November, 1925
I S D I - S T R I l L d S D ESGI-YEERISG CHEMISTRY
1165
Relation between Dye Adsorption of Clays and Their Behavior in Rubber Compounds’ By H. R . Thies h l I L L E R RUBBERCO.,AKRON. O H I O
Clays of the same chemical type do not behave simiclays. These heated clays N T E S T I S G clays for larly when compounded in rubber; one type gives good were tried in rubber. Thib use in rubber compoundcures and high tensile strengths, the other slow cures heat treatment brought down ing work a remarkable and inferior tensile strengths. These two types of clay the maximum tensile strength variation was found both in adsorb different amounts of dye from solution, the obtained with the good clay the way in w h i c h t h e y clay which is good for rubber usage adsorbing the and improved that of the poor affected the cure of a base smaller amount of dye. clay by only a few pounds. compound and in the niaxiAdsorption of different types of dye does not appear The two types of clay were mum tensile strength obtainto follow the chemical relationship of molecular treated with moist ammonia able by their use. In fact, weights. The difference i n clays is exhibited with vapor for 6 hours and then some of the clays tested were various accelerators and relationship between cure and dried a t 140’ C. until most of absolutely unusable in genamount of dye adsorbed in a standard method of measthe water and all the odor of eral rubber compounds. This ure is shown. The difference in clay behavior is very ammonia had disappeared. was illustrated when a good little in unaccelerated stocks. They were then compounded clay and a poor clay in ruband cured. This saturation ber were comDounded and cured in the base stmock,known as the First Trial Formula, with moist ammonia vapor did not alter the curing properties of the good clay, but it did imprpve the maximum tensile of the everything being the same except clay. (Table I) poor one by 700 pounds.
I
Firsf Trial Formula
Rubber Diphenylguanidine
Sulfur
Magnesium oxide Zinc oxide Clay
Table I-Tensile Minutes cured a t 60 Ibs
-
10
1.5 20 25 30 40
Per cent b y weight 63.496 0.504 2.5 2.0 5.5 26.0
Volumes pigment per 100 volumes rubber 100.00 0.446 1.83 0.966 1.464 14.64
100.000
119.346
Strengths of Good a n d Poor Clays Good clay Poor clay Lbs/sq in L b s / s q in 2080 2500 2750 2750 2620 2700 2580
600 i60 850 900 870 920 1480
Differences Found in Two Clays
The first thought was to look to the chemical analysis of the clays for an explanation of the erratic behavior. This, however, gaTe no hint as to the cause of the difference in the two, as will be shown later in the paper. The poor clay was extracted with acetone to remove any organic anti-accelerator it might contain. An oily, musty, earthy-smelling residue was obtained from this extract. This oil, when compounded in the base recipe to the extent of one per cent of the good clay did not change the degree of cure of this compound. Exaggerated amounts of phosphoric acid, manganese sulfate, and titanium oxide were next tried to determine if these would, when used in the base recipe with good clay, retard the cure as much as the poor clay did. They had no such action, and in no case was it possible by this means to approach the marked effect on cure that the poor clay exhibited. The two types of clay were heated to dull redness in a muffle, thus burning such organic matter as was present, driving off considerable water of hydration, and altering to some extent the physical properties of the two representative 1 Presented before the Dlvlslon of Rubber Chemlstry a t the 69th Meeting of the Amerlcan Chemical Soclety. Baltimore, Md , 4pril 6 t o 10 1925
Review of Literature
Ashley2 found that the adsorption of dyes by clays affords an approximate measure of their plasticity. He used malachite green and methyl violet. Gile and Middleton3extended this work and formulated a rough quantitative method for the determination of the amount of colloid present in soil based on adsorpt’ion of malachite green, water vapor, and ammonia vapor. Schidrowitz4 took out a patent using the adsorption power of clay for carrying an accelerator. Searles states: “The enormous power of adsorption possessed by colloids is due to their peculiar structure which gives them very great surface area-clay exhibits such adsorption.” Arrhenius6 found that dyes were adsorbed in stoichiometrical proportion and that several indicators were adsorbed by the same clay in proportion to their molecular weight. Davies7 calls attention to the use of clay in medicine for its adsorption ability and says it is probably this pr0pert.y that makes it, desirable for use in rubber. Since most of the work covered in this paper was finished, Weige18 has shown that in forty-four samples of Georgia clay, all prepared as pigment clay in the same manner, there is a marked difference in behavior when cured in rubber compounds. This is apparent’lythe first’published reference to the wide differences of clay as a pigment. Later Bleiningerg tells us that the powerful adsorbing power of clays is well known, and that the clay takes up the basic ion-as a rule-the adsorption taking place according to the adsorption equat’ion, but that the value of the latter as a criterion to distinguish between adsorption and chemical combination may be questioned. Bancroftlo states that the adsorption of “ T h e Colloidal Matter of Clay a n d I t s Measurement,” U.S. Geological Survey, Bull. 388. 3 “Estimation of Colloid Materials in Soils b y Adsorption,” U .S Dept. .4gr., Bull. 1193. English Patent 170,682. 6 “The Chemistry and Physics of Clay,” p. 236. 6 J . A m . Chem. Soc., 44, 523 (1922). 7 India Rubber Rea,., 82, 22 (1922). 8 Rubber Age, July, 1924. “ T h e Properties of Clays,” Colloid Symposium Monograph, Val. 11. p. 35. I D“Applied Colloid Chemistry,” p . 121.
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
1166
lime by fuller’s earth is equivalent to a 2 per cent sulfuric acid solution. Experiments on Dye Adsorption of Clays
With the foregoing information on the adsorption power of clays and knowing the difference in their behavior in rubber, a study was made of the relation of these two qualities as applied to rubber compounds. After preliminary experimentation, some good curing clay and some poor curing clay were shaken in a 0.1 per cent malachite green solution, also in 0.1 per cent solution of methyl violet, as follows: A 2-gram sample of clay was weighed into a 25-mm. test tube and suspended in 50 cc. of the dye solution. This suspension was thoroughly shaken
Vol. 17, No. If.
The lakes formed with chrysoidine Y and malachite green were of interest. With the good clay, the lake was the yellow of the alkaline condition, the solution was red of the acid condition, whereas with the poor clay, the lake was red of the acid condition but the suspending solution was also red. Further work showed that a suspension of the good clay sample gave a pH value of 7.1 while the poor clay sample gave a pH value of only 4.0. This was in accordance with the color of the lakes obtained with these dyes. I n view of Arrhenius’ statement6 that dyes were adsorbed by clay in quantities proportional to their molecular weight or that a given amount of clay adsorbs equimolecular quantities of various dyes, several dyes were examined with this in mind. Table I11 shows the results when a 2-gram sample of good clay was shaken with 50 cc. of a 0.1 per cent solution of the various dyes, and is a recalculation from data given in Table 11. This concentration of solution insures the presence of an excess of dye in every case. Table 111-Amou n t of Dye Adsorbed by Clay f r o m 0.1 Per c e n t Solution of Several Dyes Millimols/1000 TYPE Mol. wt. Mg./gram clay grams clay DYE Basic 206.6 1.97 9.7 Chrysoidine Y Basic 319.7 7.15 22.6 Methylene blue Acid 321.17 5.85 20.0 Methyl orange Basic 323.0 9.6 29.0 Basic fuchsine Basic 350.74 10.29 29.3 Safranine Y Basic 393.19 20.8 53.0 Gentian violet Basic 461.29 14.72 31.9 Bismark brown Acid 490.33 2.24 4.5 Acid scarlet Basic 505.0 24.97 49.4 Victoria blue Acid 589.0 4.2 7.0 Acid fuchsine Acid 603.0 6.0 9.9 Acid magenta Acid 752.84 9.25 12.3 Acid fast green Acid 773.0 7.6 9.9 Acid violet Acid 810.0 8.7 10.7 Acid green Acid 839.0 2.62 3.1 Acid blue Basic 928.45 11.7 12.6 Malachite green
Figure 1
This erratic amount of adsorption exhibited by good clay could be expected because, as is shown by the two colored lakes mentioned above, the adsorption is in some way affected by the hydrogen-ion concentration; probably the different dyes a t various Sorensen values are adsorbed in different amounts by a single clay. At least, it is unlikely that the clay under investigation should offer the most favorable condition for adsorption to all dyes in all cases. Gordonll has shown what a marked effect the hydrogen-ion concentration can have on adsorption of dye using orange I1 with iron hydroxide and alumina gels. Five and one-half times as much dye was adsorbed in the case of iron hydroxide a t a pH 2.3 as a t a pH of 3.2. I n trying to find a dye and a method that would give the widest differential adsorption for the two types of clay, the amount of adsorption with several of the above dyes was determined using 0.5 gram sample of clay instead of 2 grams. The results obtained further indicate that for exact determination of adsorption the clay ratio of the solution must be constant. For example, in some cases fewer milligrams of dye were adsorbed per gram of good clay when a 0.5-gram sample was used than when a 2-gram sample was used. This, however, was never the case with the poor clay, although it was found to be universally true that for basic dyes the adsorption ability of clay that was good in rubber Adsorption Tests DYE IZEMOVEDRROM S O ~ U T I O Ncompounding was much less than the adsorption ability of PER :E NT the clay that was poor in rubber work. Poor clav Good clay I n view of the above peculiar behavior a study was made 47.9 92.0 99.7 29.0 of the adsorption curve of the two clays in various concen32.1 23.4 99.5 38.4 trations of the malachite green dye using 0.5 gram of clay 41.2 99.5 and 50 cc. of dye solution in each case. Their behavior is 83.5 100.0 59.0 99.3 given in Table IV. 5.5 9.0 99.1 95.6 Figure 1, in which these values are plotted, is of interest 25.1 16.6 in showing two distinct types of adsorption. Hatchek” 21.6 24.1
and allowed to settle for 1 hour, after which samples of the clear, colored liquid were drawn off and compared in a Duboscq colorimeter with an accurately diluted standard for dye content. This method was found very useful in all subsequent investigations and, using malachite green, was finally adopted as a standard procedure. On completion of the foregoing examination, i t was found that in the methyl violet solution the poor-curing clay had adsorbed all dye present while the good one had not, but with malachite green the poor clay adsorbed a large amount of dye, the good clay little. (Table 11) I n this instance the poor clay settled out of suspension much more slowly than did the good one, whereas in another test the poor clay even bleached a colored mineral oil much better than did the good one. Since the foregoing tests showed that the ability of the poor clay to adsorb the colors present was greater than that exhibited by the clay which was good in rubber work, the question naturally arose as to whether this was true with other types of dyes. Adsorption tests were therefore made to learn the behavior of the two types of clay with various dyes. Table I1 shows the results when a 2-gram sample of clay was shaken with a 0.1 per cent solution of the dyes. Table 11-Dye
(
DYE Chrysoidine Y Methylene blue Methyl orange Basic fuchsine Safranine Y Gentian violet Bismark brown Acid scarlet Victoria blue Acid fuchsine Acid magenta Acid fast green Acid violet Acid green Acid blue Malactute green
TYPE Basic Basic Acid Basic Basic Basic Basic Acid Basic Acid Acid Acid Acid Acid Acid Basic
37.0 30.6 34.6 10.5 54.0
97.0 71.3 93.4 33.2 99.6
11 “Theory of Adsorption and Soil Gels,” Colloid Symposium Monograph, pl. 11. p. 124 12 Physics and Chemistry of Colloids,” p. 134.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
November, 1925
found night blue was adsorbed by cotton in a manner similar to the adsorption of malachite green by the good clay. The adsorption of the dye by the poor clay indicates that after a certain amount of dye is present the adsorption is constant. Table IV-Adsorption of Malachite Green by Good a n d Poor Clays -GOOD CLAY-POOR CLAYMols d e Per cent dye Mols dye Concn. of Per cent dye adsorbedfi000 removed adsorbed/1000 malachite green removed soln. from grams from grams Per cent soln. clay soh. clay 0.00625 100 78.3
0.00938 0.0125 0.01875 0.025 0.037 0.050 0.075 0.10 0.15
64.5 56.0 39.5 32.6 24.7 20.64 15.22 13.8 4.3
100 99.8 99~2 98.15 88.54 78.30 62.27 47.10 31.5
Relation of Dye Adsorption to Cure in Rubber Compounds
With the foregoing information on adsorption at hand, i t was decided to select as the standard for testing clays the 2gram sample of clay with 50 cc. of 0.1 per cent malachite green solution, chiefly because it had been found that poor curing clay gave almost 100 per cent adsorption which was quickly visible, while the good clay gave only 54 per cent adsorption and left the dye solution opaque (Table 11). The dye adsorption of such samples of the two kinds of clay as were a t hand were tested and cured in a typical factory compound, in a n attempt to establish the relationship of dye adsorption to cure in a rubber compound. The Second Trial Formula was used in these experiments. Second Trial Formula
Rubber Diphenylguanidine Sulfur Litbopone Zinc oxide Clay
Per cent by weight
Volumes pigment Der 100 volumes rubber
48.375 0.625 2.0 17.0 11.0 21.0
100.0 0.72 1.9 6 84 3.81 15.36
100.000
-128.62
Table V-Variations
SAMPLE Virginia clay Pennsylvania clay
1167
in Cure a n d Dye Adsorption of Different Clays Time of Max. Dve cure tensile adsorbed/gram Minutes strength clay at 145O C. I,bs./sq. in. Mg.
20 20 50 20 20
2380 2480 1520 2420 1250 2000 2000
14.30 10.00
24.85 11.90 24.90 22.45 21.25
nvp
rem&ed from s o h . Per cent
56.2 40.14 99.2 47.6 99.5 89.7 89.9
Comparisons of the clays in Table V shows that Pennsylvania clay with low dye adsorption gives high tensile strength, whereas Georgia Clay 1 gives high dye adsorption and low tensile strength. Samples of Georgia Clay 2 and 3 show the same behavior. Samples 4 and 5 show uniformity of results. Figure 2 gives the complete cure relations for four of these clays. Up to this time all the work on cures had been done with one accelerator, diphenylguanidine. I n order to see if this difference in behavior of clays would be experienced with other accelerators, approximately balanced cures were prepared using the Second Trial Formula with good and poor curing clays, but with the following accelerators: hexamethylenetetramine, p-nitrosodimethylaniline, thiocarbanilide, and, as before, diphenylguanidine. I n the first trial the difference in clays was noticeable with p-nitrosodimethylaniline and diphenylguanidine, but not with hexa- and thiocarbanilide. I n order to be sure that there was not sufficient accelerator present to more than saturate the adsorption power of the clay, the accelerator content of the recipe was diminished in these two cases. Hexa at once showed a difference in cure between the good and poor clays, but thiocarbanilide did not. The latter, however, was not tried in any lower amount than 1 per cent by weight of total recipe, which may yet be too high a concentration to show the difference. The accelerator in those formulas that showed marked difference in cure was then increased. This procedure did not entirely eliminate the erratic behavior of the poor clay, but did reduce the magnitude of the difference between it and the good clay (Table VI).
Figure 2
ISDCSTRIAL d S D E.VGINEERI,VG CHEMISTRY
1168 Table VI-Effect
CLAY
of Different Accelerators on Cure
Accelerator Per cent
Maximum tensile strength Lbs./sq. in.
0.25 0.25 0.15 0.15
2090 2070 1650 1280
25 25 25 30 25 23 40 40
Good Poor Good Poor
2.5 2090 2.5 2030 1.25 1480 1.26 1460 P-iVitrosodimethylaniline 0.136 1920 0.136 1280 0.1875 2420 0.1875 1750
Good Poor Good Poor
0.625 0.625 1.25 1.25
Thiocarbanilide Good
Poor
Good Poor
20 40 20 40
Diphenylguanidine 1950 1220 2330 1700
between Dye Adsorption and Cure of Clays from Various Sources Adsorption of 0.1 per cent Max. malachite , tensile Cure green strength Min. a t SOURCE OF CLAY Per cent Lbs./sq. in. 60 lbs. 29.0 15 Pennsylvania 15 25 65.6 Virginia 30 North Carolina 20 South Carolina 82.3 26 84.9 25 Georgia Florida 85.3 30 Georgia 88.0 26 Kentucky 96.0 50 40 98.7 Georgia 50 Mississippi 40 9 9 . 8 50 Kentucky
Table VII-Relation
Cure Min. a t 60 lbs.
Heramethylenetetvaminc Good Poor Good Poor
Vol. 17, No. 11
25
Sample A-1 A-2 A-3 A-4
A-5
A-6 A-7 A-8 4-9 A-10 A-11 A-12 A-13 A-I4 A-15 .4-16
t 100.0 100.0
Mississippi
50 50'
40
15 40
Table VIII-Comparison of Uniformly Treated Clay (Bureau of Mines Samples) LMax. Av. particle Dye tensile cure sizea adsorbed strength Min. a t Lbs /sq. in. 60 Ibs. Clay .Microns Per cent 40 3310 15 G-30 3.3 53 3300 20 G-2 3.3 75 3200 20 G-29 3.3 G-26 7 , .0 3050 20 75 77 3245 20 G-40 3.2 81 2960 25 G-9 3.2 82 3190 20 G-27 3.9 3130 30 82 G-7 3.3 2850 25 G-24 2.9 85 2290 40 100 G-8 3.7 40 1670 4.4 100 G- 1 a Weigel's measurements.
These observations with the two types of clay correspond exactly with the behavior of clays in the adsorption of dyes. Different dyes were adsorbed in different amounts and the adsorption was not constant with the same dye in different concentrations. This is apparently the case with accelerators, as it is logical t o assume that a clay that can adsorb a dye can adsorb an accelerator as well. Therefore, the reason for the difference in clays might be that the poor-curing clay adsorbs the rubber accelerator and removes it from action, whereas the good clay does not. The fact that yarying the amount of accelerator varies the magnitude of difference in the clays lends weight to this belief. Howerer, a great deal of experimental work would be necessary to prove it. It was desired to confirm this relation between dye adsorption and cure of clays in a rubber compound using clays from widely scattered sources. Samples were therefore obtained from various suppliers, their dye adsorption determined by the standardized method, and then cure trials run on them using the First Trial Formula. The results (Table VII) show that, in general, maximum tensile and time of cure vary inversely. For further confirmation, from W. M. Weigel, mineral technologist for the Bureau of Mines, were obtained samples of several clays he had prepared for pigment use by a uniform process and concerning which he had published the manner of their behavior in rubber compodnds.5 The uniform preparation was important, for the clays shown in Table VII had had all sorts of treatment and still gave fairly consistent results under these tests. This being true, uniformly treated clay should give a better test of the method. The data are giren in Table T'III.
Here, as with commercial clays, the time of cure to obtain maximum tensile strengths rises uniformly with the increase in percentage of dye adsorbed from our standard test solution. The maximum tensile obtainable also decreases with increased dye adsorption. Figures 3 and 4 were drawn from the composite results obtained on both the commercial and the uniformly treated clays. From the results of the tests thus far given in this paper, the extent to which adsorption by a clay renders the clay detrimental for general rubber work seems to be measurable by a dye test; and in this dye test a clay adsorbing 90 per cent or more of the dye has too great an adsorption power to be good for all rubber usage. However, it has equally well been shown that there may be a wide variation in the adsorption power below 90 per cent without affecting the tensile strength or cure of the base compound. I n fact, there is such a variation in clays obtained from the same mine although these clays show the same curing ability.
Figure 3
Figure 4
ISDCSTRIAL - 4 5 0 ESGISEERING CHEMISTRY
November, 1925
Effect of C h e m i c a l Composition of Clay on R u b b e r Behavior
Returning to the chemical analysis of the good and poor clay, we offer for comparison four samples of Bureau of Mines pigment clay. It was mentioned a t the beginning of the paper that the chemical analysis did not account for the difference in behavior of clays, and in giving the analyses of these clays together with their dye adsorption and behavior in a rubber compound (Table E),this statement seems t o be justified. Table IX-Comparison of Chemical Analysis a n d Rubber Behavior of Uniformly Treated Clays (Bureau of Mines Samples) Poor clay Good clayAnalvsiz a G-30 G-29 G- 1 G-8 45.18 44.9 43.86 44 37 SiO? 39.08 39.81 39.9s 39,96 A1203 0.65 0.43 0.71 0.65 Fez03 0.47 0.47 0.57 0.5; Ti02 0 . 5 1 0.36 0 . 4 s 0 . 3 5 K20 13.7 13.46 13.64 13 81 Ignition loss
--
Total Per cent dye adsorbed Maximum tensile strength, Ibs per sq in Cure for maximum tensile strength, minutes at 60 lbs
-
~
99 4s 40
_
_
-99 ,a
19
_
_
_
_
99 6 5
99 65
100
100
3310
3200
1670
2260
15
20
40
an
W'eigel Footnote 8.
Unaccelerated C u r e on Clays
To get further information on accelerator adsorption by clay two more experiments were conducted. 111 the first the two types of clays were used in a compound containing no organic accelerator: Unacceleraled Foi mula Rubber Sulfur Magnesium oxide Zinc oxide Clay
sulfur reaction the difference in clay should still be noticeable in this recipe. The results are given in Table X. Table X-Unaccelerated Good clay Lbs./sa. in. 96i 1765 2160 2365 2290 2270 2150
80
z.0 J.J
-_
Poor clay Lbs./sa. in. '69b 1085 1590 2460 2450 2325 2400
Effect of L i t h a r g e
I n the second experiment the 2 per cent of magnesium oxide was replaced with litharge to determine the effect of the two clays with a, rapid inorganic accelerator. Here, as in the previous case, the behavior was similar, although the effect of the poor clay is noticeable. Their cures are given in Table XI. Table XI-Inorganic
Accelerated Cure o n Clays STRENGTH--? Poor clay Lbs./sq. in. 1350 1570 1870 1950 2040 1860
-----TENSILE
Good cIay Lbs./sq. in. 1090 2190 2215 2250 2200 2020
3Iinutes cured at 60 lbs.
25
26.0
STRENGTH--
The rate of cure for the two clays is thus practically the same, both reaching maximum tensile strength a t the same cure with the high-adsorption clay a little lower in pre-cure than the low-adsorption clay. The difference in undercure, however, does not approach the magnitude of the diffePence in an accelerated stock and is probably due in this case to the difference in preparation of the clays, one being a washed clay, the other one an air-floated, dry ground clay. This test then shows little difference in the two types of clay in an unaccelerated compound.
10 15 20
4.0
Cure on Claye
-TENSILE
Minutes cured at 60 Ibs. 15 30 40 50 60 70
T.5
62.5
1169
Acknowledgment
100.0
This stock should cure practically the same for both clays, if the poor clay is really adsorbing the accelerator to remove it from action, whereas if the clay interferes with the rubber-
The writer wishes to thank AI. M. Harrison and H. A. Morton for helpful criticisms and valuable assistance in the preparation of this paper.
Welding on Boilers By S. W. Miller P.4ST P R E S I D E N T OF THE AMERICAN W E L D I N G ~ O C I E T Y
I throughout industry and the probability that repairs t o boilers made in this way will be proposed from time t o time, it
N view of the ever-widening applications of fusion welding
4-If the boiler is not insured and comes under federal, state, or municipal supervision, carry out the above program in company with the proper authority.
is well that those responsible for the results should bear the following points in mind: 1-Most boilers are insured. 2-Many boiler insurance policies are so worded that if repairs are made without the authority of the company carrying the insurance the policy becomes void. 3-There are federal, state, and municipal regulations governing this work, as well as those issued by the insurance companies. 4-Only competent welders, used to boiler work, should be allowed t o do the welding.
If the boiler is neither insured nor under supervision of some constituted authority, ample precautions should be taken by the welder and the owner to protect themselves against possible future trouble. They should make a sketch of the location and size of the repair, and a clear statement of what was found wrong and how the repair was made. They should always make a hydrostatic hammer test of the finished job, using a pressure of one and one-half times the working boiler pressure, in the presence of witnesses, and get their signature to a statement of the facts. These papers should be carefully filed. No welding should be done which is not permitted by law or by good practice. I n case of marine work the welder should pass the regular examination of the Federal Steamboat Inspection Service. In all cases the welder should make friends of the insurance and other inspectors by refusing t o do work unless authorized by them,'by being conservative in what work he recommends, and by doing only a first-class job.
Therefore, the following precautions should be observed by the owner or his representative: 1-Examine the part of the boiler to be welded in presence of the insurance company inspector, and get his approval before doing any welding. 2-Be present with the inspector a t the test after welding. 3-If possible, get the inspector t o sign a statement that the work has been properly done and that i t has passed the test successfully.
'
