Sodium hydrosulfite slurries
AssigneeVirginia Chemicals Inc.
InventorsEdwin D. Little, Karsten R. Minzghor
Life of this patent
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Abstract
Aqueous sodium dithionite slurries, which are non-settling during shipment thereof and are thereafter pumpable, and a method for their manufacture are provided. The slurries contain at least 25% by weight of crystalline pure sodium dithionite and at least about 0.13% by weight of a xanthan gum. As textile bleaching compositions, the slurries comprise, on a weight basis, at least about 36% of commercial sodium dithionite, at least about 3% of sodium hydroxide, at least about 0.25% of a chelate, and at least about 0.25% of a xanthan gum. As woodpulp bleaching compositions, the slurries comprise, on a weight basis, about 28% of commercial sodium dithionite, at least about 2% of sodium carbonate, at least about 2% of sodium tripolyphosphate, and at least about 0.13% of a xanthan gum.
Claims2
A storable and pumpable tripolyphosphate-free aqueous slurry which consists essentially of at least about 25% pure sodium dithionite by weight, at least about 0.20% Xanthan gum, by weight, a chelate, an alkali, and water, said slurry having a pH of at least 10.
A method for making a storable and pumpable aqueous dithionite slurry from crystalline dithionite which comprises, on a weight basis:
- (A) preparing a dilute hydrosol containing about 0.13-0.25% by weight of Xanthan gum;
- (B) sequentially adding aqueous solutions of a chelate and sodium hydroxide or potassium hydroxide to the dilute hydrosol, while stirring said dilute hydrosol to form an alkaline hydrosol;
- (C) cooling said alkaline hydrosol to 32.degree. F. (0.degree.) in an ice bath to form a cold hydrosol;
- (D) adding sodium dithionite to said cold hydrosol at such a rate as to maintain its temperature below 7.degree. C. and in sufficient amount to provide said dithionite slurry containing at least about 25% of pure sodium dithionite and having a pH of at least 10;
- and
- (E) recovering a storable and pumpable tripolyphosphate-free aqueous sodium dithionite slurry.
Dependencies are inferred from the claim text.