CA2066485A1

CA2066485A1 - Process for the treatment of halogenated and non-halogenated polymers

Info

Publication number: CA2066485A1
Application number: CA 2066485
Authority: CA
Inventors: Moira A. Barrell; Joseph Michaux; Robert S. Whitehouse
Original assignee: Individual
Current assignee: Cabot Plastics Ltd
Priority date: 1991-04-24
Filing date: 1992-04-21
Publication date: 1992-10-25
Also published as: AU649529B2; FI921808A0; JPH0794572B2; NO921555D0; NO921555L; JPH06128408A; AU1509592A; FI921808A

Abstract

ABSTRACT

PROCESS FOR THE TREATMENT OF MIXTURES OF HALOGENATED
AND NON-HALOGENATED POLYMERS

A process for producing stabilised useable thermoplastic compounds from mixtures of halogenated and non-halogenated polymers in any suitable thermoplastic processing equipment wherein the halogenated component is subjected to controlled thermal degradation and evolved halogen acid gas is reacted with a metal oxide, metal aliphatic carboxylic acid salt, or mixtures thereof.

Description

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PROCESS FOR THE TREATMENT OF MIXTURES OF ALOGENATED_AND
NON-~ALOGENATED POLYMERS

The present invention relates to a process for treating mixtures of halogenated and non-halogenated polymers in any 5 suitable thermoplastic processing eyuipment. The halogenated component is subjected to controlled thermal degradation to produce a stabilised useable thermoplastic compound. The process results in no evolution of halogen containing volatiles. The process can be carried out in 10 equipment such as a Banbury mixer, twin screw extruder, single screw extruder, or the like.

On such process is already known from U.S. Patent No 4,643,861. According to this a composition of PP/PVdC
~polypropylene/polyvinylidene chloride) scrap plus hydrated 15 lime ~Ca(OH)2 ) and a metal carboxylate is subjected to a densification process where the temperature is kept down to 20-100F (11-56C) below the melting point of the polymeric film by the addition of water. A reaction is said to take place durin~ this densification process lasting 5-15 20 minutes. This process differs from the present invention in a number of respects. Firstly the present invention requires a temperature above which the polymer is melted ~or the reaction to take place.

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The present invention also specifically requires the use of either a metal oxide or a metal aliphatic carboxylic acid salt whereas in the above mentioned US patent, the process requires the use of hydrated lime which is not the same as calcium oxide.

A further distinction is the requirement of the patent that water be added in an amount of 5 to 25~ by weight to maintain the reaction temperature below the melting point of the polymer, whereas in the present invention water or other 10 solvent is not added.

Also known in the prior art are Japanese Patent Specification Nos. 51-3750, 53-21277 and 56-122894 wherein waste plastics are thermally decomposed for subsequent possible utility as fuels. The patents refer to reacting 15 the waste plastics in the presence of calcium compounds including calcium oxide, calcium hydroxide or calcium carbonate~ The purpose for addiny the calcium-containing compounds is to react with any HC1 or other noxious gases produced. Contrary to the Japanese patents, however, the 20 present invention is clearly directed to recovering useable thermoplastic compositions from mixtures of halogenated and non-halogenated polymers, including waste materials thereof.

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The present process involves a controlled thermal degradation to produce a stabilised halogenated polymeric component, carried out in the presence of a specified quantity of a metal oxide or metal aliphatic carboxylic acid salt which results in the recovery of a material suita~le for reuse.

Accordingly, it is an object of this invention to provide a process enabling recovery of useable thermoplastic compounds from mixtures of halogenated and non-halogenated polymers.

10 It is another object of this invention to provide a process enabling recovery of useable thermoplastic compounds from mixtures of halogenated and non-halogenated polymers, wherein either or both of the polymers are derived from waste materials.

15 It is yet another object of this invention to provide a process enabling recovery of useable thermoplastic compounds from mixtures of halogentated and non-halogenated polymers wherein any conventional processing equipment may be utilised.

20 It is yet another object of this invention to provide a process enabling recovery of useable thermoplastic compounds from mixtures of halogenated and non-halogenated polymers whereby corrosion oE the p~ocessing equipment is minimised.

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The present invention relates to a non-solvented proce~s ~or recovering a stabilised useable thermoplastic composition from a mixture of at least one halogenated polymer and at least one non-halogenated thermoplastic polymer, wherein the 5 halogenated polymer is subjected to controlled thermal degradation while the non-halogenated thermoplastic polymer is not substantially degraded, to produce a re-useable thermoplastic composition. The mixture which may be, for example, in the form of laminated film, coated bottles, and 10 the like is first made into a processable form by any conventionally known means such as chopping, granulating or agglomerating.
The polymeric mixture is then combined with at least one metal oxide or metal aliphatic carboxylic acid salt which 15 will yield a halogenated metal salt which is stable under the conditions required to process and use the resultant ~hermoplastic composition. The metal oxide or metal aliphatic carboxylic acid salt is utilised in an amount which is at least the stoichiometric equivalent required to react with 20 all the halogen contained in the mixture. Preferably the amounts of metal oxide or metal aliphatic carboxylic acid salt range from at least l.0 to about 3.0 times the stoichiometric amount necessary to prevent evolution of all the halogen in the polymeric mixture. If insufficient 25 metal oxide o~ metal aliphatic carboxylic acid salt were to be added then halogen in the polymeric mixture could be evolved causing corrosion of the processing equipment.

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should not be used in any amount which would result in difficulties during processing of the polymeric material and/or difficulties in utilising the resulting thermoplastic compound. It is possible to utilise mixtures o~ metal oxides, or mixtures of metal aliphatic carboxylic acid salts, or mixtures of metal oxides and metal aliphatic carboxylic acid salts.

The mixture o~ polymers and metal oxide or metal aliphatic 10 carboxylic acid salt is subjected to conditions of elevated temperature such that the polymeric mixture is melted and the halogen containing polymeric compound is thermally degraded to evolve halogen acid gas which reacts with the metal oxide and/or metal aliphatic carboxylic acid salt.
15 The mixture of polymers and metal oxide or metal aliphatic carboxylic acid salt may be mixed by means of any apparatus known to those skilled in the art. Moreoever it is not critical whether the mixture of polymers and metal oxide/metal aliphatic carboxylic acid salt is premixed prior 20 to being subjected to the conditions of elevated temperature.
The following are exemplary methods known for carrying out the reaction.

2 ~ 8 5 Preferably suitable for use in processing the mixture of polymers and metal oxide/metal aliphatic carboxyl~c acid salt are Banbury mixers, extruders, two roll mills, or any other devices utilised in the industry. The polymeric mixture and metal oxide/metal aliphatic carboxylic acid salt may be premixed or fed independently as long as the metal oxide/metal aliphatic carboxylic acid salt is fed in prior to the halogenated polymeric component liberating any halogen acid gas.

10 The mixture of polymers and metal oxide/metal aliphatic carboxylic acid salt is heated to a temperature such that the polymeric mixture is melted and the halogen containing polymeric compound is thermally degraded to evolve halogen acid gas which reacts with the metal oxide/metal aliphatic 15 carboxylic acid salt. The temperatures utilised in the processing of the polymeric mixture with the metal oxide/metal aliphatic carboxylic acid salt reactants, will depend upon the ingredients utilised in the reaction. The temperature should not, however, be so high as to cause 20 either the metal oxide or metal aliphatic carboxylic acid salt to decompose, or to cause the non-halogenated polymer to significantl~ decompose. Where the metal-containing compound utilised is a metal aliphatic carboxylic acid salt, -.
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the resulting stabilised polymeric compound, containing ~he products of the reaction, is then recovered by any conventional manner, for example, by forcing through a die and forming pellets, by granulating, or the like. Where 5 the metal containing compound, however, is a metal oxide, water is evolved during the reaction. This evolved water is removed or captured by any suitable technique. For example, the water may be captured by utilising an amount of metal oxide in excess of that which is required for the 10 reaction. Alternatively, the water may be removed by vacuum extraction, or any other technique which could be easily applied for the removal of the water. Once the water has been removed or captured the resulting stabilised polymeric compound containing the product of the reaction is then 15 recovered utilising any conventional means.

Polymers suitable for use with the present invention are as follows. The halogen containing polymer may be any halogen containing polymer, preferably those where the halogen is chlorine. In particular, polyvinyl chloride and 20 polyvinylidene chloride copolymers are most likely to be used with the present process.

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'l'he non-halogen containing polymer suitable for use in the present invention may be any non-halogen containing pol~mer which will not thermally degrade prior to any substantial thermal degradation of the halogen containing polymeric 5 component of the mixture. It is particularly preferred to utilise as the non-halogen containing polymer, any polyolefin, such as polyethylene, polypropylene; styrenics, such `as polystyrene, and copolymers of olefins such as copolymers of ethylene with vinyl acetate; and copolymers of 10 styrenics.

While any metal oxide may be used in the process of the present invention provided it is one which will yield a stable halogenated metal salt, it is preferred that the metal oxide be one where the metal is selected from the 15 group consisting of calcium, magnesium and zinc. In the case where a metal aliphatic carboxylic acid salt, which will yield a stable halogenated metal salt, is to be used, it is preferred that the metal be selected from the group consisting of sodium, potassium, calcium, zinc, magnesium, ~ aluminium, tin and barium. It is preferred that the aliphatic carboxylate contain a chain of 2-30 carbon atoms, and more preferably 2-20 carbon atoms.

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2 ~ 3 Exemplary of the aliphatic carhoxylic acid radicals suitable for use in the present invention are stearates, such as calcium or zinc stearate, citrates, tartrates, adipates and resinates.

~5 The stabilised thermoplastic polymeric eompound obtained as a result of the process, can be mixed with additives of any type known within the industry. The various additives are incorporated into the polymeric compound in order to render the polymeric compound suitable for given purposes. For 10 example, there may be mixed with the pol~meric compound, antioxidants, antistatic agents, plasticisers, nucleating agents, impact modifiers, pigments, fillers, reinforeements, lubricants, processing aids, coupling agents, and the like. Examples of materials which unetion for these 15 purposes are well known to those in the industry and are generally comrnereially available.

The thermoplastie polymerie eompound o~tained as a result of the process can also be mixed with other polymeric compounds.

In order to evaluate the physical properties of the 20 polymeric materials resulting from the proeess of the present invention, there are u~ilised the following well known test procedures:

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Melt flow index "MFI" ISO 1133 Ash content ISO 247 Izod notched impact strength ISO 180 Tensile strength ISO R527 Elongation ISO R527 Flexural modulus ISO 178 This invention is further illustrated by the following examples wherein all parts are given by weight.

EXAMPLES 1-4.

Examples 1 - 4 of the present application demonstrate that different metal oxides are e~ually suitable for use in carrying out the present invention and also that mixtures of metal oxides may be satisfactorily utilised. In carrying 15 out examples 1-4, the polymeric mixture contains 90% by weight polypropylene and 10% by weight polyvinylidene chloride copolymer, wherein the chlorine content is 50~ by weight of the polyvinylidene chloride copolymer. In carrying out examples 1-4 the procéssing conditions employed are the 20 same.

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In particular, the polymeric mixture and the metal oxide utilised in examples l-4 as shown in the following Table l, are premixed and then introduced into a Haake Rheocord 90 type mixer manufactured and sold by Fisons Instruments. The 5 polymeric mixture and metal oxide premix is then mixed for a period of 8 minutes at a temperature of approximately 200C
at a mixer speed of 125 rpm. The resultant thermoplastic polymer is recovered from the mixer and, as shown in Table l, in each instance exhibits no odour of halogen.

10 From the conditions employed in carrying out examples 1-4 and the lack of any detectable odour of halogen, it can be concluded that all of the halogen acid evolved from the halogen containing polymer was reacted with the metal oxide. Moreoever, there was no odour of halogen detected 15 during the processing of examples 1-4.

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Example No. l 2 3 4 PP/PVdC*, % 92 93 94 88 Calcium oxide, % 8 3.5 _ _ 5 Magnesium oxide, % _ 3.5 6 _ Zinc oxide, % _ _ _ 12 Stoichiometric equivalent of metal oxide to halogen, % 3.63 3.06 2.65 5.02 10 Molar ratio of metal .
oxide to halogen ** 2.20 2.29 2.27 2.39 Halogen odour NO ~ NO NO

* polypropylene/polyvinylidene chloride copolymer.
** includes at least 1. a mole equivalent of metal oxide required to capture evolved water.

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In the following examples 5 and 6 there is demonstrated the use of a combination of a metal oxide together with a metal aliphatic carboxylic acid salt in carrying out the process of the present invention. Utilised as the metal oxide is .5 calcium oxide and as the metal aliphatic carboxylic acid salt is zinc stearate.

EXAMPLES 5 & 6 Formulations at two different levels of metal oxideJmetal aliphatic carboxylic acid salt concentrations are described 10in examples 5 and 6 in the processin~ of a polymeric mixture containing 90% polypropylene and 10% polyvinylidene chloride copolymer, wherein the chlorine content is 50% by weight of the polyvinylidene chloride copolymer. Also included in the formulation is waste polypropylene film.
15The formulations are shown in the following Table 2. In processing the formulations of examples 5 and 6, each of the ingredierlts of the formulation are weighed and separately added to a Banbury mixer.

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The batch wei~ht of the formulation is llOOg and the mixing is carried out at a temperature slightly above the melting temperature of polypropylene for a period of 1.5 minutes subsequent to fluxing OI the pol~ner, under a pressure of 40 ,5 psi (2.8 bar). The material is removed from the Banbury mixer and granulated prior to introduction into a Dolci single screw extruder having a 45 mm. barrel wherein, at a temperature exceeding 190C, the halogen acid gas is reacted with the combination of oxide and stearate. The resulting 10stabilised thermoplastic pol~neric material obtained from the extruder exhibits no odour of halogen.
Further characteristics of the resultant polymer obtained in example 6 are described in Table 2. Moreoever, there was no odour of halogen detected during the processing of 15examples 5 & 6.

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Table. 2 . _ Example number 5 6 _ . . _ PP/PVdC* % 73 78 Polypropylene % 10 10 5 Calcium oxide % 13 8 Zinc stearate % 4 4 Molar ratio of metal oxide/metal aliphatic carboxylic acid salt mixture to halogen** 4.64 2O72 Stoichiometric equivalent of metal oxide/metal aliphatic carboxy~ic acid salt mixture to halogen, % 3.66 4.41 15 Halogen odour NO NO
MFI, 2.16kg @ 230C, dg/min _ 5.2 Ash content, % _ 8.6 Izod notched impact strength, KJ/m2 _ 2.7 20 Tensile strength at yield, MPa 24 Tensile strength at break, MPa _ 12 Elongation at break, % _ 43 Flexural modulus, GPa 1.18 * polypropylene/polyvinylidene chloride copolymer.
25 ** includes approximately 1.0 mole equivalent of me-tal oxide required to capture evolved water.

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-In the following examples 7 and 8 there is demonstrated the use of a given metal oxide for the purpose of preventing the evolution of the halogen acid gas, at two different stoichiometric levels. As will be demonstrated hereinafter 5 it was established that both levels of metal oxide were adequate to prevent the evolution of the evolved halogen acid gas.

EXAMPLES 7 & 8 In examples 7 and 8 a polymeric mixture containing 90%
10 polypropylene and 10% polyvinylidene chloride, wherein the chlorine content is 50% by weight of the polyvinylidene chloride, is mixed with waste polypropylene film and calcium oxide in the proportions shown in Table 3. In processing the formulations, the ingredients specified in examples 7 15and 8, shown in Table 3, are séparately added into a Banbury mixer. The batch weight of llOOg is introduced into the Banbury mixer where mixing occurs at a temperature slightly above the melting temperature of polypropylene under a pressure of 40 psi ( 2.8 bar) for a period of l.5 minutes 20subsequent to fluxing of the polymer. The material is removed from the Banbury mixer and granulated.

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The granulated material is then introduced into a Betol single screw extruder, Model 2520/J, having a barrel diame-ter of 25 mm. wherein the calcium oxide reacts with the halogen acid gas at a temperature exceeding l90~C. The resulting stabilised thermoplastic polymeric mixtures recovered from the extruder exhibit no odour of halogen.
Further physical properties of the resultant polymers produced in examples 7 and 8 are shown in the following Table 3. During the process for produciny the resulting 10 thermoplastic polymeric mixtures no odour of halogen was detected.

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Table 3 .
Example number 7 8 PP/PVdC*, % 73 78 Polypropylene, % 14 14 5 Calcium oxide, % 13 8 Molar ratio of metal oxide to halogen** 4.52 2.60 Stoichiometric equivalent of metal oxide to halogen, % 2.88 3.08 10 Halogen odour NO NO
MFI, 2.16kg @ 230~C, dg/min 6.4 8.2 Ash content, % 12.6 8.2 Izod notched impact strength, KJ/m2 2.83.0 Tensile strength at yield, MPa 29 30 15 Tensile strength at break, MPa 16 25 Elongation at break, % 49 * polypropylene/polyvinylidene chloride copolymer.
** includes at least 1.0 mole equivalent of metal oxide required to capture evolved water.

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In the following example 9 there is illustrated the process of the present inventlon carried out in a twin screw extruder.

5 In this example the pol~neric mixture contains 90%
polypropylene and 10% polyvinylidene chloride copolymer, wherein the chlorine content is 50% by weight of the polyvinylidene chloride copolymer. The polymeric mixture and the calcium oxide are introduced as separate 10 ingredients directly into a Werner and Pfleiderer model ZSK40 twin screw extruder having a barrel of 40 mm.
diameter. The extruder is operated at temperatures in excess of 220C at a screw speed of 250 rpm and a pressure of 14 bar. The resulting stabilised polymeric material 15 obtained from the extruder exhibits no odour of halogen.
Further properties of the resultant thermoplastic polymeric material are found in the following Table 4.

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PP/PVdC* % 82 Calcium oxide % 18 Molar ratio of metal oxide to halogen** 5.57 Stoichiome-tric equivalent of metal oxide to halogen, % 3.23 Halogen odour NO
MFI, 2.16kg @ 230C, dg/min 5.0 Ash content, % 18.1 Izod notched impact strength, KJ/m~ 2.8 Tensile strength Q yield, MPa 26 Tensile strength ~ break, MPa 16 15 Elongation at break, % 71 Flexural modulus, GPa 1.2 .
_ * polypropylene/polyvinylidene chloride copolymer.

** i.ncludes at least 1.0 mole equivalent of metal oxide reguired to capture evolved water.

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2 ~ ~ , EXAMPLES lO-l9 Examples lO-l9 o~ the present application demonstrate that different metal aliphatic carboxylic acid salts are equally suitable for use in carrying out the present invention and also that mixtures of metal aliphatic carboxylic acid salts may be satisfactorily used. In carrying out examples lO-l9, the polymeric mixture contains 90% by weight polypropylene and 10% by weight polyvinylidene chloride copolymer, wherein the chlorine content is 50% by weight of the polyvinylidene chloride copolymer. In carrying out examples lO-l9 the processing conditions employed are the same. In particular, the polymeric mixture and the metal aliphatic carboxylic acid salt utilised in examples lO-l9 as shown in the following Table 5, are premixed and then introduced into a Haake Rheocord 90 type mixer as used in examples l-4. The polymeric mixture and metal aliphatic carboxylic acid salt premix is then mixed for a period of 5 minutes at a temperature of 210C at a mixer speed of 50 rpm. During processing, a glass rod dipped in a 5.0 N (normal) solution of ammonium hydroxide is placed at the top of the mixer where any evolved gas would escape. No white clouds of ammonium chloride are formed indicating that no halogen acid is evolved. The resultant stabilised thermoplastic polymer is recovered from the mixer.

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From the conditions employed in carrying out examples 10-19 and the lack of any detectable halogen, it is evident that all of the halogen acid evolved from the halogen containing polymer was reacted with the metal aliphatic carboxylic acid salt. Moreover there was no halogen detected while carrying out examples 10-19.

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In the following examples 20-22 there is demonstrated another manner for producing granulate from the polymeric composition of the invention and, further, the production of in~ection moulded specimens from the granulates. Also, these examples demonstrate three metal aliphatic oarboxylic acid salts utilised to react with halogen acid gas.

. . _ In examples 20-22 a polymeric mixture containing 90 polypropylene and 10% polyvinylidene chloride copolymer, wherein the chlorine content is 50% by weight of the polyvinylidene chloride copolymer, is mixed with various metal aliphatic carboxylic acid salts as shown in Table 6. In processing the formulations, the ingredients specified in examples 20 22 and shown in Table 6 are separately added into a Banbury mixer. In each case the batch weight of 1200g is introduced into the Banbury mixer where mixing occurs at a temperature slightly above the melting temperature of polypropylene under a pressure of psi (2.8 bar). Mixing is for a period of between 5 and 10 minutes subsequent to fluxing of the polymer, for examples 20 and 21; and for a period of 1.5 minutes subsequent to fluxing of the polymer, for example 22.
The material is removed from the Banbury mixer and granulated.

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~ 3 The granulated material is then introduced into a Battenfeld injection moulding machine, Model BA300 CD
plus, having a barrel diameter of 3Omm wherein the reaction of the halogen acid gas with the metal aliphatic ,5 carboxylic acid salt occurs at 230C.

The resulting moulded test pieces of polymers produced exhibited no odour of halogen. Physical properties of the resultant polymers produced in examples 20-22 are shown in the following Table 6.

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Table 6 Example ~o. 20 21 = _ PP/PVdC*, % 65 65 75 Sodium stearate, % 35 _ .5 Aluminium stearate, % _ 35 _ Sodium hydrogen tartrate, % _ _ 25 ~;
Stoichiometric equivalent of metal oxide to halogen, % 30.129.1 19.5 Molar ratio of metal aliphatic 10 carboxylic acid salt to halogen, % 1.25 1.31 1.38 Halogen odour NO NO NO
MFI, 2.16kg Q 230C, dg/min _ 34.3 4.9 Ash content, % 3.2 4.1 8.8 Izod notched impact strength, kJ/m2 1.7 2.9 2.6 15 Tensile strength at break, MPa 20 17 _ Elongation at break, % 6 10 Flexural modulus, GPa 2.09 1 0 6a * polypropylene/polyvinylidene chloride copolymer . : . .
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~ ,~3 From a review of the data shown in the foregoing tables 1-6, it will be readily observed that the stabilised thermoplastic polymeric materials obtained ky means of the process of the present invention are characterised by having ~5 physical properties comparable to those of standard commercially available grades of polypropylene having melt flow index (MFI~ properties of approximately the range shown in the examples of the invention. When drawing a comparison with the standard grades of polypropylene, the 10 thermoplastic polymeric materials of the present invention exhibit comparable values for tensile strength~ flexural modulus and Izod notched impact strength. Accordingly, the thermoplastic polymeric materials of the present invention would be suitable as starting materials for the production 15 of polymeric compounds.

While the present invention has been disclosed in connection with the embodiments hereof~ it should ~e understood that there are other embodiments which fall within the spirit and scope of the invention and that the invention is susceptible 20 to modification, variation and change without departing from the proper scope or fair meaning of the following claims.

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Claims

1. A non-solvented process for recovering a stabilised useable thermoplastic composition from a mixture of at least one halogenated polymer and at least one non-halogenated thermoplastic polymer wherein the halogenated polymer is subjected to controlled thermal degradation while the non-halogenated thermoplastic polymer is not substantially degraded, to produce a resultant stabilised thermoplastic composition, which comprises:

forming into a handleable material the mixture of polymers, combining the mixture of polymers with at least one metal oxide which will yield a halogenated metal salt, which is stable under the conditions required to process and use the resultant thermoplastic composition, in an amount which is at least the stoichiometric equivalent required to react with all the halogen contained in the mixture, subjecting the mixture of polymers and metal oxide to conditions of elevated temperature such that the polymeric mixture is melted and the halogen-containing polymers are thermally degraded to evolve halogen acid gas which is reacted with the metal oxide, removing or capturing evolved water, and collecting the resultant stabilised thermoplastic polymeric composition.

2. The process of claim 1 wherein the halogen of the halogen containing polymer is chlorine.

3. The process of claim 1 wherein the metal oxide is selected from the group consisting of calcium oxide, magnesium oxide and zinc oxide.

4. The process of claim 3 wherein the metal oxide is calcium oxide.

5. The process of claim 1 wherein the amount of metal oxide combined with the mixture of polymers ranges from at least 1.0 to about 3.0 times the stoichiometric amount necessary to react with all the halogen in the polymeric mixture.

6. The process of claim 1 wherein the evolved water is captured by adding a further amount of metal oxide.

7. A stabilised thermoplastic polymeric composition resulting from the process of claim 1.

8. The composition of claim 7 wherein at least one additive is incorporated.

9. An article of manufacture formed from the composition of claim 7 or 8.

10. A non-solvented process for recovering a stabilised useable thermoplastic composition from a mixture of at least one halogenated and at least one non-halogenated thermoplastic polymer wherein the halogenated polymer is subjected to controlled thermal degradation while the non-halogenated thermoplastic polymer is not substantially degraded, to produce a resultant stabilised thermoplastic composition, which comprises:

forming into a handleable material the mixture of polymers, combining the mixture of polymers with at least one metal aliphatic carboxylic acid salt which will yield a halogenated metal salt, which is stable under the conditions required to process and use the resultant thermoplastic composition, in an amount which is at least the stoichiometric equivalent required to react with all the halogen contained in the mixture, subjecting the mixture of polymers and metal aliphatic carboxylic acid salt to conditions of elevated temperature such that the polymeric mixture is melted and the halogen- containing polymers are thermally degraded to evolve halogen acid gas which is reacted wtih the metal aliphatic carboxylic acid salt, and collecting the resultant stabilised thermoplastic polymeric composition.

11. The process of claim 10 wherein the halogen of the halogen containing polymer is chlorine.

12. The process of claim 10 wherein the metal of the metal aliphatic carboxylic acid salt is selected from the group consisting of sodium, potassium, calcium, zinc, magnesium, tin, aluminium and barium.

13. The process of claim 10 wherein the aliphatic carboxylate contains a chain of 2-30 carbon atoms.

14. The process of claim 13 wherein the aliphatic carboxylate contains a chain of 2-20 carbon atoms.

15. The process of claim 14 wherein the metal aliphatic carboxylic acid salt is selected from the group consisting of stearates, citrates, tartrates, adipates and resinates.

16. The process of claim 10 wherein the amount of metal aliphatic carboxylic acid salt combined with the mixture of polymers ranges from at least 1.0 to about 3.0 times the stoichiometric amount necessary to react with all the halogen in the polymeric mixture.

17. A stabilised thermoplastic polymeric composition resulting from the process of claim 10.

18. The composition of claim 17 wherein at least one additive is incorporated.

19. An article of manufacture formed from the composition of claim 17 or 18.

20. A non-solvented process for recovering a stabilised useable thermoplastic composition from a mixture of at least one halogenated and at least one non-halogenated thermoplastic polymer wherein the halogenated polymer is subjected to controlled thermal degradation while the non-halogenated thermoplastic polymer is not substantially degraded, to produce a resultant stabilised thermoplastic composition, which comprises:

forming into a handleable material the mixture of polymers, combining the mixture of polymers with at least one metal oxide and at least one metal aliphatic carboxylic acid salt which will yield halogenated metal salts, which are stable under the conditions required to process and use the resultant thermoplastic composition, in an amount which is at least the stoichiometric equivalent required to react with all the halogen contained in the mixture, subjecting the mixture of polymers and metal oxide and metal aliphatic carboxylic acid salt to conditions of elevated temperature such that the polymeric mixture is melted and the halogen containing polymers are thermally degraded to evolve halogen acid gas which is reacted with the metal oxide and the metal aliphatic carboxylic acid salt, removing or capturing evolved water, and collecting the resultant stabilised thermoplastic polymeric composition.