[1]U-nited S'tates Patent Office 3@041@325 3,0-41,325 POLYM-EMATION 01@q oLEFiN AND cATALYsT oQv@STE4i)l THEREFOR Al:@rord G. F=ham, Meadham, N.J., assignor to Union 5 Carbide Co@-porailon, a corporation of New York N'o Dr2w!ng. Filed May 5, 1958, Ser. No. 732,792 15 Claims. (Cl. 260-93.5) This irlvention rciates to the polymerization of alc'iiaolefins, and more particularly to a nove). ceaivst system 10 us--fal for an exL-,-riiely rapid polymerization of alphaolefins. Crystalline polym,-rs of oleflnically unsaturated hydrocarbons containin.- asymmetrical groups have been reported by - Natta (J. Amer. Chem. Soc., 77, 1709; J. 15 Polym. Sci. XVI, 143) who has termed them "isotactic,'@ jr,aterials because of their re,-ularly ordered confi_zuration in which the arrailganent around successive asy@nmetric carboii atoms is the same for great distances alon-. flic polymer molecules. 20 T'aese isetactic or crystalline polymers have a grealer density, higher meltin.- and softening temperatures aT.,d lower solubility in organic solvents than an amori)hous polyr-rier of the same average molecular weight. For example, crystalline polystyrene is insoluble in diethyl etller 25 ani n-iethyl ethyl ketone NvEle arilorphous polystyrene is soluble in both; crystalline polypropylene is insollible in boilinldiethyl ether and coid heptane, while amorphous polypropyl ene is soluble in both. X-ray di@ffraction patterns and infra-red absorptions also differ, e.g. crystalline 30 polystyren-- shows infra-red absorption bands at 7.9, 9.25, 9.5 and 10.9 millinlicrons; amorphous polystyrene shows none of tnese absorption bands. The i--iltrinsic viscosity , measureme--ts, however, for the amorphous and - ciystalline polymers can be the same order of magnitude. 35 Ile differences in properlies between the two types of polymers -are traceable to the differing structural - features .they possess. Assuming a head-to-tail lip-kage - betnveen successive units, 40 of the Enear polymer and no branch chains other than R, structure varial,ons in t'ne polymer can occur by changes in the spatial position of R on the asynur-etric carbon atom, i.e., R can be above or beloiv thqt plane of the 45 molecule p,-rpe@ndicular to the R group axis. Where a disordered distribution of R -roups occurs, the polymer is airoi-phous, but Nvhere the R groups exhibit @a regularity of @confi-,Uration, i.e., where aH R groups are located on one side of that plane which contains the axis of the 50 molecule ald is p-@rpendici-ilar tG the axis of the R groups, then the polymer is crystalline. This application is a continuation in part of my copendin- adplication Serial No. 577,190, filed April 10, 5.5 1956, and no@v abandoned. Good yields of crystalline isotactic polymer are obtalilc,,d i-@i the method of Serial No. 677,190 usin- a catalytically active complex of a solid transition melal trihalide and an organo-alumirun copipound in a-@i inert liquid hydrocarbo-@i, but the best rate of p olymerization 60 observed in that r@iethod was less than t-,vo grams of polymer per gram of catalyst p--r hour. I have now found that a thirty-fold or greater increase in the rate of polymerizatio.,i can be achieved by em- , 65 ployin- in the catalytically activated complex a tra-ilsition n-ietq@l trihalide component with an average parti@,,Ie size of 2.0 to 0.01 microns. More particularly, a - catalyst compris;nl- a dispersion in an inert liquid hydrocarbon Patented June 26, 1962 2 c,irrier of one mol of a trirh-loride or tribromide of vanadium or titanium groun(I to an avera,-e particle size of 2.0 to 0.01 microns or smaller and 0.5 to 2.5 mols of an or.-ano-aluriinumcompouild such as triisobutyl aluminum can effect -a rnore rapid polvmerization of ali)haolefins having 3 or more caroon @atoms than has heretofore been achieved. Equally important with the increase in th.- rate of polyrreriza-lion, the percentage of crystall@ ty of the polymer ini product obtained is sarprisingly not reduced. Thus, t@he catalytically active dispp-rsion of a transition metal trihalide n-lixed with an organo-alumintim comp I ound provides the advantage of vastly inereased rales of polyrqerization and does not reducf, the amoi-int of desired product, the isotactic polyriier, obtained. The transition metal trihalide partic-les useflil in this invention are conveniently prepar,-d by grindin- in ali oscilla'Lory vibrating rnih or the lilce utider an inert atmosphere sucli as nitrogen or - argon. Ord;narily available titanium and vanadium trichlorides and tribron-.ddes have an average particle size, or average diamet-.r' of from 100 to 300 microis or larger. These Partirles car? be reduced to an avernge particle size of 2.0 to 0.1 ml:crons by grinding for 8 to 24 hours in an osr-illatory vibrating miJI, sugh as that sold by Siebtechnik A G., Mulheim, Germany, or in any device providing an e'quivalent gi-indin.- action. Th@ Siebtechnik mill imparts a rapid rotary motion to a ebarwoer fired with 1/2" steel balls. Grinding for up to 48 hours in this mill provides particles averaging 0.1 to 0.01 in dian-ieter vihic@.i are preferred in the present invention. Continiled grinding, up to 72 hours, does not reduce the average particle, size significantly, ho@vever. The smaller sized particles obtained by grindii.- for 48 hours provide the most rapid rate of polyricrization and do not decrease the percentaa of crystalline isotactic polypier in the product. By fra@,tionating the finely ground titanium or vanadium trihalide and using only the smauer particles i.e. those near 0.01 n-iieron in diameter, even more rapid polynerization can bp, obtained. For convenience in handlin- and in order to prepare the catalyst @for immediate use in polynierizing the alphaolefins, the ground trihahde p@articles ar.- suspended in all inert liqtiidhydrooarbon during the -rindilig process. Liquids suilabic for this purpose are aliphatic compounds such as kerosene, heptane, and cyclohexane; and aromat;c compounds such as benzene, isopropyl benzene, xylene, and toluene. The organo-aluminum coriipound component of the catalyst can be added to the finely ground titanium or vanadium haude as a solution in an ineit liquid hydrocarbon. Organo-alunmum compounds suitable for use in the present invention have. the @eneric formula Ri-AI-Rs I R2 ivh,-rein R, is a hydroaen atom, an alkyl groui3 or an aryl group; R2 is an alkyl or aryl group; and R3 iS an alkyl or an aryl grouv. I particularly prefer among the trialkyl-aluminum compounds and their hydrides, diisobutyl aluminl-un hydride, ttiisobutyl aluminum and triethyl -aluniinum; and among the triaryl-aluniiilum compounds, triphenyl aluminum. For best catalytic results, the mixture, is -made in the ratio, of 0.5 to 2.5 mols, preferably one mol of organo-aluminum compound to @ earh mol of titanium or vanadium trichloride. II-ligher rati6s, while catalytically operable, do not confer @any additional-
[2]3,041,325 advantages in rate, amount of yield or percentage of crystallinity in the product. The catalytically active complex of my invention can be used to effect the extremely rapid polymerization of alpha-olefins having more than-3 carbon atoms, such 5 as styrene, propylene, 11-butene, 4-phenyl butene and the like, to higwy crystalline isotactic polymers. - Generally from 25 to abotit 2000 mols of monomer @are polymerizable with eacn mol of fmely ground - catalyst. Monomer and catalyst are mixed and heated with stir- 10 nng at a temperature dependent upon the solvent used ,and the mononler undergoing polymerization. When the reaction is complete as shovin by the polymer being too thick to stir, the crude product is washed free of most catalYSt Tesidues with additional solvent, and then 15 with a 1 to 5% @aqueous acid solution to neutralize any residues which may remain. For example, to effecl -the rapid polymerization of styrene to highly crystalline isotactic polystyrene, one mol of the catalyticallv active complex hereinbefore de- 20 scribed is provided as a 10% solution in a satureed hydr<)carbon such as toluene or tl-ie like,. witn about 100 moles of the sl,yrene mo-@iorier to be polymerized. The catalyst solution is heated to 50'-60' C. with - stirring, and the styrene added slowly with contintied stirring. 25 When the resulting gelatinous mass of polymer becomes too viscous for further stirring, it is washed with water or dilute acid to remove excess catalyst; then a n . onsolvent for the polymer, i.e. methanol, ethanol, or isopropanol, is added to precipitate the polymer from the 50 toluene or other catalyst carried. A more complete removal of catalyst residues is achieved by heating the polymer with additional toluene to about 70-90' C. prior to washing' The precipitate is filtered and dried, preferably under vacuum, at ablyat 50' C. to 60' C. 35 The catalytic method and c-,ttalyst composition of this invention generally provide a polymer product of which 75% or more is crystalline and isolactic. The remainder or amorphous portion of the polymer product is "amorphous" and non-crystalline and exhibits little regularity 40 of confi.-uration. Where it is desired to remove the ,amorphous polymer, the dried polystyre-iie can be extractdd by heating the polymer product w-.Ih diethyl ether. T'@ic above-d@-scribed polymerization of styrene can be carried out at temperatures of from about 20' to abotit 45 110' C. dependin.@ on the boiling point of the catalyst - carrier usdd. With toluene as a carrier, temperatures ranging between about 80' and 100' C. are preferred. The rapid polymerization of propylene to highly crystalline polypropylene is similarly carried out. One mol 50 o'l the catalytically active complex of my invention as a 10% suspension in toluene and 100 mols of propylene to b-- polynerized is heated wilh stirring to 40-70' C. -and propylene is bubbled throligh at atmospheric pressure. Elevated temperatures, up to 150' C. and pres55 sures i-ip to 400-500 ps.i. can be employed but polymerization is quite rapid at atmospheric pressure aid moderate temperatures of 40-70' C. The polypropylene is isolated in the same rr@anner as just described for polystyrene. 60 In the followin,@ exaniples and experiments 'the rate of reaction was determined from the equation: Rate=.@. polymer/,-. catalyst/hour The Examples 1-5 are illustrati-kre of the novel method and catalyst composition of my invelition. Following 05 these examples, for the sake of comparison, are experiments showing the unimproved rates of similar reactions which do not use a finely divided catalyst. The results of the Examples 1-5 are summarized in the table following the examples. 70 EXAMPLE I One hundred nil. of purified toluene were mixed with @100 nil. of styrene, which had been purified by being p assed over activated alumina. Four millimoles of tri75 4 isobutyl aluminum, as a 20% solution in toluene, and 4 millimole of titanium trichloride, which had been ground for 8 hours in the Siebtechiiik mill, described above, to an average particle size of less than 2 microns, were then added as ja 10% to 20% solution in toluene. This n-iixture was heated to 60' C. for 10 minutes and reacted under a nitroen blanket at 75' C.-2' for one hour while being agitated. The resultin- polymerization reaction was halted by the addition of 100 ml. of isopropanol containing 0.1% of 2,6- ditertiary butyl paracresol as a polylrerl-ation inhibitor. The precipitated polymer Nvas filtered off, washed with alcohol and then dried under vacuum for a period of 8 hours. The yield was 39.t6 grams of pglymer; 90.6% of the polymer was insoluble on extraction with boiling methyl ethyl ketone. The reaction rate was 28..l. EYAMPLE 2 The procedure of Example 1 was carried out usintitaniumtrichloride which had been ground for 24 hours under nitrogen to an average particle size of less than I micron. The yield was 70.1 grams of polymer, 91.4% of which wascrystalline polystyrene. The reaction rate was 49.7. E-XAMPLE 3 T e procedure of Example 1 was carried out using -h titaniurn trichloride which had been -round in the abovedescribed manner for 48 hours to an average particle size of less than 0.1 micron. The yield was 79.3 grams of polymer; 92.4% was crystalline polystyrene. The reaction rate was 56.3. EXAMPLE 4 Into a dry flask equipped with a stirrer, gas inlet ttibe, thermometer and a condenser with a provision for positive protection by an inert gas atmosphere, were placed: 1500 ml. of di-y toluene; @10 millimoles of a solution of tiiisobutyl aluminum; and 10 millimoles of titaiiiuni trichloride prepared by grinding forty @grams of TiCI3 with 180 ml. of dry benzene in the Siebtechnik mill under nitrogen for 8 hours. The sizes of the trichloride partirles were found by means of electron microscope measurement to be in the range of 0.1 and two microns.; The mixture was a.@itated at 40' C. ar@d the propylene feed was begun. Within 15 minutes the te-@nperature was at 70'-75' C. Propylene feed was conlinued at a rate slightly in excess of its rate of absorption for a period of three hours wbile the temperature of the flask was maintained at about 75' C. 1000 n-d. of isopropanol were added and the slurry was removed from the flask. An additional 1000 ml. of isopropanol and 500 ml. of methanol we-re -used to precipit-,tte the polymer. After bein.- cooled to 30' C. the mixture was filtered. The particulate polymer was reslurried, washed with additional isopropanol, and dried to constant weight. The total yield was 144 -rams. The amount of crys@Lalline polypr6pylene as deterrni-ned by overnight extraction with boiling ethyl ether was 108 -rams or 75.3%. The rate of reaction was 13.7. EXAMPLE 5 The procedure of Example 4 was repeated e,xcept that triethyl aluminum was used in place of triisobutyl aluminum. The yield, after 2.5 hours of polymerization, was 170 g.; 89.1% was crystalline polypropylene. The reaction rate was 25.4. Films made from these polypropylenes are transparent and exceptionally impermeable to -a wide variety of vapors and cases. The results of the preceding examples are tabulated in the table following- Both polypropylene and polystyrene of high crystauinity were produced at a good rate. Comparing Examples 1, 2 and 3 it will be noted that a decrease in avera.-e particle size produces greatly increasod rates and, not a decrease, but surprisingly an in-
[3]5 crease in the percent crystallinity of the polystyrene obtained. Average Pat(, of CrystalExample particle Reac- Product linity Size I tion 2 (Percent) 1------------------- <2 28. 1 Polystyrene ------ 00.6 ------------------- <1 49.7 ----- do ------------- 91.4 ------------------- <0. 1 56.3 ----- do ------------- 92.4 4- - - -------- <2 13.7 PolyproDyleiie ---- 75.4 <2 25. 4 ----- do ------------- 89.1 -------------------- I Average particle sizes ivere determined by measurement of enlarged ele.@troia microscope pictures of the i)-,ir@icles. 2 Gram polymeri,-ram catalyst /hour For the purpose of comparison, a series of experiments were ran using a coarsely ground metal trihalide. Even a slight increase in average particle size, cf. Experiment III, severely retarded the rate of reaction. Experiment I A 5 % by weiaht suspension of titanium trichloride with a particle size of about 10 to 20 microns was prepared by ball milling in a bacteria brinder with dry cyclohexane. A 10% by volume solution of triisobutyl aluminum in dry cyclohexane was also prepared. To about 1200 ml. of dry benzene was added: 120.4 ml. of the 5% suspension of TiCI3, 98.4 ml. of the 10% triisobutyl aluminum solution and 298 ml. (270.4 @rams) of dry styrene monomer. The mixture was heated to 50'60' and stirred for about 20 hours, after which the stirrer stopped because of the high viscosity of the mixture. After standing for an additional 20 hours, the mixture was vigorously agitated with several changes of water, which were decanted off. Methanol was added to the gelatinous benzene-polymer mixture to precipitate the polymer as a granular white powder. This was futered off, washed with methanol, and dried in an oven at 100'110' C. The yield of polyriler was 221.72 grams (82% yield) of which 96.5% was insoluble on extraction with boiling diethyl ether. The meltin- point was about 230' C. The rate of reaction was 0.7. Experiment 11 Vanadium trichloride was prepared by heating 22.2 9of vanadium tetrachloride under reflux in a stream of dry carbon dioxide for 50 hours at 160-1701 C. Any unchanged vanadium tetrachloride was removed by vacuum distillation. The yield of purple solid vanadium trichloridewasl2.7g. Thiswasgroundunderbenzeneinabacteria grinder to a particle size of about 10 microns. Ten miffimoles of the above vanadium trichloride was mixed with 10 mfflimoles triisobutyl aluminum in about 500 ml. benzene and 100 ml. styrene was added. The mixture was heated with stirring in a flask 21 hours at 50-60' C. Particle formation within I hour, and noticeably increased viscosity within three hours, was evidence of polymerization. A-fter 18 hours, the product was gelatinous semi-solid mass. Toluene (100 ml.) and 2% hydrochloric acid (250 ml.) were added causing the mixture tO turn from PurPle to brown. The polymer was washed with hot water in a blender and gradually 'Lurned from brown to white. It was precipitated with methanol and futered off. Yield of polystyrene was 43.6 g. (48.5% yield); ash content, 0.9%. On extraction with boiling ether, the percent insoluble was 81. The rate of reaction was about 0.7. A disc molded at 160 to 170' C. and at 1000 p.s.i. was translucent and light gray in color. Experiment III The procedure of Example 4 was repeated except that TiCI3 with an average particle size of about 5 microns was used. The yield, after PolYmerizing for 31/2 hours, was only 6 g.; 75.1 % was crystalline polypropylene. The reaction rate was 0.5. 3,041,325 Experimeiit IV The procedure of Example 5 was repeated except that TiCI3 with a particle size of about 5 microns was -used. The yield of polymer, aiter polymerizing for 81/4 hours, was only 44 g.; 89.6% was crystalline polypropylene, The reaction rate was less than 2. The ultra-fine dispersion of the catalyst, in addition to providing greatly increased rates of polymerization, is advantageous in that the more finely dispersed catalyst is lo inore easily removed from the polymer and there is less ash content in the product due to the use of less catalyst. The highly crystalline polymers obtained with the method of this invention because of their greater densities and lower solubilities have improved utility for 15 numerous applica'Lions particularly filaments, fibers, sheets and films. They can be molded, extruded, cast from solution or calendared in conventional fashion. The materials have an essentially non-polar structure, so they exhibit excellent electrical properties even at hiah fre20 quenci-,s. Since they have practically no water absorption, the electrical properties remain virtually uneffected by humidity. Such excellent electrical properties combined with good thermal and mechanical characteristics result in superior,insulation. 25 Their heel resistance and mechanical properties, together with unusual chemical resistance, make these isotactic polymers a good choice for pipe applications. They are res;stant to acidic, alkaline, and saline solutions even. at elevated temperatures. At room temperatures they 30 resist organic solvents and polar substantces without embrittlement. Absorption of n-dneral and vegetable oils is extremely low. What is
