Note: Descriptions are shown in the official language in which they were submitted.
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CASE NO, 1694
LATEX ADHESIVE
l BONDED PILE FABRICS
The present invention relates to pile fabrics. More particularly, the
present invention relates to latex adhesive bonded pile fabrics and latex
adhesive bonded carpet tiles.
Pile fabrics such as carpeting may be manufactured in several ways such
as by weaving, tufting, needling or bonding. In each method the pile must be
secured to a base or support layer in one way or another. The present
invention is particularly concerned in one aspect with a method of manufacture
wherein the pile is bonded by means of a latex adhesive to a base layer. Such
fabrics will herein be referred to variously as latex adhesive bonded pile
fabrics, or latex adhesive bonded carpets.
A number of techniques are known for the manufacture of bonded pile
Ifabrics which involve the coating of a preformed base layer with a layer of an
ladhesive and thereafter pressing pile-forming lengths of a yarn into the
adhesive to adhere pile-forming lengths to the base layer.
Prior commercial techniques for making bonded fabrics have typically
relied on the use of polyvinyl chloride (PVC) plastisol formulations because
of the processing disadvantages thought to be associated with the use of other
adhesive formulations such as hot melt and latex adhesive systems. According
to such techniques a polyvinyl chloride plastisol is applied to the base layer
prior to positioning the pile-forming yarn relative to the base layer. Then
the pile yarn may be positioned into contact with the base layer and the
plastisol may then be fused or cured, typically by heating. When attempts
were made to substitute other adhesives, such as hot melt adhesives for the
PVC plastisol in this process difficulties were encountered. Thus, for
instance, with regard to hot melt adhesives, it has generally been thought
that the apparatus employed for positioning the yarn may become coated with
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the adhesive requiring frequent shut downs of the apparatus for cleaning which
is, of course, commercially unattractive.
Thus, while PVC plastisol has been the bonding agent of choice in the
preparation of bonded pile fabrics, there are disadvantages associated with
the use of PVC plastisol in the manufacture of such fabrics. Thus, PVC
plastisols generally may not penetrate to the desired extent into the yarn
bundles to effect complete adhesion of all pile yarn fibers of the pile yarn
bundle to the pile fabric structure. Other disadvantages typically associated
with the use of PVC plastisol as the bonding agent in the manufacture of
bonded pile fabrics are detailed in U. S. Patent Number RE31,826 to Machell
(assigned to Milliken Research Corporation),
Another disadvantage typically associated with the prior art techniques
for making bonded or non-tufted pile fabrics, that is fabrics where the pile
yarn is not tufted through the backing but simply adhered to the backing, is
that the adhesive is normally applied to the base layer on the side of the
base layer facing the pile yarns, and the base layer is normally of a
construction such that the adhesive will not flow through it but will
substantially remain on that surface with perhaps some penetration into the
base layer. Then, if it is desired to apply a backing layer, e.g., a hard
back, to the back side of the pile fabric as may be desired in the making of
carpet tiles the base layer must be either adhered directly to the backing
layer or an additional process step of applying adhesive to the back side of
the base layer may be necessary. In either event, there are created numerous
distinct layers in the finished product, namely pile layer, adhesive layer,
base layer, another adhesive layer and a hard back layer. Such constructions
may inherently have processing disadvantages and be costly to construct.
According to Machell U. S. Patent Number RE31,826, bonded pile fabrics
are provided wherein the bonding of the pile-forming yarn to the base layer
may be accomplished by means of a hot melt adhesive. A process and apparatus
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are also disclosed therein where the hot melt adhesive is applied to a liquid-
.lpermeable layer'~from the back of the base layer and it may be forced through
the base layer so that a one step adhesive layer application may both provide
' a means for bonding the pile yarn to the base layer and also provide a means
by which a backing layer may be integrally affixed to the base layer. The
,resulting product may be less complicated and costly to manufacture and may
have fewer separate and distinct layers in the final product where undesired
separation may occur.
As contrasted to conventional bonded carpet tiles water-based adhesive
backed tiles are generally easier to cut both in the production process and
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during installation. Latex adhesive based products typically also have a
relatively soft hand and are, therefore, easy to handle as compared to
conventional products.
From a production standpoint, hot melt adhesives are typically applied
at temperatures in the range of about 300F to 400F. They are difficult to
handle in the hot state and the equipment used to apply the adhesives must be
heated which may be dangerous and energy consumptive. Latex adhesives by
contrast may be applied at room temperature greatly facilitating production
operations especially safety and cost considerations.
, Furthermore, because latex adhesives typically contain a significant
aqueous component by contrast to conventional adhesives used to manufacture
bonded carpet tiles, they may be applied at significantly lower viscosities,
greatly facilitating yarn bundle penetration which is desired to achieve
;desired tuft bind and minimi~e fuzzing and other undesirable properties in the
final product. Latex adhesives may, furthermore, be stored for lengthy
periods of time without degrading and without the necessity of being heated
prior to being put into use in production.
The pile fabrics of the present invention are latex adhesive bonded
fabrics which may be comprised of a liquid-permeable base layer, a pile
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forming yarn adjacent to but not tufted through the base layer, in pile
forming, prefer~ably folded, fashion; the pile forming yarn having been bonded
to the base layer by means of a latex adhesive. Preferably, the latex
ladhesive is applied to the back of said base layer and forced through said
base layer into contact with said pile forming yarn. It should be understood,
however, that the latex adhesive may also be applied to the front surface of
the backing prior to bringing it into contact with the yarn, or it may even be
applied to the folded yarn prior to contacting it with the backing layer.
Pile forming configurations may include the so-called I-tuft
configuration, e.g., a non-folded configuration, U-tuft configurations, and
loop pile configurations, among others. With regard to the phrase "folded,
pile forming fashion," which refers to a preferred embodiment, it should be
understood that what is intended is a configuration of the pile yarns where
the yarns are provided with at least one fold at the portion of the yarn
generally most nearly adjacent to the base layer, e.g., a cut pile
configuration. Another "folded" configuration which is contemplated is a loop
pile configuration where the pile yarns remain uncut in the form of
substantially continuous folded yarns in the final product. A variety of pile
configurations, both non-folded and folded, are illustrated in the attached
drawing. According to the most preferred embodiment the pile yarns are cut to
form a folded, cut pile product.
According to the method and apparatus of the present invention a pile
forming yarn is positioned in pile forming fashion adjacent to one side of a
liquid-permeable base layer. Thereafter a latex adhesive, is applied to the
base layer on the opposite side of the base layer from the side adjacent to
the pile forming yarn. According to the next step of the method the latex
adhesive may be forced, either simultaneously with its application or in a
separate step, through the base layer into bond forming contact with the pile
forming yarn, and the adhesive is then cured by heating it to a temperature of
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from about 200F to about 400F for about 60 seconds to about 500 seconds
thereby bonding,the pile forming yarn to the base layer. The apparatus
includes a means for applying the adhesive and forcing it through the base
layer.
According to a preferred embodiment of the present invention a method
and apparatus are provided wherein two continuous, liquid-permeable base
layers are positioned in a passage where they lie in substantial parallel
relationship to one another at a predetermined distance from one another; at
least one continuous pile forming yarn is driven by folder blades
alternatively against the opposing surfaces of said base layers when they are
at or near the entrance to the above mentioned passage in such a way as to
position the pile forming yarn relative to the base layers and to fold it zig-
zag; thereafter applying to the back of said base layers a latex adhesive;
forcing said latex adhesive through said base layers so that said latex
adhesive contacts said pile forming yarn; and curing said latex adhesive to
thereby bond said pile forming yarn to said base layers. This step in the
method may accomplish an additional function, namely that of bonding the
individual pile forming yarns to themselves typically at or near the portion
of the yarns nearest the base layer, thereby imparting improved performance
characteristics to the pile fabric product. Thereafter, the base layers may
be separated from one another to form two continuous, latex adhesive bonded
products. Typically such separation may be accomplished by means of a
stationary or moving knife blade positioned between the base layers which cuts
the pile yarns along the entire width of the joined base layers to provide the
latex adhesive bonded products.
The yarn used in forming the pile may be made of any type of fiber known
to be useful for fusion bonded fabrics such as carpets, for example nylon,
! acrylics, polyester, wool, cotton and rayon.
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Any of a wide variety of late~h~i~es-used as carpet backing
adhesives for many years may be employed in connection with the present
invention. Examples include styrenebutadiene (SBR), acrylics, vinyl acetate,
Ivinyl acrylate, water-based urethanes and the like. SBR latex emulsions may
be preferred.
The SBR latex emulsion may be prepared in accordance with known
procedures such as, for example, the polymerization of the respective monomers
in appropriate proportions in an aqueous medium cont~ining an emulsifying
agent and a peroxide catalyst. An emulsion stabilizer, such as an anionic
surface-active agent, is usually added during the polymerization process. The
SBR latex is usually a binary copolymer of styrene and butadiene but
copolymers incorporating a third or fourth monomer may also be utilized in
this invention. A preferred latex in the carpet adhesive industry is a
carboxylated styrene-butadiene polymer having a fairly high styrene content.
The emulsion usually contains about 50% water, by weight, but may - `~
contain more or less, e.g. from about 40~ to about 60~. Extra water may be
added in order to attain the desired working properties of the adhesive
composition.
Other additives commonly used in carpet backing adhesives such as
fillers, thickeners, anti-oxidants, anti-freeze compositions, fungicides,
corrosion inhibitors and co~orants may be present in the carpet backing
adhesives of this invention. Sodium polyacrylate is representative of one
type of thickener that may be used. Each additive must be selected carefully
so that it is compatible with the prime ingredients of the composition and
does not adversely affect the function of the other additives.
The carpet backing adhesive of this invention may be applied to the
carpet by the techniques usually employed in the industry. A lick-roll
technique, a spreading technique and a spraying technique are described in
"High Polymer Latices" (Applied Science Publishers, Ltd., 1966). Briefly, the
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lick-roll application comprises pulling the carpet under tension through an
assembly of roliers, brushing and steaming the carpet back, pressing the back
with a lick-roller carrying the adhesive from a bath of adhesive in which the
lick-roller revolves, passing the adhesive-coated carpet back under a doctor
blade to control the thlckness of the adhesive and drying the adhesive with
heat to cure the adhesive.
Suitable liquid-permeable base layers which may be employed in the
product and process of the invention include woven fabrics, knitted fabrics,
non-woven mats or scrims, felted materials, or even flexible, foraminous
materials.
After the latex adhesive is applied the composite then travels into a
curing oven where the latex adhesive is cured and water is removed. In the
past it was considered to be impossible to remove large amounts of water from
the adhesive during the manufacture of a bonded type floorcovering product.
It has been found, however, quite to the contrary, that the majority of the
moisture actually travels into the yarn thereby causing the yarn to bulk as
the liquid phase water is converted into steam in the curing oven just prior
to removal of the steam through the exhaust fans. Thus, the moisture present
in the latex adhesive is a benefit in terms of the properties of the final
floorcovering product rather than a detriment.
~ here it is desired to provide the latex adhesive bonded pile fabrics of
the present invention as floor covering products, especially carpet tiles, it
may be desirable to apply any of a wide variety of suitable, resilient backing
layers to the fabric. Such carpet tiles are also considered to be within the
scope of the present invention. The backing layer may be formed, for example,
from a suitable thermoplastic or thermoset material such as blends containing
ethylene/vinyl acetate copolymers, atactic polypropylene, bitumen, hydrocarbon
resins, waxes, polyvinyl chloride compounds, synthetic and natural rubbers.
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In the past, use of latex adhesives in the manufacture of bonded carpet
tiles in particular was discarded because it was believed that the resilient
backing layer, whether it be polyvinyl chloride, ethylene vinyl acetate, or
~even hot melt backing materials, would be incompatible with the latex
adhesive. It has been found, however, quite to the contrary, that latex
adhesives may be quite compatible with a wide variety of resilient backing
'layers by selecting the proper combination of latex adhesive composition,
resilient backing layer composition and, furthermore, by imparting as much
mechanical bond as possible by adding only the exact amount adhesive to the
yarns as may be necessary to achieve desired yarn bundle penetration. By so
doing voids are left between and around the yarn bundles for mechanical
adhesion of the secondary backing material to the preformed composite.
The backing layer, which may be bonded to the pile layer by means of a
I separate hot melt adhesive, may be provided with at least one stiffening and
15 ' stabilizing membrane, such as woven or nonwoven glass fibers. After the
backing has been applied the consolidated material may then be severed by
suitable cutting means into a carpet tile by any of a variety of techniques
which are well-known to those skilled in the art.
I The resulting carpet tile product may be printed and even subjected to
20 Ifurther textile processing operations at relatively high temperatures without
adversely affecting its physical properties. It is suitable for use as a
floor covering in home and/or commercial use in an office environment where
; substantial high stress conditions (e.g., wheeled traffic) are applied across
, the tiles. The tiles typically have a dense pile and may not require
adhesives for installation. The individual modules may be replaced or rotated
as necessary or desired. The carpet tiles may also have excellent dimensional
stability with substantially no curling, slipping, buckling, stretching or
shrinking. In addition, the carpet tiles may have low smoke emission and low
"fuzzing" characteristics.
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The invention may be further understood by reference to the drawings and
accompanying des~cription thereof. It is to be understood, however, that
various changes may be made without departing from the scope or spirit of the
invention which is to be limited only by the scope of the appended claims.
:Referring now to the drawings:
Figure 1 is an elevation view of the apparatus; and
' Figures 2 through 6 illustrate various embodiments for forcing the latex
adhesive through the base layer.
~I Figures 7 through 10 illustrate various pile forming configurations
10 , which may be employed in the hot melt adhesive bonded pile fabrics of the
present invention. Figure 11 is a photomicrograph of the base of a pile yarn
that was bonded to a base layer by means of the latex adhesive compositions of
the present invention. Figure 12 is a representation of a pile yarn bonded to
a base layer by conventional techniques.
Referring now to Figure 1, carpet yarn 10 is supplied from a yarn source
(not shown) over and around guide rolls 12 and 14 and down to the vertical
guides 16. Base layer 17 is supplied from rolls 18 into position between the
guides 16. As the yarn 10 enters between the vertical guides 16 the folding
blades 20 and 22 alternately displace the yarn in a zig-zag fashion into one
or the other of the base layer sheets 17 as the carpet backing is being drawn
downwardly. Pivotally mounted bladelets 24 and 26 may assist in the folding
of the yarn. Folding blades 20 and 22 are mounted, respectively, to
connecting rods 28 and 30. Connecting rod 28 is pivotally connected to pivot
shafts 36 and 38 through suitable links (not shown). The shafts 32 and 38 are
oscillated by an oscillating crank arm mechanism (not shown).
It should be noted that the blade 20 is out of phase with the blade 22
so that when the blade 22 is being pivoted inwardly as shown in Figure 1 the
blade 20 is being pivoted outwardly and vice versa to provide a zig-zag
configuration of the yarn between the carpet base layers 17 which are liquid-
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permeable, that is permeable to the adhesive to be applied.
After the yarn has been positioned in zig-zag configuration between the
carpet base layers 17, latex adhesive 80 contained in trough 88 is forced
through the liquid carpet base layers 17 by rotation of applicator rolls 84
into contact with the carpet yarns 10.
After the latex adhesive has been applied to the carpet base layer and
forced through it into contact with the carpet yarn, it may be converted into
the solid phase by heating means 90 to form a bond between the carpet yarn 10
and the carpet base layer 17. Heating means 90 may be supplied with infrared
heater 92 to heat the latex adhesive causing it to cure. The yarn 10 may then
be severed, generally in the middle of the base layers 17 by cutting blade 98
to provide, simultaneously, two sheets of carpet.
Figure 2 is an alternate latex adhesive applicator means of the
embodiment 78 shown in Figure 1. The trough 100 is positioned underneath the
applicator rolls 84 which are rotated in the direction of the movement of the
fabric. Rate of application of the latex is controlled by doctor knife 102.
Figure 3 is yet another embodiment showing a trough 103 located at the side of
applicator rolls 84. Rate of application of latex adhesive is controlled by
doctor rolls 105.
Figure 4 illustrates an alternative embodiment wherein the latex
adhesive is maintained in a reservoir sided on one side by base layers 17 and
on the other side by doctor blades 104. The adhesive 80 is allowed to contact
the carpet backings and is forced therethrough by the tips 106 of doctor
blades 104.
Figure 5 illustrates yet another embodiment of the invention where the
latex adhesive is maintained in tanks 108. Application of the adhesive to the
base layers 17 is accomplished by drawing the adhesive out of the tank 80
through pumps 110 into manifolds 112. The adhesive is then forced from the
opening 114 in manifolds 112 under sufficient pressure to force the adhesive
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! through the carpet base layers 17 into contact with carpet yarn 10.
,
! FLgure 6 shows a spray application of latex adhesive by means of spray
j applicator 107. After spraying the latex it is forced through the base layer
17 into contact with pile yarns 10 by means of penetration rolls 109.
Figure 7 illustrates an embodiment of the present invention showing an
' I-tuft configuration of the pile yarns. Latex adhesive 80 is shown as a
continuous layer into which the base layer 17 of a relatively open-weave,
adhesive permeable fabric has become embedded at the base thereof. Backing
layer 150 is made of a thermoplastic material having a stabilizing layer of
10 , glass fibers 151 and is shown as having been bonded to the pile fabric by
means of thermoplastic material. Figures 8, 9 and 10 illustrate some folded
configurations of the pile forming yarns which may be preferred. Identifying
; numbers refer to the same structural components as in Figure 7. Figure 8
I shows a folded, cut pile configuration. Figure 9 shows a loop pile
configuration. Figure 10 shows another folded pile configuration where the
folded portion of the yarn is on the surface giving the appearance of a loop
pile, although the loops are not joined to one another at their base. This
configuration provides in essence a loop pile product while simultaneously
ioffering the advantages of, for instance, yarn savings of the so-called I-tuft
configuration.
Figure 11 is a photomicrograph 30X of a tuft bonded by means of the
process described in Example I. The tuft was pulled out of the latex adhesive
and a cross-section was cut at its base to show adhesive penetration. As can
' be seen, the latex adhesive showed excellent penetration contacting all of the
fibers of the yarn bundle.
Figure 12 is a yarn from a conventional, bonded product taken and cut in
the same way as the yarn from Figure 11. Adhesive has penetrated only through
the surface layer leaving many loose fibers which may result in undesired
fuzzing and pilling.
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The invention may be further understood by reference to the following
examples which are not to be construed as unduly limiting the invention.
EXAMPLE I
Employing the apparatus substantially as illustrated in Figure 1 with
the exception that the adhesive applicator means was the embodiment shown in
Figure 6, liquid-permeable base layers were provided of non-woven glass scrim
of 10 ends by 8 ends per inch. Into these base layers were positioned pile
forming yarns of stock-dyed Nylon 6,6, 2.00/2 spun yarn. The yarn was folded
, at about 8 folds per inch by 9 ends per inch construction. Fabric traveled at
about 1 ft./minute linear speed. A latex adhesive composition (a 50~ aqueous
composition of styrene butadiene supplied by Reichhold Chemical) was applied
at the rate of about 50 ozs./sq. yd. The latex adhesive composition also
contained filler at the level of about 150 parts filler per 100 parts polymer.
Viscosity of the latex adhesive composition was about 3,000 centipoise which
provided optimum yarn penetration and maximum surface area form a mechanical
bond to the tie coat. The adhesive was then cured using infrared heaters
15' (three - 18" strips at 100% output were used followed by one bank at 50~
output). Excess moisture was drawn off by exhaust fans not shown. The carpet
was then cooled and slit.
A pre-formed backing layer of filled atactic polypropylene (weighing
about 50 ozs./sq. yd.) was cast on a non-woven glass mat which was then
laminated to the slit, latex adhesive bonded carpet by casting about 20
ozs./sq. yd. of filled atactic polypropylene onto the backing layer and then
immediately pressing the carpeting into this molten material by conventional
means. The resulting product was allowed to cool and was then cut into carpet
tiles and was suitable at that time for further processing, e.g. printing,
ste~mine, washing and drying.
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EXAMPLE II
In this ex~ample carpet tile properties of tuft lock, pilling and fuzzing
were determined for the carpet tile made as described in Example I and,
furthermore, a comparison was made to those same properties in a polyvinyl
chloride bonded tile manufactured by means of the equipment essentially as
described in U. S. Patent No. 3,411,966. The PVC was applied at the rate of
55 ozs./sq. yd. (100% solids). The tuft bond was measured by ASTM Standard
Test Measure Dl335, filling and fuzzing were measured by DuPont random filling
and fuzzing tests which is the conventional test in the industry. The results
'for this latter test are measured on a scale of one to five with one being
poor and five being excellent. The results are summarized in the table below.
TABLE
TUFT LOCK PILLING ~ FUZZING
iEXAMPLE I 8 lbs. 4.0
EXAMPLE II 4.5 lbs. 3.0
The results summarized in the table above show that the product of the
present invention results in improved properties of tuft bond, pilling and
fuzzing with less than 50~ of the added weight for the adhesive component.
IThe product also had better hand and better yarn coverage due to the bulking
of the yarn which occurred during the latex cure step while water was being
driven off.
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