The move comes less than six months after Ice re-emerged from administrative receivership in an MBO (PrintWeek, 25 May).
Sullivan is understood to have suffered a period of ill health which led to his decision. In a statement CPG said that all Ice personnel would join its subsidiary Holman Kelly Paper with immediate effect.
Kelly will now be based at CPG's site in Aylesford, Kent. Former Ice Paper director Kevin O'Sullivan has been appointed to head CPG's management team and will report to chairman Graham Goodwin.
Ice Paper went into administrative receivership on 13 May with insolvency and business practitioner Smith & Williamson appointed to oversee its affairs.