PACKAGING FILMS WITH ANTI-FOGGING AGENT

Abstract

Packaging film with a coefficient of static friction >5 comprising: (i) a biodegradable polyester with a melt strength of 0.7-4 g and comprising units of at least one dicarboxylic acid and at least one diol, and (ii) an anti-fogging agent selected from the esters of a polyfunctional alcohol, provided that the ester is not a stearate.

Claims

1. A packaging film with a coefficient of static friction (COF) >5 comprising: (i) a biodegradable polyester having a melt strength of 0.7-4 g and comprising units of at least one dicarboxylic acid and at least one diol and having: Mn≥40000 Mw/q≤90000, where melt strength is measured according to ISO 16790:2005 at 180° C. and γ=103.7 s.sup.−1 using a capillary of 1 mm diameter and L/D=30 at a constant acceleration of 6 mm/sec.sup.2 and a stretching length of 110 mm; the molecular weights “Mn” and “Mw” are measured by gel permeation chromatography (GPC); “q”=the percentage by weight of polyester oligomer having a molecular weight by GPC≤10000 and (ii) an anti-fogging agent selected from an ester of a polyfunctional alcohol, provided that the ester is not a stearate.

2. The packaging film according to claim 1 for the production of thin films of thickness 3-50 μm.

3. The packaging film according to claim 1, in which said anti-fogging agent is in a quantity of 0.2-5 relative to the polyester content.

4. The packaging film according to claim 1, in which said anti-fogging agent is in a quantity of 1.0-2.0% relative to the polyester content.

5. The packaging film according to claim 1, in which said anti-fogging agent is selected from an ester of a fatty acid having 8 to 18 carbon atoms.

6. The packaging film according to claim 1, in which said anti-fogging agent is selected from polyglyceryl laurate and sorbitan monolaurate.

7. The packaging film according to claim 1, in which said anti-fogging agent is sorbitan polyoxyethylene monolaurate ester.

8. The packaging film according to claim 1, in which said anti-fogging agent is added to the polyester either by an extrusion process directly as the desired final concentration, or in a hopper during the film-forming step in the form of a “masterbatch”.

9. The packaging film according to claim 1, in which the biodegradable polyester i) has an aromatic moiety comprising at least one polyfunctional aromatic acid and an aliphatic moiety comprising at least one aliphatic diacid and at least one aliphatic diol.

10. The packaging film according to claim 1, in which the biodegradable polyester i) comprises a biodegradable aliphatic-aromatic polyester and an aliphatic polyester.

11. The packaging film according to claim 9, in which the polyfunctional aromatic acids are selected from aromatic dicarboxylic compounds of the phthalic acid type and heterocyclic aromatic dicarboxylic compounds of renewable origin, esters thereof and mixtures thereof.

12. The packaging film according to claim 1, in which in said biodegradable polyester i) said dicarboxylic acid comprises at least 50% by moles of an acid selected from azelaic acid, sebacic acid, adipic acid or mixtures thereof with respect to the total moles of aliphatic dicarboxylic acid.

13. The packaging film according to claim 1, in which the biodegradable polyester i) is mixed with one or more polymers of synthetic or natural origin.

14. The packaging film according to claim 13, in which said polymer of synthetic or natural origin is biodegradable.

15. The packaging film according to claim 13, in which said biodegradable polyester i) is mixed with at least one member selected from the group of poly L lactic acid, poly D lactic acid and poly D-L lactic acid complex stereo, poly-ε-caprolactone, poly hydroxybutyrate, poly hydroxybutyrate-valerate, polyhydroxybutyrate-propanoate, polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-octadecanoate, and poly 3-hydroxybutyrate-4-hydroxybutyrate.

16. The packaging film according to claim 13, in which the biodegradable polyester i) is mixed with 1-5% by weight of a polylactic acid polymer containing at least 75% L-lactic acid or D-lactic acid or combinations thereof, with a molecular weight Mw of over 30000.

17. The packaging film according to claim 1 for packaging of food articles, for industrial packaging, for bale compression in agriculture, or for wrapping waste.

18. A method for producing thin films having a coefficient of static friction (COF) >5 and a thickness of 3-50 μm which comprises admixing an anti-fogging agent selected from esters of a polyfunctional alcohol, with the proviso that said ester is not a stearate, with a biodegradable polyester having a melt strength of 0.7-4 g and comprising units of at least one dicarboxylic acid and at least one diol and having: Mn≥40000 Mw/q≤90000, where melt strength is measured according to ISO 16790:2005 at 180° C. and γ=103.7 s.sup.−1 using a capillary of 1 mm diameter and L/D=30 at a constant acceleration of 6 mm/sec.sup.2 and a stretching length of 110 mm; the molecular weights “Mn” and “Mw” are measured by gel permeation chromatography (GPC); “q”=the percentage by weight of polyester oligomer having a molecular weight by GPC≤10000.

19. The packaging film according to claim 2, in which the biodegradable polyester i) has an aromatic moiety comprising at least one polyfunctional aromatic acid and an aliphatic moiety comprising at least one aliphatic diacid and at least one aliphatic diol.

20. The packaging film according to claim 3, in which the biodegradable polyester i) has an aromatic moiety comprising at least one polyfunctional aromatic acid and an aliphatic moiety comprising at least one aliphatic diacid and at least one aliphatic diol.

Description

EXAMPLES

Example 1—Preparation of Biodegradable Polyesters, Description of the Antifogging Agents Used and Table of Compositions Used

[0124] P1: Poly(1,4-butylene adipate-co-1,4-butylene terephthalate) [PBAT], with a terephthalic acid content of 47% by moles with respect to the total dicarboxylic component. PBAT has an MFR of 4.1 g/10 min (@ 190° C., 2.16 kg), a shear viscosity of 1304 Pas at 180° C., a melt strength of 1.0 g and a terminal acid group content of 38 meq/kg.

[0125] P2: Poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene terephthalate) [PBATAz], having a terephthalic acid content of 47% by moles with respect to the total dicarboxylic component. PBATAz has an MFR of 4.9 g/10 min (@ 190° C., 2.16 kg), a shear viscosity of 1178 Pas at 180° C., a melt strength of 1.1 g and a terminal acid group content of 34 meq/kg. PLA: Ingeo 3251D polylactic acid characterised by an MFR of 35 g/10 min (@ 190° C., 2.16 kg) and M.sub.W=105000.

[0126] P3: Poly(1,4-butylene adipate-co-1,4-butylene terephthalate) [PBAT], with a terephthalic acid content of 47% by moles with respect to the total dicarboxylic component. PBAT has an MFR of 4.2 g/10 min (@ 190° C., 2.16 kg), a shear viscosity of 1289 Pas at 180° C., a melt strength of 0.9 g and a terminal acid group content of 33 meq/kg.

[0127] A1: polyglycerol laurate antifogging agent manufactured by Sabo©

[0128] A2: sorbitan polyoxyethylene monolaurate ester manufactured by Croda©

[0129] AC: sorbitan monostearate antifogging agent manufactured by Sabo©

[0130] S: HMV-5CA-LC hydrolysis stabiliser

TABLE-US-00001 TABLE 1 Compositions. Composition P1 P2 P3 PLA A1 A2 AC S  1 98.3 — — — 1.5 — — 0.2  2 98.8 — — — 1.0 — — 0.2  3 — 98.5 — — 1.5 — — —  4 (comparison) 99.8 — — — — — — 0.2  5 (comparison) — 100   — — — — — —  6 (comparison) 98.8 — — — — — 1.0 0.2  7 95.3 — — 3,0 1.5 — — 0.2  8 95.8 — — 3,0 1.0 — — 0.2  9 (comparison) 96.8 — — 3,0 — — — 0.2 10 — — 98.4 — — 1.5 — 0.1

[0131] The different compositions were fed to a model OMC EBV60/36 twin-screw extruder operating under the following conditions: [0132] Screw diameter (D)=58 mm; [0133] L/D=36; [0134] Screw rotation=140 rpm; [0135] Temperature profile=60-150-180-190×4-150×2° C.; [0136] Throughput: 40 kg/h; [0137] Vacuum degassing in zone 8 out of 10

[0138] The granules thus obtained were fed to a Ghioldi model blown film machine with a 40 mm screw diameter and L/D 30 operating at 30 rpm. The film-forming head had an air gap of 0.9 mm and L/D 12. Films of 18 μm thickness (9+9) [examples 1, 2, 4, 6-10] and 20 μm thickness (10+10) [examples 3, 5] were obtained using the conditions described in Table 2:

TABLE-US-00002 TABLE 2 Operating conditions used during film-forming. Film temperature Blowing ratio Drawdown ratio Composition (° C.) (BBR) (DDR) 1 145 3.2 31.7 2 145 3.2 31.7 3 145 3.2 28.5 4 (comparison) 145 3.2 31.7 5 (comparison) 145 3.2 28.5 6 (comparison) 145 3.2 31.7 7 170 3.2 31.7 8 170 3.2 31.7 9 (comparison) 170 3.2 31.7 10  170 3.2 31.7

[0139] 3 grams of film were analysed to determine the weight percentage of polyester oligomer (“q”) having a mean molecular weight of GPC≤10000 using the method described in the text. The films were analysed by gel permeation chromatography (GPC). Measurements were made at 40° C. using an Agilent® 1100 chromatograph. The determination was made using a set of two columns in series (particle diameters of 5 μm and 3 μm with mixed porosity), a refractive index detector, chloroform as eluent (flow rate 0.5 ml/min) and using polystyrene as reference standard.

TABLE-US-00003 TABLE 3 Physical and chemical characteristics of the prepared films. Oligomer Composition content (“q”) Mn Mw Mw/q 1 1.54 68720 128190 83240 2 1.55 68514 128446 82969 3 1.81 59605 115970 64072 4 (comparison) 1.60 68308 127164 79478 5 (comparison) 1.71 60933 126620 74047 6 (comparison) 1.55 68445 128434 82860 7 2.41 63884 125580 52108 8 2.42 63820 125329 51789 9 (comparison) 2.45 63628 124701 50898 10  1.52 69475 120080 79000

[0140] Mechanical properties were determined according to ASTM D882 (Tensile strength at 230° C. and 55% relative humidity and v.sub.o=50 mm/min).

[0141] Optical properties were determined according to ASTM D1003.

[0142] Water vapour permeability was determined at 23° C. and 50% relative humidity using ASTM F1249.

[0143] Cold Fog tests were performed to evaluate anti-fogging agent performance. 200 ml of water at a temperature of 30° C. was poured into a 250 ml beaker. The film under test was attached to the beaker and the sample was then placed in a refrigerator at 4° C. The change in the surface of the film in terms of water layer formation was recorded, and observations were made removing the beaker from the refrigerator after 5 min, 15 min, 30 min, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 1 day, 2 days, 3 days, 4 days and 6 days. As an indicator of the effect of the anti-fogging agent, reference is made to the moment when the transition from a layer of drops to a discontinuous film of water takes place.

Example 2 Comparison of Experimental Data

[0144]

TABLE-US-00004 TABLE 4 Comparison of clingability and transparency. Anti- Trans- Compo- fogging cling- unwind- mittance Haze Clarity sition effect ability ability (%) (%) (%)  1 30 min 5 5 92 5 99  2 60 min 4 4 92 6 98  3 30 min 5 5 92 5 99  4 (com- Not found 4 2 92 7 99 parison)  5 (com- Not found 4 2 92 6 98 parison)  6 (com- Not found 1 5 91 12  97 parison) 10 30 min 5 4 92 4 99

[0145] Key to Table 4: The term “clingability” according to the present invention defines the ability of the film to adhere to itself and to a surface on a scale from 1 (little) to 5 (much). The term “unwindability” according to the present invention is understood as ease of unwinding the film on a scale from 1 (little) to 5 (much).

TABLE-US-00005 TABLE 5 Comparison of clingability and transparency. Anti- Trans- fogging cling- unwind- mittance Haze Clarity Composition effect ability ability (%) (%) (%) 7 30 min 4 5 92 14 98 8 60 min 3 5 92 15 97 9 (com- Not found 2 4 92 15 95 parison)

[0146] Key Table 5: The term “clingability” according to the present invention defines the ability of the film to adhere to itself and to a surface on a scale from 1 (little) to 5 (much). The term “unwindability” according to the present invention is understood as ease of unwinding the film on a scale from 1 (little) to 5 (much).

TABLE-US-00006 TABLE 6 Mechanical properties and water vapour permeability of film with the anti-fogging agent according to the invention. Load Elongation Elastic at break at break modulus WVTR Composition Dir. (MPa) (%) (MPa) (g/m.sup.2/day) 1 MD 56 354 98 310 TD 48 693 118 2 MD 58 347 102 328 TD 46 704 122 3 MD 45 378 97 315 TD 43 698 115 4 (comparison) MD 59 382 119 396 TD 66 526 115 5 (comparison) MD 47 386 93 385 TD 54 518 108 6 (comparison) MD 55 338 111 170 TD 46 582 125 10  MD 54 309 115 313 TD 43 588 125

[0147] As can be seen, the high water vapour barrier in comparison example 6 (WVTR=170 g/m.sup.2/day) confirms that excessive migration of the anti-fogging agent to the surface does not confer any anti-fogging properties and results in a deterioration in optical properties compared to the reference.

TABLE-US-00007 TABLE 7 Mechanical properties and water vapour permeability of film with the anti-fogging agent according to the invention. Load Elongation Elastic at break at break modulus WVTR Composition Dir. (MPa) (%) (MPa) (g/m2day) 7 MD 43 406 179 330 TD 49 648 117 8 MD 45 400 173 338 TD 51 615 120 9 (comparison) MD 48 347 223 387 TD 52 487 146

Example 3 Film Performance in Food Tray Packaging Equipment

[0148] The film prepared according to example 1 (composition 1) was tested using the STN 8500WE © food tray packaging machine from OMORI.

[0149] The film had a nominal thickness of 16-18 micron—reel strip 400 mm; the tray used was PS with a short side circumference of 360 mm.

[0150] The packaging phase was divided into three stages: [0151] 1. Wrapping tray, central welding and tube cutting; [0152] 2. Folding head and tail flaps of the tube under the tray; [0153] 3. Transport on heated belt and flap welding.

[0154] In the first phase the film showed good machine behaviour both in the transport and conveying phase (excellent elasticity) and sealing of the central zone, which is performed by two pairs of heated rollers (set at 135° C.). No critical points were noted even in the cutting stage.

[0155] In the second phase, regular folding of the flap at the bottom of the tray brought about by running at a high packaging speed, increasing from 35 to 80-90 trays/min, with a glass fibre belt temperature set at 150° C.

[0156] No significant criticalities were identified during the stage of transport on the heated belt and welding (third phase).