| 摘要 |
<p>1,218,217. Polyethylene terephthalate. FMC CORP. 5 June, 1968 [30 Aug., 1967], No. 26734/68. Heading C3R. Polyethylene terephthalate is prepared by direct esterification of terephthalic acid with ethylene glycol, or transesterification of dialkyl terephthalate with ethylene glycol, to form a prepolymer, the prepolymer then being polycondensed in the presence of a catalytic additive of formula or any combination thereof, where M is NH 4 -, which may be substituted by at least one C 1-6 alkyl, M<SP>1</SP> is NH 4 -, or substituted NH 4 - as above, or alkali metal, M<SP>11</SP> is alkali metal or NH 4 - (as above), when x=2, or alkaline earth metal, when x-1, and M<SP>111</SP> is alkali metal or ammonium. The catalyst may be present during the esterification reaction, and may be used in an amount of 5 Î 10<SP>-8</SP> to 5 Î 10<SP>-3</SP> mole per mole of terephthalic acid, or in an amount of 0À004- 0À2% by weight of the prepolymer. Examples of catalysts are: NH 4 SbF 6 , (C 3 H 7 ) 3 NHAsF 6 , NH 4 TiF 6 and NH 4 SbF 4 .</p> |
