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 a t 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
I N D U S T R I A L A N D E N G I N E E R I N,G C H E M I S T R 1
2126
Vol. 47, No. 10
EXPERIMENTAL
Table I.
Photoactivity of H a l o m e t h y l n a p h t h a l e n e s
(Procedure B, General Electric H250 A-5 lamp, methyl methacrylate monomer) Time to Gel, Hours Best No. of estiExperimated Photosensitizer (1 %) ments Range value Benzvl bromide 2 5,21 \ 3 -1 1-Chforomethylnaphthalene 8 3.81i.3 4.Qa 2-Chloromethylnaphthelene 6 3.6-3.9 3.8 1-Bromomethylnapht halene 2 4.3-4.4 4.3 2-Bromomethvlnaahthalene 2 4.3-4.5 4 4 1,5-Dichlorometh~lnaphthalene 4 3 0-3 5 3 3 I-Chloromethyl-2-methoxynaphthalene 2 3 7 3 7 Bromomethyl phenyl ketone 7 2 2-2 8 2 4 (for comparison) Typical scatter, 3.8, 4.2, 4.0, 4.0, 4.3, 4.0, 4.0, 3.8. r
( 2 ) had exceptional photoactivity and were sufficiently efficient for commercial processes. The acyloin ethers have subsequently been reported to be even more active (36). Since the original report of Jeu and Alyea that benzoyl peroxide was a photosensitizer for the polymerization of vinyl acetate, many other workers in the field ( 7 )have utilized peroxide in laboratory studies. I n general, their efficiency has been too low to make them commercially feasible. The synthesis of allyl hydroperoxide was recently reported (87). Allyl hydroperoxide was found to have a high rate of decomposition in the presence of ultraviolet light and may be a useful photosensitizer for polymerization. Halogenated organic compounds have been investigated and found to have activity. Compounds with two or more halogens on a carbon atom ( 6 ) , hexachloroethane (9),and alkyl iodides in the presence of mercury (with ethylene) (18, 20) were reported to be effective photosensitizers. More recently the chlorinated and brominated methanes have been shown to add to olefins when irradiated (82,I S ) . Several naphthalene derivatives substituted in the 2 position (1) were described as photosensitizers foi: methyl methacrylate and styrene, as was 2,7-dichlorodiphenylene sulfone (16). Azo compounds have been utilized in some studies (40). Disulfides as a class were claimed by Richards (97) to be active. Aryl disulfides were reported to have a much higher activity than alkyl disulfides. Of the compounds described in the literature, benzoin proved to have the best general activity and applicability, while biacetyl was superior for the acrylates. These compounds are either of low solubility or deeply colored. An investigation was initiated in Kerr laboratories in order to see whether practical photosensitizers for polymerization without these undesirable characteristics could be obtained (43-46).
Table 11. Photoactivity of a-Haloketonbs (Procedure A, sunlight, methyl methacrylate monomer) % Polymera 1.5 30 48 Photosensitizer (1 %) min. min. min. Control 0.0 0.0 0.0 Chloroacetone 2.9 6.45 12.9 Chloral 2.0 3.8 1.2 Chloral hvdrate 0.0 0.0 0.0 Bromal 4.5 9.3 14.1 Acrolein diohloride 4.3 14.0 ... Acrolein dibromide 5.8 11.0 21.0 Methyl phenyl ketone 0.0 0.0 0.0 Chloromethyl phenyl ketone 0.0 0.0 0.0 Bromomethyl phenyl ketone 10.5 22.5 37.1 Benzyl phenyl ketone 0.0 0.0 0.0 a-Chlorobenzyl phenyl ketone 6.8 14.1 22.6 a-Bromobenzyl phenyl ketone 8.6 17.6 32.7 Bromomethyl naphthyl ketone 5.9c 11.Od 19.4* a Each figure represents a separate but simultaneous run. b 200 minutes. C 5.7 6.1 d 10.9,11*.2. e 1 9 . 1 , 19.7.
120
min. 0.0 Gel 10.2
3.5b
Gel Gel Gel 0.0
0.6
Gel 0.3 Gel Gel Gel
Test samples of the monomer containing the compound being investigated were irradiated, either (A) in the sunlight or ( B ) by a General Electric No. 250 A-5 250-wattjmercury vapor lamp from which the glass envelope had been removed. With the mercury vapor lamp, the samples were held in borosilicate glass test tubes on a rotating porous table a t a distance of 4 inches from the axis of the lamp. A stream of air was continuously blown through the table to minimize radiation heating. By rotating the table around the lamp the effect of variation in the radiation emitted from different parts of the lamp was minimized. The rate of polymerization was determined by measuring the gel time or the increase in viscosity by comparison with GardnerHolt tubes or by isolating the polymer by precipitation in methanol. I n the early work gel time was used as the criterion, but because of difficulties in determining the time of gelation together with possible variation due to the effect of the photosensitizers, in the later runs the polymerization was followed by isolation of the polymer. The viscosity of solutions of pblymers in acetone was determined with an Ostwald viscometer a t 25" C. Chemicals being tested as photosensitizers were checked for purity and crystallized or distilled whenever such a step was required. The monomers were of commercial grade and with the exception of methyl methacrylate were not further purified. The naphthanol peroxides were prepared as directed by Kharasch and Dannley ( 2 1 ) . During the irradiation, the samples were stoppered, but no particular attempt was made to exclude oxygen completely. Several experiments in which oxygen was rigorously excluded did not sufficiently alter the scatter or the relative order with the procedure used to warrant it. Some variation was encountered even with the most rigorously standardized conditions and most of the results recorded are the average of a t least four runs. Particularly in the case where irradiation by sunlight was used, variation of temperature and intensity with time prevented the analysis of small differences between two runs. However, the general effects and order of activity were easily reproducible. RESULTS
The efficiency as photosensitizers for the polymerization of vinyl monomers was surveyed for a number of halogen-containing compounds. A general survey in this field is beset with many variables which complicated the study-e.g., temperature, absorption spectra of the sensitizers, absorption spectra of the monomer, intensity and spectrum of the light source used, chain transfer characteristics of the sensitizer, quantum efficiency of dissooiation, and efficiency of initiation of polymerization by the radical. Thus the data obtained are largely empirical and difficult to interpret theoretically. This is particularly true where gel time (see Tables I, 11, and VII) was used as an index of activity, as it is influenced by crosslinking reactions as well as initiation. However, the activity varied widely with the type of compound and from this survey it became apparent that the chromophoric groups
C
ll
X-C-C--,
X-C-
E
-,
0 X-X-C-,
/I
and X-N-
i 4
-
0
where X is a halogen other than a fluorine atom, are particularly efficient. An investigation of the halomethyl aromatic hydrocarbons and allylic halides with methyl methacrylate demonstrated that while compounds such as allyl chloride and bromide or the benzyl halides had measurable activity, the polynuclear analogs such as the halomethylnaphthalenes were particularly efficient photosensitizers for polymerization. As shown in Table I, the chloromethylnaphthalenes were slightly more active than their bromomethyl analogs, but no significant difference was observed be-
October 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
tween the 1 and 2 positions. Substitution of a methoxyl group in the 2 position of 1-chloromethylnaphthalene appreciably increased the activity, as did another chloromethyl group in the 5 position. 9-Chloromethylphenanthrene is slightly less active. While acetone and other monocarbonyl compounds are not of sufficient activity to be commercially interesting, the a-halogen derivatives are active over a wide range of types. Chloral hydrate ( 1 7 ) was known as a photosensitizer but of low activity. It was found, as shown in Table 11, that chloral in dry monomer was much more active than chloral hydrate but less active than bromal. Simple carbonyl derivatives such as chloroacetone and dibromo- and dichloroacrolein exhibited good activity. The activity of chloromethyl phenyl ketone (phenacyl chloride) was found to be only very weak, but that of bromomethyl phenyl ketone (phenacyl bromide) and bromomethyl naphthyl ketone was strong. I n this series the phenyl radical imparts greater activity than the naphthyl. I n most cases there is little difference between the bromo and chloro compounds, the striking exception being the low activity of a chloromethyl phenyl ketone. ' The alpha-halogenated fatty acids are usuallyweakphotosensitizers, as shown in Table 111. The inactivity of bromoacetic acid is anomalous and contrary to the general activity trend from chlorine to bromine to iodine. The presence of an inhibitor. in trace quantities is a possibility. The increase in photoactivity with an increasing number of chlorine atoms was demonstrated by this series. Table 111. Photoactivity of Halogenated Acids (Procedure A, sunlight, methyl methacrylate monomer) % Polymer, 100 Min. Best No. of estiExperimated Photosensitizer (2 %) ments Range value Control 4 0.0 0.0 Chloroacetic acid 4 0.0- 0 . 3 0.1 a-Chloropropionic acid 3 0.3- 1 . 2 0.7 Dichloroacetic acid 4 0.0- 4 . 5 4.4 Trichloroacetic acid 3 7.5-11.8 11.0 Bromoacetic acid 4 0.0- 0 . 0 0.0 Iodoacetic acid 4 11.2-17.ga 15.2 a Typica! ecatter, 17.9, 17.4, 14.0, 11.2. An independent run with a lower light intensity gave 5.1, 3.9, 4.5, 3.9% polymer.
The activity of sulfonyl chlorides as shown in Table IV exhibited a marked increase as the organic radical was changed from alkyl to aryl. 2-Naphthalenesulfonyl chloride was particularly active, as was 1-naphthalenesulfonyl chloride and 1,5naphthalenedisulfonyl chloride. The nitrogen-substituted halogen derivatives of imides-e.g., N-bromosuccinimide-and sulfonamides were found to have good activity. Dichloroamine-T was characterized by the exceptionally clear and colorless polymers. However, the products were very brittle, which was undoubtedly due to the high chain transfer properties of this class of compounds (see Table VIII). That this class was active
Table IV.
Photoactivity of Sulfonyl Chlorides
(Procedure A, sunlight, methyl methacrylate monomer) Yo Polymer, 100 hfin. Best No. of estiExperimated Photosensitizer (1 %) ments Range value Control 0.0 0.0 Thionyl chloride 1.9- 4 . 3 4.1a Sulfuryl chloride 5.0- 6 . 5 5.7 Ethanesulfonyl chloride 0.0- 3 . 5 2.3 Benzenesulfonyl chloride 1.2- 6 . 4 2.9 p-Toluenesulfonyl chloride 2.3- 8 . 7 5.1 2,4-Xylenesulfonyl chloride 10.3-16.6 12.7 2-Naphthalenesulfonyl chloi*ide 27.8-34.0 31.9 a Typical scatter, 4.2, 3.9, 1.9, 4.3.
2127
was not surprising, as rearrangement of X-chloroamides and amines when irradiated was known (8, %$,66). Independent work conducted in this laboratory confirmed the results reported by Richards ( 3 7 ) that the disulfides, particularly the aromatic members, were active. Diphenyl sulfone also showed some activity. Aroyl peroxides as a class were found to be photoactive. As seen in Table V, the activity was increased by chlorine substitution and, as with the halomethyl aromatic hydrocarbons, it was greatly enhanced by the naphthyl radical. The aroyl peroxides were particularly sensitive to temperature effects, because of their thermal decomposition, Although 1-naphthoyl peroxide was usually more active (as evidenced by per cent polymer), 2-naphthol peroxide sometimes gelled first. ~~
Table V.
Photoactivity of Aroyl Peroxides
(Procedure A , sunlight, methyl methacrylate monomer) % Polymera 4? 3? Photosensitizer (1%) min. min. 4.8 8.0 Benzoyl peroxide 2,4-Dichlorobenzoyl peroxide 17.9 32.4 28.9 47.2 1-Naphthoyl peroxide 23.2 41.7 2-Naphthoyl peroxide Benzoin (for commrison) 17.5 25.4 0.0 0.0 Control Temperature rose from 25' to 41" over 65-minute radiation. Separate but simultaneous runs.
The relative efficiencies as photosensitizers of the compounds discussed above were found, in general, to be similar to those of the various acrylate monomers (such as methyl and ethyl acrylate; methyl, ethyl, butyl, and isobutyl methacrylate, and acrylonitrile). Only the results obtained with methyl methacrylate are given, in the interest of simplicity. However, marked differences were observed when the activity with methyl methacrylate, for instance, was compared with the styrene-glycol maleate polymer resins. Already noted was the striking difference observed between benzoin, which is active in both systems, and biacetyl, which is superior in the acrylates but nearly inactive in the styrene-glycol maleate polymer resins. Richards ( 3 7 ) reported that the disulfides varied in relative activity between various monomers. Differences, although not so extreme, were noted among the halogenated compounds. Table VI lists some of the results obtained with the styrene-glycol maleate polymer resins and these photosensitizers. It will be noted that differences in activity occur even between resins of this type. By comparing Table VI with previous tables it is seen that 2naphthalenesulfonyl chloride has good activity in both the acrylates and styrene-glycol maleate polymer resins, being equal to or surpassing benzoin in some resins. On the other hand, 1chloromethylnaphthalene, while an excellent photosensitizer in methyl methacrylate, is poor in the styrene-glycol maleate polymer resins. The formation of surface gels may be due to the influence of oxygen or to the high absorption of light a t the surface. The reason €or the difference in relative activity between monomer systems is not immediately apparent. Styrene and the acrylates are relatively transparent above 3000 A. The maleates, however, still absorb appreciably at 3100 A,, as do some of the inhibitors-e.g., tert-butylhydroquinone-which are used to stabilize the resin systems. Tests involving l-chloromethylnaphthalene in resins t o which no inhibitor had been added gave reasonable rates of photosensitized polymerization, indicating that the inhibitor may be responsible for the differential activity between monomer types, as very low rates of polymerization were obtained with one. However, the marked absorption of biacetyl to over 4500 A. suggests that factors other than absorption, such as polar effects, also may be important. With 1-chloromethylnaphthalene and methyl methacrylate using Corning filters and sunlight, light above 4100 A. produced
Vol. 47, No. 18
INDUSTRIAL AND ENGINEERING CHEMISTRY
2128
Table VI. Variation of Photoactivity with Several Resins (Procedure A, sunlight)
Photosensitizer (1%) pToluenesulfony1 chloride 2-Naphthalenesulfonyl chloride I-Chloromethylnaphthalene a-Chlorohenzyl phenyl ketone a-Bromoheneyl phenyl ketone Benzoin (for comparison) Control A. = Laminac 4116 B. = Selectron 5003 C. = Vibrin 140 nc. no change
--.
Rmin
Resin A
I?
Resin B
C
min.
40 min.
sl. gel
sl. gel
no
no
surf gel
hd. gel
a. gel
surf gel
10
20
min.
min.
min.
nc
no
no
no
a. gel
gel
s. gel
surf gel
no nc
gel hd. pel
no no
surf gel surf gel
nc
nc
nc no slight gel surface gel soft gel hard gel
nc
-
81. gel. surf gel. a . gel. hd. gel.
= = = =
no polymerization. The wave-length range 4100 to 3450 A. was only weakly active, while the range 3450 to 2900 A. contained most of the effective radiation. Radiation with light from a low pressure mercury vapor lamp rich in 2536 A. radiation was ineffective. As had been noted by others (9, 3) in the past, the efficiency of most photosensitizers is enhanced when they are used in combination with an acyl peroxide such as benzoyl peroxide. The activator types discussed above are no exception. The rate of polymerization was found to be a function of the efficiency of the activator, its concentration, and the intensity (see Table VII) and spectrum of the radiation. With average light intensities, the polymerization rate usually reached a maximum a t around 301, sensitizer concentration. With some photosensitizers, such as bromomethyl phenyl ketone, the rate a t high light intensities was nearly constant over a wide range of concentration. However, in general, as the light intensity was increased, the photosensitizer concentration giving a maximum rate of polymerization also increased.
ing color formation. Gregg and Mayo (16) found that nitropropane inhibited the polymerization of styrene. Polymers prepared from both 1- and 2-naphthyl peroxides yellowed rapidly on irradiation, developing about the same color as did benzoin. Polymers containing 2,4-dichlorobenzoyl peroxide were more light-stable. A striking contrast with the tendency of most classes of photosensitizers to develop color on irradiation was noted when biacetyl was used. Although polymers obtained with this photosensitizer were initially a deep yellow, after prolonged irradiation they became colorless. Mayo (26)has pointed out the similarity of the activity imparted by the C 0 0
X-C-
E-,
X-C-
E-,
and X-N-
E-
groups where X is a halogen atom other than fluorine, as photosensitizers for polymerization to the order found by Robertson and Waters (38)for the catalysis of the autoxidation of Tetralinfor example, N-bromosuccinimide was shown to be an excellent catalyst. Benzyl bromide, chloroacetone, and ethyl dichloroacetate after an induction period had good activity, while alkyl halides and benzoyl chloride were poor, Bromides in general were superior to chlorides. Compounds that are efficient photosensitizers for polymerization are also effective sensitizers in other free radical chain reactions. Thus, acetone (61),diamyl disulfide (49), and diphenyl disulfide (41) were found to accelerate the photosensitized addition of the -SH group to an olefin. This suggests that similar reactions, such as the photoaddition of trichlorosilane to olefins (33), would be similarly accelerated. ACKNOWLEDGMENT
The authors wish to acknowledge the assistance of the Office of Naval Research in making available the time of the senior author for a portion of this investigation. LITERATURE CITED
Table VII. Variation of Photoactivity with Concentration (Procedure B General Electric H250 A-6 lamp, methhl methacrylate monomer) 1-Chloromet hylTime to Cure, naphthalene,
%
9
v
0.3 0.03 0.003
1.5 4-1.5%
lauroyl peroxide
Hours 7
9.5 11
24
6
The. photosensitizers vary widely in their activity as chain transfer agents. Gregg and hlayo (16) have shown that, with styrene, benzoin is only a moderately active chain transfer agent. However, some of the alpha-halogenated carbonyl compounds have extremely large chain transfer constants. A check of several polymers obtained in this study indicated (see Table VIII) that while 1-chloromethylnaphthalene is moderately active as a chain transfer agent, dichloroamine-T is extremely active. This fact is borne out by the brittle nature of polymers obtained from methyl methacrylate using dichloroamine-T as a photoactivator. The high percentage of polymer formed before gelation with the naphthoyl peroxides suggests extensive chain transfer, which is supported by previous evidence for 2,4-dichlorobenzoyl peroxide (66). As is common with many halogen-containing organic compounds, polymers in which halogenated photosensitizers were used tended to develop color on prolonged irradiation. 2-Nitropropane when added in small quantities was effective in minimiz-
Adelson, D. E., U. S. Patent 2,236,736 (Aug. 17, 1943). Agre, C.L.,Ibid., 2,367,660 (Jan. 23, 1954). Ibid., 2,367,661. Bates, J. R., and Taylor, H. A., J. Am. Chem. Soc., 49, 2438 (1927). Ibid., 50, 771 (1928). Bock, W., and Tschunkur, E., U.8.Patent 1,898,522 (Feb. 21, 1933). Burnett, G.M.,and LMelville, H. W., Proc. Roy. SOC.,A189, 456 (1947). Chattaway, F. D.,and Orton, K. J. P., J. Chem. SOC.,75, 1053 (1899). Dreisbach, R. R.,U. S. Patent 2,386,448 (Oct. 9, 1945). Dykstra, H. B., Ibid., 1,945,307 (Jan. 30, 1934). Ellis. C..Ibid.. 2.195.362 (March 26. 1940). Evans, M. G.,’Santoppa, M., and Uri, N.; J. Polymer Sci., 7, 243 (1951).
Table VIII. Effect of Select Photosensitizers on Degree of Polymerization (Methyl methacrylate monomer) Polyrnerization c: Initiator System 60 60 60 Noon sun
Noon sun Noon sun
Relativeo Viscosity
2.08 1.34 1.28 1.81 1.55 1.30
1.80 Noon sun 1.18 Noon sun For solution of 1 gram of polymer in 100 ml. of acetone in a size 50 Ostwsld viscometer a t 25O. Acetone required 90 seconds. All samples were polymerized t o completion and no fractionation was made. b Dichloroamine-T.
October 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
(13) Flumiani, G., 2. Elektrochem., 32, 221 (1926). (14) Gee, G., Trans. Faraday Soc., 34, 712 (1923). (15) Gregg, R. A., and Mayo, F. R., J. Am. Chem. SOC.,75, 3530 (1953). (16) Hayes, R. F.,U. S. Patent 2,460,105(Jan. 25,1949). (17) Jeu, K.,and Alyea, H. N., J . Am. Chem. SOC.,55, 575 (1933). (18) Joris, G. G., and Jungers, J. C., Bull. SOC. chim. Belg., 47, 135 (1938). (19) Jungers, J. C., and Taylor, H. S., J. Chem. Phys., 4, 94 (1936). (20) Jungers, J. C.,and Yeddanopalli, L. M., Trans. Faraday Soc., 36, 483 (1940). (21) Kharasch, M. S.,and Dannley, R. L., J. Org. Chem., 10, 406 (1945). (22) Kharasch, M. S., Jensen, E. V., and Urry, W. H., J. Am. Chem. SOC.,69, 1100 (1947). (23) Kharasch, M. S., Reinmuth, O., and Urry, W. H., Ibid., 69, 1105 (1947). (24) Mathews, J. H., and Williamson, R. V., Ibid., 45, 2575 (1923). (25) Mayo, F. R., General Electric Co., private communication. (26) Melville, H. W.,Trans. Faraday SOC.,32, 258 (1936). (27) Mosher; H. S.,and Dykstra, J. S., 126th Meeting ACS, New
York, Abstracts of Papers, p. 55. (28) Olson, A. R.,and Meyers, C. H., J. Am. Chem. SOC.,48, 389 (1926). (29) Ibid., 49, 3131 (1927). (30) Oster, G., Nature, 173, 300 (1954). (31) Oster, G., Phot. Eng., 4, 173 (1953). (32) Owens, J. S., Heerema, J. H., and Stanton, G. W., U. S. Patent 2,344,781 (March 21, 1944).
2129
(33) Pietrusza, E.W., Sommer, L. H., and Whitmore, F. C., J . Am. Chem. Soc., 70, 484 (1948). (34) Pummerer, R., and Kehlen, H., Ber., 66, 1107 (1933). (35) Redington, L.E., J. Polymer Sci., 3, 503 (1948). (36) Renfrew, M. M., U. S. Patent 2,448,828(Sept. 7, 1948). (37) Richards, L. M., Ibid., 2,460,105 (Jan. 25, 1949). (38) Robertson, A.,and Waters, W. A., J. Chem. SOC.,1947, p. 492. (39) Roedel, M.J., U. S. Patent 2,484,529 (Oct. 11, 1949). (40) Rogers, D. C., Ibid., 2,480,752(Aug. 30, 1949). (41) Rueggberg, W. H. C., Chernack, J., Rose, I. M., and Reid, E. E., J . Am. Chem. Soc., 70, 2292 (1948). (42) Reuggberg, W. H. C., Cook, W. A., and Reid, E. E., J . Org. Chem., 13, 110 (1948). (43) Sachs, C. S.,and Bond, J., U. S. Patent 2,505,067 (April 25, 1950). (44) Ibid., 2,505,068. (45) Ibid., 2,579,095 (Dec. 18, 1951). (46)Ibid., 2,641,576(June 9, 1953). (47) Taylor, H.S., and Emeleus, H. S., J. Am. Chem. Soc., 53, 562 (1931). (48) Taylor, H.S., and Hill, D. G.,Ibid., 51, 2922 (1929). (49) Taylor, H. S., and Jungers, J. C., Trans. Faraday SOC.,33, 1353 (1937). (50) Toul, F.,Collection Czechoslov. Chem. Communs., 6, 163 (1934). (51) Vauehan. W. E.. and Rust. F. F.. J. Ora. Chem., 7. 472 (1942). (52) WaGzonek, S., Nelson, M. F., and TheGn, P. J., i.Am.'Chem. SOC.,73, 2806 (1951). RECEIVEDfor review November 8, 1954.
ACCEPTEDJune 13, 1955.
Contribution 1934, California Institute of Technology.
Catalytic Effects of Cobalt, Iron, Nickel, and Vanadium Oxides on Steam Carbon Reaction W. M. TUDDENHAM'
AND
GEORGE RICHARD HILL
Department of Fuel Technology, University of Utah, Salt Lake City, Utah
D
URING the past 33 years the catalytic effect of metal oxides on the steam-carbon reaction has been investigated by a number of individuals ( 1 , 8,6-9, 11-1 6). I n general all the results have been in qualitative agreement although some disagreement has existed as t o the effects of iron and aluminum oxides (6, 11, 18, 16). Iron was judged as a good catalyst by a number of workers (7, 18-14) but Taylor and Neville (16) and Long and Sykes ( 1 1 ) judged i t t o be ineffective in increasing carbon gasification. Of the other catalysts chosen for this study cobalt was found effective by Kroger and Melhorn (7, 8) when mixed with potassium carbonate and cupric oxide or lithium oxide and potassium oxide, and nickel was found effective by Kroger and Melhorn (7) and by Milner, Spivey, and Cobb (IS). While vanadium would be expected t o show catalytic activity i t was not specifically studied in any of the aforementioned work. B y and large previous experimenters have worked with relatively high catalyst concentrations and have given only fragmentary information as to temperature dependence. The purpose of this investigation was t o compare carefully the catal-ytic effects of cobalt, iron, nickel, and vanadium oxides on the steamcarbon reaction in a temperature range from the lowest temperatures practical to make measurements with the apparatus t o its upper limit, 1140' C. Catalyst concentrations as low as 0.013'% are effective in increasing the reactivity of the carbon. Some results that have a bearing on the kinetics of the system are reported. 1 Present address. Western Division Research, Kennecott Copper Corp., Salt Lake City, Utah.
EXPERIMENTAL
Apparatus and Procedure. The primary features and the arrangement of the apparatus are shown schematically in Figure 1. The steam generator, A , was heated by the constant temperature bath, B, t o produce steam at the desired pressure. The nonsubmerged portions of the steam generator were maintained at a n elevated temperature b y means of heating coils. The steam then passed into the preheating chamber, C, and thence through the jet, D, impinging on the hot carbon, E, which was clamped in water cooled copper contacts. The temperature of the carbon was controlled by a variable transformer and was measured with a n optical pyrometer. Some of the lower temperatures were measured with a thermocouple inserted through the sample. The reaction chamber was immersed in a circulating water bath. The excess steam was then frozen in the cold trap, F, which was cooled with a dry icepetroleum ether freezing mixture. The products of the reaction were collected in the weather balloon inside the bell jar, G, the pressure in the balloon being measured b y a Dubrovin gage. Test runs made by passing steam over cold carbon and through the freezing chamber showed no measureable pressure build up in G due t o steam alone. Before each run the preheating and reaction chamber as well as the balloon, bell jar, and glass tubing were evacuated to a few tenths of a micron of mercury pressure as measured by a thermocouple gage. At the completion of a run the weather balloon was collapsed, and the gas was forced into an evacuated sample bulb. Residual gas was transferred by means of the Toepler pump. The gas in
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