GB1570177A

GB1570177A - Vinyl chloride polymer composition

Info

Publication number: GB1570177A
Application number: GB42642/75A
Authority: GB
Original assignee: Durham Chemicals Ltd
Current assignee: Durham Chemicals Ltd
Priority date: 1975-10-17
Filing date: 1975-10-17
Publication date: 1980-06-25
Also published as: DE2646970A1; FR2328015B1; SE7611492L; NL7611490A; SE424734B; FR2328015A1

Description

(54) IMPROVED VINYL CHLORIDE POLYMER COMPOSITION (71) We, DURHAM CHEMICALS LIMITED, a British Body Corporate of Birtley, Chester-Le-Street, County Durham, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to an improved vinyl chloride polymer composition.

Homopolymers and copolymers of vinyl chloride find numerous industrial and commercial applications. Practical considerations dictate that the vinyl chloride polymers be formulated with various other materials to give compositions whose chemical and physical properties can be tailored to the particular application in which the composition is to be used. In order to provide the desired properties in the final product, they may be formulated with a plasticiser. The conventional plasticisers are esters e.g. of organic carboxylic acids or of phosphoric acid, di-2ethylhexylphthalate being one of the most frequently used. These esters are relatively expensive and attempts have been made to use cheaper materials to plasticise the polymer, for example chlorinated paraffins.Unfortunately, the chlorinated paraffins do not have such good plasticising properties as the carboxylic acid esters so that it is not practical to replace the ester plasticisers completely by the chlorinated paraffins but, so far as the plasticising properties are concerned, it is practical partly to replace the ester by the chlorinated paraffin.

Although the mixture of an ester and a chlorinated paraffin can provide adequate plasticising properties, the presence of the chlorinated paraffin in filled polymers tends to have an adverse effect on the stability of the composition.

We have now found that the adverse effect on heat stability resulting from the presence of the chlorinated paraffin in a filled polymer composition can be counteracted by introducing an organic nitrogen containing compound into the composition.

Accordingly, the present invention provides a stabilised vinyl chloride polymer composition comprising: a) a vinyl chloride polymer, b) an ester which is a plasticiser for vinyl chloride polymers, c) a chlorinated paraffin which is a plasticiser for vinyl chloride polymers, d) a metal compound which is a heat-stabiliser for vinyl chloride polymers, e) a non-fibrous filler, and f) a stabiliser which is an organic nitrogen containing compound.

Suitable nitrogen containing compounds include: 1. alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, mono-, di- and tri-propanolamines and butanolamines; 2. urea: quinolines such as a hydroxy-quinoline e.g. 8-hydroxy quinoline or 2,2,4-trimethyl- 1 ,2-dihydroxy quinoline (Flectol H); intercyclic dicarboxylic acid imides such as phthalimide; or Chloramine -T, (sodium p-toluene-sulphochloramine); and 3. cyclic or acylic compounds containing the molecular grouping

This last-mentioned class of compounds (3) represents a preferred class of organic nitrogen containing compound and includes, as cyclic compounds, the various nitrogen substituted triazines such as melamine, dimers and trimers of melamine (melam and melem), N,N',N"-triphenylmelamine; 2-aminopyrimidines, an imidazole such as 2-aminoimidazoles and 1,2-dimethylimidazole; acyclic compounds which can be used include the various guanidines or dicyandiamides such as dicyandiamide itself, diphenylguanidine, acetylguanidine, aminoguanidine, phenylaminoguanidine, N-oxymethyl N'-cyanguanidine, N-carboethoxy N'-cyanguanidine and N-methylguanidine.Aromatic amines, alkylamines and thioureas are not recommended as they do not always have a beneficial inf@@ence on both colour and heat stability of the composition.

The amount of organic nitrogen compound used in the composition can vary within fairly wide limits that will normally be 0.025% by weight of the vinylchloride polymer and particularly 0.11% by weight.

The vinyl chloride polymer can be any polymer of vinyl chloride. Suitable polymers include homopolymers of vinyl chloride and copolymers of vinyl chloride containing at least 50% by weight vinyl chloride monomer copolymerised with one or more copolymerisable monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinylidene chloride, styrene, methylmethacrylate or dialkyl furmarate.

The copolymers will normally be derived from at least 70% by weight vinyl chloride.

The compositions of the invention contain both an ester plasticiser and a chlorinated paraffin plasticiser. The ester plasticiser may be any one of those conventionally used for plasticising vinyl chloride polymers such as di-2-ethylhexylphthalate, dibutylsebacate, dioctylsebacate, tricresylphosphate, dipropyleneglycoldibenzoate or trixylylphosphate (TXP). The ester plasticiser will normally be present in quantities smaller than those used when the ester is the only plasticiser and in the compositions of the invention, will normally be present in an amount of 1080% by weight of the vinyl chloride polymer, particularly 2060% by weight.

The chlorinated paraffin used to plasticise the vinyl chloride polymer may be any one of the commercially available chlorinated paraffins. The chlorinated paraffin plasticiser is preferably a liquid and suitable chlorinated paraffins are those containing 4070% by weight chlorine and obtained by chlorinating straight or branched chain paraffinic hydrocarbons of molecular weight 200350. The chlorinated paraffins sold under the Registered Trade Mark Cereclor are particularly suitable. The chlorinated paraffin plasticiser will normally be present in an amount of 1060% by weight of the vinyl chloride polymer and conveniently can be used in an amount approximately equal to the amount of ester plasticiser used.

The heat stabiliser used in the present invention is a metal compound of the type customarily used to heat stabilise vinyl chloride polymers. This will normally be a lead, barium, cadmium, calcium, zinc or tin compound or a mixture thereof.

These may be (1) inorganic leads such as tribasic lead sulphate, white lead or dibasic lead phosphite; (2) organic lead compounds such as dibasic lead phthalate; (3) metal soaps such as lead stearate, barium stearate, cadmium stearate, calcium stearate or zinc stearate; (4) solvent soluble compounds such as barium phenolate or cadmium 2-ethylhexanoate or (5) organo-tin compounds such as dibutyl tin maleate or di-n-octyl tin thioglycollate. The lead compounds will normally be present in amounts of 1-10%, preferably 1--5% by weight of the vinyl chloride polymer, the barium, cadmium, calcium or zinc compounds in an amount of 1--3% by weight of the vinyl chloride polymer and the tin compounds in an amount of 0.5 to 2% by weight of the vinyl chloride polymer.Heat stabilisers (1) and (2) identified above are to be preferred, particularly a mixture of tribasic lead sulphate and lead stearate.

It is preferred that the weight ratio of the heat stabiliser present in the composition to the organic nitrogen containing compound present in the composition be 4:1 to 100:1, preferably 10:1 to 25:1, e.g. 20:1.

The composition of the invention also contains a non-fibrous filler such as calcium carbonate, calcium sulphate, silica, china clay or fullers earth. The exact nature of the filler and the proportion in which it is to be used will naturally depend upon the end use of the composition but in the compositions of the invention, fillers may be used in conventional quantities, for example 25%-l 50% by weight of the vinyl chloride polymer. The present invention is particularly applicable to the production of vinyl chloride polymer compositions for use in the cable industry.

These compositions normally contain less than 100% filler based on the weight of vinyl chloride polymer e.g. 25-75% and particularly 50% calcium carbonate filler.

The compositions of the invention may also contain pigments of the type conventionally used in vinyl chloride polymer compositions such as titanium dioxide, iron oxide or lead chromite which can be present in amounts of 0.05 to 5% by weight of the vinyl chloride polymer.

In the event that the composition does not already contain a component capable of lubricating the vinyl chloride polymer during processing, the compositions of the invention should contain a conventional lubricant which may be a metal salt of a fatty acid, such as lead stearate or a paraffin, wax, ester or alcohol. Epoxidised oils such as epoxidised soya bean oil can be used as a stabiliser/plasticiser. The lubricant is used in conventional quantities, for example 0.12% by weight based on the weight of vinyl chloride polymer.

The compositions of the invention may also contain antioxidants of the type conventionally used in vinyl chloride polymer compositions e.g. 2,2-(bis-phydroxyphenyl)propane or homologues or analogues thereof.

The compositions of the invention may be compounded by methods conventionally used for the formulation of vinyl chloride polymer compositions, for example the components can be mixed in a high speed mixer and the dry blend fed to an extruder.

It is particularly convenient first to compound the organic nitrogen containing compound with the heat stabiliser and subsequently to incorporate this composition in the vinyl chloride polymer together with the two plasticisers, the filler and any optional components.

Our divisional Application No. 20759/79 Serial No. 1,570,178 describes and claims a stabilising composition for use in the production of a stabilised vinyl chloride polymer composition including a chlorinated paraffin plasticiser and a non-fibrous filler, comprising (1) an organic nitrogen containing compound and (2) a poly basic inorganic lead compound which is a heat stabiliser for a vinyl chloride polymer, the weight ratio of the lead compound to the organic nitrogen-containing compound being 4:1 to 100:1.

In the case where this last-mentioned composition does not include a metal compound capable of lubricating a vinyl chloride polymer during compounding, a suitable lubricant may be included in the composition.

The following Examples are given to illustrate the invention.

EXAMPLES 1--6 and EXPERIMENTS A-B.

Compositions were prepared by compounding the ingredients given in Table 1 below in the proportions given in Table 1 below in the following way.

The ingredients of each formulations were weighed into a beaker and mixed with a palette knife. The contents of the beaker were then transferred onto a 2 roll mill operating at 1700C., from which after gelation and mixing for 3 minutes the composition was removed as a sheet. From this specimens were cut for heat stability tests. The PVC resin used was a vinyl chloride homopolymer which is a cable grade resin sold under the Registered Trade Mark Corvic D60/13. D.I.O.P. is an ester plasticiser di-isooctylphthalate. The chlorinated paraffin used, Cereclor S45 is a chlorinated paraffin containing 45% by weight chlorine of approximate molecular weight 610.

T.B.L.S./lead stearate 4:1 is a mixture of tribasic lead sulphate and lead stearate in a 4:1 ratio by weight. Bisphenol A is the known antioxidant 2,2-(bis-p- hydroxyphenyl)-propane. In the Table below, the amounts given are in parts by weight. Experiments A-B are not in accordance with the invention and are included for comparison purposes.

TABLE 1

Expt. Expt.

Example A 1 B 2 3 4 5 6 PVC Resin 100 100 100 100 100 100 100 100 Calcium Carbonate 50 50 50 50 50 50 50 50 D.I.O.P. 28 28 28 28 28 28 28 28 Cereclor S45 28 28 28 28 28 28 28 28 TBLS/Lead Stearate 4:1 5 5 4.5 4.5 4.5 4.33 4.33 4.33 Bisphenol A 0.5 0.25 0.25 0.42 0.42 0.42 Triethanolamine 0.25 0.25 Melamine 0.25 0.25 0.5 Dicyandiamide 0.25 The compositions formulated as indicated above where then subjected to a heat stability test.In this test, the specimens were placed in an oven and heated at 180 C., and were removed at 15 minute intervals and examined for general discolouration (yellowing) and for the appearance of spots. The samples were assessed visually on each occasion and given a discolouration index on a scale of 0 (white sample no discolouration) to 10 (Sample completely black). The following results set out in Table 1A were obtained.

TABLE 1A

0 u) \0 xD Time mins.

3 Oxx 30 45 60 75 Xo\ A 0 1 2x 4xx Sxxx 7xxxx 1 0 0 1 2x 3x 3x 4x 6xx 6xx 7xx 7xxx cos x x x < o 2 2 2 4 4 5 6 6 7 m x x o X ': :1- wO m d- X 5 0 &num; lnc\lvrmmln oO x x x t t x H o x x H m < o o o ^ o o H o o o o o o o o o E / O X = slightly spotty XX = spotty XXX = very spotty XXXX = almost completely covered by spots These results show that the presence of the chlorinated paraffin plasticiser leads to a very rapid discolouration and spotting of the samples while the spotting problem is eliminated substantially completely and the discolouration occurs much more slowly when the organic nitrogen containing compound is included in the composition.

In addition to exhibiting the favourable heat stability as illustrated above, the compositions of the invention show a significant improvement in stability as measured by the congo red test which is particularly important in compositions to be used in cable making.

EXAMPLES 7-24 and EXPERIMENTS C-M.

In these Experiments, further information about certain components is given after Experiment M.

EXPERIMENT C.

The following components were formulated into test specimens as described in Examples 16.

PVC resin (source (i)) 100 gm.

Diisooctyl phthalate (D.I.O.P.) 50 gm.

Calcium Carboante (source 1) 50 gm.

Tribasic lead sulphate (T.B.L.S.)/lead stearate 4:1 blend 4.75 gm.

2,2-(bis-p-hydroxyphenyl)propane 0.25 gm.

The specimens were then cut for heat stability and congo red tests.

EXPERIMENT D.

The procedure of Experiment C was repeated but part of the D.I.O.P. was replaced by chlorinated paraffin and the quantities adjusted to give a similar plasticising effect. The composition was as follows: PVC resin (source (i)) 100 gm.

D.I.O.P. 28 gm.

Chlorinated paraffin (source A) 28 gm.

Calcium carbonate (source 1) 50 gm.

T.B.L.S./leadstearate,4:1 blend 4.75 gm.

2,2-(bis-p-hydroxyphenyl)propane 0.25 gm.

EXAMPLES 7-18.

Specimens were prepared as described in Experiment D but with the following modifications and additions. Unless otherwise indicated the procedure, components and proportions are as in Experiment D.

Weight of 4:1 TBLS/lead stearate Example mixture N compound 7 4.5 g. 0.1 g. triethanolamine 8 4.5 g. 0.25 g. triethanolamine 9 4.5 g. 0.5 g. triethanolamine 10 4.5 g. 0.75 g. triethanolamine 11 4.5 g. 0.1 g. melamine 12 4.5 g. 0.25 g. melamine 13 4.5 g. 0.5 g. melamine 14 4.5 g. 0.75 g. melamine 15 4.5 g. 0.25 g. urea 16 4.5 g. 0.25 g. Flectol H (2,2 ,4-trimethy 1-1 ,2-dihydroxy quinoline) 17 4.5 g. 0.25 g. 1,2-dimethylimidazole 18 4.5 g. 0.25 g. diethanolamine (Flectol is a Registered Trade Mark) EXPERIMENT E.

The procedure of Experiment C was repeated using the following composition: PVC resin (source (i)) 100 gm.

D.I.O.P. 28 gm.

Chlorinated paraffin (source A) 28 gm.

Calcium carbonate (source 2) 50 gm.

T.B.L.S./lead stearate 4:1 blend 4.75 gm.

2,2-(bis-p-hydroxyphenyl)propane 0.25 gm.

EXAMPLE 19.

The procedure of Example C was repeated using the following composition: PVC resin (source (i)) 100 gm.

D.I.O.P. 28 gm.

Chlorinated paraffin (source A) 28 gm.

Calcium carbonate (source 2) 50 gm.

T.B.L.S./leadstearate4:1 blend 4.5 gm.

2,2-(bis-p-hydroxyphenyl)-propane 0.25 gm.

Triethanolamine 0.25 gm.

EXPERIMENT F.

Experiment E was*çepeated but calcium carbonate (source 3) was used as the filler.

EXAMPLE 20.

Example 19 was repeated but calcium carbonate (source 3) was used as the filler.

EXPERIMENT G.

Experiment E was repeated but china clay was used as the filler.

EXAMPLE 21.

Example 19 was repeated but china clay was used as the filler.

EXPERIMENT H.

Experiment D was repeated but chlorinated paraffin (source B) was substituted for chlorinated paraffin (source A).

EXAMPLE 22.

Example 12 was repeated but chlorinated paraffin (source B) was substituted for chlorinated paraffin (source A).

EXPERIMENT J.

Experiment D was repeated but with the substitution of PVC resin (source (ii)) in place of PVC resin (source (i)).

EXAMPLE 23.

Example 8 was repeated but with the substitution of PVC resin (source (iii)) in place of PVC resin (source i)).

EXPERIMENT K.

Experiment D was repeated but with the substitution of PVC resin (source (iii)) in place of PVC resin (source (i)).

EXAMPLE 24.

Example 8 was repeated but with the substitution of PVC resin (source (iii) in place of PVC resin (source (i)).

EXPERIMENT L.

Experiment C was repeated using the following composition: PVC resin (source (i)) 100 gm.

D.I.O.P. 50 gm.

Calcium carbonate (source 1) 50 gm.

T.B.L.S./lead stearate 4:1 blend 4.5 gm.

2,2-(bis-p-hydroxyphenyl)-propane 0.25 gm.

Triethanolamine 0.25 gm.

EXPERIMENT M.

Experiment L was repeated but with the substitution of melamine for triethanolamine.

The origin of various components in Examples 7-24 and Experiments C-M is given below.

PVC source (i) Corvic D60/13 ex I.C.I. Ltd.

PVC source (ii) Scon 5410 ex Vinatex Ltd.

PVC source (iii) Breon S125/10 ex B.P. Chemicals Ltd.

Calcium carbonate source 1 Snowcal 6ML ground natural calcium carbonate ex Cement Marketing Co. Ltd.

Calcium carbonate source 2 Winnofil S precipitated coated calcium carbonate ex I.C.I. Ltd.

Calcium carbonate source 3 Polycarb S ground coated natural calcium car bonate ex English China Clays Ltd.

China clay M 100 ex English China Clays Ltd.

Chlorinated paraffin Source A Cereclor S45 ex I.C.I. Ltd.

Chlorinated paraffin Source B Chloroparaffin 45 ex Hoechst.

Scon, Breon, Polycarb, Snowcal and Winnofil are all Registered Trade Marks.

Oven Heat Stability Tests.

In this test, specimen sheets from Examples 7-24 and Experiments C-M were placed on glass slides in an air circulating oven at 1800C. A specimen from each sheet was removed at 15 minute intervals and examined for general discolouration. The increasing discolouration represents the general degree of degradation of the PVC with time. The specimens were assessed visually and given a discolouration index on a scale of0 (unheated control specimen) to 10 (specimen completely black).

The specimens were also assessed visually for black spotting representing localised degradation. This was recorded as: X = slightly spotty XX = spotty XXX = very spotty XXXX = almost covered by spots Congo Red Test.

The method used was essentially that in B.S. 2782:Partl:1965, Method 109A except that for laboratory convenience sheet 0.030 inch thick was used instead of 0.050 inch thick.

This method is for determining the time taken for hydrogen chloride to be evolved from PVC compound when it is heated in a test tube at 1800C. The presence of hydrogen chloride is shown by its effect on Congo Red indicator paper adjacent to the sample.

The times, or 'Congo Red Values', recorded for a group of stabilisers are a comparative indication of their respective abilities to delay the onset of decomposition in a PVC compound.

TABLE 1B

a lm nooo to g e H < H H H H H H H H < H v Time mins. Congo Red Ex. or Value Expt. 15 30 45 60 75 90 105 120 135 150 165 180 (mins) C 1 1 1 X 1 2 2 3 4 5 5 5 355 D 1 1 1 lx 2x 3xx 6xxx 9xxxx 80 7 u x x so 8 1 1 1 2 2 3 4 4 5 6 7 8 170 9 1 1 1 2 3 4 5 6 6 6 7 8 170 m t X 2 3 D 6 6 6 6 V) In 11 1 2 2 3 4 4x 5x 6x 7x 7x 9x 125 o x " 1 2 2 so 3 3 4 4 5 6 7 8 138 mcr\a o 2 3 3 4 4 5 5 6 7 9 13S 15 2 2 3 3 4 4 6 8 9 105 o 2 2 2 mmm 17 1 1 2 2 3 3 4 5 5 6 7 8 135 18 1 1 2 2 3 4x Sx 7x 9x 139 xD X > f sr H < H < N cs > ef) en O ~ H H H H > (S CS > > > H H V) H E E / / m ID Q o H X Table 1B summarises results on Experiments C and D and Examples 7-18. It can be clearly seen that use of triethanolamine and melamine at a number of levels provides a significant improvement in heat stability and congo red values together 5 with the reduction or elimination of spotting. Similar improvements are shown with 5 other nitrogen compounds.

TABLE 2

a r u o o oo oo Time mins. Congo Red Ex. or Value o vor x Y)C5a\ 2 a\ V) X Cr) X rO\DQI cO o xe x X X om x x x ss x en dX x x ur 's ux) oW x N o t t < < H N e f un ~ H H Table 2 demonstrates improvements obtained with compositions containing other fillers.

TABLE 3

o oo m o o a, v, o C4 m \o 0 U o Time mins. Congo Red Ex, or Value x D 1 1 1 lx 2x 3xx 6xxx 9xxxx 80 x ox x Ol x x H x x 2 2x 2xx 2xxx 3xxx 3xxx 8xxx 9xxxx 65 t m x x 1 2 3 3 4 4 5 5 6 6 7 120 m x x Ho x x x Fo x x en vo Nx exs o Ix x X t / X i s Table 3 demonstrates the advantage of the invention with an alternative chlorinated paraffin.

TABLE 4

3 9"00Cr)009 C~ g oo o oo N Ch o mins. Congo Red Ex. or Value o io x x ~ X X D 1 1 1 lx 2x 3xx 6xxx 9xxxx 80 V) X X X X X X X t 3 1 lx lxx lxx lxx 2xxx 3xxx 4xxx 4xxxx 4xxxx 4xxxx 6xxxx 83 23 X X < + t e ', Vss X X f. X X H X X . et m t X O X X X b1 X X X H X X X 3K t t t en n t. X X X xX X X .D t e o xX x xx m X X X F N n H N > tS O X X X .o es H ~ m X X t s~ ~ H H H O ~ H X ~ H H H V) H H H H < Table 4 demonstrates the advantage of the invention with other PVC resins.

TABLE 5

a DL , In o o o oo 5 = m u V U o oo o m In oN < t t O cu mins. Congo Red Ex. or Value Expt. 15 30 m 60 75 90 105 120 135 150 165 180 (mins) vr H N L 1 1 2 2 2 3 3 4 4 5 5 5 280 M 1 < t H N N v] ~ H H E E / A; O > E Table 5 demonstrates that the nitrogen compounds used as described have a 5 slightly adverse effect in the absence of chlorinated paraffin. 5

Claims

WHAT WE CLAIM IS:

1. A stabilised vinyl chloride polymer composition comprising (a) a vinyl chloride polymer (b) an ester which is a plasticiser for vinyl chloride polymers (c) a chlorinated paraffin which is a plasticiser for vinyl chloride polymers (d) a metal compound which is a heat stabiliser for vinyl chloride polymers (e) a non-fibrous filler, and (f) a stabiliser which is an organic nitrogen containing compound.

2. A composition according to claim 1 wherein Component (f) is an alkanolamine.

3. A composition according to claim 2 wherein the alkanolamine is triethanolamine.

4. A composition according to claim 1 wherein Component (f) is a cyclic or acyclic compound containing the molecular grouping

5. A composition according to claim 4 wherein Component (f) is melamine.

6. A composition according to claim 4 wherein Component (f) is an imidazole or a guanidine.

7. A composition according to claim 1 wherein Component (f) is urea or a hydroxy quinoline.

8. A composition according to any one of the preceding claims wherein Component (f) comprises 0.025% by weight of the vinyl chloride polymer.

9. A composition according to claim 8 wherein Component (f) comprises 0.11% by weight of the vinyl chloride polymer.

10. A composition according to any one of the preceding claims wherein the filler is calcium carbonate.

11. A composition according to any one of the preceding claims wherein the filler comprises less than 100% by weight of the vinyl chloride polymer.

12. A composition according to claim 10 or 11 wherein the filler is calcium carbonate in an amount which is 2575% by weight of the vinyl chloride polymer.

13. A composition according to any one of the preceding claims wherein Component (d) is a lead, barium, cadmium, calcium, zinc or tin compound or a mixture thereof.

14. A composition according to claim 13 wherein Component (d) is a mixture of tribasic lead sulphate and lead stearate.

15. A composition according to any one of the preceding claims wherein the weight ratio of the heat stabiliser present in the composition to the organic nitrogen containing compound present in the composition is 4:1 to 100:1.

16. A composition according to any one of the preceding claims wherein the vinyl chloride polymer is polyvinyl chloride.

17. A composition according to any one of claims 1--15 wherein the vinyl chloride polymer is a copolymer of at least 50% by weight vinyl chloride with the balance being a copolymerisable monomer.

18. A composition according to any one of the preceding claims wherein the ester is diisooctyl phthalate and the chlorinated hydrocarbon is one containing 4070% by weight chlorine obtained by chlorinating a paraffinic hydrocarbon of molecular weight 200-350.

19. A composition according to any one of the preceding claims wherein the ester and the chlorinated hydrocarbon are present in substantially equal amounts by weight and each is present in an amount of 10-60% by weight of the vinyl chloride polymer.

20. A composition according to any one of the preceding claims which includes a pigment and/or an anti-oxidant and/or a lubricant.

21. A composition according to claim 1 substantially as hereinbefore described with reference to any one of the Examples.

22. A method of improving the stability of a vinyl chloride polymer composition which includes both an ester and a chlorinated paraffin as plasticisers for the vinyl chloride polymer and which also includes a non-fibrous filler, which method comprises incorporating into the composition (1) a metal compound which is a heat stabiliser for a vinyl chloride composition and (2) an organic nitrogencontaining compound.

23. A method according to claim 22 wherein the organic nitrogen containing compound is as defined in any one of claims 2-7.

24. A method according to claim 22 or 23 wherein the heat stabiliser is as defined in claim 13 or 14.

25. A method according to any one of claims 22 to 24 wherein the weight ratio of the heat stabiliser present in the composition to the organic nitrogen containing compound present in the composition is 4:1 to 100:1.

26. A method according to claim 22 substantially as hereinbefore described with reference to any one of the Examples.

27. A stabilised vinyl chloride composition obtained by a method according to any one of claims 22 to 36.