This sounds like an easy one, but it's got us in a quandry.
     
     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 poly-pro, 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
     [log in to unmask]

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************