WO2016010424A1 - Procédé permettant de régénérer au moins pratiquement de la poudre de polymère - Google Patents

Procédé permettant de régénérer au moins pratiquement de la poudre de polymère Download PDF

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Publication number
WO2016010424A1
WO2016010424A1 PCT/NL2015/050512 NL2015050512W WO2016010424A1 WO 2016010424 A1 WO2016010424 A1 WO 2016010424A1 NL 2015050512 W NL2015050512 W NL 2015050512W WO 2016010424 A1 WO2016010424 A1 WO 2016010424A1
Authority
WO
WIPO (PCT)
Prior art keywords
powder
water
polymer
elevated temperature
grains
Prior art date
Application number
PCT/NL2015/050512
Other languages
English (en)
Inventor
Ferdinand Michael VERBOOM
Original Assignee
3Dppm B.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3Dppm B.V. filed Critical 3Dppm B.V.
Publication of WO2016010424A1 publication Critical patent/WO2016010424A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/30—Auxiliary operations or equipment
    • B29C64/357—Recycling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2377/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • the present invention relates generally to layerwise building, a lso referred to as 3 D- printing, of a n object more specifica lly to layerwise Selective Laser Sintering (SLS) of polymer powder.
  • the invention relates to a process for refreshing used polymer, particula rly polya mide, conta ining powder from a SLS process for reuse in a next building process cycle. More pa rticularly the invention relates to a method for at least substa ntia lly regenerating polymer powder that has been wasted from a thermal fusion process, pa rticula rly polya mide powder that has been wasted from a selective laser sintering process that was used to create a n object.
  • a Selective Laser Sintering (SLS) process is a n additive ma nufacturing process in which layers of powder are fused together by irradiation with a laser.
  • polymer powder particularly polyam ide powder
  • a nd polymer contents is introduced in the process reactor and the powder in the machine is heated to a tem peratu re close to its melting tem perature for a long period of time.
  • poly(a mide-12) ( PA12) is used in a SLS process. U nder these conditions solid state post-condensation is likely to occur in the polyam ide powder resu lting in chain-extension.
  • a higher melt viscosity reduces the inter-particle fusion during later laser sintering, which deteriorates the performa nce a nd quality of the SLS process.
  • a product ma nufactured from non- processed re-used polymer powder, for exa mple, will show more porous parts with inferior mechanical properties, like reduced stiffness a nd reduced tensile strength.
  • the surface quality of the product will be poorer, also referred to as orange peel.
  • Blending still requires virgin powder and, due to the excess of waste powder that results from a SLS process, will only be capable of regaining use of merely part of all waste powder used in prior SLS processes.
  • a pre-treatment of waste powder or of a mixture of waste powder and fresh powder by liquefaction is proposed in order to reduce the effects of aging damages in the waste powder and, hence, to enable admixing more waste powder in the blend.
  • the pre-treatment by liquefaction does not remove all aging damages of the powder.
  • pockmarks which are also termed as sink marks or orange peel.
  • the present invention has inter a lia for its object to provide a process of regenerating waste polymer powder that has been used in a building process for a n object by selective therma l fusion of polymer powder, pa rticularly polyam ide powder, such that it may be re-used in a sim ilar process with im proved processability.
  • particula rly polya mide powder that has been wasted from a selective laser sintering process that was used to create a n object is characterized in that said polymer powder is introduced in a process cha mber, in that substantially all air is evacuated from said process cham ber to create a substa ntia lly dry, substa ntia lly oxygen free atmosphere, and in that sa id polymer powder is brought to an elevated temperature in said substantia lly dry atmosphere for a duration of time to allow a scission reaction of the polymer chain of said polymer.
  • refreshing entails the reduction of molecular weight via the hyd rolysis of polymer concerned to provide a reduced viscosity com pared to the initia l va lue of the used materia l, hereinafter a lso referred to as Old' material. Because substa ntially all air has been expelled from the reaction cha mber before starting the scission reaction, so is substantially all free oxygen. It has been found that thereby a lso a premature degradation of the powder may be cou nteracted.
  • the method accord ing to the invention is characterized in that said process cham ber is flushed with a n inert dry gas to expel substa ntially all air. Flushing with a dry gas appears to be a convenient and effective method of creating a dry atmosphere in the reaction cham ber after it has been filled with powder, wh ile the use of an inert gas does not introduce any reactants in the following hyd rolysis process.
  • a specific embodiment of the method according to the invention is cha racterized in that said elevated temperature resides between approximately 120 °C a nd at least 5 °C below a melting temperature of said polymer.
  • This tem perature ra nge offers an adeq uate reaction rate while the maxim um of at least 5 °C below a melting
  • tem perature of sa id polymer counteracts fusion of powder pa rticles a nd further degradation d uring the process.
  • Specifica lly a n embodiment of the method according to the invention is carried out such that said elevated temperature resides between approximately 120 °C and at least 5 °C below a melting temperature of said polymer.
  • a further preferred embodiment of the method according to the invention is characterized in that the powder is brought to said elevated temperature in the presence of a carrier of water that releases water at least at said elevated temperature.
  • a carrier containing water
  • the water content can be controlled and distributed in the container as desired in order to speed up and/or enhance the regeneration of the polymer powder in the reaction chamber.
  • the method according to the invention is characterized in that said carrier comprises a plurality of beads or grains that contain water, in that said beads or grains are mixed with said powder, and in that said beads or grains have a size that is considerably larger than a size of the powder particles.
  • a water delivery can be dispersed relatively well over the powder mass by using many beads or grains and mixing them with said powder. Because the beads or grains have a significantly larger size than the powder particles, the beads or grains can be filtered out relatively easily afterwards to offer clean, refreshed powder that is ready for re-use in a selective sintering process.
  • the method according to the invention is characterized in that said beads or grains comprise silica gel or ceramics.
  • a further particular embodiment of the method according to the invention is characterized in that said carrier comprises a solid body containing water, said solid body residing in the reaction chamber while the powder is brought to said elevated temperature.
  • the solid body offers a localized water dispersion system in the reaction chamber. As a result the reaction can be accelerated at a single point of the reactor, for instance the middle of the powder mass.
  • a further preferred embodiment of the method according to the invention is characterized in that said carrier is reversible carrier of water capable of releasing water at said elevated temperature and capable of absorbing water while being brought from said elevated temperature to room temperature.
  • a reversible carrier like for instance the silicagel or ceramics beads or grains referred to hereinbefore, provides for the delivery of a controllable amount of water during the reaction process at said elevated temperature simply by controlling the amount of carrier(s) added to the powder.
  • the reversible nature offers the carrier the capability of capturing the water again while the powder cools to ambient temperature at the end of the process to render a dry regenerated powder. No drying step is necessary afterwards although water has been admitted to enhance the reaction process.
  • an autoclave reactor is filled with old, i.e. used, PA12 or PA11 polyamide powder that is to be refreshed such that it may be re-used in a selective (laser) sintering process.
  • the process chamber is closed and purged with nitrogen gas. Afterwards heating is applied, preferably under mixing, to raise the chamber temperature to temperatures of at least 120 °C. The maximum temperature of the chamber is kept 5 °C below the melting temperature of the polyamide.
  • Figure 1 shows a condensation reaction of PA12, where the reaction in the opposite direction is the hydrolysis reaction of PA12 according to this embodiment of the invention.
  • the extent of the molecular weight increase of old material during the former SLS process determines the duration of the treatment and the process conditions needed. These process conditions particularly concern the temperature and the chamber pressure, which both may be varied and tailored to optimize the regeneration process.
  • an addition of water is used to enhance the reaction process.
  • other components can be added (e.g. mono and di-acids) to regulate the reactivity of the end groups of the polymer chains and control molecular weight distributions.
  • Said addition of water is realized by mixing a plurality of silica gel beads or grains with a grain size that is considerably larger than the polymer powder particles.
  • a polyamide powder is used with a steep particle size distribution around between 50 and 60 micron, while the silica gel beads or grains that are of the order of a few millimetre in size, particularly the beads or grains are of the order of 3,5 millimetre in this embodiment.
  • Said silica gel beads or grains carry water and possibly also other components that could speed up or otherwise improve the reaction process. During the process these beads or grains will release said water and said possible other components. After the process the beads or grains can easily be removed physically from the powder, for instance by sieving, while having absorbed at moderate to ambient temperature all excess water that was unused during the regeneration process.
  • a batch of approximately 250 kilograms of old, i.e. used, polyamide powder is mixed with approximately 10 kilograms of soaked silica gel beads or grains and then processed similar to the powder in the first example.
  • the powder/beads or grains mixture is kept at an elevated temperature of about 140-150 °C for a duration of roughly 48 hours.
  • the reaction chamber is flushed with nitrogen gas to expel all resident air.
  • an elevated nitrogen pressure of about 120-130 kPa is left in the reaction chamber to maintain a substantially dry, substantially oxygen free atmosphere.
  • nitrogen gas instead of nitrogen gas also noble gasses like helium and argon may be used to flush the process chamber.
  • the resultant powder has a considerably lower average molecular weight than the initial powder, as shown in table 1, which allows it to be re-used in a SLS process without further blending or other post-processing.
  • the average molecular weight (M J of both the initial powder and the resultant powder is determined by size exclusion chromatography (SEC).
  • SEC size exclusion chromatography
  • refractometer is used to obtain data on the molecular weights of all the polyamide materials.
  • the material is first dissolved in hexa-fluoro-isopropanol (HFIP). Before injection, the samples are filtered through a 200 nanometre PTFE filter (13 mm, PP housing, Alltech).
  • HFIP hexa-fluoro-isopropanol
  • the samples are filtered through a 200 nanometre PTFE filter (13 mm, PP housing, Alltech).
  • melt viscosity of the polyamide has been tested in an AR-G2 rheometer, while a parallel plate setup was used in the environmental test chamber for
  • the Mw data with the corresponding rheologica l properties show that from blend (input in the SLS printer) to old powder (output of the SLS printer) a n increase in molecula r weight leads to the increase in viscosity after the SLS process.
  • the molecular weight of the old materia l is reduced to 50% of the sta rting va lue and the melt viscosity is reduced to 40% of the starting viscosity of the old materia l.
  • This a ppea rs an accepta ble value for re-use in a SLS process.
  • Further optim ization possibilities of the refreshing process as described hereinbefore allow a fu rther reduction of the melt viscosity of old, i.e. used, material to values even closer to that of virgin material.
  • the powder ca n aga in be used in a SLS process to print, i.e. build, a next object.
  • the method according to the current invention may then aga in be used to im prove and upgrade the powder properties and generate a useable feedstock for further print cycles. This opens a path to close the loop of the expensive waste stream in current polymer powder based additive manufacturing systems.
  • polymers that could be processed in a sim ilar way a re for insta nce polyesters, like PET, PBT, PTT, PEN, PLA, PGA and co-polymers thereof, polyam ides, like PA4.6; PA6; PA6.6; PA6.12; PA6.10; PA10.10; PA10.12; PA11; PA12.12 a nd co-polymers thereof, a nd polyester urethanes.
  • a lso other reversible water absorbing materials may be used as a water carrier during the process, like for instance wood either as a solid body or as a plura lity of grains.

Abstract

L'invention concerne un procédé permettant de régénérer de la poudre de polymère qui a été perdue dans un processus de fusion thermique qui a été utilisé pour créer un objet, comme un processus de frittage laser sélectif de poudre de polyamide. Ladite poudre de polymère est introduite dans une chambre de traitement. Pratiquement tout l'air est évacué de ladite chambre de traitement afin de créer une atmosphère pratiquement sèche. Enfin, ladite poudre de polymère est amenée à une température élevée dans ladite atmosphère pratiquement sèche pendant une certaine durée pour permettre une réaction de scission de la chaîne polymère dudit polymère.
PCT/NL2015/050512 2014-07-15 2015-07-13 Procédé permettant de régénérer au moins pratiquement de la poudre de polymère WO2016010424A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201462024704P 2014-07-15 2014-07-15
US62/024,704 2014-07-15

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WO2016010424A1 true WO2016010424A1 (fr) 2016-01-21

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102016219746A1 (de) * 2016-10-11 2018-04-12 Universität Stuttgart Verfahren zum Herstellen eines Bauteils mittels Lasersinterns
US11478985B2 (en) 2017-10-18 2022-10-25 Hewlett-Packard Development Company, L.P. Build material for three-dimensional printing

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB133369A (fr) * 1900-01-01
US5304329A (en) * 1992-11-23 1994-04-19 The B. F. Goodrich Company Method of recovering recyclable unsintered powder from the part bed of a selective laser-sintering machine
DE10105504A1 (de) 2001-02-07 2002-08-14 Eos Electro Optical Syst Vorrichtung zur Behandlung von Pulver für eine Vorrichtung zum Herstellen eines dreidimensionalen Objekts, Vorrichtung zum Herstellen eines dreidimensionalen Objekts und Verfahren zum Herstellen eines dreidimensionalen Objekts
US20040138344A1 (en) 2002-10-23 2004-07-15 Jean-Philippe Allen Increase in the melting point and the enthalpy of melting of polyamides by a water treatment
WO2005097475A1 (fr) 2004-03-30 2005-10-20 Valspar Sourcing, Inc. Procede de frittage laser selectif et polymeres utilises dans ce procede
DE102004047876A1 (de) 2004-10-01 2006-04-06 Degussa Ag Pulver mit verbesserten Recyclingeigenschaften, Verfahren zu dessen Herstellung und Verwendung des Pulvers in einem Verfahren zur Herstellung dreidimensionaler Objekte
DE102008024465A1 (de) 2008-05-21 2009-11-26 Eos Gmbh Electro Optical Systems Verfahren und Vorrichtung zum schichtweisen Herstellen eines dreidimensionalen Objekts aus einem pulverförmigen Material

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB133369A (fr) * 1900-01-01
US5304329A (en) * 1992-11-23 1994-04-19 The B. F. Goodrich Company Method of recovering recyclable unsintered powder from the part bed of a selective laser-sintering machine
DE10105504A1 (de) 2001-02-07 2002-08-14 Eos Electro Optical Syst Vorrichtung zur Behandlung von Pulver für eine Vorrichtung zum Herstellen eines dreidimensionalen Objekts, Vorrichtung zum Herstellen eines dreidimensionalen Objekts und Verfahren zum Herstellen eines dreidimensionalen Objekts
US20040138344A1 (en) 2002-10-23 2004-07-15 Jean-Philippe Allen Increase in the melting point and the enthalpy of melting of polyamides by a water treatment
WO2005097475A1 (fr) 2004-03-30 2005-10-20 Valspar Sourcing, Inc. Procede de frittage laser selectif et polymeres utilises dans ce procede
DE102004047876A1 (de) 2004-10-01 2006-04-06 Degussa Ag Pulver mit verbesserten Recyclingeigenschaften, Verfahren zu dessen Herstellung und Verwendung des Pulvers in einem Verfahren zur Herstellung dreidimensionaler Objekte
DE102008024465A1 (de) 2008-05-21 2009-11-26 Eos Gmbh Electro Optical Systems Verfahren und Vorrichtung zum schichtweisen Herstellen eines dreidimensionalen Objekts aus einem pulverförmigen Material

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102016219746A1 (de) * 2016-10-11 2018-04-12 Universität Stuttgart Verfahren zum Herstellen eines Bauteils mittels Lasersinterns
US11478985B2 (en) 2017-10-18 2022-10-25 Hewlett-Packard Development Company, L.P. Build material for three-dimensional printing

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