Patent Description:
According to claim <NUM> a method for preparing a poly(phenylene ether) comprises feeding air to a continuous flow reactor that contains a reaction mixture comprising a phenol, a transition metal catalyst, and an organic solvent; and oxidatively polymerizing the reaction mixture at a temperature of <NUM> to <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM> and a pressure of greater than <NUM> kPa, preferably greater than or equal to <NUM> kPa, more preferably greater than or equal to <NUM> kPa, even more preferably greater than or equal to <NUM> kPa to form a poly(phenylene ether); wherein the reaction mixture has a residence time in the continuous flow reactor of less than or equal to <NUM> minutes, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM> minutes.

A poly(phenylene ether) is made by the method.

An article comprises the poly(phenylene ether).

The above described and other features are exemplified by the following detailed description.

The present inventors have advantageously discovered a process for preparing poly(phenylene ether) using a continuous flow reactor with short residence times (e.g., ≤<NUM> minutes), low metal catalyst concentrations, and using air as an oxidant. Continuous processes can offer advantages such as lower operating costs compared to batch production. The resulting poly(phenylene ether)s can advantageously exhibit high molecular weights and narrow molecular weight distributions, as well as reduced biphenyl and quinone side product content.

Accordingly, the present invention relates to a method for preparing a poly(phenylene ether). The method comprises, in an embodiment, feeding a reaction mixture to a continuous flow reactor. The components of the reaction mixture can be precombined or fed into the reactor separately to provide the reaction mixture in the reactor.

The continuous flow reactor allows for intense heat and mass transfer between multiple phases while offering limited back mixing of individual phases in the flow direction. The volumetric mass transfer coefficients are preferably in excess of <NUM>-<NUM>, for example, <NUM> to <NUM>-<NUM>. Heat transfer per unit volume is preferably greater than <NUM>-<NUM>. The flow reactor can also have a surface area to volume ratio of <NUM> to <NUM>-<NUM>. Suitable continuous flow reactors can include, but are not limited to microreactors and millireactors. The continuous flow reactor can be a commercially available flow reactor, for example, Advanced-Flow™ Reactor from Corning Inc. ; Modular MicroReaction System, Lonza FlowPlate™, ART™ plate reactors and Miprowa™ from Ehrfeld Mikrotechnik BTS GmbH; Qmix™ microreaction system from Cetoni; LABTRIX™ START, LABTRIX™ S1, KILOFLOW™ and PLANTRIX™ from Chemtrix; HTM™, MR-LAB™, MR PILOT™ and XXL™ SERIES from Little Things Factory; Asia™ Flow Chemistry System from Syrris; KeyChem™, CYTOS-<NUM>™ and CYTOS-<NUM>™ from YMC, AMaR-<NUM>™ and AMaR-4P™ from AMAR Equipments Pvt Ltd. The inner diameter of the flow reactor is not limited to any specific value. In a specific, nonlimiting example, an exemplary inner diameter of a reactor can be <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>. The flow reactor can have a single passage, parallel passages or serial passages.

The reaction mixture comprises a phenol, a transition metal catalyst, and an organic solvent. The phenol can be a monohydric phenol having the structure
<CHM>
wherein each occurrence of Q<NUM> is independently halogen, unsubstituted or substituted C<NUM>-<NUM> primary or secondary hydrocarbyl, C<NUM>-<NUM> hydrocarbylthio, C<NUM>-<NUM> hydrocarbyloxy, or C<NUM>-<NUM> halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and wherein each occurrence of Q<NUM> is independently hydrogen, halogen, unsubstituted or substituted C<NUM>-<NUM> primary or secondary hydrocarbyl, C<NUM>-<NUM> hydrocarbylthio, C<NUM>-<NUM> hydrocarbyloxy, or C<NUM>-<NUM> halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms. In some embodiments, each occurrence of Q<NUM> is methyl and each occurrence of Q<NUM> is hydrogen and the phenol is <NUM>,<NUM>-xylenol (also referred to as dimethyl phenol). In some embodiments, each occurrence of Q<NUM> is methyl, one occurrence of Q<NUM> is hydrogen and the other is methyl, and the phenol is <NUM>,<NUM>,<NUM>-trimethylphenol.

Suitable transition metal catalysts for the synthesis of poly(phenylene ether) include those comprising such catalyst metals as manganese, chromium, copper, and combinations thereof. Among metal complex catalysts, it is preferred to use a copper complex catalyst comprising a secondary alkylene diamine ligand. The copper source for the copper complex comprising a secondary alkylene diamine can comprise a salt of cupric or cuprous ion, including halides, oxides and carbonates. Alternatively, copper can be provided in the form of a pre-formed salt of the alkylene diamine ligand. Preferred copper salts include cuprous halides, cupric halides, and their combinations. Especially preferred are cuprous bromides, cupric bromides, and combinations thereof.

A preferred copper complex catalyst comprises a secondary alkylene diamine ligand. Suitable secondary alkylene diamine ligands are described in <CIT>and are represented by the formula.

wherein Ra is a substituted or unsubstituted divalent residue wherein two or three aliphatic carbon atoms form the closest link between the two diamine nitrogen atoms; and Rb and Rc are each independently isopropyl or a substituted or unsubstituted C<NUM>-<NUM> tertiary alkyl group. Examples of Ra include ethylene, <NUM>,<NUM>-propylene, <NUM>,<NUM>-propylene, <NUM>,<NUM>-butylene, <NUM>,<NUM>-butylene, <NUM>,<NUM>-butylene, the various pentylene isomers having from two to three carbon atoms separating the two free valances, phenylethylene, tolylethylene, <NUM>-phenyl-<NUM>,<NUM>-propylene, cyclohexylethylene, <NUM>,<NUM>-cyclohexylene, <NUM>,<NUM>-cyclohexylene, <NUM>,<NUM>-cyclopropylene, <NUM>,<NUM>-cyclobutylene, <NUM>,<NUM>-cyclopentylene, and the like. Preferably, Ra is ethylene. Examples of Rb and Rc can include isopropyl, t-butyl, <NUM>-methyl-but-<NUM>-yl, <NUM>-methyl-pent-<NUM>-yl, <NUM>-methyl-pent-<NUM>-yl, <NUM>,<NUM>-dimethyl-buty-<NUM>-yl, <NUM>,<NUM>-dimethylpent-<NUM>-yl, <NUM>,4dimethyl-pent-<NUM>-yl, <NUM>-methylcyclopentyl, <NUM>-methylcyclohexyl and the like. A highly preferred example of Rb and Rc is t-butyl. An exemplary secondary alkylene diamine ligand is N,N'-di-t-butylethylenediamine (DBEDA). Suitable molar ratios of copper to secondary alkylene diamine are from <NUM>:<NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM> to <NUM>:<NUM>, more preferably <NUM>:<NUM> to <NUM>:<NUM>.

The preferred copper complex catalyst comprising a secondary alkylene diamine ligand can further comprise a secondary monoamine. Suitable secondary monoamine ligands are described in commonly assigned <CIT> and represented by the formula.

wherein Rd and Re are each independently substituted or unsubstituted C<NUM>-<NUM> alkyl groups, and preferably substituted or unsubstituted C<NUM>-<NUM> alkyl groups. Examples of the secondary monoamine include di-n-propylamine, di-isopropylamine, di-n-butylamine, di-sec-butylamine, di-t-butylamine, N-isopropyl-t-butylamine, N-sec-butyl-t-butylamine, di-n-pentylamine, bis(<NUM>,<NUM>-dimethylpropyl)amine, and the like. A highly preferred secondary monoamine is di-n-butylamine (DBA). A suitable molar ratio of copper to secondary monoamine is from <NUM>:<NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM> to <NUM>: <NUM>, and more preferably <NUM>:<NUM> to <NUM>:<NUM>.

The preferred copper complex catalyst comprising a secondary alkylene diamine ligand can further comprise a tertiary monoamine. Suitable tertiary monoamine ligands are described in the abovementioned <CIT> and <CIT> patents and include heterocyclic amines and certain trialkyl amines characterized by having the amine nitrogen attached to at least two groups which have a small cross-sectional area. In the case of trialkylamines, it is preferred that at least two of the alkyl groups be methyl with the third being a primary C<NUM>-<NUM> alkyl group or a secondary C<NUM>-<NUM> alkyl group. It is especially preferred that the third substituent have no more than four carbon atoms. A highly preferred tertiary amine is dimethylbutylamine (DMBA). A suitable molar ratio of copper to tertiary amine is less than <NUM>:<NUM>, preferably less than <NUM>:<NUM>, preferably <NUM>:<NUM> to less than <NUM>:<NUM>, more preferably <NUM>:<NUM> to <NUM>:<NUM>.

A suitable molar ratio of metal complex catalyst (measured as moles of metal) to phenol is <NUM>:<NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM> to <NUM>:<NUM>, more preferably <NUM>:<NUM> to <NUM>:<NUM>.

The reaction conducted in the presence of a metal complex catalyst can optionally be conducted in the presence of bromide ion. It has already been mentioned that bromide ion can be supplied as a cuprous bromide or cupric bromide salt. Bromide ion can also be supplied by addition of a <NUM>-bromophenol, such as <NUM>,<NUM>-dimethyl-<NUM>-bromophenol. Additional bromide ion can be supplied in the form of hydrobromic acid, an alkali metal bromide, or an alkaline earth metal bromide. Sodium bromide and hydrobromic acid are highly preferred bromide sources. A suitable ratio of bromide ion to copper ion is <NUM> to <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>.

The reaction mixture further comprises an organic solvent. Suitable organic solvents include alcohols, ketones, aliphatic and aromatic hydrocarbons, chlorohydrocarbons, nitrohydrocarbons, ethers, esters, amides, mixed ether-esters, sulfoxides, and the like, providing they do not interfere with or enter into the oxidation reaction. Preferably, the solvent is selected so as to avoid any precipitation in the reactor. The organic solvent can comprise, for example, toluene, benzene, xylene, chlorobenzene, ortho-dichlorobenzene, nitrobenzene, trichloroethylene, ethylene dichloride, dichloromethane, chloroform, tetrachloroethane, or a combination thereof. Preferred solvents include aromatic hydrocarbons. In some embodiments, the organic solvent comprises toluene.

A suitable starting concentration of phenol can be <NUM> to <NUM> weight percent, or <NUM> to <NUM> weight percent, preferably <NUM> to <NUM> weight percent, more preferably <NUM> to <NUM> weight percent, or <NUM> to <NUM> weight percent, or <NUM> to <NUM> weight percent, based on the total weight of the phenol and solvent. All the phenol can be added at the beginning of the reaction. Alternatively, the phenol can be added in discrete or continuous amounts during the course of the reaction.

The reaction mixture can optionally further comprise one or more additional components, including a lower alkanol or glycol, a small amount of water, or a phase transfer agent. It is generally not necessary to remove reaction byproduct water during the course of the reaction. Suitable phase transfer agents can include, for example, a quaternary ammonium compound, a quaternary phosphonium compound, a tertiary sulfonium compound, or a combination thereof. Preferably, the phase transfer agent can be of the formula (R<NUM>)<NUM>Q+X, wherein each R<NUM> is the same or different, and is a C<NUM>-<NUM> alkyl; Q is a nitrogen or phosphorus atom; and X is a halogen atom or a C<NUM>-<NUM> alkoxy or C<NUM>-<NUM> aryloxy. Exemplary phase transfer catalysts include (CH<NUM>(CH<NUM>)<NUM>)<NUM>NX, (CH<NUM>(CH<NUM>)<NUM>)<NUM>PX, (CH<NUM>(CH<NUM>)<NUM>)<NUM>NX, (CH<NUM>(CH<NUM>)<NUM>)<NUM>NX, (CH<NUM>(CH<NUM>)<NUM>)<NUM>NX, CH<NUM>(CH<NUM>(CH<NUM>)<NUM>)<NUM>NX, and CH<NUM>(CH<NUM>(CH<NUM>)<NUM>)<NUM>NX, wherein X is Cl-, Br-, a C<NUM>-<NUM> alkoxy or a C<NUM>-<NUM> aryloxy. An effective amount of a phase transfer agent can be <NUM> to <NUM> wt%, or <NUM> to <NUM> wt%, each based on the weight of the reaction mixture. In a specific embodiment, a phase transfer agent is present and comprises N,N,N'N'-didecyldimethyl ammonium chloride.

In some embodiments, the reaction mixture can optionally further comprise a dihydric phenol, preferably <NUM>,<NUM>',<NUM>,<NUM>'-tetramethylbisphenol A, <NUM>,<NUM>',<NUM>-<NUM>'-tetramethylbiphenol, <NUM>,<NUM>',<NUM>,<NUM>',<NUM>,<NUM>'-hexamethyl-[<NUM>,<NUM>'-biphenyl]-<NUM>,<NUM>'-diol, or a combination thereof. When present, the dihydric phenol can be included in the reaction mixture in an amount of <NUM> to <NUM> weight percent, or <NUM> to <NUM> weight percent, based on the total weight of the reaction mixture.

The method further comprises feeding air to the continuous flow reactor containing the reaction mixture. Feeding the air can be at a flow rate effective to provide a phenol: oxygen molar ratio of <NUM>: <NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM>. In some embodiments, the air can be a combination comprising oxygen and nitrogen. In some embodiments, the air comprises less than <NUM>% oxygen, or less than <NUM>% oxygen, or at least <NUM>% oxygen or at least <NUM>% oxygen. Within this range, the air comprises <NUM> to <NUM>%, or <NUM> to <NUM>% oxygen. In some embodiments, the balance is nitrogen. The air can include less than <NUM> ppm of hydrocarbons.

Upon feeding the reaction mixture and the air to the continuous flow reactor, the reaction mixture can be oxidatively polymerized to form the desired poly(phenylene ether). The polymerization is conducted at a temperature of <NUM> to <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>. Advantageously, the reaction mixture has a residence time of less than or equal to <NUM> minutes, or less than or equal to <NUM> minutes, preferably <NUM> to <NUM> minutes, more preferably <NUM> to <NUM> minutes in the continuous flow reactor. The oxidative polymerization is performed at a pressure of greater than <NUM> kPa, preferably greater than or equal to <NUM> kPa, more preferably greater than or equal to <NUM> kPa, even more preferably greater than or equal to <NUM> kPa. In some embodiments, the pressure can be less than or equal to <NUM> kPa, or less than or equal to <NUM> kPa. In an advantageous feature, the continuous flow reactor of the present disclosure can have a significantly reduced oxygen head space compared to other conventional reactors, and thus the reaction can be performed at higher temperatures without comprising safety.

The reaction can be terminated by stopping the oxygen addition when the target intrinsic viscosity is reached. Other suitable methods for terminating the reaction include the addition of a mineral or organic acid, such as acetic acid, or the addition of a sequestrant as described in greater detail below.

The method can further comprise recovering the copper catalyst using an aqueous sequestrant solution. Suitable techniques for recovering the catalyst metal from the metal complex catalyst include those described in commonly assigned <CIT>, <CIT>, and <CIT> These techniques comprise the addition of one or more sequestrants to complex the catalyst metal and facilitate its separation from the poly(phenylene ether) product. A preferred method for removing catalyst metal from the poly(phenylene ether) product is described in <CIT>. This method, which eliminates multiple rinses with a complexing reagent, includes removing the catalyst from the polymerization mixture by mixing the polymerization mixture with a complexing reagent and liquid/liquid centrifuging the multiphase mixture. Water is then added to the polymer phase prior to a subsequent liquid/liquid centrifuge process. In general, suitable sequestrants include polyfunctional carboxylic acid-containing compounds, such as citric acid, tartaric acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, ethylenediaminedisuccinic acid, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, and the like. These sequestrants can be used as their free acids or salts of, for example, their alkali metals, alkaline earth metals, and nitrogenous cations. Preferred sequestrants include nitrilotriacetic acid, ethylenediamine tetraacetic acid and their salts. Suitable molar ratios of sequestrant to catalyst metal are <NUM>:<NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM> to <NUM>:<NUM>, more preferably <NUM>:<NUM> to <NUM>:<NUM>.

The method can further comprise isolating the poly(phenylene ether), for example, by precipitation. Precipitation of the poly(phenylene ether) can be induced by appropriate selection of reaction solvent described above, or by the addition of an anti-solvent to the reaction mixture. Suitable anti-solvents include lower alkanols having one to about ten carbon atoms, acetone and hexane. The preferred anti-solvent is methanol. The anti-solvent can be employed at a range of concentrations relative to the organic solvent, with the optimum concentration depending on the identities of the organic solvent and anti-solvent, as well as the concentration and intrinsic viscosity of the poly(phenylene ether) product. It has been discovered that when the organic solvent is toluene and the anti-solvent is methanol, a toluene:methanol weight ratio of <NUM>:<NUM> to <NUM>:<NUM> is suitable, with ratios of <NUM>:<NUM> to <NUM>:<NUM> being preferred, and <NUM>:<NUM> to <NUM>:<NUM> being more preferred. These preferred and more preferred ratios are useful for producing a desirable powder morphology for the isolated poly(phenylene ether) resin, without generating either stringy powder or excessive powder fines.

The method can optionally comprise pre-concentrating the reaction mixture prior to addition of the anti-solvent. Although it is not possible to pre-concentrate to as great a degree as for lower intrinsic viscosity poly(phenylene ether)s, pre-concentrations of, for example, <NUM> weight percent poly(phenylene ether) are possible. Any suitable method for pre-concentration can be employed. For example, the preconcentration can be carried out by preheating the solution above its atmospheric boiling point at a pressure modestly elevated above one atmosphere (so that no boiling takes place in the heat exchanger) followed by flashing the solution to a lower pressure and temperature, whereby vaporization of a substantial part of the toluene takes place and the required heat of vaporization is supplied by the heat transferred in the heat exchanger as sensible heat of the solution.

The isolated poly(phenylene ether) can have an intrinsic viscosity of greater than or equal to <NUM> to <NUM> deciliters per gram, preferably <NUM> to <NUM> deciliters per gram, more preferably <NUM> to <NUM> deciliters per gram, even more preferably <NUM> to <NUM> deciliters per gram, or <NUM> to <NUM> deciliters per gram as measured in chloroform at <NUM> using an Ubbelohde viscometer.

The isolated poly(phenylene ether) can also have a dispersity of less than <NUM>, for example <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>. Dispersity can be determined using gel permeation chromatography using chloroform relative to polystyrene standards.

In some embodiments, the poly(phenylene ether) prepared according to the method described herein can advantageously have a reduced biphenyl content, quinone content, or both. For example, the poly(phenylene ether) can have a combined biphenyl and quinone content of less than <NUM> weight percent based on the weight of the phenol used in the oxidative polymerization.

Thus, the poly(phenylene ether) prepared according to the above method represents another aspect of the present disclosure. The poly(phenylene ether) can comprise repeating structural units having the formula
<CHM>
wherein each occurrence of Q<NUM> and Q<NUM> are as defined above. The hydrocarbyl residue can also contain one or more carbonyl groups, amino groups, hydroxyl groups, or the like, or it can contain heteroatoms within the backbone of the hydrocarbyl residue. As one example, Q<NUM> can be a di-n-butylaminomethyl group formed by reaction of a terminal <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-phenyl group with the di-n-butylamine component of an oxidative polymerization catalyst.

The poly(phenylene ether) can comprise molecules having aminoalkyl-containing end group(s), typically located in a position ortho to the hydroxy group. Also frequently present are tetramethyldiphenoquinone (TMDQ) end groups, typically obtained from <NUM>,<NUM>-dimethylphenol-containing reaction mixtures in which tetramethyldiphenoquinone by-product is present. In some embodiments, the poly(phenylene ether) is substantially free of the quinone end groups. For example, the poly(phenylene ether) can include less than <NUM>% of quinone end groups. The poly(phenylene ether) can be in the form of a homopolymer, a copolymer, a graft copolymer, an ionomer, or a block copolymer, as well as combinations thereof.

Compositions and articles comprising the poly(phenylene ether) made by the above method represent another aspect of the present disclosure. For example, the poly(phenylene ether) made by the method described herein can be useful for forming a thermoplastic composition which can optionally comprises at least one of a thermoplastic polymer different from the poly(phenylene ether) and an additive composition comprising one or more additives.

The poly(phenylene ether) can be formed into articles by shaping, extruding, or molding. Articles can be molded from the composition by methods including, for example, injection molding, injection compression molding, gas assist injection molding, rotary molding, blow molding, compression molding, and the like. In some embodiments, articles can be formed by injection molding.

Materials used for the following Examples are described in Table <NUM>.

The effect of pressure and use of air as an oxidant source was first demonstrated for a copolymer of DMP and TMBPA. The reaction mixture used in this example was prepared according to the composition described in Table <NUM>. The amount of each component is given in weight percent based on the total weight of the reaction mixture. The components were stirred well to ensure dissolution prior to introduction into the reactor.

In Comparative Examples <NUM> and <NUM>, the above reaction mixture was used in a batch polymerization with pure oxygen as the oxidant and a temperature of <NUM>. These polymerizations were conducted at atmospheric pressure (i.e., <NUM> atmosphere or <NUM> kPa). Results of this polymerization are shown in Table <NUM>. For Comparative Examples <NUM> and <NUM>, HPLC was used to determine the weight percent of DMP in the reaction mixture over the course of the polymerization. For all flow reactions, the weight percent of DMP in the reaction mixture at varying times was determined by an online infrared spectroscopy method using a Mettler Toledo ReactIR™ <NUM> with fibre optic probe and Dicomp ATR crystal and a Mettler Toledo ReactIR™ <NUM> with micro flow cell and diamond ATR crystal. DMP concentration was determined from a calibration curve where the range of <NUM> to <NUM>-<NUM> was analyzed to observe the maximum peak height at <NUM>-<NUM>. This value was plotted as a linear regression with the obtained HPLC data to construct a calibration curve for determining DMP concentration.

Comparative Examples <NUM>-<NUM> in Table <NUM> below demonstrate the copolymerization of DMP and TMBPA using the Table <NUM> reaction mixture in a continuous flow reactor with pure oxygen as oxidant and at a temperature of <NUM>. An Advanced Flow Reactor AFR, available from Corning, was used for the flow polymerizations. The flow reactor used is a reactor in plate form, where there are multiple plates arranged in series to provide for sufficient reactor volume.

The polymerizations of Comparative Examples <NUM>-<NUM> in the flow reactor were conducted at a liquid flow rate of <NUM> milliliters/minute and a gas (oxygen at atmospheric condition) flow rate of <NUM> milliliters/minute. Comparative Examples <NUM>-<NUM> were conducted at atmospheric pressure (i.e., <NUM> atmosphere or <NUM> kPa). The weight percent of DMP in the reaction mixture at varying times was determined by online infrared spectroscopy as described above.

Examples <NUM>-<NUM> in Table <NUM> below demonstrate the copolymerization of DMP and TMBPA using the Table <NUM> reaction mixture in a continuous flow reactor with air as oxidant and at a temperature of <NUM>. In Example <NUM>, the reaction was conducted at a pressure of <NUM> bar (<NUM> kPa). In Example <NUM>, the reaction was conducted at a pressure of <NUM> bar (<NUM> kPa). These polymerizations in the flow reactor were conducted at a liquid flow rate of <NUM> milliliters/minute and a gas flow rate of <NUM> milliliters/minute. The weight percent of DMP in the reaction mixture at varying times was determined by online infrared spectroscopy as described above.

It can be seen from the data presented in Tables <NUM>-<NUM> that use of a flow reactor enables the use of air as an oxidant. Further, the polymerizations can be conducted under pressure to give short reaction times.

The effect of pressure and use of air as an oxidant source was also demonstrated for a homopolymer of DMP. The reaction mixture used in these examples was prepared according to the composition described in Table <NUM>. The amount of each component is given in weight percent based on the total weight of the reaction mixture. The components were stirred well to ensure dissolution prior to introduction into the reactor.

In Comparative Example <NUM>, the above reaction mixture was used in a batch polymerization with pure oxygen as the oxidant and a temperature of <NUM>. This polymerization was conducted at atmospheric pressure (i.e., <NUM> atmosphere or <NUM> kPa). Results of this polymerization are shown in Table <NUM>. The weight percent of DMP in the reaction mixture at varying times was determined by online infrared spectroscopy as described above.

Comparative Example <NUM> in Table <NUM> below demonstrates the homopolymerization of DMP using the Table <NUM> reaction mixture in a continuous flow reactor with pure oxygen as oxidant and at a temperature of <NUM>. This polymerization in the flow reactor was conducted at a liquid flow rate of <NUM> milliliters/minute and a gas flow rate of <NUM> milliliters/minute. Comparative Example <NUM> was conducted at atmospheric pressure (i.e., <NUM> atmosphere or <NUM> kPa). The weight percent of DMP in the reaction mixture at varying times was determined by online infrared spectroscopy as described above.

Examples <NUM>-<NUM> in Table <NUM> below demonstrate the homopolymerization of DMP using the Table <NUM> reaction mixture in a continuous flow reactor with air as oxidant and at a temperature of <NUM>. In Example <NUM>, the reaction was conducted at a pressure of <NUM> bar (<NUM> kPa). In Example <NUM>, the reaction was conducted at a pressure of <NUM> bar (<NUM> kPa). These polymerizations in the flow reactor were conducted at a liquid flow rate of <NUM> milliliters /minute and a gas flow rate of <NUM> milliliters. The weight percent of DMP in the reaction mixture at varying times was determined by online infrared spectroscopy as described above.

It can be seen from the data presented in Tables <NUM>-<NUM> that use of a flow reactor enables the use of air as an oxidant for homopolymerization of DMP. Further, the polymerizations can be conducted under pressure to give short reaction times.

Another advantage of the present method using a flow reactor is that the formation of side products (e.g., quinones and biphenyl) is low. Table <NUM> below shows a comparison of the weight percent of side products (tetramethyl diphenyl quinone (TMDQ) units and tetramethyl biphenyl (TMPA) units) compared to the weight of DMP (i.e., the initial weight of DMP used at the outset of polymerization) for a copolymer of DMP and TMBPA made according to a batch process (CE <NUM>) and a flow process (E5). In both CE8 and CE9, oxygen was used as the oxidant, and the reactions were conducted at atmospheric pressure. Other reaction conditions were the same as described above.

Example <NUM> in Table <NUM> below demonstrates the homopolymerization of DMP using the Table <NUM> reaction mixture in a batch reactor with air as oxidant and at a temperature of <NUM>. This polymerization was conducted at atmospheric pressure (i.e., <NUM> atmospheric or <NUM> kPa). The weight percent of DMP, TMBP and TMDQ in the reaction mixture at varying times were determined by HPLC.

As seen in Tables <NUM> and <NUM>, the amount of side products resulting from C-C coupling (e.g., quinone and biphenyl side products) can be reduced by almost half when a flow reactor is used.

Table <NUM> below shows the weight average molecular weight (Mw), dispersity (PDI) and intrinsic viscosity (IV) for the polymers prepared by the processes of CE1, CE7, E1, and E2. Intrinsic viscosity was determined at <NUM> in chloroform using an Ubbelohde viscometer, and Mw and PDI were determined using gel permeation chromatography using chloroform relative to polystyrene standards.

All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. "Combinations" is inclusive of blends, mixtures, alloys, reaction products, and the like. The terms "first," "second," and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms "a" and "an" and "the" do not denote a limitation of quantity, and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. throughout the specification to "some embodiments", "an embodiment", and so forth, means that a particular element described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. The term "combination thereof" as used herein includes one or more of the listed elements. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

Claim 1:
A method for preparing a poly(phenylene ether), the method comprising:
feeding air to a continuous flow reactor that contains a reaction mixture comprising a phenol, a transition metal catalyst, and an organic solvent; and
oxidatively polymerizing the reaction mixture at a temperature of <NUM> to <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM> and a pressure of greater than <NUM> kPa, preferably greater than or equal to <NUM> kPa, more preferably greater than or equal to <NUM> kPa, even more preferably greater than or equal to <NUM> kPa to form a poly(phenylene ether);
wherein the reaction mixture has a residence time in the continuous flow reactor of less than or equal to <NUM> minutes, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM> minutes.