Low-dust or dust-free dye preparations

Details Low-dust or dust-free dye preparations Low-dust or dust-free dye preparations

1992-11-10

1994-11-22

Lieberman, Paul

Bleaching and dyeing; fluid treatment and chemical modification

Dry dye composition other than mere mixture of two or more...

8526, 8611, C09B 6742

Patent

active

053665120

DESCRIPTION:

BRIEF SUMMARY
The invention relates to the field of dye preparations.
Pulverulent dye preparations are widely produced and used in industry, for example for preparing padding and dyeing liquors for dyeing textile materials and for preparing print pastes for printing paper and textiles. Pulverulent dye preparations are prone to dusting not only in the course of being produced but also in use. This can lead to dye losses, the contamination of places of work and materials being worked, and health hazards for the people concerned with handling such dusting preparations.
There have been various suggestions for solving this problem.
For instance, liquid preparations and granules have been developed. Liquid preparations are naturally free of dusting, but they have other disadvantages, such as limited shelf lives and low dye contents, which necessitates increased packaging, storage and transportation costs. In addition, liquid preparations can be prepared only from sufficiently soluble dyes. Granules require special production technologies and can be produced only with additional and costly apparatus. Moreover, most granular products are likewise not dust-free from the start or form dust in the course of being packaged or transferred or during transportation. Like powders they must therefore be treated with dustproofing agents, albeit with smaller amounts thereof.
On the other hand, there have been many attempts to convert pulverulent dyes into a low-dust or dust-free form with dustproofing agents. Examples of substances used for this purpose include phthalic esters, silicones, dodecylbenzene, surfactants and mineral oil alone or combined with nonionic, anionic or cationic surfactants (see for example U.S. Pat. Nos. 2,604,469 and 3,560,134, German Patent 834,237, German Offenlegungsschrift 2,523,096, German Auslegeschrift 1,117,582 and European Patent Application Publication 0 023 638A).
However, the use of any of these dustproofing agents or dust removal methods is associated with considerable risks and disadvantages. Mineral oils and other water-insoluble dustproofing agents generally have an adverse effect on the cold water solubility important for energy-saving low-temperature dyeing methods. They are also responsible for the formation of oily deposits in the dyeing liquors, which may cause spotty, unlevel dyeings. This is one of the reasons for adding surfactants, another reason being that they are intended to ensure the uniform dispersion of the water-insoluble dustproofing agents if the latter are added to the dye solutions, dispersions or suspensions even before drying, for example spray drying. Apart from the fact that surfactants give rise to unwanted foam--unwanted because it disrupts the smooth running of the dyeing process--nonionic surfactants alone or combined with a mineral oil may likewise give rise to oily deposits in the dyeing liquors in particular under the conditions customary when dyeing with reactive dyes, namely the presence of electrolytes (such as sodium chloride or sodium sulfate) and alkali (such as sodium carbonate or sodium hydroxide), either because under these dyeing conditions the mineral oil-surfactant emulsions break or the cloud point of the nonionic surfactants is lowered to the dyeing temperature or below.
Ever since it was realized that dusting dyes can also represent a health hazard to the people handling them, significantly higher standards are expected of the dustproofness of a dye. For instance, the dust values whereby "dust-free" and "low-dust" dye preparations are delimited from dusting dye preparations in the above-mentioned German Auslegeschrift and European patent application publication fall a long way short of present-day expectations. Moreover, a dye powder having a dust value of below 10 cannot in general be considered dust-free. For instance, a dye powder having a dust number of less than 5 is entirely capable of evolving sufficient fine dust as to make it impossible to rule out a possible health hazard to the people who come into contact therewith. For this reason a method

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patent: 4397652 (1983-08-01), Neumann

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