Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus acids or salts thereof
Reexamination Certificate
2000-02-17
2001-11-20
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus acids or salts thereof
Reexamination Certificate
active
06320071
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
(NOT APPLICABLE)
BACKGROUND OF THE INVENTION
This invention relates to a process for preparing 2-carboxyalkyl(phenyl)-phosphinic acid. In a specific aspect, this invention relates to an improved hydrolysis process. In a more specific aspect, this invention relates to a process for preparing 2-carboxyethyl(phenyl)-phosphinic acid using an improved hydrolysis process.
2-Carboxyethyl(phenyl)phosphinic acid, a flame retardant additive for polymers such as polyesters, has been prepared by first reacting acrylic acid with dichloro(phenyl)phosphine. This reaction mixture was then subjected to a separate hydrolysis step to obtain the 2-carboxyethyl(phenyl)phosphinic acid.
U.S. Pat. No. 4,081,463 (Birum et al.) discloses a process in which a 25-45% molar excess of acrylic acid was used in the reaction of acrylic acid with dichloro(phenyl)phosphine. For the hydrolysis step, the '463 patent discloses adding the undiluted reaction product of acrylic acid and dichloro(phenyl)phosphine to at least enough water to complete hydrolysis, with it being advantageous to use a significant excess of water to aid stirring and temperature control. In fact, use of a 5 to 15 molar excess of water is taught as being convenient. This molar excess of water is equivalent to conducting the hydrolysis using 12 to 32 moles water per mole of dichloro(phenyl)phosphine charged to the reaction of acrylic acid with dichloro(phenyl)phosphine. Conducting the hydrolysis in this manner produces 2-carboxyethyl(phenyl)phosphinic acid as a fine white solid.
U.S. Pat. No. 4,769,182 (Hazen) discloses a process in which a 0-20% molar excess of acrylic acid was used in the reaction of acrylic acid with dichloro(phenyl)phosphine. For the hydrolysis step, the '182 patent discloses that typical hydrolysis conditions for acid chlorides and similar water-reactive species are used, with a “drowning” technique being preferred. The drowning technique involves the use of significant excess water, i.e. 25.7 moles water per mole of dichloro(phenyl)phosphine charged to the reaction of acrylic acid with dichloro(phenyl)phosphine. Conducting the hydrolysis in this manner produces 2-carboxyethyl(phenyl)phosphinic acid as a white microcrystalline powder.
It is desirable to produce 2-carboxyalkyl(phenyl)phosphinic acid with improved product recovery and washing resulting in improved product quality.
It has now been surprisingly discovered that conducting the hydrolysis with significantly less water present than suggested by the prior art produces 2-carboxyalkyl(phenyl)phosphinic acid having better filterability than obtained using the prior art processes.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention to provide a process for producing 2-carboxyalkyl(phenyl)phosphinic acid having improved filterability. It is a further object of the invention to produce 2-carboxyalkyl(phenyl)phosphinic acid having improved purity. It is a still further object of the invention to provide a process for producing 2-carboxyalkyl(phenyl)phosphinic acid which results in improved product washing and faster filtration. It is yet a further object of the invention to provide a process for producing 2-carboxyalkyl(phenyl)phosphinic acid which enables HCl produced during the hydrolysis reaction to be removed prior to recovery of the 2-carboxyalkyl(phenyl)phosphinic acid from the hydrolysis reaction mixture.
According to the invention, a process for producing 2-carboxyalkyl(phenyl)phosphinic acid is provided which comprises (a) admixing water and a first reaction mixture comprising the products of the reaction of dichloro(phenyl)phosphine and a carboxylic acid selected from acrylic acid or methacrylic acid, and (b) hydrolyzing the reaction products of the first reaction mixture to produce a second reaction mixture comprising 2-carboxyalkyl(phenyl)phosphinic acid; wherein the amount of water admixed with the first reaction mixture in step (a) is about 2 to about 7.5 moles water per mole of dichloro(phenyl)phosphine charged to the reaction between dichloro(phenyl)phosphine and carboxylic acid.
Further according to the invention, a process for producing 2-carboxyalkyl(phenyl)phosphinic acid is provided which comprises (a) admixing water and a first reaction mixture comprising the products of the reaction of dichloro(phenyl)phosphine and a carboxylic acid selected from acrylic acid or methacrylic acid, and (b) hydrolyzing the reaction products of the first reaction mixture to produce a second reaction mixture comprising 2-carboxyalkyl(phenyl)phosphinic acid, and simultaneously removing at least a portion of the HCl present during the hydrolysis reaction; wherein the amount of water admixed with the first reaction mixture in step (a) is the amount effective to enable removal of at least about 20% of the theoretically available chlorine in the first reaction mixture during the hydrolysis.
REFERENCES:
patent: 4081463 (1978-03-01), Birum, et al.
patent: 4769182 (1988-09-01), Hazen
patent: 5334760 (1994-08-01), Wachi, et al.
Paulik Frank E.
Weinkauff David J.
Lathrop & Gage L.C.
McKane Joseph K.
Murray Joseph
Solutia Inc.
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