Evaluation of Quality of Paraffin Wax F. H. M A C M E N Standard Oil Company (Indiana), Whiting, Znd.
A new breaking strength
index values to tensile strength values of paraffin waxes by several currently used methods is also shown. Blocking resistance, sealing strength, and tensile strength (by various methods) of paraffin waxes are shown to vary inversely with the apparent oil content of paraffin wax as measured by the new method. Study of composition of paraffin waxes of high Indiana coating index indicates that refined paraffin waxes of good quality contain much less oil than that shown by solvent methods of analysis.
test for paraffin wax has been developed, which is simple in operation and yields closely reproducible values. Because of the close relationship between the breaking strength of paraffin wax and its quality as a paper-coating agent, results of this test are expressed in values called Indiana coating index. Data on paraffin waxes by this test are shown to give excellent correlation with data obtained by laboratory tests for sealing strength and blocking (sticking). The relationship of
P
APERS and boxes coated with paraffin wax have been used high-quality waxes as regards melting point, color, odor, oxidafor many years in the packaging of bread, cereals, etc. tion stability, and freedom from extraneous impurities. HowUse of such wax-coated wrappings makes it possible to preserve ever, there has not been a similar development toward the estabthe freshness of food for a considerable period of time, because of lishment of quantitative tests to measure blocking resistance the high resistance of wax films to the transmission of water and sealing strength. It has generally been appreciated that blocking resistance varies directly with the melting point of the vapor (4). More than 80% of all refined paraffin wax is marketed for use wax, and that both blocking resistance and sealing strength are in “wet-waxed” surface coatings. In the preparation of wetrelated in some manner to the structural strength of the wax. waxed papers, the paper is coated with melted wax in machines In the paper industry, a number of tests have been developed designed to apply a film of uniform known thickness to each side for estimating probable blocking tendencies and sealing strengths of the paper, which is then chilled on a cold roll or in a water of waxes. Various devices used for measuring tensile strength bath. The finished waxed paper is stored, shipped, and sold to of cloth, paper, metal, etc., have been modified to handle molded users in the form of rolls or in bundles of sheets. In the principal specimens of paraffin wax. Since a b u t 1930, one of tAe most application of waxed paper-the wrapping of bread-waxed commonly used instruments for measuring the tensile strength of sheets are fed into a wrapping machine which heat-seals the seam paraffi wax has been the Perkins tester (S),in which a rapidly under the load and the folded increasing pull ie applied to a molded paper a t the ends of the loaf. It test bar of wax in the Rhape of a dumbbell with a cross seetion of is necessary that these seals form a continuous film of wax and re0.25 square inch at the center. main tight, in order to retain the A l t h o u g h t h e P e r k i n s tensilemoisture within the wrapper. strength tester and other eimilar devices are simple to operate, exTwo principal performance reperience showed that they lack the quirements for paraffin wax used precision necessary for the niaking in waxed-paper wrappers are indicated by the foregoing consideraof sound deductions in regard to tions. In order that the film of wax quality and performance in service. wax on the paper itself may reIn view of the inadequacy of main free of surface damage rethese tensile-strength tests as a p sulting from the handling and plied to paraffin wax, a program storage of the waxed paper in was undertaken to devise a new large rolls or heavy stacks of TO RELAY a TIMER method for measuring structural sheeta, the wax must have good strength of waxes, and to establish resistance to “blocking.” This sound laboratory tests for meaaurterm is used to describe the sticking blocking resistance and sealing ing together of individual sheets strength of wax coatings. As a reof waxed paper, such that, in exsult of these studies, a new test treme cases, a stack of sheets bemethod has been developed which comes a solid block of wax conmeasures the breaking strength of taining layers of paper. Secondly, WEIGHT parafin wax, and laboratory techin order that heat-sealing will niques have been devised for measproduce a strong continuous wax uring blocking resistance and sealfdm, the paraffin wax must possess ing strength. The new breakingadequate sealing strength. strength method is called the Wax refiners have steadily imIndiana coating index test, to indiproved their manufacturing faciliFigure 1. Schematic Drawing of Tester cate its applicability to the evaluaties and methods of test to assure for Indiana Coating Index Test I
n
@ -
2134
October 1950
INDUSTRIAL A N D ENGINEERING CHEMISTRY
2135
tiouof waxes for coating paper. T h e method has been found to yicld reproducible m d t s a,hieh man be EDTMlated with blocking reaistanoe and seal-
ing strength, as rneaa"red in the Isboratory. BASIC TEST F O R PARAWWIN-WAX OUALITY
Exploretory ethrte 00," or mtenf-bending test for paraffin "ax red t m l in several tests which did not. give repeatable result B . IIawever, when the loading of the test bar on 8 flow-type test w m continued Figure 2. E q u i p m e n t for Indiana Coatins Index Teat to the breaking point it was found that exeellent msults were obtained on repeatability of hreukiug P ~ ~ c r s r01 o ~Mmxoo. Teats oil many saniplea u i paraffin strength. As a result, a simple bnaic teat was developed which wax, such as those shown in Table I, have shown index values to i e based 01) the uniform loading of B 0.5 X 0.5 X 3.625 inch test be olosely repepeatable. The data in Tablo I comprise all the t,est l a t the free end. bar held a s a cantilever ~ n rloaded values obtained on four refined paraffin W&XOB, and the Indiana A schematic drawing of the test apparatus ir shown in Figure mating index values show satiefactorily low standard deviationv I , and B picture of the assembled test equipment is shown in of 1.18, 2.69, 2.81, and 3.17. Talde I1 presents reprodueihility Ngure 2. t,o develop a
The test equipment consists essentially of B 8" port for the test bar and for B free-Rosting loading spindle. Theyoad is B plied in anits of 0.25 pound every 5 Booonds to the loading spindg, which
follows any detleetion of the test bar and thus permits continuous application of the inoreasin load until the teat specimen breaku.
AoontaOt switch on the lon%ingqpindIeeontroIsB timer, which reoords the total loading time. T c time, ID seoonds, from the bpn?ing of loading until the bar breaks is called the Indiana coatlog index of the wax being tested.
P n o c ~ ~ u mThe . WM sample for test is melted on B water bath at a temperature not over 180" F., and is then passed through B Ruled paper filter to remove wnter arid any extramom meterial. The filtered sample is stirred and a portion estimated st 50 pamv is quickly heated to 235" F. itrid immediately poured to fill three of the standard molds placed on olished stainloss-stoel plates on the 70" F. constant-temperature gath shown in Figure 2. (Prior to we, the molds 81.8 thoraughly washed in hot wster and dried on B clem linefree toad.) Shrinkage 01 the test bars on cmling is taken e w e of by repeated addition ofmolten wax to the specimens over B %minute eriod. This technique prevents the formation of air pofkela anjloads to test bars of uniform cross section. The specimens are allorved to set for Bo minutes, after which the e x e e ~ i ~ WBX protruding above the top of the mold is removed with the aperial Bcraping knife, 8hox.n in the foreground in Figure 2. The test bar is removed by inverting the mold in the hand and tapping tho side of the mold with B plastic hammer, while pressing upward with the firrgem on the trimmed surEaee or the test ha?. After being marked for identification on one end of the cut side, the test bnrs we placed in the 70" F. water bath for 90 minutes. The specimcn to be tested is inserted, vith the trimmed side down, in the holding jig of the tester, which is submerged in t.he 70' F. water bath. The vertical loading spindle, which weighs 0.25 vound. ia then lowered onto the bar. Contact with the bar do& B relay circuit, which starts the timer. A 0.25.pound weight is sddcd to the losding spindle 5 sor,onds sfter lire contact is closed and every 5 seconds thereafter untd tho bar breaks, at which time the circuit opens snd the timer stops. The average worded time in seconds obtained on three test ban is reported BY the Indiana coating index of the paraffin WY.
.4r. Stsndard duiiatiun
70 0 I 18
WAX B 1
I42 0.127.0. 141.3
138 h
2 3
139.0.146 2 , 146.0 136 1. 138 fi. 136 8 142 0 . 1 2 0 . 3 . i4i.i 138.0. 1 4 1 . 2 , 140 0
I43 I XI6 6
iza !$. 1 3 5 . 7 . 123 61 129 3,123.8,LZI 0 132 2 . 110 h. 119 6 134.7.188 a. 1 2 8 . 1 120 4. i 2 7 . 0 , 121.3
1% 1 124.7 122.8
4 5
L 2 3
4
5
ilJ.8 is!! !I
182
,
126.9
I". 127.0 Strndard deviation
3.17
INDUSTRIAL AND ENGINEERING CHEMISTRY
2136
Vol. 42, NQ. 10
rurfilce ia iilway~placed downward in the taater, 80 that it is wder
compreseimi. Although the Indiana coating index test as described above lils becn shown to hem adequate prreiaion, attention has becn &Yen to the modifieat,ion of the equipment to permit mtomatio loading ond thus to minimize the personal element inherent in the ad& tioo of 0.25-pound weight8 by hand. A iurther development i s t.he shot-loading attachment for the bhsie teeter, shown io Figure 3. This loading device i s based on B modification of the Rlwm (ielomrter (Precision Scientific Compnny, Chicago, III.)and h a s s solenoid-operated chute which i s owned or closed by the epindle unetnct switch. The shot-loaded t e a m hna been found to be sutidaetory in operation and to eliminate the tedioubneas nocompanying hend Ionding. A recent development of an auto. nintic beam loader har bcen atandnnlircd ior routine me. B y s a y of comparison of the preeiaion of the Perkins test with that indicated ~ I M V B for Indiana eontinE index, Table 111 summarizes rfata obtained in two laboratories on repeated Perkins tests of three wax ssmplee. Tliese data illustrrte the diffioulty encountered in attempts to cheek the tensile strength of WBXW by the Pcrkins method, in spite of the oonsidenrble effort that h a bwn made in recent yeem to improve the preeinion of this method. These findings are in agreement with tliosc olPadgettundI~i1Iing~worth (S), in their discussion of determination by the Perkins test. Padgett and Killingasorth (6) also discuss their work on the improved Tinius Olscn test, showing results by it to be more consistent and representative than those obtained by the Perkins machine. Studies in the author's la1,orstotiea have indionted that the erratic naulte frequently enoountered in the Perkins test am due to the effect of the cut surfaceof the spcimen, straios and tomima1 effects in the specimen during pulling, and the rspid rate of load application. In an effort to obtain B correlation of Indiana ooeting index with nversge Perkins tensile-strength values, teat data by both Fisure 3.
Shot-hading Tert Equipnieet 500
data obtained nil two iidw testem i n different Istwrnto&a with different operator* with the a ~ e r per ~ ~cent e difference of about 3.4%. It ir: believed that the precision of the test i s adequate.
480
460 4.w
e20
DISCUSSION OF THE MFTROD
--
ua-
The loading of tho apeaimen ii) the indox test at the rate of 0.25 pound every 5 aecnnds or 0.05 pound PCP aeeond i s much Lower then that of the Perkins test or similar methods, which apply load at the rate of 10 to 20 pounds per sccond. The low rate of load in the indox test, coupled with the provision of free-floating loading, is particulitrly suitable for wax testing, as paraffin wax is somewhat plastio under stmas. To minimize the behavior caused by irreguhtities in tho cut surfbee of the test hnr, this
WKI-
3Myo-
320 -I 300
-4 -#
Po
-&
240
-3
: 3-
TABLE If. R ~ r n o ~ u c ~ s OF r ~INDIANA r ~ r C o ~ n s oINDEXTE~TY samr,ic No.
Indiana Coating Index Lab. 1 L*b.T
5
Dieerenee
IO
--
M)-
I*
lm
Do.-
Figure 4.
Relation of Indiana Coating Index to Other Tensile Strenath Teste
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
October 19so
2131
methocla hrive bean obtained on more thnrr 1000 ailinplea ui p w rffin wax. Tho resulting relntiorinhip 18 plottod n8 the lowest
curve of Figure 4, in whioh is alao shown an lrpproriiilirte COITC~Dtion of index with strength of wsx as measured by three other methods (in cooperative work). These tests sic Tiniu8 Olscn tert (Moor0 and Munger Corporation, New York, N.Y , ) , I)illon text (Pure Pwk Division, Enoello Corporation, Detroit, Xich.), and modulus of rupture test (American Can Cornpimy, Maywood, Ill.). The modulus of rupture text ie a low rate of load test developed by L. E. Hosg and differs from most tensile tests io use of thin specimens. I t i8 obvious that the rwults of the Indiana mating index tcst are cxpressed in arbitrarv timc units, and hence do not provide a measure of atiuoturd strength in oonventioiral units. Although the distnrice from the point st which the load i s applicd to the jig supporting t.he fixed end of the teat bar varies alightly in length during the test because of defleotion, it is possible tu mtimste the actual tensile st,rength, in pounds per square inch, in the outer fibers by means of the iormuln for e. cantilever loaded at one end:
Figure 5.
Indiana Sealing Strmgth Tester
:Luteis ( 8 ) liiis l i w n u r d i n ~ l r eU . U E ~ U I . ' SIahaLwies iu IIIYA~UI.C sealing strengths of mimy papers eontecl witli paraffin WBZFS of widely virryiirg indexes. Thp s~:aIina-strcngllitestci i s shown in where '/+M ' i s t,he seetion modulus. On substitution of t,tie YUIues for 1 (length 2.5 inches), b (breadth 0.5 inch), and d (depth
0.5 inch), Equation I becomes
S = 12oP
(2)
where P i a 1 . l load. ~ At. the breirking point, the load i s one twentieth of tile index, &5 the loading rate is 0.05 pound per second. tfcncr, 1,:quetion 2 is equivalent to
S = 61
Fig"": 5.
Yieesa of waxed paper, 7 x 4.5 incht!~, cliruified as to wiglit and uniformity of added wax, arc hoat^SL'illcd on 9 hot plate at ZW' F. for 5 seeonds, and art? then cooled to 70" F. Seals we mede between inked-to-inked, iaked-to-uninked, and two uninked suriaees. The sealed sheets w e pulled spnrt on n Y ~ C U U I I Ipull-
ing device using a Dristol recorder to ahtwiii t,hc B Y ~ I R R Erate of
(3)
where f ia the Indiana mating index ConnmArIoN OF INDEX VALUES VATH SERVICE PERFORMANCE TESTY In i m ! LO ~ develop the relation of the Indituu coating index test to swvice behavior of paraffin mxe8 for coating p&perIIsborntory t?st methods have been developed to measure blocking r e siutanrv and sealing under controlled conditions.
These test methoda tire empirical in nature and arc pritrerned after service conditions. Although only limited long-range quantitative compurisons with %ctu&Iservice behavior am wailable, thc direct nature of the Inborntory testa i a suffioient to afford confideriec i n their periormance. RELATION 01INDEX TO SEALING STEENOTHOF WAXEDPAPEX. Practically every manuiaotumr of wax-coated paper has somr method for appraising senling strength of waved papers. Most oi these teste 818 simple in nature and measure the force required 10 pull apart two shoets of paper hest-seded and cooled under com trolled conditions. A mdification of a aoaling-strength test de. veloprd RL the &lamuroo Vegetable Pwehiricnt Company by Des
z
=I
j 20
INDIANA COATING INDEX Figure 6 . Sealing Strenplh 70- P. w*t ,rmprre,ure ZS.!,"""d
""if,,*
P'PCI.
2138
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 42, No. 10
The Indiaiie blmking test qumtit,atively momure~the bloekin damage to wax films Spplied to "full hard" aluminum foil 0,OOMiioh thickness. Two wax-coated aluminum sheets are
07
point of the wax. Wax films for this test are andied to the aluminum foil bv a serted in n 4 X 5inch photoeraphie-film e m & and is immersed in a borosilicate ~ I J S S dish containins the melted wax at 190' F.
70' F. in air. Ermueh coated aluminum shePt8 are ~reaaredto make tests at
2
4
e
8
a
le
w
ocher accessories are all msintainLd at35 " F. for a minimum of 0.5 hour. At this h o e r a t w e . B air of nrenarcd wax-cantrd foil 16
m
LBS. WAXIREAM Figure 7.
Sealing Test Data
%pound
e u l A t s semk
pull during 15 seeoilds. To obtain a n sversge sealirrgiitrcngth value, twelve pairs of the 7 X 4.5 inch sheets are hestsealed and pulled apart. This .everage value is expressed in grams ofpull on a 7-in~hs e d .
Data from titis twt work were obtsiiicd on [rspers matie on experimental-male waning machines of both the "dip squccm?' and the Xayer type. Waned papers used in this p m g r ~ mwuen coated with regular eommereial refined paraffin w~xes,mid with waxes of lowered quality made by the additios of increments of oil to high-quality paraffin wax. The data shown in Figures6 and 7 were obtained on wwes of 132" F. melting point. Ttiese figures show t.hxt index values eorrelste rollably with sealing strengthWBX of 135index gives about 35% hettrr seals than &index wsx, arid 50% better seals than 35.inden wax. Sealing strengtb is also n function of the thickness of the wax coating, but most self-sc!ding b r e d wraps w e coated with I1 to 14 pounds of wxx per ream. Regular b r e d wrap, which is 25.pounds-per-ream SUIlite paper coated with an average of about 13 pounds of wax pci ream, hns long givcn fairly sntiufaetory seals with wax of avcrege quality. It is evident that any substantial increase in structural strength ia extra assurance of uniformly better R T ~ S . The inrprovements in sealing strengt,hwith incremr in index seems logied becsusc it rvould he expected from the increase in stnzetural strength of the wax. I~ELATXON OF INDIANACOAT~NG INDEXTO B~ocnrncl t ~ s i s n ANCB. Many tcsts have been devised and nre in use in the pspiprr industry to memure the blocking resistance of wax-roatptl papers under Ion& and temperature conditions compsrable to thwe encountered in the manufiieture, storage, and use of waxptl psper. These tests in general involvc the loading up to 1 pound per square inch of R stnek of sheets of waved paper for periods rmging from 17 to 21 hoon, followed by pulling apart,of the sheets. The dnmnge is appraised visually in terma of smface eKcfects (picking, stripping, marring, and loss of gloss). Becsuse of paper surfnee irregularhies, reflection effeots, etc., it i s difficult to establish a quant.itative appraisal of blocking damage on psper surfnow. Accordingly, n test has been developed to measure the blocking resistance of wax films doposited on aluminum foil, which permits sccumt,e mcasurement of the blocking damage. This test is d l e d the Indiiina blocking test.
plates by a tedsioo separatbr, and the fofi specimens are immedisi& neeled mart manudlv at the test temoerature. Anv dame g d &aindiksted by stri6ping (actual trebfer of wax f&m one film Lo the other) l a mcasurrd bv URC of B nlanimeter or other
test temjfersture (5' F. hidher), &d kssubsequently repeated at sucroedingly higher temperatures until &lmmtall of the test area of1 4 , W B mm exhibits bloeking damage. (Althoug muoh of the early work employed the m&msIlosding and unloading just described, the mom recent development of mehmical loading has led to easier ways to carry out the test by mesm of B pressure balloon loader or B piston loading dcvioa.) I"igure 9 shows the rcsult~of a series of tests of different lots of p a r f i n wax, all of 132' F. melting point but varying in index. T h e blocking damage increases sharply with rising test temperawrc, p ~ ~ t i ~ u lfor ~ r the l y uunplcs of higher index, %rid blocking dnmxge drrrot~~ses as the index increases. The blocking behavior
Figero 8.
%,amplePreparation for Blocking Test
October 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
the Indiana blocking test are more severe tnan would be obtained if the wax were on paper, inasmuch as the fibrous surface of the paper furnishes a “toe hold” for the wax. Furthermore, the teet is made a t three times the load normally encountered in the industry in storage, shipment, and use of waxed paper. Wax blocking tests are in a sense hardness tests of wax films a t elevated temperature. It has been shown by work in the author’s laboratories on the hardness of paraffin wax, as measured by needle penetration and Shore hardness tests, that refined para& waxes increase in hardness with rise in index, although such measurements on crystalline wax are difficult to reproduce on a quantitative basis. Minchin (6)cites a definite trend in the rise in hardness of waxes with improved quality as indicated by degree of refinement. Considerable work has been done on storage tests of waxed papers in controlled temperature cabinets, with the papers under loads varying from 0.26 to 3 pounds per square inch and the time of tests from 1 week to 6 months. Observations on these storage tests have shown that as wax index rises from a low level, waxed papers become increasingly resistant to surface damage and to the tendency to stick together. This work was done mainly on waxed papers made on experimental waxing machines with some commercially prepared waxed papers furnished by several cooperating paper companies. Although the results of these storage tests agree qualitatively with those on aluminum foil, and further demonstrate the importance of melting point and index, it has not been found possible to develop a quantitative set of data. A dyestain technique using Rhodamine B dye to appraise blocking damage has been of considerable help in estimating blocking damage by various tests made on waxed papers. The water solution of the dye stains the damaged areas from which wax has been removed, but doesnot affect the undamaged areas. Preliminary w e of dye-staining technique and of a Hunter reflectometer for measuring blocking damage by the loss of gloss appears to have some merit in providing quantitative appraisal. Further work is in progress to obtain adequate data on paper blocking teats in relation to index and melting point, inasmuch as the recent work attempting to correlate foil and paper blocking tests has not been conclusive.
10000 so00
2139
-
TEST TEMPERATUREOF. Figure 9. Blocking Damage of 132’ F. Melting Point Paraffin Waxes
of samples differing in index by as little as 5 units is readily dttinguishable. The results of a set of blocking tests a t varying test temperature on a given sample of wax may be expressed as a single result by selection of the maximum temperature at which a certain degree of blocking damage occurs. For practical purposes, it is felt that damage of 100 sq. mm. may be considered negligible. A cross plot of the data in Figure 9 gives rise to the curve for 132’ F. CORRELATION OF INDEX WITH OIL CONTENT OF PARAFFIN melting-point wax shown in Figure 10. Included here are also WAX curves for waxes of 124O, 129O,and 137’ F. melting point, upon There never has been a precise definition of “oil” in p a r a h which were obtained basic data similar to those represented in wax, for there has been no precise method for completely partiFigure 9. These curves show for each wax an excellent correlationing oil from wax. Nevertheless, users of paraffin wax have tion of blocking damage with index, and also support past experiattempted to specify maximum oil contents, generally determined ence that melting point is a primary factor in blocking. The spread between these curves is approximately the difference in melting point. As an illustration of how index can compensate for melting point, i t can be seen in Figure 10 that the blocking behavior of wax A of 132’ F. melting point and 67 index is duplicated by that of wax B of 129’ F. melting point and 80 index and by wax C of 124’ F. melting point and 106 index. The effect of difference in index in the case of two waxes of the same melting point is shown in Figure 11, a photograph of two b l o c k i n g - t e s t p l a t e s after test. This photograph reveals the serious blocking damage on a wax of good quality (93index) as compared to the superior performance of I a wax of 140 index a t a very severe test I temperature only 7’ F. below the melting point of the waxes. (Both plates were dusted with carbon black to increase photographic contrast.) In consideration of the test conditions Figure 10. Maximum Blocking Test Temperaturefor Negligible Blocking employed, it is believed that the results of Damage vs. Indiana Coating Index
--
Vol. 42, No. 10
INDUSTRIAL AND ENGINEERING CHEMISTRY
2140
Ficiire 11.
Blockinn Test Plates
A curve of oil content of wax plotted against index FSB constructed from data obtained by adding weighed amounts of white oil to waresof 163 index (132O F. meltingpoint) and obtainingindel vdues for the blends. This CUNP, rhown in Figure 12, ww estnblished by the aolid circles, on the assumpt.ion that wax of 163 index contains O.W331% oil. Because addtd oil in mall incm mcnts rsnging from 0.W332 to 0.01% haa an extremely small effect on index, whereas increments of 0.02 to 0.3% c w 8 e the curve to break sharply, it is believed valid to r o w n that the positioning of the 160-index wax very closely spproximstw true oil eont.ent. M a n y samplce of lower-index WBX were spotted 011 the curve at the points corresponding to their index values and addition of knosn increments of oil to these samples yielded index values t.hat closely roprodurcd the shape of the m&er curve. Them added wemples are shown by t.hr points other than solid circle8 in Figure 12. A variet,y of oils haviris viscosities from 80 to 315 Saybolt meonda Uniyersal nt 1 0 " F. Hhowed no difference in effect on index. This curve applies to parsffin waxes from 122/ 24' to 135/37" molting point grades, nlthoilgir the curve was originally esf,ablislied on coating grade wanes from 130' up to 137' F. melting point. RELATION OF OLLCONTENT BY I ~ u r x CIJXVE AND BY A.S.T.M. I> 721-44. The use of the master curve in eombinstion with index vdltes of w&xyields B value for apparent oil content of wax. Dnts have been obtained on oil content of R aeries of 88mpIe8 of refmed paraffin WBX by the index test and by cooperative work smong six petroleum laboratories using A.S.T.M. Method D 72144. The averages shown in Table IV for the A.S.T.M. method are much higher than thoae indicated for the index method. Even zwuming thnt WBX of 163 index does not contain the extremely 10%. oil content used as the basis for Figure 12, results obtained by the A.S.T.M. method atilt nppear to bo inordinately high. h p l e C,foremple,isnhown bytheA.S.T.M.methodtocontain0.57% oil. Based on quality BB measured by blocking, index, and hardnew le&, this is obviously * u w of good quelity; it is extremely doubtful if it oontains oil to the extent of 0.5%. Data published by Padgett and Killingsworth ( 6 )show the difficulties of correlating tensilo strength witit oil content as determined by solvent methods. Ineamuch as index vduc~iare oloaely reproducible, the curve in Figure 12 provides B rapid method of obtaining the "ap
TASWO IF'. OILC O ~ E NOF T PILRIIPFIIN WAXES R r A.S.T.M. D 721-44 AND I N D E X CURVE % Oil --____-A B C D E
F
A r . of drterniinsll*,le in six
laboratorier by A.S.T.M. D7ZL-44 4 v . 01 two d s t wninstioos by ioder motliod
0.67
0.71
0.57
0.78
0.45
0.60
034
0.28
0.12
0.15
o.ia
0.24
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
October 19sO
parent” (effective) oil content, which appears to be closer to the true value than results obtained by solvent methods. In considering the merits of solvent methods for the determination of oil in wax, it is worth noting that all such methods are based on equilibrium partition of “oil” and wax, which depends upon wax solubility a t the separation temperature. A.S.T.M. D 721-44 makes a 0.15% allowance for solubility of wax in methyl ethyl ketone a t the separation temperature. However, the lowest melting fractions of paraffin wax are more soluble in such solvents as methyl ethyl ketone than is average paraffin wax. Data have been obtained on the effect of addition of pure hydrocarbons in the range of 60” to 100’ F. melting point to waxes of high index. The following examples indicate how low-melting waxy hydrorarbons affect the index in comparison with the effect of added oil. Hydrocarbon n-Hexadecane n-Octadecane n-Eicosane
M.P., F.
Effect on Index in Terms of Equivalent Added Oil
64.4
1.0 0.2 0.1
82.4
97.7
I t is known from other work that highly refined paraffin waxes contain small amounts of CN to Cnohydrocarbons, and that less refined waxes may contain some C18and Cip hydrocarbons. These low-melting-point compounds may well be the confusing factor in appraisals of wax quality by solvent-method oil determinations. CONCLUSION
Substantial improvement has been made in evaluation methods for para&-wax quality. A new breaking-strength test has been correlated with laboratory performance tests on blocking resistance and sealing strength. These laboratory performance tests are indicated to parallel actual service behavior of waxed paper.
2141
The breaking-strength test, designated as the Indiana coating index test, may also be used to estimate reliably the oil content of paraffin wax. ACKNOWLEDGMENT
The assistance of P. J. Gianacakes, R. A. Hunt, E. M. Pramuk, C. N. White, A. W. Weitkamp, M. D. Gjerde, and D. I. Walker t~ associates in this work is gratefully acknowledged. Thanks are also extended to T. H. Rogers and E. W. Adams for counsel in the conduct of this program. The excellent cooperation of technical personnel in the paper industry has been of substantial assistance, and specific acknowledgment is made to: G. F. Des Autels, R. H. Hurst, and M. W. Kane, Kalamaroo Vegetable Parchment Company; Glenn Rumberger and A. M. Heald, Marathon Corporation; J. A. Hawley, Warren Price, H. K. Snyder, and R. B. Donnelly, Central Waxed Paper Company; John Morrison and William Erickson, Phoenix Metal Cap Company; D. J. Crawford, Excello Corporation; T. E, Dobbins and L. E. Hoag, American Can Company; and J. W. Padgett, Moore & Munger. LITERATURE CITED (1) Carpenter, J. A., J . Znet. P e t r o h m Technol., 12, 289 (1936). (2) Des Autels, G. F., private communication. (3) Espach, R. H., U. 8.Bur. Mines, Bull. 388 (1935). (4) Hermann, D. B., Rubber Age ( N . Y,), 36,74(1934). (5) Minchin, S. T.,J . Zmt. Petroleum, 34, 558 (1948). (6) Padgett, F. W., and Killingsworth, R. B., Paper Trade J.. 122, 37-43 (May 9, 1946). (7) Wilson et aE., “Science of Petroleum,” Vol. IV, p. 2681, London and New York, Oxford University Press, 1938.
RECEIVED September 14,1949. Prasented before the Division of Petroleum CHEMICAL SOCIETY, Chemistry at the 118th Meeting of the AMEEIOAN Atlantic City# N. J.
Pvrolysis of the Calcium - Salts of Fatty Acids J
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HSIEN-LIANG HSUI, J. 0. OSBURN, AND C. S. GROVE, JR.* The State University of Zowa, Zowa City, Zowa Thermal cracking of the calcium salts of tung oil fatty acids leads to a high yield (48.6%) of residual coke and a low yield (41.5%) of cracked distillate which contains large quantities of aromatic compounds (25.8%). Similarly, cracking of the calcium salt of stearic acid leads to a low yield (17.3%) of residual coke and a high yield (76.0%) of cracked distillate which contains only 4.41% of aromatic compounds. These results were confirmed by the characterization factor and chemical analysis. A mechanism is proposed for the cracking of these calcium salts which helps to explain the propertiesof the lubricating oils formed from the distillate.
M
UCH work has been done on the conversion of vegetable or animal oils and fats, soaps, and fatty acids to artificial petroleum. Gallo and Correlli (12), Bouffort ( 4 ) , Mailhe (88-80, 32-34), Kobayashi and his co-workers (17-19), Koo and Cheng (20-22),Ping ( 4 4 43), Lo and his co-workers 1
Prwent address, Great Lakes Carbon Corporation, Chicago, 111. Present address, Syracuse University, Syracuse, N. Y.
(,@3-26),Egloff and his co-workers (&IO), Gomer (13), and Oberhausen (38) have cracked vegetable or animal oils and fate into hydrocarbons suitable for motor fuel. Thermal cracking of fatty acid salts (mostly of calcium) of various oils has been investigated by Inouye (16),Sat0 and his co-workers (46-49), Beuer and Weinmann (d), Arnoux ( I ) , Cheng (B), Delaby and Charonnat (?), Melis (86),Grun and Wirth (14), Pictet (40),and Pictet and Potok (41). Cracking of the higher fatty acids has also been studied by Mailhe (81, 36), Petrov (89), and Zelinskii and Levine (60). Chang and Wan (6) in a recent paper reported their studies on the thermal cracking of the soaps of vegetable oils; they also cracked vegetable oils thermally or catalytically into motor fuels. Only a relatively small amount of lubricants was obtained from these products. Complete data on the chemical composition of the cracked distillate have not been reported. CRACKING APPARATUS
The cracking apparatus, Figure 1, consisted of a cast iron retort, a condenser, a receiver, gas scrubbers, a gas meter, and gas collectors.
