Stabilizers for organic materials

Abstract: The invention relates to a stabilizer for organic materials, which are liable to oxidative and/or thermal decomposition under influence of actinic irradiation of formula 1, wherein R is hydrogen or a methyl group R₁ and R₂, which may be the same, or different represent a tertiary alkyl group having 4-8 C-atoms, R₃ is hydrogen or a methyl group, n = 2 and A a polyol having 3 to 6 C-atoms or a di-polyol containing 6-12 C-atoms.

Description: The invention relates to novel stabilizers for organic materials which are liable to oxidative and/or thermal decomposition and/or decomposition under influence of actinic irradiation, such as petroleum products, e.g lubricating oils and lubricating greases, and plastics, such as polyvinylchloride, polyalkylenes and polystyrene. In order to prevent oxidative and/or thermal decomposition (degradation) of petroleum products and plastics, such as polyvinylchloride, polyalkylenes and polystyrene, on large scale antioxidants and antiozonants are used, which depending on their chemical structure, inhibit the initiation or propagation of oxidation reactions. Especially as antioxidants that inhibit the propagation of oxidation reactions, secondary alkylaryl- and diarylamines and, in particular, hindered phenols are applied (vide Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd edition part 3, page 128-148 and in particular pages 130-133). In order to prevent decomposition under influence of actinic irradiation, in particular decomposition under influence of UV-irradiation, often so-called HALS (hindered amine light stabilizers) are applied, the most important ones of which are 2,2,6,6-tetramethyl-4-piperidinol and carboxylic acids, such as bis-(2,2,6,6-tetramethyl-4-piperidinyl)sebacate and - azelate, which are especially active in polypropylene, polyethylene, styrene polymers, polyurethanes and coatings containing acrylic polymer (vide Kirk- Othmer, Encyclopedia of Chemical Technology, 3rd edition, volume 23, page 615-627 and in particular pages 620-621 and page 624). Although said compounds generally have good properties, continuously novel compounds of these types are developed, in order to meet the higher and higher requirements with respect to the stability of petroleum products (e.g. lubricating oil) and of polymers. So in EP-A-89119641.2 (publication no. 366 040) hindered phenol antioxidants of formula 1 are described, wherein R is a methyl group, R 1 is an alkyl, cycloalkyl, phenyl, or aralkyl group, R 2 is hydrogen or an alkyl, cycloalkyl, phenyl or aralkyl group, R 3 is hydrogen or a methyl group, n is an integer of 1-4 or 6, wherein, if n = 2, A is preferably an alkylene dioxy group having 2-8 carbon atoms or an alkylene dioxy group interrupted by ether oxygen or a thio group. In EP-A-88108282.0 (publ. no. 300160) the ester of 2,2,6,6-tetramethyl-4-piperidinol and behenic acid is described, which serves as stabilizer against the decomposition of polymers by actinic irradiation. Now the object of the invention is to provide novel stabilizers with particularly favourable, improved properties. According to a first aspect of the invention, novel compounds of formula 1 are provided, wherein R is hydrogen or a methyl group, R 1 and R 2 , which may be the same or different, represent a tertiary alkyl group having 4-8 carbon atoms, R 3 is hydrogen or a methyl group, n = 2 and A is a polyol having 3-6 C-atoms, or a dipolyol having 6-12 C-atoms. Compared to the known stabilizers of this type, these novel compounds have improved properties with respect to the stabilization against thermal and oxidative degradation of both petroleum products and plastics. In the novel compounds of formula 1, R 1 and R 2 preferably both are a tertiary butyl group. The tertiary butyl group provides an excellent sterical hindering of the hydroxyl group of the phenol and is extremely stable itself, so that the compounds have an optimum stabilizing effect. The polyol or di-polyol group (A) has at least one free hydroxyl group, which also contributes to the stabilizing effect of the compounds. Preferably A is a glycerol or di-glycerol moiety. The stabilizing effect of the compound is then excellent, while the compounds themselves are stable. According as the number of free hydroxyl groups of the polyol or dipolyol moiety is higher, the long term thermal stability improves, but this is at the expense of the colour stability of the compounds. The novel stabilizers are included in usual amounts in the petroleum products or plastics to be stabilized that is to say amounts of 0.1-10 and preferably 0.05-5% by weight. Optimal results are generally obtained with 0.1-3 and in particular with 1-3 % by weight. The invention is further elucidated by the following examples. Example I Preparation of diglyceryl-bis[β-(3,5-di-tertiary butyl-4-hydroxyphenyl)propionic ester] (reaction scheme A, formula 5). A three-neck flask with stirrer, thermometer and cooler is filled with : 40 g (0.137 moles) β-(3,5-di-tertiary butyl-4-hydroxyphenyl)-propionic acid methyl ester (I) 12.95 g (0.078 mol) diglycerine (II) 2 g titanium butoxide The reaction mixture was heated at 160°C for 5 hours, while the methanol formed with the reaction was continuously removed by means of distillation. Subsequently the reaction mixture was cooled down. The brown-coloured residue was incorporated into the ether. The ether layer was washed with water and dried whereafter the ether was destilled. The residue was dissolved in ethanol and purified over a column of silica gel. After distilling the ethanol a yellow-coloured viscous liquid was obtained. Yield: 39.6 g = 85% The NMR spectrum is in accordance with formula 5. Example II The compound according to example I was applied as stabilizer in a softener-free, calcium-zinc-stabilized PVC composition S-PVC (K=68-70) 100 parts by weight Paraloid KM-334 (Impact-strenght additive 5-8 parts by weight Paraloid K-120N (Flow improver) 0.5-1.5 parts by weight Hydrocarb 95T (chalk) 3-10 parts by weight Titanium dioxide (Kronos-2220) 3-10 parts by weight Ca/Zn stabilizer 3.5-4.5 parts by weight Stabilizer (oxyd/therm., UV) 1-3 parts by weight Test plates of this composition which contain the stabilizer according to example I were tested on their colour stability, and compared with test plates with an analogous composition wherein only β-(3,5-di-t-butyl-4-hydroxyphenyl)propionic-n-octadecyl ester were applied. The colour stability with the stabilizer of Example I was, when applied in amounts between 1 and 3 parts by weight (on 100 parts by weight of PVC), in any case better than with the comparative stabilizer. Example III The compound according to example I was applied as stabiliser in a softener containing film composition stabilized with Ba/Zn: S-PVC (K=65) 100 parts by weight Softener (DOP) 20-25 parts by weight Epoxized soy bean oil 2-3 parts by weight Titanium dioxide 5-10 parts by weight Stabilizer 1.5-3 parts by weight Test films of this composition which contain the stabilizer of example I and films which contain a usual stabilizer pentaerythritol-tetra [β-3-(3,5-di-t-butyl-4-hydroxyphenyl)-proprionate] were tested on their resistance against thermal and oxidative degradation and the yellow coloration after the test was measured with a CIE Lab colour measuring system, manufacturer Dr. Lange. The yellow coloration of the films with the stabilizer of Example I was less than that of the films which contain the usual stabilizer.

Claims: Claims for the following Contracting States : AT, BE, CH, LI, DE, DK, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE Stabilizer for organic materials which are liable to oxidative and/or thermal decomposition and/or decomposition under influence of actinic irradiation, of formula 1, wherein R is hydrogen or a methyl group, R 1 and R 2 , which may be the same or different, represent a tertiary alkyl group having 4-8 C-atoms, R 3 is hydrogen or a methyl group, n = 2 and A is a polyol having 3-6 C-atoms or a di-polyol having 6-12 C-atoms. Stabilizer according to claim 1, wherein R 1 and R 2 both are a tertiary butyl group. Stabilizer according to claim 1 or 2, wherein A is a glycerol or di-glycerol moiety. Stabilizer according to claim 1 or 2, wherein A is a sorbitol or di-sorbitol moiety. Petroleum product or plastic material stabilized against oxidative and/or thermal decomposition and/or decomposition under influence of actinic irradiation, characterized in that it contains a compound according to any one of the preceding claims as stabilizer. Claims for the following Contracting State : ES A process for preparing a stabilizer for organic materials which are liable to oxidative and/or thermal decomposition and/or decomposition under influence of actinic irradiation, which process comprises reacting a compound of the formula with a polyol of the formula to yield a stabilizer of the formula Petroleum product or plastic material stabilized against oxidative and/or thermal decomposition and/or decomposition under influence of actinic irradiation, characterized in that it contains as stabilizer a compound of the formula prepared by the process of claim 1.

Inventors: KROON ERICA GERTRUDA ARNOLDA, OVERVEEN JAN CORNELIS, PETERS FRANS JEANNETTE MARIA, SCHMETS GERARD HUBERT FRANS, KROON, ERICA GERTRUDA ARNOLDA, OVERVEEN, JAN CORNELIS, PETERS, FRANS JEANNETTE MARIA, SCHMETS, GERARD HUBERT FRANS
Applicants: AKCROS CHEMICALS V O F, AKCROS CHEMICALS V.O.F.
Application year: 1992
Main classification: C07D211
IPC codes: C08K5, C10M129, C07C69, C10L1, C09K15, C07D211