Photodegradation-resistant biodegradable films

Abstract

This invention relates to biodegradable films characterised by high resistance to processes of the photodegradative type, mainly activated by the ultraviolet component of sunlight, which are particularly suitable for use in the mulch film sector. These films comprise a composition containing at least one polyphenol of plant origin.

Claims

1. A film comprising a composition containing at least one thermoplastic polyester and 0.5-4% by weight of a mixture of polyphenols comprising silybin, silydianin, isosilybin and silycristin, wherein the thermoplastic polyester is an aliphatic-aromatic polyester and has a dicarboxylic component comprising at least one aromatic acid having multiple functional groups in an amount of between 30 and 90% in moles with respect to the total moles of the dicarboxylic component selected from dicarboxylic aromatic compounds of phthalic acid and their esters and heterocyclic dicarboxylic aromatic compounds and their esters and at least one aliphatic diacid selected from oxalic acid, malonic acid, succinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid and brassilic acid and an aliphatic diol component comprising at least 85% by moles with respect to the total moles of the diol component of butanediol.

2. The film according to claim 1 in which the mixture comprising silybin, silydianin, isosilybin and silycristin is obtained by extraction from milk thistle seeds.

3. The film according to claim 1, in which the aromatic aliphatic polyester is selected from: (A) polyesters comprising repeated units deriving from at least one aromatic acid of phthalic acid, at least one aliphatic diacid and at least one aliphatic diol having an aromatic units content of between 35-60% in moles with respect to the total moles of the dicarboxylic component; or (B) polyesters comprising repeating units deriving from at least one heterocyclic dicarboxylic aromatic compound, at least one aliphatic diacid and at least one aliphatic diol, having an aromatic units content of between 50-85% in moles with respect to the total moles of the dicarboxylic component.

4. The film according to claim 1, in which the composition comprises one or more polymers of synthetic or natural origin.

5. A method for mulching which comprises applying a film according to claim 1 to an area of soil.

6. A mulch film comprising the film according to claim 1.

7. The film according to claim 1, wherein the composition further comprises one or more polymers of natural origin in an amount between 5 and 50% by weight based upon the total weight of the composition.

8. The film according to claim 1, wherein the composition comprises up to 30% by weight of polymers from a hydroxyacid with respect to the total weight of the composition.

Description

EXAMPLES

(1) TABLE-US-00001 TABLE 1 compositions in the examples MATER-BI Example AAPE CF04P POLYPHENOL 1 100 (comparison) 2 99 1 3 97 3 4 100 (comparison) 5 100 3

(2) Where not expressly indicated, the figures are expressed in parts.

(3) AAPE=poly(butylene sebacate-r-butylene adipate-r-butylene terephthalate) (54% mol butylenes terephthalate units; 30% moles butylene sebacate units; 16% moles butylenes adipate units) having an MFR (190 C.; 2.16 kg)=7 g/10 min, Tm=130 C.2 C.

(4) MATER-BI CF04P: biodegradable composition marketed by Novamont S.p.A (Italy) comprising aliphatic-aromatic copolyester, starch and plasticizers and having Tm (measured by DSC)=130 C., MER (ASTM D1238)=7 g/10 min at T=160 C. and 5 kg of weight, pycnometric density at 23 C.=1, 23 g/cm.sup.3:

(5) POLYPHENOL: Sylimarin containing 14% silicristin, 5% silidianin, 61% silibin, 15% isosilibin and 5% of other isomers (the percentages are calculated with respect to the area of the ion at m/z 481 measured using a mass spectrometer operating under the following conditions: ESI source, sheath gas flow 30, aux gas flow 5, sweep gas flow 0, capillary voltage8 V/4 V (positive ions), capillary temp. 275 C., tube lens70 V/40 V (positive ions), scanning: 100-1500 Da, collision (cid): 5 V).

(6) The compositions of EXAMPLES 1-2-3 reported in Table 1 were fed to an OMC EBV 60/36 extruder having LID=36 and a diameter of 60 mm with 9 heating zones.

(7) The extrusion parameters were as follows:

(8) RPM: 120

(9) Throughput: 30 kg/hour

(10) Thermal profile 6014517018041552 C.

(11) The compositions of EXAMPLES 4-5 reported in Table 1 were fed to an OMC EBV 60/36 extruder having L/D=36 and a diameter of 60 mm with 9 heating zones.

(12) The extrusion parameters were as follows:

(13) RPM: 120

(14) Throughput: 30 kg/hour

(15) Thermal profile 6014015016016531452 C.

(16) All the examples (1-2-3-4-5) obtained were made into film on a Ghioldi KE40 machine of 40 mm, die gap=0.9 mm, to obtain film having a thickness of 20-25 m. The film then underwent mechanical characterisation according to standard ASTM D882 (longitudinal directiontraction at 23 C. and 55% relative humidity and Vo=50 mm/min). The results are shown in Table 2. The mechanical characterisation was repeated on the films subjected to the radiation produced by 8 OSRAM ULTRA-VITALUX UV lamps for different times in order to reproduce the equivalent of a solar spectrum. The results are shown in Tables 3-7 below.

(17) TABLE-US-00002 TABLE 2 Mechanical characteristics of the film prior to exposure to the UV lamp Thickness .sub.b e.sub.b E En.sub.b Example (m) (MPa) (%) (MPa) (KJ/m.sup.2) 1 (comparison) 20 53 353 118 6571 2 19 47.2 415 107 6553 3 22 47 403 100 6239 4 (comparison) 19 26 399 205 3788 5 20 22 428 239 2536

(18) TABLE-US-00003 TABLE 3 Film according to Example 1 (comparison): mechanical characteristics for different exposure times to the UV lamp sb eb E Enb % with % with % with % with Exposure time Thickness respect to respect to respect to respect to days (m) (MPa) initial value (%) initial value (MPa) initial value (KJ/m.sup.2) initial value 1 20 36.5 31 347 2 129 +9 4267 35 2 19 28.4 46 257 27 130 +10 2592 61 4 18 18.4 65 123 65 120 +1 898 86 7 19 16 70 82 77 112 5 521 92 10 20 14.7 72 59 83 129 +9 333 95

(19) TABLE-US-00004 TABLE 4 Film according to Example 2: mechanical characteristics for different exposure times to the UV lamp s.sub.b e.sub.b E Enb % with % with % with % with Exposure time Thickness respect to respect to respect to respect to days (m) (MPa) initial value (%) initial value (MPa) initial value (KJ/m.sup.2) initial value 1 19 35 26 403 3 110 +2 4769 27 2 22 29.6 37 394 5 106 1 4112 37 4 19 22 53 280 33 120 +12 2483 62 7 18 17.8 62 136 67 106 1 927 86 10 19 16.4 65 121 71 102 4 769 88

(20) TABLE-US-00005 TABLE 5 Film according to Example 3: mechanical characteristics for different exposure times to the UV lamp s.sub.b e.sub.b E Enb % with % with % with % with Exposure time Thickness respect to respect to respect to respect to days (m) (MPa) initial value (%) initial value (MPa) initial value (KJ/m.sup.2) initial value 1 21 39.8 15 396 2 117 +17 5399 13 2 20 39 17 396 2 130 +30 5396 14 4 20 29.4 37 366 9 121 +21 3910 37 7 21 26.1 44 310 23 131 +21 3226 48 10 21 20.2 57 194 52 128 +28 1669 73

(21) TABLE-US-00006 TABLE 6 Film according to Example 4 (comparison): mechanical characteristics for different exposure times to the UV lamp s.sub.b e.sub.b E Enb % with % with % with % with Exposure time Thickness respect to respect to respect to respect to days (m) (MPa) initial value (%) initial value (MPa) initial value (KJ/m.sup.2) initial value 1 21 20 23 343 14 237 +15 2543 33 2 21 17 35 247 38 233 +13 1607 58 5 19 13 50 86 78 220 +7 494 87 7 19 11 58 53 87 194 6 244 94 9 18 11 58 33 92 199 3 144 96

(22) TABLE-US-00007 TABLE 7 Film according to Example 5: mechanical characteristics for different exposure times to the UV lamp s.sub.b e.sub.b E Enb % with % with % with % with Exposure time Thickness respect to respect to respect to respect to days (m) (MPa) initial value (%) initial value (MPa) initial value (KJ/m.sup.2) initial value 1 21 19 14 333 22 235 2 2426 31 2 22 17 23 279 35 240 +0 1894 46 5 21 14 36 252 41 225 6 1283 64 7 20 14 36 206 52 254 +6 1213 66 9 21 16 27 189 56 284 +18 1262 64

(23) After exposure to ultraviolet light, the films in Examples 2 and 3 and 5 according to the invention showed a smaller change in mechanical properties, in particular ultimate tensile strength, elongation on failure and breaking energy, thus revealing a resistance to photodegradative processes deriving from exposure to ultraviolet light which is significantly greater than respectively that of the film in comparison Example 1 and 4.