Conventional tin printing inks are currently based almost exclusively on alkyd technology. Unfortunately alkyds are prone to yellowing during high temperature stovings, such as those used to cure an internal lacquer on food containers, due to reactions involving residual unsaturation in the cured ink.
Polyesters are basically oil free alkyds and as such have no unsaturation to cause yellowing during subsequent stovings. Unfortunately it is the oil portion of alkyds which is primarily responsible both for cure and lithographic properties requering water repellance.
A typical formulation for UV inks tin printing:
1. Pigment
2. Inert resin
3. Epoxy acrylate
4. Urethane acrylate
5. Glycerylpropoxytriacrylate as reducer
6. PE wax
7. Talc as anti fly
8. 2.2-dimethoxy-2-phenylacetophenone as photo-initiator
9. Isopropylthioxanthone as photo-initiator
10. Aminobenzoate synergist
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