US2379458A - Laundry finishing composition - Google Patents

Description

Patented July 3, 1945 2,379,458 LAUNDRY FINISHING COMPOSITION Edward Robinson, Mount Lebanon, Pa., as-

signor to Diamond Alkali Company, Pittsburgh, Pa., a corporation of Delaware No Drawing.

Application March 18, 1942,

Serial No. 435,206

4 Claims.

This invention relates to a laundry finishing composition for shortening the laundering process in commercial laundries by reducing the number of rinses. This result, generally speaking, is accomplished by converting unrinsed soap and alkali residues into stable, inert compounds which are not affected by the subsequent ironing process.

It is the present-practice in commercial laundries to subject the fabrics to a series of rinses after they have been laundered with soap, alkali, and bleaching agents, for the purpose of removing residual materials. The usual number of rinses is 3 to 5 at elevated temperatures and then one or two at lower temperatures. At the completion of this series of rinses, the fabrics are practically free of the detergent materials except for small quantities that are held by the fabrics and cannot be removed economically by further rinsing. At this point, acid materials, called Sours, are added to neutralize the residual soap and alkali. These acid substances are of such a type that they are not harmful to cotton fabrics; sodium silico fluoride, sodium acid fluoride and acetic acid are typical materials. The sours are added to a smaller volume of water than is used in the rinses; then, after the washing machine has been run for 3 to 5 minutes, the water level is raised to to 12 inches and bluing is added to give the fabrics a pleasing blue-white shade. The final acidity of the fabrics is between pH 5.5 and 6.5.

If sours are not used, the residual soap and alkali in the clothes tend to turn the clothes yellow when they are ironed. Moreover, the sodium bicarbonate found in most natural zeolite softened water (which most laundries use) turns to soda ash during the ironing process and this compound also tends to yellow the clothes. On the other hand, if sours are used before the bulk of the soap and alkali has been rinsed out, sticky, greasy fatty acids are precipitated by the action of the sour on the soap, and, in addition, excessive amounts of expensive sour are needed to neutralize the alkali residues. When the fabrics are ironed under such circumstances the fatty acids give off an unpleasant odor and the fabrics often also turn to an undesirable yellow color.

The usual souring agents are expensive and, in addition, the volume of water used in rinsing is sometimes costly. Several procedures have been proposed to reduce the number of rinses and eliminate the use of sour. Most laundries are equipped with zeolite water softeners which provide a water supply free of calcium and magnesium salts. This prevents the formation of calcium and magnesium soaps in the detergent baths and thus saves soap. By using unsoftened water for rinsing after part of the soap and alkali has been removed with softened water, the remaining soap and alkali are converted into insoluble calcium and magnesium soaps. This permits the use of fewer rinses and in many cases the elimination of sour. The calcium soaps formed, however, are unstable to the heat of ironingand their decomposition gives an unpleasant odor to the fabric. Further. sodium bicarbonate formed by the action of calcium bicarbonate from the hard water is turned to sodium carbonate by the heat of ironing and this alkali turns the fabric yellow. Rinsing with hard water to reduce washing time is therefore considered to be poor practice by the industry.

It has also been proposed to use magnesium sulphate (MgSO4-7H2O) which is a very inexpensive chemical in the rinse baths to reduce washing time by adding it before all the soap and alkali have been removed and where the addition of sour would give the bad results that have been described. This chemical converts the soapsinto pure white magnesium soaps that are stable to the heat of ironing as compared tothe unstable soaps produced by calcium compounds. In the reaction neutral sodium sulphate is formed which is also stable to heat. The result is no discoloration of the fabric and no unpleasant odor.

In most laundering operations, however, the alkaline builders used give on hydrolysis, hydroxyl ions which on reaction with a portion of the magnesium sulphate give magnesium hydroxide. This chemical is very insoluble but it is so strongly alkaline that the presence of only small quantities of it in the fabric is undesirable for the same reasons that sodium carbonate is not wanted. Further, the insoluble magnesium soaps, hydroxide, and other magnesium compounds form a flocculent precipitate that tends to be filtered out and caught by the fabrics when the washwheel is emptied. For these reasons, the use of magnesium sulphate alone does not produce results which theoretically might be expected from it.

I have now found that uniformly good results can be obtained in using magnesium sulphate as an agent for converting soluble fatty acid soaps into inert magnesium soaps, providing the reaction takes place in the presence of boric acid. While the exact behavior of boric acid is not fully understood at present and while this compound is a very weak acid, the present experience indicates that boric acid is nevertheless sufliciently strong to neutralize the soluble magnesium hydroxide that may be formed and, in addition,

causes a dispersing action to take place so that whatever insoluble soaps and other magnesium compounds are formed are held in a condition of dispersion so fine that they are flushed out when the rinse solution is drained from the washwheel.

The introduction of boric acid with the magnesium salt reduces the pH of the rinse solution into which the material is added to a value below the phenolphthalein end-point of 8.2. This reduction in the pH value of the solution may account for the dispersion of the insoluble soap. In any event, however, any magnesium soap remaining in the fabrics is snowy white and does not tend to cause the clothes to become yellow when they are ironed. Any magnesium hydroxide formed is neutralized and the clothes consequently do not become yellow through the presence of strong alkali.

It has also been found that other soluble magnesium salts such as the chloride can be used with boric acid with the same satisfactory results. The hexahydrate (MgClzfiHaO) occurs in the form of sticky, moist crystals which prevent the production of a free-flowing product such as can be obtained with crystalline magnesium sulphate and boric acid. On the other hand, the monohydrate (MgClaHzO) is very hygroscopic. It has been found, however, that, on mixing the monohydrate with the amounts of boric acid that have been found to be effective, the resulting mixture remains free-flowing under humidity conditions that would cause serious caking of the monohydrate alone. The monohydrate is a more eflicient magnesium salt than the crystalline sulphate for it contains over twice as much magnesium, the active agent in the product.

A further peculiar advantageous property of the compositions described lies in their ability to eliminate a difiiculty known in the industry as "rolling of flat work during ironing. This is a condition in which the edges of the sheets while being ironed become rolled to such a degree that they must be rewashed and reironed with consequent loss of production. As an illustration of the results which I have obtained, one laundry plant formerly had from three hundred to four hundred pieces per day rejected because of rolling. With the use of the present material, during a period extending over a number of months, the number of pieces having to be rehandled has been reduced to two or three pieces per day.

In contrast with the results obtained with conventional acid sours such as sodium acid fluoride and the like, the use of the present compositions also enables more uniform. bluing to be obtained. The bluing distributes itself evenly and uniformly over the fabrics of the load and gives a uniform tint. Considerable difliculty has been experienced in the past in loads blued after conventional souring inasmuch as the depth or tone of the tint varies with different weights of fabrics because of the variation in the amount of acid sour retained by them.

With the usual number of rinses used in the washing formula, most of the chlorine bleaching agents used for stain removal and sanitation are removed along with the soap and alkaline detergents. Under the present method, however, chlorine compounds may be present in the fabric at the end of the washing formula because of the reduction in the number of rinses. While the magnesium salt-boric acid combination will convert unrinsed soap and alkali, it does not affect the chlorine residues, yet these are very destructive to the fabric if they are present when it is ironed. I have determined that sodium sulphite, in the amount of about 2.5% by weight, or more, may be satisfactorily incorporated in the present compositions to serve as the means for destroying any chlorine or hypochlorite present in the rinse bath to which the magnesium salt and boric acid composition is added. Sodium sulphite reacts with the sodium hypochlorite, the chlorine compound usually used by the laundry, to form neutral sodium chloride and sulphate which are harmless to cotton fabrics.

In preparing the compositions of the present invention the magnesium salt, as for example, magnesium sulphate, 71-120, is used in the proportion of about 50% to 75%. the boric acid from approximately 22/;% to 47%% and the sodium sulphite approximately 2 If desirable, sodi-um sulphite may be eliminated from the composition when no chlorine is apt to be present in the bath in which it is to be used.

In the typical washing formula, the present composition is used in the amount of approximately 2 ounces per one hundred pounds of clothes and is introduced preferably in the third hot rinse. A rinse of half hot water and half cold water, called a split rinse, preferably is then used, followed by a cold rinse in which it frequently is desirable to use from to 1 ounce of the composition per lbs. of clothes. The bluing is then added to this operation and when it is completed, the clothes are pulled from the washwheel, the water is removed by centrifugal extractor, and the clothes are then ironed. In such a rinsing cycle, at least one hot and one cold rinse are saved in comparison to the conventional washing cycles and the use of expensive sours i eliminated.

In analyzing the results obtained by this procedure, I have determined that in 20 washes the whiteness retention of fabrics laundered by this procedure was 95.5% of the original whiteness even when the test pieces were ironed after each wash. This whiteness retention is considered excellent by the laundry trade. Ash determinations on the test pieces showed no build up of magnesium or other inorganic compounds illustrating the dispersing action of the boric acid. Finally, tensile strength tests showed only 2. normal loss, showing the safety of the procedure.

The data and examples given in the foregoing illustrations are illustrative and not presented by way of limitation. I desire to be limited only by the claims which follow.

Having described my invention, I claim:

1. A laundry finishing composition to be used in laundering fabrics for converting soluble soap residues into stable, white, insoluble compounds, which composition comprises a major portion of a compound selected from the class consisting of magnesium sulphate and magnesium chloride and a minor portion of boric acid.

2. A laundry finishing composition adapted to be used in laundering fabrics for converting soluble soap residues into stable, white. insoluble compounds, which composition comprises approximately 50% to 75% magnesium sulphate and 50% to 25% of boric acid.

3. The method of laundering fabrics which comprises introducing into a rinse bath in the laundering cycle a laundry finishing composition comprising a major portion of a compound selected from the group consisting of magnesium sulphate and magnesium chloride, and a minor portion boric acid, thereby converting soluble soap residues into insoluble magnesium soaps and simultaneously effecting dispersion oi the magnesium soaps so formed to such a degree that a substantial portion or the magnesium soaps so formed is capable of being flushed from the fabrics when the rinse water is drained therefrom.

4. In the art of laundering fabrics, the method which comprises treating the clothes, when they are beingrinsed, with a laundry finishing composition comprising a major portion of magnesium sulphate'and a minor portion of boric acid, before all the soapand alkali have been removed thereby converting soluble soap residues into insoluble magnesium soaps stable to ironing and simultaneously eflecting dispersion or the magnesium soaps so formed to such a degree that a substantial portion of the magnesium soaps so formed is capable of being flushed from the fabrics when the rinse water is drained therefrom.

EDWARD A. ROBINSON.