Production of encapsulated chemical foaming concentrates

• US 5,611,962 A
• Filed: 03/09/1995
• Issued: 03/18/1997
• Est. Priority Date: 05/13/1992
• Status: Expired due to Fees

• Current Assignee: EPI Environmental Technologies (Nevada) Inc.
• Original Assignee: GAIA Research
• Inventors: Garcia, Rodrigo A., Gho, Joseph G.
• Primary Examiner(s): Lovering, Richard D.
• Application Number:
  US08/404,142
• Time in Patent Office: 740 Days
• Field of Search: 252/350, 428/402.24, 424/466, 521/76, 264/122, 264/178 R, 264/DIG. 5
• US Class Current: 524/320
• CPC Class Codes: B29B 13/065 of powder or pellets
• CPC Class Codes: B29B 7/42 with screw or helix
• CPC Class Codes: B29B 7/48 with intermeshing devices, e.g. screws
• CPC Class Codes: B29B 7/826 Apparatus therefor
• CPC Class Codes: B29B 7/88 Adding charges , i.e. additives
• CPC Class Codes: B29B 9/065 under-water, e.g. underwater pelletizers
• CPC Class Codes: B29B 9/12 characterised by structure or composition
• CPC Class Codes: B29B 9/16 Auxiliary treatment of granules
• CPC Class Codes: B29C 44/3461 Making or treating expandable particles
• CPC Class Codes: C08J 2203/22 Expandable microspheres, e.g. Expancel®
• CPC Class Codes: C08J 9/06 by a chemical blowing agent
• CPC Class Codes: C08J 9/32 from compositions containing microballoons, e.g. syntactic foams
• CPC Class Codes: Y10S 264/05 Use of one or more blowing agents together
• CPC Class Codes: Y10S 425/23 Hay wafering or pelletizing means
• CPC Class Codes: Y10T 428/2989 Microcapsule with solid core [includes liposome]

Abstract

The present invention is directed to the process and apparatus for compounding and pelletizing of chemical foaming agents in a high melt resin carrier and producing unique, uniform encapsulated and pelletized chemical foaming concentrates. More specifically, the present invention is directed to the compounding, encapsulating and pelletizing in a high melt resin carrier a highly loaded concentration (5 to 70 wt %) of foaming agents which include an endothermic foaming agent, an exothermic foaming agent or hybrid combinations of these two such that when incorporated into a thermoplastic resin to produce a foamed product will chemically react to form carbon dioxide, nitrogen or hydrogen or mixtures thereof as the active foaming gas.

Claims

1. An encapsulated chemical foaming concentrate which comprises solid extruded strand cut pellets comprising a mixture of a high melting thermoplastic resin selected from the group consisting of polyethylene, polypropylene, polystyrene, polyethylene acrylic acid, and polyethylene methacrylic acid, and foaming agents comprising an organic acid and a base in an amount necessary to result in a chemical reaction which produces a high concentration of active foaming gas;

said chemical foaming agents having been encapsulated within said pellets, said pellets having unfoamed outer surfaces solidified by an application of positive pressure during compounding of said resin and said foaming agents, said outer surfaces containing the escape of said foaming agents, both reacted and unreacted, and said outer surfaces preventing further reaction of said foaming agents.

2. A chemical foaming concentrate according to claim 1 wherein said acid is selected from the group consisting of malic acid and citric acid and said base is a carbonate.

3. A chemical foaming concentrate according to claim 1 wherein said mixture further includes calcium oxide.

4. An encapsulated chemical foaming concentrate which comprises solid extruded strand cut pellets comprising a mixture of an ionomer resin and foaming agents comprising an organic acid and a base in an amount necessary to result in a chemical reaction which produces a high concentration of active foaming gas;

said chemical foaming agents having been encapsulated within said pellets said pellets, having unfoamed outer surfaces solidified by an application of positive pressure during compounding of said ionomer resin and said foaming agents, said outer surfaces containing the escape of said foaming agents, both reacted and unreacted, and said outer surfaces preventing further reaction of said foaming agents.

5. A chemical foaming concentrate according to claim 4 wherein said acid is stearic acid and said base is sodium borohydride.

6. An encapsulated chemical foaming concentrate which comprises solid extruded strand cut pellets comprising a mixture of a polycarbonate and chemical foaming agents comprising an organic acid and a base in an amount necessary to result in a chemical reaction which produces a high concentration of active foaming gas;

said chemical foaming agents having been encapsulated within said pellets, said pellets having unfoamed outer surfaces solidified by an application of positive pressure during compounding of said polycarbonate and said foaming agents, said outer surfaces containing the escape of said foaming agents, both reacted and unreacted, and said outer surfaces preventing further reaction of said foaming agents.

7. A chemical foaming concentrate according to claim 6 wherein said acid is selected from the group consisting of malic acid and citric acid and said base is lithium carbonate.

8. An encapsulated chemical foaming concentrate which comprises solid extruded strand cut pellets comprising a mixture of polycarbonate and one or more foaming agents selected from the group consisting of an azo compound, a hydrazide, and a hydride compound in an amount necessary to result in a chemical reaction which produces a high concentration of active foaming gas;

said chemical foaming agents having been encapsulated within said pellets, said pellets having unfoamed outer surfaces solidified by an application of positive pressure during compounding of said polycarbonate and said foaming agents said outer surfaces containing the escape of said foaming agents, both reacted and unreacted, and said outer surfaces preventing further reaction of said foaming agents.

9. A chemical foaming concentrate according to claim 8 wherein said azo compound is azodicarbonamide.

10. An encapsulated chemical foaming concentrate which comprises solid extruded strand cut pellets comprising a mixture of a high melting thermoplastic resin selected from the group consisting of polyethylene, polypropylene, polystyrene, polyethylene acrylic acid, and polyethylene methacrylic acid, polycarbonate, and an ionomer resin, and chemical foaming agents comprising a mixture of an endothermic foaming agent and an exothermic foaming agent in an amount necessary to result in a chemical reaction which produces a high concentration of active foaming gas;

said chemical foaming agents having been encapsulated within said pellets, said pellets having unfoamed outer surfaces solidified by an application of positive pressure during compounding of said resin and said foaming agents, said outer surfaces containing the escape of said foaming agents, both reacted and unreacted, and said outer surfaces preventing further reaction of said foaming agents.

11. A chemical foaming concentrate according to claim 10 wherein said endothermic foaming agent and exothermic foaming agent are in relative amounts of 10/90 to 90/10 wt %.