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Expiration date for aqueous coatings

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  • Expiration date for aqueous coatings

    My company has three large containers of Rycoline semi-gloss aqueous coating. They are rarely used on our Heidelberg CD 74 but we would still like to use them from time to time. Previous jobs on cover substrates have been successful but some text stock has been bricked in the delivery as well. This is likely due to our inexperience with using the AQ but I'm curious about expiration timeframes as well.

    Because they were produced in 2007, I was wondering if any problems can be caused by their older age and if it's possible for the AQ to expire or reach a point where newer is better to run. We would also be willing to get new containers for future jobs.

    Any input from your experiences would be greatly appreciated. Thank you.
    Last edited by jeffrbauer; 04-20-2010, 01:51 PM. Reason: proofreading error

  • #2
    I cannot say that I have ever used AQ coating that old but will offer my opinion, The coating should be ok as long as it has'nt been allowed to freeze and is stored in a fairly stable climate, It would be a very good idea to stir the coating every now and again to make sure the ingredients dont 'kick out' and before running it make sure it gets a really good mixing. Maybe you should get your coatings in smaller containers so the risk is less and then you could order your coating prior to running the orders ensuring that its 'fresh'


    • #3
      My first advice would be to stir the AQ coating really thoroughly, preferably with some mechanical mixer. Sedimentation is a big problem in any AQ coating, and specially one this old.

      My other advice would be to try to use as few IR drying as possible, with as much hot air as possible in the delivery. The trick is that you should have as much hot air coming in as air coming out your exhaust. If not, you will be just creating a "sauna effect" within your delivery. Also, the longer the delivery, the better. Oh, and try not to run the machine too fast, Start slowly and if you see good results, increase the speed.


      • #4
        Expiration of AQ and drying

        I formulate and assist printers with technical issues with aqueous coatings and UV coating and was asked to comment on this thread.

        I agree with JPK; stir the coating, especailly a satin or dull because the ingredients that make an AQ coating dull tend to float to the surface. JPK is also correct that you do NOT want to add too much IR (heat.) The key to successfully drying coating is to provide maximum dry air to the sheet - put the air knives on maximum you can and keep the maximum pile temperature at 105F first side, 95F second side. Pile temperature that are too hot may resoften the coating.

        There are three other things to look for -
        1) Viscosity creep -check the viscosity of the coating with a #3 Zahn cup before use. After 3 years it might have increased. The viscosity reading should be 18-22". If it is higher, add 1% of water to reduce by 4" or so. Don't add more than 1/2 gallon at any one time and re-check. After 3 years you might have to add as much as 1-2 gallons of water.

        2) Odor! If you open the drum and detect a milldew odor, call your coating representative and ask for some biocide before you run your job. Aqueous coatings are biodegradable and are subject to microbial attack after 3 years. Adding a little biocide will kill the bugs and eliminate the odor.

        3) Particulate/lumps. After you stir the drum, check for chunks or other particualtes you feel would cause a problem in your coater or recirculation system. Either mix longer, filter or discard the coating.

        The good news is that an unopened drum of AQ should last 3 years so long as you kept the drum indoors. If you spend an hour on 3 drums, you can save about $1500. Good luck.


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