May, 1924
INDUSTRIAL A N D Eh’GINEERING CHEMISTRY
509
T h e Jellying of Asphalt Paints’ Relation of Acidity t o Jellying By Harry C. Fisher T H E RICHARDSON CO.,LOCKLAND, OHIO
main behind by escaping the N E of the types of Sulfuric acid will cause asphalt paint to jelly, no matter which alkali treatment, although bituminous paints of the following receives the acid: ( a ) the base before dissolving i f , this is not probable. widely used in in(b) the soloent before dissolving the base in i f , or (e) the finished 2-The preparation of hard dustry is asphalt paint, paint, cold or hot. The rate of jellying oaries directly as the amount asphalt paint bases by blowwhich is made by dissolving of sulfuric acid added. Under certain conditions other substances, ing soft, steam-refined asasphalt in a petroleum solsuch as sodium hydroxide and sodium sulfate, will cause definite phalt with air involves the vent. I n the manufacture removal of sulfur, free or thickening actions in asphalt paints. combined. (Mexican asphalt of this class of material, Painis from air-blown petroleurn asphalts jelly, the rate dependcontains from traces to 7 per the jellying or “livering” ing upon the formula, the acid content of the fluxes. and the solvent. cent of sulfur.) Part of this of the iinished product, A petroleum asphalt air-blown in contact with lime jellies extremely removal is due to the formawhich sometimes occurs, tion of hydrogen sulfide by slowly compared with the analogous mixture not blown in contact complex reactions with the presents a real problem to with lime. A paint which jellies slowly in an unrefined solvent asphalt, while other parts the manufacturer. This will jelly more rapidly in the same solvent after giving it an acidare due to the direct formajellying may occur within basic refining. ation of sulfur dioxide. B few hours after manufacA jellying, thin paint will precipitate out and remain as two layers, Alexander Smith2states: ture or may develop after an the top a light layer, the bottom a heavy layer. Thicker paints “Hydrogen sulfide dissociextended period of storage. may settle out. but the viscosities of the layers will so increase that ates when heated, the deIt is generally recognized in time the values will be identical. composition becoming quite that a jellied paint differs perceptible a t 310” C. and from a thick paint in that the latter presents no visible structure and displays a ten- increasing with temperature.” It therefore seems quite posdency i,o “run,” though slight, whereas a jellied paint has a sible that liberated sulfur is then free to oxidize to sulfur definite internal structure and is rigid. The progress of a dioxide, and the hydrogen to form water. Water vapor from jellying; action with time can be followed by measurements this reaction and from condensation products of the asphalt of the viscosity in machines such as the Stormer or Mac- may react, by some unknown means, with the sulfur dioxide Michael viscometers. under conditions found in a blowing mill (500’ to 550” F. Practical paint makers have suggested the following points plus slight vacuum) and eventually give acidity to the asphalt concerning the jellying of paints: A paint may remain homo- or react with it and change its character. geneous without change in viscosity (the ideal behavior), With this information in mind, the specific object of this may increase in viscosity without becoming rigid, may jelly investigation was to determine the relation of acidity from either Rpontaneously or gradually, or may thicken or jelly sulfuric acid to jellying in asphalt paints. with the formation of a lower heavy and upper light layer The method of preparing and analyzing the paint and its (syneresis). Suggestions gathered from paint makers in- components follows: clude the opinions that jellying may be caused by excess of 1-The asphalt base was heated until liquid in its original consolvent, or acidity, and that in general cold-made paints, tainer (avoiding excessive fuming), then weighed out into a or those made with carefully refined solvents, do not jelly. quart tin can, and heated to the desired temperature or slightly above it, as the case required. The solvent, a t room temperaCases me mentioned, however, where a nonjellying paint ture, was added from a dropping funnel with vigorous stirring, is produced with an impure solvent. and the stirring continued until the temperature had fallen to a It has been noticed that, when determining viscosities with predetermined value. 2-Any solvent lost by evaporation was replaced and the can a MacMichael viscometer, the surface of the jellied paint closed. seen by reflected light at some point in the process shows tightly 3-The Stormer viscosity was taken after 24 hours and then a progreseion from large flakes or a network of scales through a t intervals as desired. Before each period of testing the instrument was adjusted to record 13 seconds per 100 revolutions,with smaller scales to a homogeneous liquid. A su~nmaryof literature on jellying indicates that the jelly- a standard oil a t 25” C . Six main groups of experiments were performed, the reing of paints is influenced by (1) change in solubility of dissolved material, (2) change in concentration of solution, sults of which will not be reported in full but only the general (3) change in temperature a t which material is dissolved, data given. (4) addition of foreign materials to the solution or its com1-Paints of various characteristics and formulas were preponents, and ( 5 ) entire history of the solution. It is popu- pared under different conditions and allowed to stand for months as experiments in order to observe changes occurring in them. larly believed that the presence of acids, either organic or blank 2-Varying amounts of sulfuric acid were added t o a selected inorganic, in the paint causes it to jelly. This would be group of paints or their components, and the effects of this classed as the addition of a foreign material, or a product treatment, together with temperature changes, concentration of a foreign material, to the solution. It is possible that changes, etc., were observed. 3-Substances other than sulfuric acid were added to paints acids of some nature, probably sulfur acids, may influence and the changes observed. asphalt paints, since 4-A series of bases supposed to contain acid introduced by
0
I-Sulfuric acid is used in the refining of petroleum, where it changes the character of the distillate. Also, traces may re1
Received June 1, 1923.
the blowing process was made into paints, using an unrefined petroleum distillate. 5-A series of bases supposed to contain acids introduced by 2
“Inorganic Chemistry,” p. 416.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
510
the blowing process (same as in Experiment 4) was made into paints, using a sulfuric acid-refined petroleum distillate (solvent from Experiment 4 given a refining with acid and base). 6-The asphalt bases used in Experiments 4 and 5 were tested for acidity.
The following bases and solvents were used: 1
I-BASES FORMULA TREATMENT RESULT 90%-225-300 Pen Air-blown M. p.b = 246O F. Pen = 1 1 . 5 Hard Base Mexicam
2
A Soft Base
No
NAME
.{I ::&
10% Special Flux Oil 100 Pen Mexican Hard Base (No. 1)
Fluxed tonether
Air-blown
c
Air-blown
-
M.p. 175'F. Pen = 50 M. p. = 180OF. Pen = 20 M. p . = 241OF. Pen = 13 M. p. 235'F. Pen = 1 3 . 5
M. p. = 248'F. Pen = 1 4 . 6
Air-blown in Mexican contact Hard Base { 130 pounds, CaO to 3000 with lime E \ gallons oil E Mexican indicates steam-blown Mexican asphalt. b M. p. indicates General Electric method for melting paint.
F.
II-SOLVBNTS Base of Baume at REFINING TRADE No. Oil 60° F. PROCESS DESIGNATION Acid-basic Turpentine substitute 1 Paraffin 50.5 Acid-basic Naphtha 2 Mixed 55 Acid-basic Naphtha 3 Paraffin 55 Turpentine substitute 40 Acid-basic 4 AsDhalt Acid-basic Turpentine substitute 5 Asphalt 35 Naphtha 51 Acid-basic 6 Asphalt Naphtha 45 None 7 Mixed Naphtha 45 Acid-basic 8 Mixed Note.-Solvent 7 was a straight steam distillation product and had not been refined with acid. Solvent 8 was prepared from 7 by shaking 520 grams of oil with 15 cc. concentrated sulfuric acid in a separatory funnel until the action seemed complete, draining off the acid "foots," and repeating with fresh acid until the discoloration became red instead of dense black. Then the oil was washed with caustic solution and finally with distilled water until neutral. The water remaining in the oil was removed b y filtering through fuller's earth.
EXPERIMENTAL Series A Series A comprised six thin paints made from a hard airblown asphalt, and was prepared to show the general jellying tendencies of the materials used. Solvents 1, 2, 3, 4, 5, and 6 were used with Base 1; 1 part base to 3 parts solvent by weight; the base heated to 220" C., solvents added a t 200" C., and the mixtures stirred until the temperatures fell to 55" C. The observed viscosities are shown in the table. 100 REVOLUTIONS AT 22' c . Time in Days 51 75 86 114 154 4 6 0 . 0 Jellying (Jellied 20,000) 11.8 15(top) Ik't'op) 20.0 , 64.0 12[top, 12.5 15.0 44.0 16.0 17.0 3 3 . 4 8.0 10.0 9.0
STORMER VISCOSITIES I N SECONDS PER 7
Sample 1 1 9.5 2 7.8 3 10.0 4 9.2 5 8.8 6 6.6
9 18.0 7.8
16.0 10.0 9.0
7.0
14 25.8 9.0 18.0 10.0 9.0 7.0
... ... ... ... ...
.... . ... ... ...
The bases did not entirely dissolve when the paints were made, but in a few days complete solution was effected in all samples but No. 3, where heavy lumps remained suspended. In Samples 2 and 3 the paint showed syneresis. Series B Series B comprised six thick paints made from a soft steam-blown asphalt, and, like Series A, was prepared to show the general characteristics of the materials used. Solvents 1, 2, 3, 4, 5, and 6 were used with Base 2; 2 parts asphalt to 2l/r parts solvent by weight; the base heated to 185" C., solvents added a t 175" C., and the mixtures stirred until the temperature fell to 55" C. 100 REVOLUTIONS AT 22' Time in Days
STORMER VISCOSITIES I N SECONDS PER
SamDle
6
2
9
...
24.0
46
c.
Vol. 16, Yo. 5
The asphalts dissolved very easily to form homogeneous solutions which remained in that condition during the entire time of the test. Series B-I Series B-1 consisted of two samples, both made from Solvent 5 and Base 2, to show the effect of concentration changes with a soft steam-blown and air-blown asphalt mixture. Sample 1 contained 3 parts solvent to 1 part base by weight, and Sample 2 contained 1 part solvent to 3 parts base. The initial base temperature was 185" C., the temperature a t which solvents were added was 175" C., and the temperature a t which stirring was stopped was 55" C. The asphalts dissolved very easily to form homogeneous solutions. Sample 1 was very thin, and maintained a Stormer viscosity of 10 seconds per 100 revolutions a t 22' C. for 149 days; whereas Sample 2 formed a thick, almost immovable mass-an enormously thick paint, not a jelly. Series C Series C consisted of two samples, prepared from Base 2 and Solvents 3 and 5, and was prepared to show the effect of adding concentrated sulfuric acid to an asphalt before forming it into a paint. The acid was added to the molten base and stirred in. This treated asphalt was then made into paint by the usual procedure. Both samples contained 2 parts base to 2l/4 parts solvent by weight; the initial base temperature was 175" C., and the temperature upon solvent addition and the final temperature of the paints were 140' and 25" C., respectively. At 160" C., 18.4 grams concentrated acid were added to each 200 grams of asphalt. Upon the addition of concentrated sulfuric acid to the molten asphalts with constant stirring, the asphalts immediately assumed a grainy, porous, plastic form, and expanded with the formation of gas pockets of sulfur dioxide (odor) and steam. When the solvents were added (within 3 minutes), the asphalts curded and went into solution only after sustained and vigorous stirring with an iron rod for 20 minutes. The paints were very viscous. Within 12 to 24 hours the paints had assumed a definite jelly structure. The surfaces of these jellies appeared smooth a t first sight, but a closer examination showed them to be pocketed or scaled. The jellies were soft and holes pierced in them with a blunt instrument closed up in a few hours. Series D Series D consisted of three samples, prepared from Base 2 and Solvent 5, and was made to determine the effect on the rate of jellying of adding various amounts of sulfuric acid to paint bases before adding solvents. Each sample contained 2 parts base to 2l/4 parts solvent; the base heated to 175" C., the acid added a t 160" C., solvents added a t 140"C., and the paints stirred to a final temperature of 80' C. Samples 1, 2, and 3 contained 11.0, 5.0, and 1.8 grams concentrated sulfuric acid, respectively, to 200 grams asphalt. Sample 1 was almost jellied a t the end of 1 day and was completely jellied at the end of 3 days. Sample 2 was very thick a t the end of 1 day, and seemed to consist of two layers of paint, the top a thin layer, the bottom a heavy layer. At the end of 2 days these two layers seemed to be approaching each other in viscosity, and in 5 days the difference in viscosity seemed to be much less marked. In 14 days the two layers merged into one, the viscosity of which was 11,900 seconds per 100 revolutions a t 22" C. Sample 3 showed a viscous upper layer and a dense sludge as the lower layer a t the end of 1day. The mixed layers showed viscosities of 1230 and 1640 seconds in 58 and 64 days, respectively, while in 71 days the upper layer had a viscosity of 2240 seconds, and the lower layer was a dense sludge. I n 75 days the sample was too thick to test, but was not rigid.
INDCSTRIAL A,VD ENGINEERING CHEMISTRY
May, 1924
Series E Series E consisted of two samples made from Base 2 and Solvents 3 and 5 in the proportions of 2 parts base to 2l/4 parts solvent by weight. The series was prepared to show the effect of adding concentrated sulfuric acid to hot finished
P
512.
tained four samples made from Base 2 and Solvents 3 and 5 . Samples 1 and 2 were made from Solvent 3; Samples 3 and 4 were made from Solvent 5. Samples 1 and 3 had 3 parts base to 1 part solvent and concentrated sulfuric acid equal to 0.25 per cent the weight of paint; Samples 2 and 4 had 1 part base to 6 parts solvent, by weight and concentrated sulfuric acid equal to 0.45 per cent the weight of paint. Initial asphalt temperatures were 175" C., solvent addition temperatures 160" C., the acid added a t 150" C., and the paint stirred until temperatures dropped to 80" C. Immediately on cooling, Samples 1 and 3 were almost solid, being very thick but not jellied. Samples 2 and 4 were very thin and remained so throughout the test. After a few days, however, clots of asphalt jelly appeared near the bottom of each sample and remained suspended there. The data show that the viscosities of the mixture of clots and thin paint remained constant. Sample 2 varied in viscosity from 5.0 to 9.0 seconds per 100 revolutions in 76 days; Sample 4 varied from 6.3 to 7.2 seconds in the same time.
Series H 2
4
6
8
IO
12
I4
I6
16 20 22
24 26
28
30 32
34
36 38 40
T/me in Minufes FIG.
1
paint. Bases were heated to 175" C., solvents added a t 160" C., acid added a t 120' C., and the paints stirred until a temperature of 80" C. was reached. To each sample were added 9.2 grams concentrated acid per 100 grams asphalt. Immediately upon adding the sulfuric acid the paints showed a tendency to jelly, as denoted by the resistance to stirring and thc loss of strict liquid characteristics. Within 3 hours both the samples had jellied somewhat and a t the end of 24 hours they were completely jellied.
aeries F Series F consisted of two samples made from Base 2 and Solvent 3 in the proportion of 2 parts base to 2 l / 4 parts solvent by weight. The object of the series was to show the comparative effects of large and small amounts of sulfuric acid on cold finished paints made by dissolving the asphalts in solvents a t room temperature. Each sample contained 100 grams asphalt. To Sample 1, 9.2 grams concentrated acid were added, whereas only 0.9 gram concentrated acid was added to Sample 2. The asphalts were dissolved a t 22" C.
-
STORMER VISCOSITIESIN SECONDS PER 100 RIWOLUTIONS AT 22O C. Sample I iMinutes 0 3 5 8 12 15 21 25 30 35 22 5t1 77 138 240 390 414 714 930 1150 I n 40 minutes the viscosity was 1530 seconds, and the sample was completely jellied in 2 hours. Sample 2 MinutesDays---0 5 7 10 1 5 2 5 3 6 1 2 3 6 7 9 50 22 0 25 0 2 5 . 0 2 6 . 0 2 6 . 0 2 6 . 5 2 7 . 0 41 46 5 90 219 376 860 13 600 (jeliied)
7 -
---
____-
.
--
Since the high viscosities necessitated long periods of time for the observation of 100 revolutions, during which time the viscosities were increasing, smaller numbers of revolutions were observed and calculated to the 100-revolution basis. Despite this prrcaution many of the values required recalculation to determine the proper time element. The time figures given are the instants at which viscosity determinations were begun. After 24 hours Sample 1 was jellied, but had about 5 cc. of heavy liquid paint on top the jellied body. Sample 2 jellied completely but very slowly, requiring 9 days to become as high in viscosity as Sample 2 became in 27 minutes. Series G I n Series G the effect on the jellying properties of paint was noted when concentrated sulfuric acid was added to hot finished paints of various consistencies. The series con-
I n Series H the effect of treating a solvent with acid or base before making it into paint and the effect of adding sodium sulfate to a finished paint were noted. Three samples were prepared from Base 2 and Solvent 3, 2 parts asphalt t o 2l/4 parts solvent, by weight. Initial base temperatures were 175" C., base temperatures upon solvent additions were 160" C., and final paint temperatures, 80' C. The 200 grams of solvent for Sample 1 were agitated with 5 cc. concentrated sulfuric acid in a separatory funnel for 10 minutes, the heavy, reddish orange colored acid layer drawn off, and the solvent made into paint by the usual procedure. For Sample 2,200 grams solvent were agitated with 5 grams powdered sodium hydroxide in a separatory funnel for 10 minutes, the residual caustic drawn off, and the solvent made into paint. The treatment of Sample 3 consisted in adding 1gram anhydrous sodium sulfate to 425 grams hot finished paint. STORMER
Sample
1
2 3
100 REVOLUTIONS AT 22' Time in Days 35 42 672 Thickening 260 Thickening 408 Thickening
VISCOSITIES I N SECONDS PER
2 62 39
3 65 54 54
..
5 83 54 64
c.
10 17 23 28 176 193 300 504 (top) 86 100 149 160 124 209 352 363
On the 28th day Sample 1 showed a slight separation into heavy and light layers. Further viscosities refer to the top layer. Sample 2 remained homogeneous throughout the , test. On the 23rd day Sample 3 had a small amount of soft jelly in the bottom of the sample. None of these samples jellied; they merely thickened. 0
IO 9
e 7
P a d s mude fro mnow st~ama
6
5
4 3 2
I 2
4
6
8
IO
I2
14
I6
18
20
22 24
26
28
Time in Do y5 . FIG.2
Series J ( U ) and J ( T ) The last two series, J(U) and J(T),were made to show the effects of using various combinations of a refined and
INDUSTRIAL AND ENGINEERING CHEMISTRY
512
neutralization of refining acid with base) to a finished paint, produced definite thickening actions. Series J(U) showed that in paints made from an unrefined, mixed-base petroleum solvent and the following asphalt mixtures, which were air-blown to the same penetration and melting point-(1) 100 per cent steam-blown asphalt, (2) 90 per cent steam-blown asphalt plus 10 per cent acidic flux oil (acid value = 1.42), (3) 80 per cent steam-blown asphalt plus 20 per cent acidic flux oil, (4) 100 per cent steam-blown asphalt, air-blown in contact with lime (Ca0)-the periods for complete jellying varied inversely with the amounts of acidic flux oil used. The samples with bases composed of (1) fluxed air and steam-blown asphalts 1:1 and (2) hard steam-blown asphalt (20 pen) are not strictly comparable with the samples referred to above, but since their melting points and penetrations are of the same general magnitude, it is of interest Sam- c Time in Days ple 1 2 5 7 8 12 19 26 to note that the elimination of air-blown asphalt reduces the Series J ( U ) tendency to jelly. 1 50.8 92 201 236 330 488 1044 4360 2 51.2 101 285 384 600 660 3640 ... The hard steam-blown asphalt dissolved very easily and 3 402.0 1676 3416 .51. . . 69 . . . .77. 198 ... 832 ... did not a t any time change in viscosity. No acids are present 4 20.5 27 45 5 50.0 68 214 368 724 I016 in steam-blown asphalt. Whether this alone or in combine6 9.9 9.8 ...98 147 10.0 . . . . . . 10.4 11.0 tion with other factors is the cause of the ideal behavior of Series J(T) 1 ... ... Upper . . . . . . UDoer Mixed the sample cannot be stated now. laver I n Series J(T) the untreated solvent used in Series J(U) was given a rigorous acid-basic refining. This refining caused an acceleration of the jellying actions discussed above, ex4 23 ... cept in the case of the hard steam-blown asphalt, which 5 (No 6 10.0 10.0 maintained the same viscosities in the treated and untreated All the samples of Series J(U) jellied without the formation solvents. Despite the fact that the viscosity of the paint of layers. I n a couple of instances a small amount of as- made from 100 per cent steam-refined asphalt air-blown phalt did not dissolve immediately when the paint was pre- to a hard state remained less in the refined solvent than in pared, but complete solution occurred in two days. The the unrefined solvent, an effect due to the acid-refining is base of Sample 6 dissolved very easily and remained in solu- apparent. An immediate precipitation of asphalt occurred tion during the entire time of the test. in the former case, while 7 days were needed to show a simSamples 4 and 6 of Series J(T) remained homogeneous ilar precipitation in the latter case. throughout the test. Sample 1 precipitated a sludge in 1 Determinations of the organic acid values of the asphalts day and Sample 3 jellied a t the end of 1 day. showed free acids to be present in the air-blown samples and in the Special Flux Oil, while the hard steam-refined Acid Values The acid values of the asphalts were determined by ti- asphalt showed a neutral reaction. A 100 per cent steamtrations. Great difficulty was experienced in these titra- refined asphalt blown hard with air showed an acid reaction, tions due to the combination of obscure, fading end points while the same sample air-blown in contact with lime gave a and the extreme minuteness of the values determined. I n basic or neutral reaction. The fact that the former sample fluxing the asphalts, 20 cc. of neutral paraffin oil were used jellied very rapidly, whereas the latter jellied very slowly, for the 5 grams of each one. A volume of 140 cc. neutralised tends to show that acids are produced in the air-blowing ethyl alcohol was used in portions to extract the acids from process and that they greatly facilitate jellying actions. Evidently, the jellying properties of the air-blown asphalts each sample. Similarly, 30 cc. alcohol were used in dissolving are not due to free organic acids, since the acid numbers are the acids from the Special Flux Oil. extremely low, approximately equal, and do not increase TITRATIONS with the amounts of acidic flux oil added. There may be S ecial No. of Base 4 5 6 7 3 d u x oil a reaction between acid and the still mixture which changes 0.36 0.38 0.31 ... ... 1.52 the characteristics of the resulting asphalt. Series C and D Acid number i0.28 ... 0.33 ... ... 1.33 showed such actions. Indicator reaction Blue Blue Deep blne Yellow Yellow Deep blue b Alkali blue used as an indicator. It is of interest to note that in some cases a definite jelly Blue indicates acid reaction. was produced with a comparatively low viscosity, but in other Yellow indicates neutral or basic reaction. cases high viscosities were attained before the jelly structure DISCUSSION OF RESULTS appeared. All the foregoing results show that an asphalt paint, the The results obtained in titrating the asphalts for acids are viscosity of which has remained practically constant for weeks, not very satisfactory, but since the indicator reactions were can be made to jelly, thicken, or precipitate out very rapidly definite, and neutral or basic asphalt mixtures did not jelly by the addition of concentrated sulfuric acid to any one of in the short periods of time needed for the jellying of acidic the following series: asphalt preliminary to dissolving it in asphalts, the fact remains that acidity of some nature greatly petroleum solvent; petroleum solvent preliminary to dis- influences the jellying. solving asphalt in it; finished paint, cold or hot. It also Before definitely stating whether the jellying is due to appears that thin paints will precipitate out, whereas heavier (1) free sulfuric or organic acids, or (2) initial reactions bepainta will thicken or jelly under such treatment. tween asphalt and acid in the blowing still, it will be necessary The agitation of petroleum solvent with caustic soda, or to develop a method for accurately determining free sulfurio the addition of sodium sulfate (possibly remaining from the acid in asphalts, particularly hard asphalts. unrefined petroleum distillate as solvents for asphalts prepared according to Gfferent formulas and by different processes. Samples 1, 2, 3, 4, 5, and 6 of J(U) were made from Solvent 7 and Bases 4, 5, 6, 7, 2, and 3, respectively, in the proportions of 1 part base to 2 parts solvent. The initial asphalt temperature was 260" C., the asphalt temperature upon solvent additions was 250" C., and the final temperature 110" C. Series J(T) used the solvent from Series J(U)after giving it an acid-basic refining. Samples 1, 3, 4, and 6 were made from Solvent 8 and Bases 4, 6, 7, and 3, respectively, in the proportions of 1 part asphalt to 2 of solvent. The initial bane temperature was 260" C., the base temperature upon solvent additions was 250" C., and the final paint temperature 110"C. STORMER vISCOSITlES~IN S E C O N D S PER 100 REVOLUTIONS A T 22' c. ?
...
t
Vol. 16, No. 5
. #
