JPH0796614B2 - Method for producing aromatic polycarbonate - Google Patents

Description

The present invention relates to a method for producing an aromatic polycarbonate from a carbonate precursor and diphenols according to the phase boundary method using a phenolic chain stopper.

U.S. Patent No. 4,269,964, a method as described above to use t- butylphenol or C ₈ -C ₉ alkyl phenol as chain terminators are described. In the examples of this patent specification, the chain stopper is added first, and then the carbonate precursor is introduced into the reaction solution.

The use of the aforementioned phenolic chain terminators makes it possible to control the molecular weight of the polycarbonate formed. That is, if a relatively low molecular weight polycarbonate is desired, usually a much higher amount of chain terminator is used, or vice versa.

However, the method described above has serious drawbacks. That is, volatile components are formed from the chain terminator under the reaction conditions used, which are difficult to remove during the isolation of the polycarbonate. One example of such a volatile component is diphenyl carbonate which is produced when phenol itself is used as a chain terminator. The amount of this compound and other volatile compounds increases as the amount of chain stopper used increases. Practically what this means is that the content of volatile constituents in the relatively low molecular weight polycarbonate is higher than in the relatively high molecular weight polycarbonate. This is a serious drawback. This is because the mechanical properties of relatively low molecular weight (eg 10,000 to 25,000) polycarbonates are affected by the presence of volatile components, to a degree greater than that of relatively high molecular weight polycarbonates. Is. Furthermore, during injection molding of articles from polycarbonate, volatile components tend to form deposits (precipitates) on the surface of the injection molded matrix and on the surface of the article being molded. Presently, relatively low molecular weight polycarbonates are used in particular for the production of optically readable information carriers. In the case of such a carrier, especially the adhered matter on the surface becomes a great obstacle.

The present invention provides a method by which a polycarbonate having a low content of volatile components can be obtained even when a relatively large amount of chain terminator is used.

A feature of the process of the present invention is the use of compounds of the formula as phenolic chain terminators.

Here, R is an alkyl group or an aryl group having 1 to 12 carbon atoms, or a hydrogen atom, and n represents an integer of 0 to 5. It is preferred that n is 1 and R is para to the OCOC1 group.

For optimum results, i.e. the lowest possible content of volatile constituents, a chain terminator is added to the reaction mixture after 20-80%, more preferably 20-50% of the total carbonate precursor loading has been introduced into the reaction mixture. It has been found to be obtained when added.

In the process according to the invention, it is preferred to use the chain terminator in an amount of 2 to 7 mol% calculated on the number of moles of diphenol used.

The process according to the invention gives polycarbonates having a diphenyl carbonate content of less than 50 ppm. It is to be considered that diphenyl carbonate also includes di (alkylphenyl) carbonates and di (arylphenyl) carbonates.

Another advantage of the present invention is that the resulting polycarbonate has a lower polydispersity. What is polydispersity?
Think of it as the quotient of the weight average molecular weight (M _w ) and the number average molecular weight (M _n ). Polycarbonates obtained by the process of the invention usually have a polydispersity of less than 2.

Preferred for use as a chain terminator in the method of the present invention is phenyl chloroformate (phenyl chloroformate).
Is.

Canadian Patent No. 1173998 describes the production of polyester carbonates using phenolic chain terminators. According to its broad teaching, the chain terminator of this patent application may be present in the form of the phenol itself, the acid chloride or the chlorocarbonate. Canadian Patent No. 1173998 further states: "When using acid chlorides and chlorocarbonates as chain terminators, they are preferably used with aromatic dicarboxylic acid dichlorides and / or phosgene.
Also, these chain terminators may be added to the reaction mixture at a stage after the dicarboxylic acid chloride has reacted with phosgene almost or completely. " Canadian Patent No.
In the 1173998 example, the chain terminator is always used in the form of phenol, and the chain terminator is added to the reaction mixture either before or at the same time as phosgene. Furthermore, Canadian Patent 1173998 makes no mention of the volatile content of the polyester carbonate obtained.

U.S. Pat.No. 4,330,663 describes polyesters containing benzoic acid or substituted benzoic acid esters as end groups.
The production of carbonate polymers is described. These end groups are obtained by reacting polyester carbonates with (substituted) benzoyl chloride. These end groups give polyester carbonates having an increased heat distortion temperature.

U.S. Pat. No. 3,475,373 describes stabilizing polycarbonate with haloformates or acid halides. In this known method, a polycarbonate is prepared and the polymerized polycarbonate is then treated in a solution of haloformate or acid halide. The product obtained is then converted with a monohydroxy compound. In this method, the haloformate or acid halide is not functioning as a chain terminator.

PPG Industries' product brochure on phenyl chloroformates appears to refer to this application. The advertisement states, "Polycarbonate producers have used phenyl chloroformate as a polymerization inhibitor."

The method of the present invention relates to a phase boundary method for producing an aromatic polycarbonate using a chain terminator. Such a method is widely known. In this regard, H. Schnell, Chemistry and Physics of Polycarbonates, New York, 1964, and European Patent Publication No. 17
See 8609 and U.S. Pat. No. 4,403,087.

In this two-phase boundary process, one or more different diphenol compounds are dissolved in an alkaline aqueous phase and the diphenol is converted by a carbonate precursor in the presence of an inert organic phase.

Suitable diphenol compounds are widely known in the literature.
It is also possible to use mono- and / or bischlorocarboxylic acid esters of these diphenols.

It is possible to carry out the polymerization in the presence of trihydric or higher polyhydric phenol compounds. This gives a branched polycarbonate.

Generally, the chain terminator is added at the beginning of the reaction. Commonly used as inert organic phases are methylene chloride, chlorobenzene or mixtures of these solvents.

The polymerization reaction can be carried out in the presence of a catalyst, for example in the presence of a tertiary amine such as tributylamine or triethylamine. This catalyst may be added before, simultaneously with or after the addition of the carbonate precursor.

Examples of chain terminators suitable for the method of the present invention include phenyl chloroformate, t-butyl-phenyl chloroformate, octyl- or nonylphenyl chloroformate (wherein the octyl or nonyl group is branched). ), Para-cumyl phenyl chloroformate and other substituted phenyl chloroformates.

These are compounds known per se, and their production methods are also known.

Various compounds can be used as the carbonate precursor.
Phosgene is preferably used. The diphenol compound preferably used is 2,2-bis- (4,4'-dihydroxy-diphenyl) propane (i.e. bisphenol A). Further, for example, tetramethylphenol A, 1,1-bis- (4-hydroxyphenyl) -isobutane, 1,1-bis- (4-hydroxyphenyl) -cyclohexane, 4,4'-dihydroxydiphenyl sulfide, 4,4 ' Also suitable are'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl sulfone and their di- or tetra-halogenated derivatives.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example I 300 g of bisphenol-A and 1,00 of methylene chloride
Phosgene (5 g / min) was introduced into a reaction flask containing 0 ml, 750 ml of water and 1.9 ml of triethylamine.
Meanwhile, the pH was kept at 10.5 by adding 33% NaOH solution.

After the addition of 30 g of phosgene, the phosgene feed was interrupted and 11.65 g of phenyl chloroformate in the form of a 20% solution in methylene chloride was added dropwise.

The phosgene was fed in again and continued until a total of 145 g of phosgene had been added. The formed polymer was neutralized with 1N hydrochloric acid and then washed with water. The organic phase containing the polymer was separated from the aqueous phase and the organic solvent was evaporated to give the polymer.

The polymer obtained had an intrinsic viscosity of 42.4 parts / g (CH ₂ Cl ₂
(Measured in), the free hydroxyl group content is 60 ppm
Met. The content of diphenyl carbonate in the polymer was measured by gel permeation chromatography and was below the measurement limit of 10 ppm.

Example II (Comparative Example) Polymerization was carried out in substantially the same manner as in Example I. The difference was that 79 g of phenol had been added to the mixture at the beginning of the reaction and that the addition of phosgene was not interrupted.

The polymer obtained had an intrinsic viscosity of 43.8 parts / g and a free hydroxyl group content of 82 ppm. The diphenyl carbonate content was 1546 ppm.

Example III An aromatic polycarbonate was prepared from bisphenol A and phosgene in a series of reaction experiments in a 30 liter reactor.

At the start of the reaction, 2270 g of bisphenol A and 6 of water
Liter, 7 liters of CH ₂ Cl ₂ and 15 ml of catalyst were present. In reactions where phenol was used as a chain terminator, this phenol was always added before the start of phosgene addition. Alkaline solution was added during most of the reaction to keep the pH value at 9.5-10.5. At the end of the reaction, the pH value was adjusted higher.

Phenol or phenyl chloroformates were used as chain terminators. This phenol was always added before introducing phosgene into the reaction mixture. Phenyl chloroformate was added at various times (see Tables A and B).

Different amounts of phenol and phenyl chloroformate were used to obtain different polycarbonates with different values of intrinsic viscosity. Table A is approximately 40-45 parts / g and Table B is approximately 58-63 parts / g.

Not only diphenyl carbonate content but also the following oligomer content was measured for these polymers.

I: One in which 1 mol of bisphenol A and 2 mols of phenol or phenylchloroformate are bound, II: One in which 2 mols of bisphenol A and phenol or 2 mols of phenylchloroformate are bound, III: 3 mols of bisphenol A and phenol or phenylchloro Those obtained by combining 2 mol of formate and the obtained results are summarized in Tables A and B below. The concentration of the above oligomers was determined using GPC analysis with UV detection. The value of the detection signal was calibrated with a diphenyl carbonate calibration standard solution. That is, oligomers I, II and
The indicated concentrations of III are relative values.

The following can be derived from the results in Table A.

1) The content of diphenyl carbonate is always lower in the case of phenyl chloroformate than in the case of phenol.

2) When phenyl chloroformate is added at the start of the reaction, the content of oligomer I is higher than when phenol is used.

3) Addition of phenyl chloroformate after addition of some of the phosgene further reduces the diphenyl carbonate content and the content of oligomers, especially oligomer I.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-84822 (JP, A) JP-A-62-297319 (JP, A) JP-A-62-89723 (JP, A) JP-A-51- 20993 (JP, A) JP 62-10541 (JP, B2)

Claims (2)

[Claims] 1. A method for producing an aromatic polycarbonate by reacting a carbonate precursor with a diphenol in the presence of a chain terminator by a phase boundary method, wherein the chain terminator has the formula: [Wherein R is an alkyl group or aryl group having 1 to 12 carbon atoms or a hydrogen atom, and n is an integer of 0 to 5], and the total amount of the carbonate precursor added is 20 A method characterized by adding a chain terminator to the reaction mixture after -80% has been introduced into the reaction mixture. 2. A process according to claim 1, characterized in that the chain terminator is used in an amount of 2 to 7 mol%, calculated on the mol of diphenol used.