The present invention will now be described by way of examples which should not be construed as limiting the scope of the present invention.

EXAMPLES

Example 1

22.8 g (0.1 mol) of 2,2-bis(4-hydroxyphenyl)propane was mixed with 0.164 g (2.times.10.sup.-2 mol) of 2-methylimidazole and 21.4 g (0.1 mol) of bisphenyl carbonate, and the mixture was stirred at 180.C for 1 hour in a nitrogen atmosphere. The temperature of the system was raised while gradually evacuating the system. Finally, polycondensation was conducted at 270.C and 0.1 Torr for 1 hour and the formed phenol was distilled away to prepare a clear polycarbonate. The viscosity-average molecular weight (Mv) was determined to be 29,000. The glass transition temperature was 150.degree. C.

The viscosity-average molecular weight was determined by measuring the intrinsic viscosity [.eta.]of the polymer in the form of a methylene chloride solution at 20.degree. C. with an Ubbelohde's viscometer and calculating the viscosity-average molecular weight (Mv) according to the following equation:

[.eta.]=1.11.times.10.sup.-4 (Mv).sup.0.82

Example 2

0.0122 g (1.times.10.sup.-4 mol) of 4-dimethylaminopyridine was added, instead of 2-methylimidazole to 22.8 g (0.01 mol) of 2,2-bis(4-hydroxyphenyl)propane and 21.4 g (0.1 mol) of bisphenyl carbonate under the same condition as that of Example 1. The mixture was stirred for 2 hours in a nitrogen atmosphere, and polycondensation was conducted in the same manner as that of Example 1 to prepare a clear polycarbonate. The viscosity-average molecular weight (Mv) was determined to be 28,000. The glass transition temperature was 150.degree. C.

Example 3

11.4 g (50% by mole) of 2,2-bis(4-hydroxyphenyl) propane, 17.0 g (50% by mole) of 2,2-bis(4-hydroxy-3-tertbutylphenyl)propane, and 0.068 g (10.sup.-3 mol) of imidazole were stirred for 2 hours in a nitrogen atmosphere, and polycondensation was conducted in the same manner as that of Example 1 to prepare a clear polycarbonate. The viscosity-average molecular weight (Mv) was determined to be 25,000 and the glass transition temperature was 128.degree. C.

Comparative Example 1

The same treatment as that of Example 1 was conducted except that pyridine, instead of 2-methylimidazole, was added to 22.8 g (0.1 mol) of 2,2-bis(4-hydroxyphenyl)propane and 21.4 g (0.1 mol) of bisphenyl carbonate under the same condition as that of Example 1. However, the viscosity-average molecular weight (Mv) of the resultant polycarbonate was as low as 4,000, which was unsuitable for practical use although it was in the form of polycarbonate.

Example 4

42.09 g (0.1 mol) of bis(2,4,6-trichlorophenyl) carbonate was added to 22.8 g (0.1 mol) of 2,2-bis(4-hydroxyphenyl)propane and 0.122 g [10.sup.<2 mole based on 2,2-bis(4-hydroxyphenyl)propane] of 4-dimethylaminopyridine, and the mixture was stirred at 160.degree. C. for 1 hour in a nitrogen atmosphere. The temperature of the system was raised while gradually evacuating the system. Finally, polycondensation was conducted at 230.degree. C. and 0.1 Torr for 1 hour and the formed 2,4,6-trichlorophenol was distilled away to prepare a clear polycarbonate. The viscosity-average molecular weight (Mv) was determined to be 29,000. The glass transition temperature was 150.degree. C.

The viscosity-average molecular weight was determined by measuring the intrinsic viscosity [.eta.] of the polymer in the form of a methylene chloride solution at 20.degree. C. with an Ubbelohde's viscometer and calculating the viscosity-average molecular weight (Mv) according to the following equation:

[.eta.]=1.11.times.10.sup.-4 (Mv).sup.0.82

Example 5

0.068 g [10.sup.-2 mole based on 2,2-bis(4-hydroxyphenyl)propane] of imidazole was added, instead of 4-dimethylaminopyridine, to 42.09 g (0.1 mol) of bis(2,4,6-trichlorophenyl)carbonate and 22.8 g (0.1 mol) of 2,2-bis(4-hydroxyphenyl)propane the same condition as that of Example 4. The mixture was stirred for 2 hours in a nitrogen atmosphere, and polycondensation was conducted in the same manner as that of Example 1 to prepare a clear polycarbonate. The viscosity-average molecular weight (Mv) was determined to be 28,000. The glass transition temperature was 150.degree. C.

Example 6

11.4 g (50% by mole) of 2,2-bis(4-hydroxyphenyl) propane, 17.0 g (50% by mole) of 2,2-bis(4-hydroxy-3-tertbutylphenyl)propane, and 0.068 g [10.sup.-2 mole based on the bisphenol component] of imidazole were stirred for 2 hours in a nitrogen atmosphere, and polycondensation was conducted in the same manner as that of Example 4 to prepare a clear polycarbonate. The viscosity-average molecular weight (Mv) was determined to be 25,000 and the glass transition temperature was 128.degree. C.

Example 7

In a reaction vessel were placed 22.8 g (0.1 mol) of 2,2-bis(4-hydroxyphenyl)propane, 0.288 g (2.times.10.sup.-3 mol) of 2-methylimidazole carbonate, and 21.4 g (0.1 mol) of bisphenyl carbonate. The reactants were stirred at 180.degree. C. for 1 hour under a nitrogen atmosphere. The reaction system was heated to 270.degree. C. with gradual evacuation to 0.1 Torr. Polycondensation was carried out at this temperature and pressure for 1 hour, with continuous removal by distillation of phenol resulting from the reaction. Thus there was obtained a colorless transparent polycarbonate which has a viscosity-average molecular weight (Mv) of 27,000 and a glass transition point of 150.degree. C.

The viscosity-average molecular weight was calculated from the following formula:

[.eta.]=1.11.times.10.sup.-4 (Mv).sup.0.82

where [.eta.] is an intrinsio viscosity of the polymer solution in methylene chloride measured with an Ubbelohde viscometer at 20.degree. C.

Example 8

The same procedure as in Example 7 was repeated except that the 2-methylimidazole carbonate was replaced by 0.0184 g (1.times.10.sup.-4 mol) of 4-dimethylaminopyridine carbonate and the reactants were stirred for 2 hours. There was obtained a colorless transparent polycarbonate, which has a viscosity-average molecular weight (Mv) of 28,000 and a glass transition point of 150.degree. C.

Example 9

The same procedure as in Example 7 was repeated except that the reactants were replaced by 11.4 g (50 mol%) of 2,2-bis(4-hydroxyphenyl)propane, 17.0 g (50 mol%) of 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane, and 0.113 g (10.sup.-3 mol%) of imidazole oxalate and the reactants were stirred for 2 hours. There was obtained a colorless transparent polycarbonate, which has a viscosity-average molecular weight (Mv) of 25,000 and a glass transition point of 128.degree. C.

Example 10

In a reaction vessel were placed 22.8 g (0.1 mol) of 2,2-bis(4-hydroxyphenyl)propane, 42.1 g (0.1 mol) of bis(2,4,6-trichlorophenyl)carbonate, and 0.0182 g (10.sup.-4 mol) of dimethylaminopyridine acetate. The reactants were stirred at 180.degree. C. for 1 hour under a nitrogen atmosphere. The reaction system was heated to 280.degree. C. with gradual evacuation to 0.1 Torr. Polycondensation was carried out at this temperature and pressure for 1 hour, with continuous removal by distillation of 2,4,6-trichlorophenol resulting from the reaction. Thus there was obtained a colorless transparent polycarbonate, which has a viscosity-average molecular weight (Mv) of 27,500 and a glass transition point of 151.degree. C.

Comparative Example 2

The same procedure as in Example 7 was repeated except dine carbonate. There was obtained a colorless transparent polycarbonate, which has a viscosity-average molecular weight (Mv) of 4,000. This polycarbonate was unsuitable for practical use because of its extremely low molecular weight.

EFFECT OF THE INVENTION

The process of the present invention, which employs an electron donating amine compound as a catalyst, or a salt thereof, makes it possible to produce, without resorting to toxic phosgene, a high-molecular weight, colorless transparent polycarbonate which is substantially free of chlorine ions.