Abstract: Embodiments according to the present invention relate to sacrificial polymer compositions that include polycarbonate polymers having repeat units derived from stereospecific polycyclic 2,3-diol monomers. The sacrificial polymer compositions also include an acid generator that is selected from at least one photoacid generator and/or at least one thermal acid generator. In addition, embodiments according to the present invention relate to a method of forming a structure that includes a three-dimensional space interposed between a substrate and an overcoat layer, and a method of temporarily bonding first and second substrates together, which make use of the polycarbonate polymers.

Abstract: A resin composition containing: an ester compound including a carboxylic acid ester obtained by using (1) a monohydric alcohol having an alkyl group having 1 to 4 carbon atoms; (2) a dicarboxylic acid having an alkylene group having 2 to 4 carbon atoms; and (3) a dihydric alcohol having an alkylene group having 2 to 6 carbon atoms, the ester compound having an acid value of 1.00 mgKOH/g or less, a hydroxyl value of 5.0 mgKOH/g or less, and a number-average molecular weight of from 300 to 700; and an aliphatic polyester. Since the resin composition of the present invention inhibits the generation of volatile compounds, the resin composition can be suitably used in various industrial applications, such as daily sundries, household electric appliance parts, and automobile parts.

Abstract: A method of improving the mechanical properties of polymers is described. The method involves heat treating the polymer at a temperature below the glass transition temperature in a wet or in a dry environment. Polymer articles capable of moisture uptake in humid environments, as well as polymer articles less susceptible to moisture uptake, have improved mechanical properties, particularly improved stress relaxation behavior and set properties, when treated in accord with the heat treatment method.

Abstract: The present invention relates to a method for producing a polyester, containing conducting a transesterification reaction of at least one compound selected from compounds represented by the following formulae (1) to (3) with a diol compound in the presence of a catalyst: wherein Ar is a divalent aromatic hydrocarbon group or the like; R1 is CX1Y1R4; R2 is a hydrogen atom or CX2Y2R5; R3 is a hydrogen atom or CX3Y3R6; R7 is a perfluoroalkylene group having 1 to 5 carbon atoms; X1 to X3 are a hydrogen atom, a fluorine atom or Rf; Y1 to Y3 are a fluorine atom or Rf; R4 to R6 are a fluorine atom, Rf, ORf or the like; and Rf is a fluoroalkyl group having 1 to 4 carbon atoms.

Abstract: A method to produce a purified dihydroxy aromatic compound from a polycarbonate-containing composition is provided. The method includes depolymerizing the polycarbonate by alcoholysis using a titanium-based catalyst producing a dihydroxy aromatic compound and a dialkyl carbonate, recovering the dihydroxy aromatic compound as a crude dihydroxy aromatic compound; and contacting the recovered crude dihydroxyl aromatic compound with an acid in the presence of a solvent at an elevated temperature. Alternatively, the method comprises dissolving the recovered crude dihydroxyl aromatic compound in a solvent; contacting the dissolved crude dihydroxy aromatic compound with a base; and neutralizing the combination of the dissolved crude dihydroxy aromatic compound and the base with an acid.

Abstract: The disclosure provides a method for recovering a dihydroxy aromatic compound and a dialkyl carbonate from a polycarbonate-containing composition comprising a polycarbonate and acrylonitrile-butadiene-styrene. The method comprises heating the composition in the presence of an alcohol and a transesterification catalyst at a temperature of 70° C. to 200° C. and a pressure of 50 mbar to 40 bar in a reactor for a time sufficient to depolymerize the polycarbonate producing a dihydroxy aromatic compound and a dialkyl carbonate; removing the dihydroxy aromatic compound and the dialkyl carbonate from the reactor, the acrylonitrile-butadiene-styrene remaining as a coating on the surfaces of the reactor; adding a solvent to the reactor; and heating the solvent to remove the acrylonitrile-butadiene-styrene from the surfaces of the reactor.

Abstract: A method for highly polymerizing an aromatic polycarbonate resin, which enables the increase in molecular weight of the aromatic polycarbonate resin satisfactorily while keeping good quality of the resin. An aromatic polycarbonate is linked to an aliphatic diol compound having a boiling point of 240° C. or higher (preferably in an amount of 0.01 to 1.0 mole per mole of the total amount of the terminal of the aromatic polycarbonate) through a transesterification reaction in the presence of a transesterification catalyst under reduced pressure conditions (preferably at a reduced pressure ranging from 13 kPaA (100 torr) to 0.01 kPaA (0.01 torr)), thereby increasing the molecular weight of the resulting molecule. The weight average molecular weight (Mw) of the aromatic polycarbonate after the transesterification reaction can be increased preferably by 5,000 or more compared to that of the aromatic polycarbonate before the transesterification reaction.

Abstract: The invention provides a non-painting and high-gloss polycarbonate resin composition. Specifically, the invention provides a polycarbonate resin composition having a superior impact strength, heat-resistance, electric characteristics, weather resistance, and light resistance. In certain embodiments, the resin composition of the invention is obtained by mixing a butadiene-based impact modifier, such as acrylonitrile-butadiene-styrene (ABS) or methacrylate-butadiene-styrene and an acryl-based impact modifier in polycarbonate resin, followed by adding an ultraviolet (UV) absorbent to the mixture.

Abstract: Disclosed herein are methods and compositions of polycarbonate blends having, among other characteristics, improved heat resistance. The resulting polycarbonate blends, comprising a first polycarbonate comprising structural repeating units derived from bisphenol acetophenone and optionally a second polycarbonate polymer comprising structural repeating units derived from bisphenol A, can be used in the manufacture of articles while still retaining the advantageous physical properties of blended polycarbonate compositions with improved heat resistance. The disclosed polycarbonate blends optionally comprise one or more polycarbonate blend additives. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.

Abstract: The present invention relates to polycarbonate compositions and copolycarbonate compositions having improved optical properties, and to their production and their use for the production of shaped parts, and to shaped parts which can thereby be obtained, the compositions containing a polycarbonate or copolycarbonate which comprises bisphenol-A and at least one pair of a phosphorus compound having the oxidation number +3 and a phosphorus compound having the oxidation number +5, and the phosphorus compound having the oxidation state +5 in a pair respectively corresponding to the oxidized form of the phosphorus compound having the oxidation state +3 and the amount of more highly oxidized compound contained being less than that of the compound with the lower oxidation number.

Abstract: A modified ion exchange resin catalyst having an attached dimethyl thiazolidine promoter is disclosed. Also disclosed is a process for catalyzing condensation reactions between phenols and ketones, wherein reactants are contacted with a modified ion exchange resin catalyst having an attached dimethyl thiazolidine promoter. Also disclosed is a process for catalyzing condensation reactions between phenols and ketones that does not utilize a bulk promoter.

Abstract: Disclosed are random copoly(phosphonate carbonate)s with the high molecular weight and narrow molecular weight distribution exhibiting a superior combination of properties compared to prior art.

Abstract: A thermoplastic composition suitable for making articles having low gloss and good impact resistance at low temperatures is disclosed. The composition contains (A) 10 to 90 percent relative to the weight of the composition (pbw) of an aromatic (co)poly(ester)carbonate, (B) 10 to 90 pbw of first graft (co)polymer containing a graft base selected from the group consisting of polyurethane, ethylene vinyl acetate, silicone, ethylene-propylene diene rubbers, ethylene propylene rubbers, acrylate rubbers, diene rubbers, and polychloroprene, and a grafted phase, (C) 1 to 20 pbw of a linear glycidyl ester functional polymer comprising repeating units derived from one or more glycidyl ester monomers and (D) 1 to 20 pbw of a second graft (co)polymer containing a core and shell wherein the core contains an interpenetrated network of poly(meth)alkyl acrylate and polyorganosiloxane, and wherein the shell contains poly(meth)acrylate.

Abstract: This invention relates to a polycarbonate copolymer having a structure formed of a repeating unit represented by the following formula (100): in which a molar copolymer composition represented by Ar1/(Ar1+Ar2) is in a range of 50 mol % to 67 mol %, a reduced viscosity [?sp/C] is in a range of 0.60 dl/g to 4.0 dl/g, and a ratio of a hydroxyl group in all ends is 20 mol % or less.

Abstract: In one aspect, the present disclosure encompasses polymerization systems for the copolymerization of CO2 and epoxides comprising 1) a catalyst including a metal coordination compound having a permanent ligand set and at least one ligand that is a polymerization initiator, and 2) a chain transfer agent having two or more sites that can initiate polymerization. In a second aspect, the present disclosure encompasses methods for the synthesis of polycarbonate polyols using the inventive polymerization systems. In a third aspect, the present disclosure encompasses polycarbonate polyol compositions characterized in that the polymer chains have a high percentage of —OH end groups and a high percentage of carbonate linkages. The compositions are further characterized in that they contain polymer chains having an embedded polyfunctional moiety linked to a plurality of individual polycarbonate chains.

Abstract: Provided is a polypropylene carbonate (hereinafter, PPC) paint composition, and more particularly, a pre-coated metal (PCM) paint composition for coil coating, which is mainly applied to cases for home appliances requiring high hardness, such as cases of a refrigerator. The composition can be used to provide a PCM paint, which has very low smoke density at the time of burning and emits remarkably low amounts of combustion gas and poisonous gas due to combustion at the time of firing, as compared with the existing laminate steel plate and a high-gloss film. In addition, the composition exhibits excellent adhesion to metal materials and excellent durability so that it can be usefully used for a PCM print steel plate applied to home appliances.

Abstract: The disclosure pertains to amphiphilic block copolymers comprising an aliphatic polycarbonate chain coupled to a hydrophilic polymer. Such amphiphilic polymers may have the formula A-L-B, where A- is a polycarbonate or polyethercarbonate chain having from about 3 to about 500 repeating units, L is a linker moiety and —B is a hydrophilic oligomer having from about 4 to about 200 repeating units. Provided copolymers are useful as surfactants capable of emulsifying aqueous solutions and supercritical carbon dioxide. Provided copolymers also have utility as additives for use in enhanced oil recovery methods.

Abstract: Embodiments according to the present invention relate to sacrificial polymer compositions that include polycarbonate polymers having repeat units derived from stereospecific polycyclic 2,3-diol monomers. The sacrificial polymer compositions also include an acid generator that is selected from at least one photoacid generator and/or at least one thermal acid generator. In addition, embodiments according to the present invention relate to a method of forming a structure that includes a three-dimensional space interposed between a substrate and an overcoat layer, and a method of temporarily bonding first and second substrates together, which make use of the polycarbonate polymers.

Abstract: In some embodiments, a composition comprises a bisphenol-A polycarbonate, wherein a molded article of the bisphenol-A polycarbonate has transmission level greater than or equal to 90.0% at 2.5 mm thickness as measured by ASTM D1003-00 and a yellow index (YI) less than or equal to 1.5 as measured by ASTM D1925. In some embodiments, light emitting device comprises: a lighting element located in a housing. The housing is formed from a plastic composition comprising: the polycarbonate composition and a conversion material. After the conversion material has been exposed to an excitation source, the conversion material has a luminescence lifetime of less than 10?4 seconds when the excitation source is removed.

Abstract: This invention provides a branched polycarbonate resin obtained from a dihydric phenol compound, a branching agent, monohydric phenols and phosgene by an interfacial polymerization reaction method in the presence of an alkali aqueous solution and an organic solvent, the branched polycarbonate resin having features that: (i) the branching agent content (X) thereof is over 0.70 mol % but 1.50 mol % or less, (ii) the branching agent content (X) and the melt tension (Y) thereof at 280° C. satisfy the following expression (1), 3.8X?2.4?Y?3.8X+4.5 (1), and (iii) the entire N content in the branched polycarbonate resin is 0 to 7 ppm.

Abstract: A polycarbonate polymer or copolymer comprising pendant silylated dihydroxy aromatic compound of the formula (1a); wherein Ga and Gb are each independently C1-12 alkyl, —OSi(C1-12 alkyl)3, C1-12 arylalkyl, or —OSi(C1-12 arylalkyl)3; Za and Zb are each independently a straight or branched C2-18 is alkylene, a C8-18 arylalkylene, or a C8-18 alkylarylene, Xa is a direct bond, a heteroatom-containing group, or a C1-18 organic group, and r and s are each independently 1 or 2 is disclosed.

Abstract: The invention relates to a process for preparing a diaryl carbonate from a dialkyl carbonate and an aryl alcohol using a series of reactive distillation columns.

Abstract: The invention provides a production process of a poly(arylene sulfide), comprising a polymerization step of subjecting at least one sulfur source selected from the group consisting of alkali metal sulfides and alkali metal hydrosulfides and a dihalo-aromatic compound to a polymerization reaction in an organic amide solvent; a reaction step of adding a hydroxyl group-containing organic compound containing no bonded halogen atom in a proportion of 0.001 to 20 mol per 100 mol of the charged sulfur source into the polymerization reaction system containing the organic amide solvent and a formed polymer after the polymerization step to cause the formed polymer to react with the hydroxyl group-containing organic compound; and a collecting step of collecting a polymer from the polymerization reaction system after the reaction step, and the poly(arylene sulfide).

Abstract: In one embodiment, a process for producing a bisphenol A product comprises: reacting phenol with acetone in the presence of a sulfur containing promoter to obtain a reaction mixture comprising bisphenol A, phenol, and the promoter; after reacting the phenol with the acetone, cooling to form a crystal stream comprising crystals of bisphenol A and phenol; separating the crystals from the crystal steam; melting the crystals to form a molten stream of bisphenol A, phenol, and sulfur; contacting the molten stream with a base to reduce a sulfur concentration in the molten stream and form a reduced sulfur stream; and removing phenol from the reduced sulfur stream to form a bisphenol A product.

Abstract: Processes for preparing high purity polycarbonates having high light transmission, low yellowness, and color stability are disclosed herein. High purity starting ingredients are used to form a polycarbonate powder. The polycarbonate powder can be subsequently melt extruded at an optimum shear rate to minimize yellowness and the need to add colorant to overcome the yellowness. The lower amount of colorant increases the light transmission of the resulting polycarbonate resin.

Abstract: A polymer comprising a polymer backbone. The polymer backbone has a plurality of carbon atoms. There are two lipophobic carboxylate groups or carboxylic acid groups per repeating unit being coupled to separate carbon atoms of the backbone.

Abstract: A polycarbonate copolymer includes a repeating unit represented by a formula (1) below and a molar copolymer composition represented by Ar2/(Ar1+Ar2) in a range of 25 mol % to 50 mol %. In the formula (1): Ar1 and Ar2 represent a divalent aromatic group; a chain end is terminated by a monovalent aromatic group or a monovalent fluorine-containing aliphatic group; and n represents an average repeating number of an Ar1 block and is a numeral of 1.0 to 3.0, provided that Ar1 and Ar2 are not the same.

Abstract: This invention describes the use of resveratrol and curcumin, representatives of naturally occurring polyphenols, in their native form, after hydrogenation, and as their respective allyl derivatives, individually, in combination with themselves and other commercial monomers, to make representative varieties of polymers, e.g., polycarbonates (PC), polyurethanes (PU), co-polymers and biodegradable polymers.

Abstract: The present invention relates to polycarbonates comprising imide-containing aryl mono- or dihydroxy compounds as chain terminators and, respectively, monomer units, and also to compositions comprising the said polycarbonates, to their use for the production of mouldings, and to mouldings obtainable therefrom.

Abstract: The present invention provides a method for producing a liquid-crystalline polyester, which comprises melt-polymerizing monomers in a reactor having a draw outlet to obtain a polymer melt and drawing the polymer melt through the draw outlet, characterized in that the monomers comprise a compound selected from an aromatic hydroxycarboxylic acid and derivatives thereof, a compound selected from an aromatic dicarboxylic acid and derivatives thereof and a compound selected from an aromatic diol, an aromatic hydroxyamine, an aromatic diamine and derivatives thereof; the amount of units derived from a compound containing a 1,2-phenylene and/or a 1,3-phenylene skeleton(s) in the polyester is from 0 to 10 mol %; the melt polymerization is performed in the presence of a heterocyclic compound containing two or more nitrogen atoms; and the polymer melt has a flow initiation temperature of from 220 to 250° C.

Abstract: Polycarbonates are recovered from polymer blends by liquid chromatography. Polycarbonate recovered by the process can be reused in new applications. The invention can be extended to recycling of other polymers present in the blends.

Abstract: A polycarbonate resin which is excellent in terms of optical properties, hue, thermal stability, and mechanical properties and a transparent film formed from the resin are provided. The invention relates to a polycarbonate resin which has a glass transition temperature of 110-150° C. and a reduced viscosity, as measured at 20° C. with respect to the methylene chloride solution having a concentration of 0.6 g/dL, of 0.30-0.46, and which, when being molded, gives a film wherein the ratio of the retardation thereof measured at a wavelength of 450 nm (Re450) to the retardation thereof measured at a wavelength of 550 nm (Re550) is 0.50-0.93.

Abstract: Nanocomposites comprising a sulfonated telechelic polycarbonate and an organically modified clay are disclosed. The polycarbonate nanocomposites have improved physical and mechanical properties.

Abstract: A copolycarbonate-polyester, comprising units of formula wherein at least 60 percent of the total number of R1 groups are divalent aromatic organic radicals and the balance thereof are divalent aliphatic or alicyclic radicals; units of formula wherein T is a C7-20 divalent alkyl aromatic radical or a C6-20 divalent aromatic radical, and D is a divalent C6-20 aromatic radical; and units of the formula wherein R2 and R3 are each independently a halogen or a C1-6 alkyl group, R4 is a methyl or phenyl group, each c is independently 0 to 4, and T is as described above. A method of making a copolycarbonate-polyester is also disclosed.

Abstract: A dihydric phenol compound represented by the following formula (2), a phosgene compound, and an aliphatic tertiary amine are mixed together using a hydrophobic organic solvent to produce bischloroformate that is represented by the following formula (1) and has an average number of repeating units (n) of 1.99 or less. In the formulae (1) and (2), Ar is a divalent aromatic group.

Abstract: In one aspect, the present disclosure encompasses polymerization systems for the copolymerization of CO2 and epoxides comprising 1) a catalyst including a metal coordination compound having a permanent ligand set and at least one ligand that is a polymerization initiator, and 2) a chain transfer agent having two or more sites that can initiate polymerization. In a second aspect, the present disclosure encompasses methods for the synthesis of polycarbonate polyols using the inventive polymerization systems. In a third aspect, the present disclosure encompasses polycarbonate polyol compositions characterized in that the polymer chains have a high percentage of —OH end groups and a high percentage of carbonate linkages. The compositions are further characterized in that they contain polymer chains having an embedded polyfunctional moiety linked to a plurality of individual polycarbonate chains.

Abstract: Silicone polycarbonate block copolymers are disclosed that have a high elongation before yield, are clear, and have elastomeric properties. Generally, the silicone blocks are very short (less than about 50 organosiloxane repeat units) and the silicone blocks are substantially isolated from each other by bisphenol carbonate spacers.

Abstract: Disclosed is a method for producing a devolatilized polyolefin, wherein the method comprises a step that involves providing a twin screw extruder comprising a resin feeding port, a first molten resin kneading zone, a molten resin partially filled zone which is prevented from being fully filled with molten resin, a second molten resin kneading zone, and a devolatilization zone that are disposed in order from the upstream of a cylinder of the extruder, feeding a polyolefin through the resin feeding port, and feeding water to the molten resin partially filled zone in an amount of 0.01 to 50 parts by weight relative to 100 parts by weight of the polyolefin.

Abstract: An optical film comprising a copolycarbonate composed of 25 to 90 mol % of unit (A) of the following formula, and 10 to 75 mol % of unit (B) of the following formula, wherein the substituents are defined herein, and the optical film satisfies the following expression (1), R(450)<R(550)<R(650) (1), wherein R(450), R(550) and R(650) are in-plane retardation values of the film at wavelengths of 450 nm, 550 nm and 650 nm. The optical film exhibits a desired chromatic dispersion, low photoelasticity and excellent melt processability.

Abstract: A subject for the invention is to provide a polycarbonate having excellent mechanical strength, heat resistance, a low refractive index, a large Abbe number, reduced birefringence, and excellent transparency. The invention relates to a polycarbonate characterized by being obtained by subjecting one or more dihydroxy compounds including a dihydroxy compound having at least one linking group —CH2—O— in the molecule thereof to melt polycondensation with a carbonic acid diester, and by having a reduced viscosity of from 0.40 dL/g to 1.70 dL/g and a formic acid content lower than 5 ppm by weight.

Abstract: This invention relates to the use of polycarbonate for the production of an optical recording medium in which secure high speed operation, a transcriptability of the pit/groove structure of >85% and sufficient disc flatness can be achieved and the polycarbonate is based on bisphenol A and the polycarbonate contains a release agent in an amount less than 2000 ppm.

Abstract: A polycarbonate resin having at least one terminal group which is represented by formula (1), and a resin composition and an optical material comprising the polycarbonate resin are disclosed. In the formula, R1-R9 each independently represent a hydrogen atom, halogen atom or an alkyl group. X1 represents a direct bond or alkylene group.

Abstract: In one embodiment, a process for producing a bisphenol A product comprises: reacting phenol with acetone in the presence of a sulfur containing promoter to obtain a reaction mixture comprising bisphenol A, phenol, and the promoter; after reacting the phenol with the acetone, cooling to form a crystal stream comprising crystals of bisphenol A and phenol; separating the crystals from the crystal steam; melting the crystals to form a molten stream of bisphenol A, phenol, and sulfur; contacting the molten stream with a base to reduce a sulfur concentration in the molten stream and form a reduced sulfur stream; and removing phenol from the reduced sulfur stream to form a bisphenol A product. Also disclosed herein is a container comprising: a polycarbonate formed from a bisphenol A having a sulfur concentration of 0.5 to 15 ppm based upon the weight of the bisphenol A.

Abstract: Disclosed is a new method and compositions from the method consisting of block copolycarbonate/phosphonates that exhibit an excellent combination of flame resistance, hydrolytic stability, high Tg, low melt viscosity, low color and high toughness. Also disclosed are polymer mixtures or blends comprised of these block copolycarbonate/phosphonate compositions and commodity and engineering plastics and articles produced therefrom. Further disclosed are articles of manufacture produced from these materials, such as fibers, films, coated substrates, moldings, foams, adhesives and fiber-reinforced articles, or any combination thereof.

Abstract: Polycarbonate includes repeat units represented by Formula 1, Formula 2 and Formula 3, respectively: wherein: R1 and R2 are the same or different and are each independently substituted or unsubstituted C1 to C6 alkyl, substituted or unsubstituted C3 to C6 cycloalkyl, substituted or unsubstituted C6 to C12 aryl or halogen, a and b are the same or different and are each independently an integer from 0 to 4, and Q is substituted or unsubstituted C5 to C10 cycloalkyl.

Abstract: The presently disclosed embodiments relate generally to an image forming apparatus comprising a seamless intermediate transfer belt, and methods for making the same. The seamless intermediate transfer belt comprises a film forming A-B diblock copolymer. In other embodiment, the seamless intermediate transfer belt comprises the film forming A-B diblock copolymer and carbon black dispersion. The prepared seamless intermediate transfer belt of present disclosure provides increased mechanical strength to resist scratch/wear failure and early onset of fatigue-bend cracking development under normal dynamic intermediate transfer belt machine cycling conditions in the field, and thus extend the service life of the belt.

Abstract: The object of this invention is to provide a copolycarbonate that is excellent in heat resistance, thermal stability and moldability and that uses a renewable resource as a raw material. This invention is a copolycarbonate including 50 to 99 mol % of a carbonate constituent unit (1) of the following formula and 50 to 1 mol% of a carbonate constituent unit (2) derived from an aliphatic diol having a boiling point of 180° C. or higher under reduced pressure of 4×10?3 MPa.

Abstract: A dihydric phenol compound represented by the following formula (2), a phosgene compound, and an aliphatic tertiary amine are mixed together using a hydrophobic organic solvent to produce bischloroformate that is represented by the following formula (1) and has an average number of repeating units (n) of 1.99 or less. In the formulae (1) and (2), Ar is a divalent aromatic group.

Abstract: The invention relates to a process for the pretreatment of material surfaces in order to minimize the interaction between polycarbonate and metal and, in the processing and synthesis of polycarbonate, to obtain a high-quality polymer which in particular does not become discolored and is free of insoluble constituents.

Abstract: A method for preparing terpolymer of poly (biphenyl sulfone ether) and poly (ether sulfone) comprises: adding high-temperature organic solvent into a flask, stirring and heating to 80° C., adding 4,4?-dichlorodiphenylsulfone,4,4?-Bis(4-chlorophenyl)sulfonyl-1,1?-biphenyl and 4,4?-dihydroxydiphenylsulfone with solid content of 20-35%; stirring until monomers are completely dissolved, heating to 100° C., adding salt-forming agent and xylene; stirring while heating so that salt-forming reaction begins in the system, wherein the system temperature is controlled between 190° C. and 210° C.; when the amount of water discharged reaches the theoretical value, the first stage of salt-forming reaction is finished; heating the system to 230-236° C.