PIGMENTS | SPECIAL EFFECT
Right: New additions to the Royal Lumina range of sparkling pigments include aqua blue (left) and magenta
colour recycle stream. That aside, both conven- tional and effect pigments can also be used to create aesthetically pleasing colours even from mixed-colour recycled material, says Briggs. “For example, by covering sparkle with large particle size effect pigments, we can hide existing effects. Or, when presented with darker coloured polymer in the mixed recycle, we can create a pop of colour with transparent effects that can create a product that is both aesthetically pleasing and a good use of mixed colour recycle material,” she explains. Briggs says that Sun Chemical continues to
research pigments that can improve plastic packaging recycling and reduce carbon footprint. Another major consideration is the durability of
Recycling requirements Recycling —or the ability to recycle — is fast climbing up the list of pigment selection criteria. The impact of colours and effect pigments on recycling depends on many factors, including the type of pigment and base polymer, as well as the recycling sortation technology and the markets for the recycled material. It is a complex situation that is evolving, both as new technologies become available (for example, NIR-sortable dark-coloured pigments) and as organisations make decisions about how to improve plastics recycling. Some of the colours and effects used in certain polymers are not unrecyclable, but may be consid- ered detrimental to recycling. According to the US Association of Plastic Recyclers (APR) Design Guide, for example, an optical brightener effect used in HDPE is considered detrimental to recycling because it can create “unacceptable fluorescence for next uses of recycled HDPE.” The guide adds that “it is difficult to identify material with this negative effect until extremely late in the recycling process.” According to APR, opaque colours are not a
Right: Gabriel- Chemie’s Zenexo
GoldenWhite WB 21 YS aims to replace metallization in packaging closures
problem in HDPE because there are markets for coloured recycled material and it is economical to process. However, for PET recyclate, APR lists opaque coloured and white and transparent colours other than blue or green as “detrimental” because of reduced market value (while the mixed-colour stream is currently less valuable, it is not inconceivable that a future market opportunity may change the econom- ics of recyclability in the future). Effect pigments do not
prevent recycling, but the pigmented parts will typically become part of the mixed-
48 COMPOUNDING WORLD | March 2022
effect pigments. Shepherd Color Company’s Starlight effects, for example, can stand up to multiple processing cycles. “Starlight FL grade special effects are especially resilient to physical degradation due to their robust and inherently inert borosilicate-glass substrate and passivated silver effect layer,” says Mark Ryan, Marketing Manager for The Shepherd Color Company.
The appeal of gold There is also an ongoing trend towards the use of gold colours, extending from a reddish-gold tone up to a white-golden hue or tint, says Thomas Hummel, Head of Technical Department at master- batch producer Gabriel-Chemie. The company is using a new metallic effect pigment from Schlenk —Zenexo GoldenWhite WB 21 YS. These effect pigments are based on Ultra-Thin-Pigment (UTP) technology, which creates a thin aluminum sub- strate encapsulated with silica. It is said to give a dep and high-gloss surface, creating a metallic lustre that enables coloured plastics to replace metallized plastics. Hummel says the driver to replacing metallizing is to reduce the number of production steps and the associated costs. The pigment and masterbatches made with it are suitable for food and cosmetic packaging, as well as for more durable goods. Lifocolor Group has launched a series of highly
reflective pigment masterbatches that create a brilliant gold effect that it says is in high demand for cosmetics, beauty and personal care packaging. The effect masterbatches provide high opacity in polyolefins, even at low levels (between 2 and 3%), which gives a
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vibrant, rich appearance even for thin-wall packaging,
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IMAGE: SUN CHEMICAL
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