Process for synthesizing perfluorinated polyethers with metal carboxylate end groups
View Patent ↗A process is provided for synthesizing metal salts of perfluorinated polyethers containing at least one carboxylic acid group. The polymeric salts so provided are effective as anti-wetting and corrosion-protective agents. The metal salts of perfluorinated polyether acids may be used to prepare corrosion-protected substrates, including magnetic recording disks and magnetic recording heads.
1. A process for preparing a metal salt of a perfluorinated polyether having at least one carboxylic acid end group, comprising:
treating a fluorinated polyether having at least one carboxylic acid end group with a metal salt of a volatile organic acid under reaction conditions effective to convert all carboxylic acid end groups to the salt form and volatilize the resulting organic acid, thus providing a reaction product comprising a salt of the metal and the fluorinated polyether.
2. The process of claim 1 , wherein the fluorinated polyether is a perfluorinated polyether.
3. The process of claim 2 , wherein the perfluorinated polyether is comprised of monomer units having the structure —CF 2 —O—, —CF 2 —CF 2 —O—, —CF(CF 3 )—O—, —CF(CF 3 )—CF 2 —O—, or a combination thereof.
4. The process of claim 3 , wherein the perfluorinated polyether is a linear polymer.
5. The process of claim 4 , wherein the perfluorinated polyether has a single carboxylic acid end group.
6. The process of claim 4 , wherein the perfluorinated polyether has two carboxylic acid end groups.
7. The process of claim 2 , wherein the metal salt is an alkali metal salt.
8. The process of claim 7 , wherein the alkali metal salt is a sodium salt.
9. The process of claim 2 , wherein the volatile organic acid is acetic acid.
10. The process of claim 7 , wherein the volatile organic acid is acetic acid.
11. The process of claim 8 , wherein the volatile organic acid is acetic acid.
12. The process of claim 2 , wherein the reaction conditions comprise heating a mixture of the fluorinated polyether and the metal salt of a volatile organic acid at a temperature of at least about 130° C. for at least 48 hours.
13. The process of claim 2 , further comprising isolating the reaction product.
14. The process of claim 13 , wherein the product is isolated by an extraction process.
15. The process of claim 14 , wherein the extraction process employs a fluorinated alkane solvent and a lower alkanol.
16. The process of claim 15 , wherein the extraction process employs perfluorohexane and methanol.
17. The process of claim 2 , wherein the perfluorinated polyether has a number average molecular weight in the range of approximately 500 to 10,000.
18. The process of claim 17 , wherein the perfluorinated polyether has a number average molecular weight in the range of approximately 1000 to 5,000.
19. The process of claim 18 , wherein the perfluorinated polyether has a number average molecular weight in the range of approximately 2500 to 3500.