Patent Publication Number: US-3878179-A

Title: Polymerization of olefins

Description:
United States Patent Hogan Apr. 15, 1975 POLYMERIZATION OF OLEFINS [56] References Cited [75] Inventor: John P. Hogan, Bartlesville, Okla. OTHER CATIONS 73 A P t l C Ham, G. E. (Ed), Copolymerization, pp. 101-103, ss&#39;gnee 155535112} J. Wiley &amp; Sons, Inc, New York (1964).  
 [22] Filed: 9 Primary Examiner-Joseph L. Schofer [21] APPL No; 324,437 Assistant Exa&#39;minerA. Holler Related U-S. Application Data [63] fggs s &#39;g of 812350 High melt index polymers are produced in an olefin d an one polymerization process employing as a catalyst the hydrocarbon insoluble interreaction product resulting 76 86 1? from contacting a supported chromium oxide catalyst [58] Fie&#39;ld 260/949 D 94 9 5 94 9 E. with an aluminum hydrocarbyl oxide of the general formula R,Al(OR) which formula is defined.  
 9 Claims, No Drawings POLYMERIZATION OF OLEFINS This is a continuation-in-part of my application Ser. No. 812,850 filed Apr. 2, 1969, now abandoned.  
  This invention relates to polymerization of alpha olefins.  
  In one of its more specific aspects, this invention relates to the melt index properties or products produced by olefin polymerization.  
  Polymerization of olefins in the presence of chromium oxide catalyst system, such as the so-called particle-form or slurry process, is well known. Generally, such systems produce polymers of comparatively low melt index. Many attempts have been made to increase the melt index of the polymer produced in such polymerization reactions.  
  Frequently, an adjuvant is introduced in the catalyst system for this purpose. Many such materials can be employed, one of which is dialkylaluminum alkoxide. When a dialkylaluminum alkoxide is reacted with the CrO -silica catalyst system and the resulting system employed for olefin polymerization, polymers of high index are obtained. In a slurry process, however, the maximum melt index which can be obtained with such a catalyst system is lower than would be preferred.  
  A slurry process has now been discovered which employs a catalyst system which produces a more desirable, higher melt index produce. According to the method of this invention, there is provided a process which comprises contacting an aluminum hydrocarbyl oxide of the general formula R,Al( OR) as hereinafter defined, with a supported chromium oxide catalyst in the presence of a hydrocarbon diluent to form a reaction mixture, separating hydrocarbon-insoluble material from the reaction mixture to leave a hydrocarbon insoluble residue and employing the hydrocarboninsoluble residue as a catalyst in olefin polymerization to produce a high melt index polymer.  
  In one embodiment of this invention, an aluminum hydrocarbyl oxide is contacted with the supported chromium oxide catalyst.  
  In another embodiment of this invention, an aluminum hydrocarbyl oxide in combination with a hydro carbylmetal is contacted with the supported chromium oxide catalyst.  
  Accordingly, it is an object of this invention to provide a process for producing a polymer having melt index.  
  It is another object of this invention to provide a novel polymerization catalyst.  
  Other objects of this invention will become evident from the following disclosure.  
  The chromium catalyst systems to which this invention is particularly applicable is one in which the chromium is in the form of the oxide and is supported by at least one support component selected from the group consisting of silica, alumina, zirconia, and thoria. Generally, the support component will have been impregnated with an aqueous solution of chromium compound, calcinable to chromium oxide, the chromium consisting of at least about 0.1 weight percent of the total chromium-support or catalyst system. The resulting catalyst is particularly suitable for polymerization of monoolefins at temperatures up to about 500F., at least a portion of the chromium being in a hexavalent state upon initial contact with aluminum hydrocarbyl oxide or hydrocarbon feed.  
  The chromium oxide catalyst system is contacted, in one embodiment of this invention, with an alkoxide, preferably an aluminum hydrocarbyl oxide of the general formula R Al(RO),, in which x and y are integers from 1 to 2 inclusive and x y 3, and R is a hydrocarbyl group contatining from I to about 14 carbon atoms. The R hydrocarbyl group can be selected from such hydrocarbon groups as the alkyl, aryl, alkaryl, alicyclic, and the bicyclic. Illustrative of such hydrocarbon groups are methyl, ethyl, cyclohexyl, tetradecyl, phenyl, phenethyl, norbornyl methyl. The R groups can be identical or different. Preferred aluminum hydrocarbyl oxides are those containing the lower alkyl groups, such as diethylaluminum ethoxide, methylaluminum diethoxide, diisbutylaluminum isobutoxide, and the like.  
  In another embodiment of this invention a hydrocarbylmetal is employed in combination with alkoxide as the activating component. These hydrocarbylmetals include compounds of the formula R M where R is a hydrocarbyl radical having from 1 to 14 carbon atoms as hereinbefore defined, M is an amphoteric metal such as aluminum or zinc and x is equal to the valence of the metal M. Typical compounds are triethylaluminum, triisobutylaluminum, and diisopropylzinc.  
  The chromium oxide catalyst system is contacted with the alkoxide over the wide range of about 0.2 mol of the alkoxide to one mol of the chromium oxide, to about 20 mols of the alkoxide to one mol of the chromium oxide. If a hydrocarbylmetal is also employed it is used in an amount of about 0.1 to about 1 mole per mol of the alkoxide.  
  In the formation of the reaction mixture, the various materials are brought together in a paraffinic hydrocarbon diluent such as isobutane or n-hexane. Thereafter, the larger part of the hydrocarbon diluent, and those materials soluble in it, is separated from that portion of the reaction mixture substantially insolbule in the hydrocarbon diluent, after which additional hydrocarbonsoluble residuals are removed from the insolubles by washing the solubles with quantities of a hydrocarbon diluent. In other words, that diluent employed for removing solubles from the insoluble catalyst system can be the same or different from that material in which the formation of the reaction mixture took place. Either or both materials may be paraffins, such as butane, isobutane, pentane, or octane, cycloparaffins, such as cyclopentane, methylcyclopentane, or cyclohexane, or aromatics, such as benzene, toluene, or xylene, and the like, and mixtures thereof.  
  The polymerization conditions under which the process of this invention is conducted are conventional within the art, including a temperature from about F. to about 450 F., and a pressure high enough to maintain the hydrocarbon medium in the liquid phase. Generally, the polymer will be formed within the hydrocarbon medium in the form of a separable slurry. Prior to forming the insoluble reaction product or modified chromium oxide catalyst system, the supported chromium oxide is activated at a temperature from about 350F. to about 1,500F. by procedures known in the art.  
  US. Pat. No. 2,825,721 to I-Iogan et al, and British Pat. No. 853,414 set forth the details of the prior art process.  
  The following examples will serve to illustrate the invention but are not intended to limit the invention.  
  3 A catalyst, prepared by impregnating a microspheroidal silica with sufficient aqueous chromium trioxide solution to give a chromium content of one weight percent, was activated in air for hours at 800F. This catthe hydrocarbon-soluble reaction products from the reaction mixtute improved the melt index of the subsequently produced polymer. These data further indicate that the greater the removal of such hydrocarbonalyst served as the basic catalyst in the following prepa- 5 soluble reaction products, assuming two washings to be rations and more effective than a single washing, the greater the ef- Rhh i 135 P y weight of this basic cataiyst was feet on the melt index. It is within the scope of the inadmiXed with 500 Parts y weight of isobutahe To this vention to wash as many times as desired, such as one admixture was added a mixture of 8 parts by weight of to ten times, cliisobutylaluminum isebutoxitie and one P y weight to The invention is not to be considered as being limited of triisobutylaluminum h&#39;hexahe, the ratio of the to the specific embodiments of this disclosure. From it, tbtei weight of the aikoxide and aikyiahimihum to the various modifications will become evident. However, weight of the catalyst beihg about 8 to such are considered to be within the scope of the inven- The temperature of the mixture was raised to about tion 220F. over a 30 minute period. Without further treatw is claimed ment of this unwashed reaction mixture, polymeriza- A process for copolymerizing ethylene and buteneof ethylene to which had f added 6 percent l which comprises contacting ethylene containing a butehe was conducted, at 220 550 pslg for 2 minor proportion of butene-l under polymerization hours- Results were F Show as Rhh 1 m Table I helow&#39; conditions with a catalyst composition consisting essenln Run 2 a dry nitrogen atmosphere, 5.5 parts y tially of the hydrocarbon-insoluble reaction product weight of the h ly were h l with separated from the hydrocarbon-soluble reaction prodhexane and a mixture of dusobutylalummum isobutoxnet of an admixture formed by contacting a supported ide and triisobutylaluminum in n-hexane, in the same Chromium oxide Catalyst 3 portion of Said chromium proportions to each other and to hatalyst as in Ruh being in the hexavalent state, with an aluminum hydrowas added to the cathlyst&#39; After mhhhg th h&#39;hexahe carbyl oxide and a hydrocarbylmetal in the presence of (about 75 ml) was drained f and an hh 75 ml a liquid hydrocarbon, said aluminum hydrocarbyl oxide ofn-hexane was added to the msolubles remaining, the having the formula RJAKOR)y in which R is a hydro mixture shaken and the n-hexane drained off. The lncarbyl group containing from 1 to 14 carbon atoms and soluble catalyst was dried of n-hexane to produce a x andy are whole integers having a Sum equal to 3 and twice-washed catalyst system of this invention. 0.1 1 12 Said hydmcarbylmetal including compounds of parhbyheight of this was employed in poly mula R M in which R is a hydrocarbyl group having i under colhdhiohs 1 h g il those of Run from 1 to 14 carbon atoms M is an amphoteric metal 1. esutswereassownin a e eow.  
  The Run 3 Catalyst was prepared as in Run 2 except seleclted flrlom alummufmMand zinc and z is an integer that the insoluble catalyst, after draining of the original 2 h t e Va ehcfe F h d n-hexane diluent, was not washed thereafter. This proi c w mlxtur: duced a once-washed catalyst system which was emy h acting a oh h 0 sh} Supper e to ifiitfiiiildiif; 2:13;: that zlzazsztsfa toseo n esutswereass wnmta e, eow, all runs hai ing been made in the p resence of isobutane 40 h about mols and the hydrocarbyl metal 15 presas the only effective solvent, as was Run 1, any solvent 22%;: ah amount of about about 1 mo! of the employed for the pur ose of washing the catalyst having been, in effect, eli minated thereafter to the extent h prochss of claim h whlch the Support of Sald that the solvent employed to wash the catalyst was not chrohilhm h? catalyst l h from the ,gmup effectively present during the polymerization to the consisting of silica, alumina, zircoma and thOI&#39;la, the tent of affecting the physical properties of the polymer chromium content of said catalyst comprising at least product produced about 0.1 weight percent of the total weight of said cat- The run 4 catalyst was prepared as in Run 2, except aiystl that it was prepared in the presence of n-pentane rather The P s of claim 3 in which R is selected. from than in the presence of n-hexane, a single contact with the g p consisting of aikyi, aryi, aikaryi, aheyehe and the n-pentane being made. This produced a onecebieyeiie hydrocarbonswashed catalyst of this invention which was employed The Process of claim 1 in which said hydrocarbonin the polymerization under conditions identical to insoluble reaction Product is separated from Said those of Run 1. Results were as shown in Table I, behydrocarbon-soluble reaction Product y removing l said liquid hydrocarbon from said admixture and said Table I Productivity, Melt Index, dg/min. (a) Density Run No. Catalyst Wash lb/lb Regular High Load (g/cc. (b)  
  1 Unwashed 24l5 0.072 17.8 0.955 2 Washed Twice n-Hexane 2250 0.626 84.7 0.959 3 Washed Once n-Hexane 3| l0 0.242 47.0 0.958 4 Washed Once n-Pentane 34l0 0.280 54.0 0.957  
 (aI ASTM D l23X-6ZT; Condition E for melt index, and Condition F for high load melt index (h) ASTM D l505-63T These data indicate the operability of the process of this invention. These data also indicate that removal of hydrocarboninsoluble reaction product is washed with a second hydrocarbon liquid.  
  8. The process of claim 1 in which said hydrocarbylmetal is present in said admixture in an amount within the range of from about 0.1 to about 1 mol per mol of said aluminum hydrocarbyl oxide.  
  9. The process of claim 1 in which said hydrocarbylmetal is selected from the group consisting of triethylaluminum, triisobutylaluminum and diisopropylzinc.