IE42841B1 - Flameproofed plastics compositions - Google Patents

Abstract

1526363 Flameproofed plastics compositions RHONE-POULENC INDUSTRIES 8 June 1976 [10 June 1975] 23679/76 Headings C3L C3B and C3R [Also in Division C1] A plastics composition contains by weight 0À1-20% of red P particles of mean diameter #200 Ám. encapsulated in a polymer (A) which does not melt or soften at <90‹ C. and which has mean MW # 2000. Based on P, there may be 5-80% wt. of (A). Also present, based on wt. of P, may be #100% of oxide(s) of Cu, Zn, Ag, Fe, Sb, Mg, V, Sn, or Ti. Glass fibres, kaolin, tale., self-lubricating fillers, poly(alkyleneglycol) laurate, and conventional additives may be present. Long lists of suitable polymers (A) and of the base plastics materials (B) of the composition are given. In the Examples, (A) is a polyamideimide, polycarbonate, pyrocatechol-formaldehyde, copolyamide, or phenolformaldehyde novolac containing HMT; (B) is nylon 66, poly(tetramethylene terephthalate), polypropylene, or polystyrene; the encapsulation is performed by mixing the red P with a solution of (A), adding water, filtering, washing and drying; and the encapsulated red P and plastics (B) may be mixed in an extruder or a rotating drum. Specifications 1,526,362, 1,526,361 and 1,526,364 are referred to.

Description

The present invention relates to plastics compositions flameproofed hy means of red phosphorus.

Numerous patents deal with the use of red phosphorus for flameproofing plastics; red phosphorus is in effect a very good flameproofing agent. For a given activity it is possible to use much smaller amounts of phosphorus than, for example, of halogen derivatives. Furthermore, its use results in better mechanical properties and it does not interfere with the electrical properties of the plastics in which it is incorporated.

However, this use is restricted by the dangers encountered, such as pollution hazards, and difficulties in using the material with complete safety. In fact, the presence of traces of water in practically all the polymers results, in the presence of the heat required to use these polymers, in the formation of phosphine, which is very toxic and which ignites spontaneously in air.

British Patent Specification No. 1,435,446 describes thermoplastics compositions flameproofed by a red phosphorus and containing metal oxides to prevent any evolution of phosphine during storage at ambient temperature.

British Patent Specification No.1,437,30l„discloses that if polyolefine compositions flameproofed with a mixture of red phosphorus and a nitrogen-organic compound which carbonises on exposure to a flame are used at between 170* and 230*C, an evolution of phosphine takes place.

To reduce this evolution, the patent advocates the use of stabilisers based on amido-sulphonic acid, on a paraffin oil or silicone oil and on pentaerythritol.

It is clearly necessary to find a simple means which enables one to use the compositions in the complete absence of phosphine evolution especially where the plastics are intended for the production of shaped articles.

Plastics compositions intended especially for the production of shaped articles, which compositions are flameproofed with red phosphorus, have been found, according to the present invention, which contain from 0.1 to 20% by weight, relative to the plastics material, of red phosphorus in the form of particles having a meat diameter not exceeding 200 u, encapsulated in a polymer which does not have a melting point or softening point below 90*C and has a mean molecular weight of at least 2,000..

Very many plastics serve as the basis for compositions which can be used particularly for producing shaped articles which, more and more frequently, must be flameproofed. Amongst the thermoplastics there may be mentioned the polyolefines, such as high or low density polyethylene», polypropylene, polyfluoroethylenes and ethylene-propylene copolymers, the polyvinyl compounds such as polyvinyl chlorides and vinyl chloride copolymers, - 3 the polystyrene^ and acrylonitrile-butadiene-styrene copolymers, the polyamides such as poly (hexamethylene adipamide), poly(hexamethylene azelamide), poly(hexamethylene dodecanediamide), polycaprolactam, poly(hexamethylene sebacamide), polylauryllactam and polyundecanamide, the saturated polyesters such as poly(ethylene glycol terephthalates) or poly(butylene glycol terephthalatea), the polycarbonates, the polyacetals and the polyacrylic compounds such as poly(methyl methacrylate), and the cellulose esters, polyurethanes and polyamide-imides.

Amongst the thermosetting polymers there may be mentioned the phenolic resins, the aminoplaate end the unsaturated polyesters.

Various elastomers can also be flameproofed according to the invention, for example natural or synthetic rubbers, silicones and polyurethanes.

The compositions of this invention can contain reinforcing fillers, such as glass fibres, fillers intended to impart specific characteristics to the shaped articles, such as self-lubricating fillers, or inert fillers euch as kaolin or talc.

Numerous adjuvants can also be introduced into the compositions such as anti-oxidants, heat stabiliser· or light stabilisers, dyestuffs or pigments.

Eed phosphorus as used herein, ie intended to cover all the coloured allotropic varieties which are sold - 4 42841 commercially under the name red phosphorus and which can contain up to, say, 3% of metal oxides ox metal salts as stabilisers.

The red phosphorus is necessarily in the form of 5 particles having a mean diameter not exceeding 200 μ , preferably not exceeding 100 μ . The use of particles which are only a few microns in diameter makes it possible to flameproof spun articles for textile usage.

These particles should be encapsulated in a polymer chosen in such a way that at the moulding temperature of the flameproofed composition, the coating layer of the phosphorus particles undergoes the minimum of degradation. Of course, tlie polymers used for the coating must be film-forming, that is to say they must be capable of forming a continuous film at the surface of the phosphorus particles.

The choice of the coating polymer depends principally on the nature of the plastics material to be flameproofed and on its moulding temperature.

The term moulding temperature means the temperature or temperature level, appropriate for processing a given plasties material. This temperature depends not only on the nature of the plastics material and the conversion technique but also on the apparatus used and, to a lesser degree, on the formulation employed. - 5 -. /20 41 The polymers suitable for the encapsulation of red phosphorus, in accordance with this invention, must not have a melting point or softening point below 90 °C. Amongst the polymers which do not have such a melting point or softening > point, those having a degradation temperature not below 150°C are preferred.

Depending on the composition to be flameproofed, various polymers may be suitable, such as the polycarbonates, the polyamides, the polyesters, the polyolefines, the polymers > derived from acrylic acid or an acrylate, the polytetrafluoroethylenes, the silicone resins, the polyimide-amides, the melamine-formaldehyde resins, the phenolic resins, the epoxy resins and the polyimides.

These polymers can be deposited on the surface of ί .the phosphorus particles by numerous encapsulation processes, such as those described in the Encyclopedia of Polymer Science and Technology1', Vol. 8, page 719 et seq..

Interscience Publishers. These processes are essentially of a chemical or physical nature. Amongst the commonest ι processes there may be mentioned coacervation in an aqueous phase, or interfacial coacervation, precipitation in an organic phase by addition of a non-solvent, spray-drying, the use of a fluidised bed, interfacial polymerisation or polymerisation in. situ in the vapour phase or in a wet phase, vacuum deposition, electrostatic deposition as well - 6 42841 as numerous other processes based on methods of phase separation or of interfacial reactions.

In order that the protection provided by the coating polymer shall be satisfactory, the amount of polymer is preferably from 5 to 80% by weight relative to the red phosphorus.

It is known that the addition of metal oxides or metal salts stabilises red phosphorus; red phosphorus sold commercially usually contains these. Metal oxides, which make it possible to suppress possible evolution of phosphine, may be included in the compositions. The metal oxides which generally give the best results are the oxides of copper, zinc, silver, iron, tin, vanadium, antimony, magnesium or titanium; preferably copper oxide is used.

The amounts of metal oxides used can vary depending on the amount of polymer used., according to the moulding conditions of the plastics as well as acoording to their nature. Usually, up to 100% by weight of metal oxide, relative to the encapsulated red phosphorus, can be employed.

The use of the encapsulated particles of red phosphorus offers numerous advantages, amongst which there may be mentioned the ease of handling before and during introduction into the polymer compositions, the reduction in the pollution hazards during the preparation of the - 7 compositions and above all the absence of evolution of phosphine during use, particularly when working at temperatures above 200°C.

In Examples 1 to 11, which further illustrate the present invention a polyamide 6.6 has been chosen as the polymer to be flameproofed; its moisture absorption is, with the exception of the cellulosics, amongst the highest exhibited by polymers and, under the action of heat and in the presence of red phosphorus, leads to the greatest evolution of phosphine.

EXAMPLE 1 A 24% strength by weight solution in N-methylpyrrolidone (NMP) of a polyamide-imide prepared by condensation of trimellitic anhydride and 4,4*-diisocyanatodiphenylmethane in stoichiometric proportions is used.

The polymer has a reduced viscosity of 90 cm /g (0.5% strength by weight solution in N-methylpyrrolidone). 166.7 g of this solution are diluted with 100 cm of NMP and 60 g of a red phosphorus powder having a mean particle size of 20 to 30 μ are added whilst stirring. 1 of water are placed in a 5 1 vessel equipped with a turbine (stirrer) revolving at 2,800 rpm. The dispersion of red phosphorus obtained above is poured in whilst stirring, and the mixture is left stirring for 2 hours. It is filtered and the retained material is then - 842841 washed with 200 cm of methanol.. Thereafter it is rinsed twice with 200 cm3 of ether and dried at 50’c, 98.4 g of encapsulated red phosphorus are obtained. g of the coated red phosphorus and 300 g of poly(hexamethylene adipamide) having a mean molecular weight of 20,000 and an inherent viscosity, in meta-cresol, of 1.3 are introduced into a jacketed one litre autoclave equipped with a spiral scraper-type stirrer revolving at 20 rpm and heated by a heating fluid. The mixture is heated gradually, whilst stirring, so as to reach a temperature of 285*C after one hour. It is maintained at this temperature for 1 hour.

To determine the phosphine which may be evolved, the gases on leaving the autoclave are trapped in two 1,000 cm flasks in series, containing 750 cm of a 2% strength aqueous solution of mercuric chloride, and the acid formed is determined in the presence of methyl orange. This method of determination has been described by Mr. WILMET in Compte-rendue de l'Academie dee Sciences 185 (1927), page 206.

The weight of phosphine evolved is 17.5 mg per 1 g of red phosphorus employed.

A blank experiment carried out under the same conditions but with non-coated red phosphorus (18 g) gives an evolution of phosphine of 33.5 mg per gram of red phosphorus employed. - 9 11 Slabs are produced from the polyamide/encapsulated red phosphorus composition and from the polyamide alone, by 2 cold sintering under a pressure of 300 kg/cm . These slabs have the following sizes: 100 mm long, 6 nn wide and 3 mm thick.

The limiting oxygen index is measured (lay the LOX test in accordance with standard specification ASOM D 2863).

The following results are obtained: LOI test Polyamide,alone 20.8 Polyamide + red phosphorus 26 EXAMPLE 2 g of a polycarbonate of bisphenol A, having a mean molecular weight of 33,000 and a glass transition 3 temperature of 145°C, are dissolved in 150 cm of chloroform. 36 g of a red phosphorus powder having a mean particle size of 20 to 30 μ are added whilst stirring.

This suspension is stirred for 15 minutes. It is then poured into 3 litres of methanol, as indicated in Example 1. After filtering, rinsing with ether and drying, g of encapsulated red phosphorus powder are obtained.

Thereafter, the procedure indicated in Example 1 is followed.

An evolution of phosphine of 2.7 mg per gram of red phosphorus was obtained. — 10 «· The LOX test is carried out as indicated in Example 1.

The following results axe obtained for the polyamide composition with red phosphorus coated with polycarbonate: .5 - 26.

EXAMPLE 3 400 cm3 of ortho-dichlorobenzene, followed by 22 g 3 of pyrocatechol, 30 cm of a 30% strength aqueous formaldehyde 3 solution, 1 cm of concentrated hydrochloric acid and 42 g of red phosphorus powder having a mean particle size of 20 to 30 μ are introduced into a 1 litre reactor.

The mixture is heated to 70eC over the course of 30 minutes whilst stirring, and then to 90*C over the course of 1 hour. It is allowed to cool and is filtered, and the product is washed with acetone and then with ether and dried. 63.5 g of encapsulated red phosphorus powder are obtained□ Thereafter the procedure indicated in Example 1 is followed.

An evolution of phosphine of 2.,3 mg per gram of red phosphorus was obtained.

The following results are obtained by the LOI test; .5 - 26.

EXAMPLES 4 to 6 The treatments in an autoclave indicated in Example 1 are carried out with the three sorts of coated red phosphorus, but 6 g of copper oxide are added in each test. - 11 1 No evolution whatsoever of phosphine is found. EXAMPLE 7 g of a polyamide obtained by co-condensation of 50 molar parts of caprolactam, 30 molar parts of the condensation product of sebacic acid with hexamethylenediamine and 20 molar parts of the condensation product of adipic acid and hexamethylenediamine are dissolved in 150 cm of a mixture consisting of 20 parts by weight of water and 80 parts by weight of methanol. This copolyamide has a melting point of 150*C and a mean molecular weight of 20,000. g of a red phosphorus powder having a mean particle size of 20 to 30 μ are added to the above solution, whilst stirring.

This suspension is poured into a vessel equipped with a turbine (stirrer) and containing 5 1 of acetone.

The mixture is filtered and the product is rinsed twice with 200 cm of ether and then dried at 50 ®C. 47.5 g of encapsulated red phosphorus are obtained.

Thereafter the process in an autoclave, as indicated in Example 1, is carried out with 300 g of polyamide and 28.5 g of encapsulated red phosphorus. An evolution of phosphine of 5.2 mg per gram of red phosphorus was obtained.

An index of 25.5 is obtained by the LOI test.

EXAMPLES 8 to 10 A single-screw laboratory extruder of which the - 12 42841 screw has a length of 415 mm and a diameter of 15 mm is used. This extruder is equipped with a cylindrical die having a diameter of 3 mm. The barrel temperatures are as follows: 250°C at the material inlet, 280eC at the centre and 270*C at the die.

Compositions A, B and C, respectively containing g, 9.13 g and 9.58 g of red phosphorus encapsulated » according to Examples 1, 3 and 7, per 100 g of poly(hexamethylene adipamide) having a mean molecular weight of 20,000 and an inherent viscosity, in meta-cresol, of 1.3, and 2 g of copper oxide, are prepared by simple mixing.

' These compositions are introduced into the extruder and strands are extruded.

During the entire operation, the possible presence of phosphine in various parts of the extruder is tested for by means of a DRAEGER [Registered Trade Mark] CH 31,101 tube. Equally, attempts are made to detect phosphine when the strand which has just been extruded, and which is still hot, is broken.

Not a trace of phosphine is detected in any place whatsoever.

EXAMPLE 11 A solution of 40 g of a phenol-formaldehyde Novolac containing 3% of hexamethylenetetramine (tradename RESOPHENE PB3 of RHONE-POULENC) in 150 ml of acetone is prepared. g of red phosphorus powder having a mean particle size of 20 to 30 μ are added whilst stirring. This dispersion is 41 poured into a vessel, fitted with a degassing device and equipped with a turbine (stirrer), containing 1,500 ml of water heated to 50-60®C. The temperature is then raised to 90-100°C for 30 minutes, with violent stirring. The mixture is filtered. 82.5 g of encapsulated red phosphorus are obtained. 66.5 g of poly(hexamethylene adipamide) containing 3056 of glass fibres, 0.2 g of Cepretol (a polyalkylene glycol laurate), 0.75 g of copper oxide powder and 7.5 g of encapsulated red phosphorus are compounded by simple mixing in a rotating drum.

A strand of good quality is extruded by means of an extruder, under the conditions described in Example 8, without detecting the slightest evolution of phosphine.

EXAMPLE 12 Compositions of plastics based on the following polymers are prepared using the phosphorus encapsulated according to Example 11: a) poly(tetramethylene glycol terephthalate) (3,500 poise) b) polypropylene, d = 0.903, melting point 165170®C, melt index = 6 (at 230*C under 2.16 kg, in g/10 minutes) c) polystyrene, d « 1.05, Vicat temperature « 96®C melt index = 4-4.5 (at 200®C under 5 kg).

Xn each experiment 88 g of polymer a or b or c, g of copper oxide powder and 10 g of encapsulated red phosphorus are mixed.

The composition is introduced into the extruder and strands are extruded. No traces of phosphine are detected in any place whatsoever.

The limiting oxygen index is measured in accordance with the LOI test; the following results are obtained; Blank with phosphorus Polyterephthalate 21 23.5 Polypropylene 17 19.5 Polystyrene 20 22 Attention is drawn to the following related applications filed on even date herewiths (i) Patent’ Specification No. 42840 which describes and claims a flameproofing composition which is in the form of a pulverulent mixture comprising; a) from 50 to 95% by weight of red phosphorus in the form of a powder having a mean particle size not exceeding 200 μ , and b) from 5 to 50% by weight of one of more polymers or prepolymers derived from monomers possessing maleic, fumaric or allylic unsaturation. - 15 11 111 · Patent Specification. No. 42839 which describes and claims a flameproofing composition in the form of a powder or granules which comprises a mixture comprising: a) from 50 to 95% by .weight of red phosphorus in the form of a powder having a mean particle size not exceeding 200 μ , and b) from 5 to 50% by weight of an epoxy resin (as defined therein), and (iii) Patent Specification No. 1215/76 which describes and claims a flameproofing composition which comprisess a) from 50 to 95% by weight of red phosphorus in the form of a powder having a mean particle size not exceeding 200 μ ; and b) from 5 to 50% Toy weight of a thermoplastic phenolformaldehyde polycondensate of molecular weight from 120 to 1,500, the molar ratio of formaldehyde to phenol being from 0.7 to 0.9.

Claims (11)

1. CLAIMS:1. A plastics composition which contains from 0.1 to 20% by weight, based on.the weight of the plastics material of red phosphorus in the form of particles having a mean diameter not exceeding 200 μ , encapsulated in a

2. A composition according to claim 1 which also contains up to 100% by weight, based on the weight of the encapsulated phosphorus, of one or more oxides of copper, l0 zinc, silver, iron, antimony, magnesium, vanadium, tin or titanium.

3. A composition according to claim 1 or 2 in which the polymer does not degrade below 150 e C.

4. A composition according to any one of claims 15 1 to 3 in which the polymer is a polycarbonate, polyamide, polyester, polyolefine, a polymer derived from acrylic acid or an acrylate, a polytetrafluoroethylene, a silicone, a polyimide-ami.de, a phenolic resin, an epoxy resin or a polyimide. 5ο A composition according to any one of claims 1 to 4 in which the polymer is preeent in an amount from 5 to 80% by weight based on the weight of the red phosphorus. I

5. Polymer which does not melt or soften below 90 ”C and which has a mean molecular weight of at least 2,000.

6. A composition according to any one of claims 1 to 5 which is reinforced with glass fibres.

7. A composition according to any one of claims 1 to 6 which contains an inert filler.

8. A composition according to claim 7 in which the inert filler is kaolin or talc.

9. A composition according to any one of the preceding claims which is in the form of a shaped article.

10. A composition according to claim 1 substantially as hereinbefore described.

11. A composition according to claim 1 substantially as described in any one of Examples 1 to 12.