INDUSTRIAL AND ENGINEERING CHEMISTRY
698
composition of the spent zinc-copper mixtures, and these data are at present being supplemented by an x-ray investigation of the physical structure of the catalysts. Similar studies are also being made of the binary system zinc-chro-
VOl. 20, No. 7
mium, and finally, the data obtained on decomposition will be correlated with activity determinations made on the reverse reaction-i. e., the synthesis of methanol from carbon monoxide and hydrogen.
Characteristics and Treatment of Insulating Varnishes' P. B. Cochran and H. J. Graham WESTINGHOUSE ELECTRIC AKD hl.4NUFACTURINO COMPANY, E A S T PITTSBURGH, PA.
A saving in drying time of varnish 2 as indicated by The ozone used in this inhot-resistance measurements was effected by proper vestigation was manufactured trical apparatus certain use of ozonized air in the baking process. A pre-bake by a laboratory o z o n i z e r , types of oil v a r n i s h e s of the unvarnished piece in ozonized air assists greatly equipped with a rheostat for have found widespread and in shortening the drying time. adjustment of voltages, to consistent use for t r e a t i n g Several different methods and types of apparatus permit various concentrations cloth and tapes and for finishwere tested for possibilities in determining hardness up to 1.0 per cent. Plate 1 i n g a n d impregnating purof varnish films. Of these, the swinging beam hardillustrates the apparatus as poses. The customary proness tester proved to be the most accurate and conused, including the ozonizer. cedure for the insulation of venient and was adopted for this purpose. coils consists in treating the Drying of Varnish in DeepA n arbitrary hardness of 18 as measured by the cotton-covered winding with Seated Coils swinging beam tester was chosen as the point at which an asphaltic or baking vara varnish may be considered dry. Using this figure Before a machine is finally nish either before or after as a standard, it was found that a considerable saving assembled the coils or the winding the coil. The results in drying time may be accomplished by the use of complete rotor and stator are obtained by this treatment ozonized air or by the use of more elevated temperadipped in varnish to improve are usually satisfactory, since tures in the baking process. Rates of hardening after the insulation properties of a thoroughly dried v a r n i s h drying of the varnish film were determined, modifying the windings. Varnish 2 (as provides a tough, pliable film various conditions of the process. Baking at elevated listed in Table I) is widely of high resistance and of contemperatures or with ozonized air causes the film used for impregnating pursiderable breakdown strength. to harden at an accelerated rate. poses and was therefore used The processes of d i p p i n g Investigation of the effect of ozone on cotton insulain these tests. Test blocks and baking insulating vartion brought out rather striking results. Treatment were made to similate condinishes and the various probof cotton materials with ozone under proper conditions tions to be met when d e e p lems relating thereto are of causes an increase in tensile strength of 20 to 30 per slotted apparatus is treated great importance in the eleccent. Such a process might easily be economically w i t h i n s u l a t i o n varnish. t r i c a l industry. Too little feasible where increased tensile strength of such These blocks were of steel emphasis has been given to materials is desirable. 25.4 X 5.08 X 7.62 em. (10 the necessity of good control X 2 X 3 inches) n i t h a s l o t and a DroDer knowledge of the use- and treatment-of varnishes for insulating electrical 25.4 X 5.08 X 0.127 em. (10 X 2 X 0.5 inches) in the center of machines. This paper is a result of an attempt to obtain a the block. Test bars of cold-rolled steel 30.48 X 0.95 X 1.90 better insight into the proper use and treatment of var- em. (12 x 0.375 x 0.75 inches) were wound with two layers of 0.0177 X 1.90em. (0.007 X 0.75 inch) cotton tape each turn half nishes regularly used for insulating purposes. overlapped. A cell made of three layers of 0.330-em. (0.013inch) Cannon cloth was placed in the slot. Two taped bars, Table I-Properties of Insulating Varnishes one above the other, were placed in the cell and a fiber wedge SPECIFIC OILIN 1 . 0 ~ GRAVITY NOKwas placed over the top bar. Thermocouples and heavy insuVOLATILE (15OC.) VOLATILE \'ARNISH GUM MATTER4 As received As used RIATTERb THINNERC lated lead wire were soldered to each block. The two bars in Per cent Per cent each block were connected together and the lead wire connected by u't. by w d . Per cent to recording apparatus. Temperature readings and resistance 65.2 0.876 0.840 49.8 58.5 1 Rosin ester 14.8 0.860 50.4 55.5 2 Asphalt 0.829 measurements between the bars and the block were recorded 0.837 45.0 61.2 0.839 3 Copdl 74.9 71.4 0,872 0.841 53.9 52.1 4 Asphalt a t intervals and results plotted. 5 0 . 0 0,841 54.7 5 Copal 54.6 0.876 Six blocks were preheated in ozonized air (concentration, a Calculated from oil and varnish analysis by method of Boughton, 25 per cent, flow, 7 liters per minute) until a temperature Bur. Standards, Tech. Pa$er 66 (1916). b Determined by A. S. T. M. D-115-25T on varnish as received, Proc. of 105" C. was reached, and slowly cooled to 70" C. in an Am. Soc. Testing Materials, 26, I, 798 (1925). E Thinner determined b y steam distillation of 100 grams of varnish as atmosphere of ozonized air. They were then dipped in received. varnish 2 (sp. gr. 0.852) for 30 minutes. After draining for 10 minutes, the blocks mere placed in an oven a t 105-110" Typical insulating varnishes were used in this work. A C. Temperature ' and hot-resistance measurements (by number of different types of oil varnishes used as insulating means of a megger) were recorded a t intervals. This promaterials are included in the five varnishes tested. Table cedure was then repeated using air without ozone a t the same I lists the properties of these varnishes. flow. Results in both cases were averaged and are recorded in Tahle 11. 1 Received April 12, 1928.
I
K T H E insulation of elec-
Tim* X"24.i 10 20 30 40
Table II---Areraae Hot lleaisfance (Temperature 106" 10 1 1 0 ~ C.) OZONE U R K l l A m BAKU Mesohms MEgOhmS 2.12 1.76 13.20 3.18 44.40 9.80 117.0 18.50
These remlts indicate the wide difference in the hot resistance ~ ~ l i e!,lie i i test block is halied in ozonized air as emnparcd to straight air bake. l i i order to cleterniinc the amount of time saved hy the use of ozoiie, the results reconlcd in 'Pahle I11 u-ere ralciilatcd.
ditiorrii it and the Icso: twcrgy will be abiorbcd by the film. Consequently, the times iioted iiieasiire tlic relative hardness, siiite i i k;iLi\icvaaldefinition of this word is iinpossible. The time for 1.Re minging beam to reach the 22.5 degrees arc 1 ~ 3 1 increase as t,lie varnish hardens. Ten tests vere made on each sample, five on each side, and in t.lie same regular order starting opposite to the drainiiig eiirl. The average of these ten readiiips was t,nken as tlie coinpurntive hardness of the film. Results are recorded in Table IV.
Table Ill--Avcrage Saving In I k y h C T i m e by Use of Orortired .Ak as Indicated by Ilot-Krsiafance M e a ~ ~ r ~ m e n f ~ A i R IIAKE
K6LilSl.A'CI:
KVQiiiilrD
Ozomzrra hili 1,AKil 1trn"'KEn ilovrr
TIMI ii0U.S
I'm
/,~*,
Iii general, the resistance varies inversely wit,ll tfie teinperature. However, m the oxidation of the varnish proceeds the resistmce gradually increases. Aft.cr a number of tests i t mas found tliat tlie pre-bake (before dipping in varnish) in ozonized air with subsequent bake in ozonized air gave the best results-i. e., the resistance of this block increased inore rapidly than in any other procedure. This may indicate illat the cotton windings retain some ozonized air in the fibers and so provide a inore active oxidizing agent for the drying of the varnish after tlie block is dipped and during the baking process. Soiiic action also h k e s place bet,\veen the ozone and the Cotton fibors, as shown Inter in this paper. Tlie contlit,iirns iinposed in this cage may be considered severe, since tlie mniish is deep in tlie slot where it. is not readily accessihle to the uxidizing act,iori of t,he oziorie. Tlien, too, this particular varnish is a so-called "short-oil" varnishi. e.. relatively lorn in oxidizable oils. A "long-oil" varnish would iliidoubtedly show a greater difference in tlie rate of drying by tlie use of ozonized air.
ts for dryness of a varod prescribed by the considered stanilard
Drying and Hardenine of Varnish Films
h study was made of the drying and hardening of varirisli lihiis :it different tcrnpcratures. The varnishes listed in Table I were used and an a.dditiona1test \vas made on varnish 3 using ozonized air. 1'i~oceoclc~---Tlie varnishes were tliinned to the specific in the fact,ory. Specimens of clean copper X 2.54 X 0.0127 em. (8 X 1 X 0.005 inch) wcre dipped iri the varnish to within 2.54 em. (1 inch) of the top of the sample. They were then hung to drain and, after this liad ceased, were placed in an oven a t the teinpemturw iiidiented iii Table IV. They were removed oIie a t a time after varying baking periods. Hardrms of tlzc varnish film was determined by the swingiiig beam hardness tester (Plate 2), an apparatus developed by It. 11. Walker nnd L. L. Steel. This tester consists of a pendulum weighing 110 g r a m with two supporting ball bt!arin@ 0.127 ein, in diameter. Wit.h the balls resting 011 dlie varnish surface, the device is set in oscillation through an arc of 45 degrees. The time for the arc to decrease to 22.5 degrees is takeii as the conipamtive hardness of the filni. The 22.5 degrees arc used in making these determinations vas chosen arbitrarily for convenience. However, i t is evident that the harder the film tlie less will the balls
~lafe I~-Appnrafus C'sed for Studying l n r u l a r i n ~varnishes
hy lie swinging bctam tester. Using this figurc, thc drying tiinw for tile vnrioiis varnishes nt baking t,enii~cmtiircsof 110" and 140' C. vere dntermirled. (Table V) l'able
v--Effecr of Temperature On Drying 'rime I > R U i U O TLMC
YnKaisir
1
a 4
5
i i n y c.
xi,,, I Z i 6'1
140"
c.
.win. 18 18
27 iiu
35
i s r CZU'
37 . 0 7tI.il
"1 5 32.5 4Sl.3
Urscussror --One dip of the specimen, Euihrved ii-draiiiing in the same vertical posit,ion, lcavcs an uneven tliickixs of the film which will vary slightly from the top to the haitom of the sample. The hardness will vary accoriliirgly, the
* i+oc.nm.SOC.
.mWinis, an. I, 707 (1925).
I N D U S T R I A L AND ENO.[NEERING CHEMISTRY
700
thin tilni ai. the top liardeuing somewhat more quickly than the thickcr film ne= the hottoin of the specimen. However, as all deierminations on all specimens were made in the sa.ine regular order, the averaged results arc probably representative of the sample tested. Eepcated tests ou the same varriisli with the same thickncss of film check very slowly. TESTSON V.4n~lstr 3 USING OZONIZED Am-Previous tests in this laboratory3 indicated that a saving in drying time of a t least 50 per cent might be rffected by proper treatment with ozonized air. These earlier tests were made according to the rnetlrod of the A. 8. T. M. 192.5.' The determinations recorded in this rcport were made to check earlier results and l o obtain more accnratc d a h on t,lie drying time by the use of ozonized air as compared rwit.itlr air baking. The procedure recorded above was used escept that an air flow of 7 liteis pe,r minute tbrough one oven and a flow of ozonized air (cone 0.4 per cent) at the same rate through a second oven was maintaiuod during drying and hardening
Vol. 20, No. 7
tical conditions was also studied. Tests were made on unvarnished cotton tape and on tape dipped in varnish No. 1 (sp. gr. 0.851). Table VII-Decrease
i n Hardening Time by Appllcafion of Ozoniaed Air DIP.
HARYNSSSA m OVEN OZONDOvsrr IESBNCB Srcondr Hours PIOW HOWE 11.3 0.3 0.25 0.05 15 0.75 0.37 0.38 20 2.4 0.50 1.90 2.5 4.5 0.57 3.93 30 7.3 0.63 6.87 35 8,78 0.68 8.10 e
Tlra
I I ~ Blank
Plate 2-Swinging Beam Hard
8
NO 3Varnish during Baking
(0"en temprratuie, 108' U a ~ ~ i s Ain OYBN
flour$
V' 'yl L
Swondi 10 13 I6 1'1 14
8 0
9 0 1
4 7 19 0 17 63 5 I'iilinaniry air bdke
OZONE O
c)
Y ~ N DcPSBRRNCII LccondA S(rronds 11 3= 0 5 19 3 6 3 41 6 24 7 58 7 39 7 82 9 58 8 121 4 92 3
I~CK~ASII
Po* C I M 4 b" 48 5
148 0
204 0 244 0 318 0
Effect of Heat and Ozone on Cotton Insulation
These tests acre made to determine whether temperatures higher than 110" C. (generally used for baking varnishes) could be used without damage to the cotton insulation. The effect of ozonized air as compared with an bake under idenSpence and Cochiim. irons
16 pp (1926)
4 m Eleifroihem Soc , SO (prqpnni),
Trm
Per Lent
16.6' 50. 0
Samples of white cotton tape 0.0177 X 1.90 em. (0.007 x 0.75 inch) were cut into strips 38 em. (15 inches) long to pcrniit at least three tensile-strength tests per &rip. Nine or more strength tests were made by testing three strips in order to secure a fair average figure. Samples of varnished tape were obtained by dipping 38. cm. (15-inch) strips in varnish 1 and draining in air for 15 minutes. These were then suspended in ovens at various tempratures. Tensileatrength tests were made on varnished and unvarnished tape baked in air (flow through oven, 7 liters per minute) and in air containing 0.1 per cent ozone (flow, 7 liters per minute) for the periods and at the temperatures indicated in Table VIII. Measurements of tensile strength were made by means of a Perkins tensile strength tester. Results are recorded in Table VIII.
lL0
130
16 32 Blank 8 16 32 Rl;o~k 8
16 32
Tests
---OPON~BAEB-
---AilRAL4---
TableVI-Hardenheof
IN
79.2 87.4 91.4 92.3 40 10.2 0.74 9.46 92.8 No ozwie wed durins this period, pzeiirninary air bake.
Table Viil-Tensile-SPenBfh
of the varnish. Oven temperature in C. Samples were removed from the o ing periods and the hardness of the fi swinging beam tester. Samples bake given a prcliminary air b ling of the varnish film this step in the proredure Tables VI and VI1 show clearly in drying of the varnish by means of with air baking. The resultmg film is co way with that obtained by the usual ai sults show that a hardness of 18 (the po varnish is considered dry) can be obtained by reducing the halung time 68 per cent nhen ozonized air i i used.
D*ERG*YB
Unvarnished Vamiohed Unvirrnished Varnished tape tape thpe tap< Lbr.1 Ka./ Lbs./ KE./ I.hs.1 Kg./ Lbs./ Kg.1 ~in.> ~ . ~ ,%.n Cm.i in.,cm.i sn.l cm.z 49 3.43 53 3.71 48 3 . 3 6 76 5:82 61 4.21 84 5:88 47 3.28 85 5.95 64 4 . 4 8 93 6.51 48 3.22 e3 6 . 5 1 62 4 . 3 4 100 7 . w 49 3.43 53 3.71 48 8 . 8 6 $9 5 : 5 3 63 4.41 84 5:b 45 3.15 88 6.10 58 4 . 0 8 101 7 . 0 7 43 3.01 95 6 . 6 5 56 3.92. 103 7.21 49 3.43 54 3.78 .. 48 3 . 3 6 94 4.13 98 6:%3 6 : 5 8 59 45 3.15 103 7 . 2 1 54 3.78 101 7 . 0 7 43 3.01 101 7 . 1 4 50 3.m ~ ( T J 7 . 6 3
..
.. ..
..
Blank tests were made before each group of tests to check figures on tensile strength of the roll as received. AIR ~ A K E - - ~ a m i & d Tupe. A g~adua1 increase in tensile strength was noted for temperatures up to 130" C. Above 140" C., except for the 8-hour period, a marked decrease in strenRth occurred. Unvarnished T q e . Only slight dccrease in tensile strength was observed for temperatures up to 140" C. Eight hours at this temperature does not seem to affect the tensilestrength materially. Sixtccn hours and 32 hours a t 140" C. cause some drop in tensile strength, but the greabest decrease occurs above this temperature. OZONIZED AIR B~m-Varn&hcd Tape. Results indicate that in general the ozone treatment causes a slightly greater increase in tensile strength than the corresponding air hake up to 130" C . I n either case the increase is due to the tonghening of the varnish film by oxidation, giving added strength to the tape. However, it will be noted from the curves that
July, 1928
INDUSTRIAL AND ENGIATEERINGCHEMISTRY
too long a heating period or too elevated a temperature will cause the varnish to lose its “life” with a subsequent lowering in tensile strength. Unvarnished Tape. I n this series of tests rather striking results were obtained. Air bake of unvarnished tape caused little or no change in the tensile strength. Under identical conditions of flow and temperature a marked increase in tensile strength was observed when unvarnished cotton tape was treated with ozonized air. The increase in strength with proper treatment averages between 20 and 30 per cent. It was found that such increases may be secured in much shorter time than that indicated in the table by increasing the ozone concentration or by utilizing a higher
70 1
baking temperature. For instance, a concentration of 0.5 per cent will cause a 20 per cent increase in 1/2 hour with baking temperature a t 110” C. or a lower concentration (0.1 per cent) and a temperature of 150” C. for ‘/2 hour will affect the same increase. Additional tests were made using ozonized air on pure silk and on cotton twine and cord. No effect was observed on silk, but in the case of the twine an increase in strength of 25 per cent was noted. Tests a t room temperature on cotton tape showed no effect even when higher concentrations were used. Temperatures above 100” C. seem to be necessary to bring about the reaction resulting in increased tensile strength.
Modified Scale for Pfund Color Grader for Use on Dark Sirups’ J. J. Willaman DIVISION O F AGRICULTURAL BIOCHEMISTRY,
UNIVERSITY OF M I N N E S O T A A N D WACONIA SORGHUM MILLS, WACONIA,
T
HE Pfund color grader was designed originally for honey, and it succeeds admirably on this material. When the writer tried it on a long series of sorghum sirups, however, he found that in some instances the samples were too dark t o fall within the scale on the instrument. The manufacturers2then furnished a set of three glass plates, duplicates of the wedge in the instrument a t its thickest end. Not much success was had in using these extra glasses according to the directions of t h e manufacturers. Since, however, their use did cause readings on even the darkest sirups to fallwithin the scale, it was decided to devise a simple method for their use. A series of e i g h t sirups, v a r y i n g i n color, was s e l e c t e d , and careful readings were made on each sample with one, two, and three added glasses. W h e n t h e color values of these samples were plotted against the number of glasses used, curves r e s u l t e d that suggested logarithmic relations. W h e n t h e number of glasses was p l o t t e d against the l o g a r i t h m s of t h e color values, the results shown in Figure 1 were obtained.
Figure 1-Logarithms’of !Readings on Dark Sirups w i t h A d d e d i G l a s s e s Plotted a g a i n s t t h e N u m b e r of Glasses
1 Received March 15, 1928. Published with the approval of the director, as Paper 733, Journal Series, M i n n e s o t a Agricultural ExDeriment Station. * Hnubon Company, Newark, N. J.
MI“.
The circles represent the actual readings; and the solid lines are straight lines drawn through the experimental points as determined for each sirup. It is apparent that, within experimental error, the points do lie in a straight line. Assuming that they do, a continuation of the lines t o the axis for zero-added glasses would indicate the log of the scale reading for that sirup. This was done, as indicated by the dotted lines. From the color values so obtained a table was prepared indicating, in reference to the normal scale, the color values in accordance with the number of glasses used. The intervals were smoothed where such a procedure was o b v i o u s l y justified. This table extended the use of the instrument from 14.0, the limit of its normal scale, to 15.7. In order to obviate the use of a table, a new scale was prepared (Figure 2) and affixedto the color grader in place of the old. If a sirup is too dark to be read on the normal scale one or more added glasses are used, and the line on the scale corresponding to the number of added glasses is used in reading the color value. The manufacturers of the i n s t r u ment have indicated their willingness to supply the new scale when desired. It might be of interest to add that the writer’s scale consisted of a “positive” zinc etching. A large drawing of the scale was made and sent t o a print shop with instructions as to the exact size of the etching. A “positive” was made, and this gave an accurate metal scale with raised lines. Although the writer has used the instrument and the new scale only on sorghum sirups, he feels certain that they will apply to any dark liquids, such as molasses, the color of which matches that of the wedge of the instrument.
