July, 1925
IA’DC-STRIAL AA*D EXGILYEERIA-GCHEdIISTRY
bitumen, with its higher 2nd higher decomposition point, begins to cause swelling as soon as its decomposition point corresponds with the plastic state of the coal. All the results obtained harmonize very well, and give a clear and useful conception of the change in the properties of coals with increasing age. We consider, however, that the value of the foregoing work is not in the fact that it demonstrates again and further clarifies the genetic relationships in the series lignite to anthracite, but that it lies mainly in other fields. If we determine, for a given coal, its total bitumen content, the relative solid
711
and oily bitumen contents, and the decomposition point of the solid bitumen, then we have a very much better means of characterizing and classifying coals from the coking standpoint than has previously been available. When the necessary minimum content of oily bitumen and the maximum permissible quantity of solid bitumen (which may depend upon its decomposition point) have been determined, we will no doubt be able to calculate exactly the proportions in which different kinds of coal must be mixed in order to give a useful coke, with the restriction, however, that such mixtures must be of sufficiently small and intimately mixed material.
The Electrodeposition of Rubber’,’ By S. E. Sheppard and L. W. Eberlin EASTMAN KODAKCo., ROCHESTIGR, N. Y.
HE fact that the particles in rubber latcs are electri- plantation sheet) in benzene, which is diluted with 500 to IO00 cally charged, and in general negativcly, was observcd cc. of kerosene, are added 500 cc. of sulfonated castor oil, and by H e r ~ r i . ~It is very easy to exhibit this microscopi- this mixture is stirred into 3000 cc. of an aqueous solution concally by placing some latex on a slide having two electrodes of taining 150 grams of castile soap. Such an emulsion can be gold foil (silver or platinum), and passing a current. S o ap- considerably concentrated by evaporation under reduced presplication was made of this principle until, in 1908, Corkerell, sure and solvents may also be largely removed. Both artificial and natural emulsions are available for the of the Ceylon Technical College, Colombo, Ceylon, described process. The direct importation of latex, which increased S ~electrically coagulating ru!hrr from latex, thc a D ~ O C ~ Sfor greatly up to 1923, diminrubber being removed and ished considerably in 1924.6 dried. But this does not necessarily The object of Cockerell’s Rubber particles in natural latex (ammoniated) mean that the industrial use process was to facilitate and and in artificial rubber dispersions in water are negaof latex is going to be abanimprove the process of cotively charged. In an electric field they move to the doned. A period of experiagulating the rubber from anode. This effect has been used previously to coagumentation will necessarily latex prior to shipment. late raw rubber electrically. It has been found possible involve fluctuations of deThe processes d e s c r i b e d to admix with sulfur, pigments, and accelerators, latex mand, and i t is probable herein have as object the or rubber-in-water dispersions, and by electrolysis to that processes will be deelectrical deposition of comdeposit rubber compounds, integrally, upon both metpounded rubber, in a form v e l o p e d by which much als and other materials to form coherent, homogeneous more concentrated latex can suitable either for vulcanilayers of considerable range of thickness. These debe transported. Once suczation as a covering adherposits can be vulcanized according to any desired cure cessful processes utilizing ing to the surface on which and vukanization factor. deposited, or in sheet or latex are worked out and The process can also be used to impregnate fabrics. other form after separation readjustments made, the use The coatings can be deposited either in an adherent or of artificial dispersions will from the surface in quesnonadherent form, and be vulcanized on the support tion.6 Early cxperiments be a useful auxiliary to the or independently. The character of the coating on metshowed that not only could latex industry itself, particals depends upon the (anode) over-potential for oxygen, ularly in using up regener\rubber be deposited eleccontrol of which is therefore important. The process trically from natural latex ated rubber. As regards can be applied to the continuous coating of sheet, wire, electrodeposition, natural preserved with ammonia, and fabrics. e m u l s i o n s can be used but that also artificial disequally as well as artificial persions of rubber in aqueones, and much of the exous solutions of alkaline reaction could be used in a similar manner. The artificial disper- perimental development described in’ this paper was made sions or emulsions used were prepared in general by a method with preserved latex. that has already been described in park5 Broadly, a solution of Suspension or Emulsion rubber in an organic solvent is emulsified in an aqueous solution The condition of the particles in rubber latex has been freof soaps or equivalent emulsifiere, the mixture being thoroughly agitated and homogenized by spraying or grinding. For. ex- quently discussed, and as Whitby says, “It is a nice point ample, to IO00 cc. of a 5 per cent solution of crude rubber (say, whether latex is to be denominated a suspensoid or an emulsoid.” From recent experiments on the relation of specific 1 Presented before the Division of Rubber Chemistry at the 69th gravity to concentrations, and of viscosity to concentration, Meeting of the American Chemical Society, Baltimore, Md., April 6 to 10, 1925. Kirchhof? concludes that although externally resembling an 1 Communication No. 234 from the Research Laboratory of the Eastemulsion, it is actually a suspension. This would follow, of man Kodak Company. course, from the view that the dispersed phase is a solid in the a Caoufchouc & gufta-pncha, 8, 510 (1908). mass a t ordinary temperatures. The recent admirable work of 4 English Patent 21,441 (1908).
T
I Sheppard and Eberlin, assigned to Eastman Kodak Co. U S Patent 1,476,374 (1923); application filed March 3, 1922.
8
A. Van Rossen, J . SOC.Chem.I n d . , 44,33T (1925).
’ Kolloid-Z., 84. 362 (1 924),
I.VD USTRIAL A S D ESGINEERIh+GCHEMISTRY
712
Vol. 17, s o . 7
g per second, Hauser8 tends to confirm his view, but modifies it by suggest- duced at 20’ C. t o p . d. in millivolts = 13 volts per cm. ing that in Hevea latex the interior of the particles, beneath the protein sheath, is composite, containing an inmost sub- Although p. d.’s calculated from this may not be absolutely stance of low viscosity inclosed in one of higher viscosity. correct they are correct in so far as concerns the relation beIt is possible that a t certain stages of formation the latex is tween the rate of migration and the impressed e. m. f . The more nearly emulsoid. Lamp Bank In latex examined microscopically and kinematographically in this OC.bne l a b o r a t o r y , g it was o b s e r v e d that pearshaped and elliptical particles did not necessarily remain in this Coulometer I I shape, b u t might change shape or split off Platind Circuit a particle. The relafor tive ease of deformaDirect Currenk tion suggests t h a t many of the particles Plate Anodo Figure 3 have only a semisolid Figure 1 core. cm. per secAgain it must be remembered that in many respects an oil velocity found for the latex used was 27 X ond per volt per cm., which gives a p. d. of -35 millivolts: emulsion can behave-e. g., electrically-like an excellent model of a suspension colloid.1° Hence, for some time we may much the same value was found for the compounded rubber disregard the purists and speak indifferently of rubber emul- particles. The nature of the charge equivalent to this p. d. sions or suspensions. More important than this verbal distinc- is uncertain, but the probability is that it is due to adsorption tion is the actual make-up and behavior of the colloid particles. of OH ions. It is of the same order as that of oil emulsions or The negative charge can be reversed. Fresh latex is said to bacteria. Since the p. d. (or electrokinetic potential) meashave a p H of 5.8 to 6.4 and to coagulate with acid a t 4.8, ures to some extent the stability, it is of importance in regard which is a common isoelectric point for proteins. Generally, to the action of “sensitizers” for agglutination. Inversely, affects the conditions of electric precipitapH of 4.4 to 5.6 gives a coagulating range, but there is a region such sensiti~ation’~ of acidity in which the latex is not coagulated, and in which the tion. The process of electric coagulation probably involves particles must be negatirely charged.” The ammoniated neutralization of the charge on the particle, which may be either directly by the electrode or by oppositely charged latex had a pH of 10 and upwards. Methods of determining the charge on colloid particles de- ions afforded by the electrode. pend upon determination of the motion of the particles in an Admixture and Compounding with Latex applied electric field. If only crude rubber could be electrically precipitated there This may be done either by means of a micro- would be a very limited application for the process. It is an scope for single parti- essential point that the ammoniated latex as well as artificial cles, or by following the dispersions can be readily mixed with sulfur, fillers and other m o v e m e n t of t h e compounding ingredients, and accelerators, and the whole boundary in a L--tube. “adsorption compound” electrically precipitated as a coherent The writers have made layer. some measurements by Lamp Bank Trans Formcr the latter method with Resistance p r e s e r v e d latex and D C Line C Line with the compounded n emu1s io n, containing 1 various i n g r e d i e n t s noted later. Ftgkating Anode T h e p o t e n t i a l becou10mater tween the surface of Figure 2 P l a t l n g Circuit& Combinations @ the particle and the Alternating and Direct Currents surrounding liquid may be calculated from the LambHelmholz formula /I
--
p. d. =
4Vt 7r‘
-
KX
where Q is the viscosity, K the dielectric constant of the surface layer, v the velocity in centimeters per second, and X the potential gradient-all electric units being in electrostatic measure. For aqueous dispersions1* this may be reIndra Rubber 3..68, 7 (1924) Wightman and Trivelli, THISJOURNAL, 17, 164 (1925). 10 Ellis, Z. fihrsik. Chcm., 78, 321 (1911-2), 80, 597 (1912), Powis, I b t d , 89, 91, 179, 186 (1914-5). 1 1 Whitby, K o l l u i d - 2 , 12, 147 (1913). I* Northrup in Bogue’s “Colloid Behawor,” Vol. I, p. 75. 8 9
Figure 4
With sulfur no great difficulty exists, as it readily assumes a negative charge and is wetted by alkaline solutions. According to conditions, fine ordinary sulfur, colloidal sulfur, or polysulfide sulfur, particularly ammonium polysulfide, may be used. The writers have used chiefly ordinary and colloidal sulfur, the latter being obtained either by interaction of hydrogen sulfide with sulfur dioxide or by special grinding processes. 12
Freundlich, op. t i l , p. 308.
T i m e of Plating a n d Thickness of Coating
I t might hc thought that no appreciable thickness of deposit of a nonconductor such as rubber could be built up. Although limitations exist, they are less than might be expected, arid can tie largely ox'ercome. The writ.ers have deliberately varied the thickness deposited in sheets (measured after vulcanization) from0.025cm. (0.01 inch) toO.381 cin. (0.15 inch), using up to 1% amperes per square decimeter (1 ampere per square inch). Considerably greater thicknesses
dance. Where preserved latex is used ilr electrodeposition, the rubber formed has the full strength available. Table I11 shows results of colnparati,,e trials on rubber sheet deposited ily the writers, process and on a sample Of commercial sheet, ~ i ~ Ilrepared ~ by Greenss ~ ~ method,6h show ~ that the rubber is laminated, ~t~~ admixture of the filler (piment) is uniform, Conclusion a n d Application
The function of electrodeposition is not iieceasarily to replace existing methods of handling rubber, but rather to supplement them, just as the electrodeposition of metals supplements conventional metallurgy. In addition to direct deposition on metals, whereby a varietyof applicatious in finisliing, covering, and decorating articles is possible, the process can be used to deposit rubber in certain nonmetallic supports. This may be done by impregnating the nonconductor, when porous or permeahie, with electrolyte, and counecting this eleetrolytically with the anode, or in certain cases by grapliitiaing or metallizing the nonconductor. This modification of procedure can be used in particular for the production of rubber articles by elcctrode deposition upon collapsible forms. A further application of this procedure is theelectrodeposition of rubber upon closely woven fabrics, and the impregnation of more open weave fabrics, either individually or as continuous sllcets. thick
Fisure 8
Addendum
have been obtained and can he secured by modifications of procedure. The rubber as deposited is &ill impregnated with the iutennicellar liquid, which permits diffusion ofiuns.
also produced as sheets which were exhibited a t the Baltimore
The rubber compositions electrodeposited on metal plaques arid meeting of the Rubber Division of the AMERICANCHEMICAL Soc~srvw u e of the following composition and character:
Throwing a n d Covering Power
It is an advantage of the process that the "throwing power" in deposition is considerable, and therefore corners, edges, augles, and contours are well and uniformly covered. Adequate stirring is important, as can be seen in Figure 5, which shows deposits on rotating anodes run at 1 r. p. m. and 7 r. p. m.
1
100
4
20
15
3
1w
4 8
20
'/I
20
a/*
'vi
Soft Sol1
1%
Soft
20
1w
5
in0
4
20
Vulcanization
6
104
After washing and drying the product is ready for vulcauization. The examples shown (see Addendum) were wleanized as follows: for soft rubber, low-sulfur mixes, with diphenylguanidine, at 2.81 kg. per sq. em. (40 pounds) steam pressure, for 30 minutes to 1 hour; for hard rubber, hieh&fur mix, wlcanization was carried out in nitrogen at 121°C. (250° F.),about 3 hours.
+ carbon black 34 30 + SbiSs 30 100 15 BO + titanox 100 4
20
8
100
30
Tbicknezs Width C ~ Srection P
Breaking loid Maximum dongstion
a.5 mm. 4.5 mm. 2.25 sq. mm. (doublc-4.Sj 5.4 kg.
0.5 mm.
4.0 kg.
6.5 kg.
700%
900% 0.8 kg./sq. mm.
720%
Braking load per I. 2 kg.jsq. em. e m s aectioo C l B p lba./ S " ~ I"
Mineral filler Free sulfur Combined sulfur
i
1.0 mm. 4.0 mm. 4.0 sq. mm. (s.0)
5.0 mm.
2.5 aq. mm. (5.01
0 . 8 kg./sq. mm.
( 1 M o lbs./rq. io.)
19.0
0.70
4.2
1.20
2.7
3.14
0.70 1.20 3.15
Strength, Wearing Properties, Etc
In a later paper the writers hope to give full details on the strength, durability, etc., of electro-rubber. It is a point in its favor, as far as its use is concerned, that milling coagulated rubber is known to degrade and break down the sub-
Soft *r
1w
4
~
x/s
2
10
13 14
100
2 (st 1266i'C. (280' (260' F F j1))
Hard imr(mr-
diumj
soft
I ' / i (in Na at 121
30
'/a
20 20
'/I
21-c.
@SOa F j)
'/a
Hard Soft
soft
Soft Except aherr o f h e r d r e indicated uulcanirafion was at 2.81 k g per sq cm. (40 pounds) sfram pressure.
8
New Plant in Breslao for the Manufacture of Artificial Silk and StrperphosphatesConsul John R. Minter, Brerlau, Germany, advises that the heirs of the once powerful Gwrg von Giesche for the past twelve months have becn devoting their energies to the erection of a huge plant in Breslau for the manufacture of artificial silk and superphosphates. The new plant, on a 200-acre lot in the suburbs of Bredau. will have a daily capacity of 50,WO kilos of artificial silk. A corps of expert chemists has been employed whose aim is to reduce materially the importation into Germany of this product by placing a German article of excelient quality on the market. The viscose wood pulp method will be employed. The company has also erected a dyeing plant and a weaving mill for the production of certain fabrics. In addition to the artificial silk the company expects to be able t o produce 100 carloads (German cars) of superphosphates daily. Raw phosphates coming from arf made i o prevent the escape of noxious gases.
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