Method of printing a laminate for production of dimensionally stable food and drink product containers with application of a primer having an excess of isocyanate groups
The present invention relates to a method comprising as method steps: a) providing a sheetlike composite precursor comprising a carrier layer; b) overlaying the sheetlike composite precursor on an outer face of the sheetlike composite precursor with a liquid first polymer composition; c) hardening the liquid first polymer composition, thereby obtaining a first polymer layer; and d) overlaying the sheetlike composite precursor on the outer face of the sheetlike composite precursor with a liquid second polymer composition; wherein the first polymer layer in method step d) comprises an isocyanate content in a range from 0.1% to 50% by weight, based on the weight of the first polymer layer. The invention further relates to a sheetlike composite obtainable by the method; a container precursor and a closed container, each comprising the sheetlike composite; and to uses of a liquid primer and the sheetlike composite.
1. A method, comprising as method steps
a) providing a sheetlike composite precursor comprising a carrier layer;
b) overlaying the sheetlike composite precursor on an outer face of the sheetlike composite precursor with a liquid first polymer composition which comprises a first di- or polyisocyanate which has aromatic groups, a further di- or polyisocyanate which has aliphatic groups and at least one di- or polyol,
wherein the liquid first polymer composition is characterized by a ratio of a proportion of aromatic groups in the liquid first polymer composition to a proportion of aliphatic groups in the liquid first polymer composition in a range from 0.35 to 0.80;
c) hardening the liquid first polymer composition, thereby obtaining a first polymer layer,
wherein the hardening is effected at a temperature of the liquid first polymer composition and/or the first polymer layer in a range from 18 to 35° C.; and
d) overlaying the sheetlike composite precursor on the outer face of the sheetlike composite precursor with a liquid second polymer composition;
wherein the first polymer layer in method step c) comprises an isocyanate content in a range from 0.1% to 50% by weight, based on the weight of the first polymer layer;
wherein the liquid second polymer composition in the overlaying in method step d) comprises at least one first polyvinyl acetal in a proportion in a range from 2% to 12% by weight and a colorant in a proportion in a range from 2% to 15% by weight, in each case based on the weight of the liquid second polymer composition.
2. The method according to claim 1 , wherein the liquid first polymer composition in method step b) is characterized by a first isocyanate content based on the weight of the liquid first polymer composition;
wherein the liquid second polymer composition in method step d) is characterized by a second isocyanate content based on the weight of the liquid second polymer composition;
wherein the first isocyanate content is more than the second isocyanate content.
3. The method according to claim 1 , wherein the liquid first polymer composition in method step b) is characterized by
a. a molar OH content in mol per g of the liquid first polymer composition, and
b. a molar isocyanate content in mol per g of the liquid first polymer composition,
wherein the molar isocyanate content is more than the molar OH content.
4. The method according to claim 1 , wherein the first di- or polyisocyanate comprises tolylene diisocyanate.
5. The method according to claim 1 , wherein the further di- or polyisocyanate comprises hexamethylene diisocyanate.
6. The method according to claim 1 , wherein the liquid first polymer composition in the overlaying in method step b) further comprises a colorant in a proportion in a range from 5% to 25% by weight, based on the weight of the liquid first polymer composition.
7. The method according to claim 1 , wherein the sheetlike composite precursor in method step a) further comprises a barrier layer,
wherein the barrier layer overlies the carrier layer on a side of the carrier layer remote from the outer face of the sheetlike composite precursor.
8. The method according to claim 1 , wherein the method further comprises a method step of
f) overlaying the carrier layer with a barrier layer on a side of the carrier layer remote from the outer face of the sheetlike composite precursor.
9. The method according to claim 1 , wherein the sheetlike composite precursor in method step a) further comprises an outer polymer layer,
wherein the outer polymer layer overlies the carrier layer on a side of the carrier layer facing the outer face of the sheetlike composite precursor.
10. The method according to claim 9 , wherein the outer polymer layer comprises a polyethylene or a polypropylene or both.
11. The method according to claim 10 , wherein the outer face is formed by the outer polymer layer;
wherein the overlaying in method step b) is effected by an application to the outer face; wherein, prior to method step b), a surface tension of the outer face is increased by means of a surface treatment to a value in a range from 38 to 44 dyne/cm.