Patent Office 2,877
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Patented Nov. 28, 1939 2,87. UNITED STATES PATENT OFFICE 2,877. METRO OF POLYMERIZATIGN OF STYRENE Norgman B. Scott, Sanborn, N. Y., assignor G E. I. du Pont de Nemours & Company, Wi inington, Del, a corporation of Delaware No Drawing. Original application December 10, 1935, Serial No. 53,756. Divided and this ap plication February 1, 1938, Seria No. 188,194, 2 Claims. (C. 260-91) This invention relates to an improved method it is advisable to leave a small amount of the for polymerizing hydrocarbons. Solvent ether in contact with the Sodium come This application is a division of my copending pound, e. g., equivalent to around 20% by Weight application S. N. 53,756, filed December 10, 1935, of the compound, as this increases the stability 5 which is a continuation-in-part of application of the Sodium compound. Serial Number 726,569, filed May 19, 1934, which I have discovered that the herein described ad has issued as U. S. Patent 2,048,169. dition compounds of alkali metals and polycyclic An object of the present invention is to provide aromatic hydrocarbons have a marked polymer novel and improved methods for polymerizing 0. izing effect when contacted with an unsaturated unsaturated hydrocarbons to produce a variety hydrocarbon which does not readily form sub ...) of useful polymerized substances, as hereinafter stitution compounds of the alkali metals and described. Further specific objects will be ap which has conjugated double bonds, at least one parent from the following disclosure. of the conjugated double bonds occurring in an I have found that the addition compounds aliphatic radical. Further, I have found that 5 formed by the reaction of alkali metals with poly these addition compounds have little or no poly Cyclic aromatic hydrocarbons Such as naphtha merizing effect on unsaturated hydrocarbons lene, diphenyl and phenanthrene, and the like, Which do not have conjugated double bonds as have decided advantages as hydrocarbon poly described above. Examples of hydrocarbons merizing agents in that they are easily prepared, with conjugated unsaturation which may be 20 can be handled as solutions, do not ignite in readily polymerized by treatment with small contact with air under ordinary conditions, do 20 not elvolve hydrogen or ignite on contact with amounts of the alkali addition compounds are water, yet in general are more effective than the butadiene, isoprene, dinnethyl butadiene, styrene, free alkali metals as polymerizing agents. Cer cyclopentadiene, and 1,2-dihydronaphthalene. tain methods of forming these addition com My invention is not limited to these examples, pounds are disclosed and claimed in my Copend as other unsaturated hydrocarbons of the class ing applications Serial Numbers 638,524 and mentioned above, as well as their substitution 678,261, filed Oct. 19, 1932 and June 29, 1933, re derivatives, may likewise be polymerized by the spectively, Which have been issued as U. S. Pat method of the present invention. Also, Iny ents 2,027,000 and 2,123,793, respectively. One method may be applied to various products con convenient method is to dissolve Sodium in a so taining one or more of such unsaturated hy lution of naphthalene or other polycyclic aro drocarbons, e. g., crude gasoline or other petro matic hydrocarbon in liquid dimethyl-ether at a leum fractions. temperature Somewhat below -24° C., while The polymerizing action is rapid and complete, stirring or abrading the sodium in contact with even at relatively low temperatures, e. g., 20. to the mixture to start the reaction. When the re 30%. C. Alkali metals are known to cause poly action is once started, the solution becomes high merization of unsaturated compounds, but my ly colored and Solution of the metal occurs at herein described alkali metal addition com a rapid rate. The amount of sodium readily dis pounds differ from the alkali metals in that they solved will range in general from one to two cause more rapid and more complete polymeriza gram atoms per gram molecule of the aromatic tion of the conjugated unsaturates than do al hydrocarbon. Various other aliphatic ethers kali metals. For example, a Small amount of an may be used as Solvents in place of dimethyl ether Solution of the Sodium naphthalene addi ether, as for example, methyl ethyl ether, poly tion compound added to 1,2-dihydronaphthalene 45 ethers such as dimethyl or diethyl glycol ethers, at 20 to 30° C. rapidly and substantially com or cyclic ethers such as dioxane. pletely polymerizes the latter to a resinous Sub 45 When the solution of the sodium hydrocarbon stance, while an equivalent amount of sodium compound or mixture of compounds has been pre metal, under similar conditions polymerizes this pared, it either may be mixed with the hydrocar hydrocarbon only very slowly and incompletely, 0. bon to be polymerized, or as is usually preferable even at elevated temperatures. 50 to avoid wasting solvent, the methyl ether or I have found that the herein described alkali other special Solvent used in preparing the So metal addition compounds are selective in their dium compound may be partly distilled off and polymerizing action in that they readily poly recovered before contacting the Sodium com merize the conjugated unsaturates, while hav 53 pound. With the hydrocarbon. In the latter case, ing Substantially no polymerizing action on non s 2 2,181,771 through the dropping funnel at a rate consistent conjugated unsaturates, e. g., amylene or lin with maintaining the reaction temperature at onene. the aforesaid value of -30 °C. Water is now The Selective polymerizing action of the herein dropped into the reaction mixture until the col described alkali metal addition compounds is ill Ored Sodium compound is destroyed. The pre lustrated by the fact that whereas the sodium cipitated polymer is filtered off, washed with pure naphthalene compound causes rapid polymeriza dimethylglycol ether, then with water and finally tion of butadiene, it has substantially no action dried in an oven or vacuum desiccator. The on amylene. yield of polymer is 90% of the theory or better. My novel polymerizing agents may be contacted The polymer obtained by this procedure has O vfith the hydrocarbon to be polymerized by vari the appearance of a white amorphous powder ous methods, which will be apparent to those which is substantially insoluble in all common skilled in this art. I prefer to first dissolve the Solvents, including aliphatic and aromatic hy unsaturated hydrocarbon to be polyernized in drocarbons, Water and aliphatic alcohols. In a solvent ether of the type suitable for the for high-boiling chlorinated hydrocarbon solvents it s mation of the alkali metal addition compound, dissolves to Some extent to form colloidal solu as described above (e. g., dimethyl ethylene tions. It is Substantially infusible below decom glycol ether) and then add a small amount of the position temperatures, since when heated it does alkali metal addition compound or an ether so not melt at temperatures of 300° C., or below; at lution of the same. higher temperatures it softens and chars at the 90 The amount of the alkali metal hydrocarbon same time, but this does not take place until compound required Will vary over a Wide range, temperatures slightly below red heat have been depending upon the temperature, time of con attained. The solubility of polymer of 1,2-dihy tact, the nature and amounts of impurities in dronaphthalene-in such solvents as alpha-chloro the hydrocarbon, and the degree of polymeriza naphthalene to form colloidal solutions varies 25 tion desired. Only small amounts of the addi With the temperature at which the dihydronaph tion compound will be required, for example, thalene has been polymerized. Polymer prepared 1-10% of the Weight of the compound to be poly at approx. 65 C., dissolves to the extent of merized. Ordinarily, a mere trace of the addi about 1.36 gms. per 10 cc. of chloronaphthalene, tion compound is sufficient to effectively poly and the solution gels on cooling. If this polymer 30 30 merize the unsaturated compound; if moisture or other impurities with which the addition com is prepared at -30° C. as above described, it pound will react are present, a correspondingly dissolves only to the extent of about 0.25 gm. larger amount of the addition compound must be per 10 cc. of chloronaphthalene. added. Eacample 2 33 The polymerization will occur within a wide range of temperatures, including temperatures Twenty grams of styrene and 10 cc. dimethyl both below and above Ordinary room tempera glycol ether is placed in a small flask equipped ture. For example, I have polymerized unsat with an agitator and in which a nitrogen atmos urated hydrocarbons in accordance with the phere is maintained. With constant stirring and herein described invention at temperatiures as cooling, 10 cc. of normal sodium naphthalene so 40 40 low as -60° C., and also at relatively high tem lution is gradually added to the styrene solution. peratures, e. g., 50 to 60° C. Preferably I op Polymerization takes place with the evolution of erate at temperatures below the boiling point considerable heat. Ten cubic centineters of of the solvent employed. Generally, the physi normal sodium naphthalene solution contains cal properties of the polymer will vary, depend 0.23 gram of Sodium in the form of the Sodium 45 ing on the temperature employed, the higher addition compound. A little Water is added to temperatures favoring the formation of polymers the polymerization mixture to bleach the sodium of lower molecular weights and lower melting compounds, and carbon dioxide then is passed points. The polymers formed by my process are through the liquid to carboxylate the alkali.