US 5,746,961 AGranted

Method for enhancement of the surfaces of molded plastic products

AssigneeMichael J. Stevenson

InventorsMichael H. Stevenson, Robert A. Reeves

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Abstract

An enhancement composition and a method for its use in a molding process. The enhancement composition is applied to the interior surfaces of the mold cavity used in a molding process such as blow molding, injection molding, thermoforming or rotational molding. The enhancement composition is applied prior to closing of the mold and molding of the plastic article. The enhancement composition comprises a liquid carrier containing up to about 50 weight percent of enhancement solids which comprise a mixture of an enhancement solid such as particles of varied thermoplastic and thermosetting resins, metal flakes, glass beads, carbon, graphite, etc., and a binder solid which can be a hydrocarbon resin, wax, rosin or terpene base resin. The invention provides for almost unlimited modification of the surfaces of molded plastic products, offering the plastics fabricator the ability to mold products having very specialized surface properties with a low cost structural polymer, e.g., a product molded of low cost, low density polyethylene having the surface characteristics of Teflon.

Claims21

Dependent claims

A method for enhancement of a surface of a molded product formed by molding polyethylene in a mold against a heated mold surface with a face having an intaglio pattern of a desired configuration for said molded product which method comprises;

a. coating at least a portion of said mold surface with an enhancement composition having mechanical and chemical properties consisting essentially of:
(1) 50 to 75 weight percent of a non-oleaginous liquid carrier selected from the group consisting of inert organic solvents and water;
and
(2) 25 to 50 weight percent of enhancement solids comprising:
i. 5 to 95 weight percent of particles of an enhancement solid selected from the group consisting of:
thermoplastic and thermosetting polymer resins;
metal flakes;
glass beads;
carbon;
graphite;
antistatic agents comprising quaternary ammonium salts and esters of fatty acids;
flame retardants comprising aluminum, phosphorous and boron compounds;
lubricants comprising hydrocarbon paraffins, metal stearates, fatty acids and fatty acid amides and esters, and aliphatic alcohols and polyols;
preservatives comprising copper, tin, antimony, ammonium, arsine, and phthalimide compounds;
and polyvinyl chloride heat stabilizers comprising lead, barium, cadmium, zinc, phosphorous, nitrogen, tin and calcium compounds;
and
ii. 95 to 5 weight percent of a binder solid selected from the group consisting of:
rosins, aromatic and aliphthatic hydrocarbon resins and waxes, and terpene base resins;
and
b. forcing polyethylene against said heated mold surface coated with said enhancement composition to mold said polyethylene into said desired product configuration of said molded product while mixing said polyethylene with said enhancement composition;
and
c. extracting from said mold, said molded product having an external surface possessing said mechanical and chemical properties of said enhancement solid.

19 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/566,906Filed 4 Dec 1995
Granted: 5 May 1998
Term ends: Not estimatedThe source records don’t support an estimate.

Classification24 codes

B05D 7/02
Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying…
B29C 41/003
Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor:…
B29C 41/06
Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould: about two or more axes
B29C 70/64
Comprising fillers only , e.g. particles, powder, beads, flakes, spheres: the filler influencing the surface characteristics of the material, e.g.…