Biodegradable plastics for use in additive manufacturing processes

Abstract

Disclosed is a plastic powder for use as a building material for the additive manufacturing of a three-dimensional object by selective solidification of the building material at the points corresponding to the cross-section of the three-dimensional object in the respective layer by exposure to radiation, wherein the plastic powder comprises polymer-based particles and an additive for imparting biodegradability in an amount of 0.05 to 5% by weight based on the weight of the polymeric components in the polymer-based powder. Further disclosed is a method for the production of such powder, methods for the production of three dimensional objects using such powder as well as three dimensional objects, which have been prepared accordingly, as well as the use of corresponding additives to impart biodegradability to three dimensional objects, which have been prepared accordingly.

Claims

1. A building material used in additive manufacturing of a three-dimensional object by selective solidification at points of respective layers corresponding to cross-sections of the three-dimensional object by exposure to radiation, wherein the building material comprises: polymer-based particles; and an additive imparting biodegradability specifically in an ecological biome in which the three-dimensional object is placed for disposal, the additive being in a weight fraction of about 0.05 to about 5% based on a total weight of polymeric components in the building material, wherein the building material has a biodegradability according to ASTM D 5511-18 after about 83 days of at least 2 wt.-% relative to the total weight of the polymeric components, and/or which has a biodegradability according to ASTM D 5511-18 after about 155 days, of at least 2 wt.-% relative to the total weight of the polymeric components.

2. The building material according to claim 1, wherein the weight fraction of the additive, based on the total weight of polymeric components in the building material, is at least 0.1 and/or at most 3% by weight.

3. The building material according to claim 1, wherein the additive is incorporated into the polymer-based particles.

4. The building material according to claim 1, wherein the additive further contains a component selected from starch and/or starch mixtures, mixtures of organic acids and polyesters, and fractal polymers.

5. The building material according to claim 1, wherein the additive further contains a fatty acid for compatibilization with the polymer of the plastic powder.

6. The building material according to claim 1, wherein the polymer-based particles comprise at least one polymer, co-polymer or polymer blend selected from the group consisting of polyamides, polyolefins, polyether block amides (PEBA), polystyrene, polyaryletherketones, thermoplastic polyurethanes, polyesters, polyethers, polyhydroxy acids, polylactides, polyphenylene sulfides, polyphenylene oxides, polyimides, polyetherimides, and polycarbonates.

7. The building material according to claim 1, wherein the polymer-based particles have a mean particle diameter, determined by laser diffraction, in a range from about 20 m to 100 m.

8. The building material according to claim 1, further comprising additional particles of an NIR radiation absorbing material, which are present separately in a mixture with the polymer-based particles, absorbed onto a surface of the polymer-based particles or incorporated into the polymer-based particles.

9. A three-dimensional object, which is produced by solidification of the building material according to claim 1 at points corresponding to a cross-section of the three-dimensional object in respective layers by exposure to radiation.

10. A method for producing a three-dimensional object by solidifying the building material according to claim 1 at points corresponding to a cross-section of the three-dimensional object in respective layers, wherein the building material is selectively solidified by action of electromagnetic radiation emitted by a radiation source.

11. A system for production of three-dimensional objects by solidifying the building material according to claim 1 at points corresponding to a cross-section of the three-dimensional object in a respective layer, wherein the system has at least one radiation source that is designed to emit electromagnetic radiation, a process chamber that acts as an open container and is designed with a container wall, a carrier located in the process chamber, the process chamber and carrier being movable relative to one another in a vertical direction, the system having a storage container and a coater movable in the horizontal direction, wherein the storage container is at least partially filled with the building material according to claim 1.

12. The method according to claim 10, wherein the radiation source emits light of a wavelength in the range from 500 to 1500 nm, or light of a wavelength of about 10.6 m or in the range of 4.8 to 8.3 m.

13. The method according to claim 10, wherein the radiation source comprises at least one laser.

14. A method for producing a building material comprising: processing polymer-based particles an additive by mixing without adding a solvent, or by coextrusion and subsequently to one or more of milling, fiber spinning and fiber cutting, melt spraying, microgranulating, or by complete or partial dissolution in a solvent by adding the additive to the solution and then precipitation and/or spray drying polymer-based particles with incorporated additive, or by impregnation of the polymeric component with a solution or dispersion of the additive in a fluid, wherein the building material is used in additive manufacturing of a three-dimensional object by selective solidification at points of respective layers corresponding to cross-sections of the three-dimensional object by exposure to radiation, and wherein the building material comprises: the polymer-based particles; and the additive, which imparts biodegradability specially in an ecological biome in which the three-dimensional object is placed for disposal, the additive being in a weight fraction of about 0.05 to about 5% based on a weight of polymeric components in the building material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an example of a conventional laser sintering device for the layerwise production of a three-dimensional object.

(2) FIGS. 2 and 3 show the biodegradation behavior of nylon 11 without biodegradability imparting additive (neg) and with either 0.5% MB-67 or 1% BS-201j additive.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) In the following, the present invention will be further described by means of examples, which are however only provided for illustration purposes and should not be construed in any manner as limiting to the invention as herein above described.

EXAMPLES

Example 1: Bio Degradation of PA11 with Different Degradation Additives

(4) Several samples of polyamide 11 (Rilsan PCG-LV by Arkema) were prepared which either contained no additive (control/NEG), 0.5 wt.-% of EcoTech/Eco pure MB-67 additive or 1 wt.-% of Biosphere BS-201j additive. The polyamide 11 is compounded with the additive on a twin-screw extruder to obtain the raw material for the tests. The respective materials were processed into powders of an average particle size as indicated in table 1 below using a cryogenic grinder.

(5) Subsequently, standard test specimens of dimensions 6 inch inch inch according to ASTM D638 Type I were prepared to determine mechanical properties of the materials by means of a modified Integra ISI lasersintering system using standard polyamide 11 processing conditions.

(6) The properties of the powder materials before and after preparation of the test specimens (for the material which is not molten during the process) are given in table 1. Thermal properties were measured by DSC according to standard ASTM D3418 with heating/cooling rates of 10K/min in a temperature range between 40 C.-230 C. using a DSC Q20 by TA Instruments. eos in table 1 designates the difference of extrapolated onset-temperature (=designed intersection point of the baseline and the inflectional tangent at the beginning of the melting and respective crystallization peak for first heating run and cooling run). Melting temperature refers to the peak temperature of the melting peak on the first heating run. Particle size is given as the D50 value, which was determined by laser diffraction using Microtrac TurboSync with dry dispersion. Powder density is Apparent Density according to ASTM D1895. MFR designates the melt mass flow rate (according to ISO 1133) at 230 C., 1 kg load after 3 min dwell time using a melt density of 0.80 g/cm.sup.3 measured with a Dynisco plastic 4004 melt flow indexer.

(7) TABLE-US-00001 TABLE 1 Melting Average Powder temp. Particle size density MFR Sample eos [ C.] [ C.] D50 [m] [g/cm.sup.3] [g/10 min] nylon-11 16 189.44 79.7 0.37 75.5 nylon-11* 16 189.50 76.6 0.38 53.4 nylon-11 16 189.46 74.8 0.37 76.7 with MB-67 nylon-11 17 189.86 67.2 0.33 49.7 with MB-67* nylon-11 17 189.64 80.1 0.39 77.4 with BS201j nylon-11 20 189.29 66.2 0.37 47.5 with BS201j* *Part bed powder material, which is not molten during the process (as received after lasersintering processing)

(8) In Table 2, the mechanical properties of non-conditioned samples, as determined according to ASTM D 638 using an Instron 3365 mechanical tester with a 5 kN load cell, under laboratory conditions of 22 C. and 50% RH are provided. The part density was measured according to ASTM D792, Test method A.

(9) TABLE-US-00002 TABLE 2 Part Tensile Tensile Elongation Density strength Modulus at Sample [g/cm.sup.3] [MPa] [MPa] break [%] nylon-11 1.03 48 1673 23 nylon-11 with 1.03 50 1586 27 MB-67 nylon-11 with 1.03 49 1688 25 BS201j

(10) As can be seen from the above Tables 1 and 2, the powders prepared with biodegradation additive have very similar properties to powders without additive, so that they can replace conventional nylon-11 powder without the necessity to adjust processing parameters. Similarly, the mechanical properties are very similar for the processed materials, which shows that the incorporated additives do not negatively affect the processed products.

(11) In the following, the respective material powders were subjected to biodegradation tests according to ASTM D 5511-18. The results of these tests are provided in the following Table 3, as well as in FIGS. 2 (for 83 days) and 3 (for 205 days).

(12) TABLE-US-00003 TABLE 3 Biodegradation according to ASTM D5511-18 [%] Sample 83 days 155 days 205 days nylon-11 0.7* 0.8 0.8 nylon-11 with 4.2 7.4 10.3 MB-67 nylon-11 with 6.9 10.4 12.8 BS201j *increase in weight probably due to water absorption

Example 2 (Reference): Influence of Concentration and Degradation Time

(13) Several samples of polypropylene (PP400) were prepared which either contained no additive (control), 1 wt.-% of Biosphere BS-201j additive or 2 wt.-% of Biosphere BS-201j additive. The samples are shaped as straws by conventional plastic processing techniques.

(14) The respective test specimen were subjected to biodegradation tests according to ASTM D 5511-18. The results of these tests after 390 days and 537 days are provided in the following Table 4:

(15) TABLE-US-00004 TABLE 4 Biodegradation according to ASTM D5511-18 [%] Sample 390 days 537 days PP (control) 2.3 0.1 PP with 1% Biosphere 19.6 24.4 additive PP with 2% Biosphere 34.4 39.2 additive

(16) The data in Table 4 shows that there is higher degradation with higher content of additive. Moreover, for longer times, the degradation is higher.

(17) For samples produced by additive manufacturing, in particular by laser sintering, comparable behavior is expected.

Example 3: Biodegradation with Different Polymers, Corresponding Processing Conditions and Part Properties

(18) Different samples were prepared by compounding and grinding various base polymers with the biodegradation additive BS-201j delivered from Biosphere Plastics (see Table 5). For each sample, a reference without additive was produced with same conditions. Compounding, grinding, powder analysis and part production was performed according to the procedures in Example 1. For part production on the laser sintering system, the default process parameters for each material was used.

(19) PP400 is a polypropylene commercially available from Advanced Laser Material LLC. TPE300 is a thermoplastic polyurethane, which is commercially available from Advanced Laser Materials LLC. PEBA/30% nylon 11 and PEBA/90% nylon 11 are experimental grades of the polyether block amide copolymer family available from Arkema under the tradename PEBAX. The percentages refer to content of polyamide 11 in the copolymer.

(20) Any test results besides the biodegradation test are given as relative values compared to the respective reference materials without biodegradation additive. Processing tests refer to the general processability of the powders on the lasersintering system, in particular the recoating behavior and thermal processing window. Mechanical properties refers to the elongation at break, tendencies are stated when outside the typical deviation range. Coloring refers to color of parts produced by lasersintering, evaluated by optical inspection.

(21) TABLE-US-00005 Biode- gradation according to ASTM D5511-18 after X days BS-201j [%] Base additive Processing Mechanical (reference Polymer content tests Properties Coloring values) PP400 1% no impact 15% loss Similar Tbd (tbd) color TPE300 1% no impact no Similar Tbd (tbd) difference color TPE300 2% no impact no Similar Tbd (tbd) difference color PEBA/90% 2% no impact 20% loss discolored Tbd (tbd) nylon 11 PEBA/30% 1% no impact tbd discolored Tbd (tbd) nylon 11.