Catalyst precursor and catalyst for the high-temperature (co)polymerization of alpha-olefin

Patent metadata

Field	Value
Publication number	US-9751959-B2
Application number	US-201113995391-A
Country	US
Kind code	B2
Filing date	Dec 20, 2011
Priority date	Dec 20, 2010
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A precursor for the formation of catalysts for the (co)polymerization of α-olefins, comprising titanium, magnesium, at least one metal selected from hafnium and zirconium, aluminum and chlorine, obtained with a process comprising treatment with a siloxane compound. Said solid precursor, used in combination with a suitable co-catalyst in high-temperature (co)polymerization processes of α-olefins, shows an improved productivity, a high incorporation of co-monomers in the copolymerization of ethylene and an increased thermal stability with respect to the systems so far in use.

First claim

The invention claimed is:

1. A catalyst precursor for the (co)polymerization of alpha-olefins, comprising titanium, magnesium, aluminum, chlorine and at least one metal M selected from hafnium and zirconium characterized in that it is obtained by means of a process comprising the following steps:
(i) heating a mixture in a liquid hydrocarbon solvent comprising a magnesium chloride, a compound of titanium, a compound of said metal M, a carboxylic acid R—COOH, wherein R is an organic group having from 2 to 30 carbon atoms, in such quantities as to respect the following atomic or molar ratio ranges:
M/Ti=0.2-5.0; Mg/Ti=3.0-20.0; R—COOH/(Mg+M)=1-8
at a temperature ranging from 50 to 200° C. for at least one minute and separating the possible solid residue remaining undissolved, to obtain a solution;
(ii) adding to the solution obtained in step (i), an aluminum alkyl chloride having the following general formula (I):
AlR′ n Cl (3−n)   (I)

wherein: R′ is a linear or branched alkyl radical, containing from 1 to 20 carbon atoms, and “n” is a decimal number having values ranging from 0.5 to 2.5,
in an amount sufficient for precipitating in the form of a solid compound at least 70% of the metals Mg, M and Ti present in said solution, and heating the mixture thus obtained to a temperature ranging from 40 to 130° C. for a time ranging from 5 to 240 minutes to obtain a solid precipitate comprising Mg, M, Al and Cl in atomic ratios with respect to the Ti within the following ranges:
M/Ti=0.2-5.0; Mg/Ti=3.0-15.0; Al/Ti=0.1-4.0; Cl/Ti=15.0-60.0;
(iii) separating the solid precipitate thus formed from the residual liquid solution; and
(iv) putting said solid precipitate obtained in step (iii) in contact with a siloxane compound A, having from 2 to 40 carbon atoms and from 1 to 15 silicon atoms, comprising at least one siloxane group selected from the following formulae:
O—Si—C and Si—O—Si,

in such an amount that the atomic ratio Si/Ti between the Si atoms in the siloxane compound A and the Ti atoms in the solid precipitate, is higher than or equal to 0.1 to obtain said catalyst precursor.

2. The catalyst precursor according to claim 1 , characterized in that at the end of step (iv) it is obtained in the form of a suspension in a liquid hydrocarbon that optionally contains an excess amount of siloxane compound A.

3. The catalyst precursor according to claim 1 , wherein titanium, magnesium, said metal M, aluminum and chlorine form at least 80% by weight of the catalyst.

4. The catalyst precursor according to claim 1 , having a particle-size with a Gaussian distribution having a maximum ranging from 2 to 15 μm, and granule dimensions which are such that 80% by weight of the same ranges from 1 to 30 μm.

5. The catalyst precursor according to claim 1 , wherein the titanium is in an amount of up to 10% by weight with respect to the total weight of the solid.

6. The catalyst precursor according to claim 1 , wherein in step (i) of the preparation process, the molar ratio RCOOH/(Mg+M) ranges from 1.5 to 5.0.

7. The catalyst precursor according to claim 1 , wherein in step (i) of the preparation process, the solid residue remaining undissolved is equal to or lower than 30% by weight with respect to the total weight of the metallic compounds of the mixture which are insoluble as such in the liquid hydrocarbon solvent at room temperature.

8. The catalyst precursor according to claim 1 , wherein in step (i) of the preparation process, the heating of the mixture is effected in a closed container or under reflux conditions of the solvent.

9. The catalyst precursor according to claim 1 , wherein in said preparation step (ii), the addition of the aluminum alkyl chloride having formula (I) to the solution obtained in step (i) is effected so that the temperature of the reaction mixture is not higher than 45° C.

10. The catalyst precursor according to claim 1 , wherein at the end of the separation step (iii), the solid precipitate is subjected to washings with a hydrocarbon solvent until a molar concentration of aluminum in the hydrocarbon solvent lower than 1.5 mM, is reached.

11. The catalyst precursor according to claim 1 , wherein said step (iv) is carried out at a temperature ranging from −10 to 120 ° C.

12. The catalyst precursor according to claim 1 , wherein said siloxane compound A, in the preparation step (iv), comprises from 1 to 10 O atoms.

13. The catalyst precursor according to claim 1 , wherein said siloxane compound A, in the preparation step (iv), is selected from those included in the following formulae (II) and (III):
SiR′″ p (OR″) (4−p)   (II)

T 1 (Si(R 5 ) 2 —O—) q T 2   (III)

wherein
each R″ is independently a linear, cyclic or branched alkyl group, having from 1 to 10 carbon atoms, possibly halogenated or an aryl group having from 6 to 10 carbon atoms, possibly halogenated, or an alkyl silyl group having the formula —SiR′″ 3 ;
each R′″ is independently H, a halogen or an alkyl or aryl group included in the definition of the previous R″;
each R 5 is independently H, a halogen, preferably chlorine, or an alkyl or aryl group included in the definition of the previous R″, or an alkoxyl or aryloxy groups having the formula —OR″, wherein R″ is as previously defined,
T 1 can have any of the meanings of R 5 ;
T 2 can have any of the meanings of R″;
p is an integer ranging from 0 to 3;
q is an integer ranging from 2 to 15.

14. A catalyst for the (co)polymerization of alpha-olefins, comprising, in contact with each other, a cocatalyst consisting of a hydride or organometallic compound of a metal of groups 1, 2 or 13 of the periodic table, and a catalyst precursor according to claim 1 .

15. The catalyst according to claim 14 , wherein said cocatalyst is selected from aluminum trialkyls which contain from 1 to 10 carbon atoms in each alkyl radical.

16. The catalyst according to claim 15 , wherein the atomic ratio between the aluminum (in the cocatalyst) and the titanium (in the precursor) is within the range of 1:1 to 500:1.

17. A process for the (co)polymerization of alpha-olefins, comprising polymerizing at least one alpha-olefin, either in continuous or batchwise, in one or more steps at low (0.1 -1.0 MPa), medium (1.0 -10 MPa) or high (10-150 MPa) pressure, at temperatures ranging from 20 to 300° C. in the presence of a catalyst according to claim 14 .

18. The process according to claim 17 , wherein at least one alpha-olefin is ethylene.

19. The (co)polymerization process according to claim 17 , characterized in that it is carried out in an inert solvent solution, at temperatures ranging from 130 to 300° C. and at pressures ranging from 1 to 25 MPa.

20. The (co)polymerization process according to claim 19 , wherein the polymerization temperature ranges from 160 to 260° C.

21. The process according to claim 17 , wherein the process is carried out in an inert solvent.

Assignees

• Masi Francesco
• Menconi Francesco
• Conti Giuseppe
• Polesello Mario
• Zanellato Alberto
• Versalis Spa

Inventors

• Masi Francesco
• Menconi Francesco
• Conti Giuseppe
• Polesello Mario
• Zanellato Alberto

Classifications

• C08F210/16

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title

• C08F10/02 Primary

  Ethene · CPC title

• C08F4/16 Primary

  of silicon, germanium, tin, lead, titanium, zirconium or hafnium · CPC title

• C08F2500/12

  Melt flow index or melt flow ratio · CPC title

• C08F210/14

  Monomers containing five or more carbon atoms · CPC title