Fanal Pigments for the manufacture of flexo water-based Inks and alternatives

 

The main constituents of a flexographic water-based ink are organic polymers, pigments as dying materials, additives and water.  Pigments are substances not soluble in water neither in solvents.   The main properties that can define a pigment are:

  • Hue
  • Cleanliness
  • Colour Strength
  • Bleeding in different solvents including water
  • Temperature stability
  • Light fastness
  • Environmental toxicity
  • Human toxicity
  • Other

The pigments most commonly used in the formulation of flexographic water based inks are based in the organic chemistry. Fanal pigments are within this group. Chemically, a fanal pigment is defined as a salt of a complex inorganic acid anion with a cation of triarilcarbonium dye. This seemingly complicated denomination simply means that these pigments are synthetized from an organic dye that gives them exceptional colorimetric properties. Some of the properties of fanal pigments are:

  • Low light fastness
  • Poor resistance to solvents (bleeding).
  • They produce unstable inks.
  • High toxicity to the environment.

 

However, as mentioned, they have colour properties as HIGH CLARITY, DEPTH AND CLEANLINESS.

That means that there are colours of the visible spectrum that are not achieved with any other organic or inorganic pigment, so they are still used in Graphic Arts.

Below is a table with the main types of fanal pigments used in the manufacture of flexographic water based inks, their colour index, the main constituents and their environmental impact.

The pigments PB62, PV27 and PR169 are derived from copper ferrocyanide salts, whose residues can result in high content of soluble copper in waste-water and cyanides in sludge from wastewater treatment stations in the printing industries.  For these reasons,  Quimovil has minimized its use since 2002. Since then it is recommended to use, as alternative, fanal pigments synthetized from the same dye but in the version made with the anion of phosphor-tungsto-molybic acid. However, soluble molybdenum cations are also considered a water pollutant and their presence in them is increasingly controlled.

Due to environmental safety factors, these pigments have finally been classified as hazardous to the environment, so they must be labelled according to CLP  and have been classified as hazardous products for ADR transport, within Class 9.

All these environmental conditions, together with their properties of low light fastness and their tendency to bleed under the effect of some solvents (and therefore to migrate) have made them less and less used. However, their not very expensive prices and extraordinary colorimetric properties make them still used in the manufacture of flexographic water based inks, especially when they are not intended to use for food packaging or packaging.

It is important to note that it is not prohibited its use in food packaging. But today, legislation is not yet in place in Europe to provide formulation guidelines for inks for food packaging, so Quimovil  and other ink manufacturers use the Swiss Ordinance SR 817.023.21 as a guide. This Ordinance was first published in 2008 and was the result of collaboration between the Swiss Public Health Office and EuPIA (European Printing Ink Association), on the basis of Council of Europe resolution ResAP(2005)2 on packaging inks. In the latest version of the Swiss Ordinance (December 2020) fanal pigments are still present, i.e. their use is permitted for food packaging, but are listed in Annex 10, Part B, limiting the specific migration rate (SML) to 10 ppb (0.01 mg/kg of food). Therefore, its industrial use in food packaging and packaging is very limited.

It should also be noted that some Brand-Owners have edited their own recommendation standards on the requirements for the manufacture of inks intended for food packaging. Specifically, Nestlé discourages the use of fanal pigments in the document “Nestlé Guidance Note on Packaging Inks, October 2018”.

The Department of Colour of Quimovil S.A. offers advice to printers who wish to definitively replace the fanal pigments of the formulations of the inks they use.

The replacement of these fanal pigments involves, in some cases, an increased cost of the inks, especially in the formulation of blues and violets, so the printer must assess the type of packaging it makes and its requirements to decide to replace them in whole or in part.

Laura Pomés
Technical Direction, Quimovil
January 2021

 

Bibliography and Webgraphy

  • Annex 10 of the Ordinance of the FDHA on materials and articles intended to come into contact with foodstuffs, Federal Department of Home Affairs FDHA, Federal Food Safety and Veterinary Office FSVO, CH. Edition 2.1., Entry into force: 1 December 2020.
  • Industrial Organic Pigments, Willy Herbst and Klaus Hunger.
  • Joint safety evaluation of substances in printing inks by Germany (BfR) and Switzerland (FSVO), 5th EFSA FIP Network FCM Meeting Parma, 10.-11.7.2017, Stefan Merkel (BfR) and Stefan Kucsera (FSVO)
  • Nestlé Guidance Note on Packaging Inks, October 2018