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Laying up laminates using PVA glues

A quick guide to applying high-pressure laminate with PVA glue. September 26, 2000

Q.
I've seen many articles on using PVA adhesives with high-pressure laminates (HPLs) lately. How exactly is the PVA applied, and what is pinch rolling? I'm assuming a cold press is a large flat press that applies pressure to the HPL evenly across the face, without heat.

A.
In this kind of operation the adhesive (usually a plasticized PVA or a modified EVA) is applied to the core with an industrial glue spreader. The core is then placed on a backer, and the laminate is placed on top. Then the whole construction is run through a pinch roller, which is similar to a spreader but without glue or doctor rolls.

The pressure from the pinch roller, coupled with the tack of the adhesive, is enough to keep the pieces in intimate contact while the adhesive dries. This is generally a quicker, more cost-effective way to produce a quantity of HPL panels, versus other methods.

Your understanding of a cold press is accurate.
Jeff Pitcher - technical advisor



PVA adhesives are available in two forms. Fast-tack types are used with a pinch roller, while standard cold-press types would be used in a cold press.

The decision drivers for you are cost and volume of similar sizes. Panels made with a fast-tack PVA are ready to cut after an hour of dead stack time, while the cold-pressed panels would remain in the press for about 45 minutes. So, time is not much of a factor.

Glue-line cost for fast-tack PVAs is now about 5 to 6.5 cents per square foot, while cold-press would have a glue line cost of about 3.5 cents per square foot.

Maybe the most important question in your decision whether to use a nip (pinch) roll or a cold press would be the variety of panel sizes. If you are almost exclusively running 4-by-8 or some other standard size, the cold press is the best solution, while if you will run many different-sized panels or irregular shapes in small quanities, a nip rolled fast-tack may be the most effective for your operation.

You can find a great deal of information about the equipment used to apply the adhesive, and on nip rollers and cold presses, from Black Brothers.

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