KR20050019744A - Method for making an aromatic polycarbonate - Google Patents

Abstract

The present invention relates to an extrusion process for producing polycarbonates from oligomeric polycarbonate solutions. The mixture of bis (methyl salicyl) carbonate (BMSC), BPA and transesterification catalyst is first equilibrated at moderate temperatures to obtain a solution of polycarbonate oligomer in methyl salicylate. The solution is then fed to a devolatilizing extruder where the polymerization reaction is complete and the methyl salicylate solvent is removed. The solution comprising the oligomeric polycarbonate can also be preheated under pressure to a temperature above the boiling point of methyl salicylate and then fed to a devolatilizing extruder equipped to quickly run off the solvent. The method provides polycarbonate with greater efficiency than the corresponding method of feeding unreacted monomers to the extruder. In addition, the process of the present invention does not need to isolate precursor polycarbonates comprising ester substituted phenoxy end groups.

Description

Method for producing aromatic polycarbonate {METHOD FOR MAKING AN AROMATIC POLYCARBONATE}

The present invention relates to a process for producing polycarbonate. More particularly, the process of the present invention relates to a process for introducing a solution comprising a solvent and an oligomeric polycarbonate into a devolatilizing extruder, wherein the oligomeric polycarbonate is converted into a high molecular weight polycarbonate while simultaneously removing the solvent. More particularly, the present invention relates to a process for the production of polycarbonates with very low levels of Fries rearrangement products, high levels of endcaps and low levels of residual solvent under mild conditions.

This application is a partial continuing application of co-pending US patent application Ser. No. 10 / 167,901, filed June 12, 2002, which is incorporated herein by reference.

Polycarbonates such as bisphenol A polycarbonate are typically prepared by interfacial or melt polymerization methods. Reaction of bisphenols, for example bisphenol A (BPA), with phosgene in the presence of water, solvents such as methylene chloride, acid acceptors such as sodium hydroxide and phase transfer catalysts such as triethylamine are typical interfacial polymerization methods. Reaction of bisphenol A with a carbonate source such as diphenyl carbonate at high temperature in the presence of a catalyst such as sodium hydroxide is representative of the melt polymerization process currently used. Each method is implemented on a large scale commercially, each with significant drawbacks.

The interfacial process for producing polycarbonates has several inherent disadvantages. Firstly, there are disadvantages of running a process requiring phosgene as a reactant due to obvious safety issues. Secondly, there are disadvantages in running a process that requires the use of large amounts of organic solvents because costly precautions must be taken to prevent any adverse environmental effects. Third, the interfacial method requires relatively large equipment and cost investments. Fourth, polycarbonates produced by interfacial processes tend to have inconsistent colors, higher amounts of particles, and higher chloride contents that can cause corrosion.

Melting methods eliminate the need for solvents such as phosgene, or methylene chloride, but require high temperatures and relatively long reaction times. As a result, by-products such as products caused by the fleece rearrangement of the carbonate chains along the growing polymer chain can be produced at high temperatures. Fleece rearrangement results in undesirable and uncontrolled polymer branching that can adversely affect the flowability and performance of the polymer. Melting methods also require the use of complex processing equipment that can be operated at high temperatures and low pressures and can effectively shake very viscous polymer melts for the relatively long reaction times required to achieve high molecular weights.

Several years ago, US Pat. No. 4,323,668 reported that polycarbonates can be produced under relatively mild conditions by reacting bisphenols such as BPA with diaryl carbonates produced by the reaction of phosgene with methyl salicylate. The process used relatively high levels of transesterification catalysts such as lithium stearate to achieve high molecular weight polycarbonates. High catalyst loadings are not particularly desirable in molten polycarbonate reactions because the catalyst remains in the product polycarbonate after the reaction. The presence of the transesterification catalyst in the polycarbonate can promote increased water absorption, polymer degradation and discoloration at high temperatures, thereby shortening the useful life of the product produced therefrom.

In co-pending US patent applications Ser. Nos. 09/911439 and 10/167903, currently issued in US Pat. Nos. 6,420,512 and 6506871, respectively, ester-substituted diaryl carbonates, bisphenols such as bis-methyl salicylic carbonate. A mixture of a dihydroxy aromatic compound such as A, and a transesterification catalyst such as tetrabutylphosphonium acetate (TBPA) was extruded to obtain a high molecular weight polycarbonate. The extruder used was equipped with one or more vacuum vents to remove byproduct ester-substituted phenols. Similarly, extruding precursor polycarbonates having ester-substituted phenoxy end groups, such as methyl salicylic end groups, yielded polycarbonates with significantly increased molecular weight relative to precursor polycarbonates. The reaction to produce high molecular weight polycarbonates can be promoted by the residual transesterification catalyst present in the precursor polycarbonate, or by a mixture of any residual catalyst and additional catalyst such as TBPA introduced in the extrusion step. No fleece rearrangement product was observed in the polycarbonate product.

The methods described in co-pending U.S. patent applications 09/911439 and 10 167903 (currently issued U.S. Pat.Nos. 6,420,512 and 6506871, respectively) provide significant improvements in polycarbonate production over previous methods. However, further improvements are needed. For example, it would be highly desirable to increase the throughput of starting material through the extruder to achieve greater efficiency. It would also be highly desirable to rule out the need to isolate precursor polycarbonates having ester-substituted phenoxy end groups before extrusion to obtain high molecular weight polycarbonates.

Summary of the Invention

The present invention provides a process for preparing a polycarbonate, comprising extruding a solution comprising a solvent and an oligomeric polycarbonate in the presence of a transesterification catalyst at one or more temperatures in the temperature range of about 100 to about 400 ° C. Extrusion is carried out on an extruder equipped with one or more vents adapted for solvent removal, wherein the oligomeric polycarbonate is a polycarbonate repeat unit derived from one or more dihydroxy aromatic compounds and an ester substituted phenoxy end group of formula (I) Provides a method that includes:

Where

R ¹ is a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group, or a C ₄ -C ₂₀ aryl group;

R ² independently in each occurrence is a halogen atom, cyano group, nitro group, C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group, C ₄ -C ₂₀ aryl group, C ₁ -C ₂₀ alkoxy group , C ₄ -C ₂₀ cycloalkoxy group, C ₄ -C ₂₀ aryloxy group, C ₁ -C ₂₀ alkylthio, C ₄ -C ₂₀ cycloalkyl alkylthio group, C ₄ -C ₂₀ arylthio group, C ₁ - C ₂₀ alkylsulfinyl group, C ₄ -C ₂₀ cycloalkylsulfinyl group, C ₄ -C ₂₀ arylsulfinyl group, C ₁ -C ₂₀ alkylsulfonyl group, C ₄ -C ₂₀ cycloalkylsulfonyl group, C ₄ -C ₂₀ aryl Sulfonyl group, C ₁ -C ₂₀ alkoxycarbonyl group, C ₄ -C ₂₀ cycloalkoxycarbonyl group, C ₄ -C ₂₀ aryloxycarbonyl group, C ₂ -C ₆₀ alkylamino group, C ₆ -C ₆₀ cycloalkylamino group, C ₅ -C ₆₀ arylamino group, C ₁ -C ₄₀ alkylaminocarbonyl group, C ₄ -C ₄₀ cycloalkylaminocarbonyl group, C ₄ -C ₄₀ arylaminocarbonyl group or C ₁ -C ₂₀ acylamino group;

b is an integer of 0-4.

The invention also relates to a process for preparing a solution comprising an ester substituted phenol solvent and an oligomeric polycarbonate, and converting the oligomeric polycarbonate to a high molecular weight polycarbonate at the same time as removing the solvent. Includes:

Heating a mixture comprising at least one dihydroxy aromatic compound, an ester substituted diaryl carbonate and an transesterification catalyst at a temperature in the range from about 100 to about 300 ° C. to obtain a solution of oligomeric polycarbonate in an ester substituted phenol solvent. (I); And

The solution of the oligomeric polycarbonate in the ester substituted phenol is subjected to at least one exhaust port adapted for solvent removal at a temperature of one or more in the range of about 100 to about 400 ° C. and at one or more screw speeds in the range of about 50 to about 1200 rpm. Extruding on an extruder comprising (II).

In another aspect, the present invention relates to polycarbonates prepared according to the process of the present invention having very high levels of endcaps, very low levels of fleece products and very low levels of residual solvent.

1 illustrates a devolatilization extruder and feed system suitable for use in accordance with the method of the present invention.

Figure 2 illustrates another structure of a devolatilization extruder and feed system suitable for use in accordance with the method of the present invention.

3 illustrates another devolatilizing extruder and feed system suitable for use in accordance with the method of the present invention.

The invention may be more readily understood by reference to the following detailed description of the preferred embodiments of the invention and the examples included therein. In the following specification and claims, several terms that are defined as having the following meanings will be mentioned:

The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

“Optional” or “optionally” means that the event or situation described next may or may not occur, and the description includes cases where an event occurred and a case that did not occur.

As used herein, the term "oligomeric polycarbonate" refers to polycarbonate oligomers having a number average molecular weight of less than 5000 Daltons, and oligomeric polycarbonates comprising polycarbonate repeat units derived from one or more dihydroxy aromatic compounds. It includes.

As used herein, when describing oligomeric polycarbonates, the expression "polycarbonate repeating units derived from one or more dihydroxy aromatic compounds" refers to the reaction of dihydroxy aromatic compounds with carbonyl unit sources, e.g. For example, it means a repeating unit incorporated into the oligomeric polycarbonate by reaction of bisphenol A with bis (methyl salicylic) carbonate.

As used herein, the term "high molecular weight polycarbonate" means a polycarbonate having a number average molecular weight (M _n ) of at least 8000 Daltons.

As used herein, the term "solvent" may refer to a single solvent or a mixture of solvents.

As used herein, the term "solution comprising a solvent and oligomeric polycarbonate" refers to a liquid comprising at least 10% by weight of a solvent, including the oligomeric polycarbonate.

As used herein, the term "melt polycarbonate" refers to polycarbonates prepared by transesterification of diaryl carbonates with dihydroxy aromatic compounds.

"BPA" is defined herein as bisphenol A or 2,2-bis (4-hydroxyphenyl) propane.

As used herein, the term “prise product” refers to the carboxy-substituted die having a carboxy group adjacent to one or both of the hydroxy groups of the carboxy-substituted dihydroxy aromatic compound upon hydrolysis of the polycarbonate product. It is defined as the structural unit of a polycarbonate product that produces a hydroxy aromatic compound. For example, in bisphenol A polycarbonates produced by the melt reaction process in which the frising reaction occurs, the frising product includes the structural features of the polycarbonate that produce 2-carboxy bisphenol A upon complete hydrolysis of the polycarbonate product.

The terms “freeze product” and “freeze group” are used interchangeably herein.

The terms “freeze reaction” and “freeze rearrangement” are used interchangeably herein.

The terms "twin screw extruder" and "twin screw extruder" are used interchangeably herein.

As used herein, the term "monofunctional phenol" means a phenol comprising a single reactive hydroxyl group.

The terms "exhaust outlet" and "exhaust vent" are used interchangeably herein.

As used herein, the term "atmospheric exhaust vent" refers to an exhaust vent that is operated at or near atmospheric pressure. Thus, an atmospheric exhaust vent operated under a slight vacuum as often referred to as a "house vacuum" means to fall within the scope of the term "atmospheric exhaust vent".

As used herein, the term "aliphatic radical" refers to a radical having one or more valences, including a linear or branched arrangement of atoms that are not cyclic. The arrangement may comprise heteroatoms such as nitrogen, sulfur and oxygen, or may consist solely of carbon and hydrogen. Examples of aliphatic radicals include methyl, methylene, ethyl, ethylene, hexyl, hexamethylene and the like.

As used herein, the term "aromatic radical" refers to a radical having one or more valences, including one or more aromatic groups. Examples of aromatic radicals include phenyl, pyridyl, furanyl, thienyl, naphthyl, phenylene and biphenyl. The term includes groups containing both aromatic and aliphatic components, for example benzyl groups. Aromatic radicals are also exemplified by radicals comprising both aromatic and cycloaliphatic structural components. For example, the radical 4-cyclohexylphenyl is classified herein as an aromatic radical rather than an alicyclic radical.

As used herein, the term “alicyclic radical” refers to a radical having one or more valences, including an arrangement of atoms which are cyclic but not aromatic. The arrangement may comprise heteroatoms such as nitrogen, sulfur and oxygen, or may consist solely of carbon and hydrogen. Examples of alicyclic radicals include cyclopropyl, cyclopentyl, cyclohexyl, tetrahydrofuranyl, and the like.

The present invention provides a process for preparing polycarbonate, wherein a solution comprising an oligomeric polycarbonate comprising an ester substituted phenoxy end group of formula I is extruded through an extruder adapted to remove the solvent. The process of the present invention not only converts the oligomeric polycarbonate to a polycarbonate product having a high molecular weight, but also separates the solvent initially present in the solution of the oligomeric polycarbonate from the polycarbonate product. The process also removes other volatiles that are present in the initial solution of the oligomeric polycarbonate or that may be produced as a byproduct when the oligomeric polycarbonate is converted to a polycarbonate product in the extruder.

Oligomeric polycarbonates include polycarbonate repeat units and terminal phenoxy end groups of formula (I). Terminal phenoxy end groups having Formula I generally include ester substituted phenoxy end groups. Ester substituted phenoxy end groups are 2-ethoxycarbonylphenoxy groups, 2-propoxycarbonylphenoxy groups, 4-chloro-2-methoxycarbonylphenoxy groups and 4-cyano-2-methoxycarbonyl Illustrated by phenoxy group. Among the various ester substituted phenoxy end groups, 2-methoxycarbonylphenoxy groups (formula II) are often preferred:

Oligomeric polycarbonates comprise repeating units derived from one or more dihydroxy aromatic compounds. Dihydroxy aromatic compounds include dihydroxy benzenes such as hydroquinone (HQ), 2-methylhydroquinone, resorcinol, 5-methylresorcinol and the like; Dihydroxy naphthalene such as 1,4-dihydroxynaphthalene, 2,6-dihydroxynaphthalene and the like; And bisphenols such as bisphenol A and 4,4'-sulfonyldiphenol. Oligomeric polycarbonates typically contain polycarbonate repeat units having Formula III, derived from one or more bisphenols:

Where

R ³ to R ¹⁰ are independently a hydrogen atom, a halogen atom, a nitro group, a cyano group, a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group or a C ₆ -C ₂₀ aryl group; W is a bond, oxygen atom, sulfur atom, SO ₂ group, C ₁ -C ₂₀ aliphatic radical, C ₆ -C ₂₀ aromatic radical, C ₆ -C ₂₀ alicyclic radical, or group ego,

R ¹¹ and R ¹² are independently a hydrogen atom, a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group or a C ₄ -C ₂₀ aryl group; Or R ¹¹ and R ¹² together are one or more C ₁ -C ₂₀ alkyl, C ₆ -C ₂₀ aryl, C ₅ -C ₂₁ aralkyl, C ₅ -C ₂₀ cycloalkyl group or optionally substituted with a combination thereof C ₄ -C ₂₀ forms a cycloaliphatic ring.

Repeating units of formula III are exemplified by repeating units present in bisphenol A polycarbonate, bisphenol M polycarbonate, bisphenol C polycarbonate and the like.

In one aspect of the invention, the oligomeric polycarbonate comprises a repeating unit of formula IV derived from bisphenol A:

In an alternative aspect of the invention, the oligomeric polycarbonate comprises repeating units having Formulas IV and V, wherein the repeating units of Formula V are derived from 4,4′-sulfonyldiphenol:

The solution of oligomeric polycarbonates used in accordance with the process of the invention comprises one or more solvents. The solvent may be a single solvent or a mixture of solvents. Typically, the solvent present in the solution of the oligomeric polycarbonate comprises about 10% to about 99% by weight of the solution, preferably about 10% to about 70% by weight of the solution. For example, a solution of oligomeric bisphenol A polycarbonate comprising phenoxy end groups (II) dissolved in methyl salicylate consists of about 40 wt% of the oligomeric polycarbonate and about 60 wt% methyl salicylate . Alternatively, the solution may comprise more than one solvent, for example oligomeric bisphenol A poly comprising phenoxy end groups (II) dissolved in a mixture of ortho-dichlorobenzene (ODCB) and methyl salicylate. The solution of carbonate consists of about 40% by weight of the oligomeric polycarbonate, 30% by weight of ODCB and about 30% by weight of methyl salicylate.

In one aspect of the invention, the solvent used according to the process of the invention comprises one or more substituted phenols having the formula VI:

Where

R ¹ , R ² and b are defined as in formula (I).

Examples of ester-substituted phenols having Formula VI include methyl salicylate, ethyl salicylate, butyl salicylate, 4-chloro methyl salicylate and mixtures thereof. Solvent VI can be recovered and reused. For example, ester substituted phenols, such as formula VI, are recovered, purified, and reacted with phosgene to produce ester substituted diaryl carbonates, which are then used to prepare oligomeric polycarbonates comprising terminal phenoxy groups of formula I Can be used. Typically, purification of the recovered ester substituted phenol is effectively carried out by distillation.

Solvents used in accordance with the process of the present invention may or may not include halogenated aliphatic solvents, halogenated aromatic solvents, non-halogenated aromatic solvents, non-halogenated aliphatic solvents or mixtures thereof. Halogenated aromatic solvents are exemplified by ortho-dichlorobenzene (ODCB), chlorobenzene and the like. Non-halogenated aromatic solvents include toluene, xylene, anisole, phenol; 2,6-dimethylphenol; And the like. Halogenated aliphatic solvents include methylene chloride; Chloroform; 1,2-dichloroethane; And the like. Non-halogenated aliphatic solvents are exemplified by ethanol, acetone, ethyl acetate, cyclohexanone and the like.

In one aspect of the invention, the solvent used comprises a mixture of halogenated aromatic solvents and ester substituted phenols such as ortho-dichlorobenzene (ODCB) and methyl salicylate.

The transesterification catalyst used in accordance with the present invention may be any catalyst effective to promote chain growth of oligomeric polycarbonates during extrusion. Transesterification catalysts for use in accordance with the process of the invention may comprise onium catalysts such as quaternary ammonium compounds, quaternary phosphonium compounds or mixtures thereof.

Quaternary ammonium compounds suitable for use as transesterification catalysts according to the process of the present invention include quaternary ammonium compounds having the general formula (VII):

Where

R ¹³ to R ¹⁶ are independently C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group or C ₄ -C ₂₀ aryl group;

X ⁻ is an organic or inorganic anion.

Quaternary ammonium compounds (VII) are exemplified by tetramethylammonium hydroxide, tetrabutylammonium acetate, tetrabutylammonium hydroxide and the like.

Quaternary phosphonium compounds suitable for use as transesterification catalysts in accordance with the process of the present invention include quaternary phosphonium compounds having the formula VIII:

Where

R ¹⁷ to R ²⁰ are independently C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group or C ₄ -C ₂₀ aryl group;

X ⁻ is an organic or inorganic anion.

Quaternary phosphonium compounds (VIII) are exemplified by tetramethylphosphonium hydroxide, tetrabutylphosphonium acetate, tetrabutylphosphonium hydroxide and the like.

In formulas VII and VIII, the anion X ⁻ is typically an anion selected from the group consisting of hydroxides, halides, carboxylates, phenoxides, sulfonates, sulfates, carbonates and bicarbonates. With regard to the transesterification catalysts of formulas (VII) and (VIII), wherein X ⁻ is a polyvalent anion such as carbonate or sulfate, it is recognized that the positive and negative charges in Formulas (VII) and (VIII) are properly balanced. For example, in tetrabutylphosphonium carbonate in which R ¹⁷ to R ²⁰ in the general formula (VIII) are each a butyl group and X ⁻ represents a carbonate anion, it is recognized that X ⁻ represents ½ (CO ₃ ⁻² ).

In one embodiment, the transesterification catalyst used is a mixture of one or more alkali metal hydroxides, alkaline earth metal hydroxides or mixtures thereof and quaternary ammonium compounds, quaternary phosphonium compounds or mixtures thereof. For example, it is a mixture of tetrabutylphosphonium acetate and sodium hydroxide.

Other transesterification catalysts that may be used in accordance with the process of the present invention include one or more alkali metal salts of carboxylic acids, one or more alkaline earth metal salts of carboxylic acids and mixtures thereof. The transesterification catalyst is exemplified by salts of simple carboxylic acids such as sodium acetate, calcium stearate and the like. In addition, alkali metal and alkaline earth metal salts of organic polyacids can serve as effective transesterification catalysts according to the process of the invention. Alkali and alkaline earth metal salts of organic polyacids such as ethylene diamine tetracarboxylate can be used. Salts of organic polyacids are exemplified by disodium magnesium ethylenediamine tetracarboxylate (Na ₂ Mg EDTA).

In one aspect of the invention, the transesterification catalyst comprises one or more salts of non-volatile acids. By "non-volatile" it is meant that the acid from which the catalyst is prepared does not have a vapor pressure that is detectable under melt polymerization conditions. Examples of non-volatile acids include phosphorous acid, phosphoric acid, sulfuric acid, and metal “oxo acids” such as oxo acids such as germanium, antimony, niobium, and the like. Salts of non-volatile acids useful as melt polymerization catalysts according to the process of the present invention include alkali metal salts of phosphites; Alkaline earth metal salts of phosphites; Alkali metal salts of phosphates; Alkaline earth metal salts of phosphates, alkali metal salts of sulfates, alkaline earth metal salts of sulfates, alkali metal salts of metal oxo acids and alkaline earth metal salts of metal oxo acids. Specific examples of salts of non-volatile acids include NaH ₂ PO ₃ , NaH ₂ PO ₄ , Na ₂ HPO ₄ , KH ₂ PO ₄ , CsH ₂ PO ₄ , Cs ₂ HPO ₄ , NaKHPO ₄ , NaCsHPO ₄ , KCsHPO ₄ , Na ₂ SO ₄ , NaHSO ₄ , NaSbO ₃ , LiSbO ₃ , KSbO ₃ , Ms (SbO ₃ ) ₂ , Na ₂ GeO ₃ , K ₂ GeO ₃ , Li ₂ GeO ₃ , MgGeO ₃ , Mg ₂ GeO ₄ and mixtures thereof .

Typically, the transesterification catalyst is from about 1.0 to 10 ^-8 to about 1 x 10 ^-3 moles, preferably from about 1.0 to 10 ^-8 to about 1 x 10 ^-3 moles of transesterification catalyst per mole of polycarbonate repeat units derived from aromatic dihydroxy compounds present in oligomeric polycarbonates. It is used in an amount corresponding to 1.0 x 10 ^-6 to about 2.5 x 10 ^-4 moles.

Typically, the oligomeric polycarbonates used are prepared in a step comprising heating the dihydroxy aromatic compound with the ester substituted diaryl carbonate in the presence of a transesterification catalyst. Thus, the reactants are mixed in a vessel at a ratio of about 0.95 to 1.3 moles, preferably about 1.0 to about 1.05 moles of ester substituted diaryl carbonate per mole of dihydroxy aromatic compound. The amount of transesterification catalyst used is about 1.0 x 10 ^-8 to about 1 x 10 ^-3 moles, preferably about 1.0 x 10 ^-6 to about 2.5 x 10 ^-4 moles of transesterification catalyst per mole of dihydroxy aromatic compound used. It's a mole. When the mixture is heated at one or more temperatures in the range of about 100 to about 400 ° C., preferably about 100 to about 300 ° C., and even more preferably about 100 to about 250 ° C., a reaction occurs such that the oligomeric polycarbonate product, ester substituted A solution comprising phenol (solvent) byproduct, transesterification catalyst, and an equilibrium mixture of low levels of starting material, dihydroxy aromatic compound, and substituted diaryl carbonate. This is referred to as "equilibration" of the reactants. Typically, the equilibrium is very advantageous for the production of oligomeric polycarbonate products and ester substituted phenol byproducts, only traces of starting material are observed. The "equilibrated" product mixture can then be introduced into a devolatilization extruder to remove the byproduct ester-substituted phenol solvent while converting the oligomeric polycarbonate to a high molecular weight polycarbonate product. The transesterification catalyst is typically not consumed even at the equilibrium stage and is not removed prior to extrusion, so there is no need to add additional catalyst, which is typically an extrusion copper. If no additional catalyst is added, the amount of catalyst present during the extrusion step (expressed in units of moles of catalyst per mole of polycarbonate repeat units in oligomeric polycarbonates) is expressed in moles of catalyst per mole of dihydroxy aromatic compound. It will be in close proximity to the amount of catalyst used in the equilibration step.

Typically, ester substituted diaryl carbonates will have the general formula (IX):

Where

R ¹ , R ² and b are defined as in formula (I).

In addition, dihydroxy aromatic compounds are typically, but not always, one or more bisphenols having the general formula (X):

Where

R ³ to R ¹⁰ are defined as in Formula III.

In one aspect, the method of the present invention comprises the following steps:

Heating a mixture comprising at least one dihydroxy aromatic compound, an ester substituted diaryl carbonate and an transesterification catalyst at a temperature in the range of about 100 to about 300 ° C. to obtain a solution of oligomeric polycarbonate in an ester substituted phenol solvent. (I); And

The solution of the oligomeric polycarbonate in the ester substituted phenol is subjected to at least one exhaust port adapted for solvent removal at a temperature of one or more in the range of about 100 to about 400 ° C. and at one or more screw speeds in the range of about 50 to about 1200 rpm. Extruding on an extruder comprising (II).

In some cases, it may be desirable to remove some of the ester-substituted phenol produced upon equilibration of the monomers. This can usually be done by heating the mixture of monomer and transesterification catalyst under vacuum, typically at about 0.01 to about 0.9 atm, and distilling the ester substituted phenol. Since ester substituted phenols are distilled from the mixture where the equilibration reaction takes place, the molecular weight of the oligomeric polycarbonate will tend to increase. If sufficient ester substituted phenol byproducts are removed, the number average molecular weight (M _n ) of the polycarbonate product may exceed 5000 Daltons and in some cases exceed 8000 Daltons. Thus, in one aspect of the invention, a mixture comprising at least a dihydroxy aromatic compound is reacted with one or more ester substituted diaryl carbonates in the presence of an ester exchange catalyst at a temperature of about 100 to about 300 ° C. and by-product ester substitutions. Some of the phenols removed are removed by distillation. The equilibration product may be a mixture comprising an ester substituted phenol solvent and a polycarbonate comprising a terminal phenoxy group of formula I and having a number average molecular weight greater than 5000 Daltons. The equilibration product is then fed to a devolatilization extruder, where the polycarbonate is converted to a higher molecular weight polycarbonate product, the polycarbonate product having a high level of end capping, a low level of freeze product and a low level of Have residual solvent. In one aspect of the invention, a portion of the ester substituted phenols produced upon equilibration are distilled from the mixture where equilibration takes place, and polycarbonates, ester substituted phenols having a number average molecular weight greater than 5000 Daltons by addition of the same amount of ODCB and Obtain a solution comprising ODCB. The solution is then fed to a devolatilization extruder where the polycarbonate is converted to a higher molecular weight polycarbonate product, the polycarbonate product having a fleece content of 10 ppm or less, an end capping level of 97% or more, and 1 weight Has less than% solvent. Typically, if the polycarbonate produced in the equilibrium reaction has a number average molecular weight greater than 5000 Daltons, the polycarbonate will have an M _n value in the range of 5000 Daltons to about 15000 Daltons.

Oligomeric polycarbonates comprising ester substituted terminal phenoxy groups (I) can be prepared by a variety of other methods in addition to the equilibration methods described. For example, oligomeric bischloroformates of bisphenols can be prepared by reacting one or more bisphenols with phosgene under interfacial conditions in a methylene chloride-water mixture at low pH. The bischloroformate was then further reacted with ester substituted phenols such as methyl salicylate under interfacial conditions to yield oligomeric polycarbonates comprising ester substituted terminal phenoxy groups in methylene chloride solution. The oligomeric polycarbonate product in solution can then be applied to the process of the invention. The catalyst used in the interfacial reaction is typically removed from the oligomeric polycarbonate solution in a series of washing steps in which the methylene chloride solution of the oligomeric polycarbonate is washed repeatedly with water to remove sodium chloride. Under such circumstances, additional catalyst may be needed and may be added during or immediately before the extrusion step.

In one embodiment, a monofunctional phenol chain stopper is added to a solution of oligomeric polycarbonate comprising ester substituted phenoxy end groups, which oligomeric polycarbonates are prepared using the equilibration techniques described herein. The solution is then subjected to extrusion devolatilization to yield a polycarbonate product incorporating terminal phenoxy groups derived from the chain stopper. Suitable monofunctional phenol chain stoppers include p-cumylphenol and cardanol.

Extruders used according to the process of the invention are a devolatilizing extruder type. That is, an extruder adapted to separate a substantial amount of solvent from the polymer-solvent mixture. Therefore, the extruder should have an exhaust vent adapted for removing one or more, preferably more solvents. 1, 2 and 3 illustrate a devolatilization extruder and feed system suitable for use in accordance with the method of the present invention. In one aspect of the invention (illustrated herein in connection with FIG. 1), the reactants, ester substituted diaryl carbonates, dihydroxy aromatic compounds, and transesterification catalyst are mixed in the reaction vessel 10 and from about 100 to about At a temperature in the range of 300 ° C., preferably from about 150 ° C. to about 250 ° C., heating is carried out at about 1 to about 10 atmospheres, preferably about 1 to about 2 atmospheres, to obtain a solution of oligomeric polycarbonate in ester substituted phenols. The solution is transferred through a pipe 17 piped into a twin screw extruder 20 having 14 barrels by a gear pump 14, which has a screw design 30. The extruder is operated at a screw speed of about 50 to about 1200 rpm, at a temperature of about 100 to about 400 ° C, preferably about 200 to about 350 ° C. The solution is introduced to the upstream edge of barrel 1 (22). Split along the extruder indicates transfer from one extruder barrel to the next. Barrel 2 is labeled 24 (the remaining barrels 3 to 14 are not labeled). The extruder screw design 30 consists of a conveying screw element, illustrated at 32, and a mixing compartment comprising an initial mixing compartment 34 and four concentrated mixing zones 36. The extruder is equipped with four atmospheric vents 40, which vent branches 42 for removing ester-substituted phenol solvents and other volatile by-products generated when the oligomeric polycarbonate is converted into a polycarbonate product in the extruder. Is connected to. Solvent vapors and other volatile byproducts condense in the shell and tube condenser 44 attached to the source of the house vacuum 46. The extruder is further equipped with two vacuum vents 50. The vacuum vent 50 is connected to the vacuum pump 54 via a cold trap 52. As mentioned, the extruder includes four mixing compartments for vigorously mixing the contents of the extruder. The compartments are indicated in the screw design 30 as a mixing compartment labeled 36. The mixing section labeled 36 in the screw design corresponds to the reaction zone 26 of the extruder. The reaction zone is believed to provide increased rates of polycarbonate chain growth compared to other regions in the extruder.

In an alternative aspect of the invention (exemplified herein with reference to FIG. 2), the reactants, ester substituted diaryl carbonates, dihydroxy aromatic compounds and transesterification catalysts are mixed in the reaction vessel 10 and from about 100 to At a temperature in the range from about 300 ° C., preferably from about 150 ° C. to about 250 ° C., at about 0.001 to about 10 atmospheres, preferably from about 0.001 to about 2 atmospheres, to obtain a solution of oligomeric polycarbonate in ester substituted phenols. . The reaction vessel 10 is adapted to operate at less than ambient pressure, ambient pressure or elevated pressure, and is equipped with a mixer 11. The reaction vessel 10 is connected to the condenser 44 through a dissolution return branch 12. The solution is moved through the heat exchanger 15 by the gear pump 14, where the solution is superheated. The heat exchanger 15 is connected to a pressure regulating valve 16 piped directly in the vented twin screw extruder 20 with 14 barrels, which has a screw design 30. The extruder is operated at a screw speed of about 50 to about 1200 rpm, at a temperature of about 100 to about 400 ° C, preferably about 200 to about 350 ° C. The solution is introduced to the upstream edge of barrel 1 (22). Split along the extruder indicates transfer from one extruder barrel to the next. Barrel 2 is labeled 24 (the remaining barrels 3 to 14 are not labeled). The extruder screw design 30 consists of a conveying screw element, illustrated at 32, and a mixing compartment comprising an initial mixing compartment 34 and four concentrated mixing zones 36. The extruder is equipped with four atmospheric vents 40, which vent branches 42 for removing ester-substituted phenol solvents and other volatile by-products generated when the oligomeric polycarbonate is converted into a polycarbonate product in the extruder. Is connected to. Solvent vapors and other volatile byproducts condense in the shell and tube condenser 44 attached to the source of the house vacuum 46. The extruder is further equipped with two vacuum vents 50. The vacuum vent 50 is connected to the vacuum pump 54 via a cold trap 52. As mentioned, the extruder includes four mixing compartments for vigorously mixing the contents of the extruder. The compartments are indicated in the screw design 30 as a mixing compartment labeled 36. The mixing section labeled 36 in the screw design corresponds to the reaction zone 26 of the extruder. The reaction zone is believed to provide increased rates of polycarbonate chain growth compared to other regions in the extruder.

In another aspect of the invention (illustrated herein with reference to FIG. 3), monomers: ester substituted diaryl carbonates and dihydroxy aromatic compounds are mixed in a vessel (1), and from about 100 to about 300 ° C., preferably Preferably at a temperature in the range from about 150 to about 250 ° C. to obtain a molten mixture of monomers, which is forwarded into the system by the gear pump 14. The vessel 1 is optimally equipped with means for stirring the molten mixture. Flow meter 2 provides accurate metering of the molten mixture of monomers entering the downstream compartment of the system. The transesterification catalyst can be added to the molten mixture of monomers at point 3 or directly into the vessel 1. The molten mixture of monomers with or without the transesterification catalyst is introduced into the heat exchanger 15 through the static mixer 4 and from there into the reaction vessel 10. The reaction vessel 10 comprises one or more stirrers 11 and is adapted to remove the ester substituted phenol solvents produced as monomer equilibrium to produce a solution comprising oligomeric polycarbonate, wherein the oligomeric polycarbonate is ester-substituted Phenoxy end groups. The ester-substituted phenol solvent is removed through a solvent removal branch 12, which is attached to the condenser 44, the cooling trap 52 and the vacuum pump 54. Reaction vessel 10 is further adapted to introduce additional monomers, catalysts or solvents at one or more of points 17 and 18. Typically, the solution of oligomeric polycarbonate is heated to a temperature of about 150 to 300 ° C. The solution of oligomeric polycarbonate is then moved by means of a gear pump 14 through a pressure regulating valve 16 piped directly into the feed inlet zone of the vented twin screw devolatilizing extruder 20 having 14 barrels. The extruder has a screw design 30. The extruder is operated at a screw speed of about 50 to about 1200 rpm, at a temperature of about 100 to about 400 ° C, preferably about 200 to about 350 ° C. The solution is introduced to the upstream edge of barrel 3. Split along the extruder indicates transfer from one extruder barrel to the next. Barrel 2 is labeled 24 (the remaining barrels 3 to 14 are not labeled). The extruder screw design 30 consists of a conveying screw element, illustrated at 32, and a mixing compartment comprising an initial mixing compartment 34 and four concentrated mixing zones 36. The extruder is equipped with an atmospheric exhaust vent 40 connected to a branch pipe 42 for removing ester substituted phenol solvents and other volatiles. Solvent vapors and other volatile byproducts condense in shell and tube condensers 44 which may be attached to the source of the house vacuum or operated at atmospheric pressure. The atmospheric vent 40 is arranged such that one or more kneading blocks 34 are inserted between the feed inlet zone (the zone just below the pressure control valve 16) and the atmospheric vent. The insertion of the kneading block between the feed inlet zone and the atmospheric vent serves to prevent the incorporation of solids through the atmospheric vent by releasing solvent vapor. The extruder 20 is further equipped with four vacuum exhaust ports 50. Here again, the kneading block 34 is inserted between the feed inlet zone and the vacuum exhaust to prevent the incorporation of solids by the rapid release of the solvent vapor. The vacuum vent 50 is connected to the vacuum pump 54 through a solvent branch 42, a condenser 44 and a cooling trap 52. As mentioned, the extruder includes four mixing compartments for vigorously mixing the contents of the extruder. The compartments are indicated in the screw design 30 as a mixing compartment labeled 36. The mixing section labeled 36 in the screw design corresponds to the reaction zone 26 of the extruder. The reaction zone 26 is believed to provide increased rates of polycarbonate chain growth compared to other regions in the extruder. In addition, the system illustrated in FIG. 3 includes an optional water spray inlet 60 to increase the removal of volatile components from the polycarbonate produced. Finally, the extruder is equipped with one or more sensors 70, which may be used to monitor melt temperature, die pressure, torque or other system parameters, which may then be operated in accordance with a closed loop control method. Can be used when. For example, the melting temperature, die pressure and torque can vary greatly depending on the molecular weight of the polycarbonate product, so sensors that monitor the melting temperature and torque can be used to reduce or increase the molecular weight of the polycarbonate product exiting the extruder die surface. Upstream (eg, at inlet 17), it may be indicated whether additional monomers or catalyst should be added.

The extruder used in accordance with the process of the present invention may be a single screw or multi screw extruder, typically at a temperature of one or more in the range of about 100 to about 400 ° C., and about 50 to about 1200 rpm (rpm), preferably It is operated at one or more screw speeds in the screw speed range of about 50 to about 500 rpm.

Extruders suitable for use in accordance with the method of the present invention include co-rotating toothed twin screw extruders, counter-rotating split twin screw extruders, single screw reciprocating extruders and single screw non-reciprocating extruders.

It is a general principle of extruder operation that a corresponding increase in screw speed has to be made to accommodate the additional material fed as the feed rate increases. The screw speed also determines the residence time of the material fed to the extruder, here oligomeric polycarbonates and transesterification catalysts. Thus, screw speeds and feed rates are typically interdependent. It is useful to characterize the relationship between feed rate and screw speed as a ratio. Typically the extruder is operated such that the ratio of screw speed, expressed in rpm to starting material (lb / hour) introduced into the extruder, is in the range of about 0.01 to about 100, preferably about 0.05 to about 5. For example, the ratio of feed rate to screw speed is 2.5 when a solution comprising oligomeric polycarbonate and transesterification catalyst is introduced at 1000 lbs per hour into an extruder running at 400 rpm. The maximum and minimum feed rates and the extruder screw speed are determined by the general rule that, among other factors, the size of the extruder, the larger the extruder, the higher the maximum and minimum feed rates.

As mentioned, in one aspect of the invention, a mixture of oligomeric polycarbonate comprising a terminal group of formula I with a solvent is heated under pressure to obtain a "superheated" solution, wherein the temperature of the superheated solution is solvent at atmospheric pressure. Means higher than the boiling point. Typically, the temperature of the superheated oligomeric polycarbonate will be about 2 to about 200 ° C. higher than the boiling point of the solvent at atmospheric pressure. If several solvents are present, the solution of oligomeric polycarbonate is “superheated” to one or more of the solvent components. If the solution of oligomeric polycarbonate contains both high and low boiling solvents, it may be advantageous to overheat the oligomeric polycarbonate solution (ie, higher than the boiling point at atmospheric pressure of the highest boiling solvent) for all solvents present. have. Superheating of the oligomeric polycarbonate solution can be achieved by heating the mixture under pressure, typically at a pressure of less than about 10 atmospheres but higher than 1 atmosphere. Superheated solutions of oligomeric polycarbonates are conveniently prepared in feed tanks that are pressurized and heated, pressurized heat exchangers, extruders, pressurized reaction vessels and the like. The superheated solution is then introduced to the devolatilization extruder through a pressure control valve having a cracking pressure higher than atmospheric pressure. The back pressure generated by the pressure regulating valve prevents the solvent from evaporating before introducing the solution into the extruder. Typically, the pressure regulating valve is attached (piped) directly to the extruder and serves as the main feed inlet of the extruder. In one aspect of the invention wherein oligomeric polycarbonates comprising ester-substituted phenoxy end groups are introduced to the devolatilization extruder as a superheated solution, the extruder is equipped with one or more side feeders.

In one embodiment, the extruder having a side feeder is equipped with one or more atmospheric vents in close proximity to the main feed inlet including a pressure control valve. The side feeder is typically placed very close to the pressure regulating valve through which the superheated oligomeric polycarbonate is introduced into the extruder. The side feeder includes one or more atmospheric vents. Alternatively, a pressure regulating valve through which the superheated oligomeric polycarbonate is introduced may be attached to the side feeder itself, in which case the pressure regulating valve is located between the point where the side feeder is attached to the extruder and the atmospheric pressure vent located on the side feeder. Is attached to the side feeder. In another alternative embodiment, the superheated solution of oligomeric polycarbonate can be introduced through a plurality of pressure control valves, which can be attached to the side feeder, the extruder, or both the extruder and the side feeder. The heating zone of the extruder is typically operated at one or more temperatures between about 100 and about 400 ° C. It should be noted that the expression “when the extruder is operated at a temperature of about 100 to about 400 ° C.” refers to the heating zone of the extruder, and the extruder may include both heating zones and non-heating zones.

The superheated solution of oligomeric polycarbonate is introduced into the feed zone of the extruder through a pressure regulating valve, which is at atmospheric pressure due to the presence of the above-described atmospheric vents. The solvent present in the superheated solution of the oligomeric polycarbonate evaporates abruptly and rapidly, resulting in at least partial separation of the oligomer and solvent. Solvent vapor is released through the atmospheric vent. Atmospheric vents are attached to the solvent vapor branch and condenser to recover the solvent and prevent its accidental release. The extruder is also equipped with one or more vents operated at sub-atmospheric pressure, which serve to remove solvents not removed through the atmospheric vents. Vents operated at sub-atmospheric pressure are referred to herein as "vacuum vents" and are about 1 to about 30 inches, preferably about, as measured by a vacuum gauge measuring vacuum (as opposed to a pressure gauge measuring pressure). It is held in 10 to about 29 inches of mercury. Typically, two or more vacuum vents are preferred.

Suitable extruders for use in one aspect of the invention where superheated oligomeric polycarbonate solutions are supplied include co-rotating mated twin screw extruders, counter-rotating non-bonded twin screw extruders, single screw reciprocating extruders and single screw non-reciprocating A mold extruder is included.

In some cases, the polycarbonate product prepared according to the process of the present invention may appear to have an insufficient molecular weight or retain too much solvent originally present in the oligomeric polycarbonate solution. In such situations, simply applying the polycarbonate product to a second extrusion on the same or another devolatilizing extruder typically produces a polycarbonate product with increased molecular weight and reduced levels of residual solvent. Thus, in one aspect of the invention, a solution of oligomeric polycarbonate comprising a terminal group of formula I and a solvent is devolatilized on an extruder equipped with one or more vents adapted for solvent removal at a temperature of about 100 to about 400 ° C. Extrusion gives the initial polycarbonate product. The initial polycarbonate product is then introduced into a second extruder, which is equipped with one or more vacuum vents. The second extruder is operated at a temperature in the range of about 100 to about 400 ° C. and at a screw speed in the range of about 50 to about 1200 rpm.

The process of the invention can be carried out batchwise or continuously. In one embodiment, the process of the present invention is carried out as a batch process wherein the monomers and transesterification catalysts are equilibrated in a batch reactor to produce a solution of oligomeric polycarbonate. The solution is then fed to a devolatilizing extruder and the polycarbonate product is isolated until the solution is consumed. Alternatively, the process of the present invention can be carried out as a continuous process in which the monomer and the catalyst are continuously fed and the solution of the oligomeric polycarbonate is continuously removed from the continuous reactor. Thus, a mixture of BMSC, BPA and transesterification catalyst may be fed to one end of a tube reactor heated to a temperature of about 160 to about 250 ° C. The solution of oligomeric polycarbonate comprising phenoxy end groups (II) is withdrawn at the opposite end of the tube reactor and fed to the devolatilization extruder, from which the polycarbonate product is withdrawn.

It should be noted that, particularly in the melt reactions of the type provided in the present invention, the purity of the monomers used can strongly affect the properties of the polycarbonate product. Therefore, it is often preferred that the monomers used contain no contaminants such as metal ions, halide ions, acidic contaminants and other organic species or only contain very limited amounts of contaminants. This is especially true in applications such as optical discs (eg compact discs) where contaminants present in polycarbonate can affect disc performance. Typically, the concentration of metal ions, such as iron, nickel, cobalt, sodium and potassium, present in the monomer should be less than about 10 ppm, preferably less than about 1 ppm, even more preferably less than about 100 ppb. . The amount of halide ions, such as fluoride, chloride and bromide ions, present in the polycarbonate not only inhibits the absorption of water by the polycarbonate product, but also prevents the corrosive effect of the halide ions on the device used to make the polycarbonate. Should be minimized. Certain applications, such as optical discs, may require very low levels of halide ion contaminants. Preferably, the level of halide ions present in each monomer used should be less than about 1 ppm. The presence of acidic impurities such as organic sulfonic acids, which may be present in bisphenols such as BPA, should be minimized since only traces of basic catalyst are used for oligomerization and subsequent polymerization steps. Even small amounts of acidic impurities can greatly affect oligomerization and polymerization rates because they can neutralize a significant portion of the basic catalyst used. Finally, the tendency of polycarbonates to decompose at high temperatures, for example, during molding, is strongly correlated with the presence of contaminating species in the polycarbonates, with loss of molecular weight and discoloration. In general, the level of purity of the polycarbonate product prepared using a melt reaction method such as the present invention will closely reflect the level of purity of the starting monomer.

Polycarbonate products produced by the process of the present invention often contain only very low levels of the freeze product. In many cases, the application of the polycarbonate to the freeze product analysis does not detect the freeze product. Fleece product analysis is performed by fully hydrolyzing the polycarbonate and analyzing the hydrolysis product by HPLC. For bisphenol A polycarbonates produced by the process of the present invention, the level of the fleece product is the value expressed as parts of 2-carboxy bisphenol A per million parts of bisphenol A polycarbonate product that has been subjected to hydrolysis. In the case of bisphenol A polycarbonates prepared using the process of the invention, these values are often very close to zero or zero.

Polycarbonate products prepared according to the process of the present invention appear to have very high levels, often at least 97% endcapping. Typically, the polycarbonate product will be end capped from about 97 to about 99%. Free hydroxyl groups at the polycarbonate chain ends typically make up less than about 100 ppm of the total polymer weight. For polycarbonates prepared according to the method of the invention from BPA and BMSC, typically two types of free hydroxyl chain ends: hydroxyl groups ("BPA OH") bound to BPA residues, and salicylic ester residues A bound hydroxyl group (“salicyl OH”) is observed. Typically, the concentration of "BPA OH" end groups is less than about 100 ppm based on the total weight of the product polymer. Similarly, the concentration of "salicyl OH" is typically less than about 100 ppm. Terminal groups having a "salicyl OH" group have the structure represented by Formula XI and are quantified by nuclear magnetic resonance spectroscopy (NMR):

It should be noted that the concentration of hydroxyl end groups and the aforementioned endcapping percentages relate to polycarbonate products and not to oligomeric polycarbonates. Furthermore, if the polycarbonate product is prepared by first equilibrating a mixture of ester substituted diaryl carbonates with one or more dihydroxy aromatic compounds to obtain a solution comprising oligomeric polycarbonate, and then extruding the solution on a devolatilization extruder. The concentration and endcapping percentage of hydroxyl end groups in the polycarbonate product will reflect the molar ratio of ester substituted diaryl carbonate to total dihydroxy aromatic compound. Typically, the ratio should range from about 1.01 to about 1.1. Typically, the polycarbonate products produced by the process of the present invention contain only very small amounts of residual starting dihydroxy aromatic compounds (typically less than about 20 ppm) and ester substituted diaryl carbonates (typically less than about 350 ppm). Will contain.

The polycarbonate product produced by the process of the present invention may optionally be blended with any conventional additives used in thermoplastic applications such as the manufacture of molded articles. These additives include UV stabilizers, antioxidants, heat stabilizers, mold release agents, colorants, antistatic agents, slip agents, antiblocking agents, lubricants, antifog agents, natural oils, synthetic oils, waxes, organic fillers, inorganic fillers and mixtures thereof. This includes. Typically, it is desirable to produce blends of polycarbonates with additives that facilitate processing the blends to produce the desired shaped articles, such as optical articles. The blend may optionally comprise 0.001 to 10% by weight of a preferred additive, more preferably 0.001 to 1.0% by weight of a preferred additive.

Examples of UV absorbers include, but are not limited to, salicylic acid UV absorbers, benzophenone UV absorbers, benzotriazole UV absorbers, cyanoacrylate UV absorbers, and mixtures thereof.

Examples of the above heat resistant stabilizers include, but are not limited to, phenol stabilizers, organic thioether stabilizers, organic phosphite stabilizers, hindered amine stabilizers, epoxy stabilizers and mixtures thereof. Heat resistant stabilizers can be added in the form of solids or liquids.

Examples of mold release agents include natural and synthetic paraffins, polyethylene waxes, fluorocarbons, and other hydrocarbon mold release agents: stearic acid, hydroxystearic acid, and other higher fatty acids, hydroxyfatty acids, and other fatty acid mold release agents; Stearic acid amide, ethylenebisstearamide, and other fatty acid amides, alkylenebisfatty acid amides, and other fatty acid amide mold release agents; Stearyl alcohol, cetyl alcohol and other aliphatic alcohols, polyhydric alcohols, polyglycols, polyglycerols and other alcoholic mold release agents; Butyl stearate, pentaerythritol tetrastearate, and other lower alcohol esters of fatty acids, polyhydric alcohol esters of fatty acids, polyglycol esters of fatty acids, and other fatty acid ester mold release agents; Silicone oils and other silicone mold release agents, and mixtures of any of the foregoing release agents, are included, but are not limited to these.

The colorant may be a pigment or a dye. Inorganic and organic colorants can be used separately or together in the present invention.

The polycarbonates produced by the process of the invention may be branched or linear random copolymers, block copolymers. If the polycarbonate product is branched, suitable branching agents are used, such as THPE, 9-carboxyoctadicaedioic acid or 1,3,5-trihydroxybenzene. For example, in an equilibration reaction of 1 mole of BPA and 1.03 mole of BMSC, about 0.02 mole of THPE per mole of BPA is incorporated to produce a solution comprising oligomeric polycarbonate in methyl salicylate, and then Extruding the solution on a devolatilizing extruder will thus provide a branched bisphenol A polycarbonate.

Molded articles comprising polycarbonates produced by the process of the invention, for example molded optical articles, can be obtained by conventional molding techniques, for example by injection molding and compression molding. Molded articles can also be prepared from blends of polycarbonate products with one or more additional polymers. Typically the blend prepared using the extrusion method can be molded using conventional techniques. Injection molding is a more preferred method of making molded articles.

Since the polycarbonates produced by the process of the present invention have advantageous properties such as high impact strength, high transparency, low water absorption, good processability and low birefringence, the polycarbonates can be advantageously used for producing optical products. . End use applications for the optical products of the present invention include digital audio discs, digital general purpose discs, optical memory discs, compact discs, ASMO devices, and the like; Optical lenses such as contact lenses, spectacle lenses, telescope lenses, and prisms; Optical fibers; Magneto optical discs; An information recording medium; Information transmission medium; Discs for video cameras, discs for still cameras, and the like, but are not limited thereto.

Polycarbonates produced by the process of the present invention may serve as a medium for data storage, ie data may be specified on or in the polycarbonate. Polycarbonate can also serve as a substrate on which a data storage medium is applied. In addition, some combinations of the two functions may be used in a single device, such as when imprinting a polycarbonate with tracking to facilitate reading a data storage medium applied to the polycarbonate.

The following examples are presented to provide those skilled in the art with a detailed description of how to evaluate the methods claimed herein and are not intended to limit the scope which the inventors regard as the present invention. Unless stated otherwise, parts are by weight and temperature is in degrees Celsius.

Molecular weights are reported as number average (M _n ) or weight average (M _w ), using a polycarbonate molecular weight criterion to produce a wide range of standard calibration curves from which polymer molecular weights are determined and subjected to gel permeation chromatography (GPC) analysis. Measured. The temperature of the gel permeation column was about 25 ° C. and the mobile phase was chloroform.

The fleece content was determined by KOH methanolysis of the resin and reported in ppm. The fleece content was measured as follows. First, 0.50 g of polycarbonate was dissolved in 4.0 mL of THF (containing p -terphenyl as internal standard). Next, 3.0 ml of 18% KOH in methanol was added to the solution. The resulting mixture was stirred at rt for 2 h. 1.0 ml of acetic acid was then added and the mixture was stirred for 5 minutes. Potassium acetate byproduct was crystallized for 1 hour. The solid was filtered and the resulting filtrate was analyzed by high performance liquid chromatography (HPLC) using p -terphenyl as internal standard.

The concentrations of the "BPA-OH" and "salicyl-OH" end groups were measured by ³¹ P-NMR. Terminal hydroxyl groups were first derivatized with 2-chloro-1,3,2-dioxaphosphorane (Aldrich). The concentration of residual methyl salicylate was measured by ³¹ P-NMR or gel permeation chromatography.

Examples 1-5

A mixture of bis (methyl salicylic) carbonate (BMSC), bisphenol A (BPA) and transesterification catalyst, tetrabutylphosphonium acetate (TBPA) is equilibrated at a temperature of about 160 to about 220 ° C. in a batch melt reactor under a nitrogen atmosphere. To prepare a solution of oligomeric polycarbonate in methyl salicylate. The reaction mixture was stirred and heated until equilibrium was reached. At about 165 ° C., the equilibrium was reached in about 80 minutes and at about 220 ° C., the equilibrium was reached in about 10 minutes. At equilibrium, a solution of oligomeric polycarbonate prepared from a mixture of BMSC (1.03 moles of BMSC per mole of BPA), BPA and TBPA (2.5 × 10 ⁻⁴ moles per mole of BPA) comprises about 45% by weight of polycarbonate oligomer and about 54 to about 55 weight percent methyl salicylate.

Examples 1-5 in Table 1 illustrate both properties of solutions equilibrated at different temperatures and accurately record the oligomer properties of the material fed to the extruder. The column heading "[BMSC] / [BPA]" indicates the molar ratio of BMSC and BPA used in the equilibration reaction. The title “Mn” refers to the number average molecular weight as measured by gel permeation chromatography, measured using polycarbonate molecular weight standards. The value of M _n is given in Daltons. The data in Table 1 illustrates the rate at which equilibration of reactants can be achieved. Example 1 shows that the solid reactants can be converted to a solution of oligomeric polycarbonate and transesterification catalyst in methyl salicylate solvent within about 10 minutes. Because of the short residence time in the extruder (about 0.5 to about 2 minutes on the apparatus used in the examples below), the entire process of converting the starting monomers to the polycarbonate product can be achieved within 15 minutes.

Examples 6-101

Of oligomeric bisphenol A polycarbonate in methyl salicylate as in Examples 1-5 using TBPA alone (as in Examples 1-5) or a mixture of TBPA and sodium hydroxide as catalyst at an equilibration temperature of about 160 ° C. The solution was prepared. The amount of catalyst used was 2.5 x 10 ^-4 moles of TBPA per mole of BPA and 2 x 10 ^-6 moles of sodium hydroxide per mole of BPA (if present). After the equilibration reaction, the solution was transferred to a gear pump using nitrogen pressure (about 80 psi) which was a 25 mm diameter, 14-barrel co-rotating toothed twin screw extruder with a length to diameter ratio of 56. The solution was pumped through an insulated pipe connected directly (closely piped) to the upstream edge of barrel 1. The extruder is barrel 4 (V1, vacuum or atmospheric exhaust), barrel 5 (V2, optionally closed but operated simultaneously as atmospheric or vacuum exhaust), barrel 7 (V3, vacuum exhaust), barrel 9 (V4, vacuum exhaust), Six vents V1 through V6 located on the upstream edges of barrel 11 (V5, vacuum vent) and barrel 13 (V6, vacuum vent). Exhaust vent V1 was operated at atmospheric pressure or alternatively under weak vacuum (5 to 10 in.Hg as measured by vacuum system). Vacuum vents V3 and V4 were operated at moderate vacuum (10 to 28 in. Hg). Vacuum vents V5 and V6 were operated at high (> 29 in.Hg) vacuum. When operated at a weak or medium vacuum (5 to 28 in. Hg), the vacuum was applied to vents V2 to V6 by a "house" vacuum. In many cases, vacuum vent V5 in conjunction with vacuum vent V6 or V6 was operated under high (i.e., "full") vacuum (about 29 in. Hg as measured by vacuum system). The vacuum vent was connected to its respective vacuum source through a solvent return branch and a condenser system. When V6 alone or when V5 and V6 were operated in "full" vacuum, the exhaust or exhaust ports, which were operated in "full" vacuum, were connected to a vacuum pump via a cold trap. Exhaust vents V1 and V3 to V6 were equipped with "C" type exhaust outlet inserts. Exhaust outlet inserts are commercially available from Werner & Pfleiderer Co. The exhaust outlet inserts differ in the cross sectional area useful for solvent vapors exiting the extruder: the "A" type inserts are the most restrictive (minimum cross section) and the "C" type is the least restrictive (maximum cross section). As mentioned, V2 continued to close in some cases and open in others. The screw design included a conveying element below the feed inlet and all exhaust ports. The screw design also included a kneading block in four “reaction zones” (zones containing screw elements providing concentrated mixing) located between the vents. Four reaction zones were located between V2 and V3, between V3 and V4, between V4 and V5 and between V5 and V6, respectively. The data in Tables 2-5 below demonstrate the effect of changing reaction conditions on the properties of the polycarbonate product.

In Examples 6-11 (Table 2), the ratio of BMSC to BPA used in the equilibration reaction was 1.017. The catalyst used for the equilibration reaction was a mixture of tetrabutylphosphonium acetate and sodium hydroxide. The oligomeric polycarbonate in methyl salicylate (MS) solution was found to have a weight average molecular weight of 6865 Daltons, Mw and a number average molecular weight of 2980 Daltons, Mn. In Examples 6-11, the polycarbonate exiting the extruder was observed to be clear and colorless. The level of residual methyl salicylate present in the polycarbonate product after pelletization was determined by gas chromatography. The data provided in Examples 6-11 illustrate that polycarbonates can be prepared using the process of the present invention and the product obtained as above contains less than about 1 weight percent methyl salicylate (MS).

In Examples 12-15, a solution of oligomeric polycarbonate in methyl salicylate was prepared from a mixture of BMSC and BPA. The molar ratio of BMSC to BPA was 1.02. The catalyst used in the equilibration step was a mixture of TBPA and sodium hydroxide. The data in Table 3 illustrates that using higher levels of vacuum provides higher molecular weight polycarbonates containing lower levels of residual methyl salicylate than those observed in Examples 6-11.

In Examples 16-19, a solution of oligomeric polycarbonate in methyl salicylate was prepared from a mixture of BMSC and BPA. The molar ratio of BMSC to BPA was 1.025. The catalyst used in the equilibration step was a mixture of TBPA and sodium hydroxide. At the extrusion stage, vents V5 and V6 were connected to the vacuum pump via a cold trap. Vents V1 to V14 were connected to a "house vacuum" via solvent recovery branch and condenser. Vent V2 was connected to the same solvent recovery system and house vacuum as vents V1, V3 and V4. However, the vacuum level at which V2 is operated was not measured.

Examples 20-24 illustrate the application of the method of the invention to a solution of oligomeric polycarbonate prepared from a mixture of BMSC and BPA having an initial molar ratio of BMSC to BPA of 1.03. The catalyst used for the equilibration reaction was a mixture of tetrabutylphosphonium acetate and sodium hydroxide. Vacuum vent V2 was used as in Examples 16-19 but the exact pressure at which the vent was operated was not measured. As in the previous examples, the polycarbonate products of Examples 20-24 were clear and colorless when visually inspected. The column heading "Total OH (ppm)" refers to "BPA-OH" and "present in the polycarbonate product as determined by ³¹ P-NMR after derivatization with 2-chloro-1,3,2-dioxaphosphorane. Refers to the concentration of salicylic-OH ". The column heading "end capping (%)" refers to the percentage of product polycarbonate chain ends that are not terminated in the "BPA-OH" or "salicyl-OH" groups. The data in Table 5 provides evidence that very high levels of endcapping are achieved using the method of the present invention and that the concentration of terminal OH groups in the polycarbonate product is very low.

Examples 25-30 illustrate the application of the process of the invention to a solution of oligomeric polycarbonates prepared using only tetrabutyl phosphonium acetate and no sodium hydroxide. Here again, the solution is extruded to obtain a polycarbonate of quite high molecular weight. Vacuum vent V2 was used as in Examples 16-19 but the exact pressure at which the vent was operated was not measured. As in the previous examples, the polycarbonate products of Examples 25-30 were clear and colorless when visually inspected. The data in Table 6 also shows a high correlation between the molecular weight, feed rate and extruder screw speed of the polycarbonate product. Thus, in the data taken from Examples 25 to 30, an excellent linear correlation when plotted against the feed rate (lb / hr) of the weight average molecular weight, M _w , of the polycarbonate product divided by the extruder screw speed (rpm) Is observed. Similarly, when plotting the feed rate of residual methyl salicylate concentration (ppm) divided by screw speed, an excellent linear correlation is observed.

Examples 31 to 37: Preparation of Copolymers

In Examples 31 to 37, a mixture of bis (methyl salicyl) carbonate (BMSC), bisphenol A (BPA) and hydroquinone (HQ) was first equilibrated to obtain a copolymer. The ratio of the total moles of bis (methyl salicyl) carbonate to dihydroxy aromatic compound bisphenol A and hydroquinone was 1.017. Equilibration was performed as in Examples 1-5, and the resulting solution in methyl salicylate was extruded on the extruder configured in Examples 6-11. The catalyst was a mixture of TBPA and sodium hydroxide. The temperature of the oligomeric copolycarbonate solution supplied to the extruder was about 160 ° C and introduced into the extruder using a positive displacement pump. Examples 31 to 35 used 20 mole% hydroquinone (based on the total moles of BPA and HQ) in the equilibration step. Examples 36 and 37 used 40 mole percent hydroquinone (based on the total moles of BPA and HQ) in the equilibration step. Data on the preparation of copolycarbonates are shown in Table 7.

Examples 31 to 37 illustrate the use of the present invention in the preparation of copolycarbonates.

Examples 38 to 50 were run to demonstrate the consistency of the method of the present invention. A solution of oligomeric polycarbonate was prepared as in Example 5. The molar ratio of BMSC to BPA was 1.03. The transesterification catalyst was tetrabutylphosphonium acetate (TBPA, 2.5 x 10 ^-4 mole TBPA per mole BPA). The extruder was configured as in Examples 16-19. The data shown in Table 8 illustrates a constant molecular weight increase when converting oligomeric polycarbonates to polycarbonate products.

In Examples 38-50, a single batch of oligomeric polycarbonate in methyl salicylate solution was extruded and the polycarbonate exiting the extruder was sampled at 6 minute intervals over a course of 2 hours.

In Examples 51-74, solutions of oligomeric polycarbonates prepared as in Example 5 were extruded on the same devolatilization extruder as used in Examples 38-50. The ratio of BMSC to BPA was 1.02. Examples 51-71 demonstrate the level of consistency achieved. As in Examples 38-50, a single solution of oligomeric polycarbonate was fed to the extruder for about 2 hours. Examples 51-74 show samples of polycarbonate product collected about every 6 minutes as the polycarbonate product exited the extruder. The molecular weight and level of residual methyl salicylate were measured for each sample. Examples 72-74 show that the process can be run at feed rates higher than 17.6 lbs of solution per hour used in Examples 51-71. Examples 72 and 73 show that feed rates as high as 35.1 and 41.6 lbs of solution per hour can be used without compromising the molecular weight of the polycarbonate product. In addition, low levels of residual methyl salicylate can be maintained. Example 74 highlights the effect of screw speed on the molecular weight of the polycarbonate product and the level of residual methyl salicylate contained in the polycarbonate product.

In Table 9, the column heading "Total OH /" MS "OH" refers to the total concentration (molecule) of OH end groups (in ppm) present in the polycarbonate product and the "salicyl-OH" group (in "MS"). Represents the measured concentration (denominator) of "OH). The data shows very high levels of product polycarbonate endcaps. The polycarbonate product of Example 70 was analyzed for the presence of residual monomers. Less than 350 ppm residual BMSC and less than 20 ppm residual BPA were identified in the polycarbonate product.

Examples 75-80 illustrate the process of the invention wherein the chain stopper, p-cumylphenol, is included in the equilibration step. Thus, BMSC, BPA and p-cumylphenol (0.03 mol per mole BPA) were equilibrated as in Example 5 to obtain a solution of oligomeric polycarbonate in methyl salicylate. The molar ratio of BMSC to BPA was 1.03. As in Examples 38-50, a single solution of oligomeric polycarbonate was fed to an extruder configured as in Examples 16-19. Examples 75-80 show samples of polycarbonate products collected at regular intervals for about 1.5 hours. The molecular weight and level of residual methyl salicylate were measured for each sample. The data for Examples 75-80 are shown in Table 10, demonstrating the successful use of chain stoppers to control molecular weight within the scope of the present invention.

Examples 81-86 illustrate the use of the process of the present invention to obtain a polycarbonate comprising methyl salicyl end groups and very low levels of residual solvent in a single extrusion step. Thus, BMSC and BPA were equilibrated as in Example 5 to obtain a solution of oligomeric polycarbonate in methyl salicylate. The molar ratio of BMSC to BPA was 1.035. As in Examples 38-50, a single solution of oligomeric polycarbonate was fed to an extruder configured as in Examples 16-19. Examples 81-86 show samples of polycarbonate products collected at regular intervals for about 1.5 hours. The molecular weight and level of residual methyl salicylate were measured for each sample. The data for Examples 81-86 are shown in Table 11, demonstrating that even lower levels of residual methyl salicylate can be achieved by increasing the melting temperature and screw speed. The polycarbonate product was very transparent and colorless throughout the experiments performed in the examples of Table 11.

Examples 87-90 illustrate the use of the process of the present invention to obtain polycarbonates containing methyl salicyl end groups and very low levels of residual solvent in a single extrusion step with respect to higher initial BMSC to BPA molar ratios. . BMSC and BPA were equilibrated as in Example 5 to obtain a solution of oligomeric polycarbonate in methyl salicylate. The molar ratio of BMSC to BPA was 1.0375. As in Examples 38-50, a single solution of oligomeric polycarbonate was fed to an extruder configured as in Examples 16-19. Examples 87-90 show samples of polycarbonate products collected at regular intervals for about 1.5 hours. The molecular weight and level of residual methyl salicylate were measured for each sample. The data for Examples 87-90 are shown in Table 12, showing that very low levels of residual methyl salicylate can be achieved by increasing the melting temperature and screw speed. The lower molecular weight of the polycarbonate product reflects the higher level of BMSC used. The polycarbonate product was very transparent and colorless throughout the experiments performed in the examples in Table 12.

Examples 91-94 illustrate the preparation of copolycarbonates using the process of the present invention. Copolycarbonates are characterized by having high levels of methyl salicylic end groups, very low fris group concentrations and low levels of residual solvent. Solutions of the oligomeric copolycarbonates used in Examples 91-93 were prepared as follows. A mixture of hydroquinone (0.2 moles HQ per 0.8 mole BPA), BPA and BMSC (1.02 moles BMSC per 0.8 mole BPA) was equilibrated as in Example 5. TBPA (TBPA 2.5 × 10 ⁻⁴ per 0.8 mole BPA) was used as catalyst to obtain a solution of oligomeric copolycarbonate in methyl salicylate. The molar ratio of BMSC to BPA + HQ was 1.02. The solution of oligomeric polycarbonate used in Example 94 was prepared as follows. A mixture of hydroquinone (0.35 mole HQ per 0.65 mole BPA), BPA and BMSC was equilibrated as in Example 5. TBPA (TBPA 2.5 × 10 ⁻⁴ per 0.65 mole of BPA) was used as catalyst to obtain a solution of oligomeric copolycarbonate in methyl salicylate. The molar ratio of BMSC to BPA + HQ was 1.015. Both solutions were fed sequentially to an extruder configured as in Examples 16-19. Examples 91-94 show samples of copolycarbonate products collected at regular intervals for about 1.5 hours. The molecular weight and level of residual methyl salicylate were measured for each sample. The data for Examples 91-94 are shown in Table 13 and show that copolycarbonates are produced using the method of the present invention. The copolycarbonate product was clear but slightly yellow.

Examples 95-97 contain about 30 mole percent polycarbonate repeat units derived from biphenols (BP = 4,4'-dihydroxybiphenyl) and about 70 mole% repeat units derived from bisphenol A (BPA). Illustrates use of the method of the present invention in the preparation of copolycarbonates. The solution of oligomeric copolycarbonates used in Examples 95-97 was prepared as follows. A mixture of biphenol (0.3 mol BP per 0.7 mol BPA), BPA and BMSC (1.015 mol BMSC per 0.7 mol BPA) was equilibrated as in Example 5. TBPA (TBPA 2.5 × 10 ⁻⁴ per 0.7 mole BPA) was used as catalyst to obtain a solution of oligomeric copolycarbonate in methyl salicylate. The molar ratio of total moles of BMSC to BPA + HQ was 1.015. The solution was fed to a devolatilizing extruder configured as in Examples 16-19. Examples 95-97 show samples of copolycarbonate products collected at regular intervals for about 1.5 hours. The molecular weight and level of residual methyl salicylate were measured for each sample. The data for Examples 95-97 are shown in Table 14, consistent with the production of copolycarbonates comprising both BP and BPA residues. The copolycarbonate product sample was clear but did not show visible yellow. The molecular weight observed in the copolycarbonate samples was lower than expected, so a post extrusion test of the reaction vessel where equilibration of the initial monomers was carried out was performed. It was observed that some of the biphenols, which are relatively insoluble dihydroxy aromatic compounds, did not dissolve during the equilibration reaction. This effectively made the molar ratio of the combined moles of BMSC to BP and BPA higher than 1.015. The molecular weight observed for the polycarbonate was more consistent with the molar ratio of BMSC to BP + BPA of about 1.037 (see, for example, the data shown in Table 12 for the preparation of bisphenol A polycarbonate, where the molar ratio of BMSC to BPA). Was 1.0375).

Examples 98-101 illustrate the use of the process of the present invention in the preparation of copolycarbonates containing polycarbonate repeat units derived from 4,4'-sulfonyldiphenol (BPS) and bisphenol A (BPA). The solution of oligomeric copolycarbonates used in Examples 98-99 was prepared as follows. A mixture of 4,4'-sulfonyldiphenol (0.2 mol BPS per 0.8 mol BPA), BPA and BMSC (1.02 mol BMSC per 0.8 mol BPA) was equilibrated as in Example 5. TBPA (TBPA 2.5 × 10 ⁻⁴ per 0.8 mole BPA) was used as catalyst to obtain a solution of oligomeric copolycarbonate in methyl salicylate. The molar ratio of BMSC to BPA + BPS was 1.02. Solutions of oligomeric polycarbonates used in Examples 100-101 were prepared as follows. A mixture of BPS (0.40 mol BPS per 0.60 mol BPA), BPA and BMSC (1.022 mol BMSC per 0.60 mol BPA) was equilibrated as in Example 5. TBPA (TBPA 2.5 × 10 ⁻⁴ per 0.60 mole of BPA) was used as catalyst to obtain a solution of oligomeric copolycarbonate in methyl salicylate. The molar ratio of BMSC to BPA + BPS was 1.022. Both solutions were fed sequentially to an extruder configured as in Examples 16-19. Examples 98-101 show samples of copolycarbonate products collected at regular intervals over a total period of about 3.0 hours. The molecular weight and level of residual methyl salicylate were measured for each sample. Data for Examples 98-101 are shown in Table 15, consistent with the production of copolycarbonates comprising both BPA and BPS derived repeat units using the method of the present invention.

Example 102

A solution of oligomeric polycarbonate was prepared as in Example 5 and heated to a temperature of about 160 ° C. in a feed tank under a nitrogen atmosphere (50 to 60 psig). Sufficient pressure was provided to the feed pump head of the gear pump in communication with the feed tank using a transfer line heated with nitrogen. In addition, the polymer-solvent mixtures include the commercial stabilizer Irgafos 168 (about 0.12 weight percent based on the weight of the oligomeric polycarbonate) and Irganox 1010 (about 0.10 based on the weight of the oligomeric polycarbonate). Percent by weight). The solution was transferred from the heated feed tank to a heat exchanger maintained at about 265 ° C. at a rate of about 30 lb solution / hour using a gear pump. The solution exits the heat exchanger at a temperature of about 240 ° C., which is then barrel of a 10 mm 25 mm diameter co-rotating, twin screw extruder having a length to diameter ratio (L / D) of about 56 ° C. Feed through a pressure regulating valve piped into the upstream edge of 3. The cracking pressure of the pressure relief valve was electronically controlled to introduce a steady stream of superheated solution of oligomeric polycarbonate into the extruder, the heating zone of the extruder being maintained at a temperature in the range of about 260 to about 290 ° C. The feed rate to the extruder was about 30 lbs / hour. The transfer line between the heat exchanger and the pressure control valve was heated such that the temperature of the solution was about 20 ° C. higher than the boiling point of methyl salicylate (boiling point 221 ° C.) when the solution was introduced to the extruder through the pressure control valve. The extruder was operated at a screw speed of about 460 rpm. The extruder was further equipped with barrel 2 and a side feeder disposed perpendicular to the barrel of the extruder. The side feeder did not heat, had about 10 L / D and included two screws consisting solely of the front conveying element. As a result, at the furthest distance from the extruder barrel, the side feeder was equipped with a single atmospheric vent V1. The conveying element of the screw of the side feeder was configured to carry towards the extruder and away from the side feeder exhaust. The extruder was further equipped with two additional atmospheric pressure vents in barrel 1 (V2) and barrel 4 (V3) and a vacuum vent (vents operated at pressures below atmospheric pressure) in barrel 6 (V4) and barrel 8 (V5). Three atmospheric vents, two vents on the extruder and one vent on the side feeder, respectively, were connected to a solvent removal and recovery exhaust, including a solvent vapor removal line, a condenser and a liquid solvent receiving vessel. Vacuum vents are similarly adapted for solvent recovery. The recovered ester substituted phenol can be purified by distillation or other methods and recycled to produce additional ester substituted diaryl carbonates. The extruder screw element consisted of both a conveying element and a kneading element. All conveying elements in both the extruder and the side feeder are front continuous casing conveying elements. In barrels 2 and 3 of the extruder, a kneading block consisting of forward and neutral cascading kneading elements was used. The extruder screw was equipped with a melt seal plate consisting of a kneading block consisting of rear cascading kneading elements. The molten seal plates were located in barrels 5 and 7. The vacuum vent was located downstream of the molten seal plates on barrel 6 and barrel 8 and operated at a vacuum level of about 28 in. Hg (vacuum indicating full vacuum or zero absolute pressure, read about 30 in. Hg). The polycarbonate product exiting the die surface of the extruder (melting temperature of about 325 ° C.) was fixed and pelletized. The pelletized polycarbonate product was found to have a number average molecular weight, M _w , greater than about 20000 Daltons (GPC analysis) and to contain less than about 1 wt% residual ester substituted phenols. The polycarbonate product had a high level of endcapping and contained less than about 100 ppm of the freeze product.

General Procedure for Examples 103-181

Melting the monomer using a 30-gallon titanium reactor, mixing the molten monomer with the catalyst, pre-reacting (equilibrating) the monomer in the presence of the catalyst to prepare a solution comprising oligomeric polycarbonate dissolved in methylene salicylate Generated. The heat needed to melt the monomers and heat the resulting solution to the desired temperature was provided by a stream of heating oil heated to about 210 ° C., which could be circulated inside the reactor's heating jacket. The reactor may be pressurized with nitrogen gas to an absolute pressure of about 80 psi. The reactor was also adapted for operation under vacuum for use when removing some of the methyl salicylate by-products produced in the equilibration reaction from the solution before introducing the solution into the devolatilization extruder. The reaction vessel was connected to a tubular condenser attached to the receiver and the vacuum outlet. Methyl salicylate distilled from the reaction vessel was collected in the receiver. The receiver was mounted on a sensitive balance that monitors and measures the amount of methyl salicylate removed from the reactor when stripping is performed. A powerful shaker was used inside the reactor to homogenize the initial reaction mixture of monomers and catalyst. The shaker can also be used to mix additional monomers and catalysts in process operation. Effective mixing has been found to be advantageous in experiments in which inorganic fillers such as fumed silica or nano-clay are incorporated into the polycarbonate product. The shaker provided a uniform dispersion of the inorganic filler in the solution before introducing the solution of oligomeric polycarbonate in methyl salicylate into the extruder and converting it into a high molecular weight polycarbonate comprising the inorganic filler. A solution of oligomeric polycarbonate in methyl salicylate was transferred from the reactor to the extruder at the desired rate using a positive displacement geared pump connected to the bottom of the reactor. In some cases, a 10 ft long double tube heat exchanger was inserted between the pump and the extruder to control the temperature of the oligomeric polycarbonate solution. Typically, the temperature of the solution introduced into the extruder was about 170 to 250 ° C. A pressure control valve tightly piped to the extruder at Barrel 1 (RESEARCH pressure control valve available from Badger Meter Inc.) was located immediately downstream of the heat exchanger. A pressure regulating valve was used to isolate the extruder from the feed delivery system. The feed delivery system and the extruder were typically operated at different pressures. Thus, the feed delivery system upstream of the pressure regulating valve is typically operated at positive pressure, while the pressure in the feed inlet zone of the extruder is typically below atmospheric pressure. The “set” or “cracking” pressure of the valve can be adjusted based on the discharge temperature of the solution exiting the heat exchanger, with higher solution temperatures typically being methyl when the oligomeric polycarbonate solution enters the feed inlet zone of the extruder. Salicylate requires a higher set pressure to control the instantaneous evaporation rate. The extruder was a ZSK 25 mm co-rotating mating twin screw extruder with 14 barrels and a length to diameter ratio (L / D) of about 56. The extruder was equipped with six exhaust outlets V1 to V6 that can be operated at different vacuum levels to remove significant amounts of methyl salicylate solvent present in each solution of the oligomeric polycarbonate used. The absolute pressure at the exhaust outlet was adjusted to balance the foaming potential of the solution due to the sudden evaporation of solvent and the devolatilization efficiency. Exhaust outlets V1 and V2 were operated under light vacuum, while exhaust outlets V3 to V6 were operated under full vacuum. Exhaust outlets V1 through V6 were located along the length of the extruder in each of barrel 4 (V1), barrel 5 (V2), barrel 7 (V3), barrel 9 (V4), barrel 11 (V5) and barrel 13 (V6). . The structure of the screw used is shown in FIG.

In Examples 103-105, the catalyst tetrabutylphosphonium acetate (TBPA) was used in an amount corresponding to about 2.5 x 10 ^-4 moles of catalyst per mole of bisphenol A used. Methyl of oligomeric BPA polycarbonate comprising a methyl salicyl end group corresponding to formula II by feeding a mixture of BMSC (1.02 moles per mole BPA), BPA and catalyst to the reactor and heating to a temperature of about 180 ° C. for about 1 hour. A homogeneous solution in salicylate was achieved. The solution contained about 55% methyl salicylate by weight. The solution was transferred to the inlet zone of the devolatilizing extruder through a heat exchanger and a pressure control valve using a gear pump. The solution exiting the heat exchanger had a temperature about 9-16 ° C. higher than the solution temperature in the reactor. The extruder exhaust outlet pressure, the rate at which the solution is introduced into the extruder (see “mass flow rate (lb / hr)” in Table 16) and other operating conditions are shown in Table 16. The exhaust outlet pressure for exhaust port 2 (V2) (not shown) was the same as that of V1. The column heading "die pressure (psi)" refers to the pressure measured at the die surface of the extruder.

Data for Examples 103-105 show that high molecular weight polycarbonate was achieved under selected extruder conditions. In addition, the residual methyl salicylate (MS) solvent level in the polycarbonate product sample (see “Residual MS (ppm)” in Table 16) is low. The polycarbonate product is highly (95-96%) end capped (see "End Capping (%)" in Table 16). The free hydroxyl groups present in the polycarbonate product are terminal bisphenol A groups (see "BPA OH (ppm)") and terminal salicyl groups (ie, groups having formula IX) by ³¹ P-NMR (" And salicylic OH (ppm) ".

Examples 106-109 are examples 103 except that the catalyst used is a mixture of 2.5 × 10 ⁻⁴ moles of tetramethylammonium hydroxide (TMAH) and 1 × 10 ⁻⁶ moles of sodium hydroxide per mole of BPA used. As in 105. Data on extruder conditions and polycarbonate product properties used are shown in Table 17 below. The data in Table 17 shows that high molecular weight BPA polycarbonates containing methyl salicylic end groups (II) can be achieved under selected extruder conditions using a mixture of TMAH and sodium hydroxide as transesterification catalyst.

Examples 110-112 were performed on an extruder configured as in Examples 103-105, illustrating the use of the process of the present invention to produce copolycarbonates. Starting material: BPA, hydroquinone (HQ) and BMSC were fed to the reactor with the transesterification catalyst tetrabutylphosphonium acetate (1.0 × 10 ⁻⁴ moles per combined mole of TBPA, BPA and HQ). The mixture was heated and heated at about 195 ° C. for about 1 hour under a nitrogen atmosphere to produce a solution of oligomeric polycarbonate comprising BPA structural units, HQ structural units and methyl salicyl end groups having Formula II. The molar ratio of hydroquinone to total bisphenol (total moles of BPA + HQ) was about 0.4 and the ratio of moles of BMSC to moles of BPA and HQ was about 1.015. The polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

Examples 113-115 were carried out on an extruder configured as in Examples 103-105 and illustrate using the method of the present invention to prepare copolycarbonates comprising structural units derived from methylhydroquinone and BPA. . Starting materials: BPA, methylhydroquinone (MeHQ) and BMSC were fed to the reactor with the transesterification catalyst tetrabutylphosphonium acetate (1.0 x 10 ^-4 moles per mole of TBPA, BPA and MeHQ). The mixture was heated to about 175 to about 190 ° C. and stirred under nitrogen atmosphere for about 1 hour to produce a solution of oligomeric polycarbonate comprising BPA structural units, MeHQ structural units and methyl salicyl end groups having Formula II. The molar ratio of methylhydroquinone to total bisphenol (BPA + MeHQ) was about 0.9, and the ratio of the combined moles of BMSC to BPA and MeHQ was about 1.02. The clear, slightly dingy polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

Examples 116 and 117 were carried out on an extruder configured as in Examples 103-105 and illustrate using the method of the present invention to prepare copolycarbonates comprising structural units derived from methylhydroquinone and BPA. . Starting materials: BPA, methylhydroquinone (MeHQ) and BMSC were transesterification catalysts of tetramethylammonium hydroxide (2.5 x 10 ^-4 moles per mole of combined TMAH, BPA and MeHQ) and sodium hydroxide (NaOH, BPA and MeHQ 1 x 10 ^-6 mol per mole of)). The mixture was heated to about 185 ° C. and stirred under nitrogen atmosphere for about 1 hour to produce a solution of oligomeric polycarbonate comprising BPA structural units, MeHQ structural units and methyl salicyl end groups having Formula II. The molar ratio of methylhydroquinone to total bisphenol (BPA + MeHQ moles) was about 0.8 and the combined molar ratio of BMSC moles to BPA and MeHQ was about 1.015. The clear, slightly pinkish polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

Examples 118-120 were performed on an extruder configured as in Examples 103-105 and illustrate using the method of the present invention to prepare copolycarbonates comprising structural units derived from hydroquinone and BPA. Starting materials BPA, hydroquinone (HQ) and BMSC were transesterified catalysts of tetramethylammonium hydroxide (2.5 x 10 ^-4 moles per mole of TMAH, BPA and HQ) and sodium hydroxide (NaOH, BPA and HQ). 2 x 10 ^-6 moles per mole combined). The mixture was heated to about 175 ° C. and stirred for about 1 hour under a nitrogen atmosphere to produce a solution of oligomeric polycarbonate comprising BPA structural units, HQ structural units and methyl salicyl end groups having Formula II. The molar ratio of hydroquinone to BPA was about 2 to 8 and the combined molar ratio of BMSC moles to BPA and HQ was about 1.024. The clear colorless polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography. In Table 21, the abbreviation "TLTM" means "too low to measure."

The copolycarbonate product of Example 118 was further characterized by proton and ¹³ C-NMR, thereby yielding about 0.8 mole percent (BPA derived) repeating units having Formula XII in which methyl salicylate was fully incorporated into the backbone of the polycarbonate chain. For repeated repeat units).

In addition, the NMR study showed that the copolycarbonate product of Example 118 contained about 0.93 mole% of the methyl carbonate end group of the formula XIII (ie, 100 moles of BPA derived repeating unit) In units corresponding to 0.93 moles):

Finally, the NMR study for the copolycarbonate product of Example 118 showed that the methyl ether end group having the formula XIV is equivalent to about 0.39 mole per 100 moles of bisphenol A derived repeating unit (ie, copolycarbonate 0.39 mole%) relative to all BPA derived repeat units present in the product:

Examples 119-121 were carried out on an extruder configured as in Examples 103-105, using the process of the present invention to prepare polycarbonate terpolymers comprising structural units derived from hydroquinone, methylhydroquinone and BPA To illustrate. Starting monomers: BPA, hydroquinone (HQ), methylhydroquinone (MeHQ) and BMSC are tetramethylammonium hydroxides (2.5 x 10 ^-4 moles per sum of TMAH, BPA, HQ and MeHQ) as ester exchange catalysts, and The reactor was fed with sodium hydroxide (1 × 10 ⁻⁶ moles per combined mole of NaOH, BPA, HQ and MeHQ). The mixture was heated to about 195 ° C. and stirred under nitrogen atmosphere for about 1 hour to produce a solution of oligomeric polycarbonate comprising BPA structural units, HQ structural units, MeHQ structural units and methyl salicyl end groups having formula II. The mixture of bisphenols used included about 40 mole% BPA, 40 mole% HQ and 20 mole% MeHQ. The ratio of the combined moles of BMSC moles to BPA, HQ and MeHQ was about 1.015 (ie, BMSC moles / (BPA moles + HQ moles + MeHQ moles) = 1.015). The clear, slightly colored polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

Examples 122-124 were carried out on an extruder configured as in Examples 103-105, using the process of the present invention to prepare polycarbonate terpolymers comprising structural units derived from biphenols, methylhydroquinone and BPA. To illustrate. Starting monomers: biphenol (BP), methylhydroquinone (MeHQ), bisphenol A (BPA) and BMSC 2.5 x 10 ⁻ per mole of sum of tetramethylammonium hydroxides (TMAH, BP, MeHQ and BPA) as transesterification catalysts ⁴ moles) and sodium hydroxide (2.0 × 10 ⁻⁶ moles per combined moles of NaOH, BP, MeHQ and BPA) were fed to the reactor. The mixture was heated to about 170 ° C. and stirred under nitrogen atmosphere for about 1 hour to produce a solution of oligomeric polycarbonate comprising BP structural units, MeHQ structural units, BPA structural units and methyl salicyl end groups having formula II. The oligomeric polycarbonate fed to the extruder was characterized by GPC (M _w = 5584 and M _n = 2115). The mixture of bisphenols used included about 33 mol% BP, about 33 mol% MeHQ and about 33 mol% BPA. The ratio of the combined moles of BMSC moles to BP, MeHQ and BPA was about 1.028 (ie, BMSC moles / (BP moles + MeHQ moles + BPA moles) = 1.028). The solution introduced into the extruder contained about 59% by weight methyl salicylate. The clear, slightly colored polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

Examples 125-127 were performed on an extruder configured as in Examples 103-105, using the process of the present invention to prepare polycarbonate terpolymers comprising structural units derived from resorcinol, hydroquinone and BPA. To illustrate. Starting monomers resorcinol (RS), hydroquinone (HQ), bisphenol A (BPA) and BMSC were added 2.5 x 10 ^- per mole of total transmethylation of tetramethylammonium hydroxide (TMAH, RS, HQ and BPA) as transesterification catalyst. ⁴ mole) and sodium hydroxide (2.0 × 10 ⁻⁶ mole of NaOH per combined mole of NaOH, RS, HQ and BPA) were fed to the reactor. The mixture was heated to about 165 ° C. and stirred for about 1 hour under a nitrogen atmosphere to produce a solution of oligomeric polycarbonate comprising an RS structural unit, an HQ structural unit, a BPA structural unit, and a methyl salicyl end group having Formula II. Oligomeric polycarbonates were characterized by GPC (M _w = 1778 and M _n = 645). The mixture of bisphenols used included about 33 mol% RS, about 33 mol% HQ and about 33 mol% BPA. The ratio of the combined moles of BMSC moles to RS, HQ and BPA was about 1.02 (ie, BMSC moles / (RS moles + HQ moles + BPA moles) = 1.02). The solution introduced into the extruder contained about 61% by weight methyl salicylate. The clear, slightly orange polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

Examples 128-130 were carried out on an extruder configured as in Examples 103-105, illustrating the use of the process of the invention to produce branched copolycarbonates comprising structural units derived from biphenols and BPA. . The starting monomers, biphenol (BP), bisphenol A (BPA), BMSC and branching 1,1,1-tris (4-hydroxyphenol) ethane (THPE), are tetramethylammonium hydroxides (TMAH) as ester exchange catalysts. , 2.5 x 10 ^-4 moles per combined mole of BP and BPA) and sodium hydroxide (2.0 x 10 ^-6 moles NaOH per combined mole of NaOH, BP and BPA) were fed to the reactor. The mixture is heated to about 180 ° C. and stirred for about 1 hour under a nitrogen atmosphere to produce a solution of branched oligomeric polycarbonates comprising BP structural units, BPA structural units, THPE structural units and methyl salicylic end groups having Formula II. It was. The mixture of bisphenols used included about 40 mol% BP and about 60 mol% BPA. The ratio of THPE to total bisphenol was about 0.0025 (ie THPE moles / (BP moles + BPA moles) = 0.0025). The ratio of the combined moles of BMSC moles to BP and BPA was about 1.03 (ie, BMSC moles / (BP moles + BPA moles) = 1.03). The pressure upstream of the pressure regulating valve was about 20 psi during the experiment. The clear, slightly colored branched copolycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

The polycarbonate samples of Examples 128-130 were derivatized with 2-chloro-1,3,2-dioxaphosphorane and then characterized by ³¹ P-NMR. The column heading "BP / MS OH (ppm)" refers to the combined amount (ppm) of OH groups attributable to the residual methyl salicylate solvent with OH groups attributable to the biphenol OH polymer end groups. The concentration of hydroxy groups present in the copolycarbonate product is expressed in parts of "OH" groups per million parts of copolycarbonate. ³¹ P signal for 1,3,2-dioxaphosphorane-derivatized free methyl salicylate (MS) overlaps with signal for 1,3,2-dioxaphosphorane derivatized biphenol end group As such, the concentrations of "free methyl salicylate OH" and "biphenol end group OH" are expressed as the sum of the two concentrations. As compared to the concentration of methyl salicylate OH groups, the concentration of methyl salicylate itself was independently measured by GPC. Similarly, the column headings "salicyl OH (ppm)" and "BPA OH (ppm)" refer to salicylic OH groups (Formula XI), expressed in parts of "OH groups" (Formula = 17) per million parts of copolycarbonate product. It refers to the concentration of the OH group and the OH group bound to the bisphenol A terminal group attributable to.

Examples 131 to 135 were carried out on an extruder configured as in Examples 103 to 105 and illustrate using the method of the present invention to prepare bisphenol A polycarbonate comprising fumed silica, an inorganic filler. The starting monomers bisphenol A (BPA) and BMSC, the treated fumed silica were converted to the ester exchange catalyst tetrabutyl-phosphonium acetate (TBPA, 1.5 x 10 ^-4 moles per mole BPA) and sodium hydroxide (NaOH, NaOH per mole BPA 2.0 x 10 ^-6 mole). Fumed silica was added in the calculated amount to produce a polycarbonate product comprising 5% by weight fumed silica. The mixture was heated to about 190 to 195 ° C. and stirred for about 1 hour under a nitrogen atmosphere to produce a solution of oligomeric BPA polycarbonate comprising methyl salicyl end groups having BPA structural units and formula II. The ratio of BMSC moles to BPA moles was about 1.019. During the experiment involving Examples 131-135, the pressure upstream of the pressure regulating valve was about 20-50 psi. The opaque white polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

The polycarbonate products of Examples 131, 132 and 134 were derivatized with 2-chloro-1,3,2-dioxaphosphorane and then further characterized by ³¹ P-NMR. Typically, analysis using ³¹ P-NMR provides a lower value of residual methyl salicylate, “residual MS (ppm)” than analysis by GPC. ³¹ P-NMR values are typically considered to be more accurate than the values obtained using GPC. The polycarbonate products of Examples 131, 132 and 134 were further analyzed by proton and ¹³ C-NMR. As a result, the polycarbonate product of Example 132 was found to contain about 1.5 mole percent (relative to BPA derived repeat units) having the formula XII in which methyl salicylate was fully incorporated into the backbone of the polycarbonate chain. Based on the NMR studies, the polycarbonate products of Examples 131, 132, and 134 contained about 0.80 to 0.85 mole percent (ie, about 0.80 to 0.85 mole per 100 moles of BPA derived repeat units) relative to BPA derived repeat units. It was found to include methyl carbonate end groups (XIII) in an amount corresponding to (XIII)). Finally, from the above NMR studies on the polycarbonates of Examples 131, 132 and 134, methyl ether end groups having the formula XIV are present from about 0.30 to about 0.50 moles per 100 moles of bisphenol A derived repeating units (ie, in the polycarbonate product). To about 0.30 to 0.50 mole%) of end groups (XIV) for all BPA derived repeat units. Further polymerization is carried out in the same manner as used in Examples 131 to 135, except that less fumed silica (2% fumed silica in the polycarbonate product) or more (10% fumed silica in the polycarbonate product) is used. It was. The results were substantially the same as those observed in Examples 131-135.

Examples 136-143 were performed on extruders configured as in Examples 103-105 and illustrate the effect of feed temperature and prolonged heating on the quality of the polycarbonate products produced using the process of the present invention. Starting monomers bisphenol A (BPA) and BMSC were transesterification catalysts of tetrabutylphosphonium acetate (TBPA, 2.5 x 10 ^-4 moles per mole of BPA) and sodium hydroxide (NaOH, 1.0 x 10 ^-6 moles per mole of BPA) Was fed to the reactor together. The mixture was heated in the range of about 180-220 ° C. during the course of the experiment comprising Examples 136-143. It should be noted that the solution of oligomeric polycarbonate, which is converted to the polycarbonate product of Examples 136-143, was heated at increasingly higher temperatures for a longer period of time during the course of the experiment. Thus, the polycarbonate product of Example 136 was exposed to much milder conditions (lower temperature and shorter heating time) than the conditions where the polycarbonate product of Example 143 was applied (higher temperature and longer heating time). A solution of oligomeric BPA polycarbonate comprising BPA structural units and methyl salicyl end groups of formula II was stirred during the course of the experiment under a nitrogen atmosphere. The ratio of BMSC moles to BPA moles was about 1.02. The solution introduced into the extruder contained about 55% methyl salicylate by weight. During the experiment involving Examples 136-143, the pressure upstream of the pressure regulating valve was about 46 psi. The polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography.

The polycarbonate product was found to have a molecular weight loss under conditions of higher temperature and longer heating time (see Examples 142 and 143). In addition, extended heating at higher temperatures of Examples 142 and 143 by derivatization with 2-chloro-1,3,2-dioxaphosphorane followed by ³¹ P-NMR resulted in a higher number of BPA and salicylic hydroxyls. It has been found to provide polycarbonate products with end groups and correspondingly lower "end capping". In addition, the polycarbonate product of Example 143 has increased levels of methyl carbonate end groups (XIII) by ¹ H-NMR and ¹³ C-NMR (about 1.7 moles of structural units (XIII) per 100 moles of BPA derived repeating units). ), The methyl ether end group of formula XIV (about 3.3 moles of structural unit (XIV) per 100 moles of BPA derived repeating unit), and the "internal" salicyl group (methyl salicylate is fully incorporated into the main chain of the polycarbonate chain) Repeating units having the formula XII). “Internal” salicylic groups have been shown to be present in an amount corresponding to about 3.9 moles of repeat units (XII) per 100 moles of BPA derived repeat units. These data and the data shown in Table 27 are structural features of the polycarbonate products produced by the process of the present invention by varying the temperature at which the equilibration reaction is carried out and the length of time that the oligomeric polycarbonate solution is heated before being introduced into the devolatilization extruder. It can be controlled. It is contemplated that the structural features of the polycarbonate product can be further controlled by careful selection of the transesterification catalyst used.

Examples 144 to 153 were carried out on an extruder configured as in Examples 103 to 105, and the effect of concentrating the feed solution of the oligomeric polycarbonate before extrusion on the quality of the polycarbonate product produced using the method of the present invention and the extruder The influence of the processing speed is illustrated. Starting monomers bisphenol A (BPA) and BMSC were transesterification catalysts of tetrabutylphosphonium acetate (TBPA, 2.5 x 10 ^-4 moles per mole of BPA) and sodium hydroxide (NaOH, 1.0 x 10 ^-6 moles per mole of BPA) Was fed to the reactor together. The mixture was initially heated to about 190-195 ° C. to produce a solution of oligomeric polycarbonate comprising about 55% by weight of methyl salicylate. The solution was fed to an extruder to set baseline performance (see Examples 144 and 145), and then extrusion was stopped and methyl salicylate was removed until the concentration of methyl salicylate in the solution was reduced to about 35% by weight. Some were distilled off from the reactor under reduced pressure. Extrusion was then resumed and the polycarbonates of Examples 146 and 147 were collected on the extruder die surface. The extrusion was stopped again and the additional methyl salicylate was distilled off under reduced pressure. The oligomeric polycarbonate solution containing the resulting methyl salicylate end group (II) exhibited the following characteristics.

The influence of the extruder processing speed was measured by gradually increasing the rate at which the oligomeric polycarbonate solution was provided to the extruder during the course of Examples 144-153. In each of Examples 144-153, the polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography. As the treatment rate increased, the amount of residual methyl salicylate in the polycarbonate product was also observed to increase. Also, the higher the treatment rate, the lower the molecular weight of the polycarbonate product and the lower the end capping (“end capping (%)”). The entire experiment, including Examples 144-153, was conducted for a hypothesis of about 6 hours.

Examples 154-163 were run on an extruder configured as in Examples 103-105 and illustrate the stable operation of the process of the present invention with a concentrated feed solution of oligomeric polycarbonate in methyl salicylate. In addition, Examples 154-163 illustrate the effect of feed temperature and treatment rate on the molecular weight of the polycarbonate product. Starting monomers bisphenol A (BPA) and BMSC were transesterification catalysts of tetramethyl-ammonium hydroxide (TMAH, 1.0 x 10 ^-4 moles per mole BPA) and sodium hydroxide (NaOH, NaOH per mole BPA 2.0 x 10 ^-6 Mole). The mixture was initially heated to about 175-180 ° C. to produce a solution of oligomeric polycarbonate comprising about 55% by weight of methyl salicylate. The solution was then fed to an extruder to set baseline performance (see Example 154), then the extrusion was stopped and the methyl salicylate of methyl salicylate was reduced until the concentration of methyl salicylate in the solution was reduced to about 35% by weight. Some were distilled off from the reactor under reduced pressure. The oligomeric polycarbonate solution comprising the resulting methyl salicylate end group (II) was sampled twice in the experiment consisting of Examples 155-163, and the results were immediately after solution preparation and any methyl produced upon equilibration of the starting monomers. Comparison was made with the solution before removal of salicylate (see "Feed in Example 154"). It can be seen that the molecular weight of the oligomeric polycarbonate remains fairly stable during the course of the experiment (compare "feed of Example 155" with "feed of Example 163").

After concentration of the feed solution, extrusion was resumed and the polycarbonates of Examples 155-163 were collected at the extruder die surface. In each of Examples 154-163, the polycarbonate exiting the die surface was pelleted and characterized. Molecular weight was measured by gel permeation chromatography. The data in Table 29 illustrate that stable production of high quality polycarbonates can be achieved using concentrated feed solutions, illustrating the beneficial effects of lower reactor temperatures. The extruder used according to the process of the present invention serves two roles: (1) the extruder performs solvent removal, and (2) the extruder acts as a polymerization reactor for converting the oligomeric polycarbonate starting material into high molecular weight polycarbonate. do. Concentrating the solution fed to the extruder seems advantageous in that it provides greater room to share the two functions.

It is noteworthy that over time, the concentration of byproduct structures XII, XIII and XIV in the polycarbonate product is increased. This is strong evidence for the claim that prolonging heating at higher temperatures contributes to the appearance of the byproduct structures.

Examples 164 to 181 were performed on an extruder configured as in Examples 103 to 105, using the consistent operation of the process of the present invention, and using the extruder torque and the extruder melt temperature as key process control criteria when using the method of the present invention. Illustrate the possibilities for The starting monomers bisphenol A (BPA) and BMSC were fed to the reactor with the transesterification catalyst tetramethyl-ammonium hydroxide (TMAH, 2.5 x 10 ^-4 moles per mole BPA). Sodium hydroxide was not used. The mixture was initially heated to about 160-165 ° C. to produce a solution of oligomeric polycarbonate comprising about 55% by weight of methyl salicylate. In Examples 164-170, the molar ratio of BMSC to BPA was changed from about 1.018 to about 1.03 by adding BMSC monomer to the equilibrated mixtures of oligomers in the reactor. The molecular weight of the polycarbonate product also changed accordingly. In Examples 170-181, the molar ratio of BMSC to BPA remained constant at 1.03. The process was run for about 1 hour at a BMSC to BPA mole ratio of 1.03 to study the short term consistency of the process. The product exiting the extruder die surface was sampled every 5 minutes to obtain a total of 12 polycarbonate product samples (Examples 170-181), which were analyzed by gel permeation chromatography. The data demonstrate the remarkable stability of the process of the present invention and the standard deviation of the weight average molecular weight M _w is less than 1% of the mean M _w value for Examples 170-181. The standard deviation of residual methyl salicylate values is somewhat higher, reflecting a relatively high standard deviation associated with quantification of methyl salicylate by GPC (standard deviation in the measurement of chloroform solutions containing 1000 ppm methyl salicylate). Was about 75 ppm or about 7.5% of the mean value measured). In Table 30, the symbol """indicates that the value was not recorded but should not differ much from the value before it.

The data in Table 30 show that the melting temperature and torque can be used as part of a closed-loop control method for monitoring and controlling the molecular weight of the polycarbonate product produced by the method of the present invention. In experiments involving Examples 164 to 181, molecular weight differences greater than about 1% are statistically significant when quantifying molecular weight differences produced by mixtures containing different molar ratios of carbonate / bisphenols using this method. Can be considered. The standard deviation observed in the measurement should be considered significant considering that the measurements included not only the process itself, but also included the errors involved in the evaluation of the molecular weight and residual methyl salicylate content of the samples. Can be.

Although the present invention has been described in detail with reference to particularly preferred embodiments thereof, those skilled in the art will recognize that changes and modifications can be made within the spirit and scope of the invention.

Claims (58)

Comprising extruding a solution comprising solvent and oligomeric polycarbonate in an extruder equipped with one or more vents for solvent removal in the presence of a transesterification catalyst at one or more temperatures in the temperature range of about 100 to about 400 ° C. A process for preparing a carbonate, wherein the oligomeric polycarbonate comprises a polycarbonate repeat unit derived from one or more dihydroxy aromatic compounds and an ester substituted phenoxy end group of formula (I): Formula I Where R ¹ is a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group, or a C ₄ -C ₂₀ aryl group; R ² independently in each occurrence is a halogen atom, cyano group, nitro group, C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group, C ₄ -C ₂₀ aryl group, C ₁ -C ₂₀ alkoxy group , C ₄ -C ₂₀ cycloalkoxy group, C ₄ -C ₂₀ aryloxy group, C ₁ -C ₂₀ alkylthio, C ₄ -C ₂₀ cycloalkyl alkylthio group, C ₄ -C ₂₀ arylthio group, C ₁ - C ₂₀ alkylsulfinyl group, C ₄ -C ₂₀ cycloalkylsulfinyl group, C ₄ -C ₂₀ arylsulfinyl group, C ₁ -C ₂₀ alkylsulfonyl group, C ₄ -C ₂₀ cycloalkylsulfonyl group, C ₄ -C ₂₀ aryl Sulfonyl group, C ₁ -C ₂₀ alkoxycarbonyl group, C ₄ -C ₂₀ cycloalkoxycarbonyl group, C ₄ -C ₂₀ aryloxycarbonyl group, C ₂ -C ₆₀ alkylamino group, C ₆ -C ₆₀ cycloalkylamino group, C ₅ -C ₆₀ arylamino group, C ₁ -C ₄₀ alkylaminocarbonyl group, C ₄ -C ₄₀ cycloalkylaminocarbonyl group, C ₄ -C ₄₀ arylaminocarbonyl group or C ₁ -C ₂₀ acylamino group; b is an integer of 0-4. The method of claim 1, Wherein said ester substituted phenoxy end groups have formula II: Formula II The method of claim 1, Wherein said polycarbonate repeating units derived from at least one dihydroxy aromatic compound comprise repeating units having the formula Formula III Where R ³ to R ¹⁰ are independently a hydrogen atom, a halogen atom, a nitro group, a cyano group, a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group or a C ₆ -C ₂₀ aryl group; W is a bond, oxygen atom, sulfur atom, SO ₂ group, C ₁ -C ₂₀ aliphatic radical, C ₆ -C ₂₀ aromatic radical, C ₆ -C ₂₀ alicyclic radical, or a group ego; R ¹¹ and R ¹² are independently a hydrogen atom, a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group or a C ₄ -C ₂₀ aryl group; Or R ¹¹ and R ¹² together are one or more C ₁ -C ₂₀ alkyl, C ₆ -C ₂₀ aryl, C ₅ -C ₂₁ aralkyl, C ₅ -C ₂₀ cycloalkyl group or optionally substituted with a combination thereof C ₄ -C ₂₀ forms a cycloaliphatic ring. The method of claim 1, Wherein said polycarbonate repeating units derived from at least one dihydroxy aromatic compound comprise repeating units of formula IV and optionally repeating units of formula V derived from bisphenol A: Formula IV Formula V The method of claim 1, Wherein said solvent comprises about 10 to about 99 weight percent of said solution. The method of claim 1, Wherein said solvent comprises at least one ester substituted phenol having formula VI: Formula VI Where R ¹ is a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group, or a C ₄ -C ₂₀ aryl group; R ² independently in each occurrence is a halogen atom, cyano group, nitro group, C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group, C ₄ -C ₂₀ aryl group, C ₁ -C ₂₀ alkoxy group , C ₄ -C ₂₀ cycloalkoxy group, C ₄ -C ₂₀ aryloxy group, C ₁ -C ₂₀ alkylthio, C ₄ -C ₂₀ cycloalkyl alkylthio group, C ₄ -C ₂₀ arylthio group, C ₁ - C ₂₀ alkylsulfinyl group, C ₄ -C ₂₀ cycloalkylsulfinyl group, C ₄ -C ₂₀ arylsulfinyl group, C ₁ -C ₂₀ alkylsulfonyl group, C ₄ -C ₂₀ cycloalkylsulfonyl group, C ₄ -C ₂₀ aryl Sulfonyl group, C ₁ -C ₂₀ alkoxycarbonyl group, C ₄ -C ₂₀ cycloalkoxycarbonyl group, C ₄ -C ₂₀ aryloxycarbonyl group, C ₂ -C ₆₀ alkylamino group, C ₆ -C ₆₀ cycloalkylamino group, C ₅ -C ₆₀ arylamino group, C ₁ -C ₄₀ alkylaminocarbonyl group, C ₄ -C ₄₀ cycloalkylaminocarbonyl group, C ₄ -C ₄₀ arylaminocarbonyl group or C ₁ -C ₂₀ acylamino group; b is an integer of 0-4. The method of claim 6, Wherein said solvent further comprises a halogenated aromatic solvent, a halogenated aliphatic solvent, a non-halogenated aromatic solvent, a non-halogenated aliphatic solvent or a mixture thereof. The method of claim 1, And said solvent comprises methyl salicylate. The method of claim 8, Wherein said solvent further comprises ortho-dichlorobenzene. The method of claim 1, Wherein said transesterification catalyst comprises a quaternary ammonium compound, a quaternary phosphonium compound, or a mixture thereof. The method of claim 10, Wherein said quaternary ammonium compound has formula (VII) Formula VII Where R ¹³ to R ¹⁶ are independently C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group or C ₄ -C ₂₀ aryl group; X ⁻ is an organic or inorganic anion. The method of claim 11, Wherein said anion is selected from the group consisting of hydroxides, halides, carboxylates, phenoxides, sulfonates, sulfates, carbonates and bicarbonates. The method of claim 11, Wherein said quaternary ammonium compound is tetramethylammonium hydroxide. The method of claim 10, Wherein said phosphonium compound has the formula Formula VIII Where R ¹⁷ to R ²⁰ are independently C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group or C ₄ -C ₂₀ aryl group; X ⁻ is an organic or inorganic anion. The method of claim 14, Wherein said anion is selected from the group consisting of hydroxides, halides, carboxylates, phenoxides, sulfonates, sulfates, carbonates and bicarbonates. The method of claim 14, Wherein said quaternary phosphonium compound is tetrabutylphosphonium acetate. The method of claim 10, Wherein said transesterification catalyst further comprises at least one alkali metal hydroxide, alkaline earth metal hydroxide or mixture thereof. The method of claim 1, Wherein said transesterification catalyst comprises at least one alkali metal hydroxide, at least one alkaline earth metal hydroxide or mixtures thereof. The method of claim 18, Wherein said alkali metal hydroxide is sodium hydroxide. The method of claim 1, Wherein said transesterification catalyst comprises an alkali metal salt of at least one carboxylic acid, an alkaline earth metal salt of carboxylic acid or a mixture thereof. The method of claim 20, The alkali metal salt of the carboxylic acid is Na ₂ Mg EDTA. The method of claim 1, Wherein said transesterification catalyst comprises at least one salt of a non-volatile inorganic acid. The method of claim 22, The salt of the non-volatile acid NaH ₂ PO ₃ , NaH ₂ PO ₄ , Na ₂ HPO ₄ , KH ₂ PO ₄ , CsH ₂ PO ₄ , Cs ₂ HPO ₄ , NaKHPO ₄ , NaCsHPO ₄ and KCsHPO ₄ At least one salt selected. The method of claim 1, Wherein said transesterification catalyst is present in an amount corresponding to about 1.0 × 10 ⁻⁸ to 1 × 10 ⁻³ mole of transesterification catalyst per mole of polycarbonate repeat unit derived from an aromatic dihydroxy compound present in the oligomeric polycarbonate . The method of claim 1, Wherein said solution further comprises a monofunctional phenol chain stopper. The method of claim 25, The chain stopper is p-cumylphenol. The method of claim 1, The extruder has a specific screw speed, the solution is introduced into the extruder at a specific feed rate, the feed rate and the screw speed have a specific ratio, and the extruder has a feed rate versus revolution per minute (lb / hr) And a ratio of screw speeds expressed in numbers (rpm) to fall within the range of about 0.01 to about 100. The method of claim 27, The screw speed ranges from about 50 to about 1200 rpm. The method of claim 27, Wherein the extruder is equipped with one or more vacuum vents. The method of claim 27, Wherein said extruder is selected from the group consisting of co-rotating intertwined twin screw extruders, counter-rotating non-interlocked twin screw extruders, single screw reciprocating extruders and single screw non-reciprocating extruders. The method of claim 1, (A) heating a solution comprising a solvent and an oligomeric polycarbonate at a pressure above atmospheric pressure to a temperature above the boiling point of the solvent at atmospheric pressure to obtain a superheated mixture of the oligomeric polycarbonate and the solvent; And Introducing (B) the superheated mixture of oligomeric polycarbonate and solvent into the extruder through at least one pressure control valve. The method of claim 31, wherein Wherein said extruder is selected from the group consisting of co-rotating intertwined twin screw extruders, counter-rotating non-interlocked twin screw extruders, single screw reciprocating extruders and single screw non-reciprocating extruders. The method of claim 31, wherein Wherein the extruder is equipped with one or more vacuum vents and, optionally, one or more vents operated at approximately atmospheric pressure, and one or more side feeders equipped with one or more vents operated at atmospheric pressure. The method of claim 33, wherein Wherein said extruder is selected from the group consisting of co-rotating intertwined twin screw extruders, counter-rotating non-interlocked twin screw extruders, single screw reciprocating extruders and single screw non-reciprocating extruders. The method of claim 1, And removing the polycarbonate product from the extruder. 36. The method of claim 35 wherein Wherein said polycarbonate product is introduced into a second extruder comprising at least one vacuum vent and operated at a temperature in a range from about 100 to about 400 ° C. and a screw speed in a range from about 50 to about 1200 rpm. The method of claim 36, Wherein said second extruder is selected from the group consisting of co-rotating intermeshing twin screw extruders, counter-rotating non-engaging twin screw extruders, single screw reciprocating extruders and single screw non-reciprocating extruders. Heating a mixture comprising at least one dihydroxy aromatic compound, an ester substituted diaryl carbonate and an transesterification catalyst at a temperature in the range of about 100 to about 300 ° C. to obtain a solution of oligomeric polycarbonate in an ester substituted phenol solvent. (I); And The solution of oligomeric polycarbonate in the ester substituted phenol at one or more temperatures in the range of about 100 to about 400 ° C. and at one or more screw speeds in the range of about 50 to about 1200 rpm; Comprising extruding on an extruder (II), Method for producing polycarbonate. The method of claim 38, The ester substituted diaryl carbonate in step (I) is used in an amount corresponding to about 0.95 to about 1.05 moles per mole of said dihydroxy aromatic compound. The method of claim 38, Wherein said transesterification catalyst is present in an amount corresponding to about 1.0 × 10 ⁻⁸ to about 1 × 10 ⁻³ mole of transesterification catalyst per mole of dihydroxy aromatic compound. The method of claim 38, Wherein said ester-substituted diaryl carbonate has formula (IX): Formula IX Where R ¹ is independently at each occurrence a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group, or a C ₄ -C ₂₀ aryl group; R ² independently in each occurrence is a halogen atom, cyano group, nitro group, C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group, C ₄ -C ₂₀ aryl group, C ₁ -C ₂₀ alkoxy group , C ₄ -C ₂₀ cycloalkoxy group, C ₄ -C ₂₀ aryloxy group, C ₁ -C ₂₀ alkylthio, C ₄ -C ₂₀ cycloalkyl alkylthio group, C ₄ -C ₂₀ arylthio group, C ₁ - C ₂₀ alkylsulfinyl group, C ₄ -C ₂₀ cycloalkylsulfinyl group, C ₄ -C ₂₀ arylsulfinyl group, C ₁ -C ₂₀ alkylsulfonyl group, C ₄ -C ₂₀ cycloalkylsulfonyl group, C ₄ -C ₂₀ aryl Sulfonyl group, C ₁ -C ₂₀ alkoxycarbonyl group, C ₄ -C ₂₀ cycloalkoxycarbonyl group, C ₄ -C ₂₀ aryloxycarbonyl group, C ₂ -C ₆₀ alkylamino group, C ₆ -C ₆₀ cycloalkylamino group, C ₅ -C ₆₀ arylamino group, C ₁ -C ₄₀ alkylaminocarbonyl group, C ₄ -C ₄₀ cycloalkylaminocarbonyl group, C ₄ -C ₄₀ arylaminocarbonyl group or C ₁ -C ₂₀ acylamino group; b is independently an integer from 0 to 4 in each case. 42. The method of claim 41 wherein Wherein said ester substituted diaryl carbonate is bis (methyl salicyl) carbonate. The method of claim 38, Wherein said dihydroxy aromatic compound has the formula Formula X Where R ³ to R ¹⁰ are independently a hydrogen atom, a halogen atom, a nitro group, a cyano group, a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group or a C ₆ -C ₂₀ aryl group; W is a bond, oxygen atom, sulfur atom, SO ₂ group, C ₁ -C ₂₀ aliphatic radical, C ₆ -C ₂₀ aromatic radical, C ₆ -C ₂₀ alicyclic radical, or a group ego; R ¹¹ and R ¹² are independently a hydrogen atom, a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group or a C ₄ -C ₂₀ aryl group; Or R ¹¹ and R ¹² together are one or more C ₁ -C ₂₀ alkyl, C ₆ -C ₂₀ aryl, C ₅ -C ₂₁ aralkyl, C ₅ -C ₂₀ cycloalkyl group or optionally substituted with a combination thereof C ₄ -C ₂₀ forms a cycloaliphatic ring. The method of claim 38, Wherein said at least one dihydroxy aromatic compound comprises hydroquinone and bisphenol A. A polycarbonate product prepared by the process of claim 44. A molded article comprising the polycarbonate product of claim 45. The method of claim 38, Wherein said at least one dihydroxy aromatic compound comprises bisphenol A and 4,4'-sulfonyldiphenol. A polycarbonate product prepared by the method of claim 47. 49. A molded article comprising the polycarbonate product of claim 48. A mixture of bisphenol A, bis (methyl salicylate) carbonate and transesterification catalyst is heated at a temperature in the range of 100 to 300 ° C. and a pressure of about 0.1 to about 10 atmospheres to obtain a solution of oligomeric bisphenol A polycarbonate in methyl salicylate. Wherein the bis (methyl salicylic) carbonate is present in an amount corresponding to about 0.95 to about 1.05 moles of bis (methyl salicylic) carbonate per mole of bisphenol A, and the transesterification catalyst is an ester exchange catalyst per mole of bisphenol A (I) present in an amount corresponding to 1 x 10 ^-8 to 1 x 10 ^-3 mole, wherein said oligomeric polycarbonate comprises methoxy carbonyl phenoxy end groups; And Extruding said solution of oligomeric bisphenol A polycarbonate in methyl salicylate at one or more temperatures in the range of about 100 to about 400 ° C. and at a screw speed in one or more of the range of about 50 to about 1200 rpm. Method for producing polycarbonate. 51. The method of claim 50 wherein Wherein the transesterification catalyst comprises tetrabutylphosphonium acetate. A polycarbonate prepared by the method of claim 50 comprising less than 10 ppm Fries product. The method of claim 52, wherein Polycarbonate having a percent end capping of at least about 90%. The method of claim 52, wherein Polycarbonate having a percent end capping of at least about 97%. 53. A molded article comprising the polycarbonate of claim 52. The method of claim 55, Molded product, which is an optical disc. Polycarbonate comprising extruding a solution comprising a solvent and a polycarbonate in an extruder equipped with one or more vents for solvent removal in the presence of a transesterification catalyst at one or more temperatures in the temperature range of about 100 to about 400 ° C. A process for preparing the polycarbonate, wherein the polycarbonate comprises a polycarbonate repeating unit derived from at least one dihydroxy aromatic compound and an ester substituted phenoxy end group of formula (I): Formula I Where R ¹ is a C ₁ -C ₂₀ alkyl group, a C ₄ -C ₂₀ cycloalkyl group, or a C ₄ -C ₂₀ aryl group; R ² independently in each occurrence is a halogen atom, cyano group, nitro group, C ₁ -C ₂₀ alkyl group, C ₄ -C ₂₀ cycloalkyl group, C ₄ -C ₂₀ aryl group, C ₁ -C ₂₀ alkoxy group , C ₄ -C ₂₀ cycloalkoxy group, C ₄ -C ₂₀ aryloxy group, C ₁ -C ₂₀ alkylthio, C ₄ -C ₂₀ cycloalkyl alkylthio group, C ₄ -C ₂₀ arylthio group, C ₁ - C ₂₀ alkylsulfinyl group, C ₄ -C ₂₀ cycloalkylsulfinyl group, C ₄ -C ₂₀ arylsulfinyl group, C ₁ -C ₂₀ alkylsulfonyl group, C ₄ -C ₂₀ cycloalkylsulfonyl group, C ₄ -C ₂₀ aryl Sulfonyl group, C ₁ -C ₂₀ alkoxycarbonyl group, C ₄ -C ₂₀ cycloalkoxycarbonyl group, C ₄ -C ₂₀ aryloxycarbonyl group, C ₂ -C ₆₀ alkylamino group, C ₆ -C ₆₀ cycloalkylamino group, C ₅ -C ₆₀ arylamino group, C ₁ -C ₄₀ alkylaminocarbonyl group, C ₄ -C ₄₀ cycloalkylaminocarbonyl group, C ₄ -C ₄₀ arylaminocarbonyl group or C ₁ -C ₂₀ acylamino group; b is an integer of 0-4. The method of claim 57, Wherein said polycarbonate has a number average molecular weight of at least 5000 Daltons.