May 1, 1921 



THE INDIA RUBBER WORLD 



563 



Oils, Fats, Waxes, and Resins Used in the Rubber Industry' 



By Frederic Dannerth. Ph.D. 



INTRODUCTION 



THERE ARE a luimbcr of materials used in preparing plastic 

 masses which have two or more important and technically 

 valuable properties. In a discussion of these materials 

 we shall find that the properties or characteristics change gradu- 

 ally. For example, if we examine prcKlucts obtained from mineral 

 sources— cylinder oil, petrolatum, paraffine wax, ozokerite, ceresin, 

 and montan wax, we find that these are entirely unsaponifiable.' 

 Turning to the so-called higher falty acids, we find oleic acid 

 to be a liquid resembling an oil, while stearic acid is a hard wax- 

 like body, melting at 69 degrees C. (157 degrees F.). A chemical 

 combination of these fatty acids with glycerol (glycerin) is 

 found in the plant oils, generally obtained by pressing the seeds 

 in hydraulic presses. Peanut oil is a non-drying oil ; soya, a semi- 

 drying oil ; and tung, a drying oil. By this is meant that tung, 

 like linseed oil, has the power or ability to absorb oxygen from 

 the air and form a new substance which is dry to the touch. 



.Mthough the oils are liquid at usual room temperature (60 de- 

 grees F.), they are quite similar in chemical character to palm 

 fat, coconut fat, and Japan fat (Japan wax). In the case of 

 cottonseed stearin we have a substance which is obtained from 

 cottonseed oil merely by refrigerating the oil. It is, strictly 

 speaking, a fat. 



In the next group we find substances in which the higher fatty 

 acids are combined chemically with mon-atomic or di-atomic al- 

 cohols. They are never combined with the tri-atomic alcohol 

 (glycerol). The waxes include the products obtained from the 

 cariiauba and candelilla, plants; beeswax, and wool wax (wool 

 grease or lanolin). 



AW the plant and animal products mentioned thus far are 

 saponifiable. That is they can be converted into soaps by boiling 

 with alcoholic potash. This holds good for all but the nast named, 

 the wool grease. Here we have a product which contains 

 cholesterol and iso-cholesterol — both of them alcohols — chemically 

 combined with acetic acid. Its saponification value is 100 com- 

 pared with 190 for peanut oil. 



Next we come to a group of substances designated "resins" be- 

 cause they are obtained as exudations from plants, and from the 

 milk bearing canals of trees. Jelutong resin is a good example. 

 It has a melting point of 160 degrees C. (320 degrees F.), and is 

 therefore very brittle at room temperature, whereas wool wax 

 is of the consistency of a fat. Jelutong resin and wool wax both 

 contain esters of the cholesterol alcohols. Pine resin (colophony 

 or common rosin) melts at about 130 degrees C, while guayule 

 resin is a sticky mass resembling molasses, at room temperature 

 (60 degrees F.). 



PHYSICAL PROPERTIES 



In studying the properties of these materials, with reference to 

 their use in industrial work, we will find at once that the primary 

 consideration is their melting point. The rubber chemist and 

 the worker in plastic masses wants to know the temperature at 

 which these substances soften and assume the condition of a 

 liquid. As few if any of them are absolutely pure chemical com- 

 pounds we will find that their melting point or their solidifying 

 point varies slightly just as their other physical and chemical 

 properties vary. 



^This article may not he reprinted witliont permission of the author who 

 rcser\-es all puhlicatinn rights. 



The saponificatic»n n'lniher, or Kocttsdorfcr vahie. indicates the number 

 of milli'jra'ns of potassium hydroxide required for \]u: complete taifonifica- 

 tion ot one gram of the substance. Two grrams of the oil, fat or wax are 

 beated with 25 cubic centimeters of l/j normal alcoholic potash, in a suitable 

 flask so as to prevent the evaporation of the alcohol. 



If they were absolutely pure chemical compounds they would, 

 if they melted at all, have the property of melting at an almost 

 constant temperature. In view of the fact that commercial com- 

 modities are prepared in a variety of ways and with varying 

 degrees of carefulness, these comiiiercial products differ slightly 

 from the chemically pure article. Owing to the differences in 

 reported specific gravities by different investigators it has been 

 thought best in preparing data for the attached tables to take an 

 average of several published specific gravity figures. 



The points which are of interest to the worker in plastic masses 

 are: (1) the specific gravity; (2) saponification value; (3) melt- 

 ing point; (4) viscosity; (5) the tendency which the material has 

 to absorb or take up oxygen and change its character ; (6) the . 

 chemical composition of the material. 



In studying the solvents and tliinners we are generally careful 

 to consider the boiling point, because these materials are gener- 

 ally valuable as they are volatile; but in the case of oils, fats, 

 waxes, and resins we want materials which lose little or none of 

 their weight at 300 degrees F. (149 degrees C). This will be 

 readily understood when we consider that the latter group of ma- 

 terials are added to the rubber batch or dough in order to give 

 it certain characteristics permanently. As rubber compounds are 

 vulcanized at temperatures from 280 to 300 degrees F, they should 

 contain no substances which will vaporize below those tempera- 

 tures. 



RESUME 



Groups 



1. Higher fatty acids. 



2. Glycerides of the fatty acids. Non-drying and semi-drying. 



3. Glycerides of linolic and linolenic acids. Drying. 



4. Plant fats. Non-drying glycerides. 



5. Esters of monatomic and diatomic alcohols. 



6. Resins. Saponifiable and unsaponifiable. 



7. Resinous gums. 



8. Rubber gums. True rubbers. 



9. Mineral oils, fats and waxes. Unsaponifiable. 



10. Pitches, solid hydrocarbons, and distillation residues. 



Part I — Raw Materials 

 GRCrtjP I 



Oleic .'Vcid is a fluid of oily consistency which solidifies at 

 about 14 degrees C. Combined with glycerol as glyceryl oleate 

 it is the principal constituent of olive oil (olea europea). 



Palmitic Acid with a melting point of 62 to 63 degrees C. is 

 present as glyceryl palmitate in palm fat, forming 98 percent 

 of that fat. Japan fat is a mixture of about 10 per cent palmitic 

 acid with ahnost 90 per cent of palmitin (glyceryl palmitate). 



Stearic Acid is a type of solid acid resembling a wax in 

 appearance with a melting point of about 69 to 70 degrees C. 

 It is found as gylccryl stearate in the fat of mutton, swine and 

 beef. 



Virtually all the oils and fats obtained from plants and animals 

 are mi.xtures of glycerides of oleic, palmitic and stearic 

 acids. For that reason it is possible to split them into their two 

 constituent parts, fatty acid and glycerol or glycerine as it is 

 known in commerce. 



Lauric Acid as glyceryl laurate is the principal constituent of 

 coconut fat, and has a melting point of 43 to 47 degrees C. 



GROUP 2 



The Plant Oils known as peanut and olive are distinctly non- 

 drying. In the next section we have soya, corn, cotton and rape, 

 all of them seed oils classed as semi-drying. Here, too, belong 



