Method of producing tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl)p

Details Method of producing tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl)p Method of producing tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl)p

1988-09-28

1989-12-05

Killos, Paul J.

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

Organic compounds

Carboxylic acid esters

C07C 6976

Patent

active

048853828

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to a method of producing tetrakis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxymethyl]-methane [hereinafter sometimes referred to as "compound (I)"], which is in wide use as an antioxidant for polyolefins, among others, in the form of fine granules having good physical properties and in a purified form.


DESCRIPTION OF THE PRIOR ART

The compound (I) is commercially available in the form of white fine powders. However, such powders are still unsatisfactory from the transportation, handling, dosing and other viewpoints. For instance, they have a low bulk density, readily fly off into the air upon handling, are low in flowability and are difficult to adequately dose for extruder fusion mixing with polyolefins.
The most general method of producing the compound (I) comprises subjecting a 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid alkyl ester [hereinafter sometimes referred to as "compound (II)"] and pentaerythritol to ester exchange (transesterification) reaction. Said method gives the compound (I) in relatively good yields. Japanese Patent Publication No. 19083/1967, for instance, discloses that the desired compound (I) is obtained as crystals having a melting point of 121.degree.-122.degree. C. when isopropanol is added to the product after said ester exchange reaction between the compound (II) and pentaerythritol and the resulting molecular adduct compound is isolated and recrystallized from heptane. Japanese Patent Publication No. 18617/1967 discloses that the compound (I) is obtained as a transparent, amber-colored, glassy substance having a softening point of 50.degree.-60.degree. C. when the ester exchange reaction product is purified by chromatography on neutral almina using hexane as the eluent and the hexane is then removed. The latter further discloses, in another paragraph, that recrystallization of said reaction product from heptane gives crystals having a melting point of 119.degree.-122.degree. C. and recrystallization from cyclohexane gives crystals melting at 80.degree.-90.degree. C.
However, experiments conducted by the present inventors for checking these methods disclosed in the literature revealed that the compound (I) obtained still has those drawbacks which the above-mentioned commercial products have or that the compound (I) obtained is colored.


DISCLOSURE OF THE INVENTION

Accordingly, the present inventors conducted intensive investigations in an attempt to provide a method of producing the compound (I) in the form of fine granules having good physical properties and in a purified form without coloration by using the ester exchange reaction between the compound (II) and pentaerythritol and, as a result, have now completed the present invention.
Thus the invention provides a method of producing tetrakis[3-(3,5-di-tert-butyl-4-hydroxypenyl)propionyloxymethyl]methane by ester exchange between a 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid alkyl ester and pentaerythritol in the presence of a basic catalyst, which comprises carrying out the reaction in the presence of a 3-(3-tert-butyl-4-hydroxyphenyl)propionic acid alkyl ester [hereinafter sometimes referred to as "compound (III)"].
In accordance with the invention, the step of ester exchange between the 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid alkyl ester and pentaerythritol is to be followed by a purification step comprising recrystallization to give tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxymethyl]methane in a purified form. When said ester exchange reaction is carried out in the presence of 3(3-tert-butyl-4-hydroxyphenyl)propionic acid alkyl ester and in the presence of a basic catalyst as an ester exchange catalyst and when, in the purification step, the product from the ester exchange reaction step is purified by recrystallization from methanol and/or ethanol, the compound (I) can be obtained as fine granules with good physical properties.
As the alkyl ester compound (II), there may be mentioned straight or branched alkyl esters with 1-

REFERENCES:
patent: 3779945 (1973-12-01), Dexter et al.
patent: 4396552 (1983-08-01), Knobloch et al.
patent: 4511491 (1985-04-01), Ishii et al.
patent: 4547585 (1985-10-01), Yamanaka et al.
patent: 4594444 (1986-06-01), Orban
patent: 4683326 (1987-07-01), Orban et al.
patent: 4716244 (1987-12-01), Orban et al.

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