PROCESS FOR PREPARING SINGLE PHASE VINYLIDENE CHLORIDE-BASED ADDITIVE BLENDS
Publication Date: 2018-Jul-11
The IP.com Prior Art Database
This publication is directed to various processes for preparing PVDC-based additive blends. The first method is directed to blending an additive, such as an optical brightener (OB), into PVDC involving the addition of the OB into an acrylic polymer latex, then addition of the processing aid latex and the OB to the PVDC. The second method is directed to a water soluble fluorescent agent or an OB added to an aqueous dispersion of a suspension or an emulsion mix of PVDC.
Polyvinylidene chloride polymers (PVDC) are used in a wide variety of packaging applications due to their barrier properties. For example, PVDC is often used as a barrier layer in a film to prevent the passage of gases, such as oxygen and moisture vapor, through the film.
Barrier films comprising a layer of PVDC have found particular wide spread use in food packaging industries. In commercial practice, such barrier films may include multiple layers in which the film includes other layers that improve the films properties, such as stability, toughness, and sealability. In some cases, it may be desirable to include an additive that is blended with the PVDC in the barrier layer. However, PVDC is immiscible with many additives which makes it difficult to produce a homogenous blend in which the additive is uniformly distributed in the PVDC. As a result, regions of the barrier layer may devoid, or may not include a sufficient amount of the additive. Accordingly, there still exists a need for processes of uniformly blending additives with PVDC.
Method of blending an additive with a processing aid, then PVDC
UV indicators that are detected by spectroscopy are added in polymers by using melt compounding or dry blending. Melt compounding is not desirable for PVDC as additional heat history degrades the polymer. Dry blending to a lesser extent has the same effect. The present method incorporates the indicator, such as an optical brightener, in the suspension phase of polymerization where the effect of viscous heat on the polymer stability is negligible.
One method for blending an additive such as an optical brightener (OB) into PVDC involves addition of the OB into an acrylic polymer latex (processing aid), then addition the processing aid latex and the OB to the PVDC. In this process, an optical brightener (OB) is incorporated in an acrylic polymer latex at levels of 5ppm to 50,000ppm. The mixture is subsequently added to a PVdC polymer to coat the PVdC particles with the help of a coagulant during the residual monomers stripping stage of polymerization. The latex and the OB concentration are from...