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An inexpensive, cellular plastic mold and method of preparation, wherein the plastic mold comprises male and female mold elements which define a mold cavity therebetween, each of the elements comprising a rigid thermoplastic foam or cellular board material having a smooth, integral, solid layer of a

An inexpensive, cellular plastic mold and method of preparation, wherein the plastic mold comprises male and female mold elements which define a mold cavity therebetween, each of the elements comprising a rigid thermoplastic foam or cellular board material having a smooth, integral, solid layer of a plastic material forming the facing surface of the mold cavity and a relatively thick, solid, supporting layer of a plastic material forming the back surface of the mold elements.

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1. A method for the preparation of a rigid composite thermoplastic foam mold element of a multi-part mold comprising male and female mold elements, each mold element having a thermoplastic rigid foam body, a back surface, and a solid interior mold facing surface contoured so as to form in a closed m

1. A method for the preparation of a rigid composite thermoplastic foam mold element of a multi-part mold comprising male and female mold elements, each mold element having a thermoplastic rigid foam body, a back surface, and a solid interior mold facing surface contoured so as to form in a closed mold position a mold cavity to prepare a defined object by a molding process, which method comprises: (a) contacting under substantially continuous pressure with a heated die element one surface of a first rigid thermoplastic foam material to melt and deform the contacted foam portion of the rigid thermoplastic foam material; and (b) rapidly chilling the die element while maintaining the die element in substantially continuous contact with the thermoplastic foam material to form a thin, solid skin layer of the cooled thermoplastic foam material as a mold facing surface, which solid skin layer is integrally bonded to the underlying body of the rigid thermoplastic foam material, thereby providing either a male or female mold element of a multi-part mold. 2. The method of claim 1 wherein the rigid thermoplastic foam material comprises a polyethylene or polypropylene foam resin material. 3. The method of claim 1 wherein the thermoplastic rigid foam material has a foam density of from about 2 to 25 pounds per cubic foot. 4. The method of claim 1 which includes heating the back surface of the mold element to melt the thermoplastic foam material on the back surface and cooling the melted thermoplastic material of the back surface to form a solid, integrally bonded support layer of the thermoplastic material on the back surface. 5. The method of claim 1 which includes securing a solid thermoplastic sheet material to the back surface of the mold element to form a solid support layer on the back surface. 6. The method of claim 1 which includes: (a) inserting a thin, solid thermoplastic sheet material between the heated die element and the surface of the rigid thermoplastic foam material; (b) thermoforming the thin, solid thermoplastic sheet material with the heated die element and pressing the thermoformed thin, solid sheet material with the die element into contact with the surface of the rigid thermoplastic foam material to melt and deform the underlying portion of the rigid thermoplastic foam material; and (c) rapidly chilling the die element while maintaining the heated die element in substantially continuous contact with the thin, solid thermoformed sheet material and the rigid thermoplastic sheet material to form a thin, solid layer of the melted thermoplastic foam material integrally bonded to one surface of the thermoformed thin, solid sheet material with the other surface of the thin, solid sheet material forming a facing surface of the mold element. 7. The method of claim 6 wherein the thin, solid sheet material comprises a fluorocarbon resin or an olefinic resin, and the thermoplastic rigid foam material comprises an olefinic foam resin. 8. The method of claim 1 which includes placing a removable, thin, preformed, solid insert liner contoured to fit onto the facing surface of the mold element onto the facing surface of the mold element, the insert liner adapted to be removed from the facing surface after use of the mold element in a molding operation. 9. The method of claim 1 which includes: (a) preparing rigid composite thermoplastic foam male and female mold elements as prepared in claim 1; (b) placing the male and female mold elements in a mating closed mold position; (c) heating the back surface of the mated closed male and female mold elements while under pressure between heated platens to melt a portion of the back surfaces of the male and female mold elements to correct any bowing distortions in the mated mold elements; and (d) cooling the melted back surface of the male and female mold elements while maintaining the mold elements between the platens to form a solid back support layer of the melted thermoplastic foam material integrally bonded to the thermoplastic foam of the body of the mold elements on the back surface. 10. The method of claim 9 which includes placing a scrim-like mesh material onto the back surface of the male or female mold elements to embed the scrim-like mesh material into the solid cool back supporting layer of the mold elements to provide improved mold strength. 11. The method of claim 1 which includes rapidly chilling the die element by imersing the die element and the rigid foam thermoplastic material in a cool water bath. 12. The method of claim 1 which includes rapidly chilling the die element by circulating cooling water through the die element. 13. The rigid thermoplastic foam mold element prepared by the process of claim 1. 14. A method for the preparation of rigid composite polyolefin foam mold elements of a multi-part mold comprising male and female mold elements, each mold element having a rigid composite thermoplastic foam body, a back surface, and an interior mold facing surface contoured so as to form in a closed mold position a mold cavity to prepare a defined object by a molding process, which method comprises: (a) contacting under substantially continuous pressure with a heated die element one surface of a first rigid olefinic thermoplastic foam material to melt and deform the contacted foam portion of the rigid olefinic thermoplastic foam material; and (b) rapidly chilling the die element while maintaining the die element in substantially continuous contact with the olefinic thermoplastic foam material to form a thin, solid skin layer of the cooled olefinic thermoplastic foam material as a mold facing surface, which solid skin layer is integrally bonded to the underlying body of the rigid olefinic thermoplastic foam material thereby providing a male or female mold element; (c) repeating steps (a) and (b) with a second thermoplastic olefinic foam material to form a second mating mold element; (d) placing the male and female mold elements as prepared in a closed mold position and heating the male and female mold elements under pressure between heated platens, the back surfaces of the male and female mold elements heated to a temperature and for a time sufficient to melt a portion of the back surface of the male and female mold elements; and (e) and cooling the back surfaces of said male and female elements while under pressure between the platens to provide for correction of any bowing distortions in the male and female mold elements and to provide a relatively thick, solid, integrally bonded support layer of the solid thermoplastic cooled material on the back surface of the male and female mold elements. 15. A multi-part rigid composite foamed olefinic mold formed of the male and female mold elements as prepared in claim 14. 16. The method of claim 14 wherein the olefinic thermoplastic foam material comprises a polyethylene or polypropylene having a foam density of from about 4 to 25 pounds per cubic foot. 17. The method for the preparation of a rigid composite thermoplastic foam mold element of a multi-part mold comprising male and female mold elements, each mold element having a thermoplastic rigid foam body, a back surface, and an interior mold facing surface contoured to form in a closed mold position a mold cavity to prepare a defined object by a molding process, which method comprises: (a) inserting between the surface of a heated die element and the surface of a rigid thermoplastic foam material a thin, solid, thermoplastic sheet material; (b) contacting one surface of the solid, thin, thermoplastic sheet material with the heated die element to thermoform the thin thermoplastic sheet material; (c) contacting under substantially continuously pressure one surface of the rigid thermoplastic foam material with the thermoformed thin thermoplastic material with the heated die element on the opposite side of the thermoformed material to melt and deform a portion of the foam of the rigid thermoplastic foam material in contact thermoformed material; and (d) rapidly chilling the die element while maintaining the die element in substantially continuous contact with the one side of the thermoformed thin thermoplastic sheet material to integrally bond one surface of the cooled thermoformed sheet material to the underlying body of the rigid thermoplastic foam material and to form a solid thermoformed skin layer as a facing surface of the mold element. 18. The method of claim 17 wherein the thermoplastic foam material comprises a olefinic foam resin material and the thin thermoplastic sheet material comprises a fluorocarbon resin or an olefinic resin. 19. The method of claim 17 which includes: (a) forming a rigid thermoplastic foam male and female mold elements as prepared in claim 17; (b) placing the male and female mold elements in a mating closed mold position; (c) heating the back surface of the mated male and female mold elements under pressure to melt a portion of the back surfaces of the male and female mold elements while under pressure and to correct bowing distortions in the mated mold elements; and (d) cooling the melted back surface of the male and female mold elements while maintaining the mold elements under pressure to form a solid back support layer of the cool thermoplastic foam material integrally bonded to the thermoplastic foam material of the body of the mold elements. 20. A multi-part rigid composite foamed thermoplastic mold, which multi-part mold comprises a male and a female mold element adapted to be placed in a closed mating position to define a mold cavity therebetween for the molding of an object, each mold element having a body of rigid thermoplastic foam material and a bonded, solid back support layer, and an integrally bonded, solid thermoplastic skin layer, which skin layer forms the mold facing surface of the male and female mold elements. 21. The mold of the claim 20 wherein the thermoplastic foam material comprises an olefinic thermoplastic foam material having a density of from about 2 to 25 pounds per cubic foot. 22. The mold of claim 20 wherein the integrally bonded solid skin layer as the facing surface is derived from the melting and cooling of the thermoplastic foam material. 23. The mold of claim 20 which includes a thin, solid thermoplastic facing layer composed of a thermoplastic material integrally bonded to the thermoplastic skin layer and which thermoplastic material is a different material than the thermoplastic foam material of the mold element. 24. The mold of claim 20 which includes a thin, removable, thermoplastic insert liner sheet material which matingly fits onto the facing surface of the male or female mold elements to define a new facing surface composed of the insert liner material. 25. The mold of claim 20 wherein the back support layer comprises a solid thermoplastic material derived from the melting and cooling of the thermoplastic foam material. 26. The mold of claim 20 wherein the thermoplastic foam material comprises a closed-cell, rigid polyethylene foam board stock material and the facing surface comprises a solid polypropylene resin layer. 27. The mold of claim 20 which includes a scrim-like mesh material embedded in the solid supporting layer of the back surface. 28. The mold of claim 20 wherein the mold cavity defines a section of a shoe innersole and which mold is suitable for use in molding of elastomeric urethane foam material wherein the expansion and reaction of the urethane foam material occurs within the mold cavity. 29. A multi-part rigid composite foamed thermoplastic mold, which multi-part mold comprises a male and female mold element adapted to be placed in a closed mold position to define a mold cavity therebetween for the molding of a object, each of the male and female mold elements having a body composed of a rigid, olefinic thermoplastic foam material having a foam density of from about 4 to 25 pounds per cubic foot and an integrally bonded, solid back support layer derived from the melting and cooling of the thermoplastic foam layer and an integrally bonded, solid, thin skin layer which forms the mold facing surfaces of the male and female mold elements, which skin layer has been derived from the melting and cooling of the thermoplastic foam material.