LU88564A1 - Process for the production of thermoplastic polycarbonate - Google Patents

Description

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

BREVET D’INVENTION

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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 diaryl esters, which is characterized in that the monophenol which is released during the transesterification to the polycarbonate is in turn used to produce the aromatic diphenol.

A process for the production of polycarbonate is described in WO 93/3084 and in Chemistry and Physics of Polycarbonates, Polymer Reviews, H. Schnell, Vol. 9, John Wiley and Sons, Inc. (1964), pp. 48, 49. in which the monophenol can in turn be converted to a diaryl carbonate with a carbonyl dihalide (eg phosgene). The local decoupling of the diaryl carbonate production from the polycarbonate production in the melt is advantageous from an economic and location point of view, since one central diaiyl carbonate production site - usually equivalent to a phosgene site - can serve several polycarbonate esterification plants. When the process stages are uncoupled, the reuse of the monophenols in the diaryl carbonate synthesis is disadvantageous for logistical reasons. It has now been found that the resulting monophenol can also be used for the synthesis of the dihydroxy compound. Then a spatial separation of the phosgenation or another method of production (transesterification process) of the monophenols to the diaiyl carbonates from the melt transesterification to the polycarbonate is also possible while maintaining the monophenol utilization in the polymer production.

The method according to the invention thus comprises the following process steps (see Fig.

1): 1. Initial esterification of a diaryl carbonate and a dihydroxy compound to give the oligo / polycarbonate and the monophenol 2. Isolation or separation of the 01igo / polycarbonate and the monophenol 3. Conversion of the monophenol to the dihydroxy compound, which in turn is used in step 1.

Diaryl carbonate

Figure 1 Diphenols suitable for the process according to the invention are those of the formula (I)

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

Preferred diphenols are, for example: 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenylsulfide, 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-hydroxy phenyI) cyclohexane and 1.1 -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 diaiyl carbonates for the purposes of the present invention are di-Cg-C ^ -aiyl 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 diaiyl carbonates can be prepared, for example, by phosgenation (in solution, in the melt, in the gas phase) with monophenols, by direct synthesis from carbon monoxide and monophenol on suitable catalysts or, for example, by transesterification of dimethyl carbonate with the monophenols.

The polycarbonates can be deliberately and deleteriously decongested by using small amounts of yer branch. 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-hydroxyphenylisopropyl) phenol, 2, 6-bis (2-hydroxy-5'-methylbenzyl) -4-methylphenol,

Hexa- (4- (4-hydroxyphenyl-isopropyl) phenol) orthoterephthalic acid ester, tetrah- (4-hydroxyphenyl) methane, tetra- (4- (4-hydroxyphenyl-isopropyl) phenoxy) methane, 1, 4-bis (4 ', 4 "-dihydroxytriphenyl) methyl) benzene and in particular a, a', a" -Tris- (4-hydroxyphenyl) -l, 3,5-triisopropylbenzene.

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

The 0.05 to 2 mol% of branching agent which may be used, based on the diphenols 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 diyl ester, are free from alkali and alkaline earth ions, amounts of <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 alkali 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 melting of the aromatic dihydroxy compound and the carbonic acid diester takes place at temperatures of 80 to 250 ° C., preferably 100 to 230 ° C., particularly preferably 120 to 190 ° C. under normal pressure in 0 to 5 hours, preferably 0.25 to 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-average molar mass Mw (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 2,000 to 20,000, preferably 4,000 to 18,000. The main amount of monophenol (> 80%, preferably> 90%, particularly preferably> 95%) is recovered from the process. The monophenol of this stage is largely free of by-products. If the oligo- and polycondensation are separate process steps, it can be advantageous to recycle only those in monophenol from the oligocarbonate synthesis into the process of the dihydroxy compound. However, this can also make sense if the monophenols of the polycondensation stage are too contaminated with by-products (possible by-products see below).

In the second stage, the polycarbonate is produced in the polycondensation by further increasing the temperature to 250 to 320 ° C., preferably 270 to 295 ° C. and a pressure of <2 mm Hg. The rest of the monophenols are obtained here. With regard to the overall process balance, there are small losses of monophenols <5%, preferably <2%, particularly preferably <1%, caused by aryl carbonate end groups as potentially removable monophenol in the polycarbonate, residual monophenol in the polycarbonate and by the monophenol purification. These losses must be compensated for by adding appropriate amounts of monophenol for the preparation of the dihydroxy compound.

Catalysts for the transesterification reaction of the aromatic dihydroxy compound and carbonic acid diester 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 , -Halogenide, -phenolate, -diphenolate, -fluoride, -acetate, -phosphate, -hydrogenphosphate, -boranate, nitrogen and phosphorus bases such as tetramethylammonium hydroxide, tetramethylammonium acetate, tetramethyiammo-niumfluoride, tetramylammanylate, fluoride, , Tetraethylammonium hydroxide, DBU, DBN or guanidine systems such as, for example, 1,5,7-triazabicyclo- [4,4,0] -dec-5-ene, 7-phenyl-1,5,7-triazabi-cyclo- [4, 4,0] -dec-5-ene, 7-methyl-1,5,7-triazabicyclo- [4,4,0] -dec-5-ene, 7,7'-hexyli-den-di-l, 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-l, 5,7-triazabicyclo- [4,4,0] -dec-5- s or phosphazenes such as, for example, the phosphazene base Pj-t-Oct = tert-octyl-iminotris (dimethylamino) phosphorane, phosphazene base P ^ t-butyl = tert-butyl-iminotris (dimethylamino) ) -phosphorane, BEMP = 2-tert-butylimino-2-diethylamino-l, 3-dimethyl-perhydro-l, 3-diaza-2-phosphorine.

These catalysts are used in amounts of 10'2 to 10'8 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 the 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 above-mentioned requirement for purity of the reaction partners.

The reaction of the aromatic dihydroxy compound and the carbonic acid diester to the polycarbonate can be carried out batchwise 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 M ^ 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 use in the dihydroxy synthesis. The crude monophenols that are isolated in the transesterification process can, depending on the transesterification conditions and desulphation conditions, among others. be contaminated with diaryl carbonates, the dihydroxy compound, salicylic acid, isopropenylphenol, phenoxybenzoic acid phenyl ester, xanthone, the hydroxymonoaryl carbonate. The cleaning can be carried out according to the usual cleaning procedures, e.g. Destination or recrystallization take place. The purity of the monophenols is then> 99%, preferably> 99.8%, particularly preferably> 99.95%.

These monophenols (Π) are reacted with the ketones (ΙΠ) in a known manner (e.g. Houben Weyl, Georg Thieme Verlag, Stuttgart, Phenole Part 2, Vol. VI Ic, 1019 to 1030 and the references cited therein):

(n) mo) in which in the monophenol (Π) R = CH3, NO2, Cl or Br and n = zero, 1 or 2 and in which Z and Y in the ketone (III) = identical or different C 1 -C 6 -alkylidene or Z , Y can be a cycloalkylidene and wherein in the formula (I) of the dihydroxy compound S = Cj-Cg-alkylidene or cycloalkylidene or a single bond and R = CH3, Cl or Br and n = zero, 1 or 2.

The preferred industrial implementation of the monophenols with the ketone is carried out on acidic ion exchangers, the activities of which can be increased by cocatalysts. This procedure is described, for example, in EP 23 325 and DE 3 727 641 and the references cited therein.

Preferred phenols of the formula (II) are alkylphenols such as cresol, chlorophenol, bromophenol, particularly preferably phenol.

Preferred ketones of the formula (III) are symmetrical and asymmetrical dialkyl ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl butyl ketone, methyl pentyl ketone, aikylated cyclohexanones such as, for example, methyl cyclohexanones, dimethyl cyclohexanones, particularly preferably 3,3,5-trimethyl cyclohexanone and acetone.

Claims (5)

1. A process for the preparation of a polycarbonate, characterized by the following steps: a) transesterification of a diaiyl carbonate and a dihydroxy compound to the polycarbonate and the monophenol, b) isolation or separation of the polycarbonate and the monophenol, c) reaction of the monophenol to Dihydroxy compound, which in turn is used in step a). 2. A process for the preparation of a polycarbonate according to claim 1, characterized in that the diaryl carbonate used is diphenyl carbonate, the dihydroxy compound is bisphenol A and, accordingly, phenol with acetone is in turn used for the bisphenol A production. 3. Process for the preparation of a polycarbonate, characterized by the following steps: a) transesterification of diphenyl carbonate and bisphenol A to polycarbonate with elimination of phenol, b) isolation or separation of the polycarbonate and the phenol, c) reaction of the phenol with acetone to bisphenol A , d) recycling of the bisphenol As into the transesterification with diphenyl carbonate to the polycarbonate. 4. Process for the preparation of an oligocarbonate, characterized by the following steps: a) transesterification of a diaryicarbonate and a dihydroxy compound to the oligocarbonate and the monophenol, b) isolation or separation of the oligocarbonate and the monophenol, c) conversion of the monophenol to the dihydroxy compound, which in turn is used in step a). 5. Process for the preparation of an oligocarbonate, characterized by the following steps: a) transesterification of diphenyl carbonate and bisphenol A to the oligocarbonate with the elimination of phenol, b) isolation or separation of the oligocarbonate and the phenol, c) reaction of the phenol with acetone to Bisphenol A, d) recycling of the bisphenol As into the transesterification with diphenyl carbonate to the oligocarbonate.