Preparation of copolycarbonates

Details Preparation of copolycarbonates Preparation of copolycarbonates

2002-07-12

2004-06-22

Boykin, Terressa (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From phenol, phenol ether, or inorganic phenolate

C264S176100, C264S219000, C528S198000

Reexamination Certificate

active

06753405

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for the preparation of polycarbonates and more particularly to transparent copolycarbonates that containing more than 35 mol % structural units derived from dihydroxydiphenylene.
SUMMARY OF THE INVENTION
A process for the preparation of transparent copolycarbonate is disclosed. The copolycarbonate the molecular structure of which contains more than 35 mole % of units derived from dihydroxydiphenylene is prepared by the melt transesterification process wherein the final temperature of the reaction is reached in less than 40 minutes after reaching the starting temperature.
BACKGROUND OF THE INVENTION
Copolycarbonates based on 4,4′-dihydroxydiphenyl and 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) are already known from JP-A 5117382, JP-A 62227927 and JP-A 61264020 and are described in EP-A1 0 544 407, U.S. Pat. Nos. 5,470,938, 5,532,324 and 5,401,826 as being particularly resistant to chemicals, heat-stable and flame retardant, while having, compared with commercially available polycarbonate from pure bisphenol A, the same mechanical properties and transparency.
The preparation of copolycarbonates via the melt transesterification process is also well known. This is also described in EP-A1 0 544 407 or DE-A 196 46 401. However, the incorporation of more than 35 mol % dihydroxydiphenyl has not thus far been demonstrated, and according to our own investigations lead to products that are not transparent. There is no indication at all in the prior art, however, how to avoid this lack of transparency.
The object was therefore to develop a process for the preparation of transparent copolycarbonate having more than 35 mol % of its structural units derived from dihydroxydiphenyl (hereinafter referred to as DOD).
It has now been found, surprisingly, that transparent copolycarbonates with >35 mol % DOD are obtained if they are prepared by the melt transesterification process where the heating-up phase in the medium-viscosity range is limited to a max. of 40 min.
DETAILED DESCRIPTION OF THE INVENTION
The present invention therefore relates to a process for the preparation of transparent copolycarbonates, comprising melt transesterification of a mixture containing 35 to 60 mol %, preferably 40 to 50 mol %, of compounds of the formula (I)
wherein R
1
to R
4
independently of one another represent H, C
1
-C
4
-alkyl, phenyl, substituted phenyl or halogen, preferably H, C
1
-C
4
-alkyl or halogen, and particularly preferably all represent the same radical, in particular H or tert-butyl, and 65 to 40 mol %, preferably 60 to 50 mol %, of compounds of the formula (II)
wherein R
5
to R
8
independently of one another are H, CH
3
, Cl or Br and X is C
1
-C
5
-alkylene, C
2
-C
5
-alkylidene, C
5
-C
6
-cycloalkylene or C
5
-C
10
-cycloalkylidene, as bisphenol monomers, the percents being relative to the total molar amount of (I) and (II). The inventive process is further characterized in that the time span between the starting temperature and reaching the final temperature is less than 40, preferably less than 30 minutes.
The starting temperature of 220 to 240° C., preferably 235° C., is to be understood as meaning that the reaction mixture is first heated up, as is known from the prior art (e.g. DE-A 196 46 401), up to 220 to 240° C., preferably 235° C., during a continuous condensation reaction. In accordance with the invention the mixture must be heated up from the starting temperature within less than 40, preferably less than 30, minutes, to the final temperature of 270 to 330° C., preferably 280 to 320° C., particularly preferably 290 to 300° C., in order to obtain a transparent copolycarbonate.
Preferred compounds of the formula (I) are 4,4′-dihydroxydiphenyl (DOD), 4,4′-dihydroxy-3,3′,5,5′-tetra(tert-butyl)diphenyl, 4,4′-dihydroxy-3,3′,5,5′-tetra(n-butyl)-diphenyl, 4,4′-dihydroxy-3,3′,5,5′-tetra(methyl)diphenyl and 4,4′-dihydroxydiphenyl, and 4,4′-dihydroxy-diphenyl (DOD) is particularly preferred.
Preferred compounds of the formula (II) are 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC) and 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)-cyclo-hexane, in particular 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC), very particularly preferably 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).
It is possible to use either one compound of the formula (I), to form binary copolycarbonates, or several compounds of the formula (I).
It is also possible to use either one compound of the formula (II), to form binary copolycarbonates, or several compounds of the formula (II).
Diaryl carbonates in the context of the present invention are carbonic acid diesters of the formula (III):
and formula (IV):
wherein R, R′ and R″ independently of one another represent H, optionally branched C
1
-C
34
-alkyl/cycloalkyl, C
7
-C
34
-alkaryl or C
6
-C
34
-aryl, for example diphenyl carbonate, butylphenyl phenyl carbonate, di-butylphenyl carbonate, isobutylphenyl phenyl carbonate, di-isobutylphenyl carbonate, tert-butylphenyl phenyl carbonate, di-tert-butylphenyl carbonate, n-pentylphenyl phenyl carbonate, di-(n-pentylphenyl) carbonate, n-hexylphenyl phenyl carbonate, di(-n-hexylphenyl) carbonate, cyclohexylphenyl phenyl carbonate, di-cyclohexylphenyl carbonate, phenylphenol phenyl carbonate, di-phenylphenol carbonate, isooctylphenyl phenyl carbonate, di-isooctylphenyl carbonate, n-nonylphenyl phenyl carbonate, di-(n-nonylphenyl) carbonate, cumylphenyl phenyl carbonate, di-cumylphenyl carbonate, naphthylphenyl phenyl carbonate, di-naphthylphenyl carbonate, di-tert-butylphenyl phenyl carbonate, di-(di-tert-butylphenyl) carbonate, dicumylphenyl phenyl carbonate, di-(dicumylphenyl) carbonate, 4-phenyoxyphenyl phenyl carbonate, di-(4-phenoxyphenyl) carbonate, 3-pentadecylphenyl phenyl carbonate, di-(3-pentadecylphenyl) carbonate, tritylphenyl phenyl carbonate and di-tritylphenyl carbonate, preferably diphenyl carbonate, tert-butylphenyl phenyl carbonate, di-tert-butylphenyl carbonate, phenylphenol phenyl carbonate, di-phenylphenol carbonate, cumylphenyl phenyl carbonate and di-cumylphenyl carbonate, particularly preferred is diphenyl carbonate.
In addition, the phenolic compounds employed as carbonates may also be used directly as hydroxyaryls, in addition to one of the carbonates mentioned, in order to influence the end group of the polycarbonate. Preferred mixtures are those with diphenyl carbonate. In the process according to the invention, it is possible to add the hydroxyaryl or the hydroxyaryl-carrying compound at any point in time of the reaction, preferably at the start of the reaction, and the addition may be divided into several portions. The content of free hydroxyaryl may be 0.4-17 mol %, preferably 1.3-8.6 mol % (based on the dihydroxy compound). The addition here may take place either before the reaction or entirely or partly during the reaction.
The carbonic acid diesters and the dihydroxy compounds are used in a ratio of 1 to 1-1.1, preferably 1:1.0-1.07, particularly preferably 1:1.02-1.06. Mixtures of the above mentioned carbonic acid diesters may also be employed.
Ammonium or phosphonium compounds, subsequently also in common called onium salts, may be employed as catalysts for the synthesis. They are preferably employed in amounts of 0.0001 to 0.01 mol %, based on the total of dihydroxy compounds, particularly preferably in amounts of 0.002 to 0.006 mol %.
Phosphonium salts, optionally in combination with other suitable catalysts which do not lead to an increased intrinsic color, are preferably used as the catalyst for the preparation of the copolycarbonates according to the invention.
Phosphonium salts in the context of the invention are those of the formula (V):
wherein R
1-4
may be the same or different C
1
-C
10
-alkyls, C
6
-C
10
-aryls, C
7
-

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