Note: Descriptions are shown in the official language in which they were submitted.
~2~
The invention relates to a nonwoven backing material for tufted
carpets.
Conventionally, the secondary backing of a tufted carpet consists of
an elastomer foam or of a suitable textile material. The role of this
secondary backing is, on the one hand, to impart improved stability to the
tufted carpet and, on the other hand, to provide a surface which will slide to
some degree upon a oam underpad, when used, which ensures that when the
carpet and underpad are laid in a wall-to-wall application, deformation of
both layers, caused by traffic or other use, does not form permanent bubbling
1~ that detracts from visual appeal and causes bumps In the surface of the carpet.
~ ute Eabric is still the predominant material among those used as
secondary backing; in addition to fulfilling the roles described above, jute
also tends to make a tufted carpet appear comparable to that of a classical,
woven carpet. m e jute fabric meets the most important demands of dimensional
stability and increased strength that are required because of the weakening of
the primary t~fting layer caused by needle penetration and also permits some
degrae of sliding on the underpad; however, it also displays certain
disadvantages. Very oftPn, the jute fabric is the sole non-synthetic
component in the carpet as a whole and, as such, is not resistant to rot.
Microorganisms, such as bacteria and fungi, can breed very easily in this
layer, and this aowngradss its hygenic properties. Finally, jute is a natural
product, that is obtainable only on a limited basis. A further considerable
disadvantage of jute lies in its considerable weight per square metre of over
200 gtm2 that has to be used in order to achieve the desired effect. It is
therefore one object of the invention to develop a backing material for
carpets, with significantly lower weight factor.
Recently, attempts have been made to develop a backing mater~al
utilizing polypropylene and both woven and nonwoven materials have been used.
3~
The disadvantage of using polypropylene as a backing material is its
inadequate thermal stabililty. ~hen high temperatures are used, such
materials tend to buckle very easily; in the case of a carpet provided with a
polypropylene secondary backing, this leads to a differential expansion effect
- rather like a bimetal effect - and concomitant wrinkling. In addition,
there can be problems of adhesion during lamination to the basic carpet. As a
rule, synthetic lattices are used in the lamination, so as to bind the tufts
into the primary tufting layer, both to stabilize it and to provide an
adhesive mass for lamination to the backing. However, it has been found that
the polypropylene fabric does not have sufficient adhesion, and even when
various alternatives are employed - for example, perforating the nonwoven
material or by using spinning thread in the woven polypropylene material -
bonding with the basic carpet is inade~uate.
Therefore~ an object of the invention is to provide a secondary
backing for tufted carpets that has the required mechanical and thermal
stability and sufficiently low weight factor, and which will adhere well to
the basic carpet - for the most part, regardless of what temperature is used.
This object is achieved by using nonwoven filaments or filament
groups o~ polyesters and/or copolyesters. The secondary backing material
according to the invention is characterized in that the fleeae contains the
filaments or filament groups in a "cross-over parallel texture'l with a
coefficient of variation filament separation in excess of 100~. It is
particularly advantageous if the secondary backing material has a variation
coefficient of filament separation of at least 120~.
Spun bonded filaments or filament groups with cross-over parallel
texture are described in United States Patent No. 3,554,854. The filaments or
filament strands are, in the main, arranged parallel to each other, whereby
numerous groups are provided which cross over each other and are bonded at the
cross-over pointsb
, According to the present invention, the porosity and adhesion of the
backing material can be controlled by the degree of filament separation. The
polyester filaments in a cross-over parallel texture provide great dimensional
stability and very good strength characteristics, and the backing adheres very
well to the tufted carpet and has good eye-appeal. These advantages are
realized by the fact that the polyester threads are spun by groups or,
alternatively, drawn or spooled ofi together and then laid together to fonm a
nonwoven material having a cross over parallel texture. In this manner,
porosity can be controlled and a flat con~iguration with good adhesion
characteristics may be realized.
The secondary backing for tufted carpeting and rugs has good strength
and dimensional stability characteristics and sufficient porosity and air
permeability to ensure good adhesive penetration for laminating to a primary
bac~ing. The secondary backing comprises a non-woven fabric made from
essentially continuous polyester filaments, the non-woven fabric being built
up from single filaments and filament groupsl in a crossed-over parallel
texture with a variation coefficient of the filament separation of more than
100%. Furthermore, the fabric is of es~entially constant filament and bond
density throughout the depth of the fabric.
The porosity of the nonwoven material is adjusted initially by
spinning the polyester filaments in groups according to United States Patent
No. 3,554,854. By selection of the percentage proportion and the degree of
parallel;zation of the filaments in the groups, the degree of porosity can be
controlled for a given weight per unit area. ~y this means, it is possible to
avoid having to subsequently produce a surface structure that is suitable for
adhesion by additional needling, as is dictated by the state of the art. ~ith
a given weight per unit area, an increase in the bunching of the filaments
into filament groups will result in an increase in the degree of porosity
displaye~d by the surface structure. By building up the spun bonded material
from filament groups, the porosity and thus the adhesion characteristics can
be adjusted according to the number of single filaments that are gathered into
groups.
The porosity that results from the controlled bunching ensures good
penetration of the adhesive that is used for lamination. That is to say, the
secondary backing material of continuous polyester fibres with a controlled
degree of parallelization of the filament groups that are laid in ~ random
~'
-3a-
g~
texture results in outstanding adhesion for tufted carpeting. ~lowever, the
adhesion can be improved still further if the nonwoven material is produced
not from polyester fil~ments - e~g., polyethylene terephthalate - alone, but
is formed as a mixed fleece which is built up by laying in or spinning in
copolyester fibres. It has been found that copolyester fibres display better
adhPsion characteristics during the lamination process than do pure polyester
fibres. The surface characteristics with regard to adhesion of the spun
fleece are thus greatly improved by the co-utilization of copolyester fibres.
It is expedient to spin in or lay in filaments or threads of copolyesters,
e.g., of ethylene glycol, terephthalic acid and adipinic acid or butylene
glycol, terephthalic acid and adipinic acid or butylene glycol, terephthalic
acid and isophthalic acid.
In a preferred construction, the novel backing material can be built
up from a spun fleece of continuous filaments or filament groups in a
crossed-over parallel texture, wherein the filament groups are built up from a
mixture of polyester and copolyester filaments. The laying up of the
filaments or filament groups in a crossed-over parallel texture - i.e.,
without a particular orientation of the lay of the fibres - results in both
isotropic mechanical properties and a controlled pore structure. This results
in an ideal reinforcing material for carpetin~.
A further preferred embodiment of the lnvention comprises the dyes,
Dinders or colour pigment-binder combinations impressed in a point array or in
a raster configuration. This will result not only in a geometrical, textured
structure, but will also lead to localized compression, by which the desired
pore structure may be realized. In the packed areas, the adhesive that is
used for lamination of the prepared carpet will penetrate less intensi~ely
than in the adjacent areas, and this will lead to a suction cup effect and
high adhesion ~alues. This will also lead, as will be described later, to a
-- 4 --
specific air permeability, i.e., the degree of surface overlap will be
determined, on the one hand, by a specific degree of filament separation and,
on the other, by local overpressing based on air pe~meability.
Even though it is preferred that the backing material according to
the invention be laid as a spun bonded material with a crossed-over parallel
texture of polyester filaments or filament groups by the use of spinning
nozzles, it is also possible to produce the cross-ov~r parallel texture by
drawing out the filaments or filament bundles from spools or racks and
subsequent cros~-over lay up.
The production of the carpet bac~ings from spun fleece is well ~nown
in the art and it is well within conventional spinning technology to produce
the cross over parallel structure. Of especial value in this regard is a
device described, for example, in the aforesaid United States patent, wherein
fibre groups are spun from a number of adjacent spinning nozzles and are moved
to a take-up strip with the help of guide channels. me fibre groups are
stretched and guided after the spinning extension method. A series of
adjacent spinning nozzles is arranged in a spinning beam - for example, the
aforesaid United States patent illustrate~ a spinning beam with clusters of
three spinning nozzles from which three filaments are spun. One of the
spinning nozzles is of a different diameter from the other nozzles, by which
paralleled groups of filaments of various diameters are built up. Thus, when
producing the backing material according to the invention, the copolyesters,
for example, can be spun out of the lar~er nozzles, and the polyesters can be
spun from the smaller nozzles, whereby the filaments that build up the
filament groups can also differ chemically. The filaments that make up a
mixed nonwoven material can thus differ from each other physically as well as
chemically.
On arrival on the take-up strip, a spun fleece with a crossed-over
-- 5 --
parallel structure is obtained. In this connection, filaments that run
parallel are laid up to a fleece without any preferred orientation.
Naturally, mixed nonwoven materials with controlled porosity can also be built
up, these consisting of a mixture of single filaments with two group or
three-group filament bundles. This can be achieved without difficulty by the
appropriate arrangement of spinning orifices in the spinning nozzles, in a
suitable sequence of single, dual or triple-orifice arrangements.
During the build up of a fleece on a taXe-up strip having an
underlying vacuum extraction system, both when spinning and when drawing out
from spinning racks, the filaments will be guided to the take-up strip by
pulling and guiding air currents. The filaments of the filament groups will
be mixed in a cross-over parallel texture during the formation of a random
nonwoven material. In this context, a random nonwoven material in a
cross-over parallel texture means an isotropic depositing of the filaments or
filament groups with partially parallel oriented filaments laid crossed over,
without any preferred direction in the layO Depending upon the turbulence in
the fleece formation area, the ilaments or filament groups will be mixed to a
greater or lesser degree, and there may be partial separation of filaments
from the filament formation so that, in general, the finished nonwoven
material consists of a mixture of crossed-over single filaments with two-,
three-, or multi-filament groups.
The greater the under-pressure beneath the take-up strip when the
nonwoven material is being formed, the stronger the filaments or filament
groups will be affixed on emerging on to the take-up strip and the more firmly
their positions - predetermined by the spinning noPzle configuration - will be
maintained. If the magnitude of air currents drawn off is small, there will
be a great deal of turbulence in the capture one, and this will lead to a
great deal of mixin~, as well as to more intensive splitting of the groups
. . ~
:,
into single filaments.
For many purposes it has proved expedient to produce the nonwoven
material such that the number of filaments per square centimetre of the free
area of the extraction channel is expediently set at a little more than ten.
After leaving the withdrawal channels, the filament groups or bundles are laid
in a cross-over parallel texture, i.e., layer upon layer of filaments or
filament groups are laid upon each other and at the same time crossed over.
~fter being picked up, in the case of binding thread attachment, the nonwoven
material is secured by a pressure-thermal treatment, for example, with the
help of a heated calendar. Preferably, but not exclusively, after calendar
bonding, the nonwoven material is impressed by a point array or textured
raster. In either case, there is no total-surface application of pressure
dyes or binding agents and a specific porosity will be achieved once again by
point or raster stamping. This will result in the fact that an unimpressed
location will have a greater porosity and a higher binding agent uptake
ensuring subsequent lamination with tufted carpeting. To this end, both by
controlled bundling andior by point impression of bindors, an air permeability
of more than 3~0, preferably more than 500 dm3/m2/sec at 0.5 mbar will be
set up for the nonwoven secondary backing so produced, Subsequently, after
the pressure process, the nonwoven material i9 passed over a psrorated drum
and hot air is blown through the sheet in order to effect final fixing. The
hct air is blown from the inside of the perforated drum to the outside,
thereby pasaing through the fleece that is stretched over the drum.
In another example according to the invention, the nonwo~en material
is built up from fibres of only one kind, namely polyethylene terphthalate.
In this case, too, parallal filaments or filament groups are laid up in such a
manner that a cross-over parallel texture is formed, that is to say, the
filaments or filament groups are superimposed on top o~ and cross over each
2~
other. In this case, the result on the take-up strip will be a crossing over
of the filament or filament groups resulting from the superimposition of dual,
triple or multi-fold groups of parallel filaments. This nonwoven material is
then anchored by the raster impression of binding agent dispersion, which may
contain colouring pigments i.e. the filaments will be locally bundled.
The nonwoven material is more porous and absorbent between the
impressed binding agent areas than it is in the im~ressed areas and thus the
manufactured carpeting displays good adhesion properties during lamination.
Here, too, the porosity, measured on the basis of the above-described air
permeability, will be regulated.
The nonwoven material according to the invention that is produced by
the above-descri~ed method consists of filaments that are laid up in a
cross-over parallel texture with constantly alternating filament groups that,
in the same way, are laid randomly~ The cross-over parallel texture that is
so obtained is characterized by a high coefficisnt of variation of the
filament s~paration, that indicates marked bundling. This specific st~tcture
i~ efEective in two ways: on the one hand, it results in the large number of
filaments per unit area that is needed for the strength and mechanical
properties that are required for the material and, on the other hand, the
porosity can be ad]usted by selection of the degree to which the ~ibres are
paralleled that is desired for the adhesion of the backing to tufted
carpeting. m e degree of paralleliæation can be determined and defined by
measurement of the coefficient of variation of the filament separation.
Determination of the coefficient of variation of filament separation
is based on measuring the distance between individual filaments of the fleece
and calculating their coefficient of variation. Thin fleece materials, up to
approximately 0.15 mm thick, can be measured directly. In the case of thicker
materials, it is necessary to use a separation technique, although this must
,, ~
2~
not be allowed to change the position of the fibres. In this case of unbonded
and non-bonded materials, amongst which fleeces according to the present
invention are, as a rule, classified, this can be done by direct
delamination. In the case of strongly bonded materials, it is advisable to
first embed them in a suitable material and then remové sections approximately
100~ thick by using a microtome.
Measurement itseif is best carried out directly on a 50x microscope
that is furnished with a measuring eyepiece. The distances between parallel
filaments in both the main directions ~machine and cross rnachine) and in both
diagonal directions at an angle of ~45 to the main axes is measured.
Filaments are taken as parallel if they form an angle of no more than 2
with a selected direction. The distance between two ilaments is taken to be
the distance to the edges that dilineate the filament image in the same
sense. The number of filament intervals that is measured should amount to
200, preferably 400, in each test. During measurement, the image is divided
with a straight edge that follows the direction to be measured, and those
filaments that form an angle from 90 + 2 with this straight edge should
be followed.
The coefficient of variation of filament separation is shown
according to the formula
VFs S , lOQ rc~]
wherein VFS is the coefficient of variation of filament separation, and S is
the standard variation of the measurement body
~ -!
s = \I(Xi_x)2
~ n - 1
_ g _
represents the respective single value of the filament interval and n stands
for the number of measurements and x is the average filament interval
X 1
In addition to the adjustment of the above listed parameters of air
permeability and filament separation, weight per unit area is also a
functional characteristic. ~t weights per unit area of less than 40 g/m2,
the necessary air permeability may be adjusted by correspondingly high
over-pressure, but the essential strength of the carpeting is too low. At
weights in excess of 150 g/m2 it is possible to achieve great mechanical
strength and good adhesion b~ adjusting to a suitable porosity, measured on
the basis of air permeability, by the appropriate adjustment of filament
separation and group configuration. ~lowever, at weights ~er unit area in
excess of 150 g/m2, the secondary baaking has a tendency to separate into
layers. It i5 therefore preferable to use weights of ~0 g/m2 - 150 g/m2.
m e invention will now be described further by way of example only
and with reference to the accompanying drawings, wherein:
Figure l illustrates the cross-over parallel texture o~ filaments and
filament strands in a backing material according to the invention;
Figure 2 is a stereoscopic photograph of a random nonwoven material
with cross-over parallel texture;
Figure 3 is a schematic representation of the production of backing
material according to the invention, and
Figure 4 i5 a schematia representation of a nonwoven secondary
backing material according to the invention, having cross-over parallel
texture.
Referring to Figure l, the cross-over points d of the filaments c or
the filament strands a and b are indicated. ~t identical weights per unit
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23~
area, larger spaces or pores can be obtained between the cross-over points by
further bundling or parallelization of the filaments or filament groups.
These spaces or pores affect the adhesion properties of the secondary backing
material.
Figure 2 is a stereoscopic photograph of ~ random fleece with
cross-over parallel texture. An isotropic lay of the filaments or filament
groups with partially parallel filaments laid across them with random
directions of lay can be seen in this photograph.
Figure 3 is a schematic representation of the production of the
backing material according to the invention, and is an alternative to the
spinning process of United States Patent No. 3,554,85~. The filaments or
filament bundles are spun out of spools ox cans and laid so as to aro~s over
each other. A spool rack lO is arranged above a take-up strip ll. Fibre
bundles 12 are drawn out of the spool rack lO with the help of aerodynamic
extractors 13 and gathered on the take-up strip ll in the form of a mat ~uilt
up from continuous filament bundles, with the help of oscillators 14. This
mat also has filaments or filament bundles in the crossed-over parallel
coT~iguration according to Figure 1. In this case, anchoring is effected by
means of binding filaments that are either mixed in or by ~he subsequent
application of binding agent e.g., by impregnation. The pore structure is
controlled by the fact that various types of fibre bundles are dra~m out and
laid up from dif~erent spools that are arranged sequentially one behind the
other, these bundles being built up from one, two, or three or even more
single filaments.
Figure 4 is a schem~tic xepresentation of a nonwoven material
according to the invention with cross-over paralled texture. The single
filaments c and the filament groups comprised of filaments a and b can be seen
with the overpressed places marked e. ~lese overpressed areas e contain an
-- 11 ~
additional binding agent, e.g. a polyacrylate.
The following examples serve to describe the carpet backing material
according to the invention.
Example 1.
The apparatus employed a plurality of spinning nozzles~ each having
two different types of orifices, each orifice being connected to a pair of
polymer melt distribution systemsO The orifices were so arranged in groups
that two orifices of a first group and one of a second group were always in
close proximity. The orifices of the first group had a diameter of 0.3 mm and
those of the second group had a diameter of 0.5 mm. The filaments then passed
through an elongated air channel having air slots in its long side through
which the extractor air flowed. ~mbient air flowed freely between the
spinning no~-zle and the air channel. The filaments extracted by the air
streams were elongated and cooled and laid up as fleece on a sieve band that
runs beneath the air channels. This resulted in a structure similar to that
of Figure 1, in which the filament groups were crossed and in which some ran
irregularly with respect to the direction of motion of the sieve band and the
material that was formed.
The spinning no~7.1es of the first group were supplied with a melt of
polyethylene terephthalate, and the nozzles of the second group were supplied
with a melt of the copolyester of terephthalic acld and butylene glycol.
The fleece that was formed was passed through a calendar heated to
145C and fixed in a flow through drier heated to 195C.
The bonded nonwoven material displayed the following characteristics:
Weight per unit area (g/m2) 50
Thickness (mm) 0.2
Maximum tensile strength N/5 cm lengthways 107
crossways 98
Maximum stretch (~) lengthways 38
crossways 38
Air Permeability at 0,5 mbar ~dm3/m2/s) 1950
On microscopic examination, the material exhibited the cross-over
parallel texture. On measurement, a value of 138~ was determined for the
coefficient of filament separation.
The material was applied as a secondary backing to a printed twlst
carpet having a machine separation of 5/64" and 5~ E/10 cm, that had been
coated on the back witn approximately 700 g/m2 of a tacky latex dispersion.
This resulted in good wetting and extremely good adhesion of the backing.
Example 2.
For the produc'ion of the fleece a devi~e wa~ used that consisted of
two adjacent spinning nozzles o~ elongated configuration. 2ach spinning
nozzle was supplied with polymer melt from an extruder, through a gear pump
that was used as a metering pump.
A first spinning nozzle was used to produce matrix threads and had 64
orifices with a capillary diameter of 0.3 mm, the capillary length amounting
to 0.75 mm. The orifices were arranged in two rows over a length of 280 mm.
A second spinning nozzle served to produce binding threads and had 32
orifices, again with a capillary diameter of 0.3 mm and a capillary length of
0.75 mm. The orifices were arranged in a single row 280 mm long. me threads
that were formed were air blown beneath the spinning nozzles ~or a length of
150 mm, obliquely to the direction of movement, and finally passed through a
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protective shaft to an aerodynamic extractor. A flat injeckor, 300 mm wide
and having an entrance slot 4 mm deep, was used as the e~tractor. Beneath the
extractor injector there was an endless belt of metallic sieve material.
The matrix and the binding threads that were mixed in the e~tractor
injector wera laid up in a random fleece during the extraction of the driving
air. The speed at which the endless belt was moved determined the weight per
unit area of the fleece. Partial bundling resulted from contact of the two
thread groups, so that the filaments were extracted in frequently changing
groups and laid up in cross-over parallel texture. Polyethylene terephthalate
was used as the raw material for the matrix threads, and a copolyester of
terephthalic acid (77 mol.~), adipinic acid (23 mol.~) and ethylene glycol was
used as the raw material for the binder threads. me proportion by weight of
the matrix threads to the binder threads amounted to 80~ : 20~ and the flow
speed of the air was adjusted to 16,000 m/min. in the extractor injector.
e random filamentary nonwoven material was removed from the endless
belt and passed on by means of a press machine consistlng of two heated metal
rollers. Both rollers were preheated to 120C and the roller gap was
adjusted to 0.4 mm. Thus, the nonwoven material was pressed and pre-bonded.
The random filamentary nonwoven material was then passed to a second bonding
machine which machine essentially consisted of a circulating endless sieve
belt that was stretched tight beneath a perforated roller.
The random filamentary nonwoven material that was in a surface bonded
state had hot air blown through it when it was between the perforated roller
surface and the circulating sieve belt. The air temperature was adjusted to
225C and the surface configuration that was so bonded was continually
removed from the bonding machine and rolled.
The spun bonded material displayed the cross~over parallel texture of
Figure 2. The coefficient of variation of filament separation amountad to
,
,
; ~ ,
134~, and the material had the following characteristics:
Weight per unit area (g/m2) 70
mickness, (mm) 0.32
Maximum tensile strength N~5 cm. longways 156
crossways 142
~aximum stretch (%) longways 42
crossways 42
Air permeability at 0.5 mbar (dm3/m2/~) 1500
The spun bonded material was impressed with a pigment containing
dispersion paste and applied as a backing to a cut pile carpet with a machine
separation of l/16 inch, by means of a latex dispersion that was applied to
the back of the carpet at a rate of 900 g/m2. The adhesion of ths secondary
backiny was good.
In the impressed state, air permeability amounted to 830 dm3/m2.
In order to achieve good adhesion and bonding to the carpet it has been shown
that the air permeability of the spun fleece built up of filaments or filament
groups in a cross-over parallel texture, measured according to DIN 53 887 at
an overpressure of 0.5 mbar, should be greater than 300 dm3/m2 x s. It is
particularly advantageous to have materials that display an air permeability
of greater than 500 dm3/m2/sec.
Example 3
A polyester-filament thread with a total titer of 167 dtex at 68
filaments (filament titer 2.5 dtex) was drawn from a frame b~ a twin roller
feed device and passed to round air injectors, the exits of which were fitted
with a butterfly diffuser that caused the superimposition of the filaments.
Ten such positions were arranged per l m. width. The superimposed filaments,
which also formed bundles with varying numbers of filaments, were laid up to a
fleece on a sieve band on which the laying zone was evacuated from below. The
- 15 -
~5~;~3~
fleece so produced was consolidated by a calendar heated to 180C and
finally impressed with a dispersion of an acrylic binder with a rod-like
structure. The fibxe weight amounted to 80 g/m2 and the binder layer was at
10 g/m2, so that the finished nonwoven material had a weight of per unit
area of 90 g/m2. It displayed the following characteristics:
Thickness (mm) 0.30
Maximum tensile strength lengthways N 190
crossways N 183
Stretch lengthway3 ~) 63
crossways N (~) 63
Air permeability at 0.5 mbar ~dm3/m2/sec.)560
Coefficient of Variation of filament separation 162
The fleece material adhexed very well to the carpet after having been
coated with a latex dispersion.
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