INDUSTRIAL AND ENGINEERING CHEMISTRY
2122 k’
Boltzman constant distribution ratio of solute between two solvent layers, Co/C, number of molecules of nonelectrolyte per unit volume solution number of molecules of salt per unit volume solution vapor ressure of water a t the same temperature as the fistribution coefficient K , mm. of mercury number of molecules per unit volume before addition of electrolyte number of molecules per ‘unit volume after addition of electrolyte absolute temperature valence of ion Briggsian logarithm natural logarithm selectivity of organic solvent for formic acid solute, K of formic acid/K of sulfuric acid charge on electron activity coefficient volume of one molecule
K n
n’ P
s Sa
T 21
log
In
P
f” 211
SUBSCRIPTS form sulf
= solute formic acid =
Vol. 47, No. 10
(5) Garwin, L., and Hixson, A. N., IWD. ENG.CHEM.,41, 2298 (1949). (6) Geankoulis. C. J.. and Hixson, A. N.. Ibid., 42, 1141 (1950). I Glasstone. S.. “Textbook of Phvsical Chemistrv.” - ‘DD. - - 735-7. 2nd ed.; Van Nostrand, New York, 1946. , Gross, P. H., Chem. Revs., 13, 91 (1933). Guinot, H. M., and Chassing, P., U. S. Patent 2,437,519 (March 9, 1948). Kolthoff, I. M., and Sandell, E. B., “Textbook of Ouantitative Inorganic Analysis,” p. 329, rev. ed., Macmillan, New York, 1945. Kreager, R. M., and Geankoplis, C . J., IND.ENG.CHEM.,45, 2156 (1953). Othmer, D. F., and Thakar, M. S., Ibid., 44, 1654 (1952). Pearson, D. E., and Levine, &I.,J. Org. Chem., 17, 1356 (1952).
Perry, J. H., “Chemical Engineers’ Handbook,” p. 1373,2nd ed., -McGraw-Hill, New York, 1941. Randall, &I., and Failey, C. F., Chem. Reus., 4 , 271, 286 (1927). Rothmund, V., 2. physik. Chem., 33, 401 (1900). Seidell, A,, “Solubilities of Organic Compounds,” pp. 16-20, 2731, 3rd ed., vol. 2 , Van Nostrand, New York, 1941. Setschenow, J., 2. physik. Chem., 4 , 117 (1889). Swabb, L. E., and Mongan, E. L., Chem. Eng. Progr. Samvosium Series. No. 3. 48. 40 (1954).
solute sulfuric acid
Treybal, R. E.,’“Liquid Extraction)’ p. 26, 1st ed., McGrawHill, New York, 1951. Ibid., pp. 392-3.
literature cited
Vogt, H. J., and Geankodis, C. J., IND, ENG.CHEM:., 46, 1763
Bowsher, H. D., M.Sc. thesis, The Ohio State University, 1950. Butler, J. A. V., J. Phys. Chem., 33, 1015 (1929). Compere, E. L., and Ryland, A., IND.ENG. CHEM.,43, 239
(1954).
Weinhardt, A. E., and Hixson, A. N., Ibid., 43, 1676 (1951). Yost, J. R., Jr., M.Sc. thesis, University of Pennsylvania, 1949.
(1951).
Debye, P., and McAuley, J., Phys. Z . , 26, 22 (1925).
RECEIVEDfor review December 8, 1954.
ACCEPTEDMay 18, 1956.
E N D OF PRODUCT AND PROCESS DEVELOPMENT SECTION
Aromatics in Fibers and Films G . P. HOFF AND J. L. MARTIN E . I . du Pont de Nemours 6% Co., Inc., Wilmington 98, Del.
I
N APPROACHING the subject of “Aromatic Chemicals in Fibers and Films,” some background is offered for orientation before getting too far into the subject. While the title implies that the two classes of products can be treated together, as a practical matter, they must be analyzed separately. Man has used fibers to make his life more varied and comfortable from the beginning of civilization. We are all, from the day of our birth, in contact with fibers. Their various applications are mult$udinous and indispensable, and they are taken for granted. This is not the case with films which are a product of the present century. Because fibers, in total, outnumber films many-fold in poundage, because the fiber market for aromatic chemicals exceeds that of films, and because statistics for the textile industry are firmly grounded, fibers are discussed first. AROMATICS IN FIBERS
Of the familiar natural fibers only the four with which the manmade fibers usually compete are listed. Natural Fibers Cotton Wool Si! k Linen
Man-Made Fibers Ravon Acetate Polyamide Polyester Polyacrylic Polyethylene PolGvinGl Prdtein Glass or Mineral
Perhaps, however, it is surprising to see nine classes of man-made fibers, several of which consist of more than one variety. There are endless statistics relating to fibers; likewise, endless
forecasts. This paper is restricted to the United States market for all fibers (except the so-called hard fibers such as sisal and jute) which consumed 6.038 billion pounds in 1954. If one predicates fiber consumption of 40 pounds per capita and a population increase of +1.4% per year which is a little lower than population growth in recent years, the indicated market becomes 7.6 billion by 1965 and 8.7 billion by 1975. This is a typical kind of projection in textiles and is used as an illustrative starting point. This fiber market is currently distributed among the various fibers as follows: 1954, %
Cotton Wool Silk Man-made
69 6
0.1 26
Man-made fibers breakdown into Cellulosic Noncellulosic
19 6
and the latter into those of aromatic origin and those that are not. Among the principal noncellulosic man-made fibers not of aromatic origin are Orlon acrylic fiber, Acrilan acrylic fiber, Dyne1 vinyl fiber, saran, Vicara protein fiber, and glass. More simply, only 66 and 6 nylon, long chain polyamides, and Dacron polyester fiber, derive principally from aromatic sources. Those interested in a more complete discussion of the chemistry involved are referred t o the book by Moncrieff (3). The 66 nylon with which the American public is generally familiar is made from hexamethylenediamine and adipic acid
October 1955
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
though a small amount is the polymerized lactam of aminocaproic acid derived from cyclohexanone. If made from butadiene or from furfural, chemically identical 66 nylon does not qualify as being of aromatic origin. Although not all cyclohexane is, in fact, aromatic in origin, for the purposes of this paper, it is all so treated. Butadiene is a petroleum chemical product while furfural is derived from such vegetable sources as oat hulls, corn cobs, and bagasse. Taking into account all those companies who recently began nylon manufacture, insofar as nylon and Dacron are concerned, this covers a little over 200,000,000 pounds in 1954. That, of course, leaves plenty of room for growth provided that these products can command customer preference over other fibers. But as those in the industry know, this is quite a task and one which will not be achieved by wishful thinking. Much of the thinking about the future of aromatics in fibers has been influenced by various estimates published by the Presidents’ Materials Policy Commission-often called the Paley Report ( 4 ) . These estimates are as good a taking off point as any for some analytical discussion of the future. The various estimates of the future for man-made fibers appearing in this report ranged as high as 7 billion pounds of all man-made fibers in 1975. Billion Pounds 7 . 0 (Production) 6 . 0 (Consumption) 3 . 2 (Consumption) in 1975
The breakdown of the 7 billion figure includes 4 billion pounds of synthetics-Le., noncellulosics-of which 1 billion was forecast to be in polyester fiber, another 800,000,000 in nylon. It also includes an additional 1 billion in “miscellaneous” which could possibly refer to any new fibers whether based on aromatics or not. This 7 billion pounds is the largest forward estimate ever seen, and it compares with current volumes of about 1.5 billion pounds, of which only a little more than 300,000,000 pounds are in synthetics. When the considerably higher efficiencies of these newer, synthetic fibers are considered, it becomes perfectly apparent that if these estimates are realized, and unless new uses are found for fibers in an important way, there will be little room left for natural fibers in 1975. I n our opinion, natural fibers will still be used in abundance far beyond 1975. Whether considering short term or long term prospects, the place in the economy for fibers derived from aromatics obviously depends on the total demand for fibers of all kinds and the characteristics and prices of these particular fibers versus others. For many years, fibers in total have experienced something approaching a static market, in the sense that new uses for fibers have not been appearing in any significant quantity, even with the advent of many new fibers. This is not to say, of course, that new uses for fibers could not be an important part of future markets, a possible *largegrowth in fiber reinforced plastics being an example, but it does point up the fact that the horizon for fibers is a somewhat limited one. Certainly for the short term, then, the future for fibers based on aromatics is well defined by characteristics versus other fibers. For the longer term, more allowance would have to be made for new uses of fibers, as a generality, and consideration should be given to such things as increased use of land to supply food rather than fibers, which well might change the balance between man-made and natural fibers. But any realistic appraisal of such possibilities cannot, in our opinion, lift the outlook to the lofty heights sometimes envisioned. This is the basic argument against what might be called the ever-onward-and-upward school of thought in appraising the future of fibers based on aromatics-or of any other fibers, for that matter. It is necessary, however, to examine in somewhat more detail the three elements in the analyses-limited market,
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price, and characteristics-before offering any more concrete conclusions as to what that future is apt to be. Some may wish t o quarrel with the idea that fibers have been for some time in a more or less static mqrket, but this is stated only after some substantial and rather detailed study of individual fiber markets-of different end-uses for fibers of all kinds, now, in the past, and in the reasonably foreseeable future. The cord t,ire, perhaps coupled with upholstery and other automotive uses of fibers may come to mind as a valid exception but at once it is pointed out that the real growth in this area actually occurred many years ago, and nothing comparable has appeared in more recent years. Furthermore, there are many areas in which textiles were used which now have largely gone to paper and to plastics-bagging and shower curtains are notable examples. Of course, there has been some considerable flux-gains here and losses there-but, by and large, fibers continue to perform their age-old functions, buttressed modestly by increasing level of industrialization although even there the gain is slow and over a long period of time. Those who have examined the statistics and analyses will be aware that many analysts subscribe to population trends as prime determinants of fiber consumption levels over time. Such an explanation is somewhat over-simplified, but no doubt it has some merit, and it is pointed out as further demonstration of the inherently somewhat static scope of the fiber business. If one seeks more specific evidence of lessening rather than increasing demand for fibers, it is not hard to find. For example, the Teztile Organon figures for recent years show a decrease in civilian per capita consumption from 40.4 pounds in 1960 to 32.6 pounds in 1954. Whatever one chooses to believe about limitations in the scope of the fiber market, recognition certainly has to be accorded to the reality of what might be termed increasing “fiber efficiency.” For working purposes of comparing fiber pounds, this can be defined as unit function per unit weight. Such a concept is more complex than the simple measures of strength and abrasion resistance. I n truck and auto tires, for example, it may be possible to build satisfactory carcasses with ”/s to ‘/z the weight of nylon compared with high tenacity rayon. Moreover, the resulting tires may wear longer, and, in the truck category where this is important, a higher proportion of carcasses may be expected to be suitable for recapping. I n apparel and household uses, the importance of unit function per unit weight is a good deal less obvious, but still it is very real. I n general, fabrics made from the newer fibers are much more sheer, and last a good deal longer. hlen’s shirts made from rather fine synthetic filaments have been known to go through 400 laundering cycles, for example, which provides approximately a 10-fold greater life expectancy than that of a heavier cotton shirt. On the other hand, fiber efficieecy may not be used to complete advantage, as when a garment is discarded because of damage, or because of style obsolescence, so any given physical measure of efficiency may not be realized in practice. There is no easy way to reduce the effect of greater efficiency in newer synthetics to a “figure” basis, but the Textile Organon, which more or less is the statistical appraiser of the man-made fiber industry, has worked up a concept of “utility pounds” wherein each pound of newer synthetics is treated as equivalent to 2 pounds of rayon or acetate (6). While we do not have the knowledge specifically to endorse this ratio, we do not, on the other hand, know anything which indicates that it is seriously in error. There is a trend toward lighter-weight fabrics and, in general, less clothing worn even by men. Consider the vest which has all but disappeared as a standard part of a suit; also the shift from overcoats to topcoats. While separate figures are not available, the two classifications together accounted for 36,000,000 pounds of fiber in 1937 and only 22,000,000 in 1953, a decline in poundage of nearly 40% despite a healthy population increase in that 15year period. I n the field of so-called broad woven fabrics from
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INDUSTRIAL AND ENGINEERING CHEMISTRY
man-made fibers, the yards per pound figure (which while not precise is indicative), has increased from 3.95 to 4.95, a change of 25% during a recent 4year period. Thus, the pounds per capita figure in terms of presently established uses is not gaining, it is trending downward for valid reasons. It will take some completely new uses and demands for fibers to carry it upward again. When recognition that no major new applications are yet appearing to offset losses t o paper and to films is coupled with the idea of higher fiber efficiencies of the newer fibers, it is difficult to feel confident of marked growth in total fiber pounds in the future. If nylon becomes accepted in the tire field and 1 pound replaces a considerably greater amount .of rayon, there is a shrinkage in the total pounds of cord required excepting as more vehicles are built. When, furthermore, the more or less inherent characteristic of ever-growing capacity in manmade fibers also is taken into consideration, it is apparent that competitive conditions are apt to be quite severe. Everincreasing capacity comes about, of course, in part by the entry of new fiber candidates, and, in part, because it almost always seems economically attractive to expand capacity for whatever fibers actually are in the sold-up or oversold position a t any particular time. An evolutionary process of substituting newer fibers for older ones is expected but not neceesarily entirely a t the expense of the L‘older”natural fibers. It is abundantly clear, for example, that nylon has cut rather deeply into some formerly important markets for rayon and acetate, while still replacing some cotton as in sheets and nurses uniforms. At the same time, it is increasingly apparent that both Dacron polyester fiber and nylon are going to share many markets-such as curtains and women’s blouses-and that the market for nylon might have been somewhat larger had not Dacron been commercialized. Each new commercial fiber upsets the competitive balance, and all fibers collectively are apt to be milling around within a box Qf only slowly changing dimensions. If one looks to price as a relief from a restricted market, two aspects are to be distinguished-what lower prices do for all fibers collectively, and what a lower price for one fiber does for it versus others. With respect to fibers collectively, the effect of either higher or lower fiber prices is reduced by the fact that the cost of fiber in finished apparel and household items normally is a low percentage of what consumers actually pay for such articles, perhaps an average as low as 10% of price a t the retail level. Even a 50% decline in fiber price, then, has only a 5% “plus” effect of drawing more consumer attention--“plus” because there are elements of mark up and some costs in the consumer item not unrelated to fiber prices. Within the framework of a limited scope in textile markets, price changes find more effect in substituting one fiber for another. But price alone does not control the substitution. If it did, nylon would not have gone beyond the hosiery business, and Dacron polyester fiber would not be taking over some business formerly held by lower priced nylon as it is doing today. I n fact, it is not a t all clear that lower fiber prices do mean substantially greater volume for any one fiber, even a t the expense of others, a t least in apparel and household markets. While, during a 4year period from 1950 to 1954, nylon fabric prices declined by 46y0 and volume-net of military and industrial-increased by 133010, part of this growth-really undetermined but no doubt substantial-represented increased consumer acceptance more or less without regard to price. Furthermore, part of the gain was pipeline filling-providing working inventories to support the higher level of business. Finally, this decline in fabric price which largely came out of mill margins was possible only because mill margins were relatively high in 1950. I n fact, the fabric price decline was a good deal more than half again as large as the whole cost of the yarn entering into the fabrics. Since mill margins had about reached rock-bottom levels by the
Vol. 47, No. 10,
particular period in 1954 when this comparison was made, it is obvious that further fabric price declines must be achieved via yarn price which today is roughly only half of fabric price and, therefore, has the previously referred to reduced effect. Taking all these considerations into account, it seems highly unlikely that any fiber price decline was exceeded percentagewise or even matched by a gain in apparel or household volume. Indeed, there are many examples where both price and volume have proved persistently low, a8 has been true for most,fabrics made &om cellulosic yarns in recent years. Doubts have been expressed that the volume of synthetic fibers will attain the levels referred to earlier. What then would seem to be a more likely rate of growth? Obviously nobody knows. If these appraisals of relatively static markets and the concept of utility poundage are reasonable, then the synthetic fibers can be expected to gain steadily but not necessarily a t an accelerated pace for they must compete every step of the way in terms of performance, style, and consumer acceptance. While nobody really knows the future, there is iuch a thing as an informed guess. Because we like to know where we are going, as best we can, we employ qualified prople to make such guesses, recognizing full well that they will be in error, particularly in their details, but hoping to see ahead as well and as far as the dim vision of foresight will permit. They work, of course, within the framework of reasoning discussed, and their estimates must be adjusted accordingly. On the other hand, their objectivity just might be biased a bit in a direction favorable to the fibers in which we are interested, so some may wish to enter discounts. As far ahead as has been anticipated-it is not wise to tag it with a specific year but i t probably ip beyond 1960-little change is foreseen in total fiber poundage, a possible gain not exceeding 10% against a population gain greater than that. Within this market limitation, the man-made fiber proportion is expected to rise to possibly 39% from the 25% previously mentioned. For the presently commercial fibers based in whole or in prtrt on aromatics, a rate of advance is expected greater than that foi man-made fibers as a whole, because it is clear that such fibers will continue to take some business away from cellulosics as well as from natural fibers in the future. Nylon and Dacron can double their present share, but we are not prepared to go beyond that. AROMATICS IN FILMS
Films are in contrast to fibers in all directions. Films are new, dating from the turn of the century so there is no age-old background of existence, familiarity and use. By and large new f i l m are not expected to displace old unless the older ones prove markedly deficient. Expansion is proceeding not only as the population grows, but in many new directions concurrently. From decorative wraps on candy boxes and perfume packages to functional applications, new applications have come in a steady stream so that today cigarettes, food, shirts, and sheets increasingly are delivered in fresh and uncontaminated condition. The list of uses is endless and ranges from the wrapping of an individual cigar or the packaging of fruit and vegetables to the wrapping of pipelines 4 feet in diameter. The outlook is, therefore, dynamic as befits a young industry. Thirty years ago, the base in this country was essentially Bero. I n 1953-54 the base is over 600,000,000 pounds. I n the film category are 1. Cellulosics including cellophane, cellulose acetate sheeting and film base 2. Polyvinyl group including various copolymers 3. Polyester grouD including film for industrial uses and photographic film4. Polyethylene 5. Rubber hydrochloride
-
-
I n the film family, those used for wrapping and related purposes broadly comprising protection represent the larger and
October 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
more rapidly expanding market compared with photographic film. Estimates are offered for films 10 mils or less in thickness. Because it is necessary to distinguish between films and extruded plastics, 10 mils has arbitrarily been chosen as the appropriate dividing line. Cellophane wrapping is the most familiar film that has been produced in the country since 1923 (1). Current annual production by three manufacturers is of the order of 350,000,000 pounds. Other available films include polyethylene, the chlorinated vinyls, rubber hydrochloride, and cellulose triacetate with Mylar polyester film and Cronar polyester photographic film base (the analogs to Dacron polyester yarn) just getting started. Insofar as primary compositions are involved, only these latter two are based on aromatic chemicals-dimethyl terephthalate (8). It is premature to judge their acceptance a t this time as they are both new, with markets still under early development. However, by assuming a growth curve similar to the historical curve for total films, a market for these two products of the order of 50,000,000 to 75,000,000 pounds could be projected. The big unknown aside from commercial acceptance is the time scale. Many of the applications such as those in the electrical industry require a long time to be proved. I n addition, any forecast for Mylar polyester film must take into account that it is used in much thinner gages than the older films, so that fewer pounds will be needed to cover equivalent areas. Consequently, there will be an incubation period during which these products establish their merits followed by steady growth as befits a new product having a well-balanced collection of desired properties. Aromatic derivatives do enter into the manufacture of several of the other films as plasticizers or solvents during the manufacturing process. Current requirements for plasticizers,
2125
such as the numerous phthalates and-aromatic phosphates, are estimated at 50,000,000 to 60,000,000 pounds per year. Requirements for toluene as a solvent amount to approximately 2,000,000 pounds. While a continuation of the 15% average annual growth in film consumption experienced over the past 20 years is not expected, healthy, expanding markets are anticipated. Regardless of the future growth rate, the aromatic chemicals industry, though supplying only a small part of the total film business, seems certain to have an increasing share. SUMMARY
Nylon and Dacron polyester fiber require substantial quantities of aromatic chemicals as their raw materials. The former, however, draws on both butadiene and furfural in addition. Both fibers are believed to hold considerable promise for expansion. The polyester films Mylar and Cronar are so new that their present modest needs are overshadowed by the fiber requirements mentioned. LITERATURE CITED
(1) Hyden, W. L.,IND.ENG.CREM.,21, 405-10 (1929). (2) Izard, E.F., Chem. Eng. News, 32, 3724 (Sept. 20, 1954). (3) Monorieff, R. W., “Artificial Fibres,” 2nd ed., Wiley, New York, 1954. (4) President’s Materials Policy Commission Report, vol. 2, pp. 105, 106; vol. 4, p. 200,June 1952. (5) !fertile Organon, 25, 45 (hlarch 1954). RECEIVED for review March 14, 1955. ACCEPTED July 7, 1955. Presented at the Symposium on “Future of Aromatic Hydrocarbons,” before Division of Industrial Engineering Chemistry, 127th Meeting, ACS, Cincinnati, Ohio, March 1955.
Photosensitizers for Polvester-Vinvl Polymerization J
J
CHESTER M. McCLOSKEYl AND JOHN BOND2 Alexander H . Kerr & Co., Znc., Los Angeles, Calif., and Gates and Crellin Laboratories of Chemistry, California Znstitute of Technology, Pasadena, Calif.
T
H E commercial photopolymerization of vinyl-type monomers has received particular attention since the development of the low pressure laminating resins such as the glycol maleate polymer-atyrene systems. The photopolymerization process has several advantages over thermal polymerization and is especially useful in applications where a long pot life is desired together with a rapid gel a t a low temperature. Such diverse demands as the manufacture of boats or the bonding of acrylic domes to glass fiber laminates have been met by photopolymerization. The process is also especially useful in applications where it is necessary to cure (polymerize) one portion of a laminate prior to the rest. The fact that the vinyl monomers will polymerize when subjected to ultraviolet radiation has been known for some time. However, photosensitizers of sufficient efficiency to make photopolymerization commercially feasible were not developed until the early 1940’s. A photosensitizer of polymerization should absorb light and with the energy so acquired dissociate into radicals which have sufficient energy to initiate polymerization. It should be colorless, light-stable (noncoloring), and readily soluble, have a low 8
Present address, Office of Naval Research, Pasadena, Calif. Present address, Pittsburgh Plate Glass Co., Torrance, Calif.
chain transfer constant, and dissociate with a high quantum efficiency. However, few excel in all these traits. The early investigators employed mercury (4, 14, 26, 88, $9, 48, 60) as the photosensitizer. They demonstrated that in the presence of mercury, the rate of polymerization of ethylene and butadiene was greatly increased. Cadmium (6) and ammonia ( 4 7 )were found to be active with ethylene, and claims have been made for uranium salts (11, 13, 31), triethyllead acetate (10), iron (for recent developments with ferric salts see l a ) , and chromium and aluminum salts with liquid monomers often in the presence of peroxides. Sodium (19) was found to be inactive with ethylene, I n 1933 Jeu and Alyea ( l 7 ) , while studying inhibitors for the photopolymerization of vinyl acetate, found that a number of organic compounds accelerated the polymerization. Among these were benzoyl peroxide, acetone, chloral hydrate, and a number of dyes (for present developments with dyes see 30,31). They reported that benzil, benzophenone, and allyl alcohol were inhibitors. The same year Pummerer and Kehlen (34) found that a number of carbonyl compounds (39, 49) were photosensitizers for the polymerization of isoprene and styrene. Benzophenone and benzaldehyde were reported as active. Agre in 1945 claimed that acyloins ( 3 ) and vicinal carbonyl compounds
