| 摘要 |
1,258,393. Extruding polymeric sheet material. O-B RASMUSSEN. 30 Dec., 1968 [29 Dec., 1967], No. 59141/67. Heading B5A. An extruded sheet material comprises lamellµ of a polymeric material which are bonded together to provide a continuous core, but are disconnected or only partially connected in the surface layers of the sheet. Preferably, the sheet material comprises lamellµ 2 of a second material which may also be polymeric and which are present in the surface layers only and either provide the partial connections or are disrupted to provide partial connections. Such disruption of the second material may be effected by reducing the material to a fibrous form, e.g. by the addition of a slipping agent which bleeds out on solidification of the material. Other disruptive methods or ways of separating the lamellµ include drawing, rolling, impacting, expanding, brushing, bending and acoustic or chemical action. Alternatively, the second material may be brushed or dissolved out. Preferably, the first material is crystalline and orientated and a further polymeric material may be interposed therewith to effect the bonding in the core of the sheet. An apparatus for producing such sheet material comprises an annular die 3 having slots 8 through which the first material is extruded and pairs of slots 9 in line or offset with respect to one another, for the second material. A converging collecting chamber 7 and extrusion slot 6 are defined by die parts 4, 5. During extrusion relative rotational movement occurs between die 3 and parts 4, 5 to impart a smearing action to the lamellµ. The form shown in Fig. 2 is produced by movement of die 3 and/or both parts 4, 5 in unison. The lamellµ are first folded to lie parallel to the extrusion face of die 3, continued extrusion forcing the lamellµ through slot 6 with smearing thereof to a generally U-shape. The form shown in Fig. 1 is produced by relative movement of parts 4, 5, the lamellµ being stretched to give a flattened S form when the sheet is viewed in cross-section. In a modification, two collecting chambers in series may be used in which the upstream chamber is partitioned to divide the flow such that rows of U- or S-shaped lamellµ are produced. Only the upstream chamber is moved. Die 3 and parts 4, 5 may be linear and relatively reciprocated. |
