Process of preparing polytetramethylene terephthalate
Patent 3936421 Issued on February 3, 1976. Estimated Expiration Date: 
February 3, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
February 3, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2437232 2465319 3285855 3361846 3670489 3763109 3796691 InventorsAssigneeApplicationNo. 523362 filed on 11/13/1974US Classes:524/707, Nitrogen524/708, Phosphorus bonded directly to nitrogen524/710, Organic compound having phosphorus bonded directly to oxygen or sulfur524/712, Containing halogen DNRM524/819, Hydrocarbon monomer with carboxylic acid, salt, or nonnitrogen containing derivative monomer528/279, Material contains a Group IVB metal atom (Ti, Zr, Hf)528/283, Material contains a Group IVA metal atom (Ge, Sn, Pb)528/286Material contains a phosphorus atomExaminersPrimary: Hoke, V. P.Attorney, Agent or FirmForeign Application Priority Data1973-11-19 JAAbstractA process for preparing a polyester predominantly comprised of the units derived from terephthalic acid and butanediol-1,4 is provided. The esterification or transesterification is performed in the presence of minor amounts of a catalyst combination comprising an organo-titanium compound and an organo-tin compound. The undesirable formation of tetrahydrofuran can be avoided or minimized. | |
