Patent Application
20130131293
The present invention relates to catalyst components for the polymerization of olefins, in particular propylene, comprising a Mg dihalide based support on which are supported Ti atoms and an electron donor selected from a specific class of diolesters, said Ti atoms and electron donor being in specified molar ratio. The present invention further relates to the catalysts obtained from said components and to their use in processes for the polymerization of olefins in particular propylene.
Catalyst components for the stereospecific polymerization of olefins are widely known in the art. Concerning the polymerization of propylene, the most spread out catalyst family belongs to the Ziegler-Natta category and in general terms it comprises a solid catalyst component, constituted by a magnesium dihalide on which are supported a titanium compound and an internal electron donor compound, used in combination with an Al-alkyl compound. Conventionally however, when a higher crystallinity of the polymer is required, also an external donor (for example an alkoxysilane) is needed in order to obtain higher isotacticity. One of the preferred classes of internal donors is constituted by the esters of phthalic acid, diisobutylphthalate being the most used. The phthalates are used as internal donors in combination with alkylalkoxysilanes as external donor. This catalyst system gives good performances in terms of activity, isotacticity and xylene insolubility.
One of the problems associated with the use of this catalyst system is that the phthalates have recently raised concerns due to the medical issues associated with their use and some compounds within this class have been classified as source of heavy health problems. Consequently, research activities have been devoted to discover alternative classes of internal donors for use in the preparation of catalyst components for propylene polymerization. Among the various classes of donors tested, the broad class of diesters of diols described in U.S. Pat. No. 7,388,061 is one of the most interesting. In this document, esters belonging to the formula R1—CO—O—CR3R4-A-CR5R6—O—CO—R2 in which R1 and R2 groups, which may be identical or different, can be substituted or unsubstituted hydrocarbyl having 1 to 20 carbon atoms, R3-R6 groups, which may be identical or different, can be selected from the group consisting of hydrogen, halogen or substituted or unsubstituted hydrocarbyl having 1 to 20 carbon atoms, R1-R6 groups optionally contain one or more hetero-atoms replacing carbon, hydrogen atom or the both, said hetero-atom is selected from the group consisting of nitrogen, oxygen, sulfur, silicon, phosphorus and halogen atom, two or more of R3-R6 groups can be linked to form saturated or unsaturated monocyclic or polycyclic ring; A is a single bond or bivalent linking group with chain length between two free radicals being 1-10 atoms, wherein said bivalent linking group is selected from the group consisting of aliphatic, alicyclic and aromatic bivalent radicals, and can carry C1-C20 linear or branched substituents; one or more of carbon atoms and/or hydrogen atoms on above-mentioned bivalent linking group and substituents can be replaced by a hetero-atom selected from the group consisting of nitrogen, oxygen, sulfur, silicon, phosphorus, and halogen atom, and two or more said substituents on the linking group as well as above-mentioned R3-R6 groups can be linked to form saturated or unsaturated monocyclic or polycyclic ring.
The examples reported in the document seem to show in general good activity and stereospecificity for this class. From the reported data, it results a great variance of performances depending on the internal donor, ranging from very good performing structures to very poorly performing ones both in terms of activity and stereospecificity (see examples 68 and 86). From a review of the examples, it results that the donor/Ti molar ratio is generally higher than 0.5 and that good activity and stereospecificity are obtained in general for donor/Ti molar ratios of higher than 0.6. In fact, when, for a certain donor, the ratio is lowered to less than 0.5, a dramatic decrease in stereospecificity is observed (see comparison between example 57 and 91). This is a disadvantage because in the attempt of increasing the titanium amount in order to try to increase the activity, one should be forced to also increase the amount of donor in order not to loose stereocontrol. Of course, this is not very efficient due to the fact that using higher amounts of donor, in addition to increase costs, also involves formation of higher quantity of by-products and necessity to work under more diluted conditions. In addition, an elevated amount of donor also causes morphology problems in the catalyst preparation (formation of aggregates) which may reflect on the final polymer.
It would be therefore important to have a catalyst able to maintain high activity and stereospecificity even at reduced donor/Ti molar ratios.
Surprisingly, the applicant has found that a particular subgroup of donors is able to give good performance in terms of activity and stereospecificity also when the donor/Ti molar ratio is lower than 0.65.
Accordingly, it is an object of the present invention a catalyst component for the polymerization of olefins comprising Mg, Ti and an electron donor of formula
in which R, R1 and R4 groups, equal to or different from each other, are C1-C15 hydrocarbon groups and the R groups can be linked to form a cycle, R2-R3 groups, equal to or different from each other, are selected from hydrogen and C1-C15 hydrocarbon groups, the R1-R4 groups can optionally contain an heteroatom selected from halogen, P, S, N, O and Si, n is an integer from 0 to 5 and said electron donor and Ti atoms being present in an amount such that their molar ratio is equal to, or lower than, 0.65.
Preferably, R1 and R4 are independently selected from C1-C15 alkyl groups, C6-C14 aryl groups, C3-C15 cycloalkyl groups, and C7-C15 arylalkyl or alkylaryl groups. More preferably, R1 and R4 are selected from C1-C10 alkyl groups and even more preferably from C1-C5 alkyl groups in particular methyl.
Preferably, R2-R3 groups are independently selected from hydrogen, C1-C15 alkyl groups, C6-C14 aryl groups, C3-C15 cycloalkyl groups, and C7-C15 arylalkyl or alkylaryl groups. More preferably, R2 and R3 are selected from hydrogen or C1-C10 alkyl groups and even more preferably from hydrogen or C1-C5 alkyl groups in particular methyl. In one preferred embodiment hydrogen and methyl are preferred. In one particular preferred embodiment both R2 and R3 are hydrogen.
Preferably, R groups are selected from C1-C15 alkyl groups, C6-C14 aryl groups, C3-C15 cycloalkyl groups, and C7-C15 arylalkyl or alkylaryl groups. More preferably, R are selected from C1-C10 alkyl groups and even more preferably from C1-C5 alkyl groups. Among them particularly preferred are methyl, ethyl, n-propyl and n-butyl. The index n can vary from 0 to 5 inclusive, preferably it ranges from 1 to 3 and more preferably is 1. When n is 1, the substituent R is preferably in position 4 of the benzoate ring.
Preferred structures of Formula (I) are those in which simultaneously R1 and R4 are methyl, R2 and R3 are hydrogen and n is 1 and the R groups, which are in position 4 of the benzene ring are methyl, ethyl, n-propyl or n-butyl.
Preferably the amount of electron donor of Formula (I) is such that the electron donor/Ti molar ratio is lower than 0.6, more preferably lower than 0.55 and especially lower than 0.5.
The amount of Ti atoms in the catalyst component is preferably higher than 3% wt more preferably higher than 3.5% with respect to the total weight of said catalyst component.
Non limiting examples of Formula (I) are the following: 2,4-pentanediol dibenzoate, 3-methyl-2,4-pentanediol dibenzoate, 3-ethyl-2,4-pentanediol dibenzoate, 3-n-propyl-2,4-pentanediol dibenzoate, 3-i-propyl-2,4-pentanediol dibenzoate, 3-n-butyl-2,4-pentanediol dibenzoate, 3-i-butyl-2,4-pentanediol dibenzoate, 3-t-butyl-2,4-pentanediol dibenzoate, 3-n-pentyl-2,4-pentanediol dibenzoate, 3-i-pentyl-2,4-pentanediol dibenzoate, 3-cyclopentyl-2,4-pentanediol dibenzoate, 3-cyclohexyl-2,4-pentanediol dibenzoate, 3-phenyl-2,4-pentanediol dibenzoate, 3-(2-naphtyl)-2,4-pentanediol dibenzoate, 3-allyl-2,4-pentanediol dibenzoate, 3,3-dimethyl-2,4-pentanediol dibenzoate, 3-ethyl-3-methyl-2,4-pentanediol dibenzoate, 3-methyl-3-i-propyl-2,4-pentanediol dibenzoate, 3,3-diisopropyl-2,4-pentanediol dibenzoate, 3-i-pentyl-2-i-propyl-2,4-pentanediol dibenzoate, 3,5-heptanediol dibenzoate, 4,6-nonanediol dibenzoate, 2,6-dimethyl-3,5-heptanediol dibenzoate, 5,7-undecanediol dibenzoate, 2,8-dimethyl-4,6-nonanediol dibenzoate, 2,2,6,6, tetramethyl-3,5-hetanediol dibenzoate, 6,8-tridecanediol dibenzoate, 2,10-dimethyl-5,7-undecanediol dibenzoate, 1,3-dicyclopentyl-1,3-propanediol dibenzoate, 1,3-dicyclohexyl-1,3-propanediol dibenzoate, 1,3-diphenyl-1,3-propanediol dibenzoate, 1,3-bis(2-naphtyl)-1,3-propanediol dibenzoate, 2,4-hexanediol dibenzoate, 2,4-heptanediol dibenzoate, 2-methyl-3,5-hexanediol dibenzoate, 2,4-octanediol dibenzoate, 2-methyl-4,6-heptanediol dibenzoate, 2,2-dimethyl-3,5-hexanediol dibenzoate, 2-methyl-5,7-octanediol dibenzoate, 2,4-nonanediol dibenzoate, 1-cyclopentyl-1,3-butanediol dibenzoate, 1-cyclohexyl-1,3-butanediol dibenzoate, 1-phenyl-1,3-butanediol dibenzoate, 1-(2-naphtyl)-1,3-butanediol dibenzoate, 2,4-pentanediol-bis(4-methylbenzoate), 2,4-pentanediol-bis(3-methylbenzoate), 2,4-pentanediol-bis(4-ethylbenzoate), 2,4-pentanediol-bis(4-n-propylbenzoate), 2,4-pentanediol-bis(4-n-butylbenzoate), 2,4-pentanediol-bis(4-i-propylbenzoate), 2,4-pentanediol-bis(4-i-butylbenzoate), 2,4-pentanediol-bis(4-t-butylbenzoate), 2,4-pentanediol-bis(4-phenylbenzoate), 2,4-pentanediol-bis(3,4-dimethylbenzoate), 2,4-pentanediol-bis(2,4,6-trimethylbenzoate), 2,4-pentanediol-bis(2,6-dimethylbenzoate), 2,4-pentanediol-di-2-naphtoate, 3-methyl-2,4-pentanediol-bis(4-n-propylbenzoate), 3-i-pentyl-2,4-pentanediol-bis(4-n-propylbenzoate), 1,1,1,5,5,5-hexafluoro-2,4-pentanediol-bis(4-ethylbenzoate), 1,1,1-trifluoro-2,4-pentanediol-bis(4-ethylbenzoate), 1,3-bis(4-chlorophenyl)-1,3-propanediol-bis(4-ethylbenzoate), 1-(2,3,4,5,6-pentafluorophenyl)-1,3-butanediol-bis(4-ethylbenzoate), 1,1-difluoro-4-phenyl-2,4-butandiol-bis(4-n-propylbenz oate), 1,1,1-trifluoro-5,5-dimethyl-2,4-hexandiol-bis(4-n-propylbenz oate), 1,1,1-trifluoro-4-(2-furyl)-2,4-butandiol-bis(4-n-propylbenzoate), 1,1,1-trifluoro-4-phenyl-2,4-butandiol-bis(4-n-propylbenz oate), 1,1,1-trifluoro-4-(2-thienyl)-2,4-butandiol-bis(4-n-propylbenzoate), 1,1,1-trifluoro-4-(4-chloro-phenyl)-2,4-butandiol-bis(4-n-propylbenzoate), 1,1,1-trifluoro-4-(2-naphtyl)-2,4-butandiol-bis(4-n-propylbenzoate), 3-chloro-2,4-pentandiol-bis(4-n-propylbenzoate).
The compounds falling in formula (A) can be prepared according to generally available chemical routes such as that described in U.S. Pat. No. 7,388,061.
Very surprisingly it has been found that for the catalyst components of the invention the lower donor/Ti molar ratio does not bring a worsening of the stereospecificity. On the contrary, the activity/stereospecificity balance is substantially improved.
As explained above, the catalyst components of the invention comprise, in addition to the above electron donors, Ti, Mg and halogen. In particular, the catalyst components comprise a titanium compound, having at least a Ti-halogen bond and the above mentioned electron donor compounds supported on a Mg halide. The magnesium halide is preferably MgCl2 in active form which is widely known from the patent literature as a support for Ziegler-Natta catalysts. U.S. Pat. No. 4,298,718 and U.S. Pat. No. 4,495,338 were the first to describe the use of these compounds in Ziegler-Natta catalysis. It is known from these patents that the magnesium dihalides in active form used as support or co-support in components of catalysts for the polymerization of olefins are characterized by X-ray spectra in which the most intense diffraction line that appears in the spectrum of the non-active halide is diminished in intensity and is replaced by a halo whose maximum intensity is displaced towards lower angles relative to that of the more intense line.
The preferred titanium compounds used in the catalyst component of the present invention are TiCl4 and TiCl3; furthermore, also Ti-haloalcoholates of formula Ti(OR)m-yXy can be used, where m is the valence of titanium, y is a number between 1 and m−1, X is halogen and R is a hydrocarbon radical having from 1 to 10 carbon atoms.
The preparation of the solid catalyst component can be carried out according to several methods. One method comprises the reaction between magnesium alcoholates or chloroalcoholates (in particular chloroalcoholates prepared according to U.S. Pat. No. 4,220,554) and an excess of TiCl4 in the presence of the electron donor compounds at a temperature of about 80 to 120° C.
According to a preferred method, the solid catalyst component can be prepared by reacting a titanium compound of formula Ti(OR)m-yXy, where m is the valence of titanium and y is a number between 1 and m, preferably TiCl4, with a magnesium chloride deriving from an adduct of formula MgCl2.pROH, where p is a number between 0.1 and 6, preferably from 2 to 3.5, and R is a hydrocarbon radical having 1-18 carbon atoms. The adduct can be suitably prepared in spherical form by mixing alcohol and magnesium chloride in the presence of an inert hydrocarbon immiscible with the adduct, operating under stirring conditions at the melting temperature of the adduct (100-130° C.). Then, the emulsion is quickly quenched, thereby causing the solidification of the adduct in form of spherical particles. Examples of spherical adducts prepared according to this procedure are described in U.S. Pat. No. 4,399,054 and U.S. Pat. No. 4,469,648. The so obtained adduct can be directly reacted with Ti compound or it can be previously subjected to thermal controlled dealcoholation (80-130° C.) so as to obtain an adduct in which the number of moles of alcohol is generally lower than 3, preferably between 0.1 and 2.5. The reaction with the Ti compound can be carried out by suspending the adduct (dealcoholated or as such) in cold TiCl4 (generally 0° C.); the mixture is heated up to 80-130° C. and kept at this temperature for 0.5-2 hours. The treatment with TiCl4 can be carried out one or more times. The electron donor compound is preferably added during the treatment with TiCl4. The preparation of catalyst components in spherical form are described for example in European Patent Applications EP-A-395083, EP-A-553805, EP-A-553806, EPA601525 and WO98/44001.
The solid catalyst components obtained according to the above method show a surface area (by B.E.T. method) generally between 20 and 500 m2/g and preferably between 50 and 400 m2/g, and a total porosity (by B.E.T. method) higher than 0.2 cm3/g preferably between 0.2 and 0.6 cm3/g. The porosity (Hg method) due to pores with radius up to 10.000 Å generally ranges from 0.3 to 1.5 cm3/g, preferably from 0.45 to 1 cm3/g.
The solid catalyst component has an average particle size ranging from 5 to 120 μm and more preferably from 10 to 100 μm.
In any of these preparation methods the desired electron donor compounds can be added as such or, in an alternative way, it can be obtained in situ by using an appropriate precursor capable to be transformed in the desired electron donor compound by means, for example, of known chemical reactions such as etherification, alkylation, esterification, etc.
Regardless to the preparation method, the final amount of electron donor compounds is such that the molar ratio with respect to the MgCl2 is from 0.01 to 1, preferably from 0.05 to 0.5. The solid catalyst components according to the present invention are converted into catalysts for the polymerization of olefins by reacting them with organoaluminum compounds according to known methods.
In particular, it is an object of the present invention a catalyst for the polymerization of olefins CH2═CHR, in which R is hydrogen or a hydrocarbyl radical with 1-12 carbon atoms, comprising the product obtained by contacting:
(i) the solid catalyst component as disclosed above and
(ii) an alkylaluminum compound.
The alkyl-Al compound (ii) is preferably chosen among the trialkyl aluminum compounds such as for example triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides, such as AlEt2Cl and Al2Et3Cl3, possibly in mixture with the above cited trialkylaluminums.
Suitable external electron-donor compounds include silicon compounds, ethers, esters, amines, heterocyclic compounds and particularly 2,2,6,6-tetramethylpiperidine and ketones. Another class of preferred external donor compounds is that of silicon compounds of formula (R7)a(R8)bSi(OR9)c, where a and b are integers from 0 to 2, c is an integer from 1 to 4 and the sum (a+b+c) is 4; R7, R8, and R9, are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms. Particularly preferred are the silicon compounds in which a is 1, b is 1, c is 2, at least one of R7 and R8 is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms optionally containing heteroatoms and R9 is a C1-C10 alkyl group, in particular methyl. Examples of such preferred silicon compounds are methylcyclohexyldimethoxysilane (C donor), diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane (D donor), (2-ethylpiperidinyl)t-butyldimethoxysilane, (2-ethylpiperidinyl)thexyldimethoxysilane, (3,3,3-trifluoro-n-propyl)(2-ethylpiperidinyl)dimethoxysilane, methyl(3,3,3-trifluoro-n-propyl)dimethoxysilane. Moreover, are also preferred the silicon compounds in which a is 0, c is 3, R8 is a branched alkyl or cycloalkyl group, optionally containing heteroatoms, and R9 is methyl. Examples of such preferred silicon compounds are cyclohexyltrimethoxysilane, t-butyltrimethoxysilane and thexyltrimethoxysilane.
The electron donor compound (iii) is used in such an amount to give a molar ratio between the organoaluminum compound and said electron donor compound (iii) of from 0.1 to 500, preferably from 1 to 300 and more preferably from 3 to 100.
Therefore, it constitutes a further object of the present invention a process for the (co)polymerization of olefins CH2═CHR, in which R is hydrogen or a hydrocarbyl radical with 1-12 carbon atoms, carried out in the presence of a catalyst comprising the product of the reaction between:
(i) the solid catalyst component of the invention;
(ii) an alkylaluminum compound and,
(iii) optionally an electron-donor compound (external donor).
The polymerization process can be carried out according to known techniques for example slurry polymerization using as diluent an inert hydrocarbon solvent, or bulk polymerization using the liquid monomer (for example propylene) as a reaction medium. Moreover, it is possible to carry out the polymerization process in gas-phase operating in one or more fluidized or mechanically agitated bed reactors.
The polymerization is generally carried out at temperature of from 20 to 120° C., preferably of from 40 to 80° C. When the polymerization is carried out in gas-phase the operating pressure is generally between 0.5 and 5 MPa, preferably between 1 and 4 MPa. In the bulk polymerization the operating pressure is generally between 1 and 8 MPa, preferably between 1.5 and 5 MPa.
The following examples are given in order to illustrate the invention without limiting it.
2.5 g of polymer and 250 ml of o-xylene were placed in a round-bottomed flask provided with a cooler and a reflux condenser and kept under nitrogen. The obtained mixture was heated to 135° C. and was kept under stirring for about 60 minutes. The final solution was allowed to cool to 25° C. under continuous stirring, and the insoluble polymer was then filtered. The filtrate was then evaporated in a nitrogen flow at 140° C. to reach a constant weight. The content of said xylene-soluble fraction is expressed as a percentage of the original 2.5 grams and then, by difference, the X.I. %.
The content of electron donor has been carried out via gas-chromatography.
The melt flow rate MIL of the polymer was determined according to ISO 1133 (230° C., 2.16 Kg)
An initial amount of microspheroidal MgCl2.2.8C2H5OH was prepared according to the method described in Example 2 of WO98/44009, but operating on larger scale. This adduct is called Adduct A. This Adduct A was then subject to thermal dealcoholation at increasing temperatures from 30 to 130° C. and operating in nitrogen flow until reaching an alcohol content of 2.1 moles per mol of MgCl2. This adduct is called Adduct B.
Into a 500 ml round bottom flask, equipped with mechanical stirrer, cooler and thermometer 250 ml of TiCl4 were introduced at room temperature under nitrogen atmosphere. After cooling to 0° C., while stirring, the internal donor and 10.0 g of Adduct B were sequentially added into the flask. The amount of charged internal donor was such to obtain a Mg/donor molar ratio of 8. The temperature was raised to 100° C. and maintained for 2 hours. Thereafter, stirring was stopped, the solid product was allowed to settle and the supernatant liquid was siphoned off maintaining the temperature at 100° C. After the supernatant was removed, additional fresh TiCl4 was added to reach the initial liquid volume again. The mixture was then heated at 120° C. and kept at this temperature for 1 hour. Stirring was stopped again, the solid was allowed to settle and the supernatant liquid was siphoned off.
The solid was washed with anhydrous hexane six times (6×100 ml) in temperature gradient down to 60° C. and one time (100 ml) at room temperature. The obtained solid was then dried under vacuum and analyzed. The amount of Ti bonded on the catalyst and the molar ratio between the titanium and electron donor bounded to the catalyst are depicted in Table 1.
A 4-litre steel autoclave equipped with a stirrer, pressure gauge, thermometer, catalyst feeding system, monomer feeding lines and thermostating jacket, was purged with nitrogen flow at 70° C. for one hour. Then, at 30° C. under propylene flow, were charged in sequence with 75 ml of anhydrous hexane, 0.76 g of AlEt3, 0.076 g of dicyclopentyldimethoxysilane (D donor) and 0.006÷0.010 g of solid catalyst component. The autoclave was closed; subsequently 2.0 N1 of hydrogen were added. Then, under stirring, 1.2 kg of liquid propylene was fed. The temperature was raised to 70° C. in five minutes and the polymerization was carried out at this temperature for two hours. At the end of the polymerization, the non-reacted propylene was removed; the polymer was recovered and dried at 70° C. under vacuum for three hours. Then the polymer was weighed and fractionated with o-xylene to determine the amount of the xylene insoluble (X.I.) fraction.
Various donors were used in the preparation of the solid catalyst component, following the description given above. The donors used are listed in Table 1.
The thus obtained solid catalyst components were analyzed for their composition, and were tested in polymerization of propylene, using the method described above. The results are listed in Table 1.
The general procedure for preparation of the solid catalyst component was followed, with the exception that now the 9,9-bis(benzoyloxymethyl)fluorine was fed as internal donor, in such an amount to have Mg/ID molar ratio of 10. The obtained solid catalyst component was analyzed for its composition, and tested in polymerization of propylene, using the method described above. The results are listed in Table 1.
The general procedure for preparation of the solid catalyst component was followed, with the exception that now the 2,4-pentanediol-diheptanoate was fed as internal donor, in such an amount to have Mg/ID molar ratio of 6. The obtained solid catalyst component was analyzed for its composition, and tested in polymerization of propylene, using the method described above. The results are listed in Table 1.
A solid catalyst component was prepared according to the method describe above, with the following changes. The two titanation steps were both carried out at 100° C. The internal donor indicated in Table 1, was now charged in two separate amounts, one amount in every titanation step. Both the additions were such to have a molar ratio Mg/donor of 4. The molar ratio Mg/donor for the total amount of donor fed was thus 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10171999.5 | Aug 2010 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/063447 | 8/4/2011 | WO | 00 | 2/1/2013 |
| Number | Date | Country | |
|---|---|---|---|
| 61401240 | Aug 2010 | US |
