Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus esters
Reexamination Certificate
2000-12-04
2002-12-03
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus esters
Reexamination Certificate
active
06489502
ABSTRACT:
The present invention relates to a process for preparing phosphoric acid esters, in particular a process for preparing monomeric bridged bisaryl diphosphates, wherein a water-binding agent is added to the reaction solution.
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 polycarbonatc 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 import beneficial physical properties to the polymer, which properties are not provided by their dimeric or polymeric counterparts. For example, resins to which monormeric 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, wherein no additional auxiliary agents are used in addition to the catalyst.
WO 98/47631 discloses a process for preparing aryl diphosphate esters, which comprises a third stage of filtering off he 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 0 485 807 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 discloses 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 10/007 689 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 these processes is that water is introduced into the reaction system by the raw materials used, such as bisphenol A, resorcinol and phenol. The POCl
3
present is partially hydrolysed by water. This eventually leads to nonvolatile hydrolysis products which remain in the final product and damage the polymer during processing of the phosphates.
It is an object of the present invention to provide a process which produces oligophosphates comprising a significantly reduced proportion of hydrolysis products. It has now been found, surprisingly, that the addition of a water-binding agent to the reaction solution produces oligophosphates which comprise only small proportions of hydrolysis products.
The present invention therefore provides a process for the continuous, semicontinuous or batchwise preparation of phosphoric acid esters, characterized in that
(1) a phosphorus oxyhalide is reacted with a polyol in the presence of a waterbinding agent to produce a monomeric halophosphate intermediate, and
(2) the monomeric halophospate intermediate is reacted with an alcohol to produce the desired phosphoric acid ester.
In some preferred embodiments, the polyol in Step 1 is a dihydric alcohol, preferably bisphenol A or resorcinol, and that alcohol in Step 2 is a monohydric alcohol, preferably phenol. Conversely, in some preferred embodiments the phosphorus oxyhalide can also be reacted firstly with a monohydric alcohol to produce a monohalomonophosphoric acid diester intermediate. In some embodiments, the reaction of Step 1 and/or the reaction of Step 2 are carried out continuously. Particularly preferably, at least one step is carried out continuously or semicontinuously.
It is an object of the present invention to provide a method for continuously producing phosphoric acid esters using water-binding agents.
Another preferred 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%.
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.
In a further preferred embodiment, Step 2 can be followed by a workup step 3 in which the product from Step 2 is worked up continuously, semicontinuously or batchwise in a phase separator at temperatures of 50 to 120° C.
The workup of Step 3 comprises both an acidic wash and an alkaline wash, which can likewise be operated in contiguous, semicontinuous or batchwise mode, preferably in continuous mode.
Any aqueous acid can be used foil the acidic wash, for example HCl, H
2
SO
4
, H
3
PO
4
, CH
3
COOH. Particular preference is given to aqueous HCl, in particular in a concentration range from 0.5 to 10%. Any conventional basic salt can be used for the alkaline wash, for example NaOH, Na
2
CO
3
, NaHCO
3
, sodium acetate and corresponding potassium salts. Particular preference is given to Na salts, in particular NaOH in a concentration range from 0.5 to 10%.
The process of the invention is particularly suitable for continuously preparing bisphenol A diphosphate (BDP) or resorcinol diphosphate (RDP), in which case the polyol used is resorcinol.
A further object of the invention is to provide a process for preparing monomeric phosphoric acid ester products which can be used as flame retardants, for example in plastics.
For the purposes of promoting al 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 at least one step is performed continuously, where 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), using a dehydrating agent. 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 re
Bäcker Werner
Heinz Dieter
Janke Nikolaus
Pieroth Manfred
Bayer Aktiengesellschaft
Eyl Diderico van
Gil Joseph C.
McKane Joseph K.
Saeed Kamal
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