U.S. patent application number 12/975973 was filed with the patent office on 2011-06-23 for absorbent article comprising a synthetic polymer derived from a renewable resource and methods of producing said article.
Invention is credited to Eric Ted Addington, Bryn Hird.
Application Number | 20110152812 12/975973 |
Document ID | / |
Family ID | 38421562 |
Filed Date | 2011-06-23 |
United States Patent
Application |
20110152812 |
Kind Code |
A1 |
Hird; Bryn ; et al. |
June 23, 2011 |
Absorbent Article Comprising A Synthetic Polymer Derived From A
Renewable Resource And Methods Of Producing Said Article
Abstract
An absorbent article is disclosed having a topsheet, a backsheet
joined with the topsheet, an absorbent core disposed between the
topsheet and the backsheet, and a synthetic superabsorbent polymer
derived from a first renewable resource via at least one
intermediate compound, wherein said superabsorbent polymer exhibits
a defined Saline Flow Conductivity value and Absorption Against
Pressure value. Alternately, an absorbent article is disclosed
having a synthetic polyolefin derived from a first renewable
resource via at least one intermediate compound. The synthetic
polyolefin exhibits defined performance characteristics making the
polyolefin particularly useful in certain components of the
absorbent article. Methods for making the aforementioned absorbent
articles are also disclosed.
Inventors: |
Hird; Bryn; (Cincinnati,
OH) ; Addington; Eric Ted; (West Chester,
OH) |
Family ID: |
38421562 |
Appl. No.: |
12/975973 |
Filed: |
December 22, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11724341 |
Mar 15, 2007 |
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12975973 |
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60783274 |
Mar 17, 2006 |
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Current U.S.
Class: |
604/372 ;
206/494; 604/385.02 |
Current CPC
Class: |
A61F 13/15203 20130101;
A61L 15/60 20130101; A61F 13/84 20130101; C12P 2203/00 20130101;
A61L 15/24 20130101; A61F 13/15617 20130101; E03D 1/35 20130101;
A61F 13/551 20130101; A61L 15/40 20130101; C12P 7/42 20130101; A61L
15/28 20130101 |
Class at
Publication: |
604/372 ;
604/385.02; 206/494 |
International
Class: |
A61L 15/22 20060101
A61L015/22; A61F 13/84 20060101 A61F013/84 |
Claims
1-20. (canceled)
21. A backsheet film of an absorbent article, the backsheet film is
at least partially formed from a polymer and exhibits a .sup.14C/C
ratio of about 1.0.times.10.sup.-14 or greater, wherein the polymer
is at least partially derived from a renewable resource via at
least one intermediate compound, the polymer is synthetic, the
intermediate compound is monomeric, the polymer is a polyolefin,
the backsheet film is breathable and exhibits a Moisture Vapor
Transmission Rate from about 2000 g/m.sup.2/hr to about 3000
g/m.sup.2/hr and an MD tensile strength from about 0.5 N/cm to
about 6 N/cm.
22. The backsheet film of claim 21 having a thickness of about 0.5
mil to about 2.0 mils.
23. The backsheet film of claim 21 exhibits a .sup.14C/C ratio of
about 1.0.times.10.sup.-13 or greater.
24. The backsheet film of claim 23 exhibits a .sup.14C/C ratio of
about 1.0.times.10.sup.-12 or greater.
25. An absorbent article comprising the backsheet film of claim
21.
26. A package comprising one or more absorbent articles according
to claim 25, wherein the package comprises a communication of a
related environmental message to a consumer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/724,341, "Absorbent Article Comprising A
Synthetic Polymer Derived From A Renewable Resource And Method Of
Producing Said Article," filed Mar. 15, 2007, which claims the
benefit of U.S. Provisional Patent Application Ser. No. 60/783,274,
"Absorbent Article Comprising A Synthetic Polymer Derived From A
Renewable Resource And Method Of Producing Said Article," filed
Mar. 17, 2006, the substance of which is incorporated herein by
reference for the entire disclosures of both of these prior
applications.
FIELD OF INVENTION
[0002] The present invention relates to an absorbent article which
comprises synthetic polymeric materials derived from renewable
resources, where the materials have specific performance
characteristics making them particularly useful in said absorbent
article.
BACKGROUND OF THE INVENTION
[0003] The development of absorbent articles such as disposable
diapers, adult incontinence pads and briefs, and catamenial
products such as sanitary napkins, is the subject of substantial
commercial interest. There is a great deal of art relating to the
design of absorbent articles, the processes for manufacturing such
articles, and the materials used in their construction. In
particular, a great deal of effort has been spent in the
development of materials exhibiting optimal performance
characteristics for use in absorbent articles. Such materials
include films, fibers, nonwovens, laminates, superabsorbent
polymers, foams, elastomers, adhesives, and the like.
[0004] Most of the materials used in current commercial absorbent
articles are derived from non-renewable resources, especially
petroleum. Typically, components such as the topsheet, backsheet,
and cuffs are made from polyolefins such as polyethylene and
polypropylene. These polymers are derived from olefinic monomers
such as ethylene and propylene which are obtained directly from
petroleum via cracking and refining processes. Propylene derived
from petroleum is also used to make acrylic acid via a catalytic
oxidation process. Acrylic acid derived from petroleum is the major
feedstock used in the manufacture of modern superabsorbent polymers
utilized in absorbent cores of current commercial absorbent
articles.
[0005] Thus, the price and availability of the petroleum feedstock
ultimately has a significant impact on the price of absorbent
articles which utilize materials derived from petroleum. As the
worldwide price of petroleum escalates, so does the price of
absorbent articles.
[0006] Furthermore, many consumers display an aversion to
purchasing products that are derived from petrochemicals. In some
instances, consumers are hesitant to purchase products made from
limited non-renewable resources such as petroleum and coal. Other
consumers may have adverse perceptions about products derived from
petrochemicals being "unnatural" or not environmentally
friendly.
[0007] Certain alternative materials which are derived from
non-petrochemical or renewable resources have been disclosed for
use in absorbent articles. For example, U.S. Pat. No. 5,889,072 to
Chao describes a process for preparing a cross-linked polyaspartate
superabsorbent material. U.S. Pat. Nos. 6,713,460 and 6,444,653,
both to Huppe et al., describe a superabsorbent material comprising
glass-like polysaccharides. Furthermore, diapers having varying
degrees of biodegradability have been disclosed. U.S. Pat. No.
5,783,504 to Ehret et al. describes a composite structure, which is
suitable for use in diapers, comprising a nonwoven manufactured
from a polymer derived from lactic acid and a film manufactured
from a biodegradable aliphatic polyester polymer. PCT application
WO 99/33420 discloses a superabsorbent material comprising a
renewable and/or biodegradable raw material. However, these diapers
and materials tend to have significantly lower performance and/or
higher cost than materials derived from petrochemicals. For
example, the superabsorbent materials disclosed in WO 99/33420 show
a low absorption capacity under load and a low gel strength. A
superabsorbent material with low gel strength tends to deform upon
swelling and reduce interstitial spaces between the superabsorbent
particles. This phenomenon is known as gel-blocking. Once
gel-blocking occurs, further liquid uptake or distribution takes
place via a very slow diffusion process. In practical terms,
gel-blocking increases the susceptibility of the absorbent article
to leakage.
[0008] Accordingly, it would be desirable to provide an absorbent
article which comprises a polymer derived from renewable resources,
where the polymer has specific performance characteristics making
the polymer particularly useful in the absorbent article. Ideally,
it would be desirable to provide a consumer product including a
plurality of absorbent articles comprising said polymer derived
from renewable resources and a communication of a related
environmental message.
SUMMARY OF THE INVENTION
[0009] In accordance with one embodiment, a backsheet film of an
absorbent article is at least partially formed from a polymer and
exhibits a .sup.14C/C ratio of about 1.0.times.10.sup.-14 or
greater. The polymer is at least partially derived from a renewable
resource via at least one intermediate compound. The polymer is
synthetic. The intermediate compound is monomeric. The polymer is a
polyolefin. The backsheet film is breathable and exhibits a
Moisture Vapor Transmission Rate from about 2000 g/m.sup.2/hr to
about 3000 g/m.sup.2/hr and an MD tensile strength from about 0.5
N/cm to about 6 N/cm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is a plan view of an exemplary absorbent article in
the form of a diaper in a flat, uncontracted state.
[0011] FIG. 1B is a cross-sectional view of the diaper of FIG. 1A
taken along the lateral centerline.
[0012] FIGS. 2A-B are perspective views of a package comprising an
absorbent article.
[0013] FIGS. 3A-F are illustrations of several suitable embodiments
of icons communicating reduced petrochemical dependence and/or
environmental friendliness.
[0014] FIG. 4 is a partial cross-sectional side view of a suitable
permeability measurement system for conducting the Saline Flow
Conductivity Test.
[0015] FIG. 5 is a cross-sectional side view of a piston/cylinder
assembly for use in conducting the Saline Flow Conductivity
Test.
[0016] FIG. 6 is a top view of a piston head suitable for use in
the piston/cylinder assembly shown in FIG. 5.
[0017] FIG. 7 is a cross-sectional side view of the piston/cylinder
assembly of FIG. 5 placed on a fritted disc for the swelling
phase.
[0018] FIG. 8 is a plan view of a diaper as an embodiment of an
absorbent article.
[0019] FIG. 9 is a cross-sectional view of the diaper shown in FIG.
8 taken along the sectional line 9-9 of FIG. 8.
[0020] FIG. 10 is a cross-sectional view of a certain embodiment of
the absorbent core.
[0021] FIG. 11 is a cross-sectional view of a certain embodiment of
the absorbent core.
[0022] FIG. 12 is a perspective view of a certain embodiment of the
absorbent core.
[0023] FIG. 13 is a cross-sectional view of a certain embodiment of
the absorbent core.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The present invention relates to an absorbent article
comprising a synthetic polymer derived from a renewable resource
where the polymer has specific performance characteristics. When
the synthetic polymer derived from a renewable resource is in the
form of a superabsorbent polymer, it exhibits an Absorption Against
Pressure (AAP) value of at least about 15.0 g saline per gram
polymer and/or a saline flow conductivity (SFC) of at least about
30.times.10.sup.-7 cm.sup.3sec/g. When the polymer is a polyolefin
nonwoven suitable for use as a topsheet, it may exhibit a Liquid
Strike Through value of less than about 4 seconds. When the polymer
is a polyolefin nonwoven suitable for use as a barrier leg cuff, it
may exhibit a hydrohead of at least about 5 mbar. When the polymer
is a breathable polyolefin film suitable for use as a backsheet, it
may exhibit a Moisture Vapor Transmission Rate of at least about
2000 g/m.sup.2/24 hr. When the polymer is a polyolefin film
suitable for use as a backsheet, it may have an MD tensile strength
of at least about 0.5 N/cm.
[0025] In another aspect, the absorbent article comprises a
synthetic polymer derived from a renewable resource wherein the
polymer has a .sup.14C/C ratio of about 1.0.times.10.sup.-14 or
greater The present invention further relates to a package
comprising at least one absorbent article comprising a synthetic
polymer derived from a renewable resource and an overwrap securing
the absorbent article(s). The absorbent article comprises a
synthetic polymer derived from a renewable resource. The package
may further comprise a communication of a related environmental
message.
[0026] The present invention further relates to a method for making
absorbent articles comprising a synthetic polymer derived from a
renewable resource. The method comprises the following steps:
providing a renewable resource; deriving at least one intermediate
compound from the renewable resource, wherein the intermediate
compound comprises a monomeric compound; polymerizing the monomeric
compound to form at least one polymer, wherein the at least one
polymer exhibits the requisite performance for use in an absorbent
article; and incorporating the at least one polymer into an
absorbent article. Additional steps, as described herein, may be
incorporated into the method. Optionally the at least one polymer
may be modified after the polymerization step.
I. DEFINITIONS
[0027] As used herein, the following terms shall have the meaning
specified thereafter:
[0028] "Disposable" refers to items that are intended to be
discarded after a limited number of uses, frequently a single use
(i.e., the original absorbent article as a whole is not intended to
be laundered or reused as an absorbent article, although certain
materials or portions of the absorbent article may be recycled,
reused, or composted). For example, certain disposable absorbent
articles may be temporarily restored to substantially full
functionality through the use of removable/replaceable components
but the article is nevertheless considered to be disposable because
the entire article is intended to be discarded after a limited
number of uses.
[0029] "Absorbent article" refers to devices which absorb and
contain body exudates and, more specifically, refers to devices
which are placed against or in proximity to the body of the wearer
to absorb and contain the various exudates discharged from the
body.
[0030] Exemplary absorbent articles include diapers, training
pants, pull-on pant-type diapers (i.e., a diaper having a
pre-formed waist opening and leg openings such as illustrated in
U.S. Pat. No. 6,120,487), refastenable diapers or pant-type
diapers, incontinence briefs and undergarments, diaper holders and
liners, feminine hygiene garments such as panty liners (e.g. such
as disclosed in U.S. Pat. Nos. 4,425,130; 4,687,478; 5,267,992; and
5,733,274), absorbent inserts, and the like. Absorbent articles may
be disposable or may contain portions that can be reused or
restored.
[0031] "Proximal" and "Distal" refer, respectively, to the location
of an element relatively near to or far from the longitudinal or
lateral centerline of a structure (e.g., the proximal edge of a
longitudinally extending element is located nearer to the
longitudinal centerline than the distal edge of the same element is
located relative to the same longitudinal centerline).
[0032] "Body-facing" and "garment-facing" refer respectively to the
relative location of an element or a surface of an element or group
of elements. "Body-facing" implies the element or surface is nearer
to the wearer during wear than some other element or surface.
"Garment-facing" implies the element or surface is more remote from
the wearer during wear than some other element or surface (i.e.,
element or surface is proximate to the wearer's garments that may
be worn over the absorbent article).
[0033] "Superabsorbent" refers to a material capable of absorbing
at least ten times its dry weight of a 0.9% saline solution at
25.degree. C. Superabsorbent polymers absorb fluid via an osmotic
mechanism to form a gel, often referred to as, and used
interchangeably with the term "hydrogel".
[0034] "Longitudinal" refers to a direction running substantially
perpendicular from a waist edge to an opposing waist edge of the
article and generally parallel to the maximum linear dimension of
the article. Directions within 45 degrees of the longitudinal
direction are considered to be "longitudinal"
[0035] "Lateral" refers to a direction running from a longitudinal
edge to an opposing longitudinal edge of the article and generally
at a right angle to the longitudinal direction. Directions within
45 degrees of the lateral direction are considered to be
"lateral."
[0036] "Disposed" refers to an element being located in a
particular place or position.
[0037] "Joined" refers to configurations whereby an element is
directly secured to another element by affixing the element
directly to the other element and to configurations whereby an
element is indirectly secured to another element by affixing the
element to intermediate member(s) which in turn are affixed to the
other element.
[0038] "Film" refers to a sheet-like material wherein the length
and width of the material far exceed the thickness of the material.
Typically, films have a thickness of about 0.5 mm or less.
[0039] "Impermeable" generally refers to articles and/or elements
that are not penetrative by fluid through the entire Z-directional
thickness of the article under pressure of 0.14 lb/in.sup.2 or
less. Preferably, the impermeable article or element is not
penetrative by fluid under pressures of 0.5 lb/in.sup.2 or less.
More preferably, the impermeable article or element is not
penetrative by fluid under pressures of 1.0 lb/in.sup.2 or less.
The test method for determining impermeability conforms to Edana
120.1-18 or INDA IST 80.6.
[0040] "Extendibility" and "extensible" mean that the width or
length of the component in a relaxed state can be extended or
increased by at least about 10% without breaking or rupturing when
subjected to a tensile force.
[0041] "Elastic," "elastomer," and "elastomeric" refer to a
material which generally is able to extend to a strain of at least
50% without breaking or rupturing, and is able to recover
substantially to its original dimensions after the deforming force
has been removed.
[0042] "Elastomeric material" is a material exhibiting elastic
properties. Elastomeric materials may include elastomeric films,
scrims, nonwovens, and other sheet-like structures.
[0043] "Outboard" and "inboard" refer respectively to the location
of an element disposed relatively far from or near to the
longitudinal centerline of the diaper with respect to a second
element. For example, if element A is outboard of element B, then
element A is farther from the longitudinal centerline than is
element B.
[0044] "Pant" refers to an absorbent article having a pre-formed
waist and leg openings. A pant may be donned by inserting a
wearer's legs into the leg openings and sliding the pant into
position about the wearer's lower torso. Pants are also commonly
referred to as "closed diapers", "prefastened diapers", "pull-on
diapers", "training pants" and "diaper-pants."
[0045] "Petrochemical" refers to an organic compound derived from
petroleum, natural gas, or coal.
[0046] "Petroleum" refers to crude oil and its components of
paraffinic, cycloparaffinic, and aromatic hydrocarbons. Crude oil
may be obtained from tar sands, bitumen fields, and oil shale.
[0047] "Renewable resource" refers to a natural resource that can
be replenished within a 100 year time frame. The resource may be
replenished naturally, or via agricultural techniques. Renewable
resources include plants, animals, fish, bacteria, fungi, and
forestry products. They may be naturally occurring, hybrids, or
genetically engineered organisms. Natural resources such as crude
oil, coal, and peat which take longer than 100 years to form are
not considered to be renewable resources
[0048] "Agricultural product" refers to a renewable resource
resulting from the cultivation of land (e.g. a crop) or the
husbandry of animals (including fish).
[0049] "Monomeric compound" refers to an intermediate compound that
may be polymerized to yield a polymer.
[0050] "Polymer" refers to a macromolecule comprising repeat units
where the macromolecule has a molecular weight of at least 1000
Daltons. The polymer may be a homopolymer, copolymer, terpoymer
etc. The polymer may be produced via fee-radical, condensation,
anionic, cationic, Ziegler-Natta, metallocene, or ring-opening
mechanisms. The polymer may be linear, branched and/or
crosslinked.
[0051] "Synthetic polymer" refers to a polymer which is produced
from at least one monomer by a chemical process. A synthetic
polymer is not produced directly by a living organism.
[0052] "Polyethylene" and "polypropylene" refer to polymers
prepared from ethylene and propylene, respectively. The polymer may
be a homopolymer, or may contain up to about 10 mol % of repeat
units from a co-monomer.
[0053] "Communication" refers to a medium or means by which
information, teachings, or messages are transmitted.
[0054] "Related environmental message" refers to a message that
conveys the benefits or advantages of the absorbent article
comprising a polymer derived from a renewable resource. Such
benefits include being more environmentally friendly, having
reduced petroleum dependence, being derived from renewable
resources, and the like.
[0055] All percentages herein are by weight unless specified
otherwise.
II. Polymers Derived from Renewable Resources
[0056] A number of renewable resources contain polymers that are
suitable for use in an absorbent article (i.e., the polymer is
obtained from the renewable resource without intermediates).
Suitable extraction and/or purification steps may be necessary, but
no intermediate compound is required. Such polymers derived
directly from renewable resources include cellulose (e.g. pulp
fibers), starch, chitin, polypeptides, poly(lactic acid),
polyhydroxyalkanoates, and the like. These polymers may be
subsequently chemically modified to improve end use characteristics
(e.g., conversion of cellulose to yield carboxycellulose or
conversion of chitin to yield chitosan). However, in such cases,
the resulting polymer is a structural analog of the starting
polymer. Polymers derived directly from renewable resources (i.e.,
with no intermediate compounds) and their derivatives are known and
these materials are not within the scope of the present
invention.
[0057] The synthetic polymers of the present invention are derived
from a renewable resource via an indirect route involving one or
more intermediate compounds. Suitable intermediate compounds
derived from renewable resources include sugars. Suitable sugars
include monosaccharides, disaccharides, trisaccharides, and
oligosaccharides. Sugars such as sucrose, glucose, fructose,
maltose may be readily produced from renewable resources such as
sugar cane and sugar beets. Sugars may also be derived (e.g., via
enzymatic cleavage) from other agricultural products such as starch
or cellulose. For example, glucose may be prepared on a commercial
scale by enzymatic hydrolysis of corn starch. While corn is a
renewable resource in North America, other common agricultural
crops may be used as the base starch for conversion into glucose.
Wheat, buckwheat, arracaha, potato, barley, kudzu, cassava,
sorghum, sweet potato, yam, arrowroot, sago, and other like starchy
fruit, seeds, or tubers are may also be used in the preparation of
glucose.
[0058] Other suitable intermediate compounds derived from renewable
resources include monofunctional alcohols such as methanol or
ethanol and polyfunctional alcohols such as glycerol. Ethanol may
be derived from many of the same renewable resources as glucose.
For example, cornstarch may be enzymatically hydrolysized to yield
glucose and/or other sugars. The resultant sugars can be converted
into ethanol by fermentation. As with glucose production, corn is
an ideal renewable resource in North America; however, other crops
may be substituted. Methanol may be produced from fermentation of
biomass. Glycerol is commonly derived via hydrolysis of
triglycerides present in natural fats or oils, which may be
obtained from renewable resources such as animals or plants.
[0059] Other intermediate compounds derived from renewable
resources include organic acids (e.g., citric acid, lactic acid,
alginic acid, amino acids etc.), aldehydes (e.g., acetaldehyde),
and esters (e.g., cetyl palmitate, methyl stearate, methyl oleate,
etc.).
[0060] Additional intermediate compounds such as methane and carbon
monoxide may also be derived from renewable resources by
fermentation and/or oxidation processes.
[0061] Intermediate compounds derived from renewable resources may
be converted into polymers (e.g., glycerol to polyglycerol) or they
may be converted into other intermediate compounds in a reaction
pathway which ultimately leads to a polymer useful in an absorbent
article. An intermediate compound may be capable of producing more
than one secondary intermediate compound. Similarly, a specific
intermediate compound may be derived from a number of different
precursors, depending upon the reaction pathways utilized.
[0062] Particularly desirable intermediates include (meth)acrylic
acids and their esters and salts; and olefins. In particular
embodiments, the intermediate compound may be acrylic acid,
ethylene, or propylene.
[0063] For example, acrylic acid is a monomeric compound that may
be derived from renewable resources via a number of suitable
routes. Examples of such routes are provided below.
[0064] Glycerol derived from a renewable resource (e.g., via
hydrolysis of soybean oil and other triglyceride oils) may be
converted into acrylic acid according to a two-step process. In a
first step, the glycerol may be dehydrated to yield acrolein. A
particularly suitable conversion process involves subjecting
glycerol in a gaseous state to an acidic solid catalyst such as
H.sub.3PO.sub.4 on an aluminum oxide carrier (which is often
referred to as solid phosphoric acid) to yield acrolien. Specifics
relating to dehydration of glycerol to yield acrolein are
disclosed, for instance, in U.S. Pat. Nos. 2,042,224 and 5,387,720.
In a second step, the acrolein is oxidized to form acrylic acid. A
particularly suitable process involves a gas phase interaction of
acrolein and oxygen in the presence of a metal oxide catalyst. A
molybdenum and vanadium oxide catalyst may be used. Specifics
relating to oxidation of acrolein to yield acrylic acid are
disclosed, for instance, in U.S. Pat. No. 4,092,354.
[0065] Glucose derived from a renewable resource (e.g., via
enzmatic hydrolysis of corn starch) may be converted into acrylic
acid via a two step process with lactic acid as an intermediate
product. In the first step, glucose may be biofermented to yield
lactic acid. Any suitable microorganism capable of fermenting
glucose to yield lactic acid may be used including members from the
genus Lactobacillus such as Lactobacillus lactis as well as those
identified in U.S. Pat. Nos. 5,464,760 and 5,252,473. In the second
step, the lactic acid may be dehydrated to produce acrylic acid by
use of an acidic dehydration catalyst such as an inert metal oxide
carrier which has been impregnated with a phosphate salt. This
acidic dehydration catalyzed method is described in further detail
in U.S. Pat. No. 4,729,978. In an alternate suitable second step,
the lactic acid may be converted to acrylic acid by reaction with a
catalyst comprising solid aluminum phosphate. This catalyzed
dehydration method is described in further detail in U.S. Pat. No.
4,786,756.
[0066] Another suitable reaction pathway for converting glucose
into acrylic acid involves a two step process with
3-hydroxypropionic acid as an intermediate compound. In the first
step, glucose may be biofermented to yield 3-hydroxypropionic acid.
Microorganisms capable of fermenting glucose to yield
3-hydroxypropionic acid have been genetically engineered to express
the requisite enzymes for the conversion. For example, a
recombinant microorganism expressing the dhaB gene from Klebsiella
pneumoniae and the gene for an aldehyde dehydrogenase has been
shown to be capable of converting glucose to 3-hydroxypropionic
acid. Specifics regarding the production of the recombinant
organism may be found in U.S. Pat. No. 6,852,517. In the second
step, the 3-hydroxypropionic acid may be dehydrated to produce
acrylic acid.
[0067] Glucose derived from a renewable resource (e.g., via
enzymatic hydrolysis of corn starch obtained from the renewable
resource of corn) may be converted into acrylic acid by a multistep
reaction pathway. Glucose may be fermented to yield ethanol.
Ethanol may be dehydrated to yield ethylene. At this point,
ethylene may be polymerized to form polyethylene. However, ethylene
may be converted into propionaldehyde by hydroformylation of
ethylene using carbon monoxide and hydrogen in the presence of a
catalyst such as cobalt octacarbonyl or a rhodium complex.
Propan-1-ol may be formed by catalytic hydrogenation of
propionaldehyde in the presence of a catalyst such as sodium
borohydride and lithium aluminum hydride. Propan-1-ol may be
dehydrated in an acid catalyzed reaction to yield propylene. At
this point, propylene may be polymerized to form polypropylene.
However, propylene may be converted into acrolein by catalytic
vapor phase oxidation. Acrolein may then be catalytically oxidized
to form acrylic acid in the presence of a molybdenum-vanadium
catalyst.
[0068] While the above reaction pathways yield acrylic acid, a
skilled artisan will appreciate that acrylic acid may be readily
converted into an ester (e.g., methyl acrylate, ethyl acrylate,
etc.) or salt.
[0069] Olefins such as ethylene and propylene may also be derived
from renewable resources. For example, methanol derived from
fermentation of biomass may be converted to ethylene and or
propylene, which are both suitable monomeric compounds, as
described in U.S. Pat. Nos. 4,296,266 and 4,083,889. Ethanol
derived from fermentation of a renewable resource may be converted
into monomeric compound of ethylene via dehydration as described in
U.S. Pat. No. 4,423,270. Similarly, propanol or isopropanol derived
from a renewable resource can be dehydrated to yield the monomeric
compound of propylene as exemplified in U.S. Pat. No. 5,475,183.
Propanol is a major constituent of fusel oil, a by-product formed
from certain amino acids when potatoes or grains are fermented to
produce ethanol.
[0070] Charcoal derived from biomass can be used to create syngas
(i.e., CO+H.sub.2) from which hydrocarbons such as ethane and
propane can be prepared (Fischer-Tropsch Process). Ethane and
propane can be dehydrogenated to yield the monomeric compounds of
ethylene and propylene.
III. Exemplary Synthetic Polymers
[0071] A. Superabsorbent Polymers--Certain compounds derived from
renewable resources may be polymerized to yield suitable synthetic
superabsorbent polymers. For example, acrylic acid derived from
soybean oil via the glycerol/acrolein route described above may be
polymerized under the appropriate conditions to yield a
superabsorbent polymer comprising poly(acrylic acid). The absorbent
polymers useful in the present invention can be formed by any
polymerization and/or crosslinking techniques capable of achieving
the desired properties. Typical methods for producing these
polymers are described in Reissue U.S. Pat. No. 32,649 to Brandt et
al.; U.S. Pat. Nos. 4,666,983, 4,625,001, 5,408,019; and published
German patent application 4,020,780 to Dahmen. The processing
(i.e., drying, milling, sieving, etc.) of the resulting
superabsorbent polymer to yield a usable form is well known in the
art.
[0072] The polymer may be prepared in the neutralized, partially
neutralized, or un-neutralized form. In certain embodiments, the
absorbent polymer may be formed from acrylic acid that is from
about 50 mole % to about 95 mole % neutralized. The absorbent
polymer may be prepared using a homogeneous solution polymerization
process, or by multi-phase polymerization techniques such as
inverse emulsion or suspension polymerization procedures. The
polymerization reaction will generally occur in the presence of a
relatively small amount of di- or poly-functional monomers such as
N,N'-methylene bisacrylamide, trimethylolpropane triacrylate,
ethylene glycol di(meth)acrylate, triallylamine, and methacrylate
analogs of the aforementioned acrylates. The di- or poly-functional
monomer compounds serve to lightly cross-link the polymer chains
thereby rendering them water-insoluble, yet water-swellable.
[0073] In certain embodiments, the synthetic superabsorbent polymer
comprising acrylic acid derived from renewable resources may be
formed from starch-acrylic acid graft copolymers, partially
neutralized starch-acrylic acid graft copolymers, crosslinked
polymers of polyacrylic acid, and crosslinked polymers of partially
neutralized polyacrylic acid. Preparation of these materials is
disclosed in U.S. Pat. Nos. 3,661,875; 4,076,663; 4,093,776;
4,666,983; and 4,734,478.
[0074] The synthetic superabsorbent polymers particles can be
surface-crosslinked after polymerization by reaction with a
suitable reactive crosslinking agents. Surface-crosslinking of the
initially formed superabsorbent polymers particles derived from
renewable resources provides superabsorbent polymers having
relatively high absorbent capacity and relatively high permeabity
to fluid in the swollen state, as described below. A number of
processes for introducing surface crosslinks are disclosed in the
art. Suitable methods for surface crosslinking are disclosed in
U.S. Pat. Nos. 4,541,871, 4,824,901, 4,789,861, 4,587,308,
4,734,478, and 5,164,459; published PCT applications WO92/16565,
WO90/08789, and WO93/05080; published German patent application
4,020,780 to Dahmen; and published European patent application
509,708 to Gartner. Suitable crosslinking agents include di- or
poly-functional crosslinking reagents such as di/poly-haloalkanes,
di/poly-epoxides, di/poly-acid chlorides, di/poly-tosyl alkanes,
di/poly-aldehydes, di/poly-alcohols, and the like.
[0075] An important characteristic of the synthetic superabsorbent
polymers of the present invention is the permeability or flow
conductivity of a zone or layer of the polymer particles when
swollen with body fluids. This permeability or flow conductivity is
defined herein in terms of the Saline Flow Conductivity (SFC) value
of the superabsorbent polymer. SFC measures the ability of the
swollen hydrogel zone or layer to transport or distribute body
fluids under usage pressures. It is believed that when a
superabsorbent polymer is present at high concentrations in an
absorbent member and then swells to form a hydrogel under usage
pressures, the boundaries of the hydrogel come into contact, and
interstitial voids in this high-concentration region become
generally bounded by hydrogel. When this occurs, it is believed the
permeability or flow conductivity properties of this region are
generally reflective of the permeability or flow conductivity
properties of a hydrogel zone or layer formed from the
superabsorbent polymer alone. It is further believed that
increasing the permeability of these swollen high-concentration
regions to levels that approach or even exceed conventional
acquisition/distribution materials, such as wood-pulp fluff, can
provide superior fluid handling properties for the absorbent member
and absorbent core, thus decreasing incidents of leakage,
especially at high fluid loadings. Higher SFC values also are
reflective of the ability of the formed hydrogel to acquire body
fluids under normal usage conditions.
[0076] The SFC value of the synthetic superabsorbent polymers
derived from renewable resources useful in the present invention is
at least about 30.times.10.sup.-7 cm.sup.3 sec/g. In other
embodiments, the SFC value of the superabsorbent polymers useful in
the present invention is at least about 50.times.10.sup.-7 cm.sup.3
sec/g. In other embodiments, the SFC value of the superabsorbent
polymers useful in the present invention is at least about
100.times.10.sup.-7 cm.sup.3 sec/g. Typically, these SFC values are
in the range of from about 30.times.10.sup.-7 to about
1000.times.10.sup.-7 cm.sup.3 sec/g. However, SFC values may range
from about 50.times.10.sup.-7 to about 500.times.10.sup.-7 cm.sup.3
sec/g or from about 50.times.10.sup.-7 to about 350.times.10.sup.-7
cm.sup.3 sec/g. A method for determining the SFC value of the
superabsorbent polymers is provided hereafter in the Test Methods
Section.
[0077] Another important characteristic of the superabsorbent
polymers of the present invention is their ability to swell against
a load. This capacity versus a load is defined in terms of the
superabsorbent polymer's Absorption Against Pressure (AAP)
capacity. When a superabsorbent polymer is incorporated into an
absorbent member at high concentrations, the polymer needs to be
capable of absorbing large quantities of body fluids in a
reasonable time period under usage pressures. Usage pressures
exerted on the superabsorbent polymers used within absorbent
article include both mechanical pressures (e.g., exerted by the
weight and motions of a wearer, taping forces, etc.) and capillary
pressures (e.g., resulting from the acquisition component(s) in the
absorbent core that temporarily hold fluid before it is absorbed by
the superabsorbent polymer).
[0078] The AAP capacity of absorbent polymer of the useful in the
present invention is generally at least about 15 g/g. In certain
embodiments, the AAP capacity of absorbent polymer is generally at
least about 20 g/g. Typically, AAP values range from about 15 to
about 25 g/g. However, AAP values may range from about 17 to about
23 g/g or from about 20 to about 23 g/g. A method for determining
the AAP capacity value of these absorbent polymers is provided
hereafter in the Test Methods Section.
[0079] B. Polyolefins--Olefins derived from renewable resources may
be polymerized to yield polyolefins. Ethylene derived from
renewable resources may be polymerized under the appropriate
conditions to prepare polyethylene having desired characteristics
for use in a particular component of an absorbent article or in the
packaging for said article. The polyethylene may be high density,
medium density, low density, or linear-low density. Polyethylene
and/or polypropylene may be produced via free-radical
polymerization techniques, or by using Ziegler-Natta catalysis or
Metallocene catalysts.
[0080] The polyolefin may be processed according to methods known
in the art into a form suitable for the end use of the polymer.
Suitable forms for polyolefins include a film, an apertured film, a
microporous film, a fiber, a filament, a nonwoven, or a laminate.
Suitable nonwoven forms include spunbond webs, meltblown webs, and
combinations thereof (e.g., spunbond-meltblown webs (SM),
spunbond-meltblown-spunbond webs (SMS), etc.). The polyolefin may
comprise mixtures or blends with other polymers such as polyolefins
derived from petrochemicals. Depending on the end use and form, the
polyolefin may comprise other compounds such as inorganic
compounds, fillers, pigments, dyes, antioxidants, UV-stabilizers,
binders, surfactants, wetting agents, and the like. For example, a
polyolefin film may be impregnated with inorganic compound such as
calcium carbonate, titanium dioxide, clays, silicas, zeolites,
kaolin, mica, carbon, and mixtures thereof. Such compounds may
serve as pore forming agents which, upon straining the film, may
improve the breathability of the film. This process is described
further in U.S. Pat. No. 6,605,172. A binder may be used with a
polyolefin fibers, filaments, or nonwoven web. A suitable binder is
a styrene-butadiene latex binder available under the trade name
GENFLO.TM. 3160 from OMNOVA Solutions Inc.; Akron, Ohio. The
resulting binder/polyolefin web may be used as an acquisition
layer, which may be associated with the absorbent core. The
polyolefin materials and particularly polyolefin fibers, filaments,
and nonwoven webs may treated with a surfactant or wetting agent
such as Irgasurf.TM. available from Ciba Specialty Chemicals of
Tarrytown, N.Y.
[0081] Polyolefin nonwovens useful in an absorbent article may have
a basis weight between about 1 g/m.sup.2 and about 50 g/m.sup.2 or
between about 5 g/m.sup.2 and about 30 g/m.sup.2, as measured
according to the Basis Weight Test provided below. Polyolefin
nonwovens suitable for use as a topsheet may have an average liquid
strike-through time of less than about 4 seconds, as measured
according to the Liquid Strike-Through Test provided below. In
other embodiments the polyolefin nonwoven may have an average
strike-through time of less than about 3 seconds or less than about
2 seconds.
[0082] Polyolefin nonwoven useful as a barrier leg cuff may have a
hydrohead of greater than about 5 mbar or about 6 mbar and less
than about 10 mbar or about 8 mbar, as measured according to the
Hydrohead test provided below.
[0083] Polyolefin films suitable for use as a backsheet may have an
MD tensile strength of greater than about 0.5 N/cm or about 1 N/cm
and less than about 6 N/cm or about 5 N/cm, as measured according
to the Tensile Test as provided below. For breathable polyolefin
films suitable for use as a backsheet, the film may have a Moisture
Vapor Transmission Rate (MVTR) of at least about 2000 g/m.sup.2/hr,
preferably greater than about 2400 g/m.sup.2/hr, and even more
preferably, greater than about 3000 g/m.sup.2/hr, as measured by
the Moisture Vapor Transmission Rate test provided below. It should
be recognized that non-breathable backsheets, which are also useful
in diapers, would exhibit an MVTR value of about 0
g/m.sup.2/hr.
[0084] C. Other Polymers--It should be recognized that any of the
aforementioned synthetic polymers may be formed by using a
combination of monomers derived from renewable resources and
monomers derived from non-renewable (e.g., petroleum) resources.
For example, the superabsorbent polymer of poly(acrylic acid) may
be polymerized from a combination of acrylic acid derived form
renewable resources and acrylic acid derived from non-renewable
resources. The monomer derived from a renewable resource may
comprise at least about 5% by weight [weight of renewable resource
monomer/weight of resulting polymer.times.100], at least about 10%
by weight, at least about 20% by weight, at least about 30% by
weight, at least about 40% by weight, or at least about 50% by
weight of the superabsorbent polymer.
IV. Absorbent Articles Comprising the Synthetic Polymer Derived
from Renewable Resources
[0085] The present invention relates to an absorbent article
comprising a synthetic polymer derived from a renewable resource.
The polymer has specific performance characteristics. The polymers
derived from a renewable resource may be in any suitable form such
as a film, nonwoven, superabsorbent, and the like.
[0086] FIG. 1A is a plan view of an exemplary, non-limiting
embodiment of an absorbent article in the form of a diaper 20 in a
flat, uncontracted state (i.e., without elastic induced
contraction). The garment-facing surface 120 of the diaper 20 is
facing the viewer and the body-facing surface 130 is opposite the
viewer. The diaper 20 includes a longitudinal centerline 100 and a
lateral centerline 110. FIG. 1B is a cross-sectional view of the
diaper 20 of FIG. 1A taken along the lateral centerline 110. The
diaper 20 may comprise a chassis 22. The diaper 20 and chassis 22
are shown to have a front waist region 36, a rear waist region 38
opposed to the front waist region 36, and a crotch region 37
located between the front waist region 36 and the rear waist region
38. The waist regions 36 and 38 generally comprise those portions
of the diaper 20 which, when worn, encircle the waist of the
wearer. The waist regions 36 and 38 may include elastic elements
such that they gather about the waist of the wearer to provide
improved fit and containment. The crotch region 37 is that portion
of the diaper 20 which, when the diaper 20 is worn, is generally
positioned between the legs of the wearer.
[0087] The outer periphery of diaper 20 and/or chassis 22 is
defined by longitudinal edges 12 and lateral edges 14. The chassis
22 may have opposing longitudinal edges 12 that are oriented
generally parallel to the longitudinal centerline 100. However, for
better fit, longitudinal edges 12 may be curved or angled to
produce, for example, an "hourglass" shape diaper when viewed in a
plan view. The chassis 22 may have opposing lateral edges 14 that
are oriented generally parallel to the lateral centerline 110.
[0088] The chassis 22 may comprises a liquid permeable topsheet 24,
a backsheet 26, and an absorbent core 28 between the topsheet 24
and the backsheet 26. The absorbent core 28 may have a body-facing
surface and a garment facing-surface. The topsheet 24 may be joined
to the core 28 and/or the backsheet 26. The backsheet 26 may be
joined to the core 28 and/or the topsheet 24. It should be
recognized that other structures, elements, or substrates may be
positioned between the core 28 and the topsheet 24 and/or backsheet
26. In certain embodiments, the chassis 22 comprises the main
structure of the diaper 20 and other features may added to form the
composite diaper structure. The topsheet 24, the backsheet 26, and
the absorbent core 28 may be assembled in a variety of well-known
configurations as described generally in U.S. Pat. Nos. 3,860,003;
5,151,092; 5,221,274; 5,554,145; 5,569,234; 5,580,411; and
6,004,306.
[0089] The absorbent core 28 may comprise the superabsorbent
polymer derived from a renewable resource of the present invention
as well as a wide variety of other liquid-absorbent materials
commonly used in diapers and other absorbent articles. Examples of
suitable absorbent materials include comminuted wood pulp, which is
generally referred to as air felt; chemically stiffened, modified
or cross-linked cellulosic fibers; superabsorbent polymers or
absorbent gelling materials; melt blown polymers, including
co-form, biosoluble vitreous microfibers; tissue, including tissue
wraps and tissue laminates; absorbent foams; absorbent sponges; and
any other known absorbent material or combinations of materials.
Exemplary absorbent structures for use as the absorbent core 28 are
described in U.S. Pat. Nos. 4,610,678; 4,673,402; 4,834,735;
4,888,231; 5,137,537; 5,147,345; 5,342,338; 5,260,345; 5,387,207;
5,397,316; 5,625,222; and 6,932,800. Further exemplary absorbent
structures may include non-removable absorbent core components and
removable absorbent core components. Such structures are described
in U.S. Publication 2004/0039361A1; 2004/0024379A1; 2004/0030314A1;
2003/0199844A1; and 2005/0228356A1. Ideally, the absorbent core 28
may be comprised entirely of materials derived from renewable
resources; however, the absorbent core 28 may comprise materials
derived from non-renewable resources.
[0090] The absorbent core 28 may comprise a fluid acquisition
component, a fluid distribution component, and a fluid storage
component. A suitable absorbent core 28 comprising an acquisition
layer, a distribution layer, and a storage layer is described in
U.S. Pat. No. 6,590,136.
[0091] Another suitable absorbent core construction where the
superabsorbent polymer of the present invention may be used is
described in U.S. Publication No. 2004/0167486 to Busam et al. The
absorbent core of the aforementioned publication uses no or, in the
alternative, minimal amounts of absorbent fibrous material within
the core. Generally, the absorbent core may include no more than
about 20% weight percent of absorbent fibrous material (i.e.,
[weight of fibrous material/total weight of the absorbent
core].times.100).
[0092] The topsheet 24 is generally a portion of the diaper 20 that
may be positioned at least in partial contact or close proximity to
a wearer. Suitable topsheets 24 may be manufactured from a wide
range of materials such as woven or nonwoven webs of natural fibers
(e.g., wood or cotton fibers), synthetic fibers (e.g., polyester or
polypropylene fibers), or a combination of natural and synthetic
fibers; apertured plastic films; porous foams or reticulated foams.
The topsheet 24 is generally supple, soft feeling, and
non-irritating to a wearer's skin. Generally, at least a portion of
the topsheet 24 is liquid pervious, permitting liquid to readily
penetrate through the thickness of the topsheet 24. Suitably, the
topsheet 24 comprises a polymer (e.g. polyethylene) derived from a
renewable resource. Alternately, a suitable topsheet 24 is
available from BBA Fiberweb, Brentwood, Tenn. as supplier code
055SLPV09U.
[0093] Any portion of the topsheet 24 may be coated with a lotion
as is known in the art. Examples of suitable lotions include those
described in U.S. Pat. Nos. 5,607,760; 5,609,587; 5,635,191; and
5,643,588. The topsheet 24 may be fully or partially elasticized or
may be foreshortened so as to provide a void space between the
topsheet 24 and the core 28. Exemplary structures including
elasticized or foreshortened topsheets are described in more detail
in U.S. Pat. Nos. 4,892,536; 4,990,147; 5,037,416; and
5,269,775.
[0094] The backsheet 26 is generally positioned such that it may be
at least a portion of the garment-facing surface 120 of the diaper
20. Backsheet 26 may be designed to prevent the exudates absorbed
by and contained within the diaper 20 from soiling articles that
may contact the diaper 20, such as bed sheets and undergarments. In
certain embodiments, the backsheet 26 is substantially
water-impermeable; however, the backsheet 26 may be made breathable
so as to permit vapors to escape while preventing liquid exudates
from escaping. The polyethylene film may be made breathable by
inclusion of inorganic particulate material and subsequent
tensioning of the film. Breathable backsheets may include materials
such as woven webs, nonwoven webs, composite materials such as
film-coated nonwoven webs, and microporous films. Suitably, the
backsheet 26 comprises a polymer such (e.g. polyethylene) derived
from a renewable resource as disclosed above. Alternative
backsheets 26 derived from non-renewable resources include films
manufactured by Tredegar Industries Inc. of Terre Haute, Ind. and
sold under the trade names X15306, X10962, and X10964; and
microporous films such as manufactured by Mitsui Toatsu Co., of
Japan under the designation ESPOIR NO and by EXXON Chemical Co., of
Bay City, Tex., under the designation EXXAIRE. Other alternative
breathable backsheets 26 are described in U.S. Pat. Nos. 5,865,823,
5,571,096, and 6,107,537.
[0095] Backsheet 26 may also consist of more than one layer. For
example, the backsheet 26 may comprise an outer cover and an inner
layer or may comprise two outer layers with an inner layer disposed
therebetween. The outer cover may have longitudinal edges and the
inner layer may have longitudinal edges. The outer cover may be
made of a soft, non-woven material. The inner layer may be made of
a substantially water-impermeable film. The outer cover and an
inner layer may be joined together by adhesive or any other
suitable material or method. Suitably, the nonwoven outer cover and
the water-impermeable film comprise polymers (e.g., polyethylene)
may be derived from renewable resources. Alternatively, a suitable
outer cover and inner layer derived from non-renewable resources
are available, respectively, as supplier code A 18AH0 from Corovin
GmbH, Peine, Germany and as supplier code PGBR4WPR from RKW Gronau
GmbH, Gronau, Germany. While a variety of backsheet configurations
are contemplated herein, it would be obvious to those skilled in
the art that various other changes and modifications can be made
without departing from the spirit and scope of the invention.
[0096] The diaper 20 may include a fastening system 50. When
fastened, the fastening system 50 interconnects the front waist
region 36 and the rear waist region 38. When fastened, the diaper
20 contains a circumscribing waist opening and two circumscribing
leg openings. The fastening system 50 may comprise an engaging
member 52 and a receiving member 54. The engaging member 52 may
comprise hooks, loops, an adhesive, a cohesive, a tab, or other
fastening mechanism. The receiving member 54 may comprise hooks,
loops, a slot, an adhesive, a cohesive, or other fastening
mechanism that can receive the engaging member 52. Suitable
engaging member 52 and receiving member 54 combinations are well
known in the art and include but are not limited to hooks/loop,
hooks/hooks, adhesive/polymeric film, cohesive/cohesive,
adhesive/adhesive, tab/slot, and button/button hole. Suitably, the
fastening system 50 may comprise a polymer (e.g., polyethylene film
or a polyethylene nonwoven) derived from a renewable resource.
[0097] The diaper 20 may include front ears (not shown) and/or back
ears 42. The front and/or back ears 42 may be unitary elements of
the diaper 20 (i.e., they are not separately manipulative elements
secured to the diaper 20, but rather are formed from and are
extensions of one or more of the various layers of the diaper). In
certain embodiments, the front and/or back ears 42 may be discrete
elements that are joined to the chassis 22, as shown in FIG. 1A.
Discrete front and/or back ears 42 may be joined to the chassis 22
by any bonding method known in the art such as adhesive bonding,
pressure bonding, heat bonding, and the like. In other embodiments,
the front and/or back ears 42 may comprise a discrete element
joined to the chassis 22 with the chassis 22 having a layer,
element, or substrate that extends over the front and/or back ear
42. The front ears and back ears 42 may be extensible,
inextensible, elastic, or inelastic. The front ears and back ears
42 may be formed from nonwoven webs, woven webs, knitted fabrics,
polymeric and elastomeric films, apertured films, sponges, foams,
scrims, and combinations and laminates thereof. In certain
embodiments the front ears and back ears 42 may be formed of a
stretch laminate comprising a first nonwoven 42a, elastomeric
material 42b, and, optionally, a second nonwoven 42c or other like
laminates. The first and second nonwoven 42a, 42c may comprise a
synthetic polymer (e.g., polyethylene) derived from a renewable
resource. A suitable elastomeric material 42b may comprise a
natural elastomer such as natural rubber or may comprise a
synthetic elastomer such as the elastomeric film available from
Tredegar Corp, Richmond, Va., as supplier code X25007. An alternate
stretch laminate may be formed from the Tredegar X25007 elastomer
disposed between two nonwoven layers (available from BBA Fiberweb,
Brentwood, Tenn. as supplier code FPN332).
[0098] The diaper 20 may further include leg cuffs 32a, 32b which
provide improved containment of liquids and other body exudates.
Leg cuffs 32a, 32b may also be referred to as gasketing cuffs,
outer leg cuffs, leg bands, side flaps, elastic cuffs, barrier
cuffs, second cuffs, inner leg cuffs, or "stand-up" elasticized
flaps. U.S. Pat. No. 3,860,003 describes a disposable diaper which
provides a contractible leg opening having a side flap and one or
more elastic members to provide an elasticized leg cuff (i.e., a
gasketing cuff). U.S. Pat. Nos. 4,808,178 and 4,909,803 describe
disposable diapers having "stand-up" elasticized flaps (i.e.,
barrier cuffs) which improve the containment of the leg regions.
U.S. Pat. Nos. 4,695,278 and 4,795,454 describe disposable diapers
having dual cuffs, including gasketing cuffs and barrier cuffs.
[0099] FIGS. 1A-B shows the diaper 20 having dual cuffs: gasketing
cuff 32a and barrier cuff 32b. The barrier cuff 32b may include one
or more barrier elastic members 33b. The barrier elastic members
33b may be joined to a barrier cuff substrate 34. The barrier cuff
substrate 34 may comprise a polymer derived from a renewable
resource. In certain embodiments, the barrier cuff substrate 34 may
be a polymeric film or nonwoven. The barrier cuff 32b may be
disposed on the body-facing surface of the chassis 22. The barrier
cuff substrate 34 may extend laterally from the longitudinal edge
12 of the chassis 22 to a point inboard of the longitudinal edge
122. The barrier cuff 32b generally extends longitudinally at least
through the crotch region 37. The barrier elastic members 33b allow
a portion of the barrier cuff 32b to be spaced away from the
body-facing surface of the diaper 20.
[0100] The gasketing cuff 32a may include one or more gasketing
elastic members 33a. The gasketing elastic member 33a may be joined
to one or more of the existing elements or substrates of the diaper
20 (e.g., topsheet 24, backsheet 26, barrier cuff substrate 34,
etc.). In some embodiments, it may be desirable to treat all or a
portion of the leg cuffs 32 with a hydrophilic surface coasting
such as is described in U.S. Patent Publication 2005/0177123A1.
Suitable gasketing and barrier elastic members 33a, 33b include
natural rubber, synthetic rubbers, and other elastomers.
[0101] In other suitable embodiments, the diaper 20 may be
preformed by the manufacturer to create a pant. A pant may be
preformed by any suitable technique including, but not limited to,
joining together portions of the article using refastenable and/or
non-refastenable bonds (e.g., seam, weld, adhesive, cohesive bond,
fastener, etc.). For example, the diaper 20 of FIG. 1A may be
manufactured with the fastening system 50 engaged (i.e., the
engaging member 52 is joined to the receiving member 54). As an
additional example, the diaper 20 of FIG. 1A may be manufactured
with the front ears 40 joined to the back ears 42 by way of a bond
such as an adhesive bond, a mechanical bond, or some other bonding
technique known in the art. Suitable pants are disclosed in U.S.
Pat. Nos. 5,246,433; 5,569,234; 6,120,487; 6,120,489; 4,940,464;
5,092,861; 5,897,545; and 5,957,908.
[0102] FIG. 8 is a plan view of a diaper 820 as a certain
embodiment of an absorbent article according to the present
invention. The diaper 820 is shown in its flat out, uncontracted
state (i.e., without elastic induced contraction). Portions of the
structure are cut away to more clearly show the underlying
structure of the diaper 820. The portion of the diaper 820 that
contacts a wearer is facing the viewer. The chassis 822 of the
diaper 820 in FIG. 8 comprises the main body of the diaper 820. The
chassis 822 comprises an outer covering including a liquid pervious
topsheet 824 and/or a liquid impervious backsheet 826. The chassis
may include a portion of an absorbent core 828 encased between the
topsheet 824 and the backsheet 826. The chassis may also include
most or all of the absorbent core 828 encased between the topsheet
824 and the backsheet 826. The chassis further includes side panels
830, elasticized leg cuffs 832, and elastic waist feature 834, the
leg cuffs 832 and the elastic waist feature 834 each typically
comprise elastic members 833. One end portion of the diaper 820 is
configured as a first waist region 836 of the diaper 820. The
opposite end portion is configured as a second waist region 838 of
the diaper 820. An intermediate portion of the diaper 820 is
configured as a crotch region 837, which extends longitudinally
between the first and second waist regions 836 and 838. The waist
regions 836 and 838 may include elastic elements such that they
gather about the waist of the wearer to provide improved fit and
containment (elastic waist feature 834). The crotch region 837 is
that portion of the diaper 820 which, when the diaper 820 is worn,
is generally positioned between the wearer's legs. The diaper 820
is depicted with its longitudinal axis 810 and its transverse axis
812. The periphery of the diaper 820 is defined by the outer edges
of the diaper 820 in which the longitudinal edges 844 run generally
parallel to the longitudinal axis 810 of the diaper 820 and the end
edges 846 run between the longitudinal edges 844 generally parallel
to the transverse axis 812 of the diaper 820. The chassis also
comprises a fastening system, which may include at least one
fastening member 840 and at least one stored landing zone 842.
[0103] For unitary absorbent articles, the chassis 822 comprises
the main structure of the diaper 820 with other features added to
form the composite diaper structure. While the topsheet 824, the
backsheet 826, and the absorbent core 828 may be assembled in a
variety of well-known configurations, certain diaper configurations
are described generally in U.S. Pat. No. 5,554,145 entitled
"Absorbent Article With Multiple Zone Structural Elastic-Like Film
Web Extensible Waist Feature" issued to Roe et al. on Sep. 10,
1996; U.S. Pat. No. 5,569,234 entitled "Disposable Pull-On Pant"
issued to Buell et al. on Oct. 29, 1996; and U.S. Pat. No.
6,004,306 entitled "Absorbent Article With Multi-Directional
Extensible Side Panels" issued to Robles et al. on Dec. 21,
1999.
[0104] The topsheet 824 in FIG. 8 may be fully or partially
elasticized or may be foreshortened to provide a void space between
the topsheet 824 and the absorbent core 828. Exemplary structures
including elasticized or foreshortened topsheets are described in
more detail in U.S. Pat. No. 5,037,416 entitled "Disposable
Absorbent Article Having Elastically Extensible Topsheet" issued to
Allen et al. on Aug. 6, 1991; and U.S. Pat. No. 5,269,775 entitled
"Trisection Topsheets for Disposable Absorbent Articles and
Disposable Absorbent Articles Having Such Trisection Topsheets"
issued to Freeland et al. on Dec. 14, 1993.
[0105] The absorbent core 828 in FIG. 8 generally is disposed
between the topsheet 824 and the backsheet 826. The absorbent core
828 may comprise any absorbent material that is generally
compressible, conformable, non-irritating to the wearer's skin, and
capable of absorbing and retaining liquids such as urine and other
certain body exudates. The absorbent core 828 and any components
thereof may include polymers at least in part derived from
renewable resources as described herein. The absorbent core 828 may
further comprise minor amounts (typically less than 10%) of
non-liquid absorbent materials, such as adhesives, waxes, oils and
the like.
[0106] The backsheet 826 may be joined with the topsheet 824. The
backsheet 826 prevents the exudates absorbed by the absorbent core
828 and contained within the article 820 from soiling other
external articles that may contact the diaper 820, such as bed
sheets and undergarments. In certain embodiments, the backsheet 826
is substantially impervious to liquids (e.g., urine) and comprises
a laminate of a nonwoven and a thin plastic film such as a
thermoplastic film having a thickness of about 0.012 mm (0.5 mil)
to about 0.051 mm (2.0 mils). Other backsheet materials may include
breathable materials that permit vapors to escape from the diaper
820 while still preventing exudates from passing through the
backsheet 826. Breathable composite materials comprising polymer
blends are also available.
The diaper 820 may also include such other features as are known in
the art including front and rear ear panels, waist cap features,
elastics and the like to provide better fit, containment and
aesthetic characteristics. Such additional features are well known
in the art and are e.g., described in U.S. Pat. No. 3,860,003 and
U.S. Pat. No. 5,151,092.
[0107] In order to keep the diaper 820 in place about the wearer,
at least a portion of the first waist region 836 is attached by the
fastening member 842 to at least a portion of the second waist
region 838, to form leg opening(s) and an article waist. When
fastened, the fastening system carries a tensile load around the
article waist. The fastening system is designed to allow an article
user to hold one element of the fastening system such as the
fastening member 842, and connect the first waist region 836 to the
second waist region 838 in at least two places. This is achieved
through manipulation of bond strengths between the fastening device
elements.
[0108] Diapers 820 may be provided with a re-closable fastening
system or may alternatively be provided in the form of pant-type
diapers.
[0109] The fastening system and any component thereof may include
any material suitable for such a use, including but not limited to
plastics, films, foams, nonwoven webs, woven webs, paper,
laminates, fiber reinforced plastics and the like, or combinations
thereof, including for example, polymers at least partially derived
from renewable resources as described herein. It may be preferable
that the materials making up the fastening device be flexible. The
flexibility is designed to allow the fastening system to conform to
the shape of the body and thus, reduces the likelihood that the
fastening system will irritate or injure the wearer's skin.
[0110] FIG. 9 shows a cross section of FIG. 8 taken along the
sectional line 9-9 of FIG. 8. Starting from the wearer facing side
the diaper comprises the topsheet 824, the components of the
absorbent core 828, and the backsheet 826. The absorbent article
can comprise an acquisition system 850, which comprises an upper
acquisition layer 852 facing towards the wearer's skin and a lower
acquisition 854 layer facing the garment of the wearer. The
acquisition layer may be in direct contact with the storage layer
860.
[0111] The storage layer 860 may be wrapped by a core wrap
material. In one certain embodiment the core wrap material
comprises a top layer 856 and a bottom layer 858. The core wrap
material, the top layer 856 or the bottom layer 858 can be provided
from a non-woven material.
[0112] The top layer 856 and the bottom layer 858 may be provided
from two or more separate sheets of materials or they may be
alternatively provided from a unitary sheet of material. Such a
unitary sheet of material may be wrapped around the storage layer
860 e.g., in a C-fold.
[0113] Non-woven materials as described herein can be coated with
hydrophilic coatings.
[0114] One way to produce nonwovens with durably hydrophilic
coatings, is via applying a hydrophilic monomer and a radical
polymerization initiator onto the nonwoven, and conducting a
polymerization activated via UV light resulting in monomer
chemically bound to the surface of the nonwoven as described in
co-pending U.S. patent application Ser. No. 10/674,670.
[0115] Another way to produce nonwovens with durably hydrophilic
coatings is to coat the nonwoven with hydrophilic nanoparticles as
described in co-pending application Ser. No. 10/060,708 and WO
02/064877.
[0116] Typically, nanoparticles have a largest dimension of below
750 nm. Nanoparticles with sizes ranging form 2 to 750 nm can be
economically produced. The advantages of nanoparticles is that many
of them can be easily dispersed in water solution to enable coating
application onto the nonwoven; they typically form transparent
coatings, and the coatings applied from water solutions are
typically sufficiently durable to exposure to water.
[0117] Nanoparticles can be organic or inorganic, synthetic or
natural. Inorganic nanoparticles generally exist as oxides,
silicates, carbonates. Typical examples of suitable nanoparticles
are layered clay minerals (e.g., LAPONITE.TM. from Southern Clay
Products, Inc. (USA), and Boehmite alumina (e.g., Disperal P2.TM.
from North American Sasol. Inc.)
[0118] Certain nanoparticle coated non-woven is disclosed in patent
application publication No. 2004-0158212 entitled, "Disposable
absorbent article comprising a durable hydrophilic core wrap."
[0119] In some cases, the nonwoven surface can be pre-treated with
high energy treatment (corona, plasma) prior to application of
nanoparticle coatings. High energy pre-treatment typically
temporarily increases the surface energy of a low surface energy
surface (such as PP) and thus enables better wetting of a nonwoven
by the nanoparticle dispersion in water.
[0120] Notably, permanently hydrophilic non-wovens are also useful
in other parts of an absorbent article. For example, topsheets and
acquisition layers comprising permanently hydrophilic non-wovens as
described above have been found to work well.
[0121] In summary, in one aspect of the present invention,
absorbent articles can comprise a nonwoven fabric, the nonwoven
fabric can comprise a plurality of fibers and have a surface
tension of at least 55, at least 60 and even at least 65 mN/m or
higher when being wetted with saline solution and has a liquid
strike through time of less than 5 s for a fifth gush of
liquid.
[0122] The surface tension is a measure of how permanently a
certain hydrophilicity level is achieved. The value is to be
measured using the test method described hereinbelow.
[0123] The liquid strike through time is a measure of a certain
hydrophilicity level. The value is to be measured using the test
method described hereinbelow.
[0124] In certain embodiments the absorbent core 828 can comprise a
substrate layer 900, absorbent polymer material 910 and a layer of
adhesive 920. The adhesive layer 920 could be formed of a
thermoplastic material (e.g., hot melt adhesive). The substrate
layer 900 can be provided from a non-woven material, certain
non-wovens are those exemplified above for the top layer 856 or the
bottom layer 858.
[0125] The substrate layer 900 comprises a first surface and a
second surface. At least portions of the first surface of the
substrate layer 900 are in direct contact with a layer of absorbent
polymer material 910. This layer of absorbent polymer material 910
can be a discontinuous layer, and comprises a first surface and a
second surface. As used herein, a discontinuous layer is a layer
comprising openings. Typically these openings have a diameter or
largest span of less than 10 mm, less than 5 mm, less than 3 mm, or
even less than 2 mm, but more than 0.5 mm, more than 1 mm or even
more than 1.5 mm. At least portions of the second surface of the
absorbent polymer material layer 910 are in contact with at least
portions of the first surface of the substrate layer 900. The first
surface of the absorbent polymer material 910 defines a certain
height 912 of the layer of absorbent polymer above the first
surface of the layer of substrate material 900. When the absorbent
polymer material layer 910 is provided as a discontinuous layer,
portions of the first surface of the substrate layer 900 are not
covered by absorbent polymer material 910. The absorbent core 828
further comprises an adhesive layer 920. This adhesive layer 920
serves to at least partially immobilize the absorbent polymer
material 910.
[0126] However, in a certain embodiment the adhesive layer 920 can
be provided as a fibrous layer which is partially in contact with
the absorbent polymer material 910 and partially in contact with
the substrate layer 900. FIG. 10 shows such a structure. In this
structure the absorbent polymer material layer 910 is provided as a
discontinuous layer, a layer of fibrous adhesive layer 920 is laid
down onto the layer of absorbent polymeric material 910, such that
the adhesive layer 920 is in direct contact with the first surface
of the layer of absorbent polymer material 910, but also in direct
contact with the first surface of the substrate layer 900, where
the substrate layer is not covered by the absorbent polymeric
material 910. This imparts an essentially three-dimensional
structure to the fibrous layer of adhesive material 920 which in
itself is essentially a two-dimensional structure of relatively
small thickness (in z-direction), as compared to the extension in
x- and y-direction. In other words, the fibrous adhesive layer 920
undulates between the first surface of the absorbent polymer
material 910 and the first surface of the substrate layer 900.
[0127] Thereby, the adhesive layer 920 provides cavities to hold
the absorbent polymer material 910, and thereby immobilizes this
material. In a further aspect, the adhesive layer 920 bonds to the
substrate 900 and thus affixes the absorbent polymer material 910
to the substrate 900. Certain thermoplastic materials will also
penetrate into both the absorbent polymer material 910 and the
substrate layer 900, thus providing for further immobilization and
affixation.
[0128] Of course, while the thermoplastic materials disclosed
herein provide a much improved wet immobilisation (i.e.,
immobilisation of absorbent material when the article is wet or at
least partially loaded), these thermoplastic materials also provide
a very good immobilisation of absorbent material when the article
is dry.
[0129] A certain embodiment of the present invention is shown in
FIG. 11. The absorbent core shown in FIG. 11 further comprises a
cover layer 930. This cover layer 930 may be provided of the same
material as the substrate layer 900, or may be provided from a
different material. The substrate layer 900, the discontinuous
layer 910, the adhesive layer 920 and the cover layer 930 may be
formed from the polymers at least partially derived from renewable
resources as these polymers are described herein. In this
embodiment portions of the cover layer 930 bond to portions of the
substrate layer 900 via the adhesive layer 920. Thereby, the
substrate layer 900 together with the cover layer 930 provides
cavities to immobilize the absorbent polymer material 910.
[0130] With reference to FIGS. 10 and 11 the areas of direct
contact between the adhesive layer 920 and the substrate material
900 are referred to as areas of junction 940. The shape number and
disposition of the areas of junction 940 will influence the
immobilization of the absorbent polymer material 910. The areas of
junction can be of squared, rectangular or circular shape. Areas of
junction can be circular in shape. They have a diameter of more
than 0.5 mm, or 1 mm, or 1.5 mm and of less than 10 mm, or 5 mm, or
3 mm, or 2 mm. If the areas of junction 940 are not of circular
shape, they can be of a size as to fit inside a circle of any of
the diameters given above.
[0131] The areas of junction 940 can be disposed in a regular or
irregular pattern. For example, the areas of junction 940 may be
disposed along lines as shown in FIG. 12. These lines may be
aligned with the longitudinal axis of the absorbent core, or
alternatively they may have a certain angle in respect to the
longitudinal edges of the core. It has been found, that a
disposition along lines parallel with the longitudinal edges of the
absorbent core 828 create channels in the longitudinal direction
which lead to a lesser wet immobilization. Therefore the areas of
junction 940 are arranged along lines which form an angle of 20
degree, 30 degree, 40 degree, or 45 degree with the longitudinal
edges of the absorbent core 828. Another pattern for the areas of
junction 940 is a pattern comprising polygons, for example
pentagons and hexagons or a combination of pentagons and hexagons.
Irregular patterns of areas of junction 940 have been found to give
a good wet immobilization.
[0132] Two fundamentally different patterns of areas of junctions
940 can be chosen. In one embodiment the areas of junctions are
discrete. They are positioned within the areas of absorbent
material, like islands in a sea. The areas of absorbent materials
are then referred to as connected areas. In another embodiment, the
areas of junctions can be connected. Then, the absorbent material
can be deposited in a discrete pattern, or in other words the
absorbent material represents islands in a sea of the adhesive
layer 920. Hence, a discontinuous layer of absorbent polymer
material 910 may comprise connected areas of absorbent polymer
material 910 or may comprise discrete areas of absorbent polymer
material 910.
[0133] It has been found that absorbent cores providing for a good
wet immobilization can be formed by combining two layers as shown
in FIG. 10 and as described in the context thereof. Such an
embodiment is shown in FIG. 13. The absorbent core material shown
in FIG. 13 comprises two substrate layers 900, two layers of
absorbent polymer material 910 and two layers of materials forming
the adhesive layer 920. When two discontinuous layers of an
absorbent polymer material 910 are used, they would be typically
arranged in such a way that the absorbent polymer material of the
one layer faces the areas of junction 940 of the other layer. In
another embodiment, however, the areas of junction 940 are offset
and do not face each other. Hence, when two storage layers are
joined, this is done such that the first surface of the substrate
layer 900 of the first storage layer 860 faces the first surface of
the substrate layer 900 of the second storage layer 860.
[0134] The present invention, and specifically the certain
embodiment described with reference to FIGS. 10, 11 and 13 can be
used to provide the storage layer 860 of an absorbent core.
However, they can also be used to provide the full absorbent core
828. In that case, no further materials wrapping the core, such as
the top layer 856 and the bottom layer 858 are being used. With
reference to the embodiment of FIG. 10 the substrate layer 900 may
provide the function of the bottom layer 858 and the layer of
adhesive material 920 may provide the function of the top layer
856. With reference to FIG. 11 the cover layer 930 may provide the
function of the top layer 856 and the substrate layer 900 may
provide the function of the bottom layer 858. With reference to
FIG. 13, the two substrate layers 900 used may provide the
functions of the top layer 856 and the bottom layer 858,
respectively.
[0135] Without wishing to be bound by theory it has been found that
those thermoplastic compositions used to form the adhesive layer
920 are most useful for immobilizing the absorbent polymer material
910, which combines good cohesion and good adhesion behaviour. Good
adhesion is critical to ensure that the adhesive layer 920
maintains good contact with the absorbent polymer material 910 and
in particular with the substrate 900. Good adhesion is a challenge,
namely when a non-woven substrate is used. Good cohesion ensures
that the adhesive does not break, in particular in response to
external forces, and namely in response to strain. The adhesive is
subject to external forces when the absorbent product has acquired
liquid, which is then stored in the absorbent polymer material 910
which in response swells. A certain adhesive will allow for such
swelling, without breaking and without imparting too many
compressive forces, which would restrain the absorbent polymer
material 910 from swelling. Importantly, the adhesive should not
break, which would deteriorate the wet immobilization. Certain
thermoplastic compositions meeting these requirements have the
following features:
[0136] The thermoplastic composition may comprise, in its entirety,
a single thermoplastic polymer or a blend of thermoplastic
polymers, having a softening point, as determined by the ASTM
Method D-36-95 "Ring and Ball", in the range between 50.degree. C.
and 300.degree. C., or alternatively the thermoplastic composition
may be a hot melt adhesive comprising at least one thermoplastic
polymer in combination with other thermoplastic diluents such as
tackifying resins, plasticizers and additives such as
antioxidants.
[0137] The thermoplastic polymer has typically a molecular weight
(Mw) of more than 10,000 and a glass transition temperature (Tg)
usually below room temperature. Typical concentrations of the
polymer in a hot melt are in the range of 20-40% by weight. A wide
variety of thermoplastic polymers are suitable for use in the
present invention. Such thermoplastic polymers can be water
insensitive. Exemplary polymers are (styrenic) block copolymers
including A-B-A triblock structures, A-B diblock structures and
(A-B)n radial block copolymer structures wherein the A blocks are
non-elastomeric polymer blocks, typically comprising polystyrene,
and the B blocks are unsaturated conjugated diene or (partly)
hydrogenated versions of such. The B block is typically isoprene,
butadiene, ethylene/butylene (hydrogenated butadiene),
ethylene/propylene (hydrogenated isoprene), and mixtures
thereof.
[0138] Other suitable thermoplastic polymers that may be employed
are metallocene polyolefins, which are ethylene polymers prepared
using single-site or metallocene catalysts. Therein, at least one
comonomer can be polymerized with ethylene to make a copolymer,
terpolymer or higher order polymer. Also applicable are amorphous
polyolefins or amorphous polyalphaolefins (APAO) which are
homopolymers, copolymers or terpolymers of C2 to C8
alphaolefins.
[0139] The resin has typically a Mw below 5,000 and a Tg usually
above room temperature, typical concentrations of the resin in a
hot melt are in the range of 30-60%. The plasticizer has a low Mw
of typically less than 1,000 and a Tg below room temperature, a
typical concentration is 0-15%.
[0140] The adhesive can be present in the forms of fibres
throughout the core, i.e., the adhesive is fiberized. The fibres
can have an average thickness of 1-50 micrometer and an average
length of 5 mm to 50 cm.
[0141] To improve the adhesion of the thermoplastic material 120 to
the substrate layer 100 or to any other layer, in particular any
other non-woven layer, such layers may be pre-treated with an
auxiliary adhesive.
[0142] The adhesive will meet at least one, and more likely several
or all of the following parameters:
[0143] A certain adhesive can have a storage modulus G' measured at
20.degree. C. of at least 30,000 Pa and less than 300,000 Pa. In
another certain embodiment, an adhesive can have a storage modulus
G' measured at 20.degree. C. of at least 30,000 Pa and less than
less than 200,000 Pa. In another certain embodiment, an adhesive
can have a storage modulus G' measured at 20.degree. C. of at least
30,000 Pa and less than 100,000 Pa. The storage modulus G' at
20.degree. C. is a measure for the permanent "tackiness" or
permanent adhesion of the thermoplastic material used. Good
adhesion will ensure a good and permanent contact between the
thermoplastic material and for example the substrate layer 100. In
a further aspect, the storage modulus G' measured at 60.degree. C.
should be less than 300,000 Pa and more than 18,000 Pa. In another
certain embodiment, an adhesive can have a storage modulus G'
measured at 60.degree. C. can be less than 300,000 Pa and more than
24,000 Pa. In another certain embodiment, an adhesive can have a
storage modulus G' measured at 60.degree. C. can be less than
300,000 Pa and more than 30,000 Pa. The storage modulus measured at
60.degree. C. is a measure for the form stability of the
thermoplastic material at elevated ambient temperatures. This value
is particularly important if the absorbent product is used in a hot
climate where the thermoplastic composition would lose its
integrity if the storage modulus G' at 60.degree. C. is not
sufficiently high.
[0144] In a further aspect, the loss angle tan Delta of the
adhesive at 60.degree. C. can be below the value of 1. In another
aspect, the loss angle tan Delta of the adhesive at 60.degree. C.
can be below the value of 0.5. The loss angle tan Delta at
60.degree. C. is correlated with the liquid character of an
adhesive at elevated ambient temperatures. The lower tan Delta, the
more an adhesive behaves like a solid rather than a liquid, i.e.,
the lower its tendency to flow or to migrate and the lower the
tendency of an adhesive superstructure as described herein to
deteriorate or even to collapse over time. This value is hence
particularly important if the absorbent article is used in a hot
climate.
[0145] In a further aspect, the adhesive can have a glass
transition temperature T.sub.g of less than 25.degree. C., less
than 22.degree. C., less than 18.degree. C., or even less than
15.degree. C. A low glass transition temperature T.sub.g is
beneficial for good adhesion. In a further aspect a low glass
transition temperature Tg ensures that the adhesive thermoplastic
material does not become to brittle.
[0146] In yet a further aspect, a certain adhesive will have a
sufficiently high cross-over temperature T.sub.x. A sufficiently
high cross-over temperature T.sub.x has been found beneficial for
high temperature stability of the thermoplastic layer and hence it
ensures good performance of the absorbent product and in particular
good wet immobilization even under conditions of hot climates and
high temperatures. Therefore, T.sub.x can be above 80.degree. C.,
above 85.degree. C., or even above 90.degree. C.
[0147] In a further important aspect, adhesives can have a
sufficient cohesive strength parameter .gamma.. The cohesive
strength parameter .gamma. is measured using the rheological creep
test as described hereinafter. A sufficiently low cohesive strength
parameter .gamma. is representative of elastic adhesive which, for
example, can be stretched without tearing. If a stress of
.tau.=1000 Pa is applied, the cohesive strength parameter
.gamma.can be less than 100%, less than 90%, or even less than 75%.
For a stress of .tau.=125,000 Pa, the cohesive strength parameter
.gamma.can be less than 1200%, less than 1000%, and even less than
800%.
[0148] A certain adhesive useful as a thermoplastic material to
form the adhesive layer 920 as described herein will meet most or
all of the above parameters. Specific care must be taken to ensure
that the adhesive provides good cohesion and good adhesion at the
same time.
[0149] The process for producing certain absorbent cores 828 in
accordance with the present invention can comprise the following
steps:
[0150] The absorbent core 828 is laid down onto a laydown drum,
which presents an uneven surface. In a first process step the
substrate layer 900 is laid on to the uneven surface. Due to
gravity, or by using a vacuum means, the substrate layer material
will follow the contours of the uneven surface and thereby the
substrate layer material will assume a mountain and valley shape.
Onto this substrate layer 900 absorbent polymeric material is
disposed by means known in the art. The absorbent polymer material
will accumulate in the valleys presented by the substrate layer
900. In a further process step a hot melt adhesive is placed onto
the absorbent polymer material.
[0151] While any adhesive application means known in the art can be
used to place the adhesive layer (e.g., hot melt adhesive) on to
the absorbent polymer material, the hot melt adhesive can be
applied by a nozzle system. A nozzle system is utilised, which can
provide a relatively thin but wide curtain of adhesive. This
curtain of adhesive is than placed onto the substrate layer 900 and
the absorbent polymer material. As the mountain tops of the
substrate layer 900 are less covered by absorbent polymer material
the adhesive will make contact with these areas of the substrate
layer.
[0152] In an optional further process step a cover layer 930 is
placed upon the substrate layer 900, the absorbent polymer material
and the hot melt adhesive layer. The cover layer 930 will be in
adhesive contact with the substrate layer 900 in the areas of
junction 940. In these areas of junction 940 the adhesive is in
direct contact with the substrate layer 900. The cover layer 930
will typically not be in adhesive contact with the substrate layer
900 where the valleys of the substrate layer 900 are filled with
absorbent polymer material.
[0153] Alternatively the cover layer 930 can be laid down onto a
drum with an uneven surface and the substrate layer 900 can be
added in a consecutive process step. The embodiment shown in FIG.
11 could be produced by such a process.
[0154] In one alternative embodiment, the cover layer 930 and the
substrate layer 900 are provided from a unitary sheet of material.
The placing of the cover layer 930 onto the substrate layer 900
will then involve the folding of the unitary piece of material.
[0155] Hence, the uneven surface of the lay-down system, which can
be a lay-down drum, typically determines the distribution of
absorbent polymeric material throughout the storage layer 860 and
likewise determines the pattern of areas of junction 940.
Alternatively, the distribution of absorbent polymeric material may
be influenced by vacuum means.
[0156] The distribution of absorbent polymeric material can be
profiled and profiled in the longitudinal direction. Hence, along
the longitudinal axis of the absorbent core, which is normally
coincident with the longitudinal axis of the absorbent article, for
example of the diaper, the basis weight of the absorbent polymer
material will change. The basis weight of absorbent polymer
material in at least one freely selected first square measuring 1
cm.times.1 cm is at least 10%, or 20%, or 30%, 40% or 50% higher
than the basis weight of absorbent polymer material in at least one
freely selected second square measuring 1 cm.times.1 cm. The
criterion can be met if the first and the second square are centred
about the longitudinal axis.
[0157] It has been found beneficial to use a particulate absorbent
polymer material for absorbent cores. Without wishing to be bound
by theory it is believed that such material, even in the swollen
state, i.e., when liquid has been absorbed, does not substantially
obstruct the liquid flow throughout the material, especially when
the permeability as expressed by the saline flow conductivity of
the absorbent polymer material is greater than 10, 20, 30 or 40
SFC--units, where 1 SFC unit is 1.times.10 .sup.-7
(cm.sup.3.times.s)/g. Saline flow conductivity is a parameter well
recognised in the art and is to be measured in accordance with the
test disclosed in U.S. Pat. No. 5,599,335.
[0158] As to achieve a sufficient absorbent capacity in a certain
absorbent article and especially if the absorbent article is a
diaper or an adult incontinence product, superabsorbent polymer
material will be present with a basis weight of more than 50, 100,
200, 300, 400, 500, 600, 700, 800 or even more than 900
g/m.sup.2.
[0159] Certain articles achieve a relatively narrow crotch width,
which increases the wearing comfort. A certain article achieves a
crotch width of less than 100 mm, 90 mm, 80 mm, 70 mm, 60 mm or
even less than 50 mm. Hence, an absorbent core can have a crotch
width as measured along a transversal line which is positioned at
equal distance to the front edge and the rear edge of the core
which is of less than 100 mm, 90 mm, 80 mm, 70 mm, 60 mm or even
less than 50 mm. It has been found that for most absorbent articles
the liquid discharge occurs predominately in the front half. The
front half of the absorbent core should therefore comprise most of
the absorbent capacity of the core. The front half of said
absorbent core comprises more than 60% of the absorbent capacity,
more than 65%, more than 70%, more than 75%, more than 80%, more
than 85%, or even more than 90%.
V. Providing the Absorbent Article to a Consumer
[0160] One or more absorbent articles (e.g., diapers) 220 may be
provided as a package 200, as shown in FIGS. 2A-B. Generally, the
package 200 allows for a quantity of absorbent articles 220 to be
delivered to and purchased by a consumer while economizing space
and simplifying transport and storage. The package 200 includes at
least one absorbent article 220 secured by an overwrap 250. The
overwrap 250 may partially or fully cover the absorbent article(s),
which may be compressed or uncompressed. FIG. 2A depicts an
overwrap 250 that completely covers and encases a plurality of
absorbent articles 220. The overwrap 250 may comprise a variety of
materials including, but not limited to, thermoplastic films,
nonwovens, wovens, foils, fabrics, papers, cardboard, elastics,
cords, straps, and combinations thereof. Other suitable package
structures and overwraps are described in U.S. Pat. Nos. 4,846,587;
4,934,535; 4,966,286; 5,036,978; 5,050,742; and 5,054,619. In
certain embodiments, the overwrap 250 comprises a synthetic polymer
(e.g., a polyolefin) derived form a renewable resource. While the
package 200 is not limited in shape, it may be desirable for the
package 200 to have the shape of a parallelepiped or substantially
similar to a parallelepiped (e.g., a solid at least a substantially
planar base and four substantially planar sides). Such a shape is
ideal for packaging, stacking, and transport. The package 200 is
not limited in size; however, in certain embodiments, the size of
the package 200 should be no greater than is required to contain
the absorbent articles 220.
[0161] The package 200 may have a handle 240. In certain
embodiments, the handle 240 may be a discrete element such as a
strap that may be affixed to the overwrap 250. In the embodiment
shown in FIGS. 2A-B, the handle 240 is integral to the overwrap
250. For this embodiment, the handle 240 may comprise an extension
252 from the overwrap 250. The extension 252 may have an aperture
254 there through. The aperture 254 ideally sized to permit entry
by one or more digits of an adult hand.
[0162] An opening device 260 may be provided in the overwrap 250.
For example, the opening device 260 may comprise a line of weakness
262 (e.g., perforations) in an overwrap 250 made from paper,
cardboard, or film. The opening device 260 allows for partial or
full removal of a flap 256 which is a portion of the overwrap 250.
Partial of full removal of the flap 256 may allow for improved
access to the absorbent articles 220. The opening device 260 and
flap 256 are shown in a closed configuration in FIG. 2A and in an
open configuration in FIG. 2B. An exemplary opening device 260 is
presented in U.S. Pat. No. 5,036,978.
[0163] The package 200 may contain multiple overwraps 250. For
example, a plurality of absorbent articles may be secured with a
first overwrap such as a thermoplastic film and then a plurality of
film wrapped absorbent articles may be secured in a second overwrap
such as a cardboard box or another thermoplastic film.
VI. Communicating a Related Environmental Message a Consumer
[0164] The present invention may further comprise a related
environmental message or may further comprise a step of
communicating a related environmental message to a consumer. The
related environmental message may convey the benefits or advantages
of the absorbent article comprising a polymer derived from a
renewable resource. The related environmental message may identify
the absorbent articles as: being environmentally friendly or Earth
friendly; having reduced petroleum (or oil) dependence or content;
having reduced foreign petroleum (or oil) dependence or content;
having reduced petrochemicals or having components that are
petrochemical free; and/or being made from renewable resources or
having components made from renewable resources. This communication
is of importance to consumers that may have an aversion to
petrochemical use (e.g., consumers concerned about depletion of
natural resources or consumers who find petrochemical based
products unnatural or not environmentally friendly) and to
consumers that are environmentally conscious. Without such a
communication, the benefit of the present invention may be lost on
some consumers.
[0165] The communication may be effected in a variety of
communication forms. Suitable communication forms include store
displays, posters, billboard, computer programs, brochures, package
literature, shelf information, videos, advertisements, internet web
sites, pictograms, iconography, or any other suitable form of
communication. The information could be available at stores, on
television, in a computer-accessible form, in advertisements, or
any other appropriate venue. Ideally, multiple communication forms
may be employed to disseminate the related environmental
message.
[0166] The communication may be written, spoken, or delivered by
way of one or more pictures, graphics, or icons. For example, a
television or internet based-advertisement may have narration, a
voice-over, or other audible conveyance of the related
environmental message. Likewise, the related environmental message
may be conveyed in a written form using any of the suitable
communication forms listed above. In certain embodiments, it may be
desirable to quantify the reduction of petrochemical usage of the
present absorbent article compared to absorbent articles that are
presently commercially available.
[0167] In other embodiments, the communication form may be one or
more icons. FIGS. 3A-F depict several suitable embodiments of a
communication in the form of icon 310. One or more icons 310 may be
used to convey the related environmental message of reduced
petrochemical usage. Suitable icons 310 communicating the related
environmental message of reduced petroleum usage are shown in FIGS.
3A-B. Icons communicating the related environmental message of
environmental friendliness or renewable resource usage are shown in
FIGS. 3C-F. In certain embodiments, the icons 310 may be located on
the package 200 (as shown in FIGS. 2A-B) containing the absorbent
articles, on the absorbent article, on an insert adjoining the
package or the articles, or in combination with any of the other
forms of the communication listed above.
[0168] The related environmental message may also include a message
of petrochemical equivalence. As presented in the Background, many
renewable, naturally occurring, or non-petroleum derived polymers
have been disclosed. However, these polymers often lack the
performance characteristics that consumers have come to expect when
used in absorbent articles. Therefore, a message of petroleum
equivalence may be necessary to educate consumers that the polymers
derived from renewable resources, as described above, exhibit
equivalent or better performance characteristics as compared to
petroleum derived polymers. A suitable petrochemical equivalence
message can include comparison to an absorbent article that does
not have a polymer derived from a renewable resource. For example,
a suitable combined message may be, "Diaper Brand A with an
environmentally friendly absorbent material is just as absorbent as
Diaper Brand B." This message conveys both the related
environmental message and the message of petrochemical
equivalence.
VII. Method of Making an Absorbent Article Having a Polymer Derived
from a Renewable Resource
[0169] The present invention further relates to a method for making
an absorbent article comprising a superabsorbent polymer derived
from a renewable resource. The method comprises the steps of
providing a renewable resource; deriving a monomer from the
renewable resource; polymerizing the monomer to form a synthetic
superabsorbent polymer having a Saline Flow Conductivity value of
at least about 30.times.10.sup.-7 cm.sup.3sec/g and an Absorption
Against Pressure value of at least about 15 g/g; and incorporating
said superabsorbent polymer into an absorbent article. The present
invention further relates to providing one or more of the absorbent
articles to a consumer and communicating reduced petrochemical
usage to the consumer. The polymer derived from renewable resources
may undergo additional process steps prior to incorporation into
the absorbent article. Such process steps include drying, sieving,
surface crosslinking, and the like.
[0170] The present invention further relates to a method for making
an absorbent article comprising a synthetic polyolefin derived from
a renewable resource. The method comprises the steps of providing a
renewable resource; deriving an olefin monomer from the renewable
resource; polymerizing the monomer to form a synthetic polyolefin
having a .sup.14C/C ratio of about 1.0.times.10.sup.-14 or greater;
and incorporating said polyolefin into an absorbent article. The
synthetic polyolefin exhibits one or more of the above referenced
performance characteristics. The present invention further relates
to providing one or more of the absorbent articles to a consumer
and communicating reduced petrochemical usage to the consumer. The
polymer derived from renewable resources may undergo additional
process steps prior to incorporation into the absorbent article.
Such process steps include, film formation, fiber formation, ring
rolling, and the like.
VIII. Validation of Polymers Derived from Renewable Resources
[0171] A suitable validation technique is through .sup.14C
analysis. A common analysis technique in carbon-14 dating is
measuring the ratio of .sup.14C to total carbon within a sample
(.sup.14C/C). Research has noted that fossil fuels and
petrochemicals generally have a .sup.14C/C ratio of less than about
1.times.10.sup.-15. However, polymers derived entirely from
renewable resources typically have a .sup.14C/C ratio of about
1.2.times.10.sup.-12. When compared, the polymers derived from
renewable resources may have a .sup.14C/C ratio three orders of
magnitude (10.sup.3=1,000) greater than the .sup.14C/C ratio of
polymers derived from petrochemicals. Polymers useful in the
present invention have a .sup.14C/C ratio of about
1.0.times.10.sup.-14 or greater. In other embodiments, the
petrochemical equivalent polymers of the present invention may have
a .sup.14C/C ratio of about 1.0.times.10.sup.-13 or greater or a
.sup.14C/C ratio of about 1.0.times.10.sup.-12 or greater. Suitable
techniques for .sup.14C analysis are known in the art and include
accelerator mass spectrometry, liquid scintillation counting, and
isotope mass spectrometry. These techniques are described in U.S.
Pat. Nos. 3,885,155, 4,427,884, 4,973,841, 5,438,194, and
5,661,299.
IX. Test Methods
[0172] Saline Flow Conductivity
[0173] The method to determine the permeability of a swollen
hydrogel layer 718 is the "Saline Flow Conductivity" also known as
"Gel Layer Permeability" and is described in several references,
including, EP A 640 330, filed on Dec. 1, 1993, U.S. Ser. No.
11/349,696, filed on Feb. 3, 2004, U.S. Ser. No. 11/347,406, filed
on Feb. 3, 2006, U.S. Ser. No. 06/682,483, filed on Sep. 30, 1982,
and U.S. Pat. No. 4,469,710, filed on Oct. 14, 1982. The equipment
used for this method is described below.
[0174] Permeability Measurement System
[0175] FIG. 4 shows permeability measurement system 400 set-up with
the constant hydrostatic head reservoir 414, open-ended tube for
air admittance 410, stoppered vent for refilling 412, laboratory
jack 416, delivery tube 418, stopcock 420, ring stand support 422,
receiving vessel 424, balance 426 and piston/cylinder assembly
428.
[0176] FIG. 5 shows the piston/cylinder assembly 428 comprising a
metal weight 512, piston shaft 514, piston head 518, lid 516, and
cylinder 520. The cylinder 520 is made of transparent polycarbonate
(e.g., Lexan.RTM.) and has an inner diameter p of 6.00 cm
(area=28.27 cm.sup.2) with inner cylinder walls 550 which are
smooth. The bottom 548 of the cylinder 520 is faced with a US.
Standard 400 mesh stainless-steel screen cloth (not shown) that is
bi-axially stretched to tautness prior to attachment to the bottom
548 of the cylinder 520. The piston shaft 514 is made of
transparent polycarbonate (e.g., Lexan.RTM.) and has an overall
length q of approximately 127 mm. A middle portion 526 of the
piston shaft 514 has a diameter r of 21.15 mm. An upper portion 528
of the piston shaft 514 has a diameter s of 15.8 mm, forming a
shoulder 524. A lower portion 546 of the piston shaft 514 has a
diameter t of approximately 5/8 inch and is threaded to screw
firmly into the center hole 618 (see FIG. 6) of the piston head
518. The piston head 518 is perforated, made of transparent
polycarbonate (e.g., Lexan.RTM.), and is also screened with a
stretched US. Standard 400 mesh stainless-steel screen cloth (not
shown). The weight 512 is stainless steel, has a center bore 530,
slides onto the upper portion 528 of piston shaft 514 and rests on
the shoulder 524. The combined weight of the piston head 518,
piston shaft 514 and weight 512 is 596 g (.+-.6 g ), which
corresponds to 0.30 psi over the area of the cylinder 520. The
combined weight may be adjusted by drilling a blind hole down a
central axis 532 of the piston shaft 514 to remove material and/or
provide a cavity to add weight. The cylinder lid 516 has a first
lid opening 534 in its center for vertically aligning the piston
shaft 514 and a second lid opening 536 near the edge 538 for
introducing fluid from the constant hydrostatic head reservoir 414
into the cylinder 520.
[0177] A first linear index mark (not shown) is scribed radially
along the upper surface 552 of the weight 512, the first linear
index mark being transverse to the central axis 532 of the piston
shaft 514. A corresponding second linear index mark (not shown) is
scribed radially along the top surface 560 of the piston shaft 514,
the second linear index mark being transverse to the central axis
532 of the piston shaft 514. A corresponding third linear index
mark (not shown) is scribed along the middle portion 526 of the
piston shaft 514, the third linear index mark being parallel with
the central axis 532 of the piston shaft 514. A corresponding
fourth linear index mark (not shown) is scribed radially along the
upper surface 540 of the cylinder lid 516, the fourth linear index
mark being transverse to the central axis 532 of the piston shaft
514. Further, a corresponding fifth linear index mark (not shown)
is scribed along a lip 554 of the cylinder lid 516, the fifth
linear index mark being parallel with the central axis 532 of the
piston shaft 514. A corresponding sixth linear index mark (not
shown) is scribed along the outer cylinder wall 542, the sixth
linear index mark being parallel with the central axis 532 of the
piston shaft 514. Alignment of the first, second, third, fourth,
fifth, and sixth linear index marks allows for the weight 512,
piston shaft 514, cylinder lid 516, and cylinder 520 to be
re-positioned with the same orientation relative to one another for
each measurement.
[0178] The cylinder 520 specification details are: [0179] Outer
diameter u of the Cylinder 520: 70.35 mm [0180] Inner diameter p of
the Cylinder 520: 60.0 mm [0181] Height v of the Cylinder 520: 60.5
mm
[0182] The cylinder lid 516 specification details are: [0183] Outer
diameter w of cylinder lid 516: 76.05 mm [0184] Inner diameter x of
cylinder lid 516: 70.5 mm [0185] Thickness y of cylinder lid 516
including lip 554: 12.7 mm [0186] Thickness z of cylinder lid 516
without lip: 6.35 mm [0187] Diameter a of first lid opening 534:
22.25 mm [0188] Diameter b of second lid opening 536: 12.7 mm
[0189] Distance between centers of first and second lid openings
534 and 536: 23.5 mm
[0190] The weight 512 specification details are: [0191] Outer
diameter c: 50.0 mm [0192] Diameter d of center bore 530: 16.0 mm
[0193] Height e: 39.0 mm
[0194] The piston head 518 specification details are [0195]
Diameter f: 59.7 mm [0196] Height g: 16.5 mm [0197] Outer holes 614
(14 total) with a 9.65 mm diameter h, outer holes 614 equally
spaced with centers being 47.8 mm from the center of center hole
618 [0198] Inner holes 616 (7 total) with a 9.65 mm diameter i,
inner holes 616 equally spaced with centers being 26.7 mm from the
center of center hole 618 [0199] Center hole 618 has a diameter j
of 5/8 inches and is threaded to accept a lower portion 546 of
piston shaft 514.
[0200] Prior to use, the stainless steel screens (not shown) of the
piston head 518 and cylinder 520 should be inspected for clogging,
holes or over-stretching and replaced when necessary. An SFC
apparatus with damaged screen can deliver erroneous SFC results,
and must not be used until the screen has been replaced.
[0201] A 5.00 cm mark 556 is scribed on the cylinder 520 at a
height k of 5.00 cm (.+-.0.05 cm) above the screen (not shown)
attached to the bottom 548 of the cylinder 520. This marks the
fluid level to be maintained during the analysis. Maintenance of
correct and constant fluid level (hydrostatic pressure) is critical
for measurement accuracy.
[0202] A constant hydrostatic head reservoir 414 is used to deliver
salt solution 432 to the cylinder 520 and to maintain the level of
salt solution 432 at a height k of 5.00 cm above the screen (not
shown) attached to the bottom 548 of the cylinder 520. The bottom
434 of the air-intake tube 410 is positioned so as to maintain the
salt solution 432 level in the cylinder 520 at the required 5.00 cm
height k during the measurement, i.e., bottom 434 of the air tube
410 is in approximately same plane 438 as the 5.00 cm mark 556 on
the cylinder 520 as it sits on the support screen (not shown) on
the ring stand 440 above the receiving vessel 424. Proper height
alignment of the air-intake tube 410 and the 5.00 cm mark 556 on
the cylinder 520 is critical to the analysis. A suitable reservoir
414 consists of a jar 430 containing: a horizontally oriented
L-shaped delivery tube 418 for fluid delivery, a vertically
oriented open-ended tube 410 for admitting air at a fixed height
within the constant hydrostatic head reservoir 414, and a stoppered
vent 412 for re-filling the constant hydrostatic head reservoir
414. Tube 410 has an internal diameter of xx mm. The delivery tube
418, positioned near the bottom 442 of the constant hydrostatic
head reservoir 414, contains a stopcock 420 for starting/stopping
the delivery of salt solution 432. The outlet 444 of the delivery
tube 418 is dimensioned to be inserted through the second lid
opening 536 in the cylinder lid 516, with its end positioned below
the surface of the salt solution 432 in the cylinder 520 (after the
5.00 cm height of the salt solution 432 is attained in the cylinder
520). The air-intake tube 410 is held in place with an o-ring
collar (not shown). The constant hydrostatic head reservoir 414 can
be positioned on a laboratory jack 416 in order to adjust its
height relative to that of the cylinder 520. The components of the
constant hydrostatic head reservoir 414 are sized so as to rapidly
fill the cylinder 520 to the required height (i.e., hydrostatic
head) and maintain this height for the duration of the measurement.
The constant hydrostatic head reservoir 414 must be capable of
delivering salt solution 432 at a flow rate of at least 3 g/sec for
at least 10 minutes.
[0203] The piston/cylinder assembly 428 is positioned on a 16 mesh
rigid stainless steel support screen (not shown) (or equivalent)
which is supported on a ring stand 440 or suitable alternative
rigid stand. This support screen (not shown) is sufficiently
permeable so as to not impede salt solution 432 flow and rigid
enough to support the stainless steel mesh cloth (not shown)
preventing stretching. The support screen (not shown) should be
flat and level to avoid tilting the piston/cylinder assembly 428
during the test. The salt solution 432 passing through the support
screen (not shown) is collected in a receiving vessel 424,
positioned below (but not supporting) the support screen (not
shown). The receiving vessel 424 is positioned on the balance 426
which is accurate to at least 0.01 g. The digital output of the
balance 426 is connected to a computerized data acquisition system
(not shown).
[0204] Preparation of Reagents (not Illustrated)
[0205] Jayco Synthetic Urine (JSU) 712 (see FIG. 7) is used for a
swelling phase (see SFC Procedure below) and 0.118 M Sodium
Chloride (NaCl) Solution is used for a flow phase (see SFC
Procedure below). The following preparations are referred to a
standard 1 liter volume. For preparation of volumes other than 1
liter, all quantities are scaled accordingly.
[0206] JSU: A 1 L volumetric flask is filled with distilled water
to 80% of its volume, and a magnetic stir bar is placed in the
flask. Separately, using a weighing paper or beaker the following
amounts of dry ingredients are weighed to within .+-.0.01 g using
an analytical balance and are added quantitatively to the
volumetric flask in the same order as listed below. The solution is
stirred on a suitable stir plate until all the solids are
dissolved, the stir bar is removed, and the solution diluted to 1 L
volume with distilled water. A stir bar is again inserted, and the
solution stirred on a stirring plate for a few minutes more.
[0207] Quantities of salts to make 1 liter of Jayco Synthetic
Urine: [0208] Potassium Chloride (KCl) 2.00 g [0209] Sodium Sulfate
(Na.sub.2SO.sub.4) 2.00 g [0210] Ammonium dihydrogen phosphate
(NH.sub.4H.sub.2PO.sub.4) 0.85 g [0211] Ammonium phosphate, dibasic
((NH.sub.4).sub.2HPO.sub.4) 0.15 g [0212] Calcium Chloride
(CaCl.sub.2) 0.19 g--[or hydrated calcium chloride [0213]
(CaCl.sub.2.2H.sub.2O) 0.25 g] [0214] Magnesium chloride
(MgCl.sub.2) 0.23 g--[or hydrated magnesium chloride [0215]
(MgCl.sub.2.6H.sub.2O) 0.50 g]
[0216] To make the preparation faster, each salt is completely
dissolved before adding the next one. Jayco synthetic urine may be
stored in a clean glass container for 2 weeks. The solution should
not be used if it becomes cloudy. Shelf life in a clean plastic
container is 10 days.
[0217] 0.118 M Sodium Chloride (NaCl) Solution: 0.118 M Sodium
Chloride is used as salt solution 432. Using a weighing paper or
beaker 6.90 g (.+-.0.01 g) of sodium chloride is weighed and
quantitatively transferred into a 1 L volumetric flask; and the
flask is filled to volume with distilled water. A stir bar is added
and the solution is mixed on a stirring plate until all the solids
are dissolved.
[0218] Test Preparation
[0219] Using a solid reference cylinder weight (not shown) (40 mm
diameter; 140 mm height), a caliper gauge (not shown) (e.g.,
Mitotoyo Digimatic Height Gage) is set to read zero. This operation
is conveniently performed on a smooth and level bench top 446. The
piston/cylinder assembly 428 without superabsorbent is positioned
under the caliper gauge (not shown) and a reading, L.sub.1, is
recorded to the nearest 0.01 mm.
[0220] The constant hydrostatic head reservoir 414 is filled with
salt solution 432. The bottom 434 of the air-intake tube 410 is
positioned so as to maintain the top part (not shown) of the liquid
meniscus (not shown) in the cylinder 520 at the 5.00 cm mark 556
during the measurement. Proper height alignment of the air-intake
tube 410 at the 5.00 cm mark 556 on the cylinder 520 is critical to
the analysis.
[0221] The receiving vessel 424 is placed on the balance 426 and
the digital output of the balance 426 is connected to a
computerized data acquisition system (not shown). The ring stand
440 with a 16 mesh rigid stainless steel support screen (not shown)
is positioned above the receiving vessel 424. The 16 mesh screen
(not shown) should be sufficiently rigid to support the
piston/cylinder assembly 428 during the measurement. The support
screen (not shown) must be flat and level.
[0222] SFC Procedure
[0223] 0.9 g (.+-.0.05 g) of superabsorbent is weighed onto a
suitable weighing paper using an analytical balance. 0.9 g
(.+-.0.05 g) of superabsorbent is weighed onto a suitable weighing
paper using an analytical balance. The moisture content of the
superabsorbent is measured according to the Edana Moisture Content
Test Method 430.1-99 ("Superabsorbent materials--Polyacrylate
superabsorbent powders--MOISTURE CONTENT--WEIGHT LOSS UPON HEATING"
(February 99)). If the moisture content of the polymer is greater
than 5%, then the polymer weight should be corrected for moisture
(i.e., the added polymer should be 0.9 g on a dry-weight
basis).
[0224] The empty cylinder 520 is placed on a level benchtop 446 and
the superabsorbent is quantitatively transferred into the cylinder
520. The superabsorbent particles are evenly dispersed on the
screen (not shown) attached to the bottom 548 of the cylinder 520
by gently shaking, rotating, and/or tapping the cylinder 520. It is
important to have an even distribution of particles on the screen
(not shown) attached to the bottom 548 of the cylinder 520 to
obtain the highest precision result. After the superabsorbent has
been evenly distributed on the screen (not shown) attached to the
bottom 548 of the cylinder 520 particles must not adhere to the
inner cylinder walls 550. The piston shaft 514 is inserted through
the first lid opening 534, with the lip 554 of the lid 516 facing
towards the piston head 518. The piston head 518 is carefully
inserted into the cylinder 520 to a depth of a few centimeters. The
lid 516 is then placed onto the upper rim 544 of the cylinder 520
while taking care to keep the piston head 518 away from the
superabsorbent. The lid 516 and piston shaft 526 are then carefully
rotated so as to align the third, fourth, fifth, and sixth linear
index marks are then aligned. The piston head 518 (via the piston
shaft 514) is then gently lowered to rest on the dry
superabsorbent. The weight 512 is positioned on the upper portion
528 of the piston shaft 514 so that it rests on the shoulder 524
such that the first and second linear index marks are aligned.
Proper seating of the lid 516 prevents binding and assures an even
distribution of the weight on the hydrogel layer 718.
[0225] Swelling Phase: An 8 cm diameter fritted disc (7 mm thick;
e.g. Chemglass Inc. # CG 201-51, coarse porosity) 710 is saturated
by adding excess JSU 712 to the fritted disc 710 until the fritted
disc 710 is saturated. The saturated fritted disc 710 is placed in
a wide flat-bottomed Petri dish 714 and JSU 712 is added until it
reaches the top surface 716 of the fritted disc 710. The JSU height
must not exceed the height of the fitted disc 710.
[0226] The screen (not shown) attached to the bottom 548 of the
cylinder 520 is easily stretched. To prevent stretching, a sideways
pressure is applied on the piston shaft 514, just above the lid
516, with the index finger while grasping the cylinder 520 of the
piston/cylinder assembly 428. This "locks" the piston shaft 514 in
place against the lid 516 so that the piston/cylinder assembly 428
can be lifted without undue force being exerted on the screen (not
shown).
[0227] The entire piston/cylinder assembly 428 is lifted in this
fashion and placed on the fritted disc 710 in the Petri dish 714.
JSU 712 from the Petri dish 714 passes through the fritted disc 710
and is absorbed by the superabsorbent polymer (not shown) to form a
hydrogel layer 718. The JSU 712 available in the Petri dish 714
should be enough for all the swelling phase. If needed, more JSU
712 may be added to the Petri dish 714 during the hydration period
to keep the JSU 712 level at the top surface 716 of the fritted
disc 710. After a period of 60 minutes, the piston/cylinder
assembly 428 is removed from the fritted disc 710, taking care to
lock the piston shaft 514 against the lid 516 as described above
and ensure the hydrogel layer 718 does not lose JSU 712 or take in
air during this procedure. The piston/cylinder assembly 428 is
placed under the caliper gauge (not shown) and a reading, L.sub.2,
is recorded to the nearest 0.01 mm. If the reading changes with
time, only the initial value is recorded. The thickness of the
hydrogel layer 718, L.sub.0 is determined from L.sub.2-L.sub.1 to
the nearest 0.1 mm.
[0228] The entire piston/cylinder assembly 428 is lifted in this
the fashion described above and placed on the support screen (not
shown) attached to the ring stand 440. Care should be taken so that
the hydrogel layer 718 does not lose JSU 712 or take in air during
this procedure. The JSU 712 available in the Petri dish 714 should
be enough for all the swelling phase. If needed, more JSU 712 may
be added to the Petri dish 714 during the hydration period to keep
the JSU 712 level at the 5.00 cm mark 556. After a period of 60
minutes, the piston/cylinder assembly 428 is removed, taking care
to lock the piston shaft 514 against the lid 516 as described
above. The piston/cylinder assembly 428 is placed under the caliper
gauge (not shown) and the caliper (not shown) is measured as
L.sub.2 to the nearest 0.01 mm. The thickness of the hydrogel layer
718, L.sub.0 is determined from L.sub.2-L.sub.1 to the nearest 0.1
mm. If the reading changes with time, only the initial value is
recorded.
[0229] The piston/cylinder assembly 428 is transferred to the
support screen (not shown) attached to the ring support stand 440
taking care to lock the piston shaft 514 in place against the lid
516. The constant hydrostatic head reservoir 414 is positioned such
that the delivery tube 418 is placed through the second lid opening
536. The measurement is initiated in the following sequence: [0230]
a) The stopcock 420 of the constant hydrostatic head reservoir 410
is opened to permit the salt solution 432 to reach the 5.00 cm mark
556 on the cylinder 520. This salt solution 432 level should be
obtained within 10 seconds of opening the stopcock 420. [0231] b)
Once 5.00 cm of salt solution 432 is attained, the data collection
program is initiated. With the aid of a computer (not shown)
attached to the balance 426, the quantity of salt solution 432
passing through the hydrogel layer 718 is recorded at intervals of
20 seconds for a time period of 10 minutes. At the end of 10
minutes, the stopcock 420 on the constant hydrostatic head
reservoir 410 is closed. The piston/cylinder assembly 428 is
removed immediately, placed under the caliper gauge (not shown) and
a reading, L.sub.3, is recorded to the nearest 0.01 mm. The final
thickness of the hydrogel layer 718, L.sub.f is determined from
L.sub.3-L.sub.1 to the nearest 0.1 mm, as described above. The
percent change in thickness of the hydrogel layer 718 is determined
from (L.sub.f/L.sub.0).times.100. Generally the change in thickness
of the hydrogel layer 718 is within about .+-.10%.
[0232] The data from 60 seconds to the end of the experiment are
used in the SFC calculation. The data collected prior to 60 seconds
are not included in the calculation. The flow rate F.sub.s (in g/s)
is the slope of a linear least-squares fit to a graph of the weight
of salt solution 432 collected (in grams) as a function of time (in
seconds) from 60 seconds to 600 seconds.
[0233] In a separate measurement, the flow rate through the
permeability measurement system 400 (F.sub.a) is measured as
described above, except that no hydrogel layer 718 is present. If
F.sub.a is much greater than the flow rate through the permeability
measurement system 400 when the hydrogel layer 718 is present,
F.sub.s, then no correction for the flow resistance of the
permeability measurement system 400 (including the piston/cylinder
assembly 428) is necessary. In this limit, F.sub.g.dbd.F.sub.s,
where F.sub.g is the contribution of the hydrogel layer 718 to the
flow rate of the permeability measurement system 400. However if
this requirement is not satisfied, then the following correction is
used to calculate the value of F.sub.g from the values of F.sub.s
and F.sub.a:
F.sub.g=(F.sub.a.times.F.sub.s)/(F.sub.a-F.sub.s)
The Saline Flow Conductivity (K) of the hydrogel layer 718 is
calculated using the following equation:
K=[F.sub.g(t=0).times.L.sub.0]/[.rho..times.A.times..DELTA.P],
where F.sub.g is the flow rate in g/sec determined from regression
analysis of the flow rate results and any correction due to
permeability measurement system 400 flow resistance, L.sub.0 is the
initial thickness of the hydrogel layer 718 in cm, p is the density
of the salt solution 432 in gm/cm.sup.3. A (from the equation
above) is the area of the hydrogel layer 718 in cm.sup.2, .DELTA.P
is the hydrostatic pressure in dyne/cm.sup.2, and the saline flow
conductivity, K, is in units of cm.sup.3 sec/gm. The average of
three determinations should be reported.
[0234] For hydrogel layers 718 where the flow rate is substantially
constant, a permeability coefficient (.kappa.) can be calculated
from the saline flow conductivity using the following equation:
.kappa.=K.eta.
where .eta. is the viscosity of the salt solution 432 in poise and
the permeability coefficient, .kappa., is in units of cm.sup.2.
[0235] In general, flow rate need not be constant. The
time-dependent flow rate through the system, F.sub.s (t) is
determined, in units of g/sec, by dividing the incremental weight
of salt solution 432 passing through the permeability measurement
system 400 (in grams) by incremental time (in seconds). Only data
collected for times between 60 seconds and 10 minutes is used for
flow rate calculations. Flow rate results between 60 seconds and 10
minutes are used to calculate a value for F.sub.s (t=0), the
initial flow rate through the hydrogel layer 718. F.sub.s (t=0) is
calculated by extrapolating the results of a least-squares fit of
F.sub.s (t) versus time to t=0.
[0236] Absorption Against Pressure
[0237] This test measures the amount of a 0.90% saline solution
absorbed by superabsorbent polymers that are laterally confined in
a piston/cylinder assembly under a confining pressure for a period
of one hour. European Disposables and Nonwovens Association (EDANA)
test method 442.2-02 entitled "Absorption Under Pressure" is
used.
[0238] Basis Weight
[0239] This test measures the mass per unit area for a substrate.
European Disposables and Nonwovens Association (EDANA) test method
40.3-90 entitled "Mass Per Unit Area" is used.
[0240] Liquid Strike-Through
[0241] This test measures the time it takes for a known volume of
liquid applied to the surface of a substrate to pass through the
substrate to an underlying absorbent pad. European Disposables and
Nonwovens Association (EDANA) test method 150.4-99 entitled "Liquid
Strike-Through Time" is used.
[0242] Tensile Test
[0243] This test measures the peak load exhibited by a substrate. A
preferred piece of equipment to do the test is a tensile tester
such as a MTS Synergie100 or a MTS Alliance, fitted with a computer
interface and Testworks 4 software, available from MTS Systems
Corporation 14000 Technology Drive, Eden Prairie, Minn. USA. This
instrument measures the Constant Rate of Extension in which the
pulling grip moves at a uniform rate and the force measuring
mechanism moves a negligible distance (less than 0.13 mm) with
increasing force. The load cell is selected such that the measured
loads (e.g., force) of the tested samples will be between 10 and
90% of the capacity of the load cell (typically a 25N or 50N load
cell).
[0244] A 1.times.1 inch (2.5.times.2.5 cm) sample is die-cut from
the substrate using an anvil hydraulic press die to cut the film
with the die into individual samples. A minimum of three samples
are created which are substantially free of visible defects such as
air bubbles, holes, inclusions, and cuts. Each sample must have
smooth and substantially defect-free edges. Testing is performed in
a conditioned room having a temperature of 23.degree. C.
(.+-.1.degree. C.) and a relative humidity of 50% (.+-.2%) for at
least 2 hours. Samples are allowed to equilibrate in the
conditioned room for at least 2 hours prior to testing.
[0245] Pneumatic jaws of the tensile tester, fitted with flat 2.54
cm-square rubber-faced grips, are set to give a gauge length of
2.54 cm. The sample is loaded with sufficient tension to eliminate
observable slack, but less than 0.05N. The sample is extended at a
constant crosshead speed of 25.4 cm/min until the specimen
completely breaks. If the sample breaks at the grip interface or
slippage within the grips is detected, then the data is disregarded
and the test is repeated with a new sample and the grip pressure is
appropriately adjusted. Samples are run at least in triplicate to
account for film variability.
[0246] The resulting tensile force-displacement data are converted
to stress-strain curves. Peak load is defined as the maximum stress
measured as a specimen is taken to break, and is reported in
Newtons per centimeter width (as measured parallel to the grips) of
the sample. The peak load for a given substrate is the average of
the respective values of each sample from the substrate.
[0247] Moisture Vapor Transmission Rate (MVTR) Test
[0248] The MVTR test method measures the amount of water vapor that
is transmitted through a film under specific temperature and
humidity. The transmitted vapor is absorbed by CaCl.sub.2 desiccant
and determined gravimetrically. Samples are evaluated in
triplicate, along with a reference film sample of established
permeability (e.g., Exxon Exxaire microporous material #XBF-110W)
that is used as a positive control.
[0249] This test uses a flanged cup machined from Delrin
(McMaster-Carr Catalog #8572K34) and anhydrous CaCl.sub.2 (Wako
Pure Chemical Industries, Richmond, Va.; Catalog 030-00525).
[0250] The height of the cup is 55 mm with an inner diameter of 30
mm and an outer diameter of 45 mm. The cup is fitted with a
silicone gasket and lid containing 3 holes for thumb screws to
completely seal the cup.
[0251] The cup is filled with CaCl.sub.2 to within 1 cm of the top.
The cup is tapped on the counter 10 times, and the CaCl.sub.2
surface is leveled. The amount of CaCl.sub.2 is adjusted until the
headspace between the film surface and the top of the CaCl.sub.2 is
1.0 cm. The film is placed on top of the cup across the opening (30
mm) and is secured using the silicone gasket, retaining ring, and
thumb screws. Properly installed, the specimen should not be
wrinkled or stretched.
[0252] The film must completely cover the cup opening, A, which is
0.0007065 m.sup.2.
[0253] The sample assembly is weighed with an analytical balance
and recorded to .+-.0.001 g. The assembly is placed in a constant
temperature (40.+-.3.degree. C.) and humidity (75.+-.3% RH) chamber
for 5.0 hr.+-.5 min. The sample assembly is removed, covered with
Saran Wrap.RTM. and is secured with a rubber band. The sample is
equilibrated to room temperature for 30 min, the plastic wrap
removed, and the assembly is reweighed and the weight is recorded
to .+-.0.001 g. The absorbed moisture M.sub.a is the difference in
initial and final assembly weights. MVTR, in g/m.sup.2/24 hr
(g/m.sup.2/24 hours), is calculated as:
MVTR = ( M a .times. 24 ) ( A .times. 5 hours ) ##EQU00001##
Replicate results are averaged and rounded to the nearest 100
g/m.sup.2/24 hr, e.g., 2865 g/m.sup.2/24 hours is herein given as
2900 g/m.sup.2/24 hours and 275 g/m.sup.2/24 hours is given as 300
g/m.sup.2/24 hours.
[0254] Hydrohead
[0255] The Hydrohead test method measures the resistance of
substrates (e.g., particularly nonwovens) to the penetration of
water. World Strategic Partners (WSP) test method 80.6 (05)
entitled "Standard Test Method for Evaluation of Water Resistance
(Hydrostatic Pressure) Test" is used. WSP methods are harmonized
test methods formulated by EDANA and the Association of the
Nonwoven Fabrics Industry (INDA). The test is to be run with an
incoming water supply rate of 10.+-.0.5 cm water/minute.
X. EXAMPLES
Example 1
Polyolefin
[0256] A suitable polyolefin may be created according to the
following method. An exemplary renewable resource is corn. The corn
is cleaned and may be degerminated. The corn is milled to produce a
fine powder (e.g., cornmeal) suitable for enzymatic treatment. The
hydrolysis (e.g., liquification and saccharification) of the corn
feedstock to yield fermentable sugars is well known in the
agricultural and biofermentation arts. A suitable preparation
pathway is disclosed in U.S. Pat. No. 4,407,955. A slurry of dry
milled corn is created by adding water to the milled corn and an
aqueous solution of sulfuric acid (98% acid by weight). Sufficient
sulfuric acid should be added to provide a slurry pH of about 1.0
to about 2.5. The slurry is heated to about 140.degree. C. to about
220.degree. C. and pressurized to at least about 50 psig; however,
pressures from about 100 psig to about 1,000 psig may result in
greater conversion of the starch to fermentable sugars. The slurry
is maintained at the aforementioned temperature and pressure for a
few seconds up to about 10 minutes. The slurry may be conveyed
through one or more pressure reduction vessels which reduce the
pressure and temperature of hydrolyzed slurry. The slurry is
subjected to standard separation techniques such as by centrifuge
to yield a fermentable sugar liquor. The liquor typically has a
dextrose equivalent of at least 75. The resulting sugar liquor is
fermented according to processes well know to a skilled artisan
using a suitable strain of yeast (e.g., genus of Saccharomyces).
The resulting ethanol may be separated from the aqueous solution by
standard isolation techniques such as evaporation or
distillation.
[0257] Ethanol is dehydrated to form ethylene by heating the
ethanol with an excess of concentrated sulfuric acid to a
temperature of about 170.degree. C. Ethylene may also be formed by
passing ethanol vapor over heated aluminum oxide powder.
[0258] The resulting ethylene is polymerized using any of the well
known polymerization techniques such as free radical
polymerization, Ziegler-Natta polymerization, or metallocene
catalyst polymerization. Low density branched polyethylene (LDPE)
is often made by free radical vinyl polymerization. Linear low
density polyethylene (LLDPE) is made by a more complicated
procedure called Ziegler-Natta polymerization. The resulting
polyethylene or blends thereof may be processed to yield a desired
end product such as a film, fiber, or filament.
[0259] As an example, a linear low density polyethylene is made by
copolymerizing ethylene with other longer chain olefins to result
in a polymer having a density of about 0.915 g/cm.sup.3 to about
0.925 g/cm.sup.3. A 49 grams/meter (gsm) cast extruded film is made
comprising the linear low density polyethylene and about 35% by
weight to about 45% by weight calcium carbonate (available from
English China Clay of America, Inc. under the designation
Supercoat.TM.). The film may be made porous via several routes. The
film may be warmed and elongated to 500% of the film's original
length using well known elongation methods and machinery. The
resulting microporous film is capable of exhibiting a MVTR of at
least 2000 g/m.sup.2/24 hours. Alternately, the film may be
incrementally stretched according to the method disclosed in U.S.
Pat. No. 6,605,172. The resulting microporous film should exhibit a
MVTR of at least 2000 g/m.sup.2/24 hours.
[0260] A nonwoven spunbond web may be formed according to methods
well known in the art such as evidenced by U.S. Pat. Nos. 4,405,297
and 4,340,563. The web is formed to have a basis weight of about 5
gsm to about 35 gsm. The individual filaments can have an average
denier of about 5 or less. The individual filaments may have a
variety of cross-sectional shapes. A suitable cross-sectional shape
is a bilobal shape disclosed in U.S. Pat. No. 4,753,834. The
resultant nonwoven may be made more hydrophilic by incorporating a
surfactant in the nonwoven as described in U.S. Statutory Invention
Registration No. H1670. The nonwoven treated to be more hydrophilic
is suitable for use as a topsheet in an absorbent article. The
nonwoven should exhibit a Liquid Strike-Through Time of less than
about 4 seconds. The resultant nonwoven may be made more
hydrophobic by use of a surface coating as described in U.S.
Publication No. 2005/0177123A1. The nonwoven treated to be more
hydrophobic is suitable for use a cuff substrate in an absorbent
article. The treated nonwoven should exhibit a hydrohead of at
least about 5 mbar.
Example 2
Superabsorbent Polymer
[0261] Preparation of Glycerol
[0262] Canola oil is obtained by expressing from canola seeds.
Approximately 27.5 kg of canola oil, 5.3 kg methanol and 400 g
sodium methoxide are charged to a 50 L round-bottomed flask
equipped with a heating mantle, thermometer, nitrogen inlet,
mechanical stirrer, and reflux condenser. A glass eduction tube
(dip tube) is situated so that liquid can be removed from the
bottom of the flask by means of a peristaltic pump. The flask is
purged with nitrogen and the mixture in the flask is heated to
65.degree. C. with stirring. The mixture is allowed to reflux for
2.5 hours, then the heat is turned off, agitation is stopped and
the mixture allowed to settle for 20 minutes. The bottom layer is
pumped out of the flask and kept for further use (Fraction 1).
Approximately 1.4 kg methanol and 230 g sodium methoxide are added
to the flask, agitation is resumed, and the mixture refluxed at
65.degree. C. for another 2 hours. The heat is turned off,
approximately 2.8 L of water are added to the flask and the mixture
is stirred for 1 minute. The stirrer is turned off and the mixture
allowed to settle for 20 minutes. The bottom layer is then pumped
out of the flask and kept for further use (Fraction 2).
Approximately 1.6 L of water is added to the flask, and the mixture
is stirred for 1 minute. The stirrer is turned off and the mixture
allowed to settle for 20 minutes. The bottom layer is then pumped
out of the flask and kept for further use (Fraction 3). Fractions
1, 2 and 3 are combined in a suitable flask equipped with a
magnetic stirrer. The combined fractions are stirred to form a
homogeneous mixture and heated to 82.degree. C. Sodium hydroxide
solution (50%) is added slowly until the pH of the mixture is 11-13
and the temperature is maintained at 82.degree. C. for a further 10
minutes. The pH is checked and more NaOH solution added if <11.
The solution is concentrated at 115.degree. C. under a vacuum of
approximately 40 mm Hg until bubbling ceases (water content<5%).
The solution is transferred to a round bottomed flask and the
glycerol is vacuum distilled using a rotary evaporator with the oil
bath temperature at 170.degree. C. and the condenser at
130-140.degree. C. The vacuum is controlled to achieve a moderate
distillation rate. A center cut of distilled glycerol is
collected.
[0263] Preparation of Acrolien
[0264] Approximately 200 g of fused aluminum oxide, 6-12 US
standard mesh, primarily .alpha.-phase, is mixed with 50 g of a 20%
solution of phosphoric acid for one hour. The mixture is dried
under vacuum by means of a rotary evaporator with the oil bath
temperature at 80.degree. C. A stainless steel tube (chromatography
column) with an internal diameter of approximately 15 mm and
contour length approximately 60 cm is packed with the dried
particles. The column is installed in a gas chromatogram instrument
with the inlet connected to the injector port, and the outlet
connected to a condenser and collection vessel. The column and
injector port are heated to 300.degree. C. and a 20% aqueous
solution of glycerol derived from canola oil is injected at a rate
of 40 mL/h. An inert carrier gas such as helium is optionally
utilized to help transport the vapor through the column. The vapors
emanating from the column outlet are condensed and collected.
Acrolein is isolated from the condensate by fractional distillation
or other suitable methods known to those skilled in the art.
Preparation of Acrylic Acid
[0265] A Pyrex glass reactor approximately 12 cm.times.2.5 cm OD
equipped with a thermowell is packed with 31 g (30 mL bulk volume)
of a catalyst containing 2 wt % palladium and 0.5 wt % copper
supported on alumina. The reactor is heated in an oil bath at
152.degree. C. A gaseous stream consisting of 3.4% acrolien, 14.8%
oxygen, 22.9% steam, and 58.5% nitrogen by volume, is passed
through the heated catalyst at such a rate that the superficial
contact time was about 5 seconds. The reaction mixture is then
passed through two water scrubbers connected in series held at
0.degree. C. The aqueous solutions collected are combined and
acrylic acid separated from the mixture by fractional
distillation.
[0266] Preparation of Superabsorbent Polymer
[0267] L-Ascorbic Acid (0.2081 g, 1.18 mmol) is added to a 100 mL
volumetric flask and is dissolved in distilled water (approximately
50 mL). After approximately ten minutes the solution is diluted to
the 100 mL mark on the volumetric flask with distilled water and
the flask was inverted and agitated to ensure a homogeneous
solution.
[0268] To a 3 L jacketed resin kettle is added TMPTA (0.261 g,
0.881 mmol), acrylic acid (296.40 g, 4.11 mol), and distilled water
(250 g). Water is circulated through the jacket of the resin kettle
by means of a circulating water bath kept at 25.degree. C. To the
monomer solution is added standard 5N sodium hydroxide solution
(576 mL, 2.88 mol). The resin kettle is capped with a lid having
several ports. An overhead mechanical stirrer is set up using an
air-tight bushing in the central port. A thermometer is inserted
through a seal in another port so that the bulb of the thermometer
is immersed in the mixture throughout the reaction. The solution is
stirred using the overhead mechanical stirrer and purged with
nitrogen using a fritted gas dispersion tube for approximately
fifteen minutes. Nitrogen is vented from the kettle via an 18-gauge
syringe needle inserted through a septum in the lid.
[0269] After approximately fifteen minutes the fritted gas
dispersion tube is raised above the surface of the monomer solution
and nitrogen was kept flowing through the headspace of the kettle.
A solution of sodium persulfate (0.4906 g, 2.06 mmol) in distilled
water (5 mL), and then a small aliquot of the L-ascorbic acid
solution (1 mL, 1.18 mmol) is added via syringe. The mechanical
stirrer is stopped when the vortex in the polymer solution
disappears due to the increase in viscosity of the solution (a few
seconds after adding the L-ascorbic acid solution). The
polymerization reaction proceeds with the circulating bath at
25.degree. C. for 30 minutes. After 30 minutes the temperature of
the water bath is increased to 40.degree. C. and held for an
additional 30 minutes. The temperature of the water bath is then
increased to 50.degree. C. and held for another hour. The peak
temperature of the static polymerization is approximately
70.degree. C.
[0270] After one hour at 50.degree. C. the circulating water bath
is turned off. The resin kettle is opened; the polyacrylate gel is
removed and broken into chunks approximately 2 cm in diameter.
These are chopped into smaller particles using a food grinder
attachment with 4.6 mm holes on a Kitchen-Aid mixer (Proline Model
KSM5). Distilled water is added periodically from a squirt bottle
to the infeed portion of the grinder to facilitate passage of the
bulk gel through the grinder. Approximately 200 g of distilled
water is used for this purpose. The chopped gel is spread into thin
layers on two separate polyester mesh screens each measuring
approximately 56 cm.times.48 cm and dried at 150.degree. C. for 90
minutes in a vented oven in a fashion which allows passage of air
through the mesh.
[0271] The dried gel is then milled through a Laboratory Wiley Mill
using a 20-mesh screen. Care is taken to ensure that the screen
does not become clogged during the grinding process. The milled
dried gel is sieved to obtain a fraction with particles which pass
through a No. 20 USA Standard Testing Sieve and are retained on a
No. 270 USA Standard Testing Sieve. The `on 20` and `through 270`
fractions are discarded.
[0272] The resultant free-flowing powder fraction `through 20` and
`on 270` is dried under vacuum at room temperature until further
use.
[0273] A 50% solution of ethylene carbonate (1,3-dioxolan-2-one) is
prepared by dissolving 10.0 grams of ethylene carbonate in 10.0
grams of distilled water.
[0274] 100.00 grams of the dried `through 20` and `on 270` powder
above are added to a stainless steel mixing bowl (approximately 4
L) of a Kitchen Aid mixer (Proline Model KSM5) equipped with a
stainless steel wire whisk. The height of the mixing bowl is
adjusted until the wire whisk just contacts the bowl. The whisk is
started and adjusted to a speed setting of `6` to stir the
particles. Immediately thereafter, 15 grams of the above 50 wt %
ethylene carbonate solution is added to the stirred AGM via a 10 mL
plastic syringe equipped with a four inch 22-gauge needle. The
solution is added directly onto the stirred particles over a period
of several seconds. The syringe is weighed before and after the
addition of solution to determine the amount added to the
particles. After the solution is added, the mixture is stirred for
approximately thirty seconds to help ensure an even coating. The
resultant mixture is quite homogeneous with no obvious large clumps
of material or residual dry powder. The mixture is then immediately
transferred to a Teflon lined 20 cm.times.35 cm metal tray, spread
into a thin layer and placed into a vented oven at 185.degree. C.
for one hour.
[0275] After one hour, the mixture is removed from the oven and
allowed to cool for approximately one minute. After cooling the
powder is placed in a 12 cm diameter mortar and any agglomerated
pieces are gently broken apart with a pestle. The resultant powder
is sieved to obtain a fraction which passes through a No. 20 US
standard screen, but is retained on a No. 270 US standard
screen.
[0276] The resultant `through 20` and `on 270` superabsorbent
polymer particles are stored under vacuum at room temperature until
further use. The AAP value for this material is measured according
to the EDANA test method 442.2-02, and the SFC value is measured
according to the SFC Test Method described above. The AAP value is
found to be about 21 g/g, and the SFC value is found to be about
50.times.10.sup.-7 cm.sup.3sec/g
[0277] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm"
[0278] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention. To the
extent that any definition or meaning of a term in this written
document conflicts with any definition or meaning of the term in a
document incorporated by reference, the definition or meaning
assigned to the term in this document shall govern.
[0279] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It should be apparent that combinations of such
embodiments and features are possible and can result in executions
within the scope of this invention. It is therefore intended to
cover in the appended claims all such changes and modifications
that are within the scope of this invention.
* * * * *