Pre-treated material for laser sintering

Abstract

Disclosed is a composition, in particular a build material for an additive manufacturing process, wherein the composition is treated by heating. Furthermore, the invention relates to a method for manufacturing the inventive composition and a device comprising the inventive composition as well as the use of the inventive composition.

Description

Technical Field

[0001] This invention relates to a composition, particularly a building material for additive manufacturing processes, wherein the composition is treated by heating. Furthermore, this invention relates to a process for manufacturing the composition of the invention, an apparatus comprising the composition of the invention, and the use of the composition of the invention. Background Technology

[0002] Additive manufacturing processes, used for the industrial production of prototypes and devices based on powder-based building materials, allow for the manufacture of plastic products and are becoming increasingly important. Through the manufacturing process, layers are selectively melted and solidified, creating the desired structure by applying binders and / or adhesives, respectively. This process is also known as “additive manufacturing,” “digital manufacturing,” or “3D printing.”

[0003] For decades, industrial development processes used for prototyping (rapid prototyping) have been employed. However, with technological advancements in the system, alternatives to prototypes, or even components other than prototypes, have begun to be produced that meet the quality requirements of the final product (rapid manufacturing). In other words, technological advancements in the system now also allow for the production of components that meet the quality requirements of the final product.

[0004] In practice, the term "additive manufacturing" is often replaced by the terms "generative manufacturing" or "rapid technology." Additive manufacturing encompasses processes that use powder materials, such as sintering, melting, or bonding with binders.

[0005] Typically, polymer systems are used as powder materials for manufacturing articles. Industrial users of such polymer systems require articles manufactured from these systems to have good processability, molding accuracy, and good mechanical properties.

[0006] For manufacturing such articles, it is preferable that the melting temperature (“Tm”) and recrystallization temperature (“Trc”) of the powder have a relatively large positive difference. If a relatively large positive difference exists between the two temperatures, it is easier to maintain an operating temperature during manufacturing that both keeps the molten powder partially melted and prevents the remaining unmelted powder from melting. When the molten powder remains partially melted, the object being formed is less likely to warp or deform, and the powder can be more easily separated from the finished object while preventing the remaining unmelted powder from melting.

[0007] Therefore, in the manufacturing process of 3D products, the build temperature needs to be higher than the crystallization temperature of the polymer. On the other hand, in order to prevent the powder from melting in the build area, the build temperature is inherently required to be lower than the melting temperature.

[0008] Typically, the temperature range suitable for building objects via additive manufacturing is referred to as the polymer's process window or sintering window. In cases where polymer crystallization and melting significantly overlap, the polymer is likely unsuitable for additive manufacturing. Summary of the Invention

[0009] Therefore, one object of the present invention is to anticipate a composition suitable for use as a material in additive manufacturing processes for the production of articles exhibiting process safety, mechanical stability, and high-precision shapes. In particular, one object of the present invention is to provide a composition exhibiting optimal process window and melting properties.

[0010] Therefore, the present invention relates to a composition, particularly a building material for the above-described additive manufacturing process, comprising:

[0011] At least one polymer,

[0012] The polymer is preferably in powder form.

[0013] and

[0014] The polymer includes at least one thermoplastic polymer.

[0015] At least one thermoplastic polymer is preferably selected from polyetherimide, polycarbonate, polysulfone, polyphenylsulfone, polyphenylene ether, polyethersulfone, acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene-acrylate copolymer (ASA), polyvinyl chloride, polyacrylate, polyester, polyamide, polypropylene, polyethylene, polyaryletherketone, polyether, polyurethane, polyimide, polyamide-imide, polyolefin, polyarylether sulfide and copolymers thereof.

[0016] and

[0017] The polymer is treated by heating at a temperature at least about 0.1°C below its melting point and no more than about 2°C below its melting point.

[0018] and

[0019] The heat treatment is carried out for at least about 1 hour and / or no more than about 24 hours, preferably no more than about 12 hours, and more preferably no more than about 8 hours.

[0020] In its simplest embodiment, the composition of the present invention comprises a polymer or polymer system selected from thermoplastic polymers.

[0021] As used herein, the term "powder" refers to a loose solid composed of fine particles that can flow freely when shaken or tilted. According to the invention, such fine particles have a particle size d50 of less than about 500 μm.

[0022] Surprisingly, this heat-treated composition exhibits improved performance during the manufacture of devices or articles. Advantageously, such compositions have a larger process window, allowing for the successful completion of devices or articles during manufacturing without interruption.

[0023] Furthermore, this advantageous composition exhibits excellent flowability and melting properties, as well as a uniform structure of bulk materials (e.g., powders), resulting in improved rheological properties such as viscosity, thereby allowing for improved material deposition and mechanical properties. Bulk materials are considered to have good flowability when they are free and readily flowable.

[0024] Therefore, with the compositions of the present invention, the thickness of the components of the device or apparatus to be constructed or the height of the successfully constructed device or apparatus are no longer limited. Thus, devices or articles of any shape and size can be successfully produced.

[0025] The success of a heat treatment process can be demonstrated by differential scanning calorimetry (DSC) curves of the material before and after heat treatment. This method, for example, DIN EN ISO 11357, is known to those skilled in the art.

[0026] Advantageously, by applying the present invention, the melting and recrystallization temperatures of the powder can be improved, for example, by any one or a combination of the following: (a) increasing the difference between Tm and Trc of the powder by increasing Tm of the powder; (b) increasing the difference between Tm and Trc of the powder by decreasing Trc of the powder; (c) increasing the melting initiation temperature (“Tmo”) of the powder; and (d) decreasing the recrystallization initiation temperature (“Tro”) of the powder. The present invention can combine (a) and (c).

[0027] Furthermore, reducing the difference between Tmo and Tm significantly improves the powder's ability to prevent premature melting, which would cause the remaining unmelted powder to partially melt and fuse together.

[0028] As used herein, the term "melting temperature" (Tm) refers to the temperature or range at which a substance, preferably a polymer, copolymer, or polymer blend, changes from a solid to a liquid state.

[0029] The term “recrystallization temperature (Trc)” as used in this article refers to the temperature or range at which a molten amorphous material transforms into a crystalline material upon cooling.

[0030] The term “melting onset temperature (Tmo)” used in this article refers to the temperature at which the tangent to the melting event on the DSC curve intersects the baseline.

[0031] The term “recrystallization initiation temperature (Tro)” as used in this article refers to the temperature at which the tangent to the recrystallization event on the DSC curve intersects the baseline.

[0032] The term “about” or “approx.” as used in this article indicates that the specified number or range may vary by up to 10% to 15%.

[0033] The term "flowability" as used herein is used synonymously with the term "pouring property". The pourability of powder is measured according to DIN ENISO 6186 using a mm funnel and / or according to ASTM D 7891-15 via a shear cell.

[0034] As used herein, the term "polymer" or "polymer system" refers to at least one homopolymer and / or hybrid polymer constructed from a plurality of monomers. Homopolymers contain covalently linked identical monomers, while hybrid polymers (also called copolymers) contain different monomers covalently linked. According to the invention, a polymer or polymer system may comprise mixtures of the aforementioned homopolymers and / or hybrid polymers, or may comprise more than one type of polymer system. In this application, such mixtures are referred to as polymer blends.

[0035] In the context of this invention, a hybrid polymer may be selected from: statistical copolymers to include monomers having a random distribution; gradient copolymers that are substantially similar to statistical copolymers but wherein the content of monomers in the chain is increased or decreased; alternating copolymers to include alternating monomers; block copolymers or segment copolymers that include a longer sequence or block of each monomer; and graft copolymers, wherein a block of each monomer is grafted onto the framework of a different monomer.

[0036] The “composition” as used herein may contain one or more additives. The term “additive” as used herein refers to a substance, which may in particular be an amorphous and / or semi-crystalline and / or crystalline polymer, a polyol, a tensioning agent and / or a protective colloid.

[0037] Advantageously, the compositions of the present invention can be used in additive manufacturing processes. In the context of this application, additive manufacturing processes particularly include processes suitable for manufacturing prototypes (rapid prototyping) and articles (rapid manufacturing), preferably from the group comprising laser sintering, high-speed sintering, multi-jet melting, binder jetting, selective mask sintering, or selective laser melting powder bed processes. In particular, the compositions of the present invention can be used in laser sintering. The term “laser sintering” as used herein is used similarly to the term “selective laser sintering”; the latter represents the older designation.

[0038] Furthermore, the present invention relates to a process for manufacturing the composition of the present invention, wherein the process includes the following steps:

[0039] (i) Provide at least one thermoplastic polymer,

[0040] The polymer includes at least one thermoplastic polymer.

[0041] At least one thermoplastic polymer is preferably selected from polyetherimide, polycarbonate, polysulfone, polyphenylsulfone, polyphenylene ether, polyethersulfone, acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene-acrylate copolymer (ASA), polyvinyl chloride, polyacrylate, polyester, polyamide, polypropylene, polyethylene, polyaryletherketone, polyether, polyurethane, polyimide, polyamide-imide, polyolefin, polyarylether sulfide and copolymers thereof.

[0042] and

[0043] (ii) The polymer is heated at a temperature at least about 0.1°C below the melting point and no more than about 2°C below the melting point for at least about 1 hour and / or no more than about 24 hours, preferably no more than about 12 hours, and particularly preferably no more than 8 hours.

[0044] (iii) Optionally, the polymer is ground.

[0045] (iv) Optionally, the polymer particles are rounded in a mixer preferably by thermomechanical treatment at a temperature of at least 30°C and below the polymer melting point Tm.

[0046] As used herein, the term “provided” means the manufacture of a polymer or polymer system on-site, and / or, alternatively or additionally, the supply of a polymer or polymer system from an external on-site location.

[0047] Preferably, the polymer granules or polymer flakes from the polymerization process are ground to obtain polymer particles. These polymer flakes are coarse, porous powders obtained during the polymerization process.

[0048] Preferably, this powder has a particle size greater than 1m. 2 / g BET surface area. When using polymer granules, this grinding step is preferably carried out below room temperature, and even more preferably by adding liquid nitrogen. Advantageously, the use of liquid nitrogen results in higher powder (with a specific particle size) yield.

[0049] According to a particularly preferred embodiment, the polymer sample is ground into a powder with a particle size d50 of at least 70 μm and / or no more than 90 μm, preferably about 80 μm, in a low-temperature grinding process (Vortec, Impact Mill M-1).

[0050] To obtain spherical particles, the polymer particles are processed, preferably by thermomechanical treatment. This treatment is carried out in a mixer, preferably in a high-speed mixer, at a preferred temperature of at least 30°C and below the polymer's melting point Tm.

[0051] The terms mixing, blending, co-blending, and compounding are used as synonyms. The processes of mixing, blending, co-blending, and compounding can be carried out by extrusion in an extruder, kneader, disperser, and / or mixer, and may include one or more operations, such as melting, dispersing, etc., where appropriate.

[0052] When packaging the compositions of the present invention, such packaging process is preferably carried out under conditions of moisture removal or limited humidity.

[0053] The composition produced according to the method of the invention is advantageously used as a powder material to be cured in the layered manufacturing process of three-dimensional objects, whereby continuous layers of the object are sequentially produced at predetermined locations by means of energy, preferably by means of electromagnetic radiation, and particularly preferably by means of laser.

[0054] Finally, the compositions of the present invention manufacture objects, particularly three-dimensional objects, by applying in layers and selectively curing the building material, preferably a powder. The term "curing" as used herein refers to at least partial melting of the building material and subsequent curing or re-curing, also known as sintering.

[0055] Advantageous processes for manufacturing building components, preferably 3D objects, include at least the following steps:

[0056] (i) Applying a layer of the composition according to the invention and / or the composition, preferably powder, manufactured according to the manufacturing process according to the invention onto a production panel.

[0057] (ii) Selectively curing a layer of the composition applied at a location representing a cross-section of the object to be manufactured, preferably by using a radiation unit, and

[0058] (iii) Reduce the carrier and repeat the application and curing steps until the building element, preferably a 3D object, is completed.

[0059] As used herein, the term "construction material" preferably refers to powder or powder material that is suitably solidified by means of an additive manufacturing process, preferably by applying a powder bed-based additive manufacturing process, particularly by means of laser sintering or selective laser melting; high-speed sintering; binder spraying, such as multi-jet melting; selective mask sintering; and laser melting (obtained by applying electromagnetic radiation during subsequent material solidification). The compositions of the present invention described above are particularly suitable as construction materials.

[0060] Preferably, the process or part of the process for manufacturing the building elements is carried out in a nitrogen atmosphere.

[0061] The production panel according to the invention refers to a plate placed on a carrier within a machine for additive manufacturing and positioned at a predetermined distance from the radiation unit, the plate being suitable for curing the carrier material. A build-up material is applied to the panel so that its upper layer corresponds to the horizontal plane to be cured. During the build-up process, particularly during laser sintering, the carrier can be adjusted so that the most recently applied layer of build-up material has the same distance from the radiation unit, preferably from the laser, thereby curing through exposure to the radiation unit.

[0062] Articles produced from the compositions of this invention, particularly 3D objects, exhibit advantageous tensile strength and elongation at break. As used herein, the term "tensile strength" refers to a measure of the maximum force required to pull a material to its breaking point. The determination of tensile strength is known to those skilled in the art and can be performed according to DIN EN ISO 527. The term "elongation at break" as used herein refers to the ratio of the length of the specimen after fracture to its initial length. It represents the material's ability to resist changes in shape without cracking. Elongation at break can be determined, for example, according to DIN EN ISO 527-2.

[0063] Furthermore, build elements manufactured from the compositions of this invention exhibit improved dimensional stability and / or reduced shape deformation. As used herein, the term "dimensional stability" refers to the degree to which a material retains its original dimensions when subjected to changes in temperature, pressure, force, alteration, or humidity. For laser sintering processes, dimensional stability can be determined by the deformation of the build element's shape.

[0064] Furthermore, the present invention relates to building elements that are obtained or available through the above-described manufacturing process.

[0065] The use of the compositions of the present invention can be achieved through rapid prototyping and rapid manufacturing. Therefore, for example, additive manufacturing processes, preferably selected from the group consisting of laser sintering, high-speed sintering, binder jetting, selective mask sintering, selective laser melting, and especially laser sintering powder bed processes, are implemented to preferably produce three-dimensional objects and selectively project a laser beam with a predetermined energy onto a layer of powdered material. By applying this process, prototypes and building blocks can be produced in a time- and cost-effective manner.

[0066] As used herein, the term "rapid manufacturing" specifically refers to the manufacture of building blocks, i.e., the production of more than one identical article, where production, for example, by mold assembly, is uneconomical or impossible due to the more complex or impractical geometry of the building blocks. This is generally true when articles exhibit complex shapes. Examples include components for high-end automobiles, racing cars, or rally cars produced in small quantities, or spare parts for motorsports; for these parts, in addition to the small quantity, the time to availability is also important. Industries in which the articles of this invention can be implemented include, for example, the aerospace industry, medical engineering, mechanical engineering, automotive industry, sporting goods industry, home furnishings industry, electronics industry, or lifestyle. More importantly, it is suitable for producing many similar building blocks, such as personalized components like prostheses, (inner ear) hearing devices, etc., whose geometry can be individually tailored to the user.

[0067] Finally, the present invention includes a composition in the form of a powder material suitable for curing during the process of manufacturing a three-dimensional object from layers of such powder material, and subsequently constructing continuous layers of the object at specific locations by applying energy, preferably by applying electromagnetic radiation, and in particular by applying a laser.

[0068] Further preferred embodiments of the present invention are derived from the dependent claims together with the following description, such that a class of patent claims can be formed by dependent claims of different classes, and features of different embodiments can be combined to form new embodiments. It should be understood that the definitions and interpretations of terms above and below apply accordingly to all embodiments described in this specification and the appended claims. Specific embodiments of the method of the present invention are further described below.

[0069] Preferably, at least one polymer is selected from at least one homopolymer and / or hybrid polymer and / or polymer blend, wherein the at least one homopolymer and / or hybrid polymer and / or polymer blend preferably comprises a semi-crystalline homopolymer and / or hybrid polymer and / or amorphous homopolymer. Particularly preferably, at least one homopolymer and / or hybrid polymer and / or polymer blend is selected from at least one semi-crystalline polymer, or a semi-crystalline polymer blend of at least one semi-crystalline polymer and at least another semi-crystalline polymer, or a semi-crystalline polymer blend of at least one semi-crystalline polymer and an amorphous polymer.

[0070] As used herein, the term "semi-crystalline" is understood to refer to a substance containing both crystalline and amorphous regions. A polymer is considered substantially amorphous if the crystallinity in its solid phase is about 5 wt% or less, particularly about 2 wt% or less. Specifically, a polymer is considered substantially amorphous if its melting point cannot be determined by dynamic differential calorimetry (DSC) and / or its enthalpy of fusion in the first heating is less than 1 J / g. Semi-crystalline materials may contain up to 70 wt%, preferably up to 90 wt%, and particularly up to 95 wt% crystalline regions.

[0071] Preferably, the hybrid or copolymer comprises at least two different repeating units and / or at least one polymer blend based on the aforementioned polymer and copolymer. Advantageously, such hybrid or copolymer and / or polymer blend is semi-crystalline.

[0072] By using one or more of the above polymers (homopolymers, copolymers, or polymer blends), at least partially semi-crystalline materials, preferably powder materials, can be produced.

[0073] According to a preferred embodiment, at least one thermoplastic polymer is selected from the group consisting of polypropylene (PP).

[0074] Polypropylene (PP, syn. Polypropen, poly(1-methylethylene)) is a thermoplastic polymer manufactured by the chain polymerization of propylene. It belongs to the polyolefin family and is typically semi-crystalline and non-polar. Preferably, semi-crystalline polypropylene comprises random copolymers.

[0075] In principle, polypropylene can be atactic, syndiotactic, and / or isotactic. In atactic polypropylene, methyl groups are random; in syndiotactic polypropylene, methyl groups are alternating; and in isotactic polypropylene, methyl groups are uniformly distributed. The distribution of methyl groups can affect the crystallinity (amorphous or semi-crystalline) and thermal properties (such as glass transition temperature or melting temperature) of PP. Regularity is usually expressed as isotactic regularity (according to DIN 16774). Particularly preferred isotactic polypropylene.

[0076] More preferably, at least one polymer blend of polypropylene may include at least one ethylene vinyl acetate copolymer. Such polymer blends advantageously exhibit improved impact resistance, i.e., the ability to absorb impact energy without breaking.

[0077] If the composition of the present invention contains a polymer selected from polypropylene, particularly from isotactic polypropylene, then such polypropylene is preferably selected from polypropylene-polyethylene copolymer.

[0078] Such melting temperature and / or glass transition temperature of at least one polypropylene advantageously allows for improved melting and bonding properties, particularly for laser sintering, resulting in improved mechanical properties of building elements made from this polymer.

[0079] For advantageous compositions, Tmo is as close as possible to Tm. Preferably, by increasing Tm, Tmo also increases. Preferably, Tm is no more than 12°C greater than Tmo, more preferably no more than 10°C, and particularly preferably no more than 8°C greater.

[0080] Alternatively or additionally, advantageous compositions comprise polymers and / or copolymers and / or polymer blends having a glass transition temperature (Tg) of at least about -25°C, preferably at least about -20°C and / or no more than about -15°C, preferably no more than about -10°C.

[0081] As used herein, the term "glass transition temperature" refers to the temperature at which a polymer transitions to a gel-like, viscous state. The determination of glass transition temperature is known to those skilled in the art and can be performed, for example, by DSC (according to DIN ENISO 11357).

[0082] According to a preferred embodiment, the process window of the advantageous composition is at least about 10°C, preferably at least about 15°C, more preferably at least about 18°C, and / or not more than about 50°C, preferably not more than about 45°C, more preferably not more than about 40°C.

[0083] According to a particularly preferred embodiment, at least one thermoplastic polymer is heat-treated to increase the difference between the melting temperature and the recrystallization temperature, and / or at least one thermoplastic polymer is heat-treated to increase the temperature at which at least one polymer begins to melt.

[0084] According to the preferred embodiment, the extrapolated melting peak onset temperature T of the advantageous composition eim Compared to thermoplastic polymers that have not undergone annealing, the temperature increases by at least 1°C, preferably at least 5°C, and / or the difference between the crystallization temperature (Tc) and the melting temperature (Tm) ΔT eim / Tc increases by at least 1°C, preferably at least 5°C.

[0085] Annealing of the composition can advantageously lead to T eim The increase and / or difference ΔT eimAn increase in / Tc results in an increase in the process window. As mentioned above, the temperature range applicable to building objects by additive manufacturing is referred to as the process window or sintering window of the polymer, respectively. In particular, the term "process window" as used herein refers to the difference between the lowest possible build temperature (non-curling temperature: NCT) and the highest possible build temperature (upper build temperature: UBT). The terms "crystallization temperature" and "melting peak extrapolation onset temperature" as used herein refer to the peak temperature as defined in DIN EN ISO 11357.

[0086] The methods for determining crystallization or recrystallization temperature, melting temperature, melting onset temperature, and melting peak extrapolation onset temperature are known to those skilled in the art and can be performed by dynamic differential calorimetry (DSC) according to DIN EN ISO 11357. To compare measurements of annealed and unannealed polymers, the methods used take into account the application of the same holding time, heating rate, onset temperature, and end temperature.

[0087] Crystallinity can be measured by various analytical methods, such as DSC or X-ray diffraction. Here, crystallinity is calculated by melting enthalpy [J / g] (compared to a polymer with a theoretical crystallinity of 100%).

[0088] The term “enthalpy of fusion” as used in this article refers to the energy required to melt a substance from a solid state to a liquid state at a melting temperature and constant pressure (isobaric).

[0089] According to a particularly preferred embodiment, the heat treatment of at least one thermoplastic polymer is carried out in an inert atmosphere, optionally at a specific pressure. This specific pressure is significantly higher than atmospheric pressure at sea level. More preferably, at least one thermoplastic polymer has already been treated by heating under an inert gas atmosphere, preferably nitrogen, at a specific pressure.

[0090] As described above, advantageous compositions may contain one or more additives. According to preferred embodiments, the additives may be semi-crystalline polymers and / or semi-crystalline polyols and / or semi-crystalline surfactants and / or semi-crystalline protective colloids. Preferably, the additives are water-soluble at room temperature and / or immiscible with at least one thermoplastic polymer.

[0091] Advantageously, the additives appropriately prevent polymer particles from agglomerating and forming cavities during the pouring of the composition in the additive manufacturing process, thereby actively increasing the bulk density of the composition.

[0092] As used herein, the term "bulk density" refers to the mass of a material's many particles divided by the total volume they occupy. The total volume includes the particle volume, the interparticle void volume, and the internal pore volume. The determination of bulk density is known to those skilled in the art and can be performed according to DIN EN ISO 60:2000-01.

[0093] According to a preferred embodiment, the bulk density of the composition is at least about 0.20 g / cm³. 3 And / or not exceeding about 0.45 g / cm³ 3 Preferably at least 0.25 g / cm³ 3 and / or not exceeding 0.40 g / cm 3 Especially at least 0.28 g / cm³ 3 and / or not exceeding 0.35 g / cm³ 3 .

[0094] Typically, for compositions used in laser sintering, specific particle size or particle size distribution, appropriate bulk density, and sufficient pourability are important.

[0095] As used herein, the term "particle size" refers to the size of individual particles in a composition. Therefore, particle size distribution influences the properties of bulk materials present in pourable form (e.g., compositions present in powder form).

[0096] According to a further preferred embodiment, the polymer particles of the composition have the following particle size distribution:

[0097] -d10 = at least 30 μm, preferably at least 35 μm, and / or no more than 50 μm, preferably no more than 45 μm

[0098] -d50 = at least 70 μm, preferably at least 75 μm, and / or no more than 90 μm, particularly no more than 85 μm

[0099] -d90 = at least 90 μm, preferably at least 100 μm, and / or no more than 120 μm, particularly no more than 110 μm.

[0100] The methods for determining particle distribution or particle size distribution are known to those skilled in the art and can be performed in accordance with DIN ISO 13322-2.

[0101] According to a further preferred embodiment, the advantageous composition exhibits a distribution width (d90-d10) / d50 of at least 0.50, preferably at least 0.60, particularly preferably at least 0.65, and / or not more than 1.2, preferably not more than 1.1, particularly preferably not more than 1.

[0102] Further preferred compositions contain no more than about 5 wt%, preferably no more than about 3 wt%, particularly preferably no more than about 2 wt%, and most preferably no more than 1 wt% of fine particles. As used herein, "fine particle content" refers to particles with a particle size of less than 10 μm.

[0103] The polymer particles of the compositions of the present invention preferably exhibit a substantially spherical to lenticular shape. Particularly preferably, the polymer particles exhibit a sphericity of at least about 0.8, preferably at least about 0.85, particularly preferably at least about 0.86, and most preferably at least about 0.87. The sphericity can be determined, for example, by microscopy according to DIN ISO 13322-1 and / or according to DIN ISO 13322-2 (on a Camsizer XT device (Retsch Technology, Germany)).

[0104] The process for manufacturing this composition has been initially described. According to another preferred embodiment for manufacturing the composition, the polymer is preferably selected from polypropylene or copolymers thereof, or blends with other polymers, more preferably in powder form. Particularly preferably, the polymer is a ground polymer.

[0105] The dispersion step, preferably melt dispersion, is carried out in a dispersion device, more preferably in an extruder. Alternatively, the dispersion step can be carried out in a kneader. Preferably, the dispersion device comprises, particularly in the forward direction, several consecutive zones.

[0106] In a further process, the polymer or polymer particles are separated from the mixture or dispersion, and the separated polymer or polymer particles may then be washed and / or dried.

[0107] The components of the mixture or dispersion are preferably separated separately by centrifugation and / or filtration. Drying the solid composition to obtain a dry composition can be achieved, for example, in an oven such as a vacuum dryer.

[0108] Alternatively or additionally, advantageous compositions can be obtained by melt-blending the polymer provided in step i), further processing the polymer by spinning the fibers and shredding the fibers into microparticles.

[0109] Alternatively or additionally, advantageous compositions can be obtained by melt-blending the polymer provided in step i) and applying the high-pressure sprayed melt during the melt spraying process, preferably by means of a nozzle.

[0110] Alternatively or additionally, advantageous compositions can be obtained by dissolving a polymer, preferably at an elevated temperature, in a solvent, and precipitating the polymer from the solvent, preferably by cooling and stirring, to form a powder.

[0111] According to a particularly preferred embodiment, an advantageous process for manufacturing the composition further includes a (subsequent) step of annealing the polymer particles at a temperature above Tg and below Tm. Preferably, the annealing of the polymer particles is carried out in a furnace.

[0112] The annealing step can be performed in the same steps as the rounding step described above. Alternatively, annealing can be performed before or even after the polymer particles are rounded.

[0113] Furthermore, the present invention relates to a composition, particularly a composition comprising a polypropylene polymer, which is obtained or can be obtained by the above-described process including such an annealing step.

[0114] In the next step, an advantageous process includes the addition of an additive. In particular, this additive is selected from flow agents. Preferably, the addition of the additive, especially the flow agent, is carried out in a mixer.

[0115] Furthermore, the present invention covers building elements, preferably 3D objects, wherein the building elements are obtained or are available through the above-described manufacturing process.

[0116] Finally, the advantageous process may include packaging the composition. Packaging compositions, particularly powders, manufactured according to the process of the invention is preferably carried out under conditions of evacuation from air moisture. Such packaging materials can be stored at reduced humidity to prevent clumping, thereby improving the storage stability of the compositions of the invention. Furthermore, the advantageous packaging materials can prevent moisture, especially air moisture, from entering the compositions of the invention.

[0117] As described above, the compositions of the present invention are suitable for additive manufacturing processes, particularly laser sintering processes. Therefore, energy-absorbing and / or energy-reflecting materials can be applied to target regions of the radiating unit, which are known, for example, from high-speed sintering or multi-jet fusion processes.

[0118] It has been further discovered that the determination of tensile strength and elongation at break can be used as a measure of the processability of the compositions of the present invention or building elements made therefrom.

[0119] Therefore, another preferred embodiment includes a building element produced using the composition of the present invention. Advantageously, such a building element preferably exhibits a tensile strength in the xy direction of at least about 10 MPa, more preferably at least about 15 MPa, and especially at least about 20 MPa. The tensile strength of an advantageous building element preferably does not exceed about 35 MPa, more preferably not more than about 30 MPa, and especially not more than about 25 MPa.

[0120] Alternatively or additionally, such building elements preferably exhibit an elongation at break of at least about 20%, more preferably at least about 25%, particularly at least about 30%, and / or preferably not more than about 60%, more preferably not more than about 55%, and especially preferably not more than about 50%.

[0121] The determination of tensile strength and elongation at break is known to those skilled in the art and can be performed according to DIN ENISO 527.

[0122] According to a further preferred embodiment, an advantageous composition comprises at least one additive, preferably selected from one or more flow agents, heat stabilizers, oxidative stabilizers, UV stabilizers, colorants, and infrared absorbers. The preferred content of such additive in the composition may be at least about 0.005 wt%, preferably at least about 0.01 wt%, more preferably at least about 0.05 wt%, particularly preferably at least about 0.1 wt%, most preferably at least about 0.2 wt%, and / or the preferred composition may contain one or more additives in a content not exceeding about 3 wt%, more preferably not exceeding about 2 wt%, particularly preferably not exceeding 1 wt%, and most preferably not exceeding 0.5 wt%. The content of such additives refers to the content of each individual additive in the composition.

[0123] Other functional additives, preferably used in higher amounts (greater than 3 wt%), are selected from softeners, fillers, and reinforcing materials, as well as flame retardants, such as reinforcing fibers, SiO2 particles, carbon particles, carbon fibers, glass fibers, carbon nanotubes, mineral fibers (e.g., wollastonite), aramid fibers (especially Kevlar fibers), glass beads, mineral fillers, inorganic and / or organic pigments and / or flame retardants (especially those containing phosphates such as ammonium polyphosphate and / or bromine and / or other halogens and / or inorganic substances such as magnesium hydroxide or aluminum hydroxide). Particularly preferred are the additions, particularly carbon fibers, which include reinforcing fibers.

[0124] Further particularly preferred additives include polysiloxanes. Polysiloxanes can be used, for example, as flow agents to reduce the viscosity of polymer melts and / or particularly as softeners in polymer blends.

[0125] According to a further preferred embodiment, the advantageous composition comprises at least one flow agent. This flow agent, which is typically present in particulate form, adheres to the polymer particles, thereby preventing the composition from clumping.

[0126] This flow agent is preferably selected from the group consisting of metal soaps, and more preferably from silica, stearates, tricalcium phosphate, calcium silicate, alumina, magnesium oxide, magnesium carbonate, zinc oxide, or mixtures thereof. More preferably, at least one flow agent is selected from silica (synthetic silica). An advantageous composition contains at least about 0.01 wt% and / or no more than about 1 wt% of the flow agent. Attached Figure Description

[0127] Further features of the present invention are obtained by referring to the embodiments, claims, and drawings. In specific embodiments, a single feature may be implemented in combination with other features, and this does not limit the scope of protection of the present invention. The following description of embodiments according to the present invention may refer to the accompanying drawings, thereby...

[0128] Figure 1 The DSC curves of untreated and treated (heat-treated at 142°C for 6 hours) polymer 05 granules are shown. Both Tmo and Tm of the materials increased significantly, and the difference between Tmo and Tm decreased.

[0129] Figure 2 The DSC curves of untreated and treated (heat-treated at 147°C for 8 hours) polymer 09 granules are shown. The curves show an increase in Tmo and Tm, and a decrease in the difference between Tmo and Tm.

[0130] Figure 3 The DSC curves for untreated and treated (heat-treated at 147°C for 8 hours) polymer 18 pellets are shown. The curves show an increase in Tmo and Tm, and a decrease in the difference between Tmo and Tm. Detailed Implementation

[0131] Example

[0132] Material:

[0133] a) Polymer 05 (Braskem, polypropylene granules)

[0134] b) Polymer 09 (Braskem, polypropylene granules)

[0135] c) Polymer 18 (Braskem, polypropylene granules)

[0136] Heat treatment:

[0137] The polymer samples listed above were heated in a heating device (Grieve, Truck Oven TCH-550). The optimal heating parameters for each polymer sample are as follows:

[0138] (1) Heat polymer 05 to 142°C for 6 hours.

[0139] (2) Heat polymer 09 to 147°C for 8 hours, and

[0140] (3) Heat polymer 18 to 147°C for 8 hours.

[0141] Temperature measurement via DSC:

[0142] Temperature measurements for all samples listed above were performed using a TA Instruments TA Q20DSC tool according to ASTM D3418-03 (Standard Test Method for Determination of Transition Temperature, Enthalpy of Melting and Enthalpy of Crystallization of Polymers by Differential Scanning Calorimetry).

[0143] To evaluate Tm, Trc and the starting points Tmo and Tro, a standard aluminum pot was used and all samples were heated and cooled as follows: (1) equilibrated at 40°C, (2) heated to 175°C at 10°C / min, (3) held isothermally for 1 minute, (4) heated to 40°C at -10°C / min, and (5) held isothermally for 1 minute.

[0144] Polypropylene typically has a melting point between 120°C and 170°C.

[0145] Table 1: Melting and recrystallization data of polymer 05 samples under various heat treatments.

[0146]

[0147] Table 2: Melting and recrystallization data of polymer 09 samples under various heat treatments.

[0148]

[0149] Table 3: Melting and recrystallization data of polymer 18 samples under various heat treatments.

[0150]

[0151] Grinding

[0152] Then, during a low-temperature grinding process (Vortec, Impact Mill M-1), the polymer sample can optionally be ground into a powder with a particle size d50 of 80 μm.

[0153] Laser sintering

[0154] The polymer samples are now in powder form and can be used with SLS machines (Integra, Sinterstation 2500 Plus) and (EOS, P396).

[0155] The invention suitably described herein can be practiced without any one or more elements or limitations not specifically disclosed herein. Thus, for example, in each instance herein, any of the terms “comprising,” “substantially consisting of,” and “consisting of” can be replaced by any of the other two terms. The terms and expressions used are descriptive rather than limiting, and their use is not intended to exclude any equivalents of the features shown and described, or portions thereof; however, it should be recognized that various modifications are possible within the scope of the claimed invention. Therefore, it should be understood that while the invention has been specifically disclosed through preferred embodiments and optional features, modifications and variations of the concepts disclosed herein can be adopted by those skilled in the art, and such modifications and variations are considered to fall within the scope of the invention as defined by the appended claims.

[0156] All references cited in this specification are incorporated herein by reference in their entirety and in whole or in part as specifically mentioned herein.

Claims

1. A composition comprising: At least one polymer in powder form; The polymer described herein comprises at least one thermoplastic polymer selected from: polyetherimide, polycarbonate, polysulfone, polyphenylsulfone, polyphenylene ether, polyethersulfone, acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene-acrylate copolymer (ASA), polyvinyl chloride, polyacrylate, polyester, polyamide, polypropylene, polyethylene, polyaryletherketone, polyether, polyurethane, polyimide, polyamide-imide, polyolefin, polyarylether sulfide, and copolymers thereof. The polymer is treated by heating at a temperature at least 0.1°C below its melting point and no more than 2°C below its melting point; and The heat treatment shall be carried out for at least 6 hours and no more than 8 hours. The polymer, after treatment, satisfies the following: (a) The difference between the melting temperature Tm and the recrystallization temperature Trc of the polymer is increased compared to the untreated polymer; (b) The melting temperature Tm of the polymer is no more than 10°C greater than the melting initiation temperature Tmo.

2. The composition according to claim 1, wherein the polymer comprises: at least one semi-crystalline polymer; and / or At least one amorphous polymer.

3. The composition of claim 1, wherein the polymer blend comprises polypropylene and / or copolymers and / or polymer blends thereof.

4. The composition according to claim 1, wherein the polypropylene has a melting temperature Tm of at least 100°C, and / or wherein the polypropylene has a glass transition temperature Tg of at least -25°C.

5. The composition according to claim 2, having a process window of at least 10°C.

6. The composition according to claim 1, wherein the polymer particles of the composition have the following particle size distribution: - d10 = at least 30µm and / or no more than 50µm; - d50 = at least 70µm and / or no more than 90µm; - d90 = at least 90µm and / or no more than 120µm.

7. The composition according to claim 1, wherein the composition has a distribution width of at least 0.50 (d90-d10) / d50.

8. The composition according to claim 1, wherein the polymer particles have a sphericity of at least 0.

8.

9. The composition according to claim 1, wherein the composition comprises at least one flow agent.

10. A method for manufacturing the composition according to claim 1, wherein the method comprises the following steps: (i) Provide at least one thermoplastic polymer, The polymer comprises at least one thermoplastic polymer selected from: polyetherimide, polycarbonate, polysulfone, polyphenylsulfone, polyphenylene ether, polyethersulfone, acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene-acrylate copolymer (ASA), polyvinyl chloride, polyacrylate, polyester, polyamide, polypropylene, polyethylene, polyaryletherketone, polyether, polyurethane, polyimide, polyamide-imide, polyolefin, polyarylether sulfide and copolymers thereof; and The polymer is heated at a temperature at least 0.1°C below its melting point and no more than 2°C below its melting point for at least 6 hours and no more than 8 hours, such that the polymer, after treatment, satisfies the following: (a) The difference between the melting temperature Tm and the recrystallization temperature Trc of the polymer is increased compared to the untreated polymer; (b) The melting temperature Tm of the polymer is no more than 10°C greater than the melting initiation temperature Tmo.

11. The method of manufacturing the composition according to claim 10, wherein the method comprises the following steps: (a) By heat treatment of the at least one thermoplastic polymer, the difference between the melting temperature and / or the initial melting temperature and the recrystallization temperature and / or the initial recrystallization temperature is increased; and / or (b) By heat treatment of the at least one thermoplastic polymer, the temperature at which the at least one polymer begins to melt is increased.

12. A method for manufacturing a 3D object, comprising the following steps: (i) Applying a layer of the composition according to claim 1 onto a production panel; (ii) Selectively solidify a layer of the composition applied at a location representing a cross-section of the object to be manufactured; as well as (iii) Reduce the carrier and repeat the application and curing steps until the 3D object is complete.

13. A 3D object comprising the composition according to claim 1.

14. A method for manufacturing a 3D object, comprising: The composition according to claim 1 is applied in a manufacturing method selected from laser sintering, high-speed sintering, binder spraying, multi-jet melting, selective mask sintering, selective laser melting, and laser melting.

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