The invention relates to a process for making an opaque and glossy film from a thermoplastic polyester composition, comprising the steps of a) extruding the polyester composition through a slot die, and quenching to form a substantially amorphous film having a crystallinity of at most 5%; b) rapidly heating the amorphous film to a drawing temperature in the range from T.sub.g to (T.sub.g+50) C. while applying a draw ratio in the range of from .sub.initiation to .sub.max. in longitudinal direction, and a drawing rate of at least 1 m/min to form an oriented film showing stress-whitening, wherein .sub.initiation is the draw ratio at which a transfer from a transparent product to a stress-whitened product occurs and .sub.max. is the draw ratio at which failure of the stress whitened film occurs; and c) heat-setting the oriented stress-whitened film; the thermoplastic polyester composition substantially consisting of at least one crystallizable polyester derived from at least one aliphatic diol and at least one aromatic dicarboxylic acid. With this process it is possible to make a unitary, glossy, opaque film from a polyester composition that does not contain void-forming additives like high amounts of fine pigment particles or dispersed non-miscible polymer particles. The film obtained also has very good mechanical properties. It is a further advantage that the process can be performed continuously on conventional extrusion and stretching equipment used for making transparent film from polyesters. The invention also relates to an opaque polyester film obtainable by said process.

A process and associated system for creating color effects using extrudable material, such as plastic and metal for example, are presented. Flows of first and second viscous materials of respective colors are provided and then combined in a predetermined pattern to form a stream of combined viscous material. In a first aspect, the flow rate of the first viscous material is caused to vary over time in order to vary an amount of the first viscous material in the stream. In a second aspect, which may be used alone or in combination with the first aspect, the first and second viscous materials have distinct viscosities to reduce an amount of color blending between the first color and the second color in the stream of combined viscous material. A static mixer may then be used to apply a predetermined dividing, overturning and combining motion to the stream of combined viscous material to partially mix the first viscous material and the second viscous material, such that upon exiting the static mixer, the first material of the first color and the second material of the second color form a color pattern in the stream of combined viscous material. Sheets of extrudable material may be created using such process and used in the manufacturing of many different products including for example kayaks and stand-up paddle boards.

Flows of first and second viscous materials of respective colors are provided and then combined in a predetermined pattern to form a stream of combined viscous material. A dynamic mixer is the then used to apply a predetermined dividing, overturning and combining motion to the stream of combined viscous material to partially mix the first viscous material and the second viscous material, such that upon exiting the dynamic mixer, the first material of the first color and the second material of the second color form a color pattern in the stream of combined viscous material. The dynamic mixer has elements configured for acquiring a specific radial orientation in a range of radial orientations that may be varied during the application of the dividing, overturning and combining motion to the stream of combined viscous material to cause variations in the color pattern in the stream of combined viscous material.