Plastic Films

Abstract

The invention relates to plastic films and a silicone containing polymer blend composition that can be used in the production of the plastic films which is a polymer composition obtainable from, per 100 parts by weight of the composition, 99.99 to 90 parts by weight of a polyolefin polymer (P) and 0.01 to 10 parts by weight of a masterbatch (M).

Claims

1. A plastic packaging film comprising a core layer and two opposite outer layers, wherein an outer layer is obtainable by: (i) forming a masterbatch (M) by reactively mixing under shear an organopolysiloxane (B) containing on average at least 1 alkenyl functionality per molecule with a polyolefin polymer (A), at a temperature such that the organopolysiloxane (B) and the polyolefin polymer (A) are in liquid phase, so as to form a copolymer of (A) and (B) then cooling the formed copolymer to produce said masterbatch (M) in solid form containing organopolysiloxane (B), polyolefin polymer (A) and the copolymer of (A) and (B); then (ii) introducing, per 100 parts by weight, 0.01 to 10 parts by weight of masterbatch (M) into 99.99 to 90 parts by weight of a polyolefin polymer (P) and blending to form a composition, and (iii) making a film by processing the composition of step (ii).

2. The plastic film according to claim 1 wherein the polyolefin polymer (A) and/or the polyolefin polymer (P) is a blend of polyolefins.

3. The plastic film according to claim 1, wherein the polyolefin polymer (A) and/or the polyolefin polymer (P) are functionalized, preferably with an alkyl acrylate function such as methyl acrylate, ethyl acrylate, butyl acrylate, or an acrylic function or maleic anhydride function.

4. The plastic film according to claim 1 wherein the polyolefin polymer (P) comprises polypropylene and/or polyethylene.

5. The plastic film according to claim 1 wherein the polyolefin polymer (A) comprises polypropylene and/or polyethylene.

6. The plastic film according to claim 1 wherein the organopolysiloxane (B) has a number average molecular weight of 200,000 to 2.000,000 g/mole.

7. The plastic film according to claim 1 wherein the alkenyl functionalities of the organopolysiloxane (B) comprise vinyl functionalities and wherein the vinyl functionalities are present in an amount comprised between 0.01% and 2.00% by weight of the organopolysiloxane (B).

8. A method of making a plastic packaging film comprising a core layer and two opposite outer layers, wherein an outer layer is made by: (i) forming a masterbatch (M) by reactively mixing under shear an organopolysiloxane (B) containing on average at least 1 alkenyl functionality per molecule with a polyolefin polymer (A), at a temperature such that the organopolysiloxane (B) and the polyolefin polymer (A) are in liquid phase, so as to form a copolymer of (A) and (B) then cooling the formed copolymer to produce said masterbatch (M) in solid form containing organopolysiloxane (B), polyolefin polymer (A) and the copolymer of (A) and (B); then (ii) introducing, per 100 parts by weight, 0.01 to 10 parts by weight of masterbatch (M) into 99.99 to 90 parts by weight of a polyolefin polymer (P) and blending to form a composition and (iii) making a film by processing the composition of step (ii).

9. The method according to claim 8, wherein the polyolefin polymer (A) and/or the polyolefin polymer (P) are functionalized, preferably with an alkyl acrylate function such as methyl acrylate, ethyl acrylate, butyl acrylate, or an acrylic function or maleic anhydride function.

10. The method according to claim 8 wherein the polyolefin polymer (P) comprises polypropylene and/or polyethylene.

11. The method according to claim 8 wherein the polyolefin polymer (A) comprises polypropylene and/or polyethylene.

12. The method according to claim 8 wherein the organopolysiloxane (B) is linear.

13. The method in accordance with claim 8 wherein step (iii) is selected from one or more of extrusion, co-extrusion, lamination, melt pressing, and coating methods or a combination thereof.

14. The method in accordance with claim 8 wherein step (iii) involves one or more of cast co-extrusion or blown co-extrusion methods, adhesive lamination, extrusion lamination, thermal lamination, melt pressing and coating methods such as vapour deposition.

15. A plastic film in accordance with claim 1 wherein the polymer composition additionally comprises one or more additives selected from antistatic additives, anti-blocking additives and/or anti-fogging additives.

16. A plastic film in accordance with claim 1 wherein step (iii) is selected from one or more of extrusion, co-extrusion, lamination, melt pressing, and coating methods or a combination thereof.

17. A plastic film in accordance with claim 1 wherein step (iii) involves one or more of cast co-extrusion or blown co-extrusion methods, adhesive lamination, extrusion lamination, thermal lamination, melt pressing and coating methods such as vapour deposition.

18. The method according to claim 8 wherein the polyolefin polymer (A) and/or the polyolefin polymer (P) is a blend of polyolefins.

Description

POLYETHYLENE (PE) EXAMPLE

Example 1: Preparation of the Silicone Masterbatch of Different Viscosities and Molecular Weights

[0054] Pellets of low density polyethylene (Polyolefin polymer (A)) with a melt flow index (MFI) of 8.5 g per 10 min (using the testing conditions of a temperature of 190° C. and load of 2.16 kg) as the polymer matrix of masterbatch (M), are introduced into a co-rotative Twin screw extruder sometimes with stabilizer (see Table 1 below) (typically Irganox® 1010 antioxidant) in an amount as indicated in Table 1 below 0.5 wt. %. Then organopolysiloxane (B) is added into the already melted polyethylene phase using a gear pump. The average amount of organopolysiloxane (B) introduced into the matrix polyethylene is about 50 wt. %.

[0055] All the components are mixed in a lab twin screw extruder having a length/diameter (L/D) ratio of greater than 40 (typically 48), diameter of the screw greater than 35 mm (typically 40 mm), then average screw speed is set to 550 rpm with a specific screw profile designed to disperse finely all the components into the polyethylene. The mixtures are coiled with a water batch to room temperature and pelletized. The pellets are analysed with a rheometer with a frequency sweep test at 190° C., and deformation (Y)=2% to determine the viscosities. In Table 1 the values of complex loss modulus (G*) at 0.1 Hz are provided. Pellets of masterbatch (M) also undergo an extraction test as follows: around 0.24 g of masterbatch was accurately weighed and placed into a 20 ml headspace vial. 10 ml of p-xylene were accurately added (micropipette) and the vial was crimped. The samples were left to solubilize at high temperature (150° C.) for 20 minutes under continuous agitation using the headspace oven and the autosampler of a GC-MS (MPS from Gerstel). After cooling 10 ml of toluene were added and the samples were left under gentle stirring for 24 h (using a rotary shaker). The samples were then filtered through 0.45 μm PTFE filters into 2 ml glass auto sampler vials.

[0056] All data is compiled in Table 1.

TABLE-US-00001 TABLE 1 Table 1: Process conditions, extraction in xylene and complex modulus data for each run carried out using vinyl endcapped and pendent (0.725% of vinyl function) high molecular weight silicone polymer. Phenolic Silicone Antioxidant extraction G* at Temperature Output at 0.3% in xylene 0.1 Hz (° C.) (kg/h) (Y/N) (%) (Pa) 1 250 100 N 7.1 10332 2 250 100 Y 25.6 5294 3 250 40 N 4.2 11453 4 250 40 Y 19.2 4284 5 190 60 N 11.3 8245 6 190 60 Y 44.2 1506 7 140 100 N 34.8 2989 8 140 100 Y 44.2 1564 9 140 40 N 22.5 6182 10 140 40 Y 44.8 1445 11 190 40 N 13.9 11818 12 190 100 N 18.1 9512 13 210 40 N 10.1 12374 14 210 100 N 11.5 11490 15 230 40 N 8.5 12709 16 230 100 N 9.6 11873

[0057] The increase of the viscosity (represented by G*) and the decrease of the extraction in xylene (solvent of silicone but not of polyethylene) of silicone is proof of the reaction between the components. Table 1 shows that this reaction is dependent on the extrusion temperature, as well as, in a minor way, the output of the process.

Example 2: Preparation of the Polyethylene Films with Different Masterbatches

[0058] The polyethylene films were made on a small lab extruder having an L/D ratio of 30 and a length of 24 mm. The small extruder was equipped with a blown film die. The films were produced at 200° C., with an output around 1.5 kg/h, and to obtain 20 microns thickness, the pulling speed was set around 5-6 m/min. The same polyethylene (low density, melt flow index (MFI) 8.5) is used as the base material for film production, avoiding compatibility issues between the polyethylene in the film and the polyethylene in the masterbatch. The silicone masterbatch of this present invention or from the conventional masterbatch process described in US U.S. Pat. No. 5,844,031, is added at several rates up to 10% by manually blending the pellets of polyethylene and the pellets of masterbatch and putting the blend directly in the feeder.

Example 3: Coefficient of Friction (CoF) Data

[0059] The coefficient of friction measurements were performed with an Oscillating Tribotester. A 100Cr6 steel ball oft inch (1.27 cm) diameter and a 10 mm eccentric (giving a sliding distance of 20 mm per cycle) are used. A 2N load is applied perpendicularly and the sliding speed is set at 10 mm/s. The ball slides on the film tested with a course of 10 mm back and forth for a total length of 5 m, i.e. 250 cycles. 10 measurements by samples are performed.

TABLE-US-00002 TABLE 2 Table 2: Extraction in xylene, coefficient of friction and complex modulus data for each run carried out using vinyl endcapped and pendent (0.725% of vinyl function) high molecular weight silicone polymer. Silicone G* at extraction in CoF when 0.5% of initial silicone 0.1 Hz xylene (%) added (in masterbatch form) (Pa) 1 7.1 0.073 9880 2 25.6 0.077 6000 3 4.2 0.22 12140 4 19.2 0.08 5730 5 11.3 0.079 9090 6 44.2 0.12 1920 7 34.8 0.07 3210 8 44.2 0.12 1520 9 22.5 0.055 6150 10 44.8 0.116 1540 11 13.9 0.091 11818 12 18.1 0.088 9512 13 10.1 0.084 12374 14 11.5 0.091 11490 15 8.5 0.15 12709 16 9.6 0.09 11873

[0060] From table 2 it can be seen that the coefficient of friction decreases as the viscosity increases and the extraction in xylene decreases proving that the grafting of the gum onto the polyethylene is a key parameter to reduce the coefficient of friction of the final film. But for the highest level of grating (3), the coefficient of friction rises, indicating it is an optimum of grafting to reach to obtain the lowest coefficient of friction.

Polypropylene (PP) Example

Example 4: Preparation of the Masterbatch (M) of Different Viscosities and Molecular Weights

[0061] Pellets of polypropylene homopolymer (Polyolefin polymer (A)) with a melt flow index of 12 g/10 min (using the testing conditions of temperature of 190° C. and load of 2.16 kg) as the polymer matrix of masterbatch (M) were introduced into a co-rotative twin screw extruder sometimes with stabilizer (typically Irganox® 1010 antioxidant at a rate as indicated in Table 3 below). Then organopolysiloxane (B) was added into the already melted polypropylene phase using a gear pump. The average amount of organopolysiloxane (B) added into matrix polyethylene was about 25 wt. %.

[0062] All the components are mixed into a lab twin screw extruder having an L/D ratio greater than 40 (typically 48), diameter of the screw greater than 35 mm (typically 40 mm), then average screw speed is set to 550 rpm with a specific screw profile designed to disperse finely all the components into the polypropylene homopolymer. The mixtures are coiled with a water batch to room temperature and pelletized. The pellets are tested in melt flow index apparatus, at 190° C., under 2.16 kg. The pellets also undergo an extraction test as follows: around 0.24 g of masterbatches were accurately weighted and placed into a 20 ml headspace vial. 10 ml of p-xylene were accurately added (micropipette) and the vial was crimped. The samples were left to solubilize at high temperature (150° C.) for 20 minutes under continuous agitation using the headspace oven and the autosampler of the GC-MS (MPS from Gerstel). After cooling 10 ml of toluene was added and the samples were left under gentle stirring for 24 h (using a rotary shaker). The samples were then filtered through 0.45 μm PTFE filters into 2 ml glass auto sampler vials. All data is depicted in Table 3.

TABLE-US-00003 TABLE 3 Table 3: Process conditions, extraction in xylene and melt flow index data for each run carried out using vinyl endcapped high molecular weight silicone polymer. The 3B sample has been extruded using a high shear apparatus. Phenolic Vinyl content Silicone Melt Flow Index Screw Antioxidant of the silicone extraction (MFI) (conditions Sample speed (rpm) Output (kg/h) at 0.2% (Y/N) gum (%) in xylene (%) 190° C. & 2.16 kg load) 1B low high Y 0.012 22.7 5.44 2B High low N 0.012 23.3 9.54 3B high low N 0.012 18 11.34

[0063] The increase of the MFI values indicates that a chemical reaction occurred during the extrusion process. The higher the MFI value, the greater the degree of grafting between the organopolysiloxane (B) and the polypropylene.

Example 5: Preparation of the Bi-Oriented Polypropylene Films (BOPP) with Different Masterbatches

[0064] Polypropylene films were made on a pilot BOPP line. The process was as followed: stretching in machine direction (MDO) 5, in transverse direction (TDO) 10. The structure of the film was a standard BOPP clear film having 3 layers and being a BOPP clear film 20 um thick, having

(i) A layer of 1 micron terpolymer Adsyl 5C39F;
(ii) 18 microns thick layer of a homopolymer (Sabic 525);
(iii) 1 micron terpolymer Adsyl 5C39F.

[0065] An amount of masterbatch (M) was added to one of the Adsyl 5C39F layer (iii). The layer

(i) was Corona treated and the layer (iii) contained antiblock (silica).

Example 6: Coefficient of Friction Data: ASTM 1894-14 Film Against Film Measurements

[0066] In each of the examples, the CoF was measured in accordance with ASTM 1894-14 using a Zwick tensile machine. All data are presented in Table 4.

TABLE-US-00004 TABLE 4 Table 4: Silicone content in the external layer, coefficient of friction, melt flow index and haze for each run carried out using vinyl endcapped high molecular weight silicone polymer and polypropylene. Surface tension Dynamic Melt Flow Index (measured by drop Initial silicone Coefficient (MFI) (conditions Haze measured angle tests, in content in the of Friction 190° C. & following ASTM dynes) (1 Dyne = Sample external layer (%) Film/Film (CoF) 2.16 kg load) D1003-13 (%) 1 × 10.sup.5 N) 1B 0.5 0.300 5.44 2.77 43.1 1.25 0.410 2.57 42.4 2 0.250 2.37 40.9 2B 0.125 0.510 9.54 1.28 45.5 0.5 0.460 1.74 43.7 1.25 0.250 2.68 41.7 2 0.170 4.92 42.2 3B 0.5 0.240 11.34 2.00 43.0 1.25 0.290 2.60 44.3 2 0.210 4.40 43.8

[0067] From the Table 4, we can see that at high level of silicone (1.25 and 2%), the dynamic CoF is reduced for the high MFIs, indicating that the grafting acts in favour of a low CoF in BOPP films. We can also note that there is limited to no effect of our masterbatch on haze in the range tested. The same conclusion can be made with surface tension measurements: if a slight decrease is observed, the surface tension remains higher than 36 dynes, the limit value for printing or metallizing BOPP films.

Example 7: Coefficient of Friction (COF) Data: Steel Against Film Measurements

[0068] Coefficient of friction measurements were performed with the Oscillating Tribotester. A 100Cr6 steel ball oft inch (1.27 cm) diameter and a 10 mm eccentric (giving a sliding distance of 20 mm per cycle) are used. A 2N load is applied perpendicularly and the sliding speed is set at 10 mm/s. The ball slides on the film tested with a course of 10 mm back and forth for a total length of 5 m, i.e. 250 cycles. 10 measurements by samples are performed. The films are compared when containing 2% of masterbatch (M). All data is provided in Table 5.

TABLE-US-00005 TABLE 5 Table 5: Masterbatch content in the external layer, coefficient of friction and melt flow index for each run carried out using vinyl endcapped high molecular weight silicone polymer and polypropylene. Initial Dynamic Melt Flow silicone Coefficient Index (MFI) content in the of Friction (conditions external layer Steel/Film 190° C. & Sample (%) (CoF) 2.16 kg load) 1B 0.5 0.245 5.44 1.25 0.148 2 0.102 2B 0.125 0.248 9.54 0.5 0.132 1.25 0.066 2 0.051 3B 0.5 0.094 11.34 1.25 0.075 2 0.047

[0069] From Table 5 there is a clear correlation between the CoF and the Melt Index values: when compared at 2% loading, when the melt index increases, the CoF decreases, indicating that the grafting of the silicone and the resin decreases the CoF of the final BOPP film. The same conclusion can be made at every loadings.

Example 8: Stability of the Coefficient of Friction (Steel/Film), Surface Tension Over Time

[0070] Surface tension and coefficient of friction was followed over time after the BOPP process. The films were winding and stocked at 23° C. Surface tension evolution data is provided in Table 6.

TABLE-US-00006 TABLE 6 Table 6: Masterbatch content in the external layer, surface tension after 6 days, 45 days, 90 days, 135 days and 180 days for each run carried out using vinyl endcapped high molecular weight silicone polymer and polypropylene. Initial silicone Surface tension Surface tension Surface tension Surface tension Surface tension content in the (measured by drop (measured by drop (measured by drop (measured by drop (measured by drop external layer (%) angle tests, in dynes) angle tests, in dynes) angle tests, in dynes) angle tests, in dynes) angle tests, in dynes) Number of days after extrusion Sample NA 6 45 90 135 180 1B 0.5 43.1 37.2 35.1 36.5 36.5 1.25 42.4 37.5 36.4 35.9 35.3 2 40.9 35.7 33.7 34.6 34 2B 0.125 45.5 40.4 40.5 38 38.5 0.5 43.7 39.5 37.5 36.4 35.1 1.25 41.7 35.9 34.3 34.5 35.5 2 42.2 33.3 32.5 30 29.6 3B 0.5 43 36.2 37 34.6 33.9 1.25 44.3 39.8 39.1 35.9 38.3 2 43.8 34.9 33.3 31.7 33.1 (1 Dyne = 1 × 10.sup.5 N)

[0071] As expected, the surface tension drops from around 43 dynes to around 35 dynes after 6 months storage. But no correlation between the silicone amount, or the type of run and this drop have been found. In fact, the drop seems normal and in the same range as our reference (containing 0.125% of silicone). The additive does not seem to have effect on the surface tension of the films.

[0072] Coefficient of friction evolution data is provided in table 7.

TABLE-US-00007 TABLE 7 Table 7: Masterbatch content in the external layer, coefficient of friction after 30 days, 60 days, 90 days, 135 days and 180 days for each run carried out using vinyl endcapped high molecular weight silicone polymer and polypropylene. Dynamic Dynamic Dynamic Dynamic Dynamic Silicone content Coefficient Coefficient Coefficient Coefficient Coefficient in the external of Friction of Friction of Friction of Friction of Friction layer (%) Steel/Film (CoF) Steel/Film (CoF) Steel/Film (CoF) Steel/Film (CoF) Steel/Film (CoF) Number of days after extrusion Sample NA 30 60 90 135 180 1B 0.5 0.245 0.251 0.208 0.21 0.159 1.25 0.148 0.258 0.209 0.185 0.197 2 0.102 0.109 0.146 0.129 0.115 2B 0.125 0.248 0.345 0.329 0.314 0.346 0.5 0.132 0.1 0.108 0.109 0.104 1.25 0.066 0.077 0.061 0.071 0.057 2 0.051 0.057 0.046 0.038 0.038 3B 0.5 0.094 0.154 0.097 0.089 0.064 1.25 0.075 0.078 0.074 0.068 0.067 2 0.047 0.059 0.042 0.059 0.041

[0073] The coefficient of friction remains stable after 6 months storage, for each run. The little variation can be attributed to standard deviation of the measurement, which is around 8 to 10%. The additive presents then long term efficiency in slip properties.