Methods for producing and purifying 2-hydrocarbyl-3,3-bis(4-hydroxyaryl)phthalimidine monomers and polycarbonates derived therefrom

This application is a divisional of U.S. patent application Ser. No. 11/541,002, filed on Sep. 29, 2006, which is a divisional of U.S. patent application Ser. No. 10/878,757 filed Jun. 28, 2004, both which are fully incorporated herein by reference.

The present disclosure generally relates to methods for producing and purifying 2-hydrocarbyl-3,3-bis(4-hydroxyaryl)phthalimidine monomers (hereinafter sometimes referred to as phenolphthalein derivatives), and polycarbonates as well as other polymers derived utilizing the monomers.

3,3-Bis-(4-hydroxy-phenyl)-3H-isobenzofuran-1-one (hereinafter referred to as phenolphthalein) has been used as an aromatic dihydroxy compound monomer for preparing polycarbonates, which are generally characterized with excellent ductility and high glass transition temperatures. Certain derivatives of phenolphthalein have also been used as aromatic dihydroxy compound monomers to prepare polycarbonate resins as well as polyarylate resins. For example, polycarbonate homopolymers have been prepared by an interfacial polycondensation method using phosgene and (phenolphthalein derivative) monomers such as 3,3-bis(4-hydroxyphenyl)phthalimidine and 2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (hereinafter sometimes referred to as “PPPBP”).

Lin and Pearce (Journal of Polymer Science: Polymer Chemistry Edition, (1981) Vol. 19, pp. 2659-2670) reported the synthesis of PPPBP for preparing polycarbonates and other polymers by refluxing phenolphthalein and aniline hydrochloride in aniline for 6 hours, followed by recrystallization from ethanol. During this reaction, side products are created which, if not removed, can result in PPPBP having an unacceptable purity for use as a monomer or as a comonomer in subsequent polymerization reactions. Furthermore, the impurities in the PPPBP monomer include, for example, trace (parts per million) levels of phenolphthalein or phenolphthalein residues that can undesirably produce discoloration in the polycarbonates and other polymers derived therefrom, thereby affecting the transparency of the polymer product. Coloration is not a desirable attribute for many commercial applications. U.S. Pat. No. 5,344,910 discloses that copolymers of PPPBP were found to have poor melt stability resulting in foamy polymer melts and moldings, and discoloration of the resin during melt processing.

It would therefore be desirable to develop a process for improving the purity of phenolphthalein derivatives such as 2-hydrocarbyl-3,3-bis(4-hydroxyaryl)phthalimidine, which can then be used for producing polycarbonates and other polymers having improved properties, such as lower visual coloration and a higher weight average molecular weight.

Disclosed herein is a method for producing phenolphthalein derivatives (for example 2-hydrocarbyl-3,3-bis(4-hydroxyaryl)phthalimidine). The method comprises, heating a reaction mixture comprising a phenolphthalein compound and a primary hydrocarbyl amine, in the presence of an acid catalyst, to form the phenolphthalein derivative product. The method further comprises forming an adduct of the phenolphthalein derivative. The adduct can be formed either (i) by using an excess of the hydrocarbyl amine to cause in situ formation of the an adduct comprising phenolphthalein derivative product and primary hydrocarbyl amine or (ii) by first isolating the crude phenolphthalein derivative product and then further reacting with an additional amount of primary hydrocarbyl amine to form the adduct. The adduct is then precipitated. Finally the adduct is decomposed to produce the 2-hydrocarbyl-3,3-bis(4-hydroxyaryl)phthalimidine.

In another embodiment there is disclosed a method for producing 2-hydrocarbyl-3,3-bis(4-hydroxyphenyl)phthalimidine, comprising heating a reaction mixture comprising a phenolphthalein compound, a primary aromatic amine, and optionally a hydrogen chloride fluid, to form an adduct, neutralizing mixture with sodium bicarbonate, precipitating said adduct of the 2-hydrocarbyl-3,3-bis(4-hydroxyphenyl)phthalimidine and the primary aromatic amine by adding an aromatic hydrocarbon to the reaction mixture and heating said adduct with an alcohol to produce said 2-hydrocarbyl-3,3-bis(4-hydroxyphenyl)phthalimidine.

In another embodiment is disclosed a method for producing a 2-hydrocarbyl-3,3-bis(4-hydroxyphenyl)phthalimidine, comprising heating a reaction mixture comprising a phenolphthalein compound, a primary aromatic amine, and optionally a hydrogen chloride fluid, to form an adduct, neutralizing said mixture with sodium bicarbonate, precipitating the adduct of the 2-hydrocarbyl-3,3-bis(4-hydroxyphenyl)phthalimidine and the primary aromatic amine by adding an aromatic hydrocarbon to the reaction mixture, dissolving said adduct in an aqueous alkali metal hydroxide solution to provide a first solution, adding an aqueous acid to precipitate the 2-hydrocarbyl-3,3-bis(4-hydroxyphenyl)phthalimidine, and heating said 2-hydrocarbyl-3,3-bis(4-hydroxyphenyl)phthalimidine with an alcohol to produce a purified 2-hydrocarbyl-3,3-bis(4-hydroxyphenyl)phthalimidine.

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