Supercritical fluids as diluents in liquid spray applications of adhesives

• US 5,066,522 A
• Filed: 03/22/1989
• Issued: 11/19/1991
• Est. Priority Date: 07/14/1988
• Status: Expired due to Term

• Current Assignee: Union Carbide Chemicals & Plastics Technology Corporation (Dow, Inc.)
• Original Assignee: Union Carbide Chemicals & Plastics Technology Corporation (Dow, Inc.)
• Inventors: Cole, Thomas A., Nielsen, Kenneth A.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/326,945
• Time in Patent Office: 972 Days
• Field of Search: 118/300, 118/302, 427/27, 427/421, 427/422, 427/426, 427/384, 427/385.5, 239/9, 239/10, 239/299, 239/128, 239/597, 239/599, 239/432, 239/343, 239/DIG. 1
• US Class Current: 427/422
• CPC Class Codes: B05D 1/025 using gas close to its critical state
• 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: B29B 7/325 Static mixers in general B01F25/42
• CPC Class Codes: B29B 7/7447 including means for feeding the components
• CPC Class Codes: B29B 7/748 Plants B29B7/7433, B29B7/7485, B29B7/7495 take precedence
• CPC Class Codes: B29B 7/7495 for mixing rubber
• CPC Class Codes: B29B 7/826 Apparatus therefor
• CPC Class Codes: B29B 7/86 for working at sub- or superatmospheric pressure B01F33/70 takes precedence
• CPC Class Codes: B29B 7/94 Liquid charges
• CPC Class Codes: C09D 7/00 Features of coating compositions, not provided for in group C09D5/00 driers C09F9/00; Processes for incorporating ingredients in coating compositions
• CPC Class Codes: C09D 7/20 Diluents or solvents
• CPC Class Codes: Y02P 20/54 using solvents, e.g. supercritical solvents or ionic liquids

Abstract

The present invention relates to precursor adhesive coating compositions which optionally contain water, which are particularly suitable for being admixed with at least one supercritical fluid used as a viscosity reduction diluent and then spraying this resultant liquid mixture of supercritical fluid and precursor adhesive coating composition onto a substrate to be coated. Processes for spraying these precursor adhesive coating compositions are also disclosed.

Claims

1. A process for the liquid spray application of adhesive coatings to a substrate, which comprises:

(a) forming a liquid mixture in a closed system, said liquid mixture comprising;

(i) a solids fraction containing at least one polymeric compound capable of forming an adhesive coating on a substrate;

(ii) a solvent fraction containing at least one active solvent in which said at least one polymeric compound is at least partially soluble and which is at least partially miscible with supercritical fluid; and

(iii) at least one supercritical fluid, in at least an amount which when added to (i) and (ii) is sufficient to render the viscosity of said mixture to a point suitable for spray application; and

(b) spraying said liquid mixture, forming droplets having an average diameter of 1 micron or greater, onto a substrate to form a liquid coating thereon.

2. The process of claim 1 in which said liquid mixture is formed to further contain (iv) water which is present in an amount of less than about 30% by weight based on the weight of the solvent fraction.

3. The process of claim 2 in which the liquid mixture contains less than about 20% by weight of water based on the weight of the solvent fraction.

4. The process of claim 2 in which said liquid mixture is formed to further contain a coupling solvent in which said at least one polymeric compound is at least partially soluble and which is at least partially miscible with the water.

5. The process of claims 1, 2 or 3, wherein the viscosity of the liquid mixture ranges from about 5 to about 150 cps.

6. The process of claims 1, 2 or 3, wherein the viscosity of the mixture ranges from about 10 to about 50 cps.

7. The process of claim 1 further comprising prior to step (b), heating said liquid mixture to a temperature sufficient to prevent the adverse effect caused by rapid cooling when said liquid mixture is sprayed.

8. The process of claims 1, 2 or 3, wherein the at least one supercritical fluid comprises supercritical carbon dioxide.

9. The process of claim 1, wherein said at least one polymeric compound is selected from the group consisting of thermoplastic resins, thermosetting resins, crosslinkable film forming systems, and mixtures thereof.

10. The process of claim 9, wherein said at least one polymeric compound is selected from the group consisting of cellulose derivatives, acrylic resins, vinyl resins, styrenic resins, polyesters, alkyds, polyurethanes, urethanes, polyamides, epoxies, phenolics, cellulosic esters, amino resins, natural gums, natural resins, natural rubbers and their derivatives, nitrile rubbers, styrene-butadiene rubbers, styrene-isoprene-styrene block copolymers, polyisobutylene, thermoplastic rubbers, neoprene rubbers and interpolymers and mixtures thereof.

11. The process of claim 4, wherein the coupling solvent is selected from the group consisting of ethylene glycol ethers, propylene glycol ethers, lactams, cyclic ureas, and mixtures thereof.

12. The process of claim 4, wherein the coupling solvent is selected from the group consisting of butoxy ethanol, propoxy ethanol, hexoxy ethanol, isoproproxy 2-propanol, butoxy 2-propanol, propoxy 2-propanol, tertiary butoxy 2-propanol, ethoxy ethanol, butoxy ethoxy ethanol, propoxy ethoxy ethanol, hexoxy ethoxy ethanol, methoxy ethanol, methoxy 2-propanol and ethoxy ethanol, n-methyl-2-pyrrolidone, dimethyl ethylene urea, and mixtures thereof.

13. The process of claim 4, wherein the weight ratio of coupling solvent to active solvent is in the range of about 1:

1 to 4;

1.

14. The process of claim 13, wherein the weight ratio of coupling solvent to active solvent is in the range of from 2:

1 to 3.5;

1.

15. The process of claim 14, wherein the weight ratio of coupling solvent to active solvent is in the range of from 2.5:

1 to 3.0;

1.

16. The process of claim 1, wherein said at least one active solvent is selected from the group consisting of ketones, esters, ethers, glycol ethers, glycol ether esters, alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, nitroalkanes, unsaturated hydrocarbons, halocarbons, and mixtures thereof.

17. The process of claim 1, wherein the substrate is selected from the group consisting of cloth, masonry, stone, metal, wood, glass, ceramic, leather, rubbers, paper and plastic.

18. The process of claim 1, further comprising curing the liquid coating on the substrate.

19. The process of claim 1, wherein the liquid adhesive coating applied to the substrate is a substantially continuous film.

20. The process of claim 19 having a solvent fraction composition containing a weight % solvent distribution and relative evaporation rates of:

space="preserve" listing-type="tabular">______________________________________ Wt. % of Total Solvent Fraction RER ______________________________________ 30-100% <

50 0-70% 50-100 0-40% 101-250 <

10% >

250. ______________________________________

21. The process of claim 20 having a solvent fraction composition of:

space="preserve" listing-type="tabular">______________________________________ Wt. % of Total Solvent Fraction RER ______________________________________ 40-100% <

50 0-60% 50-100 0-30% 101-250 <

5% >

250. ______________________________________

22. The process of claim 1, wherein the liquid adhesive coating applied to the substrate is in a substantially discontinuous random droplet pattern.

23. The process of claim 22 having a solvent fraction composition containing a weight % solvent distribution and relative evaporation rates of:

space="preserve" listing-type="tabular">______________________________________ Wt. % of Total Solvent Fraction RER ______________________________________ 0-40% <

100 0-70% 101-250 30-100% >

250. ______________________________________

24. The process of claim 23 having a solvent fraction composition of:

space="preserve" listing-type="tabular">______________________________________ Wt. % of Total Solvent Fraction RER ______________________________________ 0-30% <

100 0-60% 101-250 40-100% >

250. ______________________________________

25. The process of claim 1 in which the liquid mixture is electrically charged by a high electrical voltage.

26. The process of claim 25, wherein the high electrical voltage ranges from about 30 to about 150 kilovolts.

27. The process of claim 1, wherein the predominant polymeric compound has a Mw/Mn ratio of less than about 4.

28. The process of claim 27, wherein the predominant polymeric compound has a Mw/Mn ratio of less than about 3.

29. The process of claim 28, wherein the predominant polymeric compound has a Mw/Mn ratio of less than about 2.

30. A process for the liquid spray application of adhesive coatings to a substrate, which comprises:

(a) forming a liquid mixture in a closed system, said liquid mixture comprising;

(i) a solids fraction containing at least one polymeric compound capable of forming an adhesive coating on a substrate;

(ii) a solvent fraction containing at least one active solvent in which said polymeric compound is at least partially soluble and which is at least partially miscible with the supercritical fluid of (iv) and containing at least one coupling solvent in which said at least one polymeric compound is at least partially soluble and which is at least partially miscible with water;

(iii) water, which is present in an amount of less than about 30% by weight based on the weight of the solvent fraction; and

(iv) at least one supercritical fluid, in at least an amount which when added to (i), (ii), and (iii), is sufficient to render the viscosity of said mixture to a point suitable for spray application; and

(b) spraying said liquid mixture, forming droplets having an average diameter of 1 micron or greater, onto a substrate to form a liquid coating thereon.

31. A process for the liquid spray application of adhesive coatings to a substrate, which comprises:

(a) forming a liquid mixture in a closed system, said liquid mixture comprising;

(i) a solids fraction containing at least one polymeric compound capable of forming an adhesive coating on a substrate;

(ii) a solvent fraction containing at least one active solvent in which said at least one polymeric compound is at least partially soluble and which is at least partially miscible with supercritical fluid; and

(iii) at least one supercritical fluid, in at least an amount which when added to (i) and (ii) is sufficient to render the viscosity of said mixture to a point suitable for spray application; and

(b) spraying said liquid mixture onto a substrate to form a liquid adhesive coating thereon by passing the mixture under pressure through an orifice into the environment of the substrate to form a liquid spray having droplets with an average diameter of 1 micron or greater.

32. The process of claim 31 which further comprises forming a liquid mixture which also contains water in an amount of less than about 30% by weight based on the weight of the solvent fraction.

33. The process of claim 32, wherein the solvent fraction further comprises at least one coupling solvent in which said polymeric compound is at least partially soluble and which is at least partially miscible with the water.

34. The process of claim 33, wherein the weight ratio of coupling solvent to active solvent is in the range of from about 1:

1 to 4;

1.

35. The process of claim 34, wherein the weight ratio of the coupling solvent to active solvent is in the range of from about 2:

1 to 3.5;

1.

36. The process of claims 32, 33 or 34, wherein the orifice size ranges from about 0.004 to about 0.072 inch in diameter.

37. The process of claim 36, wherein the orifice size ranges from about 0.004 to about 0.025 inch in diameter.

38. The process of claim 37, wherein the orifice size ranges from about 0.007 to about 0.015 inch in diameter.

39. The process of claims 32, 33 or 34, wherein the spray pressure ranges from about the critical pressure of the supercritical fluid to about 5000 pounds per square inch.

40. The process of claim 39, wherein the spray pressure is below about 3000 pounds per square inch.

41. The process of claims 32, 33 or 34, wherein the viscosity of the liquid mixture is less than about 300 centipoise at spray temperature.

42. The process of claim 41, wherein the viscosity of the liquid mixture ranges from about 5 to about 150 centipoise at spray temperature.

43. The process of claim 42, wherein the viscosity of the liquid mixture ranges from about 10 to about 50 centipoise at spray temperature.

44. The process of claim 32 further comprising, prior to step (b), heating said liquid mixture to a temperature sufficient to prevent the adverse effect caused by rapid cooling when said liquid mixture is sprayed.

45. The process of claim 44, wherein the liquid temperature ranges from about 35°

to about 90°

centigrade.

46. The process of claim 45, wherein the liquid temperature ranges from about 45°

to about 75°

centigrade.

47. The process of claims 32, 33 or 34 wherein supercritical fluid comprises supercritical carbon dioxide fluid.

48. The process of claims 32, 33 or 34 wherein supercritical fluid comprises supercritical nitrous oxide fluid.

49. The process of claim 32 wherein said at least one polymeric component is selected from the group consisting of thermoplastic resins, thermosetting resins, crosslinkable film forming systems, and mixtures thereof.

50. The process of claim 49, wherein said at least one polymeric component is selected from the group consisting of cellulose derivatives, acrylic resins, vinyl resins, styrenic resins, polyesters, alkyds, polyurethanes, urethanes, polyamides, epoxies, phenolics, cellulosic esters, amino resins, natural gums, natural resins, natural rubbers and their derivatives, nitrile rubbers, styrene-butadiene rubbers, styrene-isoprene-styrene block copolymers, polyisobutylene, thermoplastic rubbers, neoprene rubbers and interpolymers and mixtures thereof.

51. The process of claim 32, further comprising, prior to Step (b), filtering said liquid mixture to remove particulates that would plug said orifice.

52. The process of claim 32, further comprising, prior to step (b), promoting turbulent or agitated flow of said liquid mixture to aid atomization of said liquid spray.

53. The process of claim 32, further comprising utilizing jets of compressed gas to assist formation and atomization of said liquid spray and to modify the shape of said liquid spray.

54. The process of claim 53, wherein said compressed gas is compressed air.

55. The process of claim 54, wherein said compressed air has lowered oxygen content to reduce flammability of said liquid spray.

56. The process of claim 53, wherein said compressed gas is compressed carbon dioxide.

57. The process of claim 53, wherein said compressed gas is selected from the group consisting of compressed nitrogen, helium, argon, xenon, and mixtures thereof.

58. The process of claim 53, wherein the pressure of said compressed gas ranges from about 5 to about 80 pounds per square inch.

59. The process of claim 58, wherein the pressure of said compressed gas ranges from about 5 to about 20 pounds per square inch.

60. The process of claim 53, wherein said compressed gas is heated to supply heat to the liquid spray to prevent an adverse effect caused by rapid cooling when said liquid mixture is sprayed.

61. The process of claim 60, wherein the temperature of said compressed gas ranges from about 35°

to about 90°

centigrade.

62. The process of claim 61, wherein the temperature of said compressed gas ranges from about 45°

to about 75°

centigrade.

63. The process of claim 32, wherein the substrate is selected from the group consisting of metal, wood, glass, plastic, paper, cloth, ceramic, masonry, stone, cement, asphalt, rubber, and composite materials thereof.

64. The process of claim 32, further comprising curing said liquid coating on said substrate.

65. The process of claim 32, wherein the liquid adhesive coating applied to the substrate is a substantially continuous film.

66. The process of claim 65 having a solvent fraction composition containing a weight % solvent distribution and relative evaporation rates of:

space="preserve" listing-type="tabular">______________________________________ Wt. % of Total Solvent Fraction RER ______________________________________ 30-100% <

50 0-70% 50-100 0-40% 101-250 <

10% >

250. ______________________________________

67. The process of claim 66 having a solvent fraction composition of:

space="preserve" listing-type="tabular">______________________________________ Wt. % of Total Solvent Fraction RER ______________________________________ 40-100% <

50 0-60% 50-100 0-30% 101-250 <

5% >

250. ______________________________________

68. The process of claim 65, wherein the substantially continuous film is obtained by maintaining a relative linear traversal rate between the spray orifice and the substrate of less than about 1 m/sec.

69. The process of claim 32, wherein the liquid adhesive coating applied to the substrate is in a substantially discontinuous random droplet pattern.

70. The process of claim 69 having a solvent fraction composition containing a weight % solvent distribution and relative evaporation rates of:

space="preserve" listing-type="tabular">______________________________________ Wt. % of Total Solvent Fraction RER ______________________________________ 0-40% <

100 0-70% 101-250 30-100% >

250. ______________________________________

71. The process of claim 70 having a solvent fraction composition of:

space="preserve" listing-type="tabular">______________________________________ Wt. % of Total Solvent Fraction RER ______________________________________ 0-30% <

100 0-60% 101-250 40-100% >

250. ______________________________________

72. The process of claim 69, wherein the substantially discontinuous random droplet pattern is obtained by maintaining a relative linear traversal rate between the spray orifice and the substrate of at least about 1 m/sec.

73. The process of claim 32 in which the liquid mixture is electrically charged by a high electrical voltage.

74. The process of claim 73, wherein the high electrical voltage ranges from about 30 to about 150 kilovolts.