Snap Ability Modifier For Biogradable Polyesters

Abstract

The invention relates to an article comprising a monolayer or multilayer thermoplastic material, said material comprises (i) 38.00 to 99.95%, preferably 67.00 to 99.9%, more preferably 57.00 to 99.85%, by weight of polylactic acid, (ii) 0.05 to 4.90%, preferably 0.10 to 2.90%, more preferably 0.15 to 2.00%, even more preferably 0.2 to 1.00%, most preferably 0.25 to 0.75%, by weight of an epoxidized vegetable oil; (iii) 0 to 60.00%, preferably 0 to 40.00%, more preferably 0 to 30.00%, by weight of further additives selected from the group consisting of impact modifiers, plasticisers, crosslinking agents, foaming agents, fillers, colorants, stabilizers, lubricants, and mixtures thereof, the weight percentages being relative to total weight of the monolayer or multilayer thermoplastic material and adding up to 100%.

Claims

1. An article comprising a monolayer or multilayer thermoplastic material, wherein the material comprises (i) 38.00 to 99.95% by weight of polylactic acid, (ii) 0.05 to 4.90% by weight of an epoxidized vegetable oil; (iii) 0 to 60.00% by weight of further additives selected from the group consisting of impact modifiers, plasticisers, crosslinking agents, foaming agents, fillers, colorants, stabilizers, lubricants, and mixtures thereof, the weight percentages being relative to total weight of the monolayer or multilayer thermoplastic material and adding up to 100%.

2. An article as claimed in claim 1, wherein the material comprises: (i) 88.00 to 99.85% by weight of the polylactic acid, (ii) 0.15 to 2.00% by weight of the epoxidized vegetable oil; (iii) 0 to 10.00% by weight of the further additives selected from the group consisting of impact modifiers, plasticisers, crosslinking agents, foaming agents, fillers, colorants, stabilizers, lubricants, and mixtures thereof, the weight percentages being relative to total weight of the monolayer or multilayer thermoplastic material and adding up to 100%.

3. The article as claimed in claim 1, wherein the vegetable oil is a triglyceride of saturated or unsaturated fatty acid esters with a chain length from C.sub.6 to C.sub.22.

4. The article as claimed in claim 1, wherein the epoxidized vegetable oil is epoxidized soybean oil, epoxidized methyl soyate, epoxidized linseed oil, epoxidized tall oil, epoxidized peanut oil, epoxidized castor oil, epoxidized coconut oil, epoxidized palm oil, epoxidized corn oil, epoxidized safflower oil, or a mixture thereof.

5. The article as claimed in claim 1, wherein the article is a multilayer article comprising (A) at least one layer A of non-foamed polylactic acid and (B) at least one layer B of foamed polylactic acid, wherein either (A), or (B), or (A) and (B) contain the epoxidized vegetable oil.

6. The article as claimed in claim 1, wherein the article is a plastic sheet.

7. The article as claimed in any of claim 1 wherein the article comprises a thermoformed part.

8. The article as claimed in claim 7, wherein the article is a container.

9. The article as claimed in claim 8, being a container (1) having a hollow body (2) and optionally at least one flange (10), the hollow body defining said the thermoformed part, the hollow body having an opening (8).

10. The article as claimed in claim 9, wherein the hollow body (2) is at least partially covered by a banderole.

11. The article as claimed in claim 8, wherein the container is a cup, in a multipack form or in an individual cup form.

12. An article as claimed in claim 1, wherein the material consists of: (i) 38.00 to 99.95% by weight of the polylactic acid, (ii) 0.05 to 4.90% by weight of an the epoxidized vegetable oil; (iii) 0 to 60.00% by weight of further additives selected from the group consisting of impact modifiers, plasticisers, crosslinking agents, foaming agents, fillers, colorants, stabilizers, lubricants, and mixtures thereof, the weight percentages being relative to total weight of the monolayer or multilayer thermoplastic material and adding up to 100%.

13. A process for manufacturing an article as claimed in claim 1, comprising the steps of mixing polylactic acid, epoxidized vegetable oil and optionally the further additives in an extruder under heating to a temperature of 150 to 250° C. to form a mixture and extruding or co-extruding the mixture.

14. A process according to claim 13, further comprising a step of thermoforming.

15. The process as claimed in claim 13, wherein the epoxidized vegetable oil is added in form of a masterbatch.

16. A snap ability modifier in optionally thermoformed polylactic acid sheets comprising an epoxidized vegetable oil.

17. The article as claimed in claim 6, wherein the thermoformed part has a total stretch ratio of at least 2.5.

Description

EXAMPLES

[0128] The examples are implemented with using the following materials. Percentages mean percent by weight unless indicated otherwise.

PLA:

[0129] lngeo® 2003D marketed by NatureWorks—Polylactic acid comprising 96.3% of L-Lactide units and 3.7% of D-Lactide units.

ESBO:

[0130] Merginat ESBO marketed by HOBUM Oleochemicals GmbH.

MB1:

[0131] Masterbatch of 75% by weight of PLA and 25% of ESBO.

MB2 (Comparative):

[0132] Masterbatch of 50% by weight of PLA and 50% of Biostrength® 150 (core shell additive based on acrylate and methacrylate copolymer)

Chemical Foaming Agent (CFA-MB):

[0133] Masterbatch of 80% by weight of PLA and 20% of citric acid

Compact (Non-Foamed) PLA-Sheet:

[0134] Various mono-layer PLA plastic sheets are prepared according to the procedure below.

Procedure:

[0135] The materials (PLA and MB1 or MB2) are extruded with a Fairex® extruder having an internal diameter of 45 mm and a 24D length. The temperature along the screw is between 180 and 200° C. The molten PLA is extruded through a die with temperature between 185 and 195° C. to produce a compact sheet. The sheet is then calendered on 3 rolls having a temperature of about 40° C. to control the sheet thickness.

[0136] Sheet thickness: 0.75 mm.

Foamed PLA Sheet:

[0137] Three-layer PLA expanded plastic sheets are prepared according to the following procedure.

[0138] The multilayer structure having one internal foamed PLA layer and two external compact PLA layers is produced by co-extrusion.

[0139] The materials (PLA, CFA and MB1 or MB2) of the internal foamed PLA layer are extruded with a Fairex extruder having an internal diameter of 45 mm and a 24D length. With CFA, the temperature profile along the screw is comprised between 165 and 230° C.

[0140] The materials (PLA and MB1 or MB2) of the two external compact layers are extruded with one Scannex® extruder having an internal diameter of 30 mm and a 26D length. The obtained molten plastic material is then separated in two different flows in the feedblock to form the two external compact layers. The temperature along the screw is between 165 and 195° C. Behind the extruders, the different material flows are fed into feedblock channels through different passages separated by two thin planes (die). At the end of the separation planes, the three flows merge and form two interfaces, and the sheet is extruded through a die with a temperature of between 185 and 195° C. The sheet is then calendered on 3 rolls having a temperature of about 40° C. The pressure between the first and second calendar roll is maintained to zero to stabilize the foam structure and to avoid any collapsing of the expanded structure.

[0141] Sheet thickness: 0.95 mm.

Compact PLA Yogurt Cups:

[0142] The compact plastic sheets are thermoformed into yogurt cups according to the procedure below. The cups are then analyzed and evaluated.

Procedure:

[0143] The sheet is introduced into a F.F.S. thermoforming line and is then thermoformed in 125 g cups with the following parameters: [0144] Heating plates temperatures: 90° C.; [0145] The sheet is gradually heated thanks to six heating steps, each of the heating boxes having a closing time of 140 ms; [0146] The thermoforming step is performed with conventional felt forming plugs; [0147] Mold temperature is fixed at 20° C. to cool down the PLA material; [0148] Forming air pressure: 4.5 bars; [0149] Blowing time: 450 ms [0150] Machine speed: 30 strokes per minute. [0151] Distance between bottom of mold and plug at lowest point: 3 mm [0152] Cup shape: As shown on FIG. 1a and FIG. 1b. [0153] Banderole: None.

[0154] The yogurt cups are arranged in a pack of 4 attached cups in two rows (the pack being also referred to as a “multipack”) and are cut into ×4 attached cups (referred to as “multipack”), with a precut line or similar junction between each pair of adjacent cups amongst the four cups. The precut lines are performed on the F.F.S. (Form Fill Seal) equipment.

Foamed PLA Yogurt Cups:

[0155] The foamed plastic sheets of are thermoformed into yogurt cups according to the procedure below. The cups are then analyzed and evaluated.

Procedure:

[0156] The sheet is introduced into a F.F.S. thermoforming line and is then thermoformed in 125 g cups with the following parameters: [0157] Heating plates temperatures: 110° C.; [0158] The sheet is gradually heated thanks to six heating steps, each of the heating boxes having a closing time of 140 ms; [0159] The thermoforming step is performed with conventional felt forming plugs; [0160] Mold temperature is fixed at 40° C. to activate the label hot melt and to cool down the PLA material; [0161] Forming air pressure: 4.5 bars; [0162] Blowing time: 450 ms [0163] Machine speed: 32 strokes per minute. [0164] Distance between bottom of mold and plug at lowest point: 5 mm [0165] Cup shape: As shown on FIG. 2. The total stretching ratio is 5.6. [0166] Banderole: Yes.

[0167] The yogurt cups are arranged in a pack 14 of 4 attached cups in two rows (the pack being also referred to as a “multipack”) and are cut into ×4 attached cups (referred to as “multipack”), with a precut line 15 or similar junction between each pair of adjacent cups amongst the four cups, as in the example shown in FIG. 3.

[0168] The precut lines 15 are performed on the F.F.S. (Form Fill Seal) equipment.

Example 1

PLA Compact

[0169] PLA Compact sheet structure (thickness in each sheet: 0.75 mm)

Example 1.1

[0170] 98.0% PLA+2.0% MB1 (0.5% ESBO)

Example 1.2

[0171] 98.0% PLA+2.0% MB2 (Comparative) % Biostrength 150)

Evaluations—Snapability:

[0172] The snap ability is determined by hand measurements with a marking scale that represents the ability of the cups to be separated under flexural solicitation: [0173] Mark 0—Does not break in three solicitations or does not follow the precut line; [0174] Mark 1—Breaks in three solicitations and follow precut line [0175] Mark 3—Breaks in two solicitations and follow precut line; [0176] Mark 5—Breaks in one solicitation and follow precut line.

[0177] Then, the snapability is compared to the precut depth to determine the minimum precut depth required to obtain a good snapability. [0178] The depth of the precut line is measured by optical microscopy with at least 3 measurements.

TABLE-US-00001 TABLE 1 Snapability results for Example 1.1 Precut depth [%] 45 48 54 57 58 62 70 71 76 83 Snapability 3 3 3 3 3 5 5 5 5 5

[0179] A precut depth of at least 58-63% is needed to obtain a good snapability.

TABLE-US-00002 TABLE 2 Snapability results for comparative Example 1.2 Precut depth [%] 39 42 45 50 53 62 73 76 90 Snapability 3 3 3 3 5 5 5 5 5

[0180] A precut depth of at least about 50-55% is needed to obtain a good snapability.

[0181] Conclusion: The precut depths needed to obtain a good snapability are considered as substantially equivalent for example 1.1 and comparative example 1.2, with however an amount of additive divided by two (0.5% ESBO in example 1.1, 1% Biostrength® 150 in comparative example 1.2). Equivalent tests show that using Biostrength® 150 at 0.5% does not lead to good snapability (whatever the precut depth is).

Example 2

PLA Foam

[0182]

TABLE-US-00003 TABLE 3 PLA foam sheet structure Example 2 Layer repartition Layer repartition along sheet along sheet CFA masterbatch MB masterbatch thickness thickness PLA Content content MB content Layer (% by distance) (% by weight) (% by weight) (% by weight) reference (% by weight) Example 2.1 Compact 21.0 25 98 / MB1 2 Foam 58.0 50 97.5 2.5 / / Compact 21.0 25 88 / MB1 2 Example 2.2 Compact 21.0 25 98 / MB2 2 (Comparative) Foam 58.0 50 97.5 2.5 / / Compact 21.0 25 88 / MB2 2

Evaluations—Snapability:

[0183]

TABLE-US-00004 TABLE 4 Snapability results for Example 2.1 Precut depth [%] 32.8 34.9 37.0 40.2 41.8 42.3 . . . 62.9 Snapability 1 3 5 5 5 5 . . . 5

[0184] A precut depth of at least 35-40% is needed to obtain a good snapability.

TABLE-US-00005 TABLE 5 Snapability results for Example 2.2 Precut depth [%] 19.6 25.7 33.9 39.1 39.9 41.8 42.5 44.4 45.4 Snapability 1 1 1 1 1 5 5 5 5 Precut depth [%] 48.8 51.8 52.1 54.2 55.6 . . . 62.3 5 5 5 5 5 . . . 5

[0185] A precut depth of at least 40-45% is needed to obtain a good snapability.

Example 3

Impact Resistance

PLA Compact—Injected Tensile Bones

Example 3.1

[0186] 98.0% PLA+2.0% MB1

Example 3.2 (Comparative)

[0187] 98.0% PLA+2.0% MB2

Example 3.3 (Comparative)

[0188] 100% PLA

Evaluations—Impact Strength

[0189] Impact strength was measured by the method of notched Izod. The specimens for measuring Notched Izod have been injection moulded on Injection moulding machine Arburg Alrounder 320 M Golden Edition to produce testing specimens for measuring according to EN ISO 179-1/1eA.

TABLE-US-00006 TABLE 6 Impact strength Example 3 Example 3.3 Example 3.1 Example 3.2 Impact resistance [kJ/m.sup.2] 2.88 2.70 3.19

[0190] Surprisingly it was found that no enhancement in terms of impact strength is observed with ESBO (contrary to Biostrength 150), but ESBO helps to better manage the snap ability.

Example 4

Transparency of Sheets

[0191] PLA Compact sheet structure (thickness in each sheet 0.75 mm)

Example 4.1

[0192] 98.0% PLA+2.0% MB2 (Comparative) % Biostrength 150)

Example 4.2

[0193] 98.0% PLA+2.0% MB1 (0.5% ESBO)

Evaluations—Haze-Measurements.

[0194] The Haze-level is determined in allignment to standard ASTM D 1003.

[0195] The measurements were performed with a Minolta Spektrophotometer CM-3600d that geometries conform to the requirements of ASTM D 1003 Section 8:

[0196] Procedure B Spectrophotometer. The software used to determine haze-levels was Spectra Magic.

[0197] The standard utilizes two different CIE standard illuminants: Sources A (typical, domestic, tungsten-filament lighting) and C (average day light). Both were used.

TABLE-US-00007 TABLE 7 Transparency Virgin PLA Example 4.1 Example 4.2 Haze [%] (Source A) 2.6 53.4 2.7 Haze [%] (Source C) 2.7 56.2 2.9

Conclusion of Examples

[0198] The above shown examples prove that the ESBO (MB1) has a specific performance for the mentioned application. Even though it has no proven function as an impact modifier, it delivers a substantially equivalent snapability performance as a core/shell impact modifier but with twice less amount of additive and much better transparency.