Process for the preparation of low chloride stabilizers

Details Process for the preparation of low chloride stabilizers Process for the preparation of low chloride stabilizers

2000-10-31

2002-10-29

Higel, Floyd D. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Phosphorus esters

Reexamination Certificate

active

06472550

ABSTRACT:

The present invention relates to a new work-up process for the preparation of a stabiliser mixture containing a low amount of chloride, which are suitable for stabilising organic materials against oxidative, thermal or light-induced degradation.
U.S. Pat. No. 4,075,163 discloses the synthesis of tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphonite (column 7, Table 1, compound 12) which is suitable for stabilising organic materials against oxidative, thermal or light-induced degradation. This compound is commercially available for example as Sandostab P-EPQ (RTM) from Clariant, Switzerland.
EP-A-0 633 287 discloses in Example 1 that this commercially available Sandostab P-EPQ (RTM) is a mixture of several components comprising a) 65% by weight of tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphonite, b) 15% by weight of bis(2,4-di-tert-butylphenyl)biphenylene monophosphonite, c) 13 parts by weight of tris(2,4-di-tert-butylphenyl) phosphite, d) 1.5 parts by weight of 2,4-di-tert-butyl phenol, e) up to 1% by weight of chloride [up to 10,000 mg/kg], f) up to 0.5% by weight of volatiles, and g) 4-5% by weight of the oxidised tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphonite.
Phosphites and phosphonites are hydrolytically very labile (see Example 29 in U.S. Pat. No. 4,075,163). Therefore, during the synthesis of Sandostab P-EPQ (RTM) the reaction mixture was never brought into contact with water. In the actual large scale production of Sandostab P-EPQ (RTM) the neutralisation of the remaining aluminium trichloride/pyridine/hydrochloric acid complex is done with gaseous ammonia (see comparative Example 2 in the instant application). However, some of the formed salts like for example ammonium chloride remain in the final product. These salt impurities may be the reason why the final stabiliser mixture is slightly turbid. A turbid stabiliser for polyolefins, however, induces some haze in polyolefins which is for some applications clearly undesired.
The goal of the instant invention was therefore to find an improved work-up process for the synthesis of Sandostab P-EPQ (RTM) containing a low amount of chloride and forming a product which is not turbid and does not induce any haze into synthetic polymers.
The present invention therefore relates to a process for the preparation of a stabiliser mixture containing a low amount of chloride comprising
a) 50-80% by weight of a diphosphonite of the formula I
b) 5-25% by weight of a monophosphonite of the formula II
c) 5-25% by weight of a phosphite of the formula III
in which R is a radical of the formula IV
and where the sum of the compounds of the formula I, II and III is not greater than 100% by weight,
by reacting a biphenyl of the formula V
under Friedel-Crafts condition with phosphorus trichloride and aluminium trichloride and by reacting the product mixture with 2,4-di-tert-butyl-phenol of the formula VI
in the presence of a tertiary amine or an aromatic amine and a solvent, separating the formed two layers, which process comprises treating the solvent layer with water, a base and a desiccant, separating the precipitate from the solution containing the stabiliser mixture and evaporating the solvent.
A preferred tertiary amine is a compound of the formula VII
wherein R
1
, R
2
and R
3
are the same or different, and are C
1
-C
24
alkyl; C
4
-C
24
alkyl interrupted by one or more O-atoms; phenyl, C
7
-C
9
phenylalkyl; C
7
-C
9
alkylphenyl; or two of R
1
, R
2
and R
3
together with the N-atom to which they are attached form a 5-, 6- or 7-membered heterocyclic residue, which optionally contains further oxygen, nitrogen or sulphur atom and which is optionally substituted by one or more C
1
-C
4
alkyl groups, and the other of R
1
, R
2
and R
3
is C
1
-C
24
alkyl or C
4
-C
24
alkyl interrupted by one or more O-atoms.
Alkyl having up to 24 carbon atoms is a branched or unbranched radical, for example methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-ethylbutyl, n-pentyl, isopentyl, 1-methylpentyl, 1,3-dimethylbutyl, n-hexyl, 1-methylhexyl, n-heptyl, isoheptyl, 1,1,3,3-tetramethylbutyl, 1-methylheptyl, 3-methylheptyl, n-octyl, 2-ethylhexyl, 1,1,3-trimethylhexyl, 1,1,3,3-tetramethylpentyl, nonyl, decyl, undecyl, 1-methylundecyl, dodecyl, 1,1,3,3,5,5-hexamethylhexyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, icosyl or docosyl. One of the preferred definitions for R
1
, R
2
and R
3
is, for example, C
2
-C
18
alkyl. An especially preferred definition for R
1
, R
2
and R
3
is C
2
-C
8
alkyl, for example ethyl.
C
4
-C
24
alkyl interrupted by one or more O-atoms include, e.g. 2-ethoxypropyl, 1-methoxypropyl, 1-methoxybutyl, n-butoxyethyl, 1-methoxyoctyl, 1-methoxydecyl, 1-methoxydodecyl, 1-methoxyhexadecyl, 1-methoxyeicosyl, 1-methoxytetraeicosyl and 2-methoxyethoxymethyl.
C
7
-C
9
Phenylalkyl is, for example, benzyl, &agr;-methylbenzyl, &agr;,&agr;-dimethylbenzyl or 2-phenylethyl. Preference is given to benzyl.
Heterocyclic groups formed by two of R
1
, R
2
and R
3
are preferably 6-membered, examples of which are piperidino, morpholino, thiomorpholino and 4-C
1
-C
4
alkyl-piperazino.
A preferred aromatic amine is pyridine which is optionally substituted by one or more C
1
-C
4
-alkyl groups.
Pyridine which is optionally substituted by one or more C
1
-C
4
alkyl group is, for example, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine or 3,4-lutidine.
A preferred solvent is benzene which is optionally substituted by one or more chlorine or C
1
-C
4
alkyl groups.
Benzene which is optionally substituted by one or more chlorine or C
1
-C
4
alkyl groups is, for example, chlorobenzene, toluene or xylene. Preferred is chlorobenzene.
A preferred base is an alkaline metal- or an alkaline earth metal-hydroxide, oxide, hydrogen phosphate, dihydrogen phosphate, carbonate, hydrogen carbonate or tetraborate.
An alkaline metal- or alkaline earth metal-hydroxide, oxide, hydrogen phosphate, dihydrogen phosphate, carbonate, hydrogen carbonate or tetraborate is, for example, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, calcium oxide, sodium hydrogen phosphate, sodium dihydrogen phosphate, sodium carbonate, calcium carbonate, sodium hydrogen carbonate or sodium tetraborate decahydrate.
Advantageously, the base is used in an amount of from 0.1 to 10% by weight, especially from 0.1 to 5% by weight, e.g. from 0.1 to 2% by weight, based on the weight of the solvent layer.
A preferred desiccant is an alkaline metal sulfate, an alkaline earth metal sulfate or oxide, a molecular sieve or aluminium oxide.
An alkaline metal sulfate, an alkaline earth metal sulfate or oxide, a molecular sieve or aluminium oxide is, for example, magnesium oxide, calcium oxide, sodium sulfate, magnesium sulfate, barium sulfate, molecular sieve 3 Å, molecular sieve 4 Å, powdered aluminium oxide, basic aluminium oxide, calcined aluminium oxide, fused aluminium oxide, fused aluminium oxide, granulated aluminium oxide or sintered aluminium oxide.
Advantageously, the dessicant is used in an amount of from 0.1 to 10% by weight, especially from 0.1 to 5% by weight, e.g. from 0.1 to 2% by weight, based on the weight of the solvent layer.
Some dessicants like for example sodium sulfate can also act as a cation precipitant.
Of interest is a process for the preparation of a stabiliser mixture containing a low amount of chloride, which comprises treating the solvent layer additionally with a filter-aid before separating the precipitate from the solution containing the stabiliser mixture.
A preferred filter-aid is, for example, fuller's earth [Merck Index 10
th
Edition, 4162 (1983)] or infusorial earth [Merck Index 10
th
Edition, 4857 (1983)] which includes floridin, a nonplastic variety of kaolin containing an aluminium magnesium silicate, kieselgur, celite, diatomaceous earth like for example Hyflo Super Cel [(RTM), Aldrich 39,254-5].
Advantageously, the filter-aid is used in an amount of from 0.1 to 10% by weight, especi

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