Tuft backing

A textile composite material is used as tuft backing for tufted carpets, the composite material having at least one nonwoven fabric on which exclusively parallel-running, straight, load-absorbing, plastic, continuous filaments are rascheled, and a thin binding yarn serving as a knitting chain fixing the continuous filaments in position.

BACKGROUND OF THE INVENTION 
The invention relates to a backing for tufted carpets as are typically used 
in the living room and in the furnished area. According to DE-A1-39 41 
189, such backings consist of a non-woven, spunbonded material of 
polyester and copolyester filaments which are irregularly joined and 
autogenously, thermally agglutinated during their formation and bonding. 
This document addresses the problem that high mechanical and thermal 
stresses occur when manufacturing and processing a tufted carpet which 
lead to unwanted deformations. These are, in particular, elongations in 
the lengthwise direction and shortenings in the transverse direction. 
There should also be great dimensional stability when laying or during 
ageing. This holds true in particular for backings or underlays having low 
weight equal to or below 150 g/m.sup.2. 
The manufacture of tuft backings is explained in DE-A-39 41 189 as well. 
For example, a molten, synthetic mass of polyester, in particular 
polyethylene terephthalate or polyethylene terephthalate/polybutylene 
terephthalate, is extruded in the form of continuous filaments or 
bicomponent filaments. These filaments are bonded by needling and 
thermobonding. Lightweight, spunbonded materials are formed of between 20 
and 500 g/m.sup.2, preferably under 150 g/m.sup.2. At the same time, the 
titers of the filaments are about 7 dtex. 
In the interest of stabilizing these spunbonded materials, for example, 
polyester filaments are applied in the lengthwise direction on one or both 
of their sides. These filaments run straight, parallel to one another and 
exist as continuous, high-modulus filaments. Understood under the last 
term is a modulus of elasticity over 20 GPa, at room temperature and at 
temperatures over 200.degree. C., as well. The high-modulus filaments are 
secured to the formed fabric by means of special needling during or after 
the formation of the nonwoven fabric, starting from warp beams, with 
travelers or bobbins. The parallel-running, high-modulus filaments have 
titers of 0.28 to 27.2 dtex. Their distances from one another are 2 to 30 
mm. It is suggested to apply such a quantity of filaments that, given 
stretching of the formed fabric in the lengthwise direction, a tearing is 
first determined from 80 daN/m width. Glass filaments are named as 
preferred high- modulus threads. 
DE-U1-295 09 066 describes a textile composite material for stabilizing 
floors and ground cover! layers and as a load-absorbing filtration layer. 
In this case, the composite material consists of a formed fabric of 
plastic fibers. To attain high resistance to tearing in the main load 
direction without excessive stretching, and to absorb great tensile 
forces, exclusively parallel-running, load-absorbing, straight, plastic, 
continuous filaments are rascheled on the nonwoven fabric. Due to this, 
the textile composite material of nonwoven fabric becomes highly 
tear-resistant in the main load direction. The plastic, continuous 
filaments counteract an application of force immediately, without having 
to be substantially stretched beforehand. 
The load-absorbing threads are applied with a width on the non-woven fabric 
corresponding to the width of the formed-fabric web. Their cross-section 
lies in the range of 2 to 100 mm.sup.2, their distance to one another is 1 
to 100 mm. For example, polyester fibers form the base nonwoven fabric 
which contains the load-absorbing, parallel filaments rascheled on one or 
both of its sides. A thin binding yarn is guided as a knitting chain on 
the raschel machine and secures the load-absorbing, plastic, continuous 
filaments on the nonwoven fabric. 
In one preferred specific embodiment, the load-absorbing filaments run 
warpwise and in the lengthwise direction of the nonwoven fabric web. 
Another variant is indicated in which, in each case, the load-absorbing 
filaments are rascheled in pairs on the nonwoven fabric, the distance to 
the thread pairs being 1 to 100 mm. In each case, polypropylene is 
specified as the preferred material for the nonwoven fabric, 
load-absorbing filaments and binding yarn.

DETAILED DESCRIPTION OF THE INVENTION 
An object of the present invention is to make a tuft backing of spunbonded 
material resistant, especially with regard to shrinkage in width, to the 
effect of tension, temperature and moisture when dying, tufting and 
steaming during the manufacture and processing of a tufted carpet. In so 
doing, the use of glass filaments shall be avoided, because when tufting, 
destruction of these filaments always occurs because of their brittleness, 
and the reinforcing function is thereby canceled. In spite of the 
resistance called for, the formed fabric shall be able to be only 80 to 
150 g/m.sup.2 heavy. 
This and other objects of the invention are fulfilled by the use of a 
textile composite material in accordance with DE-U1-295 09 066 as a tuft 
backing for tufted carpets, this composite material having the following 
characteristics. The composite material has at least one nonwoven fabric 
of polyester fibers, on which exclusively parallel-running, straight, 
load-absorbing, plastic, continuous filaments of polyester are rascheled. 
The term raschel is used herein to denote to knit with a raschel machine. 
The titer of these filaments is 500 to 1500 dtex, their distance to one 
another is 4 to 20 mm. The thin binding yarn serving as the knitting chain 
secures the reinforcing filaments to the formed fabric substrate. 
In the interest of high dimensional stability, the thin binding yarn has a 
titer of 400 to 1100 dtex and a tenacity of at least 60 cN/tex. 
The 80 to 150 g/m.sup.2 heavy spunbonded material consists of spun, 
continuous filaments having titer values of 2 to 10 dtex, the filaments, 
running irregularly, being bonded to one another by thermobonding at their 
fiber intersections. 
In one preferred exemplary embodiment of the invention, a textile composite 
material having the above characteristics is used in which, in each case, 
the load-absorbing filaments are rascheled in pairs on the nonwoven 
fabric, the distance between the respective pairs of filaments being 4 to 
20 mm. 
An advantage of the invention is that it makes it possible to manufacture 
extremely light-weight carpet backs for living room carpets which 
nevertheless withstand the mechanical and thermal stresses during 
manufacture and processing without significant transverse shrinkage, while 
avoiding reinforcing glass filaments.