GB2102433A - Organotin stabiliser mixture for halogen-containing polymers - Google Patents

Description

1 GB 2 102 433 A 1

SPECIFICATION Organotin stabiliser mixture for halogen-containing polymers

This invention relates to an organotin stabiliser mixture which is essentially non-toxic and is for use in moulding materials comprising halogen-containing polymers, especially those polymers which 5 are processed to form packaging material for foodstuffs and medical or pharmaceutical goods.

The present invention provides a stabiliser mixture for use in moulding materials comprising halogen-containing polymers, which mixture comprises from 35 to 45% by weight of a didodecyltinbis-thioglycolic acid ester.

(C,H21Sn(SCH,COO-R), and from 65 to 55% by weight of a dodecyltin-tris-thioglycolic acid ester C,H21Sn(SCH,COO-FI), wherein in each case R represents a straight-chain or branched alkyl radical having from 8 to 20 carbon atoms.

Advantageously, R represents 2-ethylhexyl in the didodecyltin compound and/or in the dodecyltin compound. Preferably, in one or both of the compounds in the mixture, the dodecyl moiety isn-dodecyi. 15 R may in principle in each case be a saturated or unsaturated radical, but will normally be saturated. It has long been known that certain organotin compounds may be used to stabilise halogencontaining polymers, especially polyvinyl chloride and PVC copolymers, against the effects of the light and heat. 20 In accordance with the present invention, however, there is provided a stabiliser which, as compared with conventional organotin stabilisers (such as those comprising butyl- or octyi-tin thioglycolates), displays improved performance in terms of one or more of the following properties: stabilising action, toxicity, migration, and dependence of stabilising action on tin content. Thus, for example, in the case of conventional stabilisers, such as dibutyltin thioglycolates or dioctyltin thioglycolates, especially in admixture with the corresponding monoalkyl tin compounds, 25 there is an optimum synergistic effect, in terms of the stabilising action, with a mono- proportion of from about 25 to 30% by weight.

It has been found in accordance with the invention, however, using mixtures of bis-dodecyltin thioglycolates with the corresponding mono compounds, that an improved stabilising action can be achieved with a considerably highermono proportion. The optimum effect has been observed with a 30 stabilising mixture which comprises about 40% by weight of the didodecyltin compound and about 60% by weight of the dodecyltin compound.

As is evident from the Table below, the stabilising action of the optimum synergistic 40%: 60% mixture according to the invention is considerably better in the case of E-PVC than that of the butyltin stabiliser mixture used for comparison, and superior stabilising action was also observed in the case of 35 S-PVC.

The outstanding heat-stabilising action obtainable using stabiliser mixtures according to the invention is all the more surprising in that the tin content, for example, of the stabiliser mixture having an isooctyl thioglycolate radical and having a tin content of 13.4% is considerably below that of the $0 comparison stabiliser, which contains 17.5 percent of tin. As in also evident from the Table, if the chain 40 in the ester portion is lengthened, the stabilising action of a dodecyltin stabiliser mixture according to the invention decreases only insignificantly, despite the even lower tin content (11.5% or 9% in the case of dodecyl thioglycolate and tetradecyl thioglycolate, respectively). Hitherto, it has been true for all known organotin stabilisers that the stabilising action depends substantially on the tin content of the material, that is to say, with a failing tin content the action also clearly decreases.

Stabiliser mixtures according to the invention have the further advantage of even lower toxicity values in comparison with the common organotin stabilisers and can therefore be classified as non poisonous.

Thus, for example, representative lethal doses (LID50) for rats are as follows:

Q (C4H,)2SnTh2 50 Commerical product having 25% mono proportion = about 750 mg/kg (CAISnTh2 Commercial product having 20% mono proportion = about 2500 mg/kg rats 55 40% (CUI-12d2SnTh2 + 60% CUI-12,SnTh3=4500 mg/kg rats (Th = isooctyl thioglycolate) 2 GB 2 102 433 A 2 Investigation of systemic tolerance after 12 weeks' administration to rats in their feed revealed a very favourable---noeffect- level of 600 ppm. In contrast, the---noeffectlevel of dibutyltin thioglycolate compounds is about 10 ppm and in the case of the dioctyl compounds is about 25 ppm.

No adverse influence on the lymphatic system of warm-blooded animals could be determined 5 even at very high doses.

In inhalation studies using stabiliser mixtures according to the inveniton in rats, no acute inhalation risk could be determined.

In addition to a low toxicity for warm-blooded animals, the migration of the stabiliser from PVC is significant and it will of course be appreciated that the migration should be as small as possible.

It has been found that the migration of stabiliser mixtures according to the invention is generally 10 very much lower than in the case of other organotin stabilisers. Specifically, the migration may be less than 0.2,ug of tin/dml of a test film (in comparison with 5 pg of tin/d M2 in the case of dioctyltin thioglycolates). In both cases, the amount of stabiliser in the PVC was 1. 5% by weight.

For several points of view, therefore, a stabiliser mixture according to the invention is especially suitable for packaging materials based on PVC or on copolymers which are used for packaging 15 foodstuffs and pharmaceuticals, or in the medical field, for example for the storage of blood or for plastics tubes for infusions, where especially low toxicity values are required.

The stabiliser mixture according to the invention is not toxic and, because of its extremely low migration in comparison with other organotin stabilisers, it contaminates the packaged article to a much lesser extent. In addition, because of the good stabilising action, the amounts of stabiliser used can be 20 kept small from the outset.

Furthermore, a stabiliser mixture according to the invention has little odour and exhibits low volatility. When many of the hitherto conventionally used organotin stabilisers are thermally processed, operating personnel may be subjected to considerable stresses because of the stabiliser that is thereby released. Owing to its high boiling point and its low vapour pressure, a stabiliser mixture according to 25 the invention does not have these disadvantages.

The dodecyltin stabiliser components can be manufactured according to known methods from the corresponding dodecyltin chlorides or dodecyltin oxides and thioglycolic acid esters.

Tha stabiliser mixture according to the invention may be used optionally in conjunction with other stabilisers, stabilising auxiliaries, antioxidants, UV-stabilisers, lubricants, plasticisers, etc Advantageously, the mixture is used in amounts of from 0.1 to 3, especially from 1 to 2% by weight, based upon the polymer content of the moulding material.

The following Example illustrates the invention:

The heat-stabilising action of the dodecyltin thioglycolates according to the invention was investigated on a suspension-PVC (VESTOILIT() S 7054) and on an emulsion PVC (VESTOLIT(I) E 7003) 35 with the aid of a stabilimeter having an automatic drive.

The test temperature was 1 851C. As lubricant, 2% of NAFTOLUBE(I) FOL were added.

The Table shows resu Its for the didodecyl and monododecyl tin compounds both alone and in various mixtures.

In order to provide a further basis for comparison, a hitherto conventional stabiliser was used, 40 namely di-n-butyltin-bis-thioglycolic acid isooetyl ester having a 25% content of mono-n-butyitin-tris thioglycolic acid isooctyl ester. The tin content of the comparison stabiliser was 17.5%.

The results obtained are shown in the following Table:

3 GB 2 102 433 A 3 TABLE

VESTOLI T (' E 7003 VESTOLI T (R) S 7054 Time in minutes Time in minutes for formation of for formation of Stabiliser a dark colour a dark colour 1 % (CH,jSnTh, 60 W 1 % C12 H2. SnTh, 60 50 0.8 % (0,,H,,),SnTh, + 0.2 % C12 H2. SnTh, 65 55 0.e % (C12 H2,)2 SnTh, + 0.4 % C12 H Sn Th. 70 55 0.4 % (C,H21)2SriTh, + 0.6 % C12 H 2. SnTh, 80 65 (stabiliser mixture according to the invention) 0.2 % (C,2H2,)2SnTh. + 0.8 % C12 H2 SnTh, 65 55 0.75 % (nC,H,-)2SnTh, + 0.25 % nC4H,,SnTh, 65 55 (comparison stabiliser) 1) 0.4 % (C,H2J2SriTh2 + 0.6 % C.2H2. SnTh, 75 60 2) 0.4 % (C,,H,.,).SnTh, + 0.6 % C,1-12.SriTh, 75 60 3) 0.4 % (C,2H2,,),SnTh2 + 0.6 % C,2H2,SnTh, 70 60 4) 0.4 % ( C, H2J2SriTh2 + 0.6 % C12 H,, SnTh, 70 60 Th = thioglycolic acid isooctyl ester. In 1), Th = thioglycolic acid tetradecyl ester; in 2), Th = thioglycolic acid hexadecyl ester; in 3), Th - thioglycolic acid decyl ester; in 4), Th = thioglycolic acid dodecyl ester.

4 GB 2 102 433 A 4 The invention also provides a method of stabilising a moulding material comprising a halogencontaining polymer, which comprises incorporating with the moulding material a quantity of a stabiliser mixture according to the invention. In principle, the components of the mixture may be incorporated individually, but it will in general be preferable and more convenient to incorporate an already-prepared 5 mixture.

Claims (12)

1. A stabiliser mixture for use in moulding materials comprising halogencontaining polymers, which mixture comprises from 35 to 45% by weight of a didodcyltin-bis-thioglycolic acid ester (C 12H 2d2S n (SCH 2COO-R) 2 and from 65 to 55% by weight of a dodecyltin-tris-thioglycolic acid ester C,^,Sn(SCH,C00-R), wherein each case R represents a straight-chain or branched alkyl radical having from 8 to 20 carbon atoms.

2. A stabiliser mixture as claimed in claim 1, which comprises about 40% by weight of the 15 didodecyltin compound and about 60% by weight of the dodecyltin compound.

3. A stabiliser mixture as claimed in claim 1 or claim 2, which comprises an n-didodecyitin-bisthioglycolic acid ester.

4. A stabiliser mixture as claimed in any one of claims 1 to 3, which comprises an n-dodecyltin- tris-thioglycolic acid ester. 20

5. A stabiliser mixture as claimed in any one of claims 1 to 4, wherein R represents 2-ethylhexyl in 20 the didoecyltin compound and/or in the dodecyltin compound.

6. A stabiliser mixture as claimed in claim 1 and substantially as described in the Example herein.

7. A method of stabilising a moulding material comprising a halogen-containing polymer, which comprises incorporating with the moulding material a quantity of a stabiliser mixture as claimed in any one of claims 1 to 6.

8. A method as claimed in claim 7, wherein the proportion of the stabiliser mixture incorporated with the moulding material is in the range of from 0.1 to 3% by weight, based on the weight of the polymer.

9. A stabiliser mixture as claimed in claim 8, wherein the proportion of the stabiliser mixture incorporated with the moulding material is in the range of from 1 to 2% by weight, based on the weight 30 of the polymer.

10. A stabiliser mixture as claimed in any one of claims 7 to 9, wherein the polymer comprises a homo- or copolymer of vinyl chloride.

11. A stabilised moulding material whenever obtained by a method as claimed in any one of 35 claims7tolO.

11

12. A packaging material whenever made from a stabilised moulding material as claimed in claim Printed for Her Majesty's Stationery Office by the courier Press, Leamington Spa, 1983. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.