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gray. These formulations are typical of the one used in this experimental research. I n general these formulations consist of the following ingredients:
higher gloss than the regular production work. The saving in sanding has been estimated to be more than equal to any increase in the cost of the lacquer containing the moisturefree nitrocellulose and higher evaporating solvents.
REDUCINQ LACQUER THINNER INORWDIENT INOREDIENT Parts by weight 20-25
Pentasol Toluene Petroleum naphtha Xylene
,..
6-6.5 3-3.2 4-5.0 7-12.0
...
20-30.0 5-10.0
35-40
10-15 10-15 5-10
,..
... 15-20 20-25 20-25
...
Several automobile manufacturers have used these formulations on their production line. I n one instance forty cars ,were sprayed and finished without sanding. The results obtained were satisfactory and in accord with the laboratory spray tests, and in many cases the iilm was smoother and had
VoI. 27, No. 2
ACKNOWLEDGMENT
The authors are indebted to The Sharples Solvents Corporation of Philadelphia, which financed this work, for permission to publish this paper. LITERATURE CITED (1) Hercules Powder Company, method obtained by private communication. (2) Hochwalt and Marling, U. S. Patent 1,961,120 (May 29, 1934). R ~ C E I V ESeptember D 21, 1934. Presented before the Diviaion of Paint and Varnish Chemiatry at the 88th Meeting of the American Chemical Society, Cleveland, Ohio, September 10 to 14. 1934.
Effect of Continued Heating on Asphalts ALFREDW. SIKES'AND CALVINH. COREY,~ Western Electric Company, Chicago, Ill. Continued heating, at the temperature and under ihe conditions of the experiments reported here, appreciably affects many properties of certain asphalts and asphaltic materials. Of the materials and the characteristics studied, it was found that aiscosiiy and penetration changed most rapidly for the first few days or weeks of heating, whereas flash points were least affected, even after many weeks. The softening points changed regularly but markedly throughout the kst. A general decrease in acidity, which finally reached a constant figure, after an initial increase in the case of the two asphalts was noted in each of the rnaferials examined. It is realized that the results here reported may not be duplicated with different materials or under other conditions of heating.
T
HE authors recently became interested in
ascertaining the extent of the changes to be expected in some of the general physical and chemical properties of asphalts and asphaltic compounds resulting from heating such materials for varying periods of time a t elevated temperatures. From theoretical considerations it would seem probable that many of the characteristics of a given asphalt would change considerably under such conditions of heating, and experience based on general observation has borne out this supposition. A fairly comprehensive review of the literature, however, has revealed few data in standard reference works or in the periodical literature for the past twenty-five years concerning the extent of the progressive changes i n t h e p r o p e r t i e s of 1 Present address, Engineering Division, Publio Works Administration, Washington, D. C. 1 Prewnt address, Univenity of Michigan, Ann Arbor, Mich.
asphalts which are brought about by continued heating a t definite temperatures. Abraham (1) has tabulated a summary of the chemical changes that occur upon subjecting bitumens and pyrobitumens to increasing temperatures. He does not, however, give any data concerning the time of heating involved or the magnitude of progressive changes resulting in various properties due to continued heating a t definite temperatures. Some work was reported in 1917 by Hixon and Hands (3) concerning changes in certain chemical and physical properties resulting from heating various asphalts a t temperatures up to 300' C. (572" F.), but the time of heating in each case was limited to 5 hours, which is too short a period to use as a basis for predicting changes that might occur in similar materials after days or weeks of heating a t any given temperature. Spiel-
I20
100
M
10
40
20
0
0
IN PROPERTIES OF AN ASPHALTOF 91 O F. SOFTENING FIQURE 1. CFIANQES POINT ON C O ~ N U EHEATINQ D AT 340 O F.
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mann 14) gives examples of t h e c h a n g e s caused by heating asphalt a t 177" to 205' C. (350.6' to 401" F.) for 7 hours. Other ex100.2 amples cover the changes found after heating to 350" and 400' F., but the time of 100.0 heating is not given. Table X (4) gives data indicating the correlation of aging and effect of heat on asphalt, but the maximum time of PO* heating is only 14 hours. Carter (9) reports an investigation wherein many properties are determined upon asphalts before 99.6 and after heating for 100 hours a t 325" F. H o w e v e r , this work. does not show prog r e s s i v e c h a n g e s o v e r a long period of 09.4 time. In order to obtain actual data to indicate to what extent various properties of given 90.2 asphalts change progressively on heating, a series of experiments was undertaken for the purpose of determining quantitatively, under 0 I] controlled conditions, the magnitude of certain effects due to the continued heating of c h o s e n a s p h a l t i c materials. The results FIGURE 3. CHANGES IN PROPERTIES OF AN ASPHALT-ROSIN-ROSIN OILCOMPOUND ON CONTINUED HEATING AT 340' F. and conclusions reported make no claim to being comdete with reference to the changes OF MATERIALS BEFORE HEATING to be expected in various properties of a&halts as a result TABLEI. CHARACTERISTICS DETERMINED of continued heating, nor do they necessarily imply that all VALUES COMPOUND types of asphalts or asphaltic materials will give correspond- T ~ S T 9l0F. 106' F. (TYPICAL METHOD or TBBT ing changes in properties under similar conditions of heat- N o . CHARACTERISTICasphalt asphalt ANALYaIa) 1 Softening point (R & B). ing. They are presented only with the thought that they F. 91 106 184 A. S. T. M. D36-266 . . A. 9. T.M. D70-27 >1.000 >1.000 2 Sp.gr. may be of some value to others who may desire specific data 3 Penetration: in this connection. 32' F 200 grams 60 see 74 80 CHARACTERISTICS OF MATERIALS BEFORE HEATING The asphalts of 91' and 106" F. softening points, so designated for easy reference in the figures, were produced by the steam distillation of asphaltic-base, Midcontinent crude petroleum and were found to have the properties given in Table I. The asphalt-rosin-rosin oil compound was composed of 85 per cent steam-distilled petroleum asphalts similar to those mentioned, 10 per cent grade FF (wood) rosin, and 5 per cent second-run rosin oil. This material was
4 5
6
77O F" 100 grams' 5 see '298 115' 2 60 grams: 5 sec: F l a s h p d h , F. 560 Lossonheating 9' Ductility (at 77'O $.),om. ,
.. . ..
124
5i8 loo
440 A , S. T. M. DQ2-24b A. 8. T. M. D6-27 4',5 A. SATAW. D113-
80 at 50 at A. S?+.h DS8-26b . 300' F. 400' F. Neutral Neutral . l to litmus to litmus 9 1.7 0.55 6.7A.S.T.M.Dl8827T (method B) b 10 Soly. in CSI (total 99.92 A.S. T . M. D4-27 bitumen), % (method 1) b a Boil 20 grams of aspha!t with 50 cc. of distilled water for 10 minutes and test water extract with litmus paper. b These tests were also made on the materials subsequent to heating. 7
S
Viscosit (Saybolt Furolf: see. Reaction of water extract Acid No.
..
..
600
120
500
I00
..
made by mixing the ingredients for a short time a t a temperature just under 420' F. and pouring the resultant compound into metal pans to cool; then a representative sample has approximately the characteristics given in Table I, column 5 , designated "Compound."
METHODOF HEATING The experiments consisted in heating, without stirring, a 5-gallon sample of the material under test in a low-carbon steel container that just fitted inside an electrically heated, thermostatically con60 300 trolled, laboratory-type drying oven provided with insulated walls and double doors. The container was cubical in shape, open at the top, with sides about 12 inches long and '/Isinch thick. It was zoo about two-thirds filled with the material under test and was specifically designed as being a small-scale model of the large tanks used in industrial roc20 esses. This construction kept out light anxprevented the free circulation of air, as the doors were opened only for very short periods for the purpose of sampling. A single-point temperature recorder, 0 0 actuated by a base-metal thermocouple extending A 0 A through the top of the oven t o a point just above 0 the surface of the asphalt, was used for obtainin INPROPERTIES OF AN ASPHALT OF 106 a F. SOFTENINQ a permanent record of the temperature, maintaines FIGURE 2. CHANGES continuously at 340" P o r n ON CONTINUED HEATINQ AT 340 a F. 5" F. This arrangement 400
80
40
IO0
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7. CHANGES IN PENETRATION AT 77' F., 100 GRAMS, FIGURE 4. CHANGES IN ACIDNUMBER OF ASPHALTIC MATERIALS FIGURE 5 SECONDS, OF ASPHALTIC MATERIALS ON CONTINUED HEATING AT ON CONTINUED HEATINGAT 340 F. 340' F.
I ------___------
n
B I
_--
500-
- -.__./.--
___._._.__-.. ___._._._.-.
-.-.-..-.-.
-
_-
_____
400
01.F. S M T E N I N O POlNT ASPHALT. IO8.F. S O F T E N I N G P O I N T ASPHALT. ASPHALT-ROSIN-ROIIN OIL COMPO OU UN NDD..
10
0
20
10
40 SO 60 NO.OF D A Y S HEATED C ONTlNUOUSLI CONT~NUOUSLI
70
FIGURE 5. CHANGES IN FLASH POINT OF ASPHALTICMATERIALS ON CONTINUED HEATING AT 340' F.
_-___
\
Q
Bl'F. SOFTENINQ POINT ASPHALT IOFKSOFTENING POINT A S P H A L T ASPHALT-ROSIN-ROSIN OIL C O M P O U N D
\
i 0
10
3N0.01 0 D A V S40HEATED CONTINUOUSLV 50 60
70
FIGURE 8. CHANGES IN PENETRATION AT 115' F., 50 GRAMS, 5 SECONDS, OF ASPHALTIC MATERIALS ON CONTINUED HEATINGAT 340" F. I
FIGURE 6. CHANGES IN PENETRATION AT 32" F., 200 GRAMS, 60 SECONDS, OF ASPHALTIC MATERIALS ON CONTINUED HEATING AT 340' F. gave an accurate indication of the temperature, as thermal equilbrium was maintained a t all times. Samples were taken from the container after each 10 days of heating, for a period of about 2 months. These samples were placed immediately in clean, air-tight containers and were examined soon after they had cooled. Each sample of material was subjected to certain physical or chemical tests to determine the changes occurring in those properties which were of greatest interest or were considered most likely t o be affected by continued heating. The total amount of any one material removed for test did not exceed one gallon-that is, 20 per cent of the material in the container. The seven tests and methods used in each determination are the same as are given in columns 2 and 6 of Table I (tests 1, 3, 4, 6, 7, 9, and 10).
EFFECTS OF CONTINUED HEATING Figures 1, 2, and 3 indicate the extent t o which various characteristics of the three materials investigated were affected by the continued heating. Not all of the materials
NlNG POINT AJPHALT SIN-ROSIN
0
I
1
20
30
I
I
I
.Lo 50 e0 NO. O F DAYS H E A T E D C O N T I N U O Y 3 L I
O i L COMPOUND
I 70
FIGURE9. CHANGESIN SOFTENINGPOINTOF ASPHALTIC MATERL4LS 0.V CONTINUED HEATINGAT 340' F. were tested for each property listed in the foregoing, but, in general, it was noted that the following changes occurred: The acid number, after a n initial increase in two cases, decreased considerably; the ductility decreased markedly; the flash point did not change much throughout the test; the penetration values decreased rapidly; the softening
February, 1935
I N D U S T R I A L ANI) E N G I N E E R I N G
point increased regularly and quite markedly, and the viscosity increased rapidly. The portion of the asphaltic compound soluble in carbon disulfide, designated “total bitumen” for convenience, varied between 99.6 and 99.9 per cent without apparent congruity. Figures 4 to 9 give the individual variations among the three materials for most of the characteristics under (observation. The results, with one exception, were found to be in agreement with the preliminary expectations concerning the type of change that would be apt to be brought about by continued heating. 1.n accordance with general belief, it was thought that the acid number of the materials, particularly the two asphalts, would tend to increase over :t period of time at elevated temperatures. Nevertheless, the results revealed the opposite trend, after initial increases for the asphalts, and the authors are uncertain as to the correct explanation of this phenomenon. However, it is possible that acidic substances were produced initially upon heating and that they were volatilized later and escaped continuously from the oven throughout the duration of the test, especially a t the time the doors were opened for sampling. It may be, also, that asphaltic materials which are heated for long periods in the presence of sufficient air, or sunlight, will show a subsequent rise in acidity due to the generation of more actively acidic materials through oxidation or photochemical effects.
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It is hoped that other laboratories will be interested in examining typical asphalts that are commercially available with a view toward augmenting the data here reported, or for the purpose of ascertaining the direction and magnitude of changes in such other properties of the materials as may be of interest. It would be especially valuable to determine what changes in acidity would occur in asphalts heated continuously in the presence of the optimum amounts of air and sunlight. ACKNOWLEDQMENT The authors are indebted to the Western Electric Company for facilities and encouragement while carrying out this investigation and for permission to publish the data obtained. LITERATURE CITED
.
(1) Abraham, Herbert, “Asphalts and Allied Substances,” 3rd ed., n. 44. h-ew York. D. Van Nostrand Co.. 1929. (2) C&er,’L. E.,Olson,J. W., Hardlng, C. F., and Shreve, R. K., Eng. Bull. Purdue Univ., 16, No. 6 (h-ov., 1932). (3) Hixon, A. W., and Hands, H. E., J. I ~ DENG. . CHEM.,9, 651-5, esp. 653 (1917). (4) Spielmann, P. E., “Bituminous Substances,” Chap. IV, esp. pp. 54, 58-68, 75, New York, D. Van Nostrand Co., 1925. RECEIVED October 8, 1934. A paper under this title was presented before the Division of Industrial and Engineering Chemistry a t the 86th Meeting of the American Chemical Society, Chicago, Ill., September 10 to 15, 1933.
Utilization of Agricultural Wastes I. Lignin and Microbial Decomposition MAX LEVINE,G. H. NELSON,D. Q. ANDERSON,AND P. B. JACOBS Agricultural By-products Laboratory, Bureau of Chemistry and Soils, United States Department of Agriculture, and Engineering Experiment Station, Iowa State College, Ames, Iowa Schrader in 1921 (cited by Phillips, 7 ) reported that bacN T H E following discussion both natural and prepared lignins are considered, and it should be borne in mind that teria were incapable of breaking down prepared lignin (Willthe results obtained with prepared lignin are not neces- st5itter method) in 25 days. Phillips, Weihe, and Smith in 1930 (8) concluded that sarily applicable to natural lignin. The fate of l i g i n when exposed to the action of bacteria “under proper conditions soil organisms are capable of dehas attracted the attention of numerous investigators, but composing lignin as found in plant materials. Under suitable their observations, as reported in the literature, are in dis- conditions the rate of decomposition of the lignin may be as agreement. It is not the intention here to review in detail the great as that of the cellulose (Cross and Bevan) and pentoliterature on this subject, but the following excerpts may serve sans.” Their experiments were made under aerobic condito outline the present status of the problem. Waksman and Tenney in 1926 (IO) atI n the course of studies on the utilization qf f a r m wastes, especially tested to the extreme refractory nature of the production of fuel gas by fermentation, attempts to develop a spelignins: “Lignins are not decomposed in the cific anaerobic lignin-digesting jlora were unsuccessful. soil, a t least within the experimental period Alkali lignin, when added to an actively digesting sludge, produced of 32 to 35 days. If they are decomposed a t all, the amount of decomposition is only practically no gas, even under optimum conditions; furthermore, when insignificant in comparison with the decomsuch alkali lignin was used in conjunction with .fermenting cornstalk position of the other constituents of natural jlour or packing-house sludge, the gasification of the latter materials was organic matter.” I n 1929 Waksman and markedly inhibited. This depressitre effect is apparently not due to a Stevens (15) declared that “under anaerobic toxic action of the lignin on the bacterial jlora, but is presumably due conditions lignins do not decompose a t all, or only in mere traces, owing to the abto chemical combination, with the possible production of complexes very sence of s p e c i f i c organisms, while under resistant to microbial decompos it ion. aerobic conditions the lignins are slowly A considerable portion of the reported losses in lignin, attributed io decomposed, but here as well they are found microbial decomposition, may be explained by the technic of selection and to be the most r e s i s t a n t group of plant preparation of the sample f o r lignin analysis. constituents.”
I
