Organic compounds -- part of the class 532-570 series – Organic compounds – Nitrogen attached directly or indirectly to the purine ring...
Reexamination Certificate
2000-02-29
2001-08-21
Lambkin, Deborah C. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitrogen attached directly or indirectly to the purine ring...
C558S138000, C558S157000
Reexamination Certificate
active
06277988
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the preparation of phosphoramidates, and more particularly to their preparation from nitrogen bases and diaryl chlorophosphates.
The use of sterically hindered phosphoramidates such as N,N′-bis[di-(2,6-xylenoxy)phosphinyl]piperazine (hereinafter sometimes “XPP”) as flame retardant additives for synthetic resins, especially thermoplastic resins such as polycarbonates, ABS resins and blends thereof, has been discovered to have particular advantages including improved high temperature stability of the resulting blends. Reference is made, for example, to U.S. Pat. No. 5,973,041 and to copending, commonly owned applications Ser. Nos. 09/235,679 and 09/364,915.
XPP and analogous compounds may be conveniently prepared by the reaction of a diaryl chlorophosphate, such as di-(2,6-xylyl) chlorophosphate, with a heterocyclic compound containing two basic N—H groups, such as piperazine. According to the prior art as illustrated by Talley,
J. Chem. Eng. Data
, 33, 221-222 (1983), this reaction may be conducted in chloroform as solvent, in the presence of triethylamine as an acid acceptor. The triethylamine is employed in stoichiometric amount or in excess, and reacts with the by-product hydrogen chloride to drive the reaction to completion.
The Talley paper describes the preparation of a number of analogous compounds including those derived from such nitrogen compounds as benzylamine, cyclohexylamine, aniline, ethylenediamine and p-phenylenediamine as well as piperazine. Reported yields were as high as 90% for the reaction with aniline, and as low as 61% for the reaction with p-phenylenediamine. Piperazine afforded XPP in a yield of only 68%, one of the lowest reported.
If the use of XPP as a flame retardant additive is to be commercially feasible, it is necessary to improve its yield by a significant amount. Also, it is desirable to minimize use on a commercial scale of the relatively toxic solvent chloroform, as well as other solvents which can add complexity to the reaction by reason of the need for isolation of product from the solvent, as well as disposal or recycle of solvent and of extraneous acid acceptors such as triethylamine.
It is of interest, therefore, to develop high-yield methods for the preparation of XPP and analogous compounds with a minimum of unit operations.
SUMMARY OF THE INVENTION
The present invention is based on the discovery that the preparation of sterically hindered phosphoramidates in high yield from sterically hindered diaryl chlorophosphate and nitrogen bases may be carried out in a solvent-free reaction mixture. In addition, said reaction may also be performed in a solvent-free reaction mixture in the presence of at least one liquid carrier which is a non-solvent for the product.
Accordingly, in one embodiment the invention is a method for preparing a sterically hindered phosphoramidate which comprises contacting a sterically hindered diaryl chlorophosphate with a basic nitrogen compound containing at least two basic N—H groups in a predominantly liquid, solvent-free reaction mixture, said basic nitrogen compound being employed in an amount effective to react with both said diaryl chlorophosphate and by-product hydrogen chloride.
In another embodiment the invention is a method for preparing a phosphoramidate which comprises contacting a diaryl chlorophosphate with a basic nitrogen compound containing at least two basic N—H groups in a predominantly liquid, solvent-free reaction mixture, said basic nitrogen compound being employed in an amount effective to react with both said diaryl chlorophosphate and by-product hydrogen chloride, said phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C.
DETAILED DESCRIPTION; PREFERRED EMBODIMENTS
Within the context of the present invention a sterically hindered phosphoramidate is one in which at least one aryl substituent linked to heteroatom-phosphorus has at least one substituent on the aryl ring ortho to the aryl-heteroatom-phosphorus linkage. The sterically hindered diaryl chlorophosphates employed in the method of this invention include those having the formula
wherein Ar is an aromatic group, each R
1
is independently alkyl, aryl or halo, Q
1
is oxygen or sulfur, Q
2
is oxygen, sulfur, or NR
1
, and n has the value of 1 up to the number of free valency sites on the aromatic ring or rings, and at least one R
1
substituent on the aryl ring is ortho to the heteroatom-phosphorus linkage. Preferably, Ar is a phenyl ring and n has the value of 1-5. Preferably, each R
1
is C
1-4
primary or secondary alkyl; most preferably, methyl, and n is 2 with each substituent ortho to the heteroatom-phosphorus linkage. Thus, preferred chlorophosphates are di-(2,4,6-trimethylphenyl) chlorophosphate and di-(2,6-dimethylphenyl) chlorophosphate, also known as di-(2,6-xylyl) chlorophosphate.
Any compound, acyclic or cyclic, containing at least two basic N—H groups may be employed. Suitable compounds include those of the formula
R
2
NH—CH
2
CH
2
—NHR
2
, (II)
wherein each R
2
is a C
1-4
primary or secondary alkyl radical or both R
2
radicals taken together are ethylene. Illustrative acyclic compounds are N,N′-dimethylethylenediamine and N,N′-diethylethylenediamine. Heterocyclic compounds are generally preferred; they are illustrated by piperazine and 1,2,3,4-tetrahydroquinoxaline, both unsubstituted and substituted. Piperazine is most preferred.
In a preferred embodiment, the method of the invention may be used to produce a phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C. In particular, the method of the invention may be used to produce a phosphoramidate of the formula III:
wherein each Q
1
is independently oxygen or sulfur; and each of A
1-4
is independently an alkyloxy, alkylthio, airyloxy, or arylthio residue, or an aryloxy or arylthio residue containing at least one alkyl or halogen substitution, or mixture thereof; or an amine residue. In an especially preferred embodiment of the invention, each Q
1
is oxygen, and each A
1-4
moiety is a 2,6-dimethylphenoxy moiety or a 2,4,6-trimethylphenoxy moiety. These phosphoramidates are piperazine-type phosphorarnidates. In the above formula wherein each Q
1
is oxygen, and each A
1-4
moiety is a 2,6-dimethylphenoxy moiety, the glass transition temperature of the phosphoramidate is about 62° C. and the melting point is about 192° C.
In another preferred embodiment, the method of the invention may be used to produce a phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C., of the formula IV:
wherein each Q
1
is independently oxygen or sulfur; and each of A
5-9
is independently an alkyloxy, alkylthio, aryloxy, or arylthio residue, or an aryloxy or arylthio residue containing at least one alkyl or halogen substitution, or mixture thereof; or an amine residue; and n is from 0 to about 5. In a more preferred embodiment, each Q
1
is oxygen, and each A
5-9
moiety is independently phenoxy, 2,6-dimethylphenoxy, or 2,4,6-trimethylphenoxy, and n is from 0 to about 5.
In another embodiment the method of the invention may be used to produce a phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C., of the formula V:
wherein each Q
1
is independently oxygen or sulfur; and each of A
10-15
is independently an alkyloxy, alkylthio, aryloxy, or arylthio residue, or an aryloxy or arylthio residue containing at least one alkyl or halogen substitution, or mixture thereof; or an amine residue. In a more preferred embodiment, each Q
1
is oxygen, and each A
10-15
moiety is independently phenoxy, 2,6-dimethylphenoxy, or 2,4,6-trimethylphenoxy.
In another embodiment the method of the
Campbell John Robert
Cella James Anthony
Gillette Gregory Ronald
Kochanowski John Edward
Reitz Matthew Ladd
Brown S. Bruce
D'Souza Andrea M.
General Electric Company
Johnson Noreen C.
Lambkin Deborah C.
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