Other

Michael Stevenson & Kathleen Stevenson

Robert Alan Reeves

Michael J Stevenson

Matthew Stevenson

Corey R Dibrom

Darren Gemmill

Michael H Stevenson

Methods, apparatus and system for decorating plastic articles having an uneven surface or hollow structure are disclosed. An assembly comprising a transfer pad and a flexible heat transfer die comprising a thermal interface material (TIM) replace the hard rubber die in a hot-stamping process to fuse indicia into the surface. The assembly modifies ordinary pad printing into a hot-stamping process that transfers indicia onto uneven surfaces. A pad printing machine or other robotics is used to move the assembly from a position of heating to a position of compressing the ink transfer to the surface of the article.

Method of applying indicia onto a surface of a plastic article

Flexible heat transfer die comprising a thermal interface material

Methods and systems for decorating molded plastic articles having uneven surfaces or hollow structures

This invention comprises a self-supporting, temperature-stable, indicia-bearing laminate of at least one layer of a non-oriented polyolefin film having an indicia array and a layer of a non-oriented polyolefin support film. The indicia layer laminate is formed by printing a carrier sheet with at least one layer of a printing ink comprising a mixture of particulate polyolefin, indicia material and a polyolefin-compatible resin. The polyolefin support film is printed as a layer over the indicia layer with a mixture of a polyolefin and a polyolefin-compatible resin. The printed layers are cured into non-oriented films, forming an indicia transfer. The transfer is used by removing the indicia-bearing laminate from the carrier sheet and applying the laminate to the inside surface of a rotational mold where it melts and fuses into the outer wall of a polyolefin product during the formation of the product in the rotational molding cycle.

In-mold indicia marking of rotational molded products

The transfer of the invention is prepared by printing a layer onto a carrier substrate with an ink that comprises a mixture of finely subdivided polyethylene powder, an aliphatic or aromatic hydrocarbon solvent, a dispersing agent, and an additive material such as a dye or pigment indicia material and/or a physical property enhancing material such as alumina, glass beads, silica, metal flakes, etc. Preferably high and very high molecular weight polyethylene is used, alone or in mixture with lower density polyethylene in amounts from 25 to 45 weight percent in the ink. The printed layer is thermally treated to remove the hydrocarbon solvent resulting in a transfer having a carrier substrate coated with a printed layer consisting essentially of polyethylene and the additive material.

Printing ink, transfers, and methods of decorating polyolefin articles

The molding method of the invention is a low-temperature, liquid-phase, injection molding process using an externally heated mold. This molding process is ideally suited for production of limited quantities of molded parts, as comparatively low cost molds can be used. The molding composition used in the invention is a mixture of a carrier and binder component and a powdered polyethylene component. The carrier and binder component can be a very low density polyethylene, petroleum jelly, hydrocarbon waxes, liquid hydrocarbon oils, or mixtures thereof. The powdered polyethylene component is finely subdivided polyethylene, preferably ultra high molecular weight, having a low melt index, at least no greater than 30. The carrier and binder component is used in sufficient quantity to provide a thixotropic mixture with a consistency of toothpaste, typically having a stirred viscosity up to 30,000 centipoise at the injection temperature of the molding process. Since the process utilizes a mold which is externally heated, it can be controlled to provide minimal heating of the core of the part, thereby permitting one to incorporate components within the part without damage to temperature sensitive elements in the components.

Liquid low temperature injection molding process

The ink of the invention comprises a mixture of finely subdivided polyethylene powder, an aliphatic or aromatic hydrocarbon solvent, a dispersing agent, an indicia material additive such as a dye or pigment and/or a physical property enhancing additive such as alumina, glass beads, silica, metal flakes, etc. Preferably high and very high molecular weight polyethylene is used, alone or in mixture with lower density polyethylene in amounts from 25 to 45 weight percent in the ink. The polyethylene can have a particle size from 1 nanometer to 150 microns, preferably from 0.1 to 100 microns. The printing ink can be used to prepare a transfer having a decorative layer printed onto a carrier sheet. Various printing methods can be used to prepare the transfer such as gravure printing with etched or engraved chrome-plated or copper rolls; flexography printing with a flexible printing plate; and screen printing. The preferred method is screen printing. The printed layer is thermally treated to remove hydrocarbon solvent. The transfers are applied to the surfaces of molded polyethylene or polypropylene parts with adequate heat, pressure and time to fuse the transfers into the walls of the parts. For this application, the transfer is applied by a commercial hot-stamping, reciprocal press which heats the transfer to temperatures from 450&#xb0; F. to 650&#xb0; F., and compresses the transfers at a controlled pressure from 500 to 1000 psig. against a molded part, melting and fusing the transfers into the wall of the molded part.

This invention is an indicia transfer and method for its use to impart indicia to polyolefin objects during rotational molding. The transfer is a laminate of at least two, and preferably, three coats on a carrier sheet, which is preferably a flexible, transparent polymer sheet. The coats, as successive layers on the carrier sheet are: an optional backing coat of a backing-coat pressure sensitive adhesive, an indicia coat of a colorants in a graphic or alphanumerical array, and a top coat of a pressure sensitive adhesive. The pressure sensitive adhesive used for the backing coat has a transition melting temperature less than the surface temperature of the mold to which the transfer is to be applied while the top-coat pressure sensitive adhesive has a temperature sensitive adhesive which becomes tacky at the demolding temperature to enable transfer of the coats to the interior surface of a rotational mold. All the coats have melting temperatures which are less than the molding temperature to enable transfer and fusing of the transfers into the surface of the molded part.

Graphics transfers for use in rotational molding

A permanent, roughened or textured surface is applied to parts molded from polyolefins, particularly from polyethylene by applying to the surface of the part a coating mixture of a tackifier resin and polyolefin particles in a liquid carrier and incorporating a granular or particulate matter in the coating, either by application to the coating or by admixing the granular or particulate matter into the coating mixture. The coated surface is heated to the melt temperature of the polyolefin surface for a short time, sufficient to gel the polyolefin particles of the coating into the surface of the part, but insufficient to cause any thermal distortion of the part.

Bonding of granular materials to polyolefin surfaces

The polyethylene caulking composition of the invention is a mixture of a carrier and binder component and polyethylene powder. The carrier and binder component is a liquid hydrocarbon oil. The polymer is finely subdivided polyethylene, preferably ultra high molecular weight, having a low melt index, no greater than 30. The composition is thixotropic with a consistency of toothpaste, typically having a stirred viscosity up to 30,000 centipoise at ambient temperature, which is suitable for use as a caulking composition. The caulking composition of the invention can be extruded at low pressures through a caulking gun or from a squeeze tube to plug vent holes or perforations in molded, hollow-form polyethylene parts, or applied as a caulk onto the flange surfaces of rotational molds.

Polyethylene low temperature caulking composition

This invention is a method for the precise placement of indicia with high resolution into the wall of a hollow-form, molded plastisol part. The method includes the steps of preparing a plastisol graphic transfer by casting a base layer of plastisol onto a carrier sheet, printing indicia with pigmented plastisols onto the base layer of plastisol to form a graphic transfer, and over printing the graphic transfer with a body layer of plastisol. After each layer of plastisol is deposit, the layer cured by heating before depositing the next layer and the transfer is heated to cure the final, body layer. The transfer is applied to a selected inside surface of a conventional rotational mold by applying a high-solvent-content adhesive to the mold surface, stripping the plastisol transfer from the carrier sheet and applying it against the adhesive coated mold surface, and pressing the transfer against the adhesive-coated surface of the mold, permitting the applied transfer to dry over a short interval and then continuing with an otherwise conventional rotomolding or slush molding process to obtain a molded hollow form part having the indicia permanently fused into the wall of the part.

In-mold indicia printing of plastisol parts

This invention is an indica transfer and method for its use to impart indica to polyolefin objects during rotational molding. The transfer is a laminate of at least two coats on a carrier sheet, which is preferably a flexible, transparent polymer sheet. The coats, as successive layers on the carrier sheet are: an indica coat of indica material in a graphic or alphanumerical array and a top coat of a top-coat pressure sensitive adhesive. Preferably the transfer also includes a backing coat of a backing-coat pressure sensitive adhesive between the carrier sheet and the indica coat, The pressure sensitive adhesive used for the top coat has a transition temperature less than the mold surface temperature onto which the transfer is applied to enable transfer of the coats to the interior surface of a rotational mold. The pressure sensitive adhesive used for the backing coat has a transition temperature greater than the surface temperature of the mold to which the transfer is to be applied, and both pressure sensitive adhesives have transition temperatures which are below the molding temperature and preferably below the melt temperature of the molding polyolefin used to form the molded part.

A mixture of a carrier and binder component and polymer powders is provided as a molding composition for sealing rotational molds or for reinforcing selected areas of rotationally molded parts. The carrier and binder component can be very low density polyethylene, petroleum jelly, hydrocarbon wax, hydrocarbon tackifier, or mixtures thereof, and the polymer powders are thermoplastics having a low melt index. The molding composition is applied to selected areas of the rotational mold, such as to the mating flanges of the mold halves to seal the parting line of the mold, or to areas within the mold where it is desired to have reinforced regions of greater wall thickness, such as ribs or bosses.

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Cottonwood, AZ, United States of America

Robert Alan Reeves