| 摘要 |
<p>A cross laminate of two films, each of which is uniaxially or unbalanced biaxially oriented, the films being arranged so that the major axes of orientation criss-cross each other (steps 1 to 3), is treated in a calendering process in which machine direction ribs are formed which are thicker than the sheet between the ribs and which have a configuration which confers increased resistance to bending over a line perpendicular to the rib. The ribs are formed by a combination of passage between grooved rollers ('lateral calendering') (steps 4 and 6), the grooves of which include inclined walls on opposing grooves between which the material of the laminate is squeezed, longitudinal stretching (step 5) and heat treatment (step 10). In a preferred process a sandwich of two cross-laminates is subjected sequentially to passage between a first set of grooved rollers (step 4), longitudinal stretching (step 5) and passage through a second set of grooved rollers (step 6) in which the undulations created in the first set of rollers are registered with the second set of grooved rollers, followed by heat treatment (step 10), for instance an ironing process. The cross sandwich is then cooled (step 11) and separated into two cross laminates (step 12).</p> |
