Degradation of expandable polymer bead products

A method of expanding beads of expandable polymer, each bead comprising a mixture of polymer and a blowing agent, said polymer comprising molecules of high molecular weight, said method comprising the steps of;

• a) heating a quantity of dry gas,
• b) maintaining the heated dry gas in contact with said beads until substantially every bead is enlarged to a desired degree due to thermal expansion of said blowing agent therein to form a plurality of both peripheral and interior, mutually joined, cells, each cell comprising said polymer and a quantity of blowing agent therein,
• c) during step b), treating said beads to initiate degradation of at least some of said molecules of high molecular weight into molecules of lower molecular weight, and
• d) cooling the enlarged beads to set said cells thereof in an enlarged state thereof.

A method of molding articles from beads of expandable polymer, each bead comprising a mixture of polymer and a blowing agent, said polymer comprising molecules of high molecular weight, said method comprising the steps of;

• a) heating said beads until substantially every bead is enlarged to a desired degree due to thermal expansion of said blowing agent therein to form a plurality of both peripheral and interior, mutually joined, cells, each cell comprising said polymer and a quantity of blowing agent therein,
• b) during step a), treating said beads to initiate degradation of at least some of said molecules of high molecular weight into molecules of lower molecular weight, and
• c) cooling said beads to set cells thereof in an enlarged state thereof to thereby form pre-expanded beads,
• d) introducing said pre-expanded beads into a mold defining a shape of an article, and
• e) heating said pre-expanded beads in said mold to further expand said pre-expanded beads to form said article.

A method of molding articles from beads of expandable polymer, each bead comprising a mixture of polymer and a blowing agent, said polymer comprising molecules of high molecular weight, said method comprising the steps of;

• a) heating a quantity of dry gas,
• b) maintaining the heated dry gas in contact with said beads until substantially every bead is enlarged to a desired degree due to thermal expansion of said blowing agent therein to form a plurality of both peripheral and interior, mutually joined, cells, each cell comprising said polymer and a quantity of blowing agent therein, by:
• i) circulating heated dry gas at the bottom of a chamber, and
• ii) then introducing a batch quantity of said beads into said chamber while circulating said heated gas therein.to stir said beads,
• c) during step b), treating said beads to initiate degradation of at least some of said molecules of high molecular weight into molecules of lower molecular weight, and
• d) cooling said beads to set cells thereof in an enlarged state thereof to thereby form pre-expanded beads,
• e) introducing said pre-expanded beads into a mold defining a shape of an article, and
• f) heating said pre-expanded beads in said mold to further expand said pre-expanded beads to form said article.

An apparatus for expanding beads of expandable polymer, said apparatus comprising:

• a) a vertical expansion chamber for receiving a selected batch quantity of said beads, said expansion chamber comprising a lower portion and an upper portion, said lower portion being formed of substantially gas-impermeable material, said upper portion being formed of substantially gas-permeable material,
• b) a loading bin for discharging said selected batch quantity of beads into said lower portion,
• c) a source of dry, heated, pressurized gas connected in gas-communicating relationship with said lower portion, said source being operable to direct the heated gas into said lower portion to stir and percolate through said selected batch quantity of beads therein.
• d) a degradation device operable to treat said beads to initiate degradation of at least some of said molecules of high molecular weight into molecules of lower molecular weight.