CZ20032363A3 - Method for removing chlorine from washing baths - Google Patents

Abstract

In the present invention, there is disclosed a method of removing chlorine from washing bath comprising reduction by aldose of hypochlorite, optionally chlorine bound in a higher oxidation stage to linen in an alkali solution the pH value of which ranges within 7.5 to 10.8 at a temperature ranging from 15 to 45 degC to obtain a corresponding aldonic acid, optionally a salt thereof.

Description

(57)

Process for removing chlorine in a washing bath, characterized in that hypochlorite or chlorine compounds in a higher oxidation stage are reduced by an aldose such as glucose, ribose and the like, wherein the aldose carbon number is 4-24 and the pH of the solution is 6.5- 14 and the temperature reaches 15-100 ° C. The main advantage of the process according to the invention results from the fact that the reduction of chlorine in the higher oxidation stage arises from the weakly predominantly aldose acid. Aldose such as glucose can be added directly to the working bath. Aldonic acids resp. their sodium salts also aid in the removal of some impurities from the laundry.

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Method for removing chlorine in a washing bath

Technical field

The present invention is in the field of laundry washing and maintenance. It concerns the removal of chlorine-based bleach residues by reducing residues with aldose to form aldonic acid.

BACKGROUND OF THE INVENTION

The stain is perceived by the human eye as a more or less limited color change on the laundry. Color is related to the structure of molecules bound to the laundry and is due to the absorption of some part of the visible spectrum. The structure of organic dye molecules usually contains a plurality of conjugated multiple bonds, called chromophores. By absorbing the violet part of the spectrum, the substance has a yellow tint. Elimination of these groups results in a loss of ability to absorb part of the visible spectrum, which in the optimum case results in a loss of color. Chemical processes that eliminate chromophore are usually based on oxidative bleaching.

Peroxide compounds are most often used for oxidative discoloration. Sodium perborate is a common part of laundry detergents. Sodium hypochlorite and other chlorine releasing compounds are also very popular.

After applying chlorine compounds for both disinfection and bleaching, the laundry must be cleaned of chlorine residues as they cause skin irritation when using the laundry and complicate subsequent washing. Chlorine residues in laundry destroy enzymes and some types of wetting agents, and at the same time they cause the silicate components of the laundry laundry bath (Hong Pin Lin; Micropropous and Mesoporus Materials 2001, 48; 1-3; 135-141).

Chlorine residues are removed by reduction with sodium thiosulphate or sodium dithionite. A disadvantage of this procedure is the formation of sulphates. Calcium sulphate may form in hard water, which will contaminate the laundry. If the bath is not sufficiently alkalized, the sulfuric acid formed will damage the laundry. Other disadvantages of this process are associated with the washing of laundry contaminated with chlorine compounds. Laundry contamination occurs in operations with high demands on disinfection, such as hospitals. Decontamination of chlorine in laundry then constitutes a separate process, which increases costs and labor. SUMMARY OF THE INVENTION

According to the invention, the hypochlorite or chlorine compounds in the higher oxidation stage are reduced by an aldose such as glucose, ribose and the like, the number of aldose carbons being 4-24 and the pH of the solution being

6.5 - 14 and the temperature reaches 15 - 100 ° C.

The basic advantage of the process indicated is the formation of weak predominantly aldonic acids. (Diagram 1) Aldose, eg glucose, can be added directly to the working bath. Aldonic acids resp. their sodium salts also aid in the removal of certain impurities from the laundry.

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HHOHH-OH

-H

-OH

-OH + NaCIO

Νβ2θθ3

HHOHHCOONa-OH-H-OH-OH + NaCl ^with OH

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Scheme 1

The following examples illustrate the invention and its effects

Examples

Example # 1

To 20 liters of a working bath containing 0.012 g / liter sodium hypochlorite and 10 g soda was added 3 g glucose monohydrate. The mixture was heated to 45 ° C for 10 minutes.

The presence of chlorine is determined by introducing the sample into an acidified 5% potassium iodide solution with starch sebum. After this time, the test is negative.

Example # 2

The chlorine content in the higher oxidation stage was determined by isotachophoresis in a washing bath sample at pH - 10.3. The concentration was found to be 0.028 g / liter.

To 500 liters of this bath and 90 kg of laundry was added 250 g of glucose monohydrate. The bath was heated for 10 min. at 45 ° C. After this time, a sample was taken and the chlorine content in the higher oxidation stage was determined again. The result of the analysis did not show the presence of the monitored chlorine compounds.

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Industrial applicability

The process for removing chlorine in the laundry bath according to the invention finds application in industrial laundries and in the production of laundry detergents.

Claims (1)

Process for removing chlorine in a washing bath, characterized in that the hypochlorite or chlorine compounds in the higher oxidation stage are reduced by an aldose such as glucose, ribose and the like, the aldose carbon number being 4-24 and the pH of the solution being 6.5 - 14 and the temperature reaches 15 - 100 ° C.