Mechanical stress crystallization of thermoplastic polymers
AssigneeAgri-Nutrients Technology Group, Inc.
InventorWilliam P. Moore
Life of this patent
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Abstract
A method of crystallizing particles of amorphous thermoplastic polymer particles in a mechanically fluidizing horizontal cylindrical crystallizer so that each particle is crystallized to substantially the same degree without particle agglomeration or stickiness in the crystallizer or the product. The method comprises mechanically fluidizing the particles with fluidizing blades providing mechanical friction, heat, and deformation stress until the stress orients the polymer molecules to form polymer crystals. The method is particularly useful with polyesters, polyester copolymers and low melting blends thereof. A new crystallized polymer composition prepared by the mechanical stress method is disclosed.
Claims25
A method of crystallizing particles of amorphous thermoplastic polymers in a mechanically fluidizing crystallizer which provides heat and mechanical stress to the polymers sufficient to crystallize the polymers without agglomerization of the polymer particles in the crystallizer, the method comprising:
- (a) mechanically fluidizing amorphous thermoplastic polymer particles in a cylindrical crystallizer by means of fluidizing blades moving around, and in close proximity to, the inner perimeter wall of the crystallizer;
- (b) moving the fluidizing blades around the inner perimeter wall of the crystallizer at speeds which cause mechanical friction between the polymer particles and the wall of the crystallizer, the fluidizing blades, and other polymer particles, the friction providing heat and mechanical stress on the polymer particles by deforming them;
- and,
- (c) maintaining the mechanical stress on the polymer particles at temperatures exceeding the crystallization temperature of the polymer until sufficient stress is provided to align the molecules of the polymers into crystal lattices, forming crystallized polymer particles without agglomeration of the particles in the crystallizer.
A stepwise method of crystallization amorphous polyester polymer particles in a mechanically fluidizing horizontal cylindrical crystallizer without stickiness in the crystallizer, the method comprising:
- (a) mechanically fluidizing amorphous polyester polymer particles in a horizontal cylindrical crystallizer by means of fluidizing blades moving around, and within between 1 and 30 millimeters of the inner perimeter wall of the crystallizer;
- (b) moving the fluidizing blades around the inner perimeter wall of the crystallizer at speeds between 2 and 12 meters per second to cause mechanical friction between the polymer particles and the wall of the crystallizer, the fluidizing blades, and other polymer particles, the friction providing heat and mechanical stress to the polymer particles by deforming the particles until the stress orients the polymer molecules in the direction of the stress to form polyester polymer crystals;
- (c) adding heat, or cooling, as needed for the crystallization by contact heat transfer through the inner wall of the crystallizer to regulate the temperature of the wall of the crystallizer to within 30° C. of the temperature of the polymer particles;
- (d) maintaining the mechanical friction for a period of time between 5 and 200 minutes until sufficient mechanical friction is provided to the polymer particles to generate polymer particle temperatures exceeding the polymer crystallization temperature by between 10 and 50° C. and sufficient stress is provided to orient the polymer molecules so that the particles contain 20 and 80 percent crystals;
- and,
- (e) cooling the crystallized polyester polymer particles to ambient temperature.
Dependencies are inferred from the claim text.