August 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
desulfurization conditions are not t o be considered optimum or final; future investigation will probably establish improved conditions. Because vanadium oxide is also an effective dehydroaromatization catalyst (15),further manipulation of the process variables could lead t o a significant increase in the aromatic fraction and consequently to an improved clear octane rating. CATALYTICALLY CRACKEDGASOLINE. West Texas catalytically cracked gasoline was desulfurized under the desulfurization conditions employed for the thermally cracked gasolines-namely, 480” C., 200 pounds per square inch gage pressure, and 0.8 liquid hourly space velocity. Complete experimental data can be found in Table I11 (experiment 39). As in the case of thermally cracked gasolines under these conditions, about 90% desulfurization was achieved. The bromine number, and consequently the olefin fraction, decreased only slightly, resulting in a small drop in the clear octane rating. Thus, catalytically cracked and thermally cracked gasolines behave similarly when subjected to the aame desulfurization conditions, B
PROCESS VARIABLES
The variables affecting the hydrodesulfurization process are pressure, temperature, space velocity, and mole ratio of hydrogen to hydrocarbon. The effect of pressure on the hydrosulfurization of both straightrun and cracked gasolines at constant temperature and space velocity has been discussed (see Tables I and 11, and Figures 2 and 8). The effect of temperature on the hydrodesulfurization of Santa Maria thermally cracked gasoline is presented in Figure 9. At a constant pressure of 400 pounds per square inch gage and apace velocity of 1.0 there wa9 an increase in desulfurization from 17.0 to 42.1% as the temperature was raised from 375” to 425” C. Figure 10 illustrates the effect of space velocity on the hydrodesulfurization of Santa Maria thermally cracked gasoline. At a constant temperature of 400” C. and pressure of 400 pounds per square inch gage the desulfurization reaction was improved from 15.8 t o 98.8% by reducing the space velocity from 1.5 to 0.25. It was illustrated, in the case of the cracked gasolines, that by raising the temperature from 400’ to 480” C. the space velocity could be increased from 0.25 to 0.8 and still achieve over 90% desulfurization. No attempt was made to investigate the effect of mole ratio of hydrogen t o hydrocarbon on the desulfurization reaction.
1695
ACKNOWLEDGMENT
The authors wish to thank the Universal Oil Products Co. for the gasoline samples, and the Sinclair Refining Co. for determining the octane numbers of the gasolines. LITERATURE CITED
(1) Am. SOC.Testing Materials, Philadelphia, “Standards,” Test
D 67 (1949). (2) Ibid.. Test D 90-47T. I b i d . , Test ES 45A. Borgstrom, P., and Reid, L. S., Oil Gas J., 26, 4, 352 (1927). Byrnes, C. P., IND.ENQ.CHEM.,35, 1160 (1943). Dinneen, G. U., et al., Anal. Chem., 22, 871 (1950). Fink, D. F., et al., I b i d . , 22, 850 (1950). Gruse, W. A., and Stevens, D, R., “Chemical Technology of Petroleum,” p. 114, New York, McGraw-Hill Book Co., 1942. Haines, W. E., Wenger, A,, Helm, R. V., and Ball, J. S., Bur. Mines, R e p t . Invest. 4060. Hakewill, H., and Rueck, E. M., Am. Gas Assoc. Proc., 1946, 629-38. Komarewsky, V. I., Bos, L. B., and Coley, J. R. J . Am. Chem. SOC.,70, 428 (1948). Komarewsky, V. I., and Coley, J. R., I b i d . , 70, 4163 (1948). Komarewsky, V. I., and Knaggs, E. A., IND.ENQ.CHEM.,43, 1414 (1951). Komarewsky: V. I., Price, C. P., and Coley, J. R., J. Ant. Chem. Soc., 69, 238 (1947). Morrell, J. C., and Grosse, A. V. (to Universal Oil Products Co.), U. 8. Patents 2,157,204, 2,157,940, 2,157,941 (May 9, 1939); 2,394,170 (Feb. 5, 1946). Reed, R. M., O i l Gus J., 44, 219 (1946). Seyfried, W. D., “A.P.I. Project 48 on Synthesis, Properties and Identification of Sulfur Compounds in Petroleum,” p. 17, Division of Petroleum Chemistry, AM.CHEM.SOC., April 1949. Sinclair Refining Go., Harvey, Ill., Sinclair Laboratories Test Method, Determination of Octane Rating, Micro Research Method. Thacker, C. M. (to Pure Oil Go.), U. S. Patent 2,411,236 (Nov. 19, 1946). Thomas, C. L. (to Universal Oil Products Co.), Ibid.,2,377,113 (May 29, 1945). Universal Oil Products Co., Chicago, Ill., “Laboratory Test Methods for Petroleum and Its Products,” Method W-44-40 (1947). Wulff, C. (to I. G. Farbenindustrie, A.-G.), Grer. Patent 596,094 (April 12, 1934).
RECEIYED for review December 11, 1953. ACCEPTEDApril 26, 1954. Presented before the Division of Gas and Fuel Chemistry a t the 122nd Meeting of the AMERICANCHEMICAL SOCIETY,Atlantic City, N. J. The sixth in a series on “Vanadium Oxide, a Hydrogenation Catalyst.”
Catalyst Studies in VinyltolueneDrying Oil eactions F. J. BUEGE Coatings Technical Service, T h e Dow Chemical Co., Midland, Mich.
A S Y data have been published during the past decade describing the modification of drying oils and alkyds with styrene (1-5, 7 ) . I n recent months a similar program has been carried on in which drying oils and alkyds have been modified with styrene’s counterpart, vinyltoluene (methylstyrene). Oils modified with vinyltoluene combine the flexibility and adhesion of the oil with a measure of the chemical inertness, color retention, and durability of the polymer. I n general, these vehicles perform very satisfactorily in applications normally requiring the use of a long oil alkyd. I n the reaction of vinyltoluene with drying oils, products of improved homogeneity are usually obtained when certain peroxide catalysts are added to the reactants. I n order t o select a
catalyst which performs most satisfactorily in this type of reartion, a concerted effort was made to evaluate a number of different organic peroxides in the vinyltoluene-drying oil reaction and rate them according t o their degree of performance. FACTORS CONTRIBUTING TO HOMOGENEITY
The extent to which vinyltoluene can react with drying oils t o form clear products of potential significance in the coating industry is dependent upon a number of factors: 1. 2
3.
Type of oil Ratio of oil t o vinyltoluene Method of monomer addition
4. 5.
Temperature of reaction Catalyst
INDUSTRIAL AND ENGINEERING CHEMISTRY
1696
TABLE 1. YINYLTOLUEKE-DRY~XG OIL COPOLYMERS PREPARCU WITHOUT
Oil Type Cottonseed Alkali-refined soybean Safflower Alkali-refined linseed G-H vise. dehv-
Iodine No. 105-116
TABLE
CATALYST
fiIononierOi! VisRatio cositya 50/50 B
Copolynier Clarity Milky white
Film Clarity Hazy
125-136 145-150
50/50
50/50
A A
Cloudy Clear
Hazy .Hazy
175-180
50/50
B
Clear
S1. hazv
50/50
I
Clear
Clear
40/60
S
Si. cloudy
Clear
50/50
1-
Clear
Clear
Alkaiccefined lin50/'50 F Clear Clear seed/tung, 70/30 a 60% nonvolatile in mineral spirits. Polymerization temperature 180' C. during monomer addition. Finished off a t 230' C.
The type of oil used in a react-ion is the most significant variable to be considered. The oil constituent in many formulations constitutes 50% or more of the copolymer; consequently, variations in the chemical structure of the oil, such as the degree of unsaturation, type of unsaturation, and viscosity, all have a marked effect upon the nature of the product. In Table I products are described which were prepared without the use of a catalyst by reaction of equal parts of vinyltoluene with oils of varied degrees of unsaturation and conjugation. Conjugated oils, as well a8 blends of conjugated and unconjugated oils, react readily with vinyltoluene to form compatible products which produce clear dried films, The reactivity of vinylt,oluene with the unconjugated oils is of a leseer degree and appears to be a function of the iodine value of the oil. For example, oils such as cottonseed, soybean, and saffiower oil, which have iodine values less than 150, produce hazy products, while linseed oil, which has an iodine value above 150, produces clear solutions wit'h a slight haze in the cured films. The uncatalyzed reaction of vinyltoluene with heat-bodied, unconjugated oils shown in Table I1 always results in cloudy products. This tendency of higher viscosity oils to produce hazy product>swhen they react wit,h vinyltoluene without the use of a cat,alyst is believed t o be due to the more limited solubility of the higher viscosity oils for any homopolymer fraction of the product which might, be formed under these conditions. Products of excellent clarity, however, are produced when small amounts of organic peroxides such as di-fed-butyl peroxide are added. These products have higher viscosity, faster drying rates, and in general greater utility for protective coating than do the copolymers based upon unbodied oils. The viscosity build-up of copolyniers containing heavy-bodied oils, however, is so rapid that forinulation must be confined to the lower ratios of monomer to oil to avoid gelation. The effect of the ratio of oil to vinyltoluene upon Che homogeneity of the product varies from oil t o oil. I n Table I11 the clarity of products prepared from a broad range of oils modified
11. COMP.4TIBILITY O F yIKYLTOLVESl?2 HEAT-BODIED LINSEEDOIL
Oil Constituent Alkali-refined linseed
Q vim. bodied linseed
2-2
vise. linseed
Cottonseed Soybean Safflower Linseed
V.T.
WlTH I < A W A K D
%
MonomerOil Ratio
Catalysta
50/50
0
50/50
1
45/55 45/55
0
45/55
3
35/65 35/65 35/65
3 0
Viscosityb
1
bodied
Copolymer Clarity Clear Clear
81. hazy Clear
I
F
Opaque Clear Clear
Hazy Clear Clear
J L
Opaque S1. hazy Clear
Hazy Clear Cleai
0
0 1.5
Film Clarity
B C
T
4 Di-teri-butyl peroxide % based on monomer. b 6 0 r 0 nonvolatile in mineral spirits, Gardnei IIoldt temperature during monomer addition t o 180° C.
I'olynienaation
with vinyltoluene from 30 to 60% is described. I n manyseries the clarity of the product is improved as the ratio of the monomer to oil is increased. The stepwise or slow continuous addition of vinyltoluene to the hot oils is preferred over the mass monomer addition for producing homogeneous products. The basis for this phenomenon is twofold. By portionwise monomer addition the ratio of unreacted monomer to the oils in the reaction keltle is kept always a t a low constant, thereby reducing the tendency for homopolymerization. Because the catalyst is added with the monomer in small increments, its effectiveness in the reaction is more easily conserved. The tendency of higher temperatures t,o increase the rate of polymerization and reduce the molecular weight of the copolymers is familiar in the field of polymerization. I n each reaction involving vinyltoluene and drying oils a number of variables are brought t o bear upon the chemical nature of the finished product,. The interpretation of the data presented on catalystmeshould, t,herefore, be made in the light of these observations, as the effectiveness of a catalyst is always closely relat,ed to the particular conditions under which it is evaluated. PROCEDURE
I n the evaluation of catalysts, the variables, except for the kind and concentration of peroxide, were kept to a minimum. The oil constituent for the bulk of the reactions was a commercial heat-bodied linseed oil of Q viscosity. The vinyltoluene monomer had the following physical properties: Isomers Purity Molecular weight Specific gravity, 2:/25O C. Pounds per gallon a t 25' C. Refractive index a t 35' C. Boiling point, ' C. at 760 mni. Flash point, Cd Freezing point, C. Viscosity a t 25' C., cps. Inhibitor content
TABLE 111. CONPATIBILITY O F COPOLYblERS CoKTAIlrINQ\'.4RIED 30% Soln. Clear Clear Slight haze Clear
Vol. 46, No. 8
40% V.T.
50% Film Soh. Film Soh. Hazy Clear Hazy Clear Ckear Hazy Clear Hazy Slight haze Slight haze Blight haze Clear Very slight Clear Clear Clear haze
Fish oil, 180-190 iodine No. Slight haze Clear Slight haze Clear Dehydrated castor G-H Clear Clear Clear Clear Tall Oil Pentck ester Clear Clear Clear Clear Catalyst. 2 % di-tad-butyl peroxide based on monomer. Polymerization temperature 180' C.
m- and p-methylstyrene 99% mixed isomers
O_.S?O 118 (polymer 1.027) 1.4 1.534 (polymer 1.581)
170-171 60 -82.5 0.770 10 p.p m. tert-butylcatechol
T'INYLTOLUEKE RATIOS V.T. 6070 V.T. Film Soh. Film Slighthaze Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear
Slight haze Clear
Slight haze
Gel
Gel
Slight haze Clear
Slight haze
Clear Clear
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
August 1954
A series of copolymers containing 45 parts of vinyltoluene and 55 parts of oil was prepared, in which the kind of catalyst and the catalyst concentration were varied. Four hundred grams of each copolymer were prepared in a I-liter threenecked flask equipped with agitator, thermometer, and reflux condenser. Reactants were heated by thermostatically controlled electric heating mantles. The catalyst and vinyltoluene were premixed before being added stepwise to the hot oils in six equal increments a t 20minute intervals. The temperature of the reactants during monomer addition was held at go", 120", 150°, and 180" C., with the majority of the evaluation carried on a t 150' C. One hour a f t e r t h e final monomer addition, the temperature was raised over a 2hour period to 230" C. and held for an additional 3 hours. The products were evaluated by d e termining the homogeneity of the copolymer and cured films by visual inspection and measuring the solution viscosity at 60% nonvolatile in mineral spirits.
ethyl ketone peroxrde 5.Methyl isobutyl ketone peroxide 6.Uniperox 4. Methyl
9 . 2, 2-bis (tert-butylperoxy IO. Di-tert-butyl diperphthal 1 1 . t e r t - b u t y l hydroperoxid
50
70 80 90 100 I10 I20 CATALYST DECOMPOSITION TEMPERATURE 'C '/zLIFE/4 HRS. IN ETHYLENE DICHLORIDE
60
-
130
140
Figure 1
DISCUSSION OF RESULTS
Products obtained in this series varied in their degree of conipatibility from a two-phase product consisting of an oil phase and a polyvinyltoluene phase to products which had a bright clear sparkle. The viscosities of the copolymers also Traricd from 140 cps. t o a gelled product. An inspection of the accompanying tables and figures shows that the differences in the copolymer properties correlate closely with two variables in the catalyst: (1) decomposition rate of the catalyst, and (2) catalyst concentration. DECOhIPOSITIOI\ RATE OF CATALYST
The rate a t which peroxides decompose (6) can be regarded ass a fairly accurate indication of the effectiveness of the catalyst. In general slowly decomposing catalysts are preferred over the
VISCOSITIES OF COPOLYMERS PREPARED WITH VARIED CATALYST CONCENTRATIONS
1
COPOLYMER I 55 PARTS -'IO LINSEED OIL 45PARTS-VINYLTOLUENE
goo
1697
fasl decomposing ones, because the radicals which are formed at a slower and more uniform rate have a better chance to i n i h t e polymer chains before t,hey are thermally destroyed. Results obtained in this study bear out this theory. From the data shown in Table IV it is seen that peroxides which decompose at a rate less than 250 % per hour at 150' C. or which require a temperature of 100' C. or more for a half life of 4 hours produced the most satisfactory copolymers. The low temperature catalysts, such as those with a decomposition rate of 6000% per hour at 150' C., were too short lived to be effective. Although the data listing the decomposition rates were obtained in ethylene dichloride solution, the rate in a vinyltoluene-oil solvent should follow in much the same order. Some of the more slowly decomposing peroxides which mere found t o be the most efficient catalysts are:
1. 2. 3. 4. 5.
Di-tert-butyl peroxide 2,2-Bis (tert-butylperoxy) butane tert-Butyl hydroperoxide Di-tert-butyl diperphthalate tert-Butyl perbenzoate CATALYST CONCENTRATION
Bo 1 , , 4o i -4variation in catalyst concentration also produced a notice~
GEL
L:G
I
,
I
-
700
~ O N Y O L I T ~ -L6 0E% THINNER --MINERAL SPIRITS
6001
I
I
/
I/
-BUTANE
~
w
q
500
c > 5
8
4w 300
200 100 I
0
0.I
02
0.3
I
I
I
0 4
0.5
0.6
MOLE CATALYST PER LITER VINYLTOLUENE
Figure 2
able effect upon the clarity and viscosity of the copolymer. Its effect upon clarity is shown in Figure 1. Here it is seen that the minimum concentration of catalyst required to produce compatibility varies from one catalyst to another. In general, the high temperature catalysts can be used satisfactorily a t relatively low concentrations (1 t o 2 weight % based on the monomer), whereas much higher concentrations (3 to 6%) are required when low temperature catalysts are use. The extent t o which a low temperature catalyst can be employed satisfactorily by simply increasing its concentration undoubtedly has some limitations. For example, a linseed oil-vinyltoluene copolymer prepared with as much a8 8.3% lauroyl peroxide produces a very incompatible product. It is questionable that a higher concentration would appreciably improve this product.
INDUSTRIAL A N D ENG€NEEW'ING CHEMISTRY
1698
1 20 r
I
Q
I
I
1
20
I
I
80
VINYLTOLUENE - PERCENT BASED ON VINYLTOLUENE
*%CATALYST
V I S C O S I T Y OF A L K A L I R E F I N E D
1
POLYMERIZATION TEMPERATURE
I
- 180°C. ,?
1
60
40
Vol. 46,No. 8
VINYLTOLUENE -PERCENT
Figure 4
Figure 3
-~ 20
V I S C O S I T Y OF "Q" B O D I E D L I N S E E D OIL/VINYLTOLUENE COPOLYMERS P R E P A R E D W I T H D I F F E R E N T CATALYST
VINYLTOLUENE
__
- PERCENT
Figure 5
CATALYST CONCENTRATION V S . COPOLYMER VISCOSITY
As the catalyst concentration of some of the higher temperature catalysts such as di-fert-butyl peroxide and 2,2-bis (tertbutylperoxy) butane is increased above the minimum required to produce compatibility, other changes in the properties of the
Figure G
product are observed (see Figuie 2). The viscosity of the 56/45, linseed-vinyltoluene copolymeis is found t o be increased from 150 cps. a t 60y0nonvolatile in mineral spirits to a gelled product by merely increasing the catalyst concentration I n the field of homopolpmerization the reverse is true-Le., increased catalyst concentrations result in the formation of a g o l p e r of lower
INDUSTRIAL AND ENGINEERING CHEMISTRY
August 1954
O F CAT.4LYST DECOMPOSITION TABLEIv. EFFECTS TEMPERATURE UPON PRODUCT CLARITY
Decomposition Temp O C.;' 130 105 108 107 115
Decomposition Rate,
Product Film Catalyst %b Clarity Clarity Di-tert-butyl peroxide Clear Clear tert-Butyl perbenzoate 7:' Clear Clear Di-tert-butyl diperphthalate 210 Clear Clear 2 2-Bis-tert-butylperoxy butane 90 Clear Clear t;rt-Butyl hydroperoxide 70 ClFar Clear Cumene hydroperoxide 94 260 Slight hazy Clear Benzoyl peroxide 77 13,600 Cloudy Hazy iMethyl isobutyl ketone peroxide 85 6,000 Cloudy Hazy 83 0,500 Cloudy Hazy Methyl ethyl ketone peroxide Dichlorobenzoyl peroxide 82 13,000 Cloudy Hazy Lauroyl peroxide GO 20,000 Cloudy Hazy Copolymer. Q bodied linseed-vinyltoluene, 55/45. Polymerization temperature. 150' C. during monomer addition. Finished off a t 230' C. Monomer addition. Stepwise, six equal increments a t 20-minute intervals. Catalyst concentration. 3% based upon monomer. a
b
TEMPERATURES UPON TABLE17. EFFECTOF POLYNERIZATION PRODUCT CLARITY
150 180 90 150
180 90
150
180
90 150 180
Copolymer Clarity Very cloudy None Cloudy None Cumene hydroperoxide Very cloudy Cumene hydroperoxide Slightly cloudy Cumene hydroperoxide Clear Benzoyl peroxide Very cloudy Benzoyl peroxide Cloudy Benzoyl peroxide Clear Lauroyl peroxide Phase separates Lauroyl peroxide Phase separating Lauroyl peroxide Cloudy Catalyst
IOMER-PERCENT
35
I
I
CENTIGRADE
I
I
I
I
TIME OF MONOMER
,
I
POLYMERIZATION
I
30
25
I I I
20
l
1
I
J
5
6
7
VINYLTOLUENE
\,
- 4 5 ~
15
Half life, 4 hours in ethylene dichloride. % decomposed per hour a t 150' C. in ethylene dichloride.
Reaction Temperature during Monomer Addition, C.
1699
Film Clarity Very hazy Very hazy Haey hazy Clear Clear Hazy Hazy Hazy Hazy Hazy Hazy
IO
5
0 0
I
I
1
2
I
3 4 TIME HOURS
-
Effect of Catalyst upon Polymerization Rate
Figure 7.
Copolymer. Q bodied linseed-vinyltoluene, 55/45. Catalyst concentration. 3% by wt. based upon monomer.
average molecular weight with a reduced solution viscosity. In a copolymer reaction of this type this phenomenon does not follow. Although the physical chemistry of this reaction is not completely understood, it is highly probable that the copolymer of the higher viscosity formed in the highly catalyzed reaction is a result of more complete interreaction between the oil and the polymer. The oil molecule with a sufficient number of activated points can become trifunctional in nature, reacting with the polymer to form a gel. The tendency for di-tert-butyl peroxide t o increase the viscosity of the copolymer to an insoluble gel can also represent some formulating limitations. For example, it is shown in Figure 3 that vinyltoluene can be formulated with Castung G-H up to 75% vinyltoluene without forming a gelled product and incidentally without forming a hazy product when no catalyst is used. However, a8 di-tert-butyl peroxide is added, the per cent of vinyltoluene which can react with dehydrated castor oil before gellation occurs becomes increasingly smaller as the catalyst concentration is increased. A similar phenomena occur8 with raw,!& bodied, and 2-2 bodied linseed oils. Figures 4, 5, and 6 show that when di-mt-butyl peroxide catalyst is used, gellation occurs a t approximately 80, 60, and 40y0 vinyltoluene content when copolymerized with raw linseed, Q bodied linseed, and 2-2 bodied linseed, respectively. If 3 % cumene hydroperoxide is used, copolymers can be made with as much as 80% vinyltoluene with any of the oils without forming a gelled product. POLYMERIZATION TEMPERATURE
It is difficult to evaluate a single factor such as the catalyst without also showing the effects of other variables. Polymerization temperature, for instance, has a direct bearing upon the ef-
DEHYDRATED CASTOR OIL G - H
1
I
I
2
3 TIME
4 - HOURS
'
-
'
-
60% 40%
I
1
I
5
6
7
Figure 8. Effect of Catalyst upon Polymerization Rate
fectiveness of a catalyst and, therefore, must always be taken into consideration. It would be unfair t o evaluate low temperature catalysts such as benzoyl peroxide and lauroyl peroxide without giving some consideration to low temperature polymerization. Cumene hydroperoxide, benzoyl peroxide, and lauroyi peroxide were all evaluated at temperatures of go", 150°, and 180' C. (Table V). In no instance were the low temperature catalysts more effective when low temperatures were employed.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1700 351
I
I
I
I I
I
I
1
I
I
1
I
!
220
!
TIME OF MONOMER
25
180
GO M PO S IT1ON
-
20
VINYLTOLUENE
DI- tert- BUTYL
\
PEROXIDE
!
I
1
-
50%
,
I
4~
Vol. 46,No. 8
iodine values produce products of improved clarity. Conjugated oils are sufficiently reactive with vinyltoluene in uncatalyzed reactions to form clear products. The product clarity of vinyltoluene-modified Q viscosity linseed oil is improved by increasing catalyst concentration or using catalysts that decompose at slower rates. The viscosity of vinylt,oluene-drying oil reaction products catalyzed wit'h either di-tert-butyl peroxide or 2,2-bis (teifbutylperoxy) butane increases as the concentration of t,he catalyst is increased.
140 BASED O N MONOMER
15
I
1
100 30 -
IO
25
I
I
1
1 I
I
TEMPERATURE*
POLYMERIZATION I
I
/I /
TIME OF MONOMER
ADDITION II
I /
I
I
220
I
180
1
I,
J
I
/
5 140
2
I
I
3
4
TIME
- HOURS
5
6
7
Figure 9. Polymerization Rates of Vinyltoluene with Unbodied and Heat-Bodied Linseed Oil
On the contrary, all products shomd improved claiity ns the temperatures were increased. POLYMER1 ZATIOh RkTES
The effect of catalysts upon the rate of polymerization is shown in Figures 7 and 8. The greatest difference in polymerization rates between a catalyzed and uncatalyzed reaction is observed in the early stages of the reaction before the catalyst has become completely spent. Thirty minutes after the final monomercatalyst addition IS made in a 55/45, Q bodied linseed-vinyltoluene reaction, only 4.2% of the monomer is unreacted. At the same point in an uncatalyzed reaction 16.8% of the monomer is unreacted. Similar differences are shown in Figure 8 where the effect of catalyst is observed in a dehydrated castor oil-Yinyltoluene reaction. As the reaction proceeds to the final ttages, the differences in unreacted monomer are no longer so pronounced. I t may be theorized that in the later stages of the reaction the faster rate of polymeriiation in the uncatalyzed reaction is due to the higher concentration of unreacted monomer. Other factors, such as the viscosity of the oil (Figure 9 ) and the polymerization temperature (Figure lo), also have n marked effect upon the polymerization rate of vinyltoluene. CONCLUSIONS
The film clarity of vinyltoluene-modified unconjugated drying oils is a function of the iodine number of the oil. Oils of higher
I
2
3 TIME
4
- HOURS
5
6
7
Figure 10. Effect of Temperature upon Polymerization Kate
Product clarity of vinyltoluene-modified drying oils is improved by increasing the polymerization temperature. LITERATURE CITED
Bevan, E. A , , Offic. Dig. Federation P a i n t & Varnixh Production Clubs, KO. 314, 165 (1951). Hovey, A. G., and Jerabek, R. D., Ibid., No. 314, 171 (1951). Norris. W. C., Ibid., No. 291, 173 (1949). Patrick, W. H., and Trussell, E. H., Ibid., No. 309, 767 (1960). Peterson, N. R., Ibicl., KO.283, 696 (1948). Tubbs, B. H., and Roche, A. P.,Dow Chemical Co., Midland, Mich., meeting of AM.CHIM. Soc., April 1950. Young, A. E., Ofic.Dig. Federation Paint &: V a r n i s h Production Clubs, S o . 296, 610 (1949). RECEIVEDfor review September 9, 1953.
ACCEPTEDApril 3, 1954. Presented before the Dirision of Paint, Plastics, and Printing Ink Chemistry a t the 124th Meeting of the .49IERIChN C ~ ~ a r 1 c .SOCIETY, 4~ Chicago, Ill.
