JPH02251525A - Purification of aromatic polycarbonate - Google Patents

Abstract

PURPOSE:To obtain a polycarbonate excellent in hue in high efficiency through a simple operation by treating a polycarbonate produced by ester interchange process in a liquid phase with hydrogen, in the presence of a hydrogenation catalyst. CONSTITUTION:The objective purification can be accomplished by treating in a liquid phase (e.g. in dimethyl carbonate as solvent) with hydrogen, in the presence of a hydrogenation catalyst (e.g. metal such as Fe, Co or Ni, its oxide), a polycarbonate produced by ester interchange process from a diol compound (e.g. bisphenol A) and a carbonate (e.g. dimethyl carbonate).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for purifying polycarbonate produced from a diol compound and carbonate by transesterification.

[Conventional technology]

Polycarbonate has excellent transparency, impact resistance, mechanical strength, and heat resistance, and is widely used in various molded products such as automobile parts and precision machine parts, films, and engineering plastics.

Conventionally, as a method for producing polycarbonate using a transesterification method, a method for producing polycarbonate by transesterifying an aromatic diol compound and an aliphatic carbonate (Japanese Unexamined Patent Application Publication No. 1989-1995)
4-63023, JP-A No. 57-2334, etc.), a method of producing by transesterifying an aromatic diol compound and an aromatic carbonate (JP-A-50-11787, etc.)
No. 3, etc.).

However, the polycarbonate obtained by these methods may be colored. 1 Ordinary distillation purification methods, recrystallization purification methods,
Adsorption purification methods using activated carbon or the like have a problem in that satisfactory hue cannot be obtained.

[Problem to be solved by the invention]

The purpose of the present invention is to solve the above problems,
The purpose of the present invention is to propose a method for purifying polycarbonate that is simple and efficient, and allows polycarbonate with excellent hue to be obtained.

[Means to solve the problem]

The present invention is a method for purifying polycarbonate, which comprises treating polycarbonate produced by transesterification from a diol compound and carbonate with hydrogen in the presence of a hydrogenation catalyst in a liquid phase.

The polycarbonate to be purified in the present invention is
This is a polycarbonate produced by a transesterification method from a diol compound and carbonate.

Examples of diol compounds include bisphenol A (
2,2'-bis(4'-bitroxyphenyl)propane), PsP'-biphenol, hydroquinone, resorcinol, 2,6-cyhydroxynaphthalene, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl) Aromatic diol compounds such as ketones, 1.1-bis(4'-hydroxyphenyl)-1-phenylethane, bis(4'-hydroxyphenyl)sulfone; 1°4
Examples include aliphatic diol compounds such as -butanediol and 1,6-hexanediol.

Examples of carbonates include dimethyl carbonate,
Aliphatic carbonates such as diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methylbutyl carbonate, dioctyl carbonate, dicyclohexyl carbonate, ethylene carbonate, propylene carbonate; aromatic carbonates such as diphenyl carbonate; aliphatic aromatic carbonates such as methylphenyl carbonate, etc. can be given.

Among the above-mentioned polycarbonates, the purification method of the present invention is applicable to aromatic polycarbonates produced by a transesterification method from an aromatic diol compound and an aliphatic carbonate, and especially among them, produced from bisphenol A and dimethyl carbonate by a transesterification method. Suitable for purifying aromatic polycarbonates.

The raw material to be purified in the purification method of the present invention may be the reaction mixture obtained by the above-mentioned transesterification method, but
Polycarbonate that has been subjected to treatments such as desolvation, decatalysis, distillation purification, recrystallization purification, and adsorption purification is suitable as a raw material for purification.

In the purification method of the present invention, the above-mentioned purified raw material is treated with hydrogen in the presence of a hydrogenation catalyst in a liquid phase.

At this time, it is preferable that the purified raw material is dissolved in a solvent, but it is not necessary to dissolve it.

The proportion of the purified raw material contained in the reaction system is suitably 0.1% by weight or more, preferably 5 to 80% by weight.

Examples of solvents include aliphatic carbonates such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methylbutyl carbonate, dioctyl carbonate, dicyclohexyl carbonate, ethylene carbonate, and propylene carbonate; benzene, toluene, xylene, ethylbenzene, and hexane. , heptane, octane, and other hydrocarbons; methanol, ethanol, butanol, cyclohexanol, ethylene glycol, propylene glycol, and other alcohols; diethyl ether, tetrahydrofuran,
Examples include ethers such as l,4-dioxane, methoxybenzene, and tetraglyme. Among these, aliphatic carbonates are preferred, and those used in the production of polycarbonate can be used as the solvent. The solvents can be used alone or in combination of two or more.

Hydrogenation catalysts include Fe, Co, Ni, Ru,
Metals such as Rh, Pd, Os, Ir, Pt, and Cr, compounds such as oxides of these metals, those supported on carriers, and complexes of amines, phosphine, carbonyls, halogens, etc. can be used. These may be used alone or in combination of two or more.Supports include activated carbon, alumina, zeolite, graphite, silica, magnesium oxide, clay, barium sulfate, and calcium carbonate. etc. can be mentioned.

Specific hydrogenation catalysts include 1, for example, pto, R
h, O,, mixture of Pt and Rh, O, Raney nickel, palladium-carbon, facing-carbon, RhL, C4 (L represents tertiary phosphine such as triphenylphosphine and triethylphosphine), RhL, ( Cρ)Ill(
L is the same as above), (Rh(1,5-cyclooctadiene)ti) PF.

(L is the same as above), RuL4C (L is the same as above)
, RuL, CM, (L is the same as above), RuL, (
4H (L is the same as above), Ir(jl(Co)Lx (
Among them, Raney nickel, palladium-carbon, platinum-carbon, and Rh compounds are preferred.

The amount of hydrogenation catalyst to be used is 1X10-' to 1.0% by weight ratio of catalyst/polycarbonate. Preferably lXl0-'~1x
In the case of a catalyst supported on a carrier, the catalyst is used so that the portion excluding the carrier falls within the above range.

The treatment with hydrogen may be carried out while blowing hydrogen into the reaction system, or may be carried out under appropriate hydrogen pressure.

Specific methods for treatment with hydrogen include, for example, a method in which hydrogen gas is injected into the reaction vessel in advance and then the purified raw material is charged, or a method in which a certain amount of hydrogen gas is carried out after or at the same time as the purified raw material is charged into the reaction vessel. It is possible to adopt a method in which hydrogen gas is blown in, or a method in which hydrogen gas is blown in after refining raw materials are charged.

The amount of hydrogen gas injected when hydrogen is injected is as follows:
1 to 1000+ aQ/min, preferably 5 to 500 t12/min per 100 parts by weight of the refined raw material, and the hydrogen pressure in the case of hydrogen pressurization is 0.1 to 300 kg/aJ,
Preferably 0.5 to 100 kg/aJ.

The conditions for hydrogen treatment are usually normal pressure to 300 kg.
/ aJ, preferably normal pressure to 100 kg/cd, temperature usually room temperature to 300°C, preferably 50 to 250°C, reaction time usually 0.1 to 100 hours, preferably 0.2 to 1
0 hours is appropriate.

The treatment with hydrogen can be carried out in any type of reactor, such as a seed type, a tube wall type, or a base type reactor, and can be carried out in either a batch type or a continuous type reactor.

The desired polycarbonate can be isolated from the reaction solution after the hydrogen treatment by a method such as concentrating the solvent.

By purifying as described above, polycarbonate with excellent hue can be obtained. Such polycarbonate can be used as a raw material for polycarbonate resin, polyester carbonate resin, and the like.

〔Effect of the invention〕

According to the present invention, polycarbonate produced by a transesterification method is treated with hydrogen in the presence of a hydrogenation catalyst in a liquid phase, so a polycarbonate with an excellent hue can be efficiently obtained by a simple operation.

〔Example〕 Examples of the present invention will be described below.

Production Example 1 Bisphenol A aog, 158 g of dimethyl carbonate (DMC) and ((PhO
)BuJn)s.

(Here, Rh represents a phenyl group and Bu represents an n-butyl group.) 0.585 g was charged and heated to 250°C. DMC was supplied to this under pressure at an average rate of about 69 g/hr. The pressure at this time was about 17 to 20 kg/-.The reaction was carried out for 11.5 hours while methanol produced as the reaction progressed was distilled off under pressure from the upper part of the distillation column together with DMC.

The amount of DMC supplied during the reaction was 793 g, and the amount of distillate distilled out was 754 g. There were 21g of methanol in the distillate, and the rest was DMC.6 After the reaction, the reaction solution was collected from the reactor and the catalyst was removed by filtration.The reaction solution collected after the 0 reaction was 245g. there were. This reaction solution contained DMC and polycarbonate.

This reaction solution was subjected to GPC (gel perma- tion
As a result of analysis using chromatography, it was found that polycarbonate having a number average molecular weight (in terms of polystyrene) of 330 was produced. Also, the content of polycarbonate is 40% by weight, and the content of DNC is 60% by weight.
Met.

Example 1 233 g of the reaction solution from Production Example 1 and 1.5 g of 10% palladium-carbon were placed in a glass flask, and hydrogen gas was added to the
5mj! The mixture was heated at 90° C. under normal pressure for 2 hours and treated with hydrogen while blowing at a rate of /sin.

After the reaction, the catalyst was filtered to obtain a 0MC solution of polycarbonate. The polycarbonate content and molecular weight were the same as in the reaction solution of Production Example 1. When this solution was subjected to color difference analysis using Color Tester 5C-2-CH manufactured by Suga Test Instruments Co., Ltd., the hue value was 9 g, 23, the a value was -1.34, and the b value was 5.18.

Comparative Example 1 When the hue of the 0MC solution of polycarbonate obtained in Production Example 1 was analyzed in the same manner as in Example 1, the hue value was 9.
6.03, a value -2.99, and b value 13.06.

Agent: Patent attorney Sei Yanagi Hara

Claims (1)

[Claims] (1) A method for purifying polycarbonate, which comprises treating polycarbonate produced by a transesterification method from a diol compound and carbonate with hydrogen in the presence of a hydrogenation catalyst in a liquid phase.