Aqueous Coatings

[sabarish.ramanunni]

WE HAVE A CUSTOMER USING AQUEOUS COATINGS OVER 5 COL PRINTING. wHENEVER THERE IS A SOLID PATCH OF INK ON THE PAPER, THE WATERBASED COATING IS ABSORBED AND IT CREATES A MINUTE PATTERN ON TOP OF THE INK.
ITS LIKE A NEAT LAID EFFECT ON THE PRINT. AFTER SOME TIME THE INK IS GETTING ON TO THE ANILOX ROLLER ALSO. HOW COULD THIS BE OVER TAKEN?
THE VISCOCITY OF THE VARNISH IS 45 SECS.

 

[turbotom1052]

try running more coating!!!!!

 

[sabarish.ramanunni]

how to do that

how to do that

How to apply more volume in a coating unit?
Do he have to change the anilox or can the doctor blade be adjusted

 

[The Heidelberg Guy]

We call it "mud cracking", the coating is drying too fast on top of a heavy build (try to stay under 320% total overall coverage).

Make sure the coating is at least 20 seconds (Zahn#3)
Turn the IR's down, along with the hot air knives
Speed up the press
Increase amount of coating (if you have an adjustible coating system)

Tim

 

[RJ Litho]

The Heidelberg guy has the correct definition and a possible solution.First talk to your coating rep he will supply you with a different product for this issue .You could add glycol to your coating it will slow the drying down. I have have used a Prisco product alkaless P .Best option change you coating ..

RJ

 

[canadian printer]

coating

coating

Run your coating thinner about 23 sec . Talk to your coating supplier. Up in Can in the winter we have had coating come in that had gotten partly frozen and grief insued. Also if getting low in the barrel coating may go funky on you. We have both Analox and two roller system. Analox is pretty much turn on and go. Prefer Analox system smoother coating less hassle. Check your dryer setting also.

 

[sabarish.ramanunni]

thanks a ton guys,
Now i have something to do at the customer place.
Let me try all your suggestions and will post back!

 

[Sureseal Tech]

Hi guys, From a technical point of view it may be one or two things. The coating possibly needs more wetting agent in it as it could reticulating over the heavy ink areas. Otherwise it may be crazing (cracking) over the heavy inked areas and this means it could need a softer polymer as well (lower Tg glass transition temperature). With your problem I'd possibly run with a different coating. Be careful not to go too thick as this can create it's own problems such as orange peel. Best of luck. JT.

 

[sallak]

hi guys
got GTO52
can i use it to apply acqueous coatings on paper? any special preparations required. as we use this GTO for 4 colour printing as well would it be a problem to keep switching from inks to coating every now and then?.

 

[Cornishpastythighs]

hi guys
got GTO52
can i use it to apply acqueous coatings on paper? any special preparations required. as we use this GTO for 4 colour printing as well would it be a problem to keep switching from inks to coating every now and then?.

I would think one of the first things you would need is a aqueous coater unit. Dont know of anyone who is putting waterbase coating down with a print unit, next you will need a hot air dryer. Maybe I have misunderstood your question and the capability of a GTO52

 

[sallak]

thanks for reply
seems it costs too much to add those two units

 

[Robilious]

Geeze, sorry I'm Late?

Ok, I'm suspecting the Viscosity reading was taken with a "#4 DIN Cup", and NOT a "#3 Zahn Cup". I suspect this, because the press likely came with it, and other than North America, the "DIN Cup" is likely the most popular. (Pretty much every Heidelberg delivers with some variation of "DIN" cup)

I have a listing of approximately 37 variations of "Centipoise", which is the technical family that the Viscosity measuring devices (cups) belong to. (Norcross Corporation - Viscosity Control, Viscometers, pH Sensor, pH Controller) Therefore, the Viscosity Reading of 45 seconds DIN is approximately 23 seconds Zahn. So, Viscosity is "likely" ok. To increase coating with an annilox roller you have to change the annilox roller. Chances are pretty good that the Vendor who sold the press ensured the correct Annilox roller was installed based upon the type of work this press is printing, so, likely doesn't need changing. If the "pattern" on the Solid ink areas of the press sheet does infact look like Mud Cracking (pretty simple, looks like a dried up pond bottom) then the coating is likely drying too quickly. However, Ink getting into the annilox roller is quite "special"?! Likely ink buildup on the coating blanket, which is contaminating the press sheet? Since, the word "Ink" is used in almost every reply to Sabarish's question, it would be good to know what kind of ink it is? My suspician is Ink itself or Ink/Water balance Problem.

Regarding Sallak's question, YES! You can use Aqueous coating on your GTO52. Without adding a Coating Tower. There are many "ink train coatings" available today. Coating is used in the last unit's ink train. The water form is disengaged, and coating is transferred from the ink form rollers to the blanket. Look on the internet for Kentucky Shine, ESI Generation 3, Kelstar Actega, etc.

 

[sallak]

Geeze, sorry I'm Late?

Ok, I'm suspecting the Viscosity reading was taken with a "#4 DIN Cup", and NOT a "#3 Zahn Cup". I suspect this, because the press likely came with it, and other than North America, the "DIN Cup" is likely the most popular. (Pretty much every Heidelberg delivers with some variation of "DIN" cup)

I have a listing of approximately 37 variations of "Centipoise", which is the technical family that the Viscosity measuring devices (cups) belong to. (Norcross Corporation - Viscosity Control, Viscometers, pH Sensor, pH Controller) Therefore, the Viscosity Reading of 45 seconds DIN is approximately 23 seconds Zahn. So, Viscosity is "likely" ok. To increase coating with an annilox roller you have to change the annilox roller. Chances are pretty good that the Vendor who sold the press ensured the correct Annilox roller was installed based upon the type of work this press is printing, so, likely doesn't need changing. If the "pattern" on the Solid ink areas of the press sheet does infact look like Mud Cracking (pretty simple, looks like a dried up pond bottom) then the coating is likely drying too quickly. However, Ink getting into the annilox roller is quite "special"?! Likely ink buildup on the coating blanket, which is contaminating the press sheet? Since, the word "Ink" is used in almost every reply to Sabarish's question, it would be good to know what kind of ink it is? My suspician is Ink itself or Ink/Water balance Problem.

Regarding Sallak's question, YES! You can use Aqueous coating on your GTO52. Without adding a Coating Tower. There are many "ink train coatings" available today. Coating is used in the last unit's ink train. The water form is disengaged, and coating is transferred from the ink form rollers to the blanket. Look on the internet for Kentucky Shine, ESI Generation 3, Kelstar Actega, etc.

Thank you very much for your help
my GTO52 is single head, hope that would work fine with us

 

[Robilious]

From the ESI (Now a part of Nicoat) Data Sheets:

GENERAL WET ON WET APPLICATION

1. Generation III Ink Train Coating dries quickly. The top sheet will dry in 2-4 minutes and the stack will dry in approximately 10 minutes. Drying can be improved by the use of a hot air knife positioned before the spray powder unit.
2. Coating film thickness can be regulated through the use of your ink keys and sweep control. Maximum gloss is achieved by applying a greater film thickness. A hot air knife will assist in drying a heavier film thickness. Typical ink key settings are very similar to varnish settings.
3. The coating dries with air, not heat. If the press has an IR Dryer, it should not be turned on. If the IR Dryer has fans or an air knife associated with it then you can run the IR Dryer at the lowest possible temperature to kick on the fans. The Stack temperatures must be kept below 85°F.
4. Spray powder at a minimum (start out at about 2/3 your normal level). When applying a heavier film thickness, or coating the second side of a work and turn job, apply a greater amount of powder. The powder diameter should be 30-35 microns. A silicone encapsulated powder give higher set-off resistance.
5. Spot coating can be achieved by using Easy Lac, a Cyrel plate from Du Pont, or the Technoplast coating blanket. Pressure between the plate/blanket and blanket/substrate should be kept to a minimum. If an overall coating is to be applied, the blanket packing can be cut to the size of the print area desired, or for improved release and higher gloss Easy Lac or Technoplast can be used. Please call us for information on Easy Lac or the Technoplast coating blanket.

MAKE READY FOR COATING

1. Empty and clean the ink fountain, spray the cleaned fountain with light spray of retarder.
2. Clean ink off the rollers using your normal press wash. Then clean the rollers with Roller Shampoo to take any remaining ink pigment out of the pores. (Note, the Roller Shampoo can also be used to clean and deglaze rollers as a weekly roller cleaning maintenance).
3. Check rollers for a narrow stripe (3/16"). If possible, raise the dampener rollers off the plate (or turn the dampener off). You don't want the water forms to cycle in to hit the plate.
4. It is important to have light pressure between the plate and blanket cylinders and especially between the blanket and the impression cylinder. It is best to use a quick release conventional blanket or a polymer based coating blanket.



5. Your inks should be resistant against alcohol and alkaline. This is especially critical with metallic and fluorescent inks. Two pigments which are not alkaline resistant are reflex blue and rohdamine red. Ink should be low or no wax to maximize coating film adhesion. Ask your ink company for coatable inks.
6. Always cut blanket packing to match only the areas you want coating to cover. This prevents accumulation of coating on the impression cylinder and all of the non-printing areas.
7. After color make-ready has been completed on your printing units, put the coating into the ink fountain, set fountain to "Ink Up Rollers". Do not add any water. Spray the rollers and blanket with Retarder 1900.23. You are now ready to start coating. If the press is in a frequent start-stop mode (color OK or Feed Problems), it is recommended that you stop the press completely between sets or during a short color OK.

RUNNING THE COATING

1. Initially at start-up, apply a slightly higher thickness of coating. Coating can be controlled via the ink keys. Be sure to get enough coating down the ink train. Bring press up to speed gradually, especially when running light stocks. Too much coating will appear as an orange peel look on the coating film.
2. If you are running a narrow sheet, reduce the amount of coating being applied to the end of the rollers, and occasionally spray a little Retarder 1900.23 on the ends of the rollers to keep the coating open. Other techniques are available for long runs.
3. If you stop the press in the middle of the run:
a. Spray the rollers with a mist of Retarder 1900.23.
b. Wash the blanket and plate with warm water.
4. If you stop the press for more than 20 minutes:
a. Spray the rollers with a mist of Retarder 1900.23.
b. Spray the fountain with Retarder 1900.23.
c. Wash rollers, plate and blanket with warm water and also apply a light mist Retarder to rollers.

PRESS WASH UP PROCEDURE

1. At the end of the run:
a. Wash roller with a wash consisting of 50% Retarder 1900.23 and warm
water
b. Wash blanket and plates with warm water.
c. After the coating is off the rollers, give them a final cleaning with Roller Shampoo to remove any coating left on the pores of the rollers.