Symposium
o n Application
ile*e**rcH Methods.
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Application Research Methods for Synthetic Detergents L A W R E N C E II. F L E T T , Director, N e w 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 t h e value o f e a c h n e w c o m p o u n d · · · Synthetic detergents, latest synthetic chemicals to participate in a field built u p b y use of natural p r o d u c t s , are results of application research
. T T L P P L I C A T T O N research is as old as civili zation. W h e n prehistoric m a n tried the first bronze spear on his e n e m y , he w a s 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 n e w chemicals cannot be sold until application research finds out w h a t to d o with t h e m . Application research is not carried out o n every n e w chemical, but only on those chemicals which might be marketed. N e w chemicals are easily m a d e . T h e n u m b e r 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 applica tion research can seek out from the count less unused chemicals compounds which are invaluable to mankind. Synthetic rubber, D D T , 2 - 4 D , and synthetic resins were developed by use of chemical c o m pounds which had been k n o w n 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 underesti m a t e the accomplishment or ambitions of application research chemists. Their work affects the w a y people live and w h a t they buy. T h e first organized application re search in the chemical industry of this country was carried out in thefieldof dyestuffs. It has been so successful that al most 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 w r e have come to regard as every-day necessities. Unusual or prolonged p r o m o tion of a particular product, b y applica tion research, is certain to expand the use of that product. T h a t is w h y everyone wants things colored a n d wrapped in paper. If flavoring materials were pro
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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 n e w 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 m u s t be carried out either b y the manufacturer or the consumer. Generally it is carried o n b y both. T h e manufacturer should start applica tion research at the s a m e time that chemi cal research is started, particularly w h e n chemical research is directed to a fixed use. For example, if the object of research is the development of a n insecticide for Japanese beetles, a m o r e elastic rayon, a g u m inhibitor for gasoline, or a synthetic detergent for washing cotton, chemical re search work would be hopelessly inefficient if application research did not provide guiding counsel on the value of each new c o m p o u n d as it is prepared. Application research is the pilot that charts the course. Research is most efficiently carried out w h e n each n e w 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 w a s developed because of the dyers' troubles with the use of soap. W h e n textile materials are proc essed 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. When the material is dyed, the dye solution can not reach these waterproofed spots even though it wets and dyes the rest of the fabric. U n d y e d spots in colored goods are an expensive problem for the dyer. T h e complete history of the efforts to overcome this simple fault covers almost 100 years of chemical development and application research. It starts with the
CHEMICAL
development of the sulfonated oils. Fifty years later the development of a group of surface-active agents k n o w n as wetting agents w a s in full swing. Literally h u n dreds of wetting agents were m a d e , m a n y of which are still useful and commercially available. T h e 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. T h e y lacked the high dispersive action that m a k e s soap a wash ing agent. X w e n t y years ago, the prolonged re search for a satisfactory textile processing agent culminated with the synthesis of a detergent which w a s stable and effective in the presence of lime salts, metal salts, a n d acids. It did not take application re search 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 u p b y the use of natural products. This list embraces synthetic dyes, which have surpassed the natural dyes in importance; synthetic resins, which give u s products not obtain able with the natural resins; synthetic drngs, which cure diseases not cured by natural drugs; a n d 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 afieldwhich has been held exclusively b y soap for thou sands of years. T h e y are assuredly a prod uct of application research. T h e synthetic detergents were not de veloped as low cost substitutes; they were developed to do a job that could not be done satisfactorily with the natural prod uct. T h e present low cost c a m e 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,
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ENGINEERING
NEWS
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. T o o 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. Many 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 m e a n s 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
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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 n o w there are wetting agents with very low surface tension that do not wash a n d good detergents that d o not form suds. For the present, washing power is m e a s ured by soiling fabric and washing the dirt out. T h e 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 n o w . 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, y o u should reach that happy state where everything that y o u 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 a n d 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 w a s h ing 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 o r 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
New Text
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action the detergent has pmvi»d very useful in processing cotton.
Detergents and Speed T h e metal industry is a n industry where the speed of cleaning is important. Metals must be clean before they can be painted, plated, or treated in any other way. T h e 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 m u c h 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 a n d cleaned by simple immersion in alkaline solution. A photograph is taken by use of ultraviolet light so that the metal appears black a n d 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 s o m e processes and for s o m e people w h o cannot tolerate alkaline solution o n 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 u p a floor or a n 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 a n d 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 t h e m off and b}' the bactericidal action of the detergent.
T a b l e I. T i m e R e q u i r e d fc>y 1:500 N a c c o n o l 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 pH Time 2.0 3.8 5.1
5 minutes 5 minutes I hour
6.2 7.0 7.8 8.8
8 hours 48 hours 48 hours 48 hours
9.9 11.9
48 hours 10 minutes
In the application of determents as washing agents, it is important to knowh 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 a n d 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 s h o w n in Table I. It will be noted that the time required for bactericidal action varies from less than five minutes in acid solution to 4 8 hours in neutral solution. There arc not m a n y instances where o n e can wait 48 hours, so it is m u c h more important from a n application standpoint to k n o w 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. A t 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. T h e biological effectiveness of the synthetic detergents is not limited to bacteria.
T a b l e II. Bactericidal Activity o f 1:500 N a c c o n o l N R against Staphylo-
coccus aureus (5 minutes at 37° C . )
PH
Control Count
Nacconol N * R , which is s o m e w h a t less than the usual washing concentration. This study led "to application research which demonstrated that the synthetic detergent could he Successfully used to clean u p establishmeots where contamination b y 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 s o m e insects a n d little on others. T h e insecticidal action of the synthetic detergents would at o n c e interest the application research m e n in their use for controlling the clothes rnoth on woolens. In a typical laboratory test motli eggs are used on wool treated with. hrevv
