NL194948C - Process for the preparation of aromatic polycarbonates. - Google Patents

Description

1 194948

Process for the preparation of aromatic polycarbonates

The invention relates to a process for the preparation of aromatic polycarbonates with molecular weights (Mw) of 15,000 to 200,000 and contents of terminal OH groups of less than 250 ppm by transesterification for carbon dioxide diesters with diphenols and optionally melting branching agents into oligocarbons bonates with a Mw of 2,000 to 10,000 and contents of terminal OH groups of 20 to 50 mol%, crystallization of these oligocarbonates and polycondensation of the crystalline oligocarbonates in the solid phase in the presence of a entrainer for the polycondensation cleavage products, which entrainer does not dissolve or melt the crystalline oligocarbonates at a temperature between the glass transition temperature and the melting temperature of the crystalline oligocarbonates.

Such a method is known from the European patent application EP-A-0.338.085.

The preparation of aromatic oligo / polycarbonates according to the transesterification process in the melt has also already been described, for example, in European patent applications 360,578 and 351,168, as well as in German patent specification DP 1,031,512.

The crystallization of oligo / polycarbonates is described, for example, in J. Polymer Sci. part A-2, 4, 327 (1966); J. Polymer Sci. Phys. Ed. 14, 1367 (1976); J. Polymer Sci. Polymer Letters Ed. 16, 419 (1978); U.S. Patent Nos. 3,112,292, 4,631,338, Polymer Engineering and Science 16, 4, 276 (1976) and European Patent Application 338,085.

The solid phase polycondensation of oligocarbonates prepared by transesterification in the melt is described in European patent application 338,085, as well as in the PCT application WO 90/07536.

Both European patent application 338,085 and PCT application WO 90/07536 describe that greatly reduced pressure or large amounts of gaseous entraining agent or a combination thereof can be used to remove the cleavage products from the polycondensation. A disadvantage of using strongly reduced pressure or large amounts of gas-entraining agent or a combination thereof is that this requires large investments for technical equipment. In European patent application 338,085, inert gases such as nitrogen, argon, helium, carbon dioxide and lower hydrocarbon gases are mentioned as examples of gaseous entraining agents. In WO 90/07536, in addition to the gaseous entraining agents mentioned above, gaseous acetone is also mentioned. The boiling points of lower hydrocarbon gases and acetone (56 ° C at 1 bar) show that these substances are always completely gaseous at the temperatures at which the polycondensation is usually carried out, i.e. 180-225 ° C.

It has now surprisingly been found that the use of suitable liquid organic entraining agents makes it possible in a simple manner to remove the cleavage products formed during condensation into large-molecular polycarbonate. As a result, the use, purification and recycling of large quantities of gas and a costly technique can also be avoided for the process under reduced pressure.

The method according to the preamble is therefore characterized in that the polycondensation is carried out in a liquid entraining agent at such a pressure that the entraining agent boils, the entraining agent being a hydrocarbon with 8 to 12 carbon atoms, the weight ratio of entraining agent to oligocarbonate 1: 99 to 99: 1.

Organic liquid entraining agents within the meaning of the process according to the invention are: aliphatic hydrocarbons with 8 to 12 carbon atoms, and optionally aromatic halogen and / or aliphatic groups substituted with 8 to 12 carbon atoms, with 1 halogen atom and up to 45 alkyl substituents.

Particularly preferred organic liquid entraining agents are: mesitylene, cymene, diisopropylbenzene, limonene, iso-octane, isononane, undecane, dodecane and isododecane.

The aromatic oligocarbonates prepared as an intermediate step in the process according to the invention are understood to be the known homo-oligocarbonates, co-oligocarbonates and mixtures of these oligocarbona-50, which are derived, for example, from the following diphenols: hydroquinone, resorcinol, dehydroxybiphenyl , bis (hydroxyphenyl) alkanes, 55 bis (hydroxyphenyl) cycloalkanes, bis (hydroxyphenyl) sulfides, bis (hydroxyphenyl) ethers, 194948 2 bis (hydroxyphenyl) ketones, bis (hydroxyphenyl) sulfones, bis (hydroxyphenyl) sulfoxides, oc, a ' bis (hydroxyphenyl) diisopropylbenzenes, as well as core-alkylated and / or halogenated analogues.

Preferred defenols are, for example: 2,2-bis (4-hydroxyphenyl) propane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane, 1,1-bis (4-hydroxyphenyl) -p -diisopropylbenzene, 2,2-bis- (3-methyl-4-hydroxyphenyl) propane, 2,2-bis- (3-chloro-4-hydroxyphenyl) propane, bis- (3,5-dimethyl-4-hydroxyphenyl) ) -methane, 2,2-bis- (3,5-dimethyl-4-hydroxyphenyl) -propane, bis- (3,5-dimethyl-4-hydroxyphenyl) sulfone,

2,4-bis- (3,5-dimethyl-4-hydroxyphenyl) methyl butane

1,1-bis- (3,5-dimethyl-4-hydroxyphenyl) -p-diisopropylbenzene, 2,2-bis- (3,5-dichloro-4-hydroxyphenyl) -propane, 2,2-bis- (3,5-dibromo-4) -hydroxyphenyl) -propane, and 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane.

Particularly preferred diphenols are 4,4'-dihydroxy diphenyl, 4,4'-dihydroxyphenyl sulfide, 2,2-bis- (4-hydroxyphenyl) -propane, 2,2-bis- (3,5-dimethyl-4-) hydroxyphenyl) propane, 2,2-bis- (3,5-dichloro-4-hydroxyphenyl) propane, 2,2-bis- (3,5-dibromo-4-hydroxyphenyl) propane, 1,1-bis- (4 -hydroxyphenyl) -cyclohexane and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane.

Very particularly preferred are polycarbonates containing up to 50 mol% and moreover bisphenol A of the aforementioned diphenols.

The oligocarbonates can be branched by using small amounts of branching agents. Some suitable branching agents are: floroglucinol, 4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) -hepten-2, 4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) ) heptane, 1,3,5-tri- (4-hydroxyphenyl) -benzene, 1,1,1-tri- (4-hydroxyphenyl) -ethane, tri- (4-hydroxyphenyl) -phenylmethane, 2,2-bis- [4,4-bis- (4-hydroxyphenyl) -cyclohexyl] propane, 2,4-bis- (4-hydroxyphenylisopropyl) phenol, 2,6'bis- (2-hydroxy-5'-methylbenzyl) - 4-methylphenol, 2- (4-hydroxyphenyl) -2- (2,4-dihydroxyphenyl) -propane, hexa- (4- (4-hydroxyphenylisopropyl) -phenyl) orthoterephthalic acid ester, tetra- (4-hydroxyphenyl) -methane, 45 tetra- (4- (4-hydroxyphenylisopropyl) -phenoxy) -methane, 1,4 * bis- (4 ', 4 ", dihydroxy-triphenyl) -methyl) -benzene, and in particular a, a', a" - tris- (4-hydroxyphenyl) -1,3,5-triisopropylbenzene.

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

The branching agents which may also be used in an amount of 0.05 to 2 mol%, based on the diphenols used, can be used together with the diphenols.

Suitable carbonic acid diesters for the preparation of the oligocarbonates are diaryl carbonates, such as dikresyl carbonates, chlorophenol carbonates, isopropylphenyl carbonates, preferably diphenyl carbonate.

The ratio between the reactants diphenol and carbonic diester is 1: 1.01 to 1.30 mole, preferably 55: 1: 1.02 to 1.15 mole.

The aromatic oligocarbonates from the transesterification in the melt must have average molar masses Mw from 2000 to 10,000, determined by measuring the relative viscosity of the solution in dichloromethane or in mixtures of equal amounts by weight of phenol / o-dichlorobenzene or by measuring scattered light, and levels of terminal OH groups of less than 50 and more than 20 mol%, preferably between 45 and 30 mol%.

It may be expedient to accelerate the transesterification to the oligocarbonates by small amounts (0.05 ppm to 0.1% by weight) of catalysts. Suitable catalysts include LiOH, NaOH, Na 2 CO 3, Ca (OH) 2, CaCO 3, tetraalkyl titanate, dibutyl dibutoxytin, quinoline, triphenylphosphine, boric acid and esters, tetralalkylammonium hydroxide, Mg (OH) 2 or combinations of these catalysts. Traces (<1 ppm) of alkali metal and alkaline earth metal hydroxides are usually sufficient.

The crystallization of the oligocarbonates is possible according to the methods known from the literature; For example with the aid of solvents, for example acetone, dichloromethane or dimethyl carbonate, or by thermal crystallization, according to the aforementioned literature.

The solid phase condensation according to the process of the invention is generally carried out in such a way that the crystalline oligocarbonates are dispersed in the entraining agents, the weight ratio between entraining agent and oligocarbonate being 1:99 to 99: 1, preferably 95: 5 to 20:80 is 15. In particular, undecane is used as the entraining agent, the weight ratio between undecane and oligocarbonate being 90:10.

This suspension is then heated to a temperature that is between the glass transition temperature and the melting point of the crystal. For bisphenol A polycarbonate, this range is, for example, between 150 and 230 ° C, preferably between 160 and 230 ° C, in particular preferably between 180 and 225 ° C.

The entrainer must be brought to the boil during the condensation in the solid phase.

If the boiling point is too low, it is possible to work under a suitable underpressure if it is too high.

The cleavage product, for example phenol, must be removed from the passing distillate. This can for instance take place by extraction with a polar compound immiscible with the entraining agent, such as water, ethylene glycol, glycerol, formamide or tetramethylene sulfone. The extracted phenol can be recovered by distillation. Traces of the extractant can optionally be removed by distillation from the entrainer. For example, water can be easily removed by azeotropic distillation.

A further possibility for the purification of the entraining agent consists of the adsorption of the phenol to, for example, aluminosilicates or active carbons.

The purified entrainment agent is returned to the boiling suspension and thus recycled until the required amount of phenol is removed from the solid phase and the polycarbonate has the intended molecular weight.

The aluminosilicates to be used in the process according to the invention are known per se from the literature, see for example Kirk-Othmer "Encyclopedia of Chemical Technology" 2nd Ed. 1964, vol. 5, pp. 541-461.

Preferred are aluminosilicates of the zeolite type.

The zeolites to be used are crystalline aqueous aluminosilicates, synthesized or naturally occurring, with a skeletal structure (see DW Breek in "Zeolite Molekular Sieves", Wiley 40 Interscience, 1974, pp. 133 to 180; Ullmans Enzyklopedie of Technical Chemistry, 4th edition, vol. 17, pages 9 to 18, Chemie report, Weinheim, New York).

Activated carbon that can be used in purifying the entraining agent is activated carbon that can be prepared from various carbon-yielding precursors. The activation methods can also be very varied. Activated carbons are thereby obtained which have BET-45 surfaces of 200 to 3000 m2 g, preferably of 300 to 2000 m2 g, in particular preferably of 500 to 1500 µg.

The preparation of the active carbons is known to those skilled in the art and is described in the literature (Ullmann's Enzyklopedia of Industrial Chemistry, 5th Ed. Vol. A 5, 1986, pages 124 to 140 and the literature cited there).

During the solid phase condensation, temperature control must ensure that the suspended particles of the crystalline oligo- and polycarbonate do not stick or cake to each other. The reaction of the solid phase condensation, depending on the type, molecular weight and crystallinity of the oligocarbonate used, generally lasts between 2 to 20 hours, preferably between 4 hours and 12 hours.

55 According to the process of the invention, for the solid-phase condensation in an organic entraining agent, polycarbonates with Mw values of 15,000 to 200,000, preferably from 19,000 to 60,000 and contents of OH end groups of less than 250 ppm are obtained. (Mw determined by 194948 4 measurement of the relative viscosity of the solution in dichloromethane).

The polycarbonates obtained according to the process of the invention are obtained in crystalline form and can be converted by the usual processing method via the melt into the amorphous state and processed into randomly shaped bodies, for example into semi-finished products, plates, films and vessels, on the usual devices which, like the known thermoplastic aromatic polycarbonates, are used technically, for example in the electrical industry or in the automobile construction.

Before or during the processing of the polycarbonates to be obtained according to the invention, the usual additives, such as stabilizers, release agents, fire-resistant agents, pigments, finely divided mineral substances and fiber materials, can be added in the usual manner and in the usual amount, for example alkyl and aryl phosphites, phosphates, phosphans, low molecular weight carboxylic acid esters, halogen compounds, salts, chalk, quartz flour, glass and carbon fibers.

Furthermore, the polycarbonates obtained according to the invention can also mix other polymers, for example polyolefins, polyurethanes or polystyrenes.

These mixtures can also be prepared in the usual way, processed into shaped bodies and used in a manner known for these mixtures.

Examples

EXAMPLE 1

A) Requirement for the synthesis of an oligocarbonate

A 2 liter flat ground vessel with heating mantle, opening in the bottom, column, gas supply and discharge, and intensive stirrer is filled with 684.9 g (3 moles) of bisphenol A, 661.3 g (3.1 moles) of diphenyl carbonate and 8 mg (19.58 mole ppm Na) sodium bisphenolate as a catalyst. The reaction vessel is gassed five times with nitrogen and evacuated to remove the oxygen from the air. The reaction vessel is heated to 250 ° C under a light stream of nitrogen and stirred as soon as the reaction components are melted. The pressure is then reduced over a period of 90 minutes, taking into account a continuous distillation rate, to 1 mbar, so that after a further 5 minutes the oligocarbonate obtained has reached a relative viscosity of the solution of 1.080.

B) Crystallization of the oligocarbonate

The cooled oligocarbonate thus obtained is now ground in a universal mill from Jahnke und Kunkel GmbH & Co. KG, IKA-Werk, type M 20, for 30 seconds and then crystallized by introduction into acetone. The crystalline oligocarbonate is filtered and dried.

C) Polycondensation in the solid phase

180 g of undecane are now added to 20 g of this oligomer in a 500 ml three-necked flask with an inner thermometer and extraction device with a reflux condenser mounted. In the extraction device, 10 g of zeolite K-Y is used as the molecular sieve for the cleavage products. The mixture is now heated at 180 ° C for 1 hour under atmospheric 40 pressure and subsequently at 200 ° C for 7 hours. A crystalline colorless polycarbonate with a relative viscosity in solution (dichloromethane, 25 ° C, 5 g / l) of 1.254 is obtained.

EXAMPLE II

As Example 1, only in the final phase of the preparation of the oligocarbonate, instead of 45 minutes, a greatly reduced pressure is applied for 8 minutes. The oligocarbonate obtained has reached a relative viscosity of the solution of 1.110.

This oligocarbonate is reacted according to the procedure according to example I. A crystalline colorless polycarbonate with a relative viscosity in solution (dichloromethane, 25 ° C, 5 g / l) of 1.296 is obtained.

Example III

As Example 1, only in the last phase of the preparation of the oligocarbonate, instead of 5 minutes, a greatly reduced pressure is applied. The oligocarbonate obtained has reached a relative viscosity in solution of 1.065.

This oligocarbonate is reacted according to the procedure from example I. A crystalline 55 colorless polycarbonate with a relative viscosity in solution (dichloromethane, 25 ° C, 5 g / l) of 1.222 is obtained.

Claims (2)

Process for the preparation of aromatic polycarbonates with molecular weights (Mw) of 15,000 to 200,000 and contents of terminal OH groups of less than 250 ppm by transesterification for carbon dioxide diesters with diphenols and optionally branching agents in the melt to form oligocarbonates with an Mw of 2,000 up to 10,000 and contents of terminal OH groups of 20 to 50 mol%, crystallization of these oligocarbonates and polycondensation of the crystalline oligocarbonates in the solid phase In the presence of a entraining agent for the cleavage products of the polycondensation, which entrainer does not dissolve the crystalline oligocarbonates or melting, at a temperature between the glass transition temperature and the melting temperature of the crystalline oligocarbonates, characterized in that the polycondensation is carried out in a liquid entraining agent at such a pressure that the entraining agent boils, the entraining agent boiling a hydrocarbon with 8 to 12 carbon atom is n, wherein the weight ratio of entrainer to oligocarbonate is 1:99 to 99: 1. Method according to claim 1, characterized in that undecane is used as the entraining agent, the weight ratio between undecane and oligocarbonate being 90:10 to 30:70.