Components and catalysts for the polymerization of olefins

Details Components and catalysts for the polymerization of olefins Components and catalysts for the polymerization of olefins

1997-06-19

2002-05-14

Wilson, Donald R. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C502S008000, C502S009000, C502S111000, C502S134000, C502S118000, C502S126000, C502S127000, C526S123100, C526S124200

Reexamination Certificate

active

06388028

ABSTRACT:

The present invention relates to catalyst components for the polymerization of olefins CH
2
═CHR, wherein R is hydrogen or a hydrocarbon radical having 1-12 carbon atoms, the catalysts obtained therefrom and their use in the polymerization of said olefins.
Catalysts supported on magnesium dihalides in active form are well known in the literature. The first catalysts of this type are described in U.S. Pat. No. 4,298,718 and 4,495,338.
A further development to the supported catalysis has been given by the catalysts showing a controlled morphology, in particular having spherical shape. These catalysts are able to give polymers which, by duplicating the shape of the catalyst and showing good morphological properties, allow simplifications in the preparation and/or post treatment processes of polymers.
Examples of catalysts having controlled morphology are described in U.S. Pat. Nos. 3,953,414 and 4,399,054. In the latter patent the components are obtained starting from spherical adducts of MgCl
2
with about 3 mols of alcohol. The preparation of the catalytic component can be carried out in different ways, for example by lowering the alcohol content of the adduct, by treatment under vacuum, up to 2.5-2 mols for each MgCl
2
mole, then allowing the thus obtained support to react with TiCl
4
. Alternatively the adduct containing about 3 moles of alcohol is treated with AlEt
3
and thereafter is reacted with TiCl
4
. In each case components having a nitrogen porosity between 0.3 and 0.4 cm
3
/g, a surface area between 300 and 500 m
2
/g and an average pore radius comprised between about 15 and 30 Å are obtained.
Catalysts prepared from TiCl
4
and granular MgCl
2
by spray-drying of an alcoholic magnesium chloride solution and subsequent supporting of the titanium compound are described in patent EP-B-65700 and EP-B-243327. However, the polymer obtained with these catalysts does not show morphological characteristics of interest. In particular, the bulk density is not sufficiently high. Furthermore, the activity of the catalyst is rather low.
A method for increasing the activity of these catalysts is described in patent EP-A-281524. The catalysts are prepared by supporting titanium alcoholates on a MgCl
2
-ethanol adduct, containing from 18 to 25% by weight of ethanol, made spherical by spray-drying of the ethanol solution and subsequent chemical treatment with Et
2
AlCl or Et
3
Al
2
Cl
3
. The conditions for the preparation of the support are critical and are reflected in the morphological stability of the polymer obtained. Polymers in form of heterogeneous powders are obtained, for example, using supports with an alcohol content not comprised within the critical range of 18-25or by using compounds different from Et
2
AlCl and Et
3
Al
2
Cl
3
. Furthermore, in order to have sufficiently high yields, the Ti content in the solid component is always higher than 8% by weight.
Catalysts obtained from MgCl
2
-alcohols adducts, wherein the adduct generally containing 3 mols of alcohol for each mole of MgCl
2
is dealcoholated by thermal treatment up to alcohol levels generally comprised between 0.2 and 2 mols and thereafter is reacted with an excess of titanium tetrachloride optionally containing a dissolved electron-donor compound, are known from the patent application EP-A-395083.
These catalysts are able to give polymers in the form of spheroidal particles with good morphological properties, in particular high bulk density.
The solid components of the catalysts described in EP-A-395083 are characterized by high surface areas and microporosity (more than 50% of the pore radius are higher than 100 Å, but lower than 800 Å).
Spherical catalyst components are now unexpectedly found for the polymerization of olefins having low values of surface area (measured by the BET method) and at the same time having high values of total porosity (measured by the mercurium method, hereinafter described) and distribution of the pore radius shifted towards values higher than 800 Å.
The components of the invention are able to give catalysts characterized by a high activity in the polymerization processes of olefins CH
2
═CHR, wherein R is hydrogen or a hydrocarbon radical having 1-12 carbon atoms, and able to give polymers endowed with valuable morphological properties, in particular having high bulk density values notwithstanding the remarkable macroporosity of the solid components forming the catalyst. Therefore, they are particularly suited to the modern vapour phase polymerization processes of the olefins wherein the high productivity of catalysts must be accompanied by the morphological stability of the same.
The spherical components of the invention comprise a titanium compound, supported on a magnesium halide, containing more than one Ti-halogen bond and optionally containing groups different from halogen in amounts lower than 0.5 mole for each mole of titanium and are characterized by having a surface area, measured by the BET method, of lower than 70 m
2
/g, a total porosity, measured by the merctrium method, of higher than 0.5 cm
3
/g and a pore radius such that at least 50% have values higher than 800 Å.
The total porosity is generally comprised between 0.6 and 1.2 cm
3
/g and the area is preferably comprised between 30 and 70 m
2
/g. The porosity measured by the BET method is generally lower than 0.25 cm
3
/g.
Spherical components of particular interest are further-more characterized by the fact that at least 80% of pores have a radius up to 15,000 Å and porosity comprised between 0.6 and 0.9 cm
3
/g.
The particles of solid component have substantially spherical morphology and average diameter comprised between 5 and 150 &mgr;m. As particles having substantially spherical morphology, those are meant wherein the ratio between the greater axis and the smaller axis is equal to or lower than 1.5 and preferably lower than 1.3.
Magnesium dihalides comprised in the spherical component of the invention are in the active form and are characterized by X-ray spectra in which the most intense diffraction line which appears in the spectrum of the non active halide is diminished in intensity and is substituted by a halo of which the maximum of intensity is shifted towards angles lower than those of the most intense line.
Preferably, the magnesium dihalide is MgCl
2
.
The components of the invention-can also comprise an electron compound (internal donor), selected for example among ethers, esters, amines and ketones. Said compound is necessary when the component is used in the stereoregular (co)polymerization of olefins such as propylene, 1-butene, 4-methyl-pentene-1; the internal donor can be advantageously used also when wanting to prepare linear low density polyethylenes (LLD-PE) having a narrow molecular weight distribution.
In particular, the internal electron donor compound can be selected from the alkyl, cycloalkyl and aryl ether and esters of polycarboxylic acids, such as for example esters of phthalic and maleic acid, in particular n-butylphthalate, di-isobutylphthalate, di-n-octylphthalate.
Other electron donor compound advantageously used are the 1,3-diethers of the formula:
wherein R
I
, R
II
, the same or different from each other, are alkyl, cycloalkyl, aryl radicals having 1-18 carbon atoms and R
III
, R
IV
, the same or different from each other, are alkyl radicals having 1-4 carbon atoms.
The electron donor compound is generally present in molar ratio with respect to the magnesium comprised between 1:4 and 1:20.
The preferred titanium compounds have the formula Ti(OR)
n
X
y−n
, wherein n is a number comprised between 0 and 0.5 inclusive, y is the valency of titanium, R is an alkyl, cycloalkyl or aryl radical having 2-8 carbon atoms or a COR group, X is halogen. In particular R can be n-butyl, isobutyl, 2-ethylhexyl, n-octyl and phenyl; X is preferably chlorine.
If y is 4, n varies preferably from 0 to 0.02; if y is 3, n varies preferably from 0 to 0.015.
Components of the invention form catalysts, for the polymerization of alpha-olefins CH
2

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