Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B9/00—Making granules
  • B29B9/16—Auxiliary treatment of granules
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/02—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
  • B01J2/04—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops in a gaseous medium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/16—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by suspending the powder material in a gas, e.g. in fluidised beds or as a falling curtain
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B9/00—Making granules
  • B29B9/16—Auxiliary treatment of granules
  • B29B2009/166—Deforming granules to give a special form, e.g. spheroidizing, rounding
• • 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
  • B29C64/307—Handling of material to be used in additive manufacturing
  • B29C64/314—Preparation
• • 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
  • B33Y40/10—Pre-treatment

Definitions

• the invention relates to a method and an apparatus for converting powdered plastics into spherical powdery plastics as far as possible.
• the invention describes a method and apparatus for powder rounding.
• the invention is therefore based on powdered material, hereinafter referred to as the starting material, which is already present, but not in the most spherical structure possible.
• This material is prepared so that the individual particles are as spherical as possible, so are much rounder than the particles of the starting material.
• the volume of the particles of the starting material should essentially be retained, for example at least 90%.
• the mass of the particles should as far as possible, for example at least 90%, be maintained. There is only a reshaping of the individual particles.
• the chemical composition should remain as far as possible unchanged by the forming process.
• powdered plastics that are as spherical as possible. With ideal spherical shape of the individual particles, a product is known to have a particularly high density and good flowability, which is not the case with irregular shape of the particles.
• the powdered plastics prepared according to the invention are to be used, for example, for powder sintering, 3D printing, 3D melting and 3D sintering.
• the plastic material is made liquid by means of a solvent.
• the resulting solution can be sprayed, it usually forms particles with good spherical shape.
• chemical solvents that pollute the environment, there are waste products.
• the plastics can change chemically.
• the invention seeks to manage without such solvents.
• the aim of the invention is also not to increase the fines.
• the particles should therefore not be divided by the process. Parting would lead to a fine fraction which can be detrimental to the desired use, for example, because it occupies the lenses of the lasers and thus prevents an optimum printing result. Or it is an additional step for a dedusting of the powder necessary, which is complicated and leads to a loss of product of not infrequently in the range of 10 to 20%.
• the aim is to average grain sizes less than 500, in particular less than 100 pm, z. B. particles in the range 30 to 100 pm.
• the maximum upper limit is 800 pm.
• a fine dust content ie particles smaller than e.g. 45, 10 and 5 pm, respectively, is also a target; it is in demand for various uses by industry. Other customers want powder with grain distributions without this fine dust content.
• This object is procedurally achieved by a method for forming a starting material of powdered plastic particles in powdered plastic particles as spherical as possible with the following process steps: a) Providing powdered plastic particles as starting material, b) heating the plastic particles in a first treatment space to a first temperature Tl below the melting point of the plastic, wherein the first temperature Tl is determined so that the plastic particles do not yet stick together,
• the process takes place in a closed room.
• the apparatus has a closed housing in the form of the first treatment room and the second treatment room, including the transition area, which has openings suitable and preferably closable for the loading and the removal of the finished product.
• the process can be carried out continuously or batchwise. The rounding is achieved only by thermal means.
• the invention operates essentially in two stages. In a first stage, which is carried out in the first treatment chamber, the particles of the starting material are heated so far that they have a temperature just below the melting point of the plastic material. They should not have a sticky surface yet. It is added to them as much thermal energy, so that in the subsequent second step, which is performed in the second treatment room, only the necessary at least for the melting of an edge region heat energy must be supplied.
• polyamide 12 the melting temperature is for example at 175 to 180 ° C.
• particles of polyamide 12 are preferably heated only to a maximum of 170 ° C.
• the critical area is preferably limited by a free space, a sheath flow and / or a preferably cylindrical wall.
• This wall may be formed, for example, as a cylinder or conical glass or quartz.
• the wall preferably has means by which particles to be flown onto the wall are deflected or shaken off. For example, the wall is vibrated by ultrasound. In the z-direction, the critical region has the length d.
• a plurality of particles is directed in a stream.
• the individual particles should not touch each other, the distances between the individual particles are chosen correspondingly large. Overall, the particles should behave like an ideal gas.
• the movement of the stream of particles follows the flow of the gas in which the particles are located. This movement is preferably in the direction of gravity.
• the particles need not and should not completely change to the liquid phase. It is sufficient if outer regions, for example 60 or 80% of the volume, which is near the surface, melt sufficiently so that unevenness is compensated by the surface tension.
• the core of a particle can remain untouched in the process. It is then surrounded by a reshaped layer, which makes it outwardly as spherical as possible. This is also gentle on the plastic material.
• the temperature of the particles should remain as close to the melting temperature, in particular at most 5 ° C above.
• the temperature of the particles in the second stage for example, 175 to 180 ° C.
• the process preferably takes place in an atmosphere of inert gas, for example nitrogen.
• the oxygen content is at least in the second treatment chamber, preferably also in the first treatment chamber below the oxygen limit concentration.
• the powdered plastic material introduced as the starting material into the device can preferably be produced in a process as described in the German priority application of 19 January 2017 with the file reference 10 2017 100 981 of the same Applicant.
• the disclosure content of this application is incorporated by reference in its entirety to the disclosure content of the present application.
• FIG. 2 shows a second exemplary embodiment of the device, likewise in a basic representation
• Figure 3 is a perspective view of a portion of a flow straightener in a first embodiment
• Figure 4 is a perspective view as Figure 3 in a second embodiment.
• a right-handed xyz coordinate system is used.
• the z-axis goes up against the direction of gravity.
• FIG. 1 The first exemplary embodiment according to FIG. 1 will first be discussed below.
• the second embodiment of Figure 2 is then discussed only insofar as it differs from the first embodiment.
• Starting material 20 which has been comminuted for example in a mill (not shown), is filled in a bunker 22.
• the bunker 22 is airtight lockable, he has a corresponding flap. He preferably has cone shape.
• a rotary valve 24 At its lower end there is a rotary valve 24, whose outlet is connected to a product inlet 26 of a first treatment chamber 28.
• Zeller radschleusen 24 are known from the prior art, they are used for metered discharge silos for powders and grain sizes 0 - 8 mm. Reference is made, for example, to DE 31 26 696 C2.
• the first treatment space 28 is formed substantially cylindrical, wherein the cylinder axis coincides with the z-direction.
• the first treatment chamber 28 tapers conically and has an outlet 30 there, where it is connected to a transition region 32.
• In the lower, cone-shaped area is an annular inlet for hot air, which forms a first heater 34.
• hot gas is injected in the z direction into the first treatment space 28. This hot gas heats the starting material 20 located in the first treatment chamber 28 and brings it to a first temperature Tl. It is desirable that the individual particles of the starting material 20 in the first treatment chamber 28 are heated as uniformly as possible to the first temperature Tl.
• the first heater 34 it is also possible to form the first heater 34 differently. In this case, the introduction of hot air is maintained, because the hot air causes the transport of the particles. However, less hot air is blown in and also via a heating jacket (not shown), which is located on the cylindrical outer wall, heat supplied.
• the raw material 20 filled in the bunker 22 can be preheat the raw material 20 filled in the bunker 22 already.
• any heating device known from the prior art can be used.
• the starting material 20 can be heated as bulk material.
• the preheat temperature is as high as possible, but sufficiently below the melting point of the material, that there is no danger that the particles of the starting material 20, even though they are in direct contact, stick together. It is possible to dispense with the first treatment room 28. This especially if a preheat takes place.
• the transition region 32 is cylindrical.
• a flow straightener 38 is arranged in the transition region 32. It fills the entire cross section of the tubular transition region 32. It serves to unify the movement of the particles in the negative z-direction, in connection with the flow of hot gas originating from the first heating device 34 and which can only flow out via the flow rectifier 38. This gas flow transports and carries the particles.
• a laminar flow is obtained.
• a directional flow of particles is achieved which flows into a second treatment space 42 situated below the transition region 32. This stream of particles should behave like an ideal gas. The particles should all move linearly. They should not come in contact with each other.
• the laminar flow is a movement of liquids and gases in which (still) no visible turbulences (turbulences / cross flows) occur:
• the fluid flows in layers that do not mix with each other. Since a constant flow rate is maintained in the transition region 32, it is a steady state flow.
• Flow rectifiers 38 are known for example from DE 10 2012 109 542 AI and DE 10 2014 102 370 AI.
• Figures 3 and 4 show a detail of two possible embodiments.
• partition walls 40 are arranged to provide a honeycomb pattern in the x-y plane.
• the partition walls 40 intersect at right angles and form a square grid in the x-y plane. In the z direction, they extend both versions over several centimeters, for example 5 to 15 cm.
• the clear distance of opposite partition walls 40 in the x-y plane can be in the range 0, 5 to 5 cm.
• a second treatment space 42 Below the transition region 32 is a second treatment space 42. It is connected with its upper region to the lower end of the transitional rich 32 connected. He is essentially cylindrical. It has a second heating device 44. This is realized in the concrete embodiment by a plurality of infrared radiators 45, which are located on the inner wall of the second treatment chamber 42. They can be individually controlled and tempered individually. They are sufficiently far away from the flow of particles in the xy plane, preventing particles from getting near them. They are aligned with the flow of particles and aim to bring the particles to a second temperature T2 which is slightly above the melting temperature. As a result, the individual particles are melted at least in their superficial area, they are at least partially liquid. Due to the surface tension, these particles deform and assume a more or less spherical shape.
• the second treatment space 42 widens conically downward, corresponding to an expansion of the flow in this direction.
• the forming has taken place sufficiently and at least substantially reaches a spherical shape.
• the particles are cooled in the lower region of the second treatment chamber 42 as quickly as possible in a cooling zone to a temperature below the first temperature Tl, so that they are no longer sticky.
• the cooling takes place by introducing a Coolant gas, preferably liquid nitrogen is introduced through nozzles 46 which are directed transversely to the z-direction.
• the cooling zone is located below the distance d and ends above the bottom of the second treatment chamber 42, that is, above a product outlet 48
• the no longer sticky particles are removed at the product outlet 48, which is located in the lowest area of the second treatment chamber 42. They are promoted by the prevailing in the second treatment chamber 42 gas flow. It has its source on the one hand in the hot air from the first treatment chamber 28 and on the other hand in the pressure of the relaxing liquid nitrogen flowing from the nozzles 46. This gas flow can only escape through the product outlet 48.
• a filter 50 is connected via a line.
• a sieve 52 is below this filter 50. From this sieve 52, the now spherical particles fall into a receptacle 54, for example a sack.
• an outflow opening 56 is provided for the gas of the flow described above. It is possible to arrange in this outflow opening 56 a fan 58, which is controllable and can regulate the extent of the outflowing amount of gas.
• inlet nozzles 60 are arranged, whose outlets are oriented downwards, in the negative z-direction. Through them hot, preferably the temperature T2 exhibiting gas is introduced. It forms a sheath flow around the flow of particles.
• the hot-gas injection nozzle 60 may also be used for heating the particle to the second temperature T2 in addition to, or even without, the infrared heaters 45.
• a cylindrical wall 62 is additionally arranged in the second treatment space 42. It is preferably made of quartz glass and transparent to the light of the infrared radiator 45. It has an inner diameter which is slightly larger than the diameter of the introduction nozzles 60. The sheath flow caused by the introduction nozzles 60 is bounded outwardly by this wall 62.
• the wall 62 has an upper end that is laterally or just below the inlet nozzles 60. It has a lower end that is above the nozzles 46.
• the device preferably has a plurality of sensors, including at least one of the following sensors:
• Sensors for detecting the speed of the introduced hot gas and further comprises a control unit for the control of the process. These details are not shown in the drawing.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Processes Of Treating Macromolecular Substances (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 2018
  • 2018-08-28 CA CA3072305A patent/CA3072305A1/en not_active Abandoned
  • 2018-08-28 US US16/645,616 patent/US20200282601A1/en not_active Abandoned
  • 2018-08-28 KR KR1020207004712A patent/KR20200035275A/ko not_active Application Discontinuation
  • 2018-08-28 AU AU2018331782A patent/AU2018331782A1/en not_active Abandoned
  • 2018-08-28 JP JP2020509024A patent/JP2020533194A/ja active Pending
  • 2018-08-28 CN CN201880058888.0A patent/CN111065502A/zh not_active Withdrawn
  • 2018-08-28 WO PCT/EP2018/073137 patent/WO2019052806A1/de unknown
  • 2018-08-28 EP EP18762071.1A patent/EP3681686A1/de not_active Withdrawn
  • 2018-08-31 TW TW107130646A patent/TW201934293A/zh unknown

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