Extrusion Coating Blog

Reply to Rakatin's comment

Hi, I’m a bit confused here, when a laminated 15 micron nylon/50 micron PE runs in our TRESIDE forming machine, powder will tend to build up on the triangle forming frame. But when using a thicker 70 microns PE with same materials and slip percentage, no buildups occurs.  With the case of the PP slip that you mentioned above, as thickness increase we have to reduce slip concentration, but in this case the thinner gauge tend to powder compared to the thicker gauge.  DO I NEED TO TEST THE COF VALUE OF THESE 2 FILMS?

p.s we are planning to get either extrusion coating machine or extrusion lamination machine. would you give me an idea what the difference between this two process. Actually we want to laminate printed OPP to VMPET without the bubbles problem, that’s why we are considering this process. What the best process for our requirement.

Thanks,  Rakatin

The Value of an Annual Rate Check

Hello,  This posting is from Beth Foederer of Optex Process Solutions and represents a straightforward means of establishing and tracking screw wear and the potential need to repair or replace the screw in an extrusion process.  The method should be added to your annual maientience check of the extrusion system or in screws with high wear rates conducted at regular intervials to insure peak performance from your extrusion system and avoid an emergency rebuild and the associated lost production and potential decrease in product quality.

Sources and control of instabilities

In an earlier posting I said I would review potential source of pressure and temperature instabilities caused by the screws performance and due to process set point variations and offer some trouble shooting approaches to curing them.

In general surging, temperature and/or pressure variations, caused from the extruder will prevent you from having uniform gauge control because temperature and pressure variations result in output variations.  If you have the situation we described earlier, where there is no scanner, then use of the physical thickness measurements will likely not permit any meaningful stability in the thickness profile of the finished lamination or coating.  This is easily seen in systems where there is an inline scanner and in this case the gauge profile will appear to “float”.  Floating gauge is where each separate scan is different because it starts at a different average thickness due to the surging.  In an automatic gauging system this causes the gauge control system to hunt because there in not a time stable single to control.  This will also be true in the hand measured thickness profiles.  So for stable gauge control you must have stable discharge pressure and temperature from the extruder.

Reply to Hengky on CPP lamination

Dear sir,
We are CPP film manufacturer. One of our customer is having low bonding strength problem between LDPE and CPP on their product. The structure is OPP20/LDPE15/ALU7/LDPE15/CPP20. They used tandem extrusion lamination machine and coat the CPP film with primer offline. The primer used is polyethylenimine and the die temperature is 330 deg C. What can be the source of this problem? Can the CPP film be the source of this problem? Thank you and best regards.

Posted by: Hengky

Eldridge Replies,

Reply to Arun on how to do a tape adhesion test

Question:  How do I conduct tape test on coated BOPET film either acrylics/polyester/slip/A/S or polyurethane coating? Where I can find tape & its past to be applied prior to tape test? In India, we used to conduct tape test but I have forgot the test method & paste composition.
Pl reply me.
Thanks,

Arun oza.
SKC Inc.
Covington. GA USA

Eldridge Replies

Arun,  The best thing you can do is get the ASTM test for coating adhesion such as ASTM D3359-08 “Standard Test Methods for Measuring Adhesion by Tape Test” or F 2226-03, “Determining the adhesion of prints and laminating films”.  There are several test methods for tape adhesion which you will have to review to make the best choice for your particular product.  Go to www.astm.org put in “adhesion” in the search window and then scan the various standards.  Once you find the best standard for your case you can down load a copy for about $30 or go to a local engineering Library and check out the reference section to see if they have the ASTM standards there.

Troubleshooting Existing Feedpipes

Are you having processing problems with no idea where your gels are coming from?  It’s always a good idea to have the feedpipes checked (through the use of simulation) to see if the pipes are causing your problems.

This is submitted by 

Beth M Foederer (formerly Beth M. Wells)

Optex Process Solutions, LLC

Extrusion Stability

In my last submission I spoke about the need for understanding the extruder’s stability as an aid in determining if the simple thickness measurement technique outlined could be used to adjust the extrusion coatings TD thickness profile.  If the extruder is unstable in its output rate and melt temperature then it will not be possible to effectively adjust the TD thickness profile of the film exiting the die due to variations in output as a function of time.  This is because the die only transforms the shape of the material that is delivered to it but cannot effectively control the amount, condition or uniformity of the molten polymer delivered to it.    The condition and amount of the polymer melt is controlled by the extruder and more precisely the screw design which is generating the melt from the solid polymer feed to it.  The die functions as a choke to the polymer flow and the pressure drop in the die is controlled by the output level and melt temperature at the inlet to the die.

Gauge Control in Extrusion Coating

In several instances over the years I have had to work on extrusion coating lines which had no automatic form of thickness control.  The line was run with the added coating but no serious attempt was made to insure a uniform coating thickness was applied to the substrate.  For the most part this had been fine as far as the existing product requirements went, as there appeared to be no important needs or problem with things as they were.  However, this invariably changes when a new product is introduced or a new competitor is entering the market with a competitive product with higher quality and/or lower price. 

Where the old product was fine as things were, the new product typically has more stringent technical requirements, relating to the applied layer thickness and the status quo could produce a product with uniform properties.  Typically, the properties are good in some areas but poor in others and the variability has been traced back to coating thickness variability.  So, the question is how to determine that it is the coating thickness variability and how do we establish some sort of control while we determine what upgrades to procedures or equipment will be needed?

TD scratches in metallized OPP/poly/OPP lamination

Chemy asked a question about some TD scratches he is experiencing with a Polyethylene lamination of Metallized BOPP and Heat sealable BOPP film. HE says there is no crazing of the metal but that there are transverse direction scratches (not machine direction ).These scratches are very regular 2-4mm width (spacing) and as thick as a hair . He wonders if it's the elongation effects of BOPP and a mismatch with the elongation of the Aluminum layer.

Paper Poly applications

Hello, earlier in this space I promised to generate some cross sections of paper/poly/paper and paper/poly laminations and coatings.  But spending some time looking for them it is apparent that there are few applications readily found.  So far I have freezer paper, instant oatmeal, maybe M&M Peanuts and hot cocoa. 

So where are the applications where these structures are still being used?  Send me an e-mail with examples which you make or send a small sample so I can try to make some cross sections.  Then I can also comment on my experiences getting good pictures as a way of examining the products.

samples (SMALL please, say several sheets of 8.5x11 inch or a few square feet) can be sent to:

EMMOUNT Technologies

88 Country Downs Circle

Fairport, NY 14450