Clariant solves liquid colour problems for EBM

Colourant masterbatches promise cooler processing and faster colour changes

New liquid vehicle technology (LVT) developed by Clariant Masterbatches appears to have eliminated many of the problems that have prevented wider use of liquid colour and additive concentrates in extrusion blow moulding of polyolefins (high- and low-density polyethylene and polypropylene).

The new masterbatches incorporate suspension aids and binders to allow for higher pigment loadings and (in most cases) lower usage rates.

Past problems relating to screw slippage have been virtually solved, says the company, giving improved mixing, more complete dispersion and less streaking. Improved resin compatibility is said to have resulted in stronger weld lines in the finished container as evidenced by scores in standard burst and compression loading tests.

Raymond Sloan, head of liquid colour for Clariant Masterbatches North America says: “Extrusion blow molders and brand owners in the personal care and household products markets often find liquid masterbatches to be an attractive alternative to solid concentrates. However, until now, use of liquid colour has been limited in blow moulding of polyolefin resins because many liquid-based carrier systems (including mineral oil) would not incorporate well with the resins. It was pigment friendly, but not resin friendly.”

Benefits cited for Clariant’s new formulation include:

• Processing temperatures up to 17°C lower, necessitating less cooling;
• Faster colour changes (in minutes rather than the hours required for pellet colourants), reducing scrap and increading productivity.

Sloan concludes: “So far testing has been completed in several types of monolayer containers. We are confident that similar results can be achieved in multilayer applications involving both opaque color and pearlescent effects.”

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