LU88569A1 - Process for the production of thermoplastic polycarbonate - Google Patents

Description

Mémoire Descriptif déposé à l'appui d’une demande de

BREVET D’INVENTION

au

Luxembourg

au nom de: BAYER AG

Group headquarters RP Patente Group D-51368 Leverkusen Allemagne pour: Process for the production of thermoplastic polycarbonate

Process for the production of thermoplastic polycarbonate

The present invention relates to an overall process for the production of solvent-free polycarbonate, starting from aromatic diphenols and carbonic acid diarylestera, which is characterized in that the monophenol which is released during the conversion to the 01igo- / polycarbonate is in turn used to produce the aromatic diaryl carbonate, wherein the hydrogen halide formed in the production of the diaryl carbonate is converted into the halogen by electrolysis and this in turn is converted into carbonyl dihalide after isolation and reaction with carbon monoxide, which is then used again with the monophenol to produce the diaryl carbonate.

WO 93/3084 describes a process for the production of polycarbonate in which the monophenol which is released in the transesterification process can in turn be reacted with a carbonyldihalide (e.g. phosgene) to give the diaryl carbonate. In this process, the carbonyl dihalide is made from CO and a metal halide compound. This type of production over a catalyst is relatively complicated and uneconomical.

The overall process according to the invention, on the other hand, is flexible, simple to operate and provides products of high purity which are extremely important for the overall process and thus comprises the following process steps (cf. Fig.

1): 1. Transesterification of a diaryl carbonate and a dihydroxy compound to the oligo- / polycarbonate and the monophenol 2. Isolation or separation of the polycarbonate and the monophenol 3. Reaction of the monophenol with the carbonyl dihalide and separation of the products; the diaryl carbonate is again used in step 1. and the hydrogen halide is used in step 4. 4. electrolysis of the hydrogen halide in hydrogen and the halogen 5. conversion of the halogen with carbon monoxide to the carbonyl dihalide, which in turn is used in step 3.

Diphenols suitable for the process according to the invention are those of the formula (0

(1) where X = Cj-Cg-alkylidene or cycloalkylidene, S or a single bond and R = CH3, Cl or Br and n = zero, 1 or 2.

Preferred diphenols are e.g. For example: 4,4'-dihydroxydiphenyl, 4,4'-dihydroxy diphenyl sulfide, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2.2- Bis- (3,5-dichloro-4-hydroxyphenyl) propane, 2,2- bis (3,5-dibromo-4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane and l, l-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane.

Particularly preferred diphenols from the aforementioned are 2,2-bis (4-hydroxyphenyl) propane and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane.

Carbonic acid diesters or diaryl carbonates in the sense of the present invention are di-C6-C14-aryl esters, preferably the diesters of phenol or alkyl-substituted phenols, i.e. diphenyl carbonate or e.g. Dicresyl carbonate. Based on 1 mol of bisphenol, the carbonic diesters are used in 1.01 to 1.30 mol, preferably in 1.02 to 1.15 mol.

The diaryl carbonates are prepared in a known manner (for example LeA 27 945, 29 742, 29 785, 29 908) by phosgenation (in solution, in the melt, in the gas phase) of the monophenoia with elimination of the hydrogen halide (HC1).

The use of small amounts of branching agents allows the polycarbonates to be deliberately and controlled digestion. Some suitable branches are:

Phloroglucin, 4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) -hepten-2, 4.6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) -heptane, 1,3,5- Tri- (4-hydroxyphenyl) benzene, 1,1,1-tri- (4-hydroxyphenyl) ethane,

Tri- (4-hydroxyphenyl) phenylmethane, 2,2-bis [4,4-bis (4-hydroxyphenyl) cyclohexyl] propane, 2,4-bis (4-hydroxyphenyl isopropyl) phenol, 2.6- Bi s- (2-hydroxy-5 '-methyl-benzyl) -4-methylphenol, 2- (4-hydroxyphenyl) -2- (2,4-dihydroxyphenyl) propane, hexa- (4- (4th -hydroxyphenyl-isopropyl) -phenyl) -orthoterephthalic acid ester, tetra- (4-hy droxyphenyI) -methane, tetra- (4- (4-hydroxyphenyl-isopropyl) -phenoxy) -methane, 1.4-bis- (4 ', 4 "-dihydroxytriphenyl) -methyl) -benzene and in particular Tris- (4-hy droxy phenyl) -1,3,5 -trii sopropybenzene.

Other possible branching agents are 2,4-dihydroxybenzoic acid, trimesic acid, cyanuric chloride and 3,3-bis (3-methyl-4-hydroxyphenyl) -2-oxo-2,3-dihydroindole.

The 0.05 to 2 mol%, based on diphenols, of branching agents which may also be used can be used together with the diphenols.

Care must be taken to ensure that the reaction components for the first step, the transesterification, that is to say the diphenols and the carbonic acid diaryl esters, are free from alkali and alkaline earth ions, amounts of less than 0.1 ppm of alkali and alkaline earth ions being tolerable. Such pure diphenols or diphenols can be obtained by recrystallizing, washing or distilling the carbonic acid diaryl esters or diphenols. In the process according to the invention, the content of aicali and alkaline earth metal ions in both the diphenol and the carbonic acid diester should be a value of <0.1 ppm.

The transesterification reaction of the aromatic dihydroxy compound and the carbonic acid diester in the melt is preferably carried out in two stages. In the first stage, the aromatic dihydroxy compound and the carbonic acid diester are melted at temperatures of 80-250 ° C, preferably 100-230 ° C, particularly preferably 120-190 ° C under normal pressure in 0-5 hours, preferably 0.25- 3 hours instead. After adding the catalyst, the oligocarbonate is prepared from the aromatic dihydroxy compound and the carbonic acid diester by applying a vacuum (up to 2 mm Hg) and increasing the temperature (up to 260 ° C.) by distilling off the monophenol. The oligocarbonate thus produced has an average weight molar mass (determined by measuring the relative solution viscosity in dichloromethane or in mixtures of equal amounts by weight of phenol / o-dichlorobenzene calibrated by light scattering) in the range from 2000 to 18,000, preferably from 4,000 to 15,000 Main amount of monophenol (> 80%) recovered from the process.

In the second stage, the polycarbonate is produced in the polycondensation by further increasing the temperature to 250-320 ° C., preferably 270-295 ° C. and a pressure of <2 mm Hg. The rest of the monophenols are obtained here. There are small losses of monophenols of <5%, preferably <2%, particularly preferably <1%, caused by end groups in the polycarbonate and residual monophenol in the polycarbonate. These losses have to be compensated for by appropriate amounts of monophenol for the preparation of the diaiyl carbonate compound.

Catalysts in the sense of the process according to the invention are all inorganic or organic basic compounds, for example: lithium, sodium, potassium, cesium, calcium, barium, magnesium, hydroxides, carbonates, halides, phenolates, diphenolates , -fluoride, -acetate, -phosphate, -hydrogen-phosphate, boranate, nitrogen and phosphorus bases such as tetramethylammonium hydroxide, tetramethylammonium acetate, tetramethylammonium fluoride, tetramethy 1 am moniumtetraphenylboranate, tetraphenylphosphoniumdioxonyldehydonylphosphoniumdioxonylphosphonium fluoroniumphtheniumphosphonium fluoroniumphtheniumphosphonium fluoroniumphthonidium, Tetraethylammonium hydroxide, DBU, DBN or guanidine systems such as l, 5,7-triazabicyclo- [4,4,0] -dec-5-ene, 7-phenyl-l, 5,7-triazabicyclo- [4 , 4,0] -dec-5-ene, 7-methyl-l, 5,7-triazabicyclo- [4,4,0] -dec-5-ene, 7,7'-hexylidene-di-1,5 , 7-triazabicyclo- [4,4,0] -dec-5-ene, 7,7'-decylidene-di-l, 5,7-triazabicyclo- [4,4,0] -dec-5-ene, 7,7'-dodecylidene-di-1,5,7-triazabicyclo- [4,4,0] -de c-5-ene or phosphazenes such as, for example, the phosphazene base Pj-t-Oct = tert.-octyl-imino-tris- (dimethylamino) -phosphorane, phosphazene base Ρ, -t-butyl = tert-butyl -imino-tris- (dimethylamino) -phosphorane, BEMP = 2-tert-butylimino-2-diethylamino-l, 3-dimethyl-perhydro-1,3-diaza-2-phosphorine.

These catalysts are used in amounts of 10 '"to 10 moles, based on 1 mole of diphenol.

The catalysts can also be used in combination (two or more) with one another.

When using alkali / alkaline earth metal catalysts, it may be advantageous to add the alkali / alkaline earth metal catalysts at a later point in time (e.g. after oligocarbonate synthesis in the polycondensation in the second stage). The addition of the alkali / alkaline earth metal catalyst can e.g. as a solid or as a solution in water, phenol, oligocarbonate, polycarbonate. The use of alkali or alkaline earth metal catalysts does not contradict the aforementioned requirement for purity of the reactants.

The reaction of the aromatic dihydroxy compound and the carbonic acid diester to the polycarbonate can be carried out discontinuously or preferably continuously in the sense of the process according to the invention, for example in stirred tanks, thin-film evaporators, falling film evaporators, stirred tank cascades, extruders, kneaders, simple disk reactors and high-viscosity disk reactors.

The aromatic polycarbonates of the process according to the invention should have average molecular weights of 18,000 to 80,000, preferably 19,000 to 50,000, determined by measuring the rel. Solution viscosity in dichloromethane or in mixtures of equal amounts by weight of phenol / o-dichlorobenzene calibrated by light scattering.

It is advantageous to purify the monophenols which have been split off and isolated from the transesterification of the dihydroxy compound and the carbonic acid diester to give the polycarbonate, before being used in the dialysis carbonate synthesis. The crude mono-phenols that are isolated in the transesterification process can, depending on the transesterification conditions and distillation conditions, i.a. be contaminated with diaryl carbonates, the dihydroxy compound, salicylic acid, isopropenylphenol, phenyl phenoxybenzoate, xanthone, the hydroxymonoaiyl carbonate. The cleaning can be done according to the usual cleaning procedures, e.g. B. Destination or recrystallization. The purity of the monophenols is then> 99%, preferably> 99.8%, particularly preferably> 99.95%.

The electrolysis of the hydrogen halide is carried out by the process known from the literature, which is described, for example, in Ullmanns Encyklopadie der Technische Chemie Volume 9, Verlag Chemie, p. 355 £ and the references cited therein.

Claims (3)

Patentansnriiche 1.) Process for the production of polycarbonate, characterized by the following steps: a. Transesterification of a diaryl carbonate and a dihydroxy compound to the 01ig / polycarbonate and the monophenol b. Isolation or separation of the 01igo / polycarbonate and the monophenol c. Reaction of the monophenol with the carbonyl dihalide and separation of the products; the diaryl carbonate is again in step a. used and the hydrogen halide is in step d. used d. Electrolysis of hydrogen halide in hydrogen and the halogen e. Implementation of the halogen with carbon monoxide to the carbonyldihalide, which in turn in step c. is used. '2.) Process for the preparation of a 01igo / polycarbonate, according to claim 1, characterized in that the diaryl carbonate used is diphenyl carbonate, the dihydroxy compound is bisphenol A, the carbonyl dihalide is phosgene and, accordingly, hydrogen chloride is used in the electrolysis. 3.) Process for producing a polycarbonate, characterized by the following steps: a. Transesterification of diphenyl carbonate and bisphenol A to polycarbonate with the elimination of phenol b. Isolation or separation of the 01igo / polycarbonate and phenol c. Conversion of phenol and phosgene to diphenyl carbonate, which again in step a. is used and use of the resulting hydrogen chloride in step d. d. Electrolysis of hydrogen chloride in hydrogen and chlorine e. Implementation of the chlorine with carbon monoxide to the phosgene, which in turn in step c. is used.