration was found in all the cured
nonwovens. AUZL values of the treated nonwovens were around 7 to 8
g/g.
3TABLE 3 Extruder Spin Pump Die Cross-linker Heater 1 Heater 2
Heater 3 Die Screw Speed Speed Pressure Solution (.degree. F.)
(.degree. F.) (.degree. F.) (.degree. F.) (rpm) (rpm) (psi) 1.25%
citric 306 361 440 440 25 20 396 acid 2.5% citric 306 341 440 442
24 20 382 acid 5.0% citric 303 342 440 438 28 20 390 acid 1.25% 306
360 440 439 21 20 402 Kymene 2.5% 305 360 440 440 21 19.7 408
Kymene 5.0% 305 360 440 440 22 20 394 Kymene Note: Heat 1, Heat 2
and Heat 3 indicate the temperatures of each of 3 zones in the
extruder.
Example 4
[0064] The uncured nonwovens surface sprayed by either 5% citric
acid or KYMENE.RTM. solution and prepared from Example 3 were
treated in a microwave oven (GE Model JE125OGW, 1.5 kW, Vac/Hz
120/60) at an intensity level of 1 (lowest of the machine) for at
least 10 hours. The intensity level of the microwave oven could not
be greater than 1, otherwise the nonwoven fibers would be molten
due to too high temperature reached locally. The microwave treated
nonwovens were completely white (no discoloration) and
water-swellable, water-insoluble.
Example 5
[0065] Polyvinyl alcohol was melt blown into continuous filaments
using the Killion line. A solution including 5% KYMENE.RTM. and
0.5% surfactant Rhodamox LO, available from Rhone-Poulenc Inc., was
sprayed onto the surface of fibers at a location near the die tip.
A coform material with both commercial superabsorbent particles
FAVOR.RTM. SXM 880 and wood pulp fluff CR 1654 at a ratio of 48%
superabsorbent particles, 26% polyvinyl alcohol and 26% wood pulp
fluff was also prepared. Process parameters are listed in Table 4.
Air pressure, temperature and vacuum were the same as specified in
the examples before. The basis weight of the coform material was
484 gsm. A solution including 5% KYMENE.RTM. and 0.5% surfactant
Rhodamox LO was sprayed onto the surface of the coform material at
a location near the tie tip. The coform material was heat cured at
150 .degree. C. for 3 hours. Surprisingly, the cured coform
material had almost no discoloration probably due to the presence
of Rhodamox LO surfactant. The coform material exhibited an AUZL
value in 0.9% NaCl saline as high as 23 g/g.
4TABLE 4 Extruder Heater 1 Heater 2 Heater 3 Die Die Pressure Screw
Speed Spin Pump (.degree. F.) (.degree. F.) (.degree. F.) (.degree.
F.) (psi) (rpm) Speed (rpm) 321 401 440 443 900 27 20 Note: Heat 1,
Heat 2 and Heat 3 indicate the temperatures of each of 3 zones in
the extruder.
[0066] While the embodiments of the invention described herein are
presently preferred, various modifications and improvements can be
made without departing from the spirit and scope of the invention.
The scope of the invention is indicated by the appended claims, and
all changes that fall within the meaning and range of equivalents
are intended to be embraced therein.
* * * * *