A method for producing a polyolefin is provided. The method includes a step of feeding a polyolefin powder having a catalytic activity into a gas phase polymerization vessel in which there is a polyolefin powder and through which a gas comprising an olefin is being circulated, thereby commencing polymerization of an olefin. The following formula (1) is satisfied:

0.5<β/(αB)<24.0  (1)

In formula (1), α represents the median diameter (μm) of the catalytically active polyolefin powder to be fed into the vapor phase polymerization vessel, β represents the median diameter (μm) of the polyolefin powder that is contained in the vapor phase polymerization vessel before the feeding of the catalytically active polyolefin powder into the vapor phase polymerization vessel, and B represents the linear gas velocity (m/sec) of the gas containing an olefin within the vapor phase polymerization vessel.

A method for producing a polyolefin is provided. The method includes a step of feeding a polyolefin powder having a catalytic activity into a gas phase polymerization vessel in which there is a polyolefin powder and through which a gas comprising an olefin is being circulated, thereby commencing polymerization of an olefin. The following formula (1) is satisfied:

0.5<β/(αB)<24.0  (1)

In formula (1), α represents the median diameter (μm) of the catalytically active polyolefin powder to be fed into the vapor phase polymerization vessel, β represents the median diameter (μm) of the polyolefin powder that is contained in the vapor phase polymerization vessel before the feeding of the catalytically active polyolefin powder into the vapor phase polymerization vessel, and B represents the linear gas velocity (m/sec) of the gas containing an olefin within the vapor phase polymerization vessel.

A pipe including polyethylene produced in the presence of a solid catalyst and a co-catalyst, wherein the solid catalyst is prepared by the steps of: (a) contacting a dehydrated support having hydroxyl groups with a compound of formula MgR.sup.1R.sup.2; (b) contacting the product of step (a) with modifying compounds (A), (B) and (C), wherein: (A) is carboxylic acid, carboxylic acid ester, ketone, acyl halide, aldehyde or alcohol; (B) is of formula R.sup.11.sub.f(R.sup.12O).sub.gSiX.sub.h wherein f, g and h 0 to 4 and the sum of f, g and h=4 provided that when h=4 then compound (A) is not an alcohol; (C) is a compound of formula (R.sup.13O).sub.4M, wherein M is a titanium atom, a zirconium atom or a vanadium atom; and (c) contacting the product of step (b) with a titanium halide TiX.sub.4, whereby the polyethylene has a molecular weight of 720,000 to less than 2,500,000 g/mol.

A pipe including polyethylene produced in the presence of a solid catalyst and a co-catalyst, wherein the solid catalyst is prepared by the steps of: (a) contacting a dehydrated support having hydroxyl groups with a compound of formula MgR.sup.1R.sup.2; (b) contacting the product of step (a) with modifying compounds (A), (B) and (C), wherein: (A) is carboxylic acid, carboxylic acid ester, ketone, acyl halide, aldehyde or alcohol; (B) is of formula R.sup.11.sub.f(R.sup.12O).sub.gSiX.sub.h wherein f, g and h 0 to 4 and the sum of f, g and h=4 provided that when h=4 then compound (A) is not an alcohol; (C) is a compound of formula (R.sup.13O).sub.4M, wherein M is a titanium atom, a zirconium atom or a vanadium atom; and (c) contacting the product of step (b) with a titanium halide TiX.sub.4, whereby the polyethylene has a molecular weight of 720,000 to less than 2,500,000 g/mol.

The invention relates to a continuous process for the production of ultra-high molecular weight polyethylene with an Elongational Stress of at least 0.43 N/mm.sup.2. The polymerisation of ethylene takes place in the presence of a catalyst and hydrogen. It is an advantage of the process according to the invention that the use of small amounts of hydrogen during the production of UHM-WPE reduces reactor fouling. Furthermore, the process according to the invention results in longer run times in polymerization reactors, less cleaning cycles to remove reactor fouling and in less need for other anti-fouling agents or anti-static agents.

The invention relates to a continuous process for the production of ultra-high molecular weight polyethylene with an Elongational Stress of at least 0.43 N/mm.sup.2. The polymerisation of ethylene takes place in the presence of a catalyst and hydrogen. It is an advantage of the process according to the invention that the use of small amounts of hydrogen during the production of UHM-WPE reduces reactor fouling. Furthermore, the process according to the invention results in longer run times in polymerization reactors, less cleaning cycles to remove reactor fouling and in less need for other anti-fouling agents or anti-static agents.

The present invention relates to a process for preparing a procatalyst for polymerization of olefins, comprising contacting a magnesium-containing support with a halogen-containing titanium compound, a monoester, a first internal electron donor, wherein the internal electron donor is represented by a compound represented by Formula A, for example a Fischer projection of Formula A, and optionally a second internal electron donor selected from a group consisting of diesters and diethers, Formula A said process comprising the steps of: i) contacting a butyl Grignard compound with an alkoxy- or aryloxy-containing silane compound to give a first intermediate reaction product; ii) optionally activating the first intermediate reaction product with at least one activating compound to give a second intermediate reaction product; iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or ii), with a halogen-containing Ti-compound, the monoester, and said internal electron represented by a compound represented by Formula A, for example a Fischer projection of Formula A, as the first internal electron donor, and optionally the diester or di-ether as the second internal electron donor. The present invention also relates to a polymerization catalyst system comprising said procatalyst, a co-catalyst and optionally an external electron donor. Furthermore, the present invention relates to a polyolefin obtainable by the process according to the present invention and a shaped article thereof.

##STR00001##

The present invention relates to a process for preparing a procatalyst for polymerization of olefins, comprising contacting a magnesium-containing support with a halogen-containing titanium compound, a monoester, a first internal electron donor, wherein the internal electron donor is represented by a compound represented by Formula A, for example a Fischer projection of Formula A, and optionally a second internal electron donor selected from a group consisting of diesters and diethers, Formula A said process comprising the steps of: i) contacting a butyl Grignard compound with an alkoxy- or aryloxy-containing silane compound to give a first intermediate reaction product; ii) optionally activating the first intermediate reaction product with at least one activating compound to give a second intermediate reaction product; iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or ii), with a halogen-containing Ti-compound, the monoester, and said internal electron represented by a compound represented by Formula A, for example a Fischer projection of Formula A, as the first internal electron donor, and optionally the diester or di-ether as the second internal electron donor. The present invention also relates to a polymerization catalyst system comprising said procatalyst, a co-catalyst and optionally an external electron donor. Furthermore, the present invention relates to a polyolefin obtainable by the process according to the present invention and a shaped article thereof.

##STR00001##

Organosilicon compounds having a structure represented by the general formula ##STR00001##
and a method for using same are provided as electron donors in the Ziegler-Natta type catalyst system for the homo-polymerization or co-polymerization of alpha olefins. The organosilicon compounds may be used in the preparation of the solid catalyst component, thus serving as “internal electron donors”, or employed during or prior to polymerization as “external electron donors,” and therefore they can be used to prepare phthalate-free polyolefins.

Organosilicon compounds having a structure represented by the general formula ##STR00001##
and a method for using same are provided as electron donors in the Ziegler-Natta type catalyst system for the homo-polymerization or co-polymerization of alpha olefins. The organosilicon compounds may be used in the preparation of the solid catalyst component, thus serving as “internal electron donors”, or employed during or prior to polymerization as “external electron donors,” and therefore they can be used to prepare phthalate-free polyolefins.