C.SUB.2.C.SUB.3 .random copolymer composition

Abstract

New C2C3 random copolymer composition, which shows improved sealing behaviour due to low sealing initiation temperature (SIT) and high hot tack force. In addition, the inventive composition shows an excellent sterilization behaviour, i.e. retention of low haze level after sterilization. The present invention is furthermore related to the manufacture of said copolymer composition and to its use.

Claims

1. A C.sub.2C.sub.3 random copolymer composition comprising (A) 70.0 to 99.9 wt % of a C.sub.2C.sub.3 random copolymer having (a) an ethylene content in a range of from 2.0 to 4.8 wt %; (b) a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in a range of from 4.0 to 12.0 g/10 min; (c) a melting temperature Tm as determined by DSC according to ISO 11357 of from 120 to 135° C.; and (d) a xylene cold soluble (XCS) fraction below 10.0 wt %; wherein the C.sub.2C.sub.3 random copolymer (A) comprises: 30.0 to 70.0 wt % of polymer fraction (A-1) having (i) an ethylene content in the range of from 1.5 to 3.5 wt %, and (ii) a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in the range of 4.0 to 12.0 g/10 min and 70.0 to 30.0 wt % of polymer fraction (A-2) having (i) an ethylene content in the range of from 3.6 to 6.0 wt % and (ii) a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in the range of from 4.0 to 12.0 g/10 min; (B) 0.0 to 30.0 wt % of an ethylene-α-olefin plastomer having a density in a range of from 860 to 900 kg/m.sup.3 and an MFR.sub.2 (190° C./2.16 kg) measured according to ISO 1133 in a range of 0.5 to 50.0 g/10 min, and (C) one or more additives in a total amount of from 0.1 up to 5.0 wt %, based on the composition, comprising slip agents, anti-block agents, UV stabilizers, antistatic agents, alpha-nucleating agents and antioxidants.

2. The C.sub.2C.sub.3 random copolymer composition according to claim 1, wherein ethylene-α-olefin plastomer (B) is a copolymer of ethylene and a C.sub.4-C.sub.10 alpha olefin with a melting point in a range of from 33 to 115° C.

3. The C.sub.2C.sub.3 random copolymer composition according to claim 1, wherein the C.sub.2C.sub.3 random copolymer (A) is obtainable, preferably obtained in the presence of a metallocene catalyst.

4. A process comprising preparing articles with the C.sub.2C.sub.3 random copolymer composition according to claim 1.

5. A sterilizable or sterilized article comprising a C.sub.2C.sub.3 random copolymer composition comprising (A) 70.0 to 99.9 wt % of a C.sub.2C.sub.3 random copolymer having (a) an ethylene content in a range of from 2.0 to 4.8 wt %; (b) a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in a range of from 4.0 to 12.0 g/10 min; (c) a melting temperature Tm as determined by DSC according to ISO 11357 of from 120 to 135° C.; and (d) a xylene cold soluble (XCS) fraction below 10.0 wt %; (B) 0.0 to 30.0 wt % of an ethylene-α-olefin plastomer having a density in a range of from 860 to 900 kg/m.sup.3 and an MFR.sub.2 (190° C./2.16 kg) measured according to ISO 1133 in a range of 0.5 to 50.0 g/10 min, and (C) one or more additives in a total amount of from 0.1 up to 5.0 wt %, based on the composition, comprising slip agents, anti-block agents, UV stabilizers, antistatic agents, alpha-nucleating agents and antioxidants, wherein the article is a film and the film is characterized by (i) a seal initiation temperature (SIT) of below 120° C. (ii) a hot-tack force (determined on 50 μm cast film) of above 1.0N (iii) a haze (determined according to ASTM D1003-00 on cast film with a thickness of 50 μm) of below 5.0% and a haze (determined according to ASTM D 1003-00 measured on a 50 μm cast film) after sterilization (steam sterilization at 121° C. for 30 min) of below 10.0% and (iv) a clarity (determined according to ASTM D1003-00 on cast film with a thickness of 50 μm) of at least 75.0% and a clarity (determined according to ASTM D1003-00 on cast films with a thickness of 50 μm) after sterilization (steam sterilization at 121° C. for 30 min) of at least 65.0%.

6. The sterilizable or sterilized articles according to claim 5, wherein the film has a tensile modulus (determined according to ISO 527-3 at 23° C. on cast film with a thickness of 50 μm) in machine direction as well as in transverse direction in a range of 200 to 500 MPa.

7. The sterilizable or sterilized article according to claim 5 prepared by cast film technology.

8. The sterilizable or sterilized article according to claim 5, wherein the film forms a sealing layer in a multi-layer film.

9. A multi-layer film, comprising the sterilizable or sterilized article according to claim 5 as a sealing layer.

10. Flexible packaging systems, selected from bags or pouches for food and pharmaceutical packaging comprising the sterilizable or sterilized article according to claim 5.

11. A process for producing a C.sub.2C.sub.3 random copolymer composition comprising (A) 70.0 to 99.9 wt % of a C.sub.2C.sub.3 random copolymer having (a) an ethylene content in a range of from 2.0 to 4.8 wt %; (b) a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in a range of from 4.0 to 12.0 g/10 min; (c) a melting temperature Tm as determined by DSC according to ISO 11357 of from 120 to 135° C.; and (d) a xylene cold soluble (XCS) fraction below 10.0 wt %; (B) 0.0 to 30.0 wt % of an ethylene-α-olefin plastomer having a density in a range of from 860 to 900 kg/m.sup.3 and an MFR.sub.2 (190° C./2.16 kg) measured according to ISO 1133 in a range of 0.5 to 50.0 g/10 min, and (C) one or more additives in a total amount of from 0.1 up to 5.0 wt %, based on the composition, comprising slip agents, anti-block agents, UV stabilizers, antistatic agents, alpha-nucleating agents and antioxidants, the process comprising the steps of (i) preparing the C.sub.2C.sub.3 random copolymer (A) by polymerizing propylene and ethylene by a sequential polymerization process comprising at least two reactors connected in series in the presence of a metallocene catalyst, (ii) optionally mixing said C.sub.2C.sub.3 random copolymer (A) with an ethylene-α-olefin plastomer (B), (iii) adding one or more additives (C), to obtain a mixture of (A), optionally (B) and (C), and (iv) extruding said mixture to obtain the C.sub.2C.sub.3 random copolymer composition.

12. The process for producing a C.sub.2C.sub.3 random copolymer composition according to claim 11, wherein step (i) comprises the following steps a) polymerizing into a first reactor propylene and ethylene, and obtaining polymer fraction (A-1) of the C.sub.2C.sub.3 random copolymer (A), b) transferring said polymer fraction (A-1) and unreacted comonomers of the first reactor in a second reactor (R-2), c) feeding to said second reactor (R-2) propylene and ethylene, d) polymerizing in said second reactor (R-2) and in the presence of said polymer fraction (A-1) propylene and ethylene obtaining polymer fraction (A-2), said polymer fraction (A-1) and said polymer fraction (A-2) form a C.sub.2C.sub.3 random copolymer (A) according to claim 1 comprising: (A) 70.0 to 99.9 wt % of a C.sub.2C.sub.3 random copolymer having (a) an ethylene content in the range of from 2.0 to 4.8 wt %; (b) a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in the range of from 4.0 to 12.0 g/10 min; (c) a melting temperature Tm as determined by DSC according to ISO 11357 of from 120 to 135° C.; and (d) a xylene cold soluble (XCS) fraction below 10.0 wt %; wherein the polymerizing takes place in the presence of a metallocene catalyst comprising (i) a complex of formula (I): ##STR00018## wherein M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from —R′.sub.2C—, —R′.sub.2C—CR′.sub.2—, —R′.sub.2Si—, —R′.sub.2Si—SiR′.sub.2—, or —R′.sub.2Ge—, wherein each R′ is independently a hydrogen atom, C.sub.1-C.sub.20-hydrocarbyl, tri(C.sub.1-C.sub.20-alkyl)silyl, C.sub.6-C.sub.20-aryl, C.sub.7-C.sub.20-arylalkyl or C.sub.7-C.sub.20-alkylaryl; R.sup.2 and R.sup.2′ are each independently a C.sub.1-C.sub.20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16; R.sup.5′ is a C.sub.1-20 hydrocarbyl group containing one or more heteroatoms from groups 14-16 optionally substituted by one or more halo atoms; R.sup.6 and R.sup.6′ are each independently hydrogen or a C.sub.1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16; wherein R.sup.6 is preferably a tertiary alkyl group R.sup.7 is hydrogen or C.sub.1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16; R.sup.7′ is hydrogen; Ar is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R′; Ar′ is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R′; each R.sup.1 is a C.sub.1-20 hydrocarbyl group or two R.sup.1 groups on adjacent carbon atoms taken together may form a fused 5 or 6 membered non aromatic ring with the Ar group, said ring being itself optionally substituted with one or more groups R.sup.4; each R.sup.4 is a C.sub.1-20 hydrocarbyl group; and (ii) a cocatalyst comprising at least one or two compounds of a group 13 metal.

Description

2. EXAMPLES

(1) The catalyst used in the polymerization processes for the C.sub.2C.sub.3 random copolymer composition of the inventive example (IE1) was prepared as follows:

(2) The metallocene (MC1) (rac-anti-dimethylsilandiyl(2-methyl-4-phenyl-5-methoxy-6-tert-butyl-indenyl)(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconium dichloride) has been synthesized as described in WO 2013/007650.

(3) The catalyst was prepared using metallocene MC1 and a catalyst system of MAO and trityl tetrakis(pentafluorophenyl)borate according to Catalyst 3 of WO 2015/11135 with the proviso that the surfactant is 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-1-propanol.

(4) For Comparative Examples CE1 and CE2 a Ziegler-Natta catalyst was used.

(5) Preparation of the Ziegler-Natta Catalyst for CE1 and CE2

(6) Used chemicals:

(7) 20% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et), BEM), provided by Chemtura 2-ethylhexanol, provided by Amphochem; 3-Butoxy-2-propanol-(DOWANOL™ PnB), provided by Dow; bis(2-ethylhexyl)citraconate, provided by SynphaBase TiCl4, provided by Millenium Chemicals; Toluene, provided by Aspokem Viscoplex® 1-254, provided by Evonik; Heptane, provided by Chevron

(8) Preparation of a Mg Alkoxy Compound

(9) Mg alkoxide solution was prepared by adding, with stirring (70 rpm), into 11 kg of a 20 wt % solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et)), a mixture of 4.7 kg of 2-ethylhexanol and 1.2 kg of butoxypropanol in a 20 l stainless steel reactor. During the addition the reactor contents were maintained below 45° C. After addition was completed, mixing (70 rpm) of the reaction mixture was continued at 60° C. for 30 minutes. After cooling to room temperature 2.3 kg g of the donor bis(2-ethylhexyl)citraconate was added to the Mg-alkoxide solution keeping temperature below 25° C. Mixing was continued for 15 minutes under stirring (70 rpm).

(10) Preparation of Solid Catalyst Component

(11) 20.3 kg of TiCl4 and 1.1 kg of toluene were added into a 20 l stainless steel reactor. Under 350 rpm mixing and keeping the temperature at 0° C., 14.5 kg of the Mg alkoxy compound prepared in example 1 was added during 1.5 hours. 1.7 l of Viscoplex® 1-254 and 7.5 kg of heptane were added and after 1 hour mixing at 0° C. the temperature of the formed emulsion was raised to 90° C. within 1 hour. After 30 minutes mixing was stopped catalyst droplets were solidified and the formed catalyst particles were allowed to settle. After settling (1 hour), the supernatant liquid was siphoned away. Then the catalyst particles were washed with 45 kg of toluene at 9° C. for 20 minutes followed by two heptane washes (30 kg, 15 min). During the first heptane wash the temperature was decreased to 50° C. and during the second wash to room temperature. The thus obtained catalyst was used along with triethyl-aluminium (TEAL) as co-catalyst and dicyclopentyl dimethoxy silane (D-Donor) as donor for preparing the polymers of CE1 and CE2.

(12) The polymerization for preparing the inventive C.sub.2C.sup.3 random copolymer compositions as well as the polymers of CE1 and CE2 was performed in a Borstar pilot plant with a 2-reactor setup (loop-gas phase reactor (GPR 1))

(13) TABLE-US-00003 TABLE 1 polymerization conditions for IE1, CE1 and CE2 IE1 CE1 CE2 Prepoly reactor Temperature [° C.] 20 30 30 Pressure [Pa] 5208 5469 5472 Al/donor ratio [mol/mol] — 6 6 Al/Ti ratio [mol/mol] — 165 163 Residence time [h] 0.3 0.4 0.4 loop reactor Temperature [° C.] 70 65 65 Pressure [Pa] 5262 5425 5400 Feed H2/C3 ratio [mol/kmol] 0.4 0 0 Feed C2/C3 ratio [mol/kmol] 33.9 8 9 Polymer Split [wt %] 61 33 37 MFR2 [g/10 min] 8.0 1.6 2.0 (IE1: MFR of A-1) Total C2 loop [wt %] 3.0 4.1 4.4 (IE1: C2 of A-1) GPR1 Temperature [° C.] 80 80 80 Pressure [Pa] 2400 2600 2550 H2/C3 ratio [mol/kmol] 3.9 6.5 6.0 C2/C3 ratio [mol/kmol] 152.3 35.6 39.3 Polymer residence time (h) 2.3 1.8 1.6 Polymer Split [wt %] 39 67 63 Total MFR2 [g/10 min] 7.0 1.6 1.4 MFR2 [g/10 min] in GPR1 5.6 1.6 1.1 (IE1: MFR of A-2) Total C2 [wt %] (loop + 3.5 5.4 6.0 GPR1) C2 in GPR1 [wt %] (IE1: C2 4.2 6.0 7.0 of A-2) XCS [wt %] 2.1 14.7 17.4 Total productivity (kg PP/g cat) 166 34 30

(14) As CE3 inventive Example 1 (IE1) of EP3064514, a trimodal metallocene based copolymer composition, was used.

(15) All polymer powders were compounded in a co-rotating twin-screw extruder Coperion ZSK 57 at 220° C. with 0.2 wt % antiblock agent (synthetic silica; CAS-no. 7631-86-9); 0.1 wt % antioxidant (Irgafos 168FF); 0.1 wt % of a sterical hindered phenol (Irganox 1010FF); 0.02 wt % of Ca-stearat) and 0.02 wt % of a non-lubricating stearate (Synthetic hydrotalcite; CAS-no. 11097-59-9)

(16) TABLE-US-00004 Pellet IE1 CE1 CE2 CE3 XCS [wt %] 2.1 14.7 17.4 19.8 Total C2 [wt %] 3.5 5.4 6.0 4.6 MFR2 [g/10 min] 7.1 6.2 5.1 7.1 Tm [° C.] 133.1 139.5 137.3 136.7 Tc [° C.] 95.6 102.7 101.0 98.3

(17) For Inventive Examples 2 to 4 the C.sub.2C.sub.3 random copolymer (A) produced as described above was mixed with an ethylene-α-olefin plastomer (B).

(18) The following commercially available plastomers (B) have been used:

(19) IE2: 10.0 wt % of Queo™ 8230, ethylene-octene plastomer, density 882 kg/m.sup.3, MFR.sub.2 (190° C., 2.16 kg) 30 g/10 min and melting point 75° C., commercially available from Borealis AG

(20) IE3: 25.0 wt % of Queo™ 8230, ethylene-octene plastomer, density 882 kg/m.sup.3, MFR.sub.2 (190° C., 2.16 kg) 30 g/10 min and melting point 75° C., commercially available from Borealis AG

(21) IE4: 10.0 wt % of Queo™ 8201, ethylene-octene plastomer, density 882 kg/m.sup.3, MFR.sub.2 (190° C., 2.16 kg) 1.1 g/10 min and melting point 76° C., commercially available from Borealis AG

(22) Mixing was done in a co-rotating twin-screw extruder Coperion ZSK 57.

(23) The inventive and comparative propylene compositions were converted to monolayer cast films with a thickness of 50 μm on a PM30 cast line (type laboratory extruder provided by Plastik Maschinenbau GmbH., Germany). The equipment consists of an extruder, chill roll with air knife and a winder.

(24) A PP 3-zone screw with a diameter of 30 mm, 25 D length, 200 mm die, die gap 0.5 mm is applied in combination with a coat-hanger slit die assembly.

(25) The extrusion parameters were as follows:

(26) Extruder temperature profile: 220° C./240° C./250° C./260° C./260° C. (Melt temperature 250° C.; melt pressure 61 bar)

(27) Extruder speed: 50 rpm

(28) Chill roll temperature: 20° C.

(29) take-off speed: 10.2 m/min

(30) In Table 3 the optical parameters (before sterilization, b.s.) as well as the sealing performance, tensile modulus and hot tack force can be seen.

(31) TABLE-US-00005 TABLE 3 Sealing performance, tensile and optics before sterilization (b.s.) IE1 IE2 IE3 IE4 CE1 CE2 CE3 Tensile modulus (MD) [MPa] 429 392 327 395 349 326 351 Tensile modulus (TD) [MPa] 437 403 334 402 348 330 365 SIT [° C.] 109 106 94 105 114 109 107 Hot-tack force [N] 3.91 1.09 1.67 1.37 1.68 2.41 1.99 Haze b.s. [%] 0.22 0.34 2.29 2.4 0.35 0.31 2.1 Clarity b.s. [%] 100 99.8 83.8 94.1 99.8 99.8 96.0

(32) The films were furthermore steam sterilized.

(33) Steam sterilization was performed in a Systec D series machine (Systec Inc., USA). The samples were heated up at a heating rate of 5° C./min starting from 23° C. After having been kept for 30 min at 121° C., they were removed immediately from the steam sterilizer and stored at room temperature until being processed further.

(34) The optical parameters after sterilization (a.s.) can be seen in Table 4.

(35) TABLE-US-00006 TABLE 4 Optics after sterilization (a.s.) IE1 IE2 IE3 IE4 CE1 CE2 CE3 Haze (a.s.) [%] 0.92 1.38 5.96 4.42 17.3 18.2 19.1 Clarity (a.s.) [%] 99.3 99.0 78.0 92.0 66.0 55.6 86.0

(36) From the above tables it can be clearly seen that the inventive polypropylene compositions are characterised by an advantageous combination of low sealing initiation temperature (SIT), high hot-tack and good optical properties, like low haze and high clarity, whereby the optical parameters after sterilization are clearly better than for the comparative examples.