Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-05-10
2004-03-16
Boykin, Terressa (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000
Reexamination Certificate
active
06706848
ABSTRACT:
The present invention relates to a process for producing polycarbonate by transesterification of carbonic esters with dihydroxyl compounds, wherein the dihydroxyl compounds have a content of at least 10 mol % 2,2-bis(4-hydroxy-phenyl)propane (also referred to as bisphenol A, abbreviated below to BPA) and wherein bisphenol A is used as a mixture with phenol.
The production of polycarbonate by transesterification of carbonic esters with dihydroxyl compounds is known. This process is described, for example, in the monograph by H. Schnell, Chemistry and Physics of Polycarbonates, Polymer Reviews, Volume 9, John Wiley and Sons, 1964, pages 44-51. This process is also described in Encyclopedia of Polymer Science, Volume 10, 1969.
The process for producing polycarbonate by transesterification is particularly suitable for the production of the homopolycarbonate of bisphenol A (BPA). To this end, bisphenol A is transesterified with carbonic esters, preferably diphenyl carbonate. The process for producing polycarbonate by transesterification is also suitable for the production of copolycarbonates based on bisphenol A and further dihydroxyl compounds as participants in the copolymerisation. To this end, bisphenol A and the further dihydroxyl compounds are transesterified with carbonic esters, preferably diphenyl carbonate.
In the production of polycarbonate by transesterification, the coreactants (dihydroxyl compounds and carbonic esters and optionally further auxiliary substances and additives such as, for example, branching agents) are reacted together in an in most cases multistep reaction, preferably in the melt, preferably with addition of a transesterification catalyst or of a combination of several transesterification catalysts, with splitting-off of a hydroxyl compound from the carbonic ester. If the carbonic ester used is diphenyl carbonate, the hydroxyl compound split off is phenol.
The reaction equilibrium is constantly shifted by varying the temperature and pressure above the reaction mixture. By continued condensation, light-coloured, solvent-free polycarbonates can be obtained in this way.
A wealth of catalysts, embodiments of the process and apparatus employed have been described for the transesterification process for producing polycarbonates.
The transesterification process for producing polycarbonates has the advantage that it requires no solvent and no phosgene, which are required in the so-called phase interface process for producing polycarbonates. The transesterification process for producing polycarbonates therefore renders possible an economical and non-polluting production of polycarbonate, which moreover has the advantage of being free from chlorine.
The process for producing polycarbonate by transesterification generally requires high standards of purity in the starting materials and the auxiliary substances used. The specific form in which the starting materials and the auxiliary substances are introduced can also influence the process and the quality of the polycarbonate product.
For example, DE-A 2 439 552 reports that the use of bisphenol A and diphenyl carbonate as melts which have not passed through the solid state as pure substances leads to improved qualities in the polycarbonate product.
The effect of various forms of introducing the catalyst used has also been investigated. Thus, for example, EP-A 0 719 814 describes an embodiment wherein an alkaline catalyst is first of all dissolved in an adduct mixture of bisphenol and phenol. The phenol is subsequently removed and the resulting solution of the catalyst in the bisphenol is reacted with a suitable carbonic ester.
The production of the high-purity bisphenol A which is required for producing polycarbonate by the transesterification process can be carried out, for example, from phenol and acetone with acid catalysis, as described in DE-A 3 727 641 or in U.S. Pat. No. 2,858,342. The addition of a cocatalyst is possible.
In the conventional process for producing bisphenol A, the reaction mixture consisting of acetone and phenol is passed through the reaction zone, after which bisphenol A is obtained first of all as a solution in the reaction mixture. At this point the reaction mixture consists mainly of phenol and bisphenol A. Besides these, the reaction mixture also contains secondary products typically obtained during the production of bisphenol A, such as, for example, o,p-bisphenol A, methylated hydroxyphenylindanoles, methylated hydroxyphenylchromanoles, p-isopropenyl-phenol and its dimers, trimers and oligomers, as well as higher condensates having three or more aromatic nuclei.
For the purification of bisphenol A, bisphenol A is obtained in the form of an approximately equimolar adduct with phenol; this is typically achieved by crystallisation of bisphenol A from the reaction mixture. The bisphenol A is then further purified. This further purification can be carried out, for example, by recrystallisation from water or from suitable organic solvents or mixtures thereof, as described, for example, in U.S. Pat No. 4,354,046 or in EP-A 0 626 408. The purification and separation of phenol by melt crystallisation, desorption or by multistep distillation is also described, for example, in EP-A 0 785 181 and EP-A 0 676 626.
The separation of unwanted secondary products from the process for the production of bisphenol A and the separation of phenol from the initially isolated adduct of bisphenol A and phenol are effected through the use of the above-mentioned purification processes or through a combination of several of the above-mentioned purification processes. At high technological expense, it is thereby possible to purify bisphenol A almost completely from the secondary products typically formed during the production and from phenol, and to obtain it in a purity of up to more than 99.9%.
Bisphenol A thus produced can be stored and processed in the form of powder, flakes or pellets, or dissolved in the form of sodium salt in sodium hydroxide solution, in order to be used for the production of polycarbonate by the phase interface process. The high-purity bisphenol A thus produced can also be used as starting material for the production of polycarbonates by the transesterification process.
The object of the present invention is to provide a process for producing polycarbonate by transesterification of carbonic esters with dihydroxyl compounds which have a content at least 10 mol % bisphenol A, without this process requiring the expensive purification processes for bisphenol A which are known from prior art.
The object according to the invention is achieved by a process for producing polycarbonate by transesterification of carbonic esters with dihydroxyl compounds which contain at least 10 mol % bisphenol A, wherein bisphenol A is not used as pure substance, for example, in the form of powder, flakes, pellets or as melt, in the manner known from prior art, but wherein bisphenol A is used as a mixture with phenol.
This method of achieving the object according to the invention is surprising because, by avoiding purification steps in the production of bisphenol A, it enables bisphenol A to be made available far more simply and more economically by using the mixture of phenol and bisphenol A obtained during the production of bisphenol A directly for the production of polycarbonate. The known prior art assumes that this is not possible, and that bisphenol A has to be made available in pure form by means of expensive purification processes in order for it to be usable in a transesterification process for the production of polycarbonate.
The invention accordingly provides a process for producing polycarbonate by transesterification of carbonic esters with dihydroxyl compounds, characterised in that 10 to 100 mol % of the molar quantity of dihydroxyl compounds used in total is bisphenol A and that bisphenol A is used as a mixture of bisphenol A and 0.1 to 200 wt. % phenol, based on the weight of bisphenol A.
Preferably mixtures containing 5 to 85 wt. % phenol, particularly preferably mixtures containing 10 to 70
Hucks Uwe
Lanze Rolf
Prein Michael
Bayer Aktiengesellschaft
Boykin Terressa
Gil Joseph C.
Matz Gary F.
Preis Aron
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