CA2146558A1 - Flame retardants - Google Patents

Abstract

A non-halogen containing flame-retardant additive comprising a salt of an inorganic phosphorus-containing acid and a polymeric compound which is a homopolymer or copolymer and comprises a linear backbone formed of at least 10 repeat units and contains a plurality of basic nitrogen functionalities. The additives are suitable for use in polymer materials either alone or in combination with other flame-retardant additives, resulting in an additive having reduced smoke generation, reduced evolution of corrosive gases and improved flame-retarding properties. The flame-retardant additives of the invention are compatible with a variety of thermoplastic and thermoset polymers applicable for wire and cable insulation, heat recoverable items, electrical tape and moulded parts. The additives may also be formulated as a dispersion into coating compositions optionally comprising addi-tional ingredients such as other flame-retardants, fillers, colourants etc. In addition the additives may be employed in caulks, mastics and sealants.

Description

2~ 41 6 5 ~ 8 PCl[~/US93/10606 FLAME RETARDANTS
This invention relates to non-halogen-containing flame-retardant additives suitable for use in a variety of thermoplastic and thermoset polymer materials.
Electrical fires in machinery frequently arise as a result of an electrical fault causing ignition and combustion of polymer materials, such as the insulating cladding of wires and cables. Such fires are a serious problem presenting a potential hazard to both workers and property, not only from the fire, but also from the evolution of toxic gases derived from the thermal degradation of the polymer materials. The problem may be compounded when access to the point of ignition is physically restricted, e.g., within machines, circuitry etc., thereby limiting manual attempts to extinguish or even recognise the fire. Accordingly, there has been much interest in the development of polymer compositions having improved resistance to combustion.
It is known that blending certain compounds into a pre-polymer composition can have a flame-retarding effect on the combustion of the final product. Halogen-containing flame-retardant additives are known and have been used to reduce the flammability of polymer materials.
However, there is an increasing awareness of the problems associated with the use of halogenated flame-retardants.
For example, halogenated flame-retardants are known to cause both high smoke generation and the emission of toxic gases which present a hazard to both workers and fire fighters alike, as well as corrosive gases which may damage adjacent circuitry. In addition, these gases may also have wider reaching deleterious environmental effects. Alternatives to halogenated flame-retardants can be broadly classed into either (a) phosphorus-based materials or (b) non-phosphorus-based materials.
Most non-phosphorus-based materials comprise inert filler materials, such as calcium carbonate, which have little anticombustion effect. Alumina trihydrate, WO94/114~5 21~6558 PCT/US93/1~6~6 magnesium hydroxide and calcium carbonate have been used as flame-retardant additives for polyolefin polymers.
Unfortunately, such materials re~uire high loading by weight of the polymer composition to achieve the desired level of flammability performance. This high loading is found to have a pronounced negative effect on the physical properties of the polymer, e.g., tensile strength and/or elongation. Additionally, materials such as alumina trihydrate have poor thermal stability.
The use of phosphorus-based flame-retardants is known, particularly the use of inorganic phosphates to generate intumescent formulations which form a protective foamed char when exposed to heat, thereby preventing further combustion. Such formulations have generally found applications in cellulosic type materials, resins and formulations containing low molecular weight polyols for paints, and other such coating materials. Various phosphorus-cont~ining compounds are disclosed in, for example: Chemical Abstracts 92 111554 and 96 143939; U.S.
Patent Nos. 3485793, 3541046, 3810862, 4001177, 4140660, 4182792, 4198493, 4341694, 4433115, 4491644, 4S87362, 4642366, 4742088, 5089559 and 5010133; International Patent Nos. W085/09626 and Wo89/olO11; British Patent Nos.
2142638 and 2181141; Australian Patent Application No.
77342/87, and European Patent Publication Nos. 0026391, 0045835, 0115871, 0204027, 0413613 and 0466137. However, many of these prior art flame-retardants are found to suffer from one or more of the following disadvantages:-(i) Water sensitivity.
(ii) Migration of the additive due to non-compatibility between the component compounds and the polymer matrix.
(iii) The deleterious action of the additive on the physical properties of the polymer.
3S (iv) The high specificity of the additives.
For example, U.S. Patent No. 4491644 discloses a flame-retardant additive commercially available under the WO94~11425 2 1 ~ 6 ~ ~ 8 PCT/US93/10606 trade name CHARGARD comprising a salt formed from melamine and bis(pentaerythritol phosphate) phosphoric acid formulated for use principally in poly(propylene).
Likewise, European Patent No. 0115871 discloses flame-retardant additives comprising a nitrogen-containing oligomer and ammonium polyphosphate, which are commercially available under the trade name SPINFLAM in grades specific to a particular polymer, e.g., polyethylene. Thus, there is a continuing need for a high performance method of flame-retardation for use in polymers.
Our copending European Patent Application No.
90309092.6 filed 20th August 1990 discloses a flame-retardant additive comprising a compound having a nucleus of general formula:-G H

\~l'RI ~ ~N~

in which:
n is an integer and has a value from 2 to 25;
Rl represents an alkyl group comprising up to 20 carbon atoms, and R2 represents R3-NH where R3 represents an alkyl group comprising up to 20 carbon atoms, an aryl nucleus comprising up to 10 carbon ring atoms, or R2 represents a heterocyclic ring nucleus comprising from 4 to 8 ring atoms, at least one ring atom being nitrogen and linking the ring nucleus to the triazine ring, optionally in combination with a source of phosphorus.
Our copending British Patent Application No.
9208926.7 filed 24th April, 1992 discloses a flame-retardant additive comprising a source of phosphorus and a WO94/11425 ~1 4 6 ~ ~ 8 PCT/US93/10606 polymer or oligomer having repeating units selected from those represented by general formulae:-o R2 R4 r l R3-N-R
o R2 R4 ll l ll l3 l2 r N R3-N-in which:
Rl represents an alkyl group comprising up to 2 0 2 5 carbon atoms, an aryl group comprising up to 10 carbon ring atoms or a group represented by -Y R5 where R5 is an alkyl or other aliphatic group comprising up to 2 0 carbon atoms or an aryl group comprising up to 10 carbon ring atoms and Y is O, S or -NR6 where R6 is a hydrogen atom, an alkyl group comprising up to 2 0 carbon atoms, an aryl group comprising up to 10 carbon ring atoms or R5 and R6 may together form a heterocyclic ring (including the N
atom) wherein the other ring atoms are chosen from C, N, 0 and S;
Each R3 independently represents a divalent aliphatic linking group comprising up to 2 0 carbon atoms or a divalent aromatic linking group comprising up to 10 carbon ring atoms;
R2 and R4 independently represent a hydrogen atom, an alkyl group comprising up to 20 carbon atoms or an aromatic group comprising up to 10 carbon ring atoms or, when R3 is aliphatic, R2 and R4 may complete a heterocyclic ring including -N-- R3--N-, the remaining ring atoms being selected from C, N, O and S, and WO94/11425 ~ 1 4 ~ 5 5 8 PCT/US93/10606 X~ represents 0, S or NR2, where R2 is as defined previously, and X2 represents O, S or NR4, where RZ and R4 are as defined previously.
Alternative compounds have now been found which are suitable for use in flame-retardant additives for polymer materials having reduced smoke generation, reduced evolution of corrosive gas and improved flammability properties. The compounds are compatible with a variety of polymers applicable for wire and cable insulation, heat recoverable materials and mouldable parts.
According to one aspect of the present invention there is provided a non-halogen containing flame-retardant additive comprising a salt of an inorganic phosphorus-containing acid and a polymeric compound which is ahomopolymer or copolymer and comprises a linear backbone formed of at least ~0 repeat units and contains a plurality of basic nitrogen functionalities. The additives are suitable for use in polymer materials either alone or in combination with other flame-retardant additives, resulting in an additive having reduced smoke generation, reduced evolution of corrosive gases and improved flame-retarding properties. The flame-retardant additives of the invention are compatible with a variety of thermoplastic and thermoset polymers applicable for wire and cable insulation, heat recoverable items, electrical tape and moulded parts. The additives may also be formulated as a dispersion into coating compositions optionally comprising additional ingredients such as, other flame-retardants, fillers, colourants etc. In addition the additives may be employed in caulks, mastics and sealants.
According to further aspects of the present invention there is provided a polymer containing a flame-retardant loading of the additives of the invention and an article formed from such a polymer. The additives are WO94/11425 PCT/US93/10606 ~
i particularly suitable for use in polymers, especially, but not exclusively, polyolefin polymers.
The polymeric compound forming the salt with the phosphorous-containing acid must possess basic nitrogen functionalities which may be present in the backbone or in groups pendant thereto. The backbone of the polymer is linear and is formed of at least lO repeat units which need not be identical, i.e., the polymer may be a homopolymer or copolymer. The number of backbone atoms per repeat unit varies with the polymer type as is well known in the art. For example, a vinyl addition polymer has 2 backbone carbon atoms per repeat unit, while a polymer formed by a ring-opening process has x backbone atoms per repeat unit, where x is the number of atoms in the original ring. For a polymer formed by inter-reaction of two bifunctional monomers (ie a step-growth polymer), the number of backbone atoms per repeat unit is taken to be the sum of the number of catenary atoms per molecule of each of the monomers. For the purposes of this invention, polymers derived from vinyl addition or ring-opening polymerisation are preferred.
It follows that the backbone must possess at least 20 atoms exclusive of end-capping groups, and preferably it possesses at least 30 atoms. Carbon and nitrogen are the preferred backbone atoms, but other hetero-atoms such as O, S, P etc may also be present. Preferably at least lO
of the backbone atoms are selected from the group consisting of nitrogen atoms which form part of a basic nitrogen functionality, and carbon atoms which are bonded to a pendant group comprising one or more basic nitrogen functionalities. Basic nitrogen functionalities are nitrogen-containing groups which readily form salts with acids via protonation of the nitrogen. Typical examples include amines (primary, secondary or tertiary) and nitrogen-containing heterocycles such as pyridines, pyrollidines, piperidines, morpholines etc. The term linear backbone is used to denote that the polymer WO94/1142~ ~1 4 6 ~ ~ 8 PCT/USg3/10606 possesses a recognisable backbone and is not in the form of a three-dimensional network such as those formed by urea-formaldehyde and melamine-formaldehyde condensates.
Thus, the polymer may possess some branches from the backbone providing the polymer remains soluble prior to salt formation. The use of a linear backbone is advantageous in terms of ease of synthesis of the salt as it enables the use of homogenous solutions. The relatively high molecular weight of the polymers having at least lO repeat units render the additives non-migrating and moisture insensitive in the host polymers. The salt comprises at least one unit represented by general formula (I) (I) [RH]~.l/y[XY~]
in which;
R is a nitrogen-containing repeat unit of the polymeric compound, XY- ~s the deprotonated or partially deprotonated form of the phosphorus-containing acid, and y is an integer. The salt preferably comprises at least ten such units and more preferably from lO to 50 units.
R preferably represents a structure represented by general formula (II) or (III) :-(II) -CH2-CH2-N- (III) -CH2-C-wherein:
R1 and R2 independently represent H or an alkyl group of up to 5 carbon atoms; and R3 represents a group comprising a basic nitrogen functionality.

WO94/11425 ~ 8 PCT/US93/10606 Examples of groups represented by R3 include:

Repeat units other than those represented by formulae II and III may also be present as a result of copolymerisation with other monomers, but this is not preferred. Examples of polymers comprising repeat units of Formula II include (but are not limited to):
polyethyleneimine. Examples of polymers comprising repeat units of Formula III include (but are not limited to) polymers and copolymers of allylamine, 2-vinyl pyridine, 4-vinyl pyridine, 4-aminostyrene, N,N-dimethylaminoethyl methacrylate and N-vinyl pyrollidone. The basic nitrogen functionality may be present from the outset in the monomer(s) used to prepare the polymer (as is the case in the above examples), or may be generated by chemical conversion of precursor groups on a preformed polymer, e.g., polyvinylamine and its N-alkyl derivatives.
Other useful polymers include the cyclopolymers derived from polymerisation of diallylamine derivatives, which comprise interlinked piperidine rings, as described in "Encyclopaedia of Polymer Science and Engineering", 2nd Ed. Vol.4 p.543.
Examples of phosphorus-containing acids include (but are not limited to): orthophosphoric, hypophosphorous, trimetaphosphoric, polyphosphoric, phosphorous, hypophosphoric and pyrophosphoric acids.
As is well understood in this technical area, a large degree of substitution may be tolerated for groups represented by R1 to R3. As a means of simplifying the WO94/11425 ~1 4 6~ ~ 8 PCT/US93/10606 _g_ discussion and recitation of these groups, the terms "group", "nucleus" and "moiety" are used to differentiate between chemical species that allow for substitution or which may be substituted and those which do not or may not be so substituted. For example, the phrase "alkyl group"
is intended to include not only pure hydrocarbon alkyl ch~;nc, such as methyl, ethyl, octyl, cyclo-hexyl, isooctyl, t-butyl and the like, but also alkyl chains bearing conventional non-halogen-containing substituents known in the art, such as hydroxyl, alkoxy, phenyl, nitro, amino etc. The term "nucleus" is likewise considered to allow for substitution. Thus the phrase "pyrimidine"
nucleus would be understood to include not only an unsubstituted pyrimidine ring, but also pyrimidine rings bearing conventional substituents known in the art. The phrase "alkyl moiety" on the other hand is limited to the inclusion of only pure hydrocarbon alkyl chains such as methyl, ethyl, propyl, cyclohexyl, isooctyl, t-butyl and the like. Generaly speaking, substituents likely to give rise to toxic fumes on combustion, such as nitrile and sulphur-containing species, are not preferred.
The flame-retardant additives may optionally be prepared by blending the P/N salts with an additional phosphorus-based flame retardant. The second phosphorus-based additive may comprise any inorganic or organicphosphorus source known in the art which (in the concentration used) does not deleteriously affect the properties of the polymer to which it is added. Preferred examples of the second phosphorus source comprise ammonium polyphosphate (commercially available under the trade name PHOSCHEK P-40 from Monsanto), melamine phosphate (commercially available under the trade name AMGARD NH
from Albright and Wilson) and red phosphorus. The phosphorus source may optionally be encapsulated, e.g., in a water-insoluble resin. A preferred example is ammonium polyphosphate in melamine formaldehyde (commercially ~4~558 ~

available under the trade name EXOLIT 462 from Hoechst-Celanese).
If the P/N polymeric salt is employed in conjunction with a second phosphorus based additive, then the percentage (by weight) of the second phosphorus-based additive in the combined additive is dependent on the flammability of the polymer which is to be flame-retarded and the level of flame-retardance which is to be achieved, but preferably it is no greater than 70 percent, more preferably no greater than 50 percent and most preferably no greater than 30 percent.
The particle size of the P/N salt and the second phosphorus source is important for both flammability performance and for the physical properties of the flame-retarded material. Preferably, both additive componentsare in free flowing form and have an average particle size of less than 80~m, more preferably less than 40~m.
Conventional methods to obtain these particle sizes include using sieves, ball milling and jet milling.
Alternatively, during the preparation of the P/N compound, precipitation of the final product can be optimised to minimise particle size.
Due to the high thermal stability of the flame-retardant additive of the present invention, it is possible to impart flame-retardant properties to a wide range of polyolefins and other polymers. Preferred polymers include low density poly(ethylene) (LDPE), poly(ethylene-ethyl acrylate) (EEA), poly(ethylene-acrylic acid) (EAA), poly(ethylene-vinyl acetate) (EVA), poly(propylene) (PP), ethylene-propylene-diene monomers (EPDM) and copolymers thereof. Other preferred polymers include epoxy resins.
The choice of polymer, i.e., flammability, melt index (ASTM) and copolymer content, will affect the quantity of flame-retardant added, as will the level of flame-retardance to be achieved. Generally, the total flame-retardant loading by weight is from l0 to 60%, preferably WO94/11425 ~1 4 6 ~ 5 8 PCT/US93/10606 from 20 to 50~ of the total composition. The flame-retardant additives of the invention are particularly suitable for use in EVA and EEA formulations.
Polymers comprising flame-retardant additives of the invention, i.e., the P/N salt(s) and optionally the second phosphorus source (referred to hereinafter as the "polymers of the invention") may be cross-linked, for example, either chemically or by high energy radiation.
Examples of chemical cross-linking methods include the use of free radical initiators, such as dicumyl peroxide, together with co-curing agents, e.g., triallyl isocyanurate, or silane cross-linking technology, e.g., using products commercially available under the trade names MONSIL and SIOPLAS from Maillerfer and Dow Corning respectively. Cross-linking by high energy radiation can also be used, for example, by irradiating with an electron beam. Radiation doses in the range 2 to 40 Mrads, preferably l0 to 20 Mrads are appropriate. To promote cross-linking during irradiation, radical promoters, such as triallyl isocyanurate, can be used.
Surface treatments may be used to increase the coupling between the flame-retardant additive and the polymer host matrix. Materials such as zircoaluminates and titanates can be used or, more commonly, silane coupling agents.
Other additives, for example, smoke suppressants, anti-oxidants, heat stabilisers, W stabilisers etc., can be added. However, care must be exercised in the selection of these additives so that they do not interfere with the flame-retardant mPch~n;sm of the P/N compound(s).
Basic oxides, such as magnesium oxide or zinc oxide, are found to be particularly detrimental in large concentrations. Similarly, additives which contain water of hydration, e.g., alumina trihydrate, can also be inhibiting in large concentrations.
Polymers incorporating the flame-retardant additives of the present invention can be processed using WO94/11425 2 ~ 4 ~ 5 5 8 ~ - PCT/US93/106~6 conventional methods, e.g., Banbury or two-roll mill, and extruded or moulded, either by compression or injection methods. The polymer compositions of the invention are particularly suitable for use in wire and cable insulation, dimensionally recoverable products, especially heat recoverable products, moulded parts, extruded tubings, pipes and tape type constructions, where high levels of flame-retardency together with evolution of low quantities of smoke and toxic corrosive combustion products are required.
Dimensionally recoverable products are ones which by appropriate treatment can alter their dimensions. In the case of heat recoverable products, this treatment would be heat. Polymer compositions of the invention where the polymer is cross-linked EEA/EVA are particularly useful in the preparation of flexible, flame-retardant, heat recoverable tubing.
The P/N salts can be prepared by conventional procedures. For example, solutions of the nitrogen-containing polymer and the phosphorus-cont~; n; ng acid may be mixed in suitable proportions, causing precipitation of the desired product. Alternatively, a monomer salt m~y be prepared, and subjected to polymerisation by conventional methods.
The invention will now be described with reference to the accompanying, non-limiting Examples in which polymers and flame-retardant additives were compounded using a variety of methods. Polyolefin based formulations were compounded using either an electrically heated Schwabenthan two roll mill at 140C for LDPE and 75 to 85C for EVA and EVA/EPDM blends, or mixed using a Brabender PLASTICORDER Torque rheometer, with 30 or 300cm3 internal r;~;ng head, for 2 minutes at 100C (EVA/EPDM) AND 140C (LDPE). Formulation into other polymers will be discussed under the individual examples.
Test pieces were commonly produced by compression moulding using a Gem hydraulic press. Conditions employed WO94/11425 2 1 4 ~ 5 5 8 PCT/US93/1~06 were 110C for 10 minutes (EVA or EVA/EPDM) AND 150C for 20 minutes (LDPE) with 12 ton pressure. Formulations containing other polymers will be discussed under the individual examples.
"EXOLIT IFR-10" and "EXOLIT IFR-23" (Hoechst-Celanese), "Epsyn 7506" (Copolymer Inc.), "LUPOLEN 1812D"
(BASF), "IRGANOX 1010" and "IRGACURE651" (Ciba Geigy Chemicals), "PHOSCHEK P-30" and "PHOSCHEK P-40"
(Monsanto), "EPIKOTE 815" (Shell Chemicals), "ELVAX 470"
(Dupont) "KR38S" (Kenrich Petrochemicals Inc.), "CN-1197"
and "CHARGARD 329" (Great Lakes chemical Corporation), "SPINFLAM MF82" (Montefluos), "MONSIL" (Maillefer), "SIOPLANS" (Dow Corning), "AMGARD NH" (Albright & Wilson) and "PLASTICORDER" (Brabender) are all trade names/designations.
Polymer flammability performance in the Examples was generally evaluated by two procedures, namely: the Underwriters' Laboratory UL94 vertical bar flame test and cone calorimeter performance. The latter procedure was also used to determine the smoke and toxic gas production of the materials in the Examples.
Underwriter's Laboratory UL94 vertical bar flame test. This is a widely accepted test method and is commonly used by suppliers of flame-retardants and flame-retarded materials. In this test a vertically clampedspecimen bar is ignited by a flame from a bunsen burner.
According to Part 2 of UL94, three levels of performance are defined, designated V-0, V-1 and V-2, of which V-0 is the most stringent. In the test, samples not achieving V-0 and V-1 or V-2 are defined as fail. UL94 defines the specimen size as 12.7cm (5 inches) long and 1.27cm (1/2 inch) wide. The thickness of the sample must be no greater than 3.2mm (1/8 inch). UL94 performance obviously depends on specimen thickness and is generally quoted for 1.6mm (1/16 inch) or 3.2mm (1/8 inch).
Cone Calorimeter Evaluation. This was generally performed in accordance with ASTM E 1354-90 and/or ISO DP

5660. In this procedure horizontally mounted specimens of dimensions l0cm x l0cm x thickness (variable dependent upon application, but 3mm in most cases) are subjected to an irradiant flux, in these Examples generally 50kWm~2. An electric spark ignition is also provided, which is removed upon sustained burning of the specimen being observed.
The fire effluent is then subject to continuous monitoring to determine a range of properties. Measurement of oxygen concentration in the gas stream as a function of time enables the rate of heat release to be calculated as a function of time (via the oxygen consumption principle) -a key flammability property. Determination of the obscuration of a laser beam passing through the combustion product stream enables the smoke produced to be measured, usually expressed as a specific extinction area. A
variety of toxic gases can also be continuously monitored, in particular carbon monoxide, carbon dioxide and oxides of nitrogen, the first two by means of infrared spectroscopy and the latter by means of a chemiluminescence detector. Additionally the test specimen is mounted on a load cell throughout the test so that all the measured properties can be related to a rate of mass loss. Important abbreviations used for cone calorimeter data are as follows RHR = Rate of Heat Release (in kWm~2), t~ = Time to ignition (in s), EHC = Effective Heat of combustion (in MJkg~1), SEA = specific Extinction area (in m2kg~~, SPR = Smoke Production rate (in s~1), COPR = Carbon Monoxide Production Rate (in kgm~2s~1) NOx = Nitrogen Oxides Yield (in kgkg~~), RHR can be visualised as the intensity of the fire, so the lower the values of RHR the better in terms of flammability performance. SEA is a widely used smoke performance parameter relating the amount of smoke produced to the mass loss rate of the burning specimen.

WO94/11425 2 1 ~ 6 5 ~ 8 PCT/US93/10606 The terms SPR and COPR are defined by SPR=SEAxRHR/EHC and COPR=COxRHR/EHC. In all cases it is desirable for the values of these properties to be as low as possible.
Physical properties were determined using an Instron Model 1026, employing a crosshead speed of 500mm min~l.

PREPARATION OF POLYfALLYLAMMONIUM) PYROPHOSPHATE
poly(allylammonium hydrochloride) (120.00g; 1.27mol) (supplied by Nitto Boseki Co. Ltd under the designation PAA-HCL-105) was treated with a small excess of sodium hydroxide (65.00g; 1.63mol) in methanol (2500 ml) and refluxed for 18 hours under dry conditions. On cooling the solution was filtered to remove sodium chloride. The remaining solution was reduced in volume to ca. 800ml and further sodium chloride removed. A portion of this solution (250ml; caØ40 mol polyallylamine) was diluted to 800ml with methanol. The resulting solution was then stirred vigorously while a concentrated methanolic solution of pyrophosphoric acid (30.00g/140ml; 0.17mol) was added until pH 7 (neutrality) was reached. The copious white solid (solvent swollen) produced was filtered, washed with methanol (4xlOOml) and dried in vacuo at 160C for 18 hours. Yeild=57.00g (98%). The product is insoluble in water.
Thermal analysis of the product reveals 1 to 2% of volatiles even after prolonged drying. Thermogravimetric analysis (TGA) in air reveals the compound is stable up to ca. 200C. Ca. 50% weight of residue is retained up to 740C.
Chemical analysis of the product revealed: N=8.29%
and P=18.29% with a N/P ratio of 1:1.004 tTheoretical:
N=9.59% and P=21.20% with N/P ratio of 1:1].

.

WO94/1142~ 6558 PCT~US93/10606 ALTERNATIVE PREPARATION OF POLY(ALLYAMMONIUM) PYROPHOSPHATE
This Example illustrates an alternative procedure for the preparation of poly(allylammonium) pyrophosphate. The procedure is as disclosed in European Patent Publication No. 145220.
A 500ml flange flask was fitted with a condenser, a mech~n;cal stirrer and a nitrogen inlet. Pyrophosphoric acid (89.000g, 0.500mol) was dissolved in 30ml of distilled water with cooling. The acidic solution was ice cooled to ensure that the temperature did not exceed 20C
upon dropwise addition of allylamine (37.500ml: 0.500mol).
The addition was performed with stirring under a dry nitrogen atmosphere. The resulting solution was treated with a warm (50C) aqueous solution of 2,2' azobis[2-amidinopropane] (l.OOOg in water (lOml)) and stirred for 24 hours at 60C. The viscous product was washed with water repeatedly in a blender until nothing further dissolved. The product was then dried in vacuo at 110C
for 18 hours on siliconised (lubricated/non-stick) paper.
Yield = 58.6g.

E~MPLE 3 25OPTIMISATION OF POLY(ALLYLAMMONIUM) PYROPHOSPHATE

Phosphorus/nitrogen-containing flame-retardants conventionally comprise three active components, namely:
an acid source; a char former and a spumific or blowing agent. In some cases there may be only two active components, e.g., ammonium polyphosphate (APP) with trishydroxyethyl isocyanurate (THEIC).
Since the compounds of the invention could be envisaged as fulfilling the role of APP in a flame-retardant system, then it may be thought that they shouldbe employed in the presence of a char former, such as THEIC. Different ratios of poly(allylammonium) WO94/11425 2 1 4 6 ~ ~ 8 PCT/US93/10606 pyrophosphate:THEIC were e~Ar; ned in order to investigate the flammability performance in non-cross-linked EVA
(ELVAX 470; Dupont). The results obtained are reported in TABLE l.

TABLE l Ssmple Additive Losding (96) UL-94 Tests OL~.~, (O. 16cm) 1PAiP:llHEIC[l:l] 40 F~l 2nd Igrition 2PAP:THEICr7:5] 40 Fail 2nd Ignition 3PA~P:llHEIC[2:1] 40 Fail 2nd IgDilion 4PAiP:THEIC[3:1] 40 V-O 6 second flan~ng t~ne SPAP:THEICtS:l] 40 V-O 3 second flaming time 6 PAP 40 V-O No flaming time Unexpectedly, optimum performance was seen when poly(allylammonium) pyrophosphate was used alone.

This Example compares the flammability performance of poly(allylammonium) pyrophosphate with known phosphorus/nitrogen-containing flame-retardants: The comparative systems were: EXOLIT IFR-l0 (Hoechst Celanese) and ammonium polyphosphate (APP) (PHOSCHEK P-40, Monsanto).
The results obtained are shown in TABLE 2. All data refer to samples in non-crosslinked EVA (ELVAX 470).

Sample* Additive UL-94 Tests Observations (0. 16cm) 3 O 7 PAP V-O No flaming time 8(c) APP Fail 2nd Ignition 9(c)EXOLIT IFR-10 V-O 2 second flaming time * (c) = col,lpala~ e sample not in accordance with the invention.

:::

WO94/1142~ 2l~65s8, PCT/US93/106~6 The results suggest poly(allylammonium) pyrophosphate is a better performer than either of the known phosphorus/nitrogen-containing flame-retardants, with no flaming time observed in attaining its UL94 V-O rating.
E~MPLE 5 COMPARATIVE FLAMMABILITY PERFORMANCE - CONE CALORIMET~R
TESTING
This Example demonstrates the flammability performance of poly(allylammonium) pyrophosphate when compared with known phosphorus/nitrogen-containing flame-retardants. The comparative systems were: EXOLIT IFR-lO
and EXOLIT IFR-23 (Hoechst-Celanese). All data refers to samples in non-crosslinked EVA ELVAX 470). A standard irradiant flux level of 50kWm~2 was employed. Two runs were undertaken for each sample and the results were averaged. The results obtained are reported in TABLE 3.

S-mple~ Additive Lo~dinSRHR SE~ SPR COPR
(~`) (lcWm-2) (mZlc~ -') (1021cgm-Z~-') Pe k A~g. Pc~k A~g. Pe-k Avg. Pe~k Avg.
20 10(c) EXOLIT 40 185 80 847 466 3.92 1.37 2.59 0.65 ~R-23 lI(c)E~OL~ 40 186 77 635 361 3.94 1.15 2.66 0.76 I~:R-10 12 PAP 40 154 50 834 423 3.88 0.95 2.63 0.61 ~(c)= . .-~mple not in ~-~ - - with ~he p~cnt invention.
These results show that poly(allylammonium) pyrophosphate performs excellently as a flame retardant, being generally at least as good as the state-of-art commercial materials and noticeably better with regard to the key parameter: RHR. FIGURE l shows dramatically the improvement in RHR realised by utilising poly(allylammonium) pyrophosphate as opposed to both EXOLIT IFR-lO and IFR-23. Poly(allylammonium) pyrophosphate produces a better protective char for unburned fuel than either EXOLIT IFR-l0 or EXOLIT IFR-23 WO94/11425 2 1 ~ 6 5 5`8 PCT/US93/10606 --19 _ as evidenced by the lack of a second period of heat release up to nearly 800 seconds. Evidence of this is that upon completion of the test and removal of the sample holder assembly from the apparatus, a considerable amount of molten, unburned material is visible under the char.
Poly(allylammonium) pyrophosphate test pieces also show a much lower mass loss rate during the test.

SURFACE TREATMENT
This Example demonstrates the usefulness of surface treatment of the P/N polymeric salts to improve their dispersibility in polymers and hence the physical properties of the resulting material. A number of surface treatment agents can be used, including titanates, silanes, zirconates and zircoaluminates, but the particular example chosen here is the titanate commercially available from Kenrich Petrochemicals Inc.
Under the trade designation KR38S. The flame-retardant, in this case poly(allylammonium) pyrophosphate, was ball milled for 16 hours in a 2% w/w solution of KR38S in toluene (concentrations of between 0.5% and 5.0% could be used), resulting in a fine, easily dispersable powder.
The particle size can be reduced further by jet milling if necessary.
This surface treatment procedure enhances the dispersability of only these types of phosphorus/nitrogen compounds, not all P/N compounds, as illustrated by the corresponding data for ammonium polyphosphate PHOSCHEK
P-40. The physical/mechanical property results below apply to a polyolefin/rubber blend of EVA (ELVAX 470: melt index 0.7; vinyl acetate content 18%) : EPDM (EPsyn 7506;
Copolymer Inc.) (4:l). The particle size of the titanate treated and untreated poly(allylammonium) pyrophosphate was less than 53~m in both cases, whereas the ammonium polyphosphate has an average particle size of l0~m in each case. The results obtained for poly(allylammonium) WO94/11425 ~ 5S8i PCT/US93/10606 pyrophosphate and ammonium polyphosphate are reported in TABLE 4 below.

5 Sample Additive Loading Surface Tensile Strength at break Nm-2 F~ ifm at (%)Treated break (%) 13 PAP 26 YES 1.441x107 (2089psi) 838 14 PAP 26 NO 9.535~106 (1383psi) 690 lS(c) APP 26 YES 1.291~107 (1873psi) 921 16(c) APP 26 NO 1.257~107 (1823psi) 983 * (c) = ~ sample not in ac~.l' with the present inveation.

USE IN COMBINATION WITH AMMONIUM POLYPHOSPHATE
This Example demonstrates that the P/N polymeric salts can be used in combination with other sources of phosphorus without deleterious consequences, and in some cases with improvement upon, flammability properties. The examples quoted below are all KR38S titanate surface treated poly(allylammonium) pyrophosphate (PAP) of particle size less than 53~m, compounded in (EVA ELVAX

4 7 0: EPDM EPsyn 7 50 6 ) [ 4: 1 ] ( as per EXAMPLE 6). Cone calorimeter data were obtained at 50kWm~2 irradiant flux.
2 5 The results obtained are shown in TABLE 5 S-mple Additive l~ding Surfilce tj,(s) RHR SEA CO NO
(~) Tre~ted (kWm2) (m2k~~') (kgk~ kgk~-') pe~k ~IV. pe~k v. pe-k ~v. pe~ v.
17P~P 26 YES 36 280 98 824 601 0.07 0.04 0.009 0.006 3 0 18PAP 26 NO 17 226 92 925 785 0.08 0.06 0.009 0.006 19PAP:APP 26 YES 34 260 11~ 715 549 0.07 0.05 0.007 0.006 19:11 20PAP:APP 26 YES 29 211 86 721 421 0.07 0.05 0.007 0.006 [4:1]
21PAP:APP 26 YES 28 241 116 753 622 0.08 0.05 0.006 0.00 [7:31 W094/11425 ~ 1~ 6 5 5 8 PCT/USg3/10606 USEFULNESS OF PAP TREATED WITH VARIOUS COUPLING AGENTS
WITH A SECOND PHOSPHORUS SOURCE
This example demonstrates the performance of PAP with a variety of titanate and silane coupling agents, with or without the addition of a second phosphorus source, namely ammonium polyphosphate PHOSCHEK P-40). All materials were evaluated in EVA EPsyn [4:l] in terms of cone calorimeter performance. Coupling agents used were KR38S titanate (Kenrich Petrochemicals Inc.), 3-aminopropyltrimethoxysilane and amyltriethoxysilane. A
sample containing ammonium polyphosphate as the flame-retardant is included for comparison. All cone calorimeter experiments were performed at 50kWm-2 irradiant flux and all PAP samples were reduced to a particle size of less than 53~m. The results obtained are shown in TABLE 6.

Sample Additive Loading C~upling t4(s) RHR SEA CO
(%)Agent (kWm2) (m2kg) (kgk~
peak av. peak av. peak av.
22 PAP 26titanate 21 280 98 824 601 0.07 0.04 23 PAP:APp 26titanate 31 211 86 721 421 0.07 0.05 [4:11 24 PAP 26amino 23 221 81 696 507 0.08 0.06 silane PAP:APp 26amino 23 205 69 751 471 0.07 0.06 l4 l] silane 25 26 PAP 26 aml 29 202 95 751 544 0.09 0.06 silane 27 PAP:APP 26amyl 23 196 84 778 575 0.08 0.05 [4:1] silane 28(c) APP 26 - 50 519 178 914 659 0.04 0.03 * (c) = sample not in acco,l' ~ e with the iu~ liou.

5 ~ 8 PCT/US93/10606 SHELF LIFE TESTING
A three month old sample of PAP (KR38S titanate treated) was blended with ammonium polyphosphate (PHOSCHEK
P-4 0) t4:1] and compounded into EVA (ELVAX 4 7O):EPDM(EPsyn 7 5 06) t4:1] at a 2 6% loading level. The flammability data for this sample and that of an analogous one containing a freshly prepared batch of the same flame retardants are shown below. In both cases the data was derived from the cone calorimeter. The heat flux was 50KW~2 for both materials. The results obtained are shown in TABLE 7 .

Sample Additive Loading ~(s) RHR SEA CO NO
(%) (kWm-2) (m2kg-') (kgkg-') (kgkg-') peak av. peak av. pesk av. peak av.
15 29 PAP:APP 26 31 289 113 682 549 0.07 0.05 0.~5 0.~K
(f~h) [4:1]
30 PAP:APP 26 32 245 89 731 5~ 0.08 0.~ 0.~7 0.~5 (ag~) ~4:1]
2 0 ~MPLE 10 USE AS A F~AME RETAR~ANT IN POLYOLEFIN/RUBBER BLENDS
The flammability performance of PAP alone is compared below with the state-of-the-art commercial non-halogen flame-retardants EXOLIT IFR-10 and EXOLIT IFR-23 and a 2 5 typical halogenated flame-retardant based on the following commercially available materials - decabromodiphenyloxide (DB): antimony oxide (ATO): alumina trihydrate (ATH) (2:1:1). DB was obtained from Great lakes Chemicals, ATO
from Anzon America Inc. (11-0000-2 556-6) and ATH is the 3 0 932 grade from Solem. All cone calorimeter data refer to non-cross-linked EVA (ELVAX 47 0): EPDM (EPsyn 7 5 0 6) t4:1].
As in the previous examples a standard irradiance level of 50kW2 was employed. Again two runs were undertaken for each sample and the results averaged. The results 3 5 obtained are shown in TABLE 8 and Figure 2 of the accompanylng drawlngs.

WO94/11425 2~ 465~8 PCT/US93/10606 Sample* Additive Loading (%) RHR SPR(s) COPR
(lcWm-~ (106kgm-2s-l) Peak Avg. Peak Avg. Peak Avg.
31(c) EXOLlT 20 431 238 8.87 4.85 6.66 3.66 32(c) EXOLlT 20 497 255 10.3 5.03 5.51 3.01 33 PAP 20 346 181 8.52 4.32 5.51 2.91 34(c) DB:ATO: 20 674 196 29.70 7.98 ~3.05 10.30 ATH
* (c) = .~ sample not in ~.~' -e with the ~ )u.

USE AS FLAMB RETARDANT IN EPOXY RESINS
This Example demonstrates the utility of PAP used either alone or in conjunction with PHOSCHEK P-40 ammonium polyphosphate PHOSCHEK P-40, as a flame-retardant for thermoset epoxy resins. The particular example here consists of a resin based upon 2 parts of EPIKOTE 815 (Shell Chemicals) cured with 1 part 2,4,6-dimethylaminomethylphenol, containing between 20 and 30%
of flame-retardant. Specimens were cured at 110C for 16 hours and then evaluated on a cone calorimeter at 50kWm~2 irradiant flux. In all cases here PAP was surface treated with 3-aminopropyltrimethoxysilane and its particle size was less than 53~m. The results obtained are shown in TABLE 9.

WO 94/11425 PCr/US93/10606 2~55~

SampleAdditiveT o~lin~ (%) tj~(S) RHR(kWm~2) peak av.

37(c) APP 20 33 241 7 38 PAP:APP 20 32 238 83 [1:2]
39 PAP:APP 20 52 250 89 [1: 1]
PAP:APP 20 42 250 94 [2: 1]

* (c) = sample not in ac~l.lance with the present invention.

E~MPLE 12 USE AS A Fl,AME RETARDANT IN LOW DENSITY POLY~;lnY~ENE
This Example demonstrates the usefulness of compounds of general formula (1), with or without a second phosphorus source, as flame retardants for low density polyethylene. Formulations were prepared in the aforementioned fashion and evaluated on a cone calorimeter at an irradiant flux of 50kWm~2. Formulation constituents were as shown in TABLE 10 in which the following nomenclature is employed:

25 Sample * Co~ (%) LDPE DEDPO ATO IRGANOX 1010 Stearic Acid PAP PHOSCHKP40 45(c) 68.3 25.0 5.0 0.7 1.0 - -46 68.3 - - 0.7 1.0 30.0 47 68.3 - - 0.7 1.0 24.0 6.0 3 0 * (c) = sample not in accc,.~.ce with the present invention.

WO94/11425 214 ~ ~ ~ 8 PCT/US93/10606 LDPE = LUPOLEN 1812 D, DBDPO = decabromodiphenyl oxide (Great Lakes Chemical Corp.), ATO = antimony trioxide (Anzon America Inc.), IRGANOX l0l0 = Ciba Geigy Chemicals, Stearic Acid = Aldrich Chemical Company Ltd, PHOSCHEK P40 = ammonium polyphosphate (Monsanto), PAP = poly(allylammonium) pyrophosphate.
Cone calorimeter evaluation produced the results shown in TABLE ll.

TABLE ll Sample* Additive Loading RHR (lcWm-2) SEA (m~cg') CO (kgkg ') (%) peak av. av. av.
45(c)DBDPO:ATO30 495 92 1284 0.112 [5: 1]
15 46 PAP 30 169 91 748 0.061 47 PAP:APP 30 170 96 655 0.054 [4 1]
* (c) = sample not in a~cc,- ' -e with the present invention.

It will be noted the compounds of this invention, whether used alone or in conjunction with a second phosphorus source, confer excellent properties upon LDPE
in terms of rate of heat release, smoke generation and toxic gas yield, considerably outperforming a widely used flame retardant additive system such as decabromodiphenyl oxide/antimony trioxide.

EXAMPLE l3 USE AS A FLAME RETARDANT IN CROSS-LINKED POLYOLEFINS
This Example demonstrates the usefulness of PAP, as a 4:l blend with ammonium polyphosphate PHOSCHEK P-40, in crosslinked ethylene-vinyl acetate copolymer (ELVAX 470).
Formulations were prepared containing either 45~ or 50%
total flame retardant plus 3% trimethylolpropyl trimethacrylate electron beam prorad and l phr stearic WO94/11425 ~ 5 8 PCT/US93/10606 acid. These materials were extruded into tubing of outside diameter 0.64cm (0.25 inches) and wall thickness 25~m (25mils), which was then cross-linked by means of exposure to an electron beam dose of lOMRad.
Flammability performance was assessed by means of the Underwriters' Laboratories UL224 test for tubing materials. This involves the application of a Bunsen Flame to the vertically clamped tubing for five 15 second burns, each separated by an interval of either 15 seconds or the observed flaming time of the specimen, whichever is greater. For the specimen to attain the required pass rating, termed VW-1, the flaming time in each case must not exceed 60 seconds and the material must emit no flaming drips which ignite a cotton wool pad placed underneath the specimen. Each material is generally tested five times, and if any specimen does not meet the pass criteria it is deemed to be not VW-1 rated. It has also been found useful, although not part of the UL224 specification, to classify materials by means of an average flame number 'F' which represents the total flaming time observed for a specimen, i.e., the sum of the flaming times for each bunsen application. The lower the value of F the better is the material in terms of its flammability performance. The results obtained are shown in TABLE 12.

Sample*Additive Loading (%)UL224 Rating Average F(s) 48 PAP:APP 4S VW-1 2 [4:1]
49 PAP:APP 50 VW-1 8 14:1 50(c)EXOLIT IFR-10 45 VW-1 30 51(c)EXOLIT IFR-10 50 VW-1 17 52(c)EXOLIT IFR-23 45 not VW-l 69 53(c)EXOLIT IFR-23 50 VW-1 30 * (c) = not in accordance with co~ e sample in invention.

WO94/11425 21 4 6S~ ~ . PCT/US93/10606 -2~-The PAP used to demonstrate this example was surface treated with N-(3-acryloxy-2-hydroxypropyl)-3-aminopropyl triethoxysilane and was of particle size less than 53~m.
Comparative materials quoted are EXOLIT IFR-lO and EXOLIT
IFR-23.
Hence the blend of PAP with [4:l] outperforms both EXOLIT IFR-23 at either 45% or 50% loading in the cross-linked polyolefin of this example.

DEMONSTRATION OF A RANGE OF NITROGEN CONTAINING
POLYMERS PERTAINING TO THIS INVENTION
This Example demonstrates the performance of variety of P/N polymeric salts in addition to the erstwhile demonstrated examples regarding poly(allylammonium) as the polymeric cation in the salt. All flame retardants were evaluated as single additives, with no secondary phosphorus source, in a polyolefin/rubber blend consisting of EVA (ELVAX 470):EPDM(EPsyn 7506) [4:l], non cross-linked, at a loading of 26%. Cone calorimeter evaluationwas carried out at an irradiant flux of 50kWm~2. Materials examined were poly(allylammonium) pyrophosphate surface treated with KR38S titanate [I], poly(ethyleneiminium) pyrophosphate [II], poly(2-vinylpyridinium) pyrophosphate [III], poly(l-vinylpyrrolidonium) pyrophosphate [IV], poly(N-[2-(methacryloyl)ethyl]-N,N-dimethylammonium) orthophosphate (V) poly(N-methylvinylammonium) pyrophosphate [VI] and poly(4-styrylammonium) pyrophosphate [VII]. Comparative data is also given for the phosphorus nitrogen flame retardant CN-1197 (Great Lakes Chemical Corp.) The results obtained are shown in TABLE 13.

2 ~ 4 6 ~ ~ g TABLE l3 Sample Additive Load~g tjt(s)FUHR SEA CO NO
(%) (kWm-~ (ni2kg-') (kgkg~ kgkg-') peak av. peak av. peak av. av.
54 tI] 26 21 267 127 1000 549 0.08 0.05 ~I] 26 22 231 97 684 497 0.06 0.04 56 ~] 26 23 375 165 1093 801 0.07 0.06 57 ~V] 26 23 376 153 1061 746 0.08 0.07 58 rv] 26 29 497 164 1016 715 0.06 0.06 59 rVI] 26 21 226 102 812 608 0.06 0.06 0.0066 60 rVII] 26 31 392 133 1146 790 0.08 0.07 0.0051 60(c) CN-1197 26 20 445 179 1050 745 0.06 0.05 0.0070 The results demonstrate that a range of polymeric salts of the invention show excellent flammability properties, smoke production and toxic gas production characteristics.

DEMONSTRATION OF A RANGE OF PHOSPHORUS CONTAINING ACIDS
PERTAINING TO THIS INVENTION
This Example demonstrates the usefulness of a range of phosphorus containing acids that could be considered for compounds of general formula(I). Salts examined here are poly(allylammonium) pyrophosphate [VIII], poly(allylammonium) polyphosphate [IX), poly(allylammonium) orthophosphate [X] and poly(allylammonium) hypophosphite [XI]. None of these materials were subject to surface treatment and all were used without recourse to a second phosphorus source.
[VIII] and [IX] were evaluated at a loading of 40% in ethylene-vinyl acetate copolymer (EVA, ELVAX 470, Dupont).
[VIII], [X] and [XI] were evaluated at a loading of 26% in EVA(ELVAX 470):EPDM(EPsyn 7506) [4:l]. Cone calorimeter performance was evaluated at an irradiant flux of 50kWm~2.
The results obtained for Additives VIII and IX in EVA and WO94/11425 ~1 4 ~ PCT/US93/10606 additives VIII to XI in EVA:EPDM[4:1] are shown in TABLES
14 and 15, respectively.

Sample Additive Toa~inE RHR(kWm~2) SEA(m2kg~') ( ) p~ av. p~ av.
62~III] 26154 50 831 423 63[IX] 26180 77 883 ~8 EXOL~ 26185 80 847 Sample Additive Loading ~(s) RHR SEA CO NO
(%)(kWm-~) (m2kg') (kgkg ')(Ics~kg') peak av. peak av. pealc av. peak av.
(V~I) 26 17 226 92 925 785 0.08 0.06 0.00 0.006 66 (X) 26 28 267 109 882 696 0.08 0.06 0.00 0.006 67 (XI) 26 39 284 112 1030 797 0.13 0.10 0.00 0.006 USE AS A FLAME RETARDANT IN THERMOPLASTIC POLYURETHANE
This example demonstrates the usefulness of compounds of general formula (1) as flame retardants for thermoplastic polyurethanes. Formulations were compounded on a Schwabenthan Polymix~ two roll mill at 140-145C and test pieces were fashioned by compression moulding in a Moore hydraulic press at 170C for five minutes.
Evaluations were performed on a cone calorimeter using an external irradiant flux of 50 kW m~2. A composition containing a flame retardant in accordance with this invention was compared with Spinflam~ MF82/PU, a commercially available phosphorus/nitrogen flame retardant specifically designed for polyurethanes. Formulation constituents were as shown in Table 16:

WO94/11425 2~ 58 PCT/US93/10606 -3~-Sample* Conctit~lPnt (%) Estanen' 58315 PAP MF82/PU
68(c) 70.0 - 30.0 69 70.0 30.0 s * (c) = sample not in accordance with the present invention.

Estanen' 58315 - thermoplastic polyurethane (BF Goodrich), PAP - poly(allylammonium) pyrophosphate, MF82/PU - Spinflam~ MF82/PU (Himont Italia).
Cone calorimeter evaluation produced the results shown in Table 17, quoting the important f lammability properties time to ignition (t4 in s), peak rate of heat release (RHR pk in kW m~2) and average rate of heat release 15 (RHR av in kW m~2). Test duration in each case was ten minutes and the values quoted are a mean of duplicate runs. Data are also presented for average yield of oxides of nitrogen (NO8 av in kg per kg of specimen) a toxic gas commonly evolved upon combustion of nitrogen containing polymers . Yield of oxides of nitrogen was measured by means of an add-on unit to the cone calorimeter comprising a chemiluminescence detector (Signal 4000 Series).

Sample*t4 (s) RHR (kW m~2) NO" av (kg kg-') pk av 68(c) 25 471 141 0.0102 69 29 276 146 0.0077 * (c) = sample not in accordance with the present invention.

It can be seen by ref erence to Table 17 that PAP
shows considerably better performance than Spinflamn' MF82/PU as a flame retardant for thermoplastic polyurethane, as illustrated by longer time to ignition, WO94/11425 ~14 G 5 ~ 8 PCT/US93/10606 lower peak rate of heat release whilst showing similar average rate of heat release, and lower yield of a toxic combustion product such as oxides of nitrogen.

USE AS A FLAME RETARDANT IN POLYSTYRENE
This example demonstrates the usefulness of compounds of general formula (1) as flame retardants for polystyrenes. Formulations were compounded on a Schwabenthan Polymix~ two roll mill at 95-100C and test pieces were fashioned by compression moulding in a Moore hydraulic press at 120C for five minutes. Evaluations were performed on a cone calorimeter using an external irradiant flux of 50 kW m~2. A composition containing a flame retardant in accordance with this invention was compared with Spinflam~ MF82/PP, a commercially available phosphorus/nitrogen flame retardant. Formulation constituents were as shown in Table 18:

Sample* Conctituent(%) 70(c) 70.0 - 30.0 71 70.0 30.0 *(c) = sample not in accor~allce with the present invention.

PS - polystyrene (Aldrich Chemical Co.), PAP - poly(allylammonium) pyrophosphate, MF82/PP - Spinflam~ MF82/PU (Himont Italia).
Cone calorimeter evaluation produced the results shown in Table 19, ~uoting the important flammability properties time to ignition (t~ in s), peak rate of heat release (RHR pk in kW m~2) and average rate of heat release (RHR av in kW m~2). Test duration in each case was ten minutes and the values quoted are a mean of duplicate WO94/1142S ~1 4 6 5 5s 8 i ` PCT/US93/10606 runs. Data are also presented for average yield of oxides of nitrogen (NOX av in kg per kg of specimen) a toxic gas commonly evolved upon combustion of nitrogen containing polymers. Yield of oxides of nitrogen was measured by means of an add-on unit to the cone calorimeter comprising a chemiluminescence detector (Signal 4000 Series).
TABLE l9 Sample* tjg (s) RHR (kW m~2)NO% av (kg kg-') pk av 70(c) 18 187 1 14 0.0083 71 16 199 105 0.0061 * (c) = sample not in acco~dance with the present invention.

It can be seen by reference to Table l9 that PAP
shows better overall performance than Spinflam~ MF82/PP as a flame retardant for polystyrene, as illustrated by similar (i.e. within 10%) time to ignition, peak rate of heat release and average rate of heat release, whilst displaying a significantly lower yield of a toxic combustion product such as oxides of nitrogen.

USE AS A FLAME RETARDANT IN POLYSTYRENE-co-ACRYLONITRILE
This example demonstates the usefulness of compounds of general formula (l) as flame retardants for copolymers of polystyrene and acrylonitrile. Formulations were compounded on a Schwabenthan Polymix~ two roll mill at 130-135C and test pieces were fashioned by compression moulding in a Moore hydraulic press at 150C for five minutes. Evaluations were performed on a cone calorimeter using an external irradiant flux of 50 kW m~2. A
composition containing a flame retardant in accordance with this invention was compared with Spinflam~ MF82/PU, a commercially available phosphorus/nitrogen flame retardant. Formulation constituents were as shown in Table 20:

Sample* Con~tit~lçnt (%) 72(c) 70.0 ~ 30.0 73 70.0 30.0 * (c) = sample not in accordance with the present invention.

PSA - poly(styrene-co-acrylonitrile, 75:25) (Aldrich Chemical Co.), PAP - poly(allylammonium) pyrophosphate, MF82/PU - Spinflam~ MF82/PU (Himont Italia).
Cone calorimeter evaluation produced the results shown in Table 21, quoting the important flammability properties time to ignition (t~ in s), peak rate of heat release (RHR pk in kW m~2), and average rate of heat release (RHR av in kW m~2). Test duration in each case was ten minutes and the values quoted are a mean of duplicate runs. Data are also presented for average yield of oxides of nitrogen (NOX av in kg per kg of specimen) a toxic gas commonly evolved upon combustion of nitrogen containing polymers. Yield of oxides of nitrogen was measured by means of an add-on unit to the cone calorimeter comprising a chemiluminescence detector (Signal 4000 Series).

TABLE 2l Sample* t,g (s) RHR (kW m~2)NO,~ av (kg kg-l) pk av 72(c) 26 230 124 0.01 15 3 o 73 40 247 129 0.0103 * (c) = sample not in accordance with the present invention.

W O 94/11425 ~ ~ ~ 6 ~ ~ ~ PC~r/US93/10606 It can be seen by reference to Table 21 that PAP
shows better overall performance than Spinflam~ MF82/PU as a flame retardant for polystyrene-co-acrylonitrile as illustrated by similar (i.e. within 10%) peak rate of heat release, average rate of heat release, and yield of a toxic combustion product such as oxides of nitrogen, but a significantly longer time to ignition.

USE AS A FLAME RETARDANT IN POLY(VINYL ALCOHOL) This example demonstates the usefulness of compounds of general formula (1) as flame retardants for poly(vinyl alcohol). Formulations were compounded on a Schwabenthan Polymix~ two roll mill at 140-145C and test pieces were fashioned by compression moulding in a Moore hydraulic press at 170C for five minutes. Evaluations were performed on a cone calorimeter using an external irradiant flux of 50 kW m-2. A composition cont~;n;ng a flame retardant in accordance with this invention was compared with Spinflam~ MF82/PE, a commercially available phosphorus/nitrogen flame retardant. Formulation constituents were as shown in Table 22:

Sample* Con~titll~nt (~o) 74(c) 70.0 - 30.0 70.0 30.0 * (c) = sample not in accordance with the present invention.

PVA - poly(vinyl alcohol), Mol. wt. 15000 (Fluka Chemical Co . ) , PAP - poly(allylammonium) pyrophosphate, MF82/PE - Spinflam~ MF82/PE (Himont Italia).

WO94/11425 ~ ` 5 8 PCT/US93/10606 Cone calorimeter evaluation produced the results shown in Table 23, quoting the important flammability properties time to ignition (t~ in s), peak rate of heat release (RHR pk in kW m~2) and average rate of heat release (RHR av in kW m~2). Test duration in each case was ten minutes and the values quoted are a mean of duplicate runs. Data are also presented for average yield of oxides of nitrogen (NOX av in kg per kg of specimen) a toxic gas commonly evolved upon combustion of nitrogen containing polymers. Yield of oxides of nitrogen was measured by means of an add-on unit to the cone calorimeter comprising a chemiluminescence detector (Signal 4000 Series).

Sample* t,g (s) RHR (kW m~2)NOX av (kg kg-l) pk av 74(c) 38 189 106 0.0068 203 121 0.0061 -* (c) = sample not in accor~lance with the present invention.

It can be seen by reference to Table 23 that PAP
shows better overall performance than Spinflam~ MF82/PE as a flame retardant for polystyrene-co-acrylonitrile as illustrated by similar (i.e. within 10%) peak rate of heat release and yield of a toxic combustion product such as oxides of nitrogen, but a significantly longer time to ignition, albeit with slightly higher average rate of heat release.

t~o~q

Claims (12)

CLAIMS:

1. A non-halogen containing flame-retardant additive comprising a salt of an inorganic phosphorus-containing acid and a polymeric compound selected from the group consisting of homopolymers and copolymers comprising a linear backbone formed of at least 10 repeat units, said polymeric compound comprising a plurality of basic nitrogen functionalities, in which the backbone of the polymer and/or groups pendant thereto contain a primary, secondary or tertiary amino group.

2. A flame-retardant additive as claimed in Claim 1 in which the salt comprises from 10 to 50 units represented by general formula:
[RH]+.1/y [Xy-]
in which;
R is a nitrogen-containing repeat unit of the polymeric compound having a structure represented by general formula (II) to (III) (II) (III) in which;
R1 and R2 independently represent H or an alkyl group of up to 5 carbon atoms; and R3 represents a group comprising a basic nitrogen functionality, Xy- is the deprotonated or partially deprotonated form of the phosphorus-containing acid, and Y is an integer.

3. A flame-retardant additive as claimed in claim 2 in which R3 is selected from , , , , in which;
R1 and R2 are as defined in Claim 4.

4. A flame-retardant additive as claimed in Claim 3 wherein said polymer comprises a compound selected from the group consisting of allylamine, ethyleneimine, 2-vinyl pyridine, 4-vinyl pyridine, 4-aminostyrene, N,N-dimethylaminoethyl methacrylate, N-vinyl pyrrolidone, and mixtures thereof and the phosphorus-containing acid is orthophosphoric acid, polyphosphoric acid, hypophosphorus acid, trimetaphosphoric acid, phosphinic acid, phosphorous acid, hypophosphoric acid, or pyrophosphoric acid.

5. A flame-retardant additive as claimed in any preceding Claim further comprising a second source of phosphorus different from said salt, in which said second source comprises not more than 70% by weight of the additive.

6. A flame-retardant additive as claimed in Claim 5 in which the second source of phosphorus comprises ammonium polyphosphate, melamine polyphosphate or red phosphorus.

7. A flame-retardant additive as claimed in any preceding Claim in which the salt and/or the second source of phosphorus are prepared as dry, free flowing particles having an average particle size of less than 80µm.

8. A flame-retardant additive as claimed in any preceding Claim which has been surface treated with a material selected from zircoaluminates, titanates and silane coupling agents.

9. A polymer comprising an amount of from 10 to 60% by weight of the polymer of a flame-retardant additive as claimed in any one of Claims 1 to 8.

10. A polymer as claimed in Claim 9 in which the polymer is a homopolymer or copolymer of an olefin, an acrylate or an epoxy resin.

11. A polymer as claimed in Claim 10 in which the polymer is low density poly(ethylene), high density poly(ethylene), linear low density poly(ethylene), poly(ethylene/acrylic acid), poly(ethylene/ethyl acrylate), poly(ethylene/vinyl acetate), poly(propylene) or ethylene-propylene/vinyl acetate, poly(propylene) or ethylene-propylene-diene monomers.

12. An article comprising a polymer as claimed in any one of Claims 9 to 11 in the form of a tube, pipe, sheet, tape or other moulded article, or a caulk, mastic or sealant or other coating composition.