Classifications

• • 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
  • B29C64/10—Processes of additive manufacturing
  • B29C64/141—Processes of additive manufacturing using only solid materials
  • B29C64/153—Processes of additive manufacturing using only solid materials using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• • 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
  • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
  • B29C64/255—Enclosures for the building material, e.g. powder containers
• • 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
  • 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
  • B29C64/364—Conditioning of environment
  • B29C64/371—Conditioning of environment using an environment other than air, e.g. inert gas
• • 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
  • B33Y10/00—Processes of additive manufacturing
• • 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
  • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
• • 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
• • 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
  • B33Y70/00—Materials specially adapted for additive manufacturing
• • 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
  • B33Y80/00—Products made by additive manufacturing
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/013—Fillers, pigments or reinforcing additives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/30—Sulfur-, selenium- or tellurium-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
  • C08L77/02—Polyamides derived from omega-amino carboxylic acids or from lactams thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/0005—Condition, form or state of moulded material or of the material to be shaped containing compounding ingredients
  • B29K2105/0032—Pigments, colouring agents or opacifiyng agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/0094—Condition, form or state of moulded material or of the material to be shaped having particular viscosity
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
  • B29K2105/16—Fillers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/25—Solid
  • B29K2105/251—Particles, powder or granules
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/26—Scrap or recycled material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
  • B29K2995/0037—Other properties
  • B29K2995/0094—Geometrical properties
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
  • C08K2003/2227—Oxides; Hydroxides of metals of aluminium
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
  • C08K2003/2289—Oxides; Hydroxides of metals of cobalt
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/30—Sulfur-, selenium- or tellurium-containing compounds
  • C08K2003/3009—Sulfides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/002—Physical properties
  • C08K2201/005—Additives being defined by their particle size in general
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/01—Magnetic additives

Definitions

• the present invention relates to the manufacture of parts made of polymer materials and relates to a process for agglomeration, layer by layer, in particular by melting or sintering, of a polymer powder comprising an optical and/or magnetic detection additive.
• the present invention also relates to such a polymer powder supplied for this process and consumed during the process.
• the present invention finally relates to an object obtained by the process which has particularly advantageous properties in the field of the safety of food production lines.
• additive manufacturing or “3D printing” only designate these methods.
• 3D object will designate an object obtained by such a 3D printing method.
• the agglomeration of powders by fusion, coalescence, and/or “sintering” is caused by radiation making it possible to melt the material to be agglomerated.
• selective laser sintering SLS, abbreviated to “Selective Laser Sintering”
• Any other source of electromagnetic radiation making it possible to melt the powder can also be implemented, for example infrared, visible or UV radiation.
• Other notable powder bed fusion additive manufacturing methods include laser sintering, Multi Jet Fusion, infrared radiation sintering and high speed sintering in particular.
• thermoplastics are advantageous in industrial production chains, in particular because such objects can be produced in small series for specific uses or because they have specific structural features.
• 3D objects made of thermoplastics are difficult to detect by means of detection of foreign bodies usually implemented in the context of on-line quality control, in particular in the food industry. So if a 3D object made of thermoplastics breaks, fragments can end up in the product and represent a risk for food safety.
• the present invention aims to remedy all or part of these drawbacks.
• the present invention relates to a method for manufacturing a three-dimensional object, comprising a local rise in the temperature of a polyamide-based powder by electromagnetic radiation in a heated enclosure, causing the melting localized layer of a predetermined thickness to form, after cooling, a solid layer of polyamide, said method being characterized in that said powder comprises, over the total weight of the composition:
• an optical and/or magnetic detection additive selected from the group formed by: pigments comprising a spinel structure which contains a cation of a transition metal, sulphides of a metal of transition ;
• the powder has:
• the powder has:
• the particle size distribution D 10 is greater than 10 ⁇ m, preferentially greater than 15 ⁇ m, preferentially greater than 17 ⁇ m, preferentially greater than 20 ⁇ m.
• the particle size distribution D 50 is less than 110 ⁇ m, preferably less than 100 ⁇ m, preferably less than 95 ⁇ m, preferably less than 93 ⁇ m, preferably less than 90 ⁇ m. In embodiments, the particle size distribution D 50 is less than 80 ⁇ m.
• a mass fraction comprised between 30% and 70% of said powder is fresh polyamide powder
• a mass fraction comprised between 70% and 30% of said powder is polyamide powder recovered in said enclosure heated to the end of a previous manufacture
• said fresh polyamide powder has an internal viscosity index measured according to ISO 307:2019 of between 0.9 deciliters per gram and 1.4 deciliters per gram, at 25°C.
• the electromagnetic radiation causing the localized melting of a layer is laser radiation with an energy density greater than or equal to 25 mJ/mm 2 .
• the method used in this case is preferably the selective laser sintering method, more often called SLS (abbreviated to “Selective Laser Sintering”).
• the invention relates to a powder composition for an additive manufacturing process characterized in that it comprises, over the total weight of the composition:
• a detection additive preferably an optical detection additive and/or a magnetic detection additive, selected from the group formed by: pigments comprising a spinel structure which contains a cation of a transition metal, oxides of a transition metal, sulfides of a transition metal;
• the powder has:
• the powder composition of the invention is obtained by dry mixing a natural polyamide powder with a polyamide powder comprising a detection additive.
• the powder composition that is the subject of the invention comprises:
• an optical detection additive chosen from pigments comprising a spinel structure which contains a cation of a transition metal and
• the optical or magnetic detection additive is chosen from sulphides of a transition metal.
• the powder composition that is the subject of the invention has an internal viscosity index measured according to ISO 307:2019 of between 0.9 deciliters per gram and 1.4 deciliters per gram.
• the powder composition that is the subject of the invention comprises an optical detection additive and said optical detection additive comprises cobalt blue.
• the invention relates to a three-dimensional object obtained by additive manufacturing from a composition that is the subject of the invention.
• the three-dimensional object is colored blue in the mass by an optical detection additive.
• the optical detection additive allows optical detection in a wavelength range between 0.5 ⁇ m and 12 ⁇ m.
• the three-dimensional object has a modulus of elasticity greater than or equal to 1700 MPa, a tensile strength greater than or equal to 30 MPa, an elongation at break greater than or equal to 20% according to a first orientation and greater than or equal to 35% on a second orientation perpendicular to the first.
• FIG 1 represents particle size distribution density curves as a function of the particle size of two powder compositions according to the invention and of a natural polyamide 11 powder,
• FIG 2 represents cumulative distribution curves as a function of circularity for two powder compositions according to the invention and a natural polyamide 11 powder
• FIG 3 represents a view captured with a scanning electron microscope of a powder composition according to the invention
• FIG 4 represents a view obtained by X-ray tomography of a section of a 3D object obtained at the end of the additive manufacturing process from the powder composition illustrated in figure 3,
• FIG 5 schematically represents a section of a 3D object obtained by sintering the powder composition illustrated in figure 3,
• FIG 6 represents a view captured under a scanning electron microscope of a powder composition for additive manufacturing
• FIG 7 represents a view obtained by X-ray tomography of a section of a 3D object obtained at the end of the sintering process of the powder composition illustrated in Figure 6,
• FIG 8 schematically represents a section of a 3D object obtained by sintering the powder composition illustrated in figure 6,
• FIG 9 represents a DSC differential scanning calorimetry of a particular powder composition according to the invention.
• FIG 10 represents a graph of the force in MPa as a function of the elongation along an xy orientation, expressed in %, obtained at the end of an elongation test on a 3D object obtained by sintering a composition of powder A, according to a particular embodiment of the invention
• FIG 11 represents a graph of the force in MPa as a function of the elongation along an xz orientation, expressed in %, obtained at the end of a test of elongation on a 3D object obtained by sintering a powder composition A, according to a particular embodiment of the invention and
• FIG 12 represents a graph which shows the volumetric particle size distribution as a function of the particle size of a powder composition according to the invention.
• the powder composition for additive manufacturing process by sintering according to the invention comprises, over the total weight of the composition:
• a detection additive which may be an optical detection additive and/or a magnetic detection additive, and which is preferably selected from the group formed by: pigments comprising a structure spinel which contains a cation of a transition metal, the oxides of a transition metal, the sulphides of a transition metal;
• the powder is said to be “polyamide-based” because it mainly comprises polyamide.
• sintering powder The characteristics of the powder composition for additive manufacturing process by sintering, hereinafter "sintering powder”, and of its components are detailed below.
• the shape of the grains of the sintering powder is preferably spherical.
• said detection additive can be selected so as to allow magnetic detection or optical detection, or one can using two additives, namely a first additive allowing magnetic detection and a second additive allowing optical detection, or else an additive is used allowing both optical detection and magnetic detection.
• the polyamide can be chosen from any available polyamide, or mixture of polyamides, making it possible to obtain the particle size characteristics of the composition of the invention.
• the polyamide is chosen from polyamides comprising one of the following monomers: PA6, PA10, PA11, PA12 and mixtures thereof.
• PA11 can be used for its advantageous characteristics and its biosourced origin.
• biosourced origin we call “biobased” a product that is entirely or partially made from materials of biological origin.
• the sintering powder has a working temperature window of between 160°C and 210°C.
• the working temperature window is the temperature interval delimited by the extrapolated initial temperature of the melting peak (T ei.m or T m,onset in °C) and the extrapolated final temperature of the crystallization peak (T ef,C or T c , onset in °C).
• T ei.m or T m,onset in °C the extrapolated initial temperature of the melting peak
• T ef,C or T c the extrapolated final temperature of the crystallization peak
• the powder composition comprises a detection additive.
• This additive is advantageously an inorganic compound which is insoluble in water and non-toxic, preferably of the spinel type.
• the powder composition of the invention comprises, on the total weight of the composition, between 1% and 40% by weight of a detection additive.
• the detection additive may be an optical detection additive.
• the powder composition of the invention may comprise, relative to the total weight of the composition, between 0.05% and 5% by weight of an optical detection additive, for example between 0.05% and 0 .5%.
• the latter is advantageously selected from pigments comprising a spinel structure which contains a cation of a transition metal. This type of pigment has the advantage of not being toxic. In particular, the transition metal cation remains trapped in the spinel structure and cannot be dissolved under normal conditions of contact with food and drink, nor in the event of accidental ingestion through the intestinal transit. Spinels have good thermal stability under the laser beam implemented in the SLS laser sintering process technique. The implementation of these pigments is therefore particularly preferable for the powder compositions intended for this use.
• the pigment is a blue pigment, preferably cobalt aluminate (CAS No: 1345-16-0), which is available under the trade name PB 28.
• the detection additive optics used allows optical detection, if necessary by infrared.
• the optical detection additive used allows optical detection in a wavelength range between 0.5 ⁇ m to 12 ⁇ m.
• the pigment comprises an olivine structure or a rutile structure.
• the optical detection additive is present in a substantially homogeneous manner in the powder composition, such that the parts obtained by additive manufacturing from this powder are colored in the mass.
• the detection additive can be a magnetic detection additive.
• the powder composition of the invention may comprise, relative to the total weight of the composition, between 1% and 40% by weight of a magnetic detection additive.
• the magnetic detection additive is preferably chosen from oxides comprising a transition metal.
• the magnetic detection additive is an iron oxide, such as natural or synthetic magnetite (Fe 3 O 4 ). This spinel-like oxide is insoluble in water and non-toxic. In addition, it is not likely to form metal salts likely to be released by parts obtained by additive manufacturing from this powder. Natural magnetite will be preferred to synthetic magnetite.
• Magnetic detection additives must of course be selected to have particular magnetic properties that can be easily detected.
• the powder composition of the invention comprises both between 0.05% and 5% by weight of an optical detection additive chosen from pigments comprising and between 1% and 40% by weight of a magnetic detection additive among the oxides of the transition metals.
• composition of the invention further comprises a flow agent in sufficient quantity for the composition to flow freely, remain fluid and form a uniform, homogeneous and flat layer during the generative layering process in a PBF powder bed (Powder Bed Fusion) for example called layer by layer sintering of SLS, LS polymers.
• a flow agent in sufficient quantity for the composition to flow freely, remain fluid and form a uniform, homogeneous and flat layer during the generative layering process in a PBF powder bed (Powder Bed Fusion) for example called layer by layer sintering of SLS, LS polymers.
• composition of the invention comprises, on the total weight of the composition, between 0% and 5% by weight of a flow agent. A content between 0.1% and 4.5% by weight is preferred.
• the flow agent is chosen from those commonly used in the field of sintering polymer powders, for example from: silicas, precipitated silicas, silica fumes, hydrated silicas, vitreous silicas, fumed silicas, vitreous phosphates, vitreous oxides.
• the flow agent has a low contact surface.
• the powder composition in accordance with the invention is obtained according to a manufacturing method which comprises a first step of mixing a so-called "natural" polyamide powder with a flow agent and at least one one of the following steps:
• these last two steps of mixing with a composition comprising a detection additive are implemented successively, it is noted that their order can be reversed.
• a natural polyamide powder is a powder composition comprising between 95% and 100% polyamide, preferably at least 99% by weight of polyamide.
• the polyamide powder composition comprising an optical detection additive can be obtained by reduction to powder of a homogeneous liquid or solid mass comprising the polyamide and said optical additive or by polycondensation in the solid phase, drying then selective grinding.
• the composition comprising a magnetic detection additive can either be the magnetic additive in pure form (that is to say comprising at least 95% of magnetic detection additive) or be a composition comprising a polyamide homogenized by dry mixing with a magnetic sensing additive.
• the mixing steps mentioned above can be carried out by dry blending (known by the English term “dry blend”) or by a compounding process (known by the English term “master batch”).
• dry blend known by the English term “dry blend”
• master batch a compounding process
• Compounding requires a subsequent stage of selective grinding of the mass obtained and adjustment of the viscosity by polycondensation in the solid phase and drying; for this reason dry mixing is preferred.
• the dispersion of the flow agent requires the application of significant mixing energy to obtain good homogenization. This mixing energy is likely to damage the detection additives. It is therefore preferentially opted for a dry premix of the flow agent with a natural polyamide powder during the first mixing step, prior to at least one step of mixing with a composition comprising a detection additive, of less intensity than the first.
• the mixing steps are carried out by cryogenic grinding, this method well known to those skilled in the art is not described in detail here.
• the methods for obtaining a dry mixture of homogeneous and dispersed powder of all the components are adapted according to the initial distributions and the final target distribution, i.e.:
• the final target particle size distribution of the powder has:
• the particle size distribution D 10 of the powder composition is greater than 10 ⁇ m, preferentially greater than 15 ⁇ m, preferentially greater than 17 ⁇ m, preferentially greater than 20 ⁇ m.
• Such a particle size distribution D 10 of the powder composition is advantageous for avoiding the presence of too large a quantity of fine particles or dust liable to volatilize into the air and to present a health risk in the event of inhalation and accumulation, eye irritation and skin contact of these fine dusts.
• the D 50 particle size distribution of the powder composition is between 35 ⁇ m and 55 ⁇ m.
• the particle size distribution D 50 of the powder composition is between 38 ⁇ m and 45 ⁇ m, very preferably it is between 38 ⁇ m and 40 ⁇ m. The applicant has observed during its tests that these D 50 particle size distribution ranges make it possible to obtain the best performance in terms of final resolution, geometric definition of the parts obtained as well as better coverage and good fluidity of the powder in temperature for the PBF powder bed process using layers from 80 ⁇ m to 120 ⁇ m.
• the particle size distribution D 90 of the powder composition is less than 110 ⁇ m, preferably less than 100 ⁇ m, preferably less than 95 ⁇ m, preferably less than 93 ⁇ m, preferably less than 90 ⁇ m. In embodiments, the particle size distribution D 50 is less than 80 ⁇ m.
• Such a particle size distribution D 90 is advantageous for an implementation of the powder in an additive manufacturing process whose layer thickness is between 80 ⁇ m and 160 ⁇ m, for example for a layer thickness of 100 ⁇ m.
• the D 90 is chosen to be less than the layer size envisaged for the additive manufacturing process.
• the powder composition has:
• particle size distributions D 10 , D 50 , and D 90 are advantageous because, while it is advantageous to have a narrow distribution and of the same morphology for additive manufacturing by sintering, too great a homogeneity of particle size of the powder composition gives rise to “caking” phenomena (that is to say powder agglomeration) because geometric arrangements make the powder more agglomerated.
• these particle size distributions D 10 , D 50 , and D 90 are advantageous because they make it possible to limit the phenomena of powder agglomeration and make it easier to depowder parts obtained by additive manufacturing by sintering.
• the particle size distribution values of the powder composition D 10 , D 50 and D 90 mentioned above are determined by the static image analysis method according to standard ISO 13322-1:2014.
• Figure 1 shows the distribution density curves as a function of particle size (expressed in micrometers, abbreviated as ⁇ m) for three powders:
• curve 105 illustrates the particle size distribution of a PA11 powder called natural, that is to say comprising at least 99% of PA11,
• a curve 110 illustrates the particle size distribution of a composition A of powder according to the invention, in which the polyamide is a PA11 and which comprises an optical detection additive,
• curve 115 illustrates the particle size distribution of a powder composition B according to the invention, in which the polyamide is a polyamide 11 and which comprises both an optical detection additive and a magnetic detection additive.
• the optical detection additive and/or the magnetic detection additive are selected with a view to obtaining a particle size distribution of the powder composition as detailed above.
• the particle size distribution of the powder compositions according to the invention, with detection additive remain close to that of the particle size distribution of the distribution of the natural PA11 powder, with a density peak around 50 ⁇ m.
• the powder composition which is the subject of the invention comprises 90%, more preferentially 99%, of grains whose size is between 10 ⁇ m and 120 ⁇ m, preferentially between 20 ⁇ m and 90 ⁇ m, very preferentially between 20 ⁇ m and 80 ⁇ m .
• FIG. 12 shows the particle size distribution as a function of the size of the particles of the powder composition A, in which the polyamide is a PA11 and which comprises an optical detection additive.
• the data illustrated in FIG. 12 come from particle size measurements carried out using a Mastersizer 3000 (registered trademark) particle size analyzer from Malvern Panalytical.
• the graph presents bars 140 of a histogram illustrating the percentage of particles in the powder composition associated with each size, expressed in ⁇ m.
• a curve 150 illustrates the cumulative percentage of particles whose size is less than a threshold, expressed in ⁇ m. It can be seen in the graph of FIG. 12 that the powder composition A comprises 90% of grains whose size is between 10 ⁇ m and 120 ⁇ m.
• Shape factors are dimensionless quantities used in image analysis and microscopy that numerically describe the shape of a particle, independent of its size.
• the circularity/wax index is a form factor which is calculated as follows: [Math 1] where P is the perimeter and A looks like an image of a grain of powder
• the cumulative distribution f 10 of the powder composition according to the invention is less than or equal to 0.15.
• the cumulative distribution fio of the powder composition is less than or equal to 0.10.
• only 10% of the powder grains have a circularity index less than or equal to 0.15, preferably less than or equal to 0.10.
• 90% of the grains have a circularity index greater than 0.1, preferably greater than 0.15.
• the f 50 cumulative distribution of the powder composition is less than or equal to 0.6.
• the f 50 cumulative distribution of the powder composition is less than or equal to 0.55.
• only 50% of the powder grains have a circularity index less than or equal to 0.6, preferably less than or equal to 0.55.
• 50% of the powder grains have a circularity index greater than 0.55, preferably greater than 0.6.
• the f 90 cumulative distribution of the powder composition is less than or equal to 0.8.
• the f 90 cumulative distribution of the powder composition is less than or equal to 0.75.
• 90% of the powder grains have a circularity index less than or equal to 0.8, preferably less than or equal to 0.75.
• 10% of the powder grains have a circularity index greater than 0.75, preferably greater than 0.8.
• FIG. 2 shows a graphical representation of the cumulative distribution on the ordinate (expressed as a percentage), as a function of the circularity on the abscissa (index without unit).
• a curve 205 illustrating the cumulative distribution of a so-called natural PA11 powder, that is to say comprising at least 99% by mass of PA11
• a curve 210 illustrates the cumulative distribution of a powder composition according to the invention, in which the polyamide is a PA11 and which comprises an optical detection additive
• curve 215 illustrates the cumulative distribution of a powder composition according to the invention, in which the polyamide is a polyamide 11 and which comprises both an optical detection additive and a magnetic detection additive.
• the optical detection additive and/or the magnetic detection additive are preferably selected with a view to obtaining a cumulative distribution of the powder composition as detailed above. It can thus be seen in FIG. 2 that the cumulative distribution of the powder compositions according to the invention, with detection additive, remain close to that of the particle size distribution of the distribution of the natural PA11 powder.
• the morphology of the grains is important for the fluidity of the mixture and for the densification of the powder bed during successive coatings, but also for the residual porosity in the final parts obtained.
• a good sphericity of the powder combined with a very tight distribution, that is to say a cumulative distribution of the type presented above, make it possible to obtain a natural densification of the powder bed by compaction and by geometric arrangements of layer. This layer is then exposed to laser energy for melting and coalescence promoting the densification of parts with low residual porosity.
• a very heterogeneous powder with a wider distribution will tend to organize itself in a more chaotic way and will cause less densification of the powder bed, as some of the larger grains may not be melted.
• FIGS. 3 and 6 show two views captured under a scanning electron microscope of two powders, at the same magnification.
• FIG. 3 illustrates a powder which has a sphericity comparable to the sphericity of a powder composition which is the subject of the invention, that in FIG. 6 is presented by way of comparison.
• FIGS. 4 and 7 A schematic representation of the powders 30 and 60 illustrated in FIGS. 3 and 6 and of sections of objects 3D images obtained by sintering these powders are presented in figures 5 and 8.
• the powder 30 illustrated in FIG. 3 is a powder with a good homogeneity of circularity with a circularity of the grains comprised between 0.4 and 0.8, on average equal to 0.65.
• the powder 30, placed on a previously solidified layer 505 and subjected to an SLS laser sintering process 550 at an energy density of 34 mJ/mm 2 makes it possible to obtain a low and distributed residual porosity, as illustrated in section 410, in figure 4, obtained by tomography of the 3D object and on the section 510, in figure 5.
• the porous parts 420 which appear in black in figure 4 are illustrated in the form of white cavities in figure 5. These porous parts are less numerous and better distributed than those observed on the sections of a 3D object obtained by sintering from a powder of less homogeneity of circularity of the grains, represented in figures 7 and 8.
• the powder 60 illustrated in FIG. 6 has less homogeneity than the homogeneity of the powder 30, with a grain circularity of between 0.1 and 0.8, on average equal to 0.55.
• the powder 60, placed on a previously solidified layer 805 and subjected to an SLS laser sintering process 550 at an energy density of 34 mJ/mm 2 results in obtaining a 3D object of less good homogeneity and residual porosity larger, presented in section 710 obtained by tomography, in figure 7, and in schematic section 810 in figure 8.
• the present invention relates more particularly to an additive manufacturing process by powder bed fusion (PBF, abbreviated to Power Bed Fusion), layer by layer, from a polyamide powder in a heated enclosure.
• PPF powder bed fusion
• LS Laser Sintering
• SLS Selective Laser Sintering
• MJF Multi Jet Fusion
• HSS high-speed sintering
• the method of the invention relates to the manufacture of 3D objects in polyamide comprising a detection additive, from a composition of polyamide powder.
• the method according to the invention takes place in a closed chamber preheated to a setpoint temperature T 1 .
• the atmosphere inside the enclosure is enriched in nitrogen (or under vacuum) and depleted in oxygen, in order to limit the oxidation of the polymer powder; this oxidation gradually leads to the elongation of the macromolecules constituting the particles of polymer powder and represents the main aging mechanism of said powders. This elongation of the macromolecules tends to increase the internal viscosity of the polymer.
• the limitation of the temperature oxidation of the powders promotes the recycling of the unused powder, which contributes significantly to the economy of the process according to the invention.
• the oxygen level is less than 5% by volume, preferably less than 2%, and even more preferably less than 1%.
• the holding temperature T 1 is advantageously around 20 to 30 degrees around the crystallization temperature Te of the polymer.
• the preheating temperature T 1 is advantageously between about 140°C and about 160°C, preferably between about 142°C and about 158°C. °C.
• the heating temperature is equal to the holding temperature.
• the holding temperature T 1 is preferably between 150 and 185° C.
• the process which is the subject of the invention comprises the deposition of a uniform layer of a bed of polyamide powder in a preheated chamber.
• the surface of the powder bed is heated rapidly, typically by infrared radiation, to a temperature T 2 which is selected to be approximately 8% to 14% lower than the T m of the polyamide (i.e. 12 to 26 degrees below the melting temperature T m of the powder).
• T 2 is selected to be approximately 8% to 14% lower than the T m of the polyamide (i.e. 12 to 26 degrees below the melting temperature T m of the powder).
• This heating to a temperature T 2 makes it possible to maintain the polyamide powder at a temperature quite close to its melting temperature, without however reaching this melting temperature.
• the temperature T 2 is between about 183°C and about 204°C.
• the temperature T 2 is between 168°C and 206°C.
• the melting of the powder is necessary to obtain a compact part.
• This melting must be transitory, rapid, localized and controlled, so as to avoid the uncontrolled flow of the liquid polymer; for this reason it must be brief, that is to say that the localized melting must be followed promptly by cooling to a temperature below the melting point T m of the polymer, towards a temperature T R at which the polymer can recrystallize from the molten state.
• Said temperature TR may be in the vicinity of temperature T 2 , it is between T 1 and T 2 .
• electromagnetic radiation irradiates targeted zones of the polyamide powder, making it possible to locally increase the temperature and to agglomerate between them the polyamide grains of the targeted zones .
• the electromagnetic radiation is for example visible, infrared or near infrared laser radiation.
• the local temperature T L of the melting zone is preferably approximately 8% to 14% higher than the T m of the polyamide (ie 12 to 26 degrees higher than the melting temperature T m of the powder). A transient liquid phase is thus formed, but if T L is too high, the viscosity of the molten polymer becomes too low and there is a risk of running.
• temperatures T 1 and T 2 implemented during a sintering process according to the invention are collated in table 1 below and compared with the melting point T m and the crystallization temperature T c of the sintering powders A and B according to the invention.
• - powder A is a powder composition according to the invention, in which the polyamide is a PA11 and which comprises an optical detection additive and
• - powder B is a powder composition according to the invention, in which the polyamide is a polyamide 11 and which comprises both an optical detection additive and a magnetic detection additive.
• any interval centered on the melting temperature or the crystallization temperature one will more preferably use an extrapolated initial temperature of the melting peak (T m , onset ) and the extrapolated final temperature of the crystallization peak (T c , onset ), rather than the temperature values corresponding to the melting and crystallization peaks, although the two methods for determining these reference values can be implemented without deviating from the invention.
• FIG. 9 shows a DSC (Differential Scanning Calorimetry) of a powder composition according to the invention based on PA11.
• This DSC shows a curve 910 of initial temperature rise and a curve 920 of cooling. Melting and crystallization temperatures are shown in this graph, whether determined by identification of the corresponding peak (T c and T m ) or at the extrapolated initial temperature for the melting peak (T m , onset ) and at the extrapolated final temperature for the crystallization peak (T c.onset ).
• a new powder bed is deposited and flattened on top of the previous one. It is recalled that the powder is self-supporting, that is to say that it rests on the powder previously deposited during the process. So on, a new powder bed is deposited and the solidification of part of the new powder bed is initiated. The solidified part of each powder bed corresponds to a layer or slice of the 3D object obtained at the end of the process.
• each slice is typically between about 50 ⁇ m and about 150 ⁇ m, preferably between about 70 ⁇ m and about 120 ⁇ m, and even more preferably between about 80 ⁇ m and about 110 ⁇ m.
• the deposition of each slice is followed by heating to the temperature T 2 , as described above.
• the sintering which is the subject of the invention is carried out by SLS and the electromagnetic radiation causing the localized melting of a layer is laser radiation with an energy density greater than or equal to 25 mJ/mm 2 for a working temperature T 2 of between 180°C and 199°C, for example equal to 188°C.
• the energy density greater than or equal to 25 mJ/mm 2 makes it possible to avoid the delamination of layers, that is to say the separation between two successive layers of solidified polyamide.
• S is the spacing between scans (Hatch Gap), expressed in millimeters (mm)
• v is the laser speed, expressed in mm/second r is the laser radius, expressed in mm
• the operating conditions of sintering processes according to the invention with different SLS systems are collated in Table 2 below. These operating conditions are implemented on a sintering powder composition comprising PA 11 , with a fixed layer thickness of 100 ⁇ m, at a working temperature T 2 approximately equal to 188°C.
• part of the powder composition for additive manufacturing process by powder bed PBF (Power Bed Fusion) according to the invention introduced into the heating chamber is not solidified.
• this powder is collected and sieved with a view to its reuse as a mixture with a composition of fresh polyamide powder, that is to say with a powder which has not already been used in a sintering process.
• the powder composition according to the invention comprises a mass fraction of between 20% and 70% of fresh polyamide powder composition, and a mass fraction of between 80% and 30% of polyamide powder recovered at the end of a previous production. More preferably, the deposited powder bed comprises a mass fraction of between 25% and 55% of fresh polyamide powder composition, and a mass fraction of between 75% and 45% of polyamide powder recovered after a previous production.
• Adding fresh powder to spent powder adds undamaged (non-thermo-oxidized) polyamide grains, which are not already damaged or deformed by a previous thermo-oxidation-inducing sintering process, and thus maintains viscosity internal mixture within a given range by lowering this viscosity with each cycle as it evolves.
• the fresh polyamide powder used has an internal viscosity index measured according to ISO 307:2019 of between 0.9 deciliters per gram and 1.4 deciliters per gram.
• the method for determining the internal viscosity index of plastics and polyamides is based on the determination of the viscosity index of dilute solutions of polyamides in certain solvents specified in the aforementioned standard.
• This viscosity is involved in the rheology of melting and/or coalescence phenomena: the deposited particles must melt and coalesce to form a dense, non-porous mass, but without creeping in an uncontrolled manner.
• the internal viscosity influences the mechanical properties of the part, its appearance and the surface finish of the finished product.
• the powder composition it is advisable not to exceed a number of recycling cycles for the same powder, that is to say not to recycle again a mixture of powder which has undergone a number high thermal cycling in a PBF powder bed process.
• the collection of the cycled powder and its sieving must precede the mixing with fresh polyamide powder in order to separate the powder grain aggregates.
• the number of possible cycles depends on the degree of oxidation of the recycled powder, knowing that the internal viscosity increases with the degree of oxidation.
• the inventors note that on average the same powder can be reused in 8 to 10 recycling cycles, but this mainly depends on the duration of exposure of the powder to a high temperature and on the oxygen level in the enclosure, while throughout the thermal cycle undergone (preheating, manufacture at temperature and cooling) either during the entire manufacture in PBF or during cooling to a temperature below 60°C.
• Recycling is favored by the fact that the fresh powder has the internal viscosity indicated above. Indeed, to manufacture parts of good quality by the process according to the invention, it is possible to use a powder whose internal viscosity index is located a little outside this zone between 0.9 deciliters per gram and 1.4 deciliters per gram, but so that the fresh powder can be recycled in the PBF process, under advantageous economic conditions and according to the technical conditions indicated above (mixed with fresh powder at a rate of 30% to 60%), it It is preferable to respect, for the fresh powder, a continuous cooling at 50% and the systematic sieving of the already cycled powder.
• the composition according to the invention is powder A (already described above).
• Fresh powder A has an internal viscosity index equal to 1.3 deciliters per gram.
• a new powder composition according to the invention is formed by mixing half fresh powder and half recycled. After one or two cycles, the powder composition has an equal internal viscosity index of the order of 1.7 deciliters per gram. After three to six cycles, the powder composition has an internal viscosity index of the order of 2.05 deciliters per gram.
• the temperature time can be taken into consideration, i.e. the time during which the powder composition is subjected to heating in the heated enclosure. This approach can be more precise because the manufacturing cycles can be longer or shorter.
• the temperature times tested to arrive at the values of the internal viscosity index in the table above are also indicated. This temperature time is equal to 0 for a fresh powder, it is greater than 20 hours for a powder having undergone 1 to 2 cycles and greater than 50 hours for a powder having undergone 3 to 6 recycling cycles.
• an optical or magnetic detection additive in the powder composition of the invention allows the detection of 3D objects obtained by sintering this powder.
• the 3D objects obtained from a powder comprising a magnetic detection additive are for example detected by electromagnetic induction or according to any other method of detecting a magnetic object. These methods, which are well known to those skilled in the art, are not described here.
• 3D objects obtained by additive manufacturing of a powder composition are colored in the mass, that is to say that the material constituting the 3D object is colored and that the object does not only present a coloring on its outer surface.
• This characteristic allows a broken 3D object fragment to present on all its faces the color corresponding to the optical detection additive used.
• a fragment of a mass-colored object can be detected by optical detection methods, when the object is broken.
• the 3D object is colored in blue in the mass. Since the color blue is uncommon among food products, it stands out more easily than other colors when it is in the middle of food products.
• infrared detection by irradiation in a wavelength range between 0.5 ⁇ m and 12 ⁇ m can be implemented. These optical detection methods, even applied to fragments of plastic materials, are well known to those skilled in the art and will not be described here in greater detail.
• a 3D object obtained by sintering according to the invention has a lowest tensile strength greater than or equal to 40 MPa (megapascals), preferably greater than or equal to 44 MPa.
• the 4D object preferably has a lowest tensile strength greater than or equal to 30 MPa, very preferably greater than or equal to 35MPa.
• a 3D object obtained by sintering according to the invention has a lowest modulus of elasticity greater than or equal to 1600 MPa, preferably greater than or equal to 1750 MPa.
• standardized specimens of 3D objects obtained from a sintering process according to the invention were tested for their tensile strength and their modulus of elasticity, expressed in megapascals (MPa) and for their elongation at the rupture, expressed as a percentage.
• the 3D object tested is obtained from a sintering powder composition A according to the invention comprising an optical detection additive is in which the polyamide is PA11.
• the test method implemented complies with the ISO 527-1:2019 standard for determining tensile properties.
• the 3D objects obtained by the method of the invention have an elongation at break greater than or equal to 20% in a first orientation and greater than or equal to 35% in a second orientation, perpendicular to the first.
• Figures 10 and 11 show the graphs corresponding to the results of the tests presented above for the elongation at break.
• Figure 10 the results of the tensile elongation test along an xy orientation
• Figure 1 1 the results of the tensile elongation test along an xz orientation.

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