Process for producing polypropylene impact block copolymers

Abstract

A process for producing a polypropylene impact copolymer by polymerizing propylene and optionally a monomer selected from the group consisting of ethylene, butene-1, pentene-1, and hexene-1 in a first reactor in the presence of a titanium, magnesium, halogen, and a inside electron donor catalyst, an organoaluminum cocatalyst, and an outside electron donor, R 1 2 Si(OR 2 ) 2 , to produce a first polymer which enters a second reactor where it is reacted with propylene and another monomer in the absence of additional catalyst and in the presence of a third electron donor, Si(OR 3 ) 4 is provided.

What is claimed is: 
     
       1. A process for producing polypropylene, impact, block copolymers, which process comprises the steps of 1) polymerizing propylene and optionally less than 3 mol % of a comonomer selected from the group consisting of ethylene, butene-1, pentene-1, and hexene-1, in a first polymerization reactor under polymerization conditions in the presence of a catalyst system of: i) a solid catalyst precursor consisting essentially of magnesium, titanium, halogen, and an inside electron donor,   ii) an organoaluminum cocatalyst,   iii) an outside electron donor of the formula   R.sup.1.sub.2 Si(OR.sup.2).sub.2     wherein each R 1  is individually a cycloalkyl having 4 to 7 carbon atoms or a substituted or unsubstituted cycloaliphatic group having 4 to 7 carbon atoms and each R 2  is individually a hydrocarbon group having 1 to 20 carbon atoms to produce a first polymer; and       2) polymerizing in a second reactor the first polymer obtained in step 1 with propylene and a monomer selected from the group consisting of ethylene, butene-1, pentene-1, and hexene-1 in the absence of an additional catalyst system and in the presence of tetraethoxysilane.   
     
     
       2. The process of claim 1 wherein the solid catalyst precursor is magnesium, titanium, halide and a polycarboxylic acid ester containing two coplanar ester groups attached to adjacent carbon atoms, said catalyst component being obtained by halogenating a magnesium compound of the formula MgR'R", wherein R' and R are alkoxide groups containing from 1 to 8 carbon atoms, with titanium tetrachloride, in the presence of (1) an aromatic halohydrocarbon containing from 6 to 12 carbon atoms and from 1 to 2 halogen atoms and (2) a polycarboxylic acid ester derived from (i) a branched or unbranched monohydric alcohol containing from 1 to 12 carbon atoms and (ii) a monocyclic or polycyclic aromatic compound containing from 8 to 20 carbon atoms and two carboxyl groups which are attached to ortho carbon atoms of the ring structure. 
     
     
       3. The process of claim 2 wherein the catalyst contains an atomic ratio of aluminum in the organoaluminum cocatalyst to silicon in the electron donor of from 0.5:1 to 100:1, and an atomic ratio of aluminum in the organoaluminum cocatalyst to titanium in the solid catalyst component of from 5:1 to 300:1 and a rubber phase of the copolymer product has a Sequence Index greater than 1.3. 
     
     
       4. A process as in claim 3 wherein the magnesium compound is magnesium diethoxide or magnesium ethyl carbonate. 
     
     
       5. A process as in claim 4 wherein the halohydrocarbon is chlorobenzene. 
     
     
       6. A process as in claim 5 wherein the polycarboxylic acid ester is diisobutyl phthalate. 
     
     
       7. A process as in claim 6 wherein the halogenated product is treated twice with additional titanium tetrachloride and the second treatment is effected in the presence of a polycarboxylic acid halide containing two coplanar acid halide groups attached to adjacent carbon atoms. 
     
     
       8. A process as in claim 7 wherein the polycarboxylic acid halide is phthaloyl dichloride. 
     
     
       9. A process as in claim 8 wherein propylene is copolymerized with up to 40 mole percent ethylene in a second polymerization reactor in the presence of the product of the first polymerization reactor. 
     
     
       10. A process as in claim 6 wherein the outside electron donor is dicyclopentyldimethoxysilane. 
     
     
       11. A process as in claim 8 wherein the outside electron donor is dicyclopentyldimethoxysilane.