JPH0826141B2 - Method for producing polycarbonate - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a method for producing a polycarbonate. More specifically, the present invention provides a polycarbonate having a high hydrolysis resistance and long-term heat resistance at the time of molding and a high molecular weight, which is industrially efficiently produced by a reaction of a dialkylbiscarbonate of bisphenol A and diphenylcarbonate. The present invention relates to a manufacturing method.

BACKGROUND ART In recent years, polycarbonate has been used as an engineering plastic excellent in heat resistance, impact resistance, transparency, etc.
Widely used in many fields. Various studies have been conducted on the production method of this polycarbonate, for example, a phosgene method in which bisphenol A and phosgene are subjected to interfacial polycondensation in the presence of an alkali, a transesterification method in which bisphenol A and diphenyl carbonate are melt-polycondensed, and the like. Is being developed.

However, in the former phosgene method, a colorless transparent polycarbonate is obtained, but toxic phosgene must be used, and a step of washing and removing inorganic salts such as sodium chloride produced as a by-product is required, and a solvent is used. Since it is used, it has a drawback in that it is difficult to take out the polymer from the reaction solution and the operation is complicated because a solvent recovery step is required.

On the other hand, in the transesterification method, since it is not necessary to use a solvent, it is easy to take out the polymer from the reaction solution and the process is relatively simple, but the phenol compound is reacted for a long time at a high temperature in the presence of a catalyst. Therefore, a side reaction occurs, the produced polymer is colored, and the catalyst remaining in the polymer is disadvantageous in that the polymer does not have sufficient hydrolysis resistance stability and long-term heat resistance during molding. .

On the other hand, a method is known in which biscarbonate of bisphenol A is condensed with bisphenol A in an equimolar amount or less (US Pat. No. 2,946,766). However, this method also has the same drawbacks as the above-mentioned transesterification method due to the use of a catalyst.

As described above, a method for producing a high-molecular-weight polycarbonate that is not colored and is excellent in hydrolysis resistance during molding and long-term heat resistance in a simple process has not been known until now.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention provides a method for efficiently producing a high-molecular-weight polycarbonate which is not colored and is excellent in hydrolysis resistance during molding, long-term heat resistance and the like in a simple process. It was made for the purpose.

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have used dialkylbiscarbonate and diphenylcarbonate of bisphenol A in a specific molar ratio and used them as a catalyst. It was found that the object can be achieved by carrying out the reaction at a predetermined temperature in the absence of the, and based on this finding, the present invention was completed.

That is, the present invention has the general formula (In the formula, R ¹ and R ² are each a lower alkyl group) 2,2-bis (p-hydroxyphenyl) propane (bisphenol A) dialkyl biscarbonate and at least the dialkyl biscarbonate Equimolar diphenyl carbonate with 150-320 ℃
The present invention provides a method for producing a polycarbonate, characterized in that the reaction is carried out at the temperature of.

Hereinafter, the present invention will be described in detail.

2, which is used as one of the raw materials in the method of the present invention,
The dialkyl carbonate of 2-bis (p-hydroxyphenyl) propane (bisphenol A) has a structure represented by the general formula (I), and includes, for example, bisphenol A-dimethylbiscarbonate and bisphenol A-diethylbiscarbonate. Can be mentioned. Among these, bisphenol A-dimethylbiscarbonate is particularly preferable in that a high molecular weight polycarbonate can be obtained. These dialkyl biscarbonates of bisphenol A may be used alone or in combination of two or more.

In the method of the present invention, diphenyl carbonate is used as another raw material. This diphenyl carbonate must be used in an equimolar amount or more with respect to the dialkyl biscarbonate of bisphenol A. If this amount is less than equimolar, a high molecular weight polycarbonate cannot be obtained. However, if the amount of diphenyl carbonate is too large, it is disadvantageous because the high boiling point diphenyl carbonate must be taken out of the reaction system at the final stage of the polymerization. Therefore, the amount of diphenyl carbonate used is
It is desirable to select in the range of 1 to 3 mol, preferably 1 to 2 mol, per 1 mol of dialkyl biscarbonate of bisphenol A.

The polymerization reaction temperature in the present invention is selected in the range of 150 to 320 ° C. If this temperature is lower than 150 ° C., the progress of the polymerization reaction is slow, which is not practical, and if it exceeds 320 ° C., a side reaction may occur to deteriorate the polymer. The preferred reaction temperature varies depending on the polymerization method, and is usually selected in the range of 200 to 300 ° C in the case of the melt polymerization method, and is selected in the range of 180 to 240 ° C in the case of the solid phase polymerization method.

In the method of the present invention, other various dihydroxy compounds [for example, "Plastic Materials Course [5] (published by Nikkan Kogyo KK)", polycarbonate resin, pages 18 to 28, together with the above-mentioned dialkylbiscarbonate of bisphenol A, if desired. And the like], and may be copolymerized.

In the method of the present invention, a high-molecular weight polycarbonate can be obtained without using a catalyst, but a catalyst can be used if desired in order to further increase the reaction rate. In this case, the amount of the catalyst needs to be within the range in which the catalyst remaining in the polycarbonate does not impair the physical properties of the polycarbonate.

Next, an example of a preferred embodiment of the present invention will be described. As the polymerization method, there are a melt polymerization method and a solid phase polymerization method, and either method can be used. In the former melt polymerization method, first, a required amount of a dialkylbiscarbonate of bisphenol A and diphenyl carbonate are charged into a reactor, and then this mixture is preferably added.
The reaction is carried out by heating in an atmosphere of an inert gas such as nitrogen, argon or helium and at a temperature in the range of 150 to 320 ° C, preferably 200 to 300 ° C. Next, in order to remove the low molecular weight carbonate such as phenylalkyl carbonate to be produced outside the system, an inert gas is circulated or the system is depressurized at the same temperature range as described above, but the high molecular weight In order to obtain polycarbonate, it is preferable to circulate an inert gas and then reduce the pressure in the system. In this polymerization method, the reaction always proceeds in a state where the product is molten.

On the other hand, in the solid phase polymerization method, by a known crystallization operation such as solution crystallization, first, a crystalline solid of a polycarbonate having a low degree of polymerization is produced, and then under the flow of an inert gas or under reduced pressure, preferably 180 Solid phase polymerization is carried out at a temperature in the range of to 240 ° C.

The polycarbonate obtained by such a method has a high molecular weight without coloring and is excellent in hydrolysis resistance during molding and long-term heat resistance.

EFFECTS OF THE INVENTION According to the method of the present invention, as compared with the conventional transesterification method, it is not necessary to use a catalyst, so that a high-molecular-weight polycarbonate having excellent hydrolysis stability during molding and long-term heat resistance can be obtained. You can Further, since the obtained polycarbonate does not have a hydroxy group at the terminal,
It has the characteristic that coloring is unlikely to occur.

Further, the method of the present invention has a simplified process as compared with the conventional phosgene method because no solvent is used in the polymerization.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

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

Viscosity average molecular weight (▲ ▼) Using methylene chloride, 0.5 g of polymer per 100 cm ^{3 of} solution,
Three kinds of solutions containing 0.75 g and 1.0 g were prepared and the viscosity thereof was 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 means that the value of (ηrel-1) / C is extrapolated to the point where the concentration C is O]] to obtain the intrinsic viscosity [η]. Then, the viscosity average molecular weight (▲ ▼) was calculated from the formula [η] = 1.23 × 10 ⁻⁴ ▲ ▼ ^0.83 .

Example 1 In a separable flask equipped with a stirrer, a thermometer, and a nitrogen inlet tube, 17.22 g (50 mmol) of bisphenol A-dimethylbiscarbonate and 1 diphenyl carbonate were added.
After adding 6.07 g (75 mmol) and replacing with nitrogen, 1
The temperature was raised to 280 ° C. for an hour and kept for 1 hour. Then, nitrogen was circulated in the system, and the produced methylphenyl carbonate and the like were distilled off, and the temperature was maintained for 2 hours. The system was further evacuated (2 mmHg), reacted for 5 hours, and then cooled to room temperature to obtain a transparent solid. The yield of the obtained polycarbonate was 97% and ▲ ▼ was 22,300.

Example 2 In Example 1, 12.85 g of diphenyl carbonate
A polycarbonate having a triangle of 18,500 was obtained in the same manner as in Example 1 except that (60 mmol) was used.

Example 3 In Example 1, 19.78 g of diphenyl carbonate
A polycarbonate having a ▲ ▼ of 23,100 was obtained in the same manner as in Example 1 except that (90 mmol) was used.

Example 4 A polycarbonate having ▲ ▼ of 27,400 was obtained in the same manner as in Example 1 except that the reaction time under reduced pressure was 6 hours.

Example 5 Using an apparatus similar to that of Example 1, this was charged with 18.62 g (50 mmol) of bisphenol A-diethyl carbonate,
Add 16.07 g (75 mmol) of diphenyl carbonate,
After substituting with nitrogen, the temperature was raised to 280 ° C. in 1 hour and kept for 1 hour. Then, nitrogen was circulated in the system, and the resulting product was maintained for 2 hours while distilling off the produced ethylphenyl carbonate and the like. Further, the system was evacuated (2 mmHg) and kept for 5 hours and cooled to obtain a polycarbonate having a triangle of 20,900.

Example 6 The same apparatus as in Example 1 was used, and 17.22 g (50 mmol) of bisphenol A-dimethylbiscarbonate was used.
And 16.07 g (75 mmol) of diphenyl carbonate were added and the atmosphere was replaced with nitrogen.
Held for hours. Then, nitrogen was circulated in the system, and the produced methylphenyl carbonate and the like were distilled off and maintained for 2 hours. The system was further evacuated (2 mmHg) and kept for 1 hour, and then allowed to cool. Next, 50 ml of methylene chloride was added to dissolve and take out the polymer, and methylene chloride was distilled off from this solution with a rotary evaporator to obtain a white solid powder (Mv4500).

This white solid powder was reacted at 220 ° C. for 20 hours under a nitrogen stream to obtain {circle around (18)} 300, a white solid polycarbonate.

Claims (1)

[Claims] 1. A general formula (Wherein R ¹ and R ² are each a lower alkyl group), and the dialkyl biscarbonate of 2,2-bis (p-hydroxyphenyl) propane and at least equimolar diphenyl to the dialkyl biscarbonate. A method for producing a polycarbonate, which comprises reacting a carbonate with a temperature of 150 to 320 ° C.