Multi-layer blown film

Abstract

A multi-layer blown polymer film comprising a core layer (CL) and at least one sealing layer (SL), said sealing layer(s) (SL) comprise(s) a propylene copolymer composition (P) having a comonomer content in the range of 3.0 to 8.0 wt.-%, the comonomers are C.sub.5 to C.sub.12 -olefins, said propylene copolymer composition (P) comprises a polypropylene (A) and a polypropylene (B) in the weight ratio [(A)/(B)] of 20/80 to 80/20, wherein said polypropylene (A) has a comonomer content of equal or below 4.0 wt.-%, the comonomers are C.sub.5 to C.sub.12 -olefins, and said propylene copolymer (B) has a comonomer content of 4.0 to 20.0 wt.-%, the comonomers are C.sub.5 to C.sub.12 -olefins.

Claims

1. Process for producing a multi-layer blown polymer film comprising: providing a core layer (CL) being selected from the group consisting of polyvinyl alcohols, polyacrylates, polyamides, poly(ethylene terephthalate), polyolefins (PO) and mixtures thereof, a sealing layer (SL), and optionally an outer (OL), a further sealing layer (SL) or a metal layer (ML) wherein: (a) the core layer (CL), (a1) is coated on the one side with a propylene copolymer composition (P) obtaining a sealing layer (SL) and (a2) optionally (a2-i) is on the other side coated with a polyolefin (PO) obtaining an outer layer (OL), or (a2-ii) is on the other side coated with a propylene copolymer composition (P) obtaining a second sealing layer (SL), or (a2-iii) is on the other side metallized obtaining a metal layer (ML), wherein (b) said propylene copolymer composition (P) (b1) has a comonomer content in the range of 3.0 to 8.0 wt. %, the comonomer is C6 -olefin, (b2) comprises a polypropylene (A) and a polypropylene (B) in the weight ratio [(A)/(B)] of 35/65 to 50/50, wherein said polypropylene (A) is a propylene homopolymer (H-PP) or a propylene copolymer (C-A) having a comonomer content of below 4.0 wt. %, the comonomer is C6 -olefin, said propylene copolymer (B) has a comonomer content of 4.0 to 20.0 wt. %, the comonomer is C6 -olefin, (b3) fulfills the ratio
MFR (A)/MFR (P)1.0 wherein MFR (A) is the melt flow rate MFR2 (230 C.) [g/10 min] measured according to ISO 1133 of the polypropylene (A), MFR (P) is the melt flow rate MFR2 (230 C.) [g/10 min] measured according to ISO 1133 of the propylene copolymer composition (P), (b4) has a xylene soluble content (XCS) determined at 25 C. according to ISO 16152 of below 16.0 wt. %, (b5) has a melting temperature Tm determined by differential scanning calorimetry (DSC) of at least 135 C., (b6) has a heat sealing initiation temperature (SIT) of equal or below 115 C., (b7) is free of any elastomeric polymer component, and wherein the film is not subjected to a stretching step, and coextruding the polymer layers on a blown film line.

2. Process according to claim 1, wherein the melts of the polymer for the core layer (CL), of the propylene copolymer composition (P) for the sealing layer (SL) and optionally of the polymer for the outer layer (OL) or for a further sealing layer (SL) are extruded through an annular die and blown into a tubular film by forming a bubble which is collapsed between nip rollers after solidification.

3. Process according to claim 1, wherein the blown coextrusion is effected at a temperature in the range 160 to 240 C., and cooled by water or by blowing gas at a temperature of 10 to 50 C. to provide a frost line height of 0.5 to 8 times the diameter of the die.

4. Process according to claim 1, wherein the blow up ratio is in the range from 1.5 to 4.

5. Process according to claim 1, wherein the multi-layer film is corona-treated or flame-treated.

6. Process according to claim 1, wherein the corona treatment or flame treatment is carried out by passing the film between two conductor elements serving as electrodes with high voltage.

7. Process according to claim 1, wherein the corona treatment or flame treatment is carried out by passing the film between two conductor elements serving as electrodes with a high alternating voltage of about 10000 V and 10000 Hz.

Description

EXAMPLES

A. Measuring Methods

(1) The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

(2) Quantification of Microstructure by NMR Spectroscopy

(3) Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the isotacticity, regio-regularity and comonomer content of the polymers.

(4) Quantitative .sup.13C{.sup.1H} NMR spectra recorded in the molten-state using a Bruker Advance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 7 mm magic-angle spinning (MAS) probehead at 180 C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4 kHz. Standard single-pulse excitation was employed utilising the NOE at short recycle delays (as described in Pollard, M., Klimke, K., Graf, R., Spiess, H. W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004, 37, 813, and in Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2006, 207, 382) and the RS-HEPT decoupling scheme (as described in Filip, X., Tripon, C., Filip, C., J. Mag. Resn. 2005, 176, 239, and in Griffin, J. M., Tripon, C., Samoson, A., Filip, C., and Brown, S. P., Mag. Res. in Chem. 2007, 45, S1, S198). A total of 1024 (1 k) transients were acquired per spectra.

(5) Quantitative .sup.13C{.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

(6) The tacticity distribution was quantified through integration of the methyl region in the .sup.13C{.sup.1H} spectra, correcting for any signal not related to the primary (1,2) inserted propene stereo sequences, as described in Busico, V., Cipullo, R., Prog. Polym. Sci. 2001, 26, 443 and in Busico, V., Cipullo, R, Monaco, G., Vacatello, M., Segre, A. L., Macromolecules 1997, 30, 6251.

(7) Characteristic signals corresponding to regio defects were observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253). The influence of regio defects on the quantification of the tacticity distribution was corrected for by subtraction of representative regio defect integrals from specific integrals of the stereo sequences.

(8) The isotacticity was determined at the triad level and reported as the percentage of isotactic triad mm with respect to all triad sequences:
% mm(mm/(mm+mr+rr))*100
Characteristic signals corresponding to the incorporation of 1-hexene were observed, and the 1-hexene content was calculated as the mole percent of 1-hexene in the polymer, H (mol %), according to:
[H]=H.sub.tot/(P.sub.tot+H.sub.tot)
where:
H.sub.tot=I(B.sub.4)/2+I(B.sub.4)2

(9) where I(B.sub.4) is the integral of the B.sub.4 sites at 44.1 ppm, which identifies the isolated 1-hexene incorporated in PPHPP sequences, and I(B.sub.4) is the integral of the B.sub.4 sites at 41.6 ppm, which identifies the consecutively incorporated 1-hexene in PPHHPP sequences.

(10) P.sub.tot=Integral of all CH3 areas on the methyl region with correction applied for underestimation of other propene units not accounted for in this region and overestimation due to other sites found in this region.
and H(mol %)=100[H]

(11) which is then converted into wt % using the correlation
H(wt %)=(100Hmol %84.16)/(Hmol %84.16+(100Hmol %)42.08)

(12) A statistical distribution is suggested from the relationship between the content of hexene present in isolated (PPHPP) and consecutive (PPHHPP) incorporated comonomer sequences:
[HH]<[H].sup.2

(13) Calculation of comonomer content of the propylene copolymer (B):

(14) $\frac{C\left(P\right)-w\left(A\right)C\left(A\right)}{w\left(B\right)}=C\left(B\right)$

(15) wherein w(A) is the weight fraction of the polypropylene (A), w(B) is the weight fraction of the propylene copolymer (B), C(A) is the comonomer content [in wt.-%] measured by .sup.13C NMR spectroscopy of the polypropylene (A), i.e. of the product of the first reactor (R1), C(P) is the comonomer content [in wt.-%] measured by .sup.13C NMR spectroscopy of the propylene copolymer composition (P), C(B) is the calculated comonomer content [in wt.-%] of the propylene copolymer (B)
Mw, Mn, MWD

(16) Mw/Mn/MWD are measured by Gel Permeation Chromatography (GPC) according to the following method:

(17) The weight average molecular weight (Mw), the number average molecular weight (Mn), and the molecular weight distribution (MWD=Mw/Mn) is measured by a method based on ISO 16014-1:2003 and ISO 16014-4:2003. A Waters Alliance GPCV 2000 instrument, equipped with refractive index detector and online viscometer is used with 3TSK-gel columns (GMHXL-HT) from TosoHaas and 1,2,4-trichlorobenzene (TCB, stabilized with 200 mg/L 2,6-Di tert butyl-4-methyl-phenol) as solvent at 145 C. and at a constant flow rate of 1 mL/min. 216.5 L of sample solution are injected per analysis. The column set is calibrated using relative calibration with 19 narrow MWD polystyrene (PS) standards in the range of 0.5 kg/mol to 11 500 kg/mol and a set of well characterized broad polypropylene standards. All samples are prepared by dissolving 5 to 10 mg of polymer in 10 mL (at 160 C.) of stabilized TCB (same as mobile phase) and keeping for 3 hours with continuous shaking prior sampling in into the GPC instrument.

(18) Melt Flow Rate (MFR)

(19) The melt flow rates are measured with a load of 2.16 kg (MFR.sub.2) at 230 C. The melt flow rate is that quantity of polymer in grams which the test apparatus standardised to ISO 1133 extrudes within 10 minutes at a temperature of 230 C. under a load of 2.16 kg. Calculation of melt flow rate MFR.sub.2 (230 C.) of the propylene copolymer (B):

(20) $\mathrm{MFR}\left(B\right)={10}^{\left[\frac{l\mathrm{og}\left(\mathrm{MFR}\left(P\right)\right)-w\left(A\right)l\mathrm{og}\left(\mathrm{MFR}\left(A\right)\right)}{w\left(B\right)}\right]}$

(21) wherein w(A) is the weight fraction of the polypropylene (A), w(B) is the weight fraction of the propylene copolymer (B), MFR(A) is the melt flow rate MFR.sub.2 (230 C.) [in g/10 min] measured according ISO 1133 of the polypropylene (A), MFR(P) is the melt flow rate MFR.sub.2 (230 C.) [in g/10 min] measured according ISO 1133 of the propylene copolymer composition (P), MFR(B) is the calculated melt flow rate MFR.sub.2 (230 C.) [in g/10 min] of the propylene copolymer (B).
Xylene Cold Soluble Fraction (XCS Wt %)

(22) Content of xylene cold solubles (XCS) is determined at 25 C. according ISO 16152; first edition; 2005 Jul. 1.

(23) Hexane Solubles

(24) FDA section 177.1520

(25) 1 g of a polymer film of 100 m thickness is added to 400 ml hexane at 50 C. for 2 hours while stirring with a reflux cooler.

(26) After 2 hours the mixture is immediately filtered on a filter paper No 41.

(27) The precipitate is collected in an aluminium recipient and the residual hexane is evaporated on a steam bath under N.sub.2 flow.

(28) The amount of hexane solubles is determined by the formula
((wt. sample+wt. crucible)(wt crucible))/(wt. sample).Math.100.

(29) Melting temperature T.sub.m, crystallization temperature T.sub.c, is measured with Mettler TA820 differential scanning calorimetry (DSC) on 5-10 mg samples. Both crystallization and melting curves were obtained during 10 C./min cooling and heating scans between 30 C. and 225 C. Melting and crystallization temperatures were taken as the peaks of endotherms and exotherms.

(30) Also the melt- and crystallization enthalpy (Hm and Hc) were measured by the DSC method according to ISO 11357-3.

(31) Porosity: BET with N.sub.2 gas, ASTM 4641, apparatus Micromeritics Tristar 3000; sample preparation: at a temperature of 50 C., 6 hours in vacuum.

(32) Surface area: BET with N.sub.2 gas ASTM D 3663, apparatus Micromeritics Tristar 3000: sample preparation at a temperature of 50 C., 6 hours in vacuum.

(33) Mean particle size is measured with Coulter Counter LS200 at room temperature with n-heptane as medium; particle sizes below 100 nm by transmission electron microscopy

(34) Sealing initiation temperature (SIT); sealing end temperature (SET), sealing range: The method determines the sealing temperature range (sealing range) of polymer films. The sealing temperature range is the temperature range, in which the films can be sealed according to conditions given below.

(35) The lower limit (heat sealing initiation temperature (SIT)) is the sealing temperature at which a sealing strength of >1 N is achieved. The upper limit (sealing end temperature (SET)) is reached, when the films stick to the sealing device.

(36) The sealing range is determined on a DTC Hot tack tester Model 52-F/201 with a film of 25 m thickness with the following further parameters:

(37) Specimen width: 25 mm

(38) Seal Pressure: 0.66 N/mm.sup.2

(39) Seal Time: 1 sec

(40) Cool time: 30 sec

(41) Peel Speed: 42 mm/sec

(42) Start temperature: 80 C.

(43) End temperature: 150 C.

(44) Specimen is sealed sealing layer (SL) to sealing layer (SL) at each sealbar temperature and seal strength (force) is determined at each step. All values of the SIT and SET were measured on the multi-layer film, like the three layer film as used in the examples. In cases where the SIT and SET refer to the propylene copolymer composition (P) or the sealing layer (SL) as such the SIT and SET were measured on a monolayer cast film of the propylene copolymer composition (P) and the sealing layer (SL), respectively, having a thickness of 100 m as described in application No. 10 160 631.7. and application No. 10 160 611.9. Sealing Strength is the force measured at the temperature defined in Table 2

(45) Hot Tack Force:

(46) The hot tack force is determined on a DTC Hot tack tester Model 52-F/201 with a film of 25 m thickness with the following further parameters:

(47) Specimen width: 25 mm

(48) Seal Pressure: 1.2 N/mm.sup.2

(49) Seal Time: 0.5 sec

(50) Cool time: 0.2 sec

(51) Peel Speed: 200 mm/sec

(52) Start temperature: 90 C.

(53) End temperature: 140 C.

(54) The maximum hot tack force, i.e the maximum of a force/temperature diagram is determined and reported.

(55) Hot tack initiation temperature: is determined from the hot tack curve at the point where the force exceeds 1 N

(56) Gloss was determined on the multi-layered films according to DIN 67530 at an angle of 20 C.

(57) Transparency, haze and clarity were determined on the multi-layered films according to ASTM D 1003-00.

B. Examples

(58) The propylene copolymer compositions (P) of table I have been produced in a Borstar PP pilot plant in a two-step polymerization process starting in a bulk-phase loop reactor followed by polymerization in a gas phase reactor, varying the molecular weight as well as hexene content by appropriate hydrogen and comonomer feeds. The catalyst used in the polymerization process was a metallocene catalyst as described in example 10 of WO 2010/052263 A1.

(59) TABLE-US-00001 TABLE 1 Preparation of the propylene copolymer composition (P) P 1 P2 P 3 P4 Loop MFR.sub.2 [g/10 min] 4.6 4.3 3.4 4.0 C6 [wt.-%] 0.0 0.0 1.2 1.2 XCS [wt.-%] <1.5 <1.5 <1.5 <1.5 GPR C6 [wt.-%] 5.5 5.8 5.9 7.4 Split Loop/GPR [%] 39/61 34/66 47/53 45/55 FINAL C6 [wt.-%] 3.2 3.8 3.6 4.4 XCS [wt.-%] 2 1.9 2.3 5.5 HHS [wt.-%] 0.7 0.8 0.8 0.9 MFR.sub.2 [g/10 min] 8.6 10.0 8.2 7.9 Mw [kg/mol] 226 211 224 210 MWD [] 3.0 3.0 2.9 2.9 SIT [ C.] nm 108 nm 102 Tm [ C.] 148 149 141 141 Tc [ C.] 111 101 97 100 Loop defines the polypropylene (A) GPR defines the propylene copolymer (B) Final defines the propylene copolymer (P) C6 is 1-hexene content HHS hexane hot solubles SIT Sealing initiation temperature measured on a monolayer film [100 m] asdescribed in application Ser. No. 10/160,631.7. and application Ser. No. 10/160,611.9 nm not measured P5 is the commercial propylene-ethylene-1-butene terpolymer TD210BF of Borealis AG having a melt flow rate MFR.sub.2 (230 C.) of 6 g/10 min, a melting temperature Tm of 131 C. and a MWD of 4.9. P6 is the commercial random ethylene-propylene copolymer RB709CF of Borealis AG having a melt flow rate MFR.sub.2 (230 C.) of 1.5 g/10 min and a melting temperature Tm of 137 C. R-PP is the commercial polypropylene homopolymer RB707BF of Borealis AG having a melt flow rate MFR.sub.2 (230 C.) of 1.5 g/10 min, a melting temperature Tm of 145 C.

(60) Three layer blown polymer films were produced on a three layer blown film line. The melt temperature of the scaling layers (SL) was 185 C. to 195 C. The melt temperature of the core layer (CL) was in the range of 205 C. to 215 C. The throughput of the extruders was in sum 80 kg/h. The film structure was SL-CL-SL with a core layer of 25 m (CL) and two sealing layers (SL) of 12.5 m. For the core layer (CL) R-PP has been used, whereas for the sealing layers (SL) one of the polymers P1 to P6 have been used. Layer thickness has been

(61) TABLE-US-00002 TABLE 2 Properties of the multi-layer blown polymer film CE1 CE2 IE1 IE2 IE3 IE4 P5 P6 P1 P2 P3 P4 HTF [N] 2.7 1.8 3.6 3.5 4.0 3.5 HT-IT [ C.] 98 103 101 93 96 93 SS (A) [N] 3.3 <2 <2 <2 6 17 SS (B) [N] 20 4 10 18 22 23 SIT [ C.] 110 116 113 113 110 107 G [%] 27 91 67 66 81 81 T [%] 94 94 94 95 95 95 H [%] 22 2.4 7.4 3.2 5.1 3.3 C [%] 79 97 96 93 97 96 HTF is the hot tack force HT-IT Hot Tack initiation temperature at F. > 1N (see page 33) SS(A) is the sealing strength at 110 C. SS(B) is the sealing strength at 115 C. SIT is the heat sealing initiation temperature G Gloss 20 T Transparency H Haze C Clarity