Supercritical fluid-aided treatment of porous materials

• US 5,169,687 A
• Filed: 03/27/1990
• Issued: 12/08/1992
• Est. Priority Date: 09/16/1988
• Status: Expired due to Term

• Current Assignee: University of South Florida (State University System of Florida)
• Original Assignee: University of South Florida (State University System of Florida)
• Inventors: Sunol, Aydin K.
• Primary Examiner(s): Bell, Janyce
• Application Number:
  US07/499,862
• Time in Patent Office: 987 Days
• Field of Search: 427/297, 427/394, 427/395, 427/396, 427/397, 427/308, 427/317, 427/324, 427/325, 162/72
• US Class Current: 427/297
• CPC Class Codes: B05D 1/18 performed by dipping
• CPC Class Codes: B05D 2203/20 Wood or similar material
• CPC Class Codes: B05D 2401/90 at least one component of the composition being in supercritical state or close to supercritical state
• CPC Class Codes: B05D 7/06 to wood
• CPC Class Codes: B27K 3/15 Impregnating involving polymerisation including use of polymer-containing impregnating agents macromolecular compounds derived from lignocellulosic materials C08H; compositions of lignin-containing materials C08L97/02
• CPC Class Codes: B27K 5/007 using pressure B27K3/08 takes precedence
• CPC Class Codes: C08L 33/12 Homopolymers or copolymers of methyl methacrylate
• CPC Class Codes: C08L 97/02 Lignocellulosic material, e.g. wood, straw or bagasse manufacture of articles made from lignocellulosic material by dry processes B27N
• CPC Class Codes: Y02P 20/54 using solvents, e.g. supercritical solvents or ionic liquids

Abstract

Method and process using a supercritical fluid, with or without the aid of entrainers 1) to solubilize a monomer, monomer mixture or polymer which may or may not include additives and entrainers, 2) to carry the supercritical solvent mixture thereby created into the wood matrix, 3) to remove extractives from the wood, 4) to precipitate the monomer or polymer within the wood, and 5) to polymerize the monomer in situ in the wood.

Claims

1. A process for making a polymer impregnated material which comprises treating a porous material with a supercritical fluid containing polymerizable monomer under conditions sufficient to polymerize said monomer in situ in the material.

2. A process according to claim 1, wherein said porous material is wood.

3. A process according to claim 3, wherein the supercritical fluid is selected from the group comprising lower alkenes, lower alkanes, nitrous oxide, carbon dioxide, ammonia, and other compounds with critical temperatures in the range of 5 to 250 degrees centigrade.

4. A process according to claim 3, wherein the supercritical fluid has a critical temperature in the range of 5 to 250 degrees centigrade and a viscosity substantially less than the viscosity of water.

5. A process for making a polymer impregnated wood, comprising the steps of:

mixing a supercritical fluid with polymerizable monomer and monomer polymerization catalyst to form a supercritical wood impregnation medium;

diffusing said polymerizable monomer and monomer polymerization catalyst into said wood by contacting said wood with the supercritical wood impregnation medium in an impregnation zone under conditions sufficient to impregnate the wood with monomer and to polymerize said polymerizable material in situ in the wood; and

removing polymer impregnated wood from the impregnation zone.

6. A process according to claim 5, wherein the supercritical fluid is selected from the group comprising lower alkenes, lower alkanes, nitrous oxide, carbon dioxide, ammonia, and other compounds with critical temperatures in the range of 5 degrees to 250 degrees centigrade.

7. A process according to claim 6, wherein the supercritical fluid has a critical temperature in the range of 25 degrees to 100 degrees centigrade and a viscosity substantially less than the viscosity of water.

8. A process according to claim 7, wherein the conditions include a temperature from 25 degrees to 100 degrees centigrade, a pressure from 400 to 3,500 pounds per square inch absolute, and a contact time of from one minute to 24 hours.

9. A process of making cellulose containing material having enhanced properties, comprising the steps of:

uniformly impregnating a cellulose containing starting material with a polymerizable monomer in the presence of a fluid under supercritical conditions;

causing the monomer to polymerize in situ in the cellulose containing material, thereby imparting enhanced properties to the starting material;

completing said process within a preselected period of time;

said period of time including time periods of less than one hour.

10. A process according to claim 9, wherein the polymerization is initiated by a polymerization catalyst.

11. A process according to claim 10, wherein the catalyst is selected from the group comprising azo compounds, organic peroxides, dialyl peroxides, redox agents, and silver alkyls.

12. A process according to claim 11, wherein the cellulose containing material is wood.

13. A process according to claim 12, wherein the conditions for impregnating of cellulose containing material is at a temperature range of 25 degrees to 100 degrees centrigrade, and at a pressure range from 400 to 3,500 pounds per square inch absolute.