U.S. patent number 3,819,462 [Application Number 05/079,762] was granted by the patent office on 1974-06-25 for primary backing for tufted carpets.
This patent grant is currently assigned to Cotton, Incorporated. Invention is credited to Arthur P. Drennan, John R. Starr.
United States Patent |
3,819,462 |
Starr , et al. |
June 25, 1974 |
PRIMARY BACKING FOR TUFTED CARPETS
Abstract
A tufted carpet primary backing made up of a nonwoven base web
formed from low cost short fine fibers (e.g. cotton) and longer
coarse fibers (e.g. 4 inch, 15 denier synthetic fibers) bonded
together. The nonwoven is needled and reinforced by the addition of
other strength imparting components, such as threads or continuous
filaments stitched on the web in a tricot pattern.
Inventors: |
Starr; John R. (Belmont,
MA), Drennan; Arthur P. (Brighton, MA) |
Assignee: |
Cotton, Incorporated (New York,
NY)
|
Family
ID: |
22152645 |
Appl.
No.: |
05/079,762 |
Filed: |
October 12, 1970 |
Current U.S.
Class: |
428/93; 156/72;
428/96; 156/148; 428/359 |
Current CPC
Class: |
D05C
17/02 (20130101); D04H 1/48 (20130101); Y10T
428/2904 (20150115); Y10T 428/23964 (20150401); Y10T
428/23986 (20150401) |
Current International
Class: |
D05C
17/00 (20060101); D04H 1/48 (20060101); D05C
17/02 (20060101); D03d 027/00 (); D04h
011/00 () |
Field of
Search: |
;161/62,67,150,157,170
;156/72,148 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Van Balen; William J.
Attorney, Agent or Firm: Burns, Doane, Swecker &
Mathis
Claims
What is claimed is:
1. A tufted pile fabric comprising a primary backing and pile yarns
piercing said backing, said primary backing including
a nonwoven base web of fibers crossing in a network of individual
fibers and consisting essentially of:
25 to 75 percent by weight of a fine fiber content comprised of
fine staple fibers having widths corresponding to deniers of up to
about three and lengths less than about 3 inches, and
75 to 25 percent by weight of a coarse fiber content comprised of
synthetic fibers having deniers in the range of from about 6 to
about 20 and having lengths of at least about 4 inches,
said fibers of said network of individual fibers being bonded
together at a number of fiber crossing points to impart structural
strength to the base web.
2. A tufted pile fabric according to claim 1 wherein said fine
staple fibers include cotton fibers.
3. A tufted pile according to claim 1 wherein the denier of said
synthetic fibers is in the range of from about 10 to about 20.
4. A tufted pile fabric according to claim 1 wherein said base web
consists essentially of about 60 percent by weight of said fine
fiber content and about 40 percent by weight of said coarse fiber
content.
5. A tufted pile fabric according to claim 4 wherein said fibers of
said coarse fiber content are fifteen denier polyester fibers about
4 inches long and wherein said fibers of said fine fiber content
are cotton fibers.
6. A tufted pile fabric according to claim 1 wherein said nonwoven
base web is needled.
7. A tufted pile fabric according to claim 1 wherein said primary
backing includes reinforcing members attached to said nonwoven
web.
8. A tufted pile fabric according to claim 7 wherein said
reinforcing members comprise yarns stitched into said nonwoven base
web in a tricot pattern.
9. A tufted pile fabric comprising:
a primary backing including
a nonwoven base web of carded fibers crossing in a network of
individual fibers and being crosslapped, essentially consisting
of
50 to 75 percent by weight of a fine fiber content comprised of
cotton fibers, and
50 to 25 percent by weight of a coarse fiber content comprised of
synthetic fibers selected from the group consisting of polyolefin
and polyester, said synthetic fibers having deniers in the range
from about 10 to about 20 and having lengths of at least about 4
inches,
said fibers of said network of individual fibers being bonded
together at a number of fiber crossing points to impart structural
strength to the base web with said fibers of said coarse fiber
content serving as carriers of said fibers of said fine fiber
content during tufting, and being locked together in a
three-dimensional array, and
continuous strands reinforcing said nonwoven base web; and
pile projections piercing said primary backing.
Description
BACKGROUND OF THE INVENTION
This invention relates to nonwoven fabrics and particularly to
tufted carpet primary backings and methods of producing the
same.
Much of the carpeting that is made today is fabricated by tufting
procedures. A flat backing fabric of suitable width, typically
about 9 to 18 feet, is fed longitudinally through a tufting zone.
In this zone pile carrying tufting needles disposed across the
entire width of the primary backing are caused to penetrate the
backing so as to dispose loops of pile yarn on the bottom side
thereof. These loops may be left uncut or they may be cut to
provide the ultimate pile face of the carpet.
After tufting, the material usually is subjected to the application
of an adhesive on the back of the primary backing so as to anchor
the pile yarns more firmly in place. Piece dyeing or pile face
printing operations may be carried out on the material at this
stage also. Finally, in order to enhance the dimensional stability
of the pile fabric, a secondary backing may be adhered to the back
face of the primary backing.
The present invention is concerned primarily with primary backing
materials for use in tufted carpets. Although the backing forms an
inconspicuous part of a carpet as the user normally sees it on the
floor, such backing is from an engineering point of view a critical
component both during fabrication operations and while the fabric
is in use.
The mechanical abuse to which a primary backing is subjected during
tufting is extraordinary. The tufting needles are relatively large
and closely spaced across the width of the primary backing as the
latter is fed through the tufting machine. As these needles are
moved through the backing to insert the pile yarn loops, the
material of the backing in the needle paths must either shift or
break in order to provide the openings for the needles. Moreover,
during the time when the fabric is being so weakened, it is also
held under substantial tension in order that the desired linearity
of movement of the fabric through the machine may be obtained so as
to assure regularity in the positioning of the pile loops. The net
result is a very strong tendency for the primary backing to rupture
during tufting.
The tufting operation imposes still another mechanical requirement
upon the primary backing material. Not only must it withstand the
extraordinary loads and strains occasioned by the penetration of
the tufting needles, it must also have a capacity for closing the
needle holes sufficiently to cause the primary backing material
adjacent the holes to engage the pile yarns left by the needles and
hold the pile loops in place.
After tufting, still other loading patterns are imposed upon the
primary backing. Ordinarily the processing associated with adhesive
application, piece dyeing, etc., is carried out by moving the
fabric linearly through a treatment zone under tension; and the
fabric must of course be able to withstand the tension loads
applied during these procedures. Moreover, since the fabric pulling
forces applied to the wide widths of fabric being treated rarely
will be uniformly distributed across the width of the material, the
fabric must have a degree of crosswire rigidity sufficient to
prevent substantial bowing or skewing of the fabric as it is moved
through the processing zones.
During installation of the carpet, high loads again may be applied
in various directions in attempts to get the fabric properly
aligned on the floor, and the fabric may be cut in various
directions in making it conform to the space where it is being
installed. Hence, additional opportunities for tearing the fabric
are provided and there is also a possible raveling problem unless
the backing structure has been designed so as to have a capacity
for preventing raveling.
During use of the carpet, the backing must hold the pile in place
throughout the life of the carpet, and the primary backing must
play a role in this task. Additionally the primary backing must be
inconspicuous in the sense that it should not be allowed to "grin"
through to distract from the appearance of the pile surface.
Finally, the primary backing should not contribute to the
flammability of the fabric as a whole or to any tendency the fabric
may have to deteriorate through rot or mildew. In some instances
the primary backing may actually be designed to militate against
such undesirable effects through proper treatments.
In view of the many complex engineering criteria associated with
primary backings, it is not surprising that only a few materials
have proved really useful in large scale commercial operations. A
brief review of these will demonstrate the state of the practical
art prior to the present invention.
In the days before tufting was used for the production of carpets
as such, this process was employed to some extent in the production
of scatter rugs and the like. For such operations it was customary
to use woven cotton fabric as the backing. For scatter rug
applications cotton duck still is a widely used backing material,
but it has proved unacceptable for the carpet application. Lack of
dimensional stability severely limits the utility of backing
structures made by weaving cotton yarns, and cotton was prior to
the present invention generally considered unsuitable as the base
material for a primary backing to be used in the fabrication of
tufted carpets.
In the early days of the tufted carpet industry, woven jute was
used almost exclusively. Woven jute fabrics in the weight range of
8 to 12 ounces per square yard had the strength and stability
characteristics required for the production of many types of tufted
carpeting and such jute fabrics have been used as primary backings
for millions of square yards of tufted carpet.
Although jute is still widely used for primary backings, a number
of practical problems are associated with this material. The woven
jute comes from the Far East and carpet producers in the United
States have encountered supply shortages and unpredictable price
variations which proved to be serious hardships. Additionally, the
jute has a number of mechanical deficiencies. The coarse jute yarns
are crude mechanical structures in the sense that they vary
enormously along their lengths, being characterized by thick and
thin zones of varying mechanical properties. As a consequence
fabric failures of an unpredictable nature have occurred often
enough during the processing of jute backed tufted carpets to be
troublesome in ordinary mill operations where the maintenance of
clearly defined production schedules is of substantial importance.
The coarse jute yarns also give a primary backing formed from such
material a tendency to dispose the pile loops in irregular
patterns. This phenomenon often is referred to in terms of "needle
deflection." For example, on one stroke of a tufting needle, the
needle point may strike a jute yarn so as to dispose the pile loop
on the left side of that jute yarn while on the next stroke it may
strike the yarn in such a way as to dispose the loop on the right
side of the jute yarn. As the fabric closes around these loops,
further distortion appears so that the two successive loops will
not be aligned longitudinally along the fabric. Similar effects
prevent the attainment of perfect crosswise loop alignment, and
pile carpets tufted on jute backings typically are characterized by
irregularities in the rows of pile loops.
In an effort to obviate some of these problems, the industry has
turned increasingly in recent years to synthetics. The most wisely
used synthetic primary backings have been formed from polyolefin
materials, with polypropylene generally being the most highly
regarded material at the present time.
One type of polypropylene primary backing that has enjoyed
considerable success is a woven material employing ribbons as the
warp yarns and employing either ribbons or multifilament yarns as
the weft yarns of the woven construction. These primary backings
have many desirable qualities. However, since they are based upon
specially fabricated ribbons, price and supply problems still are
associated with such materials. Moreover, their reliance upon
discreet yarn-like components for giving the overall woven backing
fabric its mechanical properties presents some difficulties where
fine gauge tufted fabrics are involved. There is little structural
component shifting in the woven ribbon polypropylene backing during
tufting; and where the spacing between needle penetrations becomes
quite small, as in the fine gauge high pile density carpets, the
structural components of the woven backing may be broken by the
needles to an objectionable degree and the backing fabric may be
left with insufficient strength.
Another type of polypropylene primary backing that has achieved
wide acceptance in the tufted carpet industry is a nonwoven fabric.
One such fabric is a continuous filament, spunbonded product sold
by E. I. duPont de Nemours and Co. Inc. under the trademark
"Typar." Another such fabric is a staple fiber nonwoven fabric
manufactured by Phillips Fibers Division of Phillips Petroleum
Company and sold under the trademark "Loktuft." The latter is made
by garnetting polypropylene fibers of approximately 5 denier and 4
to 41/2 inch staple length, crosslapping the garnetted webs and
adding longitudinally extending cotton or rayon yarns as
reinforcing components. The composite then is subjected to needling
and is lightly heat fused.
Both of these nonwoven polypropylene products have desirable
mechanical properties but both have disadvantages associated with
the polypropylene material. The polypropylene material does not
readily accept dye and thus can "grin" through in carpets having
low face yarn content. Although some techniques have been devised
to deal with the grinning problem, these techniques in turn have
disadvantages in that they impose color coordination problems on
mill production operations.
In spite of the great volume of primary backing required by the
tufted carpet industry and the economic importance of a steady
supply at low cost, almost no progress had been made prior to the
present invention toward utilization of low cost fibers of the
types normally associated with the production of other types of
textiles. In particular, designers of primary backings have steered
away from cotton fibers even though enormous quantities of cotton
fibers are readily available at very attractive prices. For
example, virgin cottons having length and/or color characteristics
not especially desired for ordinary textile yarns and cotton and/or
cotton-synthetic blend mill wastes from textile yarn making
operations are regularly available on a continuing basis and at low
cost in the United States.
References to the possibility of using cotton fibers in primary
backings have of course appeared in patents, but no practical
approach to the production of a backing from cotton fibers which
would have satisfactory mechanical properties had been made prior
to the present invention. In fact, the shortness and thinness
qualities of cotton fibers have made it quite difficult to envision
a practical cotton fiber based composite which would withstand the
large strains and high stresses occasioned during tufting machine
needle penetrations. A typical cotton fiber may have a length on
the order of 1/2 to 11/2 inches and a width corresponding to a
denier of about 1. When one envisions an assembly of such fine
short fibers being repeatedly penetrated by a bank of closely
spaced tufting needles of substantial size, the severity of the
problem becomes evident.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of this invention to provide a
novel nonwoven fabric product made largely from such readily
available textile grade staple fibers as cotton, which product may
serve as a primary backing for tufted carpets. This backing not
only has attractive cost and performance characteristics but also
is amenable to dyeing, rot and mildew resistance treatments, and
flame retardancy treatments.
Although cotton fibers and the types of blends of cotton and other
fibers used in textile yarn making are preferred for use as a basic
material for the fabrics of the invention, this fiber content may
in a broader aspect of the invention be viewed as the "fine fiber"
content, by which is meant staple fibers having deniers of about
three or less. For example, low denier rayons or blends having
these characteristics may at times be available at attractive
prices and could be used if the basic principles of the invention
were applied in processing such materials.
In accordance with the present invention the fine fibers are
combined with smaller numbers of longer coarser fibers to form a
nonwoven base web. Although air laid webs can be employed, normally
it is preferable that the fine and coarse fiber contents be carded
together and that the card webs be crosslapped to provide the
nonwoven base material.
For the coarse fiber content, synthetic fibers of at least 6 denier
and having staple lengths at least as great as 4 inches are
suitable, with somewhat coarser (e.g. 10 to 20 denier) fibers being
preferred ordinarily. The coarse fibers may be formed from various
materials. From the standpoint of cost, polyester fibers are
particularly attractive, but good results also have been obtained
using polypropylene fibers. From the standpoint of flame
retardancy, glass fibers and modacrylic fibers have outstanding
properties, and these may be used if desired.
Some bonding together of the fibers in the web is required. In some
instances the necessary bonding effects can be obtained by using
coarse fibers of thermoplastic material or having thermoplastic
sheaths and heating the web under pressure. In most instances,
however, optimum bonding can best be achieved through the use of
added bonding agents. Under either approach, what is most desirable
is a bonding together of the individual fibers of the fiber network
at a sufficient number of the fiber crossing points to give the web
structural strength. In general, the bond strengths should be
substantially less than the strengths of the fibers employed so
that under load the bonds will break prior to rupture of the
fibers. With the bonds broken in a given area, fiber migration to
accommodate the imposed load occurs and the tendency toward
propagation of a failure to other zones of the fiber network is
minimized.
The combination of the fine and coarse fibers in the nonwoven web
has a remarkable effect upon the response of the web to the
stresses and strains imposed during tufting. A web composed solely
of fine short fibers is severely damaged during tufting because
these fibers have insufficient mobility within the web to yield
under the actions of the needles and insufficient strength to
withstand the loads imposed upon them. However, when a web of the
same overall weight additionally includes longer coarse fibers
these problems are minimized. The long coarse fibers are
individually quite strong, so that they do not break readily under
direct impact from a tufting needle but tend rather to be
displaced. The relatively long lengths of these fibers moreover
make such displacements possible without disrupting too many of the
bonds between an individual long coarse fiber and other fibers in
the web. As these long fibers undergo incremental displacement,
therefore, they carry short fine fiber segments with them. As a
result fiber mobility within the web is enhanced and fiber breakage
is minimized.
Although the fine and coarse fiber nonwoven provides a component
which is compatible in an engineering sense with the tufting
operation, it normally will be further necessary to employ still
other strength imparting techniques in order to achieve a primary
carpet backing of fully adequate properties. For example, needling
the web serves to interlock the fibers more effectively and give
the web a significantly enhanced integrity or strength, and
needling normally will be employed in connection with the
crosslapped card webs preferred for use in the practice of this
invention.
Additionally, it normally will be found desirable to include in the
backing structural components in continuous strand form. Yarns or
continuous synthetic filaments may be run in parallel sheets
extending along the longitudinal direction of the material or woven
scrims may be combined with the nonwoven.
Still another technique that has proved especially convenient and
effective is stitching added yarns into the nonwoven with these
added yarns running generally in the lengthwise and/or crosswise
direction of the material or being disposed in a tricot stitch
pattern along the length of the material .
THE DRAWINGS
A fuller understanding of these and other features and advantages
of the invention will be gained from a consideration of the
following detailed descriptions with reference to the accompanying
drawings in which:
FIG. 1 is a schematic flow chart illustrating the formation of a
primary backing according to the present invention;
FIG. 2 is an enlarged schematic view of a portion of a non-woven
base web utilized in the primary backing formed according to FIG.
1;
FIG. 3 is a cross-sectional view of a tufted carpet embodying a
primary backing formed according to FIG. 1; and
FIG. 4 is a schematic illustration of needle overlap in a tufting
zone.
DETAILED DESCRIPTION
FIG. 1 indicates at 10 a supply of short fine fibers of a type not
heretofore considered desirable for use as a major component of
primary backings. These fibers may have widths corresponding to
deniers of up to about three, and lengths of up to about 3 inches.
However, fibers having widths corresponding to deniers of about
three quarters to about 11/2 , and lengths of about 1/2 to 11/2
inches, are of greatest importance and will normally be used.
The preferred fine fiber is cotton. Virgin cottons having staple
lengths of about 1 inch or less are widely available at attractive
prices and are well suited for use in the present invention.
Additionally, mill wastes may be especially attractive from the
standpoint of availability and cost. For example, in the production
of combed cotton and cotton/polyester yarns, quantities of comber
noils containing cotton fibers are produced. These and other mill
wastes from textile yarn production operations are well suited for
use in the invention. Still other artificial cellulosic fibers may
be used either alone or in combination with other short fine fibers
for the fine fiber content 10.
FIG. 1 additionally indicates at 12 a supply of long coarse
synthetic fibers. These may be formed from polyolefin such as
polypropylene, polyesters such as polyethylene terephthalata,
glass, modacrylics and other materials. In any case these fibers
should have lengths of at least about 4 inches and deniers greater
than about 6. Fibers having deniers in the range of from about 10
to about 20 are especially preferred.
The fine fiber content 10 and the coarse fiber content 12 are
combined in the proportions of about 25 to 75% by weight of the
fine fibers and 75 to 25% by weight of the coarse fibers. Normally
it will be preferred to card the fine fibers and the coarse fibers
together to produce card webs containing the mixture and then to
crosslap the card webs so as to build up a composite structure
having a weight of at least about 4 ounces per square yard. Such a
nonwoven base web 14 is illustrated schematically in FIG. 2 where
the fine fibers are indicated at 16 and the coarse fibers are
indicated at 18. It will be appreciated, however, that air laid
webs containing the mixture of fine and coarse fibers may be
employed, if desired.
In a preferred example, the base web 14 consisted of 60% by weight
of virgin cotton fibers of the strict low middling, lightly
spotted, classification having a staple length of about 1 inch and
40% by weight of 15 denier second quality polyester staple fibers
about 4 inches long. These fibers were carded together and the card
webs crosslapped to produce a base web of about 4.7 ounces per
square yard.
Some bonding together of the fibers in the web 14 is required.
Therefore, as indicated at 20 in FIG. 1, the nonwoven must be
rendered suitable for such bondings. Where the coarse fibers 18 are
in the form of thermoplastic materials or have themoplastic
sheaths, the necessary bonding effects can be obtained through
heating the web under pressure, normally at a later stage in the
preparation of the primary backing as hereinafter described.
Generally, however, optimum bonding can be achieved through the
addition of bonding agents. For example, in FIG. 1 the addition of
a bonding agent or "binder" 21 to the nonwoven base web 14 is
indicated. Polyethylene powder such as Microthene FN 500 in an
amount equal to approximately 10% of the weight of the base web 14
has proved to be an adequate bonding agent. As in the case of
bonding by utilizing the thermoplastic properties of the fibers
themselves, actual fiber bonding with the powdering technique is
accomplished at a later stage in the preparation of the backing by
activating the bonding agent 21.
It will be readily apparent that still other bonding techniques may
be utilized. Such techniques may include the addition of polymer
lattices and polymer solutions by saturating the web, or the
coating of the fibers with adhesive materials.
Whatever technique is employed, the fine and coarser fibers should
ultimately be bonded together at a sufficient number of fiber
crossing points to impart structural strength to the base web 14.
In order to facilitate fiber migration to accommodate imposed load
and to minimize the propagation of a failure to other zones in the
fiber network, the bond strength should be substantially less than
the strength of the fibers employed in the network. Thus, bond
breakage and fiber slippage, rather than fiber rupture, will occur
during tufting. In an ideal situation, the binder would be located
between fibers at crossings to provide a more flexible joint and to
avoid plugging of open spaces between the fibers. Moreover, this
binder location minimizes binder waste on fiber surfaces where the
binding function is unimportant. Lubricity in the binder for the
purpose of minimizing heat buildup on the needle during tufting is
also desirable.
Additional treatments for enhancing the strength of the web
normally are required to produce a primary carpet backing of fully
adequate properties. As indicated in FIG. 1 at 22, mechanical
treatment of the nonwoven in the form needling may be undertaken.
Needling densifies and increases the strength of the web by pulling
its surface fibers through the web as the needles move vertically
through the web. The fibers are thus locked together in a three
dimensional array with the interlocked fibers serving to
significantly enhance the integrity or strength of the web.
Normally, such a needling technique will be employed in connection
with crosslapped card webs preferred for use in the practice of the
present invention.
Conventional needling techniques may be employed and in the case of
60/40 cotton polyester base web earlier discussed, the carded
crosslapped web was needle tacked at 800 rpm on a Hunter tacking
loom.
The needling density, i.e. the penetrations per square inch, may be
varied in accordance with the fiber content of the base web. It may
be expected that needling is more beneficial to the webs containing
higher contents of coarse fibers by reason of the fact that the
coarser fiber has additionally sufficient length to be pulled down
into the web. In connection with the needling operation, it may
sometimes be desirable to lubricate the web prior to needling in
order to minimize the tendency of cotton in the web to pill.
Other useful mechanical treatment of the nonwoven is the addition
of reinforcing members to provide a reinforced primary backing as
indicated at 24 in FIG. 1. These reinforcing members may be
provided by stitch bonding the nonwoven, with added continuous
filament or spun yarns or threads disposed in chain stitch
reinforcing patterns running generally in the lengthwise and/or
crosswise direction of the material or being disposed in tricot
stitch pattern along the length of the material. The stitching
technique of reinforcing is indicated at 26 in FIG. 1. Acceptable
results have been obtained with tricot pattern stitching of the
preferred cotton-polyester web referred to above at a stitch length
of 3.2 millimeters using 0.25 - 0.3 ounces per square yard of 70
denier continuous multifilament polyester thread. A Maliwatt
machine available from Crompton & Knowles - Malimo, Inc.,
Worcester, Massachusetts, was used for this stitch bonding. The
main function of this reinforcement is to provide tensile and tear
strength particularly after tufting, with the bonded nonwoven base
web serving to provide a uniform matrix to tuft into and to lock
the tuft in place.
When powder bonding techniques are employed to produce the
desirable bonds at the fiber crossing points, the powder addition
portion of these techniques should be instituted prior to stitching
insofar as the stitched web may be too densified for the powder to
adequately penetrate.
As indicated at 28 the reinforcing members may be supplied in the
form of a woven scrim, or yarns, continuous synthetic filament
tows, spun bonded webs, and/or split film ribbons may alternatively
or additionally be run in parallel sheets extending along the
longitudinal and/or transverse direction of the material.
With reference to FIG. 1 at 30, it will be seen that normally the
reinforced primary backing will be calendered utilizing
conventional techniques. Through calendering the nonwoven the web
tensile strength may be increased. It is at this stage that the
earlier noted fiber bonding normally will take place through heat
and pressure activating the bonding agent 21 if utilized or causing
bonding of thermoplastic fibers, if employed.
In FIG. 3 a tufted pile carpet embodying a finished primary backing
constructed in accordance with the procedures outlined in the flow
diagram of FIG. 1 is illustrated in cross-section. In this
cross-sectional view the primary backing is identified as 32. It
will be appreciated that the primary backing has been tufted using
conventional tufting processes whereby tufting needles are caused
to penetrate the backing. The needles carry pile yarn 34 and
operate to dispose pile yarn loops 36 in piercing relationship to
the backing 32. An adhesive back coating 38 may be applied to the
primary backing 32 so as to anchor the pile yarns 34 more firmly in
place. Dimensional stability of the tufted pile fabric may be
enhanced by adhering a secondary backing 40, e.g. a woven jute
scrim, to the back face of the primary backing.
The primary backing 32 of the tufted pile fabric illustrated in
FIG. 3 is designed to be amenable to rot and mildew resistance
treatments as well as flame retardancy treatments.
An example of the rot and mildew resistance treatments to which the
backing may be subjected is one in which a trimethylol melamine,
such as that sold by Ciba Company, Inc. under the designation
"Arigal C," is padded to the backing in a concentration to yield
5-7% add-on. The pad bath also contains 5-10 g/l of 30% hydrogen
peroxide. A wet fixation procedure (described in American Dyestuff
Reporter, Vol. 50, No. 20, 21, 1961) accomplishes conversion of the
trimethylol melamine to an insoluble resin within the fibers. This
treatment is permanent to washing and leaching. A further
understanding of treatments of this type may be gained from U.S.
Pat. No. 2,763,574.
Numerous durable fire retardant treatments for cotton and
semi-durable fire retardant finishes for cotton would be
acceptable. As an example of an appropriate durable treatment, the
fabric may be padded to approximately 75% wet pickup with a water
solution of the following content:
Polyvinyl chloride 9.4% Sb.sub.2 O.sub.3 10.1% Tetrakis
(hydroxymethyl) phosphonium chloride 10.4% Trimethylol melamine
7.8% Urea 3.9% Triethanolamine 3.9% Wetting Agent 0.5% Softener
1.0% Total 47.0%
The fabric is then dried on a tenter frame, cured 2 minutes at
320.degree. F., and given an alkyline, oxidizing wash.
A suitable commercial semi-durable fire retardant finish for cotton
involves padding the fabric to approximately 70% wet pickup of a
water solution of cyanamide 30% and phosphoric acid 20%. The fabric
is dried 2 minutes at 65.degree. C., and cured 4 minutes at
105.degree. C.
Thus, through the above or similar treatments, one may insure that
the backing of the present invention does not contribute to the
flammability or rot and mildew deterioration of the carpet.
It will also be seen that according to the present invention a
primary backing for a tufted fabric may be formed from cotton
fibers so that the backing has satisfactory mechanical properties
necessary for that function. Basically, these properties may be
characterized as "tuftability," or the ability of the primary
backing to maintain adequate strength across the tuft line, and
"tuft lockability," or the ablity of the backing to recover from
deformations caused by tufting needles and to thereafter squeeze in
on the pile yarns which pierce the primary backing.
The provision of tuftability and tuft locking characteristics in
the primary backing of the present invention is particularly
significant when the shortness and thinness of the fine fiber
content of the backing is considered. A typical tufting machine
provides 7 to 10 tufts per inch along the tuft line with 61/2 to 10
tuft lines per inch. The problem presented by such loading may be
readily appreciated by reference to FIG. 4 which illustrates at 42
the areas blocked off by the tufting needles 42. These needles are
mounted with their long sides set at about 30.degree. to the tuft
line, indicated at 44. The distance between the tuft lines of 3.9
millimeters is represented by the arrow 46, and the distance
between tufts in a line of 3.6 millimeters is represented by the
arrow 48.
Since, at this tuft density, the rectangles representing the area
blocked out by the needles 42 overlap along the tuft line 44, it is
readily apparent that if the backing is not able to distort ahead
of and behind the needle, all fibers crossing the tuft line will be
cut so that the backing will deteriorate. Additionally, it may be
noticed that as the fibers are displaced from the center of the
needle to the outer corners of the rectangle representing the area
blocked out by the needle along the tuft line, stresses tending to
tear the backing across a line perpendicular to the tuft line will
result. Moreover, as indicated by the circles 50 the backing must
recover a considerable amount to close about the yarn penetrating
the backing.
Through the provision of a nonwoven base web having a short fine
fiber content and a longer coarser fiber content as discussed
above, the fiber network is sufficiently mobile and deformable to
impart good tuftability and tuft locking properties to the web
despite the predominately present fine fibers.
Through the practice of the present invention, a primary backing of
attactive cost and performance characteristics is thus provided by
employing a fine fiber content which would normally be thought
non-susceptible to tufting in an acceptable manner. Moreover, the
aspect of the invention involving amenability to rot and mildew
resistance treatments and flame retardancy treatments is
particularly significant.
In addition, it will be appreciated that according to the present
invention the amenability of the backing to dyeing eliminates
grinning problems, or the need for special techniques to combat
grinning problems, while retaining the advantages of a nonwoven
fiber network.
Although the invention has been described with reference to
preferred forms and techniques, it will be appreciated by those
skilled in the art that additions, modifications, substitutions and
deletions may be made by one skilled in the art without departing
from the spirit and scope of the invention as defined in the
appended claims.
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