Polycarbonate of Cycloalkylidene Bisphenol

This invention relates to thermoplastic aromatic polycarbonates having average molecular weight Mw of at least 10,000, preferably in the range from 10,000 to 250,000, more preferably 10,000 to 120,000, more especially in the range from 15,000 to 100,000 and most preferably 20,000 to 80,000 which contain bifunctional carbonate structural units corresponding to formula (I) ##STR2## in which R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently of one another represent hydrogen, a C.sub.1 -C.sub.12 -hydrocarbon, halogen,

m is 2 or 3 and

X represents hydrogen or a C.sub.6 -C.sub.12 hydrocarbon, at least one substituent X and preferably only one or two substituents X being a C.sub.6 -C.sub.12 hydrocarbon radical,

in quantities of from 100 to 1 mol-%, preferably in quantities of from 100 to 5 mol-% and, more preferably, in quantities of 100 to 20 mol-%, based on the total quantity of difunctional carbonate structural units in the polycarbonate. Of the polycarbonates according to the invention containing 100 to 20 mol-% of bifunctional carbonate structural units of formula (I), those containing 100 to 50 mol-% of these units are preferred, those containing 100 to 80 mol-% of these units are more preferred, and those containing 100 mol-% of these units are most preferred.

The polycarbonates according to the invention show surprising technological properties compared with known polycarbonates, for example of bisphenol A and of 1,4-bis-(4-hydroxyphenyl)-cyclohexane.

Thus, they show surprisingly high glass transition temperatures Tg, even when they contain only small amounts of carbonate structural units corresponding to formula (I). They also show particularly good mold release properties and exceptionally good melt flow, particularly taking their high glass temperature Tg into consideration. In addition, the polycarbonates according to the invention show tracking resistance, hydrolysis stability, UV stability and heat ageing resistance and exhibit exceptional optical properties, such as low birefringeance.

The carbonate structural units corresponding to formula (I) are based on bisphenols corresponding to formula (II) ##STR3## in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, m and X have the same meanings as in formula (I).

In formulae (I) and (II), R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are preferably hydrogen, methyl, ethyl, phenyl, cyclohexyl, chlorine and bromine and, more preferably, hydrogen, methyl and bromine.

If more than one of the substituents R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is not hydrogen, identical substituents are preferred. If two of the substituents R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are not hyrogen, the o,o'-di-substitution, in relation to the carbonate groups (formula (I)) or respectively the phenolic OH groups (formula (II)), is preferred. If none of the four substituents R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is hydrogen, the o,o,o',o'-substitution, related as before, is preferred.

In formulae (I) and (II), m is preferably 3.

In formulae (I) and (II), X is hydrogen or a C.sub.6 -C.sub.12 hydrocarbon radical, such as n-C.sub.6 -C.sub.12 -alkyl (for example various isohexyl, isooctyl and isododecyl radicals), C.sub.6 -C.sub.12 cycloalkyl, such as cyclohexyl, n- or isoalkyl-substituted cyclohexyl (such as methyl, ethyl, isopropyl or tert.-butyl, cyclohexyl), aryl-substituted cyclohexyl (phenylcyclohexyl) and cyclohexyl onto which phenyl radicals are fused, aryl (such as phenyl and naphthyl), aralkyl (such as benzyl and cumyl), alkaryl (such as methylphenyl and isopropylphenyl), cycloalkyl-substituted alkyl (such as perhydrocumyl).

In formulae (I) and (II), X is preferably hydrogen, iso-C.sub.6 -C.sub.12 -alkyl, cycloalkyl, cycloalkyl-substituted alkyl, aryl and aralkyl, more preferably hydrogen, iso-C.sub.8 -C.sub.9 -alkyl, cyclohexyl, phenyl, cumenyl and perhydrocumenyl and, most preferably, hydrogen, 1,1,3,3-tetramethylbutyl, phenyl, and cyclohexyl.

Where m is 3 and where there is only one hydrocarbon substituent X in formulae (I) and (II), this substituent X is preferably in the 4-position of the cyclohexylidene ring when availability of the starting material is of concern, or preferably in the 3-position of the cyclohexylidene ring when especially high heat resistance of the polycarbonate is required.

At m=3 (cyclohexylidene ring) and only two hydrocarbon radicals X in formulae (I) and (II), these two hydrocarbon radicals X are preferably in 3,5-position, when high heat resistance of the polycarbonate is required.

The following are examples of bisphenols corresponding to formula (II):

1,1-bis-(4-hydroxyphenyl)-4-(1,1-dimethylbutyl)-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-4-(1,1,3,3-tetramethylbutyl)-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-4-phenyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-4-cumyl-cylcohexane,

1,1-bis-(4-hydroxyphenyl)-4-benzyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-4-cyclohexyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-4-perhydrocumyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3-phenyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3-(1,1-dimethylbutyl)-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3-(1,1,3,3-tetramethylbutyl)-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3-cumyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3-benzyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3-cyclohexyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3-perhydrocumyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3,5-[bis-(1,1-dimethylbutyl)]-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3,5-[bis-(1,1,3,3-tetramethylbutyl)]-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3,5-bis-phenyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3,5-bis-cyclohexyl-cyclohexane,

1,1-bis-(4-hydroxyphenyl)-3,5-bis-cumyl-cyclohexane,

1,1-bis-(3-methyl-4-hydroxyphenyl)-4-(1,1,3,3-tetramethylbutyl)-cyclohexane

1,1-bis-(3-methyl-4-hydroxyphenyl)-4-phenyl-cyclohexane,

1,1-bis-(3-methyl-4-hydroxyphenyl)-4-cumyl-cyclohexane,

1,1-bis-(3-methyl-4-hydroxyphenyl)-4-cyclohexyl-cyclohexane,

1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-4-(1,1,3,3-tetramethylbutyl)-cyclohe xane,

1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-4-phenyl-cyclohexane,

1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-4-cumyl-cyclohexane,

1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-4-cyclohexyl-cyclohexane,

1,1-bis-(3-methyl-5-chlor-4-hydroxyphenyl)-4-phenyl-cyclohexane,

1,1-bis-(3-methyl-5-brom-4-hydroxyphenyl)-4-cyclohexyl-cyclohexane,

1,1-bis-(3-chlor-4-hydroxyphenyl)-4-(1,1,3,3-tetramethylbutyl)-cyclohexane,

1,1-bis-(3,5-dichlor-4-hydroxyphenyl)-4-(1,1,3,3-tetramethylbutyl)-cyclohex ane,

1,1-bis-(3,5-dichlor-4-hydroxyphenyl)-4-phenyl-cyclohexane,

1,1-bis-(3,5-dichlor-4-hydroxyphenyl)-4-cumyl-cyclohexane,

1,1-bis-(3,5-dichlor-4-hydroxyphenyl)-4-cyclohexyl-cyclohexane,

1,1-bis-(3,5-dibrom-4-hydroxyphenyl)-4-(1,1,3,3-tetramethylbutyl)-cyclohexa ne,

1,1-bis-(3,5-dibrom-4-hydroxyphenyl)-4-phenyl-cyclohexane,

1,1-bis-(3,5-dibrom-4-hydroxyphenyl)-4-cumyl-cyclohexane,

1,1-bis-(3,5-dibrom-4-hydroxyphenyl)-4-cyclohexyl-cyclohexane,

1,1-bis-(3,5-dibrom-4-hydroxyphenyl)-4-perhydrocumyl-cyclohexane,

Bisphenols corresponding to formula (II) are known or may be obtained by known methods from corresponding ketones and phenols.

In addition to the carbonate structural units corresponding to formula (I), the polycarbonates according to the invention contain quantities--complementary to 100 mol-%--of other difunctional carbonate structural units, for example those corresponding to formula (III) below which are based on bisphenols corresponding to formula (IV): ##STR4##

Bisphenols corresponding to formula (IV) are those in which Z is a C.sub.6-30 aromatic radical which may contain one or more aromatic nuclei, may be substituted and may contain aliphatic radicals or other cycloaliphatic radicals than those corresponding to formula (II) or hetero-atoms as bridge members.

Examples of diphenols corresponding to formula (IV) are hydroquinone, resorcinol, dihydroxydiphenyls, bis-(hydroxyphenyl)-alkanes, bis-(hydroxyphenyl)-cycloalkanes, bis-(hydroxyphenyl)-sulfides, bis-(hydroxyphenyl)-ethers, bis-(hydroxyphenyl)-ketones, bis-(hydroxyphenyl)-sulfones, bis-(hydroxyphenyl)-sulfoxides, .alpha.,.alpha.'-bis-(hydroxyphenyl)-diisopropylbenzenes and their nucleus-alkylated and nucleus-halogenated derivatives.

These and other suitable diphenols are described, for example, in U.S. Pat. Nos. 3,028,365, 2,999,835, 3,148,172, 3,275,601, 2,991,273, 3,271,367, 3,062,781, 2,970,131 and 2,999,846; in DE-OSS Nos. 1 570 703, 2 063 050, 2 063 052, 2 211 956; in FR-PS No. 1 561 518 and in the book by H. Schnell entitled "Chemistry and Physics of Polycarbonates", Interscience Publishers, New York 1964.

Preferred other diphenols are, for example, 4,4'-dihydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl)-propane, 2,4-bis-(4-hydroxyphenyl-2-methylbutane, 1,1-bis-(4-hydroxyphenyl)-cyclohe xane, .alpha.,.alpha.'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene, 2,2-bis-(3-methyl-4-hydroxyphenyl)-propane, 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane, bis-(3,5-dimethyl-4-hydroxyphenyl)-methane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane, bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfone, 2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-cyclohexane, .alpha.,.alpha.'-bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.

Particularly preferred diphenols corresponding to formula (IV) are, for example, 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 and 1,1-bis-(4-hydroxyphenyl)-cyclohexane.

2,2-Bis-(4-hydroxyphenyl)-propane is particularly preferred.

The other diphenols may be used both individually and also in admixture.

Small quantities (from 0.05 to 2.0 mol-%, based on diphenols used) of trifunctional or more than trifunctional compounds, particularly those containing three or more than three phenolic hydroxyl groups, may optionally be used in known manner as branching agents to obtain branched polycarbonates. Some of the compounds containing three or more than three phenolic hydroxyl groups which may be used for branching are phloroglucinol, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-hept-2-ene, 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, 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane, hexa-(4-(4-hydroxyphenylisopropyl)-phenyl)-o-terephthalic acid ester, tetra-(4-hydroxyphenyl)-methane, tetra-(4-(4-hydroxyphenylisopropyl)-phenoxy)-methane and 1,4-bis-(4',4"-dihydroxytriphenyl)-methyl)-benzene.

Some of the other trifunctional compounds are 2,4-dihydroxybenzoic acid, trimesic acid, cyanuric chloride and 3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.

Monofunctional compounds are used in known manner in typical concentrations as chain terminators for regulating molecular weight. Suitable compounds are, for example, secondary amines, phenols and acid chlorides. It is preferred to use phenols, for example tert.-butylphenols, or other alkyl-substituted phenols. Small quantities of phenols corresponding to formula (V) ##STR5## in which R is a branched C.sub.8 and/or C.sub.9 alkyl radical, are particularly suitable for regulating molecular weight. The percentage of CH.sub.3 protons in the alkyl radical R is preferably from 47 to 89% and the percentage of CH and CH.sub.2 protons from 53 to 11%. In addition, R is preferably in the o- and/or p-position to the OH groups and the upper limit to the ortho component is, more preferably, 20%.

Some particularly suitable phenols are phenol, p-tert.-butylphenol, hydroxydiphenyl, p-cumylphenols and, in particular, p-3,5-dimethylheptylphenyl and m- and p-1,1,3,3-tetramethylbutylphenol. The chain terminators are generally used in quantities of from 0.1 to 10 mol-% and preferably in quantities of from 0.5 to 8 mol-%, based on diphenols used.

The polycarbonates according to the invention may advantageously be produced in known manner by the phase-interface polycondensation process (cf. H. Schnell, "Chemistry and Physics of Polycarbonates", Polymer Reviews, Vol. IX, pages 33 et seq., Interscience Publishers, 1964).

In this process, the diphenols corresponding to formula (II) are dissolved in an aqueous alkaline phase. To prepare copolycarbonates with other diphenols, mixtures of diphenols corresponding to formula (II) and the other diphenols, for example those corresponding to formula (IV), are used. Chain terminators, for example corresponding to formula (V), may be added to regulate molecular weight. The reaction with phosgene is effected by means of the phase interface polycondensation method in the presence of an inert organic liquid which preferably dissolves polycarbonate. The reaction temperature is generally in the range from 0.degree. C. to 40.degree. C.

The 0.05 to 2 mol-% of branching agents optionally used may either be initially introduced with the diphenols in the aqueous alkaline phase or may be added dissolved in the organic solvent before the phosgenation.

In addition to the diphenols of formula (II) and the other diphenols corresponding to formula (IV), it is also possible to use mono- and/or bis-chlorocarbonic acid esters thereof, which are added dissolved in organic solvents. The quantity of chain terminators and of branching agents is then determined by the mols of diphenolate structural units corresponding to formula (II) and, optionally, of the other diphenolate structural units, such as for example those corresponding to formula (IV). Similarly, where chlorocarbonic acid esters are used, the quantity of phosgene may be reduced accordingly in known manner.

Chlorinated hydrocarbons for example, such as chloroform, dichloroethane, di- and tetrachloroethylene, tetrachloroethane, methylene chloride, chlorobenzene and dichlorobenzene, and also non-chlorinated hydrocarbons, such as for example toluene and xylene, and mixtures of these solvents, particularly mixtures of methylene chloride and chlorobenzene, may be used as the organic solvent for the phase interface polycondensation and as organic solvent for the chain terminators and, optionally, for the branching agents and the chlorocarbonic acid esters. The chain terminators and branching agents used may optionally be dissolved in the same solvent.

The organic solvent used in the phase interface polycondensation may be, for example, methylene chloride, chlorobenzene or toluene and also mixtures of methylene chloride and chlorobenzene.

Aqueous NaOH solution or KOH solution for example is used as the aqueous alkaline phase.

The production of the polycarbonates according to the invention by the phase interface polycondensation process may be catalyzed in known manner by such catalysts as tertiary amines and phase transfer catalysts, particularly tertiary aliphatic amines such as, for example, tributylamine, triethylamine, N-ethyl piperidine and, in particular, quaternary ammonium and phosphonium compounds and crown ethers, such as for example tetrabutyl ammonium bromide and triphenyl benzyl phosphonium bromide. The catalysts are generally used in quantities of from 0.05 to 30 mol-%, based on the mols of diphenols used. The catalysts are generally added before the beginning of phosgenation or during or even after phosgenation.

The polycarbonates according to the invention are isolated in known manner, for example by separating off the organic phase containing the dissolved polycarbonate obtained in the phase interface processes, washing until neutral and free from electrolyte and then isolating the polycarbonate in the form of a granulate, for example in an evaporation extruder, or in the form of a powder or pellets by precipitating using a non-solvent and subsequent drying or by spray evaporation.

The high molecular weight, thermoplastic aromatic polycarbonates according to the invention may also be prepared by the known homogeneous-phase process, the so-called "pyridine process", and by the known melt transesterification process, for example using diphenylcarbonate instead of phosgene. In these cases, too, the polycarbonates according to the invention are isolated in known manner.

The additives normally used for thermoplastic polycarbonates, such as stabilizers, mould release agents, pigments, flameproofing agents, antistatic agents, conductivity increasing additives, fillers and reinforcing materials, may be added to the polycarbonates according to the invention in the usual quantities before or after their processing.

As flameproofing additives there can be used:

1. Alkali, alkaline earth and ammonium salts of aliphatic and aromatic sulfonic acids, carboxylic acids and phosphonic acids. These can be substituted in different ways, for instance, by F, Cl, Br, alkyl. Salt type flameproofing agents of this kind can also be oligomeric or polymeric. Salt type flameproofing additives are inter alia described in the following patent applications: DE-OS Nos. 1 694 640, 1 930 257, 2 049 358, 2 212 987, 2 149 311, 2 253 072, 2 703 710, 2 458 527, 2 458 968, 2 460 786, 2 460 787, 2 460 788, 2 460 935, 2 460 937, 2 460 944, 2 460 945, 2 460 946, 2 461 063, 2 461 077, 2 461 144, 2 461 145, 2 461 146, 2 644 114, 2 645 415, 2 646 120, 2 647 271, 2 648 128, 2 648 131, 2 653 327, 2 744 015, 2 744 016, 2 744 016, 2 744 017, 2 744 018, 2 745 592, 2 948 871, 2 948 439, 3 002 122.

2. Organic halogen compounds optionally combined with synergists, for instance, halogenated aromatic compounds. Such flameproofing agents are described inter alia in the following patent applications: DE-OS No. 2 631 756, JA No. 51-119 059, DE-OS No. 3 342 636, EP-A No. 31 959, DE-OS Nos. 3 010 375, 2 631 756.

3. Halogenated phthalimides or phthalimide sulfonates; DE-OS Nos. 2 703 710, 3 203 905, 3 322 057, 3 337 857, 3 023 818.

4. Salts of halogenated complexed acids such as cryolite, salts of tetrafluoroboric acid and of fluorosalicic acid described inter alia in DE-OS Nos. 2 149 311 and 3 023 818.

5. Partly or totally fluorinated polyolefines described, for instance, in DE-OS Nos. 2 535 262, 2 915 563, 2 948 439, 3 023 818.

6. Sulfonamides, disulfonamides and salts thereof: EP-A Nos. 71 125, 14 322, WO No. 86/4911.

7. Elementary sulfur or red phosphorous: DE-OS Nos. 2 345 508, 2 355 211.

8. Ferrocene or its derivatives: DE-OS No. 2 644 437.

9. Diphenylsulfone: DE-OS No. 2 129 204.

10. Nickel salts: DE-OS No. 1 918 216.

11. Polyphenylenesulfide: DE-OS No. 2 503 336, EP-A No. 87 038.

12. Alkali and alkaline earth as well as zinc salts of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, hydrogen sulfide, boric acid as well as acetic salts of these acids: WO No. 87/542, U.S. Pat. No. 4,408,005, EP-A No. 174 864.

13. Siloxanes: DE-OS No. 2 535 261.

As comonomers which are useful for flameproofing there are described:

1. Chlorinated and brominated bisphenol A and 4,4-dihydroxydiphenyl sulfide: EP-A Nos. 31 958, 61 060.

2. Siloxane blocks: DE-OS No. 3 334 782.

3. Dihydroxydiphenyl sulfone: U.S. Pat. No. 3,912,688.

4. Sulfo anilide end groups: EP-A No. 82 483.

Flameproofing methods can be applied individually or combined.

Flameproofing additives are incorporated into the polycarbonates which contain diphenols of formula (I) in polymerized form preferably in extruders or kneaders individually or combinated. In many cases the flameproofing additives can be added to the polycarbonates during the manufacture or even to the starting materials. It is also possible to add flameproofing additives to solutions of the polycarbonates with subsequent removal of the solvent. The amounts of flameproofing additives are preferably 0.001 to 50% by weight in case of monomers preferably 0.1 to 50 mol-%.

More specifically for example graphite, carbon black, metal fibres, metal powder, silica, quartz, talcum, mica, caoline, clays, CaF.sub.2, CaCO.sub.3, aluminum oxide, glass fibres, carbon fibres, ceramic fibres, organic and inorganic pigments can be added and as mould release agent, for instance, glyceral stearate, pentaerythrite tetrastearate and trimethylolpropane tristearate.

The polycarbonates according to the invention can be processed according to known methods of thermoplastic shaping to yield shaped articles. This can be done, for instance, by extruding the recovered polycarbonates to a granulate and fabricating the granulates optionally after adding the above-identified agents, for instance, by injection moulding, extrusion, blowing, rotation, casting or hot pressing. Shaped articles manufactured in this way include fibres, plates and sheets. Sheets can be for the processed by deep drawing. Also films can be manufactured and can be combined with other films. The polycarbonates of the invention can also be used in combination materials such as combined with fibres and other polymers.

Shaped articles of polycarbonates according to the invention can be used, for instance, in electrical appliances or in construction with particular advantage when complicated parts required dimensional stability under heat are to be produced.

380 g (1 mol) 1,1-bis-(4-hydroxyphenyl)-4-(1,1,3,3-tetramethylbutyl)-cyclohexane were dissolved in 3 l water. 3 l methylene chloride with 6.8 g (0.033 mol) 4-(1,1,3,3-tetramethylbutyl)-phenol dissolved therein were added to the resulting solution. 148.5 g (1.5 mol) phos-gene were then introduced into the mixture over a period of 30 minutes with intensive stirring at 25.degree. C. After the addition of 1.13 g (0.01 mol) N-ethyl piperidine, the mixture was intensively stirred for 60 minutes at 25.degree. C. The bisphenolate-free aqueous phase was separated off. After acidification with dilute phosphoric acid, the organic phase was washed with water until free from electrolyte and concentrated by evaporation. The polycarbonate obtained was then freed from the remaining methylene chloride by drying. It was colorless and showed a relative viscosity .eta..sub.rel of 1.323 (as measured on a methylene chloride solution, c=5 g/l, at 25.degree. C.).

The procedure was as in Example 1 except that 344 g (1 mol) 1,1-bis-(4-hydroxyphenyl)-4-phenyl cyclohexane was used instead of the bisphenol. The polycarbonate obtained had a relative viscosity of 1.323 (as measured on a methylene chloride solution, c=5 g/l, at 25.degree. C. The glass temperature Tg (according to differential thermal analysis) was 210.degree. C.

The procedure was as in Example 2, except that half the bisphenol used was replaced by 114 g (0.5 mol) 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A).

The polycarbonate obtained had a relative viscosity .eta..sub.rel of 1.301 (as measured in a methylene chloride solution at 25.degree. C., c=5 g/l). The glass temperature Tg (according to differential thermal analysis) was 186.degree. C.

The procedure was as in Example 1, except that the bisphenol used was replaced by 344 g (1 mol) 1,1-bis-(4-hydroxyphenyl)-3-phenyl-cyclohexane. The polycarbonated obtained had a relative viscosity of 1.295 (as measured in a methylene chloride solution, c=5 g/l, at 25.degree. C.). The glass temperature Tg (according to differential thermal analysis) was 231.degree. C.

The procedure was as in Example 1, except that the bisphenol was replaced by 386 g (1 mol) 1,1-bis-(4-hydroxyphenyl)-4-cumyl cyclohexane. The polycarbonate obtained had a relative viscosity of 1.307 (as measured in a methylene chloride solution at 25.degree. C., c=5 g/l).

The procedure was as in Example 1, except that the bisphenol used was replaced by 350 g (1 mol) 1,1-bis-(4-hydroxyphenyl)-4-cyclohexyl-cyclohexane. The polycarbonate obtained had a relative viscosity of 1.289 (as measured on a methylene chloride solution at 25.degree. C., c=5 g/l).

Example 2 was repeated but 10 mol-% of the diphenol was replaced by 3,3',5,5'-tetrabromo bisphenol A. The resulting polycarbonate had a .eta..sub.rel of 1.302.

The results of burning tests of the polycarbonates containing flameproofing agents are summarized in Table 1. The flameproofing agents were worked in with a twin screw extruder ZSK 32 of Werner & Pfleiderer Co.

The burning behaviour was determined by means of the O.sub.2 -index according to ASTM-D 2863-70. For these tests test specimen of a size of 80.times.6.times.3 mm were made by injection moulding.