Sound absorbing and decoupling syntactic foam

• US 5,422,380 A
• Filed: 06/07/1994
• Issued: 06/06/1995
• Est. Priority Date: 06/07/1994
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Bolton, Richard, Navish, Francis W. Jr., Mendelsohn, Morris A.
• Primary Examiner(s): WELSH JR, MAURICE
• Application Number:
  US08/255,859
• Time in Patent Office: 364 Days
• Field of Search: 521/107, 521/137, 521/159, 521/163, 521/164, 521/170, 521/172, 521/174
• US Class Current: 521/107
• CPC Class Codes: C08J 2325/06 Polystyrene
• CPC Class Codes: C08J 2375/04 Polyurethanes
• CPC Class Codes: C08J 2425/00 Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
• CPC Class Codes: C08J 9/0061 characterized by the use of several polymeric components
• CPC Class Codes: C08J 9/236 using binding agents
• CPC Class Codes: C08J 9/35 Composite foams, i.e. continuous macromolecular foams containing discontinuous cellular particles or fragments

Abstract

There is disclosed a sound-absorbing syntactic foam comprising expanded polystyrene microspheres, dispersed randomly in a polyurethane matrix.

Claims

1. A sound-absorbing syntactic foam comprising expanded polystyrene microspheres, dispersed randomly in a polyurethane matrix.

2. The foam according to claim 1, wherein the expanded polystyrene microspheres have a mean diameter in the range of from about 10 micrometers to about 2 millimeters.

3. The foam according to claim 1, wherein the expanded polystyrene microspheres have a mean diameter in the range of from about 20 micrometers to about 700 micrometers.

4. The foam according to claim 1, wherein the expanded polystyrene microspheres have a density in the range of from about 12 kg/m³ to about 100 kg/m³.

5. The foam according to claim 1, wherein the expanded polystyrene microspheres have a density in the range of from about 16 kg/m³ to about 40 kg/m³.

6. The foam according to claim 1, wherein the expanded polystyrene microspheres have an average molecular weight in the range of from about 40,000 to about 1,000,000.

7. The foam according to claim 1, wherein the expanded polystyrene microspheres have an average molecular weight in the range of from about 220,000 to about 280,000.

8. The foam according to claim 1, wherein the expanded polystyrene microspheres are multicellular.

9. The foam according to claim 8, wherein the multicellular expanded polystyrene microspheres contain from about 100 to about 50,000 cells per cubic millimeter.

10. The foam according to claim 8, wherein the unexpanded polystyrene microspheres are mixed with the unreacted components of the polyurethane matrix resin prior to the formation of the matrix polymer.

11. The foam according to claim 8, wherein the multicellular expanded polystyrene microspheres contain from about 1,000 to about 20,000 cells per cubic millimeter.

12. The foam according claim 8, wherein the expanded polystyrene microspheres occupy a volume in the range of from about 30% to about 80% of the volume of the foam.

13. The foam according to claim 8, wherein the expanded polystyrene microspheres occupy a volume in the range of from about 45% to about 60% of the volume of the foam.

14. The foam according to claim 8, wherein the expanded polystyrene microspheres comprise from about 1.5% to about 10% of the total weight of the foam.

15. The foam according to claim 8, wherein the expanded polystyrene microspheres comprise from about 3% to about 6% of the total weight of the foam.

16. The foam according to claim 8 in which the expandable polystyrene microspheres are initially added in their unexpanded form to its matrix resin components and are expanded on subsequent heating of the freshly mixed but not yet gelled material to temperatures above about 93°

C. to give the low density multicellular microspheres.

17. The foam according to claim 8, wherein the polyurethane matrix is the structure resulting from the reaction of at least one polyisocyanate and at least one polyfunctional active hydrogen compound.

18. The foam according to claim 17, wherein the polyfunctional compound comprises only difunctional compounds selected from the group consisting of dihydric compounds, compounds containing two hydroxyl groups, diamino compounds, monoaminomonoalcohol compounds and mixtures thereof.

19. The foam according to claim 17, wherein the polyfunctional active hydrogen compound comprises a trifunctional compound selected from the group consisting of trihydric compounds, dihydricmonoamino compounds, monohydricdiamino compounds, triamino compounds and mixtures thereof.

20. The foam according to claim 17, wherein the polyfunctional active hydrogen compound comprises up to 50 equivalent percent of a tetrafunctional compound selected form the group consisting of tetrahydric compounds, trihydricmonoamino compounds, dihydricdiamino compounds, monohydrictriamino compounds, tetraamino compounds and mixtures thereof.

21. The foam according to claim 17, wherein the active hydrogen containing polyfunctional compounds are selected from the group consisting of 1,4-butanediol, trimethyol propane, hydroquinone di(B-hydroxyethyl)ether, polyoxytetramethylene diol having a molecular weight in the range of about 600 to about 3,000, and mixtures thereof.

22. The foam according to claim 17, wherein the polyisocyanate or polyfunctional isocyanate containing compound is selected form the group consisting of trans-1,4-cyclohexane diisocyanate, 1,6-hexane diisocyanate and its biuret and isoryanurate condensation products, 2,4-toluene diisocyanate;

2,6-toluene diisocyanate, 4,4'"'"'-methylene-bis(cyclohexyldiisocyanate), isophorone diisocyanate, 4,4'"'"'-methylene-bis(phenylisocyanate), condensation and oligomeric derivatives of 4,4'"'"'-methylene-bis(phenylisocyanate) including those that have functionalities greater than 2.0, p-phenylene diisocyanate, 2,4'"'"'-methylene-bis(phenylisocyanate), and oligomeric derivatives of 2,4'"'"'-methylene-bis(phenylisocyanate) including those that have functionalities greater than 2.0, and mixtures thereof.

23. The foam according to claim 17 wherein the polyfunctional active hydrogen compounds comprise a blend of difunctional and trifunctional active hydrogen containing compounds in an equivalents ratio of from about 95:

5, respectively to about 60;

40, respectively.

24. The foam according to claim 17 wherein the polyfunctional compounds comprise a blend of difunctional and trifunctional active hydrogen containing compounds in an equivalents ratio of from about 95:

5 respectively to about 90;

10 respectively.

25. The foam according to claim 17 wherein the equivalents ratio of polyisocyanate to polyfunctional active hydrogen containing compound is within the range of about 1.00:

1.10, respectively to about 1.00;

0.85, respectively.

26. The foam according to claim 17 wherein the equivalents ratio of the polyisocyanate to polyfunctional active hydrogen containing compounds is about 1.00:

1.00 to 1.00;

0.94, respectively.

27. The foam according to claim 1 further comprising a flame retardant.

28. The foam according to claim 8 further comprising a flame retardant.

29. The foam according to claim 17 further comprising a flame retardant.

30. A polyurethane syntactic foam prepared by a one-step process in which polystyrene microspheres or multicellular polystyrene microspheres are combined with at least one polyisocyanate compound and at least one polyfunctional active hydrogen containing compound in an equivalent isocyanate to hydroxyl ratio of about 1:

1, the blend is generally heated and held at a temperature in the range of about 20°

C. to about 100°

C. for about 1 to 10 minutes under vacuum consisting of an absolute pressure of about 1 Torr to about 100 Torr.

31. The process of claim 30, wherein a catalyst is added to the reactants in a range of about 0.001 weight percent to about 0.3 weight percent.

32. The process of claim 31 in which the catalyst is diazobicyclooctane, dibutytin dilaurate, stannous octoate, iron(III) acetylacetonate, N-ethylmorpholine, a tertiary amine, a metal organic complex or an organometallic compound.

33. The process of claim 30 wherein at least one member selected from the group consisting of a flame retardant, a fire retardant or an intumescent compound is added to the starting materials.

34. The process of claim 33 in which the flame retardants are selected from the group consisting of isomeric pentabromodiphenyl oxides, tricresylphosphate and blends thereof.

35. A polyurethane syntactic foam prepared by a two-step process in which according to step 1, which consists of preparing the prepolymer, at least one polyisocyanate compound is combined with at least one polyfunctional hydroxyl containing compound in an equivalent ratio of about 1.5:

1.0, respectively to about 5.0;

1.0, respectively and the mixture heated to about 60°

C. to about 100°

C. for about 1 hour to about 4 hours to achieve an essentially complete reaction, and then in step 2 the prepolymer of step 1 is combined with polystyrene microspheres or multicellular polystyrene microspheres and sufficient equivalents of polyfunctional active hydrogen compounds to provide a composition substantially equally balanced in isocyanate and active hydrogen equivalents, and the mixture is stirred and heated under vacuum at about 25°

C. to about 80°

C. for about 1 to about 20 minutes and then poured into a mold to produce a cured composition.

36. The process of claim 35, in which the ratio of the polyisocyanate equivalents and the polyfunctional active hydrogen compound equivalents ranges from about 1.00:

0.85, respectively to about 1.00;

1.10, respectively.

37. The composition of claim 35 in which the polyfunctional active hydrogen compound of step 2 comprises a blend of difunctional and trifunctional compounds in an equivalents ratio of between about 95:

5, respectively, and 80;

20, respectively.

38. The process of claim 35 in which the polyfunctional active hydrogen compound of step 2 comprises a difunctional or a trifunctional compound or blend thereof.

39. The process of claim 38 in which said blend includes up to 20 equivalents percent of tetrafunctional compound.

40. A curable syntactic foam composition prepared by reacting and blending the admixture of:

(a) a prepolymer prepared by reacting trans-1,4-cyclohexane diisocyanate with a polyoxytetramethylene glycol having a number average molecular weight of about 1000 in the equivalents ratio of about 2.0;

1.0, respectively, in the presence from 0 to about 0.3 weight percent of a catalyst

(b) and up to 30% of the weight of the final foam of a flame retardant

(c) about 1.5 weight percent to about 10% of the total weight of the foam of hollow preexpanded multicellular polystyrene microspheres, which have a bulk density ranging from about 12 kg/m³ to about 100 kg/m³, a mean diameter ranging from about 30 micrometers to about 700 micrometers, a weight average molecular weight polystyrene shell ranging from about 40,000 to about 1,000,000, and from 100 to 50,000 inner cells per cubic millimeter of sphere volume; and

(d) about 0.85 equivalents to about 1.05 equivalents of an extender per equivalent of the prepolymer described in part (a) above, the extender comprising of trimethylol propane and 1,4-butanediol in an equivalents ratio of about 1.0;

9.0, respectively,

(e) and from 0 to 30% of the weight of the final form of an intumescent agent.

41. A composition according to claim 40 in which the fire retardant described in step (b) of claim 40 comprises a weight ratio of the pentabromodiphenyl oxides to tricresyl phosphate which ranges from 0:

100, respectively to 100;

0, respectively.

42. A composition according to claim 41 in which the trans-1,4-cyclohexane diisocyanate and the approximately 1000 molecular weight polyoxytetramethylene glycol are reacted in an equivalents ratio ranging from about 1.5:

1.0, respectively to about 3.0;

1.0, respectively.

43. A composition according to claim 40 except that in step (a) of claim 40 the molecular weight of the polyoxytetramethylene glycol used in preparing the prepolymer ranges from about 300 to about 6000.

44. A composition according to claim 40 except that in step (a) of claim 40 a polyoxypropylene polyol having a molecular weight ranging from about 300 to about 6000 is used in place of the polyoxytetramethylene glycol and reacted with the trans-1,4-cyclohexane diisocyanate in an equivalent ratio ranging from about 1.5:

1.0, respectively to about 3.0;

1.0, respectively.

45. A composition according to claim 40 except that the extender in step (d) of claim 40 consists of trimethylol propane and 1,4-butanediol in an equivalents ratio of about 0.5:

9.5, respectively to about 5.0;

5.0, respectively.

46. A composition according to of claim 43 in which an essentially chemically inert filler or pigment is added to the admixtures described therein in quantities up to about 50 weight percent of the foam.

47. A composition according to claim 43 except that instead of polyols the extender components consist either solely of polyamines, which may include one or more diamines, or a mixture of diamines and triamines, or of a mixture of at least one polyol and at least one polyamine.

48. A composition according to claim 46 except that instead of polyols the extender components consist either solely of polyamines, which may include one or more diamines, or a mixture of diamines and triamines, or of a mixture of at least one polyol and at least one polyamine.

49. A composition according to claim 46 in which a fire retardant is employed which comprises a mixture of isomeric pentabromodiphenyl oxides and tricresyl phosphate in a weight ration of about 2,9:

1.00, respectively.

50. A composition according to claim 40 except that the prepolymer in step (a) of claim 40 is prepared by using p-phenylene diisocyanate instead of the trans-1,4-cyclohexane diisocyanate.

51. A composition according to claim 50 in which the p-phenylene diisocyanate and the approximately 1000 molecular weight polyoxytetramethylene glycol are reacted in an equivalents ratio ranging from about 1.5:

1.0, respectively to about 3.0;

1.0, respectively, in the preparation of the prepolymer.

52. A composition according to claim 50 in which the molecular weight of the polyoxytetramethylene glycol used in preparing the prepolymer has a molecular weight ranging from about 300 to about 6000.

53. A composition according to claim 51 except that a polyoxypropylene polyol is used in place of the polyoxytetramethylene glycol and reacted with the p-phenylene diisocyanate in an equivalents ratio ranging from about 1.5:

1.0, respectively to about 3.0;

1.0, respectively, in the preparation of the prepolymer.

54. A composition according to claim 50 in which the fire retardant comprised a weight ratio of pentabromodiphenyl oxides to tricresyl phosphate which ranges from 0:

100, respectively to 100;

0, respectively.

55. A composition according to claim 50 in which the extender consists of trimethylol propane and 1,4-butanediol in an equivalent ratio of about 0.5:

9.5, respectively to about 5.0;

5.0, respectively.

56. A composition according to claim 51 in which at least one of the extender components, comprising of trimethylol propane and 1,4-butanediol, are replaced by low molecular weight (<

400) diols, triols, or above mixtures thereof.

57. A composition according to claim 50 in which at least one of the extender components, comprising of trimethylol propane and 1,4-butanediol, are replaced by low molecular weight (<

400) diols and/or triols or mixtures thereof, such that the equivalents ratio of diols to triols can range from 0;

1.00, respectively to 1.00;

0, respectively.

58. A composition according to claim 46 except that the prepolymer is prepared using p-phenylene diisocyanate instead of trans-1,4-cyclohexane diisocyanate.

59. A composition according to claim 58 in which the fire retardant comprised a weight ratio of pentabromodiphenyl oxides to tricresyl phosphate which ranges from 0:

100, respectively, to 100;

0, respectively.

60. A composition according to claim 50 in which the extender components consist of a diol or combination of diols.

61. A composition according to claim 50 except that instead of polyols the extender components consist of polyamines.

62. A composition according to claim 48 except that the prepolymer is prepared by using 4,4'"'"'-methylene-bis(phenylisocyanate) instead of the trans-1,4-cyclohexane diisocyanate and that its equivalents ratio of isocyanate to hydroxyl groups may range from 1.8:

1, respectively, to 5;

1, respectively.

63. A composition according to claim 40 except that the prepolymer described in step (a) of claim 40 is prepared by using 4,4'"'"'-methylene-bis(phenylisocyanate) instead of the trans-1,4-cyclohexane diisocyanate and that its equivalents ratio of isocyanate to hydroxyl groups may range from 1.8:

1.0, respectively to 5;

1, respectively.

64. A composition according to claim 41 except that the prepolymer is prepared by using 4,4'"'"'-methylene-bis(phenyllsocyanate) instead of the trans-1,4-cyclohexane diisocyanate and that its equivalents ratio of isocyanate to hydroxyl groups may range from 1.8:

1.0, respectively to 5;

1, respectively.

65. A composition according to claim 43 except that the prepolymer is prepared by using 4,4'"'"'-methylene-bis(phenylisocyanate) instead of the trans-1,4-cyclohexane diisocyanate and that its equivalents ratio of isocyanate to hydroxyl groups may range from 1.8:

1.0, respectively to 5;

1, respectively.

66. A composition according to claim 45 except that the prepolymer is prepared by using 4,4'"'"'-methylene-bis(phenylisocyanate) instead of the trans-1,4-cyclohexane diisocyanate and that its equivalents ratio of isocyanate to hydroxyl groups may range from 1.8:

1.0, respectively to 5;

1, respectively.

67. A composition according to claim 44 except that the prepolymer is prepared by using 4,4'"'"'-methylene-bis(phenylisocyanate) instead of the trans-1,4-cyclohexane diisocyanate and that its equivalents ratio of isocyanate to hydroxyl groups may range from 1.8:

1.0, respectively to 5;

1, respectively.

68. A composition according to claim 47 except that the prepolymer is prepared by using 4,4'"'"'-methylene-bis(phenylisocyanate) instead of the trans-1,4-cyclohexane diisocyanate and that its equivalents ratio of isocyanate to hydroxyl groups may range from 1.8:

1.0, respectively to 5;

1, respectively.

69. The composition according to claim 46 except that the prepolymer is prepared by using 4,4'"'"'-methylene bis(phenylisocyanate)instead of the trans-1,4-cyclohexane diisocyanate and that its equivalents ratio of isocyanate to hydroxyl groups may range from 1.8:

1.0, respectively, to 5;

1, respectively, and that the extender may consist of one or more of the following;

diol, triol, diamine or of combinations thereof; and

that the ratio of difunctional to trifunctional extender component can range from 0;

1.00, respectively, to 1.00;

0, respectively.

70. A composition according to claim 40 except that the prepolymer is prepared using either an oligomeric polyisocyanate having a functionality ranging from about 1.8 to 4.0 or using combinations of oligomeric polyisocyanates having functionalities ranging from about 1.8 to 4.0 or combinations of one or more of the above described oligomeric polyisocyanates with monomeric diisocyanates in place of the trans-1,4-cyclohexane diisocyanate used in step (a) claim 40 and that the equivalents ratio of isocyanate to hydroxyl groups in the prepolymer may range from about 1.8:

1.0, respectively, to about 5.0;

1.0, respectively.

71. A composition according to claim 40 except that the prepolymer described in step (a) of claim 40 is prepared using a polyisocyanate, which may be of aliphatic or aromatic origin and of a linear or branched or cyclic structure, or polyisocyanates which are oligomeric and have functionalities ranging from about 1.8 to 4.0 or combinations of above described polyisocyanates in place of the trans-1,4-cyclohexane diisocyanate used in step (a) claim 40, and that the equivalents ratio of isocyanate to hydroxyl groups of the prepolymer may range from about 1.8:

1.0, respectively, to about 5.0;

1.0, respectively.

72. A composition according to claim 41 except that the prepolymer is prepared using a polyisocyanate, which may be of aliphatic or aromatic origin and of a linear or branched or cyclic structure, or polyisocyanates which are oligomeric and have functionalities ranging from about 1.8 to 4.0 or combinations of above described polyisocyanates in place of the trans-1,4-cyclohexane diisocyanate used in step (a) claim 40, and that the equivalents ratio of isocyanate to hydroxyl groups of the prepolymer may range from about 1.8:

1.0 respectively to about 5.0;

1.0, respectively.

73. A composition according to claim 43 except that the prepolymer is prepared using a polyisocyanate, which may be of aliphatic or aromatic origin and of a linear or branched or cyclic structure or which may be oligomeric having a functionality ranging from about 1.8 to 4.0 or combinations of above described polyisocyanates in place of the trans-1,4-cyclohexane diisocyanate used in claim 40 step (a), and that the equivalents ratio of isocyanate to hydroxyl groups of the prepolymer may range from about 1.8:

1.0, respectively to about 5.0;

1.0, respectively.

74. A composition according to claim 44 except that the prepolymer is prepared using a polyisocyanate, which may be of aliphatic or aromatic origin and of a linear or branched or cyclic structure or which may be oligomeric having a functionality ranging from about 1.8 to 4.0 or combinations of above described polyisocyanates in place of the trans-1,4-cyclohexane diisocyanate used in claim 40 step (a), and that the equivalents ratio of isocyanate to hydroxyl groups of the prepolymer may range from about 1.8:

1.0, respectively about 5.0;

1.0, respectively.

75. A composition according to claim 45 except that the prepolymer is prepared using a polyisocyanate, which may be of aliphatic or aromatic origin and of a linear or branched or cyclic structure, or polyisocyanates which are oligomeric and have functionalities ranging from about 1.8 to 4.0 or combinations of above described polyisocyanates in place of the trans-1,4-cyclohexane diisocyanate used in claim 40 step (a), and that the equivalents ratio of isocyanate to hydroxyl groups of the prepolymer may range from about 1.8:

1.0, respectively to about 5.0;

1.0, respectively.

76. A composition according to claim 46 except that the prepolymer is prepared using a polyisocyanate, which may be of aliphatic or aromatic origin and of a linear or branched or cyclic structure, or polyisocyanates which are oligomers and have functionalities ranging from about 1.8 to 4.0 or combinations of above described polyisocyanates in place of the trans-1,4-cyclohexane diisocyanate used in step (a) claim 40, and that the equivalents ratio of isocyanate to hydroxyl groups of the prepolymer may range from about 1.8:

1.0, respectively to about 5.0;

1.0, respectively.

77. A composition according to claim 47 except that the prepolymer is prepared using a polyisocyanate, which may be of aliphatic or aromatic origin and of a linear or branched or cyclic structure, or polyisocyanates which are oligomeric and have functionalities ranging from about 1.8 to 4.0 or combinations of above described polyisocyanates in place of the trans-1,4-cyclohexane diisocyanate used in step (a) claim 40, and that the equivalents ratio of isocyanate to hydroxyl groups of the prepolymer may range from about 1.8:

1.0, respectively, to about 5.0;

1.0, respectively.

78. A composition according to claim 77 except that the extender may consist of one or more of, or combinations of the following;

diol, triol or diamine.

79. A curable syntactic foam composition prepared by reacting a polyisocyanate, consisting of an equilibrium mixture of 4,4'"'"'-methylene-bis(phenylisocyanate)(MDI), its difunctional carbodiimide and its trifunctional cycloadduct, which is a condensation product of MDI and its difunctional carbodimide, with an oligomeric diamine, polytetramethylene oxide-di-p-aminobenzoate, in which the ratio of isocyanate to amine groups ranges from about 1.15:

1.00, respectively, to about 0.9;

1.00, respectively, and to which is added by preblending with either or both of the reactive components or introduced just at the time the reactive components are brought together the multicellular expanded polystyrene microspheres in a range of about 2-15 weight percent of the foam.

80. A composition according to claim 79 wherein the hollow expanded polystyrene microspheres have a bulk density ranging from about 12 kg/m³ to about 100 kg/cm³, a mean diameter ranging from about 30 micrometers to about 700 micrometers, a shell having a weight average molecular weight of about 40,000 to 1,000,000 and from 100 to 50,000 inner cells per cubic millimeter of sphere volume.

81. The composition of claim 79 in which includes a flame retardant comprising from about 10% of the weight of the foam to about 35% of the weight of the foam.

82. The composition of claim 79 is in which includes a flame retardant comprising from zero to 35% of the weight of the foam, an intumescent agent comprising from zero to 25% of the weight of the foam and inert filler or pigment comprising from zero up to 25% of the weight of the foam.