Note: Descriptions are shown in the official language in which they were submitted.
CA 02220253 1997-11-OS
WO 96/35578 PGTJUS95/05805
TITLE
Abrasion-resistant Composite Sheet
BACKGROUND OF THE INVENTION
Field of the Invention
s This invention relates to an abrasion-resistant composite sheet and to
a process for making the sheet. More particularly, the invention concerns
such a composite sheet in which pile-like groups of fibers are immobilized
by a resin in a position that is generally vertical to the surface of the
sheet.
Description of the Prior Art
~o It is known to laminate various woven or nonwoven fabrics to resin
layers to form composite sheets intended for use in thermoforming and
molding processes. For example, such composite sheets are disclosed in
Miyagawa et al, U. S. Patent 4,298,643, Zafiroglu, U. S. Patent 5,075,142,
and in Japanese Patent Application Publications 63-111050 and 63-162238.
1s Moldable composites have been utilized in many applications. However,
such composites are in need of improvement when intended for use in
articles that are subject to strong abrasion, for example, in athletic shoe
parts,
luggage surface layers, protective work clothes, heavy duty sacks, etc.
Pile fabrics and pile-like fabrics, such as velvets, velours, terry cloths,
2o moquettes, and tufted-pile fabrics have a surface layer in which fibers are
generally vertical to the surface of the fabric. Also, Zafiroglu, U. S.
Patents
4,773,238 and 4,876,128, disclose certain stitchbonded fabrics in which
fibrous layers are contracted by means of elastic threads to form pile-like
groups of fibers. Generally, such fabrics are not disclosed for incorporation
2s into resin-impregnated composite sheets. However, Japanese Laid-open
Patent Applications 64-85614 and 64-85615 disclose a floor mat which
includes a tufted-pile fabric to which a rubber resin is added. The tufted
pile
has an 8-mm pile height and a 0.08-gJcm3 pile fiber concentration. The
combination of pile fiber and resin is 62 % by weight pile fiber and 38% by
3o weight resin. The combination has an average over-all density of 0.13
g/cm3. The mat has a pile parameter, P, as defined hereinafter, of only 0.1
g/cm3. The present inventor found that (a) such a low pile fiber
concentration in combination with such a low over-all layer density and low
pile parameter does not provide the mat with high abrasion resistance and (b)
ss even if such relatively high piles are have a dense layer of resin at the
outermost tips of the pile, (e.g., with all the resin in the top 1 mm of the
pile)
such a resin/pile layer is stretched and torn apart by strong abrasion.
Increases in the abrasion resistance of such floor mats would improve their
utility.
i
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WO 96/35578 PCT/US95/05805
Watt et al, U. S. Patent 4,808,458, discloses flocked pile fabrics
wherein a foamed resin is located primarily in the bottom 75%, preferably
the bottom 50%, of the pile leaving the remainder of the pile nearly free of
resin, for the purpose of obtaining a suede effect. Such products are
s ineffective in resisting severe surface abrasion.
Zafiroglu, International Application Publication WO 94/19523
discloses an abrasion-resistant resin-impregnated nonwoven fabric. The
fabric is made by contracting a nonwoven fibrous layer to cause groups of
fibers buckle out of the plane of the layer and form "inverted U-shaped"
io loops that project generally vertically from the layer and then
impregnating
the contracted layer with resin. Typically, within the nonwoven fibrous
layer, the fibers are positioned in all directions. The individual fibers in
the
loops of the buckled fibrous layer therefore are not positioned in a generally
perpendicular direction to the contraction, but are rather positioned in all
is directions within the loops of the buckled nonwoven fibrous layer. Even
though the groups of fibers form vertical U-shaped loops, a large fraction of
the fibers within the loops still are not oriented perpendicular to the plane
of
the layer. Resin impregnation of such contracted fibrous layers provides a
composite sheet that has an abrasion resistance that is superior to a resin-
2o impregnated flat (not contracted or buckled) nonwoven layer, but further
improvements in wear resistance are desired.
An aim of the present invention is to provide a composite sheet that
has a very high resistance to severe abrasive wear.
SUMMARY OF THE INVENTION
2s The present invention provides an abrasion-resistant composite sheet.
The sheet has an upper surface and a lower surface and comprises a resin,
groups of pile-like fibers and a planar fibrous network. The fibrous network
is located between and substantially parallel to the upper and lower surfaces
of the composite sheet. The groups of pile-like fibers are located between
so the upper and lower surfaces and are mechanically connected to and protrude
generally perpendicularly from the planar fibrous network. The composite
sheet has a stretchability in any direction that is no more than 25%. The
groups of pile-like fibers have an effective pile concentration, ce ff, of at
least
0.10 g/cm3, preferably in the range of 0.15 to 0.4 g/cm3, and are surrounded
3s and immobilized by the resin in the generally perpendicular position.
Typically, the resin amounts to 30 to 90 %, preferably at least 50%, of the
total weight of the composite sheet. The groups of pile-like fibers and planar
fibrous network are composed of fibers of textile decitex (i.e., of 0.7 to 20
dtex). Further, the pile fiber/resin layer has a thickness in the range of 0.5
to
2
CA 02220253 1999-12-14
3 mm, preferably 1 to 3 mm, an over-all density, d, of at least 0.4 g/cm3,
preferably in
the range of 0.5 to 1.2 g/cm3, a stretchability in any direction of no greater
than 25%,
preferably no greater than 10%, a vertical compressibility of no greater than
25%,
preferably no greater than 10% and a pile parameter P, calculated by the
equation, P =
S ~(Ceff)(d)~~/z, of at least 0.3 g/cm3, preferably at least 0.35. Typically,
the pile fiber/resin
layer has a unit weight that is in the range of 500 to 2,500 g/m2. The surface
of the
composite sheet is abrasion resistant and is abraded by no more than 50
microns per
1,000 cycles of 40-grit Wyzenbeek abrasion testing.
The invention also includes a process for making the abrasion-resistant
composite sheet, comprising (a) providing a fabric in which fibers form or can
form
pile-like fiber groups in a surface layer of 0.5-mm to 3 mm thickness in which
the
pile-like groups of fibers are positioned generally perpendicular to the
surface of the
fabric and an end of each pile-like group of fibers is mechanically attached
to, or is
protruding through, a generally horizontal fibrous network, (b) contracting
the area of
the fabric by a factor of at least two and usually not more than by a factor
of 15,
preferably by a factor in the range of 3 to 12, to buckle and vertically
orient groups of
fibers on the surface and to increase the concentration of generally
perpendicular
groups of pile-like fibers to a concentration of at least 0.10 g/cm3,
preferably in the
range of 0.15 to 0.4 g/cm3, (c) immobilizing the pile-like groups of fibers in
the
generally perpendicular position by incorporating a resin in the surface layer
and
providing the layer with an over-all density of at least 0.4 g/cm3 and a pile
parameter,
P, of at least 0.3 g/cm3, the resin constituting in the range of 30 to 90%, of
the total
weight of the surface layer, and (d) optionally further stabilizing the
dimensions of the
composite by attaching inelastic elements to the composite sheet.
The invention further provides a shaped article having the abrasion-resistant
composite sheet attached to at least a portion of the surface of the article.
The
composite sheets provide surface layers that are capable of withstanding
Wyzenbeek
40-grit abrasion-testing (as described hereinafter) with a loss in thickness
of no more
than 50 microns/1,000 cycles.
Further aspects of the invention are as follows:
3
CA 02220253 1999-12-14
An abrasion-resistant composite sheet having
an upper outer surface,
a lower surface,
a planar fibrous network located between and substantially parallel to the
S upper and lower surfaces,
a stratum of groups of pile-like fibers located between the lower and upper
surfaces of the sheet, the pile-like fibers being connected to and protruding
generally
perpendicularly from the planar fibrous network,
an elastomer resin immobilizing the groups of pile-like fibers in the
generally
perpendicular position and amounting to 30 to 90% of the total weight of the
resin-
impregnated pile layer, the groups of pile like fibers and the planar fibrous
network
being composed of fibers or filaments of textile denier, and
the sheet having a stretchability of no greater than 25% in any direction,
characterized by, in combination
1 S the groups of pile-like fibers extending to the upper outer surface of the
composite sheet and being present in the resin-impregnated pile-like fiber
layer in an
effective pile fiber concentration, ceff, of at least 0.1 g/cm3,
the elastomer resin extending through the stratum of groups of pile-like
fibers
from the outer surface of the sheet to a depth of at least 0.5 mm,
the resin-impregnated layer having a thickness in the range of 0.5 to 3 mm, an
over-all density, d, of at least 0.4 g/cm3, a unit weight in the range of 300
to 2,500
g/cm2, a vertical compressibility of no greater than 25% and a pile parameter,
P,
calculated by the equation, P = [(Ceff)(d)~ ~', of at least 0.3 g/em3,
and the layer exhibiting a 40-grit Wyzenbeek abrasion wear of no more than
50 microns per 1000 cycles.
A process for making an abrasion-resistant composite sheet comprising the
steps of
providing a fabric having a thickness of 0.5 to 3 mm within which groups of
pile-like fibers are generally perpendicular to the surface of the fabric and
are present
in an effective pile-fiber concentration of at least 0.1 gram/cm3 and the
groups of pile
3a
CA 02220253 1999-12-14
like fibers are connected to and protruding from a planar fibrous network
located in or
at a surface of the fabric,
immobilizing the groups of pile-like fibers in their perpendicular position by
incorporating an elastomer resin into the fabric from a surface of the fabric
to a depth
of at least 0.5 mm to form an impregnated fabric, the resin being in an amount
that
constitutes in the range of 30 to 90 % of the total weight of the impregnated
fabric and
provides the impregnated fabric with an over-all density of in the range of
0.4 to 1.2
g/cm3, and a pile parameter of at least 0.3 g/cm3.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood by referring to the attached drawings.
Figure 1 schematically represents an idealized magnified cross-section of an
abrasion-
resistant surface layer of the invention, in which pile-like groups of fibers
are in the
form of generally vertical inverted U-shaped loops 10 of height H and base B,
which
loops 10 are immobilized in resin 15 between upper surface 17 and lower
surface 18
1 S of the resin-impregnated
25
3b
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WO 96/35578 PCT/US95/05805
fibrous layer. The loops 10 are generally perpendicular to upper surface 17
of the layer and contracted elements 20 are generally parallel to surfaces 17
and 18. Surface 17 is the surface that is intended to be exposed to the
abrasive conditions. Fig. 2 represents a segment 11, of a yam or of a bundle
s of fibers in a nonwoven fibrous layer, before buckling or contraction of the
yarn or layer, the segment being located between stitches or fixed points 12
and 13, which are a distance of S apart. Fig. 3 and 4 respectively represent
segment 11 would appear after the fabric or fibrous layer in which it was
located is contracted by a factor of two (Fig. 2) or three (Fig. 3) in the
io direction of the length of the segment. Note that the greater contraction
is
accompanied by a greater verticality of the fiber bundles or yarns.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The following description of preferred embodiments is included for
the purposes of illustration and is not intended to limit the scope of the
~s invention; the scope is defined by the appended claims.
As used herein, the terms "pile-like groups of fibers" or "pile-like
fibers" includes buckled yarns, inverted-U-shaped loops formed from
buckled nonwoven layers of textile fibers, tufted yarns and the like. The
fibers within each of these pile-like groups of fibers, as well as the fibers
of
2o the nonwoven fibrous layers, are of conventional textile decitex, namely,
of
0.7 to 20 decitex.
The highly abrasion-resistant composite of the invention has a surface
layer in which pile-like groups of fibers are crowded together and
immobilized by a resin within the surface layer. The pile-like fibers protrude
2s generally perpendicularly from a fibrous network that is also located
within
the surface layer, for example at the mid-plane or at the base of the layer.
The fibrous network can be a nonwoven fibrous layer, a knitted fabric, a
woven fabric, or the like. Typically, as shown in Fig. 1, the fibrous network
20 is located no further than 3 mm from outer surface 17 of the layer that is
3o to be exposed to abrasion. The resin 15 and the fibrous network 20 prevent
the pile-like fibers 10 from moving from side to side or from collapsing into
the layer when the surface of the composite is subjected to lateral and normal
forces during repeated cycles of abrasion or rubbing. The composite has a
stretchability and the resin/pile-fiber layer has a compressibility (measured
ss as described hereinafter), each of which is no greater than 25%, preferably
no greater than 10%. Stretchability and compressibility; respectively are
measures of how much the fibers can be moved from side to side and how
much the fibers can be collapsed from their perpendicular position when the
composite is subjected to conditions of severe abrasion.
4
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w0 96/35578 PCT/US95/05805
In accordance with the invention, the surface layer of the abrasion-
resistant composite has a thickness in the range of 0.5 to 3 mm. Thicknesses
of greater than 3 mm are avoided because it is difficult to immobilize and
stabilize pile-like layers if the to-be-abraded surface is fiurther than 3 mm
s away from the horizontal fibrous network. The effective concentration, cep,
of the generally vertical pile-like fibers within the surface layer is in the
range of 0.1 to 0.5 gram/cm3, preferably in the range of 0.15 to 0.4 g/cm3.
' In the surface layer of the composite, the resin constitutes 30% to 90%,
preferably at least 50% and most preferably at least 70%, of the total weight
io of the layer. The over-all density, d, of the surface layer is at least 0.4
g/cm3. For high resistance to abrasion and wear, the surface layer of the
composite has a "pile parameter", P, ,that is at least 0.3 g/cm3. The pile
parameter, P, as defined herein is the square root of the product of the pile-
like fiber concentration and the overall density of the surface layer. The
pile
1s parameter is expressed by the formula, P = [(c)(d)] 1~2.
Typically, the surface layer of a composite sheet of the invention is
not completely filled with resin and fiber. The layer can contain many small
voids. An over-all density of the surface layer of at least 0.4 g/cm3, and
11_. -...+ +1..... 1..~~.+ !1 D /.. 3 0 + 1~ ell~r ;tnr~liAe fllP fIrPCPI'll~P
gellerally 11VL more ~uaa~ avow v.~ gia.aTi , oiivfimau~~.uy uaa~raawa uav r
..~..._....
20 of voids in the surface layer amounting to at least 10% and as much as 65%
or more of the total volume of the layer, because most fibers and resins
suitable for use in the invention have densities of at least 1.0 g/cm3.
However, overall densities of as high as 1.2 g/cm3, and accordingly resin
densities of greater than 1.0 g/cm3 are contemplated for use in the invention.
2s For lighter weight and more flexible composite sheets, surface layer void
volumes of 25 to 75% are preferred. Usually, high amounts of resin are
employed in the composites that have low concentrations of vertical fibers in
the surface layer. For example, in composite sheets of the invention having
effective pile-fiber concentrations near the lower 0.1-g/cm3 limit, a layer
3o constituting 70 to 90% resin is preferred. For relatively high effective
pile
fiber concentrations, lower percentages of resin can be used (e.g., 30-50%).
Various types of resins are suitable for immobilizing the fibers or
fiber bundles in the generally vertical position. Particularly useful
polymeric
resins include polyurethanes, epoxies , synthetic rubbers, polyesters,
ss polyacrylates, polyethers, polyetheresters, polyamides, copolymers and
mixtures thereof and the like. The resins can be thermoplastic or
thermosetting. Very soft resins, for example soft rubber latexes or resins
that
are highly foamed, generally are not suitable for use in the present
invention.
Resins suitable for use in the invention adhere well to the fibers and usually
s
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w0 96/35578 PCT/US95105805
are well distributed throughout the pile-fiber layer. However, if the resin
distribution is not fully uniformly distributed throughout the pile-fiber
layer,
the resin preferably is concentrated nearer the surface that is to be abraded
than to the end mechanically attached to the horizontal fibrous network.
s The resins can be applied to the pile-fiber layer in any of several
conventional ways, as for example, by dipping, spraying, calendering,
applying with a doctor knife, or other such techniques. The resin may be
applied from a solution, dispersion or slurry or by melting a layer of the
resin
and forcing it into the layer of vertical fibers. The resin also can be
~o introduced as adhesive particles or as binder fibers that are activated by
heat
or chemicals. Conventional coagulation and/or foaming techniques also may
be employed in applying the resin. In most instances, the resin or binder can
be introduced into the fibrous layer before, during or after the contraction
step which is required according to the process of the invention for obtaining
~s the desired density of vertical fibers in the surface layer. However, when
forming the surface layer and incorporating resin, care must be taken to
avoid deflecting the fibers from their vertical position and to avoid
immobilizing the fibers before the fibers have been positioned vertically.
After incorporation into the pile-like fiber layer, the resin is dried and/or
2o cured by conventional methods. If during resin application, the pile-like
fiber layer is compressed in thickness by as little as 25%, the pile-like
fibers
sometimes can be deflected significantly from verticality and result in the
composite sheet having decreased abrasion resistance.
The surface layer of a composite sheet of the invention is much more
2s abrasion resistant than a 100% resin layer containing no vertical fibers or
a
resin/fiber surface layer in which the fibers are not in a vertical position.
For
example, composites of the invention having vertical fibers encased in a
layer of relatively soft polyurethane resin can be SO to 150 times more
resistant to abrasion than a layer made from 100% of the same resin. When
3o harder, relatively more wear-resistant resins are employed, the advantage
of
the fiber/resin layer of the invention over a layer of 100% of the same resin
is not as great. However, compared to surface layers containing no fibers or
containing primarily horizontal fibers, surface layers of composites of the
invention still are very much more abrasion resistant.
3s In the process of the invention, the first step provides a fabric that has,
or has the capability of forming, a pile-like fiber layer. As used herein, the
term "pile-like fiber layer" means a surface layer of a fabric within which
fibers are positioned generally vertical to the surface of the fabric.
CA 02220253 1997-11-OS
WO 96135578 PCTlUS95/05905
In accordance with certain embodiments of the process of the
invention, the generally vertical fiber layer is derived from a substantially
nonbonded fibrous nonwoven layer which is subjected to a contraction step
that causes fibers or groups of fibers to buckle out of the flat plane of the
s fibrous nonwoven fabric to form the pile-like layer. The generally vertical
fibers of the pile-like layer are depicted in Figure 1 and often appear as
inverted U-shaped loops, of height H and base B. Such loops, when formed
in part from a nonbonded fibrous nonwoven, typically have an average
spacing (i.e., base B) in the range of 0.1 to 2 mm, and a height-to-base ratio
io of at least 0.5. Loop spacings as small as 0.1 mm and height to base ratios
of
as large as 15 can be achieved when the layer is highly contracted (e.g., by a
factor of 10 to 15) and additional elements capable of forming pile or pile-
like fibers are included in the structure (e.g., other non-elastic yarns in
the
stitching patterns). Practical ways to determine the H and B dimensions of
is the loops, are described below in the paragraphs on test methods.
A typical nonwoven fibrous layer for use in an embodiment of the
process of the invention is a thin, supple, substantially nonbonded web of
staple fibers or continuous filaments of textile decitex. These fibrous
materials are referred to collectively herein as "fibers". The fibers are
2o naturally occurring or formed from synthetic organic polymers. Fibers that
are smaller than 5 dtex and longer than 5-mm are preferred. Preferred
fibrous layers are capable of buckling over a relatively short interval (e.g.,
as
small as 1 mm) and typically weigh in the range of 15 to 100 grams/square
meter, preferably less than 60 g/m2. Suitable materials for the starting
2s nonwoven fibrous layer include carded webs, air-laid webs, wet-laid webs,
spunlaced fabrics, spunbonded sheets, and the like. Generally, thick lofty
webs, felts, adhesively or thermally bonded webs, or the like are not
suitable;
such materials usually are difficult to buckle over short intervals.
Contraction and buckling of the fibrous layer can be accomplished in
3o any of several ways. For example, a contractible element, or array of
contractible elements, can be intermittently attached to the fibrous layer.
The spacing between attachment locations is typically at least 1 mm to allow
for efficient buckling. Then, the element or array of elements is caused to
contract so that the area of the fibrous layer is decreased significantly and
3s groups of fibers buckle out of the plane of the layer. Before the
contractible
elements are attached, additional gathering or contraction can be imparted to
the fibrous starting layer by overfeeding the layer to the apparatus being
employed to attach the contractible elements.
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Many types of contractible elements are suitable for use in the present
invention. For example, the nonwoven fibrous layer can be stitchbonded
with elastic yarns under tension. Textured stretch yarns, covered or bare
spandex yarns and the like are suitable yarns for contractible element
s stitching. After the stitching, the tension can be released to cause the
desired
contraction and buckling of the fibrous layer. Instead of stitching, extended
elastic elements in the form of warps, cross warps, filins or the like, can be
intermittently attached to the fibrous layer by hydraulic entanglement,
adhesive or thermal point bonding, or the like. Thereafter, tension on the
to extended elements can be released to cause layer contraction and buckling.
Other types of contractible elements, which shrink on being treated
with heat, moisture, chemicals or the like can be attached intermittently to
the fibrous layer without initial tension or extension in the elements. After
attachment, the contraction of the contractible elements can be activated by
~s appropriate treatment.
Still another way of accomplishing the contraction and buckling of the
fibrous layer involves intermittently attaching the fibrous layer to a
stretchable substrate that necks-in in a direction that is transverse to the
direction in which the substrate is pulled. For example, certain substrates,
2o when stretched by 15% in one direction, can automatically experience
substantially irreversible contraction (i.e., neck in) in the transverse
direction
by an amount that is two or three times the amount of stretch. Thus,
appropriate intermittent attachment of a fibrous layer to the stretchable
substrate before the stretching and necking-in operation, and then applying
2s the stretching forces to the combined layer and substrate, can
significantly
decrease the area of the fibrous layer and cause buckling of groups of fibers
as required by the process of the invention.
In other embodiments of the invention, the pile-like layer of fibers is
derived from conventional yarns in a knit or woven fabric which is
3o constructed with contractible elements. When the contractible elements
contract, the area of the fabric decreases significantly and causes the
conventional yarns of the fabric to gather and buckle and project in a
vertical
direction from the horizontal plane of the gathered fabric. In another
embodiment, the pile-like layer includes loops of fibers that project from
ss wrapping yarns that were loosely wrapped around the axis of the
contractible
core of an elastic combination yam. Generally, yarns that can be contracted
and buckled provide denser pile-like layers than do contracted and buckled
nonwoven fibrous layers. After resin is applied according to the invention,
s
CA 02220253 1997-11-OS
WO 96135578 ~CTI(JS95I05805
the resultant composite sheets made with buckled yarns possess a higher
abrasion resistance than those made with buckled nonwoven fibrous layers.
In still other embodiments of the invention, a pile-like layer can be
derived from a combination of a contracted substantially nonbonded fibrous
s nonwoven fabric, loose wrapping yams of a contracted combination yarn
and/or a buckled non-elastic yarn. In those embodiments wherein the pile-
like layer is formed partially or totally from buckled yarns derived from a
knit or woven fabric, the knit or weave is sufficiently coarse permit
satisfactory yarn buckling. Typically, the buckled elements, before buckling,
have a flat length of at least 1 mm. In yet another embodiment of the
invention, a tufted pile fabric is contracted to increase the density of the
pile
tufts, for use in a composite sheet of the present invention.
As used herein, a combination yam means a yarn having a
contractible core (e.g., provided by an elastic or shrinkable yam) surrounded
1s by a non-contractible conventional "wrapping" yarn or "covering" yarn. The
wrapping or covering yarn may be of any natural or synthetic fiber. The
wrapping may be combined with the elastic core while the elastic core is
under tension by conventional wrapping, winding, plying, covering, air jet
entangling or intermingling, or the like. The core may be a yam or
2o monofilament of any elastic material. Cores of spandex yarn are preferred.
If the wrapping yarn is combined loosely (e.g., fewer than 3 turns/inch) with
a tensioned and extended elastic core, when the tension is released, the core
contracts and the wrapping yarn contracts and buckles perpendicular to the
core. When a fabric is knit, woven or stitchbonded with a combination yarn
2s under tension, when the tension is released from the combination yarn, the
yarn contracts and the wrapping yarn buckles contributing pile-like fibers to
the surface layer. However, if the wrapping yarn is wound too tightly
around the elastic core, the combination yarn cannot provide pile-like fibers
to the composite sheet
so In the contraction step of the process of the invention, the area of the
fabric from which the vertical fibers are derived is contracted by a factor of
at least 2, preferably in the range of 3 to 10 and sometimes by a factor as
high as 15. The contraction step is employed before or during application of
the resin. The fabric cannot be contracted after the resin has become set.
3s As a result of the contraction step, the concentration of vertical pile-
like fibers in the surface layer of the fabric is significantly increased.
Then,
the fibers are immobilized in place by adding a resin to the surface layer, in
an amount in the range of 30 to 90% of the total weight of the resin-
containing layer (i.e., weight of resin and pile-like fibers). Preferably the
CA 02220253 1997-11-OS
WO 96/35578 PCT/US95/05805
resin amounts to at least 50% and most preferably at least 70% of the total
weight of the layer. Typically, the resin is distributed uniformly throughout
the layer of pile-like fibers. However, as long as the pile-like fibers are
immobilized in a substantially vertical position, the distribution of resin
can
s be somewhat non-uniform and there also can be a fairly large void fraction
in
the layer. The voids can amount to as much as 75% or more of the total
volume of the layer. Ridding the layer of voids to completely fill the layer
with resin is unnecessary. In fact, techniques for this purpose are avoided
because the techniques often excessively crush the fibers and deflect the
io fibers from a vertical position. Vertical pile-like fibers in the
resin/fiber
layer are essential for the improvements in abrasion resistance provided by
the composite sheets of the invention.
In addition to the pile-like fabrics described above, composite sheets
according to the invention also can be produced from other types of pile
is fabrics, such as tufted pile fabrics, velvets, moquettes, and velours so
long as
the fabrics have a pile height and a pile fiber concentration within the
requirements of the present invention and the fabrics are capable of being
combined with resin to produce a layer having a pile parameter of at least 0.3
g/cm3. Such starting fabrics typically have pile-fiber concentrations in the
2o range of 0.05 to 0.15 g/cm3. In composite sheets made with such fabrics,
the
resin typically amounts to at least two-thirds of the total weight of the pile-
like fiber/resin surface layer. The over-all density of the pile-like
fiber/resin
layer is generally at least 0.4 g/cm3, preferably in the range of 0.5 to 0.9
g/cm3. Higher, rather than lower, pile densities are preferred because the
2s higher density piles are more resistant to compression and pile fiber
deflection during the resin- impregnation step and ultimately can lead to a
more abrasion resistant layer.
The abrasion-resistant surface of the composite sheet of the invention
is resistant to lateral stretch, and to vertical compression. The
stretchability
3o and compressibilty of the composite sheet can be controlled in several
ways.
The stretchability of the composite sheet is affected greatly by the
horizontal
fibrous network to which the pile-like fibers are attached and from which the
pile-like fibers protrude. An inherently non-stretchable fiber network,
located within about 3 mm of the outer surface of the composite, can impart
ss non-stretchability to the resin-fiber surface layer. For low stretchability
and
low compressibility, a hard resin, rather than a softer one, is preferred.
Lateral stability of the composite sheet in any linear direction also can be
achieved by the attachment of strong, substantially non-stretchable strips,
films, sheets, webs, cross-warps or the like to the back surface of the
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abrasion-resistant layer. The attachment may be made by any convenient
means, such as gluing, thermal bonding or the like.
Abrasion-resistant composite sheets of the invention are suitable for
use in many different articles. The sheets can be molded into various shaped
s articles, can be used as single or multiple layers, or can be attached by
various means to the surface or portions of the surface of various shaped
articles to provide the articles with abrasion resistance. For example,
composite sheets of the invention are suited for use in shoe uppers, work
gloves, automotive engine timing belts, leather-like apparel, indoor athletic
~o protective pads, women's pocketbooks, bags, luggage, saddles, seating
surfaces, etc. The more abrasion-resistant composite sheets of the invention
are especially suited for articles that are subjected to more demanding
abrasion conditions, such as toe, heel and/or sole portions of shoes, bottoms
of industrial bags that are often dragged on concrete floors, bearing surfaces
is of interacting mechanical parts, soccer balls, heavy duty work boots,
gloves,
motor-cyclist apparel pads, and the like.
Test Methods
The following methods and procedures are used to measure various
characteristics of the resin-impregnated fabrics of the invention.
20 In composite sheets of the invention, which have vertical pile-like
fibers formed by the buckling of a nonwoven fibrous layer or by the buckling
of yarn segments over short intervals, inverted U-shaped loops are formed
from buckled groups of fibers or from buckled yarns. The height H and the
base B of the U-shaped loops of buckled groups of fibers are determined
2s from magnified (e.g., 15-20~ photomicrographs of cross-sections of the
loops taken through the loops in a plane perpendicular to the plane of the
fibrous layer. The data are then used to calculate an H ratio. A low
magnification microscope with strong top and/or back lighting on the sample
permit direct measurement of H and B. Usually the average loop height H is
so equal to the thickness of the contracted fibrous layer. Alternatively, the
average loop height H can be measured directly with a "touch" micrometer
having a 1/4-inch (0.64-cm) diameter flat cylindrical probe which applies a
10-gram load to the contacted surface. A digital micrometer, model APB-
1D, manufactured by Mitutoyo of Japan is convenient for the measurement.
3s In addition to the above-described method, "verticality" of pile-like
fibers can be determined by examination of a magnified cross-section of the
fiber/resin layer. If loops are "crushed" or excessively "pushed down"
during resin application, a relatively long flat portion of the inverted U is
seen near the outer surface of the fiber/resin layer. Deflection of straight
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fibers or yarns from a vertical position also is readily observable. Such
severe deflection of pile fibers can occur during resin application. A 30%
decrease in pile-fiber layer thickness during resin application can decrease
the abrasion resistance of the final composite sheet, especially when the pile
s fiber concentration is near the lower end of the range of concentrations
suitable for use in the present invention.
Stretchability, S, is determined by: (a) cutting a specimen measuring
2-cm wide by 10-cm long sample from the composite sheet; (b) marking a
standard length, Lo, on the specimen parallel to the long dimension; (c)
to suspending a 1.0-kilogram weight from specimen for 2 minutes; (d) with the
weight suspended, re-measuring the "standard length", the re-measured
length being designated L f and (e) calculating the percent stretchability,
%S,
by the formula, %S = 100 (Lf- Lo)/Lo.
Compressibility, C, is determined by measuring the change in
is thickness of the surface pile-fiber/resin layer of the composite sheet (a)
under no pressure, to, and (b) under a pressure of 351 kiloPascals (51
lb/in2),
tf A thickness gage is employed which imparts a 2.5-pound (1.14-Kg) load
onto the pile fiber/resin composite through a cylindrical foot of 1/4-inch
(0.64-cm) diameter. Then, the percent compressibility, %C, is calculated by
2o the formula, %C = 100 (to - t~/to. To avoid possible errors in these
determinations, caused by the presence of a compressible horizontal fibrous
network within the impregnated layer and to assure that it is the
characteristics of the pile fiber/resin layer that are being measured, the
horizontal fibrous network is carefully removed by sanding until only the
2s pile/resin layer remains.
The unit weight of a fabric or fibrous layer is measured according to
ASTM Method D 3776-79. The density of the resin-impregnated fabric is
determined from its unit weight and its measured thickness. The void
fraction of the layer can be readily determined from the measurements of the
30 over-all density of the layer and the weights and densities of the fiber
and
resin in the layer.
Over-feed ratio, contraction ratio and total gather are parameters
reported herein which are measures of how much an initial fibrous layer
contracts or gathers as a result of the operations to which the layer is
ss subjected. The over-feed ratio, which applies only to the embodiments of
the invention which employ a buckled nonwoven fibrous layer, is defined as
the ratio of the initial area of a starting fibrous nonwoven layer to the area
of
the layer immediately up-stream of a first processing step (e.g., a
stitchbonding step). Over-feed causes buckling, gathering or compression of
12
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the nonwoven layer in the direction in which it is being fed to the operation.
The contraction ratio is a measure of the amount of further contraction the
nonwoven layer undergoes as a result of the specific operation to which it is
subjected (e.g., stitchbonding and release of tension from yarns to which the
s fibrous layer was intermittently attached). The contraction ratio is defined
as
the area of the fibrous layer as it enters the specific operation divided by
the
area of the fibrous layer as it leaves the specific operation. The total
gather
- is defined as the product of the over-feed and contraction ratios. The
fraction of original area is the reciprocal of the total gather and is
equivalent
io to the ratio of the final area of the fibrous layer to the initial area of
the
starting fibrous layer.
The effective pile fiber concentration is determined from the
concentration of fibers within the surface layer of the composite sheet which
are in a vertical (or pile-like) position with respect to the surface that is
to be
is exposed to abrasion. For fabrics in which the pile-Like fibers are derived
from buckled hard yams (e.g., as in a contracted knit fabric) the effective
pile fiber concentration is the weight of the hard yarns in a unit of area
divided by the thickness of the layer. Similarly, if the pile-like yarns are
provided by buckled yarns that had been loosely wrapped around a stretched
2o elastic yarn that had then been permitted to contract, the total weight of
the
wrapping yarns are included in the calculating the concentration of the pile
yarns, but the weight of the elastic core is not included. For composite
sheets in which the pile-like yarns are formed from a contracted-and-buckled
nonwoven fibrous layer, only 50% of the weight of the nonwoven fibrous
2s layer is included in the calculation of the pile-fiber concentration. The
present inventor found empirically, that the abrasion-resistance-versus-pile-
parameter data for composites of the invention correlate much better when
only half the weight of the buckled nonwoven fibrous layer is employed
rather than the full weight said layer. This reflects the fact that pile-like
so fibers formed from buckled hard yarns and tufted pile fibers, for example,
are more effective in providing abrasion resistance to the composite sheet
than are pile-like fibers formed from contracted-and-buckled nonwoven
fibrous layer. Thus, the effective pile fiber concentration, ceg, = 10-4 kw/t,
wherein k is 0.5 for pile-like fibers provided by buckled nonwoven fibrous
3s layers and 1.0 for buckled yarns or tufts, w is the unit weight of the pile-
like
yarns in grams per square meter and t is the thickness of the surface layer in
centimeters.
To determine the abrasion resistance of samples a Wyzenbeek
"Precision Wear Test Meter", manufactured by J. K. Technologies Inc. of
13
CA 02220253 1999-12-14
Kankakee, Dlinois, is employed with a 40 grit emery cloth wrapped around
the oscillating drum of the tester. The drum is oscillated back and forth
across the face of the sample at 90 cycles per minute under a load of six
pounds {2.7 Kg). The test is conducted in accordance with the general
s procedures of ASTM D 4157-82. The thickness of the sample is measured
with the aforementioned thickness gage before sad after a given number of
abrasion cycles to determine the wear rate in microns lost per 1,000 cycles.
To provide adequate wear resistance to the composite sheets of the
invention, a wear rate of no more than 50 micmns/1000 cycles is considered
to to be satisfactory.
EXAMPLES
In the following Examples, the fabrication and abrasion resistance of
various composite sheets of the invention are illustrated and compared to
similar composite sheets that are outside the invention. The composite
is sheets of the invention arc much more abrasion resistant than are the
comparison composite sheets. Samples of the invention arc designated with
Arabic numerals and comparison samples with upper case letters.
Conventional warp-knitting nomenclature is used to describe the particular
repeating stitch patterns that ware employed to prepare the various knit or
20 stitchbonded fabrics of the Facamples. A table accompanies each example
and records fabrication details, weights, composition and characteristics of
each composite sheet, as well as the abrasion performance of the sheet.
In the examples, fabrics that were made with elastic yarns were in
sequence (1) removed from the fabric forming machine, (2) allowed to
2s achieve an initial contraction, (3) subjected to a "boil-off treatment by
being
immersed in boiling water (100°C) for 1-2 minutes, (4) dried and then
(5)
heat set on a tenter frame for 1-1.5 minutes at 380°F (193°C).
The particular
amounts of stretching in the longitudinal and transverse directions during the
heat setting were used control the final amount of contraction experienced by
3o the fabric.
Two different polyurethane resins were used for impregnating the
pile-like layer of the composite samples. "ZARTM", a clear polyurethane finish
sold by United Gilsonite Laboratories of Scranton, Pennsylvania, designated
herein as "PU-1 ", was used for the samples of Examples 1 and 3. PU-2, a
3s softer polyurethane resin, sold by K.1. Quinn & Co., Inc. of Seabrook, New
Hampshire was used for all the remaining samples. PU-2 is a two-part
formulation that was mixed, applied to the pile fibers and then cured. The
samples were resin-impregnated by conventional dipping techniques. The
applied resin was smoothed with a doctor blade and dried and/or cured with
14
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the pile fibers facing downward for at least 12 hours in a hot-air oven. Oven
temperature was maintained at 65°C for fabrics impregnated with PU-1
and
at 95°C for fabrics impregnated with PU-2. The compressibility, density
and
40-grit abrasion wear rates (in microns/1000 cycles) and Shore A hardness of
s a 5-mm-thick layer of each resin containing no fibers were as follows:
Shore A % Com- Density Abrasion
Resin hardness pressibil'~tv gLcm3 wear rate
PU 1 70 0 1.1 900
PU-2 53 5 1.0 4,500
1o Example 1
This example compares two samples of resin impregnated composite
sheets of the invention with a sample drat is outside the invention. In each
sample, pile-like fibers are formed of Kevlar~ aramid fibers (sold by E. L du
Pont de Nemours & Co.). In Sample 1, the pile-like fibers are formed by the
1s budding of Kevlar~ yarns in a unit fabric. In Sample Z, the pile-like
fibers
are formed from buckled Kevlar~ stitching yarns and a buckled nonwoven
fibrous substrate of Kevlar~ in a stitchbonded fabric. In comparison Sample
A, which is outside the invention because of its low effective pile-fiber
concentration and low pile parameter, the pile-like groups of fibers are
zo formed only from a buckled nonwovea layer of Kevlar~ fibers. Samples 1
and 2 the invention are shown have between about 3 to 5 times the abrasion
resistance of comparison Sample A.
The starting fabric for the composite sheet of Sample 1 was a two bar
knit fabric that was prepared with a ~~LIBATM" machine operating at 10 gauge
2s (10 rows per inch or 4 per cm) and 22-courses per inch (8.7 per cm). The
back bar was threaded with 400 den (440 dtex) filament Kevlar~-29 yarn
forming a repeating pattern of 1-0,4-5 stitches. The front bar was threaded
with a combination yarn that consisted of a 280-den (320-dtex) Lycra~
spandex elastic core, around which was tightly wound, at about 7 turns/inch
30 (2.8/cm), a 70-den (78-dtex) 34-filament textured polyester yarn. Upon
removal of the knit fabric from the LIBA machine, the as-knit fabric weighed
159 g/m2. The as-knit fabric was then boiled-off and heat set. As a result
the fabric contracted by a factor of 2.6 and increased its weight to 413 g/m2,
The back bar yarn buckled to form groups of inverted U-shaped pile-like
3s fibers. The tight wrapping of the combination yarn of the front bar yarn
did
not contribute to the formation of pile-like groups of fibers. Then, the
fabric
was impregnated with polyurethane resin PU-1 and dried and cured in the
hot-air oven. Characteristics of the resultant composite sheet, Sample 1, are
recorded in Table I below.
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The starting fabric for the composite sheet of Sample 2 was a two-bar
stitchbonded fabric that was prepared with a 140-inch (3.6-meter) wide, two-
bar "Liba" machine adapted for stitchbonding a nonwoven fibrous layer.
Each bar was threaded to 14 gage (14 rows/inch or 5.5/cm) and inserted 9
s stitches per inch (3.Slcm) in each row. A 34-g/m2 Type Z-11 Sontara~
spunlaced fibrous substrate (made by E. I. du Pont de Nemours & Co.) of
Kevlar~29 aramid fibers of 1.5 den (1.7 dtex) per filament and 2.2 cm
length was fed to the LIBA with 47% overfeed. The back-bar and front-bar
stitching threads were the same as those used for Sample 1, but formed
to opposing 2-course Atlas stitch patterns. Upon removal of the stitchbonded
fabric from the LIBA, the fabric contracted in area and increased its weight
to 184 g/m2. The stitchbonded fabric was then boiled off, heat set and resin
impregnated in the same manner as for Sample 1, except that the area of
Sample 2 in the boiling and heat setting contracted by a factor of 2.9 and the
is nonwoven fibrous layer, which had been overfed to the stitchbonding step,
experienced a total gather of 4.3. Further details of the fabrication and
characteristics of Sample 2 are listed in Table I below.
A comparison composite sheet, Sample A, was prepared from the
same type and weight of Kevlar~ spunlaced starting fabric as was used for
2o Sample 2. A one-bar stitchbonding machine, threaded at 12 gauge (12
needles /inch or 4.7/cm) and inserting 14 stitches/inch (5.5/cm), was used for
Comparison Sample A. The nonwoven fibrous layer was overfed 25% and
stitched with the same combination yarn as was used in preparing Samples 1
and 2. A 1-0, 2-3 repeating stitch pattern was employed. Sample A was
2s resin impregnated, boiled off and heat set in the same way as Samples 1 and
2. Details of comparison Sample A are summarized in Table I.
The data of Table I clearly demonstrate the superior abrasion
resistance of composite sheet Samples l and 2 over comparison composite
sheet of comparison Sample A. Samples 1 and 2 respectively were 2.7 and
30 3.1 times as abrasive resistant as the comparison Sample A.
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Table I (Example 1)
Sample Identification ,~ ~, $
Starting Materials
Nonwoven wt., g/m2 0 34 34
Over-feed ratio na 1.47 1.25
Hard yarns wt., g/m2 135 104 0
'Contractibles wt., g/m2 24 30 44
Total wt., g/m2 159 184 87~
Gathering
Contracted wt., g/m2 413 537 361
Contraction ratio 2.6 2.9 4.15
Nonwoven wt., g/m2 0 145 176
Hard yarn wt., g/m2 351 302 0
Nonwoven total gather na 4.3 5.2
% of original area 38 35 24
Resin application
Resin wt., g/m2 306 566 510
% pile height loss 0 0 0
__.. , _. ..v,_..~..a.....s
~~a...~
~iiitaa:c tvyer vaaniw:v.c~.iav.w:o
Total wt., g/m2 657 1013 686
Thickness, mm 1.1 2.0 1.4
Density, g/cm3 0.59 0.51 0.49
Pile fiber weight, g/m2 351 445 176
Pile fiber cone , g/cm3 0.32 0.23 0.13
Effective pile conc, g/cm3 0.3Z 0.19 0.065
Pile Parameter, P, g/cm3 0.44 0.32 0.18
Loop base, B, mm 0.7 0.5 0.4
Loop H/B ratio 3.6 5.0 3.5
Wt. % resin 46 56 74
% voids 51 58 59
% stretchability 10 10 10
% compressibility 10 10 5
40-grit abrasion resistance
Test duration, 103 cycles >5 >5 >5
Wear, microns/103 cycles 23 36 110
% normalized wear* 21 33 100
Note: na = not applicable; = Normalized Sample
* to A.
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~XalriDle 2
In this example, several samples of composite sheets of the invention
and comparison samples similar to those of Example 1 are prepared, but with
softer polyurethane resin PU-2 replacing polyurethane resin PU-1 of
s Example 1. Each sample and comparison sample has groups of pile-like
fibers formed from Kevlar~ aramid fibers.
Sample 3, Sample 4 and comparison Sample E, respectively, contain
the same fabrics as Samples 1 and 2 and comparison Sample A of Example
1. The composite sheet of Sample 3 includes a contracted fabric that had
io been knit with an elastic combination yam on one bar and a non-elastic yarn
on the second bar. The composite sheet of Sample 4 includes a contracted
fabric that had been prepared by stitchbonding a fibrous layer with one bar
of elastic composite yarn and one bar of non-elastic yarn. Sample E includes
a contracted fibrous layer that had been prepared by stitchbonding the layer
~s with a single bar of elastic combination yarn. Additional composite sheet
comparison Samples B and C respectively are made with the same starting
fabrics as Samples 3 and 4, but with different amounts of resin applied.
Further details on the fabrication, characteristics and abrasion performance
of the resultant composite sheet samples are summarized in Table II. Table
2o II clearly shows the abrasion-resistance advantage of composite sheets made
with pile parameters of high value . See for example, the abrasion-test
results for Sample 3 versus comparison Sample B and Sample 4 versus
comparison Sample C. Also, the abrasion wear results for these samples,
and Sample E, versus of the corresponding samples in Example 1 show that
2s as long as the resins immobilize the fibers and provide low compressibility
and stretchability to the layer, increasing resin hardness apparently does not
increase abrasion resistance of the composites of the invention. Increases in
pile-fiber concentration and pile parameter are more effective .
In addition to the above-described composite sheets containing fabrics
3o with pile-like groups of Kevlar~ aramid fibers, two more composite sheets,
Sample 5 and comparison Sample D, are prepared. Starting fabrics for these
two samples are made by tufting a 1,000 den (1,100 dtex) Kevlar~-29 yarn
into a 119-g/m2 lightly bonded Reemay~ spunbonded polyester nonwoven
fabric (made by Reemay, Inc., of Old Hickory, Tenn.) at 16 tufts per inch
ss (5.1/cm) at 14 gauge (14 tufting needles per inch or 5.5/cm). The tufted
fabric was stretched 20%, with an accompanying necking-in of about 40%,
to contract the area of the fabric by a factor of 2. Further details of the
composite sheet construction and performance are summarized in Table II.
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Table 2)
II
(Example
Sample Identification~ $ ~ g
Starting Materials
Nonwoven wt., g/m2 0 0 34 34 119 119 34
Over-feed ratio na na 1.471.47 na na 1.25
' Hard Yarns wt., g/m2 135 135 104 104 205 205 0
Contractibles wt.,g/m224 24 30 30 0 0 44
' Total wt., g/m2 159 159 184 184 314 314 87
Gathering
Contracted wt., g/m2 413 413 537 537 636 636 361
Contraction ratio 2.6 2.6 2.9 2.9 2.0 2.0 4.15
Nonwoven wt., g/m2 0 0 145 145 0 0 176
Hard Yarns wt., g/m2 351 351 302 302 415 415 na
Nonwoven total gatherna na 4.3 4.3 na na 5.2
% of original area 38 38 35 35 49 49 24
Resin application
Resin wt., g/m2 646 102 1263192 1680 560 1020
% pile height loss 0 0 0 0 0 0 0
Surface layer characteristics
Total wt., g/m2 997 453 1710639 2095 975 1196
Thickness, mm 1.1 1.1 2.0 2.0 2.6 2.6 1.1
Density, g/cm3 0.91 0.41 0.860.32 0.81 0.381.08
Pile fiber weight 351 351 447 447 415 415 176
g/m2
Pile fiber conc g/cm30.32 0.32 0.220.22 0.16 0.160.16
Eff. pile conc, g/cm30.32 0.32 0.180.18 0.16 0.160.08
Pile Parameter, g/cm30.54 0.36 0.400.24 0.36 0.250.29
Loop base, B, mm 0.7 0.7 0.5 0.5 0.8 0.8 0.4
Loop H/B ratio 3.6 3.6 5.0 5.0 3.8 3.8 3.5
Wt. % resin 64 22 74 30 80 57 85
% voids 24 66 28 72 32 68 10
% stretchability 0 20 0 15 0 0 0
% compressibility 0 15 0 15 0 0 0
40-grit abrasion resistance
Test duration, 103 les 1.5 25 7.9 25 6 13.2
cyc 13
Wear, microns/103 es 80 25 66 30 60 50
cycl 18
% Normalized wear* 36 160 50 132 60 120 100
otes: * = normalized to le na not le;
Samp E; = applicab
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Example 3
This example further illustrates the strong effects of total gather and
of concentration of pile-like fibers on the abrasion resistance of composite
sheets of the invention. Composite sheet Samples 6, 7 and 8 and comparison
Sample F each contain. a layer in which the pile-like fibers are derived from
both a buckled fibrous nonwoven layer and buckled non-elastic stitching
yarns. In comparison Sample G, the buckled non-elastic yarns are not
present.
To prepare the starting fabric for each sample, a fibrous layer of 26-
lo g/m2 Sontara~ 8017 spunlaced fabric of nonbonded polyester fibers was
overfed to a two-bar "Liba" stitchbonding machine. The front bar of the
Liba formed a repeating pattern of 1-0,2-3 stitches with combination yarn
that was a 280-den (311-dtex) Lycra~ spandex elastic core, tightly wound 9
turns/inch (3.5/cm) with 70-den (78-dtex) 34 filament polyester yam.
is Except for the fabric of comparison Sample G, which employed no back-bar,
the back bar formed a repeating pattern of 3-4, 1-0 stitches with a 210 den
(233 dtex) 34 filament high tenacity Type 62 Dacron~ polyester yam.
Lycra~ and Dacron~ are each sold by DuPont. The Liba, a 14-gauge ( 14
needles per inch or 5.5/cm) machine, inserted 14 courses per inch (5.5/cm).
2o Different amounts of tension were imposed on the combination yarn used to
prepare each sample with a different amount of contraction when the fabric
was removed from the Liba. The contraction of the combination yarn caused
a layer of pile-like fibers to develop. The pile-like fibers were formed by
contraction and buckling of the nonwoven fibrous layer and buckling of the
2s back-bar non-elastic stitching yarns, which accompanied the contraction of
the combination yarn. Then after boil-off the contracted fabrics were heat
treated on the tenter frame to set the final dimensions of the fabric.
Thereafter, the fabric samples were impregnated with polyurethane resin PU-
1, the same resin as was used in Example 1, to immobilize the pile-like
so fibers. The impregnated samples were then dried to form the composite
sheet sample. Sample details and abrasion test results are summarized in
Table III, below.
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Table III
(Example
3)
Sample Identification ,~ 7 8 ~ G
Starting Materials
Nonwoven wt., g/m2 26 26 26 26 26
Over-feed ratio 1.2 1.2 1.2 1.2 1.3.
Hard yarns, g/m2 71 71 71 71 0
Contractibles wt., g/m2 31 31 31 31 32
Total wt., g/m2 133 133 133 133 66
Gathering
Contracted wt., g/m2 578 785 918 238 544
Contraction ratio 4.4 5.9 6.9 1.8 8.2
Nonwoven wt., g/m2 137 183 215 56 277
Hard yarn wt. g/m2 312 418 490 128 0
Nonwoven total gather 5.3 7.1 8.3 2.2 10.7
% of original area 19 14 15 45 12
Resin application
' Resin wt., g/m2 1043 884 655 499 986
% Pile height loss 10 9 15 8 O
Surface layer characteristics
Total wt., g/m2 1489 1485 1360 683 1263
Thickness, mm 1.8 2.0 1.8 1.4 1.6
Density, g/cm3 0.83 0.74 0.75 0.50 0.79
Pile fiber weight, g/m2 449 601 705 184 277
Pile fiber cone , g/cm3 0.25 0.30 0.39 0.13 0.17
Eff. pile conc, g/cm3 0.21 0.25 0.33 0.11 0.085
Pile Parameter, p, g/cm3 0.41 0.44 0.49 0.23 0.26
Loop base, B, mm 0.44 0.30 0.25 1.0 0.30
Loop H/8 ratio 4.1 6.6 7.2 1.4 5.3
% resin 70 60 48 73 78
% voids 31 38 38 58 34
% stretchability 5 5 10 5 0
% compressibility 10 5 10 15 0
40-grit abrasion resistance
Test duration, 103 cycles 23 31 25 2.3 16
Wear, microns/103 cycles 32 13 12 80 92
% normalized wear 35 14 13 87 100
Notes: *Normalized to SampleG.
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example 4
In this example composite sheet samples are prepared from contracted
fabric that was single-bar knit with an elastic combination yarn having a
loosely wound non-elastic wrapping yarn. The pile-like fibers are formed
s from the wrapping yarn when the combination yarn contracts.
Samples 9, 10 and 11 and comparison Sample H were each knit with a
one-bar "Liba" machine forming a repeating pattern of 1-0,2-3 stitches with a
combination yarn that had a 280-den (311-dtex) Lycra~ spandex elastic core
loosely wrapped at about 1.5 turns/inch (0.6/cm) with a 70-den (78-dtex) 34-
to filament textured polyester yarn. Each sample was made with the Liba
operating at 14 courses/inch (5.5/cm) and the needle bar at 20 gage (i.e., 20
needles per inch or 7.9/cm), except Sample 11 which was made at 10 gage.
The fabrics for each sample were knit with the combination yarn under a
different tension. Upon removal of the fabric from the knitting machine and
~s tension in the combination yarn was released and the as-knit area of the
fabric contracted by a factor 11.5 to 14 times, with an accompanying
buckling of the loosely wound wrapping yarn to form the pile-like layer.
Polyurethane resin, PU-2, as was used in Example 2, was applied to the pile-
like fibers of each sample. Further details of sample fabrication and abrasion
2o performance are listed below in Table IV, which also includes Sample G of
Example 3 for further comparison purposes.
The abrasion test results listed in Table IV show that high pile
concentrations and high pile parameters and accompanying high abrasion
resistance can be obtained with fabrics having pile-like groups of fibers
2s provided by only buckled yarns. The results also demonstrate the
importance of avoiding excessive stretchability in the composite sheet. Note
that the pile-like fiber/resin surface layer of the composite sheet of
comparison Sample H, having a resin content of only 25 weight %, was
readily stretchable and exhibited an 11 to 18 times greater abrasion rate than
3o did composite sheet Samples 9-11 of the invention. Unless sufficient resin
is
incorporated in the fiber/resin layer, even if other characteristics of the
layer
are in accordance with the invention, the composite sheet will still lack
resistance to stretching and abrasion. The abrasion-resistance data and other
details of the samples are summarized in Table IV and clearly demonstrate
3s the superior abrasion resistance of the composite sheets of the invention
over
the comparison samples. The data again show that a resin-impregnated pile-
like fiber layer meeting the requirements of the present invention provides a
composite sheet with highly effective abrasion resistance.
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Table IV (Example 4)
Sample Identification 9 ~ ,~l H G
Starting Materials
Nonwoven wt., g/m2 0 0 0 0 26
Over-feed ratio na na na na 1.3.
.,
Hard yarns, g/m2 0 0 0 0 0
Wrap yarn weight, g/m2 24 24 21 24 0
Contractibles wt., g/m2 22 22 20 22 32
Total wt., g/m2 46 46 41 46 66
Gathering
Contracted wt., g/m2 557 557 476 557 544
Contraction ratio 11.5 11.5 14.0 11.5 8.2
Nonwoven wt., g/m2 0 0 0 0 277
Nonwoven total gather na na na na 10.7
Wrap yarn wt. g/m2 276 276 294 276 0
% of original area 8.7 8.7 7.8 8.7 12
Resin application
Resin wt., g/m2 910 1009 987 94 986
% Pile height loss 17 17 13 17 0
Surface layer characteristics
Total wt., g/m2 1186 1285 1281 370 1263
Thickness, mm 1.5 1.5 1.4 1.5 1.6
Density, g/cm3 0.79 0.86 0.91 0.25 0.79
Pile fiber weight, g/m2 276 276 294 276 277
Pile fiber cone , g/cm3 0.18 0.18 0.21 0.18 0.17
Eff. pile cone., g/cm3 0.18 0.18 0.21 0.18 0.085
Pile Parameter, p, g/cm3 0.38 0.38 0.44 0.38 0.26
Loop base, B, mm 0.12 0.12 0.10 0.12 0.30
Loop H/B ratio 12.5 12.5 14.0 12.5 5.3
% resin 76 78 77 25 78
% voids 35 28 24 79 34
% stretchability 10 5 5 80 0
% compressibility 10 5 10 15 0
' 40-grit abrasion resistance
Test duration, 103 cycles 20 18 23 0.8 16
' Wear, microns/103 cycles 30 40 43 450 92
% normalized wear 33 43 47 489 100
Notes: *Normalized to Sample
G.
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Ex~nple 5
In this example, resin-impregnated composite sheets were prepared
from contracted two-bar warp-knit fabrics. The starting fabric for each of
Samples 12-15 and Comparison Sample I was knit on a two-bar Liba
s machine, with one bar threaded with an elastic combination yarn having a
loosely wound non-elastic wrapping yarn and the second bar threaded with
non-elastic textile yarn. The front bar formed repeating patterns of 1-0,2-3
stitches with a 280-den (311-dtex) Lycra~ spandex around which was
loosely wound, at one turn/inch (0.4/cm), a 70-den (78-dtex) 34-filament
~o textured polyester yarn. The back bar formed a repeating pattern of 3-4,1-0
stitches with a 150-denier (167-dtex) conventional polyester textile yam.
Each sample was made with the Liba operating at 14 courses/inch (5.5/cm),
except Sample 12 and comparison Sample J, which were each made with 22
courses per inch (8.7/cm) and with the machine threaded at 20 gauge, and
s Sample 13 which was made with the machine threaded at 10 gage. Tension
on the combination yarn used to prepare the samples was adjusted so that
when the knit fabric was removed from the Liba, boiled-off and heat set, the
as-knit area of the fabric contracted by a factor of 1.9 to 7. The contraction
of the fabric was accompanied by contraction and buckling of the loosely
2o wound wrapping yarn and buckling of the second bar yarn. Polyurethane
PU-2 (same as in Example 2) was applied to each sample.
Further fabrication and abrasion performance details of the samples
are summarized in Table V below, in which Sample G of Example 3 is also
included for further comparison. The abrasion wear results show that
2s Comparison Samples G and I, exhibited between about 2.5 to about 20 times
as much abrasion wear as did Samples 12-15 of the invention. The pile-like
fibers of the fabric of Sample I apparently were deflected from the vertical
position during application of resin, as indicated by the 31% loss in surface
layer height and the insufficient contraction ratio.
3o The results summarized in Table V showed that contraction of the
fabric for Samples 12-15 of the invention resulted in substantially vertical
pile-like fibers being formed. The pile-like fibers were derived from both
the contracted wrapping yarn and from the buckled second bar yarn. In
contrast, the fabrics of comparison Sample I did not provide a satisfactory
ss pile-like layer and was not adequately resin impregnated and accordingly
exhibited much inferior abrasion resistance. Sample G, despite it very high
resin density did not provide high abrasion resistance because of the low
effective pile density and low pile parameter.
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Table Y (Example
5j
Sample Identification ,~2_ ~3 ~ ~ ,~ G_
Starting Materials
Nonwoven wt., g/m2 0 O O O 0 26
over-feed ratio na na na na na 1.3
Hard yarns wt., g/m2 92 32 32 32 92 0
Wrap yarns wt " g/m2 33 23 23 23 26 0
Contractibles wt., g/m228 22 22 22 26 32
Total wt., g/m2 153 77 77 77 154 66
Gathering
Contracted wt., g/m2 554 540 870 870 299 544
Contraction ratio 3.6 7.0 11.3 11.31.9 8.2
Nonwoven wt., g/m2 0 0 0 0 0 277
Hard yarn wt., g/m2 331 224 361 361 175 0
Wrap yarn wt., g/m2 118 161 260 260 49 0
Nonwoven total gather na na na na na 10.7
% of original area 28 14 9 9 53 12
Resin application
Resin wt., g/m2 826 1098 380 920 408 986
% pile height loss 16 4 15 0 31 0
Surface layer characteristics
Total wt., g/m2 1275 1483 1001 1541632 1263.
Thickness, mm 1.6 2.4 1.7 1.9 1.3 1.6
Density, g/cm3 0.65 0.74 0.59 0.810.49 0.79
Pile fiber weight, g/m2449 385 621 621 224 277
Pile fiber conc , g/cm30.28 0.16 0.37 0.330.17 0.17
Eff. pile cone , g/cm3 0.28 0.16 0.37 0.330.17 0.085
Pile Parameter, g/cm3 0.43 0.34 0.47 0.510.28 0.26
Loop base, B, mm 0.3 0.3 0.2 0.2 0.3 0.3
Loop H/B ratio 5.3 8.9 8.5 8.5 4.3 5.3
Wt. % resin 65 74 38 60 65 78
% voids 46 38 51 33 59 34
% stretchability 10 5 10 0 5 0
' % compressibility 10 5 10 0 25 0
40-grit abrasion resistance
Test duration, 103 cycles>25 >25 >25 >25 4 16
Wear, microns/103 cycles28 40 8 5 100 92
% normalized wear* 30 40 9 5 109 100
otes: na = not applicable; = to G
* normalized sample
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Example 6
In this example, composite sheet samples were prepared which had
resin-impregnated fork-needled pile-like fibrous layers.
The starting fabrics for Sample J and 16 were prepared from a 272-
g/m2 air-laid web of 1.5-den (1.7-dtex), 3-inch (7.6-cm) long Type 54
Dacron~ polyester fiber (sold by E. I. du Pont de Nemours & Co.) that was
placed upon and fork needled into a 119-g/m2 Reemay~ spunbonded
polyester fabric with a Dilo fork needier. The needier was a 14 gauge (14
fork needles per inch or 5.5/cm) machine that made about 130 insertions
~o square inch (20/cm2). Loops of fiber were formed on the surface of the
Reemay~ that was opposite to the side the needles entered the layer. The
loops projected about 2.5 mm above the surface of the Reemay~.
Comparison Sample J was boiled off, heat set, impregnated with
polyurethane, PU-2 and then dried. Sample 16 was treated the same way,
~s except that prior to the heat-setting, resin-impregnation and drying,
Sample
16 was stretched longitudinally by 30% with a corresponding decrease to
about 37% of its original width to provide the sample with a contraction in
area by a factor of 2.1. Further fabrication details, characteristics of the
samples and abrasion wear test results are summarized in Table VI. The
2o summary also includes data for comparison Sample G of Example 3 for
further comparison purposes.
Table VI clearly shows that composite sheet Sample 16 of the
invention, containing a pile-like fiber layer prepared by fork-needling and
contraction, is 6.5 times as abrasion resistant as a similarly prepared
2s composite sheet having fork-needled pile-like layer that was not
contracted.
Also, the composite sheet of Sample 16 was 4.5 times as abrasion resistant as
the composite sheet of comparison Sample G of Example 3. These results,
emphasize, as was shown in the preceding examples as well, that the pile
parameter of the resin-impregnated pile-fiber layer is very important in
3o providing a composite sheet with abrasion resistance. Sample 16 of the
invention had a pile parameter of 0.37, while comparison Sample J and G
respectively had pile parameters of 0.22 and 0.26.
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TABLE VI (Example6)
Sample Identification J
starting Materials
Nonwoven wt., g/m2 272 272 26
Over-feed ratio na na 1.3
Contractibles wt., g/m2 119 119 32
Total wt., g/m2 391 391 66
Gathering
Contracted wt., g/m2 391 821 544
Contraction ratio 1.0 2.1 8.2
Nonwoven wt., g/m2 272 571 277
Nonwoven total gather 1.0 2.1 10.7
% of original area 100 48 12
Resin application
Resin wt., g/m2 720 930 986
% pile height loss 0 O 0
surface layer characteristics
Total wt., g/m2 992 15011263
Thickness, mm 2.4 2.5 1.6
Density, g/cm3 0.41 0.600.79
Pile fiber weight, g/m2 272 571 277
Pile fiber cone , g/cm3 0.11 0.230.17
Eff. pile cone , g/cm3 0.11 0.230.085
Pile Parameter, g/cm3 0.22 0.370.26
Loop base, B, mm 0.8 0.4 0.3
Loop H/B ratio 3.0 6.0 5.3
Wt. % resin 73 62 78
% voids 65 50 34
% stretchability 10 0 0
% compressibility 15 0 0
40-grit abrasion resistance
Test duration, 103 cycles 5 15 16
Wear, microns/103 cycles 130 20 92
% normalized wear* 141 22 100
otes: na = not applicable; normalized sample
* = to G
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Eaample 7
In this example, two composite sheet samples were prepared with
resin-impregnated velour fabrics providing the pile-like fibers for the
resin/fiber layers.
3 The starting fabrics for Sample 17 and 18 were prepared on a 130-
inch (3.3-meter) wide, 70 gauge (70 needles/inch or 27.6/cm), three-bar
warp-knitting machine which formed 64 course per inch (25.2/cm). A type
KS3P machine, manufactured by Karl Mayer of Frankfurt, Germany, was
used. The first bar was threaded with a flat (i.e., not textured) 70-den (77-
io dtex), 24-filament polyester yarn and formed a repeating pattern of 1-0, 1-
l,
2-1 stitches. The second bar was threaded with a flat, 100-den (110-dtex)
40-filament polyester yarn and formed a repeating pattern of 1-0, 0-0, 1-1
stitches. The third bar was threaded with a flat (i.e., not textured) 70-den
(77-dtex), 24-filament polyester yarn and formed a repeating pattern of 1-0,
is 0-0, 1-1 stitches. The velour fabric that was formed by the machine had a
knit backing (i.e., base) layer that weighed 347 g/m2 and layer of looped
yarns that measured 1.5 mm high, weighed 231 g/m2, had a effective pile
fiber concentration of 0.18 g/cm3 .
Sample 17, in the as-knitted condition, was impregnated with
2o polyurethane resin PU-2. After resin curing, the sample had a pile
parameter
of 0.31 g/cm3. Sample 18, in the as-knit condition, was heat set at a
temperature of 375°F (191°C) to stabilize the fabric dimensions.
Then the
loops of the heat-set Sample 18 were sheared to provide a pile thickness of
1.2 mm. Sample 18 also was impregnated with polyurethane resin PU-2,
2s which after curing also provided the sample with a pile parameter of 0.31
g/cm3.
As shown in Table VII, Samples 17 and 18 were composite sheets of
the invention that performed quite well in the 40-grit abrasion wear test.
Comparison Sample G of Example 3 was also included in the Table VII for
3o further comparison. As compared to the composite sheets of Samples 17 and
18 of the invention with their resin-impregnated velour fabrics, the
composite sheet of comparison Sample G with its resin-impregnated
contracted-and-buckled nonwoven fibrous layer abraded 2.2 to 2.4 times as
rapidly as Samples 17 and 18.
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TABLE VII (Example7)
Sample Identification
Starting Materials
Base layer weight, g/m2 347 347 na
Pile weight, g/m2 231 231 na
Pile height, mm 1.5 1.5 na
After heat setting & shearing+
Base layer weight, g/m2 347 347 na
Pile weight, g/m2 231 210 na
Pile height, mm 1.5 1.4 na
Resin application
Resin weight, g/m2 452 422 986
% pile height loss 15 15 0
Surface layer characteristics
Total weight, g/m2 683 682 1263
Thickness, mm 1.3 1.2 1.6
Density, g/cm3 0.53 0.53 0.79
Pile fiber Weight, g/m2 231 210 277
Pile fiber cone , g/cm3 0.18 0.18 0.17
Eff. pile cone., g/cm3 0.18 0.18 0.085
Pile Parameter, g/cm3 0.31 0.31 0.26
Base. B, mm 0.4 0.4 0.3
H/8 ratio 3.3 3.0 5.3
Wt. % resin 66 67 78
% voids 45 44 34
% stretchability 10 0 0
% compressibility 15 15 0
40-grit abrasion resistance
Test duration, 103 cycles 16 15 16
Wear, microns/103 cycles 41 38 92
% normalized wear* 45 41 100
Notes: + Only Sample 18 was not applicable,
sheared. "na" means
See Table III (Example 3) for furtherdetailsabout Sample
G.
' * % wear normalized to Sample G.
29
