Polyphase biodegradable compositions containing at least one polymer of vegetable origin

Abstract

Polyphase biodegradable compositions having a good resistance to ageing comprising a continuous phase comprising at least one hydrophobic polyester and at least one dispersed phase of polymer of vegetable origin. The hydrophobic polyester constituting the continuous phase is incompatible with the polymer of vegetable origin. The compositions comprise a plasticizer comprising at least 75% of a mixture of diglycerol, triglycerol and tetraglycerol.

Claims

1. A film produced from a polyphase biodegradable composition having a good resistance to aging comprising: (a) a continuous phase comprising at least one hydrophobic polyester, (b) at least one dispersed phase comprising at least one polymer of vegetable origin, in which the hydrophobic polyester of the continuous phase is an aliphatic aromatic polyester of the diacid-diol type with a content of aromatic units of from 45 to 70 mol % and is incompatible with the polymer of vegetable origin, said polymer of vegetable origin being starch, said composition comprising 2 to 70% by weight, with respect to the weight of the polymer of vegetable origin, of a plasticizer comprising at least 75 wt %, with respect to the total weight of said plasticizer, of a mixture of diglycerol, triglycerol and tetraglycerol, and less than 10% by weight of glycerin; wherein: the composition comprises from 45 to 98% by weight of component (a) and from 2 to 55% by weight of component (b) with respect to the sum of components (a) and (b); the aliphatic-aromatic polyester comprises as the aliphatic acid an acid selected from the group consisting of adipic acid, succinic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid and brassylic acid; the aliphatic-aromatic acid comprises terephthalic acid as the aromatic acid; the composition comprises from 1 to 40% by weight of a further dispersed phase comprising a polyhydroxyalkanoate which is rigid in comparison with the hydrophobic polyester of the continuous phase, with a Young's modulus of more than at least 300%; and wherein the polymer composition exhibits an Elmendorf tear strength of more than 60 N/mm in the transverse direction upon filming.

2. The polyphase biodegradable composition according to claim 1, in which the hydrophobic polyester is biodegradable according to standard EN 13432.

3. The polyphase biodegradable composition according to claim 1 in which the starch is flour, natural starch, chemically and/or physically modified starch, hydrolysed starch, destructured starch, gelatinised starch, plasticised starch, thermoplastic starch or mixtures thereof.

4. The polyphase biodegradable composition according to claim 1 in which the polyhydroxyalkanoate is a polymer or copolymer of polylactic acid containing at least 75% of L-lactic or D-lactic acid or combinations thereof having a molecular weight M.sub.w of more than 70,000 and a Young's modulus of more than 1,500 MPa.

5. The polyphase biodegradable composition according to claim 1 in which the plasticiser comprises at least 90% of a mixture of diglycerol, triglycerol and tetraglycerol.

6. The polyphase biodegradable composition according to claim 5 in which said mixture contains more than 50% by weight of diglycerol with respect to the sum of the di-, tri- and tetraglycerol.

7. The polyphase biodegradable composition according to claim 1 in which the diglycerol comprises at least 70% by weight of alpha-alpha diglycerol.

8. Bags and envelopes in general produced using the film according to claim 1, being selected from the group consisting of extruded and thermoformed bags and envelopes, laminated with board, aluminium, plastics or bioplastics, and multiply perforated bags and envelopes.

Description

EXAMPLES

(1) TABLE-US-00001 TABLE 1 Compositions with Mixture 1 plasticiser Example Starch Ecoflex Ecopla Mixture 1 Lubricant 1-1 15.5 67 12 1.55 0.3 1-2 15.5 67 12 2.33 0.3 1-3 15.5 67 12 3.1 0.3 1-4 15.5 67 12 4.65 0.3 1-5 15.5 67 12 6.2 0.3

(2) TABLE-US-00002 TABLE 2 Compositions with Mixture 2 plasticiser Example Starch Ecoflex Ecopla Mixture 2 Lubricant 2-1 15.5 67 12 3.1 0.3 2-2 15.5 67 12 4.65 0.3 2-3 15.5 67 12 6.2 0.3

(3) TABLE-US-00003 TABLE 3 Compositions with Reference plasticiser Example Starch Ecoflex Ecopla Reference Lubricant 3 15.5 67 12 3.1 0.3

(4) Where not explicitly indicated figures are expressed in parts. Mixture 1: 80% of diglycerol (84% alpha-alpha glycerol, 14% alpha-beta glycerol, 2% beta-beta glycerol), 10% triglycerol, 3% tetraglycerol and 7% glycerol. Boiling point 205 C. at 1.3 mbar. Mixture 2: 47% triglycerol, 27% diglycerol, 15% tetraglycerol, 5% pentaglycerol, 2% hexaglycerol, 1% heptaglycerol, glycerol 1%. Reference: 100% glycerol. Starch: native corn starch (containing 11% by weight of water) Ecoflex: polybutyleneadipate-co-terephthalate produced by BASF. Ecopla: polylactic acid produced by Cargill.

(5) The compositions shown in Tables 1-3 were fed to a co-rotating extruder with L/D=36 and a diameter of 60 mm with 9 heating zones.

(6) The extrusion parameters were as follows: RPM: 140 Throughput: 40 kg/hour Thermal profile 60-140-175-1804-1552 C. Screw diameter ratio (max diam./min diam.) 1.31-1.35 Final water content of the granulate 0.8%.

(7) The compositions in Table 1 were converted into film on a Ghioldi 40 mm machine, die gap=1 mm, throughput 20 kg/h, to obtain films having a thickness of 20 and 40 m.

(8) The 20 m films were then tested mechanically according to standard ASTM D882 (tensile test at 23 C. and 55% relative humidity and Vo=50 mm/min) and ASTM D1922 (tearing at 23 C. and 55% relative humidity).

(9) The results are shown in Tables 4 and 5 below.

(10) TABLE-US-00004 TABLE 4 Mechanical properties according to standard ASTM D882 (tensile strength at 23 C. and 55% relative humidity and Vo = 50 mm/min) .sub.b .sub.b E En.sub.b Sample (MPa) (%) (MPa) (kJ/m.sup.2) 1-2 MD 29 365 300 3805 TD 24 687 226 4927 1-3 MD 27 357 317 3335 TD 26 707 203 5341 1-5 MD 25 347 259 3044 TD 24 693 125 4371 3 MD 29 254 400 2494 TD 27 738 248 5672

(11) TABLE-US-00005 TABLE 5 Mechanical properties according to standard ASTM D1922 (tearing at 23 C. and 55% relative humidity). Tear strength Sample (N/mm) 1-1 MD 163 TD 148 1-2 MD 195 TD 155 1-3 MD 207 TD 91 1-4 MD 162 TD 80 1-5 MD 155 TD 72 2-1 MD 182 TD 94 2-2 MD 162 TD 81 2-3 MD 135 TD 75 3 MD 164* TD 50** *tearing deviates from the imposed direction by 90 C.; **not very tough, tending towards brittle

(12) The films obtained from compositions according to Examples 2-1 and 3 were then submitted to a migration test in water.

(13) Each migration test was carried out into a 250 ml cylinder provided with a ground glass top and containing as simulant 100 ml of water HPLC grade (Water (HPLC-gradient) PAI by Panreac Quimica S.A.U.).

(14) Before starting the migration test, the cylinder containing the simulant was placed in a thermostatically controlled chamber set at 20 C. and left therein until the simulant reached said temperature.

(15) From each film a sample having dimension 7080 mm was obtained. Each sample was weighted, then completely immersed in the simulant and maintained in the thermostatically controlled chamber set at 20 C. for 24 hours.

(16) After 24 hours the sample was removed from the simulant and rinsed with water.

(17) 25 ml of the simulant was then concentrated to a final volume of 5 ml by heating at 50 C. under a small air flow and the content of plasticizers in the simulant was determined by liquid chromatography using an HPLC Accela 600 Thermo provided with a chromatographic column Hamilton HC-75 and a refraction index detector. The eluent consisted of water with a flow of 0.5 ml/min. the system was thermostat-controlled at 85 C.

(18) The results are shown in Tables 6 below.

(19) TABLE-US-00006 TABLE Migration test in water (20 C., 24 hours). % plasticizer Example plasticizer migrated in water * 2-1 Mixture 2 21 3 Reference 100 * calculated as weight percentage with respect to the total weight of plasticizers in the samples