Oligomeric stabilizer mixture

Details Oligomeric stabilizer mixture Oligomeric stabilizer mixture

1999-03-19

2001-05-01

Sanders, Kriellion A (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S128000, C524S134000, C524S150000, C524S151000, C524S152000, C524S153000, C252S400210

Reexamination Certificate

active

06225385

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a novel stabilizer mixture which markedly slows the metal-compound-accelerated degradation and aging of organic materials, in particular of organic polymers.
There is a wide variety of ways by which organic materials, in particular plastics, can come into contact with metals, metal ions and metal-containing compounds. Contact of this type is impossible to avoid particularly in cases of residues of metallic catalysts used to prepare the plastic. There are also many ways in which organic polymers during their processing come into contact with metallic surfaces. In addition, various metal-containing compounds are intentionally admixed with the plastic to achieve specific effects: examples of these are metal-containing stabilizers, pigments and fillers. In addition, organic polymers are very frequently in direct contact with metals in end applications, as is often the case with cable sheathings, pipes and electronic components.
Like all organic compounds, plastics too are subject to natural aging. This process, which is associated with impairment of functional properties and always ends with the decomposition of the organic material, can be accelerated by accelerators and slowed by stabilizers. Metals and metal-containing compounds are generally known to be accelerators for degradation and ageing processes of this type (cf. R. Gächter, H. Müller, Taschenbuch der Kunststoff-Additive [Plastics Additives Handbook], Carl Hanser Verlag Munich, Vienna; 3rd edn. 1989; Chapter 2, pp. 109 ff).
The use of a condensation product made from phosphorus trichloride (1) and 2,2′-dimethyl-4,4′-dihydroxy-5,5′-di-tert-butyidiphenyl sulfide (2) in a mixture with other chemicals is described in DE-A-1 153 894. However, there is no indication of a stabilizing action of the product on its own. This condensation product is used in this document only in combination with the condensation product made from nonylphenol and acetone and with dilauryl thiodipropionate (Comparative Experiment No. 5). DE-A-1 153 894 describes the stabilizing action of the mixture described against the damaging action of heat and oxygen on copper-contaminated polypropylene.
The effectiveness of a condensation product made from (1) and (2) alone and its use as a stabilizer for organic material had not been described until the publication of DE-A-3 029 176. The compound described there is a three-dimensionally crosslinked polymer insoluble in all organic solvents and having a phosphorus content of 4.9% (DE-A-3 029 176, p. 2, line 17; p. 5, Example 3). This document describes the stabilizing action of the high-molecular-weight, insoluble condensation product, with a degree of polymerization of from 50 to 500, on a polymer (p. 3, line 45). Stabilization against the damaging actions of oxygen and heat is described. The starting materials (1) and (2) used there are brought together to prepare the condensation product within a period of 15 min at only 50° C. in xylene in the presence of a small amount of dimethylformamide, after stirring (50° C.) for 1 hour are heated to 135° C. and condensed at this temperature for 1 hour with elimination of hydrogen chloride.
The condensation product known from the prior art is insoluble in organic solvents and has unsatisfactory stabilizing action. The object was therefore to provide a product which has better solubility and is more effective.
SUMMARY OF THE INVENTION
Surprisingly, it has been found that suitable conduct of the reaction can prepare from the compounds (1) and (2) a stabilizer mixture which has excellent solubility in organic solvents and is soluble in the polymer and has excellent stabilizing action. The present invention relates to a novel stabilizer mixture which markedly slows the metal-compound-accelerated degradation and aging of organic materials, in particular of organic polymers.
The invention therefore relates to a stabilizer mixture obtainable by partial condensation of PCl
3
with 2,2′-dimethyl-4,4′-dihydroxy-5,5′-di-tert-butyldiphenyl sulfide, where the phosphorus content is from 2 to 4% by weight and the content of unreacted 2,2′-dimethyl-4,4′-dihydroxy-5,5′-di-tert-butyldiphenyl sulfide is from 0.5 to 50% by weight. During this, hydrogen chloride is eliminated and phosphorus-oxygen bonds are produced from some of the phenolic hydroxyl groups. Unreacted 2,2′-dimethyl-4,4′-dihydroxy-5,5′-di-tert-butyldiphenyl sulfide (2), cf. diagram 1, also remains as one of the constituents of the novel stabilizer mixture.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Phosphorus trichloride (1) is trifunctional and 2,2′-dimethyl-4,4′-dihydroxy-5,5′-di-tert-butyidiphenyl sulfide (2) is bifunctional. There is therefore a wide variety of ways in which linkage can take place to form phosphorus-oxygen bonds.
Diagram 1: Formation of the stabilizer mixture from compounds (1) and (2)
The novel stabilizer mixture is formed with an x/y ratio of from 1:2.1 to 1:4.3.
At a molar ratio (1):(2) of 1:3 a discrete monomeric compound can be formed, containing a saturated phosphorus atom as its central constituent (diagram 2). At a molar ratio (1): (2) of 1:2.5 and 1:2.3, respectively, discrete monomeric compounds can be formed which have, respectively, two and three phosphorus atoms as a discrete constituent (diagram 2). At a molar ratio of 1:2 a polymeric chain can be formed in which a saturated phosphorus atom alternates with a 2,2′-dimethyl-4,4′-oxy-5,5′-di-tert-butyldiphenyl sulfide fragment. At a molar ratio of 1:1, a highly polymeric two-dimensional sheetlike network can be formed (diagram 2).
Diagram 2: Possible types of linkage from compounds (1) and (2) as starting materials
Ratio of comp. (1):(2)
Possible linkage
1:3

1:(2.5)

1:(2.33)

1:2

1:1
In addition, disproportionation or partial oxidation can also lead to the formation of P
IV
and P
V
compounds. Cleavage of the relatively labile phenyl-S-phenyl bonds can produce fragments of compound (2) which themselves can become reincorporated via a partial condensation into the novel stabilizer mixture.
The novel stabilizer mixture is prepared by partial condensation of phosphorus trichloride (1) and 2,2′-dimethyl-4,4′-dihydroxy-5,5′-di-tert-butyldiphenyl sulfide (2) forming phosphorus oxygen bonds and at the same time eliminating hydrogen chloride. The novel stabilizer mixture also comprises, contrasting with the compound described in DE-A-3 029 176, a proportion of 2,2′-dimethyl-4,4′-dihydroxy-5,5′-di-tert-butyldiphenyl sulfide in addition to the pure condensation product and has very good solubility in organic solvents and a P content of from 2.0 to 4.0% by weight.
The invention also relates to a process for preparing the novel stabilizer mixture.
Surprisingly, a stabilizer mixture with excellent suitability for stabilizing polymeric organic material is formed if an initial charge of 2,2′-dimethyl-4,4′-dihydroxy-5,5′-di-tert-butyldiphenyl sulfide (2) in a suitable atmosphere, preferably in an inert gas, and in an organic solvent, preferably in an aromatic solvent, in particular in toluene or o-xylene, is reacted at a temperature of from 20° C. to 1 50° C., preferably from 100° C. to 140° C., in particular from 115° C. to 130° C., with phosphorus trichloride (1), where the molar ratio (1):(2) is from 1:2.1 to 1:4.3 and the phosphorus trichloride (1) is added slowly and uniformly within from 0.5 to 8 hours, preferably within from 3 to 5 hours, and the reaction mixture is stirred at the same temperature for from 3 to 20 hours, preferably from 8 to 14 hours, and the product is freed from volatile constituents over a period of from 2 to 10 hours, preferably from 4 to 8 hours, at temperatures of up to 190° C. and at a pressure which may be reduced as far as 30 mbar.
The procedure described gives a stabilizer mixture which has a content of from 0.5 to 50% by weight, preferably from 5 to 30% by weight, in particular from 8

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