Joe,
Boy do I know how you feel. I had this problem in a former
(job) life. The original rollers were polypro which leaches in
acid solutions, like peroxide sulfuric. We had to go to EPDM
rollers, I think, in the acid and acid rinse modules to get away
from this. It took months to figure this one out.
My suggestion is get with the equipment supplier and get a
material which would not leach out in an acid environment. If
your equipment supplier cannot answer this, check with your
process chemistry supplier for an answer. Good luck.
Dave Sullivan
Rockwell Collins
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Subject: FAB: chemical-clean roller marks
Author: [log in to unmask] at ccmgw1
Date: 12/4/96 3:59 PM
This sounds like an easy one, but it's got us in a quandary.
The process is traditional peroxide-sulfuric chemical clean for
innerlayer cores prior to cut-sheet-lam (including a phosphoric-based
acid cleaner/chromate remover). The equipment is a new, horizontal
conveyorized line (wetted materials are: polypro, PVC, CPVC, EPDM,
304ss, 316ss and...). The problem: conveyor rollers leave visible
"tracks" on the layers which subsequently fail water-break test within
2 seconds on a clean coupon. The original roller material was
'santoprene' - a neoprene/polypro hybrid. Other mold trials from the
manufacturer have produced samples made of PVC (soft vinyl), hypalon
and rigid polypro, all of which leave marks to varying degrees. We
have tried various lab-scale leaching procedures on each of the new
roller material samples: 10% sulfuric (no effect), 15-20% NaOH
(leached out an oily residue - a plasticizer, we're guessing), toluene
(no effect), 50% sulfuric (basically complete destruction) - all
samples still produced tracks. Even after grinding a wheel down about
a millimeter, the residue persisted.
In the past, I have only seen previously used horizontal equipment
retrofitted for use as chemical clean lines with resulting matte pink,
uniform layers. Is it possible that in those cases, the wheels were
already 'broken in' after years of use elsewhere? If we enter into
production, will the marks eventually (gulp) disappear? Are we being
too finicky? Has anyone encountered and overcome a similar situation
on a new chem-clean process with new equipment? Responses from
equipment gurus out there is certainly welcome...
J Felts, PC World, Toronto
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Subject: FAB: chemical-clean roller marks
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