BIODEGRADABLE POLYESTER AND ADHERENT PACKAGING FILMS MADE THEREFROM

Abstract

A biodegradable aliphatic-aromatic polyester for the production of packaging films, having a Poisson's ratio (RVE) between 800 and 1700, comprising units of at least one dicarboxylic acid and at least one diol, in which Mn≥40000 and Mw/q≤90000, in which q is the percentage by weight of polyester oligomers having a molecular weight≤10000.

Claims

1. A biodegradable aliphatic-aromatic polyester suitable for use in the production of packaging films, said polyester having a Poisson's ratio (RVE) between 800 and 1700 and comprising units derived from at least one dicarboxylic acid and at least one diol; and having: Mn≥40000 Mw/q≤90000, wherein: q is the percentage by weight of polyester oligomers with a molecular weight ≤10000 as determined by GPC; the molecular weights “Mn” and “Mw”, are measured by gel permeation chromatography (GPC) according to the method described in the description; the Poisson's ratio is calculated as the ratio of shear viscosity to melt strength (MS); shear viscosity is determined at 180° C. with a flow gradient of γ=103.7 s−1 using a 1 mm diameter capillary and L/D=30 according to ASTM D3835-90, melt strength (MS) is measured according to ISO 16790:2005 at 180° C. and γ=103.7 s−1 using a capillary of diameter of 1 mm and L/D=30 at a constant acceleration of 6 mm/sec2 and a stretching length of 110 mm; a film of such polyester having a friction coefficient between 5 and 10, measured with the method described in the description.

2. The biodegradable aliphatic-aromatic polyester according to claim 1, in which the shear viscosity is between 800 and 1200 Pas.

3. The biodegradable polyester according to claim 1, in which an aliphatic polyester is added to the biodegradable aliphatic polyester.

4. The biodegradable polyester according to claim 3, in which said biodegradable aliphatic polyesters comprise at least one aliphatic diacid and at least one aliphatic diol.

5. The biodegradable polyester according to claim 1, in which said biodegradable aliphatic-aromatic polyesters have an aromatic part comprising at least one polyfunctional aromatic acid and an aliphatic part comprising at least one aliphatic diacid and at least one aliphatic diol.

6. The biodegradable polyester according to claim 5, 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.

7. The biodegradable polyester according to claim 6, in which the content of polyfunctional aromatic acids is between 30 and 70% in moles relative to the total content of dicarboxylic acids in moles.

8. The biodegradable polyester according to claim 5, in which the aliphatic diacids are aliphatic dicarboxylic acids having between 2 and 22 carbon atoms in the main chain, and esters thereof.

9. The biodegradable polyester according to claim 8, in which said aliphatic dicarboxylic acids are from a renewable source.

10. The biodegradable polyester according to claim 1, in which said aliphatic dicarboxylic acids from a renewable source comprise at least 50% in moles of azelaic acid, adipic acid or mixtures thereof relative to the total moles of aliphatic dicarboxylic acids.

11. A mixture of the biodegradable polyester according to claim 1 with one or more polymers of synthetic or natural origin.

12. The mixture according to claim 11, in which said polymer of synthetic or natural origin is biodegradable.

13. The mixture according to claim 12, in which said biodegradable polymer is a biodegradable polyester of the diacid-diol, hydroxy acid or polyester type.

14. The mixture according to claim 13, in which said biodegradable polyester from hydroxy acid is selected from the group consisting of poly L lactic acid, poly D lactic acid and poly D-L lactic acid stereo complex, poly-ε-caprolactone, polyhydroxybutyrate, polyhydroxybutyrate-valerate, polyhydroxybutyrate-propanoate, polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-octadecanoate, and poly 3-hydroxybutyrate-4-hydroxybutyrate.

15. The mixture according to claim 11, in which said natural polymer is selected from the group consisting of starch, cellulose, chitin, chitosan, alginates, proteins and derivatives thereof.

16. The mixture according to claim 11, in which said polymer is selected from the group consisting of polyolefins, non-biodegradable polyesters, polyester-urethanes, polyether-urethanes, polyamides, polyamino acids, polyethers, polycarbonates and mixtures thereof.

17. A packaging film comprising the biodegradable polyester according to claim 1, or a mixture thereof with one or more polymers of synthetic or natural origin.

18. The packaging film according to claim 17 having a thickness of 3-50 microns.

19. A method of packaging a member selected from the group of food articles, industrial packaging, bale compression in agriculture, and waste wrapping, which comprises applying the packaging film according to claim 17 to the member.

20. The biodegradable polyester according to claim 6, in which the aliphatic diacids are aliphatic dicarboxylic acids having between 2 and 22 carbon atoms in the main chain, and esters thereof.

Description

EXAMPLES

Examples 1-2

[0103] Poly(1,4-butylene adipate-co-1,4-butylene terephthalate) [PBTA], with a content of 47% in moles of terephthalic acid with respect to the total dicarboxylic component. PBTA has an MFR of 4.8 g/10 min (@ 190° C., 2.16 kg), a Poisson's ratio of 1083 (shear viscosity at 180° C. of 1083 Pas and melt strength of 1, 0 g-strength) and a terminal acid group content of 34 meq/kg.

Examples 3-4 (Comparative)

[0104] Poly(1,4-butylene sebacate-co-1,4-butylene terephthalate) [PBTSeb], with a content of 56% in moles of terephthalic acid with respect to the total dicarboxylic component. PBTSeb is characterised by an MFR of 2.6 g/10 min (@ 190° C., 2.16 kg), a Poisson's ratio of 394 (shear viscosity at 180° C. of 1220 Pas and melt strength of 3, 1 g-strength) and a terminal acid group content of 40 meq/kg.

Characterisation, Film Production and Mechanical Testing

[0105] The polyesters were analysed by gel permeation chromatography (GPC). Measurements were made at 40° C. using an Agilent® 1100 chromatograph. The determination was performed 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.

[0106] Table 1 shows the characteristics of the polymers prepared

TABLE-US-00001 Oligomer Ex content (“q”) Mw Mn Mw/q PBTA 1.5 127760 72351 88110 PBTSeb 1.7 178608 83511 105064 (comparative)

[0107] The PBTA and PBTSeb granules 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 has an air gap of 0.9 mm and L/D 12.20 micron thick films (10+10) were obtained using the conditions described in Table 2 below:

TABLE-US-00002 TABLE 2 Film temperature Blowing ratio Draw-down ratio Ex. (° C.) (BBR) (DDR) 1 170 3.2 28 2 145 3.2 28 3 comparative 170 2.5 36 4 comparative 270 2.5 36

[0108] 3 grams of film were analysed to determine the weight percentage of polyester oligomer (“q”) having a molecular weight by GPC≤10000, using the method described in the text.

TABLE-US-00003 TABLE 3 Oligomer Ex content (“q”) Mw Mn Mw/q 1 1.7 126620 60933 74482 2 1.5 126610 62458 83073 3 comparative 1.7 179622 81277 105660 4 comparative 2.7 158780 78147 58807

[0109] The mechanical properties were determined according to ASTM D882 (traction at 23° C. and 55% relative humidity and vo=50 mm/min) in the longitudinal direction with respect to the film-forming direction.

[0110] The optical properties were determined according to ASTM D1003.

[0111] The coefficient of friction (COF) was determined according to the modification of the ASTM D1894 standard “Static and kinetic coefficients of friction of plastic films and sheets” described in the text.

TABLE-US-00004 TABLE 4 Breaking Tensile Modulus of behaviour strength Elongation at elasticity Transmittance Haze Clarity during Ex. (MPa) break (%) (MPa) (%) (%) (%) COF Clingability unwinding 1 50 386 104 91 12 98  7 +++ ** 2 59 402 119 91  7 99  5 ++ * 3 51 222 152 93 16 Not  4 − * comparative available 4 31 494  91 93  2 Not 32 +++ ***** comparative available Key to Table 4: the term ″Clingability″ as it is known in the art is defining the adhesion capacity of the film (stickiness). +: Increase in stickiness, on a scale of 1 to 5 *: Increased possibility of breakage, on a scale of 1 to 5 −: No appreciable stickiness detected.