13 October 2013
Year: 2013
Price: 10.00
DUMAX SRL, till the seventies, was specialized in the production and development of solvent varnishes for graphic arts. It concerned finish varnishes based on polyurethane resins at 1 or 2 components, varnishes for rolling press exct....that could be applied almost only with varnishing machines.
At that time the market began to propose raw materials (oligomers and monomers) for UV varnishes.
Immediately DUMAX realized that these innovative raw materials would dominate the market thanks to obvious advantages as:
1. high speedy production
2. possibility to use these varnishes with all types of machines
3. high brightness and particular chemical and mechanic resistances
4. absence of solvents that means reduction fire risks and pollution
However these new products showed 4 important problems:
1. inks colour change
2. refuse
3. penetration
4. adhesion on offset and water based inks
The first two problems were solved in a quite short time, while it was much more difficult to solve the other ones. But what really these last two problems consisted in?
PENETRATION: this one involved two disadvantages: let's analyze them now!
Varnished papers can show a no homogeneous aspect: high brightness on printed areas and very low brightness in those zones where there is not much ink or where it is light (this is caused by penetration of the varnish into the support). In second time varnish that penetrates can't dry anymore and this causes possibility of residual smell on the paper.
To solve this problem one solution was to improve viscosity but in this way the cost increases (because higher viscosity means more quantity on the paper) and brightness decreases because of not good spreading. Another solution was to use water based primer that can be applied in line with inks, but this means more costs and also time to clean machine if the printer normally uses a water based varnish, why?

Because the primer, as its basic characteristic, must be suitable to receive UV varnish, while water based varnish must be bright, unblocking, unscratching and all these performances can be obtained only by using additives that cause adhesion problems oF the UV varnish on it.
To solve the penetration problem,a famous supplier developed an additive that solved the problem without increasing viscosity but that showed three disadvantages: at first it increased price (because you had to add about 5% to the varnish and it was very expensive), as second it created deposit on the basin and as last it made brightness decrease.
ADHESION: this problem manifests itself specially between UV varnish and offset or water based inks.
According to our opinion this is a very important aspect because, in case the varnish comes off the support, it creates flakes and this involves three disadvantages:
1. it compromises aesthetic aspect of varnished paper
2. flakes coming from varnished box put on the table could be ingested
3. children can remove flakes from paper with their sticky hands and ingest them
2013 Conference All whishes in an unique UV varnish for paper ( what else?!)
Author: E. Marzagalli | 8 pages

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