Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus acids or salts thereof
Reexamination Certificate
2000-03-20
2002-06-04
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus acids or salts thereof
C562S023000
Reexamination Certificate
active
06399814
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for preparing 2-carboxyalkyl(aryl)phosphinic acid and its corresponding anhydride(s). More specifically, this invention relates to a process for preparing 2-carboxyethyl(aryl)phosphinic acid using an improved hydrolysis process for intermediates involved in the overall reaction. In particular, this invention relates to a process for preparing 2-carboxyethyl(phenyl)phosphinic acid and its cyclic anhydride.
BACKGROUND OF THE INVENTION
2-Carboxyethyl(phenyl)phosphinic acid, useful as a flame retardant additive for polymers such as polyesters and polyamides, has been prepared by reacting acrylic acid with dichloro(phenyl)phosphine in a reaction mixture. This reaction mixture was subjected to a separate hydrolysis step to obtain the desired product: 2-carboxyethyl(phenyl)phosphinic acid.
2-Carboxyethyl(aryl)phosphinic acid and its cyclic anhydride are useful as flame retardant additives for polymers such as polyesters, polyamides and the like.
U.S. Pat. No.5,334,760 which issued on Aug. 2, 1994, to Toshio Wachi et al. (hereinafter “the '760 patent”) discloses a process in which acrylic acid or methacrylic acid is reacted with dichloro(phenyl)phosphine in the presence of a catalyst (Column 1, lines 51-68). That reaction product is hydrolyzed as the '760 patent subsequently discloses:
With the reaction product wherein water is added at a molar amount of 5 to 20 times of the reaction product or with the reaction product dropped in water having the same molar amount as the above, a reaction is carried out at a temperature of 0° to 100° C. for 1 to 3 hours. After completion of the reaction, the resulting reaction product is cooled under stirring, so that a crystal is deposited. (Column 4, line 62-Column 5, line 1).
The '760 patent is incorporated herein in its entirety by reference.
U.S. Pat. No. 4,081,463 which issued to Birum et al. on Mar. 28, 1978 (hereinafter the “463 patent”) discloses, at column 1, lines 21-25, a process in which a 25-45% molar excess of acrylic acid was used in a reaction of acrylic acid with dichloro(phenyl)phosphine. The '463 patent is incorporated herein in its entirety by reference. 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 reportedly advantageous to use a significant excess of water to aid stirring and temperature control. Use of a 5 to 15 molar excess of water is taught at column 1, lines 58-60, as being convenient. This molar excess of water is equivalent to conducting the hydrolysis reported in this patent using 12 to 32 moles water per mole of dichloro(phenyl)phosphine charged to the reaction of acrylic acid with dichloro(phenyl)phosphine.
U.S. Pat. No. 4,769,182 which issued to James R. Hazen on Sep. 6, 1988, (hereinafter the “'182 patent”) discloses at column 2, lines 30-38, a process in which a 0-20% molar excess of acrylic acid was used in the reaction of acrylic acid with dichloro(phenyl)phosphine. The '182 patent is incorporated herein by reference in its entirety. In its 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, see column 4 lines 45-48. This “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 reportedly produces 2-carboxyethyl(phenyl)phosphinic acid as a white microcrystalline powder. However, by avoiding a solid phase and driving off hydrogen halides (e.g. HCl) to improve crystal size, the instant invention produces a purer product with less net trapped impurities.
It is desirable to produce 2-carboxyalkyl(aryl)phosphinic acid with improved product recovery and washing, resulting in improved product quality. This improved quality provides a 2-carboxyalkyl(aryl)phosphinic acid product for use in a polymerization process producing a flame retardant polymer with better color quality, lower catalyst losses in such process, and less corrosion of processing and handling equipment.
It has now been discovered that conducting the hydrolysis with significantly less water present than taught or suggested by the prior art produces 2-carboxyalkyl(aryl)phosphinic acid having enhanced filterability, washing and flowability properties along with a higher bulk density. Enhanced filterability lowers process cycle times and increases productivity.
It has been unexpectedly discovered that the controlled water addition of the process of this invention to the reaction composition avoids a premature solid phase.
Further, it has been discovered herein that by adding water to the reaction composition according to the process of the instant invention, that hydrogen halide (e.g. HCl) is given off in larger than expected quantities, allowing for the formation of larger, more durable crystal size, which improves the resultant product purity, washing, drying, and filterability.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a process for producing 2-carboxyalkyl(aryl)phosphinic acid having improved filterability.
It is a further object of this invention to provide a process to produce 2-carboxyalkyl(aryl)phosphinic acid having lower levels of impurities.
It is a still further object of the invention to provide a process for producing 2-carboxyalkyl(aryl)phosphinic acid which results in improved product washing, faster filtration and better flowability of the final product, each of which can aid in facilitating and enhancing packaging of 2-carboxyalkyl(aryl)phosphinic acid of this invention.
It is yet a further object of the invention to provide a process for producing 2-carboxyalkyl(aryl)phosphinic acid which enables hydrogen halide produced (e.g. HCl) during the hydrolysis reaction to be removed prior to recovery of 2-carboxyalkyl(aryl)phosphinic acid from the hydrolysis reaction mixture, thereby lowering the level of halide in the final product and enhancing 2-carboxyalkyl(aryl)phosphinic acid crystal size (lower levels of halide minimizes corrosion of metal equipment in uses of 2-carboxyalkyl(aryl)phosphinic acid such as in polymer applications).
It is another object of this invention to avoid an unstirrable or difficult to stir solid in a reaction producing 2-carboxyalkyl(aryl)phosphinic acid for an easier and safer process.
It is an additional object of this invention to provide a process to produce an anhydride corresponding to 2-carboxyalkyl(aryl)phosphinic acid.
These and other objects are achieved in the process of this invention which is described in more non-limiting detail hereinafter.
BRIEF SUMMARY OF THE INVENTION
The invention comprises a process for producing 2-carboxyalkyl(aryl)phosphinic acid, wherein aryl is phenyl or C
1
-C
4
alkyl substituted phenyl, comprising adding water to a first reaction mixture comprising the products of the reaction of dihalogenated (aryl)phosphine and a carboxylic acid selected from acrylic acid or methacrylic acid, and hydrolyzing said reaction products to produce a second reaction mixture comprising a corresponding 2-carboxyalkyl(aryl)phosphinic acid; wherein water is added at a controlled rate to said first reaction mixture and the temperature is controlled to maintain the reactor contents in a stirrable state, and wherein the temperature is at least about 125° C. before the end of the hydrolysis reaction.
This invention also comprises a process for producing 2-carboxyalkyl(aryl)phosphinic acid, wherein aryl is phenyl or C
1
-C
4
alkyl substituted phenyl, comprising adding water to a first reaction mixture comprising the products of the reaction of dihalogenated (aryl)phosphine and a carboxylic acid selected from acrylic acid or methacrylic acid, and hydrolyzing said reaction products to produce a second reaction mixture co
Paulik Frank E.
Weinkauff David J.
Lathrop & Gage LC
Solutia Inc.
Vollano Jean F.
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