Polypropylene composition for non-pressurized pipes

Abstract

The invention relates to a polypropylene composition comprising a propylene homopolymer or propylene-ethylene copolymer having an ethylene content of at most (1.0) wt % based on the propylene-ethylene copolymer, wherein the amount of propylene homopolymer or propylene-ethylene copolymer is at least (98) wt %, for example at least (98.5) wt %, preferably at least (99) wt %, more preferably at least (99.5), for example at least (99.75) wt % based on the polypropylene composition, wherein the polypropylene composition has a melt flow rate in the range of (0.10) to less than (0.70) dg/min as measured according to ISO1133 (2.16 kg/230° C.), an Mw/Mn in the range from (7.0) to (13.0), wherein Mw stands for the weight average molecular weight and Mn stands for the number average weight, an Mz/Mn is in the range from (20) to (50), wherein Mz stands for the z-average molecular weight and wherein Mw, Mn and Mz are measured according to ASTM (D6474-12).

Claims

1. Polypropylene composition comprising a propylene homopolymer or propylene-ethylene copolymer having an ethylene content of at most 1.0 wt % based on the propylene-ethylene copolymer, wherein the amount of propylene homopolymer or propylene-ethylene copolymer is at least 98 wt %, based on the polypropylene composition wherein the polypropylene composition has a melt flow rate in the range of 0.10 to less than 0.70 dg/min as measured according to ISO1133 (2.16 kg/230° C.); an Mw/Mn in the range from 7.0 to 13.0, wherein Mw stands for the weight average molecular weight and Mn stands for the number average weight; and an Mz/Mn is in the range from 20 to 50, wherein Mz stands for the z-average molecular weight; and wherein Mw, Mn and Mz are measured according to ASTM D6474-12.

2. Polypropylene composition according to claim 1 having a melt flow rate in the range of 0.20 to 0.50 dg/min, as measured according to ISO1133 (2.16 kg/230° C.).

3. Polypropylene composition according to claim 1, wherein the composition has an amount of xylene soluble amount (XS) as measured according to ASTM D 5492-10 in the range from 0.5 to 3.5 wt %.

4. Polypropylene composition according to claim 1, wherein the composition has a pentad isotacticity of at least 94% based on the composition, wherein the isotacticity is determined using .sup.13C NMR.

5. Polypropylene composition according to claim 1, wherein the composition is unimodal.

6. Polypropylene composition according to claim 1, further comprising additives, and wherein sum of the amount of additives and the amount of propylene homopolymer or propylene-ethylene copolymer is 100 wt % based on the polypropylene composition.

7. Polypropylene composition according to claim 1 having a flexural modulus in parallel orientation of at least 1800 MPa, as measured according to ASTM D790-10.

8. Polypropylene composition according to claim 1 having has an Izod notched impact strength in parallel orientation of at least 2.5, as measured at 23° C. according to ISO 180 4A.

9. Polypropylene composition according to claim 1, wherein the Mz/Mw of the polypropylene composition is in the range from 2.7 to 4.5.

10. Pipe comprising the polypropylene composition of claim 1.

11. Process for the preparation of the pipes of claim 10 comprising the step of providing the polypropylene composition.

12. Process for the preparation of the polypropylene composition of claim 1, comprising the step of: polymerizing propylene and optional ethylene comonomers in the presence of a catalyst, to obtain the propylene homopolymer or the propylene-ethylene copolymer, wherein said catalyst is obtainable by a process comprising the steps of A) providing a Ziegler-Natta procatalyst, wherein step (A) of providing the Ziegler-Natta procatalyst comprises the steps of contacting a magnesium-containing support with i) a halogen-containing titanium compound, ii) ethylbenzoate as an activator, iii) and as internal donor an aminobenzoate compound according to formula B: ##STR00002## wherein each R.sup.90 group is independently a substituted or unsubstituted aromatic group; R.sup.91, R.sup.92, R.sup.93, R.sup.94, R.sup.95, and R.sup.96 are each independently selected from a hydrogen or a linear, branched or cyclic hydrocarbyl group, selected from alkyl, alkenyl, aryl, aralkyl, or alkylaryl groups, and one or more combinations thereof; R.sup.97 is a hydrogen or a linear, branched or cyclic hydrocarbyl group, selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; N is a nitrogen atom; O is an oxygen atom; and C is a carbon atom; and B) contacting said Ziegler-Natta procatalyst obtained in step A) with a co-catalyst and at least one external electron donor to obtain said catalyst.

13. Process according to claim 12, wherein as external donor in step B) a phthalate free donor is used.

14. Process according to claim 11, wherein step A) to provide the Ziegler-Natta procatalyst comprises the following steps: i) contacting a compound R.sup.4.sub.zMgX.sup.4.sub.2-z with an alkoxy- or aryloxy-containing silane compound to give a first intermediate reaction product, being a solid Mg(OR.sup.1).sub.xX.sup.1.sub.2-x, wherein: R.sup.4 and R.sup.1 are each a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms; X.sup.4 and X.sup.1 are each independently selected from the group of consisting of fluoride (F—), chloride (Cl—), bromide (Br—) or iodide (I—); z is in a range of larger than 0 and smaller than 2, being 0<z<2, x is in a range of larger than 0 and smaller than 2, being 0<x<2; ii) optionally contacting the solid Mg(OR.sup.1).sub.xX.sup.1.sub.2-x obtained in step ii) with at least one activating compound selected from the group formed of activating electron donors and metal alkoxide compounds of formula M.sup.1(OR.sup.2).sub.v-w(OR.sup.3).sub.w or M.sup.2(OR.sup.2).sub.v-w(R.sup.3).sub.w, to obtain a second intermediate product; wherein M.sup.1 is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; M.sup.2 is a metal being Si; v is the valency of M.sup.1 or M.sup.2 and is either 3 or 4; w<v; R.sup.2 and R.sup.3 are each a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms; and iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or ii), with the halogen-containing Ti-compound; the activator; and the internal electron donor to obtain said Ziegler-Natta procatalyst.

15. Process according to claim 13, wherein the external donor in step B) comprises di(isopropyl) dimethoxysilane.

Description

EXAMPLES

Example 1

(1) Step A) Butyl Grignard Formation

(2) A 1.7 L stirred flask, fitted with a reflux condenser and a funnel, was filled with magnesium powder (40.0 g, 1.65 mol). The flask was brought under nitrogen. The magnesium was dried at 80° C. for 2 hours under nitrogen purge, after which dibutyl ether (200 ml), iodine (0.05 g) and n-chlorobutane (10 ml) were successively added and stirred at 120 rpm. The temperature was maintained at 80° C. and a mixture of n-chlorobutane (146 ml) and dibutyl ether (1180 ml) was slowly added over 3 hours. The reaction mixture was stirred for another 3 hours at 80° C. Then the stirring and heating were stopped and the small amount of solid material was allowed to settle for 24 hours. By decanting the colourless solution above the precipitate, a solution of butylmagnesiumchloride with a concentration of 0.90 mol Mg/L was obtained.

(3) Step B) Preparation of the First Intermediate Reaction Product

(4) The solution of reaction product of step A (500 ml, 0.45 mol Mg) and 260 ml of a solution of tetraethoxysilane (TES) in dibutyl ether (DBE), (47 ml of TES and 213 ml of DBE), were cooled to 5° C., and then were fed simultaneously to a mixing device (minimixer) of 0.45 ml volume equipped with a stirrer and jacket. The minimixer was cooled to 5° C. by means of cold water circulating in the minimixer's jacket. The stirring speed in the minimixer was 1000 rpm. From the mixing device, the mixed components were directly dosed into a 1.3 liter reactor fitted with blade stirrer and containing 350 ml of dibutyl ether. The dosing temperature of the reactor was 35° C. and the dosing time was 360 min. The stirring speed in the reactor was 250 rpm at the beginning of dosing and was gradually increased up to 450 rpm at the end of dosing stage. On completion of the dosing, the reaction mixture was heated up to 60° C. in 30 minutes and held at this temperature for 1 hour. Then the stirring was stopped and the solid substance was allowed to settle. The supernatant was removed by decanting. The solid substance was washed three times using with 700 ml of heptane at a reactor temperature of 50° C. for three times. A pale yellow solid substance, reaction product B (the solid first intermediate reaction product; the support), was obtained upon drying with a nitrogen purge. The average particle size of support was 20 microns.

(5) Step C) Preparation of the Second Intermediate Reaction Product

(6) In inert nitrogen atmosphere at 20° C. in a 1000 ml glass flask equipped with a mechanical agitator was filled with 50 g of reaction product B, dispersed in 500 ml of heptane and stirred at 250 rpm. Subsequently, a solution of 2.7 ml ethanol (EtOH/Mg=0.1) in 20 ml heptane was dosed under stirring during 1 hour. After keeping the reaction mixture at 20° C. for 30 minutes, a solution of 9.5 ml titanium tetraethoxide (TET/Mg=0.1) in 20 ml of heptane was added for 1 hour. The slurry was slowly allowed to warm up to 30° C. over 30 minutes and held at that temperature for another 2 hours.

(7) Finally, the supernatant liquid was decanted from the solid reaction product (the second intermediate reaction product C; first activated support) which was washed once with 500 ml of heptane at 30° C. and dried using a nitrogen purge.

(8) Step D) Preparation of the Third Intermediate Reaction Product

(9) In inert nitrogen atmosphere at 25° C. in a 1000 ml glass flask equipped with a mechanical agitator was filled with 50 g of second intermediate reaction product C dispersed in 500 ml of heptane and stirred at 250 rpm. Subsequently, a solution of 6.3 ml ethanol (EtOH/Mg=0.3), 20.8 ml of toluene and 37.5 ml of heptane was dosed at 25° C. under stirring during 1 hour. The slurry was slowly allowed to warm up to 30° C. over 30 minutes and held at that temperature for another 3 hours. Finally, the supernatant liquid was decanted from the solid reaction product (the third intermediate reaction product D; second activated support) which was washed once with 500 ml of heptane at 25° C. and dried using a nitrogen purge.

Preparation of the Catalyst H

(10) Steps A-D) are carried out as in Example 1. Step E) is carried out as follows.

(11) A 300 ml reactor-filter flask was brought under nitrogen and 125 mL of titanium tetrachloride was added, then 5.5 g of second activated support in 15 ml of heptane was added to the reactor. The contents of the reactor were stirred for 60 minutes at room 25° C. Then, 1.78 ml of ethylbenzoate, EB (EB/Mg=0.30 molar ratio) in 4 ml of chlorobenzene was added to the reactor in 30 minutes. Temperature of reaction mixture was increased to 115° C. and then the reaction mixture was stirred at 115° C. for 90 minutes (I stage of catalyst preparation). The contents of the flask were filtered, after which the solid product was washed with chlorobenzene (125 ml) at 100 to 105° C. for 20 minutes. Then, the contents of the flask were filtered. A mixture of titanium tetrachloride (62.5 ml) and chlorobenzene (62.5 ml) was added to the reactor. The reaction mixture was stirred at 115° C. for 60 minutes (II stage of catalyst preparation). Then, the contents of the flask were filtered. A mixture of titanium tetrachloride (62.5 ml) and chlorobenzene (62.5 ml) was added to the reactor. Then, 0.51 g of 4-[benzoyl(methyl)amino]pentan-yl benzoate (AB/Mg=0.04) in 4 ml of chlorobenzene was added to the reactor in 10 minutes. The reaction mixture was stirred at 115° C. for 30 minutes (III stage of catalyst preparation). Then, the contents of the flask were filtered. A mixture of titanium tetrachloride (62.5 ml) and chlorobenzene (62.5 ml) was added to the reactor. The reaction mixture was stirred at 115° C. for 30 minutes (IV stage of catalyst preparation). Then, the contents of the flask were filtered. The solid product obtained was washed five times with 125 ml of heptane starting at 60° C. with 5 minutes stirring per wash prior to filtration. The temperature was gradually reduced from 60 to 25° C. during the washings. Finally, the solid product obtained was dried using a nitrogen purge at a temperature of 25° C. for 2 hours. The composition of the solid catalyst H produced is given in Table 1.

(12) TABLE-US-00001 TABLE 1 Composition of solid catalyst H d50 Mg Ti ID Activator (EB) EtO Catalyst Example [μm] [%] [%] [%] [%] [%] H 8 22.16 19.65 2.40 8.41 6.68 1.48

(13) Catalyst CE

(14) Catalyst CE is prepared according to the method disclosed in U.S. Pat. No. 4,866,022, hereby incorporated by reference. This patent discloses a catalyst component comprising a product obtained by: (a) forming a solution of a magnesium-containing species from a magnesium carbonate or a magnesium carboxylate; (b) precipitating solid particles from such magnesium-containing solution by treatment with a transition metal halide and an organosilane having a formula: R.sub.nSiR′.sub.4-n, wherein n=0 to 4 and wherein R is hydrogen or an alkyl, a haloalkyl or aryl radical containing one to about ten carbon atoms or a halosilyl radical or haloalkylsilyl radical containing one to about eight carbon atoms, and R′ is OR or a halogen; (c) reprecipitating such solid particles from a mixture containing a cyclic ether; and (d) treating the reprecipitated particles with a transition metal compound and an electron donor. This process for preparing a catalyst is incorporated into the present application by reference.

(15) The process was performed in one horizontally stirred gas-phase reactor with downstream powder processing units (=degassing & catalyst deactivation) for powder collection.

(16) The reactor was operated at an average of 70° C. at 25 bar. H2/C3 ratios in both reactors were controlled such to obtain a powder having the desired melt flow rate (MFR).

(17) The catalyst was dosed through a nozzle to the reactor. Cocatalyst (triethylaluminium, TEN) and External Donor (DIPDMS or DiBDMS) were dosed via a separate nozzle to the reactor (as a premixed mixture) and in ratio to the catalyst flow.

(18) The process conditions as given in Table 2 were used:

(19) TABLE-US-00002 TABLE 2 Process conditions. Al/Mg Al/Si Si/Ti H.sub.2/C.sub.3 (mol/ (mol/ (mol/ (mol/ catalyst donor mol) mol) mol) mol) Example 1 H DiPDMS 4 7 7.8 0.056 Comparative CE DiBDMS 4 14 3.9 0.0003 example 1 (CE1) DiPDMS: di-(isopropyl)-dimethoxysilane DiBDMS: di(isobutyl)-dimethoxysilane

(20) The powder was collected and granulate was prepared by melt-mixing the powder with the appropriate additives in a single screw extruder. The additives (antioxidants, acid scavengers) were used in an amount of 1400 ppm based on the powder and mixed prior to dosing to the extruder. The temperature profile in the extruder was 20-20-30-50-100-170-220-220-240° C., at a throughput of 13 kg/h at 200 rpm.

Preparation of the Pipe

(21) A pipe with a diameter of 32 mm a 3.0 mm thickness was prepared by extrusion in a Reifenhauser S50 I with a barrier screw operated at 35 rpm. The die head temperature profile was set to 40/190/200/205/205° C. and temperature profile of the extruder was set to 205/205/205/205° C. The extruded pipes were cooled to a temperature of 20° C. The pressure sensor to measure the ‘melt pressure’ (indicated in the table below) was located in between the extruder and the die head.

(22) Methods

(23) All of the below properties were measured on the granulate.

(24) Mz, Mn, Mw

(25) Mw, Mn and Mz were all measured in accordance with ASTM D6474-12 (Standard Test Method for Determining Molecular Weight Distribution and Molecular Weight Averages of Polyolefins by High Temperature Gel Permeation Chromatography). Mw stands for the weight average molecular weight and Mn stands for the number average weight. Mz stands for the z-average molecular weight.

(26) In addition to the method specified by ASTM D6474-12, the method was performed using a configuration in which a Polymer Char 1R5 infrared concentration detector and a Polymer Char online viscosity detector was used to gain ‘absolute’ or accurate molar masses. Three columns of Polymer Laboratories 13 μm PLgel Olexis, 300×7.5 mm were used in series with 1,2,4-trichlorobenzene stabilized with 1 g/L butylhydroxytoluene (also known as 2,6-di-tert-butyl-4-methylphenol or BHT) as eluens. The molar mass was determined based on a calibration using linear PE standards (narrow and broad (Mw/Mn=4 to 15)) in the range of 0.5-2800 kg/mol. Samples of polymer granules were mixed with Tris (2,4-di-tert-butylphenyl)phosphite (Irgafos 168) and 1,1,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl)butane (Topanol CA) in a weight ratio sample: Irgafos:Topanol of 1:1:1, after which the mixture thus obtained was dissolved in 1,2,4-trichlorobenzene stabilized with 1 g/L BHT until the concentration of the mixture in 1,2,3-trichlorobenzene stabilized with 1 g/L BHT was 0.03 wt %.

(27) Xylene Solubles (XS) XS, wt % is xylene solubles, measured according to ASTM D 5492-10. 1 gram of polymer and 100 ml of xylene are introduced in a glass flask equipped with a magnetic stirrer. The temperature is raised up to the boiling point of the solvent. The so obtained clear solution is then kept under reflux and stirring for further 15 min. Heating is stopped and the isolating plate between heating and flask is removed. Cooling takes places with stirring for 5 min. The closed flask is then kept for 30 min in a thermostatic water bath at 25° C. for 30 min. The so formed solid is filtered on filtering paper. 25 ml of the filtered liquid is poured in a previously weighed aluminium container, which is heated in a stove of 140° C. for at least 2 hours, under nitrogen flow and vacuum, to remove the solvent by evaporation. The container is then kept in an oven at 140° C. under vacuum until constant weight is obtained. The weight percentage of polymer soluble in xylene at room temperature is then calculated.

(28) Pentad Isotacticity

(29) 175 mg of the polypropylene granules was dissolved in 3 ml at 130° C. in deuterated tetrachloroethylene (C.sub.2D.sub.2Cl.sub.4) containing 2,6-Di-tert-butyl-4-methylphenol (BHT) (5 mg BHT in 200 ml C.sub.2D.sub.2Cl.sub.4). The .sup.13C NMR spectrum was recorded on a Bruker Avance 500 spectrometer equipped with a cryogenically cooled probe head operating at 125° C.

(30) The isotacticity of the mmmm pentad levels was determined from the .sup.13C NMR spectrum in % based on the total pentad amount.

(31) Melt Flow Rate (MFR)

(32) For purpose of the invention the melt flow rate is the melt flow rate as measured according to ISO1133 (2.16 kg/230° C.).

(33) Tm and Tc Measurement

(34) The crystallization temperature, the crystallinity and the melting temperature are measured according to ASTM D3418-08 at a heating rate of 10° C./min in DSC. The sample is heated up to 200° C. (first heating) and then cooled at a cooling rate 10° C./min of (to measure the crystallization temperature Tc) and then heated a second time at a heating rate of 10° C./min (second heating) to measure the melting temperature (Tm). For the determination of Tc and Tm, a 5 mg polymer sample was measured.

(35) Flex. Modulus (Parallel Orientation).

(36) For purpose of the present invention, stiffness of the granulate is determined by measuring the flexural modulus according to ASTM D790-10. Flexural modulus was determined on 3.2 mm thick specimens according to ISO37/2, parallel orientation.

(37) Izod Notched Impact Strength (Parallel Orientation)

(38) For purpose of the present invention, impact strength is determined by measuring the Izod notched impact strength of the granulate at 23° C. according to ISO 180 4A, Test geometry: 65*12.7*3.2 mm, notch 45° according to ISO 37/2 parallel orientation.

(39) TABLE-US-00003 TABLE 3 Results example IE1 CE1 Mw (kDa) 600 560 Mn (kDa) 75 99 Mz (kDa) 1800 1400 Mz/Mw 2.9 2.5 Mz/Mn 24.0 14.1 MWD = Mw/Mn 9.3 5.7 XS (wt %) 2.6 2.9 Pentad isotacticity (%) 96.0 94.4 Tm (2.sup.nd heating), (°C.) 163.9 161.9 Tc (2.sup.nd cooling), °C. 114.1 114.3 MFR (g/10 min) 0.46 0.29 properties flex modulus (parallel orientation) 2002 1790 (MPa) Izod notched Impact strength 4.49 5.14 (parallel orientation) (kJ/m.sup.2) Melt pressure (kPa/cm.sup.2) 109 134

CONCLUSION

(40) As can be seen from Table 3, the polypropylene compositions of the invention show a have a higher stiffness and maintain their impact strength, which allows for the preparation of pipes with an increased stiffness and may for example increase ring stiffness.

(41) In addition, the lower melt pressure indicates that the pipes may be extruded at higher speeds, which the pipes can be produced with a higher throughput. The lower melt pressure also indicates that the pipes may be produced using less energy.

(42) In particular, when a phthalate free external donor is used (as in IE1 of the examples and not in CE1), this has the advantage that undesired phthalates (in for example a sewage pipe) will not end up in the environment. For water purification plants, this may mean that less (difficult) purification of the water is needed.