New Rare Problem. Yellow Stains on Bristol Laminated Board

Javier Martinez

New member
First of all sorry about my english.

This catalog were printed with conventional inks. The cover is an uncoated board (Bristol) with BOPP thermal lamination film and over the lamination some spot UV gloss coating.

Apparently the client store the catalogs in closed corrugated boxes but exposed to high temperatures. 3 months later when the client oppen de boxes the catalogs have some yellow stains.

My first impression was that there were some uncured coating that turns to yellow with as time passes.

Then I exposed one catalog to direct sunlight for about 4 hours an the yellow stains dissapear….

I don´t know what happend? Maybe a component of the fountain solution turns yellow? The lamination film adhesive?

Why this stains dissappear when exposed to sunlight?

I really hope somebody can give me some clues?

Javier Martínez
EPI Training
Mexico City
 

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Hello Javier


I have to say sorry about my English also.


I am BOPP Thermal Lamination Film producer myself.

We had similar problem with you in the past.

One problem was that our overall film (not just yellow stain spots) turned yellow over time.

Second problem was that outer part of the roll film turned red over time.

We exposed both roll films to direct sunlight for couple hours both yellow and red stains disappeared.


Based on your description, two possible cause and solutions came up to my mind.


The first possible cause is that your BOPP thermal lamination film are not "Virgin Grade".

Recycled film may have included certain substances that cause the yellow stain.

I have not found which substances that are recycled for BOPP film production actually cause yellow stain or red stain yet.

I will share with you when I find which substance actually causes the stains.

For this problem you may try using virgin grade BOPP film through discussing with your film producer.


The second possible cause is that your stains may have came from "Transition" of the film and paper.

Corona treatment on the film side (UV Coating side) allows "Transition" to the film from other matter that touches the film.

As your products are stacked in the box with certain pressure this may cause yellow stains on certain spot with higher pressure.

Although you have to use both side corona treated film for your Gloss UV Coating,

you may test one sided corona treated film with your products that does not need UV Coating under same packaging condition.


I hope this helps.

Brian Moon
JY High Technology
South Korea
 

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