WO2003018649A1 - Cobalt complexes useful in the polymerization of 1,3-butadiene - Google Patents

Cobalt complexes useful in the polymerization of 1,3-butadiene Download PDF

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WO2003018649A1
WO2003018649A1 PCT/EP2002/008450 EP0208450W WO03018649A1 WO 2003018649 A1 WO2003018649 A1 WO 2003018649A1 EP 0208450 W EP0208450 W EP 0208450W WO 03018649 A1 WO03018649 A1 WO 03018649A1
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general formula
process according
aluminum
cobalt
cocl
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PCT/EP2002/008450
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French (fr)
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Giovanni Ricci
Francesco Masi
Anna Sommazzi
Roberto Santi
Marco Battistella
Sandra Righi
Giuseppe Savini
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Eni S.P.A.
Polimeri Europa S.P.A.
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    • 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
    • C08F136/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds
    • C08F136/02—Homopolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds
    • C08F136/04—Homopolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds conjugated
    • C08F136/06—Butadiene
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F15/00—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table
    • C07F15/06—Cobalt compounds
    • C07F15/065—Cobalt compounds without a metal-carbon linkage

Definitions

  • the present invention relates to cobalt complexes with particular phosphines and their use in the polymerization of 1, 3-butadiene to give branched polybutadienes with a high content of 1,4-cis units.
  • Catalysts based on cobalt salts and phosphinic ligands are cited as providing polybutadienes with a high content of
  • 1,2 units for example US-A-5, 986, 026; US-A-5, 548, 045; US-A-
  • phinic ligands having well-defined ⁇ steric parameter values, combined with cobalt salts and organo-derivatives of aluminum, are capable of producing branched polybutadienes with a high content of 1,4-cis units, not only in aromatic
  • the ⁇ parameter is a measurement of the steric hindrance of phos- phine and is described by CA. Tolman in Chemical Reviews 77, 313, (1977).
  • the present invention relates to a process for the preparation of branched polybutadiene with a high content of 1,4-cis units by means of the polymerization of 1, 3-butadiene, carried out in the presence of one or more solvents and a catalytic system which comprises a Cobalt complex, preformed or formed in situ, having general formula (I) Co x+ -L ⁇ (I) wherein x is one, two or three, preferably 2; n ranges from 1 to 3; L is selected from one or more ligands of Co; the positive charge of the cobalt complex having general formula (I) being neutralized by one or more mono- or polyvalent anions; characterized in that the ligand L is selected from phosphorous derivatives having general formula (la)
  • eral formula (la) having a theta ( ⁇ ) steric hindrance value greater than 145°, preferably greater than 150°.
  • polybutadiene with a high content of 1,4-cis units refers to polybutadiene in which at least 80% of the butadiene units is concatenated in 1,4-cis position.
  • branched polybutadiene refers to a polybutadiene having a g value (defined further on in the experimental part) ⁇ 0.90, preferably ⁇ 0.85.
  • anions suitable for neutralizing the positive charge of the compound having general formula (I) are concerned, typical but non-limiting examples are halides, sulfo- cyanide, isocyanate, sulfate, acid sulfate, phosphate, acid phosphate, carboxylates, dicarboxylates .
  • the above anions are chlorides.
  • (I) is CoCl 2 -2L.
  • the catalytic system of the present invention also comprises, in addition to the cobalt complex having general formula (I) , one or more cocatalysts selected from organo- derivatives of aluminum selected from:
  • the organo-derivative of aluminum is selected from aluminoxanes and relative derivatives (a2) .
  • organo-derivatives of aluminum (al) are concerned, in the compounds having general formula (II) Al ( R a ) ( R b ) ( R c ) , R a is selected from alkyl (cycloalkyl included), aryl, alkylaryl, alkoxyl, hydrogen, fluorine; R b and R c , the same or different, are selected from alkyl (cycloal- kyl included) , aryl , alkylaryl , arylalkyl .
  • Typical organo- derivatives of aluminum are diethylaluminum hydride, di- n-propyl aluminum hydride, di-n-butylaluminum hydride, diiso- butyl aluminum hydride, diphenyl aluminum hydride, di-p-tolyl aluminum hydride, dibenzyl aluminum hydride, diethyl aluminum hydride, phenyl-n-propyl aluminum hydride, p-tolyl ethyl aluminum hydride, p-tolyl isopropyl aluminum hydride, benzyl ethyl aluminum hydride, benzyl n-propyl aluminum hydride, benzyl isopropyl aluminum hydride, diethylaluminum ethoxide, diisobutyl aluminum ethoxide, dipropyl aluminum ethoxide, trimethyl aluminum, triethyl aluminum, tri-n-propyl aluminum, triisobutyl aluminum
  • Trialkylaluminum compounds are generally preferred.
  • the preferred trialkylaluminum compounds comprise triethyl aluminum (TEA) , tri-n- propyl aluminum, triisobutyl aluminum (TIBA) , trihexyl alumi- num, diisobutyl aluminum hydride (DIBA-H) and diethyl alumi- num fluoride.
  • aluminoxanes (a2) , it is known that these are compounds containing Al-O-Al bonds, with a varying O/Al ratio, obtained by the reaction, under controlled condi- tions, of an aluminum alkyl, or aluminum alkyl halide, with water or other compounds containing pre-established quantities of available water, as, for example, in the case of the reaction of aluminum trimethyl with aluminum hexahydrate sulfate, copper pentahydrate sulfate or iron pentahydrate sul- fate.
  • Aluminoxanes preferably used for the formation of the polymerization catalyst of the present invention are cyclic and/or linear, oligo- or polymeric compounds, characterized by the presence of repetitive units having the following formula: Ris
  • Each aluminoxane molecule preferably contains from 4 to 70 repetitive units which may also not be the same, but contain dif- ferent R 15 groups.
  • organo-derivatives of aluminum (a3) are the compounds (al) to which a quantity of protonating substance has been added in a molar ratio ranging from 0.001:1 to 0.2:1 protonating sub- stance : aluminum derivative.
  • the protonating substance is usually selected from water, alcohol, acid and is preferably water. Methanol, ethanol, isopropyl alcohol, n-propyl alcohol, t-butanol, isobutyl alcohol, n-butyl alcohol, and alcohols with a higher molecular weight, however, can also be used.
  • a wide range of carboxylic acids can also be used as protonating substance. An example of these acids is stearic acid.
  • Typical examples of compounds having general formula (III) are AlEt 2 Cl (diethylchloroalumninum) , AlMe 2 Cl (dimethylaluminumchloride) , AlEtCl 2 (ethylaluminumdi- chloride) , Al(i-bu) 2 Cl (diisobutylaluminumchloride) ; typical examples of compounds having general formula (IV) are Al 2 Et 3 Cl 3 (ethylaluminumsesquichloride) , Al 2 Me 3 Cl 3 (methylalu- minumsesquichloride) .
  • the molar ratio between the complex having general formula (I) and aluminum ranges from 1:5 to 1:10000, preferably from 1:100 to 1:1000.
  • the cobalt complex having general formula (I) can be used in a molar ratio with respect to the 1, 3-butadiene ranging from 1/10 5 to 1/10 2 , preferably from l/2xl0 4 to l/l0 3 .
  • a molar ratio between ligand (L) and cobalt salt higher than the stoichiometric value preferably, when the cobalt is bivalent, from 2.1/1 to 4/1, even more preferably from 2.2 to 2.5.
  • the above polymerization is preferably effected in a polymerization medium comprising an inert hydrocarbon which is a solvent of butadiene and of the catalytic system.
  • Inert hy- drocarbons which can be used in the polymerization process comprise aliphatic hydrocarbons, olefins included, cycloaliphatic, aromatic hydrocarbons and relative mixtures. More specifically, suitable hydrocarbons are those selected within the group of C 4 to C 8 aliphatic hydrocarbons, olefins in- eluded, within the group of C 5 to C ⁇ 0 cycloaliphatic hydrocarbons, and relative mixtures.
  • Typical, non-limiting examples of the above hydrocarbons are butane, pentane, hexane, heptane, cyclopentane, cyclohexane, butenes.
  • the use of the above aliphatic and cycloaliphatic solvents is particularly advisable as it reduces problems relating to environmental impact. When operating with these solvents, it is possible to obtain a branched polybutadiene, i.e. having branchings, with a high 1,4-cis content.
  • the presence of the above branchings is an essential requisite for the use of the above polybuta- diene as modifying agent of high impact polystyrene.
  • the process of the present invention can also be carried out in the presence of aromatic solvents, particularly toluene, as such or mixed with aliphatic solvents. Branched polybutadiene with a high 1,4-cis content is also obtained in these aromatic solvents.
  • the concentration of 1, 3-butadiene in the polymerization medium can vary in relation to the particular solvent medium or diluent used.
  • concentration of 1, 3-butadiene preferably ranges from 15 to 35% by weight with respect to the total weight of the mixture.
  • the polymerization temperature of 1, 3-butadiene preferably ranges from -30°C to +60°C, the lower temperature limit being determined more by the freezing point of the reaction mixture rather than by the catalytic activity. More preferably, the polymerization process is carried out at a temperature ranging from -10°C to +40°C.
  • the process of the present invention can also be carried out (see the experimental part) in the absence of the usual molecular weight regulators well-known to experts in the field, for example butene-1.
  • the molecular weight control can be effected by varying the type of phos- phine and/or ratio between the aluminum compound, particularly MAO, and cobalt.
  • the polymerization reaction can be stopped by the addition of one or more polymerization terminators which deacti- vate the catalytic system, followed by the conventional solvent-removal (desolventizing) , washing and drying phases, which are normal operations in the production of polydienes.
  • the terminator used to deactivate the catalytic system is typically a protic compound, which includes, but is not lim- ited to, an alcohol, a carboxylic acid, an inorganic acid, and water or a combination thereof .
  • An antioxidant such as 2,6-di-ter-butyl-l,4-methylphenol can be added, before, after or with the addition of the terminator.
  • the quantity of antioxidant usually ranges from 0.2% to 1% by weight with respect to the polymer.
  • the polybutadiene can be recovered according to the standard techniques, preferably by means of the coagulation technique. Any possible residues of the solvent can be removed from the polymer by means of evaporation, which can be facilitated by high temperatures and vacuum application.
  • the process of the present invention allows polybutadiene to be produced with a reduced gel content, particularly macro gels, thus making it applicable in high impact polystyrene.
  • the present invention also relates, as a new compound, to the cobalt complex having the formula:
  • CoCl 2 [P (ter-butyl) 3 ] 2 i.e. cobalt dichloride (tri-ter-butylphosphine) 2 .
  • All the complexes having general formula (I) were prepared following the experimental procedure described in literature which comprises the reaction between a cobalt salt and ligand L in the presence of a suitable solvent (see for example F.A. Cotton, O.D. Faut, D.M.L. Goodgame and R.H. Holm, J.A . Chem. Soc. , 83, 1780, 1961).
  • the desired quantity of CoCl 2 -6H 2 0 (-28 g equal to 0.12 moles) is first heated under vacuum by means of a water bath, in order to remove part of the molecules of crystallization water.
  • the mixture is kept at reflux temperature ( ⁇ 78°C) for about 2 h, until the reaction is complete. At this point, the thionyl chloride has been almost completely used up; the mixture is left to decant and the supernatant solution is removed by siphoning.
  • Tri-n-propylphosphine (3.70 g, 2.3lxl0 ⁇ 2 moles, 4.6 ml) is added under stirring to a solution of CoCl 2 (1.20 g, 9.22xl0 "3 moles) in ethanol (50 ml). The reaction is instantaneous, the solution becomes blue. After about 20 hours, the solution is dried under vacuum at room temperature.
  • a blue-coloured crystalline product is obtained, which is washed at a low temperature with pentane (2 x 20 ml) .
  • the crystalline residue is dried under vacuum.
  • the reaction is instantaneous and the formation of a pale blue precipitate is observed, whose quantity increases over a period of time.
  • the suspension is left under magnetic stirring for about 20 h.
  • a light suspension is formed, which is kept under stirring for about 20 h. It is subsequently dried under vacuum obtaining a pitchy dark blue-coloured residue.
  • Various washings are effected with pentane (3 x 20 ml) and with ethanol at a low temperature, in order to remove traces of excess phosphine and non-reacted CoCl 2 .
  • the residue is dried under vacuum at room temperature for a whole night.
  • the suspension is left under magnetic stirring for about 20 h, and is then filtered on a vacuum filter.
  • the nitrogen in order to eliminate any possible traces of humidity and oxygen, was purified by passage through three successive columns: the first filled with calcium chloride and potassium hydroxide, the second with BTS catalyst (based on copper oxides), the third filled with molecular sieves.
  • Cobaltdichloride hexahydrate product of Strem Chemical (98% purity) .
  • Tri-n-propylphosphine product of Strem Chemical (minimum pu- rity 95%) .
  • Tri-i-propylphosphine product of Strem Chemical (minimum purity 98%) .
  • Tri-t-butylphosphine product of Strem Chemical (minimum purity 99%) .
  • Tricyclohexylphosphine product of Strem Chemical (purity 97%) .
  • Triphenylphosphine product of Strem Chemical (purity 99%).
  • Methylaluminoxane (MAO) product of Witco, toluene solution at 10% by weight, used as such.
  • 1,3-butadiene product of Air Liquide (purity of over 99.5%), purified by passage through a steel column containing sodium hydroxide and molecular sieves . Polymerization of butadiene The 1, 3-butadiene, dried by passage through a steel column containing molecular sieves, was condensed directly in the reactor maintained under vacuum and cooled to a temperature of -30°C.
  • the polymerization tests were carried out according to the following experimental procedure: after charging the bu- tadiene into the reactor, the solvent was added, the whole mixture was brought to the desired polymerization temperature and finally the aluminum compound and cobalt compound were added in succession.
  • the polymerization reaction was terminated by pouring the contents of the test-tube into a beaker containing metha- nol acidulated with small quantities of hydrochloric acid; the coagulated polymer was washed several times with metha- nol, dried under vacuum at room temperature and recovered.
  • Analytic procedures NMR ANALYSIS
  • the X H and 13 C NMR spectra were registered with a Bruker AM 270 MHz spectrophotometer. The spectra were obtained in CDC1 3 at room temperature using tetramethylsilane as internal standard or in C 2 D 2 C1 4 at a high temperature (103°C; HMDS as internal standard) . The concentration of the polymeric solutions is about 10% by weight.
  • micro-structure of the polybutadienes obtained was determined on the basis of what is already known in litera- ture (see for example V.D. Mochel, J. Polym. Sci . , A-l 10, 1009, 1972; K.F. Elgert, G. Quack, B. Stutzel, Makromol . Chem. 175, 1955, 1974; D. Morero, A. Santambrogio, L. Porri, F. Ciampelli, Chim. Ind. (Milan) 41, 758, 1958) . G.P.C. ANALYSIS Operating conditions: Agilent 1100 pump
  • Calculation of average g branching index ratio between the radius of gyration of the branched macromolecule and that of the linear macromolecule, with the same molecular weight; the ratio is determined for each point of the integrated chromatogram, and the average on all the points is then calculated.
  • a polybutadiene is considered as being branched when g 0.90.
  • Viscosity values less than 100 cP are acceptable for the modification of polystyrene.
  • the insoluble % is determined by means of gravimetry, by weighing the residue on each filter and expressing it in percentage with respect to the initial weight .
  • CoCl 2 + MAO system both in toluene and in heptane produces a cis (about 95-98%) linear (g about 1) polymer, as demonstrated by examples b228 and b335; the polymerization effected in hexane being slower.
  • the PB structure which is obtained is essentially 1,4-cis (> 80%), see Table 1.
  • the use of the hindered phosphines of the present invention has the following advantages: ** high catalytic activities also in aliphatic hydrocarbon solvents, not used so far due to their limited activity (see examples b330, b292, b332 compared with b335) ;
  • the molecular weight (200 x 10 3 ⁇ M w ⁇ 420 x 10 3 ) can, in fact, be regulated by varying the type of phosphinic ligand, the Al/Co ratio and the type of solvent; ** production of polybutadiene with a low gel content

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Abstract

Process for the preparation of branched polybutadiene with a high content of 1,4-cis units by the polymerization of 1,3-butadiene, carried out in the presence of one or more solvents and a catalytic system which comprises a Cobalt complex, preformed or formed in situ, having general formula (I) Cox+.Ln wherein x is one, two ore three, preferably 2; n ranges from 1 to 3; L is selected from one or more ligands of Co; characterized in that the ligand L is selected from phosphorous derivatives having general formula (Ia) P[-(O) mR1] [-(O) mR2] [-(O) mR3] wherein m is zero or one, preferably m=0; R1, R2, the same or different, are selected from monofunctional aliphatic and cycloalkyl radicals, R3 is selected from -H and monofunctional aliphatic and cycloalkyl radicals, the compound having general formula (Ia) having a theta (θ) steric hindrance value greater than 145°; preferably greater than 150°.

Description

COBALT COMPLEXES USEFUL IN THE POLYMERIZATION OF 1,3 BUTADIENE
The present invention relates to cobalt complexes with particular phosphines and their use in the polymerization of 1, 3-butadiene to give branched polybutadienes with a high content of 1,4-cis units.
Various types of catalysts and processes have been developed, based on cobalt for the polymerization of 1,3- butadiene. Some of these catalysts produce a polybutadiene which contains a high percentage of 1,4-cis units and which has excellent thermal and mechanical properties. Furthermore, the polybutadiene produced with catalysis based on cobalt, when the reaction is carried out in benzene in the presence of molecular weight regulators (for example butene-1) , is gel-free and contains branchings which make it ideal for the modification of polystyrene.
Examples of catalytic systems based on cobalt carried out in benzene are described in various documents: US-A- 3,135,725 describes catalysts based on cobalt salts and aluminum alkyls; US-A-3 , 046, 265 describes catalysts based on aluminum alkyls, cobalt halides and acetyl halides; US-A- 3,094,514 describes cobalt chloride-methylaluminum chloride; GB-A-916,383 describes cobalt octanoate-ethylaluminum chloride; GB-A-916,384 describes cobalt ethylhexanoate- ethylaluminum chloride; DE-A-1,495, 935 describes cobalt octa- noate-diethylaluminum chloride-water; GB-A-941,739 describes cobalt stearate-diethylaluminu chloride.
However, due to its carcinogen nature, benzene is not desired as a solvent as per the restrictions imposed by OSHA (Occupational Safety and Health Agency) on the concentration of benzene allowed in work areas. The necessity is therefore felt for finding catalytic systems based on cobalt capable of operating with the same efficiency in solvents other than benzene.
Catalysts based on cobalt salts and phosphinic ligands are cited as providing polybutadienes with a high content of
1,2 units (for example US-A-5, 986, 026; US-A-5, 548, 045; US-A-
4,463,146; US-A-4 , 182 , 813 ; US-A-4, 176 , 219 ; US-A-3 , 983 , 183 ;
US-A-3,966,697) .
It has now been found that particular trialkyl phos-
phinic ligands, having well-defined θ steric parameter values, combined with cobalt salts and organo-derivatives of aluminum, are capable of producing branched polybutadienes with a high content of 1,4-cis units, not only in aromatic
solvents, but also in aliphatic hydrocarbon solvents. The θ parameter is a measurement of the steric hindrance of phos- phine and is described by CA. Tolman in Chemical Reviews 77, 313, (1977).
In accordance with this, the present invention relates to a process for the preparation of branched polybutadiene with a high content of 1,4-cis units by means of the polymerization of 1, 3-butadiene, carried out in the presence of one or more solvents and a catalytic system which comprises a Cobalt complex, preformed or formed in situ, having general formula (I) Cox+-Lπ (I) wherein x is one, two or three, preferably 2; n ranges from 1 to 3; L is selected from one or more ligands of Co; the positive charge of the cobalt complex having general formula (I) being neutralized by one or more mono- or polyvalent anions; characterized in that the ligand L is selected from phosphorous derivatives having general formula (la)
P[-(0)mR [-(0)mR2] [-(0)mR3] (la) wherein m is zero or one, preferably m=0; Ri, R2, the same or different, are selected from monofunctional aliphatic and cy- cloalkyl radicals, R3 is selected from -H and monofunctional aliphatic and cycloalkyl, radicals, the compound having gen¬
eral formula (la) having a theta (θ) steric hindrance value greater than 145°, preferably greater than 150°.
In the case of Co+, the molar ratio between L and Co is 3/1; in the case of Co2+, the molar ratio between L and Co is 2/1 .
The term "polybutadiene with a high content of 1,4-cis units" refers to polybutadiene in which at least 80% of the butadiene units is concatenated in 1,4-cis position. The term "branched polybutadiene" refers to a polybutadiene having a g value (defined further on in the experimental part) < 0.90, preferably < 0.85.
In the preferred embodiment, in the compound having general formula (I), the cobalt is bivalent, x = 2 and n = 2. As far as anions suitable for neutralizing the positive charge of the compound having general formula (I) are concerned, typical but non-limiting examples are halides, sulfo- cyanide, isocyanate, sulfate, acid sulfate, phosphate, acid phosphate, carboxylates, dicarboxylates . In the preferred em- bodiment the above anions are chlorides. As a result the pre¬
ferred embodiment of (I) is CoCl2-2L.
With respect to the phosphorous compound having general
formula (la), this must have a θ value higher than 145°, preferably higher than 150°. In the preferred embodiment, in the compound having general formula (la) , m = Q and therefore the compound having general formula (la) is a phosphine.
Typical but non-limiting examples of compounds having general formula (la) which can be used in the process of the present invention are tri-isopropylphosphine (R1=R2=R3=isopropyl, θ=160°) ; tri-t-butylphosphine {R!=R2= 3=t- butyl, θ=182°); tri-cyclohexylphosphine (Rι=R2=R3=cyclohexyl, θ=170°); tri-cyclopentylphosphine (Rι=R2=R3=cyclopentyl) ; methyl di-t-butyl phosphine (Rι=methyl; R2=R3=t-butyl, θ=161°) ; ethyl di-t-butyl phosphine (R^ethyl; R2=R3=t-butyl, θ=165°) ; methyl dicyclohexylphosphine (Rι=methyl; R2=R3=cyclohexyl , θ=153°) ; ethyl dicyclohexylphosphine (Rι=ethyl; R2=R3=cyclohexyl , θ=157°) ; diterbutylphosphine
Figure imgf000006_0001
The catalytic system of the present invention also comprises, in addition to the cobalt complex having general formula (I) , one or more cocatalysts selected from organo- derivatives of aluminum selected from:
(al) compounds having general formula (II) Al(Ra) (Rb) (Re) • (a2) aluminoxanes and relative derivatives.
(a3) organo-derivatives of aluminum partially hydrolyzed, and relative mixtures, (a4) halogen aluminum alkyls selected from (III) AlRnX3-n (with n = 1 or 2) and (IV) Al2RnX6-n (n = 1-5), wherein R is a Ci-C20 alkyl group, X is chlorine or bromine, preferably chlorine .
In the preferred embodiment, the organo-derivative of aluminum is selected from aluminoxanes and relative derivatives (a2) . As far as the organo-derivatives of aluminum (al) are concerned, in the compounds having general formula (II) Al (Ra ) (Rb) (Rc) , Ra is selected from alkyl (cycloalkyl included), aryl, alkylaryl, alkoxyl, hydrogen, fluorine; Rb and Rc, the same or different, are selected from alkyl (cycloal- kyl included) , aryl , alkylaryl , arylalkyl . Typical organo- derivatives of aluminum (al) are diethylaluminum hydride, di- n-propyl aluminum hydride, di-n-butylaluminum hydride, diiso- butyl aluminum hydride, diphenyl aluminum hydride, di-p-tolyl aluminum hydride, dibenzyl aluminum hydride, diethyl aluminum hydride, phenyl-n-propyl aluminum hydride, p-tolyl ethyl aluminum hydride, p-tolyl isopropyl aluminum hydride, benzyl ethyl aluminum hydride, benzyl n-propyl aluminum hydride, benzyl isopropyl aluminum hydride, diethylaluminum ethoxide, diisobutyl aluminum ethoxide, dipropyl aluminum ethoxide, trimethyl aluminum, triethyl aluminum, tri-n-propyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum, tripentyl aluminum, trihexyl aluminum, tricyclohexyl aluminum, trioctyl aluminum, triphenyl aluminum, tri-p-tolyl aluminum, tribenzyl aluminum, ethyl diphenyl aluminum, ethyl di-p-tolyl aluminum, ethyl dibenzyl aluminum, diethyl phenyl aluminum, diethyl p- tolyl aluminum, diethyl, benzyl aluminum. Trialkylaluminum compounds are generally preferred. The preferred trialkylaluminum compounds comprise triethyl aluminum (TEA) , tri-n- propyl aluminum, triisobutyl aluminum (TIBA) , trihexyl alumi- num, diisobutyl aluminum hydride (DIBA-H) and diethyl alumi- num fluoride.
With respect to aluminoxanes (a2) , it is known that these are compounds containing Al-O-Al bonds, with a varying O/Al ratio, obtained by the reaction, under controlled condi- tions, of an aluminum alkyl, or aluminum alkyl halide, with water or other compounds containing pre-established quantities of available water, as, for example, in the case of the reaction of aluminum trimethyl with aluminum hexahydrate sulfate, copper pentahydrate sulfate or iron pentahydrate sul- fate. Aluminoxanes preferably used for the formation of the polymerization catalyst of the present invention are cyclic and/or linear, oligo- or polymeric compounds, characterized by the presence of repetitive units having the following formula: Ris
-(Al-O)- wherein Rι5 is a Cx-C6 alkyl group, preferably methyl. Each aluminoxane molecule preferably contains from 4 to 70 repetitive units which may also not be the same, but contain dif- ferent R15 groups.
As far as partially hydrolyzed organo-derivatives of aluminum (a3) are concerned, these are the compounds (al) to which a quantity of protonating substance has been added in a molar ratio ranging from 0.001:1 to 0.2:1 protonating sub- stance : aluminum derivative. The protonating substance is usually selected from water, alcohol, acid and is preferably water. Methanol, ethanol, isopropyl alcohol, n-propyl alcohol, t-butanol, isobutyl alcohol, n-butyl alcohol, and alcohols with a higher molecular weight, however, can also be used. A wide range of carboxylic acids can also be used as protonating substance. An example of these acids is stearic acid.
With respect to the organo-derivatives of aluminum (a4) , (III) AlRnX3-n (with n = 1 or 2) or (IV) Al2RnX6.n (n = 1-5) , wherein R is a Cι-C2o alkyl group, X is chlorine or bromine, preferably chlorine. Typical examples of compounds having general formula (III) are AlEt2Cl (diethylchloroalumninum) , AlMe2Cl (dimethylaluminumchloride) , AlEtCl2 (ethylaluminumdi- chloride) , Al(i-bu)2Cl (diisobutylaluminumchloride) ; typical examples of compounds having general formula (IV) are Al2Et3Cl3 (ethylaluminumsesquichloride) , Al2Me3Cl3 (methylalu- minumsesquichloride) .
In the process of the present invention, the molar ratio between the complex having general formula (I) and aluminum ranges from 1:5 to 1:10000, preferably from 1:100 to 1:1000.
The cobalt complex having general formula (I) can be used in a molar ratio with respect to the 1, 3-butadiene ranging from 1/105 to 1/102, preferably from l/2xl04 to l/l03.
When the preformed complex having general formula (I) is not used, but the formation technique in situ of the complex having general formula (I) is used, it is preferable to use a molar ratio between ligand (L) and cobalt salt higher than the stoichiometric value, preferably, when the cobalt is bivalent, from 2.1/1 to 4/1, even more preferably from 2.2 to 2.5.
As far as the polymerization of butadiene is concerned, the above polymerization is preferably effected in a polymerization medium comprising an inert hydrocarbon which is a solvent of butadiene and of the catalytic system. Inert hy- drocarbons which can be used in the polymerization process comprise aliphatic hydrocarbons, olefins included, cycloaliphatic, aromatic hydrocarbons and relative mixtures. More specifically, suitable hydrocarbons are those selected within the group of C4 to C8 aliphatic hydrocarbons, olefins in- eluded, within the group of C5 to Cι0 cycloaliphatic hydrocarbons, and relative mixtures. Typical, non-limiting examples of the above hydrocarbons are butane, pentane, hexane, heptane, cyclopentane, cyclohexane, butenes. The use of the above aliphatic and cycloaliphatic solvents is particularly advisable as it reduces problems relating to environmental impact. When operating with these solvents, it is possible to obtain a branched polybutadiene, i.e. having branchings, with a high 1,4-cis content. The presence of the above branchings is an essential requisite for the use of the above polybuta- diene as modifying agent of high impact polystyrene. The process of the present invention can also be carried out in the presence of aromatic solvents, particularly toluene, as such or mixed with aliphatic solvents. Branched polybutadiene with a high 1,4-cis content is also obtained in these aromatic solvents.
The concentration of 1, 3-butadiene in the polymerization medium can vary in relation to the particular solvent medium or diluent used. When solvents are used in which both 1,3- butadiene and also the polymeric product are soluble, the concentration of 1, 3-butadiene preferably ranges from 15 to 35% by weight with respect to the total weight of the mixture.
The polymerization temperature of 1, 3-butadiene preferably ranges from -30°C to +60°C, the lower temperature limit being determined more by the freezing point of the reaction mixture rather than by the catalytic activity. More preferably, the polymerization process is carried out at a temperature ranging from -10°C to +40°C.
The process of the present invention can also be carried out (see the experimental part) in the absence of the usual molecular weight regulators well-known to experts in the field, for example butene-1. This represents another significant advantage of the process of the present invention. In the process of the present invention, in fact, the molecular weight control can be effected by varying the type of phos- phine and/or ratio between the aluminum compound, particularly MAO, and cobalt.
The polymerization reaction can be stopped by the addition of one or more polymerization terminators which deacti- vate the catalytic system, followed by the conventional solvent-removal (desolventizing) , washing and drying phases, which are normal operations in the production of polydienes. The terminator used to deactivate the catalytic system is typically a protic compound, which includes, but is not lim- ited to, an alcohol, a carboxylic acid, an inorganic acid, and water or a combination thereof . An antioxidant such as 2,6-di-ter-butyl-l,4-methylphenol can be added, before, after or with the addition of the terminator. The quantity of antioxidant usually ranges from 0.2% to 1% by weight with respect to the polymer.
At the end of the polymerization, the polybutadiene can be recovered according to the standard techniques, preferably by means of the coagulation technique. Any possible residues of the solvent can be removed from the polymer by means of evaporation, which can be facilitated by high temperatures and vacuum application.
In addition to the above advantages, the process of the present invention allows polybutadiene to be produced with a reduced gel content, particularly macro gels, thus making it applicable in high impact polystyrene. The present invention also relates, as a new compound, to the cobalt complex having the formula:
CoCl2 [P (ter-butyl) 3] 2 i.e. cobalt dichloride (tri-ter-butylphosphine) 2. All the complexes having general formula (I) were prepared following the experimental procedure described in literature which comprises the reaction between a cobalt salt and ligand L in the presence of a suitable solvent (see for example F.A. Cotton, O.D. Faut, D.M.L. Goodgame and R.H. Holm, J.A . Chem. Soc. , 83, 1780, 1961).
The following examples are provided for a better understanding of the present invention.
The preparations of compounds which do not form part of the present invention, but which are used as comparative ex- amples in evaluating the polymerization catalysts, are also described in the examples . EXAMPLES ** Synthesis of anhydrous CoCl2
The desired quantity of CoCl2-6H20 (-28 g equal to 0.12 moles) is first heated under vacuum by means of a water bath, in order to remove part of the molecules of crystallization water.
It is then treated with freshly distilled thionyl chlo¬
ride (~80 ml) . The following reaction takes place: CoCl2-6H20 + 6 S0C12 → CoCl2 + 6 S02 + 12 HCl The mixture is cooled to 0°C, as there is an abundant development of gas, but once this development has diminished,
the mixture is kept at reflux temperature (~ 78°C) for about 2 h, until the reaction is complete. At this point, the thionyl chloride has been almost completely used up; the mixture is left to decant and the supernatant solution is removed by siphoning.
The anhydrous, blue-coloured CoCl2 is then dried under vacuum for a whole night . ** Synthesis of the complex CoCl2 (tri-n-propylphosphine) 2 (comparative catalyst)
Tri-n-propylphosphine (3.70 g, 2.3lxl0~2 moles, 4.6 ml) is added under stirring to a solution of CoCl2 (1.20 g, 9.22xl0"3 moles) in ethanol (50 ml). The reaction is instantaneous, the solution becomes blue. After about 20 hours, the solution is dried under vacuum at room temperature.
A blue-coloured crystalline product is obtained, which is washed at a low temperature with pentane (2 x 20 ml) . The crystalline residue is dried under vacuum.
A total of 2.79 g of pale blue/blue crystalline product are obtained, with a yield equal to 67.1%.
The results of the elemental analysis correspond to the following structure: CoCl2 (PnPr3) 2
[m.w. = 450.32 g-mol"1]
Figure imgf000015_0001
** Synthesis of the complex CoCl2 (triphenylphosphine)2 (comparative catalyst)
A solution of CoCl2 (0.25 g, 1.90xl0"3 moles) in ethanol (25 ml) is added to a suspension of triphenylphosphine (1.01 g, 3.85xl0'3 moles) in ethanol (25 ml), maintained under stir¬ ring.
The reaction is instantaneous and the formation of a pale blue precipitate is observed, whose quantity increases over a period of time. The suspension is left under magnetic stirring for about 20 h.
The suspension is then filtered; the solid remaining on the filter is washed with small quantities of ethanol and then dried under vacuum. Approximately 0.71 g of blue product are recovered, equal to a yield of 56.9%. The results of the elemental analysis correspond to the following structure: CoCl2(PPh3)2 [m.w. = 654.42 g.mol"1]
Figure imgf000016_0001
** Synthesis of the complex CoCl2 (tri-iso-propylphosphine)2
A solution of tri-iso-propylphosphine (0.96 g, 5.98xl0*3
moles) in ethanol (-20 ml) is added dropwise, under stirring, to a solution of CoCl2 (0.31 g, 2.39xl0"3 moles) in ethanol
(-30 ml) .
A light suspension is formed, which is kept under stirring for about 20 h. It is subsequently dried under vacuum obtaining a pitchy dark blue-coloured residue. Various washings are effected with pentane (3 x 20 ml) and with ethanol at a low temperature, in order to remove traces of excess phosphine and non-reacted CoCl2. The residue is dried under vacuum at room temperature for a whole night.
0.55 g of a pale blue/blue micro-crystalline powder are recovered, with a yield equal to 50.6%.
The results of the elemental analysis correspond to the following structure: CoCl2 (P1?^) 2 [m.w. = 450.32 g.mol"1]
Figure imgf000017_0001
** Synthesis of the complex CoCl2 (tri-ter-butylphosphine) 2
A solution of tri-ter-butylphosphine (1.14 g, 5.64-xlO"3 moles) in ethanol (-20 ml) is added dropwise, under stirring, to a solution of CoCl2 (0.30 g, 2.26xl0"3 moles) in ethanol
(-30 ml) .
A pale blue/blue precipitate is formed.
The suspension is left under magnetic stirring for about 20 h, and is then filtered on a vacuum filter.
The residue is dried under vacuum, washed with pentane (2 x 15 ml) and with ethanol (2 x 10 ml) at a low temperature (about -50°C) , in order to remove traces of excess phosphine and non-reacted CoCl2.
The residue is dried under vacuum at room temperature for a whole night: 0.75 g of pale blue/blue product are re¬ covered, with a yield of 62.1%.
The results of the elemental analysis correspond to the following structure: CoCl2 (PtBu3) 2 [m.w. = 534.48 g.mol"1]
Figure imgf000018_0001
I.R.: (CH3 t-bucyi) = 2972, 2906, 2875, cm"1; 5 as.(CH3) = 1476, 1483, cm"1; δ S.(CH3) = 1380 cm"1
** Synthesis of the complex CoCl (tricyclohexylphosphine)2 Tricyclohexylphosphine (6.24 g, 2.22xl0"2 moles) is added under stirring to a solution of CoCl2 (1.16 g, 8.90D10"3
moles) in ethanol (-55 ml) .
No immediate change is observed, but after a few min¬ utes, the solution becomes turquoise with the formation of a precipitate having the same colour.
The solution is left under stirring for about 20 h, af¬ ter which a residue is recovered, which is washed several times with pentane and subsequently with ethanol at a low temperature to remove any possible traces of non-reacted
CoCl2.
5.51 g of a pale blue/turquoise micro-crystalline powder are recovered, with a yield equal to 89.6%.
The results of the elemental analysis correspond to the following structure: CoCl2(PCy3)2 [m.w. = 690.70 g.mol"1]
Figure imgf000019_0001
** Synthesis "in situ" of the complex CoCl2 (triisoprop- ylphosphine) 2 26 mg (0.2 mmoles) of CoCl2 and 10 ml of toluene are charged into a 50 ml test-tube. 72 mg (0.45 mmoles) of tri- isopropylphosphine are added to the resulting suspension. The mixture is kept under stirring for 12 hours . 0.5 ml of solution are then removed and charged into the polymerization re- actor containing 10 ml of butadiene in heptane and MAO. The subsequent procedure is identical to that with the use of preformed catalyst . OPERATING PROCEDURE AND REAGENTS
All the operations and preparations described were ef- fected using a vacuum-nitrogen system.
The nitrogen, in order to eliminate any possible traces of humidity and oxygen, was purified by passage through three successive columns: the first filled with calcium chloride and potassium hydroxide, the second with BTS catalyst (based on copper oxides), the third filled with molecular sieves. REAGENTS
Cobaltdichloride hexahydrate: product of Strem Chemical (98% purity) .
Tri-n-propylphosphine: product of Strem Chemical (minimum pu- rity 95%) .
Tri-i-propylphosphine: product of Strem Chemical (minimum purity 98%) .
Tri-t-butylphosphine: product of Strem Chemical (minimum purity 99%) . Tricyclohexylphosphine: product of Strem Chemical (purity 97%) .
Triphenylphosphine : product of Strem Chemical (purity 99%). Methylaluminoxane (MAO) : product of Witco, toluene solution at 10% by weight, used as such. Diolefinic monomers
1,3-butadiene: product of Air Liquide (purity of over 99.5%), purified by passage through a steel column containing sodium hydroxide and molecular sieves . Polymerization of butadiene The 1, 3-butadiene, dried by passage through a steel column containing molecular sieves, was condensed directly in the reactor maintained under vacuum and cooled to a temperature of -30°C.
The polymerization tests were carried out according to the following experimental procedure: after charging the bu- tadiene into the reactor, the solvent was added, the whole mixture was brought to the desired polymerization temperature and finally the aluminum compound and cobalt compound were added in succession. The polymerization reaction was terminated by pouring the contents of the test-tube into a beaker containing metha- nol acidulated with small quantities of hydrochloric acid; the coagulated polymer was washed several times with metha- nol, dried under vacuum at room temperature and recovered. Analytic procedures NMR ANALYSIS
The XH and 13C NMR spectra were registered with a Bruker AM 270 MHz spectrophotometer. The spectra were obtained in CDC13 at room temperature using tetramethylsilane as internal standard or in C2D2C14 at a high temperature (103°C; HMDS as internal standard) . The concentration of the polymeric solutions is about 10% by weight.
The micro-structure of the polybutadienes obtained was determined on the basis of what is already known in litera- ture (see for example V.D. Mochel, J. Polym. Sci . , A-l 10, 1009, 1972; K.F. Elgert, G. Quack, B. Stutzel, Makromol . Chem. 175, 1955, 1974; D. Morero, A. Santambrogio, L. Porri, F. Ciampelli, Chim. Ind. (Milan) 41, 758, 1958) . G.P.C. ANALYSIS Operating conditions: Agilent 1100 pump
I.R. Agilent 1100 detector
PL Mixed-A columns
Solvent/Eluant THF
Flow 1 ml/min
Temperature 25°C
Molecular mass calculation: Universal Calibration method G.P.C. Analysis/MALLS/I.R. Operating conditions :
• Agilent 1050 pump
I.R. Agilent 1050 detector
MALLS Dawn-DSP Wyatt detector - Technology, λ = 632.8 nm Columns PL 105-105-10 -103 Solvent/Eluant THF • Flow 1 ml/min
Temperature 25°C
Calculation of average g branching index: ratio between the radius of gyration of the branched macromolecule and that of the linear macromolecule, with the same molecular weight; the ratio is determined for each point of the integrated chromatogram, and the average on all the points is then calculated. A polybutadiene is considered as being branched when g 0.90.
VISCOSITY MEASUREMENTS IN STYRENE
Solvent : Styrene • Concentration: 5% w/w
• Capillary: Cannon - Fenske series 200
• Calculation of the viscosity η = kdt wherein k = capillary constant; d = styrene density; t = fall time inside the capillary.
Viscosity values less than 100 cP are acceptable for the modification of polystyrene. DETERMINATION OF THE GEL CONTENT
• Solvent : THF • Concentration: 0.3% w/w;
• Insoluble macro: 325 mesh net;
• Insoluble micro: 0.2 ? m Teflon filter;
The insoluble % is determined by means of gravimetry, by weighing the residue on each filter and expressing it in percentage with respect to the initial weight .
Table 1
Polymerization conditions: butadiene: 10 ml; solvent: 90 ml; Co: 1x10"5 moles; temperature: +15°C
O
Figure imgf000024_0001
Figure imgf000025_0001
COMMENTS ON TABLE 1
The CoCl2 + MAO system both in toluene and in heptane produces a cis (about 95-98%) linear (g about 1) polymer, as demonstrated by examples b228 and b335; the polymerization effected in hexane being slower.
The use of a catalytic system based on cobalt complexes with phosphine (both complexes of the prior art and of the present invention) influences the catalytic activity and micro-structure of the polymer. In fact, using aryl phosphines of the prior art, a polybutadiene with a mixed 1,4-cis and 1,2- structure is obtained (see comparative examples b323 and b324) . When alkyl phosphines are used, on the other hand, it has been surprisingly found that polybutadienes are obtained, whose microstructure varies in relation to the steric hin- drance of the phosphines themselves.
When the phosphine is only slightly hindered (for exam¬
ple in the case of tri n-propylphosphine with θ = 132° as in examples b327 and b328) , polybutadienes with a mixed structure with prevalently 1,2 units are obtained. When, on the other hand, the phosphine is more hindered
(θ > 145°, as in the case of tri isopropylphosphine (θ = 160°), tri tert-butylphosphine (θ = 182°), and tri cyclohex- ylphosphine (θ = 170°), the PB structure which is obtained is essentially 1,4-cis (> 80%), see Table 1. Furthermore, the use of the hindered phosphines of the present invention has the following advantages: ** high catalytic activities also in aliphatic hydrocarbon solvents, not used so far due to their limited activity (see examples b330, b292, b332 compared with b335) ;
** production of branched polybutadiene (0.70 < g < 0.90) both in aliphatic and aromatic solvents (see b283 and b330; b292 and b290; b332 and b284) . It should be pointed out that the branching of the polybutadiene is a fundamental requisite for the use of polybutadiene itself as high impact polysty- rene modifier;
** molecular weight control of PB also without the use of butene-1. The molecular weight (200 x 103 < Mw < 420 x 103) can, in fact, be regulated by varying the type of phosphinic ligand, the Al/Co ratio and the type of solvent; ** production of polybutadiene with a low gel content
(macro < 3; micro ≤ 6) ;
** possibility of regulating the 1,4-cis content as desired, within the range of 80-96%, by varying the type of phosphine used; the content of 1,4-cis units, in fact, is greater for phosphines with a greater hindrance (see ter- butyl phosphine with respect to the other two less hindered phosphines) ;
** the polybutadiene which is obtained has a viscosity value in styrene <100 cP, which allows it to be used to pro- duce high impact polystyrene (HIPS) .

Claims

1. A process for the preparation of branched polybutadiene with a high content of 1,4-cis units by means of the polymerization of 1,3-butadiene, carried out in the presence of one or more solvents and a catalytic system which comprises a Cobalt complex, preformed or formed in situ, having general formula (I)
Cox+-Ln (I) wherein x is one, two or three; n ranges from 1 to 3; L is selected from one or more ligands of Co; the positive charge of the cobalt complex having general formula (I) being neutralized by one or more mono- or polyvalent anions; characterized in that the ligand L is selected from phosphorous derivatives having general formula (la) P[-(0)mR [-(0)mR2] [-(0)mR3] (la) wherein m is zero or one, preferably m=0; Ri, R2, the same or different, are selected from monofunctional aliphatic and cycloalkyl radicals, R3 is selected from -H and monofunctional aliphatic and cycloalkyl radicals, the compound having gen-
eral formula (la) having a theta (θ) steric hindrance value greater than 145°.
2. The process according to claim 1, characterized in that in the compound having general formula (I) x is two; n is t o.
3. The process according to claim 1, characterized in that in the compound having general formula (la) m = 0:
4. The process according to claim 1, characterized in that
θ is greater than 150°.
5. The process according to claim 1, characterized in that the compound having general formula (I) is selected from:
CoCl2 (tri-iso-propylphosphine) 2; CoCl2 (tri-ter-butylphosphine) 2; CoCl2 (tricyclohexylphosphine) 2.
6. The process according to claim 1, characterized in that the catalytic system also comprises, in addition to the cobalt complex having general formula (I) , one or more co- catalysts selected from organo-derivatives of aluminum selected from:
(al) compounds having general formula (II) Al (Ra) (Rb) (Rc) wherein Ra is selected from alkyl (including cycloalkyl) , aryl, alkylaryl, alkoxyl, hydrogen, fluorine; Rb and Rc, the same or different, are selected from alkyl (including cycloalkyl), aryl, alkylaryl, arylalkyl, (a2) aluminoxanes and relative derivatives. (a3) organo-derivatives of aluminum partially hydrolyzed, and relative mixtures,
(a4) halogen aluminum alkyls selected from (III) AlRnX3.n (with n = 1 or 2) and (IV) Al2RnX6-n (n = 1-5) , wherein R is a Cι-C20 alkyl group, X is chlorine or bromine.
7. The process according to claim 6, characterized in that in compounds (a4) X = Cl .
8. The process according to claim 6, characterized in that the organo-derivatives of aluminum are selected from aluminoxanes and relative derivatives .
9. The process according to claim 6, characterized in that the molar ratio between the complex having general formula (I) and the aluminum ranges from 1:5 to 1:10000.
10. The process according to claim 9, characterized in that the molar ratio between the complex having general formula (I) and the aluminum ranges from 1:100 to 1:1000.
11. The process according to claim 1, characterized in that the molar ratio between the cobalt complex having general formula (I) and the butadiene ranges from l/lO5 to 1/102.
12. The process according to claim 10, characterized in that the molar ratio between the cobalt complex having general formula (I) and the butadiene ranges from l/2xl04 to l/lO3.
13. The process according to claim 1, characterized in that the solvent is selected from aliphatic hydrocarbons, including olefins, cycloaliphatic, aromatic hydrocarbons and rela- tive mixtures.
14. The process according to claim 13, characterized in that the solvent is selected from aliphatic hydrocarbons, including olefins, and relative mixtures.
15. The process according to claim 1, characterized in that it is carried out at a temperature ranging from -30°C to +60 ° C .
16. The process according to claim 15, characterized in that it is carried out at a temperature ranging from -10°C to +40°C.
17. The process according to claim 1, characterized in that, in the case of the formation in situ of the compound having general formula (I) , the molar ratio between ligand (L) and cobalt salt is higher than the stoichiometric value, preferably, when the cobalt is bivalent, from 2.1/1 to 4/1, even more preferably from 2.2 to 2.5.
18. CoCl2[P (ter-butyl) 3] 2 i.e. cobalt dichloride (tri-ter- butylphosphine) 2 •
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CN1293108C (en) * 2004-04-12 2007-01-03 上海应用技术学院 Method for one-step synthesizing supper branched polymer of containing structure of benzene methylene
CN103450374A (en) * 2013-07-30 2013-12-18 浙江大学 Two-component cobalt catalyst and application thereof in solution polymerization or suspension polymerization of 1,3-butadiene
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EP1557433A1 (en) * 2004-01-22 2005-07-27 Polimeri Europa S.p.A. Process for the preparation of polybutadiene with a low branching degree
US7030195B2 (en) 2004-01-22 2006-04-18 Polimeri Europa S.P.A. Process for the preparation of polybutadiene with a low branching degree
CN100436494C (en) * 2004-01-22 2008-11-26 波利玛利欧洲股份公司 Process for the preparation of polybutadiene with a low branching degree
CN1293108C (en) * 2004-04-12 2007-01-03 上海应用技术学院 Method for one-step synthesizing supper branched polymer of containing structure of benzene methylene
CN103450374A (en) * 2013-07-30 2013-12-18 浙江大学 Two-component cobalt catalyst and application thereof in solution polymerization or suspension polymerization of 1,3-butadiene
WO2015068094A1 (en) 2013-11-05 2015-05-14 Versalis S.P.A. Stereoregular diblock polybutadienes having a 1,4-cis/syndiotactic 1,2 structure from stereospecific polymerization
WO2015068095A1 (en) 2013-11-05 2015-05-14 Versalis S.P.A. Stereoregular diblock polybutadienes having a 1,4-cis/syndiotactic 1,2 structure from stereospecific polymerization
IT201700085384A1 (en) * 2017-07-26 2019-01-26 Versalis Spa PROCEDURE FOR THE PREPARATION OF POLIBUTADIENE 1.2 SINDIOTATTICO IN THE PRESENCE OF A CATALYTIC SYSTEM INCLUDING A COBALT COMPLEX WITH A PHOSPHINIC BINDER
WO2019021195A1 (en) * 2017-07-26 2019-01-31 Versalis S.P.A. Process for the preparation of 1,2 syndiotactic polybutadiene in the presence of a catalytic system comprising a cobalt complex with a phosphine ligand
RU2772250C2 (en) * 2017-07-26 2022-05-18 ВЕРСАЛИС С.п.А. Method for producing 1,2-syndiotactic polybutadiene in the presence of a catalytic system containing a cobalt complex including a phospine ligand
IT202000028823A1 (en) 2020-11-27 2022-05-27 Consiglio Nazionale Ricerche STEREOBLOCK DIENE COPOLYMERS AND RELATED PREPARATION PROCESS.
WO2022112387A1 (en) 2020-11-27 2022-06-02 Km Technologies Gmbh Stereoblock diene copolymers and preparation process thereof.

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