HK1132285A - Process for the preparation of polycarbonate by the melt transesterification method - Google Patents

Description

Method for producing polycarbonate by the melt transesterification method

RELATED APPLICATIONS

The present application claims the benefit of german patent application No.102007052968.8 (application date 2007, 11, 7), which is incorporated herein by reference in its entirety for all useful purposes.

Technical Field

The present invention relates to a process for the preparation of polycarbonates by the melt transesterification process, polycarbonates and shaped articles or extrudates obtainable by this process, in particular optical data storage or diffusion discs comprising the polycarbonates, having a reduced build-up of electrostatic charge.

Background

Optical data storage materials are increasingly being used as variable recording and/or archiving media for large amounts of data. Examples of optical data storage of this type are CD, super audio CD, CD-R, CD-RW, DVD-R, DVD + R, DVD-RW, DVD + RW, HD-DVD and BD.

Transparent thermoplastics, such as, for example, polycarbonate, polymethyl methacrylate and chemical modifications thereof, are typically used for optical storage media. Polycarbonates as substrate material are particularly suitable for non-rewritable and rewritable optical disks and for the production of shaped articles in the automotive glazing sector, for example diffusion disks. Such thermoplastics have excellent mechanical stability, are less affected by dimensional changes, and are distinguished by high transparency and impact strength.

According to DE-A2119799, polycarbonates can be prepared by the phase boundary process and also by the homogeneous process with the participation of phenolic end groups.

Another commercially useful method for making polycarbonate is the melt transesterification process. The polycarbonates produced by this process can in principle be used for the production of optical data storage media in the above-mentioned formats, such as, for example, Compact Discs (CDs) or Digital Video Discs (DVDs).

However, this method inevitably has disadvantages: that is, it produces a polycarbonate having high electric field properties accumulated on the surface of an injection-molded article after being processed into an injection-molded body. Thus, for example, optical data storage discs comprising such polycarbonates accumulate high electric fields during their production by the injection molding process. Such high field strengths on the substrate lead, for example, to dust adsorption from the environment during the production of the optical data storage devices and to the injection-molded articles (e.g. the optical discs) adhering to one another, which reduces the quality of the final injection-molded articles and at the same time complicates the injection-molding process.

Furthermore, a high electric field on the disc (for optical data media) results in poor wetting, in particular with non-polar media, such as, for example, non-polar dyes or dye coatings comprising solvents, such as, for example, dibutyl ether, ethylcyclohexane, tetrafluoropropanol, cyclohexane, methylcyclohexane or octafluoropropanol. Thus, a high electric field on the substrate surface leads to irregularities and imperfections of the dye-coated layer during dye application, for example in the case of writable data memories, and thus to defects of the information layer.

In the case of optical data storage devices, in which the writable dye is applied to the surface in a spin-coating process, low absolute electric field strengths are therefore required in order to ensure uniform application of the writable layer and to ensure problem-free production processing.

The accumulation of electrostatic charges on the substrate material creates an electric field that can be quantified by measuring at some distance from the substrate surface.

Based on the above facts, a further disadvantage of such high electric fields is the further visible yield loss associated with the substrate material. This results in production losses and therefore in corresponding additional costs.

The electric field developed on the respective injection-molded part in the injection-molding process is not constant in the production process, but exhibits some variation as a function of time. It has therefore been found that the field strength on the respective disk changes first after the start of the injection molding process (assuming a new mold cavity is used) and reaches a steady value (steady phase) or continues with only a slight increase only after a certain period. This is an important criterion for the performance of the injection-molded part in the subsequent production steps in which, for example, a dye is applied to the substrate. The charge buildup on injection molded bodies made from polycarbonate by the melt transesterification process differs in nature from injection molded bodies made from polycarbonate by the phase boundary process. The initial value of the field strength at the start of the injection molding process for polycarbonates according to the melt transesterification process is generally in the strongly negative range compared with polycarbonates produced by the phase boundary process. In contrast to polycarbonates prepared by the phase boundary method, the stationary phase values, which are formed after certain operating times, such as, for example, 2 hours of continuous injection molding processing, are generally kept essentially in the negative range (negative field strength).

Several solutions to high electrostatic fields have been proposed. Generally, an antistatic agent is added as an additive to the base material. Such polycarbonate compositions with added antistatic agents are described, for example, in JP-A62207358, in which polyethylene or polypropylene derivatives are used as additives. Here, phosphoric acid derivatives and others are added to the polycarbonate as antistatic agents. EP-A922728 describes different antistatic agents, such as polyalkylene glycol derivatives, ethoxylated sorbitan monolaurate, polysiloxane derivatives, phosphine oxides and distearoylhydroxylamine, which may be used individually or as mixtures. Japanese application JP-A62207358 describes phosphoric esters as additives with antistatic activity. US5668202 describes sulfonic acid derivatives as additives.

US6262218 and US6022943 describe the use of phenyl chloroformate to increase the end group content of melt polycarbonate (polycarbonate prepared by the melt transesterification process). Where it is assumed that an end group content of more than 90% has a positive effect on the electrostatic properties. In WO-A00/50488, 3, 5-di-tert-butylphenol is used as chain terminator in the phase boundary process. The chain terminator produces a lower static charge buildup on the corresponding substrate material than conventional chain terminators. EP-A1304358 describes the use of short oligomers such as, for example, bisphenol A bis (4-tert-butylphenyl carbonate) as additive for the production of polycarbonates by the melt transesterification process.

However, the additives may have a negative effect on the properties of the substrate material, since at high temperatures they tend to come out of the material and may thus lead to the formation of deposits or poor mouldings. Furthermore, the content of the oligomers in the polycarbonate can also lead to a poorer degree of mechanical properties and a reduction in the glass transition temperature. In addition, these additives may cause side reactions of the additives. As a result, the thermal stability of the base material may be reduced. The subsequent "end-capping" of the polycarbonate obtained from the transesterification process is complicated. The materials required for this purpose have to be manufactured, which involves additional costs and additional processing steps for subsequent "capping".

Furthermore, it is known that various acids or acid derivatives can be added to polycarbonates as additives. Thus, for example, JP-A07-247351 describes the use of aliphatic hydroxycarboxylic acids as chelating components for catalyst systems in the preparation of polycarbonates. In US-a2005/0113534, hydroxycarboxylic acids and others are used in the mixing process for stabilizing polycarbonate/polyester blends. US-A2005/0171323 describes copolycarbonates which have quinone derivatives of specific structures. In order to stabilize these copolycarbonates, hydroxycarboxylic acids and others are added during the polycondensation as antioxidants. EP-A435124 describes the neutralization of basic catalysts by adding a weak acid to the final polycarbonate. EP-A460646 likewise describes the addition of aliphatic carboxylic acids to the finished polycarbonate powder or granules, in particular to the polycarbonates prepared by the phase boundary process, for the purpose of such stabilization. However, no advantageous effect on the build-up of electrostatic charges on the formed product was observed in any of the above cases of additive addition.

Materials which are particularly suitable for producing injection-molded bodies having a low charge are described in DE-A102004061754, DE-A102004061715, US-A2006/135736, US-A2006/135735 and US-A2006/134366. However, these materials do not include these polycarbonates prepared by the phase boundary method. The process described is not effective in the melt transesterification process.

In order to ensure good coating properties of optical data storage devices in the production process, so-called ionization sources are often used, which cause an ionized air flow over the disks. However, the use of ionization sources makes the manufacturing process more expensive, and therefore the number of ionization sources used should be reduced to a minimum for an economical process.

It has furthermore also been found that the relevant degree of electric field and the charge uniformity on injection-molded bodies, such as optical discs, play an important role with regard to the coating properties of the injection-molded bodies. Thus, for example, although a low average electric field strength can be measured over the entire disc. However, there may be high positive field strength at some surface portions and very low field strength at other portions. These charge differences result in poor wettability, although the measured average field strength may have acceptable values. For this reason, the absolute average of the measured electric field strength over certain radii of the injection-molded body and the variation in the electric field strength (field strength variation) are closely related to the optimum wettability.

Accordingly, there is a continuing need for a process for the preparation of polycarbonates by the melt transesterification process which is suitable for processing into moldings or extrudates having less electrostatic charge buildup. Furthermore, in addition to the need for as small an average electric field strength (magnitude) as possible at the respective shaped article, as small a field strength variation as possible over the substrate surface is also required.

It is therefore an object of the present invention to provide a melt transesterification process and polycarbonates produced by this process which, after processing into moldings or extrudates, satisfy the need for as little charge build-up and little charge change as possible on the substrate surface and avoid the abovementioned disadvantages.

Disclosure of Invention

One embodiment of the present invention is a method for preparing polycarbonates by the melt transesterification process, which comprises reacting at least one dihydroxyaryl compound with at least one diaryl carbonate in the presence of at least one catalyst in a multistage process, wherein at least one polymerization inhibitor is added to the melt before the last reaction stage and one or more aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof are added during or after the last reaction stage.

Another embodiment of the present invention is the above process, wherein the one or more aliphatic hydroxydicarboxylic and/or hydroxypolycarboxylic acids or derivatives thereof are one or more compounds of the general formulae (VI) or (VII):

wherein

R¹、R²And R³Independently of one another, is linear or branched C₁-C₁₀-an alkylene group;

X¹、X²and X³Independently of one another are H or OH, where X¹、X²Or X³At least one of them represents OH;

w is H, COOH, a carboxylic acid ester or an alkylcarboxyl;

n is an integer of 1 to 3;

m is 0 or an integer of 1 to 3;

o is 0 or an integer from 1 to 3; and

R⁴and R⁵Independently of one another, is linear or branched C₁-C₁₀Alkyl groups or alkali metal cations, preferably Li⁺、Na⁺Or K⁺。

Another embodiment of the present invention is the above process, wherein

R¹、R²And R³Independently of one another is a linear form C₁-C₆-an alkylene group;

w is COOH;

n is 1;

m is 0 or 1;

o is 0 or 1; and

R⁴and R⁵Independently of one another, is linear or branched C₁-C₆-an alkyl group.

Another embodiment of the present invention is the above method, wherein the one or more aliphatic hydroxy-dicarboxylic and/or hydroxy-polycarboxylic acids or derivatives thereof are one or more compounds selected from the group consisting of malic acid, malic acid esters, malic acid monoesters, tartaric acid esters, tartaric acid monoesters, tartronic acid esters, citric acid, and citric acid esters.

Another embodiment of the present invention is the above process, wherein the at least one polymerization inhibitor is a sulfur-containing acid, an ester of an organic sulfur-containing acid, or a mixture thereof.

Another embodiment of the present invention is the above process, wherein said at least one dihydroxyaryl compound is selected from the group consisting of dihydroxybenzenes, dihydroxybiphenyls, bis (hydroxyphenyl) alkanes, bis (hydroxyphenyl) cycloalkanes, bis (hydroxyphenyl) arenes, bis (hydroxyphenyl) ethers, bis (hydroxyphenyl) ketones, bis (hydroxyphenyl) sulfides, bis (hydroxyphenyl) sulfones, bis (hydroxyphenyl) sulfoxides, 1, 1' -bis (hydroxyphenyl) diisopropylbenzenes, and nuclear alkylated or halogenated derivatives thereof.

Another embodiment of the present invention is the above process, wherein the at least one diaryl carbonate has the formula (II)

Wherein

R, R 'and R' are each independently of the other hydrogen, linear or branched C₁-C₃₄Alkyl radical, C₇-C₃₄-alkylaryl or C₆-C₃₄-aryl, wherein R-is optionally COO-R ', wherein R' is hydrogen, linear or branched C₁-C₃₄Alkyl radical, C₇-C₃₄-alkylaryl or C₆-C₃₄-an aryl group.

Another embodiment of the present invention is the above process, wherein said at least one catalyst is a compound selected from the group consisting of alkali metal salts, alkaline earth metal salts and onium salts.

Another embodiment of the present invention is the above process, wherein said at least one catalyst is an onium salt.

Yet another embodiment of the present invention is a polycarbonate prepared by the above method, wherein the polycarbonate comprises one or more aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof in an amount of 5 to 500ppm, and has a phenolic terminal OH group content of greater than 150 ppm.

Still another embodiment of the present invention is a shaped article or extrudate comprising the above polycarbonate.

Still another embodiment of the present invention is an optical data storage or diffusion disc comprising the above polycarbonate.

Still another embodiment of the present invention is an optical disc for manufacturing an optical data storage device having an average electric field strength of-20 to +20kV/m and an electric field strength variation of less than 15kV/m, said optical data storage device comprising a polycarbonate comprising one or more aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof in an amount of 5-500ppm and having a content of phenolic terminal OH groups of more than 150 ppm.

Detailed Description

This object is surprisingly achieved in the following way: in a multistage melt transesterification process, at least one polymerization inhibitor is added to the melt before the last reaction stage and one or more aliphatic hydroxydicarboxylic and/or hydroxypolycarboxylic acids or derivatives thereof are added during or after the last reaction stage. The polycarbonates produced by the process of the invention do not have the disadvantages described above and are particularly suitable for processing to give moldings or extrudates having a small and uniform build-up of electrostatic charge.

The invention therefore relates to a process for the preparation of polycarbonates by the melt transesterification process, at least one dihydroxyaryl compound being reacted with at least one diaryl carbonate using at least one catalyst in a multistage process, characterized in that at least one polymerization inhibitor is added to the melt before the last reaction stage and one or more aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof are added during or after the last reaction stage.

Using the polycarbonates prepared by the process according to the invention, injection-molded bodies, such as, for example, disks for optical data media, can be produced which have average electric field strength values of-20 to +20kV/m and small field strength variations of less than 15 kV/m.

The process according to the invention is carried out by the melt transesterification process. The preparation of aromatic oligocarbonates or Polycarbonates by the melt transesterification process is known in the literature and is described, for example, in Encyclopedia of Polymer Science, volume 10 (1969), Chemistry and Physics of Polycarbonates, Polymer Reviews, H.Schnell, volume 9, John Wiley and Sons, Inc. (1964), pages 44 to 51 and in DE-C1031512, U.S. Pat. No. 3022272, U.S. Pat. No. 5,5340905 and U.S. Pat. No. 3,697,09.

According to this process, the aromatic dihydroxy compound is transesterified with the carbonic acid diester with the aid of a suitable catalyst and optionally further additives in the melt.

The process is carried out in a plurality of stages, usually in reactors connected in series and in which the molecular weight and therefore the viscosity of the polycarbonate is increased in steps.

For carrying out the process of the invention, it is possible to use, for example, a plant design as shown in WO-A02/077067. Polycarbonate synthesis is the preparation of oligocarbonates by transesterification of diaryl carbonates with dihydroxyaryl compounds in the presence of quaternary onium compounds at progressively increasing temperatures and progressively decreasing pressures in a plurality of evaporator stages, which oligocarbonates are condensed in one or two basket reactors in series at further increasing temperatures and decreasing pressures to give polycarbonates.

The dihydroxyaryl compounds suitable for the process of the invention are those of the general formula (I)

HO-Z-OH (I)

Wherein Z is an aromatic radical having 6 to 34C atoms, which may contain one or more optionally substituted aromatic rings and aliphatic or cycloaliphatic radicals or alkylaryl groups or heteroatoms as bridging members.

Examples of suitable dihydroxyaryl compounds are: dihydroxybenzene, dihydroxybiphenyl, bis (hydroxyphenyl) alkanes, bis (hydroxyphenyl) cycloalkanes, bis (hydroxyphenyl) arenes, bis (hydroxyphenyl) ethers, bis (hydroxyphenyl) ketones, bis (hydroxyphenyl) sulfides, bis (hydroxyphenyl) sulfones, bis (hydroxyphenyl) sulfoxides, 1, 1' -bis (hydroxyphenyl) diisopropylbenzenes and their ring-alkylated or ring-halogenated compounds.

These and further suitable dihydroxyaryl compounds are described, for example, in DE-A3832396, FR-A1561518, H.Schnell, Chemistry and Physics of polycarbonates, Interscience Publishers, New York 1964, page 28 and below, etc.; page 102 and below et al and d.g.legrand, j.t.bendler, Handbook of polycarbonate Science and Technology, Marcel Dekker new york 2000, page 72 and below et al.

Preferred dihydroxyaryl compounds are, for example, resorcinol, 4, 4' -dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis (3, 5-dimethyl-4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) diphenylmethane, 1, 1-bis (4-hydroxyphenyl) -1-phenylethane, 1, 1-bis (4-hydroxyphenyl) -1- (1-naphthyl) ethane, 1, 1-bis (4-hydroxyphenyl) -1- (2-naphthyl) ethane, 2, 2-bis (4-hydroxyphenyl) propane, 2, 2-bis (3-methyl-4-hydroxyphenyl) propane, 2, 2-bis (3, 5-dimethyl-4-hydroxyphenyl) propane, 2, 2-bis (4-hydroxyphenyl) -1-phenylpropane, 2, 2-bis (4-hydroxyphenyl) hexafluoropropane, 2, 4-bis (4-hydroxyphenyl) -2-methylbutane, 2, 4-bis (3, 5-dimethyl-4-hydroxyphenyl) -2-methylbutane, 1, 1-bis (4-hydroxyphenyl) cyclohexane, 1, 1-bis (3, 5-dimethyl-4-hydroxyphenyl) cyclohexane, 1, 1-bis (4-hydroxyphenyl) -4-methylcyclohexane, 1, 1-bis (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane, 1, 3-bis [2- (4-hydroxyphenyl) -2-propyl ] benzene, 1, 1 '-bis (4-hydroxyphenyl) -3-diisopropylbenzene, 1, 1' -bis (4-hydroxyphenyl) -4-diisopropylbenzene, 1, 3-bis [2- (3, 5-dimethyl-4-hydroxyphenyl) -2-propyl ] benzene, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, bis (3, 5-dimethyl-4-hydroxyphenyl) sulfone and 2, 2 ', 3, 3' -tetrahydro-3, 3, 3 ', 3' -tetramethyl-1, 1 '-spirobis [ 1H-indene ] -5, 5' -diol.

Particularly preferred dihydroxyaryl compounds are resorcinol, 4, 4' -dihydroxybiphenyl, bis (4-hydroxyphenyl) diphenylmethane, 1, 1-bis (4-hydroxyphenyl) -1-phenylethane, bis (4-hydroxyphenyl) -1- (1-naphthyl) ethane, bis (4-hydroxyphenyl) -1- (2-naphthyl) ethane, 2, 2-bis (4-hydroxyphenyl) propane, 2, 2-bis (3, 5-dimethyl-4-hydroxyphenyl) propane, 1, 1-bis (4-hydroxyphenyl) cyclohexane, 1, 1-bis (3, 5-dimethyl-4-hydroxyphenyl) cyclohexane, 1, 1-bis (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane, 1, 1 '-bis (4-hydroxyphenyl) -3-diisopropylbenzene and 1, 1' -bis (4-hydroxyphenyl) -4-diisopropylbenzene.

Very particularly preferred dihydroxyaryl compounds are 4, 4' -dihydroxybiphenyl, 2, 2-bis (4-hydroxyphenyl) propane and bis (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane.

The same dihydroxyaryl compound may be used to form a homopolycarbonate and a different dihydroxyaryl compound may be used to form a copolycarbonate.

It is also possible to use dihydroxyaryl compounds having residual amounts of monohydroxyaryl compounds used for their preparation, and to use low molecular weight oligocarbonates having residual amounts of monohydroxyaryl compounds which are eliminated during the preparation of the oligomers. The residual amount of monohydroxyaryl compound may be up to 20% by weight, preferably up to 10% by weight, particularly preferably up to 5% by weight and very particularly preferably up to 2% by weight.

Suitable for the diaryl carbonates reacted with dihydroxyaryl compounds are those of the general formula (II)

Wherein

R, R 'and R' are independent of each other, identical or different, and represent hydrogen, linear or branched C₁-C₃₄Alkyl radical, C₇-C₃₄-alkylaryl or C₆-C₃₄-aryl, and R may additionally represent-COO-R ', R' representing hydrogen, linear or branched C₁-C₃₄Alkyl radical, C₇-C₃₄-alkylaryl or C₆-C₃₄-an aryl group.

Preferred diaryl carbonates are, for example, diphenyl carbonate, methylphenylphenyl carbonate, di (methylphenyl) carbonate, 4-ethylphenylphenyl carbonate, di (4-ethylphenyl) carbonate, 4-n-propylphenyl carbonate, di (4-n-propylphenyl) carbonate, 4-isopropylphenyl carbonate, di (4-isopropylphenyl) carbonate, 4-n-butylphenyl phenyl carbonate, di (4-n-butylphenyl) carbonate, 4-isobutylphenyl carbonate, di (4-isobutylphenyl) carbonate, 4-tert-butylphenyl phenyl carbonate, di (4-tert-butylphenyl) carbonate, 4-n-pentylphenyl carbonate, di (4-n-pentylphenyl) carbonate, 4-n-hexylphenyl carbonate, bis (4-n-hexylphenyl) carbonate, 4-isooctylphenyl phenyl carbonate, bis (4-isooctylphenyl) carbonate, 4-n-nonylphenyl carbonate, bis (4-n-nonylphenyl) carbonate, 4-cyclohexylphenyl phenyl carbonate, bis (4-cyclohexylphenyl) carbonate, 4- (1-methyl-1-phenylethyl) phenyl carbonate, bis [4- (1-methyl-1-phenylethyl) phenyl ] carbonate, biphenyl-4-ylphenyl carbonate, bis (biphenyl-4-yl) carbonate, 4- (1-naphthyl) phenyl carbonate, 4- (2-naphthyl) phenyl carbonate, bis [4- (1-naphthyl) phenyl ] carbonate, bis [4- (2-naphthyl) phenyl ] carbonate, 4-phenoxyphenylphenyl carbonate, bis (4-phenoxyphenyl) carbonate, 3-pentadecylphenyl phenyl carbonate, bis (3-pentadecylphenyl) carbonate, 4-tritylphenyl phenyl carbonate, bis (4-tritylphenyl) carbonate, methylsalicylphenyl carbonate, bis (methylsalicyl) carbonate, ethylsalicyl phenyl carbonate, bis (ethylsalicyl) carbonate, n-propylsalicyl phenyl carbonate, bis (n-propylsalicyl) carbonate, isopropylsalicyl phenyl carbonate, bis (isopropylsalicyl) carbonate, n-butylsalicyl phenyl carbonate, bis (n-butylsalicyl) carbonate, isobutylsalicyl phenyl carbonate, bis (isobutylsalicyl) carbonate, t-butylsalicyl phenyl carbonate, di (t-butylsalicyl) carbonate, di (phenylsalicyl) carbonate and di (benzylsalicyl) carbonate.

Particularly preferred diaryl compounds are diphenyl carbonate, 4-tert-butylphenyl phenyl carbonate, bis (4-tert-butylphenyl) carbonate, biphenyl-4-ylphenyl carbonate, bis (biphenyl-4-yl) carbonate, 4- (1-methyl-1-phenylethyl) phenylphenyl carbonate, bis [4- (1-methyl-1-phenylethyl) phenyl ] carbonate and bis (methylsalicyl) carbonate.

Diphenyl carbonate is very particularly preferred.

It is possible to use the same diaryl carbonate and different diaryl carbonates.

Diaryl carbonates having residual amounts of the monohydroxyaryl compound used to prepare them may also be used. The residual amount of monohydroxyaryl compound may be up to 20% by weight, preferably up to 10% by weight, particularly preferably up to 5% by weight and very particularly preferably up to 2% by weight.

Based on the dihydroxyaryl compound, generally from 1.02 to 1.30mol, preferably from 1.04 to 1.25mol, particularly preferably from 1.045 to 1.22mol, very particularly preferably from 1.05 to 1.20mol, of diaryl carbonate are used per mole of dihydroxyaryl compound. It is also possible to use mixtures of the above diaryl carbonates, the above stated amounts being based on moles of dihydroxyaryl compound per mole and thus on the total amount of diaryl carbonate mixture.

In order to control or change the terminal groups, one or more monohydroxyaryl compounds (which are not used to prepare the diaryl carbonate) may additionally be used. These may be those monohydroxyaryl compounds of the general formula (III)

Wherein

R^ARepresents linear or branched C₁-C₃₄-alkyl radical, C₇-C₃₄-alkylaryl group, C₆-C₃₄-aryl or-COO-R^D，R^DRepresents hydrogen, linear or branched C₁-C₃₄-alkyl radical, C₇-C₃₄-alkylaryl or C₆-C₃₄-aryl, and

R^B、R^Cindependently of one another, identical or different and represent hydrogen, linear or branched C₁-C₃₄-alkyl radical, C₇-C₃₄-alkylaryl or C₆-C₃₄-an aryl group.

Such monohydroxyaryl compounds are, for example, 1-, 2-or 3-methylphenol, 2, 4-dimethylphenol, 4-ethylphenol, 4-n-propylphenol, 4-isopropylphenol, 4-n-butylphenol, 4-isobutylphenol, 4-tert-butylphenol, 4-n-pentylphenol, 4-n-hexylphenol, 4-isooctylphenol, 4-n-nonylphenol, 3-pentadecylphenol, 4-cyclohexylphenol, 4- (1-methyl-1-phenylethyl) phenol, 4-phenylphenol, 4-phenoxyphenol, 4- (1-naphthyl) phenol, 4- (2-naphthyl) phenol, 4-tritylphenol, methyl salicylate, ethyl salicylate, n-propyl salicylate, isopropyl salicylate, n-butyl salicylate, isobutyl salicylate, tert-butyl salicylate, phenyl salicylate and benzyl salicylate.

4-tert-butylphenol, 4-isooctylphenol and 3-pentadecylphenol are preferred.

The monohydroxyaryl compound should be selected so that its melting point is higher than that of the monohydroxyaryl compound used to prepare the diaryl carbonate used. The monohydroxyaryl compound may be added at any time during the reaction. It is preferably added at the beginning of the reaction. The proportion of the free monohydroxyaryl compound may be from 0.2 to 20 mol%, preferably from 0.4 to 10 mol%, based on the dihydroxyaryl compound.

It is likewise possible to modify the end groups of the polycarbonate formed by adding at least one further diaryl carbonate whose basic monohydroxyaryl compound has a boiling point which is higher than the boiling point of the basic monohydroxyaryl compound of the diaryl carbonate predominantly used. Here again, the additional diaryl carbonate may be added at any time during the reaction. It is preferably added at the beginning of the reaction. The proportion of the diaryl carbonate of the basic monohydroxyaryl compound having a higher boiling point may be from 1 to 40 mol%, preferably from 1 to 20 mol% and particularly preferably from 1 to 10 mol%, based on the total amount of diaryl carbonate used.

Catalysts which can be used in the melt transesterification process for the preparation of polycarbonates are basic catalysts known from the literature, such as, for example, alkali metal and alkaline earth metal hydroxides and oxides and/or onium salts, such as, for example, ammonium or phosphonium salts. Onium salts, particularly phosphonium salts, are preferably used for the synthesis. Such phosphonium salts are, for example, those of the general formula (IV)

Wherein

R^7-10Represent identical or different optionally substituted C₁-C₁₀-alkyl-, C₆-C₁₄-aryl-, C₇-C₁₅Arylalkyl or C₅-C₆Cycloalkyl radicals, preferably methyl or C₆-C₁₄Aryl, particularly preferably methyl or phenyl, and

X^-represents an anion selected from the group consisting of hydroxide, sulfate, bisulfate, bicarbonate, carbonate, halide, preferably chloride, and of the formula-OR¹¹In which R is¹¹Represents optionally substituted C₆-C₁₄-aryl-, C₇-C₁₅Arylalkyl or C₅-C₆-cycloalkyl residue (C)₅-C₆-cycloalkylrest)，C₁-C₂₀-alkyl, preferably phenyl.

Particularly preferred catalysts are tetraphenylphosphonium chloride, tetraphenylphosphonium hydroxide and tetraphenylphosphonium phenolate, very particularly preferably tetraphenylphosphonium phenolate.

The preferred amount of catalyst is 10^-8-10^-3mol, particularly preferably 10^-7-10^-4mol, based on 1 mol of the dihydroxyaryl compound.

It is also optionally possible to use cocatalysts in order to increase the polycondensation rate.

These promoters may be, for example, basic salts of alkali metals and alkaline earth metals, such as hydroxides, optionally substituted C₁-C₁₀Alkoxides and C of lithium, sodium and potassium₆-C₁₄Aryl ether, preferably hydroxide, optionally substituted C₁-C₁₀Alkoxide or sodium C₆-C₁₄-an aryl ether. Sodium hydroxide, sodium phenolate or the disodium salt of 2, 2-bis (4-hydroxyphenyl) propane is preferred.

If alkali metal or alkaline earth metal ions in their salt form are introduced, the amount of alkali metal or alkaline earth metal ions (determined, for example, by atomic absorption spectroscopy) is from 1 to 500ppb, preferably from 5 to 300ppb and most preferably from 5 to 200ppb, based on the polycarbonate to be formed. However, in a preferred embodiment of the process according to the invention, no alkali metal salts are used.

In the context of the present invention, ppb and ppm are understood to mean parts by weight, unless otherwise indicated.

The basic salts of alkali metals and alkaline earth metals may be incorporated during the preparation of the oligocarbonate itself, i.e.at the start of the synthesis, or in a subsequent process step, in order to suppress undesired side reactions. The total amount of catalyst may also be added to the process in multiple steps.

In addition to the amounts of catalyst and catalyst already mentioned above, it is also possible to add additional amounts of onium catalyst before the polycondensation. If the catalysts mentioned are themselves onium catalysts, the onium catalysts added in supplementary amounts before the polycondensation can be the same as the onium catalysts mentioned above or different from them.

The addition of the catalyst is preferably carried out in solution, in order to avoid harmful excess concentrations during the metering. The solvent is preferably a compound inherent in the system and method, such as, for example, the dihydroxyaryl compound, diaryl carbonate or optionally monohydroxyaryl compound used. Monohydroxyaryl compounds are particularly suitable because of the fact that the person skilled in the art is familiar with: that is, dihydroxyaryl compounds and diaryl carbonates tend to begin to change and decompose at even slightly elevated temperatures, particularly under the action of catalysts. As a result, the quality of the polycarbonate can be affected. In a particularly preferred embodiment of the process according to the invention, the solvent for the catalyst is phenol. In this embodiment of the process according to the invention, phenol is particularly suitable, since the preferred catalyst used in this embodiment tetraphenylphosphonium phenolate is isolated as a solid solution of phenol during its preparation.

The polycarbonates obtained from this process are distinguished by the fact that, in addition to the phenolic-terminated chains of the formula (III), they may also bear a certain proportion of uncapped phenolic end groups. Such structural components can be described by the following formula (V) for illustrative purposes

Wherein Z has the meaning indicated by the general formula (I).

The content of phenolic OH groups is preferably greater than 150ppm, particularly preferably greater than 250ppm, very particularly preferably greater than 350ppm, based on the weight of the polycarbonate.

The polycarbonates may be branched in a targeted manner by adding suitable branching agents to the reaction mixture. Suitable branching agents for the preparation of polycarbonates are known to the person skilled in the art. These are compounds having three or more functional groups, and preferably these compounds having three or more hydroxyl groups.

Suitable compounds having three or more phenolic hydroxyl groups are, for example, phloroglucinol, 4, 6-dimethyl-2, 4, 6-tris (4-hydroxyphenyl) hept-2-ene, 4, 6-dimethyl-2, 4, 6-tris (4-hydroxyphenyl) heptane, 1, 3, 5-tris (4-hydroxyphenyl) benzene, 1, 1, 1-tris (4-hydroxyphenyl) ethane, tris (4-hydroxyphenyl) phenylmethane, 2, 2-bis (4, 4-bis (4-hydroxyphenyl) cyclohexyl) propane, 2, 4-bis (4-hydroxyphenylisopropyl) phenol and tetrakis (4-hydroxyphenyl) methane.

Other suitable compounds having three or more functional groups are, for example, 2, 4-dihydroxybenzoic acid, 1, 3, 5-trimellitic acid, cyanuric chloride and 3, 3-bis (3-methyl-4-hydroxyphenyl) -2-oxo-2, 3-indoline.

Preferred branching agents are 3, 3-bis (3-methyl-4-hydroxyphenyl) -2-oxo-2, 3-indoline and 1, 1, 1-tris (4-hydroxyphenyl) ethane.

The branching agents are generally used in amounts of, for example, 0.02 to 3.6 mol%, based on the dihydroxyaryl compound.

The dihydroxyaryl compounds, diaryl carbonates and monohydroxyaryl compounds used, as well as all other starting materials, chemicals and auxiliaries added to the synthesis, may be contaminated with impurities originating from their own synthesis, handling and storage and used without further purification. However, it is desirable (but not essential) to use raw materials, chemicals and adjuvants that are as clean as possible.

The addition of the at least one polymerization inhibitor is completed before the last reaction stage. In the context of the present invention, this means that the addition can be done in at least one reaction stage before the last reaction stage or between two reaction stages. The addition is preferably carried out in a reaction stage immediately before the last reaction stage or between the penultimate stage and the last reaction stage.

Polycarbonates prepared by the melt transesterification process may contain catalytically active basic impurities after preparation. These can be firstly slight contaminants of the starting materials which have not yet been separated off, basic residues of the thermally decomposable catalyst which have not yet been separated off, or stable basic catalyst salts which have not yet been separated off. Thermally decomposable catalysts are understood to mean, for example, the onium salts mentioned above. Thermally stable catalysts are understood to mean, for example, basic salts of alkali metals or alkaline earth metals. In order to suppress these catalytically active, basic impurities, certain inhibitors can in principle be added to the polycarbonate at different times in the respective process.

Suitable inhibitors are acidic components such as Lewis orAn acid or an ester of a strong acid. The pKa value of the inhibitor should be no greater than 5, preferably less than 3. The acidic component or its ester is added in order to deactivate the above-mentioned basic impurities and thus to ideally terminate the reaction when the desired molecular weight is reached. Such inhibitors are described, for example, in EP-A1612231, EP-A435124 or DE-A4438545.

Examples of suitable acidic components are orthophosphoric acid, phosphorous acid, pyrophosphoric acid, hypophosphoric acid, polyphosphoric acids, phenylphosphonic acid, sodium dihydrogen phosphate, boric acid, arylboronic acids, hydrochloric acid (hydrogen chloride), sulfuric acid, benzenesulfonic acid, toluenesulfonic acid, dodecylbenzenesulfonic acid and all other phenyl-substituted benzenesulfonic acids, nitric acid, acid chlorides, for example phenylchloroformate, acetoxy-BP-A, benzoyl chloride and esters, monoesters and bridged esters of the abovementioned acids, for example esters such as toluenesulfonic acid, phosphoric acid esters, phosphorous acid esters, phosphonic acid esters, dimethyl sulfate, boric acid esters, arylboronic acid esters and other components which generate acids under the action of water, for example triisooctylphosphine, Ultranox 640 and BDP (bisphenol diphosphate oligomer).

The polymerization inhibitors preferably used are organic sulfur-containing acids, esters of organic sulfur-containing acids or mixtures of these. The organic sulfur-containing acid may be, for example, benzenesulfonic acid, toluenesulfonic acid, trifluoromethanesulfonic acid, naphthalenesulfonic acid or sulfonated polystyrene. The esters of organic sulfur-containing acids can be, for example, the methyl, ethyl, propyl, butyl, octyl or phenyl esters of sulfonic acid dimethyl, sulfonic acid diethyl, p-toluenesulfonic acid or benzenesulfonic acid. Furthermore, they may be full or partial esters of polyhydric alcohols, such as, for example, glyceryl triphenyl sulfonate, glyceryl diphenyl sulfonate, glyceryl monophenyl sulfonate, glyceryl tri-p-toluenesulfonate, glyceryl di-p-toluenesulfonate, glyceryl mono-p-toluenesulfonate, ethylene glycol dibenzenesulfonate, ethylene glycol monobenzenesulfonate, ethylene glycol di-p-toluenesulfonate, ethylene glycol mono-p-toluenesulfonate, pentaerythritol tetraphenylsulfonate, pentaerythritol triphenesulfonate, pentaerythritol diphenylsulfonate, pentaerythritol monobenzenesulfonate, pentaerythritol tetra-p-toluenesulfonate, pentaerythritol tri-p-toluenesulfonate, pentaerythritol di-p-toluenesulfonate, pentaerythritol mono-p-toluenesulfonate, trimethylolpropane triphenesulfonate, trimethylolpropane diphenylsulfonate, trimethylolpropane mono-benzenesulfonate, trimethylolpropane tri-p-toluenesulfonate, trimethylolpropane di-p-toluenesulfonate, trimethylolpropane mono-p-toluenesulfonate, neopentyl glycol diphenylsulfonate, neopentyl glycol monobenzenesulfonate, neopentyl glycol di-p-toluenesulfonate, neopentyl glycol mono-p-toluenesulfonate and mixtures thereof. In addition, these mixtures may also comprise residues of the starting compounds (acidic component and/or alcoholic component). EP-A-1609818 also gives an illustrative but non-limiting description of such inhibitors.

The polymerization inhibitors mentioned can be added to the polymer melt individually or as any desired mixture of two or more different mixtures.

The polymerization inhibitors can be used in amounts of less than 100ppm, preferably in amounts of from 0.1 to 50ppm, particularly preferably from 0.5 to 10ppm and very particularly preferably from 1 to 5ppm, based on the polycarbonate.

There is no limitation on the form of addition of the polymerization inhibitor. The polymerization inhibitor can be added to the polymer melt as a solid (e.g.powder), solution or as a melt. Another metering method is to use a masterbatch, i.e.a mixture of polymerization inhibitor and polymer, preferably polycarbonate, which is homogenized by mixing, which may also contain further additives, such as, for example, further stabilizers or mold release agents.

The ester of the organic sulfur-containing acid is preferably added in liquid form. Since the amounts metered are very small, it is preferred to use solutions of the esters or of the masterbatches.

The compounds selected as solvents are preferably those which have been used as a further component in the respective process. Any residual material that remains does not detract from the desired qualities, depending on the requirements of the product to be prepared.

Suitable compounds, which have already been used in the respective process, are preferably those which are chemically inert or evaporate rapidly. For example phenol and diphenyl carbonate are equally suitable in preferred embodiments.

Suitable as further solvents are all organic solvents having a boiling point at atmospheric pressure of from 30 to 300 ℃, preferably from 30 to 250 ℃ and particularly preferably from 30 to 200 ℃ and water (including water of crystallization).

Suitable solvents may be, for example, water or optionally substituted alkanes, cycloalkanes or aromatics. The substituents may be aliphatic, alicyclic or aromatic groups and halogen or hydroxyl groups in various combinations. Heteroatoms such as, for example, oxygen may likewise act as bridging elements between aliphatic, alicyclic or aromatic groups, which groups may be identical or different. Additional solvents may also be esters and cyclic carbonates of ketones and organic acids. In addition, the polymerization inhibitor can also be dissolved in glycerol monostearate and metered in. Mixtures of the above may also be used as solvents.

Examples of such solvents, in addition to water, are n-pentane, n-hexane, n-heptane and its isomers, chlorobenzene, methanol, ethanol, propanol, butanol and its isomers, phenol, o-, m-and p-cresol, acetone, diethyl ether, dimethyl ketone, polyethylene glycol, polypropylene glycol, ethyl acetate, ethylene carbonate, propylene carbonate and mixtures of these.

Preference is given to water, phenol, propylene carbonate, ethylene carbonate, toluene and mixtures of these.

Particularly preferred suitable are water, phenol, propylene carbonate and mixtures of these.

For example, static mixers or other dynamic mixers, which produce homogeneous mixing, for example in extruders, are suitable for effective mixing of the polymerization inhibitors.

One or more aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof are added to the reaction mixture (reaction mixture melt) during or after the last reaction stage of the process according to the invention. The addition is therefore preferably carried out in the so-called finishing reactor (terminating reactor) or after the finishing reactor, particularly preferably after the final reactor.

According to the invention, aliphatic hydroxy polycarboxylic acids are understood to mean those having more than two carboxyl groups. In the context of the present invention, aliphatic hydroxypolycarboxylic acids are preferably these having three, four or five carboxyl groups. An especially preferred aliphatic hydroxypolycarboxylic acid is an aliphatic hydroxytricarboxylic acid.

In a preferred embodiment, one or more aliphatic hydroxydicarboxylic and/or hydroxytricarboxylic acids or derivatives thereof are added to the reaction mixture.

Derivatives of aliphatic hydroxydicarboxylic and/or hydroxypolycarboxylic acids are understood to mean, for example, salts, esters, amides, halides or anhydrides of the corresponding acids, preferably esters of the corresponding acids, or carboxylic acids derived on the hydroxyl group, such as, for example, alkoxycarboxylic acids.

Preferred aliphatic hydroxydicarboxylic and/or hydroxypolycarboxylic acids or derivatives thereof are, for example, those of the formulae (VI) and (VII), respectively:

wherein

R¹、R²、R³Independently of one another, represents linear or branched, preferably linear C₁-C₁₀Alkylene radicals, particularly preferably linear or branched, preferably linear C₁-C₆-an alkylene group;

X¹、X²、X³independently of one another, represent H or OH, wherein X¹、X²、X³At least one of the radicals in (a) represents OH,

w represents H, COOH, a carboxylic ester or an alkylcarboxy group, preferably COOH,

n is an integer from 1 to 3, preferably 1,

m is 0 or an integer from 1 to 3, preferably 0 or 1,

o is 0 or an integer from 1 to 3, preferably 0 or 1,

R⁴，R⁵independently of one another, represents linear or branched C₁-C₁₀Alkyl radicals, preferably linear or branched C₁-C₆Alkyl groups or alkali metal cations, preferably Li⁺、Na⁺Or K⁺Particular preference is given to linear or branched C₁-C₆-an alkyl group.

Particularly preferred aliphatic hydroxy dicarboxylic and/or hydroxy polycarboxylic acids or derivatives thereof are, for example, malic acid esters, malic acid monoesters, tartaric acid esters, tartaric acid monoesters, tartronic acid or esters thereof, citric acid or esters thereof. All stereoisomers, mixtures or racemic mixtures of stereoisomers and mixtures of the above mentioned acids or esters are suitable and fall within the scope of the invention. Tartaric or malic acid or derivatives thereof or mixtures of these are particularly preferred.

The aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof are used in the final reaction stage or thereafter in the process according to the invention, for example in amounts of from 5 to 500ppm, preferably from 10 to 300ppm, particularly preferably from 20 to 200ppm, based on the polycarbonate.

By combining the addition of at least one polymerization inhibitor in a reaction stage preceding the last reaction stage with the addition of at least one aliphatic hydroxydicarboxylic and/or hydroxypolycarboxylic acid or derivative thereof in the last reaction stage, polycarbonates can be obtained by means of the melt transesterification process, which results in shaped articles having a low build-up of electrostatic charges on the surface during further processes, such as injection molding. The combination of such polymerization inhibitors and further aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof in such specific sequences in the process has not been described in the literature to date. The effect of low electrostatic charge build-up with less local variation on the surface of the moldings or extrudates formed is even more surprising, since it is known, for example, to add a polymerization inhibitor of the type described above before the end of the reactor without additionally adding at least one aliphatic hydroxydicarboxylic acid and/or hydroxypolycarboxylic acid or derivatives thereof in the last reaction stage (cf. for example EP-A1612231 and DE-A10357161), but without any positive effect on the electrostatic properties of the moldings or extrudates formed.

The process according to the invention can be carried out batchwise or continuously.

After the dihydroxyaryl compound and the diaryl carbonate, optionally with further compounds (such as, for example, higher-boiling monohydroxyaryl compounds), have been present as a melt, the reaction is started in the presence of at least one suitable catalyst. In suitable equipment and apparatus, the conversion or molecular weight is increased by increasing the temperature and decreasing the pressure by removing the monohydroxyaryl compound which is eliminated until the desired end state is reached (i.e., the desired conversion or the desired molecular weight is reached). The end groups are characterized in terms of type and concentration by the choice of the ratio of dihydroxyaryl compound to diaryl carbonate, the choice of the steam loss rate of the diaryl carbonate (which results from the procedure or equipment selected for the preparation of the polycarbonate), and the choice of optional additional compounds added (such as, for example, higher boiling monohydroxyaryl compounds).

In the context of the present invention, C₁-C₄Alkyl represents, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl; c₁-C₆Alkyl further representatives are, for example, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, neopentyl, 1-ethylpropyl, cyclohexyl, cyclopentyl, n-hexyl, 1, 1-dimethylpropyl, 1, 2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1, 1-dimethylbutyl, 1, 2-dimethylbutyl, 1, 3-dimethylbutyl, 2, 2-dimethylbutyl, 2, 3-dimethylbutyl, 3, 3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1, 1, 2-trimethylpropyl, 1, 2, 2-trimethylpropyl.1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl or 1-ethyl-2-methylpropyl; c₁-C₁₀Alkyl additionally represents, for example, n-heptyl and n-octyl, pinacyl, adamantyl (isomeric menthyl), n-nonyl or n-decyl; c₁-C₃₄Alkyl additionally represents, for example, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl. The same meaning applies to the corresponding alkyl groups, for example aralkyl or alkylaryl, alkylphenyl or alkylcarbonyl groups. The alkylene groups of the corresponding hydroxyalkyl or aralkyl or alkylaryl groups represent, for example, alkylene groups corresponding to the aforementioned alkyl groups.

Aryl represents a carbocyclic aromatic group having 6 to 34 skeletal carbon atoms. The same meaning applies to the aromatic portion of arylalkyl groups (also referred to as aralkyl groups) and the aryl component of more complex groups such as, for example, arylcarbonyl groups.

C₆-C₃₄Examples of aryl radicals are phenyl, o-, p-and m-tolyl, naphthyl, phenanthryl, anthryl or fluorenyl.

Arylalkyl or arylalkyl in each case independently denotes a straight-chain, cyclic, branched or unbranched alkyl radical as defined above which may be monosubstituted, polysubstituted or fully substituted by aryl radicals as defined above.

The foregoing examples are to be considered in all respects illustrative and not restrictive.

There is in principle no restriction as to the manner and equipment and procedures for carrying out the process. The process can preferably be carried out as follows.

Further, there are no particular limitations or restrictions on the temperature and pressure used in the process of the present invention. Any conditions are possible so long as the temperature, pressure and catalyst selected allow melt transesterification with appropriate rapid removal of the monohydroxyaryl compound(s) eliminated.

The temperature in the overall process is generally 180 ℃ and 330 ℃ and the absolute pressure is 15bar-0.01 mbar.

Preference is given to choosing a continuous procedure, since this is advantageous with regard to the product quality.

Such a continuous process according to the invention is preferably carried out in such a way that: that is, the precondensation of one or more dihydroxyaryl compounds with one or more diaryl carbonates and optionally further reactants is carried out using at least one catalyst, after which the monohydroxyaryl compound formed is not isolated, and in a plurality of subsequent reaction-evaporator stages the molecular weight of the end product is increased to the desired value with a stepwise increase in temperature and a stepwise decrease in pressure.

Suitable apparatus, devices and reactors for the individual reaction-evaporator stages are (corresponding to the process) heat exchangers, flash evaporation devices, separators, columns, evaporators, stirred vessels and reactors and other commercially available apparatus which provide the required residence time at the selected temperature and pressure. The selected devices must allow the necessary introduction of heat and be designed to make them suitable for continuously increasing the melt viscosity.

All devices are connected to each other via pumps, lines and valves. The lines between all the devices should of course be as short as possible and the number of bends in the pipe should be kept as low as possible in order to avoid unnecessarily long residence times. The external (i.e. technical constraints) and chemical plant assembly needs should be taken into account.

According to a preferred continuous procedure, for carrying out the process, the reactants can be melted together or the solid dihydroxyaryl compound can be dissolved in a diaryl carbonate melt or the solid diaryl carbonate or carbonate can be dissolved in a dihydroxyaryl compound melt or both starting materials can be combined as a melt, preferably directly from the preparation. The residence times of the individual melts of the starting materials, in particular of the dihydroxyaryl compounds, are set as short as possible. On the other hand, since the raw material mixture has a lower melting point than the individual raw materials at a correspondingly lower temperature, the molten mixture can have a longer residence time without a loss of quality.

The catalyst(s) are preferably dissolved in a suitable solvent, such as phenol for example, and then mixed and the melt heated to the reaction temperature.

In a preferred embodiment of the process according to the invention, a partial flow, into which at least one polymerization inhibitor is metered, is taken off from the melt flow between the penultimate reactor and the terminating reactor by means of a gear pump. Immediately thereafter, the mixture was pumped back into the main stream for thorough mixing by the static mixer. The entry point in the direction of flow is followed by a further static mixer which ensures a uniform distribution in the main melt stream, which then enters the final reactor. In this last reactor, which serves for reducing the residual monomers, the residual monomers are then reduced at a temperature of 260-. The charge in the last reactor is set at a low level allowed by the process engineering. The residence time in the last reactor, also referred to as the terminating reactor, is of the order of a few minutes to a few hours, preferably from 5 to 180 minutes, particularly preferably from 10 to 150 minutes and very particularly preferably from 15 to 120 minutes. The possible slight increase in molecular weight in the last reactor, in which the expulsion of residual monomers mainly takes place in the form of vapor, can be compensated for by: after the residual monomer in vapor form has been discharged, the inlet molecular weight is reduced to the point where the desired final molecular weight is just reached. The finished polycarbonate is discharged from the last reactor by means of a pump (if necessary, additives are provided by known methods to improve the properties), extruded, cooled and pelletized. The pump device used is a conventional gear pump. Alternatively, it is also possible to use screws with a very wide range of designs or specially designed positive displacement pumps.

In a particularly preferred embodiment of the process according to the invention, for example, 2-bis (4-hydroxyphenyl) propane (bisphenol a, BPA) and diphenyl carbonate (DPC) are reacted with one another to produce polycarbonate as described below for purposes of example and not limitation:

the reaction temperature at the start of this particularly preferred embodiment is 180-220 ℃, preferably 190-210 ℃ and very particularly preferably 190 ℃. In a residence time of 15 to 90min, preferably 30 to 60min, a reaction equilibrium is established and the hydroxyaryl compound formed is not removed. The reaction can be carried out at atmospheric pressure, but for technical reasons it can also be carried out at overpressure. The preferred pressure in an industrial plant is 2-15 bar absolute.

The molten mixture is placed in a first vacuum chamber, the pressure of which is adjusted to 100-. In the flash evaporation process, the monomer is still present in the evaporated hydroxyaryl compound formed. After a residence time of 5-30min in the bottom receiver (optionally circulated by a pump at the same pressure and the same temperature), the reaction mixture is placed in a second vacuum chamber, the pressure of which is 50-200mbar, preferably 80-150mbar, and immediately thereafter heated to a temperature of 190-. Here too, monomers are still present in the hydroxyaryl compound formed which is evaporated. After a residence time of 5-30 minutes in the bottom receiver (optionally circulated by a pump at the same pressure and the same temperature), the reaction mixture is placed in a third vacuum chamber, the pressure of which is 30-150mbar, preferably 50-120mbar, and immediately thereafter heated to a temperature of 220-. Here too, monomers are still present in the hydroxyaryl compound formed which is evaporated. After a residence time of 5-20 minutes in the bottom receiver (optionally circulated by a pump at the same pressure and the same temperature), the reaction mixture is placed in a fourth vacuum chamber, the pressure of which is 5-100mbar, preferably 15-100mbar, particularly preferably 20-80mbar, and immediately thereafter heated to a temperature of 250-. Here too, monomers are still present in the hydroxyaryl compound formed which is evaporated.

The number of stages (here 4 stages are for purposes of example) may be 2-6. The temperature and pressure should be suitably adapted to the number of stages varied to obtain comparable results. The relative viscosity of the oligocarbonates achieved in these stages is from 1.04 to 1.20, preferably from 1.05 to 1.15, particularly preferably from 1.06 to 1.10.

After a residence time of 5 to 20 minutes in the bottom receiver (optionally circulated by a pump at the same pressure and at the same temperature as in the last flash/evaporator stage), the oligocarbonate thus produced is transferred to a disc or basket reactor and subjected to further condensation at a temperature of 250-. The product attains a relative viscosity of from 1.12 to 1.28, preferably from 1.13 to 1.126, particularly preferably from 1.13 to 1.24.

The melt leaving the reactor reaches the desired final viscosity or final molecular weight in a further disc or basket reactor. The temperature is 270-330 ℃, preferably 280-320 ℃, particularly preferably 280-310 ℃, the pressure is 0.01-3mbar, preferably 0.2-2mbar, and the residence time is 60-180 minutes, preferably 75-150 minutes. The relative viscosity is adjusted to the extent required for the target application and is from 1.18 to 1.40, preferably from 1.18 to 1.36, particularly preferably from 1.18 to 1.134.

The polycarbonates thus obtained ideally contain less than 350ppm diphenyl carbonate (DPC), less than 40ppm 2, 2-bis (4-hydroxyphenyl) propane (BPA) and less than 150ppm phenol, preferably less than 300ppm DPC, less than 30ppm BPA and less than 100ppm phenol, particularly preferably less than 250ppm DPC, less than 20ppm BPA and less than 80ppm phenol, and very particularly preferably less than 200ppm DPC, less than 15ppm BPA and less than 70ppm phenol.

The roles of the two basket reactors may also be combined into one basket reactor.

The steam from all process stages is removed immediately, collected and finished. This work-up is usually carried out by distillation, with the aim of achieving a high purity of the recovered material. This can be carried out, for example, according to DE-A10100404. The recovery and isolation of the very pure eliminated monohydroxyaryl compounds is self-evident from an economic and ecological point of view. The monohydroxyaryl compound can be directly used for preparing dihydroxyaryl compound or diaryl carbonate.

Disc or basket reactors are distinguished in that they provide very large, continuously renewed surface area in a vacuum over a long residence time. The disk or basket reactor is geometrically configured according to the melt viscosity of the product. For example, reactors as described in DE4447422C2 and EP-A1253163 or biaxial reactors as described in WO-A99/28370 are suitable.

The above-described particularly preferred embodiments of the process according to the invention can also be used for the reaction of dihydroxyaryl compounds or diaryl carbonates, respectively, in addition to 2, 2-bis (4-hydroxyphenyl) propane (bisphenol A, BPA) and diphenyl carbonate (DPC). Adjustment of the temperature and pressure set in the individual process stages may be required if appropriate.

The oligocarbonates (including oligocarbonates of very low molecular weight) and finally the polycarbonates are generally conveyed by means of gear pumps, very widely designed screws and specially designed positive displacement pumps.

Materials particularly suitable for the manufacture of equipment, reactors, lines, pumps and fittings are stainless steels of the following types: cr Ni (Mo)18/10 types, such as, for example, 1.4571 or 1.4541(Steelkey2001, published by Stahlschlussel Wegst GmbH, Th-Heuss-Strass 36, D-71672 Marbach) and Ni-based alloys of the C type, such as, for example, 2.4605 or 2.4610(Steelkey2001, published by Stahlschlussel Wegst GmbH, Th-Heuss-Strass 36, D-71672 Marbach). The stainless steel is used at process temperatures up to about 290 ℃ and the Ni-based alloy is used at process temperatures above about 290 ℃.

The basic process parameters of the overall plant, such as the ratio of diaryl carbonate to dihydroxyaryl compound at the start of the process, the pressure, the temperature and the residence time, before the last or termination reactor should be selected so that the molecular weight is sufficient for the intended use of the product to be prepared and a certain terminal OH group content is reached before the reaction melt enters the last or termination reactor. The final molecular weight depends essentially on the selected reactor outlet temperature, pressure and terminal OH group concentration. These conditions in the penultimate reactor should therefore be chosen in order to be able to produce the desired end product. The content of terminal OH groups in the polycarbonate is preferably above 150ppm, particularly preferably above 250ppm, very particularly preferably above 350 ppm. An OH-terminal group content of between 150 and 750ppm is particularly preferred, preferably of 250-650ppm and particularly preferably of 350-600 ppm.

In order to obtain low residual monomer contents, the melt should be thoroughly mixed with at least one suitable polymerization inhibitor as described above to terminate the reaction before terminating the reactor, preferably between the penultimate and final reactor or before the devolatilization apparatus. The monomer can then be evaporated in a finishing reactor (or devolatilization device).

The polycarbonates produced by the process according to the invention are particularly suitable for optionally rewritable optical data media which have good coating properties and wetting properties and are not easily smearable. In addition, during the processing of the polycarbonates into shaped articles or extrudates, low amounts of deposits occur on the molds or on the corresponding shaped articles or extrudates.

The polycarbonates produced according to the process of the invention are also suitable for the production of injection-molded articles, which have surprisingly low values of electric field strength and high charge uniformity. For the preparation of injection-molded articles by means of known injection methods and without using an ionization source, for example, average values of electric field strength in the acceptable range from-20 kV/m to +20kV/m and average values of variation of electric field strength of less than 15kV/m can be achieved.

Such polycarbonates produced by means of the melt transesterification process have not been obtained to date and have not been described in the literature.

The present invention therefore also relates to polycarbonates resulting from the process of the invention.

These polycarbonates preferably have a content of phenolic OH groups of greater than 150ppm, preferably greater than 200ppm, particularly preferably greater than 250 ppm.

The amount of terminal OH groups can be determined by NMR measurement, IR measurement or online IR measurement of terminal OH groups. Furthermore, the OH groups can be determined photometrically. IR methods and photometry are described in Horbach, a.; veiel, u.; wunderlich, H.Makromolekulare Chemistry [ Macromolecular Chemistry ]1965, Vol.88, p.215-231. The reported values of the phenolic OH group content relevant to this invention were determined by IR measurements.

Injection molded bodies comprising conventional polycarbonates prepared by the melt transesterification process have the property of generating a cumulative high and locally inhomogeneous electric field at the surface of their injection molded articles. Thus, for example, discs for optical data media containing the polycarbonate develop high electric fields during their injection molding process. Such high electric field strengths on the substrate lead to, for example, dust adsorption from the environment or to mutual adhesion of injection molded articles, such as discs, during the production of optical data storage devices, which reduces the quality of the final injection molded article and also makes the injection molding process more complicated.

Furthermore, the accumulation of electrostatic charges, in particular on the disks (for optical data media), leads to poor wetting, in particular between nonpolar media, such as, for example, nonpolar dyes or dye coatings comprising solvents, such as, for example, dibutyl ether, ethylcyclohexane, tetrafluoropropanol, cyclohexane, methylcyclohexane or octafluoropropanol. Thus, a high charge accumulation on the substrate surface causes irregularities and imperfections in the dye-carrying coating during dye application, for example in the case of writable data memories, and thus leads to defects in the information layer.

It has been found that the polycarbonates according to the invention are particularly suitable for obtaining injection-molded articles which, after certain production cycles, do not exceed a defined electric field strength, measured at a defined distance from the substrate surface and at a defined temperature and ambient humidity. In order to achieve an acceptable coating behaviour, it is desirable that the electric field strength does not exceed ± 20kV/m after 2 hours of continuous injection molding process and that the electrostatic field is very uniform over the disc surface, i.e. has a small variation in electric field strength. The polycarbonates according to the invention preferably have average values of electric field strength of from-20 to +20kV/m and a small variation in the electric field strength of less than 15kV/m after 2 hours of processing by continuous injection moulding. The electric field strength value is usually established within 1 hour and thereafter changes only slightly or not at all per unit time. The above-described values of the electric field strength of the substrate material according to the invention can also be achieved without the use of ionization sources, with the aim that the use of ionization sources can be substantially reduced in further processing of the polycarbonate.

Injection molded bodies comprising polycarbonate, such as, for example, optical discs, having the above-described properties relating to the electric field strength are distinguished by good dye application properties. This is important to ensure defect-free application of the writable layer and thus problem-free production processing. This results in a significant reduction in the rejection rate compared to conventional substrate materials.

The electric field strength depends on the geometry and dimensions of the injection molded body and the type of injection molding process due to the surface charge on the respective substrate. The measurement of the electric field strength should therefore be carried out on the finished injection-molded body, such as, for example, a disk for optical data media.

The low values of the electric field strength are particularly surprising because of the relatively high content of phenolic OH groups in the polycarbonates according to the invention.

The weight-average molecular weight of the polycarbonates is generally Mw 10000-. The weight average molecular weight is measured via intrinsic viscosity according to the Mark-Houwink relationship (g.v. schulz, h.horbach, makromol. chem.1959, 29, 93). The intrinsic viscosity is obtained as the viscosity of a methyl chloride solution of polycarbonate at 25 ℃ as determined by an Ubbelohde capillary viscometer according to DIN EN ISO 1628. The weight average molecular weight of the polycarbonate is determined by the Mark-Houwink relationship according to [ eta. ]]＝K×M_w ^α([η]: an intrinsic viscosity; k: 11.1X 10^-3ml/g; α: 0.82).

The polycarbonates also preferably have a very low content of salt impurities. The amount of alkali metal or alkaline earth metal ions formed as a result of salt-like impurities (determined by atomic absorption spectroscopy) should be less than 60ppb, preferably less than 40ppb and particularly preferably less than 20 ppb. The salt-like impurities may originate, for example, from impurities of the starting materials used and from phosphonium and ammonium salts. Additional ions (e.g., Fe, Ni, Cr, Zn, Sn, Mo, or Al ions and their homologues) may be present in the raw material or may result from the removal or corrosion of the material of the equipment used. The total content of these ions is less than 2ppm, preferably less than 1ppm, and particularly preferably less than 0.5 ppm.

The anions present are ions of equal amounts of inorganic and organic acids (e.g. chlorides, sulfates, carbonates, phosphates, phosphites, oxalates, etc.).

Very small amounts of such cations and anions are strived for, for which reason it is advantageous to use as pure raw materials as possible. Such pure raw materials may be obtained from partially contaminated industrial raw materials, for example, by additional purification operations, such as, for example, recrystallization, distillation, washing reprecipitation, and the like, prior to their use.

Furthermore, the polycarbonates according to the invention may have further conventional additives (for example auxiliaries)Auxiliaries and reinforcing materials). The addition of additives serves to prolong the service life (e.g. hydrolysis stabilizers or degradation stabilizers), to improve the color stability (e.g. heat stabilizers and UV stabilizers), to simplify the process (e.g. mold release agents, flow improvers), to improve the performance characteristics, to improve the flame retardancy, to influence the image (e.g. organic colorants, pigments) or to adapt the polymer properties to certain loads (impact modifiers, finely divided minerals, fibrous materials, quartz powder and glass and carbon fibers). Such Additives are described, for example, in "Plastics Additives",and H.M muller, Hanser Publishers 1983.

The amounts used for the flame retardant, mold release agent, UV stabilizer and thermal stabilizer are selected in a manner known to those skilled in the art of aromatic polycarbonates. However, the amount of additives should be kept as small as possible for the reasons stated at the outset. Examples of such additives are mold release agents based on stearic acid and/or stearyl alcohol, particularly preferably pentaerythritol stearate, trimethylolpropane tristearate, pentaerythritol distearate, stearyl stearate and glyceryl monostearate, and conventional heat stabilizers.

Different additives may be combined with each other in order to achieve the desired properties. These additives can be added to the polymer melt individually or in any desired mixture or mixtures, in particular directly during the polymer separation or after melting of the particles in a so-called mixing step.

The additives or mixtures thereof may be added to the polymer melt as a solid, i.e. as a powder, or as a melt. Another metering method is the use of masterbatches (i.e.mixtures of the additive with the polymer, preferably with the polycarbonate, which are homogenized by mixing) or mixtures of additive masterbatches or additive mixtures.

These are preferably added to the final polycarbonate on conventional equipment.

Suitable Additives are described, for example, in Additives for Plastics Handbook, John graphics, Elsevier, Oxford 1999 or Plastics Additives Handbook, Hanser, Munich 2001.

The polycarbonates according to the invention are very suitable as substrate materials for transparent injection moldings, in particular for injection moldings to be coated, for example substrates such as transparent plates, lenses, optical storage media or optical storage media, or articles from the automotive glazing field (such as, for example, diffusion discs). It is thus possible to produce, in particular, optical storage media or substrates for optical storage media, such as, for example, writable optical data stores, from the polycarbonates according to the invention, which have good coating properties and wetting properties and are suitable, for example, for dye application from solutions, in particular from nonpolar media. Optical injection moldings produced from these polycarbonates have a low tendency to staining.

The invention therefore also relates to shaped articles or extrudates, such as, for example, disks for writable optical data storage or materials in the automotive glazing field, such as, for example, diffusion disks, which are produced from the polycarbonates according to the invention.

The invention also relates to an optical disc for manufacturing an optical data storage. An optical disc in the context of the present invention is an injection molded article which is manufactured by means of an injection molding process with the aid of an injection molding device or an injection mold. The optical disc is manufactured from a base material and is neither coated nor post-processed. A non-limiting manufacturing method of the optical disc is cited in the embodiments. Thus, optical discs are precursors to optical data media prior to coating and post-processing.

The following examples are intended to illustrate the invention without in any way limiting it.

Examples

Intrinsic viscosity/molecular weight:

the weight average molecular weight is determined via intrinsic viscosity according to the Mark-Houwink relationship (G.V.Schulz, H.Horbach, Makromol.chem.1959, 29, 93). Obtained by measuring the viscosity at 25 ℃ of a methyl chloride solution of polycarbonate with the aid of an Ubbelohde capillary viscometer in accordance with DIN EN ISO 1628. The weight average molecular weight of the polycarbonate is determined by the Mark-Houwink relationship according to [ eta. ]]＝K×M_w ^α([η]: an intrinsic viscosity; k: 11.1X 10^-3ml/g; α: 0.82).

Content of phenolic terminal OH group:

the content of phenolic OH groups is determined by TiCl, according to Horbach et al (Die Makromolekulare Chemie 88(1965)215-₄The photometric measurement of the complex.

Measurement of electric field intensity:

the measurement of the electric field strength is carried out on the final injection-molded part, in the present invention on a disc. The following injection molding parameters and conditions were set for the manufacture of these discs:

a machine: netstal Discjet

Die cavity: audio stamper

Cycle time: 4.4s

Melt temperature: 310 ℃ C

Substrate size: audio CD

Mold temperature of the side of the mold cavity: 60 deg.C

A new audio stamper is inserted into the machine before the injection molding process begins. Before inserting the new stamp, the entire injection moulding device is cleaned to remove the previous material, in order that the measured values are authentic. Further, the discs were initially injection molded for 2 hours with a cycle time of 4.4 s; this ensures that a stable and representative electrostatic charge accumulation state of the device or puck is achieved. After 2 hours of prior operation, the next 100 discs were all measured as follows:

each of these discs was removed from the injection mold by a robot immediately after the injection molding process was completed and placed on a turntable. The disc is held on the turntable only by means of four points in the outer area, in order that the load (electrostatic field) present on the disc hardly has an adverse effect. After the turntable brought the disc to the place where a measuring probe (probe 3455E, from TREK inc., 1160 Maple Ridge Road, Medina, n.y.14103) was present to measure the electric field strength, the disc was clamped in this position in the inner hole area by means of an elevator and raised by approximately 2 cm. The disc is thus located at a distance of 5mm from the measuring probe, which is temporarily positioned so that its measuring range subtends a radius of 35mm from the disc. Thereafter, the disc is rotated one turn under the probe by means of a lifter (which is rotated by means of a motor). The electrostatic field was recorded almost continuously (200 measurement points/revolution). For this purpose, the signal emitted by the probe is first transmitted as an analog signal to a measuring device (model 341B from TREK inc., 11601 Maple ridge rd., Medina, n.y.14103), where it is converted into a digital measurement value by means of an analog-to-digital converter, which is obtained by means of suitable software. For each disc, 200 measurements per revolution were thus recorded and evaluated. Average electric field intensity (F) of 200 values_mean) By determining the mean value and the maximum and minimum electric field strengths (F) determined in each case_minAnd F_max) Is calculated. Now the entire re-average of the F that each of the 100 disks has_mean，F_minAnd F_maxThe value is obtained. Thus, an average electric field strength and average maximum and average minimum electric field strengths of 100 sets of discs can be obtained. The difference between the average maximum and average minimum electric field strength is likewise determined by subtraction and is designated in the following as the electric field strength variation.

Example 1 (comparative example)

4.19kg/h of the catalyst mixture were added to a 7500kg/h melt mixture comprising 3741kg/h diphenyl carbonate (17.45kmol/h) and 3759kg/h bisphenol A (16.47kmol/h) and pumped from a receiver through a heat exchanger (heated here to 190 ℃) and fed through a residence column at 12bar and 190 ℃. The average residence time was 50 minutes. The catalyst mixture consisted of 0.52kg of a phenol adduct of tetraphenylphosphonium phenolate (containing 65.5% by weight of tetraphenylphosphonium phenolate 0.786mol) dissolved in 4.5kg of phenol.

The melt then passes via an expansion valve into a separator at a pressure of 200 mbar. The melt flowing off is reheated to 200 ℃ in a falling-film evaporator, likewise at 200mbar, and collected in a receiver. After a residence time of 20 minutes, the melt was pumped into the next three similar design stages. The pressure, temperature and residence time conditions in stage 2/3/4 were 90/70/40 mbar; 223/252/279 ℃ and 20/10/10 minutes. All the steam is fed under pressure to the vacuum column and removed as condensate.

Thereafter, the oligomer was condensed in a subsequent basket reactor at 280 ℃ and 4.7mbar with a residence time of 45 minutes to give a higher molecular weight product with a relative viscosity of 1.195. The vapor is condensed.

A partial stream of 150kg/h of the melt was branched off from the melt stream (which entered the further basket reactor) by means of a gear pump, 2.0g/h of 1, 2, 3-propanetriol tris (4-benzenesulfonate) were added, and the mixture was fed through a static mixer having a length to diameter ratio of 20 and recirculated back into the main melt stream. Immediately after combining, 1, 2, 3-propanetriol tris (4-benzenesulfonate) was homogeneously dispersed throughout the melt stream by means of a further static mixer. The melt thus treated is further subjected to process conditions of 294 ℃ and 0.7mbar and a residence time of on average 130 minutes in a further basket reactor, discharged and granulated.

The production of the optical molded article (disk) and the measurement of the electric field strength were carried out as follows. For this purpose, the granules obtained were dried for 6 hours and then processed by means of a Netstal Discjet injection moulding machine (see above) in a cycle time of 4.4s under the parameters described above to give discs. The cavity used was an audio stamper. To stabilize the process, discs were initially produced for 2 hours, and then the average electric field strength and electric field strength variation were measured for each of the next 100 discs.

The values of the average electric field intensity and the variation in the electric field intensity of the 100 disks are shown in table 1.

Content of phenolic OH group: 470ppm of

The intrinsic viscosity of the polymer was 36.5. This corresponds to about M_w(ii) a molecular weight of 19450 g/mol.

Examples 2 to 18 (comparative examples)

The procedure is as in example 1 except that after the last basket reactor (i.e. the last process step) different aromatic and aliphatic carboxylic acids are added to the material. Then spinning and pelletizing are carried out.

The manufacture of the discs and the measurement of the electric field strength were performed as described above.

The aromatic and aliphatic carboxylic acids added, the amounts added and the electric field strength measurements and the phenolic OH contents and the intrinsic viscosities in each case are shown in Table 1.

Example 19 (comparative example)

Polycarbonates prepared using a commercially available melt transesterification process, available from general electric (R) ((R))OQ 1025). The manufacture of the discs and the measurement of the electric field strength were performed as described above. The results are shown in Table 1.

Examples 20 to 25 (according to the invention)

The procedure is as in example 1 except that after the last basket reactor (i.e. the last process step) a different aliphatic hydroxy dicarboxylic or hydroxy polycarboxylic acid is added to the material. Then spinning and pelletizing are carried out.

The manufacture of the discs and the measurement of the electric field strength were performed as described above.

The aliphatic hydroxydicarboxylic acid or hydroxypolycarboxylic acid added in each case, the amounts added, the measurement results of the electric field strength and these phenolic OH contents of the polycarbonates obtained are shown in Table 2. All examples and comparative examples had intrinsic viscosities in the range of 35.0 to 40.0. This corresponds to M of 18500-21750g/mol_wMolecular weight. The aforementioned embodiments according to the present invention surprisingly show significantly less electrostatic charge accumulation and less variation in electric field strength than the comparative examples.

TABLE 1 (comparative example)

TABLE 2 (examples according to the invention)

Example numbering	Of the type added after the last basket reactor	Amount added after the last basket reactor [ ppm [. ]]	Electric field strength [ kV/m]	Variation of electric field intensity [ kV/m]	Phenolic OH content [ ppm ]]
						20	Tartaric acid	30	+5	9	440
21	Tartaric acid	50	0	8	440
						22	Tartaric acid	100	9	8	450
23	Malic acid	50	-18	12	550
						24	Malic acid	100	-6	12	570
25	Malic acid	200	+20	10	570

In tables 3 and 4, the individual electrostatic field measurements of example 2 and example 21 are shown in detail for the purpose of example:

for each disc, the average electric field strength (F) was determined from the 200 individual values obtained per revolution_mean). Furthermore, the respective minimum value of the electric field strength (F) determined for each disk was determined_min) And respective maximum electric field strength value (F)_max). Then from F_mean，F_minAnd F_maxThe average of all 100 disks was calculated.

TABLE 3 (Single result of electrostatic field measurement of example 2)

Single disc knitting machineNumber (C)	Fmean(kV/m)	Fmin(kV/m)	Fmax(kV/m)	Individual disc numbering	Fmean(kV/m)	Fmin(kV/m)	Fmax(kV/m)
								1	-43.7	-59.5	-21.2	51	-46.8	-63.1	-27.4
2	-43.7	-60.4	-24.5	52	-24.0	-31.1	-17.2
								3	-38.4	-59.7	-20.7	53	-35.5	-56.3	-18.2
4	-39.0	-55.1	-18.5	54	-40.8	-57.5	-24.8
								5	-45.0	-61.2	-22.7	55	-42.4	-61.8	-19.3
6	-40.5	-57.0	-23.6	56	-38.8	-61.7	-25.6
								7	-41.1	-58.5	-24.4	57	-40.5	-58.7	-22.0
8	-41.0	-57.9	-25.2	58	-42.1	-62.7	-27.4
								9	-41.0	-63.5	-28.3	59	-39.8	-57.7	-24.3
10	-40.9	-62.9	-21.0	60	-45.3	-60.7	-27.9
								11	-39.6	-57.0	-23.1	61	-42.2	-56.0	-21.7

12	-42.6	-60.9	-21.4	62	-37.6	-57.8	-19.2
								13	-37.9	-60.7	-18.9	63	-41.2	-61.6	-20.9
14	-43.0	-57.5	-24.7	64	-34.8	-55.1	-18.7
								15	-41.0	-64.4	-27.1	65	-39.6	-58.9	-18.4
16	-42.4	-58.7	-26.1	66	-41.5	-60.4	-20.4
								17	-42.0	-56.5	-23.8	67	-41.5	-60.2	-18.7
18	-41.4	-60.9	-23.0	68	-43.2	-61.6	-25.8
								19	-42.6	-63.4	-20.3	69	-41.1	-58.1	-28.7
20	-41.2	-60.5	-23.4	70	-43.6	-61.0	-20.8
								21	-47.2	-63.0	-23.2	71	-40.2	-61.9	-23.2
22	-48.2	-62.4	-27.2	72	-40.7	-58.4	-22.6
								23	-41.3	-56.8	-234	73	-47.1	-61.8	-30.1
24	-42.2	-63.3	-25.7	74	-42.4	-557	-23.0
								25	-41.3	-61.4	-19.7	75	-43.4	-58.7	-28.5
26	-40.0	-58.2	-21.1	76	-39.0	-54.0	-18.3
								27	-40.4	-58.3	-20.7	77	-39.7	-53.8	-20.2
28	-40.7	-63.5	-21.5	78	-23.4	-38.9	-14.5
								29	-42.5	-57.5	-23.7	79	-42.1	-60.7	-19.0
30	-37.6	-59.9	-18.8	80	-43.3	-59.5	-27.8
								31	-40.7	-55.9	-22.9	81	-44.8	-61.8	-23.0
32	-40.0	-60.8	-21.4	82	-42.1	-58.9	-21.7
								33	-35.9	-56.6	-21.0	83	-42.3	-58.0	-19.7
34	-44.8	-54.8	-27.9	84	-40.0	-60.0	-17.4
								35	-41.2	-57.2	-24.7	85	-44.9	-57.0	-26.2
36	-41.9	-61.7	-22.3	86	-44.5	-56.3	-24.7
								37	-40.4	-61.9	-20.4	87	-42.3	-58.7	-25.7
38	-48.1	-60.3	-29.0	88	-33.3	-52.3	-17.8
								39	-38.3	-594	-16.6	89	-43.9	-59.8	-27.6
40	-25.2	-38.1	-15.5	90	-39.6	-55.8	-23.9
								41	-39.8	-58.0	-21.1	91	-43.4	-63.0	-23.3
42	-39.2	-60.4	-20.0	92	-40.6	-57.2	-19.6

43	-40.0	-59.0	-21.0	93	-41.9	-61.8	-22.8
								44	-41.4	-61.0	-19.6	94	-42.8	-58.8	-25.4
45	-38.9	-60.0	-20.2	95	-46.1	-63.5	-27.2
								46	-20.8	-27.2	-13.8	96	-43.9	-61.4	-22.4
47	-39.4	-58.3	-18.5	97	-48.8	-61.6	-32.4
								48	-39.7	-60.0	-22.3	98	-42.8	-61.3	-22.6
49	-41.8	-60.5	-23.7	99	-27.1	-36.7	-19.0
								50	-41.3	-614	-29.3	100	-45.4	-65.8	-20.6
Average of all 100 disks	-40.7	-58.3	-22.6

Can see F_meanHas an average value of-40.7 kV/m (rounded to-41 kV/m), F_minHas an average value of-58.3 kV/m, F_maxThe average value of (a) was-22.6 kV/m. Average maximum and average minimum electric field strength F_maxAnd F_minThe difference in (which in the context of the present invention is referred to as the electric field strength variation) is thus-22.6- (-58.3) 35.7kV/m (rounded to 36 kV/m).

TABLE 4 (Single result of electrostatic field measurement of example 21)

Individual disc numbering	Fmean(kV/m)	Fmin(kV/m)	Fmax(kV/m)	Individual disc numbering	Fmean(kV/m)	Fmin(kV/m)	Fmax(kV/m)
								1	-0.3	-5.1	2.9	51	-1.2	-4.7	2.5
2	0.1	-3.2	2.9	52	-0.2	-7.0	3.5
								3	0.3	-4.0	3.7	53	0.4	-2.5	2.8
4	1.5	-3.5	4.6	54	0.5	-3.2	3.2
								5	-2.0	-5.1	0.7	55	1.1	-2.7	3.7
6	0.3	-3.8	4.8	56	-1.6	-10.0	2.2
								7	0.5	-4.0	5.2	57	1.1	-2.7	3.4
8	0.4	-2.9	4.2	58	1.7	-3.4	4.4
								9	0.6	-5.3	3.6	59	1.6	-4.3	4.4

10	1.0	-4.3	3.7	60	1.2	-3.7	4.5
								11	-1.2	-5.6	2.2	61	1.1	-4.5	4.1
12	0.0	-4.6	2.5	62	1.2	-10.7	5.1
								13	0.9	-4.1	3.8	63	-0.7	-6.0	2.2
14	0.6	-5.3	3.2	64	1.1	-3.1	3.3
								15	0.2	-4.9	2.9	65	1.7	-0.3	3.4
16	-0.7	-4.2	2.2	66	0.7	-8.3	4.3
								17	0.6	-3.9	3.9	67	1.4	-3.6	4.1
18	-0.1	-3.7	2.3	68	-1.1	-10.0	2.6
								19	-2.5	-8.3	2.0	69	0.6	-4.0	3.1
20	0.4	-5.1	4.4	70	0.5	-3.5	3.6
								21	-0.1	-4.9	3.8	71	0.5	-4.5	3.8
22	0.8	-3.8	3.4	72	-1.0	-4.8	2.6
								23	0.9	-3.4	3.1	73	-1.0	-4.4	1.6
24	0.8	-4.3	3.4	74	0.4	-4.0	5.4
								25	0.7	-6.4	4.9	75	0.9	-3.6	4.3
26	-0.9	-4.9	2.3	76	-0.8	-5.2	2.7
								27	1.2	-4.8	4.0	77	-1.1	-74	2.0
28	0.1	-5.0	4.8	78	-0.3	-6.0	2.7
								29	-0.7	-4.8	1.7	79	-0.5	-4.7	2.8
30	0.2	-3.5	2.3	80	1.5	-3.8	4.1
								31	1.3	-4.2	4.0	81	1.1	-3.2	4.0
32	0.3	-10.0	5.9	82	0.6	-4.0	2.8
								33	-0.5	-3.8	3.0	83	-0.2	-6.6	4.1
34	0.4	-4.4	3.0	84	1.3	-3.1	3.5
								35	-0.9	-7.2	2.4	85	1.2	-3.4	3.5
36	0.3	-5.3	3.2	86	-0.7	-9.1	2.4
								37	0.2	-3.6	2.7	87	1.3	-3.4	4.1
38	-2.0	-6.4	2.4	88	1.2	-3.9	4.4
								39	0.0	-4.8	3.4	89	1.2	-7.5	4.5
40	0.9	-3.0	3.1	90	0.8	-3.9	3.3

41	0.9	-3.6	3.5	91	1.7	-3.6	4.4
								42	0.5	-4.1	4.4	92	0.0	-4.2	3.7
43	0.6	-4.6	3.6	93	0.8	-4.2	4.1
								44	-1.6	-8.1	2.8	94	0.7	-3.8	3.9
45	-0.2	-4.3	4.7	95	1.1	-3.9	3.9
								46	-0.8	-5.6	24	96	0.0	-24	2.6
47	0.7	-4.8	33	97	-1.5	-6.2	2.0
								48	0.7	-3.7	3.3	98	0.7	-4.1	4.4
49	-0.8	-4.6	2.0	99	1.0	-3.8	4.3
								50	0.1	-4.3	2.7	100	1.2	-4.1	4.4
Average of all 100 disks	0.3	-4.7	3.4

Can see F_meanIs 0.3kV/m (rounded to 0kV/m), F_minHas an average value of-4.7 kV/m, F_maxThe average value of (2) was 3.4 kV/m. Average maximum and average minimum electric field strength F_maxAnd F_minThe difference between (which in the context of the present invention is referred to as the electric field strength variation) is thus 3.4- (-4.7) ═ 8.1kV/m (rounded to 8 kV/m).

All references mentioned above are incorporated in their entirety by reference for all useful purposes.

While particular arrangements are shown and described herein to embody the invention, it will be obvious to those skilled in the art that various changes and rearrangements of the parts may be made without departing from the spirit and scope of the underlying invention, and that the invention is not limited to the particular forms shown and described herein as such.

Claims (13)

1. A method for preparing polycarbonates by the melt transesterification process, which comprises reacting at least one dihydroxyaryl compound with at least one diaryl carbonate in the presence of at least one catalyst in a multistage process, wherein at least one polymerization inhibitor is added to the melt before the last reaction stage and one or more aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof are added during or after the last reaction stage.

2. The process of claim 1 wherein said one or more aliphatic hydroxydicarboxylic and/or hydroxypolycarboxylic acids or derivatives thereof are one or more compounds of the general formula (VI) or (VII):

wherein

R¹、R²And R³Independently of one another, is linear or branched C₁-C₁₀-an alkylene group;

X¹、X²and X³Independently of one another are H or OH, where X¹、X²Or X³At least one of them represents OH;

w is H, COOH, a carboxylic acid ester or an alkylcarboxyl;

n is an integer of 1 to 3;

m is 0 or an integer of 1 to 3;

o is 0 or an integer from 1 to 3; and

R⁴and R⁵Independently of one another, is linear or branched C₁-C₁₀Alkyl groups or alkali metal cations, preferably Li⁺、Na⁺Or K⁺。

3. The method of claim 2, wherein

R¹、R²And R³Independently of one another is a linear form C₁-C₆-an alkylene group;

w is COOH;

n is 1;

m is 0 or 1;

o is 0 or 1; and

R⁴and R⁵Independently of one another, is linear or branched C₁-C₆-an alkyl group.

4. The method of claim 1, wherein the one or more aliphatic hydroxy dicarboxylic and/or hydroxy polycarboxylic acids or derivatives thereof are one or more compounds selected from the group consisting of malic acid, malic acid esters, malic acid monoesters, tartaric acid esters, tartaric acid monoesters, tartronic acid esters, citric acid and citric acid esters.

5. The process of claim 1, wherein the at least one polymerization inhibitor is a sulfur-containing acid, an ester of an organic sulfur-containing acid, or a mixture thereof.

6. The process of claim 1, wherein said at least one dihydroxyaryl compound is selected from the group consisting of dihydroxybenzenes, dihydroxybiphenyls, bis (hydroxyphenyl) alkanes, bis (hydroxyphenyl) cycloalkanes, bis (hydroxyphenyl) arenes, bis (hydroxyphenyl) ethers, bis (hydroxyphenyl) ketones, bis (hydroxyphenyl) sulfides, bis (hydroxyphenyl) sulfones, bis (hydroxyphenyl) sulfoxides, 1' -bis (hydroxyphenyl) diisopropylbenzenes, and derivatives thereof alkylated or halogenated on the nucleus.

7. The method of claim 1, wherein the at least one diaryl carbonate has the general formula (II)

Wherein

R, R 'and R' are each independently of the other hydrogen, linear or branched C₁-C₃₄Alkyl radical, C₇-C₃₄-alkylaryl or C₆-C₃₄-aryl, wherein R-is optionally COO-R ', wherein R' is hydrogen, linear or branched C₁-C₃₄Alkyl radical, C₇-C₃₄-alkylaryl or C₆-C₃₄-an aryl group.

8. The process of claim 1 wherein said at least one catalyst is a compound selected from the group consisting of alkali metal salts, alkaline earth metal salts and onium salts.

9. The process of claim 8 wherein said at least one catalyst is an onium salt.

10. A polycarbonate prepared by the method of claim 1, wherein the polycarbonate comprises one or more aliphatic hydroxydicarboxylic and/or hydroxypolycarboxylic acids or derivatives thereof in an amount of 5-500ppm and has a phenolic terminal OH group content of greater than 150 ppm.

11. A shaped article or extrudate comprising the polycarbonate of claim 10.

12. An optical data storage or diffusion disk comprising the polycarbonate of claim 10.

13. An optical disc for manufacturing an optical data storage device having an average electric field strength of-20 to +20kV/m and an electric field strength variation of less than 15kV/m, said optical data storage device comprising a polycarbonate which comprises one or more aliphatic hydroxydicarboxylic acids and/or hydroxypolycarboxylic acids or derivatives thereof in an amount of 5-500ppm and which has a content of phenolic terminal OH groups of more than 150 ppm.