Expandable synthetic resinous thermoplastic particles, method for the preparation thereof and the application therefor

Claim 1

A method for the preparation of expanded monovinyl aromatic polymer particles comprising heating to a temperature of from about 20 to 60 degrees above the glass transition temperature of the polymer to cause the particles containing a blowing agent to form a plurality of closed gas containing cells, subjecting the expanded particles to an atmosphere of an inert gas capable of diffusing through walls of the gas containing cells at a rate greater than a volatile fluid foaming agent contained within the cells and subsequently heating the particles at a temperature above the glass transition temperature of the polymer to thereby increase the volume of the expanded particles to at least twice that of the volume of the particles prior to exposure to the inert gas with the further limitation that the expanded particles are resilient, wherein the particles having a swelling factor of at least 20 and a cross-linking coefficient of from about 0.8 to about 2.5 with the further limitation that the particles on heating to a temperature above the glass transition temperature of the polymer expand to at least 40 times their original volume at ambient temperature and on being pressurized at a pressure of at least 3 atmospheres in air for a period of 24 hours be capable of two-fold expansion when subjected to the conditions employed to expand the particles to at least 40 times their original volume.

Claim 2

A method for the preparation of expanded monovinyl aromatic polymer particles comprising heating to a temperature of from about 20 to 60 degrees above the glass transition temperature of the polymer to cause the particles containing a blowing agent to form a plurality of closed gas containing cells, subjecting the expanded particles to an atmosphere of an inert gas capable of diffusing through walls of the gas containing cells at a rate greater than a volatile fluid foaming agent contained within the cells and subsequently heating the particles at a temperature above the glass transition temperature of the polymer to thereby increase the volume of the expanded particles to at least twice that of the volume of the particles prior to exposure to the inert gas with the further limitation that the expanded particles are resilient, wherein the particles having a swelling factor of at least 20 and a cross-linking coefficient of from about 0.8 to about 2.5 with the further limitation that the particles on heating to a temperature above the glass transition temperature of the polymer expand to at least 40 times their original volume at ambient temperature and on being pressurized at a pressure of at least 3 atmospheres in air for a period of 24 hours be capable of two-fold expansion when subjected to the conditions employed to expand the particles to at least 40 times their original volume.

Claim 15

A method for the preparation of a resilient coherent foamed body, the body having a density of from about 0.2 pound per cubic foot to about 1.5 pound per cubic foot, the steps of the method comprising providing a plurality of heat expandable synthetic resinous particles, the particles forming a gel when placed in a solvent for an uncrosslinked composition of generally like monomeric constitution, the particles having a swelling factor of at least 20 and a crosslinking coefficient of from about 0.8 to about 2.5 with the further limitation that the particles on heating to a temperature above the glass transition temperature of the polymer expand to at least 40 times their original volume at ambient temperature and on being pressurized at a pressure of at least 3 atmospheres in air for a period of 24 hours be capable of two-fold expansion when subjected to the conditions employed to expand the particles to at least 40 times their original volume; expanding said particles; disposing said particles within a closed mold; heating said particles to a temperature sufficient to cause further expansion of said particles and to cause adjacent particles to fuse together to form a unitary body which is thermo collapse resistant and resilient.

Claim 16

A method for the preparation of a resilient coherent foamed body, the body having a density of from about 0.2 pound per cubic foot to about 1.5 pound per cubic foot, the steps of the method comprising providing a plurality of heat expandable synthetic resinous particles, the particles forming a gel when placed in a solvent for an uncrosslinked composition of generally like monomeric constitution, the particles having a swelling factor of at least 20 and a crosslinking coefficient of from about 0.8 to about 2.5 with the further limitation that the particles on heating to a temperature above the glass transition temperature of the polymer expand to at least 40 times their original volume at ambient temperature and on being pressurized at a pressure of at least 3 atmospheres in air for a period of 24 hours be capable of two-fold expansion when subjected to the conditions employed to expand the particles to at least 40 times their original volume; expanding said particles; disposing said particles within a closed mold; heating said particles to a temperature sufficient to cause further expansion of said particles and to cause adjacent particles to fuse together to form a unitary body which is thermo collapse resistant and resilient.