US3525695A - Laundry washing process - Google Patents

Description

United States Patent Int. Cl. D06l 3/00 US. Cl. 25295 5 Claims ABSTRACT OF THE DISCLOSURE A process for bleaching stained cloth which comprises pre-soaking said cloth in aqueous media and thereafter contacting said cloth with a peroxide compound at a temperature of at least 60 C. and wherein contacting of said peroxide and said cloth is prevented prior to the attainment of a temperature of at least 60 C.

The present invention relates to an improved process for washing cloth.

The use of per-compound-containing detergent compositions which liberate hydrogen peroxide as well as inorganic perhydrates, which, when dissolved, liberate hydrogen peroxide enclosed in their crystal lattice (e.g., certain perborates, perphosphates, persilicates) and peroxides which yield hydrogen peroxide by hydrolysis (e.g., sodium peroxide or certain percarbonates) of domestic or industrial laundering is well known. There are, in particular, detergent compositions in which sodium perborate frequently comprises between 1% and 35% of the total composition.

Hydrogen peroxide and the precursors which liberate it in solution are good oxidizing agents for removing certain stains from cloth, especially stains caused by wine, tea, coffee, cocoa, fruits, etc.

Hydrogen peroxide and its precursors have been found to bleach quickly and most efiectively only at a relatively high temperature, e.g., about 80 C. to 100 C. However, such compounds tend to decompose and liberate oxygen at lower temperatures. This liberation of gaseous oxygen, which is not involved in oxidation of dyed goods, needlessly consumes a sizable amount of hydrogen peroxide or precursors liberating it, both of which are expensive products. Moreover, it has been found that various stains in cloth greatly accelerate decomposition of hydrogen peroxide into gaseous oxygen during washing at ordinary temperatures.

In general, washing cloth, either in a machine, by hand, or in boiler tubs, is accomplished by dissolving a detergent composition (containing perborate, for example) in cold or lukewarm water, adding the soiled cloth (from which some of the stains have often already been removed by soaking or previous washing) and heating, often just to boiling.

However, it was found that, by a phenomenon similar to that previously mentioned, all or part of the perborate was decomposed during heating, and more specifically during the temperature rise, i.e., that all or part of the perborate was decomposed before the really effective temperature is reached.

It is believed, without wishing to be limited by any theory, that this rapid decomposition of hydrogen peroxide, perborate, or other precursors of hydrogen peroxide, into gaseous oxygen at low temperature is due to the extremely powerful catalytic action of certain redox enzymes which are always present in stain, which are found on materials to be washed, and particularly on soiled cloth, such as linen, these enzymes coming from secretions, or being of bacterial origin. Hydroxyperox- 3,525,695 Patented Aug. 25, 1970 ice idases are an especially active group of enzymes in this respect, particularly catalase, which is well known as a highly efiective catalyst for decomposing hydrogen peroxide to gaseous oxygen.

It is an object of this invention to furnish an improved washing process which will eliminate this useless decomposition of perborate or hydrogen peroxide (in any form) into gaseous oxygen.

It is a further object of this invention to provide a process utilizing all the oxidizing action of the detergent, thus reducing the amount needed (up to three times) or increasing its eifectiveness to an equal extent.

Other objects of the invention will be apparent fromthe description which follows.

In accordance with certain of its aspects this invention relates to a process of bleaching stained cloth in water at a temperature of at least 60 C. during said washing and bringing said stained cloth into contact with a peroxide compound.

In accordance with the process, enzymes present in the stained cloth are degraded by the heat treatment and cannot further decompose the hydrogen peroxide provided by the peroxide compound in solution.

According to one method of carrying out the invention, the cloth is soaked or pre-washed in pure water or water containing a detergent composition which does not include a per-compound at a temperature between about 60 C. and the boiling point of the liquid. Soaking time varies according to the temperature used; it is usually 5 to 10 minutes, but, at boiling, may be reduced to several seconds.

Peroxide compound is then added and the actual stainremoving operations commence; bleaching effectiveness is found to be greatly improved, compared with the usual process in which the peroxide compound is added with the soiled cloth to cold water and then heated to the desired temperature to C.).

According to another method of carrying out the invention process, excellent results can be obtained by placing the soiled goods in cold water, heating and adding the peroxide compound only when the temperature of both (water and goods) exceeds about 60 C. and preferably is between about 80 and 100 C.

Since the peroxide compound is decomposed only during heating, it is possible to dissolve in cold water a detergent composition which does not contain a peroxide compound and add the latter when the temperature exceeds about 60 C.

It will be understood from this process that, according to the invention, the peroxide compound should be protected from contact with the soiled goods until the temperature has reached about 60 C.

It is a preferred aspect of this invention to add the peroxide compound to cold water (or before the latter has reached about 60 C.) provided that the peroxide compound is physically protected from contact with the soiled cloth, for example, if it is contained in hermetically sealed packages whose walls are made of a material which is only soluble in water when the temperature exceeds about 60 C., or if it is coated with a thin coating of an inert water-soluble material which is, however, easily dispersed in the bath and will not dissolve below about 60 C. Saturated fatty acids containing 16 to 20 carbon atoms like palmitic, stearic, and arachidic' are examples of these materials. These will exhibit very low solubilities at ambient temperature; but at higher temperatures the solnbilities are somewhat increased, thereby permitting the thin coating to be dissolved. Stearic acid is particularly suitable. The detergent may be contained in or coated with the physically protecting material in accordance with known materials.

The peroxide compound which is employed in the instant invention may be an inorganic per-compound, typi cally alkali metal perborate, and includes perborate such as sodium perborate, perphosphate such as sodium perphosphate, persilicate such as sodium persilicate, percarbonate such as potassium percarbonate, peroxide such as sodium peroxide or hydrogen peroxide, etc.

The detergent composition employed in this invention may be a peroxide compound se or compositions which may also include soaps, various inorganic salts such as alkali metal silicates, sulfates, carbonates, etc.; products which prevent redeposition of stains such as carboxymethylcellulose, etc.; optical bluing products, anti-corrosion products, perfumes, dyes, etc.

The following examples are given to illustrate the invention.

EXAMPLE 1 This example illustrates the rate of sodium perborate decomposition when the goods are soaked by conventional methods.

Three grams of commercial sodium perborate are dissolved at ordinary temperature in 500 cm. tap water and the increase in the volume of liberated gas measured over an interval at ordinary temperature by standard methods. There is no volume of gas ten minutes after perborate is added to the water.

The preceding test is repeated, except that tap water is replaced by the same volume of an aqueous suspension of soil (this suspension is obtained by soaking one kilo of normally soiled cloth in four liters water treated with g. ordinary detergent composition for minutes at room temperature, and the soaking bath drained off). An intense liberation of gas is observed a few seconds after perborate is added to the soaking bath; this gaseous liberation is 140 cc. after five minutes and 217 cc. after ten minutes. The liberated gas was identified as oxygen. Calculation shows that the volume of gas liberated after ten minutes corresponds to the complete decomposition of three grams sodium perborate.

The above test resulted in complete decomposition of the perborate in a soaking bath of heavily soiled cloth in less than two minutes.

The following Examples 2, 3 and 4 illustrate the practice of the present invention.

EXAMPLE 2 Soiled cloth is machine Washed with commercial laundry soap powder, especially designed for machines, containing 10% sodium perborate, according to a cycle which provides for a pre-wash and washing for five minutes at boiling. A cloth dyed with pyrogene black is mixed with the soiled goods to measure bleaching effectiveness during washing. The dyed cloth is transferred It is apparent that practice of the invention by first contacting the soiled cloth with perborate at elevated temperatures vastly increased the effectiveness of the bleaching.

EXAMPLE 3 Soiled cloth is washed with a detergent composition Without perborate 30 minutes at the boil by a technique similar to that described in Example 2, except that a boiler tub (rag boiler) is used. Bleaching effectiveness is measured as described above. The two methods for introducing sodium perborate (10% by weight based on detergent composition) are compared.

Increase of brilliancy of dyed cloths after one washing (average of ten tests) Perborate added with cold detergent solution 6 Perborate added as boiling begins 23.7

It is apparent that first contacting the soiled cloth with the perborate at elevated temperature vastly increased the effectiveness of bleaching.

EXAMPLE 4 Cloth soiled by tea is washed in 1,000 grams of water containing 3 grams of sodium perborate coated with 0.005 gram of a thin coating stearic acid at 40 C. The temperature is then gradually raised to 60 C. The stearic acid dissolves and liberates the perborate as the bleaching agent. Washing is then continued for thirty minutes at this temperature during which time the soiled cloth is bleached.

What is claimed is:

1. A process of bleaching which comprises (a) presoaking stained cloth in aqueous media at a temperature below about 60 C. and (b) upon completion of said pre-soaking, contacting said cloth with an inorganic peroxide at a temperature of at least about 60 C. said peroxide being provided in coated form said coating consisting essentially of a saturated fatty acid containing from 16 to 20 carbon atoms.

2. A process according to claim 1 wherein said contacting occurs solely at a temperature of at least about C.

3. A process according to claim 1 wherein said fatty acid is stearic acid.

4. A bleaching composition adapted for use in the process of claim 1 consisting essentially of an inorganic peroxide compound coated with a saturated fatty acid containing from 16 to 20 carbon atoms.

5. A bleaching composition according to claim 4 wherein said fatty acid is stearic acid.

References Cited OTHER REFERENCES Rose et al., Condensed Chem. Dict., 6th ed. 1961, pp. 107210-73.

MAYER WEINBLATT, Primary Examiner U.S. Cl. X.R.