| 摘要 |
The polycondensation stage in a process for the batch production of granulated polycondensation polymers is carried out under specified conditions in a rotating disc reactor with a horizontal shaft and vertical product-scraping surfaces, in which the polycondensation mixture is constantly taken from the product outlet and returned to a point further away. A method for the batch production of granulated polycondensation polymers (I) with a dynamic viscosity of 100-1600 Pa.s at polycondensation temperature involves: (1) precondensation of a low-mol. wt. oligomer at 5-400 mbar in an autoclave; (2) polycondensation in a rotating disc reactor with a horizontal axis, vertical product-scraping surfaces, discharge and vapor outlets, return connections and charging inlet(s); and (3) granulation. Polycondensation is performed under vacuum at a final temperature which is 5-50[deg]C above the m.pt. of (I), with the following conditions: (a) the relative fill height (h/D) in the reactor at the discharge outlet is 0.26-0.49 (based on maximum diameter D) and this parameter (h/D) decreases in the axial direction with increasing distance from the outlet; (b) part of the reaction mixture is constantly removed from the outlet throughout stage (2) and returned at a remote point in the reactor; (c) the area of scraper surface near the discharge outlet is 1-8 m 2> per m 3> of reactor volume, increasing towards the further end by 5-35% based on the lowest value; (d) during the initial phase of polycondensation (15-30% of the total polycondensation time), the mixture is subjected to a shear rate of 2.5-250 s -> 1> and the radial acceleration at the outer edge of the scrapers is 5 times higher than at the end of polycondensation; (e) the conditions in (a-d) are adjusted to give a viscosity gradient between the outlet zone and the zone(s) furthest from it. An independent claim is also included for a heatable polycondensation reactor as described above, in which: (a) the reactor housing is in the form of a horizontal, single or double truncated cone (tapering from the outlet) with a taper angle of 5-45[deg] or the stub of a spherically tapered rotating body with vertical faces, possibly with a coaxial cylindrical part on the side with the greatest diameter, and with return connection(s) remote from the outlet; (b) the product scrapers comprise numerous parallel rotating discs with the scraper surfaces concentrated on the reactor wall side (1-8 m 2> per m 3> reactor volume, increasing by 5-35% as above); (c) a stationary separator is mounted between each pair of discs; and (d) the outlet is connected to the return inlet(s) via a product pump and circulation line(s). |
