Patent GB-1077379-A (GB)
Title: Process for preparing polyesters
IPC: C08G63/78
Filed: 1963-12-31
Abstract: A low M.W. linear polyester is prepared by adding a glycol and a dicarboxylic acid to a reactor containing a linear polyester, derived from the glycol and acid to be added and having a degree of polymerization between 1.5 and 20, mixing the glycol and acid with part of the polyester whilst heating, distilling off a portion of the glycol and allowing the reaction to continue whilst water distils off until the product has a degree of polymerization between 1.5 and 20. 1.05-1.8 moles of glycol may be used per mole of acid.  Glycols specified are ethylene, propylene, butylene, hexamethylene and decamethylene <PICT:1077379/C3/1> glycols, 2-methylpropane-1,3-diol, 2,2-dimethylpropane-1,3-diol, 2-methyl,2-ethylpropane-1,3-diol, 2,2-diethyl-propane-1,3-diol, amylene glycols, cyclohexane diols, di(hydroxymethyl) cyclohexanes, di-b -hydroxyethoxybenzene and 2,2-bis(4-b -hydroxyethoxy phenyl) propane.  Acids specified are phthalic, iso- and terephthalic acids, diphenyl-p,p1-dicarboxylic acid, naphthalene dicarboxylic acids, cyclohexane-p-dicarboxylic acid, succinic, adipic, and sebacic acids.  Mixtures of acids may be used.  The low molecular weight polyester may be added to the reactor first or all 3 reactants may be added simultaneously.  The reaction temperature may be 210-280 DEG  C. and the pressure may be atmospheric or sub- or superatmospheric.  Zinc acetate, manganous acetate or alkali metal alkoxides may be used as catalysts.  N2 may be passed through the reaction mixture to agitate it.  The process may be a batch or continuous one and the product may have a M.W. of 254-4000.  The low molecular weight polyester may be further polymerized in the absence of oxygen and at a reduced pressure to give a high molecular weight polyester of intrinsic viscosity of at least 0.40.  Catalysts specified for this reaction are antimony trioxide, zinc borate, litharge, lead acetate or MgO. Stabilizers, e.g. phosphates, phosphites or calcium compounds, may also be added. The high molecular weight polyester may be made into films and fibres.  In a particular embodiment ethylene glycol from (6) and terephthalic acid from (2) are mixed in (5) and fed into column (1) which contains low molecular weight polyester. Excess glycol distils and is returned to (6).  Water escapes at (13).  Low molecular weight polyester is withdrawn at (14) and polymerized under reduced pressure in (16) with catalyst supplied from (12). Eliminated glycol is condensed into (21) and the polymer product collected at (23).  In another embodiment terephthalic acid and an excess of glycol are added to a column containing low molecular weight polyester, the glycol being refluxed and more acid being added until the excess is exhausted.ALSO:A linear polyester is prepared by adding a glycol and a dicarboxylic to a reactor containing a linear polyester derived from the glycol and dicarboxylic acid to be added and having a degree of polymerization between 1.5 and 20, mixing the added compounds with at least part of the polymer whilst heating, distilling off part of the glycol and allowing the reaction to continue whilst water distils off until the product has a degree of polymerization <PICT:1077379/C2/1> between 1.5 and 20; 1.05-1.8 moles of glycol may be used per mole of acid.  Glycols specified include ethylene glycol. Acids specified include aliphatic acids, cycloaliphatic acids and aromatic acids, e.g. terephthalic acid. The initial polyester may be added to the reactor first or all three reactants added simultaneously. The reaction temperature may be 210-280 DEG  C. and the pressure may be atmospheric or sub- or superatmospheric. Zinc acetate, manganous acetate or alkali metal alkoxides may be present as catalysts.  N2 may be passed through the mixture to agitate it. The process may be a batch or continuous one and the product may be of M.W. 254-4000. In a particular embodiment, ethylene glycol from 6 and terephthalic acid from 2 are mixed in 5 and fed into column 1 which contains polyester.  Excess glycol distils and is returned to 6.  Water escapes at 13 and low M.W. polyester is withdrawn at 14.