Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F110/04—Monomers containing three or four carbon atoms
  • C08F110/06—Propene

Definitions

• the present invention relates to a propylene polymer having high Melt flow rate and low extractables.
• Propylene polymers have been used for years for obtaining films and molded articles. When used for particular applications such as food packaging and medical tools the value of extractables with solvents is an important parameter in order to evaluate the quality of the material. Two important parameters to be considered are the hexanes extractables according FDA regulations, and xylene solubles at 25°C. From another point of view propylene polymers having high melt flow rate have the drawback to have generally higher value of extractables. Due to process restrictions the polymerization of products with conventional Ziegler/Natta catalysts, high melt flow rates are limited to values of about 400 g/10'. To increase the melt flow rate further, the addition of peroxides is required. Despite the cost disadvantage for the peroxide, additional decomposition residuals from the peroxide have to be considered.
• US 5,741,563 relates to shrink films obtained by using a propylene polymers having a melt flow rate from 0.5 to 30 dg/min and hexane extractables are preferably less than 1% by weight.
• the object of the present invention is a polypropylene resin comprising a propylene polymer endowed with the following characteristics: a) distribution of molecular weight Mw/Mn lower than 4; preferably lower than 3; more preferably lower than 2.5; even more preferably lower than 2.3; b) the melt-viscosity measured at a temperature of 250 0 C in the shear rate range between 1000 1/s and 40000 1/s meet the following relationship: h ⁇ 9 *e (-0.00006* sr)+2 wherein h represents the me It- viscosity in Pas and sr the shear rate in 1/s c) the isotactic pentads (mmmm) measured with 13 C-NMR are higher than 90%; preferably higher than 92%; more preferably higher than 95% even more preferably higher than 96%; d) The hexane extractables determined according FDA regulations (Code of Federal Regulations, Title 21, Volume 3, Revised as of April 1, 2004, CITE: 2 ICFRl 77.1
• the process for visbreaking a polymer consists in increasing the MFR of the latter by lowering the molecular weight of the polymers by means of chemical reactions such as radical reaction initiated by peroxides.
• the polymers obtained in this way presents some drawback, such as an high yellowing index, for this reason the polypropylene resin object of the present invention does not contains residues of peroxidic compounds.
• the propylene polymer of the present invention has a melting point measured by means of DSC higher than 145°C; preferably higher than 148°C, more preferably higher than
• the propylene polymer of the present invention has a melt-viscosity at 250 0 C according the general formula h ⁇ K*e (-L*sr) + M in the shear rate range from 1000 1/s til
• melt-viscosity at a temperature of 250 0 C and a shear rate of 1000 1/s is >1 Pas.
• the propylene polymer of the present invention has preferably a content of 2,1 -insertions lower than 0.5%, more preferred ⁇ 0.3 %. measured by C NMR spectroscopy as described below.
• the content of 1,3 insertions is preferably below 0.2 % , more preferred ⁇ 0.1 %, it is measured by
• the propylene polymer of the polypropylene resin object of the present invention is a propylene homopolymer.
• the polypropylene resin of the present invention preferably further comprises customary amounts of customary additives known to those skilled in the art, e.g. stabilizers, lubricants and mold release agents, fillers, nucleating agents, antistatics, plasticizers, dyes, pigments, anti- fungal, anti-microbial agents, film cavitating agents or flame retardants. In general, these are incorporated during granulation of the powdery product obtained in the polymerization or the powder will be directly coated with the additives.
• customary additives known to those skilled in the art, e.g. stabilizers, lubricants and mold release agents, fillers, nucleating agents, antistatics, plasticizers, dyes, pigments, anti- fungal, anti-microbial agents, film cavitating agents or flame retardants.
• additives e.g. stabilizers, lubricants and mold release agents, fillers, nucleating agents, antistatics, plasticizers, dyes, pigments, anti- fungal, anti-microbial agents
• Customary stabilizers include antioxidants such as sterically hindered phenols, sterically hindered amines or UV stabilizers, processing stabilizers such as phosphites or phosphonites, acid scavengers such as calcium stearate or zinc stearate or dihydrotalcite, as well as calcium, zinc and sodium caprylate salts.
• the propylene copolymer compositions of the present invention contain one or more stabilizers in amounts of up to 2% by weight.
• Suitable lubricants and mold release agents are, for example, fatty acids, calcium, sodium or zinc salts of fatty acids, fatty acid amides or low molecular weight polyolefm waxes, which are usually used in concentrations of up to 2% by weight.
• Possible fillers are, for example, talc, calcium carbonate, chalk or glass fibers, and these are usually used in amounts of up to 50% by weight.
• nucleating agents examples include inorganic additives such as talc, silica or kaolin, salts of monocarboxylic or polycarboxylic acids, e.g. sodium benzoate or aluminum tert- butylbenzoate, dibenzylidenesorbitol or its Ci-Cs-alkyl-substituted derivatives such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol or salts of diesters of phosphoric acid, e.g. sodium 2,2'-methylenebis(4,6,-di-tert- butylphenyl)phosphate.
• the nucleating agent content of the propylene copolymer composition is generally up to 5% by weight.
• the propylene polymer compositions of the present invention contain a 1 :1 mixture of sterically hindered phenols and phosphites or phosphonites.
• the content of this mixtures ranges from 0.03% to 1% by weight, preferably from 0.05 to 0.2500% by weight and more preferred from 0.1 to 0.2% by weight ( tradename of such products are Irganox B 50 IW from Ciba Specialty Chemical).
• the polypropylene resin object of the present invention can be used in many applications, such as in compounding as masterbatchses and melt blown applications, for example hygienic fabrics and filtration applications.
• the propylene polymer of the polypropylene resin object of the present invention can be obtained by using a metallocene -based catalyst system.
• propylene polymer is obtainable by using a catalyst system obtainable by contacting: a) a metallocene compound of formula (I)
• M is a transition metal belonging to group 3, 4, 5, 6 or to the lanthanide or actinide groups in the Periodic Table of the Elements; preferably M is titanium, zirconium or hafnium;
• X is a hydrogen atom, a halogen atom, or a R, OR, OSO 2 CF 3 , OCOR, SR, NR 2 or PR 2 group, wherein R is a are linear or branched, cyclic or acyclic, Ci-C 4 o-alkyl, C 2 -C 4 0 alkenyl, C 2 -C 4 0 alkynyl, C6-C 4 o-aryl, C7-C 4 o-alkylaryl or C7-C 4 o-arylalkyl radicals; optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R is a linear or branched Ci-C 2 o-alkyl radical; or two X can optionally form a substituted or unsubstituted butadienyl radical or a OR O group wherein R is a divalent radical selected from C1-C40 alkylidene, C6-C
• L is a divalent C 1 -C 40 hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements or a divalent silylidene radical containing up to 5 silicon atom; preferably L is a divalent bridging group selected from C1-C40 alkylidene, C3-C40 cycloalkylidene, C6-C40 arylidene, C7-C40 alkylarylidene, or C7-C 4 0 arylalkylidene radicals optionally containing heteroatoms belonging to groups 13- 17 of the Periodic Table of the Elements, and silyliene radical containing up to 5 silicon atoms such as SiMe 2 , SiPh 2 ; preferably L is a group (Z(R") 2 ) n wherein Z is a carbon or a silicon atom, n is 1 or 2 and R" is a C 1 -C 2 0 hydrocarbon radical optionally containing heteroatoms belonging to groups 13
• R and R are a C 1 -C 4 0 hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R 1 and R 5 are linear or branched, cyclic or acyclic, Ci-C 4 o-alkyl, C 2 -C 4 0 alkenyl, C 2 -C 4 0 alkynyl, C 6 -C 4 o-aryl, C 7 -C 4 o-alkylaryl or C 7 -C 4 o-arylalkyl radicals; optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; more preferably R and R are a linear or branched, saturated or unsaturated Ci-C 2 o-alkyl radical;
• R , R and R are hydrogen atoms or C 1 -C 4 0 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R 2 , R 3 and R 4 , equal to or different from each other are hydrogen atoms or linear or branched, cyclic or acyclic, Ci-C 4 o-alkyl, C 2 -C 4 0 alkenyl, C 2 -C 40 alkynyl, C 6 -C 4 o-aryl, C 7 -C 4 o-alkylaryl or C 7 -C 4 o-arylalkyl radical; optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; more preferably R 2 , R 3 and R 4 are hydrogen atoms or Ci-C 2 o-alkyl radicals; R 6 , R 7 , R 8 , R 9 , and R 10 equal to or different from each other,
• the substituent R is a linear Ci-C 2 o-alkyl radical such as methyl or ethyl radicals and the substituent R is a branched Ci-C 2 o-alkyl radical, preferably the substituent R is a branched Ci-C 2 o-alkyl radical wherein the carbon atom in the alpha position is a secondary or a tertiary carbon atom, such as an isopropyl radical.
• Alumoxanes used as component b) in the catalyst system according to the present invention can be obtained by reacting water with an organo-aluminium compound of formula H j AlU3_ j or H j Al 2 Ue -) , where the U substituents, same or different, are hydrogen atoms, halogen atoms, Ci-C2o-alkyl, C3- C 20 -cyclalkyl, Co-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radicals, optionally containing silicon or germanium atoms, with the proviso that at least one U is different from halogen, and j ranges from 0 to 1 , being also a non-integer number.
• the molar ratio of Al/water is preferably comprised between 1:1 and 100:1.
• alumoxanes used in the process according to the invention are considered to be linear, branched or cyclic compounds containing at least one group of the type:
• alumoxanes of the formula can be used in the case of linear compounds, wherein n 1 is 0 or an integer of from 1 to 40 and the substituents U are defined as above; or alumoxanes of the formula:
• n 2 can be used in the case of cyclic compounds, wherein n 2 is an integer from 2 to 40 and the U substituents are defined as above.
• alumoxanes suitable for use according to the present invention are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO), tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO), tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) and tetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).
• MAO methylalumoxane
• TIBAO tetra-(isobutyl)alumoxane
• TIOAO tetra-(2,4,4-trimethyl-pentyl)alumoxane
• TDMBAO tetra-(2,3-dimethylbutyl)alumoxane
• TTMBAO tetra-(2,3,3-trimethylbutyl)alumox
• Non-limiting examples of aluminium compounds that can be reacted with water to give suitable alumoxanes (b), described in WO 99/21899 and WO01/21674, are: tris(2,3,3-trimethyl-butyl)aluminium, tris(2,3-dimethyl-hexyl)aluminium, tris(2,3-dimethyl- butyl)aluminium, tris(2,3-dimethyl-pentyl)aluminium, tris(2,3-dimethyl-heptyl)aluminium, tris(2 -methyl-3 -ethyl-pentyl)aluminium, tris(2 -methyl-3 -ethyl-hexyl)aluminium, tris(2 -methyl-3 - ethyl-heptyl)aluminium, tris(2-methyl-3-propyl-hexyl)aluminium, tris(2-ethyl-3-methyl-
• TMA trimethylaluminium
• TMA triisobutylaluminium
• TIBA tris(2,4,4-trimethyl-pentyl)aluminium
• TDMBA tris(2,3-dimethylbutyl)aluminium
• TTMBA tris(2,3,3-trimethylbutyl)aluminium
• Non-limiting examples of compounds able to form an alkylmetallocene cation are compounds of formula D + E " , wherein D + is a Br ⁇ nsted acid, able to donate a proton and to react irreversibly with a substituent X of the metallocene of formula (I) and E " is a compatible anion, which is able to stabilize the active catalytic species originating from the reaction of the two compounds, and which is sufficiently labile to be removed by an olefinic monomer.
• the anion E " comprises one or more boron atoms.
• the anion E " is an anion of the formula BAr 4 ⁇ , wherein the substituents Ar which can be identical or different are aryl radicals such as phenyl, pentafluorophenyl or bis(trifluoromethyl)phenyl. Tetrakis-pentafluorophenyl borate is particularly preferred compound, as described in WO 91/02012.
• compounds of formula BAr 3 can be conveniently used. Compounds of this type are described, for example, in the International patent application WO 92/00333.
• Other examples of compounds able to form an alkylmetallocene cation are compounds of formula BAr 3 P wherein P is a substituted or unsubstituted pyrrol radical.
• Non limiting examples of compounds of formula D + E " are:
• Tripropylammoniumtetra(dimethylphenyl)borate Tributylammoniumtetra(trifluoromethylphenyl)borate
• Triphenylcarbeniumtetrakis(pentafluorophenyl)borate Triphenylcarbeniumtetrakis(pentafluorophenyl)borate
• Organic aluminum compounds used as compound c) are those of formula H J A1U 3 _ J or H j Al 2 Ue -) as described above.
• the catalysts described above can also be supported on an inert carrier. This is achieved by depositing the metallocene compound a) or the product of the reaction thereof with the component b), or the component b) and then the metallocene compound a) on an inert support such as, for example, silica, alumina, Al-Si, Al-Mg mixed oxides, magnesium halides, styrene/divinylbenzene copolymers, polyethylene or polypropylene.
• an inert support such as, for example, silica, alumina, Al-Si, Al-Mg mixed oxides, magnesium halides, styrene/divinylbenzene copolymers, polyethylene or polypropylene.
• the supportation process is carried out in an inert solvent such as hydrocarbon for example toluene, hexane, pentane or propane and at a temperature ranging from 0 0 C to 100 0 C, preferably the process is carried out at room temperature.
• an inert solvent such as hydrocarbon for example toluene, hexane, pentane or propane
• a suitable class of supports which can be used is that constituted by porous organic supports functionalized with groups having active hydrogen atoms. Particularly suitable are those in which the organic support is a partially crosslinked styrene polymer. Supports of this type are described in European application EP-633 272.
• inert supports particularly suitable for use according to the invention is that of polyolefm porous prepolymers, particularly polyethylene.
• a further suitable class of inert supports for use according to the invention is that of porous magnesium halides such as those described in International application WO 95/32995.
• the solid compound thus obtained, in combination with the further addition of the alkylaluminium compound either as such or prereacted with water if necessary, can be usefully employed in the gas- phase polymerization.
• Molecular weights and molecular weight distribution were measured at 145°C using a Alliance GPCV 2000 instrument (Waters) equipped with three mixed-bed columns TosoHaas TSK GMHXL-HT having a particle size of 13 ⁇ m. The dimensions of the columns were 300 x 7.8 mm.
• the mobile phase used was vacuum distilled 1,2,4-Trichlorobenzene (TCB) and the flow rate was kept at 1.0 ml/min.
• the sample solution was prepared by heating the sample under stirring at 145°C in TCB for two hours. The concentration was 1 mg/ml. To prevent degradation,
• a third order polynomial fit was used for interpolate the experimental data and obtain the calibration curve.
• Data acquisition and processing was done by using Empower 1.0 with GPCV option by Waters.
• Intrinsic viscosity was measured in tetrahydronaphtalene (THN) solution obtained by dissolving the polymer at 135°C for 1 hour.
• the ISO norm describes the procedure of measuring the MFR values til 150 g/10'.
• the mmmm content was obtained modelling the experimental pentad distribution with the enantiomorphic site model.
• [H] 100 (0.5 H 2 / ⁇ [CH2]) where E 9 is the peak at 42.14 ppm, H2 is the peak at 30.82 ppm and ⁇ [CH2] is the sum of all
• the catalyst system is prepared as described in PCT/EP2004/007061 by using rac- dimethylsilylene(2-methyl-4(4'tertbutyl-penhyl)-indenyl) (2-isopropyl-4(4'tertbutyl-penhyl)- indenyl)zirconium di chloride prepared as described in US 2003/0149199 instead of rac- dimethylsilylbis(2-methyl-4, 5-benzo-indenyl)-zirconium dichloride.
• the catalyst system in the form of catalyst mud obtained as described in PCT/EP2004/007061 is fed in the precontact vessel in which it is diluted with about 5 (Kg/h) of propane. From the pre- contact vessel the catalyst system is fed to the prepolymerization loop in which propylene is fed at the same time according to the data reported in table 1. The residence time of the catalyst in the prepolymerization loop is 8 minutes. The prepolymerized catalyst obtained in the prepolymerization loop is then continuously feed into the first loop reactor in which propylene, is fed according to table 1. The polymer is discharged from the first loop reactor, separated from the unreacted monomer and dried. The reaction conditions are reported in table 1. The MFR of the product is controlled by the feed of hydrogen.
• melt-viscosity was determined according ISO 11443 at three different temperatures (200 0 C; 230 0 C and 250 0 C). The results are reported in tables 3-
• Comparative example 4 was polymerized according Example 1 -3 with the polymerization conditions reported in table 6.

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• 2006
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