US2692236A - Nonsoap detergent compositions containing antitarnishing agents - Google Patents

Description

Patented Oct. 19, 1954 NONSOAP DETERGENT'COMPOSITIONS CON- TAINING ANTITARNISHING AGENTS Warren William Sweet, Pompton Plains, and William Jasper Mead, West Orange, N. J assignors to Colgate-Palmolive Company, Jersey City, N. 3., a corporation of Delaware N Drawing. Application March 14, 1951, Serial No. 215,634

Claims. 1

The present invention relates to novel detergent compositions and, more particularly, to detergent compositions having improved anti-tarnishing properties.

Certain detergent compositions have been known for many years and have been widely accepted since their lime resistance and other valuable properties make them advantageous for many uses, e. g., dishwashing, laundering, etc. An unexpected difficulty has been noted in the cleansing of certain metallic surfaces, such as articles made of German silver or having a German silver base, by solutions of such detergent compositions, containing certain water-soluble polyphosphate compounds. For example, in the washingof household utensils such as tableware or silverware consisting of German silver with such compositions, the Washed articles may exhibit tarnishing of the metallic surfaces.

Depending upon the nature of the material, the detergent composition and the conditions employed, the undesirable effects may range from a diminution or loss of luster of the highly polished metallic surfaces to a harsh discoloration or stain, or worse. The tarnish film, if it may be so called, is of such a nature that it is difiicult to analyze, even with microscopic or X-ray means. The discoloration tarnishing effects appear to be particuanism by which these desired results are obtained larly objectionable in non-soap detergent compositions containing complex polyphosphates, usually in aqueous alkaline solutions of such detergent compositions. Such adverse effects represent a significant problem from the standpoint of consumer appeal and in the cleansing and maintenance of such susceptible metals.

It has now been discovered that detergent compositions normally tending in solution to cause tarnishing of German silver and like metals may be improved by the incorporation of a minor amount of a dibutyl thiourea to inhibit or retard the tarnishing by said detergent compositions in solution. .As a preferred embodiment, the present invention relates to detergent compositions consisting essentially of a non-soap water-soluble synthetic detergent, a water-soluble polyphosphate compound, and a minute amount (e. g. up to about 1 of a symmetrical N,N' dibutyl thiourea as a tarnish inhibitor. The specificity of action of the inhibitor in the relationship set forth is not completely understood at this time.

It is a feature of the present invention that the detergent composition may comprise water-soluble inorganic polyphosphate salts. Thesesalts have the property of inhibiting precipitation of calcium material andrthe like in aqueous solution and may be considered as derived from orthophosphoric acid or the like by the removal of water, though any suitable means of manufacture may be employed ifdesired. These molecularlydehydrated polyphosphate salts may be wholly or partially neutralized, such as the alkali metal or ammonium salts of tripolyphosphoric, tetraphosphoric, and pyrophosphoric acids. Suitable examples are sodium tripolyphosphate (NasPsOio), potassium tripolyphosphate, tetrasodium pyrophosphate, hexasodium hexametaphosphate (Grahams salt), hexasodium tetraphosphate, etc.

In detergent compositions consisting essentially of the indicated polyphosphates either with or Without admixture with synthetic detergents, it will be observed that the tarnishing action manifests itself as a marked discoloration or stain on the German silver articles. Such discoloration, usually of a yellowish, purplish or blackish shade, appears to be due primarily to some phenomenon induced or existing in the presence of these complex polyphosphates in the detergent composition. This discoloration which is obviously highly undesirable may be either retarded or inhibited markedly and even substantially eliminated by the addition of a determinable amount of the indicated dibutyl thiourea compound. The mechis not completely understood at this time.

The novel compositions of the present invention may also contain as the active ingredient a water-soluble non-soap organic synthetic detergent either with or without admixture with the polyphosphates. It is preferred to use the anionic sulphated or sulphonated synthetic detergents (including suitable mixtures thereof). Included therein are the aliphatic sulphated or sulphonated detergents, such as the sulphated aliphatic compounds having about 12 to about 26 carbon atoms, and more particularly, the aliphatic acyl-containing compounds having an acyl radical of about 8 to 22 carbon atoms such as the aliphatic carboxylic ester detergents. As suitable examples of aliphatic anionic detergents may be found the sulphuric acid esters of polyhydric alcohols incompletely esterified with higher fatty acids, e. g. coconut oil mono-glyceride mono-sulphate, tallow di-glyceride monosulphate; the long chain pure or mixed higher alkyl sulphates, e. g. lauryl sulphate, cetyl sulphate, higher fatty alcohol sulphates derived from reduced coconut oil fatty acids; the hydroxy sulphonated higher fatty acid esters e. g. higher fatty acid esters of 2,3 di-hydroxy propane sulphonic acid; the higher fatty acid esters of low molecular weight alkylol sulphonic acids, e. g. oleic ester of isethionic acid; the higher fatty acid ethanolamide sulphates, the higher fatty acid amides of amino alkyl sulphonic acids, e. g. lauric amide of taurine, and the like.

It is a feature of this invention that the desired effects are particularly enhanced with the alkyl aryl sulphonate detergents. Thesearomatic sulphonate detergents are also well known in the art. They may be monoor polynuclear in structure. More particularly, the aromatic nucleus may be derived from benzene, toluene, xylene, phenol, cresols, naphthalene, etc. The alkyl substituent on the aromatic nucleus may vary widely as long as the desired detergent power of such active ingredient is preserved.

More specific examples of suitable alkyl aromatic sulphonate detergents are the higher alkyl aromatic sulphonates. The higher alkyl substituent may vary widely. Thus, it may be branched or straight-chained in structure and comprise decyl, dodecyl, keryl, mixed long-chain alkyls from polymeric lower mono-olefins, etc. Preferred examples of this class are the higher alkyl mononuclear aryl sulphonates wherein the alkyl groups is about 8 to about 22, and preferably about 12 to about 18 carbon atoms. More particularly, it is preferred to use the higher alkyl benzene sulphonates wherein the higher alkyl group averages about 12 to about 16 carbon atoms, For example, propylene may be polymerized to the tetramer and condensed with benzene in the presence of a Friedel-Crafts catalyst to yield essentially the dodecyl benzene derivative which is suitable for sulphonation to the desired sulphonate compounds.

These various anionic detergents are generally used in the form of the water-soluble salts, such as the alkali metal, alkaline earth metal, ammonium, amine, and alkylolamine salts. While the sodium, potassium, ammonium and alkylolamine (e. g. mono-, di, and triethanolamine) salts are preferred ordinarily, other salts such as the lithium, calcium, and magnesium salts may be used if desired. For general use, it is ordinarily preferred to use the sodium and potassium salts. For certain specialized uses, it may be preferred to select the ammonium and alkylolamine salts in view of their generally greater solubility in aqueous solution.

In synthetic detergent compositions that are essentially unbuilt and consist essentially of anionic sulphated or sulphonated detergents, for example, it has been found that the tarnishing efiects on German silver and the like are generally not of as severe a character as encountered with the polyphosphates. More particularly, it may be observed either visually or by examination with suitable apparatus that anionic detergents such assodium dodecyl benzene sulphonate may have a dulling action or cause a loss of luster and even discolor the German silver articles. In. 1% aqueous solution at 50 C. for at least 30 minutes, the sodium dodecyl benzene sulfonate detergent may produce a yellow or tan-like stain or discoloration. This adverse effect may be reduced and even completely eliminated by the addition of. an appropriate amount of the dibutyl thiourea inhibitor.

It is within the scope of the present invention that non-ionic detergents may be present in the detergent composition and, if desired, in admixture with other compatible detergents such as suitable anionic sulphated or sulphonated ones described above. These non-ionic agents are also well. known in the art and include the polyoxyethylene ethers of alkyl aromatic hydroxy bodies (e. g. the alkylatedpolyoxyethylene phenols) and the polyoxyethylene ethers of long chain aliphatic alcohols, etc. Long chain derivatives of polyhydroxy compounds such as the appropriate ethers of polyalkylene glycols may also be employed therein.

As previously indicated the tarnish inhibitor is a symmetrical N,N or 1.3 dibutyl thiourea com- 4 pound; Such dibutyl thioureas as N,N' or 1,3 dibutyl thioureas having the structural formula O4H9NH-ONHC Hu are encompassed within the scope of the disclosure. The butyl substituents may be either normal butyl, isobutyl, or secondary butyl in structure as each has been employed with marked success. In contrast thereto, structurally related compounds such as symmetrical dimethyl and diisopropyl thiourea have been found generally unsatisfactory in the same relationship.

The amount of the indicated tarnish inhibitor in the detergent composition is generally extremely small and effective to produce the desired improvements in the tarnish inhibition or prevention. Generally, the amount'will be less than about 1% by weight of the composition,,and preferably a fraction of 1%, e. g. up to about 0.5%. While greater amounts, may be employed if desired it will usually be found that amounts less than about 1% are satisfactory with commercial detergent compositions, Naturally the specific amount of the tarnish inhibitor to be incorporated in a selected detergent composition will vary somewhat with the nature and concentration of the synthetic detergent and particularly of the polyphosphate builders and the contemplated field of application or manner of use. The appropriate amount of inhibitor to be employed however may readily be ascertained by means of relatively simple and standard tarnishing tests as indicated infra.

It has been found that particularly desirable eifects are observed with such additives in built synthetic detergent compositions consisting essentially of the indicated synthetic detergents and the polyphosphates. More particularly, it is preferred to use compositions consisting essentially of about 10 to about 50% and usually about 15 to about 40% synthetic detergents, preferably of an anionic sulphated or'sulphonated nature, and about 10 to about and usually about 20 to about 60% of these water soluble polyphosphates, preferably tripolyphosphate, the above percentages being by weight of total solids-of the detergent compositions. With such. compositions it has been found that amounts of inhibitor of less than about 1%, and preferably up'to about 0.5% e. g. .05-.5%, are usuallyhighly effective in achieving the desired tarnish inhibiting action on German silverand the'like.

Further conditions indicative of the complexity ofv the phenomenon involved and the specificity of action of dibutylthiourea and the like are the alkalinity of aqueous solutions'of the detergent, and the concentrationof solids'therein. Illustratively, a built detergent composition consisting essentially of 35% sodium higher alkyl benzene sulphonate, 40% sodium. tripolyphosphate and the balance essentially sodium sulphate with minor amounts of sodium silicate, carboxymethylcellulose, etc., and having a pH in 0.5% solution of about 9'1l, and usually about 9.5-10, exhibits marked discoloration of German silver-within a relatively short time. Such adverse effects are largely eliminated by the addition of a suitable amount of inhibitor. If, however, the pH of the above detergent composition without inhibitor is lowered to substantially neutral values, the degree of tarnishing appears tobe correspondingly climinished', and even to an extent that the results otherwise may not be objectionable visually. With the above composition and the like, the

critical pH'value appears to be within the range of about 7.5-8.5, and usually about 8. Above such values for aqueous solutions of the detergent composition, adverse eifects are most marked and the use of inhibitor yields optimum results.

It has been found moreover that more pronounced tarnishing is encountered using about 0.25% to 1% solids concentrations of the above detergent composition in aqueous solution than result from the use of more concentrated solutions. With the use of about 0.05 to 0.1% inhibitor (based on total solids) in such aqueous solutions containing 1.5% solids or less, the presence of the inhibitor results in considerably reduced staining on German silver in comparison to controlled articles exposed to detergent solutions of similar strength but in the absence of inhibitor.

Furthermore, a 2% or more aqueous solutions of position so that the tarnish inhibitor and detergent composition may be sold to the user as a unitary composition. Thus, the additives may be incorporated at any point during the manufacturing process at which subsequent operations will not adversely modify the properties of the detergent compositions. The various ingredients may be dry-mixed or wet-mixed in any suitable manner. A procedure which is convenient, economical and productive of the best results with synthetic detergent compositions is the addition of the inhibitor in the form of an aqueous or alcoholic slurry to an aqueous slurry of the active detersive ingredients with vigorous stirring to form a relatively smooth, uniform and homogenous paste. Thereafter these compositions may be prepared in the form of solutions, pastes or as dry or partially hydrated solid products, preferably in finely divided condition. Accordingly, the slurry of the detergent composition may be subjected to any suitable drying operation and converted to particle form. The mixture may thus be subjected to conventional spray-drying, rolldrying or drum-drying operations utilizing temperatures of above 212 to obtain heat-dried homogenous detersive particles.

It is common to employ various adjuvant materials in detergent compositions. The detergent compositions, particularly the organic synthetic type, may include any of these substances embuilders are the various alkali metal phosphates (e. g. trisodium phosphate), the alkali metal silicates, sulphates, carbonates, etc. Suitable organic materials such as sodium carboxymethylcellulose, fatty acid amides, alcohols, esters may also be employed herein.

The following examples are additionally illustrative of the nature of the present invention and it will be understood that the invention is not limited thereto:

- EXAMPLEI A detergent composition is prepared by compounding 35% sodium dodecyl benzene su1pho nate,40% sodium tripolyphosphate, 3% sodium N silicate, 0.8% carboxymethylcellulose and 0.06% optical bleach (Blancophor MVI) and the balance sodium sulphate.

An aqueous 1% solution of the foregoing detergent composition stains German silver as indicated by the following simple test which involves the immersion of metal strips in the detergent solution to be tested under selected time and temperature conditions: Approximately 20 milliliters of the 1% detergent solution is poured into a 30 milliliter beaker and placed on a hot water bath until a temperature of about 50 C. is reached. German silver strips (Whitehead metal, 14 BS it hard, approximately 18% nickel, 65% copper, 17% zinc) are cut to A x 2" size. Each strip is abraded using wet #320A Behr-Manning Durite abrasive paper. The strips are thoroughly rinsed in running tap water using a toothbrush, then dipped in denatured ethyl alcohol and airdried on a clean towel. The strips are then half immersed in the above-mentioned 1% detergent solution and after 30 minutes at 50 C. are removed and patted dry with a clean towel. This procedure produces a dark stain on the surface of the German silver.

Similar results are obtained using 0.25% solution of the above detergent composition also.

To the identical detergent composition in separate aqueous solutions of similar strengths, 1,3 di-n-butyl thiourea is added in the proportions of 0.01-0.1% by weight of total solids. Repetition of the above tests with German silver strips discloses that the staining is reduced considerably with optimum effects obtained at 0.05 to 0.1% inhibitor. Starting at about 0.05% visual staining appears to be eliminated completely in the relationship set forth.

Similar concentrations of 1,3 di-isobutyl thiourea and 1,3 (ii-secondary butyl thiourea have been found equally effective also in the same relationship.

These tests are repeated using the various thiourea compounds indicated in the table in an amount 0.5% by weight of total solids. In each case, the indicated thiourea compounds is symmetrical and has the alkyl groupsin the 1,3 positions.

1 Exhibits only a slight water-line mark at the air-liquid interface.

The marked effectiveness of the dibutyl thiourea additives is clearly evident from the data. Even increasing the amount of the lower homologues to 1% concentration did not appear to materially affect the tarnishing action.

EXAMPLE II A detergent composition is prepared by forming about a 57% solid slurry containing on a solids basis about.35% sodium dodecyl benzene asses 8B sulphonate (derived from a propylene tetramer) about 40% sodium tripolyphosphate, sodium sulphate, and the remainder minor amounts of sodium chloride, sodium hydroxide, sodium carboxymethylcellulose, etc. This slurry is agitated at about 140 F. in a conventional soap crutcher to form a relatively homogeneous mixture. 1,3 din-.butyl thiourea in .an amount of 0.1% of total solids of the slurry is added in the form of an aqueous slurry to the detergent slurry which is further agitated to form a uniform mixture. 'Iheslurry is then subjected to spray-drying with heated .air at a temperature of about 350 F. with a resultant moisture loss of about 40%. The resultant composition is recovered in the form of beads and has a pH of about 9.5-8.7 in 0.5% aqueous solution. This composition gives effective inhibition of tarnishing of German silver also.

EXAMPLE III A detergent composition is prepared by the procedure of Example II with the modification that the organic detergent is sodium lauryl sulphate in concentration of solids, and a proportionately increased amount of sodium sulphate. The presence of 0.1% di-n-butyl thiourea gives similarly satisfactory results.

Other formulations which are productive of desired results are:

EXAMPLE IV Per cent Sodium dodecylbenzene sulphonate 1- 9 .Sodium lauryl sulphate 10 Sodium tripolyphosphate 50 Tetrasodium pyrphosphate 10 Sodium sulphate 1'7 Sodium carbonate 1.8

Sodium carboxymethylcellulose 0.5

:Lauric 'monoethanolamide 1.5,

1,3 di-n-butyl thiourea 0.2

EXAMPLE V Per cent Sodium coconut monoglyceride sulfate Sodium tripolyphosphate Sodium sulphate 34.5

1,3 di-n-butyl thiourea 0.5

EXAMPLE VI Per cent Sodium trlpolyphosphate 99.5

1,3 di-n-butyl thiourea 0.5

EXAMPLE VII Per cent Sodium dodecylbenzene sulphonate 99.9

1,3 di-n-butyl thiourea 0.1

While the invention has been described in conjunction with its effect in substantially completely preventing the tarnishing of articles of German silver alloy, it is to be understood that it is also useful in conjunction with detergent compositions which are to be applied to other metals and alloys subject to tarnishing by such compositions. However, it is particularly effec- 'tive with detergent compositions intended for use with the class of predominantly copper base alloys of which German silver and brass are well known members.

The term consisting essentially of as 'u'sedin the definition of the ingredients present in the composition claimed is intended to exclude the presence or other materials in such amounts as to interfere substantially with the properties and characteristics possessed by the composition set 8 forth but to permit the presence of other :materials in such amounts as .not substantially 'to affect :said properties and characteristics adversely.

Although the present invention has been described with reference to particular embodiments and examples, it will be apparent to those skilled in the art that variations and modifications of this invention can be made and that equivalents can be substituted therefor without departing from the principles and true spirit of .the invention.

Having described the invention what is desired to be secured by Letters Patent is:

'1. A detergent composition normally tending in water solution to cause tarnishing of a copper base alloy consisting essentially of water-soluble inorganic polyphosphate salt, and having incorporated therein a small amount of 'di-butyl'thiourea sufiicient to inhibit said tarnishing.

2. A detergent composition in accordance with claim 1 which contains about 10 to about 50% of water-soluble organic detergent selected from the group consisting of the water-soluble organic sulfate, sulfonate and non-ionic detergents.

3. A detergent composition normally tending in water solution to cause tarnishing of a copper base alloy consisting essentially of water-soluble inorganic tripolyphosphate salt, and having incorporated therein a small amount of symmetrical di-butyl thiourea sufiicient to inhibit said tarnishing.

4. A detergent composition normally tending in water solution to cause tarnishing of a copper base alloy consisting essentially of water-soluble inorganic polyphosphate salt, and water-soluble organic detergent selected from the group consisting of the water-soluble organic sulfate, sulfonate and non-ionic detergents, and having incorporated therein a small amount of symmetrical di-butyl thiourea sufficient to inhibit said tarnishing.

5. A detergent composition consisting essentially 'of water-soluble inorganic polyphosphate salt and about .01-1% of N,N di-butyl thiourea.

'6. A detergent composition consisting essentially of water-soluble inorganic tripolyphosphate salt and about .01-1% of N .N di-butyl thiourea.

7. A detergent composition in accordance with claim 6 which contains about 10 to about 50% of water-soluble organic detergent selected from the roup consisting of the water-soluble organic sulfate, sulfonate and non-ionic detergents.

8. A detergent composition normally tending in water solution to cause tarnishing of a copper base alloy consisting essentially of water-soluble organic detergent selected from the group consistin of the Water-soluble organic sulfate and sulfonate detergents, and having incorporated therein a small amount of symmetrical di-butyl thiourea sufficient to inhibit said tarnishing.

9 A detergent composition consisting essentially of water-soluble higher alkyl aryl sulfonate detergent and about ill-1% of di-butyl thiourea.

10. A. detergent composition normally tending in water solution to cause tarnishing of a copper base alloy consisting essentially of water-soluble higher alkyl benzene sulfonate detergent, and having incorporated therein N,N di-butyl thiourea in an amount up to about 1% and suificient to inhibit said tarnishing.

11. A detergent composition normally tending in Water solution to cause tarnishing of a copper base alloy consisting essentially of Water-soluble higher alkyl sulfate detergent, and having incorporated therein N,N' di-butyl thiourea in an amount up to about 1% and sufficient to inhibit said tarnishing.

12. A detergent composition normally tending in Water solution to cause tarnishing of a copper base alloy consisting essentially of Water-soluble higher fatty acid monoglyceride monosulfate detergent, and havin incorporated therein 1 l,N di-butyl thiourea in an amount up to about 1% and sufficient to inhibit said tarnishing.

l3. detergent composition consisting essentially of Water-soluble organic detergent selected from the group consisting of the watensoluble organic sulfate, sulfonate and non-ionic detergents, about l080% of water-soluble inorganic polyphosphate selected from the group consisting of tripolyphosphate, pyrophosphate, hexainetaphosphate, tetraphosphate and mixtures thereof, and about 01 to about 1% of N,N di-butyl thiourea.

14. A heat-dried detergent composition in particulate form normally tending in water solution to cause tarnishing of a copper base alloy consisting essentially of water-soluble organic detergent selected from the group consisting of the Watersoluble organic sulfate, sulfonate and non-ionic detergents, and about 10% to 80% of watersoluble inorganic tripolyphosphate, and having incorporated therein a small amount of N,N' dibutyl thiourea sufiicient to inhibit said tarnishing.

15. A heat-dried detergent composition in particulate form normally tending in water solution to cause tarnishing of a copper base alloy consisting essentially of sodium higher aikyl mononuclear aryl sulfonate detergent and about 10% to about 80% sodium tripolyphosphate, and havincorporated therein N,N' di-butyl thiourea in an amount up to about 1% and sutficient to inhibit said tarnishing.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,209,464 Loane July 30, 1940 2,238,651 Keenen Apr. 15, 1941 2,618,603 Schaefier Nov. 18, 1952

Claims (2)

1. A DETERGENT COMPOSITION NORMALLY TENDING IN WATER SOLUTION TO CAUSE TARNISHING OF A COPPER BASE ALLOY CONSISTING ESSENTIALLY OF WATER-SOLUBLE INORGANIC POLYPHOSPHATE SALT, AND HAVING INCORPORATED THEREIN A SMALL AMOUNT OF DI-BUTYL THIOUREA SUFFICIENT TO INHIBIT SAID TARNISHING.

2. A DETERGENT COMPOSITION IN ACCORDANCE WITH CLAIM 1 WHICH CONTAINS ABOUT 10 TO ABOUT 50% OF WATER-SOLUBLE ORGANIC DETERGENT SELECTED FROM THE GROUP CONSISTING OF THE WATER-SOLUBLE ORGANIC SULFATE, SULFONATE AND NON-IONIC DETERGENTS.