TABLE OF CONTENTS Clarifiers have become extremely popular in the last few years, making possible the production of high clarity PP products for the packaging of food and cosmetics. Clarity is especially important in the wide, hot fill containers used in the food processing industry because the filling process has to be visually monitored. It is also useful in medical pill bottles, radiation-resistant medical syringes, drinking cups and general retail packaging. Other applications of clear PP include video boxes, the packaging used for DVDs and certain automotive parts. Injection stretch blown bottles for fresh juices and dairy products are made using clarifiers.
The early clarifiers had serious shortcomings. They left the products with poor odour and taste. They were also limited to a processing temperature of around 225 C and could cause plate-out unless an inhibitor like glycerol monostearate was added. Improvements in all these respects have since been made.
Most of the current clarifiers are sorbitol derivatives. They include Great Lakes Clearlite NU 005, and Ciba s Irgaclear additives, some of which are now manufactured by Roquette in France, as well as NC-4 sorbitol acetal clarifiers supplied by Mitsui Toatsu Chemicals in Japan. One exception is Dover Chemical s Doverlube FL-599, a polyethylene glycol ester offered for clarifying polypropylene and also as a process aid for high impact polystyrene.
The most recently developed additives are up to ten times as expensive as their predecessors but only require low dose levels (around 0.2%), so the increase in resin cost is...
