Method of producing detergent composition

United States Patent Office 3,350,31s

Patented Oct. 31, 1967

3,350,318

METHOD OF PRODUCING DETERGENT COMPOSITION

Robert L. Green, Morrisville, Pa., assignor, by mesne assignments, to EMC Corporation, Princeton, N.J., a corporation of Delaware

No Drawing. Filed Feb. 18, 1964, Ser. No. 345,594 4 Claims. (CI. 252—135)

This invention relates to low foaming detergent compositions for use in automatic dishwashers and is directed particularly to detergent compositions which do not attack overglaze colors and decorations of fine china and the aluminum of pots and pans, and do not tarnish stainless steel used in cutlery and on the surfaces of dishwashers which are exposed to them.

The dishwashing compounds used in automatic dishwashers preferably are characterized by their low foaming properties, since the washing action of such equipment relies largely on the scrubbing effect of vigorous jets or sprays of liquid which would be rendered relatively ineffective if cushioned by the action of large amounts of foam. However, the low foaming compositions heretofore used in automatic dishwashers have sometimes been relatively strong or harsh in their action on the surface or decorations carried by the articles being washed. For example, most dishwashing compounds contain polyphosphates as soil emulsifiers and water softeners; such phosphates tend to attack aluminum articles such as pots and pans and are injurious to overglaze decorations on dinnerware. The injury to decorations on fine china is particularly objectionable and is believed to be due to weakening or destruction of the bonding material by which the decoration is secured to the glaze on the china. The bond generally consists of a glass-like lead borosilicate flux containing about 60 to 65% lead and minor proportions of boric oxide and silica. The detergents used in the usual dishwashing compounds are believed to attack the flux constituents weakening the bond to such an extent that the decorative material may be washed or rubbed off the glaze.

It is known that sodium silicate serves to reduce the attack of polyphosphates on glazing and decorative material. It also has been suggested that the action of alkalicarbonates, -orthophosphates and -sulfates, also common ingredients in dishwashing compounds, can be inhibited in their attack upon vitreous and ceramic surfaces by the use of water-soluble zinc, beryllium or aluminum compounds. However, when soluble silicate and aluminate compounds have both been used in dishwashing compounds heretofore, an undesirable precipitate has been formed which tends to deposit on the dishes, cutlery and exposed surfaces of the dishwasher leaving them tarnished or unclean in appearance. While such an objectionable precipitate can be emulsified or suspended if a suitable surfactant composition is employed, the surfactants heretofore considered suitable for this purpose have been employed in such large amounts as to render the compositions unacceptable for use in automatic dishwashers due to the excessive amount of foam produced.

Accordingly, the principal objects of the present invention are to reduce the injury or attack upon decorated china by dishwashing compositions, to limit the formation of undesired precipitates in dishwashing solutions, and to assure the effective cleaning and protection of articles subjected to the action of low foaming detergent materials in automatic dishwashers.

These and other objects and features of the present invention will appear from the following description thereof wherein typical and preferred dishwashing compositions are shown and their use described.

In accordance with copending application Serial No. 314,626, now issued as U.S. Patent No. 3,255,117, the objectionable action of prior dishwashing compositions on the color or decoration of fine china and on the tarnish5 mg of metals is reduced or prevented by suitable control of the proportion and relation to the ingredient employed in the dishwashing composition and in particular by including in such composition an inhibitor in the form of an alkali compound of an amphoteric metal. For this 10 purpose, it has been recommended that from about 0.5 to 5% of a compound such as sodium aluminate may be included in the composition. The amount of the inhibitor used must be limited in order to prevent the formation of an undesired precipitate in the washing liquid. Low 15 foaming detergents of this character have been found to be quite satisfactory. However, the cost of sodium aluminate as compared with other constituents of the composition is relatively high. Furthermore, commercially available sodium aluminate is generally in the form of a 20 relatively fine powder or granules which tend to segregate and settle out or sift to the bottom of a package or container in which the composition is sold or shipped. Therefore, it is generally necessary to use upwards of 0.5%, and preferably about 1 to 3% of the inhibitor and to 25 tolerate the formation of a limited amount of precipitate in order to insure the presence of adequate inhibitor in every portion of the composition when used. If lesser amounts of the inhibitor are employed, there will always be a possibility that some portions of the composition ³θ will not contain sufficient inhibitor for adequate protection of the china decoration from attack by the detergent solution.

It has now been discovered that attack upon the decoration on fine china due to the action of polyphosphates ³⁵ and other constituents of low foaming detergents and the formation of an undesired precipitate in the dishwashing liquid can be prevented while employing an amount of an amphoteric compound far below the minimum amount ₄θ heretofore believed to be necessary. In order to attain this result in accordance with the present invention, the inhibitor is preferably associated with the granular particles and particularly the polyphosphate particles in the detergent composition in such a way as to assure intimate, uniform and permanent distribution thereof. Moreover, since the attack on china decorations by the detergent solution is caused primarily by the polyphosphates, it is desirable to associate the attack inhibiting amphoteric metal with the polyphosphate particles in such a manner 50 as to maintain such association at the time the particles actually go into solution in the dishwashing liquid. For this purpose, the sodium aluminate may be suitably distributed over or perhaps within the polyphosphate granules of the dishwashing detergent whereby solution of the 55 inhibitor and polyphosphate in the dishwashing liquid takes place simultaneously, and in the immediate presence of each other. As a result, it has been found that only about 10 to 20% of the amount of sodium aluminate heretofore required is necessary in order to attain the θθ desired inhibiting action and the elimination of an objectionable precipitate and uniformity of the composition is assured.

Detergent compositions embodying the present invention may vary considerably. However, they are prefer55 ably of the general character described in said U.S. Patent No. 3,255,117 and contain from about 20 to 50% by weight of an alkali polyphosphate such as tetrasodium pyrophosphate, sodium hexametaphosphate, sodium tripolyphosphate and the like; from about 10 to 30% by weight of sodium silicate having an Na₂O:SiO₂ ratio of about 1 to 1 to 1 to 3; from about 1 to 5% by weight of a dry chlorinated agent which yields chlorine in aqueous

3,350,318 sprayed onto the polyphosphate granules to be used in the detergent composition. However, the higher the concentration of the sodium aluminate in the solution the greater the amount of the polyphosphate necessary to produce a clear solution for application to other polyphosphate granules in producing the detergent. Generally, the aqueous solution of the polyphosphate compound in which the inhibitor is dissolved should contain from about 0.1 to 1.5% of the polyphosphate.

Sodium aluminate-polyphosphate solutions thus produced can be sprayed over polyphosphate or granules of other constituents of the detergent composition which wih not be adversely affected by such treatment so as to assure substantially uniform distribution thereof throughout the granules. The aluminate may then be said to coat or to be present throughout the surfaces of the particles, and in view of the porous nature of the polyphosphate particles, a portion of the aluminate may actually penetrate or be absorbed by and into polyphosphate particles. When the aluminate-polyphosphate solution is applied to the polyphosphate granules as an incident to the operation of increasing the bulk of the polyphosphate, relatively dilute solutions of the sodium aluminate are employed. However, in any such operation, 25 the desired distribution and intimate association of the aluminate or other inhibitor and the polyphosphate is assured so that upon subsequent solution of the. composition in forming a dishwashing solution, the inhibitor is presented in an effective solubilized form; and the 30 formation of undesired precipitate which, withdraws the aluminate from active inhibiting condition does not occur.

After the granules have been combined with the inhibitor solution, they may be dried in any suitable man35 ner. Admixture of polyphosphate-sodium aluminate particles thus treated with the remaining constituents of the detergent can then be effected in any conventional manner. Low foaming detergents adapted for use in automatic dishwashers and containing an effective amount ⁴⁰ of an inhibitor within the range of about 0.0'2 to about 1.5% of the total weight of the detergent composition can thus be produced. In most cases, when the inhibitor employed is sodium aluminate, the amount thereof should be in the neighborhood of 0.1 to 0.3% of the total weight 45 of the detergent composition. When glasses are washed in a dishwashing composition in accordance with the present invention and containing as much as 2% by weight of sodium aluminate, it is found that there is a tendency for some small amount of precipitate to be formed which ⁵⁰ may accumulate in the dishwashing equipment and flecks or spotting sometimes appear on the glasses. Accordingly, and in view of the effective action of an extremely limited amount of the inhibitor in preventing attack on the over55 glaze or other decorations on fine china when suitably presented to the washing liquid, it is desirable to limit the amount of the inhibitor employed in dishwashing detergents to about 1.5% or less and preferably only • about 0.1 to 0.3% of the total weight of the detergent 60 composition.

In order to illustrate typical practice in accordance with the present invention, the following example is cited. ¹ A sodium aluminate solution was prepared by dissolving 14.29 parts by weight of sodium tripolyphosphate in ⁶⁵ 746.2 parts by weight of water. To this solution was added 47.63 parts by weight of sodium aluminate and a small amount of a surfactant. The final solution was clear and was sprayed onto granules of sodium tripolyphosphate which were to be incorporated in the final dishwashing detergent. The batch became noticeably warm by reason of the hydration of the polyphosphate with the attendant swelling or bulking thereof. The sodium aluminate containing polyphosphate was then dried and mixed with the ³solution; about 1 to 5% of a nonionic surfactant resistant to the action of available chlorine; together with alkali salts such as sulfates, orthophosphates, carbonates, chlorides and the like.

Further, in accordance with the present invention, the detergent composition includes an inhibitor in the form of an alkali compound of an amphoteric metal such as an alkali aluminate, zincate or berylliate, and preferably sodium aluminate. Nevertheless, compounds such as sodium zincate, zinc sulfate, aluminum sulfate, beryllium ; sulfate, and reduction products of ZnO.NaOH.HjO and BeO.NaOH.H2O may be used. The amount of the inhibitor employed need only be from about 0.02 to 1.0 of the total weight of the detergent composition and preferably is within the range of about 0.1 to 0.2%. A preferred amphoteric metal compound for use as a corrosion inhibitor in dishwashing compositions embodying the present invention is sodium aluminate containing approxmately equal numbers of moles of Na₂O and A1₂O₃. The compound preferably is dissolved in water or an aqueous medium to produce the clearest possible solutions of aluminate ions. However, compounds with minor modifications such as higher alkali content and aqueous solutions containing a phosphate or other clarifying chemicals are also satisfactory for use in preparing the clear aluminate solutions.

In order to render such a limited amount of the inhibitor effective in the practice of the present invention, the inhibitor is dissolved, and the solution thus produced is sprayed onto the polyphosphate or other particles in a manner to assure substantially uniform distribution of the sodium aluminate onto or throughout the particles.

It is common practice when producing detergents wherein anhydrous polyphosphates are employed, to moisten or spray the polyphosphate particles with water. In this way, the polyphosphate is caused to swell or increase in bulk and decrease in density. Accordingly, in the practice of the present invention, the application to the polyphosphate particles of the solution of sodium aluminate or other inhibitor employed may be effected as an incident to the conventional treatment employed to increase the bulk of the polyphosphate compound.

In producing the solution of the inhibitor for application to the polyphosphate material, it is preferable first to dissolve sodium tripolyphosphate in water, and thereafter to dissolve the sodium aluminate in the resulting tripolyphosphate solution. In this way, hydrolysis of the sodium aluminate and the formation of aluminum hydroxide is prevented and a clear sodium aluminatecontaining solution is produced. For most purposes, an aqueous solution containing from about 0.1 to 6.0% of sodium tripolyphosphate is produced and from about 1 to 20% of sodium aluminate is then dissolved in the aqueous solution of the sodium tripolyphosphate. By spraying this solution onto granular polyphosphate, substantially uniform association of the inhibitor and polyphosphate is achieved. In this manner, the small content of inhibitor (the sodium aluminate) is distributed and bound up with the polyphosphate particles so that uniformity of concentration is assured, the inhibitor is stabilized against insolubilizing by the sequestering action of the polyphosphate ions, and the polyphosphate component of the detergent, which has a corrosive effect on overglaze china decorations, carries with it the amphoteric metal ion which inhibits that corrosion.

The sodium aluminate-polyphosphate solution used for this purpose preferably contains a substantially greater amount of the aluminate than polyphosphate and solutions containing up to 10 parts by weight of the aluminate for each part of the polyphosphate present may be employed. In fact, it is only necessary to employ a sufficient amount of the polyphosphate to assure the formation of a c.— --------- -10 uni OI tne poiypuospiiaic aoouiG lug l-uhuu -------= . , ,., clear solution of the sodium aluminate to be 75 other constituents of the detergent composition. The dish3,350,318 ⁵ washing detergent produced had the following composition:

. Percent

Sodium tripolyphosphate ¹40.0

Sodium aluminate 0.3

Sodium sulfate38.7

Sodium silicate17.0

Potassium dichloroisocyanurate 2.5

Nonionic surfactant 1.5 ¹ The amount of tripolyphosphate in the 'aluminate-eontainmg solution was ignored.

While the inhibitor solution can be sprayed onto other granular constituents which will not be adversely affected by the treatment and which are to be contained in the composition, it generally is applied to the polyphosphate granules only since the association of the inhibitor, and particularly sodium aluminate, with the polyphosphate material is believed to be of importance in attaining the advantages of the present invention. The addition of the nonionic surfactant to the solution of sodium aluminate in the foregoing example is optional since it may be incorporated in the mixture in any suitable manner.

Compositions of the character represented by the foregoing example are highly effective in reducing or preventing attack on. the decorations or color of tine chine and the discoloration or tarnishing of aluminum, stainless steel and other metals. Moreover, the objectionable formation of precipitate in the dishwashing solution and on the equipment is prevented and glasses, dishes and other articles washed in automatic dishwashers when using such detergent compositions do not have any observable deposits of precipitate or other residue thereon. Moreover, no observable variation in the characteristics of the dishwashing composition is found upon long standing or after prolonged vibration of a package or container in which the composition is packaged.

The effective action of detergent compositions embodying the present invention in preventing attack on the overglaze decoration on fine chine with the elimination of objectionable precipitate in the dishwashing liquid was demonstrated by the following tests:

A low foaming dishwashing composition was prepared which contained the following ingredients in parts by weight:

Sodium tripolyphosphate______________________ 43

Sodium sulfate_____________________________~ 37 3

Sodium silicate (Na₂O.₂SiO₂)___________ΣΞΞΞΞΞΞ 17½

Potassium dichlorocyanurate__________________ 2.5

The same composition was prepared but small portions of the sodium tripolyphosphate in the mixture were first sprayed .with clear solutions of sodium aluminate and mixed with the other ingredients to produce products also containing 0.2%, 1.0% and 2% of sodium aluminate . Each of the detergent compositions thus prepared was dissolved in water to produce a solution containing 0.3% of the detergent and a sample of fine china bearing over6 glaze decoration was immersed in each solution at boiling temperature. The sample treated with the detergent composition which contained no sodium aluminate showed considerable attack on the overglaze decoration with the 5 formation of rough layers of etched material over the decoration with accompanying loss in gloss and brilliance. None of the other samples showed any attack upon the decoration but only those solutions of detergent containing less than 2% of sodium aluminate were free 10 of objectionable amounts of flocculent precipitate. Those solutions produced from such compositions but containing 0.2% or less of sodium aluminate formed no observable precipitate but were still effective in preventing attack on the overglaze decoration by the sodium tripolyphosphate.

While typical dishwashing compositions and methods of producing the same have been cited for purposes of illustration, the composition of the deterbent may be changed or varied within the limits indicated above and the method of producing the detergent mixture also is 20 capable of numerous modifications. In view thereof, it should be understood that the compositions and method particularly described are intended to be illustrative only and are not intended to limit the scope of the invention.