Etude de la stabilisation du polychlorure de vinyle avec des molecules modeles—V. Stabilisation par l'α-phenyl-indole

doi:10.1016/0014-3057(76)90103-8

European Polymer Journal

Volume 12, Issue 6, 1976, Pages 357-364

https://doi.org/10.1016/0014-3057(76)90103-8 Get rights and content

Résumé

L'α-phényl-indole est un stabilisant secondaire du PCV qui réagit avec les chlores allyliques labiles en donnant une ou plusieurs réactions de substitution, sur l'hydrogène de la double liaison trisubstituée de l'hétérocycle d'abord, sur les noyaux aromatiques ensuite. La réaction est catalysée par ZnCl₂ qui forme un complexe avec l'α-phényl-indole. Le produit substitué est insensible à l'action de l'HCl et la stabilisation est done définitive. L'α-phenyl-indole peut participer à des effets de synergie avec les autres stabilisants à condition que ceux-ci soient en quantité suffisante pour neutraliser tout l'HCl produit.

Abstract

α-Phenyl-indole is a secondary stabilizer of PVC; it reacts with labile allylic chlorine atoms by one or more substitutions, first on the hydrogen atom of the trisubstituted double bond in the heterocycle, and then on the aromatic rings. The reaction is catalysed by ZnCl₂ which is complexed with α-phenyl-indole. The substituted products are insensitive to HCl so that the stabilization is definite. α-Phenyl-indole may give synergistic effects with other stabilizers, but the condition is that they must be present in amounts enough to neutralize all the HCl produced.

Références (4)

T.V. Hoang et al.
Europ. Polym. J.
(1976)
T.V. Hoang et al.
Europ. Polym. J.
(1976)

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Cited by (16)

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In the thermal stabilization of PVC, it has been shown that, by controlling the cis configuration of conjugated double bonds initially present or developing in the polymer during the stabilization, the alkyl chains attached to stabilizers favor the substitution of the allylic chlorine atoms by an esterification reaction proposed by Frye et al. By interacting with the conjugated double bonds to form polarons which inhibit the esterification reaction, the metal chloride leads to the chain dehydrochlorination of the polymer by a process reported previously.
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Stabilization of poly(vinyl chloride) with organotin compounds: Part VIII-Catalytic action of organic acids and anhydrides with organotin carboxylate
1987, Polymer Degradation and Stability
When maleic acid or maleic anhydride are added to a dichlorobutane solution of chlorohexene (as a model compound for allylic chlorides in poly(vinyl chloride)) and organotin carboxylates (maleates or laurate) heated at 80°C, the esterification reaction is strongly accelerated; moreover, the formation of hexadiene, which is the expected product of the competitive elimination reaction, is not observed. The reaction is first order with respect to both chlorohexene and the organic acid or anhydride, and may either be zero or first order with respect to the organotin carboxylate. ¹H-NMR spectra and solubility experiments indicate the formation of complexes between the organotin carboxylate and the organic acid or anhydride. A concerted mechanism between the chlorohexene and these complexes is suggested. A few experiments show that the addition of these organic acids or anhydrides to a PVC formulation leads to improvement of the thermal stability.
Finally, other organic acids and anhydrides were also used to complex the organotin carboxylate in order to rule out the complexation mechanism and to discuss the activated complex.
Synergistic mechanisms of β-diketone derivatives and zinc-calcium soaps in PVC stabilisation
1981, Polymer Degradation and Stability
It has been possible to explain the mechanisms of stabilisation and of the synergistic effects of the β-diketone derivatives claimed in a patent as new stabilisers for improving the efficiency of those recipes based upon zinc and calcium soaps in the prevention of the initial discoloration of poly(vinyl chloride).
Using chlorohexene as a model compound for allylic chloride structures and benzoylacetone as a model compound for enolised β-diketone derivatives, it has been shown that the benzoylacetone can substitute allylic chlorine atoms through a C-alkylation reaction which takes place only in the presence of ZnCl₂ as catalyst. This reaction drastically changes the percentage of the enol and causes the appearance of two bands at 1720 cm⁻¹ and 1680 cm⁻¹ in the infra-red spectrum due to the ketonic structures During the processing of the PVC on a rolling mill at 180°C in the presence of zinc and calcium stearates and benzoylacetone there is grafting of the ketone derivative through a C-alkylation reaction. There is a closed parallelism between the influence of the benzoylacetone on the dehydrochlorination of the chlorohexene and on the accumulation of chloride ions in the polymer matrix in the presence of zinc and calcium stearate. The synergistic effect of the benzoylacetone in the prevention of the initial discoloration is related to the substitution reaction through a C-alkylation which takes place only in the presence of zinc stearate which generates ZnCl₂ which, in turn, acts as a catalyst for both the C-alkylation and dehydrochlorination.
Polyvinylchloride stabilisation with organo-tin compounds—Part 1: Mechanism of the reaction of thioglycolate derivatives with allylic chlorine model compounds
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Mixtures of the isomers 4-chloro-hex-2-ene and 2-chloro-hex-3-ene of different compositions were prepared in order to study their reaction with organo-tin thioglycolate. Whatever the initial composition of the mixture, the same composition of the isomeric products is obtained. This favours an ionic mechanism in which the rate-determining step is the formation of an allylic carbocation. The substitution reaction with free thioglycolate esters is more rapid than with the tin derivative. Thus, a second possible route for the stabilisation reaction can be proposed.
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1979, Polymer Degradation and Stability
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Etude de la stabilisation du polychlorure de vinyle avec des molecules modeles—V. Stabilisation par l'α-phenyl-indole

Résumé

Abstract

Europ. Polym. J.

Europ. Polym. J.