AU427791B2 - Flame-retardant regenerated cellulose filaments - Google Patents

Description

1 4,7 5 9 /7o This invention relates to regenerated cellulose filaments having flame-retardant properties and to a process for making them. Regenerated cellulose filaments made by the viscose process have been rendered flame-retardant by the use of tris (2,3 dibromopropyl) phosphate vwhich has been applied as a solution to a fabric or garment as described in U.S. Patent Specification No. 2,574,515, and which has also been incorporated into the viscose prior to spinning the filaments as described in the specification of our U.K. Patent Specification No. 1,158,231. Regenerated cellulose fabrics and garments have also been given flame-retardant properties by impregnating them with a polymer obtained by reacting a tetrakishydroxymethyl phosphonium salt salt) with ammonia or an amino compound, for example urea or melamine. Flame-retarding polymers of this type polymers) are described in U.K. Patent Specifications Nos. 906,314, 935,098 and 938,989. The usual process of applying these T.H.P. polymers is to form a low molecular weight, water-soluble precondensate, apply this to the fabric and complete the condensation and curing reactions on the fabric, for example by an ammonia treatment. We have also put these T.H.P. polymers in the cured state into viscose by reducing their mean particle diameter to below 4 microns and then dispersing them in the viscose------ prior to spinning. However, at concentrations of T.H.P. polymer necessary to impart adequate flame-retardant properties to the regenerated cellulose filaments, it was found that the mechanical properties of the filaments became

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We have now found that certain T.H.P. polymers and

T.D.B.P.P. together in regenerated cellulose filaments made

by the viscose process have a synergistic effect on the flame-

retardant properties of the filaments, giving improved

properties compared with the sane concentrations of either

of the combinants above.

Accordingly, the present invention comprises flame-

retardant regenerated cellulose filaments incorporating both

T.D.B.P.P. and a polymer made by reacting tetrakishydroxy-

methyl phosphonium chloride or a precondensate

formed by the reaction of 2 moles of T.H.P.C. and 1 mole

of urea, with excess ammonia.

The invention includes a process for making flame-

retardant regenerated cellulose filaments comprising

incorporating in a viscose both T.D.B.P.P. and a polymer made

by reacting T.H.P.C. or a precondensate formed by the reaction

of 2 moles of T.H.P.C. and 1 mole of urea, with excess ammonia

and spinning the viscose into a regeneration bath to form filaments. The precondensate reactants may also include up to 0.12 mole melamine. The precondensate may be prepared as an aqueous solution by refluxing the reactants in an aqueous medium and then rapidly cooling the reaction mixture. Suitable conditions comprise about a 50 per cent by weight aqueous solution of the reactants with a reflux time of 30 to 60 minutes. The method of making the polymer may be the same using either an aqueous T.H.P.C. solution or the aqueous preconden- sate solution and may comprise slowly adding either of these

1 4,75 9/70 solutions to an excess of an aqueous solution of ammonia whilst stirring the mixture. The polymer formed is then preferably oxidised this may be carried out in situ using hydrogen peroxide solution to ensure that the phosphorus is all in the pentavalent state; this avoids any adverse affect on the dyeability of filaments incorporating the

polymer. The polymer may then be filtered from solution washed ith water to remove any chloride ion and then dried. The drying is preferably carried out under vacuum at a temperature of 1050 to IIO0 C as this gives a polymer which will disperse in water to an extent of 15 per cent by weight. This compares with 12 per cent by weight for polymer dried at 700C. The particle size of the polymer should be sufficiently small to be able to spin viscose containing polymer particles without blocking up the jet holes. We prefer the mean particle diameter to be preferably not greater than about 4 microns and better still not greater than 2 microns. To this end, the polymer may be ball-milled as an aqueous dispersion and a dispersing agent may also be used. The aqueous dispersion of polymer may be stirred into a batch of viscose or injected continuously into the viscose spinning line prior to extrusion as in the Imovn spin dyeing technique. The either neat or as a solution or dispersion, may be adde to the viscose in the same way but is preferably not left in-contact with the viscose too long before spinning as it is subject to hydrolysis. The order in which the polymer and the T.D.B.P.P. are added to the viscose is not critical except when the polymer is formed from a precondensate for which melamine is one of the reactants,

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1,75 9 pTo in which case the polymer should be dispersed before the

T.D.B.P.P. in order to obtain satisfactory spinning.-

The viscose is then spun into a regeneration bath to

form filaments which may be given the conventional sequence of treatments including stretching, washing, desulphurising

and finishing.

The flame-retardant properties of the filaments improve

as the concentration of the polymer and the T.D.B.P.P. is increased, but as there is a corresponding decline in the mechanical properties of the filaments at the higher levels of concentration, the concentration levels used are a compro- mise between what is acceptable for both these properties. In deciding upon the levels to be used, the end use of the filaments has to be considered because different end uses require different levels of flame-retardance and differ- ent filament strengths. An associated consideration is that the mechanical properties of heavier denier filaments are less deleteriously affected than those of finer denier filaments.

In general we have found that a concentration range of about 15 to 30 per cent by weight, based on the weight of cellulose, of total polymer and T.D.B.P.P. covers most of the possibilities, with the higher levels being more suitable for heavier deniers.

The ratio of polymer and.-T.D.B.P.P. is also a factor for -consideration. There is .preferably between about10-e---

cent and 68 per cent: y weight of T.D.B.P.P. and between about 90 per cent and 32 per cent by weight of the polymer. Within this range, the optimum :flame-retardance is obtained at between about 23 per cent and 57 per cent by weight of

1 1,75 9 m T.D.B.P.P. and between about 77 22r cent and 43 per cent

by weight of the polymer.

The invention is illustrated by the following Examples

in which percentages are by weight. Example 1

A T.H.T.C./annmonia polymer was made by the following

procedure:-

litres of demnineralised water and 2.5 litres of

0.880 ammonia solution were stirred in a stainless steel

vessel. 1560 mis. of an aqueous 80 per cent solution of

T.H.P.C. and 940 imls. of demineralised water were mixed

together and the resulting solution was slowly stirred

into the aqueous ammonia solution. Stirring was continued

after the addition was complete and after thirty minutes 1

litre of 100 volume hydrogen percNide was slowly added,

stirring continuing until the solution was cool enough

to filter. The solid polymer was filtered off under

vacuum and washed until the filtrate contained no chloride

ions when tested with silver nitrate solution. The solid

polymer was then dried in a vacuum oven at 108 The

dried polymer weighed 750 gns.

An aqueous dispersion of the polymer was prepared by

ball-milling the polymer as a 12 per cent aqueous solution

containing a dispersing agent ("Belloid TD").

The polymer dispersion was added to an aged viscose

while stirring rapidly in an amount to give a viscose

containing 10 per cent of polymer based on the weight of

cellulose. Neat T.D.B.P.P. was then rapidly stirred into

the viscose in an amount to give 10 per cent based on the

weight of cellulose.

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1 75 9 /70 The viscose was de-aerated under vacuum and then

extruded through a spinning jet into a spin bath containing

per cent of sulphuric acid, 1.0 per cent of zinc

sulphate and 17.0 per cent of sodium sulaphate, and at a 0 temperature of 45 C. The yarn was spun at a rate of

metres per ninute and comprised 50 filaments giving an

overall denier of 375.

The yarn was washed free from acid and salts, at desulphurised using 0.6 per cent sodium sulphide solution

for 25 minutes, and washed free from the

desulphurising bath. The yarn was then given an acid

scour using 0.3 per cent hydrochloric acid at ambient

temperature for 15 minutes, washed free from acid, and

then given a soap finish before drying at 7500.

As a basis for comparison to show the synergistic

effect obtained by the process of the invention, yarns

were also made according to the above conditions but

containing respectively 20 per cent of T.D.B.P.P. and

per cent of T.H.P.C./Ml 3 polymer.

The tensile properties of the three yarns are shown in

the following table in which the tenacities are shown in

grams per denier and the extensions as a percentage.

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1 4 75 9 /7 Flame -Air Dry Wet retardant Tenacity Extension Tenacity Extension

T.D.B.P.P. 1.49 22.1 0.69 31.5

per cent T.H.P.C./NH 3 polymer 1.08 21.6 0.43 19.5

per cent T.D.B.P.P. per cent T.H.P.C./H 3 polymer 1.48 19.0 0.68 23.1

per cent T.D.B.P.P. per cent T.H.P.C./hR3 polyme 1.19 24.7 0.45 22.8

The three yarns were each used to make a knitted fabric made on a circular knitting machine. The fabrics were relaxed in water and then dried flat at 80°C. Strips measuring in width and 31.8 cms. long were cut from each fabric and tested for flame-retardance in accordance with the method given in British Standard Specification 3119. The average results from this test were

i Flame retardant After Char After- flaming length glow (Seconds) (cms) (Seconds)

per cent T.D.B.P.P. 2.1 14.0 Nil

per cent T.H.P.C./NH 3 0.3 18.4 Nil

per cent per cont T.H.P.C./RH3 polymer Nil 8.9 Nil

per cent T.D.B.P.P. per cent T.H.P.C./HH3 polymer Nil 9.6 Nil I27 8 4 277 91

1 4.7 5 9 7 The above results show that the flame-retardance of the filaments according to the invention is significantly improved

compared with that of filaments containing the combinants

alone. Also, the mechanical properties of the filaments are

maintained at satisfactory values, although in .the case of

the filaments containing 15 2er cent of T.H.P.C./ammonia

polymer, the more deleterious effect which the polymer has on

these properties is shown.

Example 2 A T.H.P.C./urea/ammonia polymer was made by the following

procedure:

790 gas. of an 80 per cent aqueous solution of T.H.P.C.

was refluxed together with 100 gms. of urea and 450 gms. of demineralised water for 1 hour to form a solution of a

T.H.P.C./urea precondensate. 600 gms. of this solution was then slowly stirred into a mixture of 600 mls of 0.880

ammonia solution and 2400 mls. of demineralised water.

minutes after the addition was completed, 210 mis. of 100

volume hydrogen peroxide was slowly added and stirring was

continued until the mixture was cool. The solid polymer was then treated as in Example 1 except that drying was carried

out at 70°C. 141 gms. of white solid polymer was produced.

The procedure for forming a dispersion of the polymer,

for incorporating the dispersion and the T.D.B.P.P. in the viscose and for spinning the filaments was then as in

Example 1. The results are shown in the following table

together with the results using respectively 20 per cent

of the polymer alone and 20 per cent of T.D.B.P.P. alone for

comparison. The tenacities, (Ten.) are shown in gms. per

denier and the extensions (Ext.) as a percentage. The flame

9 427791

14,75 9 /7 retardance was tested in accordance with the method given in British Standard Specification 3119.

Tensile Properties Flame Retardance Urea/ NH 3 T.D.B.P.P. Air Dry Wet 3 T.D.B.P.P. ir Wt After- Char After- polymer per cent flaming length -low fe ent Te Ten. xt. (secs. secs.)

Nil 1.00 22.1 0.36 21.C Burnt completc3y Nil

10 1.40 19.3 0.62 21.2 Nil 8.9 Nil Nil 20 1.49 22.1 0.69 31.5 2.1 14.0 Nil

Again, the improved flame-retardance of the two additives

together is shown as well as the maintenance of satisfactory

mechanical properties. Example 3 Two T.H.P.C./urea-melamine/ammoniapolymers were made by the following procedure using respectively 5 gms. of melamine

(0.05 role) and 12.5 gis. of nelamine (0.12 mole): The melamine was refluxed with 50 gms of urea and 325 gms. of demineralised water until the solids had dissolved, when 390 gns. of an 80 per cent aqueous solution of T.H.P.C. at 900 C was added. The refluxing was continued for one hour to form a solution of a T.H.P.C./urea-melamine precondensate which was then cooled.

The procedure of Example 2 was then followed except that

the drying of the polymer was carried out at 1080 C. The polymer yields were, respectively, 141 gas. and 154 gras. The polymer had to be broken down into powder form by passage

through a hammer mill before being formed into an aqueous dispersion by ball-milling. Filaments were then spun using each of the polymers

S- 10 427791

1 4- 759 /70 together with T.D.B.P.P. according to the procedure of Example

1. The results are shown in the following table together with

the results using 20 per cent of each polymer alone and

per cent of T.D.B.P.P. alone. The tenacities (Ten.)

are shown in gms. per denier and the extensions- (Ext.)

as a percentage. The flame retardance was again tested-

in accordance with the method given in British Standard

Specification 3119.

T.H.P.C. Tensile Properties Flame retardance urea- T.D.BP.P.P. melamine Air Dry Wet After- Char After- NH 3 polymer pr cent fltning length glow S (secs.) (ems.) (secs.) per cent Ten. Ext. Ten. Ext.

(0.05 Burnt Nil mole) Nil 1.18 23.3 0.45 25.0 completely

(0.12 I mole) Nil 1.01 22.6 0.37 21.9 Burnt Nil completely

(0.05 mole) 10 1.49 20.5 0.60 23.5 Nil 6.0 Nil

(0.12 mole) 10 1.61 20.8 0.70 24.3 Nil 10.8 Nil

Nil 20 1.49 22.1 0.69 31.5 2.1 14.0 Nil

As in Examples 1 and 2, both polymers show improved

flame-retardance in combination with T.D.B.P.P. compared

with the combinants alone. Also, the mechanical properties

are maintained at good levels in both cases.

1 427791

Claims (4)

TSE GLAIMS DEFNIG TE 1I4.7 IO 5 9/7o A AS FOLLWS:-

1. Flame retardant regenerated cellulose filaments

incorporating both tris 3 dibromopropyl) phosphate

and a polymer made by reacting tetrakishydroxy-

rethyl phosphonium chloride or a precondensate formed by the reaction of 2 moles of T.H.P.C. and 1 mole

of urea, with excess ammonia.

2. Filaments as claimed in claim 1 in which the incorporated polymer is made from a precondensate which is

formed by the reaction of 2 moles of 1 mole of urea and up to 0.12 mole of melamine.

3. Filaments as claimed in claim 1 or claim 2 in

which the total concentration of the T.D.B.P.P. and the polymer comprises about 15 to 30 per cent by weight based on the

weight of cellulose.

4. Filaments as claimed in any of claims 1 to 3,

in which the proportions of the total concentration of T.D.B.P.P. and the polymer comprise about 10 to 68 per cent

by weight of T.D.B.P.P. and about 90 to 32 per cent by

weight of the polymers.

Filaments as claimed in claim 4 in which the

proportions comprise about 23 to 57 per cent by weight of

T.D.B.P.P. and about 77 to 43 per cent by weight of the polymer.

6. Filaments as claimed in any preceding claim in which the polymer comprises particles having a mean

particle diameter not greater than about 4 microns.

7. Filaments as claimed in claim 6 in which the polymer particles have a mean particle diameter not greater than

about 2 microns.

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8. 1 4 75 9 p9 Flame retardant regenerated cellulose filaments

as claimed in clain I ~ia substantially as hereinbefore

described in xanple 1 or Example 2.

9. Flame retardant regenerated cellulose filaments as

claimed in claim 2 and substantially as hereinbefore described

in Example 3. A process for making flame retardant regenerated cellulose filaments comprising incorporating in a viscose both T.D.B.P.P. and a polymer made by reacting T.H.P.C. or a precondensate formed by the reaction of 2 moles of T.H.P.C. and 1 mole of urea, with excess ammonia, and spinning the viscose into a regeneration bath to form

filaments.

11. A process as claimed in claim 10 in which the incorporated polymer is made from a precondensate which is formed by the reaction of 2 moles of 1 mole of urea and up to 0.12 mole of melamine.

12. A process as claimed in claim 11 in which the polymer is mixed into the viscose prior to the addition of the T.D.B.P.P. 13. A process as claimed in any of claims 10 to 12 including the preliminary step of treating the polymer with an oxidising agent.

14. A process as clained in any of claims 10 to 13 in which the polymer is added to the viscose as a dispersion

in aqueous solution. A process for raking flame retardant regenerated

cellulose filaments as claimed in claim 10 and substantially-. as hereinbefore described in Example 1 or Example 2.

16. A process for making flame retardant regenerated

13 427791

1 I, 759 1-7 cellulose filaments as claimed in claim 11 and substantially as hereinbefore described in Example 3.

Dated this 6th day of May 1970. COURTATJIDS 1MIITED

EMIJD WAT7IERS &S017S PATEN~T AkT ORITZYS IIELBOI RIME

AM277 91

4,79 /7o

4.27-791