US2993861A - Detergent compositions - Google Patents

Description

2,993,861 DETERGENT COMPOSITIONS Homer Wallace McCune, Wyoming, Ohio, assignor to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio No Drawing. Filed July 24, 1958, Ser. No. 750,573 6 Claims. (Cl. 252-137) effect of the phosphate upon aluminum. The corrosive action of such detergent compositions upon aluminum is usually inhibited by incorporating in the detergent composition a sodium silicate. Sodium silicates having an SiO to Na ratio of from 116:1 to 3.2:1 are most commonly used for such purposes and are usually employed in amounts of about the order of by weight of the calcium-sequestering phosphate present in the detergent composition. Various disadvantages are associated with the use of sodium silicate in this regard however. As long as the silicate is present in the detergent composition as sodium silicate, the composition is satisfactory. However, the Na O portion of the silicate tends to readily combine With acidic compounds, such as the acids formed by the hydrolysis of calcium-sequestering phosphates, and the carbon dioxide in the air. Such combination of a part of the Na O portion of the sodium silicate with these acidic compounds results in a sodium silicate which tends to be low in Na O content. This renders the silicate insoluble in water and hence, inelfective for corrosion inhibition purposes.

The insoluble silicate formed in this way in situ in the detergent composition imparts to the detergent composition several undesirable characteristics. For example, such insoluble silicate, which is normally present as a fine, sandy material, in the detergent composition, is very likely to trap air and float upon the surface of the water into which the detergent composition is poured. This floating insoluble silicate gives the impression of a scum having formed on the surface of the water and plainly indicates to the user that the detergent is not entirely soluble. Then too, in compositions in which the sodium silicate content is relatively high and sufiicient Na O has been lost through the aforementioned reaction with acidic compounds, large particles of insoluble silicate may be formed. These large particles, although they do not form a scum on the surface of the water, are especially objectionable in the hand washing of dishes since they sink to the bottom of the di'shpan and give the impression that sand has been added to the detergent composition.

A still further disadvantage which may be associated with the use of silicate as a corrosion inhibitor in 'calcium-sequestering phosphate-containing detergent compositions is encountered when such compositions are used in automatic dishwashing machines and arises as a result of its inhibiting action. Thus, while the sodium silicate does inhibit the corrosion of aluminum by the calcium-sequestering phosphates, and 'whileit also minimizes the etching of glassware and clear over-glazes on decorated china by these same phosphates, in the washing and repeated rinsing cycles of the automatic dishwashing machine it allows the aluminum surfaces to tarnish and discolor. As a result, if an aluminum article is repeatedly washed in an automatic dishwashing machine with a detergent composition which contains suflicient silicate to completely inhibit the corrosion of aluminum, undesirable tarnishing or discoloration of the aluminum is often encountered. For example, a detergent composition containing about 50% or more of calcium-sequestering phosphate can be inhibited from etching glass and from corroding aluminum through the presence in the detergent composition of about 8% of sodium silicate on a solids basis. Such detergent composition, when used in an automatic dishwasher will, however, frequently result in the darkening of aluminum articles washed repeatedly therein.

In view of the foregoing comments it is apparent that in detergent applications the adverse effects which calcium-sequestering phosphates may have on aluminum are of two types. One of these is corrosion-a portion of the aluminum is actually eaten away by the action of the phosphate in aqueous solution. The second adverse effect is tarnishing or discoloration. This is frequently experienced with calcium-sequestering phosphate-containing detergent compositions when such compositions also contain suflicient sodium silicate to substantially completely inhibit corrosion. Tarnishing can take place when metals lower in the electromotive series than alu minum, and which are dissolved in the washing and/or rinsing solutions, are plated on upon the surface of the aluminum, or as a result of the build-up of a layer of aluminum oxide upon the aluminum surface. The aluminum oxide which overlays the metal may itself be colored or may give rise to colors as a result of its optical properties. Since the present invention is directed to both of these undesirable effects it is to be understood that the term damage to aluminum as used herein and in the appended claims has reference to both elfects and not to corrosion only.

It is an object of the present invention to provide improved means for inhibiting the damage to aluminum which is caused by aqueous solutions comprising calciumsequestering phosphates.

A further object of this invention is to provide detergent compositions containing calcium-sequestering phosphates which are characterized by the substantial absence of a damaging effect upon aluminum.

Other objects and advantages will be apparent from the following detailed description.

It has now been discovered that certain 'alkyl polyamines not .only possess the advantages of sodium silicate in inhibiting corrosion of aluminum by aqueous solutions containing calcium-sequestering phosphates without the attendant disadvantages associated with the use of sodium silicate, but also possess the additional property of inhibiting the tarnishing of aluminum surfaces which often takes place when aluminum articles are repeatedly washed in an automatic dishwashing machine in aqueous solutions containing a calcium-sequestering phosphate and sodium silicate. The amines of this invention may, therefore, be employed either to replace the sodium silicate normally found present in calcium-sequestering phosphate-containing detergent compositions or, if the presence of sodium silicate is desirable in such detergent compositions for purposes of inhibiting the etching of glassware and clear over-glazes on decorated china, in conjunction with the silicate to inhibit the tarnishing or discoloration of aluminum as hereinbefore discussed.

Although it is not to be considered binding for purposes of this invention, it is believed that the alkyl polyamines referred to above and which are more fully defined hereinafter accomplish their purpose by forming a layer on the aluminum surface which inhibits damage thereto. It is thought that this film persists long enough after the generating solution is replaced to provide some protection during subsequent rinsing away of the generating or detergent solutionfrom the aluminurn'surface. It is to be appreciated that, although the polyamines of this invention may find advantageous application in aqueous solutions of any detergent compositions which contain calcium-sequestering phosphates regardless of the concentration of calcium-sequestering phosphate in said solution, as a practical matter, the polyamines will be applied only in the case of those detergent compositions which contain sufficient calcium-sequestering phosphate so that when the composition is used at concentrations normal to various detergent applications (e.g. about 0.05% to about 1.5% solutions), the calcium sequestering phosphate may be present in a concentration which will cause damage to aluminum.

Various amines of the type herein contemplated have been previously suggested for use as inhibitors against the corrosion of steel by acids and distilled water or boiler condensate. The corrosion of steel by acid involves a direct combination of the acid with iron as shown by the equation:

The corrosion of steel by distilled water or boiler condensate is caused either by dissolved carbon dioxide, which would produce acid attack as indicated by the above equation, or by dissolved oxygen according to the equation:

The corrosion of aluminum by calcium-sequestering phosphates to which this invention is directed is not identifiable with the acid corrosion described above. Nor does it comprise simple alkaline corrosion as will be more fully discussed hereinafter. It is, rather alkaline corrosion aggravated by sequestration.

The calcium-sequestering phosphates which are referred to herein are the polyphosphates corresponding to the formula Na P O where n=2, 3, 4, 5, When n=2 the above formula represents a pyrophosphate having the molecular formula Na P O when n 3 the formula is that of the tripolyphosphate Na P O when n=4 or 5 the glass phosphates Na P O and Na- P O .are'represented. These latter phosphates are not ordinarily prepared in the pure state but do occur in admixture with phosphate compounds wherein n is a higher and lower integer.

Although the corrosion of aluminum by alkaline compounds is generally well-known, little information is extant regarding the corrosion of aluminum by alkaline solutions of sequestering agents. It has now been observed that in the pH range from about 7 to about 11 the sequestering phosphates corrode aluminum to a much greater extent than non-sequestering phosphates even though the phosphate-containing solutions are at the same pH. The reason for the increased corrosive effect of the sequestering phosphates can probably best be understood from the equations for the reactions involved, although it is to be understood that the corrosion mechanism represented by the following equations is theoretical and should not be considered limiting of the invention.

Aluminum immersed in water is considered to acquire a layer of hydroxide or hydrous oxide. The following equation represents the alkaline corrosion of aluminum AlO ''-|-2H O=A1+ +4OH- A1+3+P30105=A1P3O10 2 Thus, when a sequestering agent is present to-tie up 4 (sequester) the Al ions which are in equilibrium with A10; the equilibrium is shifted to the right and the net reaction becomes It may be observed from the above equations that the hydroxide ion (OH) is formed by the sequestering of aluminum whereas in the absence of a sequestering phosphate the hydroxide ions combine with the aluminum.

The corrosive effect which the sequestering phosphates exhibit upon aluminum may be readily seen from the following example. v 1

Example I Strips of an alloy of aluminum with 1.2% manganese and bearing the Aluminum Company of America designation 38, measuring 3.0 x 0.75 x 0.041 inches were polished successively with steel wool and wet pumice, washed with water and alcohol, air dried and weighed on an analytical balance. These test strips were then immersed in 200 ml. of a 0.18% solution of the phosphate to be treated for one hour at 60 C., the'solutions being maintained at a pH of 9.5. The test solutions were contained in an Erlenmeyer flask and the aluminum strips reclined in the flask at an angle of about 40 with reference to the bottom of the flask. After the immersion period the aluminum strips were removed from the flasks and treated in accordance with the method of ASTM designation B185-43T. This comprised essentially washing the strips with water, immersing them for three minutes in concentrated nitric acid to remove any products of corrosion, washing them successively with 'water and alcohol and air drying and weighing them.

Phosphate Used N83?! 0 9 (Tllsodiumtrirnetaphosphate) N35P3010 (Sodiumtripolyphosphate) Loss in Weight, milligrams 1. 7. 5

It is evident from the above table that the sequestering tripolyphosphate caused a loss of more than 4 times that of the non-sequestering metaphosphate in the weight of the aluminum strips tested, thus indicating the much more pronounced corrosive effect of the calcium sequestering phosphates upon aluminum.

The compounds which have been found effective in minimizing the corrosion of aluminum by sequestering phosphates and which also function to inhibit the tarnishing of aluminum, as hereinbefore described, are fatty polyamines of the general formula RX NH where R is an alkyl radical of from about 10 to about 18 carbon atoms, X is selected from the group consisting of and n is an integer from 1 to 2. Where n is one 1) the polyamine is a diamine and where n is two (2) the polyamine is a triamine. The alkyl radical of the polyamine may be readily derived from coconut oil fatty 15% by weight of the calcium-sequestering phosphate.

Amounts of polyarnine less than about 5% by weight of citlcium-sequestering phosphate will not give an observatile and practical level or aluminum damage inhibition. Amounts of polyamine substantially reater fliafl 15% by weight of the calcium-"sequestering phosphate show no measurable improvement in inhibiting action over the 15% value and, consequently, the use of amounts of polyarn'ine in excess of 15% would not reflect sound-coo nomic practice.

Whenever herein an inhibiting effect is referred to, it is to be understood that it is not to be construed as connoting an absolute prevention of corrosion or tarnishing. Rather, it is intended that this connotation should be such as to indicate that corrosion and/or tarnishing are being hindered to the point where these undesirable effects are minimized.

The effectiveness of the .polyamines of this invention in minimizing corrosion of aluminum is evident from the following example wherein thehard'ness of the water stated in grains indicates the calcium carbonate equivalent in grains per US. gallon.

Example II A number of amines of the above general formula were tested for the corrosion inhibiting effect which they exhibited in accordance with the procedure of Example I except that the pH was initially adjusted to 9.5 and then left uncontrolled, and the total immersion time for the aluminum strips in the phosphate solution was three hours. The specific amines which were tested are set forth in the table below. The corrosion inhibiting action of the various amines is evident from a comparison of the loss in Weight of aluminum strips immersed in the sodium tripolyphosphate solution of Example I to which the amine inhibitor had been added with the loss in weight of aluminum strips immersed in inhibitor-free phosphate solution of the same concentration. The indicated amine inhibitors used were present in the calciumsequestering phosphate solution in an amount about 0.02% by weight of the solution.

Loss in Weight, Milligrams Zero Hard- 7 Grain ness Water Hardness Water Keryl 1 diethylenetriamine 1. 7 1. 3 N-soya 2 trimethylene diamine. 6.1 8.5 N-lauryl trimethylene diamine 0.5 0.5 N-coconut 2 trimethylene diam O. 4 0. 3 N-ta1low 2 trimethylene diamine 2.0 5. 6 N inhibitor 17 12 1 Indicates an alkyl group derived from a petroleum oil fraction containing about 12 carbon atoms in straight chain configuration.

2 Represents an allryl group derived from the mixture of fatty acids obtained 'in the reduction of the source triglycerides indicated.

Example 'III Aluminum strips such as are described in Example I above were prepared in accordance with the procedure of Example I and were immersed for about 3 hours at 60 C. in an aqueous solution containing the following constituents in the concentrations shown: 0.18% sodium pyroplrosphate; 0.06% of a condensation product of tall oil with about 9 molar equivalents of ethylene oxide ('Sterox 'CD-marketed by Monsanto Chemical co); 0.02% N-lauryl trimethylenediamine. The aqueous solution was maintained at a pH of about 9.5 throughout the immersion period. At the end of the immersion period the strips were removed from the phosphate-containi ng solution and were treated in accordance with the procedure set forth in Example I. It was found that substantially no weight loss of the aluminum strips occurred thereby indicating an inhibition of the corrosive effect of the pyrophosphate.

It is to be appreciated that corrosion inhibition comparable to that obtained with the amines set forth in the "above examples, as well as the tarnish inhibiting effects described hereinbefore, can also be obtained with mixtures of amines coming within the purview of the general formula 'set forth above.

The corrosion and tarnish inhibiting action of the aforementioned polyamines is not evidenced in the presence of anionic synthetic detergents when such detergents are present in concentrations which exceed more than about two times that of the polyamines used. It is preferred, therefore, that, if the polyamines described and claimed herein are to be utilized in calcium sequestering phosphate-containing detergent compositions, any anionic deter'gent present in such compositions be employed at -a concentration no greater than that of the polyamine. It has been found, for example, that the addition of 0.06% of the sodium salt of an alkyl sulfate, where the alkyl group is derived from a long chain primary alcohol having from about 12 to 18 carbon atoms, or of an alkyl benzene sulfonate wherein the alkyl group comprises predominantly l2 carbonatoms, to a 0.18% aqueous solu- 'tion of sodium tripolyphosphate will raise the loss in weight of an aluminum strip immersedtherein and treated in accordance with the procedure of Example II, to approximately the same value as if no inhibitor was used in the phosphate-containing solution. This nullification of the damage inhibiting capacity of the aforementioned 'polyamines is exhibited by the anionic synthetic detergents as a class.

such as the alkyl (C -C sulfates, the alkyl (C -C sulfonates, the alkyl c o aromatic sulfonates, the

monoor di-alkyl (C -C esters of sulfosuccinic acid, sulfonated or sulfated amides of higher fatty acids, sulfuric acid esters of polyhydric alcohols incompletely esterified with higher fatty acids, higher fatty acid esters of low molecular weight alkylol sulfonic acids, etc.,

usually in the form of their sodium, potassium, am- I monium or amine salts. Some of the particular detergents of this category are: sodium octyl sulfate, sodium nonyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate, sodium tetra-decyl sulfate, sodium penta-decyl sulfate,

sodium hexadecyl sulfate, sodium octadecyl sulfate, so-

dium oleyl sulfate, the corresponding alkyl sulfonate salts, sodium salt of di-octyl sulfosuccinate, sodium octyl benzene sulfonate, sodium nonyl benzene sulfonate, sodium dodecyl benzene sulfonate, sodium tetradecyl benzene sulfonate, sodium pentadecyl benzene sulfonate, sodium hexadecyl benzene sulfonate, sodium octadecyl benzene sulfonate, sodium tri isopropyl benzene sulfon'ate, sodium tri isopropyl naphthalene sulfonate, sodium salts of the oleic acid ester of isethionic acid, sodiuin salt of the aluric acid amide of taurine, coconut oil monoglyceride monosulfate, tallow diglyceride monosulfate. Mixtures of various of the anionic synthetic detergents also come within the scope of the general class definition above. For example, the commercially available detergents are generally not pure compounds but are mixtures of homologous compounds. Thus, sodium alkyl benzene sulfonate wherein the alkyl group contains 12 to 18 carbon atoms, a mixture of sodium alkyl sulfates consisting mostly of sodium lauryl sulfate and a mixture of sodium alkyl phenol sulfonates wherein the alkyl group contains from 12 to 18 carbon atoms are wellknown detergents. V

For purposes of this application it is to be understood that, in general, the classification of the anionic detergents shown in Surface Active Agents by Schwartz and Perry, 1949 Interscience Publishers, pages 15 and 16, with the exclusion of ordinary soaps, is to be employed.

It is significant that the nullification efiect referred to above which is exhibited by anionic detergents as a classis not found when the polyamines of this invention -7 are used in preparations containing nonionic synthetic detergents as a class. Consequently, these polyamines are eminently useful as aluminum damage inhibiting agents in various calcium-sequestering phosphate-containing detergent preparations which also contain a synthetic detergent of the non-ionic type. Such preparations find widespread commercial acceptance for household application.

The nonionic synthetic organic detergents include compounds produced by the condensation of alkylene oxide groups (hydrophilic in nature) with an organic hydrophobic compound which may be aliphatic or alkyl aromatic in nature. Examples of such detergents would be: the polyalkylene glycol esters, ethers and thioethers of the types:

wherein R represents long chain alkyl radicals having from about 8 to 18 carbon atoms and n is an integer from about 4 to about 30, the polyethylene oxide condensates of alkyl phenols, e.g. the condensation products of alkyl phenols having about 6 to 12 carbon atoms in the alkyl group, in either straight chain or branched chain configuration, with ethylene oxide in amounts equal to to 25 moles of ethylene oxide per mole of alkyl phenol; compounds formed by condensing ethylene oxide with a hydrophobic base formed by the condensation of, propylene oxide with propylene glycol; the condensation product of ethylene oxide with the product resulting from the reaction of propylene oxide and ethylene diamine. More specific examples of some of the nonionic detergents hereinbefore referred to are: the condensation product of lauric acid and diethanolamine, nonyl phenoxy polyoxyethylene ethanol, polyethylene glycol ester of rosin, polyethylene glycol ester of hydroabietyl alcohol, the condensation product of hydroabietin- 01 with mols of ethylene oxide, the condensation product of oleyl alcohol with 15 mols of ethylene oxide, the condensation product of isooctylphenol with from 7 to 15 mols of ethylene oxide.

The nonionic detergent actives are generally used as a constituent of commercial detergentcompositions where a minimum of foaming can be tolerated. Most significant among such preparations would be those marketed for use in the present automatic dishwashing machines and the following examples set forth detergent compositions which are suitable for such application.

Example IV A composition was prepared comprising in admixture,

" 34% of a condensation product of tall oil with about nine molar equivalents of ethylene oxide (Sterox CD- marketed by Monsanto Chemical Company) 60% sodium tripolyphosphate (anhydrous) and 6% of a fatty diamine having the general formula inhibit the corrosion or tarnishing of aluminum.

Example V A composition comprising 49.5 parts sodium tripolyphosphate, parts chlorinated trisodiumphosphate, 10 parts of sodium silicate having an average SiO /Na O ratio of 2.9 (solids basis) dissolved in 15 parts water,

' 3 parts of a condensation product of one mole of octyl phenol with about 10 moles of ethylene oxide and 2.5 parts of the diamine of Example IV was prepared. This "8 composition, upon repeated use in a domestic type automatic dishwasher was found to exhibit substantially no corrosion or tarnishing efiects upon aluminum.

Example VI The detergent composition of Example V was prepared except that the amine inhibitor used was anN- alkyl trimethylene diamine wherein the alkyl group was derived from the mixture of fatty acids obtained in the reduction of t-allow (Duomeen T--marketed by Armour & Company, Chicago, Illinois).

This composition, upon repeated use in a domestic type automatic dishwasher was found to exhibit substantially no corrosion or tarnishing effects upon aluminum.

It is to be understood that the foregoing examples are not to be construed as limiting the application of the amines of this invention to detergent compositions which contain as the active detergent agent only detergents of the nonionic class. Detergent compositions containing anionic-type synthetic detergent actives or mixtures of various synthetic detergent actives of the non-ionic and anionic type are also benefited by the presence of the polyamines herein described, so long as the anionic synthetic detergent is not present in the detergent composition in an amount more than about twice the amount of polyamine.

The aluminum corrosion inhibiting eflfect of the polyamines of this invention in the presence of anionic synthetic detergents is illustrated by the following example.

Example VII Loss in Weight, Milligrams CNAS ABS Keryl diethylenetriamine 2. 0 l. 4 N-lauryl trimethylenediamine 0. 3 0. 5

1 Denotes coconut alkyl sulfate-an alkyl sulfate wherein the alkyl group is derived from the middle cut alcohols obtained from the reduction of coconut oil (marketed by the Du Pont 00. under the trade name Lorol).

I Alkyl benzene sulfonate wherein the alkyl group contains an average of 12 carbon atoms.

The loss in weight of the aluminum strips as indicated in the table above may be compared with the 17 milligram loss in weight of aluminum strips immersed in inhibitor-free phosphate solution and with the 1.7 mg. and 0.5 mg. loss in weight in keryl diethylenetriamine-and N-lauryl trimethylenediaminecontaining phosphate solution respectively, as shown in the zero hardness water column in the table in Example H. It is evident from this comparison that the anionic synthetic detergent, in the concentration shown, had no adverse effect upon the aluminum corrosion inhibiting action of the polyamines.

It is also to be understood that the foregoing examples and discussion are not to be considered limiting of the detergent preparations with which the polyamines of this invention find application. For example, with detergent compositions suitable for use in an automatic dishwasher, and which contain suflioient silicate to effectively inhibit the corrosive effect of the calcium-sequestering phosphate component of the composition upon aluminum, the polyamines, nevertheless, funotion to prevent damage to aluminum by the inhibition of the tarnishing of aluminum .which often occures after repeated washing-rinsing cycles 9 in the machine. Where, on the other hand, the calciumsequestering phosphate-containing detergent preparations are free of silicate, the polyamines set forth herein function to inhibit corrosion of the aluminum surface and at the same time tend to prevent tarnishing of the aluminum surface.

What is claimed is:

1. A detergent composition characterized by a tendency, when employed in aqueous solution in detergent applications, to damage aluminum, consisting essentially of a calcium-sequestering phosphate and, as an inhibitor against said tendency to damage aluminum, a polyamine having the formula RX NI-I wherein R is an alkyl radical containing from about 10 to about 18 carbon atoms, X is selected from the group consisting of and and m is an integer from 1 to 2, the said polyamine being present in the detergent composition in an amount from about 5% to about 15% by weight of the calcium-sequestering phosphate.

2. The detergent composition of claim 1 wherein the calcium-sequestering phosphate is sodium tripolyphosphate.

3. The detergent composition of claim 1 containing sodium silicate in an amount insufficient to prevent the corrosion of aluminum by the calcium-sequestering phosphate.

4. The detergent composition of claim 1 containing sodium silicate in an amount sufficient to prevent the corrosion of aluminum by the calcium-sequestering phosphate.

5. The detergent composition of claim 1 containing a non-soap synthetic detergent selected from the group consisting of non-ionic synthetic detengent, anionic synthetic detergents and mixtures thereof, the anionic synthetic detergent, in all cases, being present in the said composition in an amount not greater than about twice the amount by weight of the polyamine.

6. The detergent composition of claim 3 containing a non-soap synthetic detergent selected from the group consisting of non-ionic synthetic detergent, anionic synthetic detergents and mixtures thereof, the anionic synthetic detergent, in all cases, being present in the said composition in an amount not greater than about twice the amount by weight of the polyamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,267,205 Kyrides Dec. 23, 1941 2,533,302 Watkins Dec. 12, 1950 2,731,420 Sylvester Jan. 17, 1956 2,736,658 Pfohl et a1 Feb. 28, 1956 2,741,599 McDonald Apr. 10, 1956 2,881,139 Gysling Apr. 7, 1959 FOREIGN PATENTS 516,718 Canada Sept. 20. 1955

Claims (1)

1. A DETERGENT COMPOSITION CHARACTERIZED BY A TENDENCY, WHEN EMPLOYED IN AQUEOUS SOLUTION IN DETERGENT APPLICATIONS, TO DAMAGE ALUMINUM, CONSISTING ESSENTIALLY OF A CALCIUM-SEQUESTERING PHOSPHATE AND, AS AN INHIBITOR AGAINST SAID TENDENCY TO DAMAGE ALUMIUM, A POLYAMINE HAVING THE FORMULA