Patent ID: 11964452
Assignee: SOLUTIA INC.
Field: Surface technology, coating (Chemistry)
Classification: CPC B | IPC B

Claim 7:
8. A process for making an interlayer having improved gradient quality, the process comprising the steps of:
(a) providing a sheet extrusion die having an orifice and a manifold adapted to feed a polymer melt to the orifice by way of an extrusion passage;
(b) providing a probe located within the manifold and adjacent the extrusion passage wherein the probe has in the surface adjacent the extrusion passage an extrusion orifice that extends parallel to the probe axis and wherein the probe is located in such a position that, when a main flow of a thermoplastic polymer is fed into the manifold and extruded through the slit die by way of the extrusion passage, the stream lines of the main flow as it passes by the probe orifice are substantially parallel and in the direction of extrusion;
(c) feeding a main flow of molten thermoplastic polymer to the manifold and a colored secondary flow of the molten thermoplastic polymer, at substantially the same temperature and viscosity, to the probe;
(d) extruding both flows simultaneously such that a layer of colored polymer that is constant in width but tapering in thickness at one extremity of its width, is completely encapsulated in the main flow of molten polymer; and
(e) extruding the combined flows through the slit die to produce a sheet with an encapsulated gradient color band portion, wherein the gradient color band portion has a cut-off X at the start of the gradient color band, a point Y where the % transmittance of the gradient color band is 40%, a point Z where the % transmittance of the gradient color band is 70%, a distance D that is the distance from X to Y and a distance d that is the distance from Y to Z, and wherein the distance D in the gradient portion meets the following equations: 22.9 mm<D<38.1 mm and D/d<2.00.