IE48667B1 - Polypropylene fibre which is difficult to ignite and a process for its manufacture - Google Patents

Abstract

1. Polypropylene fibre which is difficult to ignite and has an ethylene content of 0 to at most 10% by weight, characterised in that it contains 0.5 to 10% by weight of 1,3,5-tris-(2,3-dibromopropyl)-2,4,6-trioxo- hexahydrotriazine and 0.15 to 3.5% by weitht of Sb2 O3 , and per mol of the triazine compounds 0.05 to 1.5 mols of an organic tin compound of the general formula see diagramm : EP0005496,P6,F1 in which R1 and R2 , which can be identical or different, each denote an alkyl or cycloalkyl radical and X and Y, which can be identical or different, each denote an alkyl or cycloalkyl radical, the radical of an organic acid, which can optionally contain a further esterified carboxyl group, the radical of an inorganic acid or a thioalkyl group, which can optionally carry a carboxyl group esterified with aliphatic alcohols, or X and Y together denote oxygen, the radical of a dibasic inorganic or organic acid or a radical of the formula -S-(CH2 )n -COO- in which n is defined as the integer 1 or 2, if appropriate in addition to the customary lubricants, pigments and/or stabilisers.

Description

The present invention relates to a process for the manufacture of polypropylene fibres which are difficult to ignite.

In comparison with other synthetic fibres, polypropy5 lene fibres which have been manufactured by the melt spinning process have remarkably good strength and wear resistance which make them particularly suitable, in the form of textile sheetlike structures, as woven fabrics or fleeces for use as a raw material for textiles for domestic use or needle felt floor coverings, and for woven fabrics or fleeces for industrial purposes. These good mechanical properties are offset by the disadvantage of the relatively good flammability of the fibres.

As is known, in latter years, fire accidents in the home or in hotels and restaurants have greatly increased and severe damage to capital goods and also severe loss of human life have been caused with the increasing use of synthetic fibres or laminates as a result of these materials being flammable to a greater or lesser extent. In consequence, chemical compounds with which natural fibres and also synthetic fibres can be impregnated in a flame-retardant manner have been developed to an increasing extent. (See, for example, the journal Textilpraxis internat. 1975, volume 12, 1685 et seq.).

It is proposed, according to German Offenlegungsschrift 2,743,127, to flameproof fibres or fabrics of polyesters, poly25 amides or polyacrylonitrile by applying an aqueous dispersion of bromine-containing, aromatic, aliphatic or cycloaliphatic compounds, which also contains a monomeric or polymeric organic - 3 tin-IV-compound, by spraying, printing or, in particular, by absorption and subsequent fixing by treatment at temperatures up to 13O-22O°C. The amount of the bromine compound, which is preferably hexabromocyclododecane, in this instance is chosen so that, after the heat treatment, the amount of bromine present is 1 to 8% by weight, relative treated material. The amount of organic tin compound should be 5 to 20% by weight of the bromine compound employed. Finally, the addition of a dispersing agent and/or protective colloid to the aqueous liquor is furthermore also recommended, in order to facilitate the application. All these substances produce a relatively heavy coating on the surface of the fibre, resulting in a tendency of the fibre to yellow, which is to be counteracted by the addition of the organic tin compound.

Apart from the fact that a surface coating of this type cannot remain without affect on the handle and other properties which affect shape, this coating is also liable to be worn away during use and cleaning, which must lead to a reduction in the flame-retardant properties.

For polypropylene fibres, which, as is known, have hydrophobic properties, such an impregnation is hardly suitable at all.

It is an aim of the present invention to provide a polypropylene fibre which is flameproofed not by impregnation, but by incorporation of a flameproofing agent into the synthetic substance. Against this,however, was the fact that neither the properties which affect processing nor the strength, the handle and finally also the colour should suffer by this addition. Apart from this, there was the requirement that the incorporated flame-retardant should not have a corrosive action on the spinning equipment, such as the extruder, spinning pump and spinnerette plates, and that odour formation should be as - 4 low as possible, in spite of the relatively high temperatures.

Providing polypropylene mixtures with a flameproof finish using a flame-retardant system consisting of 2 to 7% by weight of 1,3,5-tris-(2, 3-dibromopropyl)-2,4,6-trioxohexa5 hydrotriazine and 0.5 to 2% by weight of antimony trioxide is described in British Patent Specification No. 1,459,383.

This flame-retardant system has on the one hand the advantage that the brominated triazine compound, being of low volatility, is not sweated out of the polypropylene, and that the mixture remains stable to heat up to about 220°C and the flame-retarding active component does not tend to split off hydrogen bromide, which other polybromine compounds do and which results in discolorations of the product, an increase in the melt index of the polymer melt and, last but not least, severe corrosion of the extruder and the like.

In contrast, at higher temperatures of about 24O-3OO°C, such as are necessary for the melt spinning process for polypropylene, partial decomposition occurs, even with this flameretardant system, and hydrogen bromide is split off, resulting in corrosion of the apparatus, which was unacceptable for the manufacture of the fibre, and discoloration of the fibre.

It could now be found, surprisingly, that a certain group of organic tin compounds which carry at least two alkyl groups have a stabilising effect on the brominated triazine compound having a flame-retarding action, so that the polypropylene mixture containing this compound can be subjected to the melt spinning process without difficulty, neither corrosion of the apparatus nor an unpleasant odour nuisance being recorded, in spite of the high temperatures· required, and the physical properties of the fibre being fully satisfactory. Above all, it was surprising that addition of these tin compounds, in contrast to other compounds having a stabilising effect on - 5 halogen compounds, does not impair the flame-retarding action of the brominated triazine compound.

The invention accordingly provides a polypropylene fibre which is difficult to ignite and has an ethylene content of 0 to at most 10% by weight, which is characterised in that it contains 0.5 to 10% by weight of 1,3,5-tris-(2,3-dibromopropyl)-2,4,6-trioxo-hexahydrotria2ine and 0.15 to 3.5% by weight of antimony trioxide, and per mol of the triazine compound, 0.05 to 1.5 mols of an organic tin compound of the general formula in which and R2, which can be identical or different, each denote an alkyl or cycloalkyl radical and X and Y, which can be identical or different, each denote an alkyl or cycloalkyl radical, the radical of an organic acid, which can contain a further esterified carboxyl group, the radical of an inorganic acid or a thioalkyl group, which can carry a carboxyl group esterified with an aliphatic alcohol, or X and Y together denote oxygen the radical of a dibasic inorganic or organic acid or a radical of the formula -S-(CH ) -C00-, in which n is defined 2 n as the number 1 or 2, if appropriate in addition to the customary lubricants, pigments and stabilisers. The alkyl radicals R^ and R2 in this compound can preferably have 3 to 10 carbon atoms.

If X and/or Y likewise denote alkyl, those radicals with 3 to 10 C atoms are also preferred here. Examples which may be mentioned of compounds of the formula I which have a good action are: dibutyl-tin oxide, dioctyl-tin oxide, tetra-n-octyl-tin, di-n-butyl-tin dilaurate, di-n-octyl-tin di-laurate, di-n-octyltin-phosphite, dioctyl-tin maleate, di-butyl-tin maleate, tri48667 - 6 phenyl-tin acetate, di-n-octyl-tin di-(thioglycolic acid n-octyl ester), dibutyl-tin di-(thioglycolic acid octyl ester), dioctyl-tin di-(maleate methyl ester), dibutyl-tin di-(maleate methyl ester), dibutyl-tin dibenzoate, dibutyl-tin phthalate and dioctyl-tin thioglycolate whilst, for example, other tin compounds such as monooctyl-tin oxide or calcium oxide or hydroxide indeed have an excellent stabilising effect but at the same time destroy the flame-retarding action of the brominated triazine compound employed according to the invention.

Those tin compounds of the formula I in which X and Y each represent a maleic acid ester radical or X and Y together are a maleic acid radical are particularly preferred.

It is very advantageous that the brominated triazine compound constituent in the fibre already displays its complete action when small amounts are added, so that the fibre properties are thereby virtually not influenced. The best combination of flame-retarding action with least influence on the properties of the fibre is achieved at a triazine compound content in the fibre of 1 to 3% by weight, whereupon the amount of synergistic agent can then preferably remain below 1% by weight. The preferred amount of tin compound of the formula I is then 0.1 to 0.3 mol per mol of triazine compound.

The present invention also relates to a process for the manufacture of the fibre, according to the invention, which is difficult to ignite, which is characterised in that a mixture of polypropylene with an ethylene content of 0 to at most 10% by weight and containing 0.5 to 10% by weight of 1,3,5-tris-(2,3dibromopropyl)-2,4,5-trioxohexahydro-triazine and 0.15 to 3.5% by weight of antimony trioxide as well as 0.05 to 1.5 mols, per mol of the triazine compound, of the organic tin compound of the formula I, and also, if appropriate, of lubricants, pigments and/or stabilisers, is subjected to the melt spinning process. - 7 In this process, the finished polypropylene mixture, which is present, for example, in the form of granules, can be melted and spun. However, it is also possible for the additives to the system having a flame-retarding action to first be added in the extruder, for example by adding the triazine compound, the Sb^O^ an<^ ^·*·η compound of the formula I to the molten polypropylene via a side extruder.

In this procedure, these additives can be handled as pure substances or as a concentrate (master batch). Either the polypropylene or other synthetic substances compatible with the polypropylene, such as, for example, other polyolefines, are used as binders in the latter case.

The polypropylene melt provided with the flame-proofing agent in this manner can be spun, either by the short spinning process, which is characterised by low take-off rates (5 to 50 m/minute), or by the conventional melt spinning process, which has typical take-off rates of 100 to 1,000 m/minutes, or by the so-called high-speed spinning process (take-off rate>1,000 m/minute), or by the so-called jet-spinning process, up to extreme rates of 4,000 n/minute, or can be processed to a continuous filament web.

The fibres produced in this manner can be stretched, crimped, further processed to staple fibres and provided with the customary finishing agents in the same way as polypropylene fibres which have not been provided with a flame-retardant finish.

Before spinning the polypropylene melt which has been provided with a flame-retardant finish, pigments, anti-oxidants, light stablisers and lubricants, and also free radical-forming peroxides can also be added, in the form of the pure substances or as concentrates, without a loss in action occurring. The peroxides cause degrading of the molecule, with a lowering of - 8 the molecular weight, and can exert a favourable influence on the fibre properties by the levelling out of the molecular weight which thereby occurs. Surprisingly, the flame-retarding action of the additives according to the invention is not im5 paired by this treatment.

The low flammability of the fibre according to the invention was examined in the small-scale burning test in accordance with DIN 53,438.

The burning test is carried out in accordance with the 10 DIN standard using textile sheet-like structures, the following assessnent criteria being used; a) The burned-out length is less than 150 mm, the sample is extinguished by itself. Class b) The tip of the flame from the burning test pieces reaches 15 the 150 mm measuring mark in 20 or more seconds. Class c) The tip of the flame from the burning test pieces reaches the 150 mm measuring mark in less than 20 seconds. Class K^. The sample is flammable.

The effects of thermal decomposition of the flame20 proofing agent, the discoloration of the polypropylene melt thereby arising and the corrosion associated with the decomposition can easily be investigated by means of multiple extrusion at high temperatures with the aid of a laboratory extruder.

Extruder data: Screw: 19.1 mm diameter, screw length 20 D, polyolefine screw, stages, compression ratio 1 : 4 Circular die: 5 mm diameter, water bath, strand-granulating device.

For all experiments, the screw speed was kept constant at 100 revolutions per minute; the material temperature data - 9 48667 relate to the temperature measurement at the screw tip.

The HBr corrosion effect of the decomposition is determined by the following method: The sample of granules, weighing 15 g, obtained after extrusion of the melt and cooling and granulation of the strand is pressed to a sheet 70 x 70 x 2 mm at 230°C in a press, in contact with a degreased and highly polished steel plate, for a period of 7 minutes. After cooling, the polypropylene sheet is removed carefully from the steel, the steel plate is then stored at 23°C and at 100% relative atmospheric humidity for 24 hours and is subsequently assessed as follows: rating 0: completely free from corrosion rating 1: slight rust formation (detectable by wiping with a clean cottonwool pad and by the discoloration of the cottonwool) rating 2: surface uniformly covered with rust rating 3: surface covered with severe rust formation.

The multiple extrusion experiments were carried out with granulated product both at 25O°C and at 28O°C. The additives were kneaded in under gentle conditions, at a material temperature of 210°C. It should be mentioned that a polypropylene with a high molecular weight was consciously chosen for the investigation of the thermal decomposition of the flame-retardant so that the multiple extrusion to be carried out at the high test temperatures (250 to 28O°C) can readily be carried out with intermediate granulation in each case.

In these experiments, it could furthermore be established that the size of the molecular weight of the polypropylene has no influence on the splitting off of HBr from the flame-retardant.

The examples which follow are intended to illustrate the manufacture and the properties of the fibre according to the invention, without intending to thereby limit the invention. - 10 Example 1 to 10: A polypropylene mixture based on a polypropylene with a melt index of 12 and having the following composition: 0.2% by weight of calcium stearate, 0.1% by weight of 2,65 di-tert.-butyl-p-cresol, 0.1% by weight of penta-erithrityl tetrakis-[3-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionate]/ 3.1% by weight of 1,3,5-tris-(2,3-dibromopropyl)-2,4,6trioxohexahydrotriazine, 1.0% by weight of antimony trioxide, 1.0% by weight or 2.0% by weight of the organic tin compound indicated in the table and 94.2% by weight of polypropylene, is spun to fibres with an overall gauge of 346 tex with 68 individual filaments on a melt spinning unit with a screw diameter of 25 mm and a length of 24 D, at a material temperature of 255°C, a screw speed of 74 revolutions per minute and a take-off rate of 470 m/minute.

The primary filaments produced in this manner were stretched on a stretch and twist machine at a temperature of 130°C and a stretching ratio of 1 : 3. The final gauge of the resulting filaments was 1.15 tex and the gauge of the individual filaments was 1.7 tex. The properties of the fibres thus obtained are shown in Table 1 which follows. σ § Ό 3 Ο Ο ρ· Φ ρ· Φ Η* Ρ* £ 0 rt tr rt 0 Ω 3* Ρ 3* Ω Ω Ρ MJ rt Μ* ft 0 ft Μ wMJ Ρ» MJ Ρ k< ρ·1 Ρ* Ρ· ρ. ρι 1 Φ 1 φ I Ω 1 rt to ft to rt ft Ρ· rt κ* rt ρ* Φ Ρ- thxoglycolate 1 0.56 Φ 3 κ ~ Ρ* Ρ· ) Φ 3 Κ Ρ. Ρ· I Φ Φ rt Φ Ω ΡΡ q, Ρ· Ο I Ω ζ-. ft ft »< 3* Μ Ρ· Φ ? ω £ κ -Ρ fc> Η* Ρ« κ; ο Ω Ω Ο ft Ρ·< Ρ· ρι Ω I ft Φ ΡΩ a Ρ· α Οι μ· ο ι ω — rt rt tr W Ρ· Ο Φ I to ft Φ Κ a σ Η Η ft Ρ· φ a κ & Η· I a σ Φ Ρ* ft Ο a* ω £ Ρ* Ρ» Φ I to rift Η· Φ 3 h Ρ. Η· I σ Ρ· tr ρ <+ Η I ft Η· Ο &* Ρ ft *ί Ρ1 ι ft Η· § Η- Ρ* Pj Φ Ρ* φ φ ft φ Φ Φ ftΦ Ο ρ ο ο Ο Ρ ο Ο • • • 00 ω ιη 4* Ο υι Ο A Ο Ο ω Ο w ω to σ> σ> -ο co ιη ιη Οι σ» οι Ο Ln «ο < οι σι σι Ο w *J Φ Μ ft Ό Κ Φ Η- Κ Φ Ν 3 Ρ- Ο 3 Η Φ Ο Ηϊ Ω ST Ν <£ Example Organic tin compound % by weight Mols of Tensile Elongation No. of compound compound I strength, at break - 12 Example 11: Polypropylene mixtures which were processed to fibres according to Examples 1 to 7 and 10 were subjected to the burn ing test according to DIN 53,438 (small-scale burning test): The fibres were wound together to form a yarn of 230 tex/136 individual filaments and the yarn was then processed on a circular knitting machine to give a knitted fabric with a 2 weight per unit area of 530 g/ra . This sheet-like structure was tested in the small-scale burning test by edge flaming.

The results are summarised in Table 2; Table 2 Average values of 5 separate determinations Example No. Burning time (seconds) Burned-out length (mm) Class 1 15 36K1 2 16 37 3 17 42 4 14 38 5 5 15 33 6 21 50Ki 7 11 35K1 10 13 68K1 Example 12: Mixtures which were processed to fibres according to Examples 1, 2, 4, 8, 9 and 10 were subjected to the corrosion test. A mixture which contains the same constituents as the mixtures according to Example 1 to 10 but to which no tin compound of the formula I has been added was also run as a blank sample. The results are summarised in Table 3. - 13 Table 3 Mixture according to Example Amount of the added, of compound formula I in % by weight Degree of corrosion 5 1 1 0 2 1 0 4 1 0 8 2 0 9 2 0 10 10 1 0 blank sample

Claims (12)

CLAIMS:

1. Polypropylene fibre which is difficult to ignite and has an ethylene content of 0 to at most 10% by weight, characterised in that it contains 0.5 to 10% by weight of 5 1,3,5-tris-(2,3-dibromopropyl)-2,4,6-trioxo-hexahydrotriazine and 0,15 to 3.5% by weight of sb 2 O 3’ and Ρθ Γ mo ^- of the triazine compound, 0,05 to 1.5 mols of an organic tin compound of the general formula (I) 10 in which R^ and R^, which can be identical or different, each denote an alkyl or cycloalkyl radical and X and Y, which can be identical or different, each denote an alkyl or cycloalkyl radical, the radical of an organic acid, which can contain a further esterified carboxyl group, the radical of an inorganic 15 acid or a thioalkyl group, which can carry a carboxyl group esterified with an aliphatic alcohol, or X and Y together denote oxygen, the radical of a dibasic inorganic or organic acid or a radical of the formula -S-(CH„) -C00-, in which n is de2 n fined as the number 1 or 2, if appropriate in addition to the 20 customary lubricants, pigments and stabilisers.

2. Polypropylene fibre which is difficult to ignite, according to Claim 1, characterised in that tin compounds of the formula I which are used are those in which X and Y each represent a maleic acid alkyl ester radical or together repre25 sent a maleic acid radical.

3. Polypropylene fibre which is difficult to ignite, according to Claims 1 and 2, characterised in that the triazine compound content is 1 to 3% by weight. - 15

4. Polypropylene fibre which is difficult to ignite, according to Claim 3, characterised in that the amount of Sb 2 0 3 is 0.3 to 1% by weight.

5. Polypropylene fibre which is difficult to ignite, according to Claims 1 to 4, characterised in that the amount of tin compound of the formula I is 0.1 to 0.3 mol, per mol of triazine compound.

6. Process for the manufacture of the polypropylene fibre which is difficult to ignite, according to Claims 1 to 5, characterised in that a mixture of polypropylene which has an ethylene content of 0 to at most 10% by weight and which contains 0.5 to 10% by weight of 1,3,5-tris-(2,3-dibromopropyll2,4,6-trioxo-hexahydrotriazine and 0.15 to 3.5% by weight of antimony trioxide, and per mol of the triazine compound, 0.05 to 1.5 mols of an organic tin compound of the general formula (I) in which and R^ each denote an alkyl or cycloalkyl radical and X and Y each denote an alkyl or cycloalkyl radical, the radical of an organic acid, which can contain a further esterified carboxyl group, the radical of an inorganic acid or a thioalkyl group, which can carry a carboxyl group esterified with an aliphatic alcohol or X and Y together denote oxygen, the radical of a dibasic inorganic or organic acid or a radical of the formula -S-(CH.) -C00-, in which n is defined as the number 2 n 1 or 2, and if appropriate also lubricants, pigments and/or stabilisers, is subjected to the melt spinning process. - 16

7. Process according to Claim 6, characterised in that the finished polypropylene mixture is melted and spun.

8. Process according to Claim 6, characterised in that the polypropylene is melted, the melt is mixed with a concentrate 5 of the triazine compound, the Sb^O^ and the tin compound of the formula I, in which polypropylene or other polyolefines are used as a binder, and, after mixing, the mixture is fed directly to the spinnerette.

9. Process according to Claims 6 to 8, characterised in 10. That the finished spinning mixture is subjected to degradation by free radical-forming substances before the spinnerette.

10. Polypropylene fibre as claimed in any one of Claims 1 to 5 and substantially as hereinbefore described.

11. A process as claimed in any one of Claims 6 to 9 and 15 substantially as hereinbefore described.

12. Polypropylene fibre whenever made by the process claimed in any one of Claims 6 to 9 and 11.