Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2410/00—Features related to the catalyst preparation, the catalyst use or to the deactivation of the catalyst
  • C08F2410/06—Catalyst characterized by its size
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S526/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S526/908—Containing catalyst of specified particle size

Definitions

• the present invention relates to an improved process for the polymerization of alpha-olefins. It also relates to a process for the preparation of solid catalytic complexes which can be used for this polymerization.
• the morphology of the particles of these polymers therefore poses problems during their drying, their storage, their transport, their handling and their use by known molding techniques.
• the attempts made so far to increase the average particle size of the polymers obtained directly by polymerization using the catalytic systems described above have not been completely satisfactory. It has thus been found that a certain increase in the average diameter of the particles can be obtained by raising the temperature at which the aluminum halide is used. This increase in the mean diameter is however unfortunately accompanied by a decrease in the apparent specific weight and a significant widening of the particle size distribution.
• the main object of the present invention is therefore to obtain, without the above-mentioned harmful side effects, polyolefins in which the percentage of fine particles is reduced and in which the average particle size is higher.
• polyolefins are increasingly used in the form of powders, that is to say in the form of dense and regular particles, a large percentage of which have an average diameter greater than 250 microns, preferably greater than 500 microns.
• Polyolefin powders are particularly appreciated for processing by injection.
• Other interesting outlets for polyolefin powders are the production of coatings by various techniques (electrostatic coating, spray coating, etc.) and the use as additives, release agents, waxes, compositions for paints, binders for nonwoven textiles. , etc.
• Another object of the present invention is the manufacture of polyolefin powders by means of polymerization processes which directly give polymers in the form of particles which have the morphological characteristics of the powders used in the processes mentioned above.
• the invention is based on the surprising discovery that a very particular class of catalytic systems described above makes it possible to obtain without affecting the advantages inherent in these systems, polyolefins in the form of dense and hard particles, of large average diameter. , of tight particle size distribution and of high apparent specific weight. These properties make them particularly suitable for being used in the form of powders when they are transformed into finished objects.
• organic oxygenated compounds of magnesium and titanium is intended to denote all the compounds in which any organic radical is linked to the metal via oxygen, that is to say all compounds comprising only metal-organic oxygen radicals per metal atom.
• the organic radicals linked to the metal via oxygen are arbitrary. They are preferably chosen from radicals comprising from 1 to 20 carbon atoms and, more particularly, from those comprising from 1 to 10 carbon atoms. The best results are obtained when these radicals contain from 2 to 6 carbon atoms.
• These radicals can be saturated or unsaturated, branched chain, straight chain or cyclic; they can also be substituted or contain heteroatoms, such as silicon, sulfur, nitrogen or phosphorus, in their chain.
• alkyl radicals linear or branched
• alkenyl aryl, cycloalkyl, arylalkyl, alkylaryl, acyl and their substituted derivatives.
• the reagents (2) used to prepare the catalytic complexes according to the invention are titanium compounds (T).
• T titanium compounds
• the tetravalent titanium compounds are preferably used because they are more often liquid and in any case more often and better soluble than those where this metal is at a valence of less than 4.
• organic oxygenated compounds (T) comprising several different organic radicals also falls within the scope of the present invention.
• alpha-olefin polymers of wide molecular weight distribution it may be advantageous, for the manufacture of alpha-olefin polymers of wide molecular weight distribution, to additionally use at least one additional transition metal compound (reagent (4)) to prepare the solid catalytic complexes of l 'invention.
• This additional compound is then a compound (Z) chosen from organic oxygenated compounds and halogenated zirconium compounds.
• the solid catalytic complexes which can be used according to the present invention are finally prepared from reagents (3) which must be organoaluminum chlorides of general formula AIR n Cl 3-n in which R is isobutyl and n is a number such that 1 ⁇ n ⁇ 1.5.
• organoaluminum chloride which is very particularly preferred and easily is isobutylaminium AI dichloride (iC 4 Hg) CI 2 .
• reagent (3) is an essential characteristic of the invention. It is indeed the nature of this reagent which, surprisingly, is at the basis of the significant improvement in the morphology of poly olefins obtained according to the process of the invention.
• organoaluminum chlorides can be prepared, optionally "in situ” and preferably prior to their use, in particular by mixing the corresponding trialkylaluminums with aluminum chlorides containing more chlorine than the chloride which it is desired to obtain.
• the scope of the invention is not limited to the use of organoaluminum chlorides consisting exclusively of compounds corresponding to the general formula above mentioned but that it extends to technical products containing, in addition to a substantial proportion of these compounds, by-products such as the reagents used for their preparation. However, it is preferred that these products contain at least 80% by weight of organoaluminum chlorides corresponding to the general formula.
• the solid catalytic complexes of the invention can be prepared from the reactants (1), (2), (3) and optionally (4) above according to all the methods inducing a chemical reaction between them. It is preferred to carry out the reaction for forming the complexes in a liquid medium. To do this, it is possible to operate in the presence of a diluent, in particular when the reagents are not themselves liquid under the operating conditions or when there are not enough liquid reagents.
• a diluent When a diluent is used, it is generally chosen from those which are capable of dissolving at least one of reagents and in particular from alkanes, cycloalkanes and aromatic hydrocarbons comprising from 4 to 20 carbon atoms such as for example the isobutane, hexane, heptane, cyclohexane, benzene, toluene, etc. It is also possible to use polar solvents such as ethers and alcohols comprising from 1 to 12 carbon atoms (ethanol and diethyl ether, for example), tetrahydrofuran, pyridine, methylene hydrochloride, etc. When a diluent dissolving at least one of the reagents is used, it is preferred that the total concentration of the dissolved reagents is greater than 5% by weight and preferably 20% by weight relative to the diluent.
• the reaction medium is preferably in the form of a relatively viscous liquid in which materials may be present. solid in dispersed state.
• reagent (3) takes place at the end of the preparation of the catalytic complexes, that is to say as soon as possible while the reagents (1) and ( 2) are brought together.
• the best results are obtained when the reagent (3) is used after the reagents (1) and (2) have been brought together in their entirety.
• the methods for preparing the solid catalytic complexes according to the invention also extend to the use, in place of the reactants (1) and (2) preformed, of magnesium, of a hydroxylated organic compound such as a alcohol and reagent (2).
• the pressure under which the preparation of the catalytic complexes is carried out, the rate of addition of the reactants and the duration of their contact are not critical factors. For reasons of convenience, one generally works under atmospheric pressure; the speed is generally chosen so as not to cause a sudden heating of the reaction medium due to a possible self-acceleration of the reaction; the duration can generally vary between 5 minutes and 12 hours.
• the reaction medium is generally stirred so as to promote its homogenization during the duration of the reaction.
• the reaction can be carried out continuously or batchwise.
• the temperature at which the reagent (1) and the reagent (2) are brought into contact is not critical. For reasons of convenience, it is generally chosen between 200 and ⁇ 50 ° C, preferably between 150 0 C and room temperature (25 ° C).
• the temperature at which this reaction is carried out has an influence on the morphology of the polyolefin powder finally obtained.
• the organoaluminum chloride in accordance with the invention it is possible to reinforce the favorable action of the organoaluminum chloride in accordance with the invention on the size, hardness and particle size of the particles of the polyolefin and on its apparent specific weight, by suitably choosing the temperature at which this reagent (3) is added or produced resulting from the prior mixing of the reagents (1) and (2).
• This temperature is between 30 and 65 ° C.
• the best results are obtained between about 45 and 60 ° C.
• the preparation of the catalytic complexes in accordance with the invention can advantageously be completed by a treatment of the ripening carried out at a temperature generally equivalent to or higher than that at which the reaction with the reagent (3) takes place for a non-critical period ranging from 5 minutes. at 12 o'clock in general, preferably for at least 1 hour.
• the amount of compound (M), compound (T) and organoaluminum chloride (A) to be used preferably are specified below.
• the quantity of the compound (s) (T) to be used is defined relative to the total quantity of the compound (s) (M) used. It can vary widely. In general, it is between 0.01 and 10 at.-g (gram atom) of metal present in the compound (T) parat.-g of magnesium present in the compound (M). It has been observed that the performance of the catalytic complexes of the invention is optimal when a ratio of between 0.025 and 5 at.-g of titanium per at-g of magnesium is used.
• the amount of organoaluminum chloride to be used is also defined relative to the total amount of the compound (s) used. It can also vary widely. In general, it is between 1 and 100 moles of organoaluminum chloride per mole of compound (M). Preferably, this amount is between 1 and 20 moles per mole. The best compromise (as defined above) is obtained when this ratio is between 2 and 10 moles per mole.
• the catalytic complexes according to the invention are solid. They are insoluble in alkanes and cycloalkanes which can be used as diluents. They can be used in polymerization as they are obtained, without being separated from the reaction reaction medium. They can however be separated from this reaction medium, in particular when they are prepared in the presence of a polar solvent, according to any known moven.
• the reaction medium is liquid, it is possible, for example, to use filtration, decantation or centrifugation.
• the catalytic complexes can be so as to remove the excess reactants of which they could still be impregnated. Any inert diluent can be used for this washing, for example those which can be used as constituents of the reaction medium, such as alkanes and cycloalkanes.
• the catalytic complexes can be dried, for example, by sweeping with a stream of dry nitrogen or under vacuum.
• the catalytic systems according to the invention also comprise an organometallic compound which serves as an activator.
• organometallic compounds of the metals of groups la, I la, Ilb, IIIb and IVb of the Periodic Table are used such as the organometallic compounds of lithium, magnesium, zinc, aluminum or tin. The best results are obtained with organoaluminum compounds.
• Fully alkylated compounds can be used, the alkyl chains of which contain from 1 to 20 carbon atoms and are straight or branched, such as, for example, n-butyllithium, diethylmagnesium, diethylzinc, tetraethyltin, tetrabutyltin and trialkylaluminiums.
• alkyl metal hydrides in which the alkyl radicals also comprise from 1 to 20 carbon atoms such as diisobutyl aluminum hydride and trimethyltin hydride.
• metal alkyl halides in which the alkyl radicals also comprise from 1 to 20 carbon atoms such as ethyl aluminum sesquichloride, diethyl aluminum chloride and diisobutyl aluminum chloride.
• organoaluminum compounds obtained by reacting trialkylaluminiums or dialkylaluminium hydrides whose radicals contain from 1 to 20 carbon atoms with diolefins comprising from 4 to 20 carbon atoms, and more particularly the compounds called isoprenylaluminiums.
• trialkylaluminiums whose alkyl chains are straight and contain from 1 to 18 carbon atoms. It is found, quite surprisingly, that when these compounds serve as activators for the catalytic complexes prepared in accordance with the invention, that is to say by involving a reagent (3) that is an organoaluminum chloride as defined above, the molecular weight distributions of the polyolefins obtained are wider, all other conditions equal, than those of the polyolefins obtained in the presence of catalytic complexes prepared by making use of the usual reagents (3) (ethyl aluminum dichloride).
• reagents (3) ethyl aluminum dichloride
• the process of the invention applies to the polymerization of terminal unsaturation olefins whose molecule contains from 2 to 20 atoms, and preferably from 2 to 6 carbon atoms, such as ethylene, propylene, butene- 1, 4-methylpentene-1 and hexene-1. It also also applies to the copolymerization of these olefins together as well as with diolefins comprising from 4 to 20 atoms preferably carbon.
• diolefins can be unconjugated aliphatic diolefins such as 1,4-hexadiene, monocyclic diolefins such as 4-vinylcyclohexene, 1,3-divinylcycyohexane, cyclopentadiene or 1,5-cycioctadiene, diolefins Alicyclics having an endocyclic bridge such as dicyclopentadiene or norbornadiene and conjugated aliphatic diolefins such as butadiene and isoprene.
• unconjugated aliphatic diolefins such as 1,4-hexadiene
• monocyclic diolefins such as 4-vinylcyclohexene, 1,3-divinylcycyohexane, cyclopentadiene or 1,5-cycioctadiene
• diolefins Alicyclics having an
• the process of the invention is particularly applicable to the manufacture of homopolymers of ethylene and of copolymers containing at least 90 mol% and preferably 95 mol% of ethylene.
• the polymerization can be carried out according to any process designed: in solution or in suspension in a hydrocarbon solvent or diluent or even in the gas phase.
• solvents or diluents similar to those employed for the preparation of the catalytic complex are used: these are preferably alkanes or cycloalkanes such as isobutane, pentane, hexane, heptane, cyclohexane, methylcyclohexane or mixtures thereof.
• the polymerization pressure is generally between atmospheric pressure and 100 k / cm 2 , preferably 50 kg / cm 2 .
• the temperature is generally chosen between 20 and 200 ° C.
• the polymerization can be carried out continuously or batchwise.
• the organometallic compound and the catalytic complex can be added separately to the polymerization medium. They can also be brought into contact, at a temperature between -40 and 80 ° C, for a period of up to 2 hours, before introducing them into the polymerization reactor. They can also be brought into contact in several stages or else add a part of the organometallic compound before the reactor or else add several different organometallic compounds.
• the total amount of organometallic compound used can vary to a large extent. It is generally between 0.02 and 50 mmol per dm 3 of solvent, diluent or reactor volume and preferably between 0.5 and 2.5 mmol per dm 3 .
• the ratio of the amounts of organometallic compound and catalytic complex is also not critical. It is generally chosen so that the organometallic compound / titanium ratio expressed in mole / at.-g is greater than 1 and preferably greater than 10.
• the average molecular weight, and therefore the melt index of the polymers produced according to the process of the invention can be adjusted by the addition to the polymerization medium of one or more molecular weight modifying agents such as hydrogen, zinc or cadmium diethyl, alcohols or carbon dioxide.
• molecular weight modifying agents such as hydrogen, zinc or cadmium diethyl, alcohols or carbon dioxide.
• the specific gravity of the homopolymers produced according to the process of the invention can also be adjusted by the addition to the polymerization medium of an alkoxide of a metal from groups IVa and Va of the Periodic Table.
• polymerization medium of an alkoxide of a metal from groups IVa and Va of the Periodic Table.
• alkoxides suitable for this adjustment those of titanium and vanadium whose radicals contain from 1 to 20 carbon atoms each are particularly effective. These include Ti (OCH 3 ) 4 , Ti (C0 2 H s ) 4 , Ti [OCH 2 CH (CH 3 3) 2] 4 , Ti (OCsH17) 4 and Ti (OC, 16 H 33 ) 4
• the process of the invention makes it possible to manufacture polyolefins with very high productivities.
• the productivity expressed in grams of polyethylene per gram of catalytic complex used regularly exceeds 10,000 and in some cases 20,000.
• the activity related to the amount of transition metals present in the catalytic complex is also very high.
• ethylene In the homopolymerization of ethylene, also expressed in grams of polyethylene per at.-g of titanium used, it regularly exceeds 200,000. In the most favorable cases, it is greater than 500,000. It is in all cases the cases at least at the level of the activities conferred on the preferred catalytic systems of the prior art, comprising the catalytic complexes solids prepared from ethyl aluminum dichloride as a reagent (3), and it is often even superior to these activities.
• the content of catalytic residues in the polymers produced according to the process of the invention is extremely low. More particularly, the content of residual transition metal is excessively low.
• the content of the annoying residues in polymers is so low that it is possible to economize on the purification treatment (for example an alcohol treatment), which is compulsory when the content of catalytic residue is high and is a costly operation in terms of raw materials and energy and requires considerable downtime.
• the purification treatment for example an alcohol treatment
• the polyolefin powders produced in accordance with the invention are therefore characterized by a remarkable morphology and can be used in this form. This is particularly the case for powders of ethylene polymers.
• the polyolefins obtained according to the invention can however be granulated and be used in the form of granules according to conventional molding techniques: by injection, by extrusion, by extrusion blow molding, by calendering, etc.
• a stock solution (S) is prepared by heating together, at 150 ° C, with stirring and for 2 hours, 9 moles of the reagent (2) and 4.5 moles of the reagent (1).
• the atomic ratio Ti / Mg is therefore approximately 2 at.-g / at.-g 500 ml of the mother solution (S), in which there has been almost complete dissolution of the reagent (1) and which has been previously cooled, 1000 ml of hexane are added, so as to obtain a solution of approximately 500 g / l.
• the organoaluminum chlorides used are commercial products sold by Schering.
• organoaluminum chlorides are used in the form of solutions in hexane at 400 g / bed. They are added gradually to fractions of stock solutions (S), diluted as indicated above, at a temperature of approximately 50 ° C and with stirring, for approximately 90 minutes. At the end of this addition, the reaction mixture is subjected to curing for 1 hour at 60 ° C.
• the amount of organoaluminum chloride used in each of the examples is such that the molar ratio of organoaluminum chloride / magnesium ethylate is approximately 10 .
• the catalytic complexes thus formed are used as such, without being separated from their reaction medium, in polymerization tests the general conditions of which are defined below. Determined quantities of catalytic complex and 0.5 mmol of triethylaluminum are introduced into a 1.5 l autoclave containing 0.5 l of hexane. The temperature of the autoclave is then brought to approximately 85 ° C. Ethylene is introduced under a partial pressure of 10 kg / cnf and hydrogen under a partial pressure of 4 kg / cnf.
• the polymerization is continued for 1 h with stirring while keeping the total pressure constant by continuous addition of ethylene. After 1 h, the autoclave is degassed and the polyethylene thus produced is collected.
• Table I lists the conditions specific to each test, the results obtained and the morphological characteristics of the polyethylenes produced.
• Table 1 shows that the use of an organoaluminum chloride meeting the definition of the invention as reagent (3), (example) leads, with improved catalytic activities, to polyethylenes which contain a much higher proportion of large particles. to that present in the polyethylenes obtained with the usual reagent (3) of the prior art (example 2R).
• Example 4R is given for comparison.
• Catalytic complexes are prepared in accordance with the preceding examples except that the reactants (2) and (1) are mixed until the atomic ratio Ti / Mg is approximately 1.2 at.-g / at.-g, that the amount of organoaluminum chloride used is such that the molar ratio of organoaluminum chloride / magnesium ethylate is approximately 3.5 and that the organoaluminum chloride is added at a temperature of approximately 30 ° C.
• Example 3 the catalytic complex is prepared using isobutylaluminium dichloride as the organoaluminum chloride.
• Example 4R the catalytic complex is prepared using ethylaluminium dichloride as the organoaluminum chloride.
• the catalytic complexes obtained are used in the form of a suspension in the medium which served to prepare them for carrying out ethylene polymerization tests under general conditions absolutely identical to those described in the previous examples.
• Catalytic complexes are prepared in accordance with Examples 1 and 2R using isobutylaluminum dichloride as the organoaluminum chloride.
• Catalytic complexes are prepared in accordance with Examples 1 to 2R using isobutylaluminum dichloride used at 50 ° C, as the organoaluminum compound in Examples 10 to 12, and ethylaluminum dichloride, used at 30 ° C, in Examples 13R to 15R.

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• Organic Chemistry (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
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