Februarv. 1930
INDUSTRIAL A X D ENGINEERING CHEMISTRY
177
Petroleum Hydrocarbons as Diluents in Lacquer' 0. R. Brunkow COMMERCIAL SOLVENTS CORPORATION, TERREHAUTE, IND.
HERE has been considerable uncertainty regarding the use of petroleum hydrocarbons in lacquer. In order that the data presented herewith may be of the greatest value to the industry, it has been necessary to make some comparison on a price basis. A lacquer diluent is a product which, in itself, is not a solvent for cellulose nitrate but may be added to such a solution in suitable amounts, in order t o reduce its cost, without impairing its utility. Yiluents consist chiefly of hydrocarbons, and in the early development of lacquer enamels the coal-tar products benzene, toluene, and xylene were used almost exclusively. Owing to its toxicity and rapid rate of evaporation, benzene was soon eliminated from good lacquer formulas. Although the use of xylene has continued, its evaporation rate is so slow that it can be used to only a limited extent. Toluene has all the characteristics of a good diluent and its use soon became universal in lacquer. The growth of the lacquer industry has probably been unparalleled in the field of protective coatings. This has created an increasing demand for solvents and diluents. The production of the active solvents has expanded as the demand increased, but that of the chief diluent, toluene, has a t times failed to keep pace with the demand. I n fact, there have been periods during the past two years when it was almost impossible to obtain this product in the open market. Some sanguine and farsighted lacquer manufacturers anticipated this situation a few years ago and realized that if the industry was to expand unhampered it would be necessary t o find a satisfactory substitute for toluene as a diluent. Since petroleum distillates had long been used by the makers of paint and varnish, the use of naphtha for this purpose was a natural step. It was found, however, that the use of a petroleum hydrocarbon such as V.M.P. naphtha presented several disadvantages. Petroleum hydrocarbons, in general, have a much lower dilution ratio than toluene, with all of the common cellulose nitrate solvents. Determination of the dilution ratios of twenty samples of naphtha from the midcontinent fields, however, showed the variation to be within the limits of experimental error. Only one sample of naphtha from a California field was obtained and this product gave a dilution ratio about 15 per cent higher than the midcontinent products. These samples ranged from low-boiling distillates, designed as benzene substitutes, up to the higher boiling fractions, such as V.M.P. naphtha. The samples from which the data in this paper were taken were toluene substitutes, and their distillation ranges are given in Figure 1. Second, until recently very little was done by the petroleum producers to make a product with an evaporation range suitable for lacquer. The wide evaporation range of V.M.P. naphtha made it necessary to use an unusually large amount of a very slow evaporating solvent in order to prevent the late precipitation of cellulose nitrate in a drying film.
T
Naphtha Tolerance of Oils, Gums, and Resins
A third objection t o the use of naphtha was occasionally made on the basis of its low solvent power for oils and gums or resins. This objection was more apparent than real, and is 1 Received September 16, 192Y. Presented before the Division of Paint and Varnish Chemistry at the 78th Meeting of the American Chemical Society, Minneapolis, Minn , September 9 to 13, 1929.
shown to be without any foundation because the addition of solvents for cellulose nitrate, in amounts much less than that required to dissolve the cellulose nitrate in a lacquer, is enough to completely overcome this defect. Castor oil, either blown or raw, forms B turbid mixture when naphtha alone is added to it, but the addition of small amounts of toluene, butanol, or butyl acetate forms a clear solution, as shown by the data in Table I. Table I-Quantity of Butyl Acetate Butyl Alcohol or Toluene Required t o Make Clear Solution with Castor Oil and Naphtha (Castor oil, 10 cc.; naphtha, 20 cc.) BUTYL
ACETATE CC. 1 8 7
CASTOR OIL Raw Blown, No. 1 B l o w n , No. 2
BUTYL ALCOHOL
TOLUENE
CC.
cc.
1 5 5
1 22 30
It will be noted that blown castor oil is much less miscible with naphtha than is the raw product. However, this does not prevent the use of naphtha and an oil of this type in the same formula, because the amount of naphtha tolerated by the active solvents in the presence of these oils is much larger than that tolerated by cellulose nitrate in the same solvents; e. g., the least compatible oil in Table I was blown castor oil
No. 1. Ten cubic centimeters of this product required 8 cc. of butyl acetate to make it miscible with 20 cc. of naphtha; whereas it can be seen from Table I11 that in the presence of cellulose nitrate 14 cc. of butyl acetate will be required to toleratethe same quantity of naphtha. Table 11-Amount of Naphtha Tolerated by Solution of G u m s in Toluene, Butyl Acetate, and Butyl Alcohol (Gum or resin, 10 grams; solvent, 5 cc ) SAMPLR KO. TOLUEIE BUTYLACETATSBUTYLALCOUOL CC.
ESTER 1 2 3
20 3 11
CC.
CC.
22
77 12
GCM
S
26
PHTHALIC ANHYDRIDE-GLYCEROL
1 2 3
6 9 17
6 S
10
60 TYPE RESIN
5 5 29
Most gums and resins are insoluble or only slightly soluble in naphtha, but a solution of gum in its solvent will tolerate
INDUSTRIAL AND ENGINEERING CHEiMlXTRY
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more naphtha than would be used in practice, as is indicated by the data shown in Table 11. It will be noted that there is considerable variation in the tolerance for naphtha between various grades of the same gum or resin, but in no case is the tolerance low enough to rule out the use of naphtha. Some of the phthalic anhydride-glycerol type resins, in solution with a single solvent, may show a tolerance for naphtha lower than that of a solution of cellulose nitrate in the same solvent. This does not prevent the use of naphtha in conjunction with these resins, because rarely, if ever, in practice is one solvent and one diluent used. The addition of other solvents and diluents increases the tolerance of the solution, so that a reasonable amount of naphtha can be added without difficulty. New Naphthas
Vol. 22, No. 2
ance from ethyl acetate to butyl acetate, after which the tolerance again decreases as the molecular weight increases. Thia fact, coupled with the decrease in the price of butyl acetate and the increase in the price of toluene within the last few years, makes the use of a certain amount of naphtha attractive a t the present time. Even a t the present price of toluene it is not practicable to replace all of it with naphtha, as is indicated by data in Table IV. Table IV-Economic
Comparison of Toluene a n d Naphtha a8 Diluents PRICEFOR TOLUENE AT
EXCESS COMPN.OF VEHICLE WHICH TOLERANCE CONTAINING NAPHTHA NAPHTHA COXPN. OF FOR BUT HAVING SAME CANBE VEHICLE CONTAINING TOLUENE EXCESS SUBTOLUENE PER 100 CC. TOLERANCE STITUTED" % cc. Yo Cenfs per Pnllnn ._.
o-
Because the use of naphtha as a lacquer diIuent offered a relatively small market, petroleum companies were reluctant to cut a naphtha fraction with a narrow boiling range, which would have an evaporation rate similar to toluene, because the remaining low- and high-boiling fractions were difficult to dispose of. Very recently a few petroleum companies have placed on the market a naphtha that is especially designed to replace toluene. Three such products from different companies have been investigated and their distillation ranges are compared with V.M.P. naphtha and toluene in Figure 1. I n comparison with V.M.P. naphtha, it will be noted that the distillation range has been considerably narrowed in these new naphthas. Only one sample, represented by curve 4, has more than 50 per cent distilling above the range of toluene, and all three products distil completely below 145' C. A portion of each naphtha tested boils above the range of toluene, except that, in the case of No. 4, the percentage is small enough to cause no trouble when a reasonable amount of high-boiling solvent is used. The low dilution ratio of naphtha necessitates the use of an extra amount of active solvents, and when a reasonable proportion of medium- or high-boiling solvent is used the danger of cotton precipitation, due to the presence of the highboiling fraction of the petroleum diluent, is overcome. Use of Naphtha with Other Solvents
The main obstacle, then, to the use of naphtha in lacquer is the low tolerance of lacquer solutions for it, and the consequent necessity for the increased use of active solvents. Table I11 gives a comparison of the dilution ratios with naphtha and toluene for some of the common solvents and mixtures. I n determining these dilution ratios the cellulose nitrate solutions had a concentration of approximately 8 per cent cellulose nitrate when the tolerance limit was reached by the addition of the diluent.
i;::]
% ]
Butyl acetate Toluene l7 Naphtha Butyl acetate 48.3 Butyl acetate 40 56 Butyl acetate 64.2 Toluene 60 Naphtha Butyl acetate 95 Rutyl acetate 79.5 Toluene Naphtha 2G.51 86.0 Ethyl acetate 17 Ethyl acetate 4 8.4 Toluene Naphtha Ethyl acetate 56 Ethyl acetate 63,0 Toluene Naphtha a In this table the following prices apply: butyl acetate, $1.32; ethyl acetate, $0.90; and naphtha, $0.20 per gallon.
1
;i:: 11 i:::]
it:;]
While these data show that it is not practicable to replace toluene entirely with naphtha, a substitution of 50 per cent becomes attractive. Using the same prices as above, the data shown in Table V have been calculated. Comparison of Toluene a n d Mixture of Naphtha a n d Toluene as Diluents PRICEFOR TOLUENE COXPN.OF VEHICLE AT WHICH EXCESS CONTAINING NAPHTHA SUBCOMPN. OF BUT STITUTION TOLERANCE AND TOLUENE VEHICLE CONTAIXING FOR TOLUENEHAVING SAME EXCESS CAN BE TOLUENE PER 100 CC. TOLERANCE MADE Cents per % cc. 7" gallon Butyl acetate 36: Butyl acetate 17 Toluene 31.1 39.3 Toluene h-aphtha 31.7 Butyl acetate 56 Toluene Rutyl acetate 48.8) Toluene Naphtha Table V-Economic
1
i:::]
Butyl acetate Toluene acetate
Toluene
:E: ] ;!,! 1
Ethyl acetate Toluene Ethyl acetate Toluene
95 17
56
2;: :]
95
Butyl acetate ~~l~~~~ iVau htha Ethyl acetate Toluene h-aphtha Ethyl acetate Toluene Nauhtha Ethyl acetate Toluene Naphtha
E6 1 . 0 )t 19.5 19.5c 34.4) 46.0) 27.0.
48.6
60.0
42.2
27.0/ 57.4)
%:8
52.1
It will be seen that it is practicable to use naphtha to replace half the toluene when the latter sells from 40 to 45 cents per gallon. The amount of naphtha actually used will, of course, be determined by the availability and price of toluene and the amount of excess tolerance to be carried in the lacquer.
Ratios of C o m m o n Solvents w i t h Naphtha a n d Toluene SOLVENT NAPHTHA TOLUENE 3.7 1.1 Ethyl acetate 2.9 1 . 4 Butyl acetate 2.2 1.3 Amyl acetate 2.6 0 . 7 Cellosolve acetate 5.3 1.0 Cellosolve 2.5 1.1 Secondary butyl acetate 5.8 0.8 Ethyl lactate 3.4 0.4 Diacetone alcohol 607' Butyl acetate 2.5 1.4 50% Butyl alcohol 50y0 Butyl acetate 2.9 1.3 50% Ethyl alcohol
The writer wishes to acknowledge his thanks for the assistance received in the preparation of this paper from C. D. Bogin, of the Research Laboratories of the Commercial Solvents Corporation.
It is well known that with toluene the dilution ratios of the acetates of the alcohol series decrease as their molecular weights increase. There is an exception to this rule when we come to naphtha. I n this case there is an increase in toler-
The manufacture of carbon dioxide gas and ice in Toronto is planned by Hiram Walker-Gooderham and Worts, Ltd. After the erection of the first plant in Toronto additional units are contemplated for Montreal and other large centers.
Table 111-Dilution
Acknowledgment
