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White Paper

May 2011


Ultramarine Pigments for Food Contact Plastics


Synthetic Ultramarine is non-toxic and inherently safe for sensitive applications including cosmetics, children’s toys and plastics that come into contact with food stuffs, but Holliday Pigments recognised it could add value to plastics packaging – and in particular the caps and closure market – by developing a



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Industrial developments

In the quest for improved productivity, injection moulders are always trying to reduce cycle times, which invariably means using high process temperatures and shear rates, – putting polymers and colourant additives under more extreme manufacturing conditions.

Ultramarine blue’s unique colour is only possible because of sulphur anions within its crystal lattice. Under extreme moulding conditions, where the pigment is exposed to high temperatures and shear rates, incorrect grade selection could lead to sulphurous taint in certain beverages. While there are many factors that could contribute to this issue, Holliday Pigments invested in improving its manufacturing process to specifically enable the production of pigments, proven to transfer no detectable taste to liquids contained in plastics packaging. Though the company’s standard Ultramarines have worldwide health and safety approvals for such applications, this added-value benefit offered its customer base new packaging options at the premium end of the market – capitalising on designer bottled drinks, for example.

Developing raw materials that are proven to minimise their organoleptic effects in food contact applications represented an important development at this time and the resulting Premier BC for still water and BC-R for carbonated soft drinks have since been widely specified across the heavily regulated European and US food and beverage sectors. Now, with health and safety issues coming increasingly to the fore at a global level, markets which have traditionally been more cost-driven are actively seeking certified products with proven performance benefits to enhance their competitive edge.

Regulatory directives

Most countries have their own systems of approval, often based on the two most commonly accepted regulations, – those of Europe and the USA.

Pigments used for colouring food contact plastics in the European Union are required to meet the purity standards listed in Resolution AP(89)1. This resolution has been adopted by all EU countries. There is another regulation, dealing with substances in plastics other than pigments which may come into contact with foodstuffs. This is Directive 2002/72/EC. Whereas the Ultramarine pigment itself is not subject to this regulation, any additives, such as the carrier used in Holliday Pigments’ Prestige series of low dust preparations, must meet its requirements.

Pigments used for colouring food contact plastics in the USA are required to be on an approved list. Until recently, the list was non-proprietary and identified only the pigment, not the manufacturer. The regulation is published in the Code of Federal Regulations, Title 21, Part 178.3297. Being a well established pigment, Ultramarine has long been included in this list. The approvals process has since changed and

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Ensuring superior pigment performance

The main contaminant which may be present in a plastic masterbatch based on Ultramarine pigment is sulphide. There are two possible reasons for its presence.

Firstly, Ultramarine pigments contain sulphur chromophores, plus small quantities of unreacted sulphur. These unreacted species are volatile at plastics processing temperatures and are released as sulphides. Normally the amount of free sulphur present even in the general purpose grades manufactured by Holliday Pigments is not enough to cause any objectionable taint or odour as it is removed along with the other volatiles such as moisture during the production process.

However, food contact plastics are especially sensitive to taint and for these applications even well processed standard grades may not be pure enough. For that reason Holliday Pigments Premier BC ranges for severely demanding food contact applications are free from unreacted sulphur and superior performance is ensured by improving the specification for volatiles to 0.05% maximum at 150°c (standard grades are tested at 105°c) and the un-reacted sulphur to 20ppm maximum (standard grades 200ppm). After thorough independent testing of bottle caps coloured with this grade and immersed in pure mineral water, no evidence of taint in the water could be detected.

Secondly, Ultramarine is sensitive to attack by acids which release sulphides. Such acids may be present as breakdown products of the polymer (such as PVC) or in some foods (sparkling mineral water and fruit juices). While the polymer may protect standard grades of Ultramarine against such weak acids for a period, it is much better to use an Ultramarine which has its own protective coating to resist such attack. The best of these is the encapsulated version of Premier BC, which is available as Premier BC-R.

Conclusion

Indeed, there are many considerations when using Ultramarine to colour plastics likely to come into contact with food stuffs, but the introduction of these specially developed grades will be particularly welcomed by any end-users struggling to balance zero organoleptic effect with maximum process speed. Furthermore, the Premier BC products share the same performance properties as Holliday Pigments’ wider plastics ranges, demonstrating excellent colour consistency; exceptional heat stability; and lightfastness. And, as an inorganic pigment, Ultramarine is especially suited for colouring closures because its composition will not affect the dimensional stability of plastic mouldings as some organic pigments can. This means that closures will not shrink or warp and are therefore more effective in maintaining a tight seal.

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About Holliday Pigments

Holliday Pigments is a world leading supplier of Ultramarine pigments, which are used in a variety of applications including plastics, coatings, cosmetics, artists’ colours and printing inks. Exporting to over 80 countries, Holliday Pigments has dedicated customer and technical service teams at its factory in France.

Holliday Pigments has a proud 125-year history in the manufacture of technical quality Ultramarine and is the only Ultramarine manufacturer in the world to have invested in Flue Gas Desulphurisation technology, reducing sulphur dioxide emissions inherent in the manufacturing process by more than 99.5%.

In August 2008, Holliday Pigments joined Rockwood Holdings Inc., becoming an important addition to the Color Pigments and Services Division.




Further information on all Holliday Pigments’ products is available from:

Holliday Pigments SA (France)
203, route de Wervicq
BP 50017
F-59559 COMINES, Cedex
Téléphone + 33 (0) 3 20 63 12 00 Télécopieur + 33 (0) 3 20 39 20 83

Email: infohp@holliday-pigments.com
Web: www.holliday-pigments.com
Or from your Holliday Pigments’ Agent

© HPSAS 2010
The information included in this literature is based on data determined by Holliday Pigments SAS under standard laboratory conditions. Such information may be affected by different working or processing conditions beyond the control of Holliday Pigments SAS and should always be verified by the end user.