US2338688A - Cleaning composition - Google Patents

Description

Jan. 4, 1944.

M. E. PARKER EI'AL CLEANING CDMPOSITION Filed July 16, 1941 grwvwtw:

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Patented Jan. 4, 1944 UNITED STATES PATENT OFFICE CLEANING COMPOSITION Milton E. Parker, Chicago, Ill., and Paul W. Bonewitz, Burlington, Iowa, assignors to The Rex Company, Burlington, Iowa, a corporation of Iowa Claims.

The present invention relates to the treatment of containers for the purpose of cleaning the same, and it is particularly concerned with the sanitizing of large metal cans generally used for the bulk transport of milk, cream and other milk products.

There are available numerous processes for cleaning such containers which utilize rinsing treatments with steam and water and generally include a chemical treatment with a suitable alkali. Careful research has developed that the use of an alkaline cleaningagent does not promote such a thorough cleaning of the can as will jpreclude microbiological microorganisms to propagate and develop a putrefactive condition on the surface of the can.

It is the principal object of the invention to eliminate such a condition and to provide a container which will not only be physically clean but bio-chemically clean as well so that objectionable microbiological activity is precluded.

Another object of this invention is to provide a method of cleaning in which a non-corrosive acid cleaning material is employed. The use of acid substances for cleaning metal containers has been avoided by reason of the corrosive action of the acid materials We have not only found that a non-corrosive acid such as gluconic or levulinic may be utilized, but also magnum that an acid may be utilized in such small amount as to give effective results with a substantial saving in expense over the usual alkali treatments.

A further object of the invention is to provide a container, the food contact surfaces of which give an acid reaction. This not only prevents the development of putrifactive and oxidizing types of microorganisms, but is beneficial in that it promotes the activity of favorable acid-forming and reducing types of microorganisms.

In addition to the foregoing objects, the invention reduces substantially the amount of steaming customarily employed in present cleaning practice, and' this is a factor which enables a considerable economy to be realized. In otner words, the cleaning action is complete. Therefore, subsequent rinsing with hot water is so effective that the usual means of heating a can with steam following such rinsing practice can be dispensed with in view of the fact that the hot water so employed rapidly drains and presents a surface which can be more readily dried by any subsequent treatment, for example, with hot air blasts.

A marked advantage of the present invention resides in maintaining both the initial rinse water has been subjected to the acid cleaning, in a condition where this water is substantially free of nutrients for putrefactive and oxidizing microorganisms. Furthermore, by the presence therein of a suitable concentration of the acid cleaning solution which maintains the rinse waters in an acid condition, there is developed a situation unfavorable to the growth of such objectionable microorganisms, but which is beneficial from the standpoint both of its cleaning action and its efiectiveness in creating a condition favorable for the development of reducing and acid forming types of organism.

We have found that the acid cleaner applied to a container which has been given a previous rinse or otherwise cleaned to remove as much as possible of the extraneous matter adherent to the wall thereof, and then subsequently rinsed, will be more sanitary than as has heretofore been possible using conventional alkali treating systems. With the present invention, the acid cleaner appears to loosen adherent objectionable films present on the wall of the container and a simple hot water rinse efiectively remove all such adhesions. A remarkable observation which we have made is that the amount of acid cleaner which may be effectively employed is but a fractional percent of the amount of alkali heretofore regarded as essential. Furthermore, the acid cleaner solution is used in an amount which constitutes but a small volume relative to the volume of the container (such as a milk transport can being cleaned) and is preferably introduced therein in finely divided form so that a thin film of the cleaning solution reaches every point in the interior area of the container to accomplish its loosening and releasing function with respect to the films of extraneous matter to be acted upon. This is another reason why a simple rinse following the acid cleaning treatment is conducive to the thorough cleaning which the can evidences upon severe tests. This method is a distinct departure from present alkali cleaning systems wherein large volumes of alkali cleaning solution are discharged under pressure against the wall of the container. That is to say, the present practice requires not only a substantial volume of the alkali cleaning solution, but relies upon the scrubbing action of hydraulically produced sprays of such solution to shear any film on the wall of the container before the same can be effectively penetrated and completely 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 the use of a simple jet spray of hot water subsequently applied. This result is ata A h tributable to the superior wetting, emulsifying, penetrating (defiocculating), 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 milkston deposits as may be adhering to the wal1 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 having 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. When the solution is prepared from even the hardest waters the beneficial effects described have been found to be obtained even though the solution is of a character which does not have a definite acid reaction. This is due to the fact that the alkalinity of the water is reduced to a point where the effectiveness of the acid is not impaired.

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 sanitzing 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 are-of an unexpected order, since the cleaning of metal containers has engaged the attention of many research workers, all of whom have apparently concluded that the use of hydraulic rinses and an alkali cleaner applied with hydraulic scrubbing action constitues the best procedure. The present invention, however, has been severely tested, and these tests disclose that 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 microo'rgams' ms. This lethal effect is a property either of an acid reaction at elevated temperatures or of the specific nature of special acid 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 be of a type to exert or contribute to a lethal effect in itself.

This invention will be described in connection with the usual milk transport can having varying capacities of about ten gallons more or less, and which is generally provided with a tin coatin; on its interior and exterior surfaces. In this connection, the cleaning method to be described 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 approache this optimum condition and maintains the same to a much greater extent than has heretofore been accomplished. For example, contaminating bacteria are present in the air and water supplies, and when the same come in 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, the numeral In 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 example. At the station I0, the amount of water necessary to efiect 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 is led 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 [0, such water being either cold or tepid or being hot if desired.

From the station I, the can is moved to station I I and treated with a scrubbing spray of hot water containing entrained acid cleaner material from a subsequent operation. At this station I I, 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 II, and this supply of rinse water is maintained substantially constant with respect to the acid cleaner solution as will be later explained. The rinse water constantly drains from the tank l2 through the outlet I 4 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 to the development of reducing and acidforming microorganisms so that at the very outset of the process, the scrubbing treatment precludes initial development of objectionable micro-biological activities. The presence of the acid cleaning solttion in the rinse water in th Col n tank I! 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 magnified 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 I! is maintained at about 140 F.

After the can has been permitted to drain, it is subjected to the acid cleaning treatment at the station l5. 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 contradistinction to a hydraulic scrubbing jet. As pointed out, the action of the cleaning agent is to penetrate the extraneous film on the can and release the same so 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 eifect 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 efiect 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 aqueous cleaning composition automatically as each can is presented to the cleaning station IS in theforrn 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 dissolves 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 efiiciency with both hard or soft water. Where hard water is used, it. must be softened or the matter of milkstone depositsmust 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 whichare precipitated from water supplies possessing any appreciable hardness. The necessity for cleaning such jets occasions frequent stoppageoi the operation, since unless the jets are cleaned, the rinses are only partially effective. In many cases, plants have been known to continue oper- L I. I

Examin ating with the jets partially closed by the deposits of precipitated calcium and magnesium compounds, with attendant inefiective 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 [5, takes place in the chamber [2, but the effective removal of the loosened film on the wall of the container is carried out at rinsing station l8. At this rinsing station either a jet spray of fresh water is directed upon the interior of the can to remove the loosened film or the rinse is obtained by pumping Water from the tank I1 which also contains the acid cleaner solution rinsed from the can at the station l6. From the rinsing station IS, the can is conducted tothe rinsing station [8 and is treated with a spray of fresh hot water or a spray of water containing the acid solution which is drained into the tank l1. Where the treatment at station l6 was with fresh hot water, an acid reaction may be imparted to the can at [8 by using the rinse water from the tank II. On the other hand, if the rinse employed at station [6 was obtained from the tank H, a rinse with fresh water may be utilized at station l8 to impart a neutral reaction to the can. In this connection, the rinses at stations l6 and I8 may both be fresh water or may both be obtained from the tank l1. When it is desired that the cans have an acid reaction, this may be imparted whenever the container, after treatment at stations l6 and I8, has a neutral reaction, by giving the container a further rinse at 20 with liquid from the tank H, or a treatment with acid cleaner similar to that at station l5 or the food contact surface may be rendered acid, for example, as described in the application of Parker and Bonewitz, Serial No. 359,785, by introducing as a fog or mist or as an aqueous solution, an acid 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 I1.

It is to be observed that the tank IT has an outlet l9 from which hot water containing the acid cleaning solution constantly overflows to the tank l2. In this tank I1, there is thus maintained a substantially constant concentration of acid cleaner and, since the liquid is constantly overflowing into the tank 12 and from this tank to waste through the outlet l4, the concentration of bacteria and nutrient in the tanks l2 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 l2 and I1 is favorable to the development of favorable reducing and acid-forming types of microorganisms. In other words, by having the continuous flow from tank I1 to tank 12 with discharge at outlet M, 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 l1 objectionable as a contaminating infiuence, but on the contrary, it exercises by reason of the presence of the acid solution a definite detergent and germicidal action.

At station 2|, containers treated at stations l6 and i8, and 20 in case this station is used, are permitted to drain into tank l1 and thereafter are suitably dried at 22 as by means of a hot airblast if desired. At this point, it is important to note that the temperature of the rinses, either fresh hot water or from the tank I! supplied at stations l6 and I8, are in the neighborhood of 190 F. or higher, and hence no extensive drying procedure is normally necessary; although in some cases 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 effective 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, and sodium acid pyro-phosphate or mono-ammonium phosphate.

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, which is dodecyl benzene sodium sulphonate or sulphonated petroleum fractions which are e1: fective bactericidal agents. Other wetting agents may emp oye c as 3,9-diethyl tridecanol, 7-etliyl-2 methyluhdecanol and 2-ethy1 hexonal, but these are not preferred In addition, Duponol which is an aliphatic alcohol sulphate and Alkanol WXN of Dupont Company a sulphonated hydrocarbon, as well as ,liacconol of National Aniline and Chemical Company which is an alkyl aryl sulphonate, and the Areskap products of Monsanto Chemical Company which are monobutyl phenol sodium monosulfonatesmay 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 but is not always required, while the use of the enzyme is optional. About of a water soluble oil may also be included. The composition is added to water to form an acid cleaning 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 35%, a wetting agent in about 10%, a water soluble oil in about 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 to dairy metal and also exerts detergent properties. The gluconic acid is likewise noncorrosive to dairy metal and exercises a buffering action.

The wetting agent contains no fillers which would react with the acids, thereby removing any likelihood of the formation of corrosive acids. For example, should the wetting agent contain an excess of sulphates, there may result the formation of sulphuric acid, the corrosiveness of which would be highly objectionable.

The water soluble oil gives a superior result in 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 oflndiana is a most desirable soluble oil for our purposes. This compound is an acid soap composed of a mixture of alkali metal soaps of sul- 'phonic acids. It is alkaline and is a product obtained in the tailings from the production of white mineral oil, 1. e., in the treatment of mineral oil with concentrated or fuming sulphuric acid, and is water soluble. We also have found satisfactory as the soluble oil, a mixture of Petromix #l-B, which is a rosin soap, and Klearol white mineral oil, which is a 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.

IZBQSPIIOIiC 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 efiective to preclude corrosion. When the phosphoric acid is used in the proportions stated in the foregoing examples, at least 25% of the soluble oil 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 such as specified in the foregoing examples. In this connection, dry compositions may be produced containing these materials and a wetting agent; water may be added to the powder by the user. Further, with such substances, it is not necessary to use a water soluble oil.

It is preferred to use the organic acids, since should the same be present in excess, there is little or no hkelihood of corrosion, whereas when inorganic acids of the order of phosphoric are employed, a careful control must be exercised to prevent corrosion efiects.

It is to be understood that all of the acids referred to above, or any two or three of them, may be used as a mixture to provide the acid constituent of our improved cleaner.

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 a cid, since in the latter case it acts to coiitrolcorrosiveness, should the phosphoric acid be present in excess.

Examz'nj" Referring to the chambers l2 and II, when the operation is initially started, water is introduced in the tanks, together with sufiicient acid cleaner to give the same an effective acid reaction. Thereafter, the communicating tanks I2 and H are replenished and maintained with an effective acid reaction by drainage from the stations l6, I8, 20, and 2| and to some extent by drainage from the station IS.

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.

We claim:

1. An acid cleaning composition for chemically reacting with and releasing calcareous films including calcium and magnesium and calcareous films including protein and fat, which films are adhered to metal surfaces such as dairy equipment by the cementitious action of the calcareous constituents, said cleaner comprising an organic acid selected from the group consisting of levulinic, gluconic, and hydroxyacetic acids and mixtures of the same, which acids are substantially non-toxic, and a wetting agent compatible with the acid and chemically non-reactive therewith, the cleaning composition in aqueous solution penetrating said films and reacting with their calcareous constituents to solubilize the same whereby to release and loosen the adherent films, said acid cleaning composition being substantially non-reactive with the metal surfaces of the dairy equipment, and the said organic acid constituting the sole effective acid cleaning agent in the composition.

2. An acid cleaning composition for chemically reacting with and releasing calcareous films including calcium and magnesium and calcareous films including protein and fat, which films are adhered to metal surfaces such as dairy equipment by the cementitious action of the calcareous constituents, said cleaner comprising an organic acid selected from the group consisting of levulinic, gluconic, and hydroxyacetic acids and mixtures of the same, which acids are substantially non-toxic, and a wetting agent compatible with the acid and chemically non-reactive therewith, the cleaning composition in aqueous solution penetrating said films and reacting with their calcareous constituents to solubilize the same whereby to release and loosen the adherent films, said acid cleaning composition being substantially non-reactive with the metal surfaces of the dairy equipment, and the said organic acid constituting the sole effective acid cleaning agent in the composition, said composition containing a water-soluble oil as a corrosion inhibiting agent.

3. An acid cleaning composition for chemically reacting with and releasing calcareous films including calcium and magnesium and calcareous films including protein and fat, which films are adhered to metal surfaces such as dairy equipment by the cementitious action of the calcareous constituents, said cleaner comprising levulinic,

acid, which acid is substantially non-toxic, and a Wetting agent compatible with the acid and chemically non-reactive therewith, the cleaning composition in aqueous solution penetrating said films and reacting with their calcareous constituents to solubilize the same whereby to release and loosen the adherent films, said acid cleaning composition being substantially nonreactive with the metal surfaces of the dairy equipment, and the said organic acid constituting the sole effective acid cleaning agent in the composition.

4. An acid cleaning composition for chemically reacting with and releasing calcareous films including calcium and magnesium and calcareous films including protein and fat, which films are adhered to metal surfaces such as dairy equipment by the cementitious action of the calcareous constituents, said cleaner comprising gluconic acid, which acid is substantially non-toxic, and a wetting agent compatible with the acid and chemically non-reactive therewith, the cleaning composition in aqueous solution penetrating said films and reacting with their calcareous constituents to solubilize the same whereby to release and loosen the adherent films, said acid cleaning composition being substantially non-reactive with the metal surfaces of the dairy equipment, and the said organic acid constituting the sole eflective acid cleaning agent in the composition.

5. An acid cleaning composition for chemically reacting with and releasing calcareous films including calcium and magnesium and calcareous films including protein and fat, which films are adhered to metal surfaces such as dairy equipment by the cementitious action of the calcarstituting the sole effective acid cleaning agent in the composition.

MILTON E. PARIER. PAUL W. BONEWITZ.

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