Low density aerospace compositions and sealants

Patent metadata

Field	Value
Publication number	US-11066584-B2
Application number	US-201916354338-A
Country	US
Kind code	B2
Filing date	Mar 15, 2019
Priority date	Jan 31, 2017
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

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 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;

(b) a curing agent comprising groups reactive with thiol groups; and
(c) from 35 vol % to 55 vol % of coated low-density thermoplastic microcapsules, wherein,
the coated low-density thermoplastic microcapsules comprise a coating of an aminoplast resin;
the coated low-density 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 groups reactive with thiol groups are selected from Michael acceptor groups, alkenyl groups, and epoxide groups.

3. 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.

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

5. The composition of claim 4 , wherein the polyepoxide comprises a hydroxyl-functional difunctional polyepoxide and a trifunctional polyepoxide.

6. The composition of claim 4 , wherein the polyepoxide comprises a diglycidyl ether of bisphenol A and a novolac epoxy resin.

7. The composition of claim 1 , wherein the coated low-density 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.

8. The composition of claim 1 , wherein the coated low-density thermoplastic microcapsules comprise coated thermally expanded thermoplastic microcapsules.

9. The composition of claim 1 , wherein the aminoplast resin comprises a condensation reaction product of an alcohol and formaldehyde with melamine, urea, or benzoguanamine.

10. The composition of claim 1 , wherein the aminoplast resin comprises a condensation reaction product of a melamine and a formaldehyde.

11. The composition of claim 10 , wherein the melamine comprises a methylated melamine resin.

12. The composition of claim 1 , wherein the aminoplast resin comprises a methylated melamine resin, a mixed ether melamine resin, a butylated melamine resin, a urea resin, a butylated urea resin, a benzoquanamine resin, a glycoluril resin, or a formaldehyde-free resin.

13. The composition of claim 1 , wherein the coated low-density thermoplastic microcapsules have a mean diameter (d0.5) from 1 μm to 100 μm determined according to ASTM D1475.

14. The composition of claim 1 , wherein the aminoplast resin coating has a thickness less than 25 μm.

15. The composition of claim 1 , wherein the composition comprises from 2.6 wt % to 4.0 wt % of the coated low-density thermoplastic microcapsules, wherein wt % is based on the total weight of the composition.

16. 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).

17. The composition of claim 1 , wherein the composition further comprises an inorganic filler, an adhesion promoter, a reactive diluent, or a combination of any of the foregoing.

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

19. The cured sealant of claim 18 , wherein the cured sealant meets or exceeds the requirements for aerospace sealants as set forth in AMS 3277 and/or AMS 3281.

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

21. The part of claim 20 , wherein the part is an aerospace part.

22. 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.

23. A sealed part prepared using the method of claim 22 .

24. 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 polythioether;
the second component comprises the curing agent; and
the first component, the second component, or both the first and second components comprise the coated low-density thermoplastic microcapsules.

Assignees

• Prc Desoto Int Inc

Inventors

• Virnelson Bruce

Classifications

• C08L81/04

  Polysulfides · CPC title

• C08L81/02

  Polythioethers; Polythioether-ethers · CPC title

• C08L63/04

  Epoxynovolacs · CPC title

• C08G75/12

  Polythioether-ethers (C08G75/0245 takes precedence) · CPC title

• C08G75/0263

  using elemental sulfur · CPC title