Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-04
2002-07-16
Lambkin, Deborah C. (Department: 1626)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C558S092000
Reexamination Certificate
active
06420465
ABSTRACT:
The present invention relates to a process for preparing phosphoric acid esters, in particular a continuous process for preparing monomeric bisaryl diphosphates, or bridged phosphates.
Bisaryl diphosphates, such as bisphenol A bis(diphenyl)phosphate and resorcinol bis(diphenyl)phosphate are known to be effective flame retardants for polymer resins. For example, a variety of polyphenylene oxide/high-impact polystyrene (“PPO/HIPS”) and polycarbonate/acrylonitrile-butadiene-styrene (“PC/ABS”) blends can be improved with bisaryl diphosphate flame retardants.
When using bisaryl diphosphates to impart flame retardancy to plastics it is desired to use compounds having a high percentage of the monomer. This is because monomeric bisaryl diphosphates impart beneficial physical properties to the polymer, which properties are not provided by their dimeric or polymeric counterparts. For example, resins to which monomeric bisaryl diphosphates have been added exhibit improved impact strength, melt flow index, tensile properties and flexural properties when compared to resins combined with dimeric or polymeric aryl phosphates.
Because of their commercial utility, various processes for the manufacture of monomeric bisaryl diphosphates have been developed. For example, it is known that bisphenol-A bis(diphenyl)phosphate can be obtained by catalytically reacting a phosphorus oxyhalide with bisphenol A (BPA) and then reacting the intermediate with phenol.
WO 99/55771 describes a process for continuously preparing monomeric bisaryl diphosphates, which, however, are not worked up and thus do not meet all requirements of a flame retardant for polymer resins with regard to certain product properties (catalyst content, acid number, hydrolysable chlorine).
It is known from EP 936243 A2 that acid components and/or precursors thereof which, under conditions of heat and humidity, lead to the formation of acid components, are typically present in the bisaryl diphosphates. These impurities may originate from, for example, catalyst residues, unreacted starting materials, such as phosphoryl halides and/or phosphoric acid ester derivatives, or from decomposition products of unstable phosphoric acid esters. It has also been found that such impurities as flame retardant additives in polymer resins compromise the hydrolytic stability.
WO 98/47631 discloses a process for preparing aryl diphosphate esters, which comprises a third stage of filtering off the catalyst which is unsoluble in the reaction medium.
WO 98/35970 describes a semicontinuous process for preparing bisaryl diphosphates using magnesium chloride as a catalyst. The reaction product is not worked up here either.
EP 0485 807 B1 describes a process for preparing aryl diphosphate esters in eight process steps, a workup or extraction of the catalyst being carried out in aqueous alkaline solution.
JP-A 10/017 583 dicloses a batchwise synthesis for preparing phosphate ester oligomers, the reaction being controlled via the liberation rate of HCl gas. Excess phenol is removed by distillation, whereas the catalyst, for example magnesium chloride, is removed by washing.
Finally, JP-A 10/00 7689 discloses a process for removing the metal chloride catalyst by means of an acidic aqueous solution (pH≦3) and at a temperature of at least 65° C.
A disadvantage of the prior art preparation processes is that, in the absence of a workup procedure, the desired products can be obtained only in a form contaminated with catalyst and other acidic minor components, or that, in the case of bridged aryl phosphates, in particular the reaction products of bisphenol A or resorcinol, the workup or washing prodecures suggested lead to considerable difficulties in largescale plants owing to the poor phase separation between the product phase and the water phase and to the strong hydrolysis tendency in particular in alkaline media. At present, these difficulties prevent the realization of a continuous and thus industrialscale production of these products.
The present invention therefore provides a process for preparing phosphoric acid esters, in particular monomeric bisaryl diphosphates or bridged phosphates, characterized in that
(1) a phosphorus oxyhalide is reacted continuously, semicontinuously or batchwise with a polyol to produce a content of at least about 60% monomeric halophosphate intermediate,
(2) the monomeric halophosphate intermediate is reacted continuously, semicontinuously or batchwise with an alcohol to produce the desired phosphoric acid ester, and
(3) the product from Step 2 is worked up continuously, semicontinuously or batchwise in a phase separator at temperatures of 50 to 120° C.
In some preferred embodiments, the polyol in Step 1 is a dihydric alcohol and the alcohol in Step 2 is a monohydric alcohol. Conversely, in some preferred embodiments the phosphorus oxyhalide is reacted with a monohydric alcohol to produce a content of at least about 60% monohalomonophosphoric acid diester intermediate. In a preferred embodiment, all three steps are carried out continuously.
It is an object of the present invention to provide a method for continuously producing phosphoric acid esters, wherein at least one step is carried out continuously. Particularly preferably all three steps are carried out continuously.
Another object of the present invention is to provide a method for producing phosphoric acid esters in a continuous reaction, wherein the monomeric halophosphate intermediate content of a reaction between phosphorus oxyhalide and a polyol is at least about 60%, preferably at least about 70% and particularly preferably at least about 80%.
A further object of the invention is to provide a method for producing monomeric phosphoric acid ester products which can be used as flame retardants, for example, in plastics.
Further objects and advantages of the present invention will be apparent from the following description.
The term continuous as used herein means that the reactants are fed into the apparatus at a constant flow rate and the reaction mixture is removed in an equally continuous manner. All reaction parameters are kept constant over time.
The term semicontinuous as used herein means that one reactant is introduced into the apparatus whereas another reactant is added slowly and continuously.
The term batchwise or discontinuously as used herein means that the reactants are introduced together into the apparatus, where they remain for a defined reaction time under set reaction conditions.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to preferred embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated methods, and such further applications of the principles of the invention as illustrated therein, being contemplated as would normally occur to one skilled in the art to which the invention relates.
Preferably, the present invention relates generally to a continuous process for producing phosphoric acid esters, wherein all three steps are run continuously, so that a product can be produced which has a high monomeric halophosphate intermediate content relative to dimeric halophosphate intermediate content, along with high productivity, when the reaction is carried out in a continuous reactor system, such as a continuous stirred tank reactor (CSTR). The intermediate can be used, in certain embodiments, to form a desired monomeric phosphoric acid ester, including BPA bis(diphenyl)phosphate.
The preferred reactor design (i.e., a continuous reactor) allows the production of product ratios otherwise unattainable in commercial quantities at high productivity.
The degree of oligomerization or polymerization can further be controlled to some extent by the degree of reaction completion in individual stages of a multiple stage continuous reactor series.
In one aspect of the invention, phosphoric acid esters are continuously produced by
Bäcker Werner
Chrisochoou Andreas
Hallenberger Kaspar
Heinz Dieter
Janke Nikolaus
Bayer Aktiengesellschaft
Eyl Diderico van
Gil Joseph C.
Lambkin Deborah C.
LandOfFree
Process for preparing phosphoric acid esters does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for preparing phosphoric acid esters, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing phosphoric acid esters will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2874840