Strange exothermic reaction – need help from ink chemists

[cementary]

My co-workes from binding workshop told me about strange reaction with printed and folded sheets.
We've got an order with very big ink coverage % (i don't mean 400% or smth, i mean sheets full of rich black background).
After printing the order (4+4, two passes + two passes with spot matte varnish) sheets were cut, folded and sewed.
Then sewed blocks were stored in a pile somewhere around workshop for about 12-24 hours
When time came for further processing my colleagues couldn't do that, 'cause blocks in the pile were very hot – about 60 deg. C.

This happened with 2 orders same coverage same processin'.

Is there any explanation for such phenomena?

PS i'm not joking, i'm quite embarrased

 

[maxon]

Shot in the dark could be heat generated during coating polymerization - what the heck varnish did you use and why hasn't it been cured completely ?

 

[cementary]

Varnish was printlac matt 10L9300 from huber with cobalt octoate as surface drier in it. Why it hasn't cured i don't know, but the thing that is new for us for the last 3 months is a new fountain solution concentrate (from huber, yes) substifix hd.
Again i don't know why, personally i don't believe that there is something better than isopropanol

 

[engin]

Dear cementary,
cobalt octeate in offset system makes them dry, and in offset opv's there are china wood oil as an hard drying vegi oil.During drying mechanism, the heavy smell come out from drying of china wood oil.
For the black ink, the pigment ( which is carbon black from petroleum sources) is a combustable material. During the storage, was there around any heat source nearby the pile since this source could lead to decompose the carbon black may be? and for the blocking of the products, the heat generated could soften the dried vegi oil to tick each other?
Regards,
engin

 

[cementary]

No, there was no heat source near the pile. And yes, sheets ticked to each other at least in one order 'cause I saw result.

 

[Dan Roll]

Oxidation produces heat. Sheetfed inks dry for the most part by oxidation and cobalt is an oxidation stimulant.

 

[engin]

Oxidation produces heat. Sheetfed inks dry for the most part by oxidation and cobalt is an oxidation stimulant.

Dryers aids oxidation and you feel as smell for this to follow.Here , oil based opv contains china wood oil which is the strongest oxidative vegi oil, and its smell is very hard during drying.

I did not have any experience from my sheetfed customers when used oil based opv as heat generated.
May be they should check the smell coming out from the stock if it is unusual that they are failiar with.

by the way cemetary, dio not add any extra sicative into the inks, since excessive dryers reverse the oxidation reaction.

regards,

engin

 

[cementary]

I'm not an ink chemist – just started to read "the printing ink manual". Sorry but what is "opv"?
We didn't add any extra siccative.
My shot in the dark for now – varnish was applied while ink (reflecta rl 250 – by the way our supplier didn't explain us what's the difference in compare to standard reflecta) was in most active oxidatin' state and cobalt from varnish geometrically increased strength of reaction.

 

[JohnMcGrath]

Oxidation produces heat. Sheetfed inks dry for the most part by oxidation and cobalt is an oxidation stimulant.

I had a similar experience when printing a solid Pantone on both sides of very thin 50gsm stock. A pile of about 7,000 B2 sheets where printed by perfect and about 36 hours off press when we went to cut them i was called over. The temperature was over 70 centigrade smell was rancid, we use vegetable based oil inks from Huber.
We monitored the temperature with a probe in the pile and when we saw it was still rising I has it pulled out into the yard and restacked on to smaller pallets.
When I contacted the local huber people I was told it was caused by the additional driers in the formulation for the thin print.

The job was ruined and we reprinted printing a single side at a time waiting between passes for it to cure.

 

[engin]

I'm not an ink chemist – just started to read "the printing ink manual". Sorry but what is "opv"?
We didn't add any extra siccative.
My shot in the dark for now – varnish was applied while ink (reflecta rl 250 – by the way our supplier didn't explain us what's the difference in compare to standard reflecta) was in most active oxidatin' state and cobalt from varnish geometrically increased strength of reaction.

OPV - over print varnish
I know you did not add extra siccative, I said adding excessive siccative into the system reverse the oxidarion reaction resulting in poor drying instead of accelarating, also yellows in non inked areas of the surface.

Cobalt now in EU out of use, and mangan dryers replaced it. As I said oi based opv's are very hard drying systems due to ch,na wood oil contents.

Here in Turkey, I see reflecta also other HUBER vegi series, FLINT vegi series, SunChemical vegi series and in any use of these inks no such problems I heart as temoerature increase, rather heart extra smells which is result of vegi oils's oxidation.

regards,
engin

 

[mazengh]

I have had this issue happen with flint F918 series, which is Vegetable based, and with a flint OVP varnish which is the protection varnish flint caries. The result was very high temperatures, scary, that we stopped the export of the job because we felt it's not safe to ship on the plane.

 

[cementary]

Thank you people. I think now i'm ready to have a little talk with supplier.

 

[engin]

Just one more suggestion, may you can use water based opv from duct instead of oil based opv which gives more gloss and quick drying.

regards,

engin

 

[cementary]

engin Can you advice non agressive water based opv with matt effect?

 

[engin]

Dear Cemetary,
I do not understand by non agressive you mean.
water based OPV's, are containing ammonia to balance their pH the only aggresiveness comes out from this to disturb the non-alkali resistant pigments if there is in the print, behind this they are drying very quick ( about in 10 sec) after application.

You have to ask to your supplier. But, I offered to you ink duct applicable water based OPV since you applied oil based opv from ink duct isn't it? Again, ask to your supplier a suitable water based opv from ink duct.

One more information from ink duct water based opv, they are transffered from ink rollers so have higher viscosity and takes longer time to reach the subsrate, their drying mechanism slowed down, even on the subsrate it would be wet,but after 5-10 seconds on the subsrate they will dry up.

Since they dried up quickly, there would not sticking to each other and temparature increase ( in this case we assumed that it resulted in together vegi oil drying and cobalt conteted opv together) and ship to the customer safely.

If you will apply as flexo, then ask flexo version as matt.

one more gain to use water based, since oil based opv reacts very hardly resulting in excessive smell, now it will eliminate also this extra smell which might disturb some sensitive customers.

I hope these will help.

Regards,

Engin

 

[cementary]

Thank you for extensive answer.
The first thing our supplier told us upon arrival – that's paper problem!
We specify that problem occured on different papers.
After that supplier told us that we need to use aquos coating. We remind him that there is only one press in our shop with coating tower. And i ask if there is a water based varnish to apply from ink duct. The answer was – yes, there are such varnishes but they are very agressive to equipment (rollers, blankets etc) and we'll need an extra spray to apply on rollers.

PS supplier come also to consider our new-old chemical ghosting problem which increases after varnish is applied. And he bring an powerfull inner drier (monsun i guess) to mix with the varnish (which contain cobalt). I think something is wrong with logic.

 

[engin]

Thank you for extensive answer.
The first thing our supplier told us upon arrival – that's paper problem!
We specify that problem occured on different papers.
After that supplier told us that we need to use aquos coating. We remind him that there is only one press in our shop with coating tower. And i ask if there is a water based varnish to apply from ink duct. The answer was – yes, there are such varnishes but they are very agressive to equipment (rollers, blankets etc) and we'll need an extra spray to apply on rollers.
For the agressiveness, now understand, is quick drying on the rollers, but the formula hould be ajduted accordingly otherwisw will not be used as a duct varnish, to aid this you can ask them to supply to you a glycol type retarder which reduces the drying speed on the rollers before it reaches to the subsrate.
PS supplier come also to consider our new-old chemical ghosting problem which increases after varnish is applied. And he bring an powerfull inner drier (monsun i guess) to mix with the varnish (which contain cobalt). I think something is wrong with logic.

Monsun is containing permanganate type salt which is called as water active dryer ( which is co-dryer of oil based foils inks and IML inks), when comes into contact with water ( here the varnish absorbs water while on the plate by 15-20 %) and this water acts with the permanganate compound to release extra oxygen while the pile is there and this excessive oxygen accelarates the drying mechanism with the cobalt octeate in the varnish.

Normally, water active dryers are added into the inks as a co-dryer if the final usage will be on a non-absorbant subsrate like al foils, plastic films like IML application etc.

regards,

engin

 

[engin]

Thank you for extensive answer.
The first thing our supplier told us upon arrival – that's paper problem!
We specify that problem occured on different papers.
After that supplier told us that we need to use aquos coating. We remind him that there is only one press in our shop with coating tower. And i ask if there is a water based varnish to apply from ink duct. The answer was – yes, there are such varnishes but they are very agressive to equipment (rollers, blankets etc) and we'll need an extra spray to apply on rollers.

PS supplier come also to consider our new-old chemical ghosting problem which increases after varnish is applied. And he bring an powerfull inner drier (monsun i guess) to mix with the varnish (which contain cobalt). I think something is wrong with logic.

For the agressiveness, now understand, is quick drying on the rollers, but the formula should be ajdusted accordingly otherwise will not be used as a duct varnish, to aid this you can ask them to supply to you a glycol type retarder which reduces the drying speed on the rollers before it reaches to the subsrate.

 

[cementary]

And here we go again.
So same problem (2 orders, big ink coverage etc. – just like 1st post) BUT no varnish and same 60 degrees in the pile after sewing textblocks. Pages ticked together so that's more a "brick rather block"
Just ink. Futhermore, the ink – Resista – is the same we've been using for almost 5 years (well the mark is changed: it was Resista F 50 RS, now it is Resista RS 250, but our supplier assured us that that's same ink)
The only thing that has changed is our fountain solution.
Was Wassertop 3.0, now – Substifix HD

I need help again – is there a possibility that fountain solution could accellerate oxipolimerisation? If yes, what's the mechanism of that?
And maybe there are huber guys at printplanet who can explain the difference f50rs and rs250?

PS – ph was ok (4.9-5.1) IPA around 5%. Water – reversed osmos. Dampening system 2 days after cleaning. No additional siccatives.