Biodegradable polymer composition for the manufacture of articles having a high heat deflection temperature

Abstract

This invention relates to a biodegradable polymer composition which is particularly suitable for use in the manufacture of articles having a high heat deflection temperature (HDT) by injection moulding and thermoforming.

Claims

1. A biodegradable polymeric composition for preparing articles having high heat deflection temperature comprising: i) 50-95% by weight, based on the sum of components i. and ii., of a polyester of lactic acid; ii) 5-50% by weight, based on the sum of components i. and ii., of at least one aliphatic-aromatic polyester (AAPE) comprising a dicarboxylic component and a dihydroxylic component which comprise the following structural units:
—[—O—(R11)-O—C(O)—(R13)-C(O)—]—
—[—O—(R12)-O—C(O)—(R14)-C(O)—]— wherein the dihydroxylic component comprises units —O—(R11)-O— and —O—(R12)-O— deriving from diols, wherein R11 and R12 are the same or different and are selected from the group consisting of C2-C14 alkylenes, C5-C10 cycloalkylenes, C2-C12 oxyalkylenes, heterocyclic groups and mixtures thereof, wherein the dicarboxylic component comprises units —C(O)—(R13)-C(O)— deriving from one or more aliphatic diacids and units —C(O)—(R14)-C(O)— deriving from one or more aromatic diacids, wherein R13 is selected from the group consisting of C2-C20 alkylenes and their mixtures and the molar percentage of the units deriving from aromatic diacids is of 40-50% of the dicarboxylic component, wherein the one or more aromatic diacids are selected from dicarboxylic aromatic compounds of the phthalic acid type and their esters, and from 2,5-furandicarboxylic acid and its esters, and from mixtures thereof; iii) 4-15% by weight, with respect to the total weight of the biodegradable polymer composition, of cellulose fibres; iv) 2-6% by weight, with respect to the total weight of the biodegradable polymer composition, of a nucleating agent and wherein the nucleating agent comprises.

2. The biodegradable composition according to claim 1, wherein the polyester of lactic acid is selected from the group consisting of poly-L-lactic acid, poly-D-lactic acid and stereo complex of the poly-L-lactic acid, poly-D-lactic acid or mixtures thereof.

3. The biodegradable The biodegradable composition according to claim 1, wherein the aliphatic diacid of the AAPE are succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, brassylic acid, hexadecandioic acid and octadecandioic acid and mixtures thereof.

4. The biodegradable composition according to claim 1, wherein the one or more aromatic diacids comprises diacids are selected from dicarboxylic aromatic compounds of the phthalic acid type and their esters.

5. The biodegradable composition according to claim 4, wherein the dicarboxylic aromatic compound of the phthalic acid type is terephthalic acid.

6. The biodegradable composition according to claim 1, wherein the one or more aromatic diacids comprise 2, 5-furandicarboxylic acid, an ester thereof or mixture thereof.

7. The biodegradable composition according to claim 1, wherein the AAPE is biodegradable according to the EN 13432 norm.

8. The biodegradable composition according to claim 1, wherein the nucleating agent comprises a mixture of polyesters comprising repeating units of 1,4-butylene succinate and talc, said mixture comprising 10-95% by weight of said polyesters.

9. The biodegradable composition according to claim 1, wherein the fibers show a length/diameter ratio <40.

10. The biodegradable composition according to claim 1, wherein the polyester comprising repeating units of 1,4-butylene succinate is poly(1,4-butylene succinate).

11. An injection molded article comprising the biodegradable composition according to claim 1.

12. An annealing process of the injection molded article according to claim 11, said process being performed at a temperature comprised between 70 and 150° C.

13. The process according to claim 12, performed in a non-confined environment at a constant temperature.

14. The process according to claim 13, performed at a temperature between 80 and 150° C. and with residence time between 30 seconds and 60 minutes.

15. The process according to claim 12, performed in a confined environment.

16. The process according to claim 15, performed in constant temperature preheated molds.

17. The process according to claim 16, performed at a temperature between 80 and 100° C. and with residence time between 1 and 5 minutes.

18. An annealed product obtainable by the annealing process according to claim 12.

19. A thermoformed article comprising the biodegradable composition according to claim 1.

Description

(1) FIG. 1 and FIG. 2 respectively show the front and side view of a fork manufactured with the biodegradable composition according to the invention wherein “L” represents the length, “W” the width and “H” the height of the fork.

(2) The invention will now be illustrated by a number of embodiments which are to be regarded by way of example and not restrictive of the scope of the protection of this patent application.

EXAMPLES

(3) In the examples described below: Shear viscosity was measured using a Goettfert Rheotester 2000 model rheometer according to standard ASTM-D3835 at a temperature of 190° C. using a capillary with D=1 mm and L/D=10 flat entry. Heat deflection temperature (HDT) was measured according to standard ASTM-D648 using two different loads, 0.455 MPa and 1.82 MPa, on moulded test specimens of the “bar” type (length 127 mm, width 12.7 mm, thickness 3.2 mm) using Ceast 6510 Test-A-Matic model equipment. HDT values were determined in triplicate for each composition. The value stated corresponds to the arithmetic mean of the measured values. Dimensional stability for “bar” type specimens: it was measured on moulded test specimens of the “bar” type (length 127 mm, width 12.7 mm, thickness 3.2 mm) using a Mitutoyo Digimatic CD-20D model micrometer with an accuracy of ±0.01 mm Dimensional stability values were determined in triplicate for each composition. The value stated corresponds to the arithmetic mean of the measured values. The method for measuring dimensional stability comprises calculating the percentage dimensional change (PDC) experienced by the object following annealing treatment. The percentage dimensional change (PDC) is determined using the following formula:
PDC=[(D.sub.f−D.sub.0)/D.sub.0]×100 where: D.sub.f is the dimension of the test specimen after treatment, and D.sub.0 is its initial dimension. A positive value for PDC indicates expansion of the test specimen, while a negative value indicates contraction. The lengths and widths of the test specimens have been taken into consideration in this invention. Test specimens having a PDC<1% for both dimensions measured are regarded as being dimensionally stable. Dimensional stability for “fork” type specimens: it was measured on moulded test specimens of the “fork” type as shown in FIGS. 1 and 2 (length “L” 168.62 mm, width “W” 22.57 mm, height “H” 14.36 mm) using a digital caliper mod. MIB (Germany) with a resolution of 0.01 mm and measuring range 0±150 mm The method for measuring dimensional stability for the “fork” type specimens comprises calculating the Average Percentage Height Reduction (APHR) experienced by the object following an annealing treatment. The Average Percentage Height Reduction (APHR) is determined using the following formula:

(4) $\mathrm{APHR}=\frac{\underset{i=1}{\overset{n}{.Math.}}{\left(\mathrm{PHR}\right)}_i}{n}$ where: n is the total tine number of a fork. (PHR)i is the percentage height reduction of the tip of the i.sup.th tine of a fork and is calculated by the following formula:

(5) $\mathrm{PHR}=\frac{\left(H_0-H_f\right)}{H_0}*100$ where: H.sub.0 is the height of the tine tip before annealing, measured with respect to a reference plane H.sub.f is the height of the same tine tip after annealing, measured with respect to said reference plane. and H.sub.f e H.sub.0 are measured according to the following procedure: before the annealing process the fork is set on a flat horizontal plane (defined herein as reference plane) with the tine tips upward. Using the digital caliper, the vertical distance of the tips of each tine from the reference plane is measured as H.sub.0. Each H.sub.0 measured is therefore the single tine tip vertical distance from the reference plane of the fork. The fork is then annealed, with tine tips oriented upwards, into the above mentioned oven at the desired condition of temperature and time. After annealing the fork is cooled down to room temperature and left to rest for 24 hours. After 24 hours, the annealed fork is put onto the reference plane with tine tips upward. Using the digital caliper, the vertical distance of each tine tip from the reference plane is measured as H.sub.f. Each H.sub.f measured value represents the single tine tip vertical distance from the reference plane of the annealed fork. Mechanical properties were measured according to standard ASTM D790-03—Method B−V.sub.0=13 mm/min on standard test specimens of the “bar” type using an Instron 4301 model dynamometer. The following were determined: Elastic Modulus (in MPa), deformation on failure (as %) and ultimate tensile strength (in MPa).

Example 1

(6) TABLE-US-00001 TABLE 1 Compositions in Example 1 Anti- Nucle- Cell- Inor- agent ating ulose ganic Hydrolysis Example PLA AAPE caking agent fibre filler stabiliser 1 70.40 10.40 0.6 3 15 0.6 0.04

(7) Where not explicitly indicated the figures are expressed in parts. PLA=polylactic acid containing 98% of L-Lactic and 2% of D-Lactic, melting point Tm=165° C., weighted mean molecular weight Mw=166000, intrinsic viscosity=0.97 dl/g and shear viscosity □□=120 Pas measured according to standard ASTM-D3835 at T=190° C., shear rate=1000 s.sup.−1, and capillary D=1 mm with L/D=10. AAPE=poly(butylenesebacate-co-butyleneterephlate) (PBST) having 56% in moles of terephthalic acid with respect to the sum of the aliphatic diacids and aromatic diacids, and having MFI=14 g/10 min (at 190° C. and 2.16 kg), and shear viscosity η=570 Pas measured according to standard ASTM-D3835 at T=180° C., shear rate=104 s.sup.−1, and capillary D=1 mm with L/D=30.

(8) Anti-caking agent=oleamide of plant origin

(9) Nucleating agent=micronised talc (particle size=2-10 microns)

(10) Cellulose fibre=100% pure cellulose fibre having L/D=18

(11) Inorganic filler=Titanium dioxide

(12) Hydrolysis stabiliser=styrene-glycidyl ether-methylmethacrylate copolymer having Mw=7300, Mn=2750, Tg=54° C., equivalent weight of epoxide=285 g/mol, number of epoxides per molecule=10.

(13) The composition in Table 1 was fed to a model APV2030 co-rotating twin-screw extruder under the following conditions:

(14) D=30 mm;

(15) L/D=40;

(16) RPM=170;

(17) thermal profile=30° C.-90° C.-140° C.-150° C.-9×200° C.-3×150° C.

(18) The extrudate was cooled in a water bath and granulated. The granules obtained were dried for 3 hours in a Moretto DH100 model plastics dryer with air circulating at T=60° C. After drying the granules had a shear viscosity of 180 Pas measured according to standard ASTM-D3835 at T=190° C., shear rate=1000 s.sup.−1, and capillary D=1 mm with L/D=10.

(19) The granules were then injection moulded in a Sandretto S7/60 model press in a mould to produce standard “bar” type test specimens (length 127 mm, width 12.7 mm, thickness 3.2 mm) and “fork” type specimens (length “L” 168.62 mm, width “W” 22.57 mm, height “H” 14.36 mm) suitable for HDT tests according to standard ASTM-D648 and also suitable for mechanical bend tests according to standard ASTM-D790, using the following injection moulding operating conditions:

(20) injection T=200° C.;

(21) Injection pressure=1250 bar;

(22) Injection time=0.7 sec;

(23) Injection flowrate=25 cm.sup.3/sec;

(24) Holding pressure=200 bar;

(25) Holding time=11 sec;

(26) Cooling time=25 sec;

(27) Mould temperature=20° C.;

(28) Screw rotation=80 rpm.

(29) The test specimens were examined to determine their thermal, mechanical properties and their dimensions. The results of the characterisations are shown in Table 5-6.

Example 2

(30) The moulded test specimens were then subjected to annealing treatment in an unconfined environment in a Venti-Line VL115 model stove with circulating air using the following operating conditions: Temperature=90° C., time=60 minutes.

(31) After cooling and reconditioning at T=23° C. and 55% RH for 1 day the annealed test specimens were then examined to determine dimensional stability, mechanical properties and heat deflection temperature HDT.

(32) The results of this characterisation are shown in Tables 5-7.

Examples 3-5

(33) The moulded test specimens according to Example 1 were subjected to three different annealing treatments using the operating conditions shown in Table 3:

(34) TABLE-US-00002 TABLE 3 Annealing conditions Example 3 Example 4 Example 5 T (° C.) 90 150 150 time (minutes) 5 15 2.5

(35) After cooling and reconditioning at T=23° C. and 55% RH for 1 day the annealed test specimens were examined to determine their dimensional stability (PDC) and heat deflection temperature (HDT) (Tables 6-7).

Examples 6-11

(36) The compositions in Table 4 have been extruded and moulded according to Example 1 to obtain “fork” type samples.

(37) TABLE-US-00003 TABLE 4 Compositions in Examples 6-11 Anti- Nucleating caking agent Cellulose Inorganic Hydrolysis Example PLA AAPE agent talc PBS fibre filler stabiliser 6 83.13 11.87 0.6 0.6 2.4 0 0.6 0.04 (comparison) 7 72.625 15 0.6 0 0 10.375 0.6 0.04 (comparison) 8 70 15 0.6 3 0 10 0.6 0.04 9 70 15 0.6 0 3 10 0.6 0.04 10 70 15 0.6 0.6 2.4 10 0.6 0.04 11 69 9.80 0.6 0 5 15 0.6 0.04

(38) Where not explicitly indicated the figures are expressed in parts. PLA=polylactic acid containing 98% of L-Lactic and 2% of D-Lactic, melting point Tm=165° C., weighted mean molecular weight Mw=166000, intrinsic viscosity=0.97 dl/g and shear viscosity □□=120 Pas measured according to standard ASTM-D3835 at T=190° C., shear rate=1000 s.sup.−1, and capillary D=1 mm with L/D=10. AAPE=poly(butylenesebacate-co-butyleneterephlate) (PBST) having 56% in moles of terephthalic acid with respect to the sum of the aliphatic diacids and aromatic diacids, and having MFI=14 g/10 min (at 190° C. and 2.16 kg), and shear viscosity η□=570 Pas measured according to standard ASTM-D3835 at T=180° C., shear rate=104 s.sup.−1, and capillary D=1 mm with L/D=30. Anti-caking agent=oleamide of plant origin Nucleating agent: talc=micronised talc (particle size 2-10 microns) PBS=poly(1,4-butylene succinate) MFR 46 g/10′ (measured according to ASTM 1238-10 at 190° C./2.16 kg)

(39) Cellulose fibre=100% pure cellulose fibre having L/D=18

(40) Inorganic filler=Titanium dioxide

(41) Hydrolysis stabiliser=styrene-glycidyl ether-methylmethacrylate copolymer having Mw=7300, Mn=2750, Tg=54° C., equivalent weight of epoxide=285 g/mol, number of epoxides per molecule=10.

(42) The forks according to Examples 2 and 6-11 thus obtained were annealed at 95° C. for 4 minutes in a tunnel oven mod. AIR JET-1STD5M manufactured by Sermac (Italy) with length=2.5 m. The forks were placed onto a belt moving along into the oven at a constant speed. The belt was made by a PTFE/Glass-Fiber perforated tissue to ensure uniform temperature everywhere around the fork.

(43) The oven was uniformly heated by a circulating stream of hot air and the effective temperature inside the oven was monitored by four thermal sensors type “K” mod. Lutron TM-947SD placed along the oven near the moving belt.

(44) After cooling and reconditioning at T=23° C. and 55% RH for 1 day the annealed test specimens were examined to determine their Average Percentage Height Reduction (APHR) (Table 8).

(45) TABLE-US-00004 TABLE 5 Mechanical characterisation according to ASTM-D790 Elastic modulus Deformation on Ultimate tensile (MPa) failure (%) strength (MPa) Example 1 3680 3.3 73 Example 2 3974 2.5 70

(46) TABLE-US-00005 TABLE 6 HDT according to ASTM-D648 HDT (° C.) load = 0.455 MPa load = 1.82 MPa Example 1 51 48 Example 2 113 68 Example 3 110 64 Example 4 129 71 Example 5 118 67 Example 6 97 62 (comparison) Example 7 117 64 (comparison) Example 8 111 67 Example 9 108 66 Example 10 110 65 Example 11 109 68

(47) TABLE-US-00006 TABLE 7 Dimensional stability PDC for “bar” type specimens PDC (%) width Length Example 2 −0.42 −0.49 Example 3 −0.18 −0.49 Example 4 −0.47 −0.67 Example 5 −0.47 −0.59 Example 11 −0.15 .0.52

(48) TABLE-US-00007 TABLE 8 Dimensional stability APHR for “fork” type specimens APHR (%) Example 2 12 Example 6 65 (comparison) Example 7 55 (comparison) Example 8 32 Example 9 20 Example 10 18 Example 11 15