Symposium o n Application ile*e**rcH Methods. . .

Application Research Methods for Synthetic Detergents

L A W R E N C E II. FLETT, Director, New Products Division, National Aniline Division, Allied Chemical & Dye Corp., 40 Rector St., New York 6, Ν . Υ .

Application research m u s t provide guiding counsel o n the value of each n e w c o m p o u n d · · · Synthetic detergents, latest synthetic chemicals to participate in a field built u p by use of natural products, are results of application research

. T T L P P L I C A T T O N research is as old as civili­zation. W h e n prehistoric m a n tried the first bronze spear on his enemy, he was carding out application research in the chemical field.

Organized application research is the child of industrial research. Industrial chemical research is paid for by the profit from the sales of n e w chemicals, but new chemicals cannot be sold until application research finds out what to do with them.

Application research is not carried out on every new chemical, but only on those chemicals which might be marketed. N e w chemicals are easily made . The number of chemical compounds which have been prepared is almost countless, but only a few of these are commercially useful. E x ­perience has shown, however, that applica­tion research can seek out from the count­less unused chemicals compounds which are invaluable to mankind. Synthetic rubber, D D T , 2 -4D, and synthetic resins were developed by use of chemical com­pounds which had been known for m a n y years. Application research of the future m a y find a cure for cancer, an ingredient for indestructible paint, or other treasures a,mong the chemical compounds described in scientific libraries. Never underesti­mate the accomplishment or ambitions of application research chemists. Their work affects the w a y people live and what they buy. The first organized application re­search in the chemical industry of this country was carried out in the field of dye-stuffs. It has been so successful that al­most any manufactured article you can lay your eyes on is colored. Application research in the paper industry and in the plastics industry has introduced products which wre have come to regard as every-day necessities. Unusual or prolonged promo­tion of a particular product, b y applica­tion research, is certain to expand the use of that product. That is w h y everyone wants things colored and wrapped in paper. If flavoring materials were pro­

moted as actively as color, the back of the stamp would be as attractive as the front.

Unfortunately, application research is very time-consuming as compared with chemical research. A chemist can m a k e 50 new dyes in a single day, whereas it would take years of application research to determine the commercial utility of those 50 dyes. Nevertheless, if a product is to be marketed, application research must be carried out either by the manufacturer or the consumer. Generally it is carried on b y both.

The manufacturer should start applica­tion research at the same time that chemi­cal research is started, particularly when chemical research is directed to a fixed use. For example, if the object of research is the development of an insecticide for Japanese beetles, a more elastic rayon, a g u m inhibitor for gasoline, or a synthetic detergent for washing cotton, chemical re­search work would be hopelessly inefficient if application research did not provide guiding counsel on the value of each new compound as it is prepared. Application research is the pilot that charts the course. Research is most efficiently carried out when each new step can be taken with a full understanding of the significance of all past results.

The synthetic detergent is a product of application research. It was developed because of the dyers' troubles with the use of soap. W h e n textile materials are proc­essed with soap, they often become spotted with aggregates of sticky, insoluble lime soaps. T h e lime soaps waterproof the textile material where they spot it. W h e n the material is dyed, the dye solution can­not reach these waterproofed spots even though it wets and dyes the rest of the fabric. Undyed spots in colored goods are an expensive problem for the dyer.

The complete history of the efforts to overcome this simple fault covers almost 100 years of chemical development and application research. It starts with the

development of the sulfonated oils. Fifty years later the development of a group of surface-active agents known as wetting agents was in full swing. Literally hun­dreds of wetting agents were m a d e , m a n y of which are still useful and commercially available. The sulfonated oils and the wetting agents had valuable properties and were free from m a n y of the faults of soap, but they did not have all of the valuable properties of soap. They lacked the high dispersive action that makes soap a wash­ing agent.

Xwen ty years ago, the prolonged re­search for a satisfactory textile processing agent culminated with the synthesis of a detergent which was stable and effective in the presence of lime salts, metal salts, and acids. It did not take application re­search m e n very long to realize that in the synthetic detergents they had a product the utility which would go far beyond the field of textile chemistry.

T h e synthetic detergents are, indeed, the latest addition to the lengthening list of synthetic chemicals, which participate in fields originally built up by the use of natural products. This list embraces synthetic dyes, which have surpassed the natural dyes in importance; synthetic resins, which give us products not obtain­able with the natural resins; synthetic drngs, which cure diseases not cured by natural drugs; and synthetic fibers like rayon and nylon, which for m a n y purposes are superior to silk, cotton, and wool. T h e synthetic detergents enter a field which has been held exclusively by soap for thou­sands of years. They are assuredly a prod­uct of application research.

T h e synthetic detergents were not de­veloped as low cost substitutes; they were developed to do a job that could not be done satisfactorily with the natural prod­uct. The present low cost came later with quantity production. Originally they were high in cost and sold at 5 to 10 times the price of soap, but, in spite of the high cost,

1368 C H E M I C A L A N D E N G I N E E R I N G N E W S

the use of the synthetic detergents by the textile industry expanded rapidly. It is not surprising that products so successful in the textile industry soon found use in every other large industry. This expan­sion is probably one of the greatest tri­u m p h s of application research. T h e market development of the synthetic detergents is one of the most rapid which the chemical industry has seen. In the space of two decades, since' the synthetic detergents were developed to fulfill a small need in the textile industry, production capacity has increased to about 300 million lb. annually.

Practical Nature of Tests

Tests used in detergent application re­search are of the most practical nature. T h e application test which most closely approximates the operation itself is most likely to succeed. As a matter of fact, the most reliable estimation of the value of a synthetic detergent is not obtained by laboratory testing but by a comprehen­sive study under practical operating con­ditions.

In application research care must be taken at all times to m a k e certain that testing methods are indicative of the prac­tical value of the material. Too often testing methods are developed which be­c o m e so important to the operator that he is not able to visualize the utility of a product unless it satisfies certain arbitrary testing methods. Chemists will painstak­ingly test hundreds of surface-active agents b y a simple test and render an unqualified report on the results, w h e n an unimportant change of the testing procedure might show entirely different results. M a n y companies fail to use n e w chemicals which would lower their cost and improve their product because they lack adequate application research.

Application research is effective when it is applied to products with interesting properties. It does not matter m u c h what those properties are. In other words, it doesn't matter whether a product is a wetting agent or a waterproofing agent, whether it washes the dirt out of the fab­ric or penetrates the dye into the fabric, whether it is an oxidation accelerator or a n oxidation inhibitor—if it has valuable properties it will have a use.

Detergent application research recog­nizes that the synthetic detergents are interesting because of their powerful sur­face action. That means they are gener­ally effective wherever water treating solutions must be brought into contact with solids, liquids, or gases. This is the property which makes them valuable for washing, for promoting chemical reactions with insoluble materials, for entraining air, and for the preparation or preservation of emulsions. T h e washing property is the property which sharply distinguishes the few synthetic detergents from the host of other surface-active agents. T h e science of washing has not advanced to the high

V O L U M E 2 6, N O . 1 9 » . .

degree to which other sciences have. While there are theories concerning wash­ing, no physical property has ever been correlated with the property of washing. In times gone by surface tension and suds were considered marks of detergency, but now there are wetting agents with very low surface tension that do not wash and good detergents that do not form suds. For the present, washing power is meas­ured by soiling fabric and washing the dirt out.

The general laboratory appraisal of a synthetic detergent is m a d e through its wetting, foaming, and, particularly, its washing properties. T h e methods which have been developed are thoroughly fa­miliar to industry.

Clean as Well as Colored

Wetting, foaming, and washing proper­ties are particularly important to the re­search chemist, but the application re­search chemist has a m u c h broader horizon. Wetting and washing are proper­ties which soap possesses to a high degree. T h e real future for synthetic detergents does not lie in their replacement of soap. It lies in the development of uses which were not possible with soap. There is a great soap market now. It is one of the largest of the chemical markets amounts ing to about 3.5 billion pounds a year. In spite of this huge use of soap, it is pos­sible to look anywhere and see things that need cleaning. A n y street or sidewalk needs a good detergent wash. Buildings, cars, floors, rugs, chairs, clothes, and practically every object of our crowded communities can profit from more fre­quent cleaning. If the application re­search m e n are as successful with syn­thetic detergents as with dyestuffs, you should reach that happy state where every­thing that you see is clean as well as col­ored.

In detergent application research, there are different methods of approach. O n e method of approach is to find the things which the synthetic detergents will do

more easily or more quickly than soap. The amount of detergent used for washing is going to be very greatly affected b y the ease of washing because if washing is m a d e easier, people will wash oftener and use more detergent. If washing m e a n s 15 minutes of hard scrubbing people will avoid it. Another method of approach is to consider the limitations of soap. Soap must be used in w a r m to hot alkaline soft water. It, therefore, becomes of interest to know what can be done with detergents which clean in cold water or acid water or water which is too hard for the practical use of soap.

If the use of a synthetic detergent de­pends on the speed of washin % the appli­cation research m a n needs information on comparative rates of washing. Obviously, no benefit will result from the faster wash­ing action unless the washing time is re­duced. In a simple washing test o n the usual wool soiled with Îamp black, and greases, the square which is squeezed eight times in the Nacconol N R solution be­comes substantially clean. This is very quick and easy washing. In the case of soap, eight squeezes give very little clean­ing. It is necessary to squeeze it 48 times before a reasonable degree of cleaning is achieved. T h e speedy action with the synthetic detergents has m a d e possible a saving of time in substantially all woolen textile processes. W h e r e the synthetic detergents are effective, they generally work with very great speed. This is im­portant in the household as it is in indus­try. People w h o wash their socks or their sweaters with little effort wash them, more often. In the case of cotton, the situation is reversed. It takes the same synthetic detergent an impossibly long time to> wash the cotton. This is due to the fact that this detergent causes the lamp black to penetrate into the cotton fiber. This property is harmful for washing soiled fabric but very useful for washing cotton prints, since an agent wrhich causes the dye to penetrate the cotton fiber is very valuable. In spite of the slow washing

Tests prove the superiority of soap for washing cotton

M A Y 10, 1948 1369

New Text

action the detergent has pmvi»d very use­ful in processing cotton.

Detergents and Speed

T h e metal industry is an industry where the speed of cleaning is important. Metals must be clean before they can be painted, plated, or treated in any other way. The size of plant required for metal cleaning will be proportional to the time the metal must remain in the cleaning equipment. It is important that the cleaning be speeded up as much as possihle. Metals can be cleaned with ordinary solutions of alkali, but the cleaning action is slow. A deter­gent is used to speed up the cleaning; and to prolong the life of the cleaning bath. In one test metal strips are covered with oil and cleaned by simple immersion in alkaline solution. A photograph is taken by use of ultraviolet light so that the metal appears black and the oil fluoresces brightly. It can be seen that when syn­thetic detergent is added to the alkaline bath, the metal is completely clean in less than one minute. With the alkali alone the metal is still soiled after eight minutes of immersion.

T h e utility of soap is limited to alkaline solutions. Detergent application research is interested in the effectiveness of deter­gents which are completely stable in neu­tral or strongly acid solutions. Studies are m a d e of comparative results of washing soiled wool with soap and synthetic deter­gents in acid solutions with a pli of 4, neutral solutions with a p H of 7, and alka­line solutions with a pli of 10. T h e syn­thetic detergents can be used in alkaline solutions where soap must always be used, and they can also be used effectively in neutral or acid solutions when» soap breaks down to give the fatty acids. Washing in neutral solution is a requirement for some processes and for some people w h o cannot tolerate alkaline solution on their skin. The synthetic detergents are particularly effective where they must be used in acid treating solutions.

Application research methods have been developed to demonstrate that the forma­tion of lime soaps in hard water can be avoided by the use of synthetic deter­gents. Microscopic views of silk stockings washed in hard water reveal that particles of lime soap cling to the fabric of those with which soap is used. M a n y people find these soap residues irritating.

Soap should be used in w a r m to hot water, whereas the synthetic detergents m a y be used in cold water. There is an applica­tion study which shows that the detergents are effective even in ice water. Cold wash­ing is important for most scrubbing opera­tions. A pail of w a r m soapy water doesn't heat up a floor or an automobile. A detergent, to be effective, must perform well at the surface temperature. T h e syn­thetic detergent is making a considerable contribution to cleanliness and sanitation by making possible the easy cleaning of cold surfaces.

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Sterilising Value

Cleanliness not only involves the re­moval of dirt; it requires the removal or control of bacteria. This is particularly important in the processing of food. A surface m a y be shiny white and clean by visual standards, but biologically it m a y be filthy. Bacteria can be disposed of by washing them off and b}' the bactericidal action of the detergent.

Table I. T i m e Required fc>y 1:500 Nacconol N R to R e d u c e the Staphylo­coccus aureus C o u n t to Zero a t 3 7 0 e C

p H Time 2 . 0 5 minutes 3 . 8 5 minutes 5.1 I hour 6.2 8 hours 7.0 48 hours 7.8 48 hours 8.8 48 hours 9 . 9 48 hours

11.9 10 minutes

In the application of determents as washing agents, it is important to know-h o w m u c h sterilizing action will be ob­tained under the usual washing condi­tions. T h e killing action of the detergents will vary, of course, with every type of agent and every type of organism. Pre­liminary tests are usually m a d e with Staphylococcus aureus because it is a very resistant organism. T h e rate of killing of an ordinary washing solution of Nacconol N R is shown in Table I. It will be noted that the time required for bactericidal action varies from less than five minutes in acid solution to 48 hours in neutral solution. There arc not m a n y instances where one can wait 48 hours, so it is m u c h more important from an application stand­point to know h o w m a n y of the organisms are killed in a reasonable period of time. Table II shows the bactericidal action at the end of five minutes. At a pli of 7, 99.5% of the organisms are dead in that time. Application research has shown that this bactericidal action is effective for the cleaning of food processing equipment, with resultant improvement in the quality of food products. For example, a better grade of butter will be obtained where this detergent is used to clean dairy equipment.

The biological effectiveness of the syn­thetic detergents is not limited to bacteria.

Table II. Bactericidal Activity of 1:500 Nacconol N R against Staphylo­

coccus aureus (5 minutes at 37° C. )

Nacconol N * R

PH

2.0 3.8 5.1 6.2 7.0 7.8 8.8 9.9

11.9

Control Count

Millions

1 17,000 9.000 3,000

30.000 17.000 27.000 12.000

600

Count

per ml.

0 0 1

50 140 180 160 150

7

<% Bacteria killed

100. 10O. 99.99 98.33 99.53 98.94 99.41 98.75 98.83

C H EM I C A L

T h e y are also effective in controlling mold. In tliis case, ordinary ca.nned tomatoes were used to show the m o l d growth. As progressively larger amounts of the N a c ­conol were added, the ainoxintof mold was reduced. Complete elirrrination of the mold is obtained at about Ve%>, which is somewhat less than the usual washing concentration. This study led "to applica­tion research which demonstrated that the synthetic detergent could he Successfully used to clean up establishmeots where contamination by wild m o l d spores must be avoided.

Like soap, the synthetic determents are insecticides. In c o m m o n with all insecti­cides they show a remarkably powerfu) effect on some insects a n d little on others.

T h e insecticidal action of the synthetic detergents would at once interest the application research men in their use for controlling the clothes rnoth on woolens. In a typical laboratory test motli eggs are used on wool treated with. hrevv<;r's yeast. T h e moths did not mature on wool washed in the ordinary washing solution. T h e material m a y be rinsed on<re, but. repeated rinsing cuts d o w n the mothproofing effect. Unwashed wool controls were completely consumed by the larvae in this test.

O n e of the most valuahle amplication tests for synthetic detergents is the dish­washing test, which is m a d e in the labora­tory by washing dishes uniformly soiled with a greasy food mixture. In. one prac­tical dishwashing test, in spite of the fact that sea water is used, there are plenty of suds and the dishes are tho roughly cleaned. T h e best application method t o appraise synthetic detergents for household usee is practical use over a fair period.

T h o examples which h a v e been given of studies and methods used in application research are illustrative of the m a n y , m a n y studies which are m a d e for the pur­pose of expanding the application of the synthetic detergents. Trie synthetic de­tergent business is in the growing stage. The ingenuity and effort used in expanding markets is quite as great as the ingenuity used in developing the detergont in the first place.

Today the detergent application m a n ' s position is relatively easy, lie is past the stage where he must induce somebody to m a k e the first trial of his product. M o r e often today he is approached h y the m a n u ­facturer w h o knows that the synthetic detergents are new tools whicfci might be used profitably. The business is no longer in the ephemeral stage; it is fir-mly estab­lished with trained men openimg up more and more new outlets. The detergent application m a n is working ha^rd on new washing methods which will make this country a cleaner place to live. There will be detergent application research as long as there is anything to \va.sh.

T H I S is the fourth in the series of papers pre­sented during the Sympos ium on Application Research Methods at the 112 th A C S Meeting in N e w York City, Sept. C, 1947 . Others will be published in succeeding issues.

A N D E N G I N E E R I N G N E W S