| 摘要 |
<p>1,055,803. Laminates. NATIONAL DISTILLERS & CHEMICAL CORPORATION. Jan. 13, 1964 [Jan. 23, 1963], No. 1462/64. Heading B5N. A method for the preparation of a heatsealable polypropylene laminate suitable for packaging comprises intimately contacting a layer of polypropylene film with at least one layer of a heat sealable thermoplastic film and subsequently stretching the resultant combination of films to bond them firmly together. Preferably the polypropylene film is first stretched in a longitudinal direction in a ratio of at least 1.2 to 1 by passing it over a series of heated rollers, a layer of polyethylene film is applied to at least one side of the longitudinally stretched polypropylene film, and the resulting combination of films is stretched at a temperature above the heat softening point of the polyethylene, e.g. 250‹ F., in a transverse direction, preferably in a tenter frame, the transverse stretch being in a ratio of at least 3:1. The films may then be subjected to a further longitudinal stretching step. However, the films may be brought into intimate contact before the initial longitudinal stretching of the base polypropylene, subsequent to the initial longitudinal stretching but prior to the transverse stretching or subsequent to the transverse stretching but prior to the second longitudinal stretching step. Simultaneous biaxial orientation may be employed. Suitable thermoplastic materials include polyethylene, polyethylene copolymers, polyallomers (defined in the Specification), polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, vinylacetate-ethylene copolymers and nitrocellulose. The untreated polypropylene has a thickness of at least 0À2 mil., and the thermoplastic layer a thickness of at least 0À02 mil.</p> |
