U.S. patent application number 13/166531 was filed with the patent office on 2011-10-13 for non-woven fabric composites from coir fibers.
This patent application is currently assigned to BAYLOR UNIVERSITY. Invention is credited to Walter Bradley, David Stanton Greer.
Application Number | 20110250814 13/166531 |
Document ID | / |
Family ID | 44761255 |
Filed Date | 2011-10-13 |
United States Patent
Application |
20110250814 |
Kind Code |
A1 |
Bradley; Walter ; et
al. |
October 13, 2011 |
NON-WOVEN FABRIC COMPOSITES FROM COIR FIBERS
Abstract
A non-woven fabric composite containing coir fibers and a method
for producing such composites. The non-woven fabric composite is
comprised of coir fibers, which are large diameter, lignin-rich
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 ("PP"),
polyethylene ("PE"), polylactic acid ("PLA"), and polyester ("PET")
or mixtures 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) |
Assignee: |
BAYLOR UNIVERSITY
Waco
TX
|
Family ID: |
44761255 |
Appl. No.: |
13/166531 |
Filed: |
June 22, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13161316 |
Jun 15, 2011 |
|
|
|
13166531 |
|
|
|
|
12574518 |
Oct 6, 2009 |
|
|
|
13161316 |
|
|
|
|
61176422 |
May 7, 2009 |
|
|
|
61103173 |
Oct 6, 2008 |
|
|
|
Current U.S.
Class: |
442/341 ;
264/103; 442/334; 442/405; 442/411 |
Current CPC
Class: |
Y10T 442/615 20150401;
D04H 1/4382 20130101; D04H 1/425 20130101; D04H 1/48 20130101; D04H
1/12 20130101; D04H 1/4291 20130101; D04H 1/435 20130101; D04H 1/46
20130101; Y10T 442/692 20150401; Y10T 442/686 20150401; D04H 1/04
20130101; D04H 3/015 20130101; D04H 1/558 20130101; Y10T 442/608
20150401; D04H 1/4266 20130101; D04H 1/74 20130101; Y10T 442/637
20150401; D04H 1/64 20130101; D04H 1/54 20130101 |
Class at
Publication: |
442/341 ;
442/411; 442/334; 442/405; 264/103 |
International
Class: |
D04H 5/06 20060101
D04H005/06; D04H 1/58 20060101 D04H001/58; D04H 1/48 20060101
D04H001/48 |
Claims
1. A non-woven fabric composite material, comprising: coir fiber;
and a fiber made from or including a synthetic thermoplastic
polymer, wherein the synthetic thermoplastic polymer is selected
from the group consisting of polypropylene ("PP"), polyethylene
("PE"), polylactic acid ("PLA"), and polyester ("PET"), and
mixtures thereof, wherein the coir fiber and the fiber made from
the synthetic thermoplastic polymer are matted together to form a
matted material, wherein the coir fiber has a higher viscous flow
temperature and a higher degradation temperature than that of the
fiber made from the synthetic thermoplastic polymer, and wherein
the matted material has been heated to a temperature throughout the
matted material that is higher than the melt temperature of the
fiber made from or including the synthetic thermoplastic polymer
but less than the degradation temperature of the coir fiber and hot
pressed at that temperature at a compression pressure range of 25
psi or more.
2. The non-woven fabric composite material of claim 1, wherein the
length of the coir fiber and the fiber made from the synthetic
thermoplastic polymer is from 10 mm to 100 mm.
3. The non-woven fabric composite material of claim 1, wherein the
diameter of the coir fiber is from 150 .mu.m to 500 .mu.m.
4. The non-woven fabric composite material of claim 1, wherein the
coir fiber and the fiber made from the synthetic thermoplastic
polymer are matted together using carding and needle punching,
cyclone air deposition, chemical, heat, or solvent treatment.
5. The non-woven fabric composite material of claim 1, wherein the
weight ratio of the coir fiber to the fiber made from the synthetic
thermoplastic polymer is from 95:5 to 20:80.
6. The non-woven fabric composite material of claim 1, wherein the
synthetic thermoplastic polymer is PP, and wherein the matted
material has been heated to a temperature throughout the matted
material above 180.degree. C.
7. The non-woven fabric composite material of claim 1, wherein the
fiber made from the synthetic thermoplastic polymer comprises PP
and wherein the matted material has been heated to a temperature
throughout the matted material above 180.degree. C. and lower than
240.degree. C.
8. The non-woven fabric composite material of claim 1, wherein the
matted material has been heated to a temperature throughout the
matted material between 150.degree. C. and 230.degree. C. and
pressed at that temperature.
9. The non-woven fabric composite material of claim 1, wherein the
coir fiber and the fiber made from the synthetic thermoplastic
polymer are pressed at a compression pressure ranging from 25 psi
to 400 psi.
10. A method of preparing a non-woven fabric composite material
comprising: obtaining coir fiber; milling the coir fiber to a
desired fiber length; mixing the milled coir fiber with a fiber
made from or including a synthetic thermoplastic polymer, wherein
the synthetic thermoplastic polymer is selected from the group
consisting of polypropylene ("PP"), polyethylene ("PE"), polylactic
acid ("PLA"), and polyester ("PET"), and mixtures thereof, and
wherein the fiber made from the synthetic thermoplastic polymer has
a lower viscous flow temperature than the degradation temperature
of the coir fiber; creating a matted 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; heating the matted material to
a temperature throughout the matted material that is higher than
the melt temperature of the fiber made from or including the
synthetic thermoplastic polymer; and pressing the heated matted
material while at that temperature at a compression pressure range
of 25 psi or more.
11. The method of claim 10, wherein the coir fiber is stripped of
its waxy coating and the coir fiber or the fiber made from the
synthetic thermoplastic polymer is treated with a chemical
compatibilizer to yield a graft copolymer.
12. The method of claim 10, further comprising pressing the heated
matted material using a die in a compression molding machine to
become a shaped rigid part.
13. The method of claim 10, wherein the fiber made from the
synthetic thermoplastic polymer comprises PP and further comprising
heating the matted material to a temperature above 180.degree. C.
and lower than the degradation temperature of the coir fiber and
pressing the heated matted material at that temperature.
14. The method of claim 10, wherein the fiber made from the
synthetic thermoplastic polymer comprises PP and further comprising
heating the matted material to a temperature above 180.degree. C.
and lower than 240.degree. C.
15. The method of claim 10, further comprising heating the matted
material to a temperature between 200.degree. C. and 230.degree. C.
and pressing the heated matted material at that temperature.
16. The method of claim 10, further comprising pressing the heating
matted material at a compression pressure range of 25 psi to 400
psi.
Description
[0001] The present invention in a continuation-in-part of and
claims priority to U.S. patent application Ser. No. 13/161,316,
filed on Jun. 15, 2011, which is a continuation of U.S. patent
application Ser. No. 12/574,518, filed on Oct. 6, 2009, which
claims the benefit of U.S. Provisional Patent Application No.
61/176,422 filed May 7, 2009, and U.S. Provisional Patent
Application No. 61/103,173, filed Oct. 6, 2008, the entire content
of which are 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 coir fibers that are rich in lignin, with large
diameters, 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 PP: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 coir fibers and a method for producing
such composites. The non-woven fabric composite may be comprised of
coir fibers, which are large diameter, lignin rich 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, polyethylene, polyester, or a
biodegradable thermoplastic polymer fiber such as polylactic acid,
or a combination thereof. The fibers can be a mono-component fiber
or a bi-component fiber such as with a higher melt temperature core
and a lower melt temperature sheath. The processing window for hot
pressing this composite is above the viscous flow temperature of
the thermoplastic (or the sheath thermoplastic material if the
fiber is bi-component) and the lower of the degradation temperature
or the viscous flow temperature of the coir fiber.
[0017] The disclosure provides a non-woven fabric composite
material, comprising: coir fiber; and a fiber made from or
including a synthetic thermoplastic polymer, wherein the synthetic
thermoplastic polymer is selected from the group consisting of
polypropylene ("PP"), polyethylene ("PE"), polylactic acid ("PLA"),
and polyester ("PET"), and mixtures thereof, wherein the coir fiber
and the fiber made from the synthetic thermoplastic polymer are
matted together to form a matted material, wherein the coir fiber
has a higher viscous flow temperature and a higher degradation
temperature than that of the fiber made from the synthetic
thermoplastic polymer, and wherein the matted material has been
heated to a temperature throughout the matted material that is
higher than the melt temperature of the fiber made from or
including the synthetic thermoplastic polymer but less than the
degradation temperature of the coir fiber and hot pressed at that
temperature at a compression pressure range of 25 psi or more.
[0018] The disclosure also provides a method of preparing a
non-woven fabric composite material comprising: obtaining coir
fiber; milling the coir fiber to a desired fiber length; mixing the
milled coir fiber with a fiber made from or including a synthetic
thermoplastic polymer, wherein the synthetic thermoplastic polymer
is selected from the group consisting of polypropylene ("PP"),
polyethylene ("PE"), polylactic acid ("PLA"), and polyester
("PET"), and mixtures thereof, and wherein the fiber made from the
synthetic thermoplastic polymer has a lower viscous flow
temperature than the degradation temperature of the coir fiber;
creating a matted 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; heating the matted material to a temperature
throughout the matted material that is higher than the melt
temperature of the fiber made from or including the synthetic
thermoplastic polymer; and pressing the heated matted material
while at that temperature at a compression pressure range of 25 psi
or more.
[0019] 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 thermoplastic 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 thermoplastic 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 thermoplastic fibers but
below the degradation temperature of the coir fiber, 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
[0020] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawings(s) will be provided by the Office
upon request and payment of the necessary fee.
[0021] 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.
[0022] FIG. 1 shows an open coconut and husk with fibers, usually
called coir fibers.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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).
[0027] 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.
[0028] FIG. 7 shows at a magnification of 10.times. an unpressed
felt (mass density approximately 0.1 g/cm.sup.3) composed of 50%
coir fiber and 50% PP fiber.
[0029] FIG. 8 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.
[0030] FIG. 9 shows the tensile strength vs. mass density for
coir:PP for a comparison between the tensile strength values for
170.degree. C. and 210.degree. C.
[0031] FIG. 10 shows the flexural modulus strength vs. mass density
for coir:PP for a comparison between the flexural modulus values
for 170.degree. C. and 210.degree. C.
[0032] FIG. 11 shows a comparison of (1) flexural modulus vs.
density for coir with a coarse denier (12-24), mono-component PP
binder fiber to (2) coir with a fine denier (4) bi-component
polyester binder fiber with machine direction (WMD) and against
machine direction (AMD).
[0033] FIG. 12 shows the flexural rigidity (or stiffness) vs.
density for 25 mm wide specimen at 65 wt % coir and 35 wt % PET
bi-component binder fiber.
[0034] FIG. 13 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.
[0035] FIG. 14 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.
[0036] FIG. 15 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.
[0037] FIG. 16 shows the flexural modulus vs. density for 65 wt %
coir and 35 wt % PLA (both mono-component and bi-component) binder
fiber.
[0038] FIG. 17 shows an enlarged photograph of a pressed felt
having 65 wt % coir and 35 wt % bi-component PET binder fiber.
[0039] FIG. 18 shows an enlarged photographs of a pressed felt
having of 65 wt % coir and 35 wt % mono-component PLA binder
fiber.
[0040] FIG. 19 shows an enlarged photographs of a pressed felt
having of 65 wt % coir and 35% bi-component PLA binder fiber.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Definitions
[0041] 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.
[0042] 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.
[0043] 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.
[0044] The phrase "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.
[0045] 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.
[0046] 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"), polylactic
acid ("PLA"), and polyester ("PET").
[0047] 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. Further, the
thermoplastic fiber can itself be a combination of fiber materials,
such as a bi-component fiber having a core and sheath, or two fiber
materials bonded side-by-side. In general, the bi-component fiber
will have one component with a lower melt temperature (such as for
the sheath) and another component with a higher melt temperature
(such as for the core).
[0048] 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"), a
polyethylene ("PE"), biodegradable fibers such as polylactic acid
("PLA"), or polyester "(PET"), 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 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.
[0049] 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
%).
[0050] 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.
[0051] 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 about
1-2%.
[0052] 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.
[0053] 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 are 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 PP, PE, PLA, PET, or copolymers of
the 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 thermoplastic
fibers made from recycled material as they are in this invention,
the resultant non-woven fabric composite materials are very
environmentally-friendly indeed.
[0054] I Non-Woven Fabric Composite Material Utilizing Coir
Fibers
[0055] In a preferred embodiment, the invention comprises a
non-woven fabric composite material which includes a blend of at
least two types of fibers, at least one fiber with a higher
degradation temperature or viscous flow melt temperature and at
least one fiber with a lower viscous flow melt temperature. The
fiber with the higher viscous flow melt 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 fibers such as PET fiber. The fiber with
the lower viscous flow temperature can be a thermoplastic fiber,
such as PP, PE, PLA, PET, or a mixture thereof. Thus, the non-woven
fabric composite material could include a mixture of coir fibers
and PP; coir fibers and PE; coir fibers and PLA; coir fibers and
PET; coir fibers, PP and PET; coir fibers, PE and PET; coir fibers,
PP and PE; coir fibers, PP and PLA; coir fibers, PLA and PET; and
other combinations with mono-component and bi-component
variations.
[0056] 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.
[0057] Different types of fibers can be made to cohere in a felt,
or matted together, by the following methods: [0058] Thermal
bonding [0059] Using a large oven for curing [0060] 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. [0061]
Hydro-entanglement: mechanical intertwining of fibers by water jets
(called spunlace) [0062] Ultrasonic pattern bonding, often used in
high-loft or fabric insulation/quilts/bedding [0063] 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 [0064] 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 [0065] 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 [0066] 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 [0067] One
unusual polyamide spunbond (Cerex) is self-bonded with gas-phase
acid.
[0068] 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, and in at least one embodiment the fibers can 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.
[0069] 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.
[0070] 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.
[0071] II Method for Producing a Non-Woven Fabric Composite
Material Utilizing Coir Fibers
[0072] 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.
[0073] 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).
[0074] The appropriate temperature and pressure for compression
molding a non-woven fabric composite material felt made of coir
fibers and thermoplastic fibers depends on the application and the
combination of mechanical and physical properties that best serve
the application. The most critical parameter for hot pressing
non-woven fabric composite material felt into rigid parts is the
pressing temperature. For example, 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. 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 PP fibers as the lower viscous flow
temperature constituent. Surprisingly, this has proven to not be
the case.
[0075] The larger diameter and resultant greater flexural stiffness
of the coir fiber makes it necessary to process the nonwoven fabric
composites containing coir fiber at somewhat higher temperatures
and/or pressures to get a particular bulk density than would be
used for nonwoven fabric composites made with two or more synthetic
fibers with smaller diameters and lower flexural moduli. For
example, U.S. Pat. No. 5,948,712 by Tanabe recommends compression
molding of coir with PP at 170.degree. C.-180.degree. C., but
without substantive experimental data to support this
recommendation. This temperature was most likely suggested because
PET with PP is typically compression molded at 170.degree.
C.-180.degree. C.
[0076] 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. FIG. 7 is a photograph that shows
at a magnification of 10.times. an unpressed felt (mass density
approximately 0.1 g/cm.sup.3) composed of 50% coir fiber and 50% PP
fiber.
[0077] 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 PP 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.
[0078] As the pressing temperature is increased from 180.degree. C.
to 210.degree. C., 220.degree. C., up to around 240.degree. C.
(because of the limiting degradation temperature of coir fibers),
and any temperature in between, 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 typical
170.degree. C.-180.degree. C. temperature range often used for
thermoforming PP sheet is necessary to get sufficient flow of the
PP fibers to securely attach the fibers, creating a rigid web. The
difference in the flow of the PP and coir fibers and the wetting of
the coconut fibers by the PP fiber as it flows is seen in FIG. 8 to
compare heating the pressed non-woven fabric on the left at
180.degree. C. with a low degree of viscous flow and heating the
fabric on the right at 220.degree. C. with significantly more flow.
FIG. 9 is a graph that shows the tensile strength vs. density for
coir:PP for a comparison between the tensile strength values for
170.degree. C. and 210.degree. C. The mass densities for
compression molding at 170.degree. C. and at 210.degree. C. are
indicated with the vertical lines. The associated tensile strength
values for 170.degree. C. vs. 210.degree. C. are seen to be
.about.3 MPa and .about.12 MPa, respectively. FIG. 10 is a graph
that shows the flexural modulus strength vs. density for coir:PP
for a comparison between the flexural modulus values for
170.degree. C. and 210.degree. C. the mass densities for
compression molding at 170.degree. C. and 210.degree. C. are
indicated by the vertical lines. The associated flexural modulus
values for compression molding at 170.degree. C. and 210.degree. C.
are seen to be less than .about.100 MPa and .about.600 MPa,
respectively. Heating the non-woven fabric composite felted
material to 180.degree. C. without the application of pressure will
produce insufficient flow of the PP (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.
[0079] Not all methods are equally efficacious for heating the
non-woven fabric composite felt of coir and binder fibers to a
suitable temperature for compression molding. Preheated molds,
platen ovens or contact heaters, compression oven, and convective
ovens are effective for heating low density felt (.about.0.1-0.2
g/cm.sup.3). However, the rapid surface heating provided by
infrared heat sources can burn low-density felt before the
temperature at the center of the felt can be suitably heated. For
infrared heaters, the coir/binder-fiber felt needs to be
pre-compressed prior to heating using infrared sources.
[0080] 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.
[0081] The denier is the mass in grams per 9000 meters of fiber
length. A smaller denier binder-fiber corresponds to a smaller
binder-fiber diameter. The denier of the binder-fiber will
significantly impact the time at a given temperature that it takes
to melt the binder-fiber, with smaller denier (and diameter)
binder-fibers melting more quickly at a given temperature allowing,
a shorter cycle time in compression molding of parts.
Alternatively, a lower forming temperature can be used for a given
cycle time in compression molding of parts. A second benefit of
smaller denier fibers is that they are more flexible, and
therefore, more able to efficiently fill the spaces between the
coir fibers. The more dense the felt, the more dense will be the
compression molded part. As previously noted, a higher density part
provides more points of load transfer between the coir fibers,
enhancing both tensile strength and flexural modulus of the
part.
[0082] Some smaller denier, binder fibers with a denier of 2-3 can
have one potential drawback. They are more likely to have residual
stresses that can result in some shrinkage on reheating. Laboratory
tests appear to show that fibers with a denier of 2-3 have
unacceptable levels of shrinkage, while fibers with a denier of 4
or greater seem to have an acceptable level of shrinkage.
Increasing the volume percentage of coir fiber which is very stiff
also seems to reduce the amount of shrinkage on reheating prior to
compression molding.
[0083] While not intending to be limiting, one hypothesis for why
small denier fibers have more shrinkage when heated prior to
compression molding is that during the manufacturing of synthetic
fibers, the polymer chains in the fiber develop some degree of
chain extension along the fiber axis. If the fiber is cooled
relatively quickly at the end of the fiber manufacturing process,
this chain extension (from a more randomly kinked polymer chain
morphology) can be "frozen" in place, since a lower temperature
does not allow the necessary local segment rotations that must
occur to re-kink chain extended polymers. The extended polymer
chains in the synthetic fiber create an associated residual stress
that can cause the fibers to shrink when they are reheated, which
they will be prior to compression molding of the felt into which
the synthetic fiber has been incorporated by carding and needle
punching.
[0084] Mono-component fibers have a melting temperature that is
essentially constant across the diameter of the fiber. Bi-component
fibers have a higher melting temperature core and a lower melting
temperature sheath. The bi-component fiber has a higher cost, but
may have some advantages. First, it may produce a stronger
non-woven fabric composite with coir fiber. Because the outer
sheath has a lower melting temperature than mono-component fibers,
it will have more flow than a typical mono-component fiber, giving
more area for load transfer from one coir fiber to the next.
Second, the core part of the bi-component fiber will be retained
without substantial melting, reinforcing the coir fiber lattice
structure with additional elements, which gives a higher strength
and flexural modulus. Third, because the outer sheath of the
bi-component fiber melts at a lower temperature than a
mono-component fiber of the same polymer family, the forming
operations can be performed at a lower temperature. This may also
allow a nicer appearance for the finishing cloth (which is usually
on the blank at the time that the part is formed) than can be
achieve for a non-woven fabric composite made with a mono-component
binder fiber.
[0085] The effect of using a finer denier, bi-component binder
fiber is illustrated in FIG. 11. FIG. 11 is a graph that shows a
comparison of [1] flexural modulus vs. density for coir with a
coarse denier (12-24), mono-component PP binder fiber to [2] coir
with a fine denier (4) bi-component PET binder fiber (with machine
direction (WMD) and against machine direction (AMD). First, a much
higher density can be achieved with the finer denier, binder fiber.
Second, the small denier, bi-component binder fiber at the same
density gives a significantly higher flexural modulus
(approximately twice the flexural modulus of coir with the (12-24)
denier mono-component PP binder fiber).
[0086] When PET is used with PP to make non-woven fabric composites
(which is widespread), the PET used has a melt flow temperature of
greater than 230 C and serves as the "backbone" while the PP
functions as the binder fiber. However, PETs with lower melt flow
temperatures can be used with coir as the binder fiber. Any PET
with a melt flow temperature lower than about 230.degree. C. can be
used as a mono-component binder fiber as a practical upper
temperature for normal processing conditions with coir fiber,
although theoretically a temperature of 240.degree. C. could be
used. For example, bi-component fibers with a melt flow temperature
of greater than 230.degree. C. for a PET core and a melt flow
temperature below 180.degree. C. of a different PET for a sheath
can be used as a binder fiber with coir fiber. In particular,
bi-component PET fiber with a denier of (4), a core melt flow
temperature of greater than 230.degree. C., and a sheath melt flow
temperature of .about.110.degree. C. has been successfully used by
the inventors as a binder fiber (35 wt %) with coir fiber (65 wt %)
in a non-woven fabric composite. The results of extensive research
on this non-woven fabric composite pressed into flat plaques to
give densities ranging from 0.25 to 0.8 g/cm.sup.3 are seen in FIG.
11. In the density range of 0.4 to 0.5 where the greatest flexural
stiffness (EI) occurs (see FIG. 12), remarkably the flexural
modulus is seen to be fully twice as great for the small denier
(4), bi-component PET binder fiber with coir as for the larger
denier (12-24), mono-component PP binder fiber with coir. In other
embodiments, a PET core could be used with a different
thermoplastic sheath, such as PE, PP, and so forth.
[0087] Flexural stiffness is a characteristic of the part or test
specimen, determined by a combination of flexural modulus (as seen
in FIG. 11) and geometry of the part or test specimen, in
particular the thickness of the part or test specimen. The
thickness of the test specimen is given by thickness=areal
density[g/cm.sup.2]/mass density [g/cm.sup.3]. The flexural
rigidity of a test specimen or part with a rectangular cross
section is given by flexural
rigidity=E.sub.fwidth[thickness].sup.3/12. As the mass density is
increased (for a felt with a given areal density), the thickness
decreases, as explained above. Thus, with increasing mass density,
Ef is increasing while [thickness].sup.3 is decreasing, given a
peak flexural rigidity at some intermediate mass density, as seen
in FIG. 12. FIG. 12 shows the flexural rigidity (or stiffness) vs.
density for 25 mm wide specimen at 65 wt % coir and 35 wt % PET
bi-component binder fibers. This maximum occurs for a mass density
of between 0.4 and 0.5 g/cm.sup.3 for the material in FIG. 12,
which is the reason comparisons of coir with various binder fibers
should be made in this region, as was previously done in previous
discussions of FIG. 11.
[0088] 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, such as consisting of PP, PE, PLA, PET, and mixtures
thereof, where other fibers can be mixed therewith.
Example 1
[0089] The first example is for compression molded parts of a
non-woven fabric composite material that utilizes a coir fiber and
a thermoplastic with a viscous flow temperature that is
significantly lower than the degradation temperature of the natural
fiber.
[0090] Production of Non-Woven Fabric Composite Material Felt--
[0091] The natural fibers, specifically coir 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 coir fibers
and thermoplastic fibers. The ratio of coir 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 coir 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 in some 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.200g/m.sup.2 and should not be degraded at the temperature
the felt is subsequently compression molded since it is typically
pure PET.
[0092] Compression Molding of Non-Woven Fabric Composite Material
into Parts--
[0093] 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 PP) 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 PP fibers to increase the density or attach the
randomly oriented unwoven fibers into a rigid network. Thus, for
example, for coir fibers blended with PP fibers, the temperature
ranges from about 180.degree. C. to about 240.degree. C.,
preferably from above 180.degree. C. to about 240.degree. C. 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
processing. 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. 13 and 14. For
example, automobile trunk liners might be made with non-woven
fabric composite materials of coir and PP 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 PP 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.
[0094] The preferred large diameter, natural fiber rich in lignin
is coir fiber, and in at least one embodiment a thermoplastic fiber
is PP 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. 15.
Example 2
[0095] 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., PP, PE, PLA, PET, or mixtures thereof).
[0096] The non-woven fabric composite felt is made from large
diameter, natural fibers, rich in lignin like coir and
thermoplastics fibers like PP, 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 coir 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.
[0097] 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
[0098] 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.
[0099] 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 is 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.
[0100] 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.
[0101] 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
[0102] 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 (150.degree.
C.-230.degree. C. depending on the binder fiber used and viscous
flow melting temperature) to achieve the distinctive properties
required. This versatility is another benefit of this
invention.
[0103] In this example, natural coir fibers are combined with
petroleum based PP fibers (FIG. 3) in a blending process that
results in a matt of blended but unwoven coir and PP fibers (FIG.
3) with an areal density of 1000 g/cm.sup.2.
[0104] The coir fiber is limited to a hot pressing temperature of
about 240.degree. C. depending on pressing time by oxidative
degradation. The PP 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 PP. 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. 8 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 PP fibers necessary to firmly join the coir
fibers into a rigid web.
[0105] For this application, it is necessary that the PP's
viscosity be sufficiently low 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. 8, 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 FIGS. 9, 10). In commercial production, the matted material
seen in FIG. 4 and FIG. 15 (strip across bottom) is pressed into
automotive parts like the trunk liner and the door panel presented
in FIG. 15. 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.
[0106] 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. 7. 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.
Example 5
[0107] Binder fibers to be used with coir can be made from PLA
using corn starch, sugar cane, or other renewable sources. Two PLA
binder fibers have been tried with coir with quite surprising
results. A mono-component PLA binder fiber (35 wt %) with a denier
of (4) and a melt flow temperature of 160.degree. C.-180.degree. C.
has been used with coir (65 wt %). The compression molding
temperature used was 200 C and the resultant density obtained by
using stops in the press was .about.0.45. The flexural modulus as
seen in FIG. 8 was 5.times. greater than coir with bi-component PET
and 10.times. greater than coir with mono-component PP binder
fibers, as seen in FIG. 11 at the same mass density.
[0108] A second non-woven fabric composite was made with a
bi-component PLA binder fiber (35 wt %) with a denier of (4) and
coir (65 wt %). Both the sheath and the core of the binder fiber
were made with PLA that was formulated to have two different melt
flow temperatures. The bi-component PLA binder fiber had a sheath
with a melt flow temperature of .about.150.degree. C. Compression
molding of the resulting felt was done at 200.degree. C. with stops
used to get a mass density of .about.0.4 g/cm.sup.3. The resultant
flexural modulus is presented in FIG. 16. FIG. 16 shows the
flexural modulus vs. density for 65 wt % coir and 35 wt % PLA (both
mono-component and bi-component) binder fiber. Comparing these
results with those in FIG. 11 indicate a remarkable increase of
flexural modulus of as much as 15.times. that for PP binder fiber
with coir and 7.times. the flexural modulus for bi-component PET
binder fiber with coir.
[0109] Pictures of the compression molded non-woven fabric
composites with binder fibers of bi-component PET and
mono-component and bi-component PLA, all with coir fiber, are seen
in FIGS. 17-19. FIG. 17 shows a pressed felt having 65 wt % coir
and 35 wt % bi-component PET binder fiber with both components of
the binder fiber being PET with the sheath having a lower melt
temperature. FIG. 18 shows a pressed felt with 65 wt % coir and 35
wt % mono-component PLA binder fiber. FIG. 19 shows a pressed felt
having of 65 wt % coir and 35% bi-component PLA binder fiber. In
this example, PLA with a lower melting temperature is used for the
sheath, and a different PLA with a higher melting temperature is
used for the coir. Thus, the binder fiber can still be viewed as a
fiber after compression molding in FIGS. 18 and 19). In both cases,
only the lower melting point sheath is giving the flow to bind the
fibers together while the core is part of the resultant web.
[0110] Further, the various methods and embodiments described
herein can be included in combination with each other to produce
variations of the disclosed methods and embodiments. Discussion of
singular elements can include plural elements and vice-versa.
References to at least one item followed by a reference to the item
may include one or more items. Also, various aspects of the
embodiments could be used in conjunction with each other to
accomplish the understood goals of the disclosure. Unless the
context requires otherwise, the word "comprise" or variations such
as "comprises" or "comprising," should be understood to imply the
inclusion of at least the stated element or step or group of
elements or steps or equivalents thereof, and not the exclusion of
a greater numerical quantity or any other element or step or group
of elements or steps or equivalents thereof. The device or system
may be used in a number of directions and orientations.
[0111] The order of steps can occur in a variety of sequences
unless otherwise specifically limited. The various steps described
herein can be combined with other steps, interlineated with the
stated steps, and/or split into multiple steps. Similarly, elements
have been described functionally and can be embodied as separate
components or can be combined into components having multiple
functions.
[0112] The invention has been described in the context of preferred
and other embodiments and not every embodiment of the invention has
been described. Apparent modifications and alterations to the
described embodiments are available to those of ordinary skill in
the art given the disclosure contained herein. The disclosed and
undisclosed embodiments are not intended to limit or restrict the
scope or applicability of the invention conceived of by the
Applicants, but rather, in conformity with the patent laws,
Applicants intends to protect fully all such modifications and
improvements that come within the scope or range of equivalent of
the following claims.
REFERENCES CITED
[0113] 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
[0114] U.S. Pat. No. 6,939,903 issued on Sep. 6, 2005, with
Sigworth et al. listed as inventors. [0115] U.S. Pat. No. 6,682,673
issued on Jan. 27, 2004, with Skwiercz listed as the inventor.
[0116] U.S. Pat. No. 6,648,363 issued on Nov. 18, 2003, with Gordon
listed as the inventor. [0117] U.S. Pat. No. 5,948,712 issued on
Sep. 7, 1999, with Tanabe et al. listed as inventors. [0118] U.S.
Pat. No. 5,709,925 issued on Jan. 20, 1998 with Spengler et al.
listed as inventors. [0119] U.S. Pat. No. 5,976,646 issued on Nov.
2, 1999, with Stevens et al. listed as inventors. [0120] U.S.
Patent Publication No. 2008/0081188 issued on Apr. 3, 2008, with
Chang et al. listed as inventors. [0121] U.S. Patent Publication
No. 2007/0116923 published on May 24, 2007, with Kasuya et al.
listed as inventors. [0122] U.S. Patent Publication No.
2004/0185239 published on Sep. 23, 2004, with Nakamura et al.
listed as inventors.
Non-Patent Documents
[0122] [0123] 1. Polymer Data Handbook., Editor: Mark, James E.
(New York: Oxford University Press), 1999. [0124] 2. Polymer
Handbook, 4.sup.th Edition, Editors: J. Brandrup, E. H. Immergut,
E. A. Grulke. (New York: John Wiley & Sons, Inc), 1999. [0125]
3. Throne, Jim, "Let's Thermoform PP", A Technical Minute.
Copyright 2007: Sherwood Technologies. throne@foammandform.com.
[0126] 4. Parikh, D. V. et al. "Thermoformable automotive
composites containing kenaf and other cellulosic fibers" Textile
Research Journal, August 2002.
* * * * *