US2486922A - Stabilized detergent composition - Google Patents

Description

Patented Nov. 1, 1.949

s'ranruznn DETERGENT comosrrron Bruce StrainrWyoming, Ohio, assignmto The Procter & Gamble Company, lvorydale, Ohio. a corporation of Ohio No Drawing: Application November 9, 1945, Serial N0. 627,787

"1 Claims. (Cl- 252-138) This invention relates to the manufacture of detergent compositions, and more particularly is concerned with the provision of a lime-resistant cleansing agent for use in the home laundry.

It is known that synthetic detergents such as water-soluble salts of higher organic sulfuric reaction products containing true sulfonate or sulfuric acid ester groups may be mixed with large amounts of alkali metal tripolyphosphates to give detergent compositions which combine heavyduty cleansing performance, resistance toward the formation of objectionable curd in hard water, mildness toward colored fabrics and the skin, and economy in use. These detergent compositions, in general, comprise essentially a mechanical mixture of the synthetic detergent and tripolyphosphate, and when dissolved in hard or soft water in the ordinary concentrations employed in laundering in the home, that is, about 0.6%, they impart to the solution at about 25 C. a pH value of about 8.8 or slightly higher, depending on the purity of tripolyphosphate. These compositions are efiicient in their cleansing power and are adapted for use either on delicate fabrics or on wearing apparel which has become heavily soiled, including work clothes for example.

In the preparation of such mechanical mixtures in particulate form, it is advantageous to have the constituents in such physical condition that the rates of solubility of the tripolyphosphate and synthetic detergent are about the same. In general the solubility rates of the synthetic detergents are higher than the solubility rate of the tripolyphosphate, and in order to minimize this difference it has been found necessary to reduce the tripolyphosphate to a fine powder. When this is done, and the tripolyphosphate is mixed with the synthetic detergent in spray dried or ground flake form, the resulting composition is dense, tends to pack in the container, and has the undesirable quality of being dusty during use.

These disadvantages can be overcome by first mixing the tripolyphosphate with an aqueous slurry of the synthetic detergent and then heat drying the mixture as by spray drying into particle form, or by drum drying followed by reduction of the product to desired particle size,.

thus giving a product in desired particulate form which is free from dust and has good rate of solubility in water.

Compositions so produced meet with acceptance in most cleansing or washing operations, but they do not cleanse as efliciently asthe mechanical mixture under normal conditions encountered in the home laundry where the same solution of the composition is used repeatedly to wash successive loads of laundry. In this connection it has been observed under controlled conditions that about 25 per cent more of a spray dried mixture of tripolyphosphate and alkyl sulfate detergent is required to do a laundering job equal to that obtainable with a comparable mechanical mixture of spray dried alkyl sulfate and powdered tripolyphosphate.

It is an object of the present invention, therefore, to provide a heat dried mixture of synthetic detergent and tripolyphosphate equal in performance under home laundry conditions to the corresponding mechanical mixture.

Other objects and advantages of the present invention will appear from the detailed description hereinafter set forth.

In the examination of heat dried products resulting, for example, from the spray drying of a slurry containing three parts sodium tripolyphosphate and one part of the sodium salt of the sul- -furic acid esters of higher alcohols produced by reduction of coconut oil, it was discovered that the alkalinity of the product had been slightly reduced, For example, a solution of about 0.6

per cent concentration had a pH value of about 8 as compared with a pH value of 8.8 in the case of the corresponding mechanical mixture. Although this small difference in pH may appear insignificant, it has been found to be critical in connection with the provision of a detergent composition which will be efficient in use in the household laundry where a solution of the composition is used repeatedly in cleansing successive loads of laundry.

Further examination of products produced by the heat drying of a mixture of alkyl sulfate detergent and tripolyphosphate at temperatures in excess of 212 F. for example has shown that, depending on the conditions of drying, about 10 to 35 per cent of the tripolyphosphate decomposes during drying to give a mixture of phosphates including undecomposed tripolyphosphate, acid tripolyphosphate, pyrophosphate, acid pyrophosphate, orthophosphate, acid orthophosphate, etc. Although the development of acid compounds due to the decomposition of the normal tripolyphosphate is not sufiicient to render the composition acid reacting, it is sufficient to reduce the alkalinity of the composition so that at least a part of the tripolyphosphate will exist as an alkali-metal-acid-tripolyphosphate.

Since the decomposition of the tripolyphosphate in the drying operation may be appreciable as above noted, it was originally believed that the reduction in the efliciency of the detergent composition in operations involving repeated use of a solution was the result of the lower content of tripolyphosphate. I have discovered, however, that such is not the case as long as the ratio'of tripolyphosphate to synthetic detergent in the composition before drying is above 1:1, but rather that the lower eiiiciency is the result of the reduction in pH value which permits the existence of the tripolyphosphate as an alkali-metal-acid trlpolyphosphate. For example, I have shown that adjustment of the alkalinity of the spray dried composition to a range equal to that of the mechanical mixture will restore the spray dried material to an efficiency equal to that of the mechanical mixture. Similarly I have shown that a reduction in the alkalinity of a mechanical mixture to that of a corresponding unadjusted spray dried-mixture will reduce the efficiency of such mechanical mixture to that ofthe latter. Thus it is definitely shown that the alkalinity of the composition is critical, especially when employed in the home laundry where asolution thereof is used repeatedly in cleansing successive loads of laundry.

The present invention, therefore, contemplates the control of the alkalinity of heat dried mixtures of synthetic detergent and tripolyphosphate so that the latter constituent exists as a non-acid alkali metal tripolyphosphate. An efflcient detergent especially useful in the home laundry where a solution of the detergent is repeatedly used is thereby obtained.

In the practice of this invention the alkalinity of the mixture may be adjusted either before or after the heat drying step. Adjustment prior to the drying step is preferred not only because of simplified processing but also because in the presence ofthe alkalizing agent there is less decomposition of the tripolyphosphate. In the event the preferred procedure is employed, an amount of alkalizing agent sufficient to insure alkalinity of the final composition at least equal to that of the corresponding mechanical mixture is used. Any acidity produced in the drying step is thus immediately neutralized by the presence of the alkalizing agent and the tripolyphosphate exists in the final product as a non-acid alkali metal tripolyphosphate.

If the alkalizing step is performed on the composition after heat drying, then a suitable amount of alkalizing agent may be mechanically mixed with the heat dried material or it may be sprayed on the product as it travels on a moving belt, or it may be added to a solution of the product connection with the maximum limit of alkalinity), and on neutralization of the acid conprior to the use of the solution in the laundering v operation.

Any material which will alkalize the composi-- tion such that it will have a pH value compatible with the existence of the tripolyphosphate as non-acid, normal alkali metal tripolyphosphate, that is, about 8.8 or above in 0.6 per cent solution may be suitably employed. Thus, for example, sodium hydroxide, potassium hydroxide, triso-' dium orthophosphate, tetra sodium pyrophosphate, or buffering agents such as the alkali metal carbonates may be employed with excellent effect. The alkali metal carbonates, such as sodium carbonate, have a number of advantages and their use as alkalizing agents in the practice of the invention is preferred. For example, they do not carbonate in the presence of air to become more acid, they are good alkaline buffering agents, they have a maximum pH of about 10 (the importance of which is pointed out below in stituents they leave no acid residue.

For the sake of simplicity the alkalizing agents generally and specifically referred to above are generically designated as alkalies in the claims.

The maximum limit of alkalinity is not critical, bu.- there are advantages in maintaining it at a point such that 0.6 per cent solutions of the compositions in water have'a pH value not substantially higher than 10.7. Higher alkalinities may be irritating to the skin and detrimental to colored fabrics, and furthermore at pH values above 10.7 it has been found that iron in .the composition will precipitate as iron hydroxide and thereby give an off-color to an otherwise nearly white composition. As pointed out above, the alkali metal carbonates such as sodium carbonate and potassium carbonate have characteristics regarding maximum alkalinity which make them especially suitable for alkalizing the detergent-tripolyphosphate mixtures either before or after the heat drying step.

The amount of alkalizing agent needed to adjust the alkalinity of the d'etergent-tripolyphosphate mixtures to give a composition which is efficient in laundering operations involving repeated use of a solution of the composition in laundering successive batches of laundry will vary depending in large measure on the kind of alkalizing agent employed. I have found, for example, that in the customary spray drying operations involving the use of heated air in the processing, a mixture of 3 parts tripolyphosphate and 5.4 parts synthetic detergent paste containing 18.5 per cent of the sodium salt of the higher alkyl sulfuric acids of higher coconut oil alcohols, about 1.5 per cent unsulr'ated material, about 12 per cent sodium sulfate and about 68 per cent water (tripolyphosphate:alkyl sulfate=3:1) the amount of sodium carbonate consumed in neutralizin the acid products formed is about 0.25 part by weight or about 5 per cent of the weight of the solids in the mixture of paste and trlpolyphosphate. To insure desired pH range, therefore, an amount of sodium carbonate over and above this figure should be employed. The use of 10 per cent, for example, will result in a finished product having a pH of about 9.3. Also I have found that the addition of 4 per cent sodium hydroxide based on the solids in the detergent-tripolyphosphate mixture produced a spray dried detergent composition of 9-10 pH. Similarly the use of 15 per cent trisodium phosphate resulted in a pH of about 9.4.

, Since the compositions of the present invention are especially designed for use in the home laundry, it is desirable to combine mildness, balanced sudsing and detergency characteristics and heavy-duty performance with economy in use, and therefore the compositions preferably contain the tripolyphosphate and synthetic detergent in the ratio from 2:1 to 5:1. However the lower limit of this range can be extended to 1:1 with some sacrifice in balanced sudsing and detergency. This balanced sudsing and detergent action is of especial advantage to the housewife who ordinarily judges the amount of detergent to be used in a cleansing operation from the amount of suds that is formed on adding the detergent to the water. If the detergent composition has lower sudsing than detergent efficiency, more may be used than is necessary to accomplish a cleansing Job. On the other hand, if the composition has superior efliciency in sudsing, an amount may be used which is insuflicient to accomplish adequate cleansing. According to a number of tests which have been performed, it has been established that ratios of tripolyphosphate to synthetic detergent from 2:1 to 5:1 possess this balanced sudsing and detergent quality, and therefore the present invention is especially useful in the provision of such cleansing compositions.

The invention will be more clearly understood from the following examples in which parts are shown by weight. In these examples all pH values were determined on 0.6 per cent solutions in water and it is to be noted here that at such concentration the pH value will not vary appreciably with hardness of the water from 0 to 21 grains.

Example 1.--A paste was prepared by adding 24.6 parts water to 18.2 parts of a powdered commercial synthetic detergent containing as the active ingredient 28% of the sodium salt of the sulfuric acid ester of monoglycerides prepared from coconut oil. The pH value of this paste was 7.2. To the paste was then added 14.0 parts of sodium tripolyphosphate and 312 parts of sodium carbonate, the ratio of tripolyphosphatetsynthetic detergent therefore being 2.75:1. The mixture was heated to about 160 F. and thoroughly mixed in a crutcher such as is ordinarily used in incorporating added ingredients in molten soap. The crutched mixture had a pH value of 10.0 and was sprayed in the customary manner into a countercurrent stream of air heated to 350 to 400 F. to yield a product in particulate form. This product had a pH value of 9.5 and was excellently suited for use in laundering operations involving repeated use of the solution in washing successive loads of laundry.

Instead of the monoglyceride sulfate used in the above example, the sodium salt of the coconut oil fatty acid monoester of l,2dihydroxy-propane-3-sulfonic acid may be employed.

Example 2.To 12.2 parts of a commeruial synthetic detergent containing as the active ingredient 55% of the sodium salt of sulfonic acids derived from the condensation product of benzene and av chlorinated kerosene fraction containing predominantly about 12 carbon atoms per molecule were added 25 parts of water to form a paste having a pH value of 9.9. To this paste were added 19.2 parts of sodium tripolyphosphate and 3.6 parts of sodium carbonate to results in the home laundry under conditions involving repeated use of the solution to wash successive batches of clothes.

Example 3.-To 16.2 parts of a synthetic detergent paste consisting of 18.5% of the sodium salt of the alkyl sulfuric acids derived from the higher alcohols obtained by the reduction of coconut oil, 1.5% unsulfated material, 12.0% sodium sulfate, and 68% water, and having a pH value of about 10.5, were added 9 parts of sodium tripolyphosphate. The pH value of the mixture was 9.5. To this mixture were added 2.1 parts of trlsodium phosphate. The mixture was crutched at about 150 F. and then sprayed into a countercurrent stream of air heated to 350 to 400 F. The resulting spray dried product had a pH value of about 9.4, was equal in washing efficiency to a comparable mechanical mixture of alkyl sulfate powder and tripolyphosphate, and in laundering operations involving repeated use of a solution of the composition in washing successive batches of clothes was much more efficient than a similar product obtained without the use of the trisodium phosphate.

Example 4.A spray dried detergent composition was made in accordance with the process described in Example 3, except that no trisodium phosphate was added prior to the spray drying operation. To the dried product was added 5% sodium carbonate. The product had a pH value of 9.0, and was much more efficient in laundering operations than was the spray dried product before the addition of the sodium carbonate.

The above examples are not to be construed as limiting the invention and have been nade a part of the specification merely for the purpose of exemplifying the manner of preparing compositions coming within the scope thereof. For example, other heat drying conditions such as drum drying or heated belt drying and other alkalizing agents and detergents may be employed without departing from the spirit of the invention.

I have shown above that my invention comprises essentially a water-soluble salt of an organic sulfuric reaction product having pronounced detergent power and resistance to the lime, magnesia, etc. compounds contained in hard water, and from one to five times its weight of an alkali metal tripolyphosphate, the term alkali metal being used throughout the specification and claims to include ammonium as well as the true alkali metals such as sodium and potassium for example.

All of the various synthetic sulfate and sulfonate detergents well known in the art are useful in the practice of my invention, and of outstanding interest in this connection are the water-soluble salts of high molecular aliphatic sulfuric acid esters such as the alkali metal salts of sulfuric acid esters .of normal primary aliphatic alcohols having eight to eighteen carbon atoms,

particularly those whose principal active ingredient is a water-soluble salt of lauryl sulfuric acid or oleyl sulfuric acid. Specific examples are the sodium alkyl sulfates obtained from the mixed higher alcohols produced by the reduction of coconut oil, palm kernel oil or other oil of the coconut oil group (a group of tropical nut oils characterized by their high content of combined fatty acids having ten to fourteen carbon atoms) or the sodium alkyl sulfate derived from the higher alcohols of sperm oil.

In addition to the alkyl sulfates above mentioned, water-soluble salts of other aliphatic sulfuric acids having pronounced detergent power may be used. Thus, for example, water-soluble salts of sulfuric acid esters of higher fatty acid monoglycerides (e. g. sodium salt of the coconut oil fatty acid monoester of 1,2-dihydroxy propane-3-sulfuric acid ester) and of the sulfated higher fatty acid alkylolamides (e. g. sodium salt of sulfated coconut oil fatty acid ethanolamide) may be employed.

Synthetic detergents having a, true sulfor'i'ate 7 Also, water-soluble salts of higher fatty acid monoesters of lower molecular weight hydroxy alkyl sulfonic acids (e. g. oleic acid ester of the sodium salt of isethionic acid) and ofsthe higher fatty acid amides of lower molecular amino alkyl sulfonic acids (e. g. ammonium salt of oleic acid amide of N-methyl taurine) may be employed. Likewise, heavy-duty detergents may be prepared from synthetic detergents such as the watersoluble salts of the higher alcohol esters of sulfocarboxylic acids (e. g. sodium salt of the lauryl alcohol ester of sulfoacetic acid), lower sulfocarboxylic acid amides of alkylolamine esters 01. higher fatty acids (e. g. sodium salt of sulfoacetamide of amino ethyl laurate), higher alkylated benzene sulfonic acids (e. g. potassium salt of the sulfonic acid derived from the condensation product of benzene and a chlorinated kerosene fraction containing predominantly twelve carbon atoms per molecule) and ethers of high molecular alcohols and lower hydroxy sulfonic acids (e. gjmonolauryl ether of ,2-dihydroxy propane-3-sodium sulfonate).

Specific reference to the above detergents is given only for the purpose of illustrating the various types of detergent compounds which can be used in the practice of my invention and I do not wish to be limited thereto. Although I have pointed out that the higher aliphatic sulfuric acid esters are of particular value and of outstanding interest in the preparation of detergents of this invention, the invention is to be understood as being sufllciently broad to cover the use of all sulfate and sulfonate synthetic detergents which are resistant to the calcium and magnesium salts of hard water and which have suflicient detergent power to be classed as cleansing or laundering agents. In this connection it is to be observed from the preceding description that all of the synthetic detergents above mentioned contain a high molecular alkyl radical, it being understood that the term alkyl" is used here and in the appended claims to include an unsaturated as well as a saturated open chain monovalent radical.

While the cleansing agent of the composition of the present invention comprises essentially a mixture of a detergent of the class herein described with a tripolyphosphate and alkalizing agent, it will be appreciated that the incorporation in the mixture of additional ingredients commonly used with cleansing agents, such as soap, perfume, inorganic salts, etc., is contemplated as part of the instant invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A cleansing and laundering composition as claimed in claim 3, in which the alkali is an alkali metal carbonate.

2. A cleansing and laundering composition as claimed in claim 3, in which the water-soluble reaction product comprises essentially a mixture of alkyl sulfates containing predominantly 12 to 18 carbon atoms in the alkyl radical, and the alkali is an alkali metal carbonate.

3. A heat dried cleansing and laundering composition in particulate form consisting essentially of a mixture of water-soluble salts of organic sulfuric reaction products having in their molecular structures a higher alkyl radical and aradical selected from the group consisting of sulfonic acid and sulfuric acid ester radicals, said salts having pronounced detergent power, and from one to five times as much by weight of amixture of phosphates consisting principally of'normal sodium tripolyphosphate and from about 10% to of thermal decomposition products of sodium tripolyphosphate resulting from drying sodium tripolyphosphate at a drying medium temperature in excess of 212 F., and added alkali in amount to bring the alkalinity of water solu-. tions of said composition in ordinary concentrations for laundering within a range compatible with the existence of tripolyphosphate wholly as a non-acid normal alkali metal tripolyphosphate and from about pH 8.8 to about pH 10.7, said composition having a greatly enhanced laundering performance, on repeated use of water solutions in washing successive batches of laundry, over that of an otherwise identical heat dried composition lacking said alkali and containing significant amounts of acid phosphates resulting from said thermal decomposition of normal sodium tripolyphosphate.

4. A cleansing and laundering composition as claimed in claim 3, in which the, higher alkyl radical of the water-soluble organic sulfuric reaction product contains 8 to 18 carbon atoms.

5. In the process of making a cleansing and laundering composition having stability and efficient cleansing performance under laundering conditions involving repeated use in washing successive batches of laundry, the steps of preparing an aqueous mixture of (1) a water-soluble salt of an organic sulfuric reaction product having in its molecular structure a higher alkyl radical and a radical selected from the group consisting of sulfonic acid and sulfuric acid ester radicals and having pronounced detergent power, and (2) from one to five times its weight of Sodium tripolyphosphate, heat drying the mixture at a drying medium temperature in excess of 212 F. to produce a mixture in which the phosphates consist principally of normal sodium tripolyphosphate and from about 10% to 35 of thermal decomposition products of sodium tripolyphosphate, and at any stage in the process adding an alkali, the amount of alkali being sufiicient to give a solution of the final heat dried product in ordinary concentrations for laundering a pH from about 8.8 to about 10.7, and sufilcient alkalinity to be compatible with the existence of the tripolyphosphate wholly as a non-acid normal alkali metal tripolyphosphate.

6. In the process of making a cleansing and laundering composition having stability and efllcient cleansing performance under laundering conditions involving repeated use in washing successive batches of laundry, the steps which comprise heat drying at a drying medium temperature in excess of 212 F. a mixture of (l) water-soluble salt of an organic sulfuric reaction product having in its molecular structure a higher alkyl radical and a radical selected from the group consisting of sulfonic acid and sulfuric acid ester radicals, said salt having pronounced detergent power, (2) from one to five times its weight of sodium tripolyphosphate, and (3) an alkali, to produce a mixture in which the phosphates consist principally of normal sodium tripolyphosphate and from about 10% to 35% of thermal decomposition products of sodium tripolyphosphate, the amount of alkali being suflicient to give a solution of the heat dried mixture, in ordinary concentrations for laundering, a pH from about 8.8 to about 10.7 and suflicient alkalinity to be compatible with the existence of the tripolyphosphate wholly as a non-acid normal alkali metal tripolyphosphate.

1 '7. In the process of making a cleansing and assaoss 9 laundering composition having stability and emcient cleansing performance under laundering conditions involving repeated use in washing successive batches of laundry, the steps which com- .10 solution of the mixture, in ordinary concentrations for laundering, a pH from about 8.8 to about 10.7 and suflicient alkalinity to be compatible with the existence of the tripolyphosphate wholly as a group consisting of sulionic acid and sulfuric 10 me of this patent:

prise spray drying at a drying medium tempera- 5 non-acid normal sodium tripolyphosphate.

ture in excess of 212 F. a mixture of (1) water- BRUCE STRAIN. soluble salt of an organic sulfuric reaction product having in its molecular structure a higher REFERENCES CITED alkyl radical and a radical selected from the The following references are of record in the acid ester radicals, said salt having pronounced detergent power, (2) from one to live times its weight of sodium tripolyphosphate, and (3) more UNITED STATES PATENTS Date Number Name than 5 per cent, based on the weight of the sul- 2,365,215 Rhodes Dec. 19, 1944 iuric reaction product and the tripolyphosphate, 15 2,383,502 Quimby Aug. 28, 1945 oimsoditiilm charbonate to produce a mixture in 2,396,278 Lind Mar. 12, 1946 w ch e p osphates consist principally of normal sodium tripolyphosphate and from about FOREIGN PATENTS 10% to 35% of thermal decomposition products Number Country Date 01' sodium tripolyphosphate, the m n of 20 547,688 Great Britain Sept. '1, 1942 551,616 Great Britain Mar. 3, 1943 sodium carbonate being suiiicient to give a water