Patent GB-719706-A (GB)
Title: Improvements in polyesters and their intermediates
Inventor: LINCOLN JAMES
IPC: C08G63/06
Filed: 1951-07-25
Abstract: New polyesters having high-melting points are prepared by heating 4-(b -hydroxyethoxy)-3-methyl benzoic acid or an ester-forming derivative thereof (see Group IV (b)).  To facilitate melt spinning, the polyesters may be mixed with another polymer, preferably another polyester, or the monomeric acid may be copolymerized with one or more other reagents capable themselves of yielding a polyester such as hydroxy-polymethylene carboxylic acids or polymethylene dicarboxylic acids with polymethylene glycols or preferably the aromatic-type reagents capable themselves of yielding a polyester of high melting point of the order of 200 DEG  C. or above, e.g. 4-(b -hydroxy ethoxy)-benzoic acid, terephthalic acid with ethylene glycol or 4 : 41-dicarboxy-diphenyl with ethylene glycol.  Thus, the poly-4-(b -hydroxy ethoxy)-3-methyl benzoic acid may be mixed with another pre-formed polyester and quickly melted to form a mixture or further heated to form a copolymer or alternatively the monomeric compounds may be mixed together and the whole condensed to form the copolymer.  The copolymers preferably contain at least 50 per cent. by weight of the residue of the hydroxyethoxy methyl benzoic acid and preferably melt at not lower than 230 DEG  C., e.g. 240-270 DEG  C. The polyester forming reaction may be carried out by standard methods.  When the carboxylic and hydroxy groups are in the free state the monomers are preferably condensed in the presence of an esterification catalyst such as p-toluene sulphonic acid, phosphoric acid or sulphonic acid.  Desirably the carboxylic groups are present as esters of volatile monohydroxy compounds, e.g. methanol, ethanol or phenol in which event an ester-interchange catalyst is preferably used such as magnesium, sodium or sodium and magnesium or lithium. Alternatively, the hydroxyl groups of the monomers may be esterified with an acid which is readily volatile under the poly-esterification conditions, e.g. formic or acetic acid.  Moreover, both the hydroxyl and carboxylic groups may be so esterified as in the case of methyl-4-(b -formyloxy-ethoxy)-3-methyl-benzoate.  The esterification is effected at elevated temperatures of the order of 200-250 DEG  C. initially and subsequently higher, e.g. up to 300 DEG  C.  When there is present a component which is volatile at these temperatures, e.g. glycol, that component is used in excess. Heating is normally continued until the product has fibre-forming properties; reduced pressure is used in the last stages to remove volatile products.  In examples: (1) ethyl-4-(b -hydroxyethoxy)-3-methyl benzoate is heated with a small quantity of magnesium ribbon and sodium methylate at a rising temperature at which the mixture remains molten, the final polymer having a M.P. of 290-292 DEG  C.; (2) the polymer of (1) and a polyester of terephthalic acid and ethylene glycol are powdered and heated in the molten state to yield a copolymer M.P. 250-255 DEG  C. having cold-drawing properties; (3) the monomer of (1) is heated with ethylene glycol and dimethyl terephthalate in presence of magnesium ribbon and sodium methylate as in (1) yielding a copolymer M.P. 240-245 DEG  C.  Specifications 578,079, 579,462, 588,497 and 604,985 are referred to. p ALSO:The invention relates to 4-(b -hydroxyethoxy)-3-methyl benzoic acid and its esters with monohydroxy compounds and/or monocarboxylic acids, for example, its methyl, ethyl and phenol esters and its formyl and acetyl esters.  The acid may be prepared by reacting 4-hydroxy-3-methyl-benzoic acid with ethylene chlorhydrin and the esters by esterification of the free acid or by acidylation, e.g. with formic acid, acetic anhydride or halide, of the free alcoholic group.  The compounds may be polymerized to polyesters (see Group IV (a)).  In examples: (1) ethylene chlorhydrin is gradually added to 4 - hydroxy-3-methyl-benzoic acid in aqueous caustic soda, the mixture refluxed and the desired acid obtained by acidification with HCl; (2) the ethyl ester is obtained by refluxing the free benzoic acid with dry alcohol using sulphuric acid as catalyst and the product worked up to recover crystalline ester. Methyl-4 - (b  - formyloxy - ethoxy) - 3 - methyl benzoate is given as an example of the acid esterified in both the hydroxyl and carboxylic groups.  Specifications 578,079, 579,462, 588,497 and 604,985 are referred to.