DE4039023A1 - Two=stage prodn. of halogen-free aromatic polycarbonate - by interfacial precondensation using halogen-free organic solvent then melt or solid phase condensation - Google Patents

Abstract

2-Stage prodn. of halo-free aromatic polycarbonate (I) involves: (1) prodn. of a partly crystalline oligomeric precondensate (II); and (2) further condensn. to high mol. (I) in the melt or in the solid phase. Claims also cover (I) produced in this way. Pref. (II) has Mw = 1000-15000 and contains the end gps. allowing further condensn. End gps. are phenyl carbonate and/or alkyl carbonate gps. and opt. some (up to 45%) OH gps.; or approx. equimolar amts. of carbonate and aryl and/or alkyl carbonate gps. (II) contains 1 ppm to 1 wt.% condensn. catalyst (alkali hydroxide, alkaline earth hydroxide, (bi)carbonate or acetate, quinoline, PPh3 and/or organic Ti and/or Sn cpds.) for further condensn. USE/ADVANTAGE - (III) can be used instead of the usual halogenated solvents, which are ecologically harmful and very difficult to remove quantitatively. (I) are useful for making semi-finished prods., mouldings and films, e.g. for use in the electrical industry and vehicle construction.

Description

The present invention relates to a 2-step process for the production of halogen-free aromatic polycarbonates, in a first stage after the known phase boundary process in the presence of a halogen-free orga African solvent as a solvent that is only slightly miscible with water Carbonate oligomer is produced, either in a second stage after Crystallization in the solid phase or in the melt in the extruder or Kneader at high temperature to high molecular weight aromatic polycarbonate is condensed.

The present invention also relates to those according to the inventive method available polycarbonates.

The production of aromatic polycarbonates after the phase interfaces procedure is known. It is used here as an organic solvent preferred their good solubility for high molecular weight polycarbonates halogenated solvents, e.g. B. chlorobenzene, dichloromethane, 1,1-dichloroethane. However, these halogen-containing solvents have been shown to be ecologically unsafe proven and can be extremely difficult from the finished polycarbonate be quantitatively separated.

It has now been found that oligomeric aromatic carbonates are also advantageous in halogen-free, organic solvents that are only slightly miscible with water the interfacial process can be made that this oligo  carbonate easily obtained in semi-crystalline form and in the solid phase elevated temperature or in the melt in the extruder or kneader too high molecular weight laren polycarbonates can be post-condensed.

The two-stage polycarbonate synthesis by combination is known from JP-52-1 09 591 Nation of melt transesterification with subsequent solid phase polycondensation (see also JP-63-2 23 035, JP-64-1 725, JP-01-4 617 and EP-A-03 38 085).

Polycarbonate synthesis by multi-stage melt transesterification is also known (see for example DE-AS 12 28 417, DE-OS 15 70 640, JP-78-5 718, JP-01-16 826 and JP-01 38 433).

It is also known to carry out the phase interface method in several stages (see for example US-PS 40 38 252).

From Japanese Laid-Open Publication 1-2 71 426 of October 30, 1989 is a three step process known, which results from prepolymer production by means of phosgene, Crystallization of the prepolymer and subsequent solid phase polymerization of the composed of crystalline prepolymers.

The production of chlorine-free polycarbonates is not discussed here. This is by the applicant in her earlier European patent application EP-A-03 38 085 (loc-cit) on page 4, lines 24 to 32, explains that, for example, table salt, the arises in the phosgene process, is difficult to remove.

In the aforementioned Japanese Laid-Open Publication 1-2 17 426, as State of the art also the combination of prepolymer production by means of Phosgene and subsequent melt transesterification dealt with (pages 5/6 of this translation).

However, it does not follow that, according to this prior art, halo gene-free or chlorine-free polycarbonates can be obtained.  

It is also highlighted in 1-2 71 426 that this combination of processes is still associated with disadvantages.

As a halogen-free organic solvent for the process according to the invention come into consideration: toluene, ethylbenzene, anisole, xylenes, cyclohexane, methyl cyclohexane.

Aromatic polycarbonates in the sense of this invention are the known homopolycarbonates, copolycarbonates and mixtures of these poly understood carbonates, which z. B. at least one of the following diphenols underlying:

Hydroquinone,
Resorcinol,
Dihydroxybiphenyls,
Bis (hydroxyphenyl) alkanes,
Bis (hydroxyphenyl) cycloalkanes,
Bis (hydroxyphenyl) ether,
Bis (hydroxyphenyl) ketones,
Bis (hydroxyphenyl) sulfoxides,
Bis (hydroxyphenyl) sulfones and
α, α′-bis (hydroxyphenyl) diisopropylbenzenes

as well as their nuclear alkylated and nuclear halogenated derivatives.

These and other suitable diphenols are e.g. B. in US-PS 30 28 365, 32 75 601, 31 48 172, 30 62 781, 29 91 273 and 29 99 846.

Preferred diphenols are e.g. B.

4,4'-dihydroxybiphenyl,
2,4-bis (4-hydroxyphenyl) -2-methylbutane,
α, α′-bis (4-hydroxyphenyl) -p-diisopropylbenzene,
2,2-bis (3-methyl-4-hydroxyphenyl) propane and
2,2-bis (3-chloro-4-hydroxyphenyl) propane.

Particularly preferred diphenols are e.g. B.

2,2-bis (4-hydroxyphenyl) propane (BPA),
2,2-bis (3,5-dichloro-4-hydroxyphenyl) propane,
2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane and
1,1-bis (4-hydroxyphenyl) cyclohexane.

The aromatic oligo- and polycarbonates can be reduced by incorporation Amounts, preferably from 0.05 to 2.0 mol% (based on the amount used Diphenols), three or more than three-functional compounds, for example those with three or more than three phenolic hydroxyl groups.

The aromatic oligocarbonates of the first stage of the process according to the invention should have average molecular weights _w (weight average) of 1000 to 15,000, preferably 2000 to 10,000, determined by measuring the relative solution viscosity (η _rel ) in dichloromethane or in mixtures of equal amounts by weight of phenol / o-dichlorobenzene or by light scattering.

The polycarbonates obtained in the post-condensation in the second stage of the process according to the invention are said to have _w values of 20,000 to 80,000, preferably 22,000 to 60,000.

To limit the molar masses _w in the 1st stage of the process according to the invention, chain terminators such as, for example, phenol, alkylphenol, phenylchlorocarbonate, alkylchlorocarbonate, aromatic and aliphatic carboxylic acid halides are used in the amounts calculated or to be tested.

The selection of the chain terminator (s) in the 1st stage depends on the or the desired volatile condensation products that occur during the 2nd stage  of the method according to the invention should arise. For example, if phenol Chain terminators are used, so diphenyl carbonate is used in the post-condensation and optionally phenol separated from the reaction mixture. Becomes alkyl chlorine carbonic acid ester used, dialkyl carbonate is formed in the post-condensation and optionally aliphatic alcohol. When using phenols and Carboxylic acid halides at the same time, phenyl esters of carboxylic acids released.

Preferred chain terminators are phenols and alkyl chlorocarbonic acid esters.

According to a variant of the method, the amounts of the chains used terminator and the phosgene selected so that the oligocarbonates of the 1st Stage of the process also contain OH end groups in addition to, for example Phenyl carbonate end groups. The condensation of such oligocarbonates can then with the release of phenol.

The oligocarbonates capable of post-condensation can up to 45% of all End groups have OH end groups.

It is also possible to use oligocarbonates in addition to phenyl carbonate or Alkyl carbonate end groups contain very little OH end groups Implementation with a diphenol to create OH end groups.

In a preferred embodiment of the first stage of the process, the Concentrations of the starting materials chosen so that the resulting oligo carbonates dissolved in the selected organic halogen-free solvents remain until the organic phases are cleaned and the separation of Oligocarbonate by concentration of the solutions or precipitation is desired.

However, it is also possible to work with larger concentrations of the starting materials are, whereby the oligocarbonates are deposited in a very fine distribution. In this case it is advantageous to pre-solid the oligocarbonate Processing of the organic solution by filtration, centrifugation or the like  Separate operations and process them separately. For example the fixed portion after washing and drying immediately after the solid phase condensation are supplied.

The solubility of the oligomers in the organic halogen-free solvents is depending on the type of solvent, diphenols, diphenol mixtures and the concentrations. The oligomers are more soluble than the polymers, which as particular advantage of the method according to the invention can be seen.

If the oligocarbonates according to the invention prepared in the 1st stage from the Crystallize solutions in halogen-free solvents quickly Separation of the oligomers also possible in extruders, which are at temperatures are kept below the melting points of the crystallites and in which the Oligomers with evaporation of the solvent as free-flowing solids attack. - The oligocarbonates can also from their solutions with z. B. Methanol / cyclohexane, acetone are precipitated.

The post-condensation of the oligomeric carbonates in the 2nd stage of the invention according to the method can advantageously be carried out in the solid phase if the products can be easily crystallized.

If the crystallization of the oligocarbonates of the 1st stage is delayed, they often by tempering below the temperature of the crystallite melting point be accelerated.

For the solid phase post-condensation, the crystalline or semi-crystalline Pre-condensates either in a vacuum or under an inert gas under normal pressure or heated to temperatures below crystalline melting point, wherein do not soften, cake or stick the particles of the pre-condensates should.  

As an alternative to solid phase post-condensation, post-condensation can also be carried out in the Melt in extruders, kneaders or similar units, preferably in Vacuum.

It can be advantageous to accelerate the post-condensation of the oligocarbonates by small amounts (1 ppm - 1% by weight) of catalysts. Possible catalysts include: alkali metal hydroxides, alkaline earth metal hydroxides, salts of these hydroxides with weak acids, organotitanium, organotin compounds, tertiary nitrogen and phosphorus bases, e.g. B. LiO, NaOH, KOH, Na ₂ CO ₃ , Ca (OH) ₂ , CaCO ₃ , tetraalkyl titanate, dibutyl-dibutoxy tin, quinoline, triphenylphosphine. Traces of alkali hydroxide are usually sufficient.

To improve the properties, auxiliaries and reinforcing materials can be mixed into the polycarbonates produced according to the invention. The following should be considered as such: stabilizers, flow aids, mold release agents, fire retardants, pigments, finely divided minerals, fibrous materials, e.g. B. alkyl and aryl phosphites, phosphates, phosphines, low molecular weight carboxylic acid esters, Halo gene compounds, salts, TiO ₂ , chalk, quartz powder, talc, glass and carbon asers.

Other polymers can also be used in the polycarbonates according to the invention be admixed, e.g. B. polyolefins, polyurethanes.

These substances are preferably added to conventional aggregates for manufacture polycarbonate, however, depending on the requirements, on another Stage of the method according to the invention.

In addition, the modification of the poly is also for special applications carbonate by condensation of blocks, segments and comonomers possible, e.g. B. siloxane blocks with OH end groups, aromatic dicarboxylic acid di chloride, in amounts up to 30 mol%, based on diphenols. The condensation these substances are preferably already in the 1st stage of the invention Procedure.  

The polycarbonates produced according to the invention can in conventional machines Semi-finished products, moldings, foils are processed. The use of this pro Products are used, for example, in electrical engineering and automotive engineering.

Examples example 1

In a glass apparatus with stirrer, dropping funnel and gas inlet tube

22.8 g (0.1 mole) BPA
15 ml 45% NaOH
250 ml water
1.59 g (0.0169 mol) phenol

stirred under N ₂ until the BPA is completely dissolved. After adding 175 ml of toluene, the mixture was stirred vigorously

15.8 g (0.16 mol) of COCl ₂

initiated and the pH of the aqueous phase by adding NaOH Held 12-13. Then 0.1 ml of N-ethylpiperidine was added and the mixture was kept at pH for 45 min Stirred 12-13.

The precipitated solid was filtered off, the filter cake washed well with water. The phases were separated in the filtrate, the toluene phase was washed out, and the toluene was then distilled off. The residue, like the product in the filter cake, proved to be partially crystalline according to differential thermal analysis. The mass ratio of the products from toluene and in the filter cake was approximately 1: 5. The relative solution viscosities (η _rel ) of the products were 1.083 and 1.068, respectively, measured with solutions of 0.5 g substance per 100 ml phenol / dichlorobenzene solution at 25 ° C.

5 g of the dry filter cake material were heated in a 250 ml glass flask at 20 mbar for 1 hour in a salt bath at 340 ° C. η _{rel of} the colorless product was then 1.427. The toluene content was 2 ppm.

Another 5 g of the dry, powdery filter cake were heated in a 250 ml flask on a rotating Rotavapor for 48 hours in an oil bath at 20 mbar (initially 2 hours at 180 ° C, then 2 hours at 200 ° C, the rest of the time 240 ° C). η _{rel of} the colorless product had risen to 1.263, the toluene content was 3 ppm. Halogen was not detectable in the end products.

Example 2

Example 1 was repeated, but 250 ml of anisole were used instead of toluene. In this case, no solid precipitated out in the phase interface reaction. The organic phase of the batch was worked up as in Example 1, in each case again 5 g in the melt and in the solid phase after-condensed Conditions of Example 1.

η _rel rose from 1.085 to 1.318 in the melt and to 1.257 in the solid phase. The anisole content was 7 ppm after the melt post-condensation and 4 to 5 ppm after the solid-phase condensation. All end products were colorless. Halogen was not detectable in the end products.

Example 3

Example 1 was repeated, but instead of BPA 0.1 mol of bis (4-hydroxyphenyl) ether and cyclohexane instead of toluene. In this case, only a trace of substance was dissolved in the organic phase. A filter cake of oligomers with η _rel 1.062 was obtained analogously to Example 1.

The post-condensation in the melt and in the solid phase gave colorless products with η _rel 1.419 and 1.307 cyclohexane contents of <2 ppm in both cases. Halogen was not detectable in the end products.

Example 4

Example 2 was repeated, but only 12.5 g of phosgene were used, and the organic phase was washed only briefly. η _{rel of} the oligocarbonate was 1.073. 8.7% of the total end groups were OH end groups. The Na content of the oligomers was 6 to 7 ppm.

h _rel rose to 1.36 in the melt after-condensation and to 1.263 in the solid phase.

Comparative Example 2

Example 1 was repeated, but only 0.28 g of phenol was used (= approx. 3 mol%, based on BPA). In this case, the toluene phase contained only traces of solid substance after the reaction was carried out. The substance of the filter cake had η _rel of 1.091 and proved to be non-condensable. It tanned over time when trying to condense.

Claims (8)

1. 2-stage process for the production of halogen-free aromatic polycarbonate, characterized in that partially crystalline oligomeric precondensate is produced in a 1st stage according to the interfacial process using halogen-free organic solvents which are only slightly miscible with water, which is produced in a 2nd stage can be condensed to high molecular weight polycarbonate in the melt or in the solid phase. 2. The method according to claim 1, characterized in that the oligomeric carbonates _w produced in the 1st stage have in the range from 1000 to 15,000 and the end groups permitting post-condensation. 3. The method according to claims 1 and 2, characterized in that the oligomeric carbonates of the 1st stage of the process phenyl carbonate and / or Alkyl carbonate end groups and optionally partial OH end groups have. 4. The method according to claims 1 and 2, characterized in that the oligomeric carbonates of the 1st stage of the process have approximately equimolar proportions on the one hand of carbonic ester end groups and on the other hand aryl and / or Contain alkyl carbonate end groups. 5. The method according to claims 1 to 3, characterized in that the oligomeric carbonates of the 1st stage of the process up to 45% of the entire end groups OH end groups in addition to phenyl carbonate and / or Contain alkyl carbonate end groups. 6. The method according to claims 1 to 5, characterized in that the Oligocarbonates of the 1st stage of the process for post-condensation 1 ppm to Contain 1% by weight of condensation catalysts.   7. The method according to claim 6, characterized in that as catalysts either individually or together alkali metal hydroxides, alkaline earth metal hydroxides, their carbonates, bicarbonates, acetates, quinoline, triphenylphosphine, organic titanium and / or tin compounds are used. 8. polycarbonates obtainable by the process of claims 1 to 7.