Bleaching and dyeing; fluid treatment and chemical modification – Dye or potential dye composition – additive – treatment,... – Fluorescent dye – e.g. – stilbene – benzimidazole – benzoxazole,...
Patent
1992-02-19
1993-11-30
Clingman, A. Lionel
Bleaching and dyeing; fluid treatment and chemical modification
Dye or potential dye composition, additive, treatment,...
Fluorescent dye, e.g., stilbene, benzimidazole, benzoxazole,...
8584, 8594, 8919, 252 86, D06L 312, D21H 2130, D21H 3766, C11D 944
Patent
active
052660788
DESCRIPTION:
BRIEF SUMMARY
This invention relates to enhancing the whiteness of a cellulosic material, typically paper or cotton.
It is well known that paper and other cellulosic materials which are essentially white have a certain degree of yellowness. This results from a reduced blue remission. Accordingly, various ways have been found of reducing this deficiency, typically using a fluorescent whitening agent. Unfortunately, though, the use of such agents does not wholly eliminate the problem efficiently and some discolouration can still occur.
The present invention is directed to improving the efficiency of fluorescent whitening agents. It has surprisingly been found, according to the present invention, that if the fluorescent whitening agent is applied in combination with certain phosphonates and/or carboxylates an enhanced effect can be obtained.
According to the present invention there is provided a method of enhancing the whiteness of a cellulosic material which comprises incorporating therein, or applying thereto, a fluorescent whitening agent and a water soluble phosphonate having 1 to 5 phosphonate groups and/or a water soluble carboxylate having 2 to 5 carboxylate groups but no chain nitrogen atoms, at a neutral or alkaline pH.
The present invention is of general applicability and the specified additives can be used to enhance the effect of a wide range of fluorescent whitening agents. These are chemicals having the capability of increasing the apparent blue remission of a material in or on which they are applied by absorbing UV radiation and by re-emitting visible blue light. Conventional fluorescent whitening agents which can be used in the prevent invention are generally stilbene compounds, especially: ##STR1## wherein R.sub.1 can be ##STR2## --and R.sub.2 can be N(CH.sub.2 --CH.sub.3).sub.2, N(CH.sub.2 --CH.sub.2 --OH).sub.2 or ##STR3## coumarin and carbostyril compounds such as ##STR4## 1,3-diphenyl-2-pyrazoline compounds such as ##STR5## and naphthalimide compounds such as ##STR6## Other fluorescent whitening agents which can be used include those mentioned in "Fluorescent Whitening Agents", edited by R. Anliker and G. Muller, Georg Thieme, Stuttgart, 1975, Chapter III.
In general any water soluble phosphonate having 1 to 5 phosphonate groups can be used in the method of the present invention; substantially colourless phosphonates are preferred. A preferred phosphonate is diethylenetriamine-pentamethylene phosphonic acid (DTPMPA) (and its water soluble salts). Other preferred phosphonates are hydroxy alkylidene diphosphonic acids having the formula: ##STR7## wherein R.sub.1 is OH or NH.sub.2 and R.sub.2 is an alkyl group of 1 to 5 carbon atoms, and water soluble salts of said diphosphonic compounds. A particularly preferred phosphonate is 1-hydroxyethylidene-1,1-diphosphonic acid (HEDPA) (and its water soluble salts).
The carboxylates which can be used in the present invention are generally substantially colourless and preferably contain 2 or 3 carboxyl groups. They may also contain a hydroxyl group. They are preferably aliphatic and preferably also have carboxyl groups at opposite ends of the aliphatic chain. The aliphatic chain contains no chain nitrogen atom. Typical carboxylates are those having the formula: ##STR8## wherein R.sub.1 is OH or H, R.sub.2 and R.sub.3 are each independently H, OH or COOH, and R.sub.4 is H, OH, COOH, CH.sub.2 OH or CH.sub.2 COOH, and n=0 to 6, which do not contain more than 5 carboxyl groups, and water soluble salts thereof.
Preferred carboxylates include sebacic acid and succinic acid. A particularly preferred compound is citric acid.
Typical water soluble salts include sodium, potassium and ammonium salts.
It will, of course, be appreciated that a mixture of phosphonates and/or carboxylates can be used, for example a phosphonic acid together with a water soluble salt of said acid or a phosphonate and a carboxylate. In this connection it is also possible to use a single compound, i.e. a di- or higher carboxylate containing at least one phosphonate group such as 2-phosphonobutane-1,2
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Hakansson Gunilla
Hassler Thord
Welkener Ulrich
Barr James P.
Clingman A. Lionel
W. R. Grace & Co.,-Conn.
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