Low density aerospace compositions and sealants

Patent metadata

Field	Value
Publication number	US-11760909-B2
Application number	US-202117352419-A
Country	US
Kind code	B2
Filing date	Jun 21, 2021
Priority date	Jan 31, 2017
Publication date	Sep 19, 2023
Grant date	Sep 19, 2023

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:
(a) a thiol-terminated polythioether prepolymer;
(b) a curing agent comprising groups reactive with thiol groups; and
(c) from 35 vol % to 55 vol % of coated thermally-expanded thermoplastic microcapsules, wherein,
the coated thermally expanded thermoplastic microcapsules comprise a coating of an aminoplast resin;
the coated thermally expanded thermoplastic microcapsules have a mean diameter from 1 μm to 100 μm, wherein the diameter is determined according to ASTM D1475;
the coated thermally expanded thermoplastic microcapsules are characterized by a specific gravity less than 0.1;
vol % is based on the total volume of the composition; and
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 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 ), — 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.

3. The composition of claim 1 , wherein the groups reactive with thiol groups are selected from Michael acceptor groups, alkenyl groups, and epoxide groups.

4. The composition of claim 1 , wherein the composition comprises from 10 wt % to 30 wt % of the curing agent, wherein wt % is based on the total weight of the composition.

5. The composition of claim 1 , wherein the curing agent comprises a polyepoxide.

6. The composition of claim 5 , wherein the polyepoxide comprises both a hydroxyl-functional difunctional polyepoxide and a trifunctional polyepoxide.

7. The composition of claim 5 , 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.

8. The composition of claim 1 , wherein the coated thermally expanded thermoplastic microcapsules are characterized by a specific gravity within a range from 0.02 to 0.08, wherein the specific gravity is determined according to ASTM D1475.

9. The composition of claim 1 , wherein the aminoplast resin comprises a melamine-formaldehyde resin.

10. The composition of claim 1 , wherein the aminoplast resin comprises a urea-formaldehyde resin.

11. The composition of claim 1 , wherein the composition comprises from 2.6 wt % to 4.0 wt % of the coated thermally expanded thermoplastic microcapsules, wherein wt % is based on the total weight of the composition.

12. 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).

13. The composition of claim 1 , further comprising
from 10 wt % to 16 wt % of an inorganic filler,
wherein wt % is based on the total weight of the composition.

14. The composition of claim 1 , further comprising from 1.8 wt % to 3.8 wt % of an adhesion promoter, wherein,
wt % is based on the total weight of the composition; and
the adhesion promoter comprises:
from 45 wt % to 65 wt % of a thiol-functional 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.

15. The composition of claim 14 , 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.

16. A cured sealant prepared using the composition of claim 1 .

17. The cured sealant of claim 16 , wherein the cured sealant meets or exceeds the requirements for aerospace sealants as set forth in AMS 3277 and/or AMS 3281.

18. A part comprising the cured sealant of claim 16 .

19. The part of claim 18 , wherein the part is an aerospace part.

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 sealed part prepared using the method of claim 20 .

22. A sealant system for preparing the composition of claim 1 , wherein the sealant system comprises a first component and a second component, wherein,
the first component comprises the thiol-terminated polythioether prepolymer;
the second component comprises the curing agent; and
the first component, the second component, or both the first and second components comprise the coated thermally expanded thermoplastic microcapsules.

Assignees

• Prc Desoto Int Inc

Inventors

• Virnelson Bruce

Classifications

• C08G59/66 Primary

  Mercaptans · CPC title

• C08G59/188 Primary

  using encapsulated compounds · CPC title

• C09J181/02 Primary

  Polythioethers; Polythioether-ethers · CPC title

• C08L63/00

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

• C08L81/02

  Polythioethers; Polythioether-ethers · CPC title