INDUSTRIAL AND ENGINEERING CHEMISTRY
948
Vol. 38, No. 9
may cause emulsions due t,o additional extractable msttlrial &jL\.EST REC~VER-I Broths from corn steep media have been successfully studied ir PROCESS t'he extraction tube (step 1). Tower extraction with buffer soluStep No. I 2 3 4 tion of the amyl acetate solution of penicillin from corn stecyj Broth+.%A -+Buffer+CHCla--+ S a salt -1011t. medium has not been studied. However, it is worth consid(1r:iVol. ratio 0.4 0.2 0.4 0 4 2.0 7.4 2.0 ti and 7 tion, especially as smaller amounts of corn steep solids arc' bring g:aagent R HsPO4, 10 Phosphate, 2 HsSOb, 10 NaOH, 2 Contact 'time. used in fermentation media. min. 0.3 2.5 5.0 Tu coiibcaiii p H Table VI1 summarizes data for the recovery of penicillin fruri. Method Continuous Continouous Batchwise Batchu-ise Bow counterfour broths. The general method for recovery and purification (I: current tlicl penicillin from each broth n-as thc same and coiisisted of foil1 c,straction steps. These steps, :ilong xvith cJttier pertincwt d:it:i, : I W siinimarizrd in Tab10 1.111. liquid. A one-my stopcock, 31, adjusts the flon rat0 to extrai.tion tower 32. \ C h h \ O l Lk:I)G\IENT The buffer reservoir, 33, is connected with vacuuni line 17 ioi lopmelit n-ork is part of a prog1:iiii > ~ O I P the purpose of charging through a line, 34, from the buffer storngi', oductiori Rmearch and Devclopnient o! 35. It is also connected with pressure line 21 for fccding thtb the K a r Production Board. Tlie authors wish to thank 1,. A . buffer under a constant pressure head. A take-off line, 36, lend. Elder, L.A. Monroc. and .J. P. Kilkins, formerly of that o f i c ~ . . through the buffer flowmeter, 37, and a stopcock, 38, to cxtrncfor their help. They also n-ish to thank heartily the Bncteriolog> tion tower 32. One-way stopcock 38 controls the ratc of flon.. Department, of the Pixnnsylvariia Stste College, for the ferniwiThe buffer extract, 39, is continuously d r a m off from the bottoni t:ition and assay nork necessary for this project,. Help on s p of the tower and the spent nmyl ncc~tati~, -10, from thi? top o f tlii, rially trouhlc>oniepoints was received from Tcnncssmt tower. ('orpor:itirrn and Heyden Chemical Corporstinn. The two-step contiiiuous estractioii niodi.1 has beeii used s u r cessfully in the proccsqing of batrhes of broth vai,yiny in volunw from 6 to 200 liters. S o de-emulsifying :igents Iiavc. I i o t ~ i inc'cei.sary. H o m v e r , the use of the 1attPr may depeiid upon tlic clinracter of the broth. In the prewnt \\-ark a synthetic nicdium :iloiig xit,h a moId strain (SIinn, Culture Xl612) v a s used for the fermentation of thc penicillin. Thus, a broth i- obtained n-liicli contains rery little extractable solids. The conventional submerged broth resulting from ii nicdiuni using corn steq) liqiiot
TABLE \'m.
SCMYARY OF COXDITIOSS FIIR
Effect of Polvmolecularitv on J J
Deformation of Butyl Polvmers R. L. Z-kPY
.ml) F.
P. BALDWIJ
Esso Laboratories, Standurd Oil Dez.elopmen t Company. Elizabeth, ,\. J .
M
OST high polymers exist in a polgmulec*ularatate i i i varying
pi,c'cipitatioii of all niolecular weight tpecies. (6) Butyl rubber degree dependent upon variations of conditions, modificais not readily changed by short term storage a t room temperature and, in the case of normal molecular weights, manipulntione tions, and courses of reaction during polymerization and chain such as slight milling and molding of samples result in littlc termination (7, 16). The extent, of heterogeneity oi molecular molecular weight change. weight profoundly affect,s the de€ormation behavior of high polyI t is realized that various type2 of elastomeric moleculix-. differ meric substances, a3 noted in the case of unvulcanized Butyl in esteiit of branching, amount and type of substituted sidt polymers during a study of their elastic-plastic properties (17 ) , groups, unsaturstion, and degree of rhuin kinking. However. Differences in physical properties of cellulose derivatives atit is hrlieved that differences in deformation behavior attributablr tributable t o polymolecularity were recently reported ( 1 2 ) , arid to niolwular weight distribution as measured for one polymer improvements in some Buna S processing qualities Twre preshould have some interrelation ivith other types. Tliercfore, dicted if narroiver distributions of molecular \wight could bc, obtained (8). the effcct of vsriutioris in nivlecular weight and of nioltcular Previous study of the processing heliaviUr uf elaitoniers iridiiveigtit,distribution upon Butyl properties should be oi universal intcrcst in ronnci~tiiin\\-ifli thi. suhjert of rubbtxrlike b~~1i:ivio~ cated the desirability of investigating tlie effects of carefully controlled molecular n eight and moleculur ivciglit distribution upon the deformation characteristics of the material. Butyl 3 \ \ I P L E PKEl'.A.K4TIOl rubber lends itself n-ell to the study of individunl nioleculnr species and combinations of them because of 6 l i i gciierai tlie fractionation pruccdurc 1v:is siniilnr to th:it cvolvcd by Flory for polyiwbutylenes ((i). One hundred-gram purticlii. of a ) Butyl rubber is essentially a long-chain polymc~rn.ith no detectable branching (ti) or cross linking. For tlii. ~ C : I F U I ~it i? :I Butyl rubber !veri' &solved in 10,000 cc. of dried \j~117CWcarid completely soluble (that is, free of gel 1~olytii~r) : thih wluhilit>tliix precipitation ~ i 1 3carried oilt Ivitli dricd acetone at 25' C facilitate6 a fractionation procedure hy solutio~i:ind i i . ~ ~ j . c ~ c ~ u r ~ i t 111 :I coiiitsnt temperaturc~n-:itcxr bath. Eight 100-gram port inn^
September, 1946
were fractionated into niiie relatively narrow molecular weight cuts; the respective cuts viere then comb i n e d b y s o l u t i o n in naphtha, reprecipitated, and dried in vacuo at' 80 C. The fractionation was so designed that the middle oI fifth fraction of the nine obtaincd xould be a central building block for blends of greater molecular n-eight distribution with constant average molecular weight. INDIvIDVAL FRACTIOSS ~ S D MOLECULAR WEIGHTS.
INDUSTRIAL AND ENGINEERING CHEMISTRY
949
The extent of molecular weight heterogeneity in elastomeric materials profoundly affects the deformation behavior of such Polymers. By using Butyl polymers which are relati*ely stable and readily fractionated into narrow molecular weight components, the effect of molecular weight distribution in deformations at constant load and constant deformation rates was studied. .For a constant \ iscosity-average molecular weight, broadening the molecular weight distribution results in a less thermoplastic polymer. Liider constant load the elastic and \iscous components of deformation w ere isolated; b? this analy sis a broader molecular weight distribution yields a softer, more elastic material. For a gi\en viscosity-average molecular weight, tiscous deformation remains independent of molecular weight distribution, whereas elastica deformation is directly related to the molecular propert!.
Blend 1 is fraction 5 , and its originally determined molecular weight of 295,000 is similar t o the average molecular weights of blends 2, 3, and 4. With blend 4 the fractional components were recombined in the same proportions in which they were originally precipitated. Below the original experimental molecular n-eight of blend I , Figure 1, gives a redetermined molecular weight after this fraction had been sheeted on a mill and molded for plasticity determinations. Only a slight decreare in molecular w i g h t was noted, and this was within experimental error of the determinations. Aftcr blends 2, 3, and 4 had been formed by the solution method, experimental molecular weights were compared t o those obtained by calculating an arithmetic average of the component intrinsic viscosities. (These experimental values were determined after the blend: had been sheeted and molded for plasticity tests.) Although the experimental values are a little lower than the arithmetic averages, a11 blends shoiv similar experimental molecular ryeights. Comparisons are made in Figure 1.
Table I lists the fractions obtained and their wspective riscosity-ai\.(iragr molecular weights ( 6 ) , obtained from intrinsic viscosities in diisobutylene. An estimated limit for the fraction is placed between each molecular weight value for the various fract,ions. Air initial threshold molecular weight value ( D I ~ upper limit' for fraction 1) was determined on a similar sample of Butyl polymer by another member of these laboratories (11). I n estimating !imits beh-een fractions, it is fully realized that such values are only idealistic in nature since, in any fractionation process, a certain amount of overlapping of the molecular species betiyeen two adjacent cuts always exists (13). T h e degree of overlapping is largely dependent upon the dilution of the polymer in the solEFFECT OF MOLECULAR WEIGHT VARIATIONS UXDER vent prior to fractionation ( 2 ) . CONSTANT DEFORRIATION RATE I n order t o check the reproducibility of the fractionating prciA large variety of operations for the processing of rubberlike cedure and the molecular weight determinations, a second seriei substances deform the material under conditions of constant deof fractionations were run. In the second check fractionation, formation a t a given rate-for example, mising mills, calenders, two 100-gram portions were precipitated into the same nine and generally tubers operate a t a predetermined speed, regardless components as in the previous experiment. Their molecular of t'he original consistency of the polymer. The resistance to deweights are listed in the right-hand rolumns of Table I. Fracformation offered by the particular polymer or compound is tion for fraction, comparable viscosity-average molecular weights manifested in the power requirements for the operation. were obtained. This justifies confidence in the fractionatioii I n a previous publication from this laboratory (17) it was recprocedure and subsequent combination of the respective fracognized that measuring plasticity and elasticity of elastomers tions from t,he original eight 100-gram portions. BLESDSOF ISCREASISG MOLECTLAR KEIGHT DISTRIBUTIVS under some condition of constant deformation rate n-ould be helpful in predicting the processing behavior of a variety of polymers. T h e fractionnKITH COSSTXSTAVERAGE MOLECCLIR VEIGHT. By this method certain elastic-plastic properties of Butyl were tion \vas designed to obtain a middle fraction from nine cuts as 3 correlated with extrusion swell and, later, n i t h mill behavior. building stone around which blends of increasing distribution would be based. This is shon-n ;thematically in Figure 1, n-here The arbitrary conditions of ronstant deformation were estabfraction 5 (Table I) stands as a central component of the variety of blends representing increasing molecular weight TAmL: I . ( ' o w o w n : C)F FRI('moss F R O N ORI(,ISALfirmi, distribution. Each fraction Check Fractionation Composite of Fraction8 Curnposire of Fractions from Eight 100-Gram Portions of [numbered as in Table I ) used Original Butyl from T w o 100-Gram Portions of Original Butyl as a component of t!ie varioui E?td. liniit Cc. acetone Cc. acetone hetaeen per 100 cc. Weight Intrinsic ViscosityFf"c,- per 100 cc. Weight, Intrinsic Viscosityblend. is depicted by a recfractions -ion c; viscosity a v . mol. w t . % viscoiity a\'. mol. w t . henzene henzene tangle defined by the n eight I .oon,ooo per cent in the blend and by 8.0 1.892 .54.5,000 570.000 I 0-1 0&4 . 0 13.0 1.648 5 1J,000 its ideo1 molecular weight > 4-4.5 16.2 1.518 5no.ooo -1 0-1 5 500,000 li.7 1 203 480,ooo limits. The four blends of 14.0 .i 4.5-50 1.381 440,000 4 . .5-.5. 0 420,onn 14.6 1.330 increasing molecular weight, 400,000 340.000 13:O 1,249 378,000 5.0-3.0 9.0 1.152 t .i.0-3.5 distribution were made up by 330,000 280,00(1 .i d.5-0.0 9.0 I . 089 2'J5.000 .i.?-e 0 7.5 1.026 dissolving the various fractions 260,000 in naphtha, concentrating 2-1o.ono 0.936 m,om I0 -1 0.944 ii ii 0-7.0 8.4 6 0-7.0 220,000 these solutions on a water 190.000 7 7 0-8 0 7.6 0.853 206.000 7.3 0.798 7.0-8 0 170,000 bath, and precipitating the 130,000 I .34.000 8 8 0-10 0 8.4 0.648 8 0-10 (1 ij.4 0.658 blend with acetone and methyl 85,000 i c , onn flow rate. Check rune can rtxiidily be made v-ith only tvio or three pellets to determint, the elasto-viscous properties of a certain polymer sample under the established coiiditioiis ni' constant load deformation. The first eight fractions of Figurt, 1 (in thic t e s t fraction 9 \vas too soft for significant readings) n-ere aubjected to deformation undw the constant load conditions defined: thc data are lion-n in Figure 6. The graph or wries of curves c-onsist of two parts; the solid ('11 line represents total deformation ivitli timc, under a load of 630 ,grams per q u a r e em. at 40' C., and the straight dotted lines ~ c p r c ~ st.ut that portion of the dcforniutioli n.hich i3 ii Thus, the ,slope of the dotted line IT-ouldrepresent' the rate of flon-, and the difference betneen tlic total deformation curve and the flow curve at a given time interval \ ~ o u l dbe a measure of the clastic component of defoimation. Ais the molecular weight (if each spc:cics is decreased, large differencesin rate of deformation and rate of flon- are notid. DEFORXITIOX ,4SD FLOK TTITH ~ I R T I X G hIoLECI-LAI3 ll-EIGH1 DISTRIBCTIOX. The polymers of coIlStnllt average mokcular w i g h t , made up of various distributions of molecular species, exhibit significantly different defornintion behaviors under constant load. Total deformation undu the conditions shown in Figure 8 is represented by the upper series of curves, and viscouq deformation rvith respect to time is given by the lon-er series of straight lines. Because there was :L need to conserve frnctioiis for other n-ork, blend 2 ivas eliminated from this series of experiments. The two sets of deformation curves indicate that, as molecular weight distribution is hroadened (for a*given avrr:ige molecular weight,), a greater total deformation for the same rate of floiv is obtained. In other words, a softer but more elastic suhstance results as molecular !wight distribution hecomes wider. In the sections devoted to constant rat'e oi deformation, it Tvas indicated that the narrow molecular w i g h t distribution was the morr processable polymer for a given average molecular \%-eight. Constant, load concept F reveal that this advantage i6 realized n-ith an increase in high elastic modulus of the polymer. I n Figure 8 the various molecular w i g h t distributions develop more total deformation as the distribution is increased. Since thc flow is the same, increases in the heterogtxneity of molecular weight must be accompanied b y an increase in elastic deformation. If the sensation of stiffness is defined as time rate of development of high elastic deformation upon the application of a f i x d load, then the polymer ble.nds of ridening niolccular iveight distribution n-ill exhibit a progrcs-ive decrease is, their high in sensation of stiffness-that elastic moduli will be less. From inspection nf .4kxandrov and Lazurkin's expression for
953
the development, of high elastic doformation :is an cxponcntial function of time,
(3) :t plot of high elastic deformation against, lognritlini of timc is suggested. However, Rehner (10) shon-s mathematically, by operating on Equation 3, that high elastic deformation under constant applied stress is directly related to the logarithm of time, provided the proper time limitations are chosen. His cquation takes the form
!\-here the symbols have the same definitions as those of Equation 2 . From Equation 4 the slope of the plot of elastic deformation
DEFORMATIONpAND FLOW WITH RESPECT TO TIME UNDER CONDITIONS OF CONSTANT LOAD FOR G R - I FRACTIONS
100
2 00
3 00
TIME IN SECONDS Figure 10
400
500
INDUSTRIAL AND ENGINEERING CHEMISTRY
954
[q J = k',.llo."', from :I weight+% tge inolt~cularweight calcu1:itctl i r o n intrinsic viscosities by the Striudinger relation [71 = \heviscous component of deformation is independent of molecular weight distribution and dependent only on averagts constant 16ad deformation test described of estimating average molecular weight. hich is independent of time if precautions erved in the testing procedures, has been tietcrmined for individual fractions as well as for blends of varying molecular weight distribution. The logarithm of flow rat(’ the square root of the viscosity-avetxpc, -uggcsted by Flory’s viscosity eqiiatioii. .iCKNOW LEDGMENT
Thcs authors \vis11 t o thank J. Rehner, Jr., for :t constructive revielv of this paper and for permission to use the mathematical expression derived for the propagation of elastic deformation with time. For the layout and construction of the finished graphs JVC arc indebted to C. IT. Haemrr.
955
LITERATURE CITED
6. S.,Acta Physicochin. I‘.R.S.S., 12, ti47 (1940). ( 2 ) CtLinpbell, H., arid Johnson. l’., T J X ~ LFaraday S. Soc., 40, ‘ 2 1 (1) Alexairdrw, .A, l ’ ~ ,a n d Laziirkin,
(1944). (3) Diene arid KI(WIIII, paper presented before Soc. of Rheolorz.. O r t . 24, 1945. (4) I)unstsn, A . E., Z . j ~ h y s i k Chaui., . 56, 370 (1906). ( 5 ) Flory, P. J., J . Am. Chem. Yoc., 62, 1057 (1940). (ti) Ibid.. 65, 372 (1943); Rubhel- (’hem. Tech., 16, 493 (1943). ( 7 ) Gee, G., and Melville, H. W., Trnns. Faraday Soc., 40, 2 4 ) (1944); Rubbe,. C‘hem. Tech., 18, 223 (1945); Herringtoit, E.F. G., T r a m . Faraday SOC.,40, 236 (1944). (8)Kernp., A. R., and Straitiff, IT.L., IND. ENG.CHEM.,36, 707 (1944); Rubber Chem. Tech., 18, 41 (1945). ( 9 ) Kehner, J., Jr., IND.ENG.CHEM..36, 46 (1944): Ktrhhev C‘hvni. Tech., 17, 346 (1944). (10) Rehner, J., Jr., to be published. i l l ) Rehner, J., Jr., unpublished data. (12) Sookne, .4. M., and Harris, XI., I s u . Esu. CHERI.. 37. 4 i S (1946). (13) Spurlin, H. M., Ihid., 30, 538 (l93X). (14) Stefan, h1. .J., Sitzber. A k a d . Wiss. W’I.’~~/L., .1Jathitntiirw, Klasae 36, Abt., 69, 713 (1874); Foote. N. 51.. ISD. ENG.CHWY., 244 (1944). (15) Tuckett, R. F., Chemistry & I n d u s t ~ . y /62, , 130 (1943). (16) Wall, F. T., J . Am. Chem. Soc., 67, 1939 (1945). (17) Zapp, R. L., and Gessler, A. Xl., h n . EXG.CHEY.,35, 666 (1944); Rubber Chem. Tech.. 17, 88% (1944). PRESENTED before the Division of Rubher Chemistry a t t h e 109th \Iret,ioa the .%\fERICAX C F i E J r l C A L SOCIETY, .Atlnlltir City, N. .I.
Of
Styrene-Diene Resins in Rubber Compounding \. 34.
BORDERS, R. D. JUVN,
AND
L. D. HESS
Goodyear Tire & Rubber Cornpart.v, Akron, Ohio
A copolymer of approximately 15 parts butadieiie and 85 parts styrene (Pliolite S-3) is a thermoplastic resin with excellent oiygen and chemical resistance. It is compatible with natural rubber and with most synthetic rubbers. I11 mixtures with rubbers as a reinforcing resin, it is valuable for improvement of smoothness during extrusion or calendering and for reduction of shrinkage. Although Pliolite S-3 alone is brittle at room temperatures, in mixtures w ith rubber (up to 50-50), it does not increase the rate at w hich the mixture stiffens with reduction in temperature. Data are tabulated H hich illustrate the effect of 15 butadiene85 styrene copolymer in GR-S or natural rubber compounds upon hardness, stiffness, extrudability, tenbile strength, and impact resistance. The low moisture absorption and excellent electrical propertiek ha\e encouraged the use of the copolymer in rubber rompoundk for elevtriral insulation.
E
ARLl- in the investigation of butadiene-styreric copolymeIs
‘
as synthet,ic rubbers, this laboratory became interested in copolymers containing much more styrene than ally of the American or German synthetics. This interest was soon directed to the resinous copolymers obt.ained when styrene content is increased beyond the range in which rubberlike properties are observed a t room temperature. The exploratory work, therefore, involved preparation and evaluation of butadiene-styrene copolymers containing from 65 to 98% st,yrc!nc>. No description of similar polymers has bwn
found. Konrad and Ludivig ( 4 ) claimed the improvtxnrnt of rubberlike properties of butadiene-styrene copolymers by increasing the styrene content from the normal range to “between about 47.5 and about 70%”. The claims and examples of this patent emphasize the improvement of rubberlike properties, such as tensile, elongation, and rebound, a t high temperatiires. It is well known in this country, however, that increase in styrene content beyond a certain point, perhaps 50-55%, is accompanied by a loss of over-all balance of rubber characteristics. Therefore, the copolymers a t the upper end of the range described by Korirad and Ludwig have definite limitations for rubber iiscsfor example, low rebound, high brit,tle point, shortness, et,c. In the writers’ laboratory useful resins have been propared From dienes and vinyl aryl hydrocarbons in the range 5 to 2094 diene and 80 t,o 9570 vinyl aryl hydrocarbon. This papw doscribes the properties and certain uses of one of these copolynir~n containing approximately 15 parts of butadiene and &5 parts of styrene. This material possesses a combination of physical and chemical properties which permit its use in several applications where cyclized natural or synthtxtic rubbers are commonly tmiployed. Cyclized natural rubber has been described by Rruson (f), Endres (S), and Thies and Clifford ( 5 ) . Cyclized synthetic rubbers were described recontly by Endres ( 2 ) . One product of this type is made from a special synthetic rubber. The new 15 butadiene45 styrene copolymer is now identified as Pliolite 5-3, since i t may be used in many Pliolite applications, often with distinct advant,agcs ovrr either t,he natural or synthotic rubber derivat.ives.
