Process for rapidly molding articles from foamable thermoplastic particles involving multiple foaming operations

Claim 2

THE PROCESS OF RAPIDLY MOLDING ARTICLES FROM FOAMABLE BEADS COMPRISING PRE-EXPANDING FOAMABLE BEADS CONTAINING AN EXCESS OF A VOLATIZABLE LIQUID FOAMING AGENT WITH HEAT UNDER CONDITIONS TO FORM PRE-EXPANDED BEADS CONTAINING AT LEAST SUFFICIENT, RESIDUAL QUANTITY OF FOAMING AGENT ABOUT 0.05 TO 2% IN THE EXPANDED PERIFERAL PORTIONS OF SAID BEADS TO ALLOW RAPID HEAT TRANSFER AND EFFECT FURTHER EXPANSION OF SAID PREEXPANDED BEADS WITH HEAT, CONTACTING SAID PRE-EXPANDED BEADS WITH A HOT GASEOUS HEATING MEDIUM FOR A SHORT PERIOD SUFFICIENT TO CONTACT THE OUTER PERIFERAL EXPANDED PORTIONS OF

Claim 3

The process as defined in claim 1 wherein the residual foaming agent in the expanded portion of said beads is supplied by impregnating the bead before heating with such excess of foaming agent as will allow a residual overall content of at least 4% of foaming agent to remain distributed throughout the beads including the periferal portions after pre-expansion.

Claim 4

The process of rapidly molding foamable beads into an agglomerate foamed product comprising pre-expanded foamable beads, impregnating the pre-foamed beads with an extra portion of liquid foaming agent applied to the outer expanded surface portions of said beads to effect further expansion of said pre-expanded beads with heat, contacting said pre-expanded beads with a hot gaseous heating medium for a short period sufficient to contact the outer periferal expanded portions of said pre-expanded beads and to continue expansion thereof by activating the residual foaming agent in the expanded portion of said beads said heat supplied by said medium being sufficient to soften the surface portions of said beads enough to cause the expanded bead surface to cohere, and molding said beads continuously in a molding channel in which the moldable mass of heated beads is moved at a rate exceeding about 50 feet per minute.

Claim 5

The process of rapidly molding foamable beads into an agglomerate foamed product comprising pre-expanded foamable beads, impregnating the pre-foamed beads with an extra portion of liquid foaming agent applied to the outer expanded surface portions of said beads to effect further expansion of said pre-expanded beads with heat, contacting said pre-expanded beads with a hot gaseous heating medium for a short period sufficient to contact the outer periferal expanded portions of said pre-expanded beads and to continue expansion thereof by activating the residual foaming agent in the expanded portion of said beads said heat supplied by said medium being sufficient to soften the surface portions of said beads enough to cause the expanded bead surface to cohere, and molding said beads continuously in a molding channel in which the moldable mass of heated beads is moved at a rate exceeding about 50 feet per minute.

Claim 6

The process as defined in claim 3 wherein the liquid foaming agent is supplied by spraying said liquid foaming agent upon the outer surface portions of said pre-foamed beads.

Claim 7

The process as defined in claim 3 wherein the residual foaming agent in the expanded portion of said beads is supplied by prefoaming the beads under reduced pressure and spraying the hot pre-foamed beads with a liquid foaming agent to cool the beads while returning to atmospheric pressure.

Claim 8

The process as defined in claim 5 wherein the cooled beads containing the additional quantity of foaming agent supplied by spraying are again heated slowly under reduced pressure to further expand said beads by expansion of the periferally added portions of expanding agent, and are again cooled and returned to atmospheric pressure while spraying with a second portion of liquid expanding agent.

Claim 9

The process of highly expanding foamable beads containing a foaming agent comprising pre-expanding the foamable beads by slowly heating to allow said beads to expand and then cooling said beads by spraying with a volatilizable liquid foaming agent and then further expanding the beads by slowly heating the beads to soften and allow the foamed beads to further expand.

Claim 10

The process of highly expanding foamable beads containing a foaming agent comprising pre-expanding the foamable beads by slowly heating to allow said beads to expand and then cooling said beads by spraying with a volatilizable liquid foaming agent and then further expanding the beads by slowly heating the beads to soften and allow the foamed beads to further expand.

Claim 11

The process as defined in claim 7 wherein the beads are simultaneously molded while the final expansion is taking place, the expansion temperature being sufficient to soften the beads to allow them to cohere one to the next in the highly expanded form.

Claim 12

The process as defined in claim 7 wherein following the last expansion of the beads with heat, the expanded beads are again quenched and returned to normal pressure by spraying the wet beads with more expanding agent, whereby the beads are capable of still further expansion with heat.

Claim 13

The process as defined in claim 7 wherein the heating of the beads is effected, at least in the first stage expansion, at reduced pressure.

Claim 14

The process as defined in claim 10 wherein the bEads are simultaneously molded while the final expansion is taking place, the expansion temperature being sufficient to soften the beads to allow them to cohere one to the next in the highly expanded form.

Claim 15

The process as defined in claim 10 wherein following the last expansion of the beads with heat, the expanded beads are again quenched and returned to normal pressure by spraying the hot beads with more expanding agent, whereby the beads are capable of still further expansion with heat.

Claim 16

The process as defined in claim 1 wherein the beads are continuously molded into a foamed molded product in a longitudinal molding machine operated at a rate exceeding 50 linear feet per minute.

Claim 17

The process as defined in claim 1 wherein the beads are continuously molded into a foamed molded product in an arcuate drum and plate type of molding machine operated at a rate in the range of 50 to 600 linear feet per minute.

Claim 18

The process as defined in claim 1 wherein the foamable beads before molding consist largely of foamed scrap formed by grinding a foamed molded product formed in an earlier molding, said scrap being impregnated with sufficient additional foaming agent to impart to the outer periferal portions thereof a substantially similar content of expanding agent as the pre-foamed beads with which it is mixed.

Claim 19

The process as defined in claim 15 wherein the additional foaming agent is added to the said scrap by spraying a liquid foaming agent upon the particle surfaces of the ground scrap material before mixing with said foamable particles.