S22 - Session O3 - Natural pigments for(bio)-plastics colouring

Authors: Christine Brunet *

The development of new biopolymers and the recycling of polymers for the plastics industry, which are booth booming, represent a pivotal tool in the fight against global warming and against the pollution of inland and marine environments. To answer to industrial demands for plant-based colouring of such new materials, Couleur de Plantes (CDP), alongside CRITT horticole , conducted a 4 years project of testing and development. CDP cultivates its own tinctorial plants and also by tropical resources in order to expand its product range, to produce natural dyes and insoluble pigments at large scale, which are applied in cosmetic, textile, paint and (bio)polymer colouring The pigment uses for the laboratory studies and industrial pilots were from Madder, Weld, Sorghum, Goldenrod, Chestnut, Lucerne, Indigo, Quebracho, Indigo and Sappanwood. The first step of the process meant mixing and extruding the natural-coloured pigment with the bio-based polymer granules to obtain "master -batches". Then the coloured master batches were mixed with various plastic biopolymers and were applied industrially in different processes of transformation: injection, extrusion, thermoforming, blow moulding, 3D printing These industrial tests have shown that natural pigments are compatible with biocomposite-polymers to give bright and intense colours, and proved to be resistant to the process parameters: high temperature (up to 320°C) and high pressure (up to 800 bars). The naturally coloured plastics obtained (bottles, jars, trays, reels, tubes, cards, boxes…) were tested for light fastness, conformity to cosmetic and food contact regulations (toxicity, migration, purity, compostability…). Also, the influence of parameters such as the use of master-batches or powder pigment, the nature of the polymer, the concentration of the pigments have been tested and compared on the lightfastness of coloured bio-polymers. A selection of natural pigments that proved to be suitable for colouring bio-based or recycled polymers, in accordance with the regulations and polymer transformation processes, was done in order to develop sustainable plastic packaging.