U.S. patent number 3,917,448 [Application Number 05/320,924] was granted by the patent office on 1975-11-04 for random fiber webs and method of making same.
This patent grant is currently assigned to Rondo Machine Corporation. Invention is credited to Dennis E. Wood.
United States Patent |
3,917,448 |
Wood |
November 4, 1975 |
Random fiber webs and method of making same
Abstract
Random fiber webs are made from fibers, having different
coefficients of heat shrinkage. When the web is subjected to heat
the shrinking of the heat-shrinkable fibers causes the lower
shrinkage fibers to buckle and loop so that air spaces are created
and the bulk and texture of the web is improved. Various types of
fibers, natural, synthetic, mineral, etc., may be employed. Also
composite synthetic filaments may be used in which the core and
sheath have different coefficients of heat shrinkage.
Inventors: |
Wood; Dennis E. (Rochester,
NY) |
Assignee: |
Rondo Machine Corporation
(Mocedon, NY)
|
Family
ID: |
26982730 |
Appl.
No.: |
05/320,924 |
Filed: |
January 4, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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841215 |
Jul 14, 1969 |
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Current U.S.
Class: |
8/125; 19/296;
28/247; 428/113; 428/222; 442/415; 19/145.5; 28/103; 428/114;
428/362; 156/62.2; 156/62.8 |
Current CPC
Class: |
D04H
1/06 (20130101); Y10T 442/697 (20150401); Y10T
428/24132 (20150115); Y10T 428/2909 (20150115); Y10T
428/249922 (20150401); Y10T 428/24124 (20150115) |
Current International
Class: |
D04H
1/00 (20060101); D04H 1/06 (20060101); D06m
001/02 () |
Field of
Search: |
;19/145.5,155
;28/72.2R,76R ;117/15 ;161/79,80,152,153,154,166,169,72,59,47
;8/125 ;156/62.2,62.8 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Cannon; J.
Attorney, Agent or Firm: Shlesinger, Fitzsimmons &
Shlesinger
Parent Case Text
This application is a continuation of my application, Ser. No.
841,215, filed July 14, 1969 and now abandoned.
Claims
Having thus described my invention, What I claim is:
1. A process of making a non-woven fabric having a high degree of
loft, which comprises
aerodynamically depositing different types of fibers, some
retractable and others non-retractable under the conditions of the
process, simultaneously in an area where said fibers intermingle to
form a web having a random pattern of fiber arrangement throughout
the entire length, breadth and depth of said web,
systematically controlling the deposition of said fibers in said
area to
vary the predominance of one type of fiber over others of said
different types of fibers in zones arranged depthwise of and
essentially parallel with the major surfaces of said web, a zone
delimited by a major face of said web being composed of
predominantly different fibers than those of a zone immediately
adjacent thereto, and to
position said fibers so that some extend from one zone into another
and some through all of the plurality of zones lying between the
major surfaces of said web and, thereafter,
subjecting said zoned web to a retracting operation to effect
shrinkage of said retractable fibers and cause said retractable
fibers to loop, buckle and curl and, thereby, lock adjacent fibers
together at their points of contact and tie said web structure
together from within without significantly elimiating interfiber
voids.
2. The method of making a nonwoven fabric according to claim 1,
wherein the retractable fibers are heat-shrinkable, and the other
fibers are non-heat-shrinkable, and heat is applied to the web
after its formation to retract the heat-shrinkable fibers.
3. The method of making a monwoven fabric according to claim 1,
wherein the retractable fibers are natural cellulosic fibers and
retraction is effected by treating the web with a sodium hydroxide
solution of mercerizing strength.
4. The method of making a nonwoven fabric according to claim 1,
wherein the retractable fibers are water-shrinkable, and shrinkage
is effected by treating the web with water.
5. The method of making a nonwoven fabric according to claim 1,
wherein one major surface, at least, of the web is ornamented with
an in-depth colored design by printing a colored design on said one
surface, and causing the retractable fibers to shrink, whereby the
colored surface extends in depth down into the retracted
material.
6. A non-woven fiber web produced by the process of claim 1.
Description
The present invention relates to nonwoven fabrics and more
particularly to random fiber webs.
The characteristics of nonwovens are determined by the properties
of their component fibers and finishing.
Since the properties of the established fibers and those of the new
synthetics differ greatly, the application of these synthetics to
nonwovens has ofter been found unsatisfactory. Physical properties
such as denier and staple length together with various blends of
different fibers can be varied so that greatly diverse nonwovens
can be manufactured. However, although these nonwovens offer
functional performance they lack the esthetic qualities of handle
and appearance.
The primary object of this invention is to produce nonwoven fabrics
of great resilience, improved softness, and luxurious tactile
handle.
Another object of the invention is to produce nonwoven fabrics
having the qualities mentioned in which the nonwoven fabrics are a
blend of natural and synthetic fibers or of various types of
synthetic fibers.
Other objects of the invention will be apparent hereinafter from
the specification and from the recital of the appended claims
particularly when read in conjunction with the accompanying
drawing.
It has long been known that synthetic fibers differ from natural
fibers in four important respects.
A. Heat sensitivity
B. Feltability
C. Slickness, and
D. Chemical reactivity
It is the first of these differences, heat sensitivity, the ability
of man-made fibers to shrink with the application of heat, that is
primarily taken advantage of in practicing the present invention.
In fact, variation in two properties of the fiber used in the
nonwoven, denier and the shrinkage, have proven most valuable in
achieving improvements in fabric esthetics.
Although most of the applications have been made using acrylic or
polyester fibers, any synthetic fiber may be used which has the
ability to shrink, such as "Dacron 61", plasticized cellulose
acetate, copolymers of polyvinyl chloride and polyvinyl acetate
known as vinyon, and polyvinyl alcohol fibers which have not been
formaldehyde-treated. Other suitable fibers will readily occur to
those skilled in the art.
Lofty nonwovens of acrylic fibers are made by blending fibers
possessing different levels of heat shrinkage. Upon hot finishing,
the more heat shrinkable fibers cause the nonwoven to shrink so
that the lower shrinkage fibers buckle and loop, giving a lofty
appearance. It has also been found that after shrinking, the high
shrinkage fibers become stable and no further shrinkage will occur
in normal use. This effect called the differential shrinkage can be
used in nonwovens to improve texture, give light weight, bulky
fabrics, improve cover and body, and preferentially place low
shrinkage fibers on the nonwoven surface. Cover, bulk and improved
texture are caused by the low shrinkage fibers being forced into
the spaces previously existing between adjacent fibers. This
smooths out the appearance of the nonwoven particularly on the
surface of the fabric, making the fibers less apparent both
visually and to the touch. The bulk and the amount of shrinkage of
a given nonwoven depend on the relative amounts of high shrinkage
fibers used and the residual shrinkage of those fibers.
Bulk is important in nonwovens, since it is an indication of the
thermal efficiency of the nonwoven structure. It can be defined as
the volume in cubic centimeters of a piece of nonwoven material
weighing one gram. The bulk in nonwoven webs is a function of the
amount and number of air spaces between the individual fibers
within the structure. If straight fibers are used, they tend to lie
closely together. Also, the more compact the web the less the
covering power. So that if the fibers are curled or crimped, air
spaces will be created and the structure will occupy a volume
greater than the density of the total fibers. This "bulk" creates a
better yield, more warmth and greater aesthetic appeal.
By comparison a nonwoven made of a blend of 70% orlon, 20% wool,
10% rayon without high shrinkage "orlon" fibers gave an overall
shrinkage of 10% yet the appearance was hard and the fibers
distinct; the different fibers stood out too sharply, and the
fabric felt rough. Yet in a nonwoven with the same parameters but
with 30% of the 70% of "orlon" as high shrinkage fibers, the
individual fibers become indistinct, the appearance is softened,
and the surface feels smooth and continuous, the overall shrinkage
is 24%.
It can be shown that an increase in the amount of high shrinkage
fibers from 0 to 35% will raise the bulk or a representative
nonwoven from 3.4 to 4.5 cm.sup.3 /gr. This is caused by the
increase in bulk brought about by greater shrinkage. However, if
the amount of high shrinkage fiber be increased from 35% to 100%,
the bulk becomes less and less due to the steady decrease in the
number of bulk-forming loops of the low shrinkage fibers. It will
therefore be seen that these nonwovens contain a considerably
greater volume of air than fiber and that the warmth of the
nonwoven is dependent primarily on the amount of air within the
material. Therefore the number of fibers and amount of air spaces
influence the insulating properties.
The amounts of high shrinkage fiber become increasingly less
effective because the decrease in shrinkage forces becomes less as
the shrinkage approaches its maximum potential. The use of 30 to
40% high shrinkage fiber has been found to give the best results
because at this level the fabric shrinkage is more uniformly
controlled and less sensitive to variations in blend
composition.
Most nonwovens made of low shrinkage man-made fibers shrink about
10 to 15% depending upon the fiber lay and bonding treatment
whereas nonwovens containing high shrinkage fibers can shrink up to
40%. This shrinkage is dependent upon the residual shrinkage of the
fiber. Normal residual shrinkage is about 20% but ultra high
residual shrinkage fiber of about 50% shrinkage gives very good
results.
In general, the objects of this invention are accomplished by
forming a nonwoven material with a percentage of shrinkage
synthetic fibers blending with non-shrinkable fibers either of
natural, sythetic, vegetable, animal, or mineral types into a web
in which the fibers have haphazard arrangement. The web is made of
non-matted uncompressed fibers, which are arranged randomly in
three dimensions, namely, in all directions along the length,
width, and depth of the web. These nonwoven webs may be
manufactured by machines which use the air lay principle, where the
fibers are collected upon a foraminous surface aided by suction or
a reduced pressure such as disclosed in my pending application Ser.
No. 691,544, filed Dec. 18, 1967 now U.S. Pat. No. 3,535,187,
issued Oct. 20, 1970.
In this machine two different types of fibers may first be formed
into two separate fiber mats, and the fibers are combed from the
two mats by rotating lickerins, are doffed from the lickerins by
centrifugal force and air streams, and are carried in the air
streams through separate ducts into a condensing chamber in the nip
between two oppositely rotating foraminate condensers, and
simultaneously continuous filaments or another type of fiber may be
fed into the condensing chambers between said ducts and also into
the nip between the two oppositely rotating condensers. Thus a
random fiber is formed, in which different fibers may predominate
in different zones of the web but which is different from the
ordinary laminated web because of the interfiber entanglement
throughout the web and of the blending of fibers at the interface
areas of the various zones of the web. The random web formed on the
condensers is delivered onto a conveyer which carries it out of the
machine.
After formation, the web is exposed to treatment effective to
shrink the retractable fibers. The shrinking of these retractable
fibers gives the web bulk, increased density, improved softness and
luxurious tactile handle not heretofore attained in a nonwoven
web.
A web constructed in accordance with the invention comprises a
plurality of non-matting fibers, either straight or curled or
crimped, of various lengths and types, with a percentage of
shrinkable fibers in random arrangement throughout the web. The
shrinkable fibers may be blended in such way that a preponderance
of shrinkable fibers are arranged on one or both surfaces, or may
be arranged only within the center structure of the web. The
lengths of the fibers may vary from 1/2 inch to 2 inches.
The truly nonwoven random or haphazard arrangement of the web
constructed in accordance with this invention is easily
distinguished for prior art webs, which are sometimes referred to
as nonwovens, such as batts made by felting, garnetting or carding
machinery. In these processes the batts so made have a predominate
arrangement of fibers which lay parallel to each other giving
strength principally in one direction. These batts are usually
light in weight and with little loft. The batts are either laid up
by tandem systems or formed by a laminating technique using a
series of individual webs and tieing these together; or they may be
cross lapped, or formed by a combination of these two methods,
whereby suitable weights are built up. These methods are, however,
slow and time-consuming. Also, these systems give a layer of
fibrous masses and not a true blend as is required by this
invention.
Also the process of this invention should not be confused with felt
making where a carded batt or a cross-laid material is built up by
interlocking the fibers by mechanical work, chemical action,
moisture and heat, without spinning, weaving or knitting, the
ordinary process being by hardening the batt by rubbing the
felting, or fulling, to produce a dense, compact material. Nor
should this process be confused with semifelted materials which may
also be made of a carded type batt built up by cross-laying or
similar means which contain retractable materials. Such materials
must be severely needled to secure the layers of material together;
and thereby a compacting effect is caused which may reduce the batt
in volume by as much as 50%, so that, after heat-working, the web
will be shrunk at least 60% and more. This reduces the number of
air spaces or voids thereby lowering the porosity, resilience, and
loft.
Preferably with this invention truly isotropic nonwovens are
produced with the fibers intermingled randomwise in
three-dimensional arrangement throughout length, width, and depth
of the web with individual fibers extending transversely throughout
the depth of the web to opposite upper and lower surfaces thereof
and tying the web into a intergral structure from said upper and
lower surfaces. The importance of having a random,
three-dimensional arrangement of uncompressed fibers cannot be
over-emphasized.
Preferred embodiments of the present invention are illustrated on
the attached drawing, and are as follows:
In the drawing:
FIG. 1 is a fragmentary sectional view of a random fiber web made
according to one embodiment of this invention;
FIG. 2 is a similar view of a web made according to another
embodiment of the invention;
FIG. 3 is a corresponding view of a web made according to a further
embodiment of the invention;
FIG. 4 is a similar view of a web made according to another
embodiment of the invention;
FIG. 5 is a sectional view of a web made according to a still
further embodiment of the invention; and
FIG. 6 is a similar view of a web made according to still another
embodiment of the invention.
FIRST EXAMPLE
The nonwoven web 10 (FIG. 1) is made on a machine such as mentioned
above so that the fibers are preferably of various lengths from
about 1/2 inch to 2 inches and are a blend of 70% orlon 11, 20%
wool 12 and 10% rayon 14. The 70% of orlon fibers 11, which is made
up of 30% high shrinkage fiber with a residual shrinkage of 17% is
intermingled in random arrangement so that these fibers lay at
various angles, both horizontally and vertically to form a
three-dimensional web with the individual fibers contacting each
other at their separate points of contact throughout the web.
Relatively few pairs of individual fibers contact at more than one
point; and each fiber of the web contacts a plurality of other
fibers at spaced points which may be in the same or in different
planes, there being individual fibers extending transversely
throughout the depth of the web to opposite upper and lower
surfaces, thereby tying the web into an integral structure from
said upper and lower surfaces.
The web, after formation, is transported by a continuous conveyor
to a heating chamber for heating to a temperature of say
80.degree.C for 5 minutes. The amount of heat is sufficient to
retract the shrinkable fibers but not allow them to become
completely amorphous in character. The residual shrinkage of the
30% of high shrinkage fiber causes them to buckle and loop causing
them to be forced into the spaces previously existing between
adjacent fibers providing coherence of the already integral web,
imparting texture, also lightness and weight, bulky softness and
porosity.
SECOND EXAMPLE
The required web 15 (FIG. 2) is prepared from 70% polyacrylonitrile
fibers 16, 20% wool fibers 17, and 10% staple 150 "Lurex" MM
metallic fibers 18, so that 60% of the acrylic fibers are
retractable with a residual shrinkage of 25%. These fibers are
blended in three groups; (a&b) 5% Lurex, 10% wool and 23%
acrylic shrinkable fibers per group, and (c) 10% non-shrinkable,
14% shrinkable acrylic fiber. Blends (a&b), 24 and 26,
respectively, are processed through the outside randomizing
chambers of the machine disclosed in the above-noted U.S. Pat. No.
3,535,187; blend (c), 25, is processed through the center section
of this machine, giving a truly isotropic web; yet arranging the
blends in three zones 24, 25, 26, so that the wool and "Lurex"
fiber appear in both the upper and lower surfaces of the web. The
web so formed is needled and heat treated so that the overall
shrinkage is only 27% with a bulk of a little over four cubic
centimeters per gram.
This example is given to illustrate the interesting and novel types
of webs which may be formed from materials dissimilar in
characteristics and from fibers of differentially retractable
residual shrinkages. For example, a three blend web may be prepared
with two zones of one material and a third zone of a different
material, so that when the web is treated, only two zones retract
at the outer surfaces providing an integral inner cushion of
material securely held by the outer two zones.
THIRD EXAMPLE
Another interesting and novel product that may be formed comprises
a 50/50 blend of 15 denier 2 inch staple polyethylene terephthalate
fibers, with 50% residual shrinkage fibers, and 6 denier alginate
fibers, that will constitute a truly isotropic web of a depth of
11/2 inches. This web is passed through a needle loom with regular
barbed needles so that the web receives about 450 penetrations per
square inch on each surface. The needled web is then immersed in
boiling water for two minutes so that the web shrinks 26% in area
at the same time the polysaccharide material is removed by the
water so as to achieve a fineness not otherwise obtainable and
increase the porosity of the web some 180%.
FOURTH EXAMPLE
A further interesting product, produced in accordance with this
invention, comprises an isotropic web 30 (FIG. 3) prepared from two
fibrous materials, one, a very coarse fiber 31 of 200 denier
"Dacron 61" with a 17% residual shrinkage and a fiber length of
11/2 inch staple; and another, very fine fiber 32 of micro denier
"beta" glass with a fiber length of between 3/4 inch and 11/4 inch
staple. These fibers may be processed through the three-zone
machine disclosed by my patent mentioned above, the "Dacron 61"
polyester fiber being processed through the center section, and the
glass fiber 22 through the two outer randomizing chambers. These
fibers are processed simultaneously and are atomized within the
condensing chambers and deposited upon the pair of suction rolls or
condensers of the machine, which are set so that the distance
between these rolls corresponds to the web thickness of 11/2
inches. The fibers are carried in the air currents the width of the
machine and are deposited upon these suction rolls or condensers in
such a manner that the fibers build up into the roller gap and over
their entire width in a three-zoned random arrangement throughout
the structure so that the two outer surfaces contain a majority of
glass fibers while the inner region contains the polyester fiber
which protrudes into the outer areas of the upper and lower
surfaces of the web. The fibers so positioned are intermingled in a
random arrangement so that they lay at various angles, both
horizontally and vertically to form a uniform three-dimensional
structure in length, width and depth, there being individual
polyester fibers extending transversely throughout the depth of the
web to its upper and lower surfaces. Both fibrous materials contact
each other at their various points of contact throughout the web,
there being relatively few pairs of individual fibers which contact
at more than one point; and each fiber of the web contacts a
plurality of other fibers at spaced points which may be in the same
or in different planes throughout the web, thereby tying the web
into an intergral structure in length, width, and depth.
The web is then transported by a continuous conveyor to a needle
punch loom and lightly needled on both sides so that the structure
receives about 80 penetrations per square inch, thereby increasing
the specific gravity. The resulting web is then heat treated
sufficiently to retract the shrinkable fibers. Upon shrinkage the
polyester fibers buckle, curl, loop, and generally deform causing
interlocking of the structure and providing coherence to the
already integral web. A nonwoven so made has a three-zoned porous
structure whose upper and lower surfaces or zones are an
arrangement of fine glass fibers while its inner core is largely
constructed of the coarse fiber which in turn causes a difference
in the air spaces or voids within the web such that the inner core
will have the larger voids while these will become more numerous
and smaller in size towards the outer surfaces; giving the
structure a differential filtering characteristic.
FIFTH EXAMPLE
By the way of another example: a blend 40 (FIG. 4) of 50% 80s wool
41 and 50% 6 denier polyester fiber 42, both nonshrinkable, are
processed through the outside chamber or zones of the machine
disclosed in U.S. Pat. No. 3,535,187. A heat shrinkable
premanufactured polyester or acrylic scrim or netting material is
run through the center section so that a web is formed around the
plastic netting within the center zone. The web so formed is
transported to a needle loom where the web is lightly needled to
give about 20 penetrations per square inch on both sides. The
needled web is the exposed to dry heat at 280.degree.F for 5
minutes with the result that the polyester netting retracts causing
the fiber blend trapped between the netting squares to fluff up and
contract the fibers around the adjacent open square of the
netting.
SIXTH EXAMPLE
Yet another example is a blend as above but instead of a shrinkable
netting material being encapsulated in the isotropic web,
continuous shrinkable filaments are projected into the web in a
completely random fashion so that after needling and the required
heat treatment the retracted filaments impart a curious surface
effect such that random hills and valleys are formed.
SEVENTH EXAMPLE
In another example the required web 50 (FIG. 5) is produced, using
the methods disclosed by my patent application above mentioned,
where a polyvinyl alcohol fiber 51 known as Vinal VP-101 was
processed through one of the outer zones of the preferred machine
to produce an outer zone 54 of approximately 21/2 oz. per sq. yard
using a staple length mixture of 1/2 inch to 2 inches. Through the
center section 55 a light weight web 52 of about 1/2 oz. per sq.
yard is processed using Du Pont's "Dacron 54" polyester fiber of 1
inch staple length and in the other outer zone 56 of the machine a
wool web 53 is manufactured at 3 oz. per sq. yard.
The resultant 3-zoned composite nonwoven is then transported to a
two roll calender where one roll is heated and has an embossed
pattern upon its surface and the other is a filled roll of 100%
cotton fibers. The two rolls have different surface speeds. The web
is processed through the calender so that with the combination of
heat and pressure the nonwoven web is consolidated into an integral
matrix so that the retractable fibers are drawn together and are
thrust upwards out of the plane of the web into a series of buckled
ridges which are further extended with the use of the embossing
roll. The differential shrinkage of the matrix is 35% which gives
the polyvinyl alcohol surface of the web firm, highly pronounced
and deeply textured surface ridges which have an extremely good
resemblance to the material known as Persian lamb since it consists
of wool fibers and hard wearing polyester fibers organized into the
tightly looped ridges of the skin-like polyvinyl alcohol fibers,
giving a flexible and fine grained surface.
The following examples are given to illustrate the embodiment of
this invention when using composite fibers known as bicomponent and
biconstituent or biconjugate.
The bicomponent fiber is a composite synthetic fiber formed by
combining two or more components of the same type but with various
characteristics. The biconstituent fiber is a composite synthetic
fiber formed by combining at least two different compositions in
conjugation sometimes referred to as "Hetero-filaments". The
biconjugate fiber is a composite synthetic compound fiber formed in
conjugation so that each of the two or more main constituents
contain one or more different polymers being a combination of the
bicomponent and biconstituent types.
The nonwoven matrix is formed using the method as disclosed by my
above-mentioned patent, where the isotropic web 60 (FIG. 6) is
prepared from 50% of bicomponent fibers 61 formed from two
copolymers 62, 63 of acrylonitrile, which in their separate fiber
form differ in shrinkage characteristics, 10% wool and 40% of the
triacetate fiber "Arnel". These fibers are of various lengths from
about 1/2 inch to 2 inches and various deniers from 5 denier to 50
denier, blended in three groups, 66, 67, 68:
a&b. 20% of the bicomponent fiber and 20% of the "Arnel"
fiber
c. 10% of the bicomponent fiber and the wool fiber.
Blends (a&b) are processed through the outside randomizing
chambers of the aforementioned machine while the third blend c is
processed through the center section giving a truly isotropic web
yet arranging the blends in three regions or zones so that the two
outer zones are of the same configuration while the center zone is
formed with the wool-synthetic blend which protrudes into the inner
areas of the upper and lower surfaces of the web. The fibers so
positioned are intermingled in a random arrangement and lie at
various angles both horizontally and vertically to form a uniform
three-dimensional structure in length, width, and depth. The web so
formed is passed through a needle loom with regular barbed needles
so that the web receives about three hundred penetrations per
square inch on each surface. The needled web is then exposed to
heat designed to retract the bicomponent shrinkable fibers so that,
because of the differing shrinkage characteristics, the fiber
becomes highly crimped; and it buckles and loops into the spaces
previously existing between adjacent fibers providing interfiber
locking giving coherence of the already integral web, imparting
texture, porosity and bulky softness.
EIGHTH EXAMPLE
In a further instance, the manufacture of the fiber nonwoven is
performed by vertical and horizontal deposition of continuous
elements within a matrix of staple fibers and combining the two
constituents into one integrated structure. The materials used in
this example were a biconstituent staple fiber known as "Tricelon"
which is a combination of triacetate and "Nylon 6" in various
deniers over the range 15 to 30 and in lengths of between 1/2 inch
and 11/4 inches processed through the outer chambers of the
aforementioned machine, while simultaneously continuous filaments
are processed through the center section of the machine. These
continuous filaments are a bicomponent fiber where two or more
species of polyvinyl chloride, both or all of high syndiotactic
index but differing in shrinkage characteristics, have been
extruded under conditions that the polymers are not uniformly mixed
in the filaments so that one component may be in the form of a
sheath around a core of the other.
The fibers and filaments are processed simultaneously and are
intermingled in the condensing chamber air stream and deposited
upon the pair of condensing cylinders which are so set that the
distance between these suction rolls corresponds approximately to
the desired thickness of the web, in this case 1 inch. The fibers
and filaments are carried in the current of gas the width of the
machine and deposited upon the suction rolls in such a manner that
the fibers and filaments build up into the roller gap and over its
entire width. Due to the turbulence of the air stream, the
filaments begin to swing and oscillate back and forth in front of
the condensing rolls. They are therefore seized in irregular order,
sometimes by one suction roll, sometimes by the other. As they
advance between the roller gap they are embedded within the staple
fibers. Since the rate of delivery of the continuous filaments is a
multiple of the rate at which the matrix is formed, a short length
of an individual filament is drawn to one side of the condenser
suction area, and, due to the oscillation of the air stream
carrying the fibers and filaments, an adjacent part of the same
filament is seized in the next moment by the opposite suction roll
and thus the filament is disposed in a horizontal orientation
within the staple fiber structure. Since the air stream oscillates
not only back and forth but also from side to side, the next moment
another continuous filament is laid crosswide at a random angle to
the previously deposited filament. This process is repeated in
rapid succession over the entire fiber forming apparatus such that
a random homogeneous fiber structure is produced between the staple
fiber and continuous filaments in length, width, and depth. Thus,
in this example my invention comprises advancing a plurality of
continuous filaments along a path leading to the nip between spaced
web forming condensing members so that the filaments move adjacent
and onto said members while at the same time a matrix of the staple
fiber is being formed. The gas streams within the condensing
chamber are passed in a direction extending transversely to the
continuous filaments and the gas streams have a component
horizontal to the fiber and filament flow path, so that movement of
the filaments, as they pass between the matrix-forming cylinders,
is disrupted, and individual filaments are caused to be dispersed
in a side to side and back and forth random array within the staple
fiber structure.
The bicomponent continuous filaments have been so engineered that
the inner core has a higher differential shrinkage than that of the
outer sheath, so that, when the nonwoven web is exposed to heat,
the bicomponent polyvinyl chloride shrinks at different rates
causing the continuous filament to crimp, buckle, and loop
imparting to the structure improved texture, cover and body while
having a full natural luxurious silky handle and great resilience,
together with inherent fiber to fiber and filament integrated
locking, imparting cohesion to the nonwoven web which is an
important characteristic of this invention.
The webs formed as described above are mostly uncompressed yet
self-sustaining and have considerable strength in their lateral,
longitudinal, and transverse dimensions. They can be handled and,
if required, spray-bonded and are capable of being stitched and cut
without the addition of any backing material. The web so formed may
be stitched directly to woven fabrics to form a laminated
fabric.
The webs have excellent air-retaining properties; and the
insulating values therefore are high. Because of the random
three-dimensional arrangement of the fibers, there are innumerable
intercommunicating voids in the web and air can pass through that
batt, but only at a relatively slow rate. The web can be compressed
without the loss of loft provided the memory factor of the fiber to
its recovery rate is good.
While the invention has been described particularly in connection
with use of heat-shrinkable fibers, it will be understood that
fibers retractable by other media also may be used. For instance,
when natural cellulosic fibers are employed, the shrinkage may be
effected by treating the web with a sodium hydroxide solution of
medium strength. Water-shrinkable fibers may also be used, and
shrinkage effected by treating the web with water. Steam may be
used also to effect shrinkage of fibers when they are susceptible
to shrinkage with heat and water.
Because of the deeply textured surfaces ridges that may be produced
with the process of the present invention, the fibrous surface of a
web formed according to this invention may be ornamented with an
in-depth colored design by printing such a design onto one or both
surfaces of the matrix prior to effecting shrinkage of the web, so
that when the retractable fibers in the web are shrunk, the colored
surface will extend in depth down into the retracted and textured
material.
Other modifications and applications of the invention will occur to
those skilled in the art.
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