| 摘要 |
1,030,288. Films. FMC CORPORATION. Aug. 4, 1964 [Aug. 27, 1963], No. 30811/64. Heading B5B. A strap of hot polymeric material is oriented by imparting stretch to a straight line segment of the strap while positively preventing any stretch from being imparted to any other portion of the strap. Specified polymeric materials include polyethylene and polypropylene, polycarbonates, polyesters, polyamides, e.g. polyhexamethylene adipamide, acrylic resins and polystyrene. Stretch may be imparted to the strap between a relatively slow hot drum 32 or 42 and a relatively fast cold drum, 34 or 44, any stretch on the curved surface of the hot drum being prevented by nipping the strap against the hot drum at the point of departure of the strap therefrom, e.g. by rolls 33 or 43. As in Fig. 2, the strap may be directed tangentially of the cold drum and nipped against the drum at the point of tangency. One side of the strap is rapidly cooled by contact with drum 34 while the other side of the strap cools more slowly and shrinks to a narrower width than the rapidly cooling side, thus producing a cambered strap as in Fig. 4 (not shown), the convex side 15<SP>1</SP> being that which was in contact with the drum. Such straps have some coil set due to the passage of film about drum 23, but this can be substantially eliminated by winding the strap in the opposite direction on reel 27. Alternatively, both sides of the strap may be brought to the same temperature while in engagement with the fast drum, suitably, as in Fig. 3, by immersing the strap in a liquid medium while the stretch is being imparted thereto. Straps so made are free from camber owing to the absence of a temperature differential between the two sides of the strap, and are free from coil set as the drum 23 of Fig. 3 is at substantially the same temperature as the strap. |
