Process for producing sodium and zinc pyrithione
AssigneeOlin Corporation
InventorsDouglas A. Farmer, Jr., Lawrence E. Katz
Life of this patent
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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.
Claims12
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.
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.
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.
Dependencies are inferred from the claim text.