Low density aerospace compositions and sealants

{
  "publication_number": "US10280348B2",
  "country": "US",
  "kind": "B2",
  "title": "Low density aerospace compositions and sealants",
  "abstract": "Low density aerospace compositions and sealants are disclosed. The low density compositions and sealants are characterized by a high volume percent loading of low density microcapsules.",
  "claims": [
    "1. A composition comprising: from 50 wt % to 70 wt % of a thiol-terminated polythioether prepolymer having an average thiol functionality from 2.05 to 2.8, wherein the thiol-terminated polythioether prepolymer comprises the chemical structure of Formula (1): R 1 - [- S - (CH 2) 2 - O - [- R 2 - O -] m - (CH 2) 2 - S - R 1] n - (1) wherein, each R 1 is independently selected from a C 2-10 n-alkanediyl group, a C 3-6 branched alkanediyl group, a C 6-8 cycloalkanediyl group, a C 6-10 alkanecycloalkanediyl group, a heterocyclic group, and a - [(- CHR 3 -) p - X -] q - (CHR 3) r - group, wherein each R 3 is independently selected from hydrogen and methyl; each R 2 is independently selected from a C 2-10 n-alkanediyl group, a C 3-6 branched alkanediyl group, a C 6-8 cycloalkanediyl group, a C 6-14 alkanecycloalkanediyl group, a heterocyclic group, and a - [(- CH 2 -) p - X -] q - (CH 2) r - group; each X is independently selected from O, S, and - NR -, wherein R is selected from hydrogen and methyl; m ranges from 0 to 50; n is an integer ranging from 1 to 60; p is an integer ranging from 2 to 6; q is an integer ranging from 1 to 5; and r is an integer ranging from 2 to 10; from 15 wt % to 21 wt % of a polyepoxide; and from 35 vol % to 55 vol % of a low density filler, wherein, the low density filler is characterized by a specific gravity less than 0.1; the low density filler comprises low density microcapsules comprising a coating of an aminoplast resin; the aminoplast resin comprises a melamine-formaldehyde resin or a urea-formaldehyde resin; and the coated low density microcapsules are characterized by a specific gravity within a range from 0.03 to 0.06, wherein the specific gravity is determined according to ASTM D1475; wherein wt % is based on the total weight of the composition, and vol % is based on the total volume of the composition, and wherein the composition is characterized by a specific gravity less than 0.9, wherein the specific gravity is determined according to ASTM D1475 (modified).",
    "2. The composition of claim 1, wherein when cured, the cured composition meets or exceeds the requirements for aerospace sealants as set forth in AMS 3277 and/or AMS 3281.",
    "3. The composition of claim 1, wherein the composition is characterized by a specific gravity within a range from 0.65 to 0.85, wherein the specific gravity is determined according to ASTM D1475 (modified).",
    "4. The composition of claim 1, wherein the polyepoxide comprises: from 86 wt % to 99 wt % of a hydroxyl-functional diglycidyl ether of bisphenol A; and from 1 wt % to 11 wt % of a novolac polyepoxide; wherein wt % is based on the total weight of the polyepoxide in the composition.",
    "5. The composition of claim 1, wherein the composition comprises: from 86 wt % to 99 wt % of a hydroxyl-functional difunctional polyepoxide; and from 1 wt % to 11 wt % of a trifunctional polyepoxide, wherein wt % is based on the total weight of the polyepoxide in the composition.",
    "6. The composition of claim 1, wherein the polyepoxide comprises: from 86 wt % to 99 wt % of the diglycidyl ether of bisphenol A; and from 1 wt % to 11 wt % of the novolac epoxy resin, wherein wt % is based on the total weight of the polyepoxide in the composition.",
    "7. The composition of claim 1, wherein, the composition comprises from 2.8 wt % to 4.0 wt % of the low density filler; and the aminoplast resin comprises a melamine-formaldehyde resin or a urea-formaldehyde resin; and the coated low density microcapsules are characterized by a specific gravity within a range from 0.03 to 0.06, wherein the specific gravity is determined according to ASTM D1475.",
    "8. The composition of claim 1, further comprising: from 10 wt % to 16 wt % of an inorganic filler; from 1.8 wt % to 3.8 wt % of an adhesion promoter; and from 0.2 wt % to 3 wt % of an epoxy-functional reactive diluent, wherein wt % is based on the total weight of the composition.",
    "9. The composition of claim 8, wherein the inorganic filler comprises precipitated calcium carbonate, hydrated alumina, fumed silica, calcium hydroxide, carbon black, or a combination off any of the foregoing.",
    "10. The composition of claim 8, wherein the adhesion promoter comprises: from 45 wt % to 65 wt % of a phenolic adhesion promoter; and from 35 wt % to 55 wt % of an amine-functional silane, wherein wt % is based on the total weight of the adhesion promoter in the composition.",
    "11. The composition of claim 10, wherein the amine-functional silane comprises; from 40 wt % to 60 wt % of a primary amine-functional silane; and from 40 wt % to 60 wt % of a secondary amine-functional silane; wherein wt % is based on the total weight of the amine-functional silane in a composition.",
    "12. The composition of claim 8, wherein the epoxy-functional reactive diluent comprises an epoxy-functional reactive diluent characterized by a weight average molecular weight from 100 Daltons to 1,000 Daltons, wherein the weight average molecular weight is determined by gel permeation chromatography, using a polystyrene standard.",
    "13. The composition of claim 1, comprising: from 50 wt % to 70 wt % of the thiol-terminated polythioether prepolymer; from 15 wt % to 21 wt % of the polyepoxide; from 2.5 wt % to 4.0 wt % of the low density filler, wherein the low density filler is characterized by a specific gravity within a range from 0.01 to 0.09, wherein the specific gravity is determined according to ASTM D1475; from 10 wt % to 16 wt % of an inorganic filler; from 1.8 wt % to 3.8 wt % of an adhesion promoter; and from 0.2 wt % to 3 wt % of an epoxy-functional reactive diluent, wherein wt % is based on the total weight of the composition.",
    "14. The composition of claim 13, wherein, the polyepoxide comprises a diglycidyl ether of bisphenol A and a novolac epoxy resin, wherein the composition comprises: from 10 wt % to 25 wt % of the diglycidyl ether of bisphenol A; and from 0.2 wt % to 2 wt % of the novolac epoxy resin; and the adhesion promoter comprises a phenolic adhesion promoter and an amine-functional silane, wherein the composition comprises: from 1 wt % to 3 wt % of the phenolic adhesion promoter; and from 0.5 wt % to 2 wt % of the amine-functional silane; wherein wt % is based on the total weight of the composition.",
    "15. The composition of claim 14, wherein the amine-functional silane comprises a primary amine-functional silane and a secondary amine-functional, wherein the composition comprises: from 0.4 wt % to 0.9 wt % of the primary amine-functional silane; and from 0.4 wt % to 0.9 wt % of the secondary amine-functional silane, wherein wt % is based on the total weight of the composition.",
    "16. The composition of claim 1, comprising: from 50 wt % to 70 wt % of the thiol-terminated polythioether prepolymer; from 15 wt % to 21 wt % of the polyepoxide, wherein the polyepoxide comprises a diglycidyl ether of bisphenol A and a novolac epoxy resin, wherein the composition comprises: from 10 wt % to 25 wt % of the diglycidyl ether of bisphenol A, wherein the diglycidyl ether of bisphenol A comprises pendent hydroxyl groups; and from 0.2 wt % to 2 wt % of the novolac epoxy resin; from 2.5 wt % to 4.0 wt % of the low density filler, wherein the low density filler is characterized by a specific gravity within a range from 0.01 to 0.09, wherein the specific gravity is determined according to ASTM D1475; from 10 wt % to 16 wt % of the inorganic filler; from 1.8 wt % to 3.8 wt % of the adhesion promoter, wherein the adhesion promoter comprises a phenolic adhesion promoter and an amine-functional silane, wherein the composition comprises: from 1 wt % to 3 wt % of the phenolic adhesion promoter; and from 0.5 wt % to 2 wt % of the amine-functional silane; and from 0.2 wt % to 3 wt % of an epoxy-functional reactive diluent, wherein the epoxy-functional reactive diluent comprises an aliphatic diglycidyl ether, wherein wt % is based on the total weight of the composition.",
    "17. A cured sealant prepared using the composition of claim 1.",
    "18. The cured sealant of claim 17, wherein the cured sealant meets or exceeds the requirements for aerospace sealants as set forth in AMS 3277 and/or AMS 3281.",
    "19. A part comprising the cured sealant of claim 17.",
    "20. A method of sealing a part, comprising: applying the composition of claim 1 to at least one surface of a part; and curing the applied composition to seal the part.",
    "21. A sealant system comprising a first component and a second component, wherein, the first component comprises: from 50 wt % to 70 wt % of a thiol-terminated polythioether having an average thiol functionality from 2.05 to 2.8, wherein the thiol-terminated polythioether prepolymer comprises the chemical structure of Formula (1): - R 1 - [- S - (CH 2) 2 - O - [- R 2 - O -] m - (CH 2) 2 - S - R 1] n - (1) wherein, each R 1 is independently selected from a C 2-10 n-alkanediyl group, a C 3-6 branched alkanediyl group, a C 6-8 cycloalkanediyl group, a C 6-10 alkanecycloalkanediyl group, a heterocyclic group, and a - [(- CHR 3 -) p - X -] q - (CHR 3) r - group, wherein each R 3 is independently selected from hydrogen and methyl; each R 2 is independently selected from a C 2-10 n-alkanediyl group, a C 3-6 branched alkanediyl group, a C 6-8 cycloalkanediyl group, a C 6-14 alkanecycloalkanediyl group, a heterocyclic group, and a - [(- CH 2 -) p - X -] q - (CH 2) r - group; each X is independently selected from O, S, and - NR -, wherein R is selected from hydrogen and methyl; m ranges from 0 to 50; n is an integer ranging from 1 to 60; p is an integer ranging from 2 to 6; q is an integer ranging from 1 to 5; and r is an integer ranging from 2 to 10; from 2.5 wt % to 4.0 wt % of a low density filler, wherein, the low density filler is characterized by a specific gravity within a range from 0.01 to 0.09, wherein the specific gravity is determined according to ASTM D1475; and the low density filler comprises low density microcapsules comprising a coating of an aminoplast resin; the aminoplast resin comprises a melamine-formaldehyde resin or a urea-formaldehyde resin; and the coated low density microcapsules are characterized by a specific gravity within a range from 0.03 to 0.06, wherein the specific gravity is determined according to ASTM D1475; wherein wt % is based on the total weight of the first component; and the second component comprises: from 75 wt % to 95 wt % of a polyepoxide, wherein wt % is based on the total weight of the second component, wherein the first component and the second component combined provide the composition of claim 1."
  ],
  "description_excerpt": "The present disclosure relates to low density compositions and sealants. The compositions and sealants are characterized by a high volume percent loading of low density microcapsules.\n\nAerospace sealants must satisfy demanding mechanical, chemical, and environmental requirements. The sealants can be applied to a variety of surfaces including metal surfaces, primer coatings, intermediate coatings, finished coatings, and aged coatings. Sealants comprising sulfur-containing prepolymers that exhibit acceptable fuel resistance, thermal resistance, and flexibility for aerospace applications are described, for example, in U.S. Pat. No. 6,172,179. In sealants such as those described in U.S. Application Publication Nos. 2006/0270796, 2007/0287810, and 2009/0326167, a sulfur-containing polymer such as a thiol-terminated polythioether prepolymer can be reacted with a polyepoxide curing agent in the presence of an amine catalyst to provide a cured product. These systems are useful as sealants and can meet the demanding performance requirements of the aerospace industry including fuel resistance. Cured aerospace sealants must exhibit acceptable tensile strength, elongation, and adhesion to a variety of aerospace substrates and must maintain these properties following exposure to aviation fluids.\n\nReducing the weight of aerospace components including coatings and sealants can significantly increase fuel economy. To reduce the weight of aerospace vehicles low density filler can be added to a coating composition. Coatings and sealants having a specific gravity of about 1 are commercially available.",
  "cpc": [
    "C08G 59/66",
    "C08G 59/188",
    "C08G 59/50",
    "C08G 75/0263",
    "C08G 75/12",
    "C08J 11/08",
    "C08K 7/22",
    "C08K 9/08",
    "C08L 63/00",
    "C08L 63/04",
    "C08L 81/02",
    "C08L 81/04",
    "C09J 11/04",
    "C09J 11/08",
    "C09J 181/02"
  ],
  "ipc": [
    "C09J 11/04",
    "C09J 11/08",
    "C09J 181/02",
    "C08G 59/66",
    "C08L 63/00",
    "C08L 81/02"
  ],
  "assignees": [
    "PRC Desoto International Inc"
  ],
  "inventors": [
    "Bruce Virnelson"
  ],
  "filing_date": "2017-01-31",
  "publication_date": "2019-05-07",
  "grant_date": "2019-05-07",
  "priority_date": "2017-01-31",
  "application_number": "US-201715420138-A",
  "family_id": "61386888",
  "cited_by_count": 7,
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}