Low density aerospace compositions and sealants

Patent metadata

Field	Value
Publication number	US-10280348-B2
Application number	US-201715420138-A
Country	US
Kind code	B2
Filing date	Jan 31, 2017
Priority date	Jan 31, 2017
Publication date	May 7, 2019
Grant date	May 7, 2019

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.

First claim

What is claimed is:

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

Assignees

• Prc Desoto Int Inc

Inventors

• Virnelson Bruce

Classifications

• C08G59/66 Primary

  Mercaptans · CPC title

• C08L63/00

  Compositions of epoxy resins; Compositions of derivatives of epoxy resins · CPC title

• C09J181/02 Primary

  Polythioethers; Polythioether-ethers · CPC title

• C08L81/02

  Polythioethers; Polythioether-ethers · CPC title

• C09J11/08

  Macromolecular additives · CPC title