# US 8,784,612 B2 · Storage stable solutions of optical brighteners

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,784,612 B2
- Document ID: US8784612B2
- Status: Granted
- Kind: B2
- Application number: 12/746,024
- Filed: 2008-12-09
- Published: 2010-11-25
- Granted: 2014-07-22
- Earliest claimed: 2007-12-12
- Assignees: Clariant Finance (BVI) Limited
- Applicants: John Martin Farrar; Andrew Clive Jackson; Margaret Mahon; Martin Oberholzer
- Inventors: John Martin Farrar; Andrew Clive Jackson; Margaret Mahon; Martin Oberholzer
- Web page: https://patentgrep.com/patent/US8784612B2

## Abstract

The instant invention relates to storage stable solutions of optical brighteners based on certain salt forms of anilino-substituted bistriazinyl derivatives of 4,4′-diaminostilbene-2,2′-disulphonic acid and of organic acids which do not need extra solubilizing additives.

## Claims

### Claim 1

An aqueous solution consisting essentially of 15 to 35% by weight of a compound of formula (1)
wherein
R is hydrogen or a methyl radical,
M+ is Li+, Na+, or K+,
n is less than or equal to 1.5, and
of 0.1 to 2.0% by weight of an organic acid selected from the group consisting of citric acid, glycolic acid, acetic acid and formic acid.

### Claim 2 (depends on 1)

An aqueous solution according to claim 1, consisting essentially of 15 to 35% by weight of a compound of formula (1) and wherein
R is hydrogen or a methyl radical,
M+ is Na+, and
n is less than or equal to 1.5, and of 0.1 to 2% by weight of citric acid.

### Claim 3 (depends on 2)

An aqueous solution according to claim 2, wherein
R is hydrogen,
M+ is Na+, and
n is less than or equal to 1.5.

### Claim 4 (depends on 2)

An aqueous solution according to claim 2, wherein
R is hydrogen,
M+ is Na+, and
n is less than or equal to 1.2.

### Claim 5 (depends on 1)

An aqueous solution according to claim 1, further comprising one or more carriers, antifreezes, defoamers, solubilizing aids, preservatives, complexing agents or organic by-products.

### Claim 6

A process for preparing an aqueous solution, wherein the aqueous solution comprises 10 to 40% by weight of a compound of formula (1)
wherein
R is hydrogen or a methyl radical,
M+ is Li+, Na+, or K+,
n is less than or equal to 1.5, and of 0.05 to 5% by weight of an organic acid selected from the group consisting of citric acid, glycolic acid, acetic acid and formic acid, comprising the step of converting a compound of formula (2)
wherein
R is defined as above,
in the form of an aqueous solution to a mixed salt form (1) in which at least 25% of the M+ ions associated with the sulphonate groups have been replaced by (CH3)2NH+CH2CH2OH ions, by treatment with 2-dimethylaminoethanol and an organic acid.

### Claim 7 (depends on 1)

An optical brightener for textiles, paper, board and non-wovens comprising an aqueous solution as claimed in claim 1.

### Claim 8 (depends on 1)

An aqueous suspension of pulp comprising an aqueous solution as claimed in claim 1.

### Claim 9

A process for whitening of paper comprising the steps of
providing a pulp suspension,
adding 0.01 to 2% by weight based on dry fibre of an aqueous solution
wherein the aqueous solution consists essentially of 15 to 35% by weight of a compound of formula (1)
wherein
R is hydrogen or a methyl radical,
M is Li+, Na+, or K+,
n is less than or equal to 1.5, and
0.1 to 2% by weight of an organic acid selected from the group consisting of citric acid, glycolic acid, acetic acid and formic acid,
producing a paper sheet from the pulp suspension,
pressing and drying the paper sheet.

### Claim 10

A process for whitening of paper comprising the steps of
preparing an aqueous coating composition by mixing together chalk or other white pigments, one or more dispersing agents, a primary latex binder and optionally a secondary binder, and optionally other additives,
adding 0.01 to 3% by weight based on dry pigment of an aqueous solution
wherein the aqueous solution consists essentially of 15 to 35% by weight of a compound of formula (1)
wherein
R is hydrogen or a methyl radical,
M+ is Li+, Na+, or K+,
n is less than or equal to 1.5, and
of 0.1 to 2% by weight of an organic acid selected from the group consisting of citric acid, glycolic acid, acetic acid and formic acid,
applying the coating composition to a paper sheet to form a coated paper sheet, and
drying the coated paper sheet.

### Claim 11 (depends on 1)

An aqueous solution according to claim 1, which is free from solubilising auxiliaries.

### Claim 12 (depends on 1)

An aqueous solution according to claim 1, which is stable to storage at 4° C. for at least two weeks either in the absence or presence of crystal seeds.

### Claim 13 (depends on 1)

An aqueous solution according to claim 1, wherein the organic acid comprises citric acid.

### Claim 14 (depends on 1)

An aqueous solution according to claim 1, wherein the organic acid comprises glycolic acid.

### Claim 15 (depends on 1)

An aqueous solution according to claim 1, wherein the organic acid comprises acetic acid.

### Claim 16 (depends on 1)

An aqueous solution according to claim 1, wherein the organic acid comprises formic acid.