# US 4,395,264 A · Azo coupling process

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- Number: US 4,395,264 A
- Document ID: US4395264A
- Status: Granted
- Kind: A
- Application number: 06/318,750
- Filed: 1981-11-06
- Granted: 1983-07-26
- Earliest claimed: 1981-11-06
- Assignees: BASF Wyandotte Corporation
- Inventors: George W. Fenwick
- Web page: https://patentgrep.com/patent/US4395264A

## CPC

- C09B 41/006: {characterised by process features}
- C09B 41/001: {characterised by the coupling medium}
- C09B: ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES {, e.g. PIGMENTS}; MORDANTS; LAKES (fermentation or enzyme using processes to synthesise a desired chemical compound C12P)

## Abstract

The present invention relates to a process for coupling beta-naphthol with a diazotized amine as follows: 1. (a) Dissolving a beta-naphthol in water with a strong base (b) Precipitating the beta-naphthol with a strong acid and (c) Cooling the slurry. 2. Adding a diazotized amine to the beta-naphthol solution and 3. Increasing the pH in two steps, first with a strong base and then with a weak base.

## Claims

### Claim 1

A process for coupling a beta-naphthol with a diazotized amine comprising
1. (a) dissolving a beta-naphthol in water with a strong base
(b) precipitating the beta-naphthol with a strong acid and
(c) cooling the slurry to about 0.degree. C. to 15.degree. C.
2. (a) adding a diazotized amine and
3. (a) increasing the pH to about 1.0 to 4.0 with a strong base and
(b) further increasing the pH to about 5.0 to 10.0 with a weak base.

### Claim 2 (depends on 1)

The process of claim 1 wherein in all steps said strong base is sodium hydroxide or potassium hydroxide, said strong acid is hydrochloric acid or sulfuric acid and said weak base is sodium acetate, sodium carbonate or ammonia.

### Claim 3 (depends on 1)

The process of claim 1 wherein said solution of beta-naphthol in water and strong base contains sufficient strong base to achieve a pH of 10 to 12, said precipitation with a strong acid results in a pH of 0.5 to 2.0 and the pH is increased in said step 3(a) to a value greater than the pH resulting from steps 1 and 2, said greater pH falling within the range of about 1.0 to 4.0.

### Claim 4 (depends on 3)

The process of claim 3 wherein in all steps said strong base is sodium hydroxide, said strong acid is hydrochloric acid and said weak base is sodium acetate.

### Claim 5

A process for producing an azo coloring material comprising:
1. diazotizing a substituted a amine by
(a) mixing said amine with water
(b) adding a strong base in amount sufficient to dissolve said amine
(c) adding a strong acid in an amount sufficient to obtain a pH of less than about 2
(d) cooling to about -5.degree. to 15.degree. C. and
(e) slowly adding a slight molar excess of sodium nitrite solution and
2. (a) dissolving a beta-naphthol in water with a strong base
(b) precipitating the beta-naphthol with a strong acid and
(c) cooling the slurry to about 0.degree. C. to 15.degree. C.
3. (a) mixing the diazotized amine and said precipitated beta-napthol
4. (a) increasing the pH to a value greater than the pH resulting from steps 1-3, said greater pH falling within the range of about 1.0 to 4.0 with a strong base and
(b) further increasing the pH to about 5.0 to 10.0 with a weak base.

### Claim 6 (depends on 5)

The process of claim 5 wherein in all steps said strong base is sodium hydroxide or potassium hydroxide, said strong acid is hydrochloric acid or sulfuric acid and said weak base is sodium acetate, sodium carbonate or ammonia.

### Claim 7 (depends on 5)

The process of claim 5 wherein said strong base is added in step 1(b) in amount sufficient to obtain a pH of about 9.0 to 12.0 and said solution of beta-naphthol in water and strong base contains sufficient sodium hydroxide to have a pH of 10 to 12 and said precipitation with a strong acid results in a pH of 0.5 to 2.0.

### Claim 8 (depends on 7)

The process of claim 7 wherein in all steps said strong base is sodium hydroxide, said strong acid is hydrochloric acid and said weak base is sodium acetate.