IE904423A1

IE904423A1 - Flame-retardant web with binder filaments

Info

Publication number: IE904423A1
Application number: IE442390A
Authority: IE
Original assignee: Hoechst Ag
Priority date: 1989-12-09
Filing date: 1990-12-07
Publication date: 1991-06-19
Also published as: KR910012448A; JPH03260155A; EP0432620A1; PT96114A; CA2031812A1; DE3940713A1

Abstract

There is described a flame-resistant, fusion-consolidated spunbonded composed of load-bearing filaments and fusible binding filaments. The binding filaments consist of a modified polyethylene terephthalate into whose polymer chain have been condensed phosphorus-containing chain members and which as a result has permanently flame-resistant properties.

Description

Flame-retardant web with binder filaments The present invention relates to a flame-retardant, 5 binder-consolidated spunbonded web composed of loadbearing filaments and flame-retardant binder filaments made of a modified polyester.

Binder-consolidated spunbondeds and flame-retardant spunbondeds are already known.

For instance, DE-C-22 40 437 and DE-A-36 42 089 describe binder-consolidated spunbondeds in which not only the load-bearing filaments but also the binder filaments can consist of polyesters. The spunbonded web described in DE-C-22 40 437 is based on relatively coarse filaments of more than 8 dtex. The proportion of binder filaments is 10-30%, preferably between 15-25%. In respect of the spunbonded web described in DE-A-36 42 089 filament deniers of 5 dtex and 12 dtex are reported in the Examples; the proportion of binder filaments is between and 50%, preferably between 15 and 30%. The basis weight is reported to be greater than 120 g/m2.

A similar spunbonded web is described in DE-A-34 19 675. This spunbonded web, which is to be used as a reinforcing layer in roof and sealing membranes, possesses load25 bearing filaments made of polyethylene terephthalate and binder filaments made of polybutylene terephthalate. The proportion of binder filaments is supposed to be 10 to 30%. The Examples record basis weights of 100, 140 and 180 g/m2, filament deniers of 4.5 and 5.6 dtex and a binder filament proportion of 10 to 30%.

Low-flammability polyesters which contain phosphoruscontaining compounds are known for example from FR Patent 1,196,971. It describes copolyesters which contain - 2 phosphoric acid units and are fire- and heat-resistant. These copolyester products can be used as flameproofing and impregnating agents and as adhesives or coatings and also as intermediates. However, spinning them into filaments and fibers is not possible, since a high phosphorus content causes embrittlement of the products.

It is also known to manufacture spunbondeds from flameretardant polyesters by incorporating into the polyesters phosphorus compounds (for example polyphosphonates or certain phosphoric esters with halogen-containing aromatic dihydroxy compounds) which will not form part of the polymer chain. Although use of such additives led to good, albeit impermanent, fire resistance properties, it is impossible to overlook some disadvantages which are due in particular to the appreciable migration of the additives within the polymers.

On the one hand, this makes the polymer products toxic to a certain degree; on the other hand, however, the additives become easily removable, for example in the course of the dry cleaning of fiber articles produced from the polymer products. As a consequence of removal of the additives the polymer products then of course lose their flame-resistant properties.

In some instances, furthermore, the fairly viscous polymeric additives are difficult to mix completely homogeneously with the polyesters and, what is more, they lead to undesirably high glycol contents if they are added even as the polyester is being formed. Compared with polymers which contain P-compounds built into the chain molecules, the polymers which contain P-compounds as additives also have poorer dyeing properties.

All the prior art spunbondeds are either relatively heavyweight, coarse-denier products having a comparatively high binder content but inadequate flame-retardant properties, or else flame-resistant polyester spunbondeds - 3 which admittedly have proper flame resistant properties but are difficult to process and have unsatisfactory textile properties. Polyesters which combine good flameretardant properties with good spinning and textile properties are described in DE-C-23 46 787. However, spunbondeds produced from such modified polyesters, like all purely thermally consolidated spunbondeds, can be made only up to a basis weight of about 50 g/m2, since above this limit an increase in delamination tendency is observed.

Thermoplastic polyesters (specifically polyethylene terephthalate and polybutylene terephthalate) are relatively nonflammable, since they melt on heating and drip away from the flame. To manufacture spunbondeds of high basis weights, therefore, mixtures are frequently used of the two polyesters in which the polybutylene terephthalate filaments serve as binder filaments on account of their lower melting point. Surprisingly, however, this leads to a deterioration in the flame-resistant proper20 ties compared with those of pure polyethylene terephthalate spunbondeds.

It is an object of the present invention to produce a flame-resistant, binder-consolidated, low-denier lightweight spunbonded web which has a basis weight of above 50 g/m2, and a high dynamical efficiency, i.e. a long flex life.

This object is achieved by a flame-resistant binderconsolidated unmodified polyester, preferably polyethylene terephthalate, spunbonded web as classified at the beginning, wherein the binder filaments are low-flammability polyesters formed from dicarboxylic and diol components and containing cocondensed P-containing chain members. Preferably, the basis weight of the spunbonded web is above 50 g/m2, and particularly preferably the load-bearing filaments and the binder filaments have a linear density within the range between 1 and 7 dtex. The - 4 proportion of binder filaments can also be below 10% by weight, depending on the intended use.

It has been found, surprisingly, that the novel polyester webs with the specifically modified polyesters as binder filaments possess very good flame-retardant properties, but they can also be manufactured in the form of lowdenier lightweight products and what is more that they also have good strength properties.

In the case of fiber blend textiles, including those 10 involving polyester fibers, it is a well known fact that the flammability rating of the blend fabric can never be predicted from the flammability rating of the individual components, so that the properties of the spunbonded web according to the present invention were not foreseeable.

This is true of blend fabrics even if they are made lowflammable in some way; for instance, polyethylene terephthalate is relatively fire-resistant, whereas blend fabrics of polyethylene terephthalate with polybutylene terephthalate binder fibers are surprisingly signifi20 cantly more flammable.

The fact that polyester and also cellulose are significantly less flammable alone than their blends is also repeatedly confirmed by the literature (Textilveredelung 8., 1973, pages 310/311).

Preferably, the basis weight of the spunbonded web is between 50 and 200 g/m2, the filament denier between 1 and 10 dtex, in particular 1 and 5 dtex, and the proportion of binder filament is between 5 and 20 percent by weight. The binder filaments preferably have a smaller denier than the load-bearing filaments.

The load-bearing filaments of the spunbonded webs according to the present invention preferably consist of polyethylene terephthalate. The binder filaments are preferably made of a modified polyethylene terephthalate, - 5 for example as described in DE-C-23 46 787, having a correspondingly reduced melting point. The melting point of the binder filaments of the spunbonded web according to the present invention is 20°C, preferably 15eC, below the melting point of the matrix filaments. It is also very surprising that even such a small difference between the melting points of the binder and matrix filaments ensures satisfactory consolidation of the webs without as much as incipiently melting the matrix filaments.

The polyesters of the binder filaments consist of dicarboxylic acid and diol components together with phosphorus-containing chain members which comprise structural units of the formula II -O-P-R-C' I· RX O which account for about 3-20 mole percent of the acid 15 component of the polyester, in which R is a saturated, open-chain or cyclic alkylene radical of preferably 1-15 carbon atoms or an arylene or aralkylene radical and Rx is an alkyl radical of preferably up to 6 carbon atoms, or an aryl or aralkyl radical.

The preferred dicarboxylic acid component is terephthalic acid, but other dicarboxylic acids are used as well, preferably as cocomponents. Examples are isophthalic acid, 5-sulfoisophthalic acid, 5-sulfopropoxyisophthalic acid, naphthalene-2,6-dicarboxylic acid, biphenyl-p,p'dicarboxylic acid, p-phenylene diacetic acid, 4,4'oxydibenzoic acid, diphenoxyalkanedicarboxylic acids, trans-hexahydroterephthalic acid, adipic acid, sebacic acid and 1,2-cyclobutanedicarboxylic acid.

Suitable diol components, besides ethylene glycol, - 6 include as cocomponents for example 1,3-propanediol, 1,4butanediol and higher homologs of 1,4-butanediol and also 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, etc.

If in addition to a terephthalic acid another one of the abovementioned dicarboxylic acids is used, it is preferably used in an amount not significantly more than about 10 mole percent of the total acid component. A similar rule applies to the composition of the diol component. If here for example a further diol component is used as a cocomponent with ethylene glycol, the amount of the former is preferably likewise not significantly more than 10 mole percent of the total diol component.

In a further embodiment of the invention, the binder filaments are used to introduce an antistat, for example carbon black, into the spunbonded web.

The spunbonded web according to the present invention can be produced by means of any known web formation process, in particular by one involving the use of a rotating infringement plate and downstream guide surface. The web is preferably laid from successive rows of spinnerets to produce a layered structure composed of load-carrying filaments and flame-resistant binder filaments. Advantageously, the two outer layers do not contain any binder filaments.

If the matrix and binder filaments are spun simultaneously from adjacent spineret packs or else from a single pack, it is important to achieve very uniform intermingling of the two types of fiber in order to ensure a stochastic distribution of the bonds within the mixed web. However, the binder filaments can also be extruded together with the load-carrying filaments in the form of combined filaments in which the two components are arranged side by side and which are customarily produced by the spinning/extrusion technique. The - 7 cross-sections of individual fibers can be varied widely with this technique, being for example round, sickleshaped or multilobal. This technique and other possible techniques for introducing binder fibers are described for example in DE-A-34 19 637 and DE-C-22 40 437.

Usually, no needling of the laid filaments is necessary, only a thermal preconsolidation, followed by a final thermal consolidation, for example with a smooth or an embossed roll. Particularly preferably, thermal con10 solidation is effected with hot air, for example in perforated cylinder fixing means, which may be followed by a pair of embossing rolls.

Particularly lofty spunbonded webs are obtained with a minimum proportion of binder filaments and perforated drum fixation. These spunbonded webs then also have a surface structure of many fiber ends, which distinctly increases the adhesion of coating materials, for example of PVC or bitumen. Such lofty spunbondeds with a fiberrich surface are also suitable for manufacturing filter materials.

The advantages of the subject-matter of the present invention are in particular the following: 1. Unproblematical formation of the spunbonded web from load-carrying filaments and flame-resistant binder filaments. 2. Low flammability, even from low proportions of flame-resistant binder filaments. 3. The textile and comfort properties of the spunbondeds produced from the filaments according to the present invention, compared with those of the corresponding products which have not been rendered flame-resistant, are as good as unchanged. By contrast, most known fire-retardant finishes have a - 8 fairly adverse effect on textile structures in respect of the properties mentioned. 4. Excellent laundering and drycleaning resistance of the flameproofing.

. Excellent dyeability of filaments of the spunbonded webs according to the present invention and of textile products produced therefrom, since the flameproofing effect is not due to a superficial finish. 6.

There is no danger of the flameproofing agent being rubbed off. 7. On application of a flame to the web or to textiles manufactured therefrom virtually no melt droplets appear; instead, the product becomes only carbonized.

A significant advantage here is the fact that there is less skin contact with burning material and hence a low risk of burns. 8. Production of fine-denier lightweight spunbondeds. 9. High dynamical efficiency.

Flame-resistant webs can be used in the production of textiles for many purposes, for example for making protective clothing for firefighting and for other types of work at risk from fires (refinery and blast furnace work, welding), as furnishings and curtain fabrics, for upholstery materials, as roof membranes, military fabrics, tent fabrics and awnings, but also for textile floor coverings or else as components of seat covers in motor vehicles or aircraft.

The addition of antistats - carbon black in the simplest 30 case - in the melt cylinder, moreover, makes it possible to use the spunbonded web according to the present - 9 invention in explosion hazard zones or else as medium for clean rooms. filter

Claims

Claims:

1. A flame-resistant binder-consolidated spunbonded web formed from load-carrying filaments and binder filaments made of polyester, wherein the binder filaments are made of a modified polyethylene terephthalate which has flame-resistant properties.

2. The spunbonded web as claimed in claim 1, having a basis weight of about 50 g/m 2 , preferably between 50 and 200 g/m 2 , preferably between 50 and 150 g/m 2 .

3. . The spunbonded web as claimed in at least one of the above claims, wherein the load-carrying filaments and binder filaments have deniers between 1 and 10 dtex, preferably between 1 and 5 dtex.

4. The spunbonded web as claimed in at least one of the above claims, wherein the denier of the binder filaments is less than that of the load-carrying filaments.

5. The spunbonded web as claimed in at least one of the above claims, wherein the proportion of binder filaments is not more than 20% by weight, preferably between 5 and 20% by weight.

6. The spunbonded web as claimed in at least one of the above claims, wherein the load-carrying filaments are made of polyethylene terephthalate.

7. The spunbonded web as claimed in at least one of the above claims, wherein the low-flammability binder filaments are made of polyesters into which phosphorus-containing chain members have been condensed. 8

8. The spunbonded web as claimed in at least one of the above claims, wherein the low-flammable binder filements are made of polyesters formed from - 11 dicarboxylic acid and diol components and containing as cocondensed units the P-containing chain members comprising structural units of the general formula O (I - O - P - R I R 1 c ii which account for 3 to 20 mole percent of the acid component of the polyester and in which R is a saturated, open-chain or cyclic alkylene radical or an arylene or aralkylene radical, and Ri is an alkyl radical up to 6 carbon atoms, or an aryl or aralkyl radical.

9. The spunbonded web as claimed in claim 8, wherein in the P-containing structural units R is -CH 2 -CH 2 - or -C 5 H 4 - and R x is -CH 3 or C s H 5 .

10. The spunbonded web as claimed in at least one of the above claims, wherein the binder filaments contain an antistat, in particular carbon black.

11. A flame-resistant binder-consolidated spunbonded web according to claim 1, substantially as hereinbefore described.