MICROPOROUS POLYPROPYLENE FILMS FOR TAPE AND LABEL APPLICATIONS

摘要

We have developed a unique masterbatch that can be used to produce extruded polypropylene sheet containing high levels of beta phase crystallinity. When this sheet is stretched either uniaxially or biaxially to produce MOPP or BOPP film, the sheet undergoes extensive microvoiding resulting in a white/opaque appearance, a significantly reduced density, and improved printability. Under certain circumstances it is possible to produce a microvoided film that has very high moisture vapor transmission rates, so that the film is "breathable" while also being waterproof. These microvoided films are less expensive to produce than conventional white films since the density reduction yields more square yards of film per pound of resin used, and the level of TiO_2 pigment that is required is drastically reduced. Application areas for these films include tape, labels, synthetic paper, and protective clothing.