# US 11,898,082 B1 · Fire resistant phosphate cyanate esters

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- Number: US 11,898,082 B1
- Document ID: US11898082B1
- Status: Granted
- Kind: B1
- Application number: 17/065,321
- Filed: 2020-10-07
- Granted: 2024-02-13
- Earliest claimed: 2015-09-09
- Assignees: The United States of America as represented by the Secretary of the Navy
- Applicants: The United States of America, as represented by the Secretary of the Navy
- Inventors: Benjamin G. Harvey; Andrew P. Chafin; Michael D. Garrison
- Web page: https://patentgrep.com/patent/US11898082B1

## CPC

- C09K 21/14: Macromolecular materials
- C07F 9/12: with hydroxyaryl compounds
- C08G 79/04: Phosphorus linked to oxygen or to oxygen and carbon
- C09K 21/12: containing phosphorus
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C07F: ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM (metal-containing porphyrins C07D487/22)
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS

## Abstract

This invention describes resins with phosphate cores and a simple, three-step process for their synthesis. Preferred resins are cyanate ester resins with bridging phosphate groups. These resins can be cured to produce thermoset polymers having Tgs of between 131 and >360° C. depending on the number of cyanate ester groups per phosphate and the substitution pattern of the aromatic rings. The high char yields of these resins, up to about 67%, coupled with the phosphate core means that these materials will have applications as fire-resistant polymers. Additionally, these materials can potentially be blended with conventional cyanate esters or other compatible thermosetting resins to improve the fire resistance of composite materials. Other applications may include use in fire-resistant circuit boards, or as surface coatings to reduce flammability of conventional composite materials or thermoplastics.

## Claims

### Claim 1

A method for producing a phosphate-bridged cyanate ester comprising:
reacting a phenol with a chlorophosphate in the presence of base to make a phosphate ester;
hydrolyzing ether substituents on the resulting phosphate ester to generate a phosphate-polyphenol; and,
converting the phosphate-polyphenol to a phosphate-bridged cyanate ester, wherein the phosphate-bridged cyanate ester is characterized by the, formula:
where R1 is alkyl group, aromatic group,
and,
where R2 and R3 are each
where R1, R2, and R3 can each have up to four additional substituents independently selected from an alkyl or an aromatic group.

### Claim 2 (depends on 1)

The method of claim 1 wherein the phenol is an alkoxy or benzyloxy functionalized phenol.

### Claim 3 (depends on 1)

The method of claim 1 wherein the phenol is a bisphenol or trisphenol.

### Claim 4 (depends on 1)

The method of claim 1 wherein the chlorophosphate is a dichlorophosphate or trichlorophosphate.