318 



THE INDIA RUBBER WORLD 



[March 1, 1917. 



it would be preferable if 95 per cent of it boiled under 300 

 degrees F. rather than under 314 degrees F. Sample B is much 

 less desirable, chiedy on account of the high final boiling point. 

 The initial boiling point is a little lower than in the case of A, 

 but scarcely sufficient to have it react to its disfavor. Sample 

 C is considerably too low in boiling points for advantageous 

 use in spreading. Sample D is much less desirable than sample 

 A, for the reason that its extremes show wider fluctuations. 

 For spreading purposes, it is undesirable to have the initial 

 boiling points much under 160 degrees F., for the reason that 

 if such is the case, large losses of gasolene are apt to take 

 place while the rubber compound is being churned and also 

 while the churned mass lies in the spreading room prior to use. 

 The majority of the material boiling below 160 degrees F. is 

 lost before the rubber dough reaches the spreading machine. 

 An even more serious objection is the fact that these low boil- 

 ing portions are not only non-solvents for rubber, but actually 

 inhibit the dissolving action which the higher boiling portions 

 exercise. The result is that these low boiling fractions, when 

 present, actually tend to decrease the solvent power of gasolene. 



On the other hand, if the gasolene contains an excessive 

 amount of high boiling material, it is difficult to drive off the 

 last traces on the spreading machine. The result is that the 

 latter are retained by the coating and as a result of being sub- 

 sequently vaporized by the higher heat of vulcanization be- 

 come the most fruitful cause of what is known as "pin holes." 

 To be sure, it is possible to overcome the danger of "pin holes'" 

 even when a gasolene is used containing much high boiling ma- 

 terial, but not without seriously impairing the output of the 

 spreading machine. 



Dipped Goods. Since the evaporation of the gasolene used 

 in dipped goods has to be accomplished without the aid of heat, 

 comparatively high volatility is required. As in the case of 

 spreading work, initial low boiling points are undesirable in 

 that they inhibit the dissolving power of the gasolene and for 

 the further reason, that they tend to produce blisters. If the 

 nature of the gasolene is such that it evaporates too quickly, 

 the outside surface of the cement dries, with the formation of 

 a film, enclosing some gasolene underneath it. In the course 

 of time this gasolene will tend to vaporize, and as the pressure 

 of the latter becomes sufficient to rupture the outer "film," a 

 blister results. On the other hand, if the boiling points are too 

 high, blisters will also occur, as some gasolene will be retained. 

 When the dipped articles are then subjected to the slightly 

 elevated temperatures of the acid cure, the retained gasolene 

 will be vaporized, again with the formation of blisters. A 

 composite sample of C and D would be the most desirable; 

 that is, a sample having the initial boiling points of D and the 

 end boiling points of C. 



Cements. The gasolene requirements for a cement are es- 

 sentially ease of volatility, and what is closely related thereto, 

 complete vaporization of the solvent. Any residue greatly im- 

 pairs the adhesive qualities of the cement and also its lasting 

 qualities. Boiling points similar to those desirable for dipped 

 goods will generally be found satisfactory. 



The price of gasolene having steadily risen owing to the 

 enormous increased demand, it is natural that attempts should 

 be made for the purpose of obtaining substitutes for gasolene 

 or at least of converting less valuable petroleum products into 

 material having essentially the same properties. While it has 

 not yet been possible to find such a substitute, two products 

 are known which are used quite extensively in admixture with 

 gasolene. The two materials in question are: (1) casing-head 

 gasolene and (2) cracked gasolene. 



Casing-Head Gasolene. The source of this material is 

 natural gas, from which it is obtained either by compression 

 or else by so-called "washing" with oils of high boiling point. 

 Casing-head gasolene is an exceedingly volatile material and for 

 this reason comes on the market only in admixture with in- 



ferior grades of gasolene. It is used primarily as a "sweetener," 

 that is to say, for decreasing the boiling points of gasolene 

 which would otherwise be unsatisfactory owing to excessively 

 high boiling points. FVom the -standpoint of the rubber manu- 

 facturer the addition of casing-head gasolene is undesirable, for 

 the reason that the resulting mixed gasolene shows low initial 

 boiling points and lijgh end boiling points. As has been pointed 

 out above, the rubber manufacturer is interested in a gasolene 

 having relatively narrow extremes of boiling points. Even 

 though the boiling points of the mixed casing-head gasolene 

 show these variations, by suitable manipulation of the mixture 

 the gravity is such as to give no indication of the presence of a 

 mixture. This again shows the fallacy and undesirabilitj, from 

 the rubber manufacturer's standpoint, of estimating the value 

 of gasolene purely on a gravity consideration. 



Cracked Gasolene. The cracking of petroleum oils is a 

 relatively old art, but it is only within recent years that special 

 attention has been given to this process. Cracked gasolene is 

 obtained usually from kerosene or fuel oil, and consists in sub- 

 jecting either of the latter to high temperature and pressure. 

 By means of the cracking process the high-boiling petroleum 

 hydrocarbons are converted into hydrocarbons of much lower 

 boiling points ; so much so, that a large proportion of the. ma- 

 terial resulting from the cracking process boils within the 

 limits of the average gasolene. However, a wide variety of 

 substances are formed in this operation, some of which have 

 markedly different properties than the paraffin hydrocarbons 

 which constitute gasolene as we know it. Cracked gasolene is 

 especially rich in a group of substances known as "olefines." 

 These olefines are very undesirable from the standpoint of 

 motor gasolene and are largely responsible for the so-called 

 "carbon" deposits in the cylinders. This is one of the reasons 

 why cracked gasolene comes on the market only in the form 

 of an admixture with natural gasolene, and then only mixed in 

 relatively small proportions. From the standpoint of the rub- 

 ber manufacturer it is rather doubtful if these olefines are a 

 detriment, except for the fact that their boiling points are rela- 

 tively low. To be sure, if gasolene which contains much 

 cracked material is allowed to lie in the tank for an extended 

 period, the olefines have a tendency to go over into a thick viscous 

 oil which settles at the bottom. However, in most rubber fac- 

 tories the gasolene does not have a chance to be stored suffi- 

 ciently long, prior to use, to enable the formation of tliis heavy 

 oil to take place. 



Solvent Recovery. Many attempts have been made to re- 

 cover or partially recover the gasolene used in certain branches 

 of the rubber industry, notably in the spreading operation. The 

 volume of gasolene in a spreading plant vaporized in the course 

 of a month's operation reaches staggering figures and it is only 

 natural that the recovery of the solvent should have l)een given 

 serious thought. While theoretically the recovery of gasolene 

 from the spreading operation is a simple matter, the practical 

 difficulties and cost of equipment have so far stood in the way 

 of its applicability. In this connection it is not generally 

 recognized that even if all the gasolene which is vaporized in 

 the spreading room were successfully condensed, the resulting 

 iTiaterial would have properties differing materially from those 

 of the original gasolene. Owing to the relatively low initial 

 boiling points of gasolene, considerable losses take place dur- 

 ing the churning operation ; so much so, that if only the gaso- 

 lene which is vaporized in the spreading room were condensed, 

 its boiling points would be very much higher than those of the 

 original gasolene. The recovery process, in order to make it 

 complete, would have to be extended to the churn room. It 

 can readily be seen, therefore, that the size and cost of equipment 

 of such a complete recovery plant would be high. Neverthe- 

 less, there is every reason to expect that a recovery plant would 

 be a good investment if the purely mechanical and engineering 

 difficulties are solved. 



