U.S. patent number 3,673,295 [Application Number 05/085,692] was granted by the patent office on 1972-06-27 for process for shaping textile articles using fluid thermoforming techniques.
This patent grant is currently assigned to Allied Chemical Corporation. Invention is credited to George Howard Collingwood, Gene Clyde Weedon, Robert Charles Winchklhofer.
United States Patent |
3,673,295 |
Winchklhofer , et
al. |
June 27, 1972 |
PROCESS FOR SHAPING TEXTILE ARTICLES USING FLUID THERMOFORMING
TECHNIQUES
Abstract
Articles are manufactured from textile material composed of
filaments prepared from blended fiber-forming polymers having
different chemical properties, at least one of the fiber-forming
polymers being dispersed as fibrils in a lower melting point
polymeric matrix. The article is produced by heating the material
to a temperature above the melting point of the matrix-forming
polymer but below the melting point of the dispersed fibrils to
shrink said article thereby decreasing the porosity thereof and
afterwards forming the heated material into a three-dimensional
shape using vacuum or other fluid pressure.
Inventors: |
Winchklhofer; Robert Charles
(Richmond, VA), Weedon; Gene Clyde (Richmond, VA),
Collingwood; George Howard (West Warwick, RI) |
Assignee: |
Allied Chemical Corporation
(Broadway, NY)
|
Family
ID: |
26772988 |
Appl.
No.: |
05/085,692 |
Filed: |
October 30, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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761447 |
Sep 23, 1968 |
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Current U.S.
Class: |
264/546; 264/230;
264/548; 428/475.2; 156/84; 264/342R; 264/550; 428/375; 428/480;
442/409 |
Current CPC
Class: |
B29C
51/004 (20130101); D06C 29/00 (20130101); B29C
2791/007 (20130101); Y10T 442/69 (20150401); Y10T
428/31736 (20150401); B29C 2791/006 (20130101); Y10T
428/2933 (20150115); Y10T 428/31786 (20150401) |
Current International
Class: |
B29C
51/00 (20060101); D06C 29/00 (20060101); B29c
017/04 (); B29c 023/00 (); D02g 003/04 () |
Field of
Search: |
;264/89,90,92,93,94,230,235,342R,346 ;161/150,170,176 ;18/19F |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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899,646 |
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Jun 1962 |
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GB |
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988,370 |
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Apr 1965 |
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GB |
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Primary Examiner: White; Robert F.
Assistant Examiner: Silbaugh; J. H.
Parent Case Text
This invention is a continuation-in-part of application Ser. No.
761,447 filed Sept. 23, 1968 and now abandoned.
Claims
We claim:
1. A process for permanently shaping textile articles from
heat-shrinkable and heat-settable matrix fibers having a higher
melting component dispersed throughout said matrix which
comprises:
a. positioning a layer of a porous textile material prepared from
said matrix fibers adjacent to a three-dimensional form,
b. heating the layer of porous textile material at least to about
the melting temperature of the matrix but below the melting
temperature of the dispersed component to shrink the fibers and
thereby reduce the porosity of said layer of material enough to
enable shaping of the material by applied differential fluid
pressure alone,
c. applying a differential fluid pressure against said layer of
material while in a heat-setting condition to conform said fabric
to the shape of said three-dimensional form without the use of a
non-air permeable sheet, and
d. cooling said material to provide a permanently shaped
three-dimensional textile article.
2. A process as described in claim 1 wherein the layer of textile
material is cooled after the heating step so that a heat-stabilized
intermediate product of reduced porosity is achieved and then
reheating said material to a temperature below the melting
temperature of the dispersed component just prior to applying the
differential fluid pressure.
3. A process as described in claim 1 wherein the matrix is composed
of greater than 50 parts by weight polyamide and the dispersed
component is composed of discontinuous fibrils of polyester.
4. A process as described in claim 3 wherein the polyamide is
polycaproamide and the polyester is polyethylene terephthalate.
5. A process as described in claim 3 wherein the said material is
heated to about 200.degree. C. to about 250.degree. C.
6. A process as described in claim 5 wherein the porosity of the
starting material is reduced from an air permeability rate of about
15 cubic feet per minute per foot square to about 5 by said heat
treating.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for making a textile
article from multi-constituent filaments using heat and fluid
pressure. Preferably the filaments have a nylon matrix with
microfibers of polyester dispersed therein and the heat is applied
at such a temperature that the nylon matrix begins to fuse but the
polyester with its higher melting point does not. Preferably the
fluid pressure is vacuum (negative pressure) air pressure. These
filaments (described and claimed in Twilley U. S. Pat. No.
3,369,057 which patent is hereby incorporated by reference as if
fully set out herein) were originally prepared for employment in
high strength yarns useful in yarn or cord form as reinforcing
strands in elastometric tires and the like.
2. Description of the Prior Art
Heretofore fluid thermoforming such as the heating of a non-air
permeable vinyl film and vacuum forming it to a desired shape has
been widely practiced in industry. However, such has not been
practical in connection with open mesh textile articles because the
porosity of the articles permitted the ready passage of the
pressure-applying fluid and also because the plastic properties of
the material at elevated temperatures was not conducive to
satisfactorily utilizing them for such a process unless a non-air
permeable sheet was employed in combination with the article as
disclosed in British Pat. No. 899,646. If heated, these fabrics
have a tendency to sag thereby increasing the openness or porosity
of said fabric. Further heating causes the polymer constituent to
flow before heat setting is achieved and thereby destroys the
textile appearance of the fabric.
It is well known that the physical characteristics of one polymer
or a mixture of polymers can be varied greatly by changing the
relative ingredient proportions or by mixing with another polymeric
or additive material. Usually these are blend systems of polymers
and/or copolymers wherein the various materials are mixed together
to form a homogeneous mass which is then conventionally molded,
calendered, etc., as described, for example, in Renfroe U.S. Pat.
No. 3,336,173 wherein polyamide is blended with a polyolefin to
improve the high frequency welding ability of the latter; Yasui et
al. U.S. Pat. No. 3,322,854 disclosing homogeneous mixtures of
polymers and/or copolycondensated polymers to improve polyester
moldability, resistance to wrinkle and dyeability; and Fukushima
U.S. Pat. No. 3,359,344 disclosing improved polyethylene,
polypropylene or polystyrene calendered films made by incorporating
chopped strands of a blended fiber comprised of polyolefin and a
high molecular weight material.
SUMMARY OF THE INVENTION
In accordance with the present invention unique new articles of
textile materials having widespread useful value for clothing,
automotive products, seating and many other applications is readily
and economically carried out using highly developed thermoforming
practices modified to accommodate the special characteristics of
the unique poly-constituent materials used in the invention. These
multi-constituent materials have a matrix containing a dispersion
of discontinuous microfibers of fibrils with a substantially higher
melting point than the polymer matrix in which they are present.
When heated to a temperature near or above melt temperature of the
lower melting polymer but below the melt temperature of the higher
melting polymer, these materials shrank a substantial amount.
Although the various polymers are mixed together in this invention,
they are not entirely intermiscible due to their physical
properties and/or the mixing technique employed to assure a
dispersion of microfibers. Microsized globules or fibrils are
usually initially produced in the matrix, which when spun into
filaments and drawn, produce the desired microfibrillar dispersion
in the lower melting matrix material.
In accordance with this invention, it has been discovered that a
textile fabric composed of filaments of the type described in U.S.
Pat. No. 3,369,057 may be heat-treated and fluid-formed to a
desired shape and yet the fabric will largely retain its original
textile appearance. This is accomplished by heating the fabric to a
temperature between the melting point of the polymers forming said
filaments thereby shrinking and heat setting the filaments in situ
in said fabric without significant flow, cross-sectional
flattening, disfiguration, or sagging and at the same time a
reduction in porosity of the fabric. As the filaments shrink, their
diameter is increased to reduce the interstices of a fabric
construction comprised thereof. Thus an important feature of this
invention is that the fabric is heated to a heat-setting condition
and maintained thereat throughout the fluid thermoforming phases of
article production whereby permanent shaping is imparted to said
articles when cooled. With the above as a basis, it was further
discovered that various other polymer blend systems having at least
two polymers of varying melt temperatures, one polymer being
dispersed as discontinuous fibrils in a matrix of the other, can be
employed to produce fluid thermoformed articles of
three-dimensional shape, and although nylon-polyester blends of the
type mentioned in the Twilley patent provide the best results, such
other blend systems as will be described are intended to be
embraced by, and included in, this invention. The principal objects
of this invention are, therefore, to provide novel fluid
thermoformed textile articles and methods of producing the same,
without limitation to specific shapes or forms.
As used herein these terms are intended to have the following
meaning:
Multi-constituent or matrix filaments - filaments made by inclusion
of at least one polymeric material in a matrix of another as
discontinuous fibrils, the two materials having substantially
different melt temperatures such that fibrous constructions
composed thereof can be heat-set and plastically formed by
application of heat below the melt temperature of one and equal to
or above that of the other, the entire filament composition or any
component thereof optionally including any secondary material
compatible with the heat-set property of the fabric as a whole such
as antioxidants and other stabilizing agents, reinforcing
particles, fillers, adhesion promoting agents, fluorescent
materials, dispersing agents, and others useful in polymerization,
extruding, spinning, fabric forming and shaping, heat-setting and
product finishing techniques. If desired, inorganic materials such
as metal whiskers, fiber glass fibrils, asbestos particles and the
like may be incorporated for conductive and/or reinforcement
purposes.
Textile material - any woven, knitted or non-woven fibrous
structure.
Fluid thermoforming - includes heating the textile material to a
temperature whereby the lower melting matrix is at or above the
temperature of fusion so that the fibers will begin or completely
fuse together and shrink a sufficient amount to decrease the
porosity of the textile material. The temperature should be
maintained below the fusion point of the discontinuous fibrils to
avoid unnecessary degradation of the textile material. While so
heated, the heat-settable and heat-shrunk textile material has a
differential pressure applied to it by means of a fluid in order to
form it to a desired shape. The fluid can broadly include liquids
as well as gasses and the pressure may either be direct pressure of
the fluid itself or negative pressure by drawing a vacuum onto the
textile material. The forming can be assisted by a combination of
vacuum and pressure, by the use of slip rings around a die, the use
of a plug as assistance, etc. Preferably, the article is formed by
the use of ambient air pressure through pulling a vacuum on one
side of the textile material after it has been partially fused.
This can be accompanied by a plug assist if the shape of the
textile material and conditions under which it is being formed
indicate its use.
In general the invention is applicable to textile material prepared
from heat shrinkable and heat-settable multi-constituent filaments
or yarn of any combination of polymeric materials capable of
creating a matrix and having a relatively higher melting dispersion
of discontinuous fibrils; however, it is clear that a
polyester-polyamide combination produces outstanding articles over
the other materials. These compositions may contain 50-90 parts by
weight nylon and 50-10 parts by weight polyester dispersion. Other
materials useful in multi-constituent fibers are polyolefins,
polysulfones, polyphenyl oxides, polycarbonates, and other
polyamides and polyesters. In any combination of any of the
foregoing, the higher melting material is dispersed in the form of
fibrils in a matrix of the other. In all of the blends mentioned
hereinafter, heat-shrinkage, heat-setting and improved shape
stability were achieved. Examples of the most useful polyolefin
materials are polyethylene, polypropylene, poly-1-butene,
polyisobutylene and polystyrene. In addition to the preferred nylon
6 (polycaproamide), other suitable polyamides are nylon 6-10
(hexamethylene-diamine-sebacic acid), nylon 6--6
(hexamethylene-diamine-adipic acid), methanol- and ethanol-soluble
polyamide copolymers and other substituted polyamides such as the
alkoxy-substituted polyamides. The preferred polyester is
polyethylene terephthalate; others are polyesters of high T.sub.g
useful in the practice of the present invention, including those
polymers in which one of the recurring units in the polyester chain
is the diacyl aromatic radical from terephthalic acid, isophthalic
acid, 5-t-butylisophthalate, a naphthalene dicarboxylic acid such
as naphthalene 2,6 and 2,7 acids, a diphenyldicarboxylic acid, a
diphenyl ether dicarboxylic acid, a diphenyl alkylene dicarboxylic
acid, a diphenyl sulphone dicarboxylic acid, an azo dibenzoid acid,
a pyridine dicarboxylic acid, a quinoline dicarboxylic acid, and
analogous aromatic species including the sulfonic acid analogues;
diacyl radicals containing cyclopentane or cyclohexane rings
between the acyl groups; and such radicals substituted in the ring,
i.e., by alkyl or halo substituents.
Many objects and advantages of the present invention will become
apparent from the following description taken in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial sectional view in schematic form showing a
drape-forming step where the textile material is being heated.
FIG. 2 is similar to FIG. 1 with the textile material being draped
and vacuum formed to final shape.
FIG. 3 is similar to FIG. 1 except showing a slip ring and a
different apparatus.
FIG. 4 is similar to FIG. 3 but shows the slip ring contacting the
textile material and the beginning of the forming of the material
into a three-dimensional shape.
FIG. 5 is similar to FIG. 4 with the material being formed into its
final shape and the slip ring being further compressed.
FIG. 6 is similar to FIG. 1 but shows the utilization of a plug
assist and a different type of apparatus.
FIG. 7 is similar to FIG. 6 but shows the heater removed and the
plug in its descended position.
FIG. 8 is similar to FIG. 7 with a vacuum utilized to pull the
fabric into its final shape.
FIG. 9 is similar to FIG. 1 showing the use of a different
apparatus where pressure is used on one side and vacuum is used on
the other side.
FIG. 10 is similar to FIG. 9 with the heater plate descended
against the textile material which is locked against the forming
cabinet.
FIG. 11 is similar to FIG. 10 with the textile material in its
finally formed shape.
DESCRIPTION OF THE INVENTION
As a first example of the practice of this invention,
multi-constituent filament is produced in accordance with the
formulation of Example 1 in U.S. Pat. No. 3,369,057, i.e., granular
polyethylene terephthalate polymer was used, melting about
255.degree. C. (DTA) and about 265.degree. C. (optical), having
density (when amorphous) of about 1.33 grams per cc. at 23.degree.
C. and about 1.38 grams per cc. in the form of drawn filament,
having reduced viscosity of about 0.85 and having T.sub.g about
65.degree. C. The polyester in the form of drawn filament drawn to
give ultimate elongation not above 20 percent will have tensile
modulus (modulus of elasticity) ranging from about 70 to about 140
grams per denier, depending on spinning conditions employed.
This polyester (30 parts) was mixed with 70 parts of granular
polycaproamide having reduced viscosity about 1.04, T.sub.g about
35.degree. C. and density about 1.14 grams per cc. at 23.degree. C.
Amine groups in this polycaproamide had been blocked by reaction
with sebacic acid, bringing the amine group analyses thereof to 11
milliequivalents of NH.sub.2 groups per kilogram of polymer. This
polycaproamide contained as heat stabilizer, 50 ppm copper as
cupric acetate.
The mixture of polyamide and polyester granules was blended in a
double cone blender for 1 hour. The granular blend was dried to a
moisture content of no more than 0.01 percent; then melted at
285.degree. C. in a 3-1/2-inch diameter screw extruder operated at
a rotational speed of about 39 rpm to produce a pressure of 3,000
psig at the outlet. A dry nitrogen atmosphere was used to protect
the blend against absorbing moisture. Residence time in the
extruder was 8 minutes.
The molten mixture thereby obtained had melt viscosity of about
2,000 poises at 285.degree. C. The polyester was uniformly
distributed throughout and had average particle diameter of about 2
microns, as observed by cooling and solidifying a sample of the
melt, leaching out the polyamide component with formic acid and
examining the residual polyester material.
The multi-constituent blend thus produced was extruded through a
spinneret plate and the resulting solidified fibers were drawn and
wound at 1,000-2,000 feet per minute under tensions of about 0.01
gram per denier. The filaments were then drawn 4-6 times their
length in order to impart orientation and maximum strength thereto.
The fibers were then formed into a yarn denier of 150 grams per
9,000 meters. This 150 denier yarn was made up of 32 individual
fibers. The yarn was then woven into a plain-weave fabric and fused
on a tenter frame traveling at the rate of 7 yards per minute with
a traction of -4 percent and an overfeed of +10 percent at between
215.degree. C. and 230.degree. C. and preferably 226.degree. C. The
air permeability or porosity was reduced from approximately 17
cubic feet per minute per square foot before heat treatment to 5
cubic feet per minute per square foot as measured by a standard
test. A 6-inch by 6-inch sample of this fabric was clamped in a
standard vacuum forming machine over a circular female mold one
inch deep and 2-5/8 inches in diameter. The retractable heaters
were maintained at a temperature of 700.degree. F. in a vicinity
close to the heating elements so that the fabric is heated to below
226.degree. C. and preferably to a temperature of between
218.degree. and 226.degree. C. prior to the application of the
vacuum for approximately 20 seconds. The vacuum was then applied
and the material readily assumed the 1-inch deep by 2-5/8 inch in
diameter three-dimensional shape and demonstrated the ease with
which a textile article can be made by vacuum forming utilizing the
principles of the present invention without the use of an
impervious sheet material.
The machinery used in the above example is quite well known in the
field of vacuum forming. Other types of machinery as illustrated in
the drawings FIGS. 1 through 11 will now be described. In FIGS. 1
and 2 there is shown a drape-forming method and apparatus. The
textile sheet is clamped by clamps 20 and heated by heater 21 to
the desired temperature. The sheet is then drawn over the mold 22
or else the mold is forced up into the sheet. When the mold has
been forced into the sheet and a seal 23 created, vacuum is then
applied through opening 24 into cavity 25 and through second vacuum
opening 26 so that atmospheric pressure is used in causing the
heated textile material to stretch slightly and assume the shape of
the mold. During the stretching operation there may be some
tendency to reduce the normal decrease in porosity created by the
spaced between the individual yarns opening up. However, in a
properly selected textile material treated with proper fusion
temperatures and sufficient capacity in the vacuum apparatus, such
openings are insufficient to prevent the practice of the
process.
In FIGS. 3, 4 and 5 there is shown a slip ring forming process. The
heated textile material is placed across the female die 27. As the
press closes pressure pads 28 clamp the textile material tightly to
allow it to slip under control tension as the mold 27 is pushed
into the material. During the descent, air beneath the sheet is
either vented or else a vacuum is drawn through opening 30. As the
mold finally closes the pressure pads exert maximum holding
pressure against the textile material restraining it enough to
avoid losing the final form shape. In the final view as seen in
FIG. 5 vacuum can be applied through second opening 31 and if
desired air pressure can be supplied through opening 30.
In FIGS. 6 through 8 are shown three sequences using vacuum forming
plug assistance. After the textile material is heated by
retractable heater 32 and sealed across the mold cavity 33, a plug
34 shaped roughly as the mold cavity but smaller is plunged into
the textile material and prestretches it when the plug platen 35
has reached its closed position as shown in FIG. 7. A vacuum is
drawn on the mold cavity through opening 31 to complete the
formation of the textile object as is shown in FIG. 8.
In FIGS. 9 through 11 there is shown a sequence of steps using a
trapped textile layer with contact heat and pressure forming. The
textile material is inserted between the mold cavity 37 and a hot
mold plate 38. The plate is flat and porous and allows air to be
blown through its face. The mold cavity seals the material against
the hot plate. Air pressure applied from the female mold cavity 37
through opening 39 beneath the sheet blows the sheet totally
against the contact hot plate for the best thermal conductivity for
rapid heating of the material. A vacuum can also be drawn on the
hot mold plate. After a predetermined heating the textile material
is ready for forming and air pressure is applied to the hot plate
to form the sheet into the female mold as shown in FIG. 11. Venting
can be used on the opposite side of the material or a vacuum can be
applied through opening 39.
As a second example in practicing the process and making articles
as a result thereof, the first example above is repeated except
that the step by which the material was heat-set or fused in a
tenter frame was omitted. Instead the material was directly used in
apparatus similar to FIGS. 3, 4 and 5, utilizing a heating
temperature of 218.degree.- 226.degree. C. The fabric exhibited a
high shrinkage and was permitted to pull out of the clamping frame
under controlled pressure of the clamping pads. This pressure was
adjusted to apply a restraining force just sufficient to prevent
wrinkling of the side walls of 1-inch deep by 2-5/8-inch diameter
cup which was formed. The free unrestrained shrinkage of this
fabric, which was soft and flexible, was determined beforehand in
an air circulating oven with the sample lying flat and
unrestricted. At a temperature of 180.degree. C. for 5 minutes it
shrank 16 percent in the machine or warp direction and 14 percent
in the transverse or fill direction. When heated to 200.degree. C.
for 5 minutes it shrank 21 percent in the machine or warp direction
and 19 percent in the transverse or fill direction. In all of the
above instances the shrinkage of the fabric was sufficient to close
the interstices of the fabric to the extent that a differential air
pressure could be imposed against said fabrics.
As a third example, the poly-constituent fiber of the first example
was made into a yarn of 840 denier using 136 individual filaments.
This yarn was then used for the warp and an 840 denier polyester
yarn was used for the fill in producing a satin weave. A 6- by
6-inch sample of the fabric was placed in a plug-assisted vacuum
forming apparatus similar to that of FIGS. 6 through 8. It was
first heated to between 226.degree. and 232.degree. C. prior to
forming into a cup 1-inch deep by 2-5/8-inch in diameter. While the
cup formed was satisfactory, the weave had a tendency to open up
and be more porous during the forming operation, for it was
necessary to use a plug for assistance and likewise a greater
capacity to the vacuum pump was needed to continue to maintain
sufficient differential pressure to adequately form the material
into the corners cavity.
As a fourth example, the third example was repeated with the only
difference being that the weave was a plain weave rather than a
satin weave. The results were identical to those of the third
example.
As a fifth example of practicing the invention, the first example
was repeated except the fibers of the textile material were not
prefused in a tenter frame and the fibers used in making the
textile material were only partially drawn. In the first example
above the fibers had been substantially fully drawn in their
manufacture, that is with a draw ratio of 4 to 6 or higher in order
to confer molecular orientation along the filament axis to increase
the strength of the filaments. While these high-strength filaments
are usually desired, in some instances it has been found their
tendency to shrink when heated to the fusion temperature of the
matrix polymer creates more shrinkage than is desired to some uses.
In this fifth example, the fibers were only drawn 2X. Their
extruded length provided some molecular orientation and increase in
strength but not nearly to the degree a further drawing would have
provided. The fabric woven from this filament was similar to the
first example and was heated in the first instance just prior to
being vacuum formed in an apparatus similar to that of FIGS. 1 and
2. The 1-inch deep by 2-5/8-inch diameter cup was readily formed in
the apparatus with small clamping forces since the tendency to
shrink had been reduced. It is to be noted that the fusion or heat
stabilization in a tenter frame was omitted in this example.
As an example of a blend of two different materials in the same
general class, a blend was prepared consisting of 30 percent
polyethylene and 70 percent polypropylene by weight. Both resins
were commercially available grades. The blend was spun into a
filament employing conventional spinning techniques. After spinning
and drawing, the filament was used to produce a fabric which was
heat-set in accordance with the principles outlined above except
the temperature was kept below about 180.degree. C.
In addition, still other blends are satisfactory for purposes of
this invention, including those disclosed in U. S. Pat. Nos.
3,378,055, 3,378,056 and 3,378,602; British Pat. No. 1,097,068;
Belgian Pat. No. 702,803 and Dutch Pat. No. 66,06838. Usually, the
melt temperatures of the blended polymers differ by about
10.degree. C. or more.
For any given multi-constituent formulation, the temperature and
time and fluid pressure will vary depending on the polymeric
materials, article size, shape, desired rigidity, mode of heat
application and other variables. In general, it is necessary to
apply heat without excessive degradation of sufficient intensity
and duration at least as high as the melting point of the matrix
component until the fabric yarns have fused to each other and the
porosity reduced whereby differential air pressure may be imposed
yet still retain the yarn or fabric identity. If the fabric yarns
are spun from polyblend staple fibers, the fibers forming said yarn
will fuse together individually in addition to fusion at the cross
points of said fabric. Fusion can be achieved without undesirable
flow and no sag when initially heated and before forming.
In test results, the general observation is made that as the
fabrics become increasingly fused at temperatures above the melting
point of the higher melting component their strength, elongation
and wrinkle resistance is reduced while their abrasion resistance,
stiffness, dimensional stability, and gas and liquid permeability
are increased. Fusing does not seem to affect the fabrics ability
to be dyed, colorfastness to light and washing, or their wash
stability. The invention is applicable to many fields such as
apparel, home furnishings, transportation vehicles, sporting goods,
and the like.
The invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
present embodiments are therefore to be considered in all respects
as illustrative and not restrictive, the scope of the invention
being indicated by the appendant claims rather than by the
foregoing description and all changes which come within the meaning
and range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *