The discovery of traces of photoinitiators in foodstuffs has demonstrated the importance of migration values and residual content.
Herethe suitability of printing inks for use in the packaging of foodstuffs is a crucial issue. This will be essential for the further use of UV technology in the packaging industry as well as in conjunction with other possible applications.
UV radically curing technology is used in many applications. In response to upcoming legislation on migration levels for inks used in food packagingRahn has introduced its new Genopol product line.
Genopol photoinitiators are polymeric products with almost no odour. Combined with the ability to link into the UV cured acrylate matrixthe polymeric Genopol photoinitiators exhibit extremely low tendency to migrate. HereGenopol polymeric photoinitiators are compared with with standard grades in terms of formulation and performance.
The printing inks used for this presentation are purely a test formulation. They are strongly simplifiedhighly pigmented and are only for the purpose to compare properties of inksformulated with alternative photoinitiator packages. Data for food packaging should be generated under realistic and practical conditionsconsidering commercial printing inkssubstratespre-treatmentprinting conditionsetc.
The results were as follows:
- Cure speed: It has been found that with a direct replacement of ITX with Genopol TX-1the amount has to be significantly increased to maintain cure speed. Therefore Genopol TX-1 should always be used in combination with Genopol AB-1. The synergistic effect of this polymeric amino benzoate versus the use of straight EPD/EHA allows for the use of similar amounts of Genopol TX-1 compared to straight ITX while still maintaining the cure speed. Finally straight benzophenone has been replaced by Genopol BP-1. With this stepthe photoinitiators with the lowest molecular weighthighest odour and tendency to migrate have all been fully replaced by polymeric ones. Genopol BP-1 is also used in UV varnishes where combinations with reactive oligoamines synergists such as Genomer 5275or Genopol AB-1 are recommended.
- Migration and odour: During the production process of the polymeric Genopol product rangethe low molecular weight substances are removed. ThereforeGenopol photoinitiators are very low in odour. Combined with the ability to link into the UV cured acrylate matrixGenopol photoinitiators will exhibit extreme low tendency to migrate.
The results show that it is possible to formulate UV-printing inks with low migration and odour and which exhibit good cure speed. Genopol BP-1Genopol TX-1 and Genopol AB-1 combine to form a package of polymeric photoinitiators: high molecular weightliquidexcellent compatibility in UV-systems.
As the spotlight of suitability of printing ink systems for food packaging intensifiesthe ability of a UV curing system to be truly polymeric in all of its component partswill encourage the further use of this technology .
Rahn AG is based in ZürichSwitzerland. www.rahn-group.com
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