KR20030068199A - Process for the production of polycarbonate - Google Patents

Abstract

The present invention relates to a method for preparing polycarbonate by melt-polycondensation of an aromatic dihydroxy compound and diphenyl carbonate, the method comprising adding a compound of formula 1 to the polycarbonate under melting conditions:

Formula 1

Where

R ₁ and R ₃ may be the same or different and are selected from the group consisting of alkoxy, phenoxy, benzoxy, aryloxy, phenyl and aryl groups;

R ₂ is selected from the group consisting of alkyl, phenyl, aryl or aralkyl groups.

Description

PROCESS FOR THE PRODUCTION OF POLYCARBONATE}

Polycarbonates are excellent in mechanical properties such as impact resistance, exhibit excellent heat resistance and transparency, and are widely used for various technical purposes. In the method for producing a polycarbonate, an aromatic dihydroxy compound such as bisphenol and a diaryl carbonate such as diphenyl carbonate are subjected to transesterification in a molten state (melt-polycondensation method). In the melt-polycondensation method, it is known to add a polymerization promoter to the reaction system to improve the degree of polymerization of polycarbonates. Increasing molecular weight accumulation increases the yield of polycarbonate through shorter residence times and lower reactor temperatures in the reactor, and consequently facilitates simpler and lower cost reactor designs.

Japanese Patent Application No. Hei 7-90074 is a method for preparing polycarbonates from divalent compounds and carbonic acid diesters using a transesterification method, wherein a high activity having two or more functional groups when the transesterification rate exceeds 70% A process for the addition of diesters, acid halides or acid anhydrides to obtain polycarbonates with improved degree of polymerization is disclosed. Japanese Patent Application No. 7-90074 discloses 4-nitrophenol, 4-cyanophenol and chlorinated phenols such as bis (4-nitrophenyl) carbonate, bis (4-cyanophenyl) carbonate and It should be noted that the teaching of the use of highly active carbonic acid diesters based on bis (4-chlorophenyl) carbonate. The use of such compounds results in the production of colored or potentially toxic or explosive by-products, or substances which produce chlorine-containing gas products on combustion. Therefore, there is a need for the use of a polymerization promoter that does not contain chlorine, cyano- and nitroactive groups in terms of product quality (transparency), handling and environmental issues.

U.S. Pat.No. 5,696,222 discloses certain polymerization promoters such as bis (2-methoxyphenyl) carbonate, bis (2-ethoxyphenyl) carbonate, bis (2-chlorophenyl) carbonate, bis (2-methoxyphenyl) A process for producing polycarbonates having improved degree of polymerization is disclosed by adding carbonates and dicarboxylic acid aryl esters comprising terphthalates and bis (2-methoxyphenyl) adipates. It is to be noted that U. S. Patent 5,696, 222 teaches the introduction of ester linkages when using esters as polymerization promoters, resulting in polyester carbonate copolymers (instead of homopolymers) and lower hydrolytic stability.

There is still a need for an improved process for producing polycarbonates having an improved degree of polymerization.

Summary of the Invention

The present invention relates to a method for preparing a polycarbonate comprising the step of adding a polymerization promoting compound of formula (I):

Where

R ₁ and R ₃ may be the same or different and are selected from the group consisting of alkoxy, phenoxy, benzoxy, aryloxy, phenyl and aryl groups;

R ₂ is selected from the group consisting of alkyl, phenyl, aryl or aralkyl groups.

The phenyl, aryl or aralkyl may be optionally substituted. The alkyl group can be any linear, branched and cyclic alkyl group.

In one embodiment, the polymerization promoter is selected from the group made from salicylate esters of bisphenols and bis-chloroformates.

In one embodiment, the polymerization promoter is selected from the group consisting of BPA-bis-methyl salicylic carbonate, BPA-bis-n-propyl salicyl carbonate, BPA-bis-benzyl salicylic carbonate and mixtures thereof.

In another embodiment of the invention, the polymerization promoter is added to the oligomer after the number average molecular weight of the polycarbonate oligomer reaches about 2,500-15,000 Daltons.

The present invention relates to a method for producing a polycarbonate. More specifically, it is related with the manufacturing method of the polycarbonate which improved the degree of polymerization by using a polymerization promoter.

Polymerization Accelerator / Coupling Agent

In the process of the invention, the compound of formula 1 is added to the polycarbonate oligomer to accumulate molecular weight:

Formula 1

Where

R ₁ and R ₃ may be the same or different and are selected from the group consisting of alkoxy, phenoxy, benzoxy, aryloxy, phenyl and aryl groups;

R ₂ is selected from the group consisting of alkyl, phenyl, aryl or aralkyl groups.

The phenyl, aryl or aralkyl may be optionally substituted. The alkyl group can be any linear, branched and cyclic alkyl group. In one embodiment, R ₁ and R ₃ are selected from the group consisting of methoxy, ethoxy, n-propoxy, benzoxy, phenoxy, phenyl and methoxycarbonyl. In another embodiment, the polymerization promoter is selected from the group prepared from bis-chloroformates of bisphenols. In another embodiment, the polymerization promoter is BPA bis-methyl salicyl carbonate.

Preparation : In one embodiment of the invention, the polymerization promoter is selected from the group consisting of activated bis-chloroformates (e.g. BPA-bis-chloroformates) in the presence of a base in a solvent such as methylene chloride. Prepared by neutralizing free HCl by reacting with 2 equivalents of methyl salicylate, for example. In the reaction further catalysts can be used to promote the condensation reaction. After completion of the condensation reaction, the product solution is washed with an acidic aqueous solution and a basic aqueous solution and washed with water until the wash is neutral. The organic solvent is distilled off and the polymerization accelerator is recovered by crystallization.

The condensation reaction for preparing the polymerization promoter of the present invention is carried out under anhydrous conditions known in the art using at least one equivalent of tertiary amine per equivalent of chloroformate, or in the presence of an aqueous sodium hydroxide in the presence of a condensation catalyst. Can be carried out under interfacial conditions well known in the art using as a base. In one embodiment, the condensation catalyst is triethyl amine, quaternary alkyl ammonium salt or mixtures thereof.

Polycarbonate Production Process : The polymerization promoter of the present invention may be used to accumulate the molecular weight of the polycarbonate oligomer prepared by one of the above interfacial or melting processes. The polymerization promoter acts as a coupling agent and is a terminal hydroxy group of the polycarbonate as shown in Scheme 1 below. Reacts with the end of to increase the molecular weight of the polycarbonate.

Once added to the melting reactor, the ortho-substituted phenol is removed by distillation into the tower system to promote end blockage in high yield. The phenol can be recovered and recycled / reused to produce additional polymerization promoters.

Increased molecular weight polycarbonates may still contain minor amounts of unrecovered phenols, unreacted polymerization promoters, along with byproducts of side reactions of the polymerization promotion reactions, such as terminal 2- (alkoxycarbonyl) phenyl groups and the like. In one embodiment, the end-blocked polycarbonate contains less than about 500 ppm of ortho-substituted phenol and about 500 ppm of unreacted polymerization promoter of the present invention. In another embodiment, the increased molecular weight polycarbonate contains up to about 2,500 ppm of terminal 2- (alkoxycarbonyl) phenyl groups.

Molten Polycarbonate Process: In one embodiment of the present invention, the promoter is added to the melt or transesterification process. The preparation of polycarbonates by transesterification is well known in the art, see, for example, Organic Polymer Chemistry by K. J. Saunders, 1973, Chapman and Hall Ltd. and US Pat. No. 3,442,854; 5,026,817; 5,026,817; 5,097,002; No. 5,142,018; 5,151,491; And US Pat. No. 5,340,905.

In the melting process, the polycarbonate is produced by melt polycondensation of an aromatic dihydroxy compound (A) and a carbonic acid diester (B). The reaction can be carried out batchwise or continuously. The apparatus in which the reaction is carried out can be any suitable type of tank, tube or column. In a continuous process, at least one CSTR and at least one finishing reactor are generally used.

Examples of aromatic dihydroxy compounds (A) include bis (hydroxyaryl) alkanes such as bis (4-hydroxyphenyl) methane; 1,1-bis (4-hydroxyphenyl) ethane; 2,2-bis (4-hydroxyphenyl) propane (also known as "bisphenol A"); 2,2-bis (4-hydroxyphenyl) butane; 2,2-bis (4-hydroxyphenyl) octane; Bis (4-hydroxyphenyl) phenylmethane; 2,2-bis (4-hydroxy-1-methylphenyl) propane; 1,1-bis (4-hydroxy-t-butylphenyl) propane; And 2,2-bis (4-hydroxy-3-bromophenyl) propane; Bis (hydroxyaryl) cycloalkanes such as 1,1- (4-hydroxyphenyl) cyclopentane and 1,1-bis (4-hydroxyphenyl) cyclohexane; Dihydroxyaryl ethers such as 4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxy-3,3'-dimethylphenyl ether; Dihydroxydiaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; Dihydroxydiaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfoxide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide; And dihydroxydiaryl sulfones such as 4,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone. In one embodiment, the aromatic dihydroxy compound is bisphenol A (BPA).

Examples of the carbonic acid diester (B) include diphenyl carbonate; Ditolyl carbonate; Bis (chlorophenyl) carbonate; m-cresyl carbonate; Dinaphthyl carbonate; Bis (diphenyl) carbonate; Diethyl carbonate; Dimethyl carbonate; Dibutyl carbonate; And dicyclohexyl carbonate. In one embodiment of the industrial process, diphenyl carbonate (DPC) is used.

In one embodiment of the invention, a polymerization promoter is added with DPC or another diaryl carbonate to form a high end-cap level of polycarbonate.

In addition, the carbonic acid diester component may contain a small amount of dicarboxylic acid or ester thereof (for example, terephthalic acid or diphenyl isophthalate), for example, to prepare a polyester carbonate.

In the production of polycarbonates, generally from about 1.0 mole to about 1.30 mole of carbonic acid diester per mole of aromatic dihydroxy compound is used. In one embodiment, about 1.01 mole to about 1.20 mole of carbonic acid diester is used.

Terminator / Capping Agent : In one embodiment of the melting process, a terminator or capping agent may be used to prepare the polycarbonate. Examples of terminators include phenol, pt-butylphenol, p-cumylphenol, octylphenol, nonylphenol and other capping agents well known in the art.

Branching Agent: In one embodiment of the process of the present invention, a branching agent is used as needed. Branching agents are well known and may include multifunctional organic compounds having three or more functional groups (which may be hydroxyl, carboxyl, carboxylic anhydride and mixtures thereof). Specific examples include trimellitic acid, trimellitic anhydride, trimellitic trichloride, tris-p-hydroxy phenyl ethane, isatin-bis-phenol, tris-phenol TC (1,3,5-tris ((p- Hydroxyphenyl) isopropyl) benzene), tris-phenol PA (4 (4 (1,1-bis (p-hydroxyphenyl) -ethyl) alpha, alpha-dimethyl benzyl) phenol, trimesic acid and benzophenone tetra Carboxylic acids.

Optional Catalyst: The polycarbonate synthesis can be carried out in the presence of a catalyst to promote the transesterification reaction. Examples include alkali metals and alkaline earth metals as such or as oxides, hydroxides, amide compounds, alcoholates and phenolates; Basic metal oxides (eg, ZnO, PbO and Sb ₂ O ₃ ); Organo titanium compounds; Soluble manganese compounds; Nitrogen-containing basic compounds; And acetates of calcium, magnesium, zinc, lead, tin, manganese, cadmium and cobalt; And boron compounds, nitrogen-containing basic compounds and alkali metal (alkaline earth metal) compounds; And nitrogen-containing basic compounds, alkali metal (alkaline earth metal) compounds, and boron compounds.

In one embodiment of the invention, the transesterification catalyst is a quaternary ammonium compound or quaternary phosphonium compound. Non-limiting examples of these compounds are tetramethyl ammonium hydroxide, tetramethyl ammonium acetate, tetramethyl ammonium fluoride, tetramethyl ammonium tetraphenyl borate, tetraphenyl phosphonium fluoride, tetraphenyl phosphonium tetraphenyl borate, tetrabutyl Phosphonium hydroxide and dimethyl diphenyl ammonium hydroxide.

The catalysts described above can be used on their own or in combination of two or more types, depending on the intended use. If more than one catalyst is used, each catalyst may be incorporated into the melt at different stages of the reaction.

The appropriate level of catalyst will depend in part on the number of catalysts used, for example one or two. Generally, the total amount of catalyst is about 1 × 10 ⁻⁸ to about 1.0 mole per mole of dihydroxy compound. In one embodiment, the level is about 1 × 10 ⁻⁵ to about 5 × 10 ⁻² moles per mole of the dihydroxy compound. If more than one catalyst is used, each catalyst may be incorporated into the melt at different stages of the reaction.

Any component of the polycarbonate : In the present invention, the polycarbonate obtained is a heat stabilizer, ultraviolet absorber, mold releasing agent, colorant, antistatic agent, lubricant, anti-fogging agent generally used in the art. fogging agents), natural oils, synthetic oils, waxes, organic fillers and inorganic fillers.

Addition of Polymerization Accelerator to Melting Process : The method for adding the promoter of the present invention to a polycarbonate is not particularly limited. For example, an accelerator may be added to the polycarbonate as the reaction product during polycarbonate formation or during the melting step, or added during extrusion or pelletization, or the polycarbonate is still between the final polymerization reactor and the extruder or pelletizer. It may be added to the polycarbonate when present in the molten state.

The polymerization promoter is added at a stoichiometric ratio of about 0.1 to 2.5 with respect to the free OH content of the polycarbonate oligomer to be added. In one embodiment, it is added at a stoichiometric ratio of about 0.2 to 1.5. In another embodiment, the addition is at stoichiometric ratios of about 0.3 to 1.2.

Accelerators of the present invention can be added to the polycarbonate oligomer by various means and various steps depending on the equipment and process conditions used (eg batch reactors, continuous reactor systems or extruders). In another embodiment of the melting process, the promoter is added to the post reactor of the continuous reaction system. In another embodiment the promoter is added between the final reactor of the system and the first polymerizer in the continuous melt reactor system. In another embodiment, it is added between the first and second polymerizers in a continuous melt reactor system. The reactor used in the reaction may be in the form of one of any vessel, tube or column.

In one embodiment, the promoter is added after the polycarbonate oligomer is formed in the molten state. In a preferred embodiment, the promoter is added in an amount of at least 80% (more preferably at least 90%) of the total amount of promoter after the number average molecular weight of the polycarbonate oligomer reaches about 2,500-15,000 Daltons. In another embodiment of the invention, the polymerization promoter is added after the Mn of the polycarbonate oligomer reaches about 4,000 to 10,000 Daltons.

In one embodiment, the promoter is added to the process of the present invention after forming the polycarbonate oligomer at a reaction temperature of about 200 to 350 ° C. for about 10 to 90 minutes in the molten state. In a second embodiment, the reaction time is about 30 to 60 minutes at a reactor temperature of about 300 ° C.

The device / process for supplying the accelerator is not particularly limited. The promoter may be added in the form of a solution in a solid, liquid, melt or solvent thereof. In addition, the promoter may first be added once in a predetermined amount, or may be added over several times separately in a predetermined amount. In one embodiment, an accelerator is added to the process as a powder by means of an electrostatic mixer.

The present invention will be described with reference to the following examples, which are not intended to limit the invention to the following examples. In the following examples, the following measurements were made.

a) Molecular weight: Mw and Mn were determined by GPC analysis of a solution of polymer in methylene chloride (1 mg / ml) versus polystyrene standard.

Polymerization Accelerator : In Examples 1 to 4, the polymerization promoter used was BPA bis-methyl salicylate carbonate. The polymerization promoter was prepared by the following two methods and used interchangeably in Examples 1-4.

a) Anhydrous method: A solution of 16.80 g (0.0476 mol) of BPA chloroformate in 50 ml of anhydrous toluene over 1 hour 14.6 g (0.0957 mol) of methyl salicylate in 100 ml of toluene and 10.164 g (0.01006 mol) of triethylamine , 14 ml). After addition of the chloroformate the mixture was stirred by machine for 2 hours. The resulting mixture was filtered and the solids washed with toluene. The combined filtrate and washes were transferred to a separatory funnel and washed with equal volumes of H ₂ O, 10% HCl (twice), 2.5% NaOH (once) and brine (once). The organic layer was further dried by passing through a cone of anhydrous CaSO ₄ and the solvent was removed using a rotary evaporator. The crude residue was seeded using small crystals of the product and then solidified with cooling. The solid was recrystallized from ether-hexane to give about 24.2 g (87%) of pure BPA bis-methyl salicylate carbonate.

b) Interfacial method: 4.14 g (0.104 mol) of sodium hydroxide in 75 ml of water and 0.035 ml of a 70% aqueous solution of methyl tributyl ammonium chloride were extracted with hexane (2 x 75 ml) and then 150 methylene chloride for 15 minutes. 14.58 g (0.0096 mol) of methyl salicylate and 16.80 g (0.0476 mol) of BPA bis-chloroformate in mL were added to the stirred solution. The mixture was further stirred for 10 minutes and phase separated. The organic phase was washed with equal volume of 10% HCl, 5% Na ₂ CO ₃ , water and brine (saturated NaCl) and dried by passing through a cone of anhydrous CaSO ₄ . The solvent was evaporated to yield 27.3 g (98.3%) of pure BPA bis-methyl salicylate carbonate.

Starting Material Polycarbonates : In all examples, the properties of the starting material polycarbonate grades produced by the melting process are as follows:

Weight average molecular weight (Mw): 18.3 × 10 ³ g / mol

Number average molecular weight (Mn): 7.52 × 10 ³ g / mol

Free OH Content: 670ppm

Examples 1-4 : In Examples 1-4, batch reactor tubes were placed under nitrogen at 25 g starting material polycarbonate and various amounts (0.3167 g (5.420 x 10 ^-4 moles or 0.55 moles per mole of -OH group) to 0.633525 Charged with g (1.084 × 10 ⁻³ moles or 1.1 moles per mole of —OH group) BPA-bis-methyl salicylic carbonate. The mixture was heated to 300 ° C. and stirred for about 20 minutes. After the melt mixing step, a vacuum was applied to bring the pressure in the system to 0.5 mbar and the reaction was continued for 10-40 minutes. The formed phenol was removed by distillation. After the reaction step, polymers were sampled from the reaction tubes for number average molecular weight and weight average molecular weight.

Comparative Example 1: A residence time of 20 minutes in a reaction under a vacuum step, except that instead of using BPA-bis-methyl salicylic carbonate, bis-methyl salicylic carbonate disclosed in US Pat. No. 5,696,222 is used as a polymerization promoter. It was carried out under the same conditions as in Example 1.

Comparative Example 2: The reaction under the vacuum step was carried out under the same conditions as in Example 2 with a residence time of 10 minutes, and the promoter of bis-methyl salicyl carbonate of US Pat. No. 5,696,222 was prepared using BPA-bis-methyl salicylic acid. It was used instead of carbonate.

Comparative Example 3: The reaction was carried out under the same conditions as in Example 3 with a residence time of 20 minutes in the reaction under a vacuum step. The promoter, US Pat. No. 5,696,222, bis-methyl salicylic carbonate was used in place of the BPA-bis-methyl salicyl carbonate of the present invention.

Comparative Example 4: Under the same conditions of the 40 minute reaction under vacuum in Example 4, the promoter, bis-methyl salicyl carbonate, of US Pat. No. 5,696,222 was used in place of BPA-bis-salicyl carbonate.

Comparative Example 5: A residence time of 20 minutes in the reaction under a vacuum step was carried out under the same conditions as in Example 1, using a different non-activated carbonate instead of BPA-bis-methyl salicylic carbonate as the polymerization promoter. .

Comparative Example 6: For 20 minutes in the reaction under vacuum step, no polymerization promoter was used for all coupling reactions of Example 1.

The results of the polymerization promotion reaction examples are shown in Table 1 below.

Example Use accelerator Usage (mol / -OH) Reaction time (minutes) Mw (g / mol) Mn (g / mol) Example 6 - - 20 20992 11740 Comparative Example 1 Bis-methyl salicylate carbonate 1.1 20 21471 9446 Comparative Example 2 Bis-methyl salicylate carbonate 0.55 10 20968 9299 Comparative Example 3 Bis-methyl salicylate carbonate 0.55 20 21430 9576 Comparative Example 4 Bis-methyl salicylate carbonate 0.55 40 22655 9842 Comparative Example 5 Diphenyl carbonate 1.1 20 21058 11692 One BPA-bis-methyl salicylic carbonate 1.1 20 31062 11349 2 BPA-bis-methyl salicylic carbonate 0.55 10 22035 8950 3 BPA-bis-methyl salicylic carbonate 0.55 20 35530 13489 4 BPA-bis-methyl salicylic carbonate 0.55 40 51576 18374

Although forms of the invention have been illustrated and described, modifications can be made without departing from the spirit and scope of the invention. Therefore, it is not intended that the present invention be limited thereto.

Claims (16)

A process for preparing an aromatic polycarbonate, comprising adding a compound of formula 1 to a polycarbonate oligomer reaction mixture under melting conditions to form a polycarbonate having an increased molecular weight in a polymerization promotion reaction, After the number average molecular weight of the polycarbonate oligomer reaches about 2,500 to 15,000 Daltons, at least 80% by weight of the total amount of the compound of formula 1 is added, Process for preparing aromatic polycarbonates: Formula 1 Where R ₁ and R ₃ may be the same or different and are selected from the group consisting of alkoxy, phenoxy, benzoxy, aryloxy, phenyl and aryl groups; R ₂ is selected from the group consisting of alkyl, phenyl, aryl or aralkyl groups. The method of claim 1, A process for producing an aromatic polycarbonate, wherein the polycarbonate is produced by melt polymerization of a reaction mixture comprising an aromatic dihydroxy compound and diphenyl carbonate. The method of claim 1, The compound of formula 1 is added to the reaction mixture under melting conditions of about 200 ° C. to 300 ° C. for at least 10 minutes. The method of claim 1, A compound of formula (1) is selected from the group consisting of BPA-bis-methyl salicylic carbonate, BPA-bis-n-propyl salicylic carbonate, BPA-bis-benzyl salicylic carbonate and mixtures thereof . The method of claim 1, A method of preparing an aromatic polycarbonate, wherein the compound of formula 1 is added in an amount of about 0.1 to 20 moles, based on 1 mole of terminal hydroxyl groups of the polycarbonate formed upon addition. The method of claim 1, A method of preparing an aromatic polycarbonate, wherein the compound of formula 1 is added in an amount of about 0.2 to 1.25 moles, based on 1 mole of the terminal hydroxyl groups of the polycarbonate oligomer formed upon addition. The method of claim 1, A method of preparing an aromatic polycarbonate, wherein the compound of formula 1 is added in an amount of about 0.3 to 0.9 moles, based on 1 mole of terminal hydroxyl groups of the oligomer of the polycarbonate formed upon addition. The method of claim 1, A method of producing an aromatic polycarbonate, wherein the compound of formula 1 is added after the number average molecular weight (Mn) of the polycarbonate reaches about 4,000 to 10,000 Daltons. The method of claim 2, A process for producing an aromatic polycarbonate, wherein the compound of formula 1 is a polymerization promoter for the reaction of an aromatic dihydroxy compound and a diphenyl carbonate compound. The method of claim 4, wherein A process for producing an aromatic polycarbonate, wherein the polymerization promoter is added in an amount of about 0.1 to 2.0 moles, based on 1 equivalent of the terminal hydroxyl groups of the polycarbonate formed upon addition. The method of claim 1, A method for producing an aromatic polycarbonate, wherein the polycarbonate formed comprises ortho-substituted phenol generated in the polymerization promotion reaction in an amount of 500 ppm or less. The method of claim 1, A method for producing an aromatic polycarbonate in which the polycarbonate formed comprises an ortho-substituted phenol generated in a polymerization promotion reaction in an amount of 100 ppm or less. The method of claim 1, A method for producing an aromatic polycarbonate, wherein the polycarbonate formed contains a polymerization accelerator in an amount of 500 ppm or less. The method of claim 1, A method for producing an aromatic polycarbonate, wherein the polycarbonate formed contains a polymerization accelerator in an amount of 100 ppm or less. The method of claim 1, A method for producing an aromatic polycarbonate, wherein the polycarbonate formed comprises a terminal 2- (alkoxycarbonyl) phenyl group in an amount of 2,500 ppm or less. The method of claim 1, A method for producing an aromatic polycarbonate, wherein the polycarbonate formed comprises a terminal 2- (alkoxycarbonyl) phenyl group in an amount of 1,000 ppm or less.