DE102004043114A1 - Process for the production of polycarbonate - Google Patents

Abstract

The invention describes a process for producing polycarbonate by the melt transesterification process by reacting at least one aromatic dihydroxyaryl compound and a diaryl carbonate in the melt, at least in the presence of a catalyst, using a carbonate forming reagent containing at least: DOLLAR A - at least 99.9% of a diaryl carbonate of the general formula ArO (C =O) OAr DOLLAR A - 0.5 to 500 ppm of a hydroxyaromatic of the general formula ArOH DOLLAR A - 2 to 300 ppm of arylurethanes of the general formula ArO (C =O) NR ·1 ·R ·2 · DOLLAR A - 2 to 100 ppm in total of (methylaryl) arylcarbonates of the general formula (CH¶3λAr · 1 ·) O (C = O) OAr DOLLAR A - at most 100 ppm in total of (aryloxy) arylcarboxylic acid derivatives of the general Formula Ar · 2 · O-Ar · 3 · COOZ · 1 · DOLLAR A - maximum 100 ppm in total of hydroxyarylcarboxylic acid derivatives of general formula Z · 2 · O-Ar · 4 · COOAr DOLLAR A - maximum 10 ppm in total of o, o'-biphen ylencarbonate, dibenzofuran and biphenyldiol derivatives of the general formula Z.times.3 OAr.sup.5 -Ar.sup.5.OZ.sup.4 DOLLARs A-maximum 10 ppm in total of aryloxyhydroxyaryl derivatives of the general formula Ar.sup.6.OArOZ.sup.5.sup.AOL A-maximum 10 ppm in total of halohydroxyaromatic derivatives of the general formula (X) ¶m¶Ar · 7 · OZ · 6 · DOLLAR A - a maximum of 10 ppm in total of o-arylene carbonate, of dihydroxyaromatics and derivatives of the general formula Ar (OZ · 7 · ) ¶2¶ DOLLAR A - maximum 10 ppm of alkylaryl carbonates of the general formula ArO (C = O) OR · 3 · ...

Description

The The invention relates to a process for the production of polycarbonate after the transesterification process by reaction of an aromatic Dihydroxyaryl compound and a diaryl carbonate in the melt.

at the melt transesterification for the production of polycarbonate in the industrial scale For the most part, diphenyl carbonate is used. For the synthesis of diphenyl carbonate (DPC) are known various technical routes. Many of the well-known Procedures forego the use of phosgene.

A newer, phosgene-free method for the preparation of diphenyl carbonate is the oxidative direct carbonylation, in which phenol is oxygenated and carbon monoxide is reacted. Here are complex catalyst systems used, which is typically a palladium compound, at least a transitional or main group metal compound and an inorganic or quaternary salt bromide exhibit. In side reactions in this less selective process oxidation products of phenol such as dihydroxybiphenyls, Phenoxyphenols and bromine compounds such as mono- or dibromophenols generated. The complete Separation of traces of these by-products, as well as volatile organometallic species or thermal decomposition products is on an industrial scale difficult to accomplish.

A A number of DPC manufacturing processes use dialkyl carbonates such as dimethyl carbonate (DMC) or dibutyl carbonate (DBC) or dialkyl oxalates as starting materials. Also in these reactions by-products such as salicylic compounds, Alkylaryl carbonates, alkylphenyl derivatives (e.g., (methylphenyl) phenylcarbonates), Dialkyl and alkylaryl ether produced, which together with volatile Derivatives of the metals used as transesterification catalysts (e.g., Zn, Ti, Sn, Pb, Ti) contaminate the generated diphenyl carbonate can.

When Contamination of the dialkyl carbonates or oxalates may be further Substances enter the DPC. Commercial procedures too their preparation is based on the carbonylation of alcohols under copper catalysis in the presence of hydrochloric acid. here we can Chloroorganic or copper organyls be introduced. In synthetic routes over the Transesterification of ethylene carbonate can Traces of ethylene glycol, ethylene carbonate or their derivatives such as (2-hydroxyethyl) methyl carbonate, 1,2-ethylene (bismethylcarbonate) or 2-phenoxyethanol get into the product.

A blatant disadvantage of all these methods is low compared to the phosgenation selectivity, ie the generation of by-products, and often the use of metallic catalysts. The manufacturing process is generally followed by only a distillative purification of the product, so that separation of impurities on a trace scale is difficult to accomplish. This means that impurities are generated in the DPC via these synthetic routes, which have a very disturbing effect on the transparency and quality of the melt polycarbonate. A complete separation of these contaminants often turns out to be too costly in economic terms, such as in EP 592 900 A and EP 677 545 A As shown in the prior art.

It is desirable the occurrence of contaminants in general and those described in particular to avoid. At the same time, however, the claim an economical process for the preparation of diphenyl carbonate provide. In this context, contaminants are tolerable, as long as the quality of the melt polycarbonate, e.g. Color, mechanics, weather resistance and thermal stability not significantly affected is.

outgoing Therefore, the object of the prior art is to provide a method for the production of polycarbonate, wherein the quality of the polycarbonate is not affected by impurities of the diaryl carbonate.

• – mindestens 99,9 % eines Diarylcarbonats der allgemeinen Formel ArO(C=O)OAr
• – 0,5 bis 500 ppm eines Hydroxyaromaten der allgemeinen Formel ArOH
• – 2 bis 300 ppm von Arylurethanen der allgemeinen Formel ArO(C=O)NR¹R²
• – 2 bis 100 ppm in Summe von (Methylaryl)arylcarbonaten der allgemeinen Formel (CH₃Ar¹)O(C=O)OAr
• – maximal 100 ppm in Summe von (Aryloxy)arylcarbonsäurederivaten der allgemeinen Formel Ar²O-Ar³COOZ¹
• – maximal 100 ppm in Summe von Hydroxyarylcarbonsäurederivaten der allgemeinen Formel Z²O-Ar⁴COOAr
• – maximal 10 ppm in Summe von o,o'-Biphenylencarbonat, Dibenzofuran und Biphenyldiolderivaten der allgemeinen Formel Z³OAr⁵-Ar⁵OZ⁴
• – maximal 10 ppm in Summe von Aryloxyhydroxyarylderivaten der allgemeinen Formel Ar⁶OArOZ⁵
• – maximal 10 ppm in Summe von Halogenhydroxyaromatenderivaten der allgemeinen Formel (X)_mAr⁷OZ⁶
• – maximal 10 ppm in Summe von o-Arylencarbonat, von Dihydroxyaromaten und -derivaten der allgemeinen Formel Ar(OZ⁷)₂
• – maximal 10 ppm von Alkylarylcarbonaten der allgemeinen Formel ArO(C=O)OR³
• – maximal 10 ppm in Summe von Ethern der allgemeinen Formel ArOR⁴
• – maximal 5 ppm Chlorameisensäurearylester der allgemeinen Formel Cl(C=O)OAr
• – jeweils maximal 1 ppm von Benzofuran-1,3-dion, Diphenyloxalat und p-Chlorbenzoat
• – maximal 10 ppm Gesamtgehalt an Chlor
• – jeweils maximal 1 ppm von Pb, Cu, Zn, Pd, Sn und Ti, wobei Z¹ bis Z⁷ jeweils unabhängig voneinander für eines oder mehrere Elemente der Gruppe -H, -Ar oder -(C=O)OAr, Ar, Ar¹ bis Ar⁷ jeweils unabhängig voneinander für einen Arylrest, X für -Cl oder -Br, m für eine ganze Zahl von 1 bis 3 und R¹ bis R⁴ jeweils unabhängig voneinander für einen linearen, zyklischen oder verzweigten Alkylrest mit 1-20 C-Atomen steht, wobei R¹ und R² ggf. zusammen einen Zyklus bilden, stehen.

The invention provides a process for preparing polycarbonate by the melt transesterification process by reacting at least one aromatic dihydroxyaryl compound and a diaryl carbonate in the melt, at least in the presence of a catalyst, using a carbonate formation reagent which contains at least

• - At least 99.9% of a diaryl carbonate of the general formula ArO (C = O) OAr
• 0.5 to 500 ppm of a hydroxyaromatic of the general formula ArOH
• 2 to 300 ppm of arylurethanes of the general formula ArO (C =O) NR ¹ R ²
• - 2 to 100 ppm in total of (methylaryl) arylcarbonates of the general formula (CH ₃ Ar ¹ ) O (C = O) OAr
• - A maximum of 100 ppm in total of (aryloxy) arylcarbonsäurederivaten the general formula Ar ² O-Ar ³ COOZ. ¹
• - A maximum of 100 ppm in total of Hydroxyarylcarbonsäurederivaten the general formula Z ² O-Ar ⁴ COOAr
• - A maximum of 10 ppm in total of o, o'-biphenylene carbonate, dibenzofuran and biphenyldiol derivatives of the general formula Z ³ OAr ⁵ -Ar ⁵ OZ. ⁴
• - A maximum of 10 ppm in total of Aryloxyhydroxyarylderivaten the general formula Ar ⁶ OArOZ. ⁵
• - A maximum of 10 ppm in total of Halogenhydroxyaromatenderivaten the general formula (X) _m Ar ⁷ OZ. ⁶
• - A maximum of 10 ppm in total of o-arylene carbonate, of dihydroxyaromatics and derivatives of the general formula Ar (OZ ⁷ ) ₂
• - A maximum of 10 ppm of alkylaryl carbonates of the general formula ArO (C = O) OR ³
• - a maximum of 10 ppm in total of ethers of the general formula ArOR ⁴
• - A maximum of 5 ppm of aryl chloroformate of the general formula Cl (C = O) OAr
• In each case not more than 1 ppm of benzofuran-1,3-dione, diphenyl oxalate and p-chlorobenzoate
• - maximum 10 ppm total chlorine content
• In each case not more than 1 ppm of Pb, Cu, Zn, Pd, Sn and Ti, where Z ¹ to Z ^{7 are} each independently of one another one or more elements of the group -H, -Ar or - (C =O) OAr, Ar, Ar ¹ to Ar ^{7 are} each independently an aryl radical, X is -Cl or -Br, m is an integer from 1 to 3 and R ¹ to R ^{4 are} each independently a linear, cyclic or branched alkyl radical of 1-20 C atoms are where R ¹ and R ² together possibly form a cycle, stand.

The in the method according to the invention Carbonate formation reagent used for the production of polycarbonate contains no impurities which affect the quality of the melt polycarbonate prepared according to the invention, e.g. in terms of color, mechanics, weather resistance and thermal stability, essential Reduce.

• (a) Umsetzung einer alkalischen wässrigen Lösung einer Verbindung ArOH mit einer Lösung von Phosgen in einem inerten organischen Lösungsmittel, ggf. in Gegenwart eines organischen Katalysators, wenigstens unter Bildung eines Diarylcarbonats
• (b) Mindestens einfache, vorzugsweise mehrfache, Extraktion des gemäß Schritt (a) erhaltenen Reaktionsgemisches mit einer wässrigen Lösung
• (c) Behandlung des gemäß Schritt (b) erhaltenen organischen Extrakts, enthaltend das Lösungsmittel mit einer Restfeuchte von mindestens 0,5 Gew.%, mittels Destillation und/oder Wasserdampfdestillation unter Einleiten von Wasser oder Wasserdampf bei Temperaturen von 40 bis 180°C, bevorzugt 50 bis 150°C, besonders bevorzugt 60 bis 135°C
• (d) Destillative Reinigung der gemäß Schritt (c) erhaltenen Reaktionsmischung, welche ggf. eingeengt ist, wobei das Diarylcarbonat als Kopfprodukt oder im Seitenstrom abgenommen und mindestens 0,2 Gew.%, bevorzugt mindestens 0,3 Gew.%, besonders bevorzugt mindestens 0,5 Gew.% (bezogen auf die eingesetzte ArOH-Masse) aus dem Sumpfprodukt entnommen wird.

In a preferred embodiment, the carbonate formation reagent used according to the invention for the production of polycarbonate is prepared by a process comprising at least the following steps:

• (a) reacting an alkaline aqueous solution of a compound ArOH with a solution of phosgene in an inert organic solvent, if appropriate in the presence of an organic catalyst, at least to form a diaryl carbonate
• (b) at least one simple, preferably multiple, extraction of the reaction mixture obtained according to step (a) with an aqueous solution
• (c) treating the organic extract obtained according to step (b), containing the solvent having a residual moisture content of at least 0.5% by weight, by means of distillation and / or steam distillation with introduction of water or steam at temperatures of from 40 to 180 ° C., preferably 50 to 150 ° C, more preferably 60 to 135 ° C.
• (d) Distillative purification of the reaction mixture obtained according to step (c), which is optionally concentrated, the diaryl carbonate being taken off as top product or in the side stream and at least 0.2% by weight, preferably at least 0.3% by weight, more preferably at least 0.5% by weight (based on the ArOH mass used) is taken from the bottom product.

One Carbonate formation reagent prepared by this method contains none Impurities, byproducts or the like., Which produced from a Melt polycarbonate significantly impaired in its quality. The quality of the carbonate-forming reagent prepared by means of phosgene made of a melt polycarbonate of excellent quality and transparency manufacture. Existing impurities or the like. do not affect reduce the quality on the melt polycarbonate. In contrast, it was found that at the phosgene-free diphenyl carbonate process or diaryl carbonate process Systemimmanente by-products arise, which the use of a phosgene-free generated Diphenylcarbonatgemisches or Diarylcarbonatgemisches in the synthesis of polycarbonate or the quality of the produced Minimize polycarbonate.

Furthermore is the carbonate formation reagent by this method due to its comparatively simple technical implementation economically very efficient produced.

The Preparation of carbonic acid diaryl esters (Diaryl carbonates) by the interfacial process is in principle known from the literature (for example EP-A 12 16 981, EP-A 12 16 982 or EP-A 12 19 589). Subsequently, the carbonate formation reagent in Scope of the present invention also simplistic as carbonic acid diaryl ester designated.

The according to step (a) Alkali used can be an alkali lye (Na, K, Li, Ca hydroxide) be preferred soda lye and is in the process of the invention preferably as 20 to 55 wt .-%, more preferably 30 to 50% strength by weight solution used.

Hierin bedeutet R Wasserstoff, tert.-Butyl, Halogene, ein verzweigter oder unverzweigter C₁-C₄₂-Alkyl, C₇-C₄₂-Alkylaryl oder ein C₆-C₄₂-Arylrest, ein Carboxyalkyl oder -arylrest (-CO₂R⁶). Die Substituenten R¹, R², R³, R⁴, R⁵ und R⁶ sind unabhängig voneinander Elemente der durch R definierten Menge von Struktureinheiten, wobei allerdings R⁶ nicht H oder Halogen sein sollte. Geeignet sind somit also Phenol selbst, Alkylphenole wie Kresole, Xylenole, p-tert.-Butylphenol, p-Cumylphenol, p-n-Octylphenol, p-iso-Octylphenol, p-n-Nonylphenol und p-iso-Nonylphenol, Halogenphenole wie p-Chlorphenol, 2,4-Dichlorphenol, p-Bromphenol und 2,4,6-Tribromphenol, Arylphenole wie 4-Phenylphenol, Hydroxybenzoesäureester wie Methyl-, isopropyl- oder Phenylsalicylat oder p-Hydroxy(benzoesäuremethylester). Bevorzugt sind die Kresole und Hydroxybenzoesäureester, besonders bevorzugt ist Phenol.Phosgene can be used liquid, gaseous or dissolved in an inert solvent. Suitable monophenols ArOH for use in the reaction are phenols of the formula (I) or (II)

Herein, R denotes hydrogen, tert-butyl, halogens, a branched or unbranched C ₁ -C ₄₂ -alkyl, C ₇ -C ₄₂ -alkylaryl or a C ₆ -C ₄₂ -aryl radical, a carboxyalkyl or -aryl radical (-CO ₂ R ⁶ ). The substituents R ^1, R ^2, R ^3, R ^4, R ⁵ and R ⁶ are independently members of the set of moieties defined by R, except that R ⁶ should not be H or halogen. Also suitable are therefore phenol itself, alkylphenols such as cresols, xylenols, p-tert-butylphenol, p-cumylphenol, pn-octylphenol, p-iso-octylphenol, pn-nonylphenol and p-iso-nonylphenol, halophenols such as p-chlorophenol, 2,4-dichlorophenol, p-bromophenol and 2,4,6-tribromophenol, arylphenols such as 4-phenylphenol, hydroxybenzoic acid esters such as methyl, isopropyl or phenyl salicylate or p-hydroxy (benzoic acid methyl ester). Preference is given to the cresols and hydroxybenzoic acid esters, particularly preferably phenol.

In For example, inert organic solvents used in this process are Dichloromethane, toluene, the various dichloroethanes and chloropropane compounds, Chlorobenzene and chlorotoluene, preferably dichloromethane is used.

The reaction according to step (a) is preferably continuous and preferably in a plug flow without size backmixing carried out. This can thus be done for example in tubular reactors. The mixing of the two phases (aqueous and organic phase) can be achieved by built-in tube diaphragms, static Mixer and / or example pumps can be realized. The reaction is divided into two successive stages.

In the first stage becomes the watery Phase with the organic phase in a diaphragm, a nozzle or mixed with a dynamic mixer. It is preferable to use a nozzle for example, a drilled confuser-diffuser combination or a cracked tube. Behind the mixer is a Cooler, preferably with a liquid distributor, for cooling of the reaction mixture to a maximum of 50 ° C, preferably a maximum of 40 ° C.

If the mixing power is too low, the reaction is incomplete, ie the monophenol is not completely reacted with the phosgene, so that, on the one hand, monophenol enters the wastewater and, on the other hand, the aryl chloroformate is dragged into the end product. At too high mixing performance occurs a higher saponification and cleavage of the phosgene and the carbonic acid diarylester, so that on the one hand monophenol enters the wastewater and on the other hand, a significantly increased Phos surplus is needed.

The The first stage reaction is started by the reaction components Phosgene, inert solvent, which preferably only as a solvent for the Phosgene, and phenol, which is preferably already in the alkali solution dissolved is to be contacted. The residence time in the continuous process the first stage is in the range of 2 seconds to 300 seconds, preferably in the range of 4 seconds to 200 seconds. Preferably becomes the pH the first stage by the ratio of alkali lye / phenol / phosgene adjusted so that the pH in the range of 11.0 to 12.0, preferably 11.2 to 11.8, especially preferably at 11.4 to 11.6. The reaction temperature in the first stage is due to cooling maximum 40 ° C, preferably a maximum of 35 ° C held.

In the second stage of the continuous process according to step (a) the reaction is completed to the carbonic acid diarylester. The mixing of the two phases (aqueous and organic phase) in the second stage takes place at regular intervals by preferably static or dynamic dispersing agents. As static elements come preferably diaphragms, nozzles or narrowed tube cross sections are used. In the latter can additionally installations (static mixers) used for stream splitting and mixing become. The pressure drop per dispersing element is preferably 0.1 to 0.5 bar. The speed in the narrowest section of the Elements is typically 2 to 10 m / s, preferably 3 to 9 m / s, most preferably 4 at 7 m / s. The mixing time (residence time in the dispersing organ) a maximum of 0.5 s, preferably 0.01 to 0.1 s. The residence time between two successive dispersing agents is 3 to 12 s, preferably 5 to 10 s. Suitable dynamic mixers are e.g. Pumps or generally rotor-stator systems. The residence times of second stage are 1 minute to 2 hours, preferably 2 minutes to 20 minutes, most preferably 3 minutes to 15 minutes.

In a preferred embodiment a catalyst is fed at the beginning of the second stage. Directly after or during the addition of the catalyst, the reaction of the method is preferred cooled. The reaction temperature is by cooling to a maximum of 50 ° C, preferably maximum 40 ° C, most preferably held at a maximum of 35 ° C. It can be beneficial be the catalyst at several, preferably at two, points of second stage of the reaction in a continuous process. Between the first and the second stage can also be an intermediate buffering e.g. in a stirred Residence vessel under Maintaining the mixed phases are carried out.

Suitable catalysts are, for example, tertiary amines, N-alkylpiperidines or onium salts. Among onium salts, the scope of the present invention is understood to mean compounds such as PR ₄ X and NR ₄ X, where R can be an alkyl and / or aryl radical and / or an H and X is an anion. Tributylamine, triethylamine and N-ethylpiperidine are preferably used. Very particular preference is given to N-ethylpiperidine. The concentration of the catalysts is 0.0001 mol% to 0.1 mol%, preferably 0.01 mol% to 0.075 mol%, based on the phenol used.

Preferably In the second stage of the process, the pH is measured of the pH (is in the continuous process preferred online from the state measured by the technique known) and appropriate adjustment the pH is controlled by adding the alkali metal hydroxide. The amount of added alkali metal hydroxide is adjusted so that the pH after the second stage of the process in the range of 7.5 to 10.5, preferably 8 to 10, particularly preferred 8.2 to 9.5.

phosgene is relative to the phenol in the ratio of 1.01 to 1.14 mol %, preferably 1.05 to 1.10 mol%, driven. The solvent is admixed so that the diphenyl carbonate in a 5 to 60% solution, preferably 20 to 45% solution, after the reaction is present.

After the reaction, the organic phase containing the carbonic acid diarylester is usually washed with an aqueous liquid and separated from the aqueous phase as much as possible after each washing (extraction with an aqueous solution according to step (b)). The laundry is preferably carried out with desalinated water. The carbonic acid diarylester solution is usually cloudy after washing and separation of the washing liquid. The washing liquid used are aqueous liquids for separating off the catalyst, for example dilute mineral acids such as HCl or H ₃ PO ₄ , and deionized water for further purification.

The concentration of HCl or H ₃ PO ₄ in the washing liquid may be, for example, 0.5 to 1.0% by weight. The extraction takes place at least twice.

When Phase separation devices for separating the washing liquid from the organic phase can in principle known separation devices such as separation vessels, phase separators, centrifuges and coalescers or combinations of these devices become.

in the Subsequent step (c) is the treatment of the organic Extract containing the solvent with a residual moisture content of at least 0.5% by weight, from step (b) thermally with water. This step is carried out at temperatures of 40 ° C to 180 ° C, preferably 50 to 150 ° C, more preferably 70 to 135 ° C, by distillation and / or steam distillation with introduction of water or steam (steam stripping). The in the organic Extract contained residual moisture or possibly added liquid water or the added water vapor acts as a drag gas (stripping gas) to remove the solvent, residual phenol and impurities.

A first possible embodiment is the distillation of the organic extract with a residual moisture of at least 0.5% by weight in the said temperature range. It will the organic extract, which is optionally concentrated, of solvent and residual phenol freed. A second preferred embodiment is the steam distillation of the optionally concentrated organic extract while introducing water or steam.

Subsequently, will the distillate preferably condensed and the resulting solvent-water mixture, preferably without prior phase separation, returned to the reaction.

The Treatment according to step (c) may be in one or more temperature and pressure stages, e.g. in different distillation columns and / or stripping vessels. If several stages are used, it is preferable to use one in the flow direction increasing temperature profile and / or decreasing pressure profile worked.

Then done according to step (D) a distillative purification (fine distillation) of the in the sump in step (c) remaining diaryl carbonate. Characteristic of this Step is that at least 0.2% by weight, preferably at least 0.3 Wt.%, Particularly preferably at least 0.5 wt.%, (Based on the used ArOH mass) is taken from the bottom product. The diaryl carbonate obtained from the bottom product will not be recovered traced back to the process. step (d) may be one or more stages. Hereby, different can be used in principle known distillation methods are used.

To the For example, the distillation can be carried out in two stages, in which a first column first ArOH and other lower boiling compounds taken overhead and the diaryl carbonate remains in the sump. The high boiler fraction may possibly be returned to the process. In a second Column at higher Temperature and / or lower pressure than in the first column can thereafter the diaryl carbonate as an overhead product or on one of the upper shelves be removed. The e.g. circulated by a circulation evaporator sump This column then becomes a corresponding subset as purge taken.

A alternative variant is the use of a dividing wall column, in the high boiler as a top product, a circulating bottoms product, from which a purge stream is branched off, and diaryl carbonate as a side stream is removed.

A preferred variant is based on the embodiment developed for a substance phosgenation method EP 784 048 A , The fine distillation of the diaryl carbonate takes place here in a single distillation column. The reaction mixture from step (c) is fed to one of the upper trays, at the top of the column, a product is withdrawn, the bottom is circulated by means of a circulation evaporator, wherein a purge stream is removed and the diaryl carbonate in the side stream preferably on a bottom below the height taken from the feed feed. Before the removal of the purge stream, a further separation step can be carried out, in which, by known methods, such as distillation, extraction, membrane separation or precipitation, an enrichment of the high boilers to be separated from the present in high concentration diaryl carbonate is made. For example, a stream comprising about 0.5 to 5% of the feed stream from step (c) may be withdrawn from the bottoms and subjected to further distillation, eg, in a column or a falling film evaporator. The bottom of this distillation, the said portion is removed as purge, while the distillate can be recycled to the Feindestillationskolonne or to another point in the process. For example, these purification stages can be carried out continuously such that the bottom temperature during the distillation is at least 150.degree. C. to 310.degree. C., preferably at least 160 to 230.degree. The pressure necessary to carry out the distillation is from 1 to 1000 mbar, preferably at 5 to 100 mbar.

The Diaryl carbonates produced by the preferred method using phosgene are distinguished due to a very high purity with GC purities (cool on column method) of at least 99.99%, preferably at least 99.9925%, especially preferably at least 99.995%, and an extremely good transesterification behavior made out so that a polycarbonate in excellent quality can be.

• • mindestens 99,9 %, bevorzugt mindestens 99,95 %, besonders bevorzugt mindestens 99,97 % (Nachweis per cool-on-column-GC-Methode), eines Diarylcarbonats der allgemeinen Formel ArO(C=O)OAr, das aus den Phenolen der Formel (I) oder (II) hergestellt wird, wobei Diphenylcarbonat besonders bevorzugt ist.
• • 0,5 bis 500 ppm, bevorzugt 1 bis 300 ppm, besonders bevorzugt 2 bis 150 ppm, eines Hydroxyaromaten der allgemeinen Formel ArOH, bevorzugt der Formel (I) oder (II), wobei Phenol besonders bevorzugt ist.
• • 2 bis 300 ppm, bevorzugt 4 bis 150 ppm, besonders bevorzugt 5 bis 100 ppm, von Arylurethanen der allgemeinen Formel ArO(C=O)NR¹R². Wichtige Vertreter dieser Gruppe sind Dealkylierungsprodukte der als Katalysatoren eingesetzten Trialkylamine und Alkylpiperidine. Insbesondere Phenylpiperidylurethan ist hier zu nennen.
• • 2 bis 100 ppm, bevorzugt 3 bis 80 ppm, besonders bevorzugt 4 bis 60 ppm, in Summe von (Methylaryl)arylcarbonaten (CH₃Ar¹)O(C=O)OAr. Beispiele für diese Gruppe sind o-, m- und p-Kresol sowie Kresylarylcarbonate und gemischte oder einheitliche Dikresylcarbonate. Mengenmäßig am wichtigsten sind die o-Kresolderivate. Es ist einerseits wichtig, ein möglichst kresolarmes Phenol, d.h. bevorzugt ein Phenol mit weniger als 300 ppm Kresolen, besonders bevorzugt mit weniger als 100 ppm Kresolen, einzusetzen. Außerdem ist es wichtig, bei Phosgenverfahren das Reaktionsgemisch frei von Alkylarylcarbonaten oder Dialkylcarbonaten zu halten oder zumindest nicht bei hohen Temperaturen diesen Substanzen auszusetzen, da ansonsten Kresolderivate entstehen können.
• • Maximal 100 ppm, bevorzugt maximal 50 ppm, besonders bevorzugt maximal 25 ppm in Summe von Aryloxyarylcarbonsäurederivaten der allgemeinen Formel Ar²O-Ar³COOZ¹. Wichtige Vertreter sind die p- und vor allem die o-Phenoxybenzoesäurederivate und hier wiederum vor allem die Phenylester.
• • Maximal 100 ppm, bevorzugt maximal 10 ppm, besonders bevorzugt maximal 5 ppm, in Summe von Hydroxyarylcarbonsäurederivaten der allgemeinen Formel Z²O-Ar⁴COOAr. Wichtige Vertreter sind die p- und vor allem die o-Hydroxybenzoesäurephenylester und ihrer Carbonate. Aufgrund des ähnlichen Siedepunkts ist die Trennung von Phenylsalicylat von Diphenylcarbonat destillativ besonders schwierig. Durch die Extraktion gemäß Schritt (b) kann es allerdings deutlich abgereichert werden.
• • Maximal 10 ppm, bevorzugt maximal 5 ppm, besonders bevorzugt maximal 1 ppm, in Summe von o,o'-Biphenylencarbonat, Dibenzofuran und Biphenyldiolderivaten der Formel Z³OAr⁵-Ar⁵OZ⁴. Wichtige Vertreter sind die o,o'-, o,p'- und p,p'-Dihydroxybiphenyle, sowie deren Mono- und Diarylcarbonate. Um deren Gehalt zu minimieren ist es wichtig, ein möglichst biphenyldiolarmes Phenol einzusetzen und während des Verfahrens oxidative Bedingungen wie z.B. die Gegenwart von Sauerstoff zu vermeiden. Dies kann durch dem Fachmann bekannte Verfahren wie z.B. Durchblasen oder Überleiten von Inertgasen, Entgasen der Eduktströme oder Zugabe von Reduktionsmitteln erreicht werden.
• • Maximal 10 ppm, bevorzugt maximal 5 ppm, besonders bevorzugt maximal 1 ppm in Summe von Aryloxyhydroxyarylderivaten der allgemeinen Formel Ar⁶OArOZ⁵. Wichtige Vertreter sind die o und p-Phenoxyphenole sowie deren Carbonate. Um deren Gehalt zu minimieren, ist es wichtig, ein möglichst phenoxyphenolarmes Phenol einzusetzen und während des Verfahrens oxidative Bedingungen, wie z.B. die Gegenwart von Sauerstoff, zu vermeiden. Dies kann durch dem Fachmann bekannte Verfahren wie z.B. Durchblasen oder Überleiten von Inertgasen, Entgasen der Eduktströme oder Zugabe von Reduktionsmitteln erreicht werden.
• • Maximal 10 ppm, bevorzugt maximal 5 ppm, besonders bevorzugt maximal 1 ppm, in Summe von Halogenhydroxyaromatenderivaten der allgemeinen Formel (X)_mAr⁷OZ⁶. Wichtige Vertreter sind die o- und p-Halogenphenole, die 2,4- und 2,6-Dihalogenphenole sowie ihre Carbonate. Wichtig ist hierbei, die Verwendung eines chlorarmen und (C=O)ClBr-armen Phosgens.
• • Maximal 10 ppm, bevorzugt maximal 5 ppm, besonders bevorzugt maximal 1 ppm, in Summe von o-Arylencarbonat, von Dihydroxyaromaten und -derivaten der Formel Ar(OZ⁷)₂. Bevorzugt wird deshalb zur Diphenylcarbonatsynthese ein Phenol eingesetzt, das weniger als 500 ppm, bevorzugt weniger als 200 ppm, besonders bevorzugt weniger als 100 ppm, Dihydroxybenzole enthält.
• • Maximal 10 ppm, bevorzugt maximal 5 ppm, besonders bevorzugt maximal 1 ppm, von Alkylarylcarbonaten der allgemeinen Formal ArO(C=O)OR³
• • Maximal 10 ppm, bevorzugt maximal 5 ppm, besonders bevorzugt maximal 1 ppm in Summe von Ethern ArOR⁴
• • Maximal 5 ppm, bevorzugt maximal 3 ppm, besonders bevorzugt maximal 1 ppm, Chlorameisensäurearylester der allgemeinen Formal Cl(C=O)OAr. Chlorameisensäurephenylester ist als starker Inhibitor der Reaktion bekannt. Er kann durch ausreichend lange Nach reaktion sowie durch die bei der Extraktion gemäß Schritt (b) ablaufende Hydrolyse und anschließende Wasserdampfßehandlung und/oder Wasserdampfdestillation weitgehend entfernt werden.
• • Jeweils maximal 1 ppm von Benzofuran-1,3-dion, Diphenyloxalat, p-Chlorbenzoat
• • Maximal 10 ppm Gesamtgehalt an Chlor
• • Jeweils maximal 1 ppm von Pb, Cu, Zn, Pd, Sn und Ti, wobei Z¹ bis Z⁷ jeweils unabhängig voneinander für eines oder mehrere Elemente der Gruppe -H, -Ar oder -(C=O)OAr, Ar, Ar¹ bis Ar⁷ jeweils unabhängig voneinander für einen Arylrest, bevorzugt jeweils für einen Phenylrest, X für -Cl oder -Br m für eine ganze Zahl von 1 bis 3 und R¹ bis R⁴ jeweils unabhängig voneinander für einen linearen, zyklischen oder verzweigten Alkylrest mit 1-20 C-Atomen steht, wobei R¹ und R² zusammen einen Zyklus bilden können, stehen.

The carbonate forming reagent which is used in the process according to the invention for the production of polycarbonate is characterized by a content of

• At least 99.9%, preferably at least 99.95%, particularly preferably at least 99.97% (detection by cool-on-column GC method) of a diaryl carbonate of the general formula ArO (C =O) OAr, which consists of the phenols of formula (I) or (II) is prepared, with diphenyl carbonate is particularly preferred.
• 0.5 to 500 ppm, preferably 1 to 300 ppm, more preferably 2 to 150 ppm, of a hydroxyaromatic of the general formula ArOH, preferably of the formula (I) or (II), with phenol being particularly preferred.
• 2 to 300 ppm, preferably 4 to 150 ppm, particularly preferably 5 to 100 ppm, of arylurethanes of the general formula ArO (C =O) NR ¹ R ² . Important representatives of this group are dealkylation products of the trialkylamines and alkylpiperidines used as catalysts. In particular phenylpiperidylurethane should be mentioned here.
• • 2 to 100 ppm, preferably 3 to 80 ppm, particularly preferably 4 to 60 ppm, in the sum of (methylaryl) arylcarbonates (CH ₃ Ar ¹ ) O (C = O) OAr. Examples of this group are o-, m- and p-cresol as well as cresylaryl carbonates and mixed or uniform dicresyl carbonates. Most important are the o-cresol derivatives. On the one hand, it is important to use a phenol which is as low in cresol as possible, that is to say preferably a phenol having less than 300 ppm cresols, more preferably less than 100 ppm cresols. In addition, it is important in phosgene process to keep the reaction mixture free of alkylaryl carbonates or dialkyl carbonates or at least not at high temperatures suspend these substances, otherwise cresol derivatives may arise.
• Not more than 100 ppm, preferably not more than 50 ppm, particularly preferably not more than 25 ppm in total of aryloxyarylcarboxylic acid derivatives of the general formula Ar ² O-Ar ³ COOZ ¹ . Important representatives are the p- and especially the o-Phenoxybenzoesäurederivate and here again especially the phenyl esters.
• At most 100 ppm, preferably at most 10 ppm, particularly preferably at most 5 ppm, in total of hydroxyarylcarboxylic acid derivatives of the general formula Z ² O-Ar ⁴ COOAr. Important representatives are the p- and especially the o-Hydroxybenzoesäurephenylester and their carbonates. Due to the similar boiling point, the separation of phenyl salicylate from diphenyl carbonate is particularly difficult by distillation. However, it can be significantly depleted by the extraction according to step (b).
• At most 10 ppm, preferably at most 5 ppm, particularly preferably at most 1 ppm, in the sum of o, o'-biphenylenecarbonate, dibenzofuran and biphenyldiol derivatives of the formula Z ³ OAr ⁵ -Ar ⁵ OZ ⁴ . Important representatives are the o, o'-, o, p'- and p, p'-Dihydroxybiphenyle, and their mono- and diaryl carbonates. In order to minimize their content it is important to use a phenol which is as low in biphenyl diol as possible and to avoid oxidative conditions such as the presence of oxygen during the process. This can be achieved by methods known to the person skilled in the art, for example by blowing or passing inert gases, degassing the educt streams or adding reducing agents.
• At most 10 ppm, preferably at most 5 ppm, more preferably at most 1 ppm in total of Aryloxyhydroxyarylderivaten the general formula Ar ⁶ OArOZ. ⁵ Important representatives are the o and p-Phenoxyphenole and their carbonates. In order to minimize their content, it is important to use phenol phenol phenol which is as low in phenoxyphenol as possible and to avoid oxidative conditions such as the presence of oxygen during the process. This can be achieved by methods known to the person skilled in the art, for example by blowing or passing inert gases, degassing the educt streams or adding reducing agents.
• At most 10 ppm, preferably at most 5 ppm, particularly preferably at most 1 ppm, in total of halohydroxyaromatic derivatives of the general formula (X) _m Ar ⁷ OZ ⁶ . Important representatives are the o- and p-halophenols, the 2,4- and 2,6-Dihalogenphenole and their carbonates. Important here is the use of a low-chlorine and (C = O) ClBr-poor phosgene.
• At most 10 ppm, preferably at most 5 ppm, particularly preferably at most 1 ppm, in total of o-arylene carbonate, of dihydroxyaromatics and derivatives of the formula Ar (OZ ⁷ ) ₂ . For this reason, preference is given to using a phenol for diphenyl carbonate synthesis which contains less than 500 ppm, preferably less than 200 ppm, more preferably less than 100 ppm, of dihydroxybenzenes.
• At most 10 ppm, preferably at most 5 ppm, particularly preferably at most 1 ppm, of alkylaryl carbonates of the general formula ArO (C =O) OR ³
• At most 10 ppm, preferably at most 5 ppm, particularly preferably at most 1 ppm, in total of ethers ArOR ⁴
• At most 5 ppm, preferably at most 3 ppm, particularly preferably at most 1 ppm, aryl chloroformate of the general formula Cl (C =O) OAr. Chloroformic acid phenyl ester is known as a strong inhibitor of the reaction. It can be largely removed by sufficiently long after reaction and by the in the extraction according to step (b) proceeding hydrolysis and subsequent steam treatment and / or steam distillation.
• • A maximum of 1 ppm of benzofuran-1,3-dione, diphenyloxalate, p-chlorobenzoate
• • Maximum 10 ppm total chlorine content
• Each of a maximum of 1 ppm of Pb, Cu, Zn, Pd, Sn and Ti, wherein Z ¹ to Z ⁷ each independently of one another for one or more elements of the group -H, -Ar or - (C = O) OAr, Ar, Ar ¹ to Ar ^{7 are} each independently an aryl radical, preferably in each case a phenyl radical, X is -Cl or -Br m is an integer from 1 to 3 and R ¹ to R ^{4 are} each independently a linear, cyclic or branched Alkyl radical having 1-20 C atoms, wherein R ¹ and R ^{2 can} form a cycle together, stand.

Prefers contains the carbonate forming reagent no further organic impurities in an amount of more than 100 ppm and no further elements except C, H, N, P, Cl and O in scale of more than 5 ppm. Possibly. existing metals are particularly preferred only in quantities of max. 1 ppm.

The Carbonate formation reagent is used in the production of polycarbonate after the melt transesterification process by reacting at least an aromatic dihydroxyaryl compound and the carbonate formation reagent, containing a diaryl carbonate, in the melt at least in the presence a catalyst used. The melt transesterification process is basically known from the prior art. The implementation of the method is, for example in WO 02/077067.

For the preparation of polycarbonates, suitable dihydroxyaryl compounds are those of the formula HO-Z-OH in which Z is an aromatic radical having 6 to 30 C atoms, which may contain one or more aromatic nuclei, may be substituted and may contain aliphatic or cycloaliphatic radicals or alkylaryls or heteroatoms as bridge members.

Examples for dihydroxyaryl compounds are: dihydroxybenzenes, dihydroxydiphenyls, bis (hydroxyphenyl) alkanes, bis (hydroxyphenyl) -cycloalkanes, Bis (hydroxyphenyl) aryls, bis (hydroxyphenyl) ethers, bis (hydroxyphenyl) ketones, Bis (hydroxyphenyl) sulfides, bis (hydroxyphenyl) sulfones, bis (hydroxyphenyl) sulfoxides, 1,1'-bis (hydroxyphenyl) -diisopropylbenzenes, and their nuclear alkylated and nuclear halogenated compounds.

preferred Dihydroxyaryl compounds are, for example: resorcinol, 4,4'-dihydroxydiphenyl, bis (4-hydroxyphenyl) -methane, Bis- (3,5-dimethyl-4-hydroxyphenyl) -methane, bis- (4-hydroxyphenyl) -diphenyl-methane, 1,1-bis- (4-hydroxyphenyl) -1-phenyl-ethane, 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-phenyl-propane, 2,2-bis (4-hydroxyphenyl) hexafluoro-propane, 2,4-bis (4-hydroxyphenyl) -2-methyl-butane, 2,4-bis (3,5-dimethyl-4-hydroxyphenyl ) -2-methyl-butane, 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-disopropylbenzene, 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'-spirobi- [1H- indene] -5,5'-diol.

Particularly preferred dihydroxyaryl compounds are: resorcinol, 4,4'-dihydroxydiphenyl, bis- (4-hydroxyphenyl) -diphenyl-methane, 1,1-bis- (4-hydroxyphenyl) -1-phenyl-ethane, 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-diisop ropyl-benzene and 1,1'-bis (4-hydroxyphenyl) -4-diisopropylbenzene.

All particularly preferred are: 4,4'-dihydroxydiphenyl, 2,2-bis (4-hydroxyphenyl) propane and bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane.

It can both a dihydroxyaryl compound to form homopolycarbonates as well as several dihydroxyaryl compounds to form copolycarbonates be used.

Instead of The monomeric Dihydroxyarylverbindungen can also low molecular weight, predominantly OH endgruppengestoppte Oligocarbonate be used as starting compound.

The Dihydroxyaryl compounds can also with residual contents of Monohydroxyarylverbindungen, from which they were prepared, or the low molecular weight oligocarbonates with residual contents of monohydroxyaryl compounds used in the preparation were eliminated from the oligomers used. The contents can up to 20%, preferably 10%, more preferably up to 5% and most preferably up to 2%.

Based on the Dihydroxyarylverbindung be the diphenyl carbonate with From 1.02 to 1.30 moles, preferably from 1.04 to 1.25 moles, more preferably with 1.06 to 1.22 mol, most preferably with 1.06 to 1.20 Mol used per mole Dihydroxyarylverbindung.

wobei R, R' und R'' unabhängig voneinander H, gegebenenfalls verzweigtes C₁-C₃₄ Alkyl/Cycloalkyl, C₇-C₃₄-Alkylaryl oder C₆-C₃₄-Aryl darstellen. R kann auch -COO-R''' bedeuten, wobei R''' H, gegebenenfalls verzweigtes C₁-C₃₄ Alkyl/Cycloalkyl, C₇-C₃₄-Alkylaryl oder C₆-C₃₄-Aryl sein kann. In diesem speziellen Fall kann R nicht H sein, wohl aber R' und R".For influencing or changing the end groups, it is additionally possible to use a monohydroxyaryl compound which was not used for the preparation of the diphenyl carbonate used. It is represented by the following general formula:

wherein R, R 'and R "independently of one another are H, optionally branched C ₁ -C ₃₄ alkyl / cycloalkyl, C ₇ -C ₃₄ -alkylaryl or C ₆ -C ₃₄ -aryl. R can also be -COO-R ''', where R''' H, optionally branched C ₁ -C ₃₄ alkyl / cycloalkyl, C ₇ -C ₃₄ alkylaryl or C ₆ -C ₃₄ aryl may be. In this particular case, R can not be H, but R 'and R ".

Such Monohydroxyaryl compounds are, for example: 1-, 2- or 3-methylphenol, 2,4-dimethylphenol 4-ethylphenol, 4-n-propylphenol, 4-iso-propylphenol, 4-n-butylphenol, 4-iso-butylphenol, 4-tert-butylphenol, 4-n-pentylphenol, 4-n-hexylphenol, 4-iso-outylphenol, 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, iso-propyl salicylate, n-butyl salicylate, iso-butyl salicylate, tert-butyl salicylate, phenyl salicylate and benzyl salicylate.

Prefers are 4-tert-butylphenol, 4-iso-octylphenol and 3-pentadecylphenol.

there is to choose a Monohydroxyarylverbindung whose boiling point above the the monohydroxyaryl compound used to make the Diarylcarbonates is used. The monohydroxyaryl compound can be added at any time in the course of the reaction. she is preferably added at the beginning of the reaction or else at Any point in the process. The proportion of free monohydroxyaryl compound can be 0.2-20 Mole%, preferably 0.4-10 Mole%, based on the dihydroxyaryl compound.

The End groups can also by concomitant use of a diaryl carbonate, its base Monohydroxyarylverbindung a higher one Boiling point as the basic Monohydroxyarylverbindung of the main used Diarylcarbonates has changed become. Again, the diaryl carbonate at any time be added in the course of the reaction. It is preferred at the beginning the reaction added or else at any point in the process. The proportion of the diaryl carbonate with the higher-boiling base monohydroxyaryl compound on the total Diarylcarbonatmenge used 1-40 mol %, preferably 1-20 Mole% and more preferably 1-10 Mole%.

wobei R^1-4 dieselben oder verschiedene C₁-C₁₀-Alkyle, C₆-C₁₄-Aryle, C₇-C₁₅-Arylalkyle oder C₅-C₆-Cycloalkyle, bevorzugt Methyl oder C₆-C₁₄-Aryle, besonders bevorzugt Methyl oder Phenyl sein können, und X^– ein Anion wie Hydroxyd, Sulfat, Hydrogensulfat, Hydrogencarbonat, Carbonat oder ein Halogenid, bevorzugt Chlorid oder ein Alkylat bzw. Arylat der Formel -OR sein kann, wobei R ein C₆-C₁₄-Aryl, C₇-C₁₅-Arylalkyl oder C₅-C₆-Cycloalkyl, bevorzugt Phenyl sein kann.As catalysts in the melt transesterification process for the preparation of polycarbonates the in the literature known basic catalysts such as alkali and alkaline earth hydroxides and oxides, but also ammonium or phosphonium salts, hereinafter referred to as onium salts used. Onium salts, more preferably phosphonium salts, are preferably used in the synthesis. Phosphonium salts in the context of the invention are those of the general formula:

where R ^{1-4 are the} same or different C ₁ -C ₁₀ -alkyls, C ₆ -C ₁₄ -aryls, C ₇ -C ₁₅ -arylalkyls or C ₅ -C ₆ -cycloalkyls, preferably methyl or C ₆ -C ₁₄ -aryls , particularly preferably methyl or phenyl, and X ^{- may be} an anion such as hydroxide, sulfate, hydrogensulfate, bicarbonate, carbonate or a halide, preferably chloride or an alkylate or arylate of the formula -OR, where R is a C ₆ -C ₁₄ -aryl, C ₇ -C ₁₅ -arylalkyl or C ₅ -C ₆ -cycloalkyl, preferably phenyl.

preferred Catalysts are tetraphenylphosphonium chloride, tetraphenylphosphonium hydroxide and Tetraphenylphosphonium phenolate, particularly preferred is tetraphenylphosphonium phenolate.

They are preferably used in amounts of from 10 ^-8 to 10 ^-3 mol, based on 1 mol of dihydroxyaryl compound, more preferably in amounts of from 10 ^-7 to 10 ^-4 mol.

Further Catalysts can alone or in addition to the onium salt as cocatalyst, to speed to increase the polycondensation.

To belong the alkaline salts of alkali metals and alkaline earth metals, such as hydroxides, alkoxides and aryl oxides of lithium, sodium and potassium, preferably hydroxides, alkoxides or aryloxyde of sodium. At the Most preferred are sodium hydroxide and sodium phenolate, as well also the disodium salt of 2,2-bis (4-hydroxyphenyl) propane.

The Amounts of alkaline salts of alkali metals and alkaline earth metals alone or as cocatalyst in the range of 1 to 500 ppb, preferably 5 to 300 ppb and on most preferably 5 to 200 ppb, each calculated as sodium and based on polycarbonate to be formed.

The alkaline salts of alkali metals and alkaline earth metals can already in the production of oligocarbonates, that is at the beginning the synthesis, used or even before the polycondensation be mixed to unwanted Suppress side reactions.

Further there is also the possibility supplementary Amounts of onium catalysts of the same type or another add to the polycondensation.

The Addition of the catalysts takes place in solution in order to dosing harmful excess concentrations to avoid. The solvents are systemic and procedural inherent Compounds such as dihydroxyaryl compounds, diaryl carbonates or monohydroxyaryl compounds. Particular preference is given to monohydroxyaryl compounds, because the expert is familiar is that the dihydroxyaryl and diaryl carbonates already slightly elevated Temperatures, especially under the influence of the catalyst, easily change and decompose. These include polycarbonate grades. At the technically significant transesterification process for the production of polycarbonate is the preferred compound phenol. Phenol is also suitable for this reason already mandatory, because the catalyst preferably used Tetraphenylphosphoniumphenolat is isolated in the production as a mixed crystal with phenol.

beschrieben. Die Klammer bezeichnet eine sich n-mal wiederholende Struktureinheit, wobei Z wie oben definiert ist.

ist in diesem Fall als ganze Gruppe auch H.The thermoplastic polycarbonates are represented by the formula

described. The bracket denotes a n-times repeating structural unit, wherein Z defi as above is defined.

is in this case as a whole group also H.

The Polycarbonates have an extremely low Content of cations and anions of not more than 60 ppb, preferably a maximum of 40 ppb and more preferably a maximum of 20 ppb (calculated as Na cation), where as cations are those of alkali and alkaline earth metals, which, for example, as an impurity from the raw materials used and the phosphonium and ammonium salts can originate. Further Ions such as Fe, Ni, Cr, Zn, Sn, Mo, Al ions and their homologues can be contained in the raw materials or by erosion or corrosion come from the materials of the plant used. The content of these ions is a total of at most 2 ppm, preferably at most 1 ppm and especially preferably at most 0.5 ppm.

When Anions are those of inorganic acids and of organic acids in equivalent amounts (e.g., chloride, sulfate, carbonate, phosphate, phosphite, oxalate).

The aim So are the smallest amounts, only by using purest Raw materials can be achieved. Such pure raw materials are e.g. only after cleaning procedures like Recrystallize, distill, wash down available.

The weight average molecular weights (M _w ) obtained are from 15,000 to 40,000, preferably from 17,000 to 36,000, more preferably from 17,000 to 34,000 g / mol, where M _{w is} the relative viscosity according to the Mark-Houwink correlation (JMG Cowie, Chemie und Physik der synthetischen Polymer, Vieweg textbook, Braunschweig / Wiesbaden, 1997, page 235) is determined.

The Polycarbonates can be specifically branched. Suitable branching agents are those for polycarbonate production known compounds having three or more functional groups, preferably those having three or more hydroxyl groups.

Some the useful compounds having three or more phenolic hydroxyl groups are, for example, phloroglucinol, 4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) -hepten-2, 4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) heptane, 1,3,5-tri- (4-hydroxyphenyl) -benzene, 1,1,1-tri- (4-hydroxyphenyl) -ethane, Tri- (4-hydroxyphenyl) phenylmethane, 2,2-bis (4,4-bis (4-hydroxyphenyl) cyclohexyl] -propane, 2,4-bis (4-hydroxyphenyl-isopropyl) -phenol and tetra (4-hydroxyphenyl) -methane.

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

preferred Branches are: 3,3-bis (3-methyl-4-hydroxyphenyl) -2-oxo-2,3-dihydroindole and 1,1,1-tri- (4-hydroxyphenyl) -ethane.

The Branches are used in amounts of from 0.02 to 3.6 mol%, based on the Dihydroxyarylverbindung used.

The Process for the preparation of polycarbonate by the transesterification process can be designed discontinuously or continuously. After the dihydroxyaryl compounds and the diphenyl carbonate, if necessary, with further compounds, present as a melt is in The presence of suitable catalysts started the reaction. Of the Sales or the molecular weight is at increasing temperatures and falling pressures in suitable apparatus and devices by discharging the the cleaving monohydroxyaryl compound increases until the desired final state is reached. By choice of the ratio Dihydroxyaryl compound to diphenyl carbonate, which by choosing the Procedure or plant given for the preparation of the polycarbonate Loss rate of the diphenyl carbonate over the vapors and possibly added compounds, such as a higher-boiling one Monohydroxyaryl compound, the end groups are in kind and concentration embossed.

Regarding the way in which plant and according to which method of the process There is no limitation and limitation.

Further There is no specific limitation and limitation on the temperatures, the Press and the catalysts used to the melt transesterification reaction between the dihydroxyaryl compound and the diphenyl carbonate, if appropriate also to perform other added reactants. Any condition is possible as long as the chosen ones Temperatures, pressures and catalysts a melt transesterification under correspondingly faster Allow removal of the cleaved Monohydroxyarylverbindung.

The Temperatures above the entire process is at 180 to 330 ° C, the pressures at 15 bar absolute to 0.01 mbar absolute.

Most of time a continuous procedure is chosen because it is beneficial to product quality.

Preferably is the continuous process for the production of polycarbonates characterized in that one or more Dihydroxyarylverbindungen with the diphenyl carbonate, if appropriate also other added reactants, using catalysts, after a precondensation without Separating the monohydroxyaryl compound formed in then adjoining it several reaction-evaporator stages at gradually increasing Temperatures and gradually falling pressures push the molecular weight up to the desired Size built up becomes.

The for the individual reaction-evaporator stages suitable devices, Apparatus and reactors are according to the process heat exchangers, Expansion apparatus, separators, columns, evaporators, stirred tanks and Reactors or other commercially available Apparatus which the necessary Dwell time at selected Provide temperatures and printing. The selected devices must the necessary heat input enable and be engineered to be the ever-growing one melt viscosities satisfy.

All Devices are over Pumps, piping and valves connected. The pipelines between all facilities should of course be as short as possible and the bends the lines as low as possible be kept to unnecessary extended To avoid residence times. Here are the outer, that is technical General conditions and concerns for Assemblies of chemical plants.

to execution the method according to a preferred continuous procedure can they Reactants either melted together or the solid Dihydroxyarylverbindung in the Diphenylcarbonatschmelze or the solid diphenyl carbonate is dissolved in the melt of the dihydroxyaryl compound or both raw materials are called melt, preferably directly from the Production, merged. The residence times of the separate melting of the raw materials, in particular those of the melt of the dihydroxyaryl compound become as short as possible set. The melt mixture, however, because of the comparison to the individual raw materials lowered melting point of the raw material mixture stay longer at correspondingly lower temperatures without sacrificing quality.

After that the catalyst is added, preferably dissolved in phenol, and the melt heated to the reaction temperature. This is at the beginning of the technical significant process for the production of polycarbonate from 2,2-bis (4-hydroxyphenyl) propane and diphenyl carbonate 180 to 220 ° C, preferably 190 to 210 ° C, most preferably 190 ° C. At residence times of 15 to 90 minutes, preferably 30 to 60 minutes, the reaction equilibrium is adjusted without the formed Hydroxyarylverbindung is removed. The reaction can be carried out at atmospheric pressure, but for technical reasons also with overpressure be driven. The preferred pressure in technical systems is 2 to 15 bar absolute.

The melt mixture is in a first vacuum chamber, the pressure of 100 to 400 mbar, preferably adjusted to 150 to 300 mbar, relaxed and then directly heated in a suitable device at the same pressure back to the inlet temperature. In the relaxation process, the resulting hydroxyaryl compound is evaporated with remaining monomers. After a residence time of 5 to 30 minutes in a sump original, if necessary with pumping at the same pressure and temperature, the reaction mixture is in a second vacuum chamber whose pressure is 50 to 200 mbar, preferably 80 to 150 mbar, relaxed and then directly in a suitable Device at the same pressure to a temperature of 190 to 250 ° C, preferably 210 to 240 ° C, more preferably 210 to 230 ° C, heated. Again, the resulting Hydroxyarylverbindung is evaporated with remaining monomers. After a residence time of 5 to 30 min in a sump template, possibly with pumped circulation, at the same pressure and temperature is the Reaction mixture in a third vacuum chamber whose pressure is 30 to 150 mbar, preferably 50 to 120 mbar, relaxed and directly thereafter in a suitable device at the same pressure to a temperature of 220 to 280 ° C, preferably 240 to 270 ° C, particularly preferably 240 to 260 ° C, heated. Again, the resulting Hydroxyarylverbindung is evaporated with remaining monomers. After a residence time of 5 to 20 minutes in a sump original, possibly with pumping at the same pressure and temperature, the reaction mixture is in a further vacuum chamber whose pressure at 5 to 100 mbar, preferably 15 to 100 mbar, particularly preferably 20 to 80 mbar , Relaxed and immediately thereafter in a suitable device at the same pressure to a temperature of 250 to 300 ° C, preferably 260 to 290 ° C, more preferably 260 to 280 ° C, heated. Again, the resulting Hydroxyarylverbindung is evaporated with remaining monomers.

The Number of these stages, here exemplarily 4, can vary between 2 and 6. The temperatures and pressures are correspondingly when changing the step to get comparable results. The in these Levels reached rel. viscosity of the oligomeric carbonate is 1.04 to 1.20, preferably 1.05 to 1.15, more preferably 1.06 to 1.10.

The Oligocarbonate is after a residence time of 5 to 20 min in one Sump template, if necessary, with pumping at the same pressure and the same Temperature as in the last flash / evaporator stage into a disk or basket reactor promoted and at 250 to 310 ° C, preferably 250 to 290 ° C, more preferably 250 to 280 ° C, when pressed from 1 to 15 mbar, preferably 2 to 10 mbar, at residence times from 30 to 90 minutes, preferably 30 to 60 minutes, further condensed. The product achieves a relative viscosity of 1.12 to 1.28, preferably 1.13 to 1.26, more preferably 1.13 to 1.24.

The leaving this reactor melt is in another disk or basket reactor to the desired final viscosity or brought the final molecular weight. The temperatures are 270 to 330 ° C, preferably 280 to 320 ° C, particularly preferably 280 to 310 ° C, the pressure 0.01 to 3 mbar, preferably 0.2 to 2 mbar, at residence times from 60 to 180 minutes, preferably 75 to 150 minutes. The rel. Viscosities are on the for the intended application necessary Level and are 1.18 to 1.40, preferably 1.18 to 1.36, more preferably 1.18 to 1.34. The function of the two Basket reactors can also be summarized in a basket reactor.

The vapors from all process stages are directly derived, collected and worked up. This workup is usually carried out by distillation, to high purities of the recovered To reach substances. This can, for example, according to DE-A 10 100 404 done. A recovery and isolation of the cleaved Monohydroxyarylverbindung in purest Shape is more economical and more ecological Of course. The monohydroxyaryl compound can be used directly for the preparation of a Dihydroxyaryl compound or a diaryl carbonate can be used.

The Disc or basket reactors are characterized by the fact that they At high residence times a very large, constantly renewing surface on the vacuum provide. The disk or basket reactors are corresponding the melt viscosities the products formed geometrically.

Suitable are, for example, reactors, as described in EP-A 1 253 163, or Two-shaft reactors, as described in WO-A 99/28 370.

The Oligocarbonates, also very low molecular weight, and the finished polycarbonates are usually using gear pumps, screws different Type or displacement pumps promoted special design.

Farther can the obtained polycarbonate to change properties with other conventional additives and additives (eg auxiliaries and reinforcing agents). The addition of additives and additives serves as an extension the service life (e.g., hydrolysis or degradation stabilizers), the Improvement of color stability (e.g., thermal and UV stabilizers), the simplification of the processing (for example demoulding, flow aids), improving the performance properties (e.g., antistatic agents), the improvement of flame retardancy, the influence of the optical Impression (e.g., organic colorants, pigments) or adaptation the polymer properties to specific loads (impact modifiers, finely divided minerals, pulps, quartz flour, glass and carbon fibers).

These additives and additives can be added individually or in any mixtures or several different mixtures of the polymer melt directly in the isolation of the poly mers or after melting of granules in a so-called compounding step.

Determination of composition of the carbonate forming reagent:

Of the Content of impurities is determined by gas chromatography (GC). To avoid the decomposition of DPC is used for the determination of DPC and of the phenol content the cool-on-column method used. Metal determinations are carried out by ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy).

Determination of the relative Viscosity:

The relative solution viscosity was in dichloromethane at a concentration of 5 g / l at 25 ° C.

Determination of the share on phenolic OH groups:

Of the Content of phenolic OH is obtained by IR measurement. To this The purpose is a differential measurement of a solution of 2 g of polymer in the 50th ml of dichloromethane Measure pure dichloromethane and the extinction difference at 3582 cm 1 determined.

Determination of the color number:

The Color number was as difference of absorbance at 420 nm and 700 nm in dichloromethane at a concentration of 2.4 g / 50 ml and a Layer thickness of 10 cm determined.

The Results are summarized in Table 1.

Comparative Example 1

In a 500 ml three-necked flask with stirrer, internal thermometer and Vigreux column (30 cm, mirrored) with bridge were 0.5 mol of bisphenol A, 0.55 mol of diphenyl carbonate and 0.002 mol of tetraphenylphosphonium phenolate weighed. At the same time, 5 ppm of o, o'-biphenylene carbonate based on diphenyl carbonate added. The apparatus was by applying vacuum and rinsing with Nitrogen (three times) freed from atmospheric oxygen and the mixture at 150 ° C melted. The temperature was raised to 190 ° C and the resulting phenol over 30 minutes distilled off. Then the pressure was regulated to 100 mbar and continued Distilled off the resulting phenol 20 minutes. In 10 minutes was the temperature at 235 ° C elevated and 15 minutes distilled off the resulting phenol. Then it became within 5 minutes the vacuum increased to 60 mbar and the Temperature kept for 15 minutes before coming within 10 minutes was increased to 250 ° C. At 250 ° C was over Distilled off the phenol for 15 minutes and then within 10 minutes the Reduced vacuum to 5 mbar. After another 15 minutes was within from 10 minutes to 280 ° C elevated. After another 15 minutes, the vacuum was reduced to 0.5 mbar and stirred for a further 15 minutes. Then increased in 10 minutes to 300 ° C and distilled from the resulting phenol for another 30 minutes. The Polycarbonate showed a pink color.

Comparative Example 2-12

Implementation like in Example 1. Instead of 5 ppm o, o'-biphenylene carbonate based on diphenyl carbonate were the impurities listed in Table 1 added based on diphenyl carbonate.

example 1

In a 500 ml three-necked flask equipped with stirrer, internal thermometer and Vigreux column (30 cm, mirrored) with bridge, 0.5 mol of bisphenol A, 0.55 mol of diphenyl carbonate and 0.002 mol of tetraphenylphosphonium phenolate were weighed. The diphenyl carbonate used contained 0.5 ppm phenyl salicylate, 0.5 ppm o-phenoxybenzoic acid, 2 ppm phenyl-o-phenoxybenzoate, 98 ppm Phenylpiperidinurethan, less than 1 ppm phenyl chloroformate, 47 ppm o-Kresylphenylcarbonat and less than 1 ppm chlorine. The apparatus was freed from the atmospheric oxygen by applying a vacuum and purging with nitrogen (three times) and the mixture was melted at 150 ° C. The temperature was raised to 190 ° C and the resulting phenol over 30 minutes distilled off. The pressure was then adjusted to 100 mbar and the resulting phenol distilled off for a further 20 minutes. In 10 minutes, the temperature was raised to 235 ° C and distilled off for 15 minutes, the resulting phenol. Then the vacuum was raised to 60 mbar over 5 minutes and the temperature was maintained for 15 minutes before being raised to 250 ° C. within 10 minutes. At 250 ° C, the phenol was distilled off over 15 minutes and then reduced within 10 minutes, the vacuum to 5 mbar. After a further 15 minutes, the mixture was raised to 280 ° C. within 10 minutes. After another 15 minutes, the vacuum was reduced to 0.5 mbar and stirred for a further 15 minutes. The mixture was then increased to 300 ° C. in the course of 10 minutes and the phenol formed was distilled off for a further 30 minutes.

Example 2

Out a template were 9000 kg / h melt mixture, consisting of 4600 kg of diphenyl carbonate / h (21473 mol / h) containing 0.5 ppm of phenyl salicylate, 0.5 ppm of o-phenoxybenzoic acid, 2 ppm phenyl-o-phenoxybenzoate, 101 ppm phenylpiperidinurethane, smaller 1 ppm of phenyl chloroformate, Contained 37 ppm of o-cresylphenyl carbonate and less than 1 ppm of chlorine, and 4400 kg of bisphenol A / h (19273 mol / h) with the addition of 0.2628 kg of a phenol adduct of tetra-phenylphosphonium phenolate / h (.771 mol / h) dissolved in 1.87 kg of phenol / h pumped through a heat exchanger, heated to 190 ° C and passed through a residence column at 12000 mbar and 190 ° C. The mean residence time was 45 minutes.

The Melt was then over a relaxation valve in a below 200 mbar separator directed. The outflowing Melt was in a, also below 200 mbar standing, falling film evaporator back to 190 ° C heated and caught in a template. After a residence time of 20 Minutes, the melt was in the next three, the same structure Pumped stages. The conditions in the 2nd, 3rd and 4th stages were 100, 75 and 60 mbar; 220, 255 and 270 ° C and 20, 10 and 10 minutes. The resulting oligomer had a rel. Viscosity of 1.068. All vapors were over Guided pressure controls in a column under vacuum and derived as condensates.

The Oligomer was in a downstream basket reactor at 280 ° C and 7.0 mbar at a residence time of 45 minutes to a high molecular weight Condensed oligomers. The relative viscosity was 1.134. The vapors were condensed.

The Oligomers were used in another basket reactor at 295 ° C and 1.3 mbar to a relative viscosity of 1.278 condensed. The mean residence time was 130 minutes determined. The vapors are condensed behind or in the vacuum system. The total residence time was 274 minutes.

Example 3

Procedure as in Example 1. Instead of 5 ppm o, o'-biphenylene carbonate based on diphenyl carbonate 2000 ppm Phenylpiperidylurethan were added. Table 1

Out Comparative Examples are unique compared to Example 1 a negative effect of the added impurities either on the color of the polycarbonate or on the molecular weight build up detect. Example 2 illustrates that a melt polycarbonate of excellent color by the method of the invention using of the carbonate forming reagent can be obtained. Example 3 shows that there are impurities that have no negative effect.

Example 4-7

The carbonate formation reagent containing a diphenyl carbonate used in the method of the present invention was analyzed for the content of impurities to obtain the results shown in Tables 2 and 3. Table 2

• (n.g. = not measured, neg. = negative, undetectable),
• ^a : double determination

For example 7, the metal content was determined: TABLE 3

Claims (5)

A process for the preparation of polycarbonate according to the melt transesterification process by reacting at least one aromatic dihydroxyaryl compound and a carbonate formation reagent in the melt at least in the presence of a catalyst, characterized in that a carbonate formation reagent is used which contains at least: at least 99.9% of a diaryl carbonate of the general formula ArO (C = O) OAr - 0.5 to 500 ppm of a hydroxyaromatic of the general formula ArOH - 2 to 300 ppm of arylurethanes of the general formula ArO (C =O) NR ¹ R ² - 2 to 100 ppm in total of (methylaryl ) arylcarbonates of the general formula (CH ₃ Ar ¹ ) O (C = O) OAr - at most 100 ppm in total of (aryloxy) arylcarboxylic acid derivatives of the general formula Ar ² -Ar ³ COOZ ¹ - at most 100 ppm in total of hydroxyarylcarboxylic acid derivatives of the general formula Z ² O-Ar ⁴ COOAr - a maximum of 10 ppm in total of o, o'-biphenylenecarbonate, dibenzofuran and biphenyldiol derivatives of the general en Formula Z ³ OAr ⁵ -Ar ⁵ OZ ⁴ - a maximum of 10 ppm in total of Aryloxyhydroxyarylderivaten the general formula Ar ⁶ OArOZ ⁵ - a maximum of 10 ppm in total of Halogenhydroxyaromatenderivaten the general formula (X) _m Ar ⁷ OZ ⁶ - 10 ppm in Total of o-arylene carbonate, of dihydroxyaromatics and derivatives of the general formula Ar (OZ ⁷ ) ₂ - at most 10 ppm of alkylaryl carbonates of the general formula ArO (C = O) OR ³ - at most 10 ppm in total of ethers of the general formula ArOR ⁴ - maximum of 5 ppm of aryl chloroformate of the general formula Cl (C = O) OAr - in each case not more than 1 ppm of benzofuran-1,3-dione, diphenyl oxalate and p-chlorobenzoate - a maximum of 10 ppm total chlorine content - in each case not more than 1 ppm of Pb, Cu , Zn, Pd, Sn and Ti, wherein Z ¹ to Z ⁷ each independently represent one or more elements of the group consisting of -H, -Ar, or - (C = O) OAr, Ar, Ar ¹ to Ar ⁷ each independently an aryl radical, X is -Cl or -Br, m is an integer of 1 to 3 and R ¹ to R ^{4 are} each independently a linear, cyclic or branched alkyl radical having 1-20 C atoms are where R ¹ and R ² together possibly form a cycle, stand. Method according to claim 1, characterized in that that the carbonate forming reagent is prepared by at least the following steps: (a) reaction of an alkaline aqueous solution a compound ArOH with a solution of phosgene in an inert organic solvents, optionally in the presence of an organic catalyst, at least under formation a diaryl carbonate (b) At least simple, preferably multiple, extraction of the step (A) Reaction mixture obtained with an aqueous solution (c) Treatment of according to step (b) the obtained organic extract containing the solvent with a residual moisture of at least 0.5% by weight, by distillation and / or steam distillation with introduction of water or Water vapor at temperatures of 40 to 180 ° C, preferably 50 to 150 ° C, especially preferably 60 to 135 ° C. (D) Purification by distillation according to step (c) the resulting reaction mixture, which is optionally concentrated, wherein the diaryl carbonate removed as overhead product or in the side stream and at least 0.2, preferably at least 0.3, more preferably at least 0.5% by weight (based on the ArOH mass used) of the bottom product is removed. Method according to one of claims 1 or 2, characterized in that Ar, Ar ¹ to Ar ⁷ phenyl, R ³ and R ^{4 is} a linear C ₁ -C ₆ alkyl radical and R ¹ and R ² together represent a piperidyl radical. Method according to one of claims 1-3, characterized in that the carbonate forming reagent contains - at least 99.95% diphenyl carbonate, - 0.5 to 500 ppm phenol, - 4 to 150 ppm Phenylpiperidylurethan, - 3 to 80 ppm in total of (methylphenyl ) phenylcarbonates, - a maximum of 50 ppm phenyl o-phenoxybenzoate, - a maximum of 10 ppm Phenylcsalicylat, - a maximum of 5 ppm in total of o, o'-biphenylene carbonate, dibenzofuran and biphenyldiol derivatives of the formula Z ³ OAr ⁵ -Ar ⁵ OZ ⁴ - 5 maximum ppm in total of Aryloxyhydroxyarylderivaten of the formula Ar ⁶ OArOZ ⁵ , - a maximum of 5 ppm in total of Halogenhydroxyaromatenderivaten of formula (X) _m Ar ⁷ OZ ⁶ , - a maximum of 5 ppm in total of o-arylene carbonate, of dihydroxyaromatics and derivatives of the formula Ar (OZ ⁷ ) ₂ - a maximum of 5 ppm of alkylaryl carbonates ArO (C = O) OR ³ , - a maximum of 5 ppm in total of ethers ArOR ⁴ , - a maximum of 3 ppm phenyl chloroformate, - a maximum of 1 ppm each of benzofuran-1,3-dione , Diphenyloxalate, p-Ch lorbenzoate, - at most 10 ppm total chlorine content - at most 1 ppm each of Pb, Cu, Zn, Pd, Sn and Ti, where Z ¹ to Z ^{7 are} each independently one or more elements of the group -H, -Ar or - (C = O) OAr, Ar, Ar ¹ to Ar ^{7 are} each independently an aryl radical, -X is -Cl or -Br, m is an integer between 1 and 3 and R ¹ to R ^{4 are} each independently one linear, cyclic or branched alkyl radical having 1-20 C atoms, wherein R ¹ and R ² together form a cycle, stand. Method according to claim 2, characterized in that that a phenol is used which contains a maximum of 100 ppm cresols, maximum 10 ppm dihydroxybiphenyls, maximum 10 ppm phenoxyphenols and contains at most 100 ppm of dihydroxybenzenes.