U.S. patent application number 12/574518 was filed with the patent office on 2010-04-15 for non-woven fabric composites from lignin-rich, large diameter natural fibers.
This patent application is currently assigned to Baylor University. Invention is credited to Walter Bradley, David Stanton Greer.
Application Number | 20100093245 12/574518 |
Document ID | / |
Family ID | 41268326 |
Filed Date | 2010-04-15 |
United States Patent
Application |
20100093245 |
Kind Code |
A1 |
Bradley; Walter ; et
al. |
April 15, 2010 |
NON-WOVEN FABRIC COMPOSITES FROM LIGNIN-RICH, LARGE DIAMETER
NATURAL FIBERS
Abstract
A non-woven fabric composite containing natural fibers and a
method for producing such composites. The non-woven fabric
composite is comprised of large diameter, lignin-rich natural
fibers with a high viscous flow temperature and a high degradation
temperature combined with fibers made of a thermoplastic polymer
with a lower viscous flow temperature such as polypropylene,
polyethylene or a biodegradable thermoplastic polymer fiber such as
polylactic acid, or mixture thereof. A hot-pressed non-woven fabric
composite material prepared from the non-woven fabric
composite.
Inventors: |
Bradley; Walter; (Woodway,
TX) ; Greer; David Stanton; (Hewitt, TX) |
Correspondence
Address: |
JACKSON WALKER LLP
901 MAIN STREET, SUITE 6000
DALLAS
TX
75202-3797
US
|
Assignee: |
Baylor University
Waco
TX
|
Family ID: |
41268326 |
Appl. No.: |
12/574518 |
Filed: |
October 6, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61103173 |
Oct 6, 2008 |
|
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|
61176422 |
May 7, 2009 |
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Current U.S.
Class: |
442/341 ; 19/65A;
442/414; 442/416 |
Current CPC
Class: |
D04H 1/46 20130101; D04H
1/558 20130101; D04H 1/425 20130101; D04H 1/48 20130101; D04H 1/435
20130101; D04H 1/732 20130101; Y10T 442/615 20150401; Y10T 442/698
20150401; D04H 1/64 20130101; Y10T 442/686 20150401; D04H 1/74
20130101; D04H 1/04 20130101; D04H 1/54 20130101; D04H 1/4382
20130101; D04H 1/4291 20130101; Y10T 442/692 20150401; Y10T 442/696
20150401; D04H 1/70 20130101; Y10T 442/608 20150401; D04H 1/12
20130101 |
Class at
Publication: |
442/341 ;
442/414; 442/416; 19/65.A |
International
Class: |
D04H 5/00 20060101
D04H005/00; D04H 1/00 20060101 D04H001/00; D01G 21/00 20060101
D01G021/00 |
Claims
1. A non-woven fabric composite material comprising: a natural
fiber and a fiber made from a synthetic thermoplastic polymer,
wherein the natural fiber and the fiber made from a synthetic
thermoplastic polymer are matted together and wherein the natural
fiber has a higher viscous flow temperature and a higher
degradation temperature than that of the fiber made from the
synthetic thermoplastic polymer.
2. The non-woven fabric composite material of claim 1, wherein the
natural fiber has been mixed with a polyester fiber.
3. The non-woven fabric composite material of claim 1, wherein the
length of the natural fiber and the fiber made from the synthetic
thermoplastic polymer is from about 25 mm to about 75 mm.
4. The non-woven fabric composite material of claim 1, wherein the
diameter of the natural fiber is from about 150 .mu.m to about 500
.mu.m.
5. The non-woven fabric composite material of claim 1, wherein the
natural fiber and the fiber made from the synthetic thermoplastic
are matted together using carding and needle punching, cyclone air
deposition, chemical, heat, or solvent treatment.
6. The non-woven fabric composite material of claim 1, wherein the
natural fiber has a lignin content of about 33 wt. %.
7. The non-woven fabric composite material of claim 1, wherein the
natural fiber is coir.
8. The non-woven fabric composite material of claim 1, wherein the
synthetic thermoplastic polymer is polypropylene, polyethylene,
polylactic acid, or a mixture thereof.
9. The non-woven fabric composite material of claim 1, wherein the
synthetic thermoplastic polymer is polypropylene.
10. The non-woven fabric composite material of claim 1, wherein the
weight ratio of the natural fiber to the fiber made from the
synthetic thermoplastic is from about 95:5 to about 20:80.
11. A non-woven fabric composite material comprising: a coir fiber
and a fiber made from a synthetic thermoplastic polymer, wherein:
the coir fiber and the fiber made from the synthetic thermoplastic
polymer are matted together; the coir fiber has a diameter of from
about 150 .mu.m to about 500 .mu.m, and a length of from about 25
mm to about 75 mm; and the fiber made from a synthetic
thermoplastic polymer is a polyethylene, polypropylene, polylactic
acid, or mixture thereof having a diameter of from about 30 .mu.m
to about 50 .mu.m, and a length of from about 25 mm to about 75
mm.
12. A hot-pressed non-woven fabric composite material comprising: a
natural fiber and a fiber made from a synthetic thermoplastic
polymer, wherein the natural fiber and the fiber made from a
synthetic thermoplastic polymer are matted together and
hot-pressed, and wherein the natural fiber has a higher viscous
flow temperature and a higher degradation temperature than that of
the fiber made from the synthetic thermoplastic polymer.
13. The hot-pressed non-woven fabric composite material of claim
12, wherein the length of the natural fiber and the fiber made from
the synthetic thermoplastic polymer is from about 25 mm to about 75
mm.
14. The hot-pressed non-woven fabric composite material of claim
12, wherein the diameter of the natural fiber is from about 150
.mu.m to about 500 .mu.m.
15. The hot-pressed non-woven fabric composite material of claim
12, wherein the natural fiber has a lignin content of about 33 wt.
%.
16. The non-woven fabric composite material of claim 12, wherein
the natural fiber is coir.
17. The hot-pressed non-woven fabric composite material of claim
12, wherein the natural fiber is coir.
18. The hot-pressed non-woven fabric composite material of claim
12, wherein the synthetic thermoplastic polymer is polypropylene,
polyethylene, polylactic acid, or a mixture thereof.
19. The hot-pressed non-woven fabric composite material of claim
12, wherein the synthetic thermoplastic polymer is
polypropylene.
20. The hot-pressed non-woven fabric composite material of claim
12, wherein the weight ratio of the natural fiber to the fiber made
from the synthetic thermoplastic is from about 95:5, to about
20:80.
21. The hot-pressed non-woven fabric composite material of claim
12, wherein the matted natural fiber and the fiber made from the
synthetic thermoplastic is hot pressed at a temperature ranging
from about 180.degree. C. to about 240.degree. C. and above.
22. The hot-pressed non-woven fabric composite material of claim
12, wherein the matted natural fiber and the fiber made from the
synthetic thermoplastic is hot pressed at a pressure ranging from
about 25 psi to about 400 psi and above.
23. A hot-pressed non-woven fabric composite material comprising: a
coir fiber and a fiber made from a synthetic thermoplastic polymer,
wherein: the coir fiber and the fiber made from the synthetic
thermoplastic polymer are matted together and hot pressed; the coir
fiber has a diameter of from about 150 .mu.m to about 500 .mu.m,
and a length of from about 25 .mu.m to about 75 .mu.m; and the
fiber made from a synthetic thermoplastic polymer is a
polyethylene, polypropylene, or polylactic acid, having a diameter
of from about 30 .mu.m to about 50 .mu.m, and a length of from
about 25 .mu.m to about 75 .mu.m.
24. A method of preparing a non-woven fabric composite material
comprising: obtaining a natural fiber, with a sufficiently high
viscous flow temperature and degradation temperature, having a
suitable combination of stiffness, strength, and ductility; milling
the higher melting point natural fiber to a desired fiber length;
mixing the milled natural fiber with a thermoplastic fiber, wherein
the thermoplastic fiber has been cut to similar lengths as those of
natural fiber, and wherein the thermoplastic fiber has a lower
viscous flow temperature than the viscous flow temperature and the
degradation temperature of the natural fiber; creating a matted or
felted material from the blended fibers using carding and needle
punching, air deposition of fibers sprayed with a light glue, or
other processes, to give a matted non-woven fabric composite
material.
25. The method of claim 24, wherein the natural fiber is stripped
of its waxy coating and the natural fiber or the thermoplastic
fiber is treated with a chemical compatibilizer to yield a graft
copolymer.
26. The method of claim 24 wherein the natural fiber has been mixed
with a polyester fiber.
27. A method of preparing a hot-pressed non-woven fabric composite
material: heat pressing the matted non-woven fabric composite
material of claim 24 using a die in a compression molding machine
under a suitable temperature whereby the non-woven fabric composite
becomes a rigid part that has the shape of the die.
Description
[0001] The present invention claims priority to U.S. Provisional
Patent Application Ser. No. 61/103,173, filed Oct. 6, 2008, and
U.S. Provisional Patent Application 61/176,422 filed May 7, 2009,
the entire content of both of which is hereby incorporated by
reference.
BACKGROUND
[0002] The present invention pertains to a non-woven fabric
composite material, its manufacture and its uses. More
specifically, it relates to a non-woven fabric composite materials
containing natural fibers that are rich in lignin, with large
diameters including but not limited to coir fibers, combined with
fibers made from a thermoplastic polymer such as polypropylene and
including fibers that are made from polymers biodegradable.
[0003] German Patent DE 19711247 to Mieck and Reussmann describes a
process for the production of long fiber granulates from hybrid
bands. This process involves moving flax and hemp hybrid bands
through a 200.degree. C. preheated zone, and pulling the material
through a heated nozzle, followed by cooling.
[0004] German Patent DE 4440246 to Michels and Meister describes a
process for production of a fiber reinforced composite with at
least a thermoplastic polymer as matrix material, and cellulose
fibers or filaments as reinforcing material.
[0005] U.S. Pat. No. 5,948,712 to Tanabe describes a fabric
comprising a stiff fiber and a thermoplastic fiber. The fabric is
made by heating the stiff fiber and thermoplastic fiber at ambient
pressure, followed by compression molding at ambient temperature.
The resulting fabric would tear under any substantial force,
however, and the two-step process for producing it is
expensive.
[0006] German Patent DE 19934377 to Bayer and Koine describes a
process for producing a polyester-strengthened polypropylene
compounds, and involves a polypropylene material with a natural
material such as Jute, flax, hemp, or recycled cellulose.
[0007] German Patent DE 10052693 to Kitsayama and Yoshinori
describes laminate and materials with natural fiber content with
focus on automobile interiors. A process is described which
involves mixing a material with a weight of 150 g/cm.sup.2 with
Jute fibers and propylene fibers, followed by needle punching, and
baking of the resulting material at 180 C. This process, however,
is expensive, and results in a heart of thermoplastic material
rather than an equal distribution of materials.
[0008] United States Patent Publication 2006/0099393 describes a
composite thermoplastic sheets including natural fibers, wherein
the sheet material comprises discontinuous fibers bonded by
thermoplastic resin.
[0009] German Patent DE 10151761 to Mueller et al. describes a
process for production of semi-finished fiber strengthened
thermoplastics for high load construction materials. A process for
producing thermoplastic materials is described wherein a material
comprising thermoplastic matrix and long fibers is pulled through
pots to orient the fibers within the matrix. The material is
subsequently heated using infrared radiation.
[0010] United States Patent Publication 2007/0116923 describes a
fiber reinforced thermoplastic resin molding, wherein the fiber
comprises linen fiber which is spun into yarns.
[0011] German Patent Publication DE 102004054228 to Wittig and
Retzlaff describes methods and preparations for production of a
group part-binding/forming natural fiber materials to man-made
materials. This publication describes an improved method for
forming a natural fiber to a separate functional piece which is
man-made, using a glue and specially designed openings in each
piece.
[0012] Coconuts are an abundant, renewable resource in countries
within 20.degree. of the equator. The coconuts, or coco-nuts,
develop inside a husk that provides protection to the nut. The nut
is widely used to produce coconut oil from the white coconut meat,
called copra, as seen in FIG. 1. Approximately 50% of the biomass
in the husk is in the form of fibers, which are typically called
coir or coir fibers. The husk is often discarded as trash and
burned, polluting the atmosphere with greenhouse gases and other
contaminates. Replacing petroleum based fibers with natural fibers
like coir from coconut husks rather than burning the husks makes
this new invention very environmentally friendly.
[0013] One of the largest applications for the current invention of
non-woven fabric composite materials is for parts for automobiles.
Non-woven fabric composite materials for trunk liners, floor mats,
door panels, dash boards and other parts of automobiles are
currently made by combining fibers like polyester with a higher
viscous flow temperature with fibers with a lower viscous flow
temperature like polypropylene. Both fibers are derived from
petroleum. The present invention involves replacing some or all
petroleum-based fibers with the higher viscous flow temperature in
the non-woven fabric composite material with a lignin-rich natural
fiber like coir fiber that is less expensive, makes the composite
more sustainable and environmentally friendly, and provides
suitable and in some cases superior physical and mechanical
properties to the FP:PET composites that are now used. The
non-woven fabric composite felted material made by combining large
diameter, lignin-rich natural fibers like coir blended with fibers
made from thermoplastics such as polypropylene or polyethylene can
be compression molded into automotive parts using the same dies and
processing equipment (approximately same temperatures and pressures
that are currently used for PP:PET felted material) that is
currently used to make parts for automobiles, making possible a
seamless, barrier free entry into the marketplace for non-woven
fabric composites for automobile parts using the invention
described herein. This should also be true for many other
industries where the current invention can be utilized.
[0014] A humanitarian benefit of this invention is that it will
create a demand for coir fiber, giving their husks that are now
usually burned some value, and thus will provide additional income
to the 11 million very poor coconut farmers, many of whom subsist
on less than a few hundred U.S. dollars of income per year.
[0015] A further environmental benefit of the current invention is
that it will "utilize" the coir fiber which is abundant in certain
parts of the world and avoid discarding and burning as waste the
coconut husks from which the fibers are extracted.
SUMMARY
[0016] One aspect of the present invention pertains to non-woven
fabric composites containing large diameter, lignin rich natural
fibers and a method for producing such composites. The non-woven
fabric composite may be comprised of large diameter, lignin-rich,
natural fibers with a higher viscous flow temperature and
degradation temperature and fibers made of a thermoplastic polymer
with a lower viscous flow temperature such as polypropylene or a
biodegradable thermoplastic polymer fiber such as polylactic acid.
The processing window for hot pressing this composite is above the
viscous flow temperature of the thermoplastic and the lower of the
degradation temperature or the viscous flow temperature of the
natural fiber.
[0017] An example of the method to be used for hot pressing coir
fiber and polypropylene requires the following steps: (1) removing
the natural fibers called coir, which has a relatively high
degradation temperature from the coconut husk; (2) securing
thermoplastic fibers made from recycled polypropylene that has a
lower viscous flow temperature than the degradation temperature of
coir; (3) cutting the fibers to 25-75 mm length but preferably
50-75 mm lengths; (4) blending the milled 50-75 mm coir fibers with
the polypropylene fibers to form a very flexible non-woven fabric
material felt (or non-woven fabric material mat); and depending on
the application (4) hot pressing the flexible non-woven fabric
material felt at elevated temperatures above the viscous flow
temperature (or melt temperature) of the polyproplyene fibers,
using a die or a flat platen press to form rigid parts with a
desired shape or a flat panel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The following drawings form part of the present
specification and are included to further demonstrate certain
aspects of the present invention. The invention may be better
understood by reference to one or more of these drawings in
combination with the detailed description of specific embodiments
presented herein.
[0019] FIG. 1 shows an open coconut and husk with fibers, usually
called coir fibers;
[0020] FIG. 2 shows opened coconut husk with coconut, a portion of
the husk and long coir fibers that may be milled into approximately
50-75 mm lengths to be processed into felted material in accordance
with the present invention;
[0021] FIG. 3 shows short coir fibers (upper left) and short
polypropylene fibers (lower left) prior to being blended, carded
and needle punched into felted material (right) in accordance with
the present invention;
[0022] FIG. 4 shows felt comprised of 50% polyester/50%
polypropylene fiber matting which is widely used at present (left)
and felt comprised of coir fiber/polypropylene fiber (right) in
accordance with the present invention;
[0023] FIG. 5 shows felted material comprised of 50 wt % coir fiber
and 50 wt % polypropylene fiber prior to hot pressing (which is the
same as compression molding at elevated temperature), as seen at
10.times. (left) and 40.times. (right);
[0024] FIG. 6 shows non-woven fabric composite material made from
polyester fiber and polypropylene fibers (left) and non-woven
fabric composite material made from coir fiber and polypropylene
fibers (right) with each plaque produced by hot pressing the
respective felted materials at about 207.degree. C. and about 150
psi of pressure
[0025] FIG. 7 shows the difference in hot pressing a non-woven
fabric composite material felt at 180.degree. C. (left) and at
220.degree. C. (right), indicating the dramatic difference
40.degree. C. can make in the flow of the PP fiber and the degree
of wetting of the coir fiber by the PP;
[0026] FIG. 8 shows a hot pressed door panel (top), a hot pressed
trunk liner (middle), and a polyester/propylene non-woven fabric
composite material felt (bottom) prior to hot pressing. One aspect
of this invention would substitute coir fibers for polyester fibers
in such parts;
[0027] FIG. 9 shows tensile strength as a function of density for
non-woven fabric composite materials after hot pressing, using
various combinations of temperature and pressure to achieve the
range of densities;
[0028] FIG. 10 shows flexural modulus as a function of density for
non-woven fabric composite materials after hot pressing, using
various combinations of temperature and pressure to achieve the
range of densities;
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Definitions
[0029] The term "natural fiber" as used herein, refers to any
continuous filament which is derived from a natural, renewable
sources such as plants or animals. The words "fiber" and "fibers"
are used interchangeably. Natural fibers may include, but are not
limited to, seed fibers such as cotton and kapok; leaf fibers such
as sisal and agave; bast fiber or skin fiber such as flax, jute,
kenaf, hemp, ramie, rattan, soybean fiber, vine fibers, and banana
fibers; fruit fiber such as coconut fiber; stalk fiber such as
straws of wheat, rice, barley, bamboo, grass, and tree wood; animal
hair fiber such as sheep's wool, goat hair (cashmere, mohair),
alpaca hair, horse hair; silk fiber; avian fiber such as feathers;
Preferably, the natural fiber used in this invention should possess
at least moderate strength and stiffness and good ductility. It
should also have sufficient adhesion to the lower melting point
fiber, or be surface treatable to increase chemical compatibility
and provide adequate adhesion between the natural fiber and the
thermoplastic fibers. Natural fibers that are rich in lignin are
especially desirable, preferably with a lignin content of greater
than about 20 wt %. Fibers with larger diameters are also
preferable to give greater fiber stiffness and lower density felted
material and lower density parts pressed from the felted
material.
[0030] The phrase "coir fiber" as used herein refers to any type of
fiber derived from the coconut husk of the coconut palm tree, Cocos
nucifera.
[0031] The phrases "fiber with a higher viscous flow temperature"
and "fiber with a lower viscous flow temperature" as used herein,
refer to the temperatures at which the viscosity of the respective
fibers reach a suitably low value that viscous flow occurs
relatively easily. The degradation temperature for fibers is the
temperature at which the fiber begins to oxidize and degrade. This
will not be a unique temperature but will depend on the time at
temperature, with a shorter time at the elevated temperature
resulting in a somewhat higher degradation temperature and a longer
time at temperature resulting in a lower degradation temperature.
The processing window for hot pressing the non-woven fabric
composites defined in this invention will be between the viscous
flow temperature for the thermoplastic fibers (which must have a
lower viscous flow temperature than the natural fiber) and the
lower of either the degradation temperature or the viscous flow
temperature of the natural fiber. Generally, the processing window
for hot pressing the non-woven fabric composites made using natural
and thermoplastic fibers will have the upper bound for processing
being the degradation temperature of the natural fiber (which is
usually lower for natural fibers than the temperature at which
viscous flow occurs easily) and the lower bound will depend on the
viscous flow temperature of the thermoplastic, where sufficient
flow of these thermoplastic fibers to "bond" to the natural fibers
will be take place under a given pressure.
[0032] The phrase "non-woven fabric composite material" as used
herein refer to any material comprising two or more fibers that are
neither woven nor knitted, that is to say fibers that have been
blended and laid into a matted form with the fibers randomly
oriented in the mat, or felt as it usually called. The 50-75 mm
long fibers are bonded together by chemical, mechanical, pressure
at elevated temperature without any surface treatment or pressure
and temperature applied after surface treatments to enhance
adhesion between the two types of fibers. The composite can exist
in two forms: a very flexible felt (or mat) and a more rigid form
that is produced by hot pressing (or compression molding). The
non-woven fabric composite should not be confused with conventional
fiber reinforced plastic composites that are comprised of a
continuous matrix of polymer with discontinuous fibers reinforcing
the plastic. The non-woven fabric composite consists of a blending
of two or more types of fibers rather than a mixing of one fiber
type in a viscous polymer melt that is subsequently cooled to a
solid plastic reinforced with fibers.
[0033] The term "thermoplastic polymer fiber" as used herein,
refers to any fiber comprising a polymer which is easily formed at
higher temperatures because its viscosity decreases monotonically
with increasing temperature, and rapidly above the melt
temperature. By contrast, thermosetting polymers chemical react
when heated and cannot be easily formed subsequently. For purposes
of this invention, thermoplastic polymers include, but are not
limited to, polypropylene ("PP"), polyethylene ("PE"), and
polylactic acid ("PLA").
[0034] The ratios of fibers that are given in this patent are in
weight fractions. Therefore a ratio of 50:50 of Fiber A to Fiber B
in a mixture would indicate that 50% of the total mass in the
mixture consists of Fiber A, and 50% of the total mass in the
mixture consists of Fiber B. The range of weight ratios in this
invention go from 20:80 to 95:5 coir fiber to thermoplastic fiber.
The higher the coir fiber, the lower will be the density of the
non-woven fabric composite material felt and the lower will be the
density of the non-woven fabric composite material after it has
been hot pressed into the shape of a part.
[0035] In one preferred embodiment of the non-woven fabric
composite material designed for manufacturing into higher density,
more rigid parts by hot pressing (or other high temperature forming
processes that convert felted material into rigid material), the
present invention pertains to a non-woven fabric composite
comprised of (1) a natural fiber with a relatively higher viscous
flow temperature and/or biodegradation temperature than that of the
thermoplastic fiber, matted together at around room temperature;
and (2) a thermoplastic fiber with a lower viscous flow
temperature, preferably made from recycled material or a
thermoplastic fiber that is a biodegradable fiber. In preferred
embodiments, the natural fibers may comprise lignin rich natural
fibers with relatively larger diameters such as coir fibers, and
the thermoplastic fibers may be a polypropylene ("PP") or a
polyethylene ("PE") or biodegradable fibers such as polylactic acid
("PLA"), or mixtures thereof. Such composites can be used in
automobile parts and other products such as those made by elevated
temperature compression molding. In a second preferred embodiment
where the non-woven fabric composite is to be used in a low
density, soft, flexible form, and therefore, does not need to be
hot pressed into a rigid part, a large diameter fiber rich in
lignin such as coir fiber can be used by itself or with a small
additions (5-30%) of any other fiber (does not need to be a
thermoplastic, but can be a polyester fiber such as PET), but
preferably one with a small diameter to facilitate the processing,
and more preferably a second natural fiber to make the non-woven
fabric composite more environmentally friendly. Flexible non-woven
fabric composites as described in this second embodiment can be
used for such applications as insulation, cushioning in packaging
or for padding in children's toys.
[0036] Natural fibers that are rich in lignin have some distinctive
physical and mechanical properties that can be extremely beneficial
in particular applications. First, lignin rich fibers do not burn
as rapidly as natural fibers that are richer in cellulose. Second,
lignin rich fibers are less susceptible to developing odors due to
molds and other microbials. Third, lignin rich fibers are more
durable when exposed to water. Coir fiber is a lignin rich fiber
with 33 wt % lignin compared, for example, to flax (2.8 wt %),
sisal (10 wt %), jute (12 wt %), kenaf (15 wt %) or cotton (15 wt
%).
[0037] Fibers that have larger diameters also have advantages for
some applications of non-woven fabric composite materials. Fibers
with larger diameters will be stiffer in bending and have more
resilience. They will also process differently into non-woven
fabrics, giving lower density felted material due to the fiber
stiffness than non-woven fabric made with fibers that are all
smaller diameter. After hot pressing, non-woven fabrics made with a
mixture that includes some larger diameter fibers will also have a
much lower density than non-wovens made entirely with small
diameter fibers.
[0038] Coir fibers also have much larger average diameters than do
most natural or synthetic fibers, with diameters ranging from
.about.150 .mu.m to about 500 .mu.m compared to most natural or
synthetic fibers that have diameters of .about.40 .mu.m. Coir
fibers also have attractive mechanical properties including an
elongation of .about.15-20% compared to most natural fibers with an
elongation of 1-2%.
[0039] The lignin-rich fibers (e.g., coir fiber) can be
incorporated into two kinds of non-woven fabric composites: (1)
those that will be produced and used as a non-woven fabric
composite material in felted or matted form, which is soft and
flexible and (2) those that will be produced as non-woven fabric
composite material in felted form but will subsequently be molded
at elevated temperatures into more rigid parts or panels.
[0040] For non-woven fabric composite materials that will be molded
at elevated temperatures into more rigid parts, the second type of
fiber that is blended with the lignin rich natural fiber must have
a viscous flow temperature (sometimes called a melt temperature)
that is less than the temperature at which the natural fiber
degrades, and this degradation temperature depends on the length of
time the fibers arc at maximum molding temperature during
processing. Higher molding temperatures can be tolerated for a
shorter time and lower molding temperature can be tolerated for
longer time. Fibers made from polypropylene, polyethylene or
copolymers of the two monomers flow at temperatures below the
degradation of lignin-rich natural fibers such as coir.
Furthermore, there is a large supply of these fibers that are made
from recycled material. When lignin-rich fibers such as coir are
combined with polypropylene fibers made from recycled material as
they are in this invention, the resultant non-woven fabric
composite materials are very environmentally friendly indeed.
I Non-Woven Fabric Composite Material Utilizing Natural Fibers
[0041] In a preferred embodiment, the invention comprises a
non-woven fabric composite material which includes a blend of at
least two types of fibers, one fiber with a higher degradation
temperature or viscous flow temperature and the other fiber with a
lower viscous flow temperature. The fiber with the higher viscous
flow or degradation temperature will be a natural fiber, preferably
a coir fiber, and can be physically mixed (such as in a hopper)
with some higher temperature viscous flow thermoplastic fiber such
as "PET," or polyester fiber. The fiber with the lower viscous flow
temperature can be a thermoplastic fiber, such as polypropylene
("PP"), polyethylene ("PE"), polylactic acid ("PLA"), or mixture
thereof. Thus, the non-woven fabric composite material could
include a mixture of coir fibers, PP and PET.
[0042] The lengths of the natural fibers and the thermoplastic
fibers can vary from about 10 mm to 100 mm, preferably from about
25 mm to about 75 mm. Also, preferably, the natural fibers and the
thermoplastic fibers have approximately the same length. The
thermoplastic fiber can have a diameter of from about 30 .mu.m to
about 50 .mu.m.
[0043] Different types of fibers can be made to cohere in a felt,
or matted together, by the following methods: [0044] Thermal
bonding [0045] Using a large oven for curing [0046] Calendering
through heated rollers (called spunbond when combined with
spunlaid), calendars can be smooth faced for an overall bond or
patterned for a softer, more tear resistant bond. [0047]
Hydro-entanglement: mechanical intertwining of fibers by water jets
(called spunlace) [0048] Ultrasonic pattern bonding, often used in
high-loft or fabric insulation/quilts/bedding [0049] Needled felt
or needle punched felt: mechanical intertwining of fibers by
needles pushing fibers that are layed in the plane of the felt
through the thickness of the felt, increase the cohesion of the
fibers in the felt [0050] chemical bonding (wetlaid process): use
of binders (such as latex emulsion or solution polymers) to
chemically join the fibers. A more expensive route uses binder
fibers or powders that soften and melt to hold other non-melting
fibers together [0051] one type of cotton staple nonwoven is
treated with sodium hydroxide to shrink bond the mat, the caustic
causes the cellulose-based fibers to curl and shrink around one
another as the bonding technique [0052] meltblown or air carding
randomly laying two or more types of fibers that are very weakly
bonded from the air attenuated fibers intertangling with themselves
during web formation as well as the temporary tackiness they have
as they laid randomly into a matted or felted material [0053] one
unusual polyamide spunbond (Cerex) is self-bonded with gas-phase
acid.
[0054] There are four preferred means for making two or more types
of fibers cohere in this invention of non-woven fabric composite
materials. First, the non-woven fibers can be laid randomly into a
loose mat where the fibers all lie in parallel planes. Needle
punching will then bend some of the fibers and push them partially
or totally through the thickness of the mat, making the mat more
cohesive, giving it very modest tensile strength but high
flexibility for handling purposes and making it easy to compression
mold. Such matted material is also suitable for insulation, padding
and other applications where low strength and low density are
desired. The fibers in this process are not truly bonded but just
mechanically entangled sufficiently to perform as a
"quasi-mechanical bonding". A second way to join the fibers that
also gives weak bonding between fibers, again with low strength and
density, is using various adhesives that may be sprayed during air
carding of fibers, making them "tacky" and giving very weak
attachment between fibers, again making the matted or felted
material low in strength but with high flexibility, good for
insulation, padding and other similar applications. A third way
that the fibers can be joined that results in much higher strengths
and stiffnesses, making rigid parts, is hot pressing that causes
the thermoplastic fiber to locally melt and flow, wetting adjacent
natural fibers, effectively "gluing" the whole fibers network
together into a rigid web, giving significant strength and
stiffness to the hot pressed part. A fourth approach gives the
highest strength and stiffness to the non-woven fabric composite by
enhancing the adhesion between the natural and the thermoplastic
fibers. This can be done by using chemical cleaning of the natural
fiber, for example removing the waxy coating that is present on
coir fibers, and by using chemical compatibilizers to treat the
natural or thermoplastic fibers; for example using maleic anhydride
to make graft copolymer with polypropylene, since the maleic
anhydride can chemically react to form strong bonding to a cleaned
coir fiber (but not a coir fiber with waxy coating), giving an
interfacial strength that is three times that observed for
polypropylene and coir fibers that have not been cleaned. The
felted material must still be hot pressed to achieve this high
tensile strength and stiffness, as the flow of the thermoplastic is
essential to increase the interfacial bonding area between the two
fibers.
[0055] The non-woven fabric composite of this invention can be made
with various combinations of fibers, areal densities and weight
percentages of each fiber, depending on the application and the
specific family of physical and mechanical properties that are
desired. For automotive applications, for example, trunk liners are
less stiff, door panels are moderately stiff, and dashboards
require the greatest stiffness.
[0056] For non-woven fabric composite materials that will not be
hot pressed (e.g., building insulation, cushioning for packaging),
it is not necessary to use a thermoplastic fiber at all and the
degradation temperature of the natural fiber is less critical since
no elevated temperature processing is required.
II Method for Producing a Non-Woven Fabric Composite Material
Utilizing Natural Fibers
[0057] In a further preferred embodiment, the invention comprises a
method for producing a non-woven fabric composite material
utilizing fiber with a higher viscous flow temperature and a fiber
with a lower viscous flow temperature. The higher melting point
fiber is a larger diameter preferably lignin-rich, natural fiber,
more preferably coir fiber.
[0058] The method comprises the steps of: (1) obtaining a natural
fiber (see FIG. 2) with a sufficiently high viscous flow
temperature and degradation temperature and suitable combination of
stiffness, strength, and ductility; (2) mill the higher melting
point natural fiber to a desired fiber length determined by the
processing equipment to be used to make the felted material
subsequently, which was 50-75 mm in the carding and needle punching
equipment used in developing this invention (FIG. 3); (3) mixing
this milled natural fiber, which has a higher viscous flow
temperature, with a thermoplastic fiber that has been cut to
similar lengths and that has a lower viscous flow temperature; (4)
create a matted (or felted) material (FIGS. 4 and 5) from the
blended fibers using carding and needle punching, air carding with
light adhesives as previously described, or other suitable
processes; and if so desired, (5) hot pressing the felted material
using a die (to give the desired shape to the part) in a
compression molding machine with the felted material at a suitable
temperature and pressure so that the non-woven fabric composite
assumes the rigid shape needed for a particular part (FIG. 6).
[0059] The most critical parameter for hot pressing non-woven
fabric composite material felt into rigid parts is the pressing
temperature. When PP sheet is shaped using thermoforming, it is
generally formed at temperatures between 165.degree. C. and
180.degree. C., since the PP used is an isotactic, semi-crystalline
polymer whose crystalline regions melt in this temperature range.
Viscous flow can only occur easily in semi-crystalline PP when the
crystals melt, and this occurs between 165.degree. C. and
180.degree. C. in various isotactic PP. In fact, the viscosity of
PP drops by a factor of 500 between 170.degree. C. and 180.degree.
C., with the properties changing from a stiff, rubbery solid to a
viscous liquid.sup.3. If one presses at too low a temperature, the
crystals make permanent shape changes (via permanent viscous
deformation) difficult to produce. If one presses at too high a
temperature (generally thought to be >180.degree. C. in the
literature), the resulting low viscosity allows considerable
sagging. Therefore, one might assume this temperature range to be
optimal for compression molding of non-woven fabric composite
material felt with polypropylene fibers as the lower viscous flow
temperature constituent. Surprisingly, this has proven to not be
the case.
[0060] The appropriate temperature and pressure for compression
molding a non-woven fabric composite material felt made of coir
fibers and polypropylene fibers depends on the application and the
combination of mechanical and physical properties that best serve
the application. For some applications where thermal insulation or
sound damping are required, the felt may be used directly without
hot pressing and the felt can be very high in coir fiber content
(80:20 to 95:5), with the fiber blended in with the coir fiber also
being a natural fiber, with a lower diameter (<80 .mu.m is
preferred) to facilitate processing into felted material. Some
packaging applications where energy absorption during impact is the
primary function might also use coir rich felt with a density of
.about.0.15 g/cm.sup.3 without hot pressing it, which increases the
density of the non-woven fabric composite material. Energy
absorption during impact, thermal insulation properties (i.e., low
thermal conductivity) and sound damping characteristics (i.e., low
sound transmission coefficient) are all optimized at low densities,
preferably with non-woven fabric composite felt that has not been
hot pressed into a more dense and rigid material, giving mechanical
properties that are minimal but unnecessary for this family of
applications. The large fiber diameter of the coir fiber give great
resilience to insulation, minimizing packing and settling over
time, which allows the insulation to maintain its "R" value. R is
calculated as insulation thickness divided by the thermal
conductivity of the insulation.
[0061] To achieve improved mechanical properties, the non-woven
fabric composite felted material needs to be hot pressed or
compression molded to both increase the density (more fibers per
square centimeter to support the load) and securely attach the coir
and polypropylene fibers in the felt to each other (by increasing
the contact area where two fibers are being "bonded" as previously
described), forming a strong web. As the pressing temperature is
increased from 180.degree. C. to around 240.degree. C. and the
pressure is increased from 25 psi to 300 psi or more, the density
of the compression molded felt increases from about 0.3 g/cm.sup.3
to 0.7 g/cm.sup.3 or more. It should be noted that a temperature
higher than the 170.degree.-180.degree. C. temperature range often
used for thermoforming polypropylene sheet is necessary to get
sufficient flow of the polypropylene fibers to securely attach the
fibers, creating a rigid web. The difference in the flow of the
polypropylene and coir fibers and the wetting of the coconut fibers
by the polypropylene fiber as it flows is seen in FIG. 7. Heating
the non-woven fabric composite felted material to 180.degree. C.
without the application of pressure will produce insufficient flow
of the polypropylene (or to the melt temperature of whatever
thermoplastic fiber is used to "glue" the fiber network together)
to give strong joints where the thermoplastic fibers overlay the
natural fibers, giving insufficient strength and stiffness. In
summary heating the non-woven fabric composite felt material to
180.degree. C. without pressure is unnecessary for applications
where a low density felt is desired and inadequate for higher
density applications where a more rigid part with better tensile
strength and stiffness is required.
[0062] In all preferred embodiment, the natural fiber has a larger
diameter (most of fibers above 100 .mu.m) and with a higher lignin
content (>20%), more preferably coir fiber.
[0063] In a preferred embodiments for non-woven fabric composites
that will be hot pressed, the fiber with the lower viscous flow
temperature is a thermoplastic fiber, preferably a petroleum-based
polymer fiber, most preferably polypropylene (PP).
Example 1
[0064] The first example is for compression molded parts of a
non-woven fabric composite material that utilizes a large diameter,
natural fiber that is rich in lignin and a thermoplastic with a
viscous flow temperature that is significantly lower than the
degradation temperature of the natural fiber.
Production of Non-woven Fabric Composite Material Felt
[0065] The natural fibers and thermoplastic fibers are cut to
lengths that depend on the equipment that is to be used to make the
non-woven fabric composite material felt, typically lengths between
25 mm and 75 mm. These two types of fibers are blended together
into a mixture of natural fibers and thermoplastic fibers. The
ratio of natural fibers to thermoplastic fibers might be 50:50 by
weight, but can range from 20:80 to 95:05 depending on the
combination of mechanical properties needed. The non-woven fabric
composite material in the form of a felt (or mat) can be made from
the blended fibers using carding and needle punching to bind the
carded layers together or air carding, using a lightly sprayed
adhesive to bond the fibers together. The felt can be produced in
widths of up to 1.5-2.0 m (or more depending on the equipment used)
and in any lengths that are that are convenient for shipping. For
example, 2 m wide by 3 m long mats might be produced, stacked on
skids and shrink wrapped for shipping. Alternatively, rolls of a
convenient size for shipping (for example, 1.5 m wide by 100 m
long) can be made and shrink wrapped for shipping. Because the
fibers are only held together by needle punching or very light
adhesive, the felt of non-woven fabric composite material made in
these ways is very flexible, allowing it to be produced in rolls
suitable for shipping, and more importantly, with the necessary
flexibility to assume the shape of the mold when subsequently hot
pressed at elevated temperatures between the viscous flow
temperature of the thermoplastic fiber and the degradation
temperature of the natural fiber. It is important to note that the
fibers are not heated during production of the non-woven fabric
composite felt (unless a very modest heating is used is used to
cure spray adhesives or adhesives applied insome other way to make
the fibers tacky instead of using needle punching to give the felt
some coherence). It should be noted that heating the felted
material to the melt temperatures of the thermoplastic fibers in
the absence of pressure to increase bonding between fibers to
enhance the cohesion of the felt is unnecessary, will reduce the
flexibility of the felt, and will incur unnecessary costs in
processing. The bulk density of the non-woven fabric composite felt
after needle punching will typically be between 0.1 and 0.2
g/cm.sup.3 prior to hot pressing. A finishing cloth can be added to
the felted material to produce parts that are more aesthetically
pleasing after subsequent hot pressing felt into rigid parts at
elevated temperatures. The finishing cloth is typically .about.200
g/m.sup.2 and should not be degraded at the temperature the felt is
subsequently compression molded since it is typically pure
polyester.
[0066] Compression Molding of Non-Woven Fabric Composite Material
into Parts--
[0067] Pieces of felt of non-woven fabric composite material of
suitable sizes are subsequently cut from the roll and heated to a
suitable temperature, which is greater than the temperature at
which the thermoplastic fiber readily manifest viscous flow
(>180.degree. C. for polypropylene) but less than the
degradation temperature of the natural fiber (which is
.about.240.degree. C. for coir fiber depending, on the time at
temperature) and hot pressed into the desired shape using a
suitable die. Heating to 180.degree. C. in the absence of pressure
will produce insufficient flow of the polypropylene fibers to
increase the density or attach the randomly oriented unwoven fibers
into a rigid network. Thus, for example, for coir fibers blended
with polypropylene fibers, the temperature ranges from about
180.degree. C. to about 240.degree. C. Preferably from above
180.degree. to about 240.degree. The compression molding pressure
can range from about 25 psi to about 400 psi or more. The
particular combination of temperature and pressure used depends on
the hot pressed density that is desired to give a particular family
of physical and mechanical properties. The density of the
compression molded non-woven fabric composite parts will typically
be between 0.3 and 0.7 gm/cm.sup.3 depending on the combination of
temperature, pressure and time at pressure used in processings. The
mechanical, thermal and acoustic properties will all vary
significantly with density, allowing the properties to be tailored
to the needs of a specific application by choosing suitable
processing conditions, as seen in FIGS. 9 and 10. For example,
automobile trunk liners might be made with non-woven fabric
composite materials of coir and polypropylene fibers in a felt with
an areal density of 1000 g/m.sup.2 that has subsequently been
compression molded to a thickness of 2 mm and a density of 0.5
g/cm.sup.3. Dashboards for automobiles might be made with non-woven
fabric composite felt of coir and polypropylene fibers with an
areal density of 2000 g/m.sup.2 that has been compression molded to
a thickness of 3.4 mm and a bulk density of 0.6 g/cm.sup.3,
depending on the specific design and the combination of physical
and mechanical properties that are desired. If desirable,
industrial coloring agents or dyes can be added in the
manufacturing process of the thermoplastic fiber to give a certain
color to non-woven fabric composite material felt.
[0068] The preferred large diameter, natural fiber rich in lignin
is coir fiber, and the preferred thermoplastic fiber is
polypropylene for automotive trunk liners. These two fibers can be
blended, produced as a non-woven fabric that is then needle punched
to increase coherence of the non-woven fabric composite material
felt as described above. It can subsequently be hot pressed at a
suitable temperature and pressure into a wide variety of products
for automobiles (e.g., trunk liners, door panels, dashboards, head
liners, package carriers, floor boards, mud flaps etc.) and other
products produced by hot pressing non-woven fabric composite such
as interiors for truck and tractor cabs, or toys for children.
Automobile parts that have been hot pressed from non-woven fabric
composite material felt are seen in FIG. 8.
Example 2
[0069] The second example is for products that can be made from
(1-12.5 mm or possibly thicker) rigid sheets of non-woven fabric
composite material using large diameter natural fibers that are
rich in lignin (e.g., coir fiber) combined with thermoplastic
fibers (e.g., polypropylene).
[0070] The non-woven fabric composite felt is made from large
diameter, natural fibers rich in lignin like coir and
thermoplastics fibers like polypropylene, which has a viscous flow
temperature well below the degradation temperature of the coir
fibers using the processes described in Example 1. The non-woven
fabric composite material felt (or mat) made from natural fibers
and thermoplastic fibers can be pressed into flat, rigid sheets (as
distinct from more complex shapes made in compression molding)
using a combination of pressure and temperature to get the density
that will give the desired combination of mechanical and physical
properties, as previously described.
[0071] The flat, non-woven fabric composite sheets can be used for
building materials such as wall panels, ceiling panels, furniture
and other applications requiring a light-weight composite with
moderate strength and stiffness and/or low sound transmission
coefficient, and low thermal conductivity.
Example 3
[0072] The third example is for products that can be made from
non-woven fabric composite material felt that has been made using
large diameter, natural fibers rich in lignin (e.g., coir fiber)
but where the felt will not be processed at elevated temperatures
and pressures to make rigid composites like those described by
Examples 1 and 2.
[0073] The non-woven fabric composite felt is made primarily
(>80%) from a large diameter, natural fibers rich in lignin. The
felt can be made of 100% natural fiber rich in lignin (e.g., coir
fiber) if it is air carded with the fibers held together by sprayed
on adhesive. If the non-woven fabric composite made of lignin rich,
large diameter (150-500 um) fibers like coir fibers, the felt can
be produced by carding and needle punching but may require 0-20%
natural fibers with smaller diameters (.about.40 um) such as kenaf
that are more flexible and will easily be bent during needle
punching to penetrate through the thickness, giving cohesiveness to
the felt. The felt need not include thermoplastic fibers since for
these applications, hot pressing to give a high density rigid
material as is done in Examples 1 and 2 is undesirable. A smaller
amount (.about.5%) of a third type of fiber that is a thermoplastic
might be included to melt and then cohere the two natural fibers
together, which would require heating to the temperature required
to melt the third type of fiber, but not hot pressing.
[0074] In this application, the emphasis is on products that
require a very low thermal conductivity, a low sound transmission
coefficient, and/or a high level of cushioning for energy
absorption. These properties are achieved for woven fabric
composite materials that are very low density; namely, felt that
will not be subsequently processed at higher temperatures and
pressures into a higher density, rigid material.
[0075] Applications for non-woven fabric composites of primarily
(or exclusively) large diameter natural fibers that are rich in
lignin like coir include building/housing insulation, packing for
packaging and under-the-hood applications in automotive.
Example 4
[0076] One application of this patent is composite materials for
the automotive industry. In particular, trunk liners, truck
decking, truck lid liners, door panels and floor mats are all
potential applications can be made as described in what follows.
Each part may require different strength and stiffness, and thus,
need slightly different percentages of the two fibers (20:80 to
80:20) used and different hot pressing temperatures (200.degree.
C.-230.degree. C.) to achieve the distinctive properties required.
This versatility is another benefit of this invention.
[0077] In this example, natural coir fibers are combined with
petroleum based polypropylene (PP) fibers (FIG. 3) in a blending
process that results in a malt of blended but unwoven coir and PP
fibers (FIG. 3) with an areal density of 1000 g/cm.sup.2.
[0078] The coir fiber is limited to a hot pressing temperature of
about 240.degree. C. depending on pressing time by oxidative
degradation. The polypropylene fiber has the lower viscous flow
temperature, with its viscosity dropping dramatically by 500.times.
between 170.degree. C. and 180.degree. C. as the crystals in this
semi-crystalline polymer melt. As previously noted, 180.degree. C.
or less is the usual thermoforming (or hot pressing) temperature
for sheet polypropylene. This temperature limit is due to sag
issues in PP sheet above 180.degree. C. However, as previously
explained, this temperature is too low to make PP:coir non-woven
fabric composites with suitable combinations of strength and
stiffness, since at 180.degree. C., there is relatively little flow
of the PP fibers, as seen in FIG. 7 with flow at 220.degree. C.
shown for comparison. Note that at 180.degree. C. without any
pressure, there would be very little flow of the polypropylene
fibers necessary to firmly join the coir fibers into a rigid
web.
[0079] For this application, it is necessary that the PP's
viscosity be sufficiently low, not just to allow the PP fibers to
flow under at a modest pressure of 100 to 150 psi. Furthermore, the
flow of the PP fibers needs to be sufficient to wet the coir fiber
to effectively "glue" the coir fibers together to create a web
structure, with moderate strength and stiffness. The degree of flow
can be increased by increasing the hot pressing temperature, as
seen in FIG. 7, where the degree of flow of the PP at 180.degree.
C. may be compared to the degree of flow of the PP at 220.degree.
C. The strength and stiffness of the specimen hot pressed at
180.degree. C. is much less than the one pressed at 220.degree. C.
(see FIG. 7). In commercial production, the matted material seen in
FIG. 4 and FIG. 8 (strip across bottom) is pressed into automotive
parts like the trunk liner and the door panel presented in FIG. 8.
The matted material is heated to the specified hot pressing
temperature in a furnace and then placed into a hot pressing unit
with dies to create the desired shape for the part. Usually the die
surfaces are also heated, but to a lower temperature than the
specified hot pressing temperature to facilitate more rapid cooling
and reduced cycle times. The heated material can also be pressed in
a cold mold.
[0080] A thin, non-woven finishing fabric made with only one type
of fiber that has a higher viscous flow temperature than the hot
pressing temperature to be used can be attached with stitching to
the matted fiber blend, as seen in FIG. 4. During hot pressing this
woven fabric is unaffected, but becomes even more securely attached
to the hot pressed composite due to flow of the PP at the interface
between the finishing fabric and the composite backing. The
resulting panel is moderately stiff with an attractive fabric
finish so that the hot formed part is ready to be installed into an
automobile without further processing.
REFERENCES CITED
[0081] The following references, to the extent that they provide
exemplary procedural or other details supplementary to those set
forth herein, are specifically incorporated herein by
reference.
U.S. PATENT DOCUMENTS
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[0084] U.S. Pat. No. 6,648,363 issued on Nov. 18, 2003, with Gordon
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NON-PATENT DOCUMENTS
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