JPH0826142B2 - Polycarbonate manufacturing method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to improvements in the production of polycarbonate. More specifically, the present invention is a polycarbonate capable of producing a high-molecular-weight polycarbonate without a catalyst from a dialkylbiscarbonate and a diphenylcarbonate, and recycling by-products produced at that time. Of the manufacturing method of.

2. Description of the Related Art In recent years, polycarbonate has been widely used in many fields as an engineering plastic excellent in heat resistance, impact resistance, transparency and the like. Various studies have hitherto been carried out on the production method of this polycarbonate, for example, a phosgene method in which 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) and phosgene are subjected to interfacial polycondensation in the presence of an alkali, Bisphenol A
A transesterification method or the like in which polyphenylene and diphenyl carbonate are melt-polycondensed is known.

However, in the former phosgene method, although a colorless and transparent polycarbonate is obtained, it requires complicated steps such as washing and removal of by-produced salts, removal of the polymer from the polymer solution, and recovery of the solvent. There are drawbacks such as having to use highly corrosive phosgene.

On the other hand, in the transesterification method, since there is no solvent,
The polymer is easy to take out and the process is simple.However, since the phenol compound is reacted in the presence of a catalyst at high temperature for a long time, a side reaction occurs, the generated polymer is colored, and the catalyst remains in the polymer. In order to
The polymer is unavoidably deteriorated in hydrolysis resistance and long-term heat resistance at the time of molding, and moreover, in order to reuse phenol produced as a by-product in the polymerization step as diphenyl carbonate, it is also highly toxic and corrosive. It has the disadvantage that phosgene must be used.

As another production method, there is known a method of producing a polycarbonate by condensing a biscarbonate of bisphenol A and an equimolar amount or less of bisphenol A (US Pat. No. 2,946,766). However, even in this method, since bisphenol A and a catalyst are used, as in the case of the transesterification method, the polymer is likely to be colored, and the hydrolysis resistance and long-term heat resistance are inferior.

That is, there is no coloring, and a high molecular weight polycarbonate excellent in hydrolysis stability and long-term heat resistance during molding, by recycling and recycling by-products, without using toxic or corrosive strong phosgene, Moreover, a method of manufacturing by a simple process has never been known.

Problems to be Solved by the Invention Under the circumstances, the present invention provides a polycarbonate which is not colored and is excellent in hydrolysis stability and long-term heat resistance during molding without using phosgene. The process
In addition, the present invention has been made for the purpose of providing a method that can be economically produced by recycling the by-product.

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the inventors have polymerized a dialkylbiscarbonate of bisphenol A and a diphenyl carbonate at a specific molar ratio, And by converting the alkyl phenyl carbonate produced as a by-product into a dialkyl carbonate and a diphenyl carbonate, and recycling them by recycling them in the monomer synthesis step and the polymerization step, respectively, it was found that the objective can be achieved, and to this finding Based on this, the present invention has been completed.

That is, the present invention relates to (A) 2,2-bis (p-hydroxyphenyl) propane (hereinafter referred to as bisphenol A) (Wherein R ¹ is a methyl group or an ethyl group) is reacted with a dialkyl carbonate represented by
General formula (Wherein R ¹ has the same meaning as described above), the first step for producing 2,2-bis (p-hydroxyphenyl) propanedialkylbiscarbonate, and (B) the first step 2,2-bis (p-hydroxyphenyl) propanedialkylbiscarbonate and an equivalent molar amount or more of diphenylcarbonate are
A second step of reacting at a temperature of 0 to 320 ° C. to form a polycarbonate, and (C) a general formula by-produced in the second step. (Wherein R ¹ has the same meaning as described above), an alkylphenyl carbonate represented by the formula: (In the formula, R ¹ has the same meaning as described above) and a dialkyl carbonate represented by the following third step, and the dialkyl carbonate and the diphenyl carbonate produced in the third step are respectively treated in the first step and The present invention provides a method for producing a polycarbonate, which is characterized by being recycled to the second step.

 Hereinafter, the present invention will be described in detail.

In the step (A) in the method of the present invention, that is, the first step, bisphenol A is reacted with a dialkyl carbonate represented by the general formula (I) to give a bisphenol A represented by the general formula (II). This is a step of producing dialkylbiscarbonate. Examples of the dialkyl carbonate include dimethyl carbonate and diethyl carbonate, and examples of the dialkyl biscarbonate of bisphenol A include bisphenol A corresponding to the dialkyl carbonate.
Dimethyl bis carbonate and diethyl bis carbonate.

A catalyst is usually used in the reaction of the first step. The catalyst is not particularly limited, and any one can be selected from those conventionally used in the transesterification method and used. Examples of such materials include Sn ⁴⁺ , Zn ²⁺ , Al ³⁺ , Ti ⁴⁺ , Mg ²⁺ , Zr ⁴⁺ , F
^Examples include metal alkoxy compounds such as e ³⁺ and Pb ²⁺ , aryloxy compounds, alkyl compounds, acetoxy compounds, and oxides. Specifically, di-n-butyltin oxide, di-n-butyl-diphenoxytin. , Tin acetate, zinc acetate, tetraisopropoxy titanium, and the like.

These catalysts may be used alone or in combination of two or more, and the amount used is not particularly limited, but usually 0.01 to bisphenol A is used.
It is selected in the range of 5 mol%.

The ratio of bisphenol A to dialkyl carbonate used is usually in the range of 1: 1 to 1: 100, preferably 1: 2 to 1:50 on a molar basis. If the amount of dialkyl carbonate used is less than the above range, the yield of the product will be low, and even if it is more, the yield will not increase, which is not advantageous.

Further, the reaction temperature is usually 100 to 250 ° C., preferably 12
It is selected in the range of 0 to 220 ° C. This reaction generally does not use a solvent, but a solvent may be used if desired.

The step (B), that is, the second step, is a step of reacting the dialkylbiscarbonate of bisphenol A represented by the general formula (II) obtained in the first step with diphenyl carbonate to produce a polycarbonate. is there.

The amount of the diphenyl carbonate used in the reaction in the second step must be equimolar or more to the dialkyl biscarbonate of bisphenol A. If it is less than this, a high molecular weight polycarbonate cannot be obtained. Further, if the amount of diphenyl carbonate used is too large, it is disadvantageous because the high boiling point diphenyl carbonate must be extracted at the final stage of the polymerization. The preferred proportion of diphenyl carbonate used is 1 to 3 mol per 1 mol of the dialkyl biscarbonate of bisphenol A,
Particularly preferably, it is selected in the range of 1 to 2 mol.

The reaction temperature is selected in the range of 150 to 320 ° C, preferably 200 to 300 ° C. The polymerization reaction may be carried out by melt polymerization of the product in a molten state, or after producing a crystalline solid by solution crystallization or melt crystallization of a low polymerization degree polycarbonate, under the flow of an inert gas or under reduced pressure. The solid phase polymerization may be carried out below preferably in the range of 180 to 240 ° C.
This polymerization reaction is preferably carried out without a catalyst, but a known polymerization catalyst used in the transesterification method may be used as necessary in order to increase the reaction rate. The catalyst used in this case is preferably as small as possible within a range that does not adversely affect the performance of the produced polymer. In the polymerization reaction of the second step, the alkylphenyl carbonate represented by the general formula (III) is by-produced. Specific examples of the alkyl phenyl carbonate include methyl phenyl carbonate and ethyl phenyl carbonate.

In the step (C), that is, the third step, a diphenyl carbonate and a dialkyl carbonate represented by the general formula (I) are obtained from the alkylphenyl carbonate represented by the general formula (III) which is by-produced in the second step. Is a step of generating.

The reaction in the third step is carried out in the presence of a catalyst, and as the catalyst, a catalyst conventionally used in a transesterification reaction can be used. Such catalysts include, for example, Sn ⁴⁺ , Zn ²⁺ , Al ³⁺ , Ti ⁴⁺ , Mg ²⁺ , Zr ⁴⁺ , Fe ³⁺ , metal alkoxy compounds such as Pb ²⁺ , aryloxy compounds,
Examples thereof include acetoxy compounds, oxides and alkyl compounds. Specific examples include di-n-butyltin oxide, tin acetate, zinc acetate, and tetraisopropoxytitanium.

The amount of the catalyst used is not particularly limited, but is usually 0.01 to 5 mol% relative to the alkylphenyl carbonate.
Used in the range of. The reaction temperature is usually 100 to 300.
C., preferably in the range of 150 to 200.degree. This reaction generally does not use a solvent, but can be carried out using a solvent if desired.

The dialkyl carbonate and the diphenyl carbonate obtained in the third step are the first step and the second step, respectively.
It is recycled to the process and reused.

Next, one of preferred embodiments of the manufacturing method of the present invention will be described.
Explaining an example, first, in a first step, a reactor is charged with a required amount of bisphenol A, a dialkyl carbonate represented by the general formula (I), and a catalyst, and the reaction system is preferably nitrogen, argon, helium, or the like. After replacement with an inert gas, the mixture is heated, and the reaction is carried out by maintaining the mixture at a predetermined temperature, and the produced methyl alcohol or ethyl alcohol is removed by distillation or circulation of an inert gas according to the above general formula. A dialkyl carbonate of bisphenol A represented by (II) is produced.

Next, the thus-obtained dialkyl carbonate and diphenyl carbonate of bisphenol A are put into reactors in required amounts, respectively, and the polymerization reaction of the second step is carried out. Specifically, after the reaction system is preferably replaced with an inert gas, it is heated and maintained at a predetermined temperature, and an inert gas is circulated, or the system is depressurized to generate the by-product of the general formula (III). By removing the alkylphenyl carbonate represented by the formula from outside the system, a polymerization reaction is carried out to form a polycarbonate. In order to obtain a high-molecular-weight polycarbonate, it is preferable to remove the alkylphenyl carbonate produced as a by-product, to pass an inert gas and then to reduce the pressure of the system. In this polymerization reaction, as described above, it is also possible to carry out solid phase polymerization using a polycarbonate which is taken out and crystallized in a low polymerization state.

Next, in the third step, a required amount of catalyst is added to the alkylphenyl carbonate produced as a by-product in the second step,
Preferably by heating in the presence of an inert gas, by distilling off the dialkyl carbonate produced, the equilibrium reaction is transferred to the production system side, the isomerization reaction proceeds, and dialkyl carbonate and diphenyl carbonate Is generated. The dialkyl carbonate thus obtained is returned to the first step, and the diphenyl carbonate is returned to the second step for recycling.

EFFECTS OF THE INVENTION The method of the present invention is an integrated one in which a high-molecular-weight polycarbonate is obtained in a short time even without a catalyst, and by-products are circulated and used, which has an extremely high industrial value.

In the method of the present invention, in the polymerization step which is the second step,
It is not always necessary to use a polymerization catalyst, which was essential in the conventional transesterification method, and besides, the hydrolysis resistance during molding and the long-term heat resistance are excellent, and coloring occurs because there is no hydroxyl group at the end. A difficult polycarbonate is obtained.

Furthermore, since no solvent is used in the polymerization, the process is simple as compared with the conventional phosgene method. Further, it is one of the important features of the present invention that no toxic and highly corrosive phosgene is used.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

The viscosity average molecular weight of the polymer was determined as follows.

That is, methylene chloride was used to prepare three kinds of solutions containing 0.5 g, 0.75 g and 1.0 g of the polymer per 100 cm ³ of the solution, and the viscosities thereof were measured at 25 ° C., and the formula [η] = {(ηrel− 1) / C} _{c → o} [where ηrel is the relative viscosity, c is the concentration (g / 100 ml), and c → o is the value of (ηrel-1) / C extrapolated to the point where the concentration c is 0. Then, the intrinsic viscosity [η] is obtained according to
The viscosity average molecular weight v was calculated according to the formula [η] = 1.23 × 10 ⁻⁴ v ^0.83 .

Example 1 (A) First Step Bisphenol A 22.8 g (100 mmol), dimethyl carbonate 270 g (3 mol), dibutyltin oxide 0.50
g (2 mmol) was put into an autoclave and replaced with nitrogen, then heated and kept at 160 ° C. and 7 Kg / cm ² , nitrogen was passed through the system to distill off methanol, and accompany with methanol. The reaction was continued for 10 hours with the addition of dimethyl carbonate for distillation. Then, the reaction solution was recrystallized from hexane to obtain bisphenol A dimethylbiscarbonate.

(B) Second step In a separable flask equipped with a stirrer, a thermometer, and a nitrogen inlet tube, 17.22 g (50 mmol) of bisphenol A dimethyl biscarbonate obtained in the first step and 16.07 g (75 mmol) of diphenyl carbonate were obtained. (Mmol) and replaced with nitrogen, the temperature was raised to 280 ° C in 1 hour, and the temperature was maintained for 1 hour. Then, nitrogen is passed through the system, and while maintaining the same temperature for 2 hours while distilling off the generated methylphenyl carbonate, the system is further depressurized (2 mmHg) and reacted for 5 hours, then cooled to room temperature. To give a transparent solid. The yield of this product was 97%, and v was 22,300.

(C) Third Step 13 g of the distillate obtained in the second step was distilled under reduced pressure to obtain 10.5 g (69 mmol) of methylphenyl carbonate.

In a flask equipped with an agitator, a thermometer, and a condenser tube, 10.5 g (69 mmol) of methylphenyl carbonate and di-
0.10 g (0.42 mol) of n-butyltin oxide was added, the system was replaced with nitrogen, and the system was heated in a nitrogen atmosphere and reacted at 160 ° C. for 10 hours. The obtained distillate was 2.40 g (53 mmol) of dimethyl carbonate, and 1.22 g (8 mmol) of methylphenyl carbonate and 5.71 g (53 mmol) of diphenyl carbonate were present in the reaction solution.

Methylphenyl carbonate was distilled off from this reaction solution and recrystallized from hexane to obtain diphenyl carbonate.

Example 2 A polymer having v of 18,500 was obtained in the same manner as in Example 1 except that 12.85 g (60 mmol) of diphenyl carbonate was used in the second step of Example 1.

Example 3 A polymer having v of 23,100 was obtained in the same manner as in Example 1 except that 19.78 g (90 mmol) of diphenyl carbonate was used in the second step of Example 1.

Example 4 In the second step of Example 1, the reaction time under reduced pressure was 6
In the same manner as in Example 1 except that time was set, v was 27,4.
Thus, a polymer No. 00 was obtained.

Example 5 (A) First step In the same manner as in Example 1, bisphenol A dimethyl biscarbonate was obtained.

(B) Second Step Using the same apparatus as in the second step of Example 1, the bisphenol A dimethyl biscarbonate obtained in the first step was used.
17.22 g (50 mmol) and 16.07 g diphenyl carbonate
(75 mmol) was added and the atmosphere was replaced with nitrogen.
The temperature was raised to 280 ° C., and the temperature was maintained for 1 hour. Then, nitrogen is circulated in the system, and the by-produced methylphenyl carbonate is distilled off and maintained for 2 hours, and then the system is depressurized (2 m
mHg) and held for 1 hour and then allowed to cool. 50 ml of methylene chloride was added to this reaction liquid to dissolve the polymer, and the product was taken out. Methylene chloride was distilled off from this solution with a rotary evaporator to obtain a white powdery solid of v4,500.

Next, the white powdery solid was heated to 220 ° C. under nitrogen flow.
After reacting for 20 hours, a white solid-state polycarbonate of v18,300 was obtained.

(C) Third Step In the same manner as in the third step of Example 1, dimethyl carbonate and diphenyl carbonate were obtained from the methylphenyl carbonate by-produced in the second step.

Claims (1)

[Claims] (A) 2,2-bis (p-hydroxyphenyl) propane (A) and a compound of the general formula (Wherein R ¹ is a methyl group or an ethyl group) is reacted with a dialkyl carbonate represented by
General formula (Wherein R ¹ has the same meaning as described above), the first step for producing 2,2-bis (p-hydroxyphenyl) propanedialkylbiscarbonate, and (B) the first step 2,2-bis (p-hydroxyphenyl) propanedialkylbiscarbonate and an equivalent molar amount or more of diphenylcarbonate are
A second step of reacting at a temperature of 0 to 320 ° C. to form a polycarbonate, and (C) a general formula by-produced in the second step. (Wherein R ¹ has the same meaning as described above), an alkylphenyl carbonate represented by the formula: (In the formula, R ¹ has the same meaning as described above) and a dialkyl carbonate represented by the following third step, and the dialkyl carbonate and the diphenyl carbonate produced in the third step are respectively treated in the first step and A method for producing a polycarbonate, characterized in that it is circulated in the second step.