PLASTIC FILMS

Abstract

Use of olefin-based plastic films for obtaining labels in rolls for high speed roll-fed applications from about 8,000 to about 75,000 containers/hour, the films having a thickness comprised between 10 and 22 μm, flexural rigidity (N.Math.mm) in the range 0.5×10.sup.−2-4.5×10.sup.−2 save for a constant 1/[12×(1−ν.sup.2)] wherein ν is the Poisson modulus, the elongation at break in MD determined according to ASTM D 882 lower than 130%, dimensional stability measured according to the OPMA TC 4 standard at 130° C. for 5 minutes in the air in MD comprised between 0 and −10% and in TD between −4 and +4%.

Claims

1. Use of polyolefin-based plastic films for obtaining labels from rolls for high speed roll-fed applications higher than about 8,000 to about 75,000 containers/hour, the films having a thickness in the range from 10 to 22 μm, flexural rigidity (N.Math.mm) in the range 0.5×10.sup.−2-4.5×10.sup.−2 neglecting a constant 1/[12×(1−ν.sup.2)] being ν the Poisson modulus, an elongation at break in MD, determined according to ASTM D 882, lower than 130%, a dimensional stability, determined according to the OPMA TC 4 standard at 130° C. for 5 minutes in air in MD in the range from 0 to −10% and in TD from −4 to +4%.

2. Use of polyolefin-based plastic films according to claim 1 wherein the plastic films have an elastic modulus in TD lower than 3,500 N/mm.sup.2 and in MD from 2,600 to 3,800 N/mm.sup.2.

3. Use of polyolefin-based plastic films according to claim 2 wherein the polyolefin-based plastic films have an elastic modulus in TD lower than 3,500 N/mm.sup.2 and in MD in the range from 3,000 to 3,600 N/mm.sup.2.

4. Use of polyolefin-based plastic films according to claims 1-3 wherein the film thickness is in the range from 14 to 20 μm.

5. Use of polyolefin-based plastic films according to claims 1-4 wherein the flexural rigidity is in the range from 0.7×10.sup.−2 to 3.5×10.sup.−2 N.Math.mm.

6. Use of polyolefin-based plastic films according to claim 5 wherein the flexural rigidity is in the range from 0.8×10.sup.−2 to 3.0×10.sup.−2 N.Math.mm.

7. Use of polyolefin-based plastic films according to claim 6 wherein the flexural rigidity is in the range from 0.9×10.sup.−2 to 2.8×10.sup.−2 N.Math.mm.

8. Use of polyolefin-based plastic films according to claims 1-7 wherein the elongation at break is lower than 120%.

9. Use of polyolefin-based plastic films according to claims 1-8 wherein the dimensional stability in MD is in the range from −4 to −8.5% and in TD in the range from 0 to +2.5%.

10. Use of polyolefin-based plastic films according to claims 1-9 wherein the plastic films are based on propylene homopolymers having an extractable amount in n-hexane lower than 10% by weight as determined according to the FDA 177 1520 standard.

11. Use of polyolefin-based plastic films according to claims 1-10 wherein the plastic films are multilayers comprising: core: propylene homopolymers, skin layers, equal to or different from each other, based on propylene homopolymers and/or olefinic copolymers.

12. Use of polyolefin-based plastic films according to claim 11 wherein the olefinic copolymers of the skin layers are selected from copolymers of propylene with at least another ethylenic unsaturation containing comonomer, preferably selected from ethylene and alpha-olefins having a number of carbon atoms ranging from 4 to 12, the total comonomer amount being comprised between 0.5 and 25% by weight on the total monomers.

13. Use of polyolefin-based plastic films according to claims 11-12 wherein the propylene copolymers have a concentration of extractables lower than 10%.

14. Use of polyolefin-based plastic films according to claims 1-13 wherein the polyolefin-based plastic films have a thickness in the range from 14 to 20 μm, flexural rigidity from 0.7×10.sup.−2 to 3.5×10.sup.−N.Math.mm, elongation at break in MD lower than 120%, elastic modulus in TD is lower than 3,500 N/mm.sup.2 and in MD in the range from 3,000 to 3,600 N/mm.sup.2, dimensional stability in ND in the range from −4 and −8.5%, and in TD from 0 to +2.5%.

15. Use of polyolefin-based plastic films according to claims 11-14 wherein the skin layers comprise optional components selected from slip agents and anti-blocking agents; the core layer comprises optional components-selected from antistatic agents, dyestuffs, hydrogenated hydrocarbon resins in amounts from about 2% to 40% by weight on the total weight of the olefinic polymer plus the core hydrocarbon resin, propylene copolymers or ethylene copolymers in amounts from 0 to 20% with respect to the propylene homopolymer amount.

16. A process for preparing a plastic film according to claims 1-15 comprising the following steps: coextrusion of the film sheet; sheet cooling on the surface of cooled chill roll dipped in a water bath; sheet heating; sheet stretching and orientation by a simultaneous orientation process in MD and TD direction by taking the sheet edges, having an higher thickness than the sheet, with a series of pliers/clamps independently driven by linear synchronous induction motors, wherein the pliers/clamps set runs on divergent stretching rails; For the stretching step a stretching frame comprising one or more sections located inside an oven at temperatures comprised between about 150° and 190° C., is used; the MD longitudinal stretching ratios being comprised from about 4:1 to about 9:1 and the TD transversal stretching ratios from about 3:1 to about 8:1. heat setting in TD, preferably through a convergence of the stretching rails and heat setting in MD by decreasing the linear pliers speed.

17. Polyolefin-based plastic films according to claims 1-15.

18. Plastic films according to claim 17 wherein the elastic modulus in TD is lower than 3,500 N/mm.sup.2 and in MD ranges from 2,600 to 3,800 N/mm.sup.2, preferably from 3,000 to 3,600 N/mm.sup.2.

19. Plastic films according to claim 17 obtainable by the process of claim 16.

20. Labels obtainable from plastic films of claims 17-19.

Description

EXAMPLES

Characterization

Melt Flow Index (MFI)

[0084] The melt flow index was determined at 230° C. for 10 min with a load of 2.16 Kg according to ISO 1133.

Extractables Amounts of Propylene Polymers

[0085] The extractables are determined by extracting a sample of the polymer with n-hexane at 50° C. for two hours according to FDA 177 1520 Standard.

Film Dimensional Stability

[0086] The film dimensional stability is determined according to OPMA TC 4 standard by heating a sample having 20 cm×1 cm sizes at 130° C. for 5 minutes in the air.

[0087] If the sample shrinks, the number of the dimensional stability is preceded by −, if the sample dilates, by +.

Young Modulus (Elastic Modulus)

[0088] The modulus of Young, or elastic modulus (N/mm.sup.2) has been determined according to the ASTM D 882 standard both in MD direction and in TD direction.

Elongation at Break and Tensile Strength at Break

[0089] The elongation at break and tensile strength at break (N/mm.sup.2) of the film are determined by ASTM D 882.

Flexural Rigidity

[0090] The flexural rigidity, or rigidity (N.Math.mm), is given by the following formula:

R=[E.Math.d.sup.3]/12(1−ν.sup.2)

wherein R is the rigidity, E the Young modulus and d is the thickness in mm. In the calculation of flexural rigidity calculation ν.sup.2 is neglected as it is very low compared to 1.

Haze

[0091] The Haze values are determined according to ASTM D 1003.

Gloss

[0092] The Gloss values are determined according to ASTM D 2457 standard.

Scraps

[0093] In the transformation step scraps are calculated with reference to the weight of the starting film roll. In the application step scraps are calculated with reference to the number of containers discarded with respect to those obtained.

FORMULATION EXAMPLES

Process for the Preparation of the Film of the Invention

[0094] The film has been obtained by coextruding through a flat head three polymeric layers, respectively, the core and the skin layers.

[0095] The core has been extruded at extruder temperatures in the range 235° C.-255° C., the skin layers at extruder temperatures comprised between 260° C.-275° C. The three layers have been coextruded in a flat head at the temperature of 245° C. The so obtained sheet has been cooled to a temperature of 25° C. on a chill roll, partly dipped in a water bath having a temperature of 28° C. The chilled sheet passed through an infrared heating battery wherein the surface temperature of the heating panels was comprised between 200° C. and 320° C. Then the sheet entered a simultaneous stretching oven Lisim® wherein:

[0096] the temperature set of the preheating zone was in the range 165° C.-170° C.;

[0097] the temperature set of the stretching zone was in the range 159° C.-163° C.;

[0098] the temperature set of the annealing zone was in the range 164° C.-170° C.;

[0099] the longitudinal and transversal stretching ratios at the outlet of the stretching frame were respectively of 7 and 6.5. The so obtained film was flame treated on a surface obtaining a surface tension value≧44 dyne/cm at t=0.

Example 1

[0100] By the process above reported a multilayer film according to the invention was prepared, having thickness 19 μm and the following composition:

[0101] core layer 100% by weight of PP homopolymer, MFI 2, (HP522H LyondelBasell® polymers) having thickness 17 μm,

[0102] skin layer 1 (skin 1 flame surface treated, to be printed): 99% by weight of a PP homopolymer having MFI 2.0 (HP422H LyondelBasell® polymers), +1% by weight of a polypropylene silica masterbatch (AB 6001PP Schulmann®-anti-block agent). Skin 1 thickness is 1 μm.

[0103] skin layer 2 (skin 2, not surface treated): 93% by weight of PP homopolymer, +6% by weight of slip agent ABVT34SC (Schulmann®) masterbatch based on silicone particles having a 2 μm diameter, +1% by weight of a silica masterbatch with polypropylene carrier as in skin 1. Skin 2 thickness is 1 μm.

[0104] The characterization data are reported in Table 1.

[0105] The flexural rigidity of the film was 2.20×10.sup.−2N.Math.mm.

[0106] The Young modulus of the film in TD direction was 2780 N/mm.sup.2.

Example 2

[0107] Example 1 was repeated but using in the core 90% by weight of propylene homopolymer of Example 1 +10% by weight of masterbatch of amorphous hydrocarbon resins with polypropylene carrier Constab MA00929PP (see for example the technical card KafritGroup of July 2010).

[0108] The thickness of the core and of the skin layers was as in the film of example 1.

[0109] The characterization data are reported in Table 1.

[0110] The flexural rigidity of the film was 2.61×10.sup.−2N.Math.mm.

[0111] The Young modulus of the film in TD direction was 3152 N/mm.sup.2.

Example 3

[0112] Example 2 was repeated but using in the core 89% by weight of propylene homopolymer of example 1, +1% by weight of antistatic agent ASPA2446 (Schulmann®) masterbatch with propylene homopolymer carrier, instead of 90% by weight of propylene homopolymer.

[0113] In skin 2 a polypropylene ADSTIFHA612M (LyondellBasell®) having MFI=6 has been used. The core thickness was 14 μm, the thickness of each skin layer was 2.5 μm.

[0114] The characterization data are reported in Table 1.

[0115] The flexural rigidity of the film was 2.47×10.sup.−2 N.Math.mm.

[0116] The Young modulus of the film in TD direction was 3374 N/mm.sup.2.

Example 4

[0117] Example 3 was repeated but skin 1 was 100% by weight of propylene-ethylene copolymer with MFI=5.5.

[0118] Skin 2 was 94% by weight of propylene homopolymer +6% by weight of masterbatch comprising the slip agent in polypropylene carrier as used in skin 2 of example 1.

[0119] The core thickness was of 17 μm, the thickness of each skin layer was 1 μm.

[0120] The characterization data are reported in Table 1.

[0121] The flexural rigidity of the film was 2.17×10.sup.−2N.Math.mm.

[0122] The Young modulus of the film in TD direction was 2904 N/mm.sup.2.

Example 5

[0123] Example 4 was repeated but with skin 2 having the same composition as skin 2 of the film of example 3. The thickness of each of the three layers was as in the film of example 4.

[0124] The characterization data are reported in Table 1.

[0125] The flexural rigidity of the film was 2.24×10.sup.−2N.Math.mm.

[0126] The Young modulus of the film in TD direction was 2928 N/mm.sup.2.

Example 6

[0127] Example 1 was repeated but the core was the same as in example 3 i.e., 94% by weight of PP homopolymer, +5% by weight of the masterbatch of amorphous hydrocarbon resins with polypropylene carrier Constab® MA00929PP, +1% anatistatic masterbatch. The thickness of each of the three layers was as in the film of example 4.

[0128] The characterization data are reported in Table 1.

[0129] The flexural rigidity of the film was 2.24×10.sup.−2N.Math.mm.

[0130] The Young modulus of the film in TD direction was 2878 N/mm.sup.2.

Example 7

[0131] Example 6 was repeated but in the core 94% polypropylene was formed of 84% by weight of propylene homopolymer used in example 6 +10% of reclaim (regranulated) propylene polymers. The thickness of each of the three layers was as in the film of example 4.

[0132] The characterization data are reported in Table 1.

[0133] The flexural rigidity of the film was 2.24×10.sup.−2N.Math.mm.

[0134] The Young modulus of the film in TD direction was 3100 N/mm.sup.2.

APPLICATION EXAMPLES

Example 7A

[0135] The film of Example 7 was wound in a roll (extrusion mother roll) that was cut to obtain extrusion daughter rolls having width 630 mm and film length 22,000 m, external diameter 780 mm, density 0.91 g/cm.sup.3, for the 2 colour reverse rotogravure printing for preparing labels to be applied on 0.5 liter PET bottles.

[0136] During the transformation step the roll film has been printed at a line speed of 280 meters/min for 80 minutes. The print scraps amounted to 400 meter corresponding to a weight of 4.5 kg.

[0137] Further, the extrusion daughter rolls were cut to obtain transformation daughter rolls, each having width 68 mm width, roll diameter 600 mm and film length 10,000 m. 18 rolls were overall obtained in two working cycles. Cutting was carried out at a line speed of about 600 m/min without the formation of creases and folds. The total amount of scraps in the transformation step (cutting+printing), net of trimmed edges, was lower than 3%.

[0138] From the transformation daughter rolls about 46,500 labels having length 215 mm and height (width) 68 mm by a roll-fed labelling machine were obtained, for application to 0.5 liter PET bottles.

[0139] The roll fed application lasted 2 hours. The line speed was up to 60,000 bottles/h (bph) (average speed line about 55,000 bph), and the label cut from the roll was found to be precise and clear, the print pitch regular and constant. The discarded bottles were 92 on about 115,000 (0.08%).

[0140] This example shows that the rolls of the films of the present invention can be used in roll-fed application to manufacture labels without jamming at a speed line also of 60,0000 bph).

Example 7B

[0141] The printed transformation daughter rolls obtained in example 7A having film length 10,000 m, roll diameter 600 mm but width 85 mm, were used to obtain labels having length 287 mm and width 85 mm for application on a roll-fed labelling machine to 1.5 liter cylindrical PET bottles. The roll fed application lasted 2 hours. The line speed was up to 44,000 bph (average speed line 42,000 bph) and the label cut resulted precise and clearcut, the print pitch regular and constant. The discarded bottles were 43 over about 85,000 (0.05%).

Example 7C

[0142] The printed transformation daughter rolls obtained in example 7A, having length 10,000 m, roll diameter 600 mm but width 85 mm, were used to obtain labels having length 320 mm and width 59 mm for application on a roll-fed labelling machine to 2.0 liter cylindrical PET bottles.

[0143] The roll fed application lasted 2 hours. The line speed was up to 36,000 bph (average speed 34,000 bph) and the label cut resulted precise and clearcut, the print pitch regular and constant.

[0144] The discarded bottles were 18 over about 70,000 (0,024%).

FORMULATION EXAMPLES

Example 8

[0145] Example 7 was repeated but substituting in the core 94% of PP homopolymer with 69% of PP homopolymer +25% of masterbatch of titanium dioxide (white 70) with polypropylene carrier. The masterbatches of amorphous resin and of antistatic were in the same amounts as in ex. 7. The thickness of each of the three layers was as in the film of example 4.

[0146] The characterization data are reported in Table 1.

[0147] The flexural rigidity of the film was 2.26×10.sup.−2N.Math.mm.

[0148] The Young modulus of the film in TD direction was 3192 N/mm.sup.2.

Example 9

[0149] According to the process reported above a multilayer film was prepared, having thickness 15 μm and the following composition:

[0150] core: 89% by weight PP homopolymer MFI 2, (HP522H LyondellBasell® polymers), +10% by weight of masterbach of amorphous hydrocarbon resins in propylene homopolymer carrier Constab MA00929PP, +1% by weight of antistatic agent ASPA2446 (Schulmann®) masterbatch with polypropylene carrier; the core thickness was 13 μm,

[0151] skin 1: 99% by weight of a propylene homopolymer having MFI 2.0 (HP422H LyondelBasell® polymers), +1% by weight of a silica masterbatch in propylene homopolymer carrier (AB 6001PP Schulmann® anti-block agent); the layer thickness was 1 μm,

[0152] skin 2: 93% by weight of polypropylene homopolymer HP522H LyondellBasell® polymers), +6% by weight of slip agent ABVT34SC (Schulmann®) masterbatch based on silicone particles having a 2 μm diameter, +1% by weight of a silica masterbatch in polypropylene AB 6001PP; the layer thickness was of 1 μm.

[0153] The characterization data are reported in Table 2.

[0154] The flexural rigidity of the film was 1.22×10.sup.−2N.Math.mm.

[0155] The Young modulus of the film in TD direction was 3107 N/mm.sup.2.

Example 10

[0156] Example 9 was repeated but the core thickness was 11 μm and the thickness of each skin layer was 2 μm.

[0157] The composition of skin 2 was 93% by weight of polypropylene homopolymer ADSTIFHA612M (LyonellBasell®) having MFI 6, +6% by weight of slip agent ABVT34SC (Schulmann®) masterbatch based on silicone particles having a 2 μm diameter, +1% by weight of a silica masterbatch in polypropylene AB 6001PP.

[0158] The characterization data are reported in Table 2.

[0159] The flexural rigidity of the film was 1.25×10.sup.−2 N.Math.mm.

[0160] The Young modulus of the film in TD direction was 3163 N/mm.sup.2.

Example 11

[0161] Example 9 was repeated but the layer composition was the following:

[0162] core: 84% by weight of propylene homopolymer of example 9, +10% by weight of reclaim (regranulated) propylene homopolymer, +5% by weight of masterbach of amorphous hydrocarbon resins Constab MA00929PP, +1% by weight of antistatic agent ASPA2446,

[0163] skin 1: 100% by weight of propylene-ethylene copolymer having MFI=5.5,

[0164] skin 2: 93% by weight of PP homopolymer, +6% by weight of slip agent ABVT34SC (Schulmann®) masterbatch based on silicone particles having a 2 μm diameter, +1% by weight of a silica masterbatch with polypropylene carrier (AB 6001PP Schulmann® anti-block agent).

[0165] The thickness of the layers was as in example 9.

[0166] The characterization data are reported in Table 2.

[0167] The flexural rigidity of the film was 1.0×10.sup.−2 N.Math.mm.

[0168] The Young modulus of the film in TD direction was 3050 N/mm.sup.2.

COMPARATIVE APPLICATION EXAMPLE

Example 12 Comparative

[0169] Example 7A was repeated but using a commercial film Stilan® TP 35 having thickness 35 μm.

[0170] The film length of the extrusion daughter rolls was of 13,500 m, that is about one half that of the corresponding rolls of example 7A (22,000 m). During the processing step it was compulsory to slow down line speed to change the rolls and make the relevant joints.

[0171] Therefore the printing step was discontinuous and with line speed changes with respect to that of example 7A.

[0172] The scraps obtained for 400 linear meters amounted to 8.26 Kg, that is about twice the scraps of example 7A.

[0173] Furthermore, being the diameter the same, with the transformation daughter roll of this example labels were about 28,000, about 40% less than those obtained with the transformation daughter roll of example 7A).

TABLE-US-00001 TABLE 1 Skin 1 Elastic (subjected Ultimate Elongation modulus Dimensionalstability Thickness to surface tensile in MD in MD in % Ex. μm Core treatments) Skin 2 stress % N/mm.sup.2 MD TD 1 19 PP Homopolymer 99% PP 93% PP 226 102 3200 −7.3 +1.4 homopolymer + homopolymer + 1% silica 1% silica masterbatch masterbatch + 6% slip agent masterbatch 2 19 90% PP 99% PP 93% PP 209  97 3800 −9 +0.9 homopolymer + homopolymer + homopolymer + 10% masterbatch of 1% silica 1% silica amorphous resins masterbatch masterbatch + 6% slip agent masterbatch 3 19 89% PP 99% PP 93% PP 211 109 3596 −8.1 +0.7 homopolymer + homopolymer + homopolymer + 10% masterbatch of 1% silica 1% silica amorphious resins + masterbatch masterbatch + 1% antistatic 6% slip agent masterbatch masterbatch 4 19 89% PP CopolymerP/E 94% P/E 177  93 3170 −7.3 +1.4 homopolymer + copolymer + 10% masterbatch of 6% slip agent amorphous resins + masterbatch 1% antistatic masterbatch 5 19 89% PP P/ECopolymer 93% PP 213 121 3273 −7.3 +1.1 homopolymer + homopolymer + 10% masterbatch of 1% silica amorphous resins + masterbatch + 1% antistatic 6% slip agent masterbatch masterbatch 6 19 94% PP 99% PP 93% PP 206 111 3267 −7.4 +1.2 homopolymer + homopolymer + homopolymer + 5% masterbatch of 1% silica 1% silica amorphous resins + masterbatch masterbatch + 1% antistatic 6% slip agent masterbatch masterbatch 7 19 94% PP 99% PP 93% PP 217 117 3100 −7.3 +1.0 homopolymer + homopolymer + homopolymer + 5% masterbatch of 1% silica 1% silica amorphous resins + masterbatch masterbatch + 1% antistatic 6% slip agent masterbatch masterbatch 8 19 69% PP 99% PP 93% PP 178 101 3297 −6.0 +1.0 homopolymer + homopolymer + homopolymer + 5% masterbatch of 1% silica 1% silica amorphous resins + masterbatch masterbatch + 1% antistatic 6% slip agent masterbatch + 25% masterbatch masterbatch TiO.sub.2

TABLE-US-00002 TABLE 2 Ultimate Skin 1 tensile Elastic (subjected stress Elongation modulus Dimensionialstability Thickness to surface in MD in MD in MD in % Ex. μm Core treatments) Skin 2 N/mm.sup.2 % N/mm.sup.2 MD TD  9 15 89% PP 99% PP 93% PP 221 108 3612 −8.7 +1.5 homopolymer + homopolymer + homopolymer + 10% masterbatch of 1% silica 1% silica amorphous resins + masterbatch masterbatch + 1% antistatic 6% slip agent masterbatch masterbatch 10 15 89% PP 99% PP 93% PP 215 105 3719 −8.2 +1., 3 homopolymer + homopolymer + homopolymeer + 10% masterbatch of 1% silica 1% silica amorphous resins + masterbatch masterbatch + 1% antistatic 6% slip agent masterbatch masterbatch 11 15 94% PP P/Ecopolymer 93% PP 212 104 3050 −8.1 +1., 2 homopolymer + homopolymer + 5% masterbatch of 1% silica amorphous resins + masterbatch + 1% antistatic 6% slip agent masterbatch masterbatch