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resent only small concentrations of these compounds even if the peak is considered as being solely due to these compounds. For example, the highest gravity fraction at the benzene boiling point (80" C.), represent,ing 0.31 per cent of
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the gasoline, has a specific gravity of 0.76. Assuming that this is a mixture of benzene (sp. gr. 0.88) and hexane (sp. gr. 0.66) only, it would contain only 45 per cent of benzene, calculated from its gravity or 0.14 per cent based on the gasoline charged. The results of this work are of considerable speculative interest but are not considered as warranting conclusions.
CALIFORNIA G A S 0 L IN€
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Rubber as a Solution of Corrosion and Abrasion Problems' By H. E. Fritz2 MECHANICAL SALES DEPT.,THEB. F. GOODRICH RUBBERCo., AKRON, OHIO
HE chemical industries have long felt the need of cor-
T
rosion and abrasion resisting materials which, when subjected to general factory conditions, such as shock, vibration, and strain, will be serviceable through long periods of time. Such material would greatly decrease replacement and maintenance and would help to revive many chemical manufacturing processes now in the discard for want of suitable construction substances. Iron and steel or sheet metal, if corrosion-resisting, would be the ideal chemical engineering construction material. As there is grave doubt that such a material will ever be develoDed, we are forced to utilize that which is best suited to our-purpose, regardless of its disadvantages. Rubber or rubber compounds and combinations are often satisfactory from the standpoint of resistance to corrosion, but they have lacked the combination of rigidity and strength than limited. necessary to make their application 1 2
Received July 24, 1926. Sales Engineer.
It has been known for some time that hard rubber can be applied to clean metal surfaces with a measure of success from the standpoint of adhesion. It is also a well-known fact that hard and soft rubber can be united with very desirable adhesion. I n this way, by use of a combination stock, fairly good adhesion of rubber to metal was obtained. Materials lined or covered by this process must be classified as fragile equipment, because flexing, shock, strain, differences of expansion, etc., tend to crack or destroy the hard rubber backing. The Vulcalock Process3
The objections t o the old process were the stimulus for the development of a process for attaching soft rubber to metal with sufficient adhesion to insure a perfect union of the two surfaces. The Vulcalock process, in which adhesions up to 700 pounds per square inch have been obtained, makes it possible 8
Canadian Patents 266,967 (1923) and 256,797 (1925).
January, 1927
IXDUflTRIAL A X D ENGINEERIXG CHEMIXTR Y
to fasten pliable rubber, as well as hard rubber, to metals and other rigid construction materials in such a manner that the two substances are practically integral. This produces a material with the corrosion-resisting properties of rubber and the rigidity and durability of the base material. The bond or union between rubber and the other surfaces is so nearly perfect that a separation a t the junction point cannot be effected without cutting or other abnormal treatment. The end of a soft rubber strip, of 1 inch cross-sectional area, was attached by the T’ulcalock process to a steel bar. It supported the weight of two large men with no sign of failure. This new process has been successful in attaching rubber to other metals, such as brass and aluminum, and also t o wood and concrete. The Vulcalock process brings into use a new industrial material which incorporates, with certain exceptions, the strength and workability of metal with the desirable abrasion and corrosion-resisting properties of rubber. The attachment requires the processing of the metal surface and special preparation of the rubber stock in its uncured form. The pliable, semiplastic gum is applied to the metal and cured in place. The remarkable adhesion is set up during the curing operation. The plates are thoroughly cleaned by sand blasting or pickling to remove the scale and rust which may form on metal surfaces. The adhesion between the metal proper and the rust is not very good, and, although the adhesion of the rubber to the rust or scale may be excellent, the actual adhesion t o the metal would be very poor because the rust and scale would pull off with the rubber if any direct strains were put on it. The one limiting factor of the Vulcalock att:tchment is temperature. At present its application cannot be conservatively recommended where the temperature exceeds 180O F., except in rery special cases. Abrasion-Resisting Material Tires, sand blast hose, and conveyor belts exemplify the abrasion-resisting properties of rubber. The Vulcalock process of attaching rubber to metal has broadened this field of application, so that agitator blades, sand and gravel chutes, fan blades, wearing plates, and dredge pump liners can be treated t o expose only the rubber surfaces to the scouring action of severe abrasives. The problem of attaching soft rubber mechanically to metal, wood, or concrete to prevent abrasion had not been satisfactorily solred and it was believed that the ultimate solution of the problem was in direct adhesion by vulcanization. The Vulcalock process offers an admirable solution of this problem. Corrosion-Resisting Material The hard rubber jars which contain the electrolyte in accumulators, spinning bowls, bleach and dye rods, the soft rubber lining in wooden tanks and the soft-rubber-lined eggs for holding muriatic acid, the soft-rubber-lined steel tanks for dilute acids, salt brine, and bleach liquids, and the soft rubber stoppers for sealing off fuming materials show the corrosion-resisting value of rubber. The muriatic wid transportation problem, which has always been a source of annoyance to manufacturers and consumers, has been almost completely solved through the use of soft-rubber-lined tank cars and drums. Distilled water storage and transportation in rubber in which no leakage or pollution results is now feasible. Dilute sulfuric, hydrochloric, hydrobromic, hydrofluoric, phosphoric, and sulfurous acids, as well as other corrosive chemical solutions, can be readily handled and transported in rubber without appreciable effect on the material.
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Table I lists some of the chemicals which can be advantageously handled in rubber-lined equipment. Table I MAXIMI!M CONCENTSATION BY WEIGHT
TEMPERATURE
F.
L i g u i d acids Hydrobromic Hydrofluoric Hydrofluosilicic Muriatic (hydrochloric) Phosphoric Sulfuric Carbonic Pyroligneous Sulfurous
Concentrated Concentrated Any concentration Concentrated Up to 75 per cent Up to 50 per cent Any concentration Any concentration Any concentration
100 150 150 150 125 150 150 150 150
Solulions Caustic soda and potash Calcium chloride Calcium hypochlorite Copper sulfate Sodium acid sulfate Milk of lime Zinc chloride Aqua ammonia Ferrous sulfate ’ Sodium chloride Zinc sulfate Aluminum sulfate (alum) Acetone Ethanol Methanol
Up to saturation Up to saturation Up to saturation U p to saturation Up to saturation Any concentration 30 per cent Any concentration Saturation Saturation Saturation Saturation Ovganic liquids
150 150 100 150 150 123 100 125 150 150 150 I50 130
Any concentration .%ny concentration
1.10 150
For many years the generally accepted equipment for muriatic acid storage has been the wooden tank lined with unvulcanized fine Para rubber. The use of the Vulcalock process in attaching vulcanized rubber to the inside of steel tanks not only offers a durable substitute for wooden equipment, but also makes it possible to introduce air pressure for discharging the contents. This type of con~bination storage tank and blow case is rapidly gaining favor. I t s advantages may be summarized as follows: (1) Ease of erection; ( 2 ) freedom from buckling and warping; (3) easy transference without dismantling; (4) freedom from leakage; ( 5 ) elimination of pumps, as corrosives may be transported over long distances or to great heights by the application of air pressure. The Vulcalock process has also made possible a step forward in the evolution of railroad containers for muriatic acid and other corrosives. Vulcanized rubber can be applied to standard-design steel tank cars with sufficient adhesion to insure safety and prolonged service, even with the abnormal treatment t o which a car is subjected. Some twenty cars have been lined by this process during the past two years with uniformly satisfactory results. The oldest car is still in service with no signs of deterioration. The steel tank car is not only stable and durable, but it provides a capacity up to 8000 gallons, whereas the sectional wooden tanks heretofore commonly used seldom provided a capacity of more than 5000 gallons to the car. The wooden tanks were also objectionable because they tended to shift position with respect t o the underframes, because the staves were crushed by the impact of the contents, because the staves expanded and contracted under different temperatures and humidity conditions, and because the unvulcanized rubber linings were torn and broken from shock and impact. The steel car is free from all of these drawbacks. Rubber - Covered Material Rubber-covered sheet metal, which is almost as readily workable as sheet metal alone, has been developed as a result of the Vulcalock process. It can be cut, bent, and riveted into many desired shapes. This makes it very valuable in the transportation of gases contaminated with gritty material and cement dust, where abrasion on metal flues and pipes is appreciable, and in the construction of flue liners for conducting corrosive acids. A full line of steel pipe and fittings, with either soft or hard
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rubber lining attached inseparably to the steel by this process, is now available. It is of all flanged construction, with '/cinch rubber for corrosive service and '/rinch rubber for abrasion. This piping, which has been found adaptable in many process industries, promises to have an extended application. Rubber-lined relinable valves, which are highly satisfactory in handling corrosive and abrasive liquids, have been developed. The new process also permits of lining fans and pumps, centrifugal machines, mixers, eggs, lifts, thickeners, classifiers, rolls, vats, and bins. The Cutless rubber bearing, consisting of a resilient rubber lining vulcanized to a rigid sleeve, such as bronze, cast iron, steel, and hard rubber, is another development. The only lubricant for this bearing is water. Installations rang-
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ing in diameter from l / 2 inch to 15 inches have been made. These bearings are particularly serviceable in sand and slime pumps in the mining and chemical field. Summary The Vulcalock process for vulcanizing rubber to various materials affords a new chemical engineering material with all the physical properties of the material to which it is attached and in addition the useful abrasion-resisting properties of a soft vulcanized surface and the corrosion-resisting properties of either soft or hard rubber, without hazard of breaking or cracking in transportation, construction, or operation. The most likely source of difficulty or failure of this material lies in misapplication. The manufacturers should therefore be consulted in all cases of doubt on highly specialized problems.
Action of Sodium Hydroxide on Cellulose under High Pressure' By Sven O d h a n d S. Lindberg ORCANISKALABOUTORIETKGL. TEKNISKA H~CSKOLAU. STOCKHOLM, SWBDEN
ELLULOSE is known to be very resistant to weak alkaline solutions (1 to 2 per cent), a t temperatures below 120" C., and on this fact the well-known alkaline paper pulp process of Watt, Burgess, and others is founded. With increasing temperature and concentration certain changes occur, so that at a normality of about 3 to 4 and a temperature between 200' and 300" C., the cellulose passes completely into solution with the formation of a mixture of organic acids. At the same time methanol and acetone (mesitylene) are formed. When the methanol and acetone are distilled off and the solution containing the mixture of salts is concentrated and finally dry-distilled with water vapor, further quantities of acetone and methanol are obtained, together with oils and pitch. While the formation of acids under the conditions mentioned above has been studied by several investigators, the formation of methanol and acetone seems to have escaped observation. Historical In 1871 and 1889 Hoppe-Seylerz treated cellulose (Swedish filter paper) with water and alkalies up to temperatures of about 250' C. He found that up to 200' C. no appreciable reaction could be traced except that the cellulose had increased in volume and had become more translucent-i. e., the process known as mercerization had taken place. With concentrated alkalies (about 9 N) the cellulose went into solution a t 220-240" C. with the formation of about 360 cc. of gas per gram of cellulose. The gas was chiefly hydrogen (86.8 per cent hydrogen, 0.9 per cent methane by volume) and in the solution the following acids were obtained: formic acid, acetic acid, and other fatty acids (altogether 15.2 grams per 100 grams), oxalic acid 2437 grams per 100 grams, protocatechuic acid 1275 grams per 100 grams, together with protocatechol. Since the quantity of gas amounts to about 2.7 grams, it is evident that 21.6 per cent of the cellulose was isolated as known substances. The amount of carbon dioxide formed was not determined. Tauss3 found that pure water dissolved up to 9.4 per cent of the cellulose at 181" C., while 14 per cent sodium hydroxide a t 152' C. dissolved 77 per cent. No detailed investigation of the products was undertaken. In 1920 Fischer and Schrader4 made a more thorough investiReceived June 9, 1926. Bcr.. 4, 15 (1871); 2. physiol. Chem., 13. 66 (1889). a Dinglers polyfech. J . , 273, 286 (1889); 516, 411 (1890). 4 Ges. Abhandl. Krnninis Kohlc. 5 , 332 (1920). 1
f
gation. Filter paper was treated with 47 grams of 4.1 N potassium hydroxide and 27 grams of 5.0 N sodium hydroxide per 100 grams of cellulose a t temperatures from 200' to 300" C. The insoluble residue varied between 2 and 36 per cent according to temperature. Using NaOH a t 300" C. a quantity of carbon dioxide equivalent to 9.3 grams per 100 grams cellulose was obtained and in the solution the following acids (about 20 grams per 100 grams cellulose) were identified: formic, acetic, protocatechuic, and lactic (?). Material and Method Two experiments were made, the first with filter-paper cellulose and the second with cotton. Both kinds of cellulose were tested for methoxyl, but none was found. EXPERIMENT 1-Filter paper (1157 grams) containing 1.4 grams of ash (0.12 per cent) and 48.6 grams (4.23 per cent) of moisture and 1107 grams of dry organic substance (95.5 per cent) was disintegrated with 1100 grams of fused sodium hydroxide and 7000 grams of water. The sodium hydroxide contained 90.64 per cent NaOH and 7.52 per cent Na2C03, the remainder being water. This is equivalent to 100 grams NaOH and 83 grams NazO, or 90 grams NaOH and 7.5 grams NazC03, per 1000 grams cellulose. The normality of the disintegrated mixture was about 3.56. A portion of this mixture weighing 600 grams (71 grams cellulose, 64 grams NaOH, and 5.3 grams NaZC03) was slowly heated in an autoclave to 102' C. until 400 cc. of air were drawn off, and then for 5 hours to 372" C., at which point the pressure was 241 atmospheres. After this temperature had been maintained for some time the autoclave was cooled down to 30" C. and the gas formed (7300 cc. a t 0" C. and 760 mm.) was drawn off and analyzed, with the following results: Hydrogen Methane Other hydrocarbons Oxygen Nitrogen
Per cent by volume 93.5 1.9 1.9 1.9 0.8
The experiment was repeated six times with similar results and altogether 39,000 cc. of gas and 3885 grams of solution were obtained. The solution was yellow to brown in color, quite transparent, and had a strong odor of methanol and mesitylene.
