# US 4,396,766 A · Process for producing sodium and zinc pyrithione > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,396,766 A - Document ID: US4396766A - Status: Granted - Kind: A - Application number: 06/372,510 - Filed: 1982-04-28 - Granted: 1983-08-02 - Earliest claimed: 1982-04-28 - Assignees: Olin Corporation - Inventors: Douglas A. Farmer, Jr.; Lawrence E. Katz - Web page: https://patentgrep.com/patent/US4396766A ## CPC - C07D 213/89: with hetero atoms directly attached to the ring nitrogen atom - C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08) ## Abstract Disclosed is a process for producing a zinc pyrithione product having an acceptable white or off-white color and containing substantially no undesired 2-hydroxypyridine-N-oxide or metal salt complexes thereof, by (1) making sodium pyrithione by reacting a 2-halopyridine-N-oxide with sodium hydrosulfide and sodium carbonate (or a mixture of sodium carbonate and sodium hydroxide) under selected addition temperatures and reaction temperatures and in selected mole ratios; followed by (2) making zinc pyrithione by reacting the sodium pyrithione with a zinc salt. ## Claims ### Claim 1 A process for preparing zinc pyrithione comprising the steps: (a) adding sodium hydrosulfide and a base selected from the group consisting of sodium carbonate and sodium hydroxide to an aqueous solution of a 2-halopyridine-N-oxide selected from the group consisting of 2-bromopyridine-N-oxide and 2-chloropyridine-N-oxide, at a temperature below about 70.degree. C. (i) wherein the mole ratio of the sum of moles of said sodium hydrosulfide and said base to said 2-halopyridine-N-oxide is at least about 2:1; (ii) wherein the mole ratio of said sodium hydrosulfide to said 2-halopyridine-N-oxide is at least about 1:1; (iii) wherein the mole ratio of said base to said 2-halopyridine-N-oxide is at least about 0.75:1; and (iv) wherein said base is comprised of at least about 10 mole % of sodium carbonate; (b) heating the resultant mixture of step (a) to about 75.degree. C. to about 105.degree. C. for sufficient time to form sodium pyrithione; and (c) reacting said sodium pyrithione with a zinc salt to form zinc pyrithione. ### Claim 2 (depends on 1) The process of claim 1 wherein said 2-halopyridine-N-oxide is 2-chloropyridine-N-oxide. ### Claim 3 (depends on 1) The process of claim 1 wherein said base is 100 mole % of sodium carbonate. ### Claim 4 (depends on 3) The process of claim 3 wherein said sodium carbonate is added in solid form. ### Claim 5 (depends on 1) The process of claim 1 wherein the mole ratio of the sum of moles of said sodium hydrosulfide and base to said 2-halopyridine-N-oxide is from about 2:1 to about 3:1. ### Claim 6 (depends on 1) The process of claim 1, wherein the mole ratio of said sodium hydrosulfide to 2-halopyridine-N-oxide is from about 1:1 to about 1.25:1. ### Claim 7 (depends on 1) The process of claim 1, wherein the mole ratio of said base to said 2-halopyridine-N-oxide is from about 1:1 to about 1.2:1. ### Claim 8 (depends on 1) The process of claim 1, wherein the temperature at which said base and sodium hydrosulfide is added is from about 20.degree. C. to about 65.degree. C. ### Claim 9 A process for preparing zinc pyrithione comprising the steps: (a) adding sodium hydrosulfide and a base selected from the group consisting of sodium carbonate and sodium hydroxide to an aqueous solution of 2-chloropyridine-N-oxide at a temperature from about 20.degree. C. to about 65.degree. C. (i) wherein the mole ratio of the sum of moles of said sodium hydrosulfide and said base to said 2-chloropyridine-N-oxide is from about 2:1 to about 3:1; (ii) wherein the mole ratio of said sodium hydrosulfide to said 2-chloropyridine-N-oxide is from about 1:1 to about 1.25:1; (iii) wherein the mole ratio of said base to said 2-chloropyridine-N-oxide is from about 1:1 to about 1.2:1; and (iv) wherein said base is comprised of at least about 10 mole % of sodium carbonate; (b) heating the resultant mixture of step (a) to about 75.degree. C. to about 105.degree. C. for sufficient time to form sodium pyrithione; and (c) reacting said sodium pyrithione with a zinc salt to form zinc pyrithione. ### Claim 10 (depends on 9) The process of claim 9, wherein said base is 100 mole % of sodium carbonate. ### Claim 11 (depends on 10) The process of claim 10, wherein said sodium carbonate is added in solid form. ### Claim 12 In a process for preparing sodium pyrithione which comprises reacting a 2-halopyridine-N-oxide with sodium hydrosulfide and a base to form sodium pyrithione, the improvement which comprises (a) adding said sodium hydrosulfide and a base selected from the group consisting of sodium carbonate and sodium hydroxide to an aqueous solution of a 2-halopyridine-N-oxide selected from the group consisting of 2-bromopyridine-N-oxide and 2-chloropyridine-N-oxide, at a temperature below about 70.degree. C. (i) wherein the mole ratio of the sum of moles of said sodium hydrosulfide and said base to said 2-halopyridine-N-oxide is at least about 2:1; (ii) wherein the mole ratio of said sodium hydrosulfide to said 2-halopyridine-N-oxide is at least about 1:1; (iii) wherein the mole ratio of said base to said 2-halopyridine-N-oxide is at least about 0.75:1; and (iv) wherein said base is comprised of at least about 10 mole % of sodium carbonate; (b) heating the resultant mixture of step (a) to about 75.degree. C. to about 105.degree. C. for sufficient time to form said sodium pyrithione.