US 2424049 A
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y 1947' M. E. PARKER ET AL 2,424,049
METHOD OF CLEANING CONTAINERS Original Filed July 16, 1941 i; Inveniars:
1 I Milton .EZPar/Eer;
\J Jiaul WBpne 'z'z,
3. such solution to shear any film on the wall of the container before the same can be effectively penetrated andcompletely released. With the present invention, however, the acid cleaner is deposited as a thin film upon the container wall, for example, as from a mist and has the quality of penetrating through the adhering substances so as to release and loosen them whereupon they are thoroughly removed by theuse of a simple jet spray of hot water subsequently applied. This result is attributable to the superior wetting, emulsifying, penetrating (deflocculating), dispersing and solvent properties of the acid cleaner.
An important feature of the present invention using an acid cleaning solution is its effect upon milkstone deposits. The acid cleaning solution has the property of dissolving such milkstone deposits as may be adhering to the wall of the container and also of preventing their original formation due to the softening properties of the acid cleaner on any water in which it is carried.
It will be recognized then, that the acid cleaning solution is not dependent upon the type of water available at a particular plant or depot but is equally effective with water havin all kinds and degrees of hardness and does not necessitate any complicated procedures of water treatment where, for example, hard water is encountered. This acid treatment of the water has a definite economical advantage in preventing the closing or clogging of hydraulic jets, which frequently occurs when hard waters are subjected to reaction with alkali substances occasioning a resultant precipitation of calcareous deposits.
The method of cleaning comprehended by this invention is continuous and is practically foolproof in its operation so that relatively inexperienced personnel may carry out the sanitizing of cans with the assurance that the quality of the cleaned containers will meet the most severe tests.
The results achieved by the present invention.
a very substantial improvement is possible in the.
use of an acid cleaning solution applied in very small concentration and without the use of the hydraulic scrubbing effect in the application of the acid cleaning solution to the container.
Of equal importance with the foregoing, is the provision of an acid solution which exerts a germicidal action, 1. e., a lethal effect upon microorganisms. This lethal effect is a property either of an acid reaction at elevated temperatures or of the specific nature of special acids regardless of temperature or both the acid and elevated temperature. The use of a wetting agent in the acid cleaning solution itself enhances this lethal effect by providing for a greater penetration of the acid principle in destroying germ life. This wetting agent also may 4 is equally applicable wherever films of extraneous matter are strongly adhered to such metal surfaces, and we have been successful in cleaning dairy equipment such as pasteurizing vats, holding tanks, pipe lines, milk and cream coolers and other types of dairy processing equipment. The important advantage which we find, in addition to the thorough cleaning which is achieved. as has been explained above, namely, the acid condition of such cleaned equipment is favorable to the development of the more desirable reducing and acid-forming bacteria. It is recognized, of course, that perfect sterility cannot be achieved, but the present invention approaches this optimum condition and maintains the sameto a much greater extent than has heretofore been accomplished. For example, containing bacteria are present in the air and water supplies, and when the same come in ample.
contact with surfaces which have been cleaned in accordance with this invention, the opportunity for their development and objectionable activity is very substantially lessened over containers and equipment cleaned by present practice with alkaline cleaners,
Referring to the drawing, thenumeral ill indicates a position at which a milk transport can C and its top T is subjected to a cold or tepid water rinse preferably applied by means of a hydraulic spray device or Jet. The can has previously preferably been steamed, if necessary, to remove as far as possible adhering cream in the case of cans transporting sour cream, for ex- At' the station ill, the amount of water necessary to effect the rinse may be only a fractional volume of the total volume of the container,'i. e., 1 to 2'pints in the case of a ten-gallon can, but with the present invention this is quite satisfactory. The water is preferably supplied from a source of fresh water and the soiled rinse water isled to waste. In this connection, in some cases instead of using a fresh supply of water, rinse water from a subsequent operation and containing the acid cleaner solution may be used to accomplish the rinse at the station l0, such water being either cold or tepid or being hot if desired.
From the station ill, the can is moved to station II and treated with a scrubbing spray of hot water containing entrained acid cleaner material from a subsequent operation. At this station ii, most of the nutrient and microorganisms are removed and continue to drain at the draining station l3. It is to be noted that the tank I! contains the hot water rinse utilized for the hydraulic scrubbing at the station i I, and this supply of rinse water is maintained substantially constant with respect to the acid cleaner solution as will be laterexplained. The rinse be of a type to exert or contribute to a lethal water constantly drains from the tank I 2 through the outlet i4 and at no time does this rinse water approach anywhere near the viscosity of the customary alkali rinse waters. Such alkali rinse waters are used over and over again and after one hundred cans have been washed, develop an objectionable viscosity in addition to providing a favorable environment for the development and propagation of oxidizing and putrefactive microorganisms. The presence of the acid cleaner solution in the rinse water contained in the tank i2 is at all times in an amount effective to give the rinse water an acid reaction which, as explained above, is unfavorable to the growth of the objectionable microorganisms, but favorable t9 the development of reducing and acid-forming the station release the same so of the tion in the rinse water in the tank I2 also has. the effect of preventing any objectionable viscosity' developing in that unlike an alkali cleaning solution which combines with the protein ingredients of milk and cream for example, to form viscous products the acid cleaner has a dispersing effect upon such constituents which is magnifled by the presence of a suitable wetting agent and thereby precludes the development of .any similar viscosity noted in the case of alkali cleaning solutions. The temperature of the rinse water in the tank I2 is maintained at about 140 F.
After the can has been permitted to drain, it is subjected to the acid cleaning treatment at I5. This treatment is carried out by injecting the acid cleaner through the medium of steam, hot water or air. It is preferably introduced to the interior of the can in a state of fine subdivision, for instance as a mist, in contradlstinction to a hydraulic scrubbing jet. As pointed out, the action of the cleaning agent is to penetrate the extraneous film on the can and that it may be readily removed by a conventional water rinse. In addition to its detergent effect, the cleaner exerts a lethal effect upon objectionable microorganisms, and this effect is facilitated by reason of its own specific bactericidal properties as well as its penetration into and through the extraneous film on the food contact surface of the receptacle, which has the added effect of augmenting any specific bactericidal properties of special acids used in the acid cleaner composition. Preferably, a wetting agent is included in the acid cleaner composition which accelerates both the detergent and germicidal effect. The acid composition is supplied from a suitable source not shown and any appropriate type of ejector or atomizing device may be employed to produce and maintain the finely divided condition of the acid cleaning solution within the container. In this connection, we preferably employ a valve mechanism which will introduce a definite volume of the treatment precludes initial aqueous cleaning composition automatically as.
each can is presented tothe cleaning station I5 in the form of a fog or mist.
The predetermined quantity of the cleaning agent so supplied is of very small volume, and is practically non-corrosive. The concentration of the active cleaning ingredients is about one and one quarter percent and a charge will consist of about ounce of the aqueous acid cleaning composition, for a ten gallon can.
As pointed out above, the acid cleaner dis solves milkstone deposits and likewise prevents their precipitation as calcareous deposits upon the wall of the container.
A further advantage of the acid cleaning solution is its equal efilciency with both hard or soft water. Where hard water is used, it must be softened or the matter of milkstone deposits J must be neglected if used with alkali cleaners,
it being a characteristic of the acid cleaning composition that it so softens the water as to make the formation of milkstone deposits impossible. This property, moreover is highly important in relieving a very serious condition occasioned by the use of alkali cleaners, namely, the clogging of the jets with calcium and magnesium solids which are precipitated from water supplies possessing any appreciable hardness. The necessity 6 for cleaning such jets occasions frequent stoppage -of the operation, since unless the jets are cleaned, the rinses are only partially efiective. In many cases, plants have been known to continue operating with the jets partially closed b the deposits of precipitated calcium and magnesium compounds, with attendant ineffective cleaning results. All of this is overcome by the present invention.
Any draining, by reason of the activity of the mist at the cleaning station I5, takes place in the chamber I2, but the effective removal of the loosened film on the wall of the container is carried out at rinsing station I6. At this rinsing station either a jet spray of fresh water is di/ rected upon the interior of the can to remove the loosened film or the rinse is obtained by pumping water from the tank I! which also contains the acid cleaner solution rinsed from the can at the station I6. From the rinsing station IS, the can is conducted to the rinsing station I8 and is treated with a spray of fresh not water or a spray of water containing the acid solution which is drained into the tank I'I. Where the treatment at the station I6 was with fresh hot water, an acid reaction may be imparted to the can at I8 by using the rinse water from the tank I'I. On the other hand, if the rinse employed at station I6 was obtained from the tank IT, a rinse with fresh water may be utilizedat station I8 to impart a neutral reaction to the can. In this connection, the rinses at stations I6 and I8 may both be fresh water or may both be obtained from the tank II. When it is desired that the cans have an acid reaction, this may be imparted whenever the container, after treatment at stations I6 and I8, has a neutral reaction, by giving the container 2. further rinse at 20 with liquid from the tank I1, or a treatment with acid cleaner similar to that at station I5 or the food contact surface may be rendered acid, for example, as described in the application of Parker and Bonewitz, Serial No, 359,785, filed October 4, 1940, by introducing as a fog or mist or as an aqueous solution, anacid cleaner, e. g., a solution containing gluconic or levulinic acid and forming a, film having an acid reaction on the food contact surface of the container. Any drainage from the can at station 20 is into the tank II.
It is tobe observed that the tank II has an outlet I8 from which hot water containing the acid cleaning solution constantly overflows to the tank I2. In this tank II, there is thus main-, tained a substantially constant concentration of acid cleaner and, since the liquid is constantly overflowing into the tank .I2 and from this tank to waste through the outlet I4, the concentration of bacteria and nutrient in the tanks I2 and I1 is reduced to a satisfactory minimum, and the acid present will preclude the propagation and development of oxidizing and putrefactive microorganisms; yet, such acid condition in the tanks I2 and I1 is favorable to the development of favorable, reducing and acid-forming types of microorganisms. In other words, by having the continuous fiow from tank IT to tank I2 with discharge at outlet I4, a proper substantially constant dilution of such germ life is provided and an acid reaction is maintained. Hence, at no time is the rinse water from the tank I2 or the tank II objectionable as a contaminating influence, but on the contrary, it exercises by reason of the presence of the acid solution a definite detergent and germicidal action.
At station 2 I, containers treated at stations I5 and II, and 20 in case this station is. used, are
permitted to drain into tank I! and thereafterare suitably dried at 22 as by means of a hot air blast'if desired. At this point, it is important to note that the temperature of the rinses, either fresh hot water or from the tank l1 supplied at stations l8 and it, are in the neighborhood of 190"F. or higher, and hence no extensive drying procedure is normally necessary; although in somecases drying may be hastened by means of an air, blast.
In practicing the method hereinabove described, using an acid cleaner, it is necessary that the acid employed be one which is non-corrosive or can be used in low' enough concentration to be non-corrosive, and at the same time, is eifec tive to insure the desired cleaning. We have found that gluconic and levulinic acids are preferable in view of their relatively non-corrosive character.
Other acids effective to insure the optimum cleaning results described without being objectionably corrosive may be utilized, such as phosphoric acid in properly dilute solution, as well as hydroxy-acetic acid, as prepared by Du Pont Company, and sodium acid pyro-phosphate or mono-ammonium phosphate, as made by Monsanto Chemical Company and others.
While it is not always necessary, we prefer to employ a wetting agent in the acid cleaner composition such as alkyl aryl sulphonate, preferably "Santomerse #3 of Monsanto Chemical Company, or 'sulphonated petroleum fractions which are eifective bactericidal agents. Othervwetting agents may be 'employed, such as 3, 9-.-diethyl' tridecanol, 7-ethyl-2 methylundecanol and 2 ethyl hexonal, but these are not preferred. In addition, Duponol" and fAlkanol WXN of Du Pont Company, as well as Nacconol of National Aniline and Chemical Company, and the Areskap products of Monsanto Chemical Company may be used.
A suitable acid cleaning composition comprises a solution of gluconic or levulinic acids or mixtures of the same in. about 50%, a wetting agent, in about 10%, a suitable enzyme such as pepsin,
trypsin, or papain, in about 1%, and the remainder ,water. The wetting agent, as stated above, is preferred butfiis not always required, while the use of the enzyme is optional. About 20% of a water soluble oil may also be included.
The composition is addedto water to form an acidcleaning solution having a concentration of about 2%. ,By reason of' the" method employed, this solution gives the highly satisfactory results above mentioned.
Another suitable cleaning composition comprises a mixture of levulinic acid and gluconic acid in about a wetting agent in about 10%, a water soluble oil in about 25% and the remainder water. 'An enzyme as with the previous composition may or may not be employed.
In the several formulae described above, the levulinic acid is present in amount of about 2 to 5%. It imparts a desirable odor and exercises an inhibiting effect on the growth of microorganisms, particularly molds. The levulinic acid is non-corrosive todairy metal and also exerts detergent properties. The gluconic acid is likewise non-corrosive to dairy metal and exercises a buffering action. I
The wetting agent contains no fillers which wouldreact with the acids, thereby removing any likelihood of the formation of corrosive acids. For example, should the wetting agent contain many cases and is of a type which makes for a true solution with no oiling off, even at high temperatures. Preferably the oil has detergent properties and protects the solution against formation of corrosive substances which might otherwise be formed when the solution is further diluted with water containing sulphates, etc., as when the stock solution is diluted for use in the plant.
With respect to the water soluble oil, there are many varieties available, but the important characteristic which such oil must possess for our purposes is that it remain in true solution in an acid reacting composition. That is, the oil must not be aii'ected by pH or temperature changes in the solution, as distinguished from oils frequently used in making emulsions. We have found that #25 acid compound" prepared by Standard Oil of Indiana is a most desirable soluble oil for our purposes, and we also have found satisfactory as the soluble oil, a mixture of Petromix #l-B and Klearol White Mineral Oil" as prepared by L. Sonneborn Sons, Inc., Chicago, Illinois.
As pointed out above, the acid constituent may be entirely levulinic or entirely gluconic, or any proportions of mixtures of the same. The two examples are illustrations of preferred compositions which'have been found highly useful.
Phosphoric acid is used in the proportions specified in the above examples, and it is important to utilize an amount of the soluble oil or other corrosion inhibiting agent eiiective to precludecorrosion. When the phosphoric acid is used in v the proportions stated in the foregoing examples,
inorganic acids of the order of phosphoric are.
at least 25% of the soluble 011 should be employed for this purpose.
Where hydroxyacetic acid or sodium acid pyrophosphate or' mono ammonium phosphate are used, they will be employed in the proportions employed, a careful control must be exercised to I be used as a mixture to prevent corrosion effects.
It is to be understood that all of the acids referred to above, or any two or three of them, may
provide the acid constituent of our improved cleaner. 1
It is preferred to use, in all of the cleaning compositions or solutions, a wetting agent and a water soluble oil. The compositions or solutions may, however, be prepared without the use of.the enzyme or the oil, but we prefer to use the oil with the gluconic and levulinic acids and particularly with phosphoric acid, since in the, latter case it acts to control corrosiveness. should the phosphoric acid be present in excess.
Referring to the chambers i2 and II, when the operation is initially started, water is introduced in the tanks, together with sufficient acid cleaner to give the same an effective acid reaction.-
9 2d, and 2! and to some extent by drainage from the station ll.
The method illustrated in the drawing is the preferred manner of carrying out the invention. If desired, the acid cleaning solution can be used with ordinary can washing equipment, for example, such as now employed with alkali cleaners. Under these circumstances, the alkali cleaner solution is .replaced with an initial charge of approximately 8 ounces of acid cleaning material and 60 gallons of water which is Placed in the conventional tank associated with such apparatus. The solution is supplied from said tank to a can and injected therein, preferably as a fog or mist, although the usual hydraulic spray may be used. The can is permitted to drain so that the acid washing solution returns to the tank for continuous reuse on subsequent cans. After about 300 cans have been so washed,
an additional charge of approximately 1 ounce of acid cleaner per 100 cans to be washed is added.
The term fresh" as used in the specification is intended to describe virgin rinse water and cleaning solution which has not heretofore been used but is fed directly and fresh from the source of supply.
It is to be understood that the body and top are successively treated in the manner above described to produce a dry or moist container and top which are not only visibly clean, but free from microorganisms detrimental to quality.
Where the acid cleaner is used with ordinary can washing equipment, the cans may be given a final acid reaction in the manner explained herein.
fIfhis application is a division of our application Serial No. 402,722, filed July 16, 1941, Patent No. 2,338,688, patented January 4, 1944.
We claim: a
1. The method of cleaning a plurality of containers comprising treating each container with an aqueous solution of acid cleaner which contains an organic acid and which is non-corrosive to the container material and prevents substanprecipitation of calcium and magnesium 45:
5 tainer, the said solution at all times preventin calcium and mag-' substantial precipitation of nesium solids.
2. The method of cleaning a plurality of containers successively comprising treating each 10 container with an aqueous solution of acid cleaner which contains an organic acid and which is noncorrosive to the container material and prevents substantial precipitation of calcium and magnesium solids at temperatures in excess of 190 F.,
is rinsing each of the containers with an aqueous solution of the acid cleaner having a temperature in excess of 190 F., draining the containers and continuously collecting the drained solution, and employing the said drained solution in the go treatment of the said containers. the said solution at all times preventing substantial precipitation of calcium and magnesium solids.
- MILTON E. PARKER. PAUL W. BONE-WITZ.
REFERENCES crrnn UNITED STATES PATENTS Number Name Date 2,291,085 Lehmkuhl et a1. July 28, 1942 764,222 Adams et al. July 5, 1904 1,914,145 McClatchie June 13, 1933 35 1,737,938 Miller Dec. 3, 1929 1,642,419 Loew et al. Sept. 13, 1927 2,232,803 Rodda Feb. 25, 1941 2,338,689 Parker Jan. 4, 1944 864,133 Hood Aug. 20, 1907 40 2,338,688 Parker Jan. 4, 1944 FOREIGN PA'I'ENTS Number Country Date 313,164 Great Britain Aug. 25, 1930 488,972 Great Britain July 18, 1938