New liquid vehicle technology from Clariant Masterbatches, Holden, Mass., is designed to eliminate problems that have prevented wider use of liquid color in extrusion blow molding of polyolefins. In 2009, the company introduced a new liquid-color vehicle for easier blow molding of HDPE (see Dec. ’09 Keeping Up). Many of the same benefits are now available for blow molding LDPE and PP—such as the ability to use higher pigment loadings and lower liquid-colorant amounts, while practically eliminating past problems with screw slippage.
One result is better mixing and reduced streaking. Improved resin compatibility is said to provide stronger weld lines, as evidenced by standard burst and compression-loading tests on molded containers. The reformulated colorants reportedly also enhance flow, allow for much faster color changes, and eliminate smoking and fuming at the die head.