March, 1926
INDUSTRIAL A X D ENGINEERING CHE;MISTRY
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Industrial Requirements for Dry-Cleaner’s Naphtha’ By Lloyd E. Jackson2 MELLON INSTITCTE OF INDUSTRIAL RESEARCH, PITTSBURGH, PA.
BROAD study of materials of possible application as dry-cleaning solvents was begun by the writer about five years ago, in an endeavor to find a solvent that would be more satisfactory in practice than motor gasoline. Motor gasoline has been and probably still is the most widely used dry-cleaning solvent, notwithstanding the fact that other solvents now available have decided advantages over it. One reason is that motor gasoline is readily obtainable a t a comparatively low cost in all parts of the country. Other products that have been proposed, some of which are being used to a limited extent, are natural gasoline, carbon tetrachloride-naphtha mixtures, benzene and other coal distillates, and special petroleum naphthas. The literature contains little or no reference to any previous investigation of the requirements for an efficient drycleaner’s naphtha. For the most part the cleaning industry has been content merely to use solvents that could be procured easily and cheaply.
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run, well-refined naphtha, boiling between, say, 350 O and 360” F. To make such a close boiling range naphtha under present conditions is not practicable, however, and consequently the ideal solvent can only be approached. Experience has shown that a well-refined petroleum naphtha boiling between 280” and 400” F. can be produced economically and that it is a dry-cleaning sol>-entof efficiency. Solvents That Have Been Used
Briefly described, the dry-cleaning process consists in washing wearing apparel, house furnishings, etc.., which are made of textile fabrics, fur, or feathers, by means of such solvents as petroleum naphtha and specially prepared soap.3 Properly dry-cleaned materials are odorless, free from dirt, and unchanged in shape and color. The term Lidry’lis used in contradistinction to “wet” in the sense of wet with water. The dry-cleaning process is carried out in much the same manner as the washing of textile fabrics with water and laundry soap, except that so-called “dry” solvents, such as petroleum naphtha, are used instead of water. For economic reasons, dry-cleaning solvent must be regenerated in the dry-cleaning plant, and used over and over again. The loss entailed by evaporation, leaks, etc., is made up with fresh solvent. A desirable dry-cleaning solvent is one that, is readily available a t a low cost in all parts of the country. Efficient dry-cleaning does not require a liquid of supersolvent power for all kinds of mat,erials. The dry-cleaning process depends on colloidal phenomena as well as on the solvent power of the liquid used. The fallacy that supersolvent power is needed has led occasionally to the employment, of liquids that remove too much oil, and even dyestuffs, from the materials cleaned. The evaporation loss must be low, because (1) most solvents suitable for dry-cleaning are inflammable and the fire hazard is directly in proportion to the volatility, (2) as a rule the breathing of the vapors is not healthful for the operators in the plants, and (3) it is not economical to have to replace large losses due to evaporation. Although the evaporation loss must be low, the solvent must be so volatile that it can be evaporated readily from all materials cleaned. A satisfactory solvent must be free from impurities that will develop odor or color. It must be one that can be economically purified for re-use in the plant.
Motor gasoline will clean fabrics, but properties which are essential for a motor fuel make it uneconomical for cleaning purposes. The light fractions are necessary to facilitate the starting of a motor, but when present in a cleaning solvent these mean loss, because they evaporate the first time it is used. The higher-boiling fractions of motor gasoline are objectionable, because that part is difficult to remove from fabrics and therefore gives a malodor. Unsaturated hydrocarbons are not objectionable when present in limited quantities in motor fuel, but are troublesome in cleaning solvent because they impart foreign odor. h-atural gasoline has been and still is used to a limited extent for dry-cleaning. It has the advantage of drying readily, but it is so volatile that the evaporation in handling is excessive. Also, so much vapor escapes into the cleaning room that a great fire hazard exists, and the atmosphere is unhealthy for the cleaning operators. Carbon tetrachloride and petroleum-naphtha mixtures have been proposed to reduce fire hazard. The difficulty has been the relatively high evaporation loss and consequently the expensiveness of making up the carbon tetrachloride evaporated. These special mixtures also possess corrosive and anesthetic properties. Benzene and other coal distillates are employed to some extent, although not so much as they were several years ago. As odd as it may seem, one of the outstanding disadvantages of these products is that they are too efficient as solvents. They remove all the oil and grease from the materials cleaned and leave them lifeless. Furthermore, the evaporation loss and consequently the cost, fire hazard, and toxicity to workmen are too great to make them of desired utility. Petroleum spirits has been purchased under such names as 1‘. 31. and P. naphtha, mineral turpentine, etc., for use by dry-cleaners. Some petroleum spirits have given satisfaction, but often the end point is too high or the percentage of unsaturated hydrocarbons is too great, or they are not sufficiently refined to produce a satisfactory dry-cleaning solvent. hfost of the special dry-cleaner’s petroleum naphthas on the market have been well-refined, fairly close boiling range, straight-run naphthas. The boiling range has been too low, however, to make them efficient as dry-cleaning solvents. The advantages of low evaporation loss and decreased fire hazard, which are essential for an efficacious dry-cleaner’s naphtha, have been sacrificed for quick drying of the naphtha from the garments cleaned.
Petroleum Most Economical Source of Solvent
Problem Presented by “Stoddard Solvent”
Dry-cleaning Solvent Requirements
A petroleum product meets these requirements to the greatest extent. The ideal petroleum product would be a straightReceived November 24, 1925. Senior Industrial Fellon., Mellon Institute of Industrial Research. 8 For a detailed description of the process see Scz. A m . , 127, 396 (1922), J. Home Econ., 16, 673 (1924). 1
Recently the h’ational Association of Dyers and Cleaners announced a cleaner’s naphtha, termed “Stoddard Solvent,” that is less inflammable than other products. N o l c I t is appropriate to mention here that Mr. Stoddard has based his specifications on those worked out during the past five years by the
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Ih'DUSTRIdL A N D ENGINEERING CHE-MISTRY
writer, for the Mundatechnical Society of America. He has, however, given a flash point of 105' F . , which is not mentioned in the Mundatechnical Society's specifications.
Stoddard naphtha presents a problem to petroleum refiners, because it is quite difficult, if not impossible, to make a naphtha with a flash point of 105" F. that has the distillation range specified. In order to obtain the flash point specified, the initial boiling point must be raised to the neighborhood of 325' F. or above. This means that there results a naphtha with considerably less than 100" F. boiling range. The problem is complicated further by the fact that many drycleaning establishments, with their present drying equipment, cannot remove naphtha of this boiling range from the materials cleaned. Consequently the use of the naphtha will be limited to the few plants that can successfully evaporate it. Specifications Recommended
The specifications proposed for a petroleum naphtha that it is practicable to produce and that is efficient for dry-cleaning are given below. Petroleum naphtha described by these specifications has the property of low evaporation loss, with decreased fire hazard, etc., together with the property of relatively rapid drying time. Practically all dry-cleaning plants can successfully use naphtha of this description, without encountering the problem of drying materials cleaned with it. No fires caused by static electricity have been reported in plants of members of the Mundatechnical Society after they started to use this particular naphtha, whereas a number of fires occurred in these plants when motor gasoline was employed. Specifications f o T Petroleum Naphtha to Be Used for DryCleaning 1-This specification covers the grade of cleaner's naphtha (gasoline) used by the members of the Mundatechnical Society of America as a solvent for cleaning textiles and other materials where the highest efficiency is required. The tests shall be made and interpreted in accordance with Bulletin 5, Report of Committee on Standardization of Petroleum Specifications, published by the United States Bureau of Mines. 2-The cleaner's naphtha shall be free from undissolved water and suspended matter. &-color: The color shall be water-white.
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4-Doctor test, The doctor test shalt be negative. 5-Unsaturated hydrocarbons: Not more than 2 per cent of the naphtha shall be soluble in concentrated sulfuric acid. 6-Distillation range: The temperature limits for the distillation are as follows: The initial boiling temperature shall not be less than 137.8" C. (280" F.), The end point shall be a temperature not greater than 204.5' C. (400' F,). 7-Acidity: The residue remaining in the flask after the distillation is completed shall not show a n acid reaction. 8-Aromatic hydrocarbons: The naphtha shall not contain aromatic hydrocarbons, such as benzene, toluene, etc. 9-Odor: The odor shall be sweet.
The naphtha must be free from water and dirt, because, as the name dry-cleaning implies, the cleaning process must be dry and clean. The color must be water-white, because the naphtha is used to clean white garments. Colored naphtha imparts some color to white materials. The doctor test must be negative, because it has been observed that doctor "sour" naphtha readily becomes colored and sour in use or in storage. The unsaturated hydrocarbons must be low, because they impart a foreign disagreeable odor to the naphtha and to materials cleaned with it. The distillation range of 280" to 400" F. produces a balance between the advantages of low evaporation loss and the disadvantage of long drying time. Practically every cleaning plant can readily evaporate a naphtha of this boiling range from materials cleaned. If the initial point or end point is materially raised, difficulty in evaporating the naphtha from garments will be encountered in many dry-cleaning plants. The flash point of a naphtha of this distillation range will be somewhat below 100" F., but will be sufficiently high that there will be little danger of fire from static electrical discharges in cleaning rooms operated in the ordinary manner. The acidity test must be negative, because acidity may indicate incomplete removal of sulfuric acid used in refining. Traces of sulfuric acid readily destroy textile fabrics. The naphtha must not contain aromatic hydrocarbons, because these compounds, if present in considerable quantity, cause troublesome emulsions. The odor must be sweet, because malodorous naphtha is difficult to expel from materials cleaned.
Large Fund Sought for National Research Endowment The urgent need for additional funds for research in pure science in the United States has been emphasized in the following statement recently issued by the National Research Endowment, established by the National Academy of Sciences. The Trustees of the National Research Endowment, recognizing that human progress depends in large degree upon research in pure science, declare their conviction : (1) That the United States, which already occupies a leading position in industrial research, should rank with the most enlightened nations in the advancement of pure science. ( 2 ) That it is wiser to make large expenditures for scientific research, thus advancing civilization, improving human welfare, conserving health, and saving countless useful lives, than to tolerate unnecessary suffering and then endeavor to alleviate i t at still greater cost. (3). That research in all branches of the mathematical, physical, and biological sciences should be encouraged, because of the intellectual and spiritual value of adding to knowledge and because the greatest advances in science and in industry often result from apparently useless abstract discoveries. (4) That scientists exceptionally qualified to widen fundamental knowledge through research are of such value to the nation that every effort should be made to facilitate their work (5) That the overcrowding of educational institutions, and the consequent excessive demands of teaching and administration, have further reduced the limited opportunities for research previously enjoyed by the members of their faculties.
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That the funds now available for the support of research
in pure science in the United States are far below what our population, education, and material resources demand. (7) That the National Academy of Sciences, created by Congressional charter the scientific adviser of the Government, and composed of leading investigators in the closely interlocked and mutually dependent mathematical, physical, and biological sciences, is peculiarly qualified to evaluate the needs of pure science in America, to stimulate its progress, and to insure the wisest use of funds provided for research. In view of these considerations, the Trustees of the National Research Endowment, established by the National Academy of Sciences, propose immediately to secure adequate funds for the encouragement of research in pure science. The Board of Trustees, of which Secretary Hoover is chairman, is made up as follows: Elihu Root Andrew W. Mellon Charles E. Hughes Edward M. House John W. Davis Julius Rosenwald Owen D. Young Henry M. Robinson Felix lvarburg Henry S. Pritchett Cameron Forbes Albert A. Michelson John C. Xerriam
Robert A. Millikan Gano Dunn Vernon Kellogg William H. Welch Thomas H. Morgan John J. Carty Simon Flexner Oswald Veblen James H. Breasted Lewis R . Jones Arthur B. Lamb George E. Hale
