Storage stable solutions of optical brighteners
View Patent ↗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 which do not need extra solubilising additives.
1. A compound of formula (1)
in which
R is hydrogen,
R 1 is —CH 2 CH 2 OH,
R 2 is hydrogen,
M + is Na + , and
n is less than or equal to 1.2.
2. An aqueous solution containing from 20 to 40% by weight of at least one compound of formula (1) according to claim 1 .
3. An aqueous solution containing from 25 to 35% by weight of at least one compound of formula (1) according to claim 1 .
4. An aqueous solution according to claim 2 containing at least one additional component selected from the group consisting of: carriers, antifreezes, defoamers, solubilizing aids, preservatives, complexing agents, and any organic by-products formed during the preparation of the aqueous solution.
5. A process for preparing a compound of formula (1) according to claim 1 comprising the steps of converting a compound of formula (2)
in the form of an aqueous solution to a mixed salt of formula (1) in which at least 25% of the M + ions associated with the sulphonate groups have been replaced by (CH 3 ) 2 NH + CH 2 CH 2 OH ions, either by treatment with 2-dimethylaminoethanol and a mineral acid or by sequential treatment with a cationic ion-exchange resin and 2-dimethylaminoethanol.
6. A process according to claim 5 wherein the compound of formula (1) is isolated and further separated from excess salts and alkanolamine by membrane filtration.
7. A process for preparing an aqueous solution according to claim 4 wherein the additional components selected from the group consisting of: carriers, antifreezes, defoamers, solubilizing aids, preservatives and complexing agents are added to the aqueous solution.
8. A process for optical brightening of a textile, paper, board or non-woven comprising the step of contacting the textile, paper, board or non-woven with at least one compound according to claim 1 .
9. A process for optical brightening of an aqueous suspension of pulp comprising the step of adding at least one compound according to claim 1 to the aqueous suspension of pulp.
10. 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 according to claim 2 ,
producing a paper sheet from said pulp suspension,
pressing and drying the sheet.
11. 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, and a primary latex binder
adding 0.01 to 3% by weight based on dry pigment of an aqueous solution according to claim 2 ,
applying the coating composition to a paper sheet,
drying the coated paper sheet.
12. A textile, paper, board or non-woven made by a process according to claim 8 .
13. A paper whitened by a process according to claim 10 .
14. A paper whitened by a process according to claim 11 .
15. A paper produced by draining an optically brightened aqueous suspension of pulp according to claim 9 .