Process for the preparation of ligands for metallocene catalysts

Abstract

Amorphous polymers of alpha-olefins, particularly of propylene, having high molecular weights and narrow molecular weight distributions, in which the isotactic sequences are more abundant than the syndiotactic ones, can be obtained in high yields at temperatures of industrial interest by carrying out the polymerization reaction in the presence of metallocene catalysts comprising particular bridged bis-indenyl compounds substituted in the 3-position on the indenyl groups. The obtained amorphous polymers are particularly useful for the preparation of miscible compositions with substantially isotactic alpha-olefins.

1 . A process for the preparation of amorphous polymers of alpha-olefins, comprising the polymerization reaction of at least one alpha-olefin containing from 3 to 20 carbon atoms in the presence of a catalyst obtainable by contacting: 
 (A) a metallocene compound in the racemic form of the formula (I):                          wherein    substituents R 1  are hydrogen atoms;    R 2  and R 3  are, independently from each other, C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 6 -C 20 -aryl, C 7 -C 20 -alkylaryl or C 7 -C 20 -arylalkyl radicals, optionally containing silicon or germanium atoms;    or where R 2  and R 3  can be joined together to form a 4 to 6 membered ring or a 6 to 20 fused ring system;    R 4  and R 5 , same or different, are hydrogen atoms or —CHR 8 R 9  groups;    R 4  and R 5  can form a ring having 3 to 8 carbon atoms which can contain hetero atoms;    the R 8  and R 9  substituents, same or different, are hydrogen atoms, C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 6 -C 20 -aryl, C 7 -C 20 -alkylaryl or C 7 -C 20 -arylalkyl radicals, which can form a ring having 3 to 8 carbon atoms which can contain hetero atoms;    the R 6  and R 7  substituents, same or different, are hydrogen, C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 6 -C 20 -aryl, C 7 -C 20 -alkylaryl or C 7 -C 20 -arylalkyl radicals, optionally containing silicon or germanium atoms; and optionally two adjacent R 6  and R 7  substituents can form a ring comprising from 5 to 8 carbon atoms;    M is a transition metal selected from those belonging to group 3, 4, 5, 6 or to the lanthanide or actinide groups in the Periodic Table of the Elements (new IUPAC version),    X, same or different, is a monoanionic ligand, such as a hydrogen atom, a halogen atom, an R 10 , OR 10 , OSO 2 CF 3 , OCOR 10 , SR 10 , NR 10   2  or PR 10   2  group, wherein the substituents R 10  are a C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 2 C 20 -alkenyl, C 6 -C 20 -aryl, C 7 -C 20 -alkylaryl or C 7 -C 20 -arylalkyl radical, optionally containing silicon or germanium atoms;    p is an integer from 0 to 3, p being equal to the oxidation state of the metal M minus two; and    (B) an alumoxane and/or a compound capable of forming an alkyl metallocene cation.    
     
     
         2 . The process according to  claim 1 , wherein said alpha-olefin is propylene.  
     
     
         3 . The process according to  claim 1 , wherein in the metallocene compound of formula (I) the transition metal M is selected from titanium, zirconium and hafnium.  
     
     
         4 . The process according to  claim 1 , wherein in the metallocene compound of formula (I) the transition metal M is zirconium.  
     
     
         5 . The process according to  claim 1 , wherein in the metallocene compound of formula (I) the X substituents are chlorine atoms or methyl groups.  
     
     
         6 . The process according to  claim 1 , wherein in the metallocene compound of formula (I) the substituents R 6  and R 7  are hydrogen atoms.  
     
     
         7 . The process according to  claim 1 , wherein the metallocene compound of formula (I) is selected from methylene-bis(3-isopropylindenyl)zirconium dichloride and isopropylidene-bis(3-isopropyl-indenyl)zirconium dichloride.  
     
     
         8 . The process according to  claim 1 , wherein said alumoxane is obtained by reacting water with an organo-aluminium compound selected from those of formula AlR 11   3  and Al 2 R 11   6 , wherein at least one R 11  is not halogen,  
     
     
         9 . The process according to  claim 8 , wherein the molar ratio between the aluminium and water is in the range of 1:1 and 100:1.  
     
     
         10 . The process according to  claim 1 , wherein said alumoxane is methylalumoxane (MAO), isobutylalumoxane (TIBAO), 2,4,4-trimethyl-pentylalumoxane (TIOAO), 2,3-dimethylbutylalumoxane (TDMBAO) and 2,3,3-trimethylbutylalumoxane (TTMBAO).  
     
     
         11 . The process according to  claim 1 , wherein the molar ratio between the aluminium and the metal of the metallocene compound is comprised between 100:1 and 5000:1.  
     
     
         12 . The process according to  claim 1 , wherein the compound capable of forming a metallocene alkyl cation is a compound of formula Y + Z − , wherein Y +  is a Bronsted acid, able to give a proton and to react irreversibly with a substituent X of the metallocene of formula (I) and Z −  is a compatible anion, which does not coordinate, which is able to stabilize the active catalytic species originating from the reaction of the two compounds, and which is sufficiently labile to be able to be removed from an olefinic substrate.  
     
     
         13 . The process according to  claim 12 , wherein the compound of formula Y + Z −  is tetrakis-pentafluorophenylborate.  
     
     
         14 . The process according to any of  claims 1  to  13 , wherein said process is carried out at a temperature comprised between 0 and 250° C. and at a pressure comprised between 0,5 and 100 bar.  
     
     
         15 . The process according to any of  claims 1  to  14 , wherein the process is carried out in the presence of ethylene or of a C 4 -C 10  alpha-olefin comonomer.  
     
     
         16 . A thermoplastic composition comprising: 
 (A) 1 to 99% by weight of a propylene polymer optionally containing from 0.1 to 20% by moles of units deriving from an olefin of formula CH 2 ═CHR, R being hydrogen, a C 2 -C 20 -alkyl or a C 6 -C 12 -aryl group, having the following characteristics: 
 melting enthalpy<70 J/g;  
 the ratio of the pentads (mmmm)/(rrrr)=1,5; and  
 the ratio of the pentads (mmmm)/(mmmr)=0.8;  
   (B) 1 to 99% by weight of a propylene polymer, optionally containing from 0.1 to 20% by moles of units deriving from an olefin of formula CH 2 ═CHR, R being hydrogen, a C 2 -C 20 -alkyl or a C 6 -C 12 -aryl group, having the following characteristics: 
 melting enthalpy>70 J/g, and  
 % of isotactic dyads (m)−% of syndiotactic dyads (r)>0.  
   
     
     
         17 . The composition according to  claim 16 , wherein the ratio of the quantities by weight of the components (A)/(B) is comprised between 10:90 and 90:10.  
     
     
         18 . The composition according to any of claims  16  and  17 , wherein the ratio of the quantities by weight of the components (A)/(B) is comprised between 30:70 and 70:30.  
     
     
         19 . The composition according to any of  claims 16  to  18 , wherein the amorphous propylene polymer of component (A) has a melting enthalpy lower than 50 J/g.  
     
     
         20 . The composition according to  claim 19 , wherein the amorphous propylene polymer of component (A) has a melting enthalpy lower than 20 J/g.  
     
     
         21 . The composition according to any of  claims 16  to  20 , wherein the amorphous propylene polymer of component (A) has intrinsic viscosity values [η] of greater than 0.5.  
     
     
         22 . The composition according to any of  claims 16  to  21 , wherein in component (A) the ratio of the pentads (mmmm)/(rrrr)=2.0.  
     
     
         23 . The composition according to any of  claims 16  to  22 , wherein in component (A) the ratio of the pentads (mmmm)/(mmmr)=0.9.  
     
     
         24 . The composition according to  claim 23 , wherein in component (A) the ratio of the pentads (mmmm)/(mmmr)=1.0.  
     
     
         25 . The composition according to any of  claims 16  to  24 , wherein the amorphous propylene polymer of component (A) has less than 1% of the CH 2  groups contained in (CH 2 ) n  sequences wherein n=2.  
     
     
         26 . The composition according to any of  claims 16  to  25 , wherein the amorphous propylene polymer of component (A) has a M w /M n  ratio of lower than 4.  
     
     
         27 . The composition according to any of  claims 16  to  26 , wherein the amorphous propylene polymer of component (A) has a M w /M n  ratio of lower than 3.  
     
     
         28 . The composition according to any of  claims 16  to  27 , wherein the isotactic propylene polymer of component (B) has a melting enthalpy greater than 90 J/g.  
     
     
         29 . The composition according to any of  claims 16  to  28 , wherein the component (B) has the following characteristics: 
 melting point of between 110° C. and 160° C.;  
 [η]>1 dl/g.  
 
     
     
         30 . The composition according to any of  claims 16  to  29 , wherein the component (B) is a propylene copolymer having an essentially isotactic structure, which has the following characteristics: 
 melting point of between 110° C. and 140° C.;  
 [η]>1 dl/g;  
 fraction soluble in xylene at 25° C. of less than 10%.  
 
     
     
         31 . Manufactured articles obtainable from a composition according to any of  claims 16  to  30 .  
     
     
         32 . A low-temperature-heat-sealing film obtainable from a composition according to any of  claims 16  to  29 .  
     
     
         33 . A process for the preparation of a compound of formula (II)  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and R 7  are defined as in  claim 1 ,  
       and/or its double bond isomers  
       comprising the following steps: 
 a) contacting a compound of formula (III)  
                     
 and/or its double bound isomer  
 wherein R 1 , R 6  and R 7  have the meaning as described in  claim 1   
 with a base selected from the group consisting of alkali and earth alkali metal hydroxides or alkoxides in the presence of an oxygen containing solvent;  
 b) treating the obtained corresponding anionic form with a compound of general formula R 4 R 5 CO, wherein R 4  and R 5  are as defined in  claim 1 , in order to obtain a compound of the formula (IV)  
                     
 wherein R 1 , R 4 , R 5 , R 6  and R 7  have the meaning as described in  claim 1;   
 c) contacting the compound of formula (IV) with a base, wherein the molar ratio between the base and the compound of formula (IV) is equal to or greater than 2;  
 d) treating the corresponding di-anionic form of formula (IV) with a compound of formula (V) CHR 2 R 3 L, wherein R 2  and R 3  are defined as above and L is a halogen atom selected from the group 17 of the Periodic Table of the Elements (new IUPAC version), and the molar ratio between the compound (V) and the corresponding di-anionic form of formula (IV) is equal to or greater than 2.  
 
     
     
         34 . The process according to  claim 33 , wherein the base used in step a) is sodium or potassium hydroxide, the molar ratio between said base and the compound of formula (III) is in the range from 0.01 to 1.  
     
     
         35 . The process according to any of claims  33  and  34 , wherein the oxygen containing solvent is dimethylsulfoxide (DMSO) or 1-Me-2-pyrrolidinone.  
     
     
         36 . The process according to  claim 33 , wherein L is selected from chlorine, bromine, iodine and fluorine.  
     
     
         37 . The process according to  claim 36 , wherein L is bromine.  
     
     
         38 . The process according to  claim 37 , wherein the base used in step c) is selected from alkali and earth alkali metal hydroxides, organic lithium compounds and metallic sodium or potassium.  
     
     
         39 . The process according to  claim 38 , wherein the base is buthyllithium.