Method and apparatus for forming expanded foam articles

Claim 1

A method of pre-expanding beads of synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, until said beads reach their softening point and expand in volume; (c) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (d) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 2

A method of pre-expanding beads of synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, until said beads reach their softening point and expand in volume; (c) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (d) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 3

A method of pre-expanding beads of polystyrene containing an n-pentane blowing agent comprising the steps of: (a) heating the beads in a chamber having an interior surface which is heated to a temperature of from 180° to 250° F.; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration so that the beads absorb heat from the interior surface of the chamber, soften and expand in volume; (c) reducing the pressure in said chamber to from 10" to 25" Hg to reduce the weight percent of the n-pentane in the polystyrene to about 0.75% to 2%; (d) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 4

A method of pre-expanding beads of polystyrene containing an n-pentane blowing agent comprising the steps of: (a) heating the beads in a chamber having an interior surface which is heated to a temperature of from 180° to 250° F.; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration so that the beads absorb heat from the interior surface of the chamber, soften and expand in volume; (c) reducing the pressure in said chamber to from 10" to 25" Hg to reduce the weight percent of the n-pentane in the polystyrene to about 0.75% to 2%; (d) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 5

A method of pre-expanding beads of synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, until said beads reach their softening point and expand in volume; (c) introducing steam at a temperature above the temperature of said expanded beads into direct contact with said expanded beads so as to further heat and expand said expanded beads; (d) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (e) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 6

A method of pre-expanding beads of synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, until said beads reach their softening point and expand in volume; (c) introducing steam at a temperature above the temperature of said expanded beads into direct contact with said expanded beads so as to further heat and expand said expanded beads; (d) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (e) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 7

A method of pre-expanding beads of synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, while passing a non-flammable gas through said chamber, until said beads reach their softening point and expand in volume, said non-flammable gas serving to sweep out the volatilized blowing agent which escapes during the heating and expanding step; (c) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (d) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 8

A method of pre-expanding beads of synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, while passing a non-flammable gas through said chamber, until said beads reach their softening point and expand in volume, said non-flammable gas serving to sweep out the volatilized blowing agent which escapes during the heating and expanding step; (c) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (d) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 9

A method for pre-expanding beads of synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, while passing a non-flammable gas through said chamber, until said beads reach their softening point and expand in volume, said non-flammable gas serving to sweep out the volatilized blowing agent which escapes during the heating and expanding step; (c) introducing steam at a temperature above the temperature of said expanded beads into direct contact with said expanded beads so as to further heat and expand said expanded beads; (d) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (e) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 10

A method for pre-expanding beads of synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, while passing a non-flammable gas through said chamber, until said beads reach their softening point and expand in volume, said non-flammable gas serving to sweep out the volatilized blowing agent which escapes during the heating and expanding step; (c) introducing steam at a temperature above the temperature of said expanded beads into direct contact with said expanded beads so as to further heat and expand said expanded beads; (d) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (e) permitting the expanded beads to return to substantially atmospheric pressure.

Claim 11

A method of forming an expanded synthetic thermoplastic resin article from a synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, until said beads reach their softening point and expand in volume; (c) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (d) permitting the expanded beads to return to substantially atmospheric pressure; (e) conveying the expanded beads to a mold cavity; (f) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (g) discontinuing the supply of heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture; (h) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (i) removing the thus formed article from the mold cavity.

Claim 12

A method of forming an expanded synthetic thermoplastic resin article from a synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, until said beads reach their softening point and expand in volume; (c) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (d) permitting the expanded beads to return to substantially atmospheric pressure; (e) conveying the expanded beads to a mold cavity; (f) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (g) discontinuing the supply of heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture; (h) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (i) removing the thus formed article from the mold cavity.

Claim 13

A method of forming an expanded polystyrene article from polystyrene beads containing an n-pentane blowing agent comprising the steps of: (a) heating the beads in a chamber having an interior surface which is heated to a temperature of from 180° to 250° F.; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration so that the beads absorb heat from the interior surface of the chamber, soften and expand in volume; (c) reducing the pressure in said chamber to from 10" to 25" Hg to reduce the weight percent of the n-pentane in the polystyrene to about 0.75% to 2%; (d) permitting the expanded beads to return to substantially atmospheric pressure; (e) conveying the expanded beads to a mold cavity; (f) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (g) discontinuing the supply to heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture. (h) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (i) removing the thus formed article from the mold cavity.

Claim 14

A method of forming an expanded polystyrene article from polystyrene beads containing an n-pentane blowing agent comprising the steps of: (a) heating the beads in a chamber having an interior surface which is heated to a temperature of from 180° to 250° F.; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration so that the beads absorb heat from the interior surface of the chamber, soften and expand in volume; (c) reducing the pressure in said chamber to from 10" to 25" Hg to reduce the weight percent of the n-pentane in the polystyrene to about 0.75% to 2%; (d) permitting the expanded beads to return to substantially atmospheric pressure; (e) conveying the expanded beads to a mold cavity; (f) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (g) discontinuing the supply to heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture. (h) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (i) removing the thus formed article from the mold cavity.

Claim 15

A method of forming an expanded synthetic thermoplastic resin article from a synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, until said beads reach their softening point and expand in volume; (c) introducing steam at a temperature above the temperature of said expanded beads into direct contact with said expanded beads so as to further heat and expand said expanded beads; (d) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (e) permitting the expanded beads to return to substantially atmospheric pressure; (f) conveying the expanded beads to a mold cavity; (g) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (h) discontinuing the supply of heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture; (i) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (j) removing the thus formed article from the mold cavity.

Claim 16

A method of forming an expanded synthetic thermoplastic resin article from a synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, until said beads reach their softening point and expand in volume; (c) introducing steam at a temperature above the temperature of said expanded beads into direct contact with said expanded beads so as to further heat and expand said expanded beads; (d) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (e) permitting the expanded beads to return to substantially atmospheric pressure; (f) conveying the expanded beads to a mold cavity; (g) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (h) discontinuing the supply of heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture; (i) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (j) removing the thus formed article from the mold cavity.

Claim 17

A method of forming an expanded synthetic thermoplastic resin article from a synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, while passing a non-flammable gas through said chamber, until said beads reach their softening point and expand in volume, said non-flammable gas serving to sweep out the volatilized blowing agent which escapes during the heating and expanding step; (c) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (d) permitting the expanded beads to return to substantially atmospheric pressure; (e) conveying the expanded beads to a mold cavity; (f) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (g) discontinuing the supply of heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture; (h) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (i) removing the thus formed article from the mold cavity.

Claim 18

A method of forming an expanded synthetic thermoplastic resin article from a synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously, at substantially atmospheric pressure, agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, while passing a non-flammable gas through said chamber, until said beads reach their softening point and expand in volume, said non-flammable gas serving to sweep out the volatilized blowing agent which escapes during the heating and expanding step; (c) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (d) permitting the expanded beads to return to substantially atmospheric pressure; (e) conveying the expanded beads to a mold cavity; (f) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (g) discontinuing the supply of heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture; (h) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (i) removing the thus formed article from the mold cavity.

Claim 19

A method of forming an expanded synthetic thermoplastic resin article from a synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, while passing a non-flammable gas through said chamber, until said beads reach their softening point and expand in volume, said non-flammable gas serving to sweep out the volatilized blowing agent which escapes during the heating and expanding step; (c) introducing steam at a temperature above the temperature of said expanded beads into direct contact with said expanded beads so as to further heat and expand said expanded beads; (d) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (a) permitting the expanded beads to return to substantially atmospheric pressure; (f) conveying the expanded beads to a mold cavity; (g) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (h) discontinuing the supply of heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture; (i) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (j) removing the thus formed article from the mold cavity.

Claim 20

A method of forming an expanded synthetic thermoplastic resin article from a synthetic thermoplastic resin material containing a blowing agent, comprising the steps of: (a) heating the beads in a chamber having an interior surface heated to about the fusion temperature of the beads and above the boiling point of the blowing agent; (b) continuously agitating the beads to prevent agglomeration while the beads absorb heat from the interior surface of the chamber, while passing a non-flammable gas through said chamber, until said beads reach their softening point and expand in volume, said non-flammable gas serving to sweep out the volatilized blowing agent which escapes during the heating and expanding step; (c) introducing steam at a temperature above the temperature of said expanded beads into direct contact with said expanded beads so as to further heat and expand said expanded beads; (d) reducing the pressure in said chamber to extract a substantial portion of the gaseous blowing agent from the expanded beads so that the blowing agent content of the expanded beads is from about 0.75 to 2% by weight; (a) permitting the expanded beads to return to substantially atmospheric pressure; (f) conveying the expanded beads to a mold cavity; (g) introducing a heated fluid medium from one side of the mold cavity, while maintaining a negative pressure on the opposite side of the mold cavity to further expand the beads and until the beads are completely fused; (h) discontinuing the supply of heated fluid medium after the fusion is completed and maintaining a negative pressure on the mold cavity to remove residual blowing agent and moisture; (i) returning the mold cavity to atmospheric pressure after said residual moisture and blowing agent are removed; (j) removing the thus formed article from the mold cavity.