| 摘要 |
1,128,809. Extruding foamed polyethylene. MONSANTO CHEMICALS Ltd. 14 Sept., 1966 [28 Oct., 1965], No. 45658/65. Heading B5A. [Also in Division C3] Foamed polyethylene sheet is produced from blown tubing extruded through a die 1, 2. The die has an annular passageway comprising a first portion 3 which is substantially parallel sided, e.g. having a width from 0À01-0À05 inch and extending axially more than 0À3 inch from the inlet, a second restricted portion 4, e.g. having a width 0À2-0À9 times the width of portion 3 and extending axially less than 0À2 inch, and a divergent mouth portion 5 whose faces include, e.g. an angle between 10 degrees and 40 degrees and extend axially between 0À05 and 0À2 inch. The first portion 3 may taper slightly in the downstream direction and have an inlet mouth 8. In a second embodiment, Fig. 2 (not shown), the restricted portion occurs further downstream at (12) and the divergent mouth portion imparts a radially outward component of movement to the extrudate. The mouth portion 5 may be cooled by, e.g. air or water, to a temperature below the rest of the die. Duct 7 allows air or other gas access to the extruded tube, which tube may proceed over one or more sizing mandrels, be cooled or heated by currents of air and is flattened by rollers to form lay flat tubing. Take-up rollers may stretch the tubing by as much as a factor of two. The lay flat tubing provides single or double thickness sheeting, whose single thickness may be in the range 0À003-0À25 inch and whose density is preferably less than 5 lbs./cu. ft. Numerous blowing and nucleating agents are mentioned and three examples are given. |
