U.S. patent application number 09/853131 was filed with the patent office on 2003-04-24 for multicomponent fibers comprising starch and polymers.
This patent application is currently assigned to THE PROCTER & GAMBLE COMPANY. Invention is credited to Autran, Jean-Philippe Marie, Bond, Eric Bryan, Mackey, Larry Neil, Noda, Isao, O'Donnell, Hugh Joseph, Phan, Dean Van.
Application Number | 20030077444 09/853131 |
Document ID | / |
Family ID | 25315144 |
Filed Date | 2003-04-24 |
United States Patent
Application |
20030077444 |
Kind Code |
A1 |
Bond, Eric Bryan ; et
al. |
April 24, 2003 |
Multicomponent fibers comprising starch and polymers
Abstract
The present invention is directed to multicomponent fibers. The
fibers may be in a side-by-side, sheath-core, segmented pie,
islands-in-the-sea configuration, or any combination of
configurations. Each component of the fiber will comprise
destructurized starch and/or a thermoplastic polymer. The present
invention is also directed to nonwoven webs and disposable articles
comprising the multicomponent fibers. The nonwoven webs may also
contain other synthetic or natural fibers blended with the
multicomponent fibers of the present invention.
Inventors: |
Bond, Eric Bryan;
(Maineville, OH) ; Autran, Jean-Philippe Marie;
(Wyoming, OH) ; Mackey, Larry Neil; (Fairfield,
OH) ; Noda, Isao; (Fairfield, OH) ; O'Donnell,
Hugh Joseph; (Cincinnati, OH) ; Phan, Dean Van;
(West Chester, OH) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY
INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Assignee: |
THE PROCTER & GAMBLE
COMPANY
|
Family ID: |
25315144 |
Appl. No.: |
09/853131 |
Filed: |
May 10, 2001 |
Current U.S.
Class: |
428/364 ;
428/373 |
Current CPC
Class: |
D01F 8/12 20130101; D01F
8/10 20130101; A61F 2013/51028 20130101; Y10T 428/2929 20150115;
Y10T 442/641 20150401; Y10T 428/2904 20150115; Y10T 428/2913
20150115; D04H 1/42 20130101; D01F 8/14 20130101; D04H 1/54
20130101; Y10T 428/2924 20150115; Y10T 428/2931 20150115; A61F
2013/51035 20130101; D01F 8/06 20130101; Y10T 442/642 20150401;
D01F 8/18 20130101; A61F 2013/51026 20130101; Y10T 428/2927
20150115; Y10T 442/637 20150401; Y10T 442/652 20150401; Y10T
442/651 20150401 |
Class at
Publication: |
428/364 ;
428/373 |
International
Class: |
D02G 003/00 |
Claims
What is claimed is:
1. A multicomponent fiber having a configuration selected from the
group consisting of sheath-core, islands-in-the-sea, ribbon,
segmented pie, side-by-side, and combination thereof; wherein each
component of the multicomponent fiber comprises a material selected
from group consisting of destructurized starch, thermoplastic
polymer having a molecular weight of less than 500,000 g/mol, and
combinations thereof.
2. The multicomponent fiber of claim 1 wherein one component
comprises: a. destructurized starch, b. a thermoplastic polymer
having a molecular weight of less than about 500,000, and c. a
plasticizer.
3. The multicomponent fiber of claim 1 wherein one component
comprises destructurized starch and a second component comprises a
thermoplastic polymer having a molecular weight of less than about
500,000 g/mol.
4. The multicomponent fiber of claim 1 wherein the fiber has a
diameter of less than 200 micrometers.
5. The multicomponent fiber of claim 1 where the fiber is
splittable.
6. The multicomponent fiber of claim 1 wherein the fiber is
thermally bondable.
7. A nonwoven web comprising the multicomponent fibers of claim
6.
8. A nonwoven web wherein the multicomponent fibers of claim 6 are
blended with other synthetic or natural fibers and bonded
together.
9. A disposable article comprising the nonwoven web of claim 7.
10. A nonwoven web comprising multicomponent fibers having a
configuration selected from the group consisting of sheath-core,
islands-in-the-sea, ribbon, segmented pie, side-by-side, and
combination thereof; wherein each component of the multicomponent
fiber comprises a material selected from group consisting of
destructurized starch, thermoplastic polymer having a molecular
weight of less than 500,000 g/mol, and combinations thereof.
11. A nonwoven web wherein the multicomponent fibers of claim 9 are
blended with other synthetic or natural fibers and bonded
together.
12. A disposable article comprising the nonwoven webs of claim
9.
13. A bicomponent fiber having a sheath-core configuration wherein
the sheath comprises destructurized starch and a plasticizer and
the core comprises a thermoplastic polymer having a molecular
weight of less than 500,000 g/mol.
14. A bicomponent fiber having a sheath-core configuration wherein
the sheath comprises a thermoplastic polymer having a molecular
weight of less than 500,000 g/mol and the core comprises
destructurized starch and a plasticizer.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to multicomponent fibers
comprising starch and polymers and specific configurations of the
fibers. The fibers are used to make nonwoven webs and disposable
articles.
BACKGROUND OF THE INVENTION
[0002] There have been many attempts to make nonwoven articles.
However, because of costs, the difficultly in processing, and
end-use properties, there are only a limited number of options.
Many compositions have limited processability.
[0003] Useful fibers for nonwoven article are difficult to produce
and pose additional challenges compared to films and laminates.
This is because the material and processing characteristics for
fibers is much more stringent than for producing films,
blow-molding articles, and injection-molding articles. For the
production of fibers, the processing time during structure
formation is typically much shorter and flow characteristics are
more demanding on the material's physical and rheological
characteristics. The local strain rate and shear rate are much
greater in fiber production than other processes. Additionally, a
homogeneous composition is required for fiber spinning. For
spinning very fine fibers, small defects, slight inconsistencies,
or non-homogeneity in the melt are not acceptable for a
commercially viable process.
[0004] Attempts have been made to process natural starch on
standard equipment and existing technology known in the plastic
industry. Fibers comprising starch are desired as the starch is
environmentally degradable. Since natural starch generally has a
granular structure, it needs to be "destructurized" before it can
be melt processed into fine denier filaments. Modified starch
(alone or as the major component of a blend) has been found to have
poor melt extensibility resulting in difficulty in successfully
production of fibers, films, foams or the like. Additionally,
starch fibers are difficult to spin and are virtually unusable to
make nonwovens due to the low tensile strength, stickiness, and the
inability to be bonded to form nonwovens.
[0005] To produce fibers that have more acceptable processability
and end-use properties, thermoplastic polymers need to be combined
with starch. Selection of a suitable polymer that is acceptable for
blending with starch is challenging. The polymer must have good
spinning properties and a suitable melting temperature. The melting
temperature must be high enough for end-use stability to prevent
melting or structural deformation, but not too high of a melting
temperature to be able to be processable with starch without
burning the starch. These requirements make selection of a
thermoplastic polymer to produce starch-containing multicomponent
fibers very difficult.
[0006] Consequently, there is a need for a cost-effective and
easily processable multicomponent fibers made of natural starches
and thermoplastic polymers. Moreover, the starch and polymer
composition should be suitable for use in commercially available
equipment used to make the multicomponent fibers. There is also a
need for disposable, nonwoven articles made from these
multicomponent fibers.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to multicomponent fibers.
The configuration of the multicomponent fibers may be side-by-side,
sheath-core, segmented pie, islands-in-the-sea, or any combination
of configurations. Each component of the fiber will comprise
destructurized starch and/or a thermoplastic polymer.
[0008] The present invention is also directed to nonwoven webs and
disposable articles comprising the multicomponent fibers. The
nonwoven webs may also contain other synthetic or natural fibers
blended with the multicomponent fibers of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] These and other features, aspects and advantages of the
present invention will become better understood with regard to the
following description, appended claims, and accompanying drawings
where:
[0010] FIG. 1 is schematic drawings illustrating a cross-sectional
view of a bicomponent fiber having a sheath-core configuration.
[0011] FIG. 2 is schematic drawings illustrating a cross-sectional
view of a bicomponent fiber having a segmented pie
configuration.
[0012] FIG. 3 is schematic drawing illustrating a cross-sectional
view of a bicomponent fiber having a ribbon configuration.
[0013] FIG. 4 is schematic drawings illustrating a cross-sectional
view of a bicomponent fiber having a side-by-side
configuration.
[0014] FIG. 5 is schematic drawings illustrating a cross-sectional
view of a bicomponent fiber having an islands-in-the-sea
configuration.
[0015] FIG. 6 is schematic drawing illustrating a cross-sectional
view of a tricomponent fiber having a ribbon configuration.
[0016] FIG. 7 is schematic drawing illustrating a cross-sectional
view of a tricomponent fiber having a concentric sheath-core
configuration.
[0017] FIG. 8 is schematic drawing illustrating a cross-sectional
view of a multicomponent fiber having a eight segmented pie
configuration.
[0018] FIG. 9 is a schematic drawing illustrating a cross-sectional
view of a tricomponent fiber having an islands-in-the-sea
configuration.
DETAILED DESCRIPTION OF THE INVENTION
[0019] All percentages, ratios and proportions used herein are by
weight percent of the composition, unless otherwise specified. The
Examples are given in parts of the total composition.
[0020] The specification contains a detailed description of (1)
materials of the present invention, (2) configuration of the
multicomponent fibers, (3) material properties of the
multicomponent fibers, (4) processes, and (5) articles.
[0021] (1) Materials
[0022] Starch
[0023] The present invention relates to the use of starch, a low
cost naturally occurring polymer. The starch used in the present
invention is destructurized starch, which is necessary for adequate
spinning performance and fiber properties. The term "thermoplastic
starch" is used to mean destructured starch with a plasticizer.
[0024] Since natural starch generally has a granular structure, it
needs to be destructurized before it can be melt processed and spun
like a thermoplastic material. For gelatinization, the starch can
be destructurized in the presence of a solvent which acts as a
plasticizer. The solvent and starch mixture is heated, typically
under pressurized conditions and shear to accelerate the
gelatinization process. Chemical or enzymatic agents may also be
used to destructurize, oxidize, or derivatize the starch. Commonly,
starch is destructurized by dissolving the starch in water. Fully
destructured starch results when no lumps impacting the fiber
spinning process are present.
[0025] Suitable naturally occurring starches can include, but are
not limited to, corn starch, potato starch, sweet potato starch,
wheat starch, sago palm starch, tapioca starch, rice starch,
soybean starch, arrow root starch, bracken starch, lotus starch,
cassava starch, waxy maize starch, high amylose corn starch, and
commercial amylose powder. Blends of starch may also be used.
[0026] Though all starches are useful herein, the present invention
is most commonly practiced with natural starches derived from
agricultural sources, which offer the advantages of being abundant
in supply, easily replenishable and inexpensive in price. Naturally
occurring starches, particularly corn starch, wheat starch, and
waxy maize starch, are the preferred starch polymers of choice due
to their economy and availability.
[0027] Modified starch may also be used. Modified starch is defined
as non-substituted or substituted starch that has had its native
molecular weight characteristics changed (i.e. the molecular weight
is changed but no other changes are necessarily made to the
starch). If modified starch is desired, chemical modifications of
starch typically include acid or alkali hydrolysis and oxidative
chain scission to reduce molecular weight and molecular weight
distribution. Natural, unmodified starch generally has a very high
average molecular weight and a broad molecular weight distribution
(e.g. natural corn starch has an average molecular weight of up to
about 60,000,000 grams/mole (g/mol)). The average molecular weight
of starch can be reduced to the desirable range for the present
invention by acid reduction, oxidation reduction, enzymatic
reduction, hydrolysis (acid or alkaline catalyzed),
physical/mechanical degradation (e.g., via the thermomechanical
energy input of the processing equipment), or combinations thereof.
The thermomechanical method and the oxidation method offer an
additional advantage when carried out in situ. The exact chemical
nature of the starch and molecular weight reduction method is not
critical as long as the average molecular weight is in an
acceptable range. Ranges of molecular weight for starch or starch
blends added to the melt is from about 3,000 g/mol to about
2,000,000 g/mol, preferably from about 10,000 g/mol to about
1,000,000 g/mol, and more preferably from about 20,000 g/mol to
about 700,000 g/mol.
[0028] Although not required, substituted starch can be used. If
substituted starch is desired, chemical modifications of starch
typically include etherification and esterification. Substituted
starches may be desired for better compatibility or miscibility
with the thermoplastic polymer and plasticizer. However, this must
be balanced with the reduction in the rate of degradability.
[0029] The degree of substitution of the chemically substituted
starch is from about 0.01 to 3.0. A low degree of substitution,
0.01 to 0.06, may be preferred.
[0030] Typically, the composition comprises from about 1% to about
99%, preferably from about 10% to about 85%, more preferably from
about 20% to about 75%, and most preferably from about 40% to about
60%, of the starch and polymer composition or of the total fiber.
Alternatively, the thermoplastic starch (starch combined with a
plasticizer) may comprise up to 100% of one component of the
multicomponent fiber with this component not containing any
thermoplastic polymer. The weight of starch in the composition
includes starch and its naturally occurring bound water content.
The term "bound water" means the water found naturally occurring in
starch and before mixing of starch with other components to make
the composition of the present invention. The term "free water"
means the water that is added in making the composition of the
present invention. A person of ordinary skill in the art would
recognize that once the components are mixed in a composition,
water can no longer be distinguished by its origin. The starch
typically has a bound water content of about 5% to 16% by weight of
starch. It is known that additional free water may be incorporated
as the polar solvent or plasticizer, and not included in the weight
of the starch.
[0031] Thermoplastic Polymers
[0032] Thermoplastic polymers which are substantially compatible
with starch are also required in the present invention. As used
herein, the term "substantially compatible" means when heated to a
temperature above the softening and/or the melting temperature of
the composition, the polymer is capable of forming a substantially
homogeneous mixture with the starch after mixing with shear or
extension. The thermoplastic polymer used must be able to flow upon
heating to form a processable melt and resolidify as a result of
crystallization or vitrification.
[0033] The polymer must have a melting temperature sufficiently low
to prevent significant degradation of the starch during compounding
and yet be sufficiently high for thermal stability during use of
the fiber. Suitable melting temperatures of polymers are from about
80.degree. to about 190.degree. C. and preferably from about
90.degree. to about 180.degree. C. Thermoplastic polymers having a
melting temperature above 190.degree. C. may be used if
plasticizers or diluents are used to lower the observed melting
temperature. In one aspect of the present invention, it may be
desired to use a thermoplastic polymer having a glass transition
temperature of less than 0.degree. C. Polymers having this low
glass transition temperature include polypropylene, polyethylene,
polyvinyl alcohol, ethylene acrylic acid, and others.
[0034] The polymer must have a rheological characteristics suitable
for melt spinning. The molecular weight of the polymer must be
sufficiently high to enable entanglement between polymer molecules
and yet low enough to be melt spinnable. For melt spinning,
biodegradable thermoplastic polymers having molecular weights below
500,000 g/mol, preferably from about 5,000 g/mol to about 400,000
g/mol, more preferable from about 5,000 g/mol to about 300,000
g/mol and most preferably from about 100,000 g/mol to about 200,000
g/mol.
[0035] The thermoplastic polymers must be able to solidify fairly
rapidly, preferably under extensional flow, and form a thermally
stable fiber structure, as typically encountered in known processes
as staple fibers (spin draw process) or spunbond continuous
filament process.
[0036] Suitable thermoplastic polymers include polypropylene and
copolymers of polypropylene, polyethylene and copolymers of
polyethylene, polyamides and copolymers of polyamides, polyesters
and copolymers of polyesters, and mixtures thereof. Other suitable
polymers include polyamides such as Nylon 6, Nylon 11, Nylon 12,
Nylon 46, Nylon 66, polyvinyl acetates, polyethylene/vinyl acetate
copolymers, polyethylene/methacrylic acid copolymers,
polystyrene/methyl methacrylate copolymers, polymethyl
methacrylates, polyethylene terephalates, low density
polyethylenes, linear low density polyethylenes, ultra low density
polyethylenes, high density polyethylene, and combinations thereof
Other nonlimiting examples of polymers include atactic
polypropylene, polybutylene, polycarbonates, poly(oxymethylene),
styrene copolymers, polyetherimide, poly(vinyl acetate),
poly(methacrylate), poly sulfone, polyolefin carboxylic acid
copolymers such as ethylene acrylic acid copolymer, ethylene maleic
acid copolymer, ethylene methacrylic acid copolymer, and ethylene
acrylic acid copolymer, and combinations thereof. Other suitable
polymers include acid substituted vinyl polymers such as ethylene
acrylic acid which is commercially available as PRIMACOR by Dow.
The polymers disclosed in U.S. Pat. No. 5,593,768 to Gessner are
herein incorporated by reference. Preferred thermoplastic polymers
include polypropylene, polyethylene, polyamides, polyvinyl alcohol,
ethylene acrylic acid, polyolefin carboxylic acid copolymers,
polyesters, and combinations thereof.
[0037] Depending upon the specific polymer used, the process, and
the final use of the fiber, more than one polymer may be desired.
The thermoplastic polymers of the present invention is present in
an amount to improve the mechanical properties of the fiber,
improve the processability of the melt, and improve attenuation of
the fiber. The selection of the polymer and amount of polymer will
also determine if the fiber is thermally bondable and effect the
softness and texture of the final product. Typically, when present
in the starch and polymer blend, the thermoplastic polymers are
present in an amount of from about 1% to about 99%, preferably from
about 10% to about 80%, more preferably from about 30% to about
70%, and most preferably from about 40% to about 60%, by weight of
the fiber. Alternatively, one component of the multicomponent fiber
may contain up to 100% of one or more thermoplastic polymer with
this component not containing any starch.
[0038] Plasticizer
[0039] A plasticizer can be used in the present invention to
destructurize the starch and enable the starch to flow, i.e. create
a thermoplastic starch. The same plasticizer may be used to
increase melt processability or two separate plasticizers may be
used. The plasticizers may also improve the flexibility of the
final products, which is believed to be due to the lowering of the
glass transition temperature of the composition by the plasticizer.
The plasticizers should preferably be substantially compatible with
the polymeric components of the present invention so that the
plasticizers may effectively modify the properties of the
composition. As used herein, the term "substantially compatible"
means when heated to a temperature above the softening and/or the
melting temperature of the composition, the plasticizer is capable
of forming a substantially homogeneous mixture with starch.
[0040] An additional plasticizer or diluent for the thermoplastic
polymer may be present to lower the polymer's melting temperature
and improve overall compatibility with the thermoplastic starch
blend. Furthermore, thermoplastic polymers with higher melting
temperatures may be used if plasticizers or diluents are present
which suppress the melting temperature of the polymer. The
plasticizer will typically have a molecular weight of less than
about 100,000 g/mol and may preferably be a block or random
copolymer or terpolymer where one or more of the chemical species
is compatible with another plasticizer, starch, polymer, or
combinations thereof.
[0041] Nonlimiting examples of useful hydroxyl plasticizers include
sugars such as glucose, sucrose, fructose, raffinose,
maltodextrose, galactose, xylose, maltose, lactose, mannose
erythrose, glycerol, and pentaerythritol; sugar alcohols such as
erythritol, xylitol, malitol, mannitol and sorbitol; polyols such
as ethylene glycol, propylene glycol, dipropylene glycol, butylene
glycol, hexane triol, and the like, and polymers thereof; and
mixtures thereof. Also useful herein as hydroxyl plasticizers are
poloxomers and poloxamines. Also suitable for use herein are
hydrogen bond forming organic compounds which do not have hydroxyl
group, including urea and urea derivatives; anhydrides of sugar
alcohols such as sorbitan; animal proteins such as gelatin;
vegetable proteins such as sunflower protein, soybean proteins,
cotton seed proteins; and mixtures thereof. Other suitable
plasticizers are phthalate esters, dimethyl and diethylsuccinate
and related esters, glycerol triacetate, glycerol mono and
diacetates, glycerol mono, di, and triprpionates, butanoates,
stearates, lactic acid esters, citric acid esters, adipic acid
esters, stearic acid esters, oleic acid esters, and other father
acid esters which are biodegradable. Aliphatic acids such as
ethylene acrylic acid, ethylene maleic acid, butadiene acrylic
acid, butadiene maleic acid, propylene acrylic acid, propylene
maleic acid, and other hydrocarbon based acids. All of the
plasticizers may be use alone or in mixtures thereof. A low
molecular weight plasticizer is preferred. Suitable molecular
weights are less than about 20,000 g/mol, preferably less than
about 5,000 g/mol and more preferably less than about 1,000
g/mol.
[0042] Preferred plasticizers include glycerin, mannitol, and
sorbitol, with sorbitol being the most preferred. The amount of
plasticizer is dependent upon the molecular weight, amount of
starch, and the affinity of the plasticizer for the starch.
Generally, the amount of plasticizer increases with increasing
molecular weight of starch. Typically, the plasticizer present in
the final multicomponent fiber composition comprises from about 2%
to about 90%, more preferably from about 5% to about 70%, most
preferably from about 10% to about 50%. The plasticizer may be
present in one or more of the components.
[0043] Optional Materials
[0044] Optionally, other ingredients may be incorporated into the
spinnable starch composition. These optional ingredients may be
present in quantities of less than about 50%, preferably from about
0.1% to about 20%, and more preferably from about 0.1% to about 12%
by weight of the composition. The optional materials may be used to
modify the processability and/or to modify physical properties such
as elasticity, tensile strength and modulus of the final product.
Other benefits include, but are not limited to, stability including
oxidative stability, brightness, color, flexibility, resiliency,
workability, processing aids, viscosity modifiers, and odor
control. Nonlimiting examples include salts, slip agents,
crystallization accelerators or retarders, odor masking agents,
cross-linking agents, emulsifiers, surfactants, cyclodextrins,
lubricants, other processing aids, optical brighteners,
antioxidants, flame retardants, dyes, pigments, fillers, proteins
and their alkali salts, waxes, tackifying resins, extenders, and
mixtures thereof. Slip agents may be used to help reduce the
tackiness or coefficient of friction in the fiber. Also, slip
agents may be used to improve fiber stability, particularly in high
humidity or temperatures. A suitable slip agent is polyethylene. A
salt may also be added to the melt. The salt may help to solubilize
the starch, reduce discoloration, make the fiber more water
responsive, or used as a processing aid. A salt will also function
to help reduce the solubility of a binder so it does not dissolve,
but when put in water or flushed, the salt will dissolve then
enabling the binder to dissolve and create a more aqueous
responsive product. Nonlimiting examples of salts include sodium
chloride, potassium chloride, sodium sulfate, ammonium sulfate and
mixtures thereof.
[0045] Other additives are typically included with the starch
polymer as a processing aid and to modify physical properties such
as elasticity, dry tensile strength, and wet strength of the
extruded fibers. Suitable extenders for use herein include gelatin,
vegetable proteins such as sunflower protein, soybean proteins,
cotton seed proteins, and water soluble polysaccharides; such as
alginates, carrageenans, guar gum, agar, gum arabic and related
gums, pectin, water soluble derivatives of cellulose, such as
alkylcelluloses, hydroxyalkylcelluloses, and
carboxymethylcellulose. Also, water soluble synthetic polymers,
such as polyacrylic acids, polyacrylic acid esters,
polyvinylacetates, polyvinylalcohols, and polyvinylpyrrolidone, may
be used.
[0046] Lubricant compounds may further be added to improve the flow
properties of the starch material during the processes used for
producing the present invention. The lubricant compounds can
include animal or vegetable fats, preferably in their hydrogenated
form, especially those which are solid at room temperature.
Additional lubricant materials include mono-glycerides and
di-glycerides and phosphatides, especially lecithin. For the
present invention, a preferred lubricant compound includes the
mono-glyceride, glycerol mono-stearate.
[0047] Further additives including inorganic fillers such as the
oxides of magnesium, aluminum, silicon, and titanium may be added
as inexpensive fillers or processing aides. Other inorganic
materials include hydrous magnesium silicate, titanium dioxide,
calcium carbonate, clay, chalk, boron nitride, limestone,
diatomaceous earth, mica glass quartz, and ceramics. Additionally,
inorganic salts, including alkali metal salts, alkaline earth metal
salts, phosphate salts, may be used as processing aides. Other
optional materials that modify the water responsiveness of the
thermoplastic starch blend fiber are stearate based salts, such as
sodium, magnesium, calcium, and other stearates, and rosin
components including anchor gum rosin. Another material that can be
added is a chemical composition formulated to accelerate the
environmental degradation process such as colbalt stearate, citric
acid, calcium oxide, and other chemical compositions found in U.S.
Pat. No. 5,854,304 to Garcia et al., herein incorporated by
reference in its entirety.
[0048] Other additives may be desirable depending upon the
particular end use of the product contemplated. For example, in
products such as toilet tissue, disposable towels, facial tissues
and other similar products, wet strength is a desirable attribute.
Thus, it is often desirable to add to the starch polymer
cross-linking agents known in the art as "wet strength" resins. A
general dissertation on the types of wet strength resins utilized
in the paper art can be found in TAPPI monograph series No. 29, Wet
Strength in Paper and Paperboard, Technical Association of the Pulp
and Paper Industry (New York, 1965). The most useful wet strength
resins have generally been cationic in character.
Polyamide-epichlorohydrin resins are cationic polyamide
amine-epichlorohydrin wet strength resins which have been found to
be of particular utility. Glyoxylated polyacrylamide resins have
also been found to be of utility as wet strength resins.
[0049] It is found that when suitable cross-linking agent such as
Parez.RTM. is added to the starch composition of the present
invention under acidic condition, the composition is rendered water
insoluble. Still other water-soluble cationic resins finding
utility in this invention are urea formaldehyde and melamine
formaldehyde resins. The more common functional groups of these
polyfunctional resins are nitrogen containing groups such as amino
groups and methyl groups attached to nitrogen. Polyethylenimine
type resins may also find utility in the present invention. For the
present invention, a suitable cross-linking agent is added to the
composition in quantities ranging from about 0.1% by weight to
about 10% by weight, more preferably from about 0.1% by weight to
about 3% by weight. The starch and polymers in the fibers of the
present invention may be chemically associated. The chemical
association may be a natural consequence of the polymer chemistry
or may be engineered by selection of particular materials. This is
most likely to occur if a cross-linking agent is present. The
chemical association may be observed by changes in molecular
weight, NMR signals, or other methods known in the art. Advantages
of chemical association include improved water sensitivity, reduced
tackiness, and improved mechanical properties, among others.
[0050] Other polymers, such as rapidly biodegradable polymers, may
also be used in the present invention depending upon final use of
the fiber, processing, and degradation or flushability required.
Polyesters containing aliphatic components are suitable
biodegradable thermoplastic polymers. Among the polyesters, ester
polycondensates containing aliphatic constituents and
poly(hydroxycarboxylic) acid are preferred. The ester
polycondensates include diacids/diol aliphatic polyesters such as
polybutylene succinate, polybutylene succinate co-adipate,
aliphatic/aromatic polyesters such as terpolymers made of butylenes
diol, adipic acid and terephtalic acid. The poly(hydroxycarboxylic)
acids include lacid acid based homopolymers and copolymers,
polyhydroxybutyrate, or other polyhydroxyalkanoate homopolymers and
copolymers. Preferred is a homopolymer or copolymer of poly lactic
acid having a melting temperature from about 160.degree. to about
175.degree. C. Modified poly lactic acid and different stero
configurations may also be used. Preferably, molecular weights of
from about 4,000 g/mol to about 400,000 g/mol are found for the
poly lactic acid.
[0051] An example of a suitable commercially available poly lactic
acid is NATUREWORKS from Cargill Dow and LACEA from Mitsui
Chemical. An example of a suitable commercially available
diacid/diol aliphatic polyester is the polybutylene
succinate/adipate copolymers sold as BIONOLLE 1000 and BIONOLLE
3000 from the Showa Highpolmer Company, Ltd. Located in Tokyo,
Japan. An example of a suitable commercially available
aliphatic/aromatic copolyester is the poly(tetramethylene
adipate-co-terephthalate) sold as EASTAR BIO Copolyester from
Eastman Chemical or ECOFLEX from BASF. The amount of biodegradable
polymers will be from about 0.1% to about 40% by weight of the
fiber.
[0052] Although starch is the preferred natural polymer in the
present invention, a protein-based polymer could also be used.
Suitable protein-based polymers include soy protein, zein protein,
and combinations thereof. The protein-based polymer may be present
in an amount of from about 1% to about 80% and preferably from
about 1% to about 60%.
[0053] After the fiber is formed, the fiber may further be treated
or the bonded fabric can be treated. A hydrophilic or hydrophobic
finish can be added to adjust the surface energy and chemical
nature of the fabric. For example, fibers that are hydrophobic may
be treated with wetting agents to facilitate absorption of aqueous
liquids. A bonded fabric can also be treated with a topical
solution containing surfactants, pigments, slip agents, salt, or
other materials to further adjust the surface properties of the
fiber.
[0054] (2) Configuration
[0055] The multiconstituent fibers of the present invention may be
in many different configurations. Constituent, as used herein, is
defined as meaning the chemical species of matter or the material.
Multiconstituent fiber, as used herein, is defined to mean a fiber
containing more than one chemical species or material. Generally,
fibers may be of monocomponent or multicomponent in configuration.
Component, as used herein, is defined as a separate part of the
fiber that has a spatial relationship to another part of the fiber.
The term multicomponent, as used herein, is defined as a fiber
having more than one separate part in spatial relationship to one
another. The term multicomponent includes bicomponent, which is
defined as a fiber having two separate parts in a spatial
relationship to one another. The different components of
multicomponent fibers are arranged in substantially distinct
regions across the cross-section of the fiber and extend
continuously along the length of the fiber.
[0056] Spunbond structures, staple fibers, hollow fibers, shaped
fibers, such as multi-lobal fibers and multicomponent fibers can
all be produced by using the compositions and methods of the
present invention. The bicomponent and multicomponent fibers may be
in a side-by-side, sheath-core, segmented pie, ribbon,
islands-in-the-sea configuration, or any combination thereof. The
sheath may be continuous or non-continuous around the core. The
ratio of the weight of the sheath to the core is from about 5:95 to
about 95:5. The fibers of the present invention may have different
geometries that include round, elliptical, star shaped,
rectangular, and other various eccentricities.
[0057] The fibers of the present invention may also be splittable
fibers. Rheological, thermal, and solidification differential
behavior can potentially cause splitting. Splitting may also occur
by a mechanical means such as ringrolling, stress or strain, use of
an abrasive, or differential stretching, and/or by fluid induced
distortion, such as hydrodynamic or aerodynamic.
[0058] A plurality of microfibrils may also result from the present
invention. The microfibrils are very fine fibers contained within a
multi-constituent monocomponent or multicomponent extrudate. The
plurality of polymer microfibrils have a cable-like morphological
structure and longitudinally extend within the fiber, which is
along the fiber axis. To enable the microfibrils to be formed in
the present invention, a sufficient amount of polymer is required
to generate a co-continuous phase morphology such that the polymer
microfibrils are formed in the starch matrix. Typically, greater
than 15%, preferably from about 15% to about 90%, more preferably
from about 25% to about 80%, and more preferably from about 35% to
about 70% of polymer is desired. A "co-continuous phase morphology"
is found when the microfibrils are substantially longer than the
diameter of the fiber. Microfibrils are typically from about 0.1
micrometers to about 10 micrometers in diameter while the fiber
typically has a diameter of from about (10 times the microfibril)
10 micrometers to about 50 micrometers. In addition to the amount
of polymer, the molecular weight of the thermoplastic polymer must
be high enough to induce sufficient entanglement to form
microfibrils. The preferred molecular weight is from about 10,000
to about 500,000 g/mol. The formation of the microfibrils also
demonstrates that the resulting fiber is not homogeneous, but
rather that polymer microfibrils are formed within the starch
matrix. The microfibrils comprised of the degradable polymer will
mechanically reinforce the fiber to improve the overall tensile
strength and make the fiber thermally bondable. Alternatively,
microfibrils can be obtained by co-spinning starch and polymer melt
without phase mixing, as in an islands-in-a-sea bicomponent
configuration. In an islands-in-a-sea configuration, there may be
several hundred fine fibers present.
[0059] There are many different combinations for the multicomponent
fibers of the present invention. A starch/polymer blend may be both
the sheath and the core with one of the components containing more
starch or polymer than the other component. The starch in the
starch/polymer blend may be in any suitable amount depending upon
desired use of the multicomponent fiber. Alternatively, the
starch/polymer blend may be the sheath with the core being pure
polymer or starch. The starch/polymer composition could also be the
core with the sheath being pure polymer or starch. For example, a
bicomponent fibers with a core of pure starch and the sheath
containing either pure polymer or a starch/polymer blend may be
desired where the fibers are used in a thermal bonding process.
This configuration allows for high biodegradability and low cost
due to the high content of starch, but the fiber is still thermally
bondable.
[0060] The present invention may have any variations on the
bicomponent fibers in a sheath-core configuration. For example, the
core or sheath may contain microfibrils. The sheath may be
continuous or noncontinuous around the core. The sheath-core
configuration may also be found in multicomponent fibers. There may
be more than one sheath surrounding the core. For example, an inner
sheath may surround the core with an outer sheath surrounding the
inner sheath. Alternatively, the core could have an
islands-in-the-sea configuration or a segmented pie.
[0061] The exact configuration of the multicomponent fiber desired
is dependent upon the use of the fiber. A major advantage of the
multicomponent fiber compared to the monocomponent fiber is that
there is spatial control over the placement of the starch and/or
polymer in the fiber. This is advantageous for enabling thermal
bonding, reducing stickiness of the starch, and other resulting
properties of the fiber. A preferred configuration is a bicomponent
fiber with starch contained in the core and the thermoplastic
polymer in the sheath. This configuration will help the starch to
have improved long term stability by protecting the starch from
aging, discoloration, mold, an other things in the environment.
Also, this particular configuration will reduce the potential
stickiness of the feel of the starch and allow for the fiber to be
easily thermally bondable. The multicomponent fibers can be used as
a whole fiber or the starch can be removed to only use the
thermoplastic polymer. The starch can be removed through bonding
methods, hydrodynamic entanglement, post-treatment such as
mechanical deformation, or dissolving in water. The fibers having
the starch removed may be used in nonwoven articles that are
desired to be extra soft and/or have better barrier properties.
Additionally, because starch is an inexpensive material, the starch
and polymer fibers with the starch removed will be a more
cost-effective fiber.
[0062] FIG. 1 is schematic drawings illustrating a cross-sectional
view of a bicomponent fiber having a sheath-core configuration.
Components X and Y may be a thermoplastic starch, a thermoplastic
polymer, or a blend of the starch and polymer.
[0063] FIG. 1A illustrates a concentric sheath-core configuration
with Component X comprising the solid core and Component Y
comprising the continuous sheath.
[0064] FIG. 1B illustrates a sheath-core configuration with
Component X comprising the solid core and Component Y comprising
the shaped continuous sheath.
[0065] FIG. 1C illustrates a sheath-core configuration with
Component X comprising the hollow core and Component Y comprising
the continuous sheath.
[0066] FIG. 1D illustrates a sheath-core configuration with
Component X comprising the hollow core and Component Y comprising
the shaped continuous sheath.
[0067] FIG. 1E illustrates a sheath-core configuration with
Component X comprising the solid core and Component Y comprising
the discontinuous sheath.
[0068] FIG. 1F illustrates a sheath-core configuration with
Component X comprising the solid core and Component Y comprising
the discontinuous sheath.
[0069] FIG. 1G illustrates a sheath-core configuration with
Component X comprising the hollow core and Component Y comprising
the discontinuous sheath.
[0070] FIG. 1H illustrates a sheath-core configuration with
Component X comprising the hollow core and Component Y comprising
the discontinuous sheath.
[0071] FIG. 1I illustrates an eccentric sheath-core configuration
with Component X comprising the solid core and Component Y
comprising the continuous sheath.
[0072] FIG. 2 is schematic drawings illustrating a cross-sectional
view of a bicomponent fiber having a segmented pie configuration.
Components X and Y may be a thermoplastic starch, a thermoplastic
polymer, or a blend of the starch and polymer.
[0073] FIG. 2A illustrates a solid eight segmented pie
configuration.
[0074] FIG. 2B illustrates a hollow eight segmented pie
configuration. This configuration is a suitable configuration for
producing splittable fibers.
[0075] FIG. 3 is schematic drawing illustrating a cross-sectional
view of a bicomponent fiber having a ribbon configuration.
Components X and Y may be a thermoplastic starch, a thermoplastic
polymer, or a blend of the starch and polymer.
[0076] FIG. 4 is schematic drawings illustrating a cross-sectional
view of a bicomponent fiber having a side-by-side configuration.
Components X and Y may be a thermoplastic starch, a thermoplastic
polymer, or a blend of the starch and polymer.
[0077] FIG. 4A illustrates a side-by-side configuration.
[0078] FIG. 4B illustrates a side-by-side configuration with a
rounded adjoining line. The adjoining line is where two components
meet. Component Y is present in a higher amount than Component
X.
[0079] FIG. 4C is a side-by-side configuration with Component Y
being positioned on either side of Component X with a rounded
adjoining line.
[0080] FIG. 4D is a side-by-side configuration with Component Y
being positioned on either side of Component X.
[0081] FIG. 4E is a shaped side-by-side configuration with
Component Y being positioned on the tips of Component X.
[0082] FIG. 5 is schematic drawings illustrating a cross-sectional
view of a bicomponent fiber having an islands-in-the-sea
configuration. Components X and Y may be a thermoplastic starch, a
thermoplastic polymer, or a blend of the starch and polymer.
[0083] FIG. 5A is a solid islands-in the-sea configuration with
Component X being surrounded by Component Y. Component X is
triangular in shape.
[0084] FIG. 5B is a solid islands-in the-sea configuration with
Component X being surrounded by Component Y.
[0085] FIG. 5C is a hollow islands-in the-sea configuration with
Component X being surrounded by Component Y.
[0086] FIG. 6 is schematic drawing illustrating a cross-sectional
view of a tricomponent fiber having a ribbon configuration.
Components X, Y, and Z may be a thermoplastic starch, a
thermoplastic polymer, or a blend of the starch and polymer.
[0087] FIG. 7 is schematic drawing illustrating a cross-sectional
view of a tricomponent fiber having a concentric sheath-core
configuration with Component X comprising the solid core, Component
Y comprising the inside continuous sheath, and Component Z
comprising the outside continuous sheath. Components X, Y, and Z
may be a thermoplastic starch, a thermoplastic polymer, or a blend
of the starch and polymer.
[0088] FIG. 8 is schematic drawing illustrating a cross-sectional
view of a multicomponent fiber having a solid eight segmented pie
configuration. Components X, Y, Z, and W may be a thermoplastic
starch, a thermoplastic polymer, or a blend of the starch and
polymer.
[0089] FIG. 9 is a schematic drawing illustrating a cross-sectional
view of a tricomponent fiber having a solid islands-in-the-sea
configuration. Component X surrounds the single island comprising
Component Y and the plurality of islands comprising Component Z.
Components X, Y, and Z may be a thermoplastic starch, a
thermoplastic polymer, or a blend of the starch and polymer.
[0090] (3) Material Properties
[0091] A "highly attenuated fiber" is defined as a fiber having a
high draw down ratio. The total fiber draw down ratio is defined as
the ratio of the fiber at its maximum diameter (which is typically
results immediately after exiting the capillary) to the final fiber
diameter in its end use. The total fiber draw down ratio via either
staple, spunbond, or meltblown process will be greater than 1.5,
preferable greater than 5, more preferably greater than 10, and
most preferably greater than 12. This is necessary to achieve the
tactile properties and useful mechanical properties.
[0092] Preferably, the highly attenuated multicomponent fiber will
have a diameter of less than 200 micrometers. More preferably the
fiber diameter will be 100 micrometer or less, even more preferably
50 micrometers or less, and most preferably less than 30
micrometers. Fibers commonly used to make nonwovens will have a
diameter of from about 5 micrometers to about 30 micrometers. Fiber
diameter is controlled by spinning speed, mass through-put, and
blend composition. The fibers produced in the present invention are
environmentally degradable.
[0093] The multicomponent fibers produced in the present invention
may be environmentally degradable depending upon the amount of
starch that is present and the specific configuration of the fiber.
The starch contained in the fibers of the present invention will be
environmentally degradable. "Environmentally degradable" is defined
being biodegradable, disintigratable, dispersible, flushable, or
compostable or a combination thereof. In the present invention, the
multicomponent fibers, nonwoven webs, and articles may be
environmentally degradable. As a result, the fibers may be easily
and safely disposed of either in existing composting facilities or
may be flushable and can be safely flushed down the drain without
detrimental consequences to existing sewage infrastructure systems.
The flushability of the multicomponent fibers of the present
invention when used in disposable products such as wipes and
feminine hygiene items offer additional convenience and discretion
to the consumer.
[0094] Biodegradable is defined as meaning when the matter is
exposed to an aerobic and/or anaerobic environment, the ultimate
fate is eventually reduction to monomeric components due to
microbial, hydrolytic, and/or chemical actions. Under aerobic
conditions, biodegradation leads to the transformation of the
material into end products such as carbon dioxide and water. Under
anaerobic conditions, biodegradation leads to the transformation of
the materials into carbon dioxide, water, and methane. The
biodegradability process is often described as mineralization.
Biodegradability means that all organic constituents of the fibers
are subject to decomposition eventually through biological
activity.
[0095] There are a variety of different standardized
biodegradability methods that have been established over time by
various organization and in different countries. Although the tests
vary in the specific testing conditions, assessment methods, and
criteria desired, there is reasonable convergence between different
protocols so that they are likely to lead to similar conclusions
for most materials. For aerobic biodegrability, the American
Society for Testing and Materials (ASTM) has established ASTM D
5338-92: Test methods for Determining Aerobic Biodegradation of
Plastic Materials Under Controlled Composting Conditions. The test
measures the percent of test material that mineralizes as a
function of time by monitoring the amount of carbon dioxide being
released as a result of assimilation by microorganisms in the
presence of active compost held at a thermophilic temperature of
58.degree. C. Carbon dioxide production testing may be conducted
via electrolytic respirometry. Other standard protocols, such 301B
from the Organization for Economic Cooperation and Development
(OECD), may also be used. Standard biodegradation tests in the
absence of oxygen are described in various protocols such as ASTM D
5511-94. These tests are used to simulate the biodegradability of
materials in an anaerobic solid-waste treatment facility or
sanitary landfill. However, these conditions are less relevant for
the type of disposable applications that are described for the
fibers and nonwovens in the present invention. The multicomponent
fibers of the present invention may be biodegradable.
[0096] Disintegration occurs when the fibrous substrate has the
ability to rapidly fragment and break down into fractions small
enough not to be distinguishable after screening when composted or
to cause drainpipe clogging when flushed. A disintegradable
material will also be flushable. Most protocols for
disintegradability measure the weight loss of test materials over
time when exposed to various matrices. Both aerobic and anaerobic
disintegration tests are used. Weight loss is determined by the
amount of fibrous test material that is no longer collected on an
18 mesh sieve with 1 millimeter openings after the materials is
exposed to wastewater and sludge. For disintegration, the
difference in the weight of the initial sample and the dried weight
of the sample recovered on a screen will determine the rate and
extent of disintegration. The testing for biodegradability and
disintegration are very similar as a very similar environment, or
the same environment, will be used for testing. To determine
disintegration, the weight of the material remaining is measured
while for biodegradability, the evolved gases are measured. The
fibers of the present invention may rapidly disintegrate.
[0097] The fibers of the present invention may also be compostable.
ASTM has developed test methods and specifications for
compostability. The test measures three characteristics:
biodegradability, disintegration, and lack of ecotoxicity. Tests to
measure biodegradability and disintegration are described above. To
meet the biodegradability criteria for compostability, the material
must achieve at least about 60% conversion to carbon dioxide within
40 days. For the disintegration criteria, the material must have
less than 10% of the test material remain on a 2 millimeter screen
in the actual shape and thickness that it would have in the
disposed product. To determine the last criteria, lack of
ecotoxicity, the biodegradation byproducts must not exhibit a
negative impact on seed germination and plant growth. One test for
this criteria is detailed in OECD 208. The International
Biodegradable Products Institute will issue a logo for
compostability once a product is verified to meet ASTM 6400-99
specifications. The protocol follows Germany's DIN 54900 which
determine the maximum thickness of any material that allows
complete decomposition within one composting cycle.
[0098] The multicomponent fibers described herein are typically
used to make disposable nonwoven articles. The articles are
commonly flushable. The term "flushable" as used herein refers to
materials which are capable of dissolving, dispersing,
disintegrating, and/or decomposing in a septic disposal system such
as a toilet to provide clearance when flushed down the toilet
without clogging the toilet or any other sewage drainage pipe. The
fibers and resulting articles may also be aqueous responsive. The
term aqueous responsive as used herein means that when placed in
water or flushed, an observable and measurable change will result.
Typical observations include noting that the article swells, pulls
apart, dissolves, or observing a general weakened structure.
[0099] The tensile strength of a starch fibers is approximately 15
Mega Pascal (MPa). The multicomponent fibers of the present
invention will have a tensile strength of greater than about 20
MPa, preferably greater than about 35 MPa, and more preferably
greater than about 50 MPa. Tensile strength is measured using an
Instron following a procedure described by ASTM standard D 3822-91
or an equivalent test.
[0100] The multicomponent fibers of the present invention are not
brittle and have a toughness of greater than 2 MPa. Toughness is
defined as the area under the stress-strain curve where the
specimen gauge length is 25 mm with a strain rate of 50 mm per
minute. Elasticity or extensible of the fibers may also be
desired.
[0101] The multicomponent fibers of the present invention may be
thermally bondable if enough polymer is present. Thermally bondable
fibers are required for the pressurized heat and thru-air heat
bonding methods. Thermally bondable is typically achieved when the
polymer is present at a level of greater than about 15% preferably
greater than about 30%, most preferably greater than about 40%, and
most preferably greater than about 50% by weight of the fiber.
Consequently, if a very high starch content is in the sheath, the
fiber may exhibit a decreased tendency toward thermal
bondablility.
[0102] The nonwoven products produced from the multicomponent
fibers will also exhibit certain mechanical properties,
particularly, strength, flexibility, softness, and absorbency.
Measures of strength include dry and/or wet tensile strength.
Flexibility is related to stiffness and can attribute to softness.
Softness is generally described as a physiologically perceived
attribute which is related to both flexibility and texture.
Absorbency relates to the products' ability to take up fluids as
well as the capacity to retain them.
[0103] (4) Processes
[0104] The first step in producing a multicomponent fiber is the
compounding or mixing step. In the compounding step, the raw
materials are heated, typically under shear. The shearing in the
presence of heat will result in a homogeneous melt with proper
selection of the composition. The melt is then placed in an
extruder where fibers are formed. A collection of fibers is
combined together using heat, pressure, chemical binder, mechanical
entanglement, and combinations thereof resulting in the formation
of a nonwoven web. The nonwoven is then assembled into an
article.
[0105] Compounding
[0106] The objective of the compounding step is to produce a
homogeneous melt composition comprising the starch, polymer, and/or
plasticizer. If a constituent is being produced that is only starch
or polymer and not both, the compounding step will be modified to
account for the desired composition. Preferably, the melt
composition is homogeneous, meaning that a uniform distribution is
found over a large scale and that no distinct regions are
observed.
[0107] The resultant melt composition should be essentially free of
water to spin fibers. Essentially free is defined as not creating
substantial problems, such as causing bubbles to form which may
ultimately break the fiber while spinning. Preferably, the free
water content of the melt composition is less than about 1%, more
preferably less than about 0.5%, and most preferably less than
0.1%. The total water content includes the bound and free water. To
achieve this low water content, the starch and polymers may need to
be dried before processed and/or a vacuum is applied during
processing to remove any free water. Preferably, the thermoplastic
starch is dried at 60.degree. C. before spinning.
[0108] In general, any method using heat, mixing, and pressure can
be used to combine the polymer, starch, and/or plasticizer. The
particular order or mixing, temperatures, mixing speeds or time,
and equipment are not critical as long as the starch does not
significantly degrade and the resulting melt is homogeneous.
[0109] A preferred method of mixing for a starch and two polymer
blend is as follow:
[0110] 1. The polymer having a higher melting temperature is heated
and mixed above its melting point. Typically, this is
30.degree.-70.degree. C. above its melting temperature. The mixing
time is from about 2 to about 10 minutes, preferably around 5
minutes. The polymer is then cooled, typically to
120.degree.-140.degree. C.
[0111] 2. The starch is fully destructurized. This starch can be
destructurized by dissolving in water at 70.degree.-100.degree. C.
at a concentration of 10-90% starch depending upon the molecular
weight of the starch, the desired viscosity of the destructurized
starch, and the time allowed for destructurizing. In general,
approximately 15 minutes is sufficient to destructurize the starch
but 10 minutes to 30 minutes may be necessary depending upon
conditions. A plasticizer can be added to the destructurized starch
if desired.
[0112] 3. The cooled polymer from step 1 and the destructurized
starch from step 2 are then combined. The polymer and starch can be
combined in an extruder or a batch mixer with shear. The mixture is
heated, typically to approximately 120.degree.-140.degree. C. This
results in vaporization of any water. If desired to flash off all
water, the mixture should be mixed until all of the water is gone.
Typically, the mixing in this step is from about 2 to about 15
minutes, typically it is for approximately 5 minutes. A homogenous
blend of starch and polymer is formed.
[0113] 4. A second polymer is then added to the homogeneous blend
of step 3. This second polymer may be added at room temperature or
after it has been melted and mixed. The homogeneous blend from step
3 is continued to be mixed at temperatures from about 100.degree.
C. to about 170.degree. C. The temperatures above 100.degree. C.
are needed to prevent any moisture from forming. If not added in
step 2, the plasticizer may be added now. The blend is continued to
be mixed until it is homogeneous. This is observed by noting no
distinct regions. Mixing time is generally from about 2 to about 10
minutes, commonly around 5 minutes.
[0114] The most preferred mixing device is a multiple mixing zone
twin screw extruder with multiple injection points. The multiple
injection points can be used to add the destructurized starch and
the polymer. A twin screw batch mixer or a single screw extrusion
system can also be used. As long as sufficient mixing and heating
occurs, the particular equipment used is not critical.
[0115] An alternative method for compounding the materials is by
adding the plasticizer, starch, and polymer to an extrusion system
where they are mixed in progressively increasing temperatures. For
example, in a twin screw extruder with six heating zones, the first
three zones may be heated to 90.degree., 120.degree., and
130.degree. C., and the last three zones will be heated above the
melting point of the polymer. This procedure results in minimal
thermal degradation of the starch and for the starch to be fully
destructured before intimate mixing with the thermoplastic
materials.
[0116] Another process is to use a higher temperature melting
polymer and inject the starch at the very end of the process. The
starch is only at a higher temperature for a very short amount of
time which is not enough time to burn.
[0117] Spinning
[0118] The present invention utilizes the process of melt spinning.
In melt spinning, there is no mass loss in the extrudate. Melt
spinning is differentiated from other spinning, such as wet or dry
spinning from solution, where a solvent is being eliminated by
volatilizing or diffusing out of the extrudate resulting in a mass
loss.
[0119] Spinning will occur at 120.degree. C. to about 230.degree.,
preferably 185.degree. to about 190.degree.. Fiber spinning speeds
of greater than 100 meters/minute are required. Preferably, the
fiber spinning speed is from about 1,000 to about 10,000
meters/minute, more preferably from about 2,000 to about 7,000
meters/minute, and most preferably from about 2,500 to about 5,000
meters/minute. The polymer composition must be spun fast to avoid
brittleness in the fiber.
[0120] Continuous fibers can be produced through spunbond methods
or meltblowing processes or non-continuous (staple fibers) fibers
can be produced. The various methods of fiber manufacturing can
also be combined to produce a combination technique.
[0121] The homogeneous blend can be melt spun into multicomponent
fibers on conventional melt spinning equipment. The equipment will
be chosen based on the desired configuration of the multicomponent.
Commercially available melt spinning equipment is available from
Hills, Inc. located in Melbourne, Fla. The temperature for spinning
range from about 100.degree. C. to about 230.degree. C. The
processing temperature is determined by the chemical nature,
molecular weights and concentration of each component. The fibers
spun can be collected using conventional godet winding systems or
through air drag attenuation devices. If the godet system is used,
the fibers can be further oriented through post extrusion drawing
at temperatures from about 50.degree. to about 140.degree. C. The
drawn fibers may then be crimped and/or cut to form non-continuous
fibers (staple fibers) used in a carding, airlaid, or fluidlaid
process
[0122] (5) Articles
[0123] The multicomponent fibers may be converted to nonwovens by
different bonding methods. Continuous fibers can be formed into a
web using industry standard spunbond type technologies while staple
fibers can be formed into a web using industry standard carding,
airlaid, or wetlaid technologies. Typical bonding methods include:
calendar (pressure and heat), thru-air heat, mechanical
entanglement, hydrodynamic entanglement, needle punching, and
chemical bonding and/or resin bonding. The calendar, thru-air heat,
and chemical bonding are the preferred bonding methods for the
starch and polymer multicomponent fibers. Thermally bondable fibers
are required for the pressurized heat and thru-air heat bonding
methods.
[0124] The multicomponent fibers of the present invention may also
be bonded or combined with other synthetic or natural fibers to
make nonwoven articles. The synthetic or natural fibers may be
blended together in the forming process or used in discrete layers.
Suitable synthetic fibers include fibers made from polypropylene,
polyethylene, polyester, polyacrylates, and copolymers thereof and
mixtures thereof. Natural fibers include cellulosic fibers and
derivatives thereof. Suitable cellulosic fibers include those
derived from any tree or vegetation, including hardwood fibers,
softwood fibers, hemp, and cotton. Also included are fibers made
from processed natural cellulosic resources such as rayon.
[0125] The multicomponent fibers of the present invention may be
used to make nonwovens, among other suitable articles. Nonwoven
articles are defined as articles that contains greater than 15% of
a plurality of fibers that are continuous or non-continuous and
physically and/or chemically attached to one another. The nonwoven
may be combined with additional nonwovens or films to produce a
layered product used either by itself or as a component in a
complex combination of other materials, such as a baby diaper or
feminine care pad. Preferred articles are disposable, nonwoven
articles. The resultant products may find use in filters for air,
oil and water; vacuum cleaner filters; furnace filters; face masks;
coffee filters, tea or coffee bags; thermal insulation materials
and sound insulation materials; nonwovens for one-time use sanitary
products such as diapers, feminine pads, and incontinence articles;
biodegradable textile fabrics for improved moisture absorption and
softness of wear such as micro fiber or breathable fabrics; an
electrostatically charged, structured web for collecting and
removing dust; reinforcements and webs for hard grades of paper,
such as wrapping paper, writing paper, newsprint, corrugated paper
board, and webs for tissue grades of paper such as toilet paper,
paper towel, napkins and facial tissue; medical uses such as
surgical drapes, wound dressing, bandages, dermal patches and
self-dissolving sutures; and dental uses such as dental floss and
toothbrush bristles. The fibrous web may also include odor
absorbents, termite repellants, insecticides, rodenticides, and the
like, for specific uses. The resultant product absorbs water and
oil and may find use in oil or water spill clean-up, or controlled
water retention and release for agricultural or horticultural
applications. The resultant starch fibers or fiber webs may also be
incorporated into other materials such as saw dust, wood pulp,
plastics, and concrete, to form composite materials, which can be
used as building materials such as walls, support beams, pressed
boards, dry walls and backings, and ceiling tiles; other medical
uses such as casts, splints, and tongue depressors; and in
fireplace logs for decorative and/or burning purpose. Preferred
articles of the present invention include disposable nonwovens for
hygiene and medical applications. Hygiene applications include such
items as wipes; diapers, particularly the top sheet or back sheet;
and feminine pads or products, particularly the top sheet.
EXAMPLES
[0126] The examples below further illustrate the present invention.
The starch used in the examples below are StarDri 100, StaDex 10,
StaDex 65, all from Staley. The polycaprolactone (PCL) is Tone 767
purchased from Union Carbide. The polyethylene is Aspin 6811A
purchased from Dow and the polypropylene is Achieve 3854 purchased
from Exxon.
Example 1
Sheath-Core Bicomponent Fiber
[0127] The blend for the core is compounded using 70 parts StarDri
100, 10 parts polyethylene and 30 parts sorbital. The blend for the
sheath is compounded using 67 parts low density polyethylene, 19
parts StarDri 100 starch, 10 parts PCL and 4 parts glycerol. Each
ingredient is added concurrently to an extrusion system where they
are mixed in progressively increasing temperatures. This procedure
minimizes the thermal degradation to the starch that occurs when
the starch is heated above 180.degree. C. for significant periods
of time. This procedure also allows the starch to be fully
destructured before intimate mixing with the thermoplastic
materials.
Example 2
Sheath-Core Bicomponent Fiber
[0128] The blend for the sheath contains polypropylene. The blend
for the core is compounded as in Example 1 using 66 parts
polypropylene, 20 parts StarDri 100, 9 parts PCL, and 5 parts
glycerol.
Example 3
Hollow Eight Segmented Pie Bicomponent Fiber
[0129] The blend for the first segment contains polyethylene. The
blend for the second component is compounded as in Example 1 using
70 parts StarDri 100, 10 parts polyethylene and 30 parts
sorbital.
Example 4
Sheath-Core Bicomponent Fiber
[0130] The blend for the core contains polyethylene. The blend for
the sheath is compounded as in Example 1 using 30 parts StaDex 10,
15 parts polypropylene, 45 parts polyethylene and 15 parts
sorbital.
Example 5
Side-by-Side Bicomponent Fiber
[0131] The blend for the firsts segment contains polypropylene. The
blend for the second component is compounded as in Example 1 using
70 parts StarDri 100 and 30 parts sorbital.
Example 6
Sheath-Core Bicomponent Fiber
[0132] The blend for the sheath segment contains polyethylene. The
blend for the core is compounded as in Example 1 using 50 parts
StaDex 15 and 50 parts sorbital.
Example 7
Sheath-Core Bicomponent Fiber
[0133] The blend for the core contains polypropylene. The blend for
the sheath is compounded as in Example 1 using 70 parts StarDri 100
and 30 parts sorbital. After the bicomponent fiber is spun, the
starch containing sheath is dissolved in water. The remaining
polypropylene fiber can then be used to make a nonwoven web. The
dissolved starch and water can be recycled and used again.
Example 8
Islands-in-the-Sea Fiber
[0134] The "islands" in the multicomponent fiber contain Dow
Primacor 59801. The matrix blend is compounded according to Example
1 with 10 parts Dow Primacor 59801, 70 parts StarDri 100 and 30
parts sorbitol.
Example 9
Side-by-Side
[0135] Fibers can be produced by melt spinning a composition
comprising 36 parts polypropylene, 37 parts StarDri 100 starch, 18
parts PCL and 9 parts glycerol. The second component comprises 48
parts polypropylene, 33 parts Star Dri 100 starch, 14 parts PCL,
and 5 parts glycerol. Both component are compounded according to
Example 1.
Example 10
Segmented Pie
[0136] One component of the fiber can be produced by melt spinning
a composition comprising 20 parts polypropylene, 20 parts
polyethylene, 20 parts EAA, 25 parts StaDex 10, and 15 parts
sorbitol. The second component can be produced by melt spinning a
composition comprising 80 parts polypropylene, 10 parts PCL, 10
parts StaDex 15, and 5 parts sorbitol. Both component are
compounded according to Example 1.
Example 11
Hollow Non-Continuous Sheath-Core
[0137] The sheath can be produced by melt spinning a composition
comprising 50 parts PVA, 30 parts StaDex 65, and 20 parts mannitol.
The hollow core comprises 50 parts StaDex 65 and 50 parts
sorbitol.
Example 12
Three Part Ribbon
[0138] One component of the ribbon fiber is be produced by melt
spinning a composition comprising 20 parts PVA, 60 parts StaDex 10,
and 20 parts mannitol. This component is located on either side of
the middle component which comprises 70 parts StarDri 100 and 30
parts glycerin.
Example 13
Hollow Segmented Pie
[0139] One segment of the fiber can be produced by melt spinning a
composition comprising 50 parts Nylon 6, 30 parts StaDex 15, and 20
parts suitable diluent for lowering the melting temperature of
Nylon 6. The other segment will comprise 30 parts Nylon 12, 50
parts StaDex 15, and 20 parts of a suitable diluent for lowering
the melting temperature of Nylon 6.
[0140] While particular examples were given, different combinations
of materials, ratios, and equipment such as counter rotating twin
screw or high shear single screw with venting could also be
used.
[0141] The disclosures of all patents, patent applications (and any
patents which issue thereon, as well as any corresponding published
foreign patent applications), and publications mentioned throughout
this description are hereby incorporated by reference herein. It is
expressly not admitted, however, that any of the documents
incorporated by reference herein teach or disclose the present
invention.
[0142] 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 is intended to cover in the appended claims all such
changes and modifications that are within the scope of the
invention.
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