DE1189269B - Process for the production of polycarbonates - Google Patents

Description

Process for the production of polycarbonates It is known, polycarbonates by preparing phosgene with a bisphenolalkane, -cycloalkane or -aralkane or its derivatives that contain a halogen atom on the aromatic ring, implements.

It is known that in the manufacture of such polycarbonates first a mixture of a bisphenol, an aqueous caustic alkali solution, an organic one Solvent for phosgene, in which bisphenol polycarbonates are soluble, and a catalyst that can increase the molecular weight of the polycarbonate causes, produced. Quaternary ammonium bases are generally used as catalysts or a tertiary amine is used. The bisphenol can be complete or incomplete be dissolved in the aqueous alkali solution as the alkali salt of bisphenol. In this Mixture is then introduced phosgene gas to the polycarbonate of the bisphenol form. After the introduction of phosgene has ended, the reaction mixture becomes ordinary circulated or stirred for a certain time so that the existing low molecular weight Polycarbonate achieved the desired higher molecular weight.

In this way, polycarbonates with an extremely high molecular weight are obtained. For most uses, however, it is desirable to increase molecular weight interrupt at reasonably defined average molecular weights. Since this becomes too uniform with repeated implementation of the polycarbonate production and reproducible values is to lead, the one to be treated with phosgene has already been implemented Mixture mixed with a chain terminator, which with the end groups of the growing Polycarbonate chain reacts and limits this growth. As such a chain terminator are known to be monohydric phenols, e.g. B. the actual phenol, or substituted Phenols such as p-tert-butylphenol, cyclohexylphenol and 4-oxyphenyl-4'-methoxyphenyl-2,2-propane, used. In general, however, the phenols also react with the catalysts, which should promote the molecular weight growth of the polycarbonates. This will especially at relatively high catalyst concentrations, namely from about 1 mole percent or more of the catalyst based on the bisphenol, a large amount of the added phenol consumed by reaction with the catalyst. So it is not possible, a uniform and reproducible control of the molecular weight growth of polycarbonates. When to achieve a satisfactory control the molecular weight, however, worked at lower catalyst concentrations longer reaction times and / or higher temperatures are necessary to Obtain polycarbonates with a certain molecular weight.

The invention now relates to a process for the production of polycarbonates by reacting phosgene with a mixture of a bisphenol of the general formula in which R is an alkylene, a cycloalkylene or an aralkylene radical, R 'is an alkyl radical and n is zero or whole numbers from 1 to 4, the aromatic rings can also be substituted by halogen, an aqueous alkali metal hydroxide solution, an organic solvent for the phosgene, in which the polycarbonate obtained is soluble, a catalyst and a small amount of a monohydric phenol as a chain terminator. This process is characterized in that the monohydric phenol is fed to a mixture of the bisphenol, the alkali metal hydroxide solution, the organic solvent and the catalyst at the same time as the phosgene and at approximately the same rate as the phosgene.

The monohydric phenol is obtained in amounts of 1.5 to 5 mole percent on the bisphenol.

Suitable bisphenols are e.g. B. (4,4'-Dioxy-diphenyl) -methane, 2,2- (4,4'-Dioxy-diphenyl) -propane (also known as bisphenol A), 1,1- (4,4'-dioxy-diphenyl) -cyclohexane, 1,1- (4,4'-dioxy-3,3'-dimethyl-diphenyl) -cyclohexane, 2,2- (2,2'-Dioxy-4,4'-di-tert-butyl-diphenyl) propane.

3.4- (4.4'-Dioxy-diphenyl) -hexane, 1,1- (4,4'-Dioxy-diphenyl) -1-phenyl-ethane, 2,2- (4,4'-Dioxy-diphenyl) -butane, 2,2- (4,4'-Dioxy-diphenyl) -pentane, 3,3- (4,4'-Dioxy-diphenyl) -pentane , 2,2- (4,4'-Dioxy-diphenyl) -3-methyl-butane, 2,2- (4,4'-Dioxy-diphenyl) -hexane, 2,2- (4,4'-dioxy- diphenyl) -4-methyl-pentane, 2,2- (4,4'-dioxy-diphenyl) -heptane, 4,4- (4,4'-dioxy-diphenyl) -heptane, 2,2- (4,4'-dioxy-diphenyl) -tridecane , 4,4'-dioxy-3,3'-dichloro-diphenyl-2,2-propane, 4,4'-dioxy-3,3 ', 5,5'-tetrabromo-diphenyl-2,2-propane or their mixtures. Preferably the amount of catalyst is from about 0.1 to about 2.2 mole percent, based on the bisphenol, so that the polycarbonate grows rapidly to the desired molecular weight at low temperatures of about 10 to 50 ° C is reached.

The polycarbonates which can be produced according to the invention have molecular weights in the range from about 10,000 to 30,000. They can be used for the production of compression-molded articles or coating compositions.

In the following, the invention will be explained in more detail by means of examples. The specified molecular weights are calculated from the outflow times of a 0.1% polycarbonate solution in ethylene chloride and the ethylene chloride solvent in an Ostwald-Fenske viscometer at 25 ° C. using the following equations: Ni = N, - 0.02, in which N = reduced viscosity, Ni = intrinsic viscosity, MW = molecular weight, T = outflow time of the polycarbonate solution, ' = inflow time of the solvent, C = concentration of the polycarbonate in the solution in granules per 100 ml of solvent. If one plots the values of MW (as ordinate) with different values of Ni (as abscissa) on an ordinary logarithmic log-log paper, a straight line is obtained. which is used for direct reading of the molecular weight.

EXAMPLE 1 A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping funnel and gas inlet tube was charged with 500 ml of water, 31.5 g of sodium hydroxide and 57 g of bisphenol A with constant introduction of nitrogen. The mixture was stirred until the caustic soda and bisphenol A had dissolved in the water, after which the solution was cooled to room temperature. Then 508 ml of ethylene dichloride were added to the reaction vessel and 6.4 ml of a 10% aqueous benzyltriethylammonium chloride solution were added as a catalyst, which corresponded to a catalyst content of 1.13 mol percent, based on bisphenol A. The nitrogen flow was interrupted and 27.5 g of phosgene were bubbled into the stirred mixture as a gas and 0.64 g of phenol (2.7 mol percent, based on bisphenol A) dissolved in 64 ml of ethylene dichloride was added to the reaction mixture, both the phosgene and the phenol solution being added to the reaction mixture Over the course of an hour were fed at a steady rate.

The reaction mixture was cooled during this time to keep it at Leave 30 ° C. After the addition of the phosgene gas and the phenol was complete The reaction mixture is stirred for a further 15 minutes to reduce the molecular weight of the ethylene dichloride to allow dissolved polycarbonate to grow. The resulting solution of polycarbonate in ethylene dichloride was separated from the aqueous phase with dilute hydrochloric acid and then washed with water. This washed solution was used for precipitation of the polycarbonate 300 ml of acetone and then 500 ml of methanol are stirred in. That Solid polycarbonate was filtered off and dried in air at 120.degree. The dried one Polycarbonate had a molecular weight of 28,000. Comparative Experiment A In one further experiment according to the method described in Example 1 and using of the same reaction mixture, but without the addition of the one dissolved in the ethylene dichloride Phenol, the polycarbonate had a molecular weight of 49,000.

COMPARATIVE EXPERIMENT B If the same conditions as in Example 1 and the same reaction mixture were used, but instead of the phenol solution in ethylene dichloride, everything was passed into the reaction mixture before the phosgene gas was introduced, a polycarbonate with a molecular weight of 86,000 was obtained.

Examples 2 to 7 The same apparatus was used and after worked the same procedure as in Example 1, but now the aqueous Alkali solution contained 35.7 g of NaOH and 500 ml of ethylene chloride as Solvents for the phosgene and polycarbonate were used. The one in table 1 specified amounts of phenol were given as a 1 o (above solution in methylene chloride with more uniform Rate added to each reaction mixture over the course of one hour, with during this time 30 g of phosgene were bubbled into the reaction mixture. In connection to the introduction of phosgene, the reaction mixture was a further hour Stirred at 30'C.

The results of the individual examples are listed in Table I below, the amounts of phenol added to the reaction mixture being listed in mol percent based on bisphenol A, and the molecular weights of the polycarbonates obtained. Table 1 Example mole percent phenol molecular weight of polycarbonate 2 1.35 50,000 3 2.70 25000 4 3.00 23000 5 3.38 21000 6 3.87 16000 7 4.51 14000 COMPARATIVE EXPERIMENT C Table 2 below shows the molecular weights of the polycarbonates produced by the process of Examples 2 to 7, but the stated amounts of phenol dissolved in methylene dichloride were added to the reaction mixture before the phosgene was added and not during the phosgene treatment. Table 2 Mole percent phenol molecular weight of polycarbonate 0.00 50000 0.27 57000 2.70 53000 8.10 59000 The values from Tables 1 and 2 clearly show that the addition of the phenol chain terminator during the phosgene treatment changes the molecular weight of the polycarbonate obtained inversely to the mole percent of the chain terminator used. According to the invention, polycarbonates with the desired lower molecular weight can therefore be obtained. If, on the other hand, the monohydric phenol (chain terminator) is added to the reaction mixture before the phosgene treatment, as has been the case up to now, the bisphenol polycarbonates have essentially the same or even higher molecular weights than if no chain terminator is used, and there is no consistent relationship between the molecular weight of the Polycarbonates and the amount of monohydric phenol used.

Other monohydric phenols, such as o-cresol, o-phenylphenol, p-benzylphenol, Nonylphenol can be used in place of the phenol used in the examples will.

Claims (1)

Claim: Process for the production of polycarbonates by reacting phosgene with a mixture of a bisphenol of the general formula in which R is an alkylene, cycloalkylene or aralkylene radical, R 'is an alkyl radical and n is zero or whole numbers from 1 to 4, the aromatic rings can also be substituted by halogen, an aqueous alkali metal hydroxide solution, an organic solvent for Phosgene, in which the polycarbonate is soluble, a catalyst and a small amount of a monohydric phenol, characterized in that the monohydric phenol is a mixture of the bisphenol, the caustic alkali hydroxide solution, the organic solvent and the catalyst simultaneously with the phosgene and with about the the same speed as the phosgene supplies. Referred to U.S. Patent No. 2,970,131.