posted December 08, 2003 01:12 PM               

Welcome to the single screw forum -what are you "setting" and "getting" as far as process parameters (screw speeds, melt temp & pressure, die/adaptor temps). Are you blending any additives into any of the layers? Are these(if any) being dosed in accurately?

posted December 08, 2003 10:11 PM               

All of the resins you are using will potentailly suffer from thermal degradation due to shear heating. LLDPEs are known for a lack of shear thinning, and fractional melt has high viscosity and will shear heat. Your melt temperatures seem high which would validate this statement. By what technique are you getting the melt temperatures? Be very specific.

posted December 09, 2003 11:31 AM               

Also please consider that the types of resins you are using can produce momentary temperatures of 1000 F. Please check the degradation temperatures of your additives.

posted December 10, 2003 06:50 AM               

A Mass Spec GC can identify what these odors are. From this, you should easily single out the culprit(s). Your material's supplier may do this for you at no charge. It is a serious issue, so don't wit for to many other replies.

posted December 11, 2003 03:31 AM               

Tom and Ken have given you some avenues to check out, if you have any static mixing sections lurking in any of the adaptors of your line, these can have dead spots and cause material to degrade.

Have you stripped your die, adaptors and pulled the screws lately.

posted December 11, 2003 11:30 PM               

I don't know much about the chemistry used in resin production, but this seems like one of those items that needs to be deactivated in the resin reactor.

Given that your melt temperature tranducers are not in the melt stream, yet show high melt temperatures, I would bet your real melt temperatures are even higher still. It is hard to say whether the high melt temperatures have anything to do with the smell.

It is likely that:

A resin supplier screwed up and gave you bad resin.

A change in process conditions or screw design will help produce a higher quality product.

The adaptors, manifolds, and die need a good cleaning.

Tom C

posted December 13, 2003 05:18 PM               

quote:

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Originally posted by Tom C:
Given that your melt temperature tranducers are not in the melt stream, yet show high melt temperatures, I would bet your real melt temperatures are even higher still. It is hard to say whether the high melt temperatures have anything to do with the smell.

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posted December 13, 2003 09:48 PM               

Mercatone can be smelled in very low concentrations. It was mentioned that the product did not smell for a couple of days after production. It is likely that when extruded the mercatone near the product surface is quickly devolitilized at the surface and then the mercatone in the center needs some time ot diffuse to the surface.

The problem shows up intermitently. My guess would be that the reaction needs only a small amount. A slight deviation from that amount, or poor distrbution of the mercatone could result in product that smells. In that case when one opens the package of new resin the problem should be quite evident, unless pumped into a silo.

Having been in production for a long time, I know that these kinds of problems occur every day. I often think it is a miracle that anything gets produced with any kind of quality or consistency in the plastics business. Sounds like a whole new topic starter.