| 摘要 |
<p>1,140,418. Rotational casting poly (epsilon caprolactam). ALLIED CHEMICAL CORP. 28 March, 1967 [29 March, 1966], No. 13989/67. Heading B5A. Large hollow articles i.e. articles having at least two dimensions greater than 10 inches are rotationally cast in a process which involves: (a) Providing in a metal mould a liquid charge comprising epsilon caprolactam and an anionic catalyst and catalyst promoter for its polymerization, the charge being heated to 140-180‹ C. and kept under a dry inert atmosphere while in the mould, the charge being a mixture which when polymerized at 140-180‹ C. increases in viscosity from 10 to 100 centipoises in 1 to 3 minutes and from 1,000 to 10,000 centipoises in 1 to 6 minutes, from 100 to 400 centipoises in not more than 2 minutes at 150-180‹ C., the charge being sufficient to form a layer of average thickness between 10 and 100 mils. (b) Closing the mould and rotating it at a rate of between 1 and 20 r.p.m., until the liquid charge has been distributed over all the surface; this being accomplished while its viscosity is less than 10,000 centipoises. (c) Heating the mould at 150 to 175‹ C. after the completion of step (b) until the polymer has crystallized to at least 20% crystallinity, this step taking 3 to 30 minutes and its end being marked by contraction of the hollow object away from the walls. (d) Providing within the hollow article another liquid charge of the same composition of the first under a dry inert atmosphere, rotating the hollow article either alone or in the mould under the same conditions as in (b) to form a second layer in the hollow article and heating the mould as in (c) to crystallize this layer. The successive layers preferably have an average thickness of not more than 70 mils and the whole process lasts not more than 20 minutes. The mould may be rotated about two intersecting axes, the angular rotation rates about these axes being in the ratio between 2 and 5:1. The anionic catalyst may be a reaction product of lithium hydride and epsilon-caprolactam and the promoter a polyfunctional (trifunctional or higher) compound, preferably a trifunctional triazine.</p> |
