I N D U S T R I A L A N D ENGINEERING CHEMISTRY
January, 1927
Acro1ite"-A
"
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111
New Synthetic Resin' By James McIntosh
DIAMOND STATSFIBRECo., BRIDGEPORT,PA.
temperature the neutralked resin is permanently soluble and fusible. When cut with alcohol it makes an excellent insulating varnish, the dry film from which gives a brilliant luster and is flexible. I n carrying out this reaction it is helpful to use an excess of phenol; otherwise the resin has a tendency to be rubbery or slightly insoluble. The use of an excess of phenol is commercially feasible as it can he recovered and used again. On the other hand, a slight excess of glycerol impairs the hardness and is detrimental to dielectric and other properties of the resin. The foregoing reaction is a progressive condensation, and can be stopped a t different stages. The yield will vary somewhat, depending upon how far the reaction has been carried. Bt the beginning of the reaction there is a watery white limpid solution, which gradually changes to pink and finally to a deep, dark, almost black resin solid a t room temperature. If the acid catalyst is not neutralized, heat alone will easily cause the condensation to carry over to the insoluble, infusible state. This new synthetic resin can be heated over a direct flame to 325" C. or even higher after the acid has been neutralized. At this high temperature the resin will pour with water fluidity and on cooling it will set hard, with a brilliant luster, easily soluble in alcohol, acetone, and other solvents. Furthermore, 'it can be made potentially reactive by adding an aldehyde or other derivative of the methylene group. In practice it is advisable to add from 4 to 12 per cent of a hardening agent, preferably formaldehyde, paraformaldehyde, or hexamethylenetetramine, to the neutralized soluble, fusible resin. These hardening agents speed the curing period; in other words, they enable the resin to change quickly from the soluble, fusible to the insoluble, infusible state. The resin in the insoluble and infusible stage will char and not soften when subjected to excessive heat. hIolding powders can be made from this glycerol phenolic resin by the dry or wet process. In the wet process the resin is cut with alcohol and the wood flour, color, and hardenPlace 1000 grams C P. crystal phenol, 700 grams C. P. glycerol ing agents are kneaded in. In the dry process the resin (sp. gr. 1.25), and 10 cc. sulfuric acid (sp. gr. 1.84) in a round- is broken down and rubber compounding rolls are used to bottom, short-neck, 2-liter flask. Place a thermometer through the work the wood flour, color, etc., into the resin while in the cork into the solution and heat the flask over a direct flame, holding plastic state. the temperature between 160" and 190" C. As fast as the water Laminated materials are made by impregnating paper, of reaction is formed it is fractionated off through a 2-bulb stillhead filled with glass beads, connected with a water-cooled fabric, or asbestos sheets with liquid varnish. The solvent condenser. During the reaction some phenol is carried over. in the varnish is driven off by heat, leaving the fibrous From time to time separate the phenol from the water in a sheet impregnated with the potentially reactive resin. separating funnel and return to the original flask. When apArticles can be molded from the impregnated sheet or proximately 350 grams of water have been distilled, allow the remolding powder by subjecting it to hydraulic pressure action flask to cool slightly and neutralize any acid with barium carbonate, calcium carbonate, or calcium oxide. Calcium or of 1000 pounds per square inch and a t a temperature of barium compounds are preferable because they give insoluble about 300" F. The molding operation is carried out in sulfates, which do not impair the dielectrical properties of the hydraulic presses equipped with steam-heated platens. resin During the pressing the resin is chemically changed from the I n the acid state the resin is reddish brown; i n the alkaline soluble, fusible to an insoluble, infusible condition. The state it is a deep pkrple. The color change is very sharp molded articles are chemically inert, water-repellent, and and pronounced. When not subjected to polymerization unaffected by atmospheric conditions. They possess a dielectric resistance of 700 to 800 volts per mil and can be 1 Received August 9, 1926. Presented before the Section of Paint and Varnish Chemistry a t the 72nd Meeting of the American C!hemical Society, machine-punched. sawed, or drilled. Philadelphia, Pa., September 5 to 11, 1926. "Acrolite" will withstand a higher continuous temperature 2 DIvglers polyfech. J , 235, 232 (1880). than any other synthetic resins now on the market. Its 8 U. S. Patent 906,219 (1908). ' French Patents 335,584 (1903) and 341,013 (1904). luster is superior to that of any resin heretofore manufactured.
NEIV synthetic resin, the result of the condensation reaction between glycerol and phenol, or the homologs of phenol, has been discovered and developed in this laboratory. It has all the desirable properties, both physical and mechanical, of the well-known phenol-formaldehyde resin. The literature contains no reference to a resinous product obtained by reacting phenol and glycerol, capable of polymerization with heat alone or with heat and a hardening agent, to form a hard, infusible, insoluble commercial synthetic resin. As early as 1879 Reichlz investigated the possibility of obtaining a new class of dyestuffs from the reaction of phenol and glycerol in the presence of large quantities of sulfuric acid. He obtained a satisfactory dye by heating the components for a long time between 110" and 120" C., but did not obtain a resinous material which was potentially reactive as that term is used in the synthetic resin industry. Reichl's new dye was soluble in boiling water. Grognot3 in 1908 took out a patent for the manufacture of a synthetic resin from phenol and formaldehyde. He used an intermediary substance, such as glycerol, to retard the otherwise fairly violent reaction, malfing it more easy to control. He first reacted the formaldehyde and the glycerol and then added phenol, whereupon the glycerol was regenerated and could be recovered and used over again. Fayole4 in 1903 and 1904 obtained French patents for a process of manufacturing products to be used as substitutes for rubber or gutta-percha. Formaldehyde was reacted with phenol in the presence of glycerol and large quantities of sulfuric acid a t a relatively low temperature. The product obtained was rubbery. The novelty of the new resin here discussed is that it is formed by the reaction between glycerol aud phenol. This reaction is easily controlled. On a commercial scale it is carried out in a pressure-jacketed autoclave, provided with a mechanical stirrer and so equipped that it can be steamdistilled under vacuum. I n the laboratory the reaction can be studied in a glass flask or in a pressure bomb. The following is a typical illustration:
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