GB2175026A - Contractile non-woven interlinings and process for their manufacture - Google Patents

Abstract

Contractile non-woven interlinings are composed of thermoplastic fibres which are settable by hot pressing. The non- woven fabric has elongate narrow pores distributed over its surface, formed for example by embossing with a heated roll, fibres of the fabric immediately surrounding the pores being bonded together. Preferable the bores are disposed in rows parallel to the longitudinal axis of the fabric and the fabric is stretched transversely after hot embossing. <IMAGE>

Description

SPECIFICATION Contractile non-woven interlinings and process for their manufacture The invention relates to a contractile, optionally iron-on non-woven interlining made of thermoplastic fibres for use in the making-up of garments, and to a process for its manufacture.

Non-woven interlinings have the advantage, compared with woven material, of better shape retention and higher fraying resistance at the cut edges. However, owing to their compactness they are difficult to shape; more particularly they lack the requisite contractility, as a consequence of fibre entanglement or of being consolidated by a bonding agent or bonding fibres. For these reasons the individual fibres have a severely impaired individual mobility. Woven fabrics, on the other hand, have excellent shaping and contracting properties, owing to the large fibre interspaces and also the mobility of individual fibres (lattice structure), but for the same reasons retention of their given shape is significantly worse.

To overcome the dilemma between the contrary properties of shapeability and shape retention, it has already been attempted to use partial heat bonding of fusible or heat-shrinkable fibres.

However, the partially heat-bonded products likewise lack contractility, and, if the number of bonding sites is further reduced in favour of more free fibres, the cohesion and the dimensional stability are lost. It is true that interlinings with heat-shrinkable fibres can be made to undergo local contractile shaping by means of directed application of heat; but any further supply of heat, as is required for example when heat-bonding the interlining into a garment or in the final processing of the latter, for example by ironing, leads to further, whole-area shrinkage of the whole non-woven and thus again to destruction of the predetermined shape.

The present invention seeks to provide a contractile non-woven interlining of high shapeability, with high dimensional stability and intrinsic strength even during further processing.

According to the invention there is provided a contractile non-woven interlining comprising a non-woven fabric composed of thermoplastic fibres which are settable by hot pressing, wherein the non-woven fabric has elongate, narrow pores distributed over its surface, fibres of the non-woven fabric immediately surrounding said pores being heat bonded to one another.

The invention also provides a method for the preparation of a contractile non-woven interlining in which a web comprising thermoplastic fibres having a single fibre strength of 1.0 to 4.0 g/d is heat-pressed by an embossing roll having linear embossed pattern so as to form one or more lines of elongate, narrow pores on said web and simultaneously to heat bond fibres of the non-woven fabric immediately surrounding said pores to one another, the resulting non-woven fabric is then extended transversely to the lines of elongate narrow pores to an extent depending on the desired contraction ratio, and the extended fabric is heat set.

The non-woven interlinings according to the invention are readily able to absorb the disorders in the fibre arrangement which arise locally as a result of contraction and/or to compensate stresses which arise, because of the alignment of their longitudinal perforations trassversely to the direction of contraction.

On hot-pressing the shaped interlining onto a fabric, e.g. by ironing, the given shape is fully retained. Dimensional stability and high shapeability are thus combined here in a nonwoven interlining. At the same time the interlining has a high intrinsic strength, since the rims of the pores-and only these-are consolidated by fibres which are thermally bonded to one another.

According to the invention, the pores have an elongate shape e.g. a length averaging at least twice their width and suitably 3 to 10 times their width prior to expansion transversely, in which their longitudinal axes extend predominantly parallel to the longitudinal axis of the non-woven interlining, when the interlining is to be contracted in the transverse direction. Examples of expedient pore shapes are narrow rectangles, ellipses and lenticular perforations.

Preferably, any line running across the interlining from one side to the other transversely to the direction of contraction passes through at least one pore. As a result, the non-woven will be contracted at every point along its length. Irregularities in contraction of the fibre assembly can thus reliably be avoided.

The intrinsic strength of the non-woven is the exclusive result, as already explained, of the fibre bonding at the pore rims; the free mobility of the other fibres is retained in favour of the shapeability and softness of the interlining. The proportion of the total area of the non-woven interlining that is occupied by the pores can be varied in accordance with the required degree of contraction, and usually ranges from 5 to 50%.

Lower values than 5% tend to lead to a lower compensative capacity with respect to contraction stresses and hence to the formation of folds and irregularities. Moreover, the strength of the composite, which relies solely on the fibre bonding at the pore edges, suffers. Higher proportions than 50% tend to weaken the non-woven structurally to too great an extent because too little fibre material is present per unit area.

The non-woven interlining according to the present invention must contain thermoplastic, heat-settable fibres. Although its pores compensate the shaping stresses in the fibre assembly, the latter tends on removal of the applied external forces to resume its previous, flat shape. The particular shape to be conferred on the non-woven should therefore be set by hot-pressing, which is expediently done by means of an ironing press. The customary heat-setting conditions are 100 to 180"C and 0.2 to 1.5 N/cm2. Particularly preferred fibres are acrylic fibres, since they are particularly readily shapeabie at the heat-setting temperatures with only a small amount of pull tension required.This is because it has been found experimentally that the modulus of elasticity of an acrylic fibre drops sharply from 4915 MN/m2 at 20"C to 1913 MN/m2 at 100"C and finally to 245 MN/m2 at 1500C. Shaping disorders in the fibre assembly which are not compensated by the pores can therefore be arrested by the use of these acrylic fibres, owing to the favourable relationship between extensibility and temperature.

The thermoplastic fibres used according to the invention suitably have a denier-specific strength of 0.88 to 3.53 cN/dtex (single fibre strength 1.0 to 4.0 g/den, preferably 1 to 3.0 g/den). With higher strength values than these it is difficult for the shearing forces produced by the embossing roll to cut out the perforations completely. With lower strength values than these, the interlining lacks mechanical stability, a factor which is of importance for frequently worn pieces of clothing.

The pores can be embossed into the web in a known manner by using a pair of rollers, one of which is flat and the other has linear bosses which correspond in shape to the pores to be produced. The roller temperature is advantageously 180 to 210"C, and the linear pressure is advantageously 98 to 981 N/cm. At the same time as the formation of the linear pores the fibres are welded to one another around the edges of the pores. In setting the rollers care needs to be taken to ensure that the fibres which are not subjected to perforation are not exposed to any significant compressive force.

The non-woven thus treated is subsequently stretched by an amount which needs to be somewhat higher than corresponds to the contraction ratio required for the shaping. The term "contraction ratio" or "contractility" indicates the percentage reduction of a given length. This can be represented in terms of a formula as

where L,: original length, L1: length after contraction has taken place.

The process according to the invention additionally offers further advantages, namely as follows: 1. Owing to the linear shape of the pores the fibrous dust produced in the course of the perforating operation is limited.

2. Since it is possible to vary the contractility of the non-woven according to the inven tion over a wide range of values by prior stretching to an appropriate extent, there is no need for a large number of appropri ately designed embossing rollers to be kept available for different contraction ca pacities. The possibility of restricting the rollers to a few pore patterns therefore significantly facilitates the manufacturing process and reduces its cost.

The non-woven interlinings according to the invention are distinguished by a very soft, textile handle and exceilent intrinsic strength and shape stability because the fibre bonding occurs only in the pore walls. Owing to their good contraction properties they are equally suitable for collar interlinings, and for stiffening and shaping interlinings in front pieces of outerwear.

Example An embossing roll was used at 195"C and at a linear pressure of 490.5 N/cm to emboss a web having a weight per unit area of 100 g/m2 and consisting of acrylic fibres having a denier-specific strength of 2.47 cN/dtex (2.8 g/den) with a linear pore pattern extending parallel to the longitudinal axis of the web, and at the same time to heat-weld the pore edges. This was followed by stretching the non-woven in the transverse direction by a linear 30% and subsequent heat-setting at 1 50"C. The pore content relative to the total area was 23%, and the highest obtainable, length-specific contractility was 23%.

This non-woven was shaped into a collar interlining which, on ironing on, was found to be readily contractile on the inner side of the collar and similarly extensible on the outer side, without the appearance of any folds or other undesirable deformations. The interlining permanently retained its given curvature.

The invention is further illustrated by the accompanying drawings in which Figure 1 shows a web being pressed between a flat roll and an embossed roll having a linear embossed pattern as shown in Fig.

2A. The embossed portion generates in the web linear pores having a heat bonded periphery as shown in Fig. 2B, because a single fibre strength is weak. Afterwards the prepared non-woven fabric is extended transversely to the machine direction (MD), for example by a tenter machine, to produce a product as shown in Fig. 3 and this fabric is then heat-set.

Fig. 4A shows an interlining for a collar, which can be contracted by hot pressing us ing an iron so that the pores progressively contracted more and more from the top to the bottom of the material so as to produce a contracted fabric as shown in Fig. 4B.

It is preferred that any transverse line across the interlining passes through at least one pore, as shown in Fig. 5.

Claims (8)

1. A contractile non-woven interlining comprising a non-woven fabric composed of thermoplastic fibres which are settable by hot pressing, wherein the non-woven fabric has elongate, narrow pores distributed over its surface, fibres of the non-woven fabric immediately surrounding said pores being heat bonded to one another.

2. A contractile non-woven interlining as claimed in claim 1, wherein said pores are distributed so that any transverse line across the interlining passes through at least one pore.

3. A contractile non-woven interlining as claimed in claim 1 or 2, wherein the pores have the shape of narrow rectangles, ellipses or lenses with a length at least 3 times their average width prior to expansion and are arranged in lines generally parallel to one another along the fabric, occupying 5 to 50% of the total area thereof.

4. A contractile non-woven interlining as claimed in any of claims 1 to 3, wherein the non-woven fabric comprises acrylic fibres.

5. A contractile non-woven interlining as claimed in any of claims 1 to 4, wherein the fibres have a single fibre strength of 1 to 4 g/d.

6. A method for the preparation of a contractile non-woven interlining in which a web comprising thermoplastic fibres having a single fibre strength of 1.0 to 4.0 g/d is heatpressed by an embossing roll having a linear embossed pattern so as to form one or more lines of elongate, narrow pores on said web and simultaneously to heat bond fibres of the non-woven fabric immediately surrounding said pores to one another, the resulting non-woven fabric is then extended transversely to the lines of elongate narrow pores to an extent depending on the desired contraction ratio, and the extended fabric is heat set.

7. A method as claimed in claim 6, wherein the hot pressing to form narrow elongate pores is carried out at 180 to 210 C and 98 to 981 N/cm.

8. A method as claimed in claim 6 and substantially as hereinbefore described or illustrated.