US2756214A

US2756214A - Tahiwiivtk

Info

Publication number: US2756214A
Authority: US
Publication date: 1956-07-24
Anticipated expiration: 1973-07-24

Description

United States Patent MECHANICAL DISHWASHING COMPOSITION AND METHOD OF USING SAME Kurt Albrecht, Pleasant Hills, Pa assignor to Calgon,

Incorporated, Pittsburgh, Pa a corporation of Pennsylvania No Drawing. Application August 1, 1952, Serial No. 302,249

Claims. (Cl. 25299) This invention relates to improved dishwashing and glasswashing compositions having unique properties which combine to produce results heretofore never obtainable with the most efiective compositions of the prior art, and to methods of washing with these compositions.

Within the past decade the use of the so-called automatic electric dishwashing machine in the home has increased at a rapid rate. Although the automatic dishwasher has been widely employed in hotels, restaurants, hospitals and the like for well over a quarter of a century, the home type machine is a relatively new appliance.

Prior to the commercial development of the polyphosphates, i. e. the alkali-metal salts of the several polyphosphoric acids, the home dishwasher had not been a success because of the inability of the machine to remove soil deposits on glassware, chinaware, and silverware. The early machines failed principally because of the calcium and/or magnesium present in most household water supplies. When the hardness-precipitating type of dishwashing composition was used, the calcium and/or magnesium salts quickly precipitated from the water and were deposited on the ware as a film or scum. Typical hardnessprecipitating compositions in use were the sodium orthophosphates, sodium carbonate, sodium bicarbonate, sodium silicate or mixtures of two or more of these salts.

The commercial dishwashing machines for years had been operated with these compositions as the source of cleaning power, but with mediocre to poor results. Dishes and glasses were frequently towelled or otherwise rubbed by hand to remove the film, and often a strong bleaching solution or china dip was used for a like purpose as a standard practice. The need for such procedures was a natural deterrent to the widespread use of dishwashers in the home.

With the advent of the polyphosphates for water conditioning in the mid-l930s, commercial detergent mixtures of various types became available to the householder. Such mixtures enabled the home-type dishwashing machine to function quite efliciently and the need for towelling and china dipping did not exist since the objectionable film or deposit did not form on the wares. The polyphosphates are not hardness-precipitating salts but are rather hardness sequestering. The soluble calcium and/or magnesium salts such as calcium carbonate or bicarbonate and the corresponding magnesium salts are sequestered or locked up into a water soluble complex 2,756,214 Patented July 24, 1956 "ice which is not adherent to glassware, chinaware, and silverware as are the precipitated calcium or magnesium salts.

The most widely used polyphosphates in the dish-washing composition field are the glassy sodium phosphates known as commercial sodium hexametaphosphate, and the glassy sodium tetraphosphate. Other glassy phosphates having a molar ratio of NaaO to P205 of from about 0.9 to 1 to about 1.7 to 1 are employed. The crystalline polyphosphates such as sodium tripolyphosphate (NasPsOm) and tetra sodium pyrophosphate (NarPzOv) are also present to a varying degree in certain compounded mixtures. The most acceptable mixtures of glassy phosphates and alkaline salts contain such as sodium metasilicate or other alkaline compounds, contain from 20% to 40% by weight of the hardness-sequestering phosphate. The balance of the formula provides emulsifying and saponifying action to enable the wash solution to remove all types of soil which may be encountered.

The ready public acceptance of the first home type dishwasher, after the development of the then new compositions, led to various mechanical improvements by the several machine manufacturers. The basic design of the dishwasher was changed to meet certain requirements, and various refinements were added as time went on. For example, electrically-operated heating elements were installed so that the wares would dry in situ whereas previously the operator could not be sure whether the hot steam-laden air emanating from the machine at the end of the washing operation would help or hinder the so-called air-drying of the wares. Other structural changes were made in the various dishwashers to achieve more rapid washing, more thorough cleansing and other related desirable results.

In spite of the many structural changes in the washers themselves, there has been surprisingly little change in the detergent compositions which are used in the washers. Certain such as the sodium salts of lauryl alcoh'o the petro eum sulfonates, the olyether alcohols, and other orgamc materials have been added in varying amounts ostensibly to improve the overall detergency of the compositions. In addition these materials are ostensibly added to promote freedom from water spotting on glassware. However, all of these 0 anic materials have a pronounced tendency to hen dissolved in water, and foaming is highly undesirable in the mechanical dishwasher because it drastically reduces its mechanical efficiency. Hence, the concentration of the surface active type of washing adjunct is necessarily limited to such a degree that it cannot adequately accomplish its intended purpose.

One of the most persistent objections to the use of a home-type dishwasher is the development of so-called water-spots on glassware after it dries. The usual cycle of operation of a dishwasher is first, the application of hot detergent solution which is subsequently drained to waste; second, the application of hot rinse water which is also drained to waste; and lastly, the drying in situ of the wares. The rinse water usually contains traces of certain dissolved salts such as calcium sulfate along with residual soil which deposit on the surface of the wares as the water evaporates in the drying process. These deposits are unnoticeable on opaque chinaware but on glassware they are readily observable and are deemed quite objectionable. Such deposits may be removed by towelling which is a time-consuming chore as well as a source of annoyance and possible contamination of an ostensibly clean glass.

I have found that by admixing detergent salts in a properly balanced ratio, water spotting can be virtually eliminated, thereby enabling the housewife to take the dry glassware directly from the machine without towelling. My preferred compositions not only eliminate the objectionable spotting but are completely free from foaming agents and thus for the first time, to my knowledge, a dishwashing composition capable of preventing waterspotting without attendant foaming has been created.

In addition, these compositions have prevented for the first time the staining of plastic tableware which has come into wide usage particularly in cafeterias, hospitals, and other institutions during recent years. There are various types of plastics used in making tumblers, cups, saucers, plates, etc., but each type of plastic seems to be extremely susceptible to food and beverage stains, particularly to coffee and tea stains. The absence of a hard glaze which is present on ceramic ware may contribute to the susceptibility of plastic ware to staining, or it may be due to a chemical reaction between the ware and the tannin bodies in the tea and coffee. Whatever the reason, the result is most obvious and my new compositions are the only effective detergents which can be used to wash plastic wares in mechanical dishwashers and achieve acceptable results.

Essentially, my preferred compositions are dry mixtures of chlorinated trisodium phosphate and sodium tripolyphosphate. Although other alkaline salts may be added, their incorporation serves no useful purpose and actually lessens the efficacy of the binary mixtures. I prefer to formulate my composition on the basis of:

20%-60 weight sodium tripolyphosphate 80%40% by weight chlorinated trisodium phsp h ate, with the preferred optimum being about 40% by weight tripolyphosphate and about 60% by weight chlorinated trisodium phosphate for home-type dishwaters and about 30% by weight tripolyphosphate and about 70% by weight chlorinated trisodium phosphate for commercial 4 or institutional operations.

I have found that a composition containing less than about 20% chlorinated trisodium phosphate is not effective in achieving the desired results which my preferred materials are capable of producing. In other words, there must be a minimal amount of the chlorinated trisodium phosphate to prevent the formation of coffee and tea stains on plastic ware and prevent the formation of objectionable water sports on glassware.

Oddly enough the chlorinated trisodium phosphate used alone as a detergent causes pronounced darkening of both sterling silverware and silver-plated ware. By compounding it with the sodium tripolyphosphate, however, in the ratios previously indicated, there is no darkening of silverware mechanically washed in a solution of the mixture, the mixture seemingly being inhibited against darkening.

Chlorinated trisodium phosphate has been used as a combination detergent and bactericide for many years, particularly in the washing of dairy utensils and equipment. U. S. Patent No. 1,965,304 discloses a method of manufacturing the salt. It has been compounded in small amounts with other alkaline detergents such as sodium metasilicate, soda ash, sodium bicarbonate, etc., but none of these mixtures has, to my knowledge, ever been suitable for mechanical dishwashing where complete freedom from the staining of plastic ware and spotting of glassware was desired. In addition, since the chlorinated trisodium phosphate is a hydrated salt, admixture of it with most of these other materials always resulted in a composition which either caked and hardened noticeably on storage after packaging or lost its available chlorine or both. This is not true of by binary mixtures of chlorinated trisodium phosphate and sodium 5 tripolyphosphate.

I may use either the hydrated sodium tripolyphosphate or the anhydrous salt. The crystalline anhydrous salt exists in two known forms designated as NasPsOtoI and NasPsOmII as shown in Journal of the American Chemical Society, vol. 63, pages 461-462. I have found that the former (NasPsOiol) is considerably more ,suitable in mixtures'wltli'clil'ofi'fiated trisodium phosphate since there is better chlorine stability than when the latter (NasPaOmH) is used. For example, when my preferred compound containing about 30% by weight NasPsOml and 70% chlorinated NaaPOr is dry mixed and stored at 120 F. for four weeks, the percentage loss of available chlorine is half the loss when NasPsOmlI is used in an identical mix under identical test conditions. This is an important matter where the product may be stored for long periods of time.

Obviously the germicidal or bactericidal action of the chlorinated trisodium phosphate is of advantage in a mechanical dishwashing compound but I lay no claim to novelty through utilizing a chlorine-containing salt of this sort in a dishwashing compound purely for its germicidal effect which has for years been well known in other washing applications such as in the combined washing and sterilizing of dairy equipment, etc.

I prefer to mix the dry ingredients, i. e., chlorinated trisodium phosphate and sodium tripolyphosphate or other non-chlorinated alkali metal polyphosphate in the usual way to form a homogeneous dry mix granulated in form without adding any other materials, but any suitable surface activeagent may be incorporated time ,mixtures if desired. M

'surprtsirigryeneugh it I combine chlorinated trisodium ,oflbophgsphgte with any of the glassy alkali metal poly- 3565mm such as sodium hexametaphosphate (NaPOa)s and the sodium tetraphosphate (N86P4013) which are commercially available, the products cake rapidly on storage and lose their available chlorine and hardness sequestering properties. Obviously, such products are totally unfit for use. 5 To test the efliciency of one of my preferred compositions consisting of 60% by weight chlorinated trisodium phosphate and 40% by weight crystalline sodium tripolyphosphate (NasPsOmI), I evaluated this product in direct comparison with one of the most effective commercially available mechanical dishwashing compositions. In conducting this test I followed the soiling procedure set out in the February, 1945, edition of Industrial & Engineering Chemistry by Ray C. Hughes and Rubin Bernstein of the Industrial Test Laboratory, U. S. Navy Yard, Philadelphia, Pennsylvania.

In running the test, I used a conventional home-type dishwashing machine in which both the wash water and the rinse water were maintained at a temperature of between 145 F. and 160 F. The detergent concentration throughout was 0.25% by weight.

In preparing the soil and applying it according to the methods of Hughes & Bernstein, a soiling mixture having the properties of a food residue is applied to plate glass squares which are washed under controlled conditions 65 along with 8 water glasses in solutions of the compound under test and the amount of soil remaining on the surfaces of the 8 glasses after the test is then measured. Rather than measure the soil, I made actual counts of the residual spots on the water glasses.

A mixture of two parts peanut butter, one part hydrogenated vegetable shortening, and one part butter was used for soiling the glass squares. It was prepared by weighing out the ingredients and mixing at a temperature suificiently elevated to melt the fats.

75 The soiling was applied to the previously prepared glass squares by a soiling tube. This tube was essentially of the same construction as that used by Hughes 8: Bernstein, and the method of applying the soil to the glass surfaces was essentially that of the authors.

To evaluate the ability of my preferred composition to water spotting on glasses, 1 made actual spot counts on eight separate glasses following the washing and rinsing operation. The operational cycle is a 5-minute wash in a detergent solution followed by a 5-minute preliminary rinse with plain water and a 1-minute rinse with plain water, followed by still another l-minute rinse with plain water. At the end of this final rinse the glasses remained in the machine for approximately 20 minutes for complete drying. The dishwashing machine used for the test was equipped with an electric heating element to assist in drying.

The comparison composition which I used had the following approximate composition:

Pittsburg tap water was used throughout the test in the detergent solution and for rinsing the glasses.

The results of the comparison tests are as follows:

Comparison composition Actual S t Counts Average Run Number (8 Gases) of Spot Counts Glass 143 Glass...

Preferred composition Actual S t Counts (8 flg sses) Run Number Glass Glass..

Gleam-..

when using only creamery butteras the soiling material in place of the Hughes and Bernstein soil, the following data were obtained:

Comparison composition It is therefore quite apparent that in the removal of both types of soil my preferred mixture of 60% chlorinated trisodium phosphate-40% crystalline sodium tripolyphosphate (NasPsOmI) is vastly superior to the best of the prior art materials in turning out glasses which are relatively free from objectionable water spotting.

While no particular minimum or maximum concentrations of my compositions are indicated, the preferred solutions contain from about 0.1% to about 0.5% by weight of composition in the washing solution. Obviously I may use smaller or greater amounts but optimum results compatible with overall economy are obtained at the preferred levels.

I claim:

1. An improved dishwashing composition consisting essentially of a mixture of from about per cent by weight to about 20 per cent by weight of sodium tripolyphosphate and from about 20 per cent by weight to about 80 per cent by weight of hydrated chlorinated trisodium phosphate.

2. A composition as described in claim 1 consisting essentially of a mixture of about 30 per cent by weight of sodium tn'polyphosphate and about 70 per cent by weight of chlorinated trisodium phosphate.

3. A composition as described in claim 1 consisting essentially of a mixture of about 40 per cent by weight of sodium tripolyphosphate and about 60 per cent by weight of hydrated chlorinated trisodium phosphate.

4. A method of washing eating utensile and tableware mechanically which comprises subjecting them to an agitated aqueous solution containing from about 0.1% to about 0.5% by weight of a detergent consisting essentially of (A) from about 30 per cent by weight to about 70 per cent by weight of chlorinated trisodium phosphate and (B) from about 70 per cent by weight to about 30 per cent by weight of crystalline sodium tripolyphosphate.

5. The method as described in claim 4 where the detergent consists essentially of (A) chlorinated trisodium phosphate from about 70 per cent to about 60 per cent by weight; (B) crystalline sodium tripolyphosphate from about 30 per cent to about 40 per cent by weight.

6. The method as described in claim 4 where the detergent consists essentially of (A) chlorinated trisodium phosphate about 70 per cent by weight; (8) crystalline sodium tripolyphosphate about 30 per cent by weight.

7. The method as described in claim 4 where the detergent consists essentially of (A) chlorinated trisodium phosphate about 60 per cent by weight; (B) crystalline sodium tripolyphosphate' about 40 per cent by weight.

8. The method as described in claim 4 where the detergentconsists essentially of (A) chlorinated trisodium weight to about 60 percent by weight of chlorinated phosphate from about percent by weight to about 80 trisodium phosphate and from about percent by weight percent by weight, (B) crystalline sodium tripolyphosto about percent by weight of sodium tripolyphosphate from about percent to about 20 percent by phate.

weight. 5

9. An improved dishwashing composition consisting Ram cued m the me of mm patent essentially of a mixture of from about 30 percent by UNITED STATES PATENTS weight to about 70 percent by weight of chlorinated 1,555,474 Mathias Sept 1925 N trisodium phosphate and from about 70 percent by weight 1,965,304 Adl July 3, 1 1 1 -97 p to about 30 percent by weight of sodium tripolyphos- 10 2,324,302 Hun July 13, 1943 an 67 phate. 2,524,394 Madorsky Oct. 3, 1950 2.

10. A composition as described in claim 1 consisting 2,534,781 MacMahon Dec. 19, .25 1.- 17

essentially of a mixture of from about 70 percent by 2,689,225 Anderson et a1 Sept. 14, 19541 L 7,

Claims

1. AN IMPROVED DISHWASHING COMPOSITION CONSISTING ESSENTIALLY OF A MIXTURE OF FROM ABOUT 80 PER CENT BY WEIGHT TO ABOUT 20 PER CENT BY WEIGHT OF SODIUM TRIPOLYPHOSPHATE AND FROM ABOUT 20 PER CENT BY WEIGHT TO ABOUT 80 PER CENT BY WEIGHT OF HYDRATED CHLORINATED TRISODIUM PHOSPHATE.