A polyester resin composition is calendered to produce a film or a sheet. The polyester resin composition is a polyester having a crystallization half time from a molten state of at least 5 minutes combined with an additive for preventing sticking of the polyester to calendering rolls.

Polyester resin compositions for calendering

SUMMARY In a forward-roll coating gap or nip, steady laminar flow of liquid between counter-rotating cylinders or rolls is used to split the flow into a coated layer on one roll and a rejected layer on the other. Both layers have free surfaces in contact with air. Liquid may be carried into the gap as a layer on one or both rolls. If the arriving layer is not too thick, all of the liquid flows through the gap, a situation called pre-metered. If the arriving layer is too thick, part of the liquid is rejected and runs back down the lower roll. The flow rate through the gap is said to be metered and is not known a priori. The transition from a pre-metered regime to the metered situation was examined by solving the Navier‐Stokes system for steady, two-dimensional flow in a domain bounded by free surfaces, two rigid roll surfaces and chosen inflow and outflow surfaces. The free boundary condition, as described by Papanastasiou et al. (Int. j. numer methods fluids, 14, 587 (1992)), was explored and proved to accommodate both the pre-metered and metered regimes. A run-back flow state across the synthetic inlet plane was obtained, provided a condition on the thickness of the arriving layer was replaced by a kinematic condition at a certain stage. The coupled equation system was solved by Galerkin’s method with finite element basis functions. The resulting non-linear algebraic system was solved by Newton’s method with initialization by pseduo-arc-length continuation and automatic parameter step adjustment. Results show the existence of multiple solutions which can lead to hysteresis. Flow regime maps were constructed to portray the operating parameter range in which a coating bead can exist and the ranges in which a coating gap operates in either the pre-metered or the metering regime. 1997 by John Wiley & Sons, Ltd. Int. j. numer. methods fluids 24: 813‐831, 1997.

Multiple states of a viscous free surface flow: transition from pre‐metered to a metering inflow

According to Griffin1 the word ‘calender’shares a common Greek antecedent with ‘roller’, and the first recorded reference to calendering appears to be a description, in an 18th century publication, of a smoothing treatment for textile fabrics, carried out by means of individually operated, weighted rolls. The multi-roll machine of the general type still represented by the modern calender, was developed for the processing of rubber around the mid-1800s.

W. V. Titow

Papers

Calendering of PVC