US2042347A - Chemical cleaning process - Google Patents

Description

Patented May 26, 1936 PATENT OFFICE CHEMICAL CLEANING PROCESS Franklin H. Mackenzie, Bywood, Pa., assignor to American Chemical 'Paint Company,

Ambler, Pa.

No Drawing. Application March 13, 1935, Serial No. 10,937-

2 Claims.

5 bottles, barrels, etc., and the invention is applicable in connection with any industrial process where the cleaning solutions are used in tanks or cleaning equipment. The present application is a continuation in part of my application Serial I No. 557,717, filed August 17, 1931.

Such chemical cleaners in general include two principal'actlve agents, namely, an alkali agent and any emulsifying compound. The alkali agent is composed of salts of the alkali metals, such as sodium or potassium phosphates, silicates, carbonates, hydroxides, borates, etc., mixed to have the proper buffering and inhibiting properties together with the-cleaning ability for the work to be done. I I

v The emulsifying compound is composed of sub.- stances that will reduce the inter-facial 'tension. There are a great number and variety of these materials, only a few of which will be mentioned here, i. e., soaps, fatty acids, glues, proteins, sulphonated'oils, rosin, finely divided and cellular inert materials, etc.

These two factors, namely, the alkali and the emulsifier, which together go to make up the ordinary alkali chemical cleaning compound, give rise to two distinct detergent properties or functions in the chemical cleaner. Thus the action of the alkalies is principally chemical in its nature, tending to soften the water, saponify vegetable and animal oils, neutralize acids and conduct electricity. The action of the emulsifier, on

the other hand, is the reduction of inter-facial tension, colloidal suspension or adsorption and results in wetting out the dirt and oil, deflocculating and suspending the same; or the adsorption of oil by finely divided inert materials. This action is mainly mechanical and depends upon 1 agitation for its proper functioning. Since the two factors are distinct in their nature, it is desirable that eachshould-be separately regulatable according to the requirements of any particular cleaning operation. It is common practice for manufacturers to make up ready-mixed cleaners which are combinations of an emulsifying agent and an alkali 50 mixture. Certain compounds are found, in practice, to be far superior to others for certain classes of work, and it is accordingly necessary to provide an almost infinite numberof compounds diflerlng from each other in the relative proper- 55 ties of the two principal factors.

Such ready-mixed compounds possess the disadvantage that it is impossible to accurately control the emulsification properties of the cleaning solution employed, because in most instances soaps are formed by the action of the chemicals on the oils removed from the article being cleaned, and thus additions of the ready-mixed cleaner containing both the alkali mixture and the emulsifier must necessarily increase the emulslfying power of the solution, whether such ad- -dition of emulsifier is necessary or not, thus resulting in a waste of the emulsifier.

The use of too great a proportion of the emulsifier will, moreover, cause too much oil and inert matter to be held in the solution by the emulsifier. The solution thus tends to become progressively more and more viscous, and even though the alkalinity may be raised to a considerable degree, the detergent properties of the cleaner fall off considerably, and after a period of time, the solutions have to be dumped and renewed, owing to the excess of the emulsifier contained therein. v

A very unsatisfactory condition will also result if too small an amount of emulsifier is used in the mixture or if the amount of saponifiable material coming into the tank from the work is not sumcient or if it varies in quantity, as the solution will then lack the ability to remove mineral oils and foreign material. The emulsification prop- 30 erty in a metal cleaner is very important as practically all steel is slushedat the mill with a mineral oil and picks up inorganic matter or unsaponifiable dirt. I;

A close observation of the detergent properties 35 of alkali cleaners reveals the fact that it is almost .an impossibility to keep a cleaning solution working at maximum efliciency with cleaners having the emulsifying agent incorporated in them, as any change in'the character of the work 40 will throw the solution out of balance for most eficient cleaning. Also considerable research work is. necessary to compound a cleaner correct ly even where the work remains constantly the same. I v I ,According totmy invention, the alkali mixture and the emulsifier are furnished separately and a cleaning solution prepared at the place of use by mixing proper quantities of the alkali mixture and of the emulsifier with water.

The resultant solution is heated to the 'desired temperature and the work to be cleaned is treated with the cleaningsolution in the usual manner whether it be soaking in a boiling solution, agitating in solutions'of various temperatures,

spraying the solution on the work, using direct or alternating current from work to the tank or anodes or by a process of dipping work in solution and wringing. During the process of cleaning, the cleaning solution is tested at suitable intervals for both alkalinity and emulsifying power, and the necessary quantities of one or both ingredients are added according to the results of the test.

It will be understood that the present inven tion is not concerned with the particular manner in which the materials undergoing treatment are cleaned, as this varies with circum-" stances and is also dependent on the character of the materials being cleaned, the invention being applicable to the various commonly known types of cleaning processes enumerated above."

Also, the present application is not primarily concerned with the particular manner of testing the cleaning solution for alkalinity or emulsifying power, but for the purpose of illustration the preferred methods of carrying out these individual steps which form a part of the combined process constituting the principal feature of the present application will be dacrlbed in Special vforms of equipment for carrying out these tests for alkalinity and emulsifying power have been designed, which I term testing kits.

The testing may be carried out in the followingmanner:

Alkaliaitytest The test for the alkali mixture may consist of the titration "of a 10 cc., portion of the cleaning solution with an acid solution of known strength using phenolphthalein as an indicator as in chemical analysla, The preferred process, however,-is distinetive in that it has been simplified for'prcduetion use. The normality of the acid is sdiustedtoavaluewhichwill makethecalculk tions involve no more than two digits. The indicatorisincorporatedintheacidbyusinganalcoho] solution of theindieator instead of distilledwatermadimt the normality. The alkali mixtures are numbered according to the amount of material present that is capable of being titrated (with v the particular normality acid and indicator described above) in such a manner that the titration of a 10 cc.'sample of the cleaner solution multiplied by the number of the material equalsouncespergallonofthecleanerinsolution.

In the form of an example, the titration of a 10 cc. portion of the cleaning bath is as follows: Numbu-ofccofacidusedtimesnumberof materialequalsoimcespergallonofcleanerin solution.

Still further simplification is elected in 'theprocesses actuallycarriedout,whichconsistsof atankfactorforeachtankandthis,

when multiplied by the titration. equals pounds r their efl'ectiveness to keep the emulsifying power cause a seriom error.

applied to all systems of weights and measures;

Emulsifier test The problem of testing for emulsifying power is not to show'the amount of the emulsifier as in -5 ordinary analysis (as emulsifiers are constantly coming into the bath in'the proces's of cleaning and it would be to analyze-for each type of emulsifier, separate them, andalso know of the bath constant), but to show the eifectiveness in such a way that it can be inte'rpreted'in terms of a known emulsifier.

The best emulsifier available for the operation is usedand for a "given concentration in the bath its properties, i. e., inter-facial tension reduction and colloidal suspension, are measured in a unique manner suitable for production conditions. The result in minutes is converted into a factor which when multiplied by the time in future tests will indicate the amount of emulsifier present, not by actual quantity, but by its effectiveness.

Itisobviousthatanyemulsifiermaycomeinto the solution, and without knowing its characteristics or concentration, its eifectiveness in the bathmaybeandthebathadiusted" to the proper emulsification value with the orig-,

A suitable device for measuring the emulsifyingpowerofthebathmayconsistofatallnarrow glass cylinderor bottlehaving a broad base' suitable for supporting it in a vertical position, a the bottle being preferably provided with a ground glass stopper; A glass bottle six inches highandone-half inchindiameterhasprovedsatisfactoryinaetualprsetiee. Thisbottleis marked with suitably selected graduatiom desig-' nated as "Time", Oil and 801 (solution). .Of

thesethetimegraduationislowest,thesolgrad- 40;

uationnextandtheoilgraduationuppermost.

.lLhetestisconductedinthefollowingmannen The cylinder is filled to tbe-solutionlevelisollmarkedonthebottlawithasampleofthecleaningbathwhenfirstm'adeup. Aclearwhite mineral oILVIseosityHOtOlSOseeondsatIOOI". (Sayboltl is addcdnmtil it'seaehesm graduation onthebottlemarked0ll"level. Iormostaccurate work, the cylinder is stoppered and immersedina waterhathatlwrsthebathallowedtocooltolso'l' andthecyiinderremoved. Inordinarycommercialoperatiomthewaterbath treatmentneednotbe'resortedto,asthevaria-' tion in temperature is wally not sufilc'ient to The cylinderisshakenrapidlyzlitimesand stoodverticallyonitsbese. Thetimeisaccurately recorded, from the moment the cylinder; is placed in a vertical position, until-the emulsion levelreachesagraduationonfliebottlemarked "Time". Tbeemulsion levelisthelevelwherethe cleaningsolution meets the-emulsion. Asthe emulsion breaks, the cleaning solution falls to =alkali tank factor.

thebottolmforcingtheemukion higher. Themeetingpointofthecleaningselutlonandthe emulsionformsadefinitelinethatcannotbem mistamasthesolutioniscimrandtheemul sifyingpowerofthebathandllsoinadirect proportiontotheamountofemulsifiq-med. H

'lhistimeisindirectpmtimtotheemul- The time in minutes is divided into the number of fluid ounces of emulsifier used, which gives the emulsification factor for that particular tank,

Number fluid ounces of emulsifier used Number minutes required for emulsion level to rise to line mark Tests in the future are run inthe same manner. The time multiplied by the emulsification tank factor equals number of fluid ounces of emulsifier or its equivalent in emulsifying power in the bath, from which information the proper additions may be made,-

Timexemulsification tank factor=number of fiuid ounces of emulsifier in tank or its equivalent in emulsifying power.

It is evident from the above method of test that when saponifiable material comes into the bath from the work and is saponified, account is taken of its emulsifying power which reduces the amount of original emulsifier needed to keep the proper concentration of emulsifier. In this mannerfthe saponifiable material is utilized and excessive amounts of emulsifier are avoided. With my proposed method of control, the chemical cleaner solution may be run almost indefinitely on any type of work, as the emulsification factor may be raised to the point necessary to do the work properly-band the quantity limited so that the emulsifier will not hold oil or foreign matter in suspension too long. The dirt which precipitates may be removed from the bottom of the cleaning tank by hoeing it out or pushing it over toward the drain and allowing it to pass down the drain.

Any oil which precipitates may be removed by bringing the level up to the overflow and allowing it to pass over the overflow, or by skimming the oil off with a skimmer. The removal of dirt and excess oil may be performed periodically, generally each morning, after the solutionhas been allowed to settle overnight, for the oil, and once a week for the dirt.

By employing my process, marked-economies result which consist of the elimination of frequent dumping, due to solution going out of balance with respect to the emulsifier content and the resultant building up of a heavy dirt and oil load; keeping the bath uniform produces uniform work, thus eliminating rejects and producing a more stable solution for automatic equip-- ment where the work must be cleaned in a definite time; saving in the amount of emulsifier used where saponifiable material is coming into the cleaning bath; elimination of losses by poor guesswork in rule of thumb methods of control and with mixed cleaners where it is necessary to add emulsifier, when it is not needed, because the alkalinity is low.

The process will be more readily understood by reference to a specific example. For cleaning steel, an alkali mixture consisting of 55% NaOI-I, Na3PO4 and 15% NazCOs may be employed. Any suitable emulsifier may be used in conjunction with the alkali, as for example, rosin or rosin soap. The alkali mixture and the emulsifier are added to a suitable quantity of water, using about 3 to 4 ounces of the alkali mixture per gallon of water. The quantity of emulsifier initially introduced is about 10-to'15% by weight of the quantityof alkali. The bath is then ready to be used for cleaning purposes. of cleaning, the concentration of the alkali and of the emulsifier will vary, and these variations may be determined by tests, as outlined, both for During the process alkalinity and for emulsification. A lack of either alkali or emulsifier may be determined in this manner, and the bath brought to proper concen- =emulsification tank factor tration by separately adding the alkali or emulsifier or both.

For cleaning brass, an alkaline mixture of 50% NazCOa 25% Na3PO4 and 25% NaOH may be employed, using initially 5 to 5% ounces per gallon of water, and separately adding rosin or other emulsifier in the proportion of 10 to 15% by weight of the alkaline mixture.

For cleaning other materials, the composition of the alkaline mixture or emulsifier may be varied according to requirements.

My process makes it possible to maintain the solution at its maximum efficiency on varying kinds of work at considerable savings in the amounts of materials used. -The process eliminates the necessity of making a large number of mixtures-for different classes of work.

Where ready-mixed compounds are employed and a slight mistake, is made in the quantity of either the emulsifier or the alkali, more of the .entire mixture must be used to build up the property necessary. For example, suppose a four ounce concentration gives the right alkalinity, but only one-half the necessary amount of emulsifying power, then it would be necessary to use an eight ounce concentration with consequential waste of material. On the other hand, where four ounces would give the right alkalinity and twice the emulsifying power, in keeping the alka'- linity to the correct degree, the solution would soon be saturated because the emulsifiers would carry too great an oil and dirt load. In this case,

the whole solution would have to be dumped. These disadvantages are avoided by my process.

It will be understood that in the accompanying claims the terms alkali,"alkaline agent, emulsifier and emulsifying agent are intended to cover active ingredients of chemical cleaners which are well known in the cleaning art, andwhich are customarily referred to inthe art by these terms, representative ingredients having been set forth in the present specification for the purpose of illustration;

What I claim is 1. A process for continuously maintaining a chemical cleaning solution at maximum operating efhciency, which comprisesinitially forming an aqueous alkaline solution by admixing predetermined quantities of water, a water-soluble alkaline detergent, and an emulsifying agent capable of reducing the interfacial tension, operating said solution for removing extraneous matter from materials such as metals, clothing, textiles and the like; periodically-testing the solution to determine its alkalinity, separately testing the so-' 'lution for emulsifying power by physically agitating a test portion of the solution with a standard mineral oil and allowing it to separate therefrom, and adjustingthe solution by adding. the required amount of water-soluble alkaline detergent or water as indicated by the alkalinity test, and the required amount of emulsifying agent or water as indicated by the test for emulsifying power, to restore the solution to its original condition..

2. A process for continuously maintaining a chemical cleaning solution at maximum operating efiiciency, which comprises initially forming an aqueous alkaline solution by admixing predetermined quantities of water, a water-soluble alkaline detergent, and an emulsifying agent capable of reducing the interfacial tension, operating said solution for removing extraneous matter for materials such as metals. clothing, textiles and the like; periodically testing the solution to determine its alkalinity, separately testing the solution for emulsifying power by physically agitating a test portion oi. the solution with a standard mineral oil and allowing it to separate therefrom, adjusting the solution by adding the required amount of water-soluble alkaline deterand the required amount of emulsifying agent or water as indicated by the test for emulsifying.

power, to restore the solution to its original condition, and periodically permitting said solution 'to rest to allow excess oil to rise and other extraneous matter removed during the cleaning operation. to settle, and removing the said oil and extraneous matter from the solution.

FRANKLIN H.