Photoinitiators (PIs) are a key component and a cost driver for UV curing products. They are capable, as their name implies, of initiating or starting a photoreaction. This occurs when a PI absorbs radiation energy from light exposure to produce highly reactive free radicals and ionic species. These have the capability of catalyzing or starting chemical reactions, or changes in certain formulated materials. One such photoinitiator is Benzophenone.
Benzophenone (BP) or Benzo, has been generally recognized as the most used PI globally. It is known for its effectiveness as an initiator, and its relative low cost.
In the last several years, a health concern has developed, especially in Europe, regarding the migration of small molecule PIs, into foods from indirect food contact packaging materials. It is thought that a PI like methyl benzophenone (MPB) can reach packaged food in two ways, (1) an indirect transfer from the vapor phase of semi-volatile PIs, (2) from direct contact stemming from permeation or set-off when cured printing inks and coatings come in contact with the inside of a package surface as packaging material is stacked or processed in roll form. When migration into food has been found, the packaged food and the packaging materials used have been removed from use.
In California, Prop 65 requires the state to publish a list of chemicals known to cause cancer, birth defects or reproductive harm. The law requires a warning label on anything containing these. Benzophenone was listed in 2012. Benzophenone (BP) or Benzo, has been generally recognized as the most used Photoinitiator (PI) globally. It is known for its effectiveness as an initiator, and its relative low cost.
UV printing ink and coating manufacturers have responded by replacing low molecular weight, high migration potential PIs. As a result, benzophenone & ITX free formulations have been made available, notably for food packaging. In other moves, raw material suppliers continue to develop self-curing resin solutions, new large molecule, low migration, low odor polymeric photoinitiators (PPIs), and co initiators. Significantly, these changes have become price drivers for UV curing products.
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