JPH0753704A - Production of polycarbonate - Google Patents

Abstract

PURPOSE:To prevent the side reaction to thereby produce a polycarbonate improved in hue. CONSTITUTION:A process for producing a polycarbonate by the melt polycondensation through transesterification between a dihydroxy compound and a bisaryl carbonate, wherein a single compound formed from an alkali metal or alkaline earth metal compound and a nonvolatile acid or a mixture of them is used as the catalyst and wherein the single compound or the mixture is weakly acidic in the aqueous solution.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polycarbonate by a transesterification reaction. More particularly, it relates to a method for producing a high molecular weight aromatic polycarbonate having an improved color tone by transesterification of an aromatic diol compound and a carbonic acid diester compound.

[0002]

2. Description of the Related Art In recent years, aromatic polycarbonates have been widely used in many fields as engineering plastics having excellent mechanical properties such as impact resistance, heat resistance and transparency. .
As a method for producing this aromatic polycarbonate, a so-called phosgene method in which an aromatic diol such as bisphenol and phosgene are reacted by an interfacial polycondensation method has been industrialized. However, the phosgene method currently used industrially requires the use of extremely toxic phosgene, the problem of treating a large amount of by-produced sodium chloride, and the hygiene problem of methylene chloride which is usually used as a reaction solvent. Many problems have been pointed out, such as air pollution and atmospheric environment problems.

As a method for producing an aromatic polycarbonate other than the phosgene method, a melting method by a transesterification reaction between an aromatic diol compound and a carbonic acid diester is known. It is said that this method has the advantages that the above-mentioned phosgene method does not have the problems and that the aromatic polycarbonate can be produced at low cost. However, for example, in a melting method using a catalyst containing only an alkali metal compound from bisphenol A and diphenyl carbonate, in order to obtain a high molecular weight polycarbonate having excellent mechanical properties, a high viscosity polycarbonate melt is used. It is necessary to distill phenol and diphenyl carbonate from the inside, and the resulting polycarbonate is exposed to a high vacuum for a long time at a high temperature of 250 to 330 ° C. Therefore, the alkali metals act as a catalyst for the transesterification reaction and also cause side reactions such as a decarboxylation reaction and a Kolber-Schmitt-like reaction. It has been pointed out that these side reactions cause branching / crosslinking and cause coloring, and that it is generally difficult to obtain a product having an excellent balance of color tone / molecular weight by the melting method. ("Polycarbonate resin" published by Nikkan Kogyo Shimbun on September 30, 1969)

In order to solve these problems, for example, JP-A-4-89824 discloses (1) a nitrogen-containing basic compound, (2) an alkali metal compound or an alkaline earth metal compound, and (3) ) A catalyst composed of boric acid or boric acid ester, JP-A-4-46928 discloses, (1) an electron-donating amine compound, and (2) a catalyst composed of an alkali metal compound or an alkaline earth metal compound, or Japanese Patent Laid-Open No. 4-175368 discloses a method of performing melt polymerization in the presence of an alkaline compound catalyst, and then adding an acidic compound and an epoxy compound to the obtained reaction product. However, the above method is not always satisfactory in improving problems such as coloring.

[0005]

An object of the present invention is to provide a method for producing a polycarbonate by a transesterification method, in which a side reaction is suppressed and a hue is improved.

[0006]

[Technical Means for Solving Problems] The present invention relates to a method for producing a polycarbonate in which a divalent hydroxy compound and a bisaryl carbonate are melt-polycondensed by a transesterification method. As a catalyst, a single compound formed from a group metal compound and (b) a non-volatile acid, or (2) a mixture of (a) an alkali metal compound or an alkaline earth metal compound and (b) a non-volatile acid Use, and a method for producing a polycarbonate, characterized in that the single compound or the mixture exhibits weak acidity in an aqueous solution.

Specific examples of the divalent hydroxy compound used in the present invention include 2,2-bis- (4-hydroxyphenyl) propane (hereinafter abbreviated as bisphenol A) and bis (4-hydroxyphenyl) methane. , 2,2-bis- (4-hydroxyphenyl) butane, 2,2-bis- (4-hydroxyphenyl) -4-methylpentane, 2,2-bis- (4-hydroxyphenyl) octane, 4,4 '-Dihydroxy-2,2,2-triphenylethane, 2,2-bis- (3,5-dibromo-4-hydroxyphenyl) propane, 2,2-bis- (4-hydroxy-3-methylphenyl) Propane, 2,2-bis- (4-hydroxy-3-isopropylphenyl) propane, 2,2-bis- (4-hydroxy-3-sec-butylphenyl) propane, 2,2-bis- (3,5 -
Dimethyl-4-hydroxyphenyl) propane, 2,2-bis
-(4-hydroxy-3-tert-butylphenyl) propane, 1,
1'-bis- (4-hydroxyphenyl) -p-diisopropylbenzene, 1,1'-bis- (4-hydroxyphenyl) -m-diisopropylbenzene and other bis (hydroxyaryl) alkanes, 1,1-bis Bis (hydroxyaryl) cycloalkanes such as-(4-hydroxyphenyl) cyclohexane and 1,1-bis- (4-hydroxyphenyl) cyclopentane, bis (hydroxyaryl) sulfides such as 4,4'-dihydroxydiphenyl sulfide And the like. Of these, bisphenol A is preferably used. Furthermore, it is also possible to produce a copolycarbonate by combining two or more divalent hydroxy compounds.

Specific examples of the bis aryl carbonate used in the present invention include diphenyl carbonate and bis aryl carbonate.
(2,4-dichlorophenyl) carbonate, bis (2,4,6-
Examples thereof include trichlorophenyl) carbonate, bis (2-cyanophenyl) carbonate, bis (o-nitrophenyl) carbonate, ditolylcarbonate, m-cresylcarbonate, dinaphthylcarbonate and bis (diphenyl) carbonate. Of these, diphenyl carbonate is preferably used.

A single compound produced from (a) an alkali metal compound or an alkaline earth metal compound of the catalyst used in the present invention and (b) a nonvolatile acid is potassium dihydrogen phosphate (KH ₂ PO ₄ ), sodium dihydrogen phosphate (NaH ₂ PO
₄ ), weakly acidic salts such as potassium dihydrogen phosphite (KH ₂ PO ₃ ) and sodium dihydrogen phosphite (NaH ₂ PO ₃ ).

Specific examples of the (a) alkali metal compound or alkaline earth metal compound include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, sodium acetate, potassium acetate, Lithium acetate, sodium stearate,
Potassium stearate, lithium stearate, sodium borohydride, lithium borohydride, sodium benzoate, potassium benzoate, lithium benzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, dilithium hydrogen phosphate, bisphenol A Disodium salt, bisphenol A dipotassium salt, bisphenol A dilithium salt, calcium hydroxide, barium hydroxide, magnesium hydroxide, strontium hydroxide, calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, calcium acetate, Examples thereof include barium acetate, magnesium acetate and strontium acetate. Of these, potassium hydroxide is preferably used.

As the non-volatile acid (b), a non-volatile acid that does not evaporate during preliminary vacuum drying and melt polycondensation of the monomer mixture is preferably used. As the compound, a Lewis acid compound or a Bronsted acid compound, or a protonic acid or a mineral acid thereof can be preferably used. Specific examples include hypophosphorous acid, phosphorous acid, phosphoric acid,
Pyrophosphoric acid, polyphosphoric acid, sulfuric acid, arsenic acid, chromic acid, molybdic acid, selenious acid, selenic acid, vanadic acid, tungstic acid, p-toluenesulfonic acid and the like can be mentioned.
Of these, phosphoric acid is preferably used.

The catalyst of the present invention is a single compound produced from (1) (a) an alkali metal compound or an alkaline earth metal compound and (b) a non-volatile acid, or (2) (a) an alkali metal compound. Alternatively, it is a mixture of an alkaline earth metal compound and (b) a non-volatile acid, but the above single compound or mixture needs to exhibit weak acidity in an aqueous solution. As the degree of weak acidity, for example, when the concentration of the alkali metal compound or the alkaline earth metal compound is 0.1 mol / L,
The pH is preferably in the range of 3.0 to 6.5 at room temperature. In that case, if the pH is less than 3.0, the polymerization rate of the polycarbonate may be low, and a high molecular weight product may not be obtained. On the other hand, if the pH is higher than 6.5, coloring tends to occur, and a polycarbonate having a good hue may not be obtained. In addition, salts such as potassium dihydrogen phosphate that show weak acidity alone are used as they are.

The catalyst of the present invention is prepared as an aqueous solution. Generally, in the transesterification reaction, the hydrolysis reaction proceeds in the presence of water. Therefore, it is preferable that water does not exist under high temperature conditions in which a transesterification reaction between a dihydric phenol such as bisphenol A and a bisaryl carbonate proceeds. Therefore, it is preferable that after the catalyst is added to the monomer mixture at room temperature, it is usually dried under reduced pressure at a temperature of 150 ° C. or lower, more preferably 100 ° C. or lower to substantially remove water.

In the present invention, the alkali metal compound or the alkaline earth metal compound is present in the reaction system.
The amount of the alkali metal or alkaline earth metal is usually 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol, preferably 1 × 10 ⁻⁶ to 5 × 10 ⁻⁴ mol, relative to 1 mol of the phenol. .

The amount of the bisaryl carbonate used is usually 1 to 1 mol with respect to 1 mol of the divalent hydroxy compound.
It is 1.3 mol, and more preferably 1.01 to 1.2 mol.

[0016]

EXAMPLES Examples of the present invention will be described below. (Measurement method) The physical property measurement methods and test methods shown in the examples of the present invention are shown below. (1) Logarithmic viscosity (η _inh ); in chloroform at 30 ℃
It was measured at a concentration of 0.5 g / dl using a Cannon-Fenske viscometer. η _inh was calculated according to the following equation. η _inh
= ln (t / t ₀ ) / c where t ₀ is the chloroform drop time,
t is the drop time of the sample solution and c is the concentration of the sample. (2) Glass transition temperature (Tg); Seiko Denshi Kogyo D
The sample was heated in nitrogen at 10 ° C./min using an SC220C apparatus, and the inflection point of the endothermic curve was taken as Tg. (3) Hue (A ₃₅₀ -A _600): a Hitachi Ltd. self-recording spectrophotometer 330 type device apparatus, the difference in absorbance at a wavelength range of 350nm and 600nm of 10% methylene chloride solution of polycarbonate (A ₃₅₀ -A ₆₀₀ ) was measured. The larger this value is, the more colored it is.

Example 1 22.8 g (0.1 mol) of bisphenol A purified by recrystallization with a toluene-ethanol mixed solution after washing with methylene chloride,
After washing with warm water at 80 ° C, 22.7 g (0.106 mol) of diphenyl carbonate purified by vacuum distillation and 29 μl of 0.1 mol / L potassium dihydrogen phosphate aqueous solution (pH = 4.5) (2.9 × 10 ^-6 mol as potassium metal) ) Was added to a 100 mL reaction kettle made of SUS316L and dried under reduced pressure at 80 ° C. for 30 minutes to remove water.
Then, under nitrogen flow, stir at 200 ° C for 30 minutes, gradually reduce the pressure, raise the temperature, and finally melt polycondense at 0.1 Torr, 270 ° C for 1 hour, distill off the phenol produced, and remove the polycarbonate. Obtained. The polycarbonate obtained is
η _inh is 0.443, Tg is 145 ° C, and (A ₃₅₀ −
A ₆₀₀ ) was 0.015, and it was a tough colorless and transparent polymer.

Example 2 As a catalyst, an aqueous solution containing potassium hydroxide and phosphoric acid and adjusted to pH = 4.0 at a potassium metal concentration of 0.1 mol / L was used.
The reaction was performed in the same manner as in Example 1 except that 9 μl (5.9 × 10 ⁻⁶ mol as potassium metal) was used. The obtained polycarbonate had a η _inh of 0.378, a Tg of 142 ° C., and an (A ₃₅₀ -A ₆₀₀ ) of 0.012, and was a tough colorless and transparent polymer.

Example 3 As a catalyst, an aqueous solution containing potassium hydroxide and phosphoric acid and adjusted to pH = 5.1 with a potassium metal concentration of 0.1 mol / L was used.
The reaction was performed in the same manner as in Example 1 except that 9 μl (2.9 × 10 ⁻⁶ mol of potassium metal) was used. The obtained polycarbonate had a η _inh of 0.532, a Tg of 150 ° C., and an (A ₃₅₀ -A ₆₀₀ ) of 0.016, and was a tough colorless and transparent polymer.

Example 4 As a catalyst, an aqueous solution of potassium hydroxide and sulfuric acid adjusted to pH = 4.5 at a potassium metal concentration of 0.1 mol / L was used.
The reaction was performed in the same manner as in Example 1 except that μl (2.9 × 10 ⁻⁶ mol of potassium metal) was used. The obtained polycarbonate had a η _inh of 0.332, a Tg of 141 ° C., and an (A ₃₅₀ -A ₆₀₀ ) of 0.016, and was a tough colorless and transparent polymer.

Comparative Example 1 As a catalyst, an aqueous solution containing potassium hydroxide and phosphoric acid and adjusted to pH = 2.5 at a potassium metal concentration of 0.1 mol / L was used.
The reaction was performed in the same manner as in Example 1 except that 9 μl (2.9 × 10 ⁻⁶ mol of potassium metal) was used. Almost no formation of phenol was observed, and no polycarbonate was obtained.

Comparative Example 2 As a catalyst, an aqueous solution containing potassium hydroxide and phosphoric acid and adjusted to pH = 9.0 with a potassium metal concentration of 0.1 mol / L was used.
The reaction was performed in the same manner as in Example 1 except that 9 μl (2.9 × 10 ⁻⁶ mol of potassium metal) was used. The obtained polycarbonate was a tough polymer with η _inh of 0.620 and Tg of 151 ° C, but it was colored a little yellow,
(A ₃₅₀ -A ₆₀₀₎ was 0.138.

Claims (1)

[Claims] 1. A method for producing a polycarbonate by melt polycondensation of a divalent hydroxy compound and a bisaryl carbonate by a transesterification method, which comprises (1) (a) an alkali metal compound or an alkaline earth metal compound and (b) a nonvolatile Using a single compound formed from an acid or (2) (a) an alkali metal compound or an alkaline earth metal compound and (b) a non-volatile acid as a catalyst, and the single compound or the A method for producing a polycarbonate, wherein the mixture exhibits weak acidity in an aqueous solution.