| 摘要 |
<p>A polyester having a molecular weight of 3000-5000 and a softening point of at least 80 DEG C. is produced by interacting a polyhydric alcohol component and a dicarboxylic acid component in within 10 mole per cent of equimolar proportions, the polyhydric alcohol component containing at least 75 mole per cent of a glycol of formula <FORM:1026993/C3/1> in which R and R1 are alkyl groups of 1-4 carbon atoms and the dicarboxylic acid component containing a dicarboxylic acid or esterforming derivative thereof, 25 mole per cent of which is iso- and/or terephthalic acid, the reaction mixture also containing in one or other component at least 1 mole per cent of either (a) a polyglycol having 4-18 carbon atoms or (b) a dicarboxylic acid of formula HOCO(CH2)nCOOH having 4-10 carbon atoms. The poyhydric alcohol component may comprise 75-99% of neopentylene glycol and 25-1% of diethylene glycol. Other glycols specified are propane-1,3-diol and its 2-ethyl-2-butyl-, 2,2-diethyl- and 2 - methyl - 2 - ethyl - derivatives. The dicarboxylic acid component may contain up to 90% iso-or terephthalic acid giving a concentration in the whole mixture of 50% or more. The total amount of (a) and (b) may be up to 25 mole per cent. Acids (b) specified are succinic, adipic and sebacic. The polyhydric alcohol component may also contain a compound having 3-6 carbon atoms and at least 3 hydroxyl groups which may provide 3-20% of all the hydroxyl groups. Alcohols of this type specified are glycerol, trimethylol propane and pentaerythritol. The mixture may also contain 10-50% of an unsaturated a ,b -dicarboxylic acid. Such acids specified are maleic, fumeric, itaconic, citraconic, mesaconic and chloromaleic. Litharge may be added as a polyesterification catalyst. Unsaturated polyesters can be cured by cross-linking either in a hot molten state or in solution in styrene or diallyl phthalate. In the latter case copolymerization will occur. The products may have softening points up to 200 DEG C. They may be granulated, mixed with glass fibres, melted and then cooled to bond them together. In Example (1) the polymerization is carried out under N2 in the presence of toluhydroquinone.</p> |
