Copolymers of propylene with hexene-1 and blown films obtained from them

Abstract

A copolymer of propylene with hexene-1 containing from 5 to 9% by weight of recurring units derived from hexene-1, having a melting temperature from 125 C. to 140 C. and Melt Flow Rate (ASTM D1238, 230 C./2.16 Kg) from 0.1 to 3 g/10 min., is used to produce blown films having valuable mechanical and optical properties.

Claims

1. A propylene copolymer comprising: 5-9% by weight of recurring units derived from hexene-1; wherein the propylene copolymer has a melting temperature from 125-140 C., a melt flow rate (ASTM D1238, 230 C./2.16 kg) from 0.1 to 3 g/10 min, and a solubility in xylene at room temperature of 18.1% to 25% by weight.

2. A polymerization process for preparing a copolymer of propylene with hexene-1 containing from 5 to 9% by weight of recurring units derived from hexene-1, said copolymer having a melting temperature from 125-140 C., a Melt Flow Rate (ASTM D1238, 230 C./2.16 kg) from 0.1 to 3 g/10 min, and a solubility in xylene at room temperature of 18.1% to 25% by weight, the process comprising polymerizing monomers in the presence of a stereospecific Ziegler-Natta catalyst comprising a solid component containing a titanium compound and an electron-donor compound supported on magnesium chloride, an aluminum alkyl compound and an external electron-donor compound.

3. The polymerization process of claim 2, wherein the external electron-donor compound is selected from silicon compounds containing at least one SiOR bond, where R is a hydrocarbon radical.

4. The polymerization process of claim 2, wherein the external electron-donor compound is thexyltrimethoxysilane.

5. A blown film comprising the propylene copolymer of claim 1.

6. The blown film of claim 5, comprising a thickness of less than 250 m.

7. An article comprising the blown film of claim 5, selected from an industrial package, a food package, a bag, a sack, a lamination film, a barrier film, an agriculture film and a hygienic product.

8. A process comprising blow molding a film comprising at least one film layer in a blown film process, the film layer comprising a copolymer of propylene with hexene-1 containing from 5 to 9% by weight of recurring units derived from hexene-1, said copolymer having a melting temperature from 125-140 C., a Melt Flow Rate (ASTM D1238, 230 C./2.16 kg) from 0.1 to 3 g/10 min, and a solubility in xylene at room temperature of 18.1% to 25% by weight.

9. The process of claim 8, carried out under the following conditions: a screw length from 20 to 40 times the screw diameter; a barrel and die temperature from 160 to 270 C.; an annular die gap of at most 3 mm; a blow-up ratio from 2.2 to 4; and a cooling medium temperature from 5 to 20 C.

10. The copolymer of claim 1, further comprising a clarifying agent.

11. The copolymer of claim 10, wherein the clarifying agent is selected from the group consisting of 3,4-dimethylbenzylidene sorbitol and hexafluoropropylene (HFP)-vinylidene fluoride (VF)-tetrafluoroethylene (TFE).

12. The copolymer of claim 1, comprising a molecular weight distribution from 4 to 7.

13. The copolymer of claim 1, comprising an isotacticity index equal to or higher than 97%.

Description

EXAMPLES 1 AND 2 AND COMPARISON EXAMPLES 1 TO 4

(1) Three layer films are prepared on a Collin three layer coextrusion line. The film of Example 1 is prepared by using COPO-1 for all the three layers. The film of Example 2 is prepared by using COPO-2 for all the three layers.

(2) In Comparison Example 1 the polymer material used for the all the three layers is a copolymer of propylene with butene-1 containing 15% by weight of butene-1 and having a MFR value of 0.8 g/10 min., previously extruded with 500 ppm by weight of Dynamar FX5911.

(3) In Comparison Example 2 the same copolymer of propylene with butene-1 as in Comparison Example 1 is used for all the three layers, but previously extruded with 500 ppm by weight of Dynamar FX5911 and 1800 ppm by weight of Millad 3988.

(4) In comparison Example 3 the polymer material used for all the three layers is copolymer of propylene with ethylene containing 5% by weight of ethylene and having a MFR value of 2 g/10 min., previously extruded with 1800 ppm by weight of Millad 3988.

(5) In comparison Example 4 the polymer material used for all the three layers is a copolymer of propylene with ethylene containing 6.5% by weight of ethylene and having a MFR value of 2.3 g/10 min., previously extruded with 500 ppm by weight of Dynamar FX5911 and 1800 ppm by weight of Millad 3988.

(6) All the said extrusions with Dynamar FX5911 and Millad 3988 are carried out in a co-rotating twin screw three lobs profile extruder (ZSK53 type, length/diameter ratio of 20, manufactured by Coperion Werner&Pfleiderer) under nitrogen atmosphere in the following conditions:

(7) TABLE-US-00002 Rotation speed: 220 rpm; Extruder output: 80 kg/hour; Melt temperature: 250-260 C.

(8) In the said Collin coextrusion line, the screw length/screw diameter ratios are 30 mm/30 xD for extruders A & C while 45 mm/30D for the B one. No IBCS system (Internal Bubble Cooling System) is used. During the extrusion trials, the melt is extruded through an annular die with a diameter of 100 mm and a quite narrow gap (0.8 mm for the trials). At the exit from the die, the melt tube is subjected to intensive air cooling, immediately blown up to about three times the diameter of the die and stretched in the direction of the flow.

(9) The main operating conditions in Examples 1 and 2 are: Barrel temperature: 200-240-220-220-220 C.; Adaptor temperature: 220 C.; Die temperature: 230-250-230-225-230 C.; Screw speed: 30 rpm for all the three extruders; Blow-up ratio: 3.1; Line speed: 5.3 m/min.

(10) In Comparison Examples 1 and 2 the same conditions as in Examples 1 and 2 are used, except for the following: Screw speed: 50 rpm for all the three extruders; Blow-up ratio: 3; Line speed: 10 m/min.

(11) In Comparison Examples 3 and 4 the same conditions as in Examples 1 and 2 are used, except for the following: Barrel temperature: 200-240-220-210-210 C.; Adaptor temperature: 210 C.; Die temperature: 240-250-240-250-250 C. in Comparison Example 3 and 230-245-230-230-230 C. in Comparison Example 4; Blow-up ratio: 2.8 in Comparison Example 3 and 2.9 in Comparison Example 4; Line speed: 7 m/min.

(12) The final film thickness of the films is approximately 50 micron, with a thickness distribution (in percentage) of 20/60/20.

(13) The properties of the so obtained films are reported in Table 1.

(14) TABLE-US-00003 TABLE 1 EXAMPLE No. 1 2 Comp. 1 Comp. 2 Comp. 3 Comp. 4 Elmendorf (MD) g/m 1.3 1.1 0.5 0.4 0.2 0.3 Elmendorf (TD) g/m 1.8 1.7 1.1 0.8 0.3 0.4 Puncture N 9.7 12.8 7.2 11.1 9.5 7.5 resistance Puncture mm 10.3 13.7 9.3 13.3 12.3 14.3 deformation Haze % 8.7 4.2 9.0 6.6 7.4 4.0 Clarity % 96.1 98.1 88.3 87.4 95.0 92.5 Gloss at 45 63.5 80.0 63.0 69.8 63.8 75.1 Dart test g/m 11.33 7.47 2.27 1.43 1.32 1.54 Tensile Modulus MPa 329 511 587 575 638 480 (MD) Tensile Modulus MPa 321 518 606 645 671 515 (TD) Stress at yield MPa 14.1 24.8 22.0 21.5 23.1 18.8 (MD) Stress at yield MPa 14.2 23.0 20.3 20.8 22.2 18.5 (TD) Elongation at % 14.9 15.9 13.1 12.5 15.1 16.0 yield (MD) Elongation at % 14.8 15.1 12.5 11.7 13.8 15.0 yield (TD) Stress at break MPa 38.1 42.0 36.9 43.5 31.0 37.6 (MD) Stress at break MPa 38.9 34.0 28.5 41.9 30.0 32.9 (TD) Elongation at % 668 670 700 850 870 1000 break (MD) Elongation at % 718 626 710 990 970 1000 break (TD) Note: Comp. = Comparison