Process for producing polyamide powder

Abstract

The present invention relates to a method for producing a compound having a unimodal melting endotherm and a single melting temperature (T f1 max 1. A method for producing a polyamide powder having a i) contacting a polyamide with a solvent to obtain a mixture; ii) heating the mixture to dissolve the polyamide in the solvent; iii) heating the mixture in the solvent to a precipitation temperature (T p ), which results in a non-unimodal melting endotherm and (T f1 max ) is the highest melting temperature; iv) The precipitated polyamide powder exhibits a unimodal melting endotherm and melting temperature (T f1 max ) until the temperature of the mixture reaches at most T p temperature, especially T p -0.1℃~T p maintaining a temperature in the range of -15°C; and (ii) recovering the resulting polyamide powder The present invention relates to a method comprising:

Description

[Technical Field]

[0001] The present invention relates to the difference between the melting temperature and the crystallization temperature (T f1 -T c The present invention relates to a method for producing a polyamide powder that increases the molecular weight of the polyamide powder.

[0002] Polyamide-based powder T f1 and T c The large difference between is useful in many applications, especially in the technique of powder agglomeration by melting or sintering induced by radiation, such as a laser beam (laser sintering), infrared or UV radiation, or any electromagnetic radiation source capable of melting powders to produce articles.

[0003] The present invention also relates to the polyamide powder obtainable according to this method.

[0004] Finally, the invention relates to the use of this powder and to articles made from it. [Background technology]

[0005] The agglomeration of polyamide powder under a laser beam is used in a variety of fields to manufacture three-dimensional objects such as prototypes and models.

[0006] The thin layer of polyamide powder is heated to the crystallization temperature T c and melting temperature T f1 The powder is deposited on a horizontal plate held in a chamber heated to a temperature between 0 and 1000 K. The laser causes the powder particles to aggregate at different points in the powder layer according to the geometry corresponding to the article, for example by using a computer that stores the shape of the article in a memory and reproduces this shape in the form of slices. The powder areas exposed to the laser reach a temperature above the crystallization temperature T c, solidifies as soon as the temperature drops below 0.05°C. The horizontal plate is then lowered a distance corresponding to the thickness of the powder layer, a new layer of powder is then deposited, and the laser agglomerates the powder particles according to the geometry corresponding to this new slice of the article, and so on. This procedure is repeated until the entire article is produced. In the chamber, an article is obtained surrounded by unagglomerated powder. The assembly is then slowly cooled. Once completely cooled, the article is separated from the powder, which can be reused in another process.

[0007] Immediately after the action of the laser beam, the temperature of the exposed area rises above the crystallization temperature (T c ), but if the temperature drops below this temperature too quickly, for example by applying a new layer of cold powder, it will cause deformation ("curl") in the workpiece being printed. Similarly, if the temperature of the powder drops below the powder's melting temperature (T f1 ) can cause caking around the workpiece, manifested by the formation of powder clumps that affect print quality.

[0008] Therefore, in order to avoid these phenomena, T f1 Temperature T as far away as possible from c It is important that powders with the difference T f1 -T c determines the working temperature range of the equipment used to agglomerate powder particles by radiation-induced melting. This working range is defined by its upper and lower temperature limits. The upper limit of the working range corresponds to the temperature at which agglomeration or caking occurs. The lower limit of the working range corresponds to the temperature at which distortion, deformation, or curling occurs. This working range should be greater than the temperature fluctuations within a 3D printing machine, which are typically around ±3°C.

[0009] Furthermore, the high enthalpy of fusion (ΔH f) is advantageous for optimizing the geometric definition of the workpiece to be produced. In particular, if it is too low, there is a risk that the energy delivered by the laser will sinter, by heat conduction, the powder particles around the workpiece being built, which will reduce the geometric precision of the resulting workpiece.

[0010] It is clear that everything that has been said so far regarding the agglomeration of polyamide powder under a laser beam applies regardless of the electromagnetic radiation that causes the melting and whether the melting process is selective or non-selective.

[0011] U.S. Patent No. 5,932,687 discloses a method for preparing precipitated polyamide powders with narrow particle distribution and low porosity. The method comprises a first step of cooling a polyamide predissolved in an alcohol solvent to a temperature T1 (higher than the precipitation temperature of the polyamide in the solvent) to achieve polyamide nucleation, followed by a second cooling step of achieving supersaturation of the medium and thus precipitation of the polyamide at a temperature T2. The resulting suspension is directly cooled and dried to recover the polyamide powder.

[0012] U.S. Patent Application Publication No. 2008 / 0166496 discloses polyamide 11 powders that can be used in powder agglomeration processes, particularly for the production of three-dimensional articles. These powders are prepared according to a method that involves cooling a polyamide predissolved in ethanol to a temperature at which the polyamide precipitates. Due to the heat generated by the precipitation, the medium is held at this temperature for 25 minutes, after which the temperature is slightly reduced and an isothermal hold is performed for 35 minutes. At the end of this constant temperature phase, the mixture is cooled and the precipitated polyamide powder is separated.

[0013] However, the inventors have observed that the prior art methods result in polyamide powders whose analysis by differential scanning calorimetry shows, upon the first heating, the presence of two temperature peaks associated with two relatively close but different melting temperatures, revealing the presence of different crystalline phases.For the reasons stated above, this heterogeneity in the thermal properties of the powder narrows the working range and can therefore have a negative effect on the quality of the products produced by the method of powder agglomeration by melting with the aid of electromagnetic radiation, in particular their definition.

[0014] There is therefore a real need for a method for preparing polyamide powders that is useful in the technique of powder agglomeration by electromagnetic radiation induced melting, making it possible to overcome these drawbacks. Summary of the Invention

[0015] The inventors have discovered the difference between existing polyamides f1 -T c We developed a dissolution / precipitation method that effectively increases the solubility of the solubility-in-water mixture and obtains a unimodal melting endotherm.

[0016] More specifically, by introducing a constant temperature phase of sufficient duration at the end of the polyamide precipitation phase, a non-unimodal melting endotherm and (T f1 max ) is the highest melting temperature, f1 ) and a unimodal melting endotherm (T f1 max ) is equal to the single melting temperature (T f1 ) and converted into polyamide powder characterized by the temperature difference (T f1 -T c It has been found that it is possible to increase the temperature of the crystals. The inventors have been able to demonstrate in particular that this constant temperature step leads to an intensification of the crystallinity and thus makes it possible to obtain a single crystalline phase.

[0017] The polyamide powders obtained are therefore particularly advantageous for use in methods of powder agglomeration by melting with the aid of electromagnetic radiation, in particular in that the working range can be increased and therefore the quality and / or definition of the articles produced from these powders can be improved.

[0018] Thus, according to a first aspect, it is an object of the present invention to provide a polymer having a unimodal melting endotherm and a single melting temperature (T f1 max 1. A method for producing a polyamide powder having a i) contacting a polyamide with a solvent to obtain a mixture; ii) heating the mixture to dissolve the polyamide in the solvent; iii) heating the mixture in the solvent to a precipitation temperature (T p ), which results in a non-unimodal melting endotherm and (T f1 max ) is the highest melting temperature; iv) The precipitated polyamide powder exhibits a unimodal melting endotherm and melting temperature (T f1 max ) until the temperature of the mixture reaches at most T p temperature, especially T p -0.1℃~T p maintaining a temperature in the range of -15°C; and v) recovering the resulting polyamide powder The object of the present invention is to provide a method comprising:

[0019] The method advantageously also has one or more of the following additional features:

[0020] Thus, in some embodiments, the method according to the present invention comprises: the solvent contacted with the polyamide is an alcohol, in particular a C1-C4 aliphatic alcohol, preferably ethanol; - heating the mixture is carried out at a temperature of 100°C to 200°C, preferably 120°C to 160°C; and / or heating the mixture is carried out for a period of 1 to 6 hours, preferably 1 to 3 hours; - the cooling of the mixture in step iii) is carried out at a rate of from 1°C to 100°C per hour, preferably from 10°C to 60°C per hour; - the polyamide is polyamide 11, polyamide 6, or polyamide 10.10, or polyamide 10.12, or polyamide 6.10; - Polyamide precipitation temperature T p is between 80°C and 130°C, in particular between 100°C and 120°C; In step iv), the mixture is heated for a period of at least 2 hours, in particular between 3 and 12 hours, starting from the start of precipitation of the polyamide, until at most T p maintained at a temperature equal to; - also comprising a step vi) of drying the precipitated polyamide powder recovered in step v) or obtained at the end of step iv), in particular at a temperature between 10°C and 150°C, more particularly between 50°C and 100°C; and / or - Drying of the precipitated polyamide powder is carried out at pressures ranging from 10 mbar to atmospheric pressure It is a method.

[0021] According to a second aspect, the object of the present invention is also to provide a method for producing a unimodal melting endotherm and a single melting temperature (T f1 max The object of the present invention is to provide a polyamide powder having a molecular weight of 1.001 to 1.001.

[0022] The powder advantageously further has one or more of the following additional properties:

[0023] Thus, in some embodiments, the powder is characterized in that it has a volume-average diameter between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 40 μm and 80 μm; the powder is characterized in that it has a diameter Dv10 of more than 5 μm, in particular between 10 μm and 70 μm, preferably between 20 μm and 60 μm; the powder is characterized in that it has a diameter Dv90 of less than 350 μm, in particular between 30 μm and 200 μm, preferably between 50 μm and 150 μm; the powder is characterized in that it has a median diameter Dv50 between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 30 μm and 90 μm; the powder is characterized in that it has a span factor between 0.1 and 1.5, preferably between 0.1 and 1.0, more preferably between 0.5 and 1.0; - the polyamide is polyamide 11; - The powder has a melting temperature (T) between 195°C and 205°C. f1 max and / or - Melting temperature (T f1 max ) and crystallization temperature (T c ) is between 35℃ and 45℃ It is a powder.

[0024] According to a third aspect, the present invention also provides a polymer having a unimodal melting endotherm and a single melting temperature (T) between 195°C and 205°C. f1 max ) and further having the following properties: - a volume average diameter between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 40 μm and 80 μm; - diameter Dv10 of more than 5 μm, in particular between 10 μm and 70 μm, preferably between 20 μm and 60 μm; - a volume median diameter Dv50 between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 30 μm and 90 μm; - a diameter Dv90 of less than 350 μm, in particular between 30 μm and 200 μm, preferably between 50 μm and 150 μm; - a span coefficient between 0.1 and 1.5, preferably between 0.1 and 1, more preferably between 0.5 and 1.0; - an enthalpy of fusion greater than 100 J / g, preferably between 110 J / g and 160 J / g; and / or - an intrinsic viscosity between 0.8 and 1.8, preferably between 1.0 and 1.5 The present invention relates to a polyamide 11 powder having at least one of the following:

[0025] According to a fourth aspect, the present invention relates to a composition in powder form, in particular for 3D printing by laser sintering, comprising: - polyamide powder according to the invention; and - at least one filler or additive A composition comprising:

[0026] According to a fifth aspect, the present invention relates to a method for producing a polyamide article by powder agglomeration of a powder as defined herein by melting using electromagnetic radiation.

[0027] According to a sixth aspect, the present invention relates to an article of manufacture obtainable by melting a powder or a composition according to the invention with the aid of electromagnetic radiation.

[0028] According to a seventh aspect, the present invention provides a method for producing a polyamide having a melting temperature (T f1 ) and crystallization temperature (T c ) and the difference (T f1 -T c The present invention provides the use of the method according to the invention for increasing the amount of hydroxybenzoates present in the blood. [Brief explanation of the drawings]

[0029] [Figure 1] Figure 1 shows thermograms obtained by differential scanning calorimetry of polyamide 11 of Comparative Example 2 showing the heat flow Φ as a function of temperature: (a) first heating, (b) subsequent cooling, (c) second heating, and the corresponding enthalpy of fusion ΔHf. [Figure 2]Figure 2 shows thermograms obtained by differential scanning calorimetry of polyamide 11 of Example 3 showing the heat flow Φ as a function of temperature: (a) first heating, (b) subsequent cooling, (c) second heating, and the corresponding enthalpy of fusion ΔHf. [Figure 3] Figure 3 shows thermograms obtained by differential scanning calorimetry of polyamide 11 of Comparative Example 4 showing the heat flow Φ as a function of temperature: (a) first heating, (b) subsequent cooling, and (c) second heating, and the corresponding enthalpy of fusion ΔHf. DETAILED DESCRIPTION OF THE INVENTION

[0030] Detailed Description The invention is explained in more detail and in a non-limiting manner in the description that follows.

[0031] definition It should be noted that the expressions "from to" and "between and" used in this description should be understood as including both the limitations mentioned.

[0032] The term "powder" is understood to refer to a solid substance in finely divided form, generally provided in the form of particles of very small size, not exceeding a few hundred micrometers.

[0033] The powders are generally characterized by a thermogram obtained by differential scanning calorimetry (DSC) according to the following: - a first heating, which makes it possible to characterize the melting of the polyamide powder; - cooling, which makes it possible to characterize the crystallization of the polyamide material; - a second heating, which makes it possible to characterize the melting of the polyamide material itself.

[0034] The following terms, in the context of thermal properties, are understood as defined in ISO standard 11357-1:2016: "Peak" refers to a portion of a thermogram obtained by differential scanning calorimetry (DSC) that moves away from the baseline, reaches a maximum or minimum, and then returns to the baseline. Such a peak may represent a first-order transition (crystallization exotherm or melting endotherm); a melting peak, for the purposes of this description, may specifically include multiple peaks or a shoulder before the signal returns to the baseline. - "Baseline" refers to the portion of the recorded thermogram that is free of any transitions, in this case specifically the portion that is free of first-order transitions of the melting or crystallization type. Within the transition region, it is possible to define a virtual baseline. This is an imaginary line plotted through the transition region, assuming zero heat due to the transition. The virtual baseline can be plotted by interpolating the baseline of the test sample with a straight line. - "Peak area" refers to the area enclosed by the peak and the interpolated imaginary reference line. This is considered as the transition enthalpy expressed in J / g. The term "melting enthalpy" is understood to refer to the heat required to melt the composition, corresponding to the area under the melting peak of the thermogram, measured according to ISO standard 11357-3:2018.

[0035] The term "melting temperature" is understood to refer to the temperature, measured in accordance with ISO standard 11357-3:2018, at which an at least partially crystalline polyamide powder or polyamide material exhibits the phenomenon of melting, transitioning into a viscous liquid state. For the purposes of the present description, a melting peak comprising several peaks or shoulders will therefore be associated with several melting temperatures, i.e., one melting temperature for each peak or shoulder.

[0036] The "melting temperatures in the first and second heats" are measured by DSC according to ISO standard 11357-3:2018, corresponding to the maximum signal intensity of the melting peak in the first heat and the second heat, respectively, both performed with a temperature ramp of 20°C / min, and are T for the first heat. f1 , and T for the second heating f2Therefore, for the purposes of this description, multiple melting temperatures (T f1 ) is detected, the difference (T f1 -T c ) is used to calculate the T corresponding to the lowest melting temperature. f1 Temperature, i.e., T f1 min T f1 max is the maximum melting temperature (T f1 ) and refers to the only melting temperature (T f1 ) corresponds to

[0037] T below c The term "crystallization temperature" is understood to mean the temperature at which an at least partially crystalline compound transitions from a viscous liquid state to a semi-crystalline state, measured with a temperature gradient of -20 °C / min, in accordance with ISO standard 11357-3:2018. The crystallization temperature corresponds more specifically to the temperature measured during cooling after the first melting (first heating) of the compound and before the second melting (second heating), which allows the compound's thermal history to be erased. Unless otherwise specified, this is the temperature of the crystallization peak corresponding to the maximum intensity of the DSC signal. Therefore, for the purposes of this description, if multiple crystallization temperatures are detected during cooling, the T c corresponds to the highest crystallization temperature, and the difference (T f1 -T c It is this value that must be used to calculate

[0038] A "unimodal melting endotherm" of a polyamide powder means the portion of a thermogram obtained by differential scanning calorimetry (DSC) that corresponds to the first melting of the polyamide powder, and which exhibits a single melting temperature T f1In other words, the melting peak corresponding to the first heat contains only a single peak. In contrast, a multimodal melting endotherm is characterized by a melting peak in the first heat having multiple peaks, i.e., multiple melting peak temperatures. Similarly, a melting endotherm in the first heat in which the melting peak has a shoulder would not be considered a unimodal endotherm for purposes of this description.

[0039] T below p The term "precipitation temperature", as used herein, is understood to mean the temperature at which the mixture formed by the polyamide and the solvent used in the process passes from a homogeneous to a heterogeneous state. The precipitation temperature is detected by a temperature sensor (PT100 type) connected to a dynamic temperature regulation system (for example the "Petite Fleur" system sold by Huber). At the moment of precipitation, the temperature regulation system is unable to compensate instantaneously for the heat generated. The precipitation temperature is also accurately detected as a perturbation of the derivative of the temperature of the reaction medium as a function of the detection time. The temperature corresponding to the onset of the perturbation of the derivative is called the precipitation temperature (T p ) is considered to be

[0040] The term "Dv50" refers to the volume median diameter of powder particles where the volume-weighted cumulative particle size distribution function is equal to 50%. Similarly, "Dv10" and "Dv90" are the corresponding diameters where the volume-weighted cumulative particle size distribution function is equal to 10% and 90%, respectively. These values ​​are measured, for example, using a Coulter Counter Multisizer 3 particle size analyzer in accordance with ISO standard 13319-1:2021. Rules for expressing particle size distribution results are specified by parts 1 to 6 of ISO standard 9276.

[0041] The "span" factor is understood to mean the factor characterizing the width of the particle size distribution, defined as Span = (Dv90 - Dv10) / Dv50, where the diameters "Dv10", "Dv50", and "Dv90" are as defined above.

[0042] The term "mean diameter" refers to the volume-average diameter value of the particles, which corresponds to the volume-weighted arithmetic mean of the particle sizes, as measured, for example, using a Coulter Counter Multisizer 3 particle size analyzer in accordance with ISO standard 13319-1:2021.

[0043] The term "viscosity" is understood to refer to the intrinsic viscosity measured with an Ubbelohde viscometer according to ISO standard 307:2019, except that m-cresol is used as the solvent and the temperature is 20°C. Intrinsic viscosity has the dimension of the reciprocal of concentration and is equal to the natural logarithm of the relative viscosity divided by the concentration of the polymer dissolved in the solvent.

[0044] The term "3D printing" is understood to refer to a technology for producing workpieces by additive manufacturing, in which powder is selectively melted by electromagnetic radiation, such as laser or infrared radiation.

[0045] Process for producing polyamide powder Thus, according to a first aspect, it is an object of the present invention to provide a polymer having a unimodal melting endotherm and a single melting temperature (T f1 max 1. A method for producing a polyamide powder having a i) contacting a polyamide with a solvent to obtain a mixture; ii) heating the mixture to dissolve the polyamide in the solvent; iii) heating the mixture in the solvent to a precipitation temperature (T p ), which results in a non-unimodal melting endotherm and (T f1 max ) is the highest melting temperature; iv) The precipitated polyamide powder exhibits a unimodal melting endotherm and a single melting temperature (T f1 max ) until the temperature of the mixture reaches at most T p temperature, especially T p ~T p maintaining a temperature in the range of -15°C; and v) recovering the resulting polyamide powder The object of the present invention is to provide a method comprising:

[0046] In the following description, the term "monomer" should be understood to mean "repeating unit." In a special case, the repeating unit may consist of a combination of a diamine and a diacid. In this case, the combination of a diamine and a diacid, i.e., a diamine-diacid pair, is considered to correspond to the monomer, because a diamine and a diacid cannot form an amide functional group by themselves.

[0047] For the purposes of the present invention, "polyamide" is understood to mean the condensation product of a lactam, an amino acid, or a diamine-diacid pair. It may be a homopolymer, i.e. a polymer obtained by condensation of the same repeating unit, i.e. the same monomer, or it may be a copolymer obtained by condensation of at least two repeating units, i.e. two different monomers called "comonomers", i.e. at least one monomer and at least one comonomer (a monomer different from the first monomer), to form a copolymer such as a copolyamide (abbreviated CoPA) as defined below.

[0048] "Copolyamide" (abbreviated CoPA) is understood to mean the polymerization product of at least two different monomers selected from: - amino acid or aminocarboxylic acid type monomers, preferably α,ω-aminocarboxylic acids; - lactam type monomers; - "diamine-diacid" type monomer pairs resulting from the reaction of diamines with dicarboxylic acids; and - In the case of mixtures of amino acid type monomers and lactam type monomers, their mixtures with monomers having different numbers of carbon atoms.

[0049] These monomers may be linear, branched, or substituted as desired.

[0050] According to some embodiments, the polyamide is a homopolymer.

[0051] According to a first type, the polyamides result from the condensation of aliphatic, cycloaliphatic or aromatic dicarboxylic acids, in particular containing from 4 to 36 carbon atoms, preferably from 6 to 18 carbon atoms, with aliphatic, cycloaliphatic or aromatic diamines, in particular containing from 2 to 20 carbon atoms, preferably from 6 to 14 carbon atoms.

[0052] Examples of dicarboxylic acids include 1,4-cyclohexanedicarboxylic acid, butanedioic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, terephthalic acid, and isophthalic acid, but also dimerized fatty acids.

[0053] Examples of diamines include tetramethylenediamine, hexamethylenediamine, 1,10-decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, bis(4-aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), isomers of 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), para-aminodicyclohexylmethane (PACM), isophoronediamine (IPDA), 2,6-bis(aminomethyl)norbornane (BAMN), and piperazine (Pip).

[0054] Advantageously, the polyamide is chosen from PA 4.6, PA 4.10, PA 4.12, PA 4.14, PA 4.18, PA 6.10, PA 6.12, PA 6.14, PA 6.18, PA 9.12, PA 10.10, PA 10.12, PA 10.14 and PA 10.18. In the notation PA XY, according to convention, X represents the number of carbon atoms derived from the diamine residue and Y represents the number of carbon atoms derived from the diacid residue.

[0055] In certain embodiments, the polyamide is selected from polyamide 11, polyamide 6, polyamide 10.10, polyamide 10.12, or polyamide 6.10. Preferably, the polyamide is PA 11.

[0056] Steps i) and ii) The indefinite article "a" or the definite article "the" used before the term "polyamide" in the process according to the invention means, in the context of the present specification, "at least one polyamide" and "said at least one polyamide", respectively.

[0057] Thus, in a first step i), at least one polyamide is contacted with a solvent to obtain a mixture.

[0058] Preferably, in this method only one polyamide is used.

[0059] However, it is also possible to use a mixture of two or more, in particular two, polyamides, preferably such that the mixture comprises a predominant polyamide, in particular a polyamide representing more than 80% by weight of the total weight of the polyamides used in step i), so as to obtain a co-precipitation of a polyamide mixture.

[0060] In certain embodiments, the solvent contacted with the polyamide may be selected from ethanol, propanol, butanol, isopropanol, heptanol, formic acid, acetic acid, N-methylpyrrolidone, N-butylpyrrolidone, butyrolactam, and caprolactam.

[0061] Preferably, the solvent contacted with the polyamide is a C1-C4 aliphatic alcohol, more preferably ethanol, and even more preferably 96% pure technical grade ethanol (containing water and modified with 2-butanone and propan-2-ol).

[0062] The polyamide may have a weight fraction in the solvent of 0.01 to 0.30, preferably 0.1 to 0.3, in particular 0.01 to 0.05; 0.05 to 0.1; or 0.1 to 0.15 or 0.15 to 0.2; or 0.2 to 0.25; or 0.25 to 0.3.

[0063] The resulting mixture is then heated in step ii) until the polyamide is dissolved, ie a homogeneous mixture is obtained.

[0064] Heating of the mixture can be carried out in particular at temperatures between 100°C and 200°C, preferably between 120°C and 160°C.

[0065] In certain embodiments, the mixture can be heated to a temperature of, for example, 100°C to 105°C; or 105°C to 110°C; or 110°C to 115°C; or 115°C to 120°C; or 120°C to 125°C; or 125°C to 130°C; or 130°C to 135°C; or 135°C to 140°C; or 140°C to 145°C; or 145°C to 150°C; or 150°C to 155°C; or 155°C to 160°C; or 160°C to 165°C; or 165°C to 170°C; or 170°C to 175°C; or 175°C to 180°C; or 180°C to 185°C; or 185°C to 190°C; or 190°C to 195°C; or 195°C to 200°C.

[0066] In certain embodiments, heating of the mixture, particularly maintaining the mixture at the dissolution temperature, can be for a period of 1 to 6 hours, preferably 1 to 3 hours. Thus, heating of the mixture can last for 1 hour to 1 hour 30 minutes; or 1 hour 30 minutes to 2 hours; or 2 hours to 2 hours 30 minutes; or 2 hours 30 minutes to 3 hours; or 3 hours to 3 hours 30 minutes; or 3 hours 30 minutes to 4 hours; or 4 hours to 4 hours 30 minutes; or 4 hours 30 minutes to 5 hours; or 5 hours to 5 hours 30 minutes; or 5 hours 30 minutes to 6 hours.

[0067] In a particular embodiment, the heating comprises at least one step of increasing the temperature to reach a maximum temperature between 100°C and 200°C, in particular between 120°C and 160°C.

[0068] In a particular embodiment, the heating comprises at least one step in which the temperature is kept essentially constant at a value between 100°C and 200°C, in particular between 120°C and 160°C.

[0069] Process iii) Then, in step iii), the mixture is cooled in order to precipitate the polyamide in the form of a powder.

[0070] Precipitation temperature (T p ) may vary depending on the solvent, even for the same polyamide. Likewise, it may vary depending on the polyamide, even for the same solvent. Specifically, precipitation of polyamide is accompanied by the release of heat, resulting in a slight increase in internal temperature. At the end of precipitation, heat is no longer released and the internal temperature returns to its nominal temperature.

[0071] The precipitation temperature may be between 80°C and 130°C, especially between 100°C and 120°C, especially when the solvent is a C1-C4 aliphatic alcohol.

[0072] This cooling can be carried out to reduce the temperature to 50° C. or higher. Thus, cooling can be carried out to reduce the temperature, for example, to 50° C. Thus, cooling can be carried out to reduce the temperature, for example, to a range of 50° C. to 60° C., or 60° C. to 70° C., or 70° C. to 80° C., or 80° C. to 90° C., or 90° C. to 100° C., or 100° C. to 110° C., or 110° C. to 120° C., or 120° C. to 130° C.

[0073] Furthermore, this cooling can be carried out at a rate of 1 to 100° C. per hour, preferably 10 to 60° C. per hour, and more preferably 20 to 50° C. per hour. For example, cooling may be carried out at a rate of 1 to 5°C per hour; 5 to 10°C per hour; 10 to 15°C per hour; or 15 to 20°C per hour; or 20 to 25°C per hour; or 25 to 30°C per hour; or 30 to 35°C per hour; or 35 to 40°C per hour; or 40 to 45°C per hour; or 45 to 50°C per hour; or 50 to 55°C per hour; or 55 to 60°C per hour; or 60 to 65°C per hour; or 65 to 70°C per hour; or 70 to 75°C per hour; or 75 to 80°C per hour; or 80 to 85°C per hour; or 85 to 90°C per hour; or 90 to 95°C per hour; or 95 to 100°C per hour.

[0074] In a particular embodiment, in order to promote precipitation, a certain amount of polyamide can be introduced in step i) of charging the starting materials. Preferably, the amount of this polyamide is 20% by weight or less, preferably 10% by weight or less, based on the total mass of polyamide used in this step. The polyamide may be the same or different from the one dissolved in the solvent, preferably the same. The polyamide may be selected from polyamide 11, polyamide 6, polyamide 10.10, polyamide 10.12, and polyamide 6.10, in particular.

[0075] Thus, the amount of polyamide added may represent 0.1% to 1% by weight, or 1% to 2% by weight, or 2% to 3% by weight, or 3% to 4% by weight, or 4% to 5% by weight, or 5% to 8% by weight, or 8% to 12% by weight, or 12% to 16% by weight, or 16% to 20% by weight, relative to the total mass of polyamide used in the process.

[0076] Step iii) is advantageously carried out with stirring. In a given stirring system, the volume-average diameter of the particles can be controlled by the stirring speed. Generally, as the stirring speed increases, the average diameter of the polyamide particles decreases. Conversely, as the stirring speed decreases, the average diameter of the polyamide particles increases.

[0077] Process iv) If, during the cooling step, the precipitation temperature of the polyamide in the solvent is reached, then the precipitation stage begins, which corresponds to the start of step iv) of the process according to the invention.

[0078] In step iv), the mixture is heated to a temperature at which the polyamide is precipitated in the solvent (T p ), at most equal to this precipitation temperature, in particular within a range of −0.1° C. to −15° C. of this precipitation temperature, for a time sufficient to allow a precipitated polyamide powder to be obtained having a monomodal melting endotherm and an elevated melting temperature.

[0079] In other words, the method comprises in step iv) a constant temperature stage in which the temperature is held constant for a time t. More specifically, the temperature is held constant for the entire duration of the polyamide precipitation stage, i.e. for a time t1, and then for an additional time t2 so as to allow strengthening of the crystal lattice of the precipitated polyamide, thereby obtaining a polyamide powder with a unimodal melting endotherm and an elevated melting temperature.

[0080] Generally, time t1 is significantly shorter than time t2, so that the total time t of the constant temperature step is generally very close to t2.

[0081] The additional time required to obtain a unimodal melting endotherm can be determined by analyzing samples collected at various intervals by differential scanning calorimetry (DSC) according to ISO standard 11357-3.

[0082] As an example, at the end of the precipitation stage of polyamide 11, i.e., at the end of time t1, the inventors observed that in the first heating in the DSC, a bimodal melting endotherm characterized by two different melting temperatures was obtained. By holding the temperature constant for a sufficient additional time t2 at a temperature close to the precipitation temperature of the polyamide in the solvent, the inventors were able to observe a change from the bimodal melting endotherm of the polyamide particles to a unimodal melting endotherm, as indicated by the disappearance of the peak associated with the lowest melting temperature in favor of the peak associated with the highest melting temperature in the DSC thermogram. This constant temperature stage of total time t1 + t2 therefore advantageously results in a difference T f1 -T c This makes it possible to simultaneously increase the melting point and obtain a unimodal melting endotherm.

[0083] According to some embodiments, in step iv), the mixture is maintained at a constant temperature for a time t2 starting from the end of polyamide precipitation, for at least 2 hours, particularly 3 to 12 hours, preferably at least 4 hours, particularly 4 to 12 hours. This additional time after the end of polyamide precipitation can be 2 to 3 hours; or 3 to 4 hours; or 4 to 5 hours; or 5 to 6 hours; or 6 to 7 hours; or 7 to 8 hours; or 8 to 9 hours; or 9 to 10 hours; or 10 to 11 hours; or 11 to 12 hours.

[0084] In a particular embodiment, in step iv), the mixture is maintained at a constant temperature for a time t, starting from the onset of polyamide precipitation, of at least 2 hours, in particular 3 to 12 hours, preferably at least 4 hours, in particular 4 to 12 hours. This time from the onset of polyamide precipitation can be 2 to 3 hours; or 3 to 4 hours; or 4 to 5 hours; or 5 to 6 hours; or 6 to 7 hours; or 7 to 8 hours; or 8 to 9 hours; or 9 to 10 hours; or 10 to 11 hours; or 11 to 12 hours.

[0085] Steps v) and vi) After the end of the constant temperature phase carried out in step iv), the precipitated polyamide particles are recovered in powder form from the mixture in step v) by conventional solid-liquid separation means.

[0086] This step generally involves cooling the resulting mixture to allow the liquid to be drained from the reactor, and then separating the resulting precipitated polyamide particles from the solvent, notably by filtration.

[0087] The process for producing a polyamide powder may also comprise a step vi) of drying the polyamide powder obtained in step iv) or recovered in step v). The drying step may be carried out, for example, in an agitator dryer or a rotary dryer.

[0088] In certain embodiments, drying may be carried out at a temperature of 10° C. to 150° C., particularly 50° C. to 100° C., preferably 25° C. to 85° C., and more preferably 70° C. to 80° C. Drying may be carried out at a temperature of, for example, 10° C. to 20° C., or 20° C. to 30° C., or 30° C. to 40° C., or 40° C. to 50° C., or 50° C. to 60° C., or 60° C. to 70° C., or 70° C. to 80° C., or 80° C. to 90° C., or 90° C. to 100° C., or 100° C. to 110° C., or 110° C. to 120° C., or 120° C. to 130° C., or 130° C. to 140° C., or 140° C. to 150° C., or 150° C. to 160° C.

[0089] In certain embodiments, drying can be carried out under reduced pressure of less than 100 mbar, preferably less than 50 mbar. Thus, drying can be carried out at a pressure of 1 to 10 mbar; or 10 to 20 mbar; 20 to 30 mbar; 30 to 40 mbar; 40 to 50 mbar; 50 to 60 mbar; 60 to 70 mbar; 70 to 80 mbar; 80 to 90 mbar; 90 to 100 mbar; 100 to 150 mbar; 150 to 200 mbar; 200 to 250 mbar; or 250 to 300 mbar; or 300 to 500 mbar; or 500 to 700 mbar; or 700 mbar to less than 1 bar (absolute).

[0090] Alternatively, drying may be carried out at atmospheric pressure.

[0091] Polyamide powder obtainable by the production method of the present invention According to a second aspect, the present invention provides a method for producing a unimodal melting endotherm and a single melting temperature (T f1 max ) polyamide powder.

[0092] In certain embodiments, the polyamide powder has an intrinsic viscosity of 0.8 to 1.7, preferably 1.0 to 1.5. Thus, the powder may have an intrinsic viscosity of, for example, 0.8 to 0.9; or 0.9 to 1.0; or 1.0 to 1.1; or 1.1 to 1.2; or 1.2 to 1.3; or 1.3 to 1.4; or 1.4 to 1.5; or 1.5 to 1.6; or 1.6 to 1.7. In the above, intrinsic viscosity is (g / 100g) -1 It is expressed as:

[0093] Intrinsic viscosity is measured using a micro-Ubbelohde tube. Measurements are carried out at 20°C on 75 mg of powder sample at a concentration of 0.5% (m / m) in m-cresol. Intrinsic viscosity is (g / 100g) -1 and is calculated according to the following formula: Intrinsic viscosity=ln(t s / t0)x1 / C, where C=m / px100, t s is the flow time of the solution, t0 is the flow time of the solvent, m is the mass of the sample whose viscosity is to be measured, and p is the mass of the solvent.

[0094] In a particular embodiment, the precipitated polyamide powder has a crystallization temperature (T c The polyamide powder may in particular have a crystallization temperature of 100°C to 110°C; or 110°C to 120°C; or 120°C to 130°C; or 130°C to 140°C; or 140°C to 150°C; or 150°C to 160°C; or 160°C to 170°C; or 170°C to 180°C; or 180°C to 190°C; or 190°C to 200°C.

[0095] In certain embodiments, the polyamide powder has a melting enthalpy of 60 J / g or more, preferably 100 J / g or more, which can be, for example, 60-80 J / g; or 80-100 J / g; or 100-110 J / g; or 110-120 J / g; or 120-130 J / g; or 130-140 J / g; or 140-150 J / g; or 150-160 J / g.

[0096] In a particular embodiment, the polyamide powder has a melting temperature T between 130°C and 260°C, preferably between 160°C and 210°C. f1 In particular, the polyamide powder may have a melting temperature of 130°C to 140°C, or 140°C to 150°C, or 150°C to 160°C, or 160°C to 170°C, or 170°C to 180°C, or 180°C to 190°C, or 190°C to 200°C, or 200°C to 210°C, or 210°C to 220°C, or 220°C to 230°C, or 230°C to 240°C, or 240°C to 250°C, or 250°C to 260°C.

[0097] The melting temperature (T f1 ) is determined during the first heating, as explained above. According to the method of the invention, at the end of the constant temperature phase at the end of step iv), a single melting temperature of the polyamide is observed.

[0098] In certain embodiments, the polyamide powder has a molecular weight of 0.1 to 50 m. 2 / g, preferably 1 to 10m 2 / g. Thus, the precipitated polyamide powder has an apparent specific surface area of ​​0.1 to 1 m 2 / g; or 1 to 5 m 2 / g; or 5 to 10 m 2 / g; or 10-20m 2 / g; or 20-30m 2 / g; or 30-50m 2 / g. The apparent specific surface area (SSA) is measured according to the Brunauer-Emmett-Teller (BET) method, known to those skilled in the art. This is described in particular in The Journal of the American Chemical Society, Vol. 60, p. 309, February 1938, and corresponds to the ISO International Standard 9277:2010. The specific surface area measured according to the BET method corresponds to the surface porosity of the powder, i.e., it includes the surface area formed by the pores on the surface of the particles.

[0099] According to a particular embodiment, the polyamide powder obtained by the process of the present invention comprises: - a volume average diameter between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 40 μm and 80 μm; - diameter Dv10 of more than 5 μm, in particular between 10 μm and 70 μm, preferably between 20 μm and 60 μm; - a volume median diameter Dv50 between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 30 μm and 90 μm; - a diameter Dv90 of less than 350 μm, in particular between 30 μm and 200 μm, preferably between 50 μm and 150 μm; - span coefficient between 0.1 and 1.5, preferably between 0.5 and 1.0; - an enthalpy of fusion greater than 60 J / g, preferably between 100 J / g and 160 J / g; and / or - an intrinsic viscosity between 0.5 and 2.0, preferably between 1.0 and 1.5 The present invention is characterized by having the following.

[0100] In a preferred embodiment, the monomodal melting endotherm and single melting temperature (T f1 max ) is characterized by having a span factor between 0.1 and 1.5, preferably between 0.1 and 1.0, more preferably between 0.5 and 1.0.

[0101] Polyamide 11 powder According to another aspect, the present invention provides a thermoplastic elastomer having a unimodal melting endotherm and a T between 195°C and 205°C, particularly about 200°C. f1 max The single melting temperature T during the first heating is equal to f1 and / or a crystallization temperature T between 150°C and 165°C, in particular about 158°C c The present invention relates to a polyamide 11 powder characterized by having the following properties:

[0102] The polyamide 11 powder is in particular a powder characterized by one or more of the following properties, preferably by all of the following properties: - a volume average diameter between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 40 μm and 80 μm; - diameter Dv10 of more than 5 μm, in particular between 10 μm and 70 μm, preferably between 20 μm and 60 μm; - a volume median diameter Dv50 between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 30 μm and 90 μm; - a diameter Dv90 of less than 350 μm, in particular between 30 μm and 200 μm, preferably between 50 μm and 150 μm; - span coefficient between 0.1 and 1.5, preferably between 0.5 and 1.0; - an enthalpy of fusion greater than 100 J / g, preferably between 110 J / g and 160 J / g; and / or - an intrinsic viscosity between 0.8 and 1.8, preferably between 1.0 and 1.5.

[0103] Preferably, the polyamide 11 powder has a unimodal melting endotherm, a T between 195°C and 205°C. f1 max The single melting temperature T during the first heating is equal to f1 and a span coefficient between 0.1 and 1.5, preferably between 0.1 and 1, and more preferably between 0.5 and 1.0.

[0104] Composition in powder form, especially for 3D printing by selective laser sintering According to yet another aspect, the present invention relates to a composition in powder form, in particular for 3D printing by selective laser sintering, comprising a polyamide powder as defined above in combination with one or more conventional fillers or additives (i.e., suitable for 3D printing techniques).

[0105] The composition is advantageously a ready-to-use composition.

[0106] The composition may include additives that help improve the deformation characteristics of the powder for use with 3D printing techniques.

[0107] The additives generally account for less than 5 wt. % of the total weight of the composition. Preferably, the additives account for less than 1 wt. % of the total weight of the composition. Additives include flow agents, stabilizers (light stabilizers, especially UV stabilizers, and heat stabilizers), optical brighteners, dyes, pigments, and energy absorbing additives (including UV absorbers).

[0108] The fluidizing agent may be, for example, hydrophilic or hydrophobic silica. The fluidizing agent advantageously represents from 0.01% to 0.5% by weight relative to the total weight of the composition. Preferably, the composition comprises from 0.1% to 0.4% by weight of fluidizing agent.

[0109] The composition may also comprise one or more fillers that make it possible in particular to improve the mechanical properties (stress at break and elongation at break) of the workpiece obtained by 3D printing.

[0110] The fillers generally represent less than 50% by weight, preferably less than 40% by weight, of the total weight of the final powder, and include reinforcing fillers, especially inorganic fillers such as carbon black, talc, carbon or non-carbon nanotubes, fibers (glass, carbon, etc.), optionally milled.

[0111] The additives or fillers may be mixed with the polyamide before, during (e.g., before dissolving the polyamide in step i) or after precipitation in step iv), or after the polyamide powder production process. Preferably, the additives are introduced after the polyamide powder production process by mixing the additives with the polyamide powder.

[0112] The composition preferably comprises polyamide in an amount of 80% or more, or 81% or more, or 82% or more, or 83% or more, or 84% or more, or 85% or more, or 86% or more, or 87% or more, or 88% or more, or 89% or more, or 90% or more, or 91% or more, or 92% or more, or 93% or more, or 94% or more, or 95% or more, or 96% or more, or 97% or more, or 98% or more, or 99% or more, or 99.1% or more, or It may contain 99.2% or more, or 99.3% or more, or 99.4% or more, or 99.5% or more, or 99.6% or more, or 99.7% or more, or 99.8% or more, or 99.9% or more, or 99.91% or more, or 99.92% or more, or 99.93% or more, or 99.94% or more, or 99.95% or more, or 99.96% or more, or 99.97% or more, or 99.98% or more, or 99.99% or more by weight.

[0113] In some embodiments, the polyamide included in the composition is polyamide 11.

[0114] In some embodiments, the polyamide 11 has a melting temperature (T f1 )

[0115] In some embodiments, the melting temperature (T f1 ) and crystallization temperature (T c The difference between the two temperatures is between 35℃ and 45℃.

[0116] Use of the polyamide powder obtained by the method of the present invention or a composition in powder form containing the same in a method for powder agglomeration by melting The present invention also provides a method for producing a polyamide article by powder agglomeration of a polyamide powder or a composition in powder form as defined above by melting using electromagnetic radiation.

[0117] The electromagnetic radiation can be infrared, ultraviolet or visible radiation. Preferably, it is laser radiation (in which case the manufacturing method is known as selective laser sintering).

[0118] According to this method, thin layers of powder are deposited on a horizontal plate maintained in a chamber heated to a temperature called the build temperature. The term "build temperature" refers to the temperature to which the layers of powder of the constituent layers of the three-dimensional article being built are heated during the layer-by-layer sintering process of the powder. This temperature is determined by the T f1 -T c is selected within the difference of T f1 -5℃~T c +5°C, more preferably T f1 -10℃~T c +10° C. The electromagnetic radiation then provides the energy necessary to sinter the powder particles at different points in the powder layer according to the geometry corresponding to the article (for example, using a computer that stores the shape of the article in a memory and recreates this shape in the form of slices).

[0119] The horizontal plate is then lowered a distance corresponding to the thickness of the layer of powder, and a new layer is deposited. The layer thickness is typically between 0.05 mm and 2 mm, and generally around 0.1 mm. Electromagnetic radiation provides the energy necessary to sinter the powder particles into the geometry corresponding to this new slice of the article, and so on. This procedure is repeated until the article is produced.

[0120] The powders are used in a method of agglomeration by melting or sintering. These powders can have a volume average diameter between 10 μm and 200 μm, and advantageously between 20 μm and 100 μm.

[0121] Preferably, the volume average diameter is between 40 μm and 80 μm.

[0122] The invention also relates to an article of manufacture, in particular an article of manufacture produced by 3D printing, obtained by sintering the above-mentioned powder using electromagnetic radiation.

[0123] The products may be selected from prototypes and models, especially in the automotive, marine, aviation, aerospace, medical (prosthetics, hearing systems, tissue, etc.), textile, clothing, fashion, decoration, housings for electronic devices, telephony, home automation, IT, and lighting sectors.

[0124] More generally, the present invention relates to the melting temperature (T f1 ) and crystallization temperature (T c ) and the difference (T f1 -T c The present invention also relates to the use of the above-mentioned manufacturing method for increasing the amount of [Example]

[0125] The following examples illustrate embodiments of the present invention, but do not limit the invention.

[0126] In all of the following examples: - The particle size of the powders was characterized by measuring the particle size distribution with a Coulter Counter-Multisizer 3 instrument (Beckmann Coulter) according to ISO standard 13319-1:2021. From this, the volume mean diameter and the diameters Dv10, Dv50, and Dv90 were determined. The span values ​​were calculated from these volume mean diameters. - The analysis of the thermal properties is carried out by DSC according to ISO standard 11357-3 "Plastics - Differential Scanning Calorimetry (DSC) Part 3: Determination of the temperature and enthalpy of melting and crystallization". The temperatures of particular interest here are the melting temperature (T f1 ) and crystallization temperature (T c) Specifically, as known to those skilled in the art (in the field of manufacturing 3D articles by powder agglomeration by melting), the difference "T f -T c " is T f1 -T c Corresponds to. - The intrinsic viscosity of polyamides is measured in accordance with ISO standard 307:2019 using an Ubbelohde viscometer, using m-cresol as the solvent, at a temperature of 20°C. - Acidity (which can be considered as the concentration of COOH chain ends of the polyamide) and basicity (which can be considered as the concentration of NH2 chain ends of the polyamide) are measured potentiometrically. Acidity is measured according to the following method: a polyamide sample is dissolved in benzyl alcohol at a concentration of 0.6% by weight, and then this sample is measured potentiometrically using a 0.02N tetrabutylammonium hydroxide solution. Basicity is measured according to the following method: a polyamide sample is dissolved in meta-cresol at a concentration of 0.6% by weight, and then this sample is measured potentiometrically using a 0.02N perchloric acid solution.

[0127] Example 1 Preparation of Polyamide 11 Polyamide 11 is obtained by polycondensation of 11-aminoundecanoic acid in the presence of 3000 ppm orthophosphoric acid used as a catalyst. This PA11 has an intrinsic viscosity of 1.40, combined with a concentration of chain-end COOH groups equal to 55 mmol / kg and a concentration of chain-end NH groups equal to 51 mmol / kg, and a melting temperature of 189 °C (second heat in DSC according to ISO standard 11357-3:2018).

[0128] Example 2 (Comparative) A reactor (working volume 1 L) is charged with 85 g of PA11 prepared in Example 1 and 425 g of technical-grade ethanol (purity 96%), and mechanical stirring is performed using an impeller-type turbomixer. The stirrer is operated at a speed of 500 rpm throughout the test, after which the medium is heated to 160 ° C, followed by an isothermal hold for 1 hour to dissolve the polyamide 11. Controlled cooling to 20 ° C at a rate of -60 ° C / h is performed to precipitate the polyamide. The precipitation temperature is 120 ° C. The reactor is then drained, and the dispersion is dried in an oven at 75 ° C under atmospheric pressure.

[0129] The resulting PA11 powder has the following properties: intrinsic viscosity of 1.25, volume average diameter of 66 μm, and diameters Dv10=33 μm, Dv50=75 μm, and Dv90=108 μm, thus span=1.00. DSC analysis of this PA11 powder showed, upon the first heating, a bimodal melting endotherm with two distinct peaks at 191 °C and 199 °C, associated with a melting enthalpy of 137 J / g (FIG. 1), and a crystallization temperature T c = 159°C. f1 -T c It is the lower of the two melting temperatures that is used to calculate , therefore this difference is equal to 32 °C.

[0130] Example 3 (Comparative): A reactor (working volume 1 L) was charged with 85 g of PA11 prepared in Example 1 and 425 g of technical grade ethanol (purity 96%), and mechanical stirring was performed using an impeller-type turbomixer. The stirrer was operated at a speed of 500 rpm throughout the test, after which the medium was heated to 160°C, followed by an isothermal hold for 1 hour to dissolve the polyamide 11. Controlled cooling was performed at a rate of -60°C / h to 115°C to precipitate the polyamide, followed by an isothermal hold for 4 hours at this same temperature to strengthen the crystallinity. The precipitation temperature (T p ) is 120° C. Controlled cooling is then resumed at this same rate of −60° C. / h down to 20° C., then the reactor is drained and the dispersion is dried in an oven at 75° C. under atmospheric pressure.

[0131] The resulting PA11 powder has the following properties: intrinsic viscosity of 1.28, volume average diameter of 40 μm, and diameters Dv10=27 μm, Dv50=42 μm, and Dv90=53 μm, thus span=0.62. DSC analysis of this PA11 powder shows, upon the first heating, a unimodal melting endotherm at 200 °C associated with a melting enthalpy of 140 J / g (FIG. 1), and a crystallization temperature T c = 157°C (Fig. 2). f1 -T c is equal to 43°C.

[0132] Example 4 (Comparative) from U.S. Patent Application Publication No. 2008 / 0166496 Diamine-terminated PA11 was prepared by polymerizing 250 g of 11-aminoundecanoic acid in the presence of 1.25 g of 4,4'-diaminocyclohexylmethane (PACM, mixture of isomers) and has an intrinsic viscosity of 1.42 in combination with a concentration of chain-end COOH groups equal to 19 mmol / kg and a concentration of chain-end NH2 groups equal to 67 mmol / kg.

[0133] A reactor (working volume 1 L) is charged with 85 g of this diamine-terminated PA11 and 425 g of technical-grade ethanol (purity 96%), and mechanical stirring is performed using an impeller-type turbomixer. The stirrer is operated at a speed of 500 rpm throughout the test. The medium is heated to 152°C and then isothermally held at this temperature for 1 hour. The medium is then cooled to 112°C at a rate of -25°C / h and then maintained at this temperature for 1 hour. The precipitation temperature (T p ) is 112°C. The medium is then cooled to ambient temperature at a rate of -25°C / h. The reactor is then drained and the ethanol is distilled off in a stirred oven at 70°C / 400 mbar, and the powder is then dried at 84°C / 20 mbar.

[0134] The resulting PA11 powder has the following particle size characteristics: volume mean diameter 89 μm, and diameters Dv10=65 μm, Dv50=93 μm, and Dv90=123 μm, thus span=0.62. DSC analysis of this PA11 powder showed, upon the first heating, a bimodal melting endotherm with a shoulder at 193 °C and a peak at 202 °C, associated with a melting enthalpy of 140 J / g (FIG. 1), and a crystallization temperature T c = 162°C (Fig. 3). f1 -T c It is the lower of the two melting temperatures that is used to calculate , and therefore this difference is equal to 29 °C.

Claims

1. A unimodal melting endotherm and a single melting temperature (T ｆ１ ｍａｘ 1. A method for producing a polyamide powder having a i) contacting a polyamide with a solvent to obtain a mixture; ii) heating the mixture to dissolve the polyamide in the solvent; iii) heating the mixture in the solvent to a precipitation temperature (T ｐ ), which results in a non-unimodal melting endotherm and a (T ｆ１ ｍａｘ ) is the highest melting temperature; iv) the precipitated polyamide powder has a unimodal melting endotherm and melting temperature (T ｆ１ ｍａｘ The temperature of the mixture is increased to at most T ｐ temperature, in particular T ｐ -0.1℃~T ｐ maintaining a temperature in the range of −15° C.; and v) recovering the resulting polyamide powder A method comprising:

2. The solvent to be brought into contact with the polyamide is an alcohol, particularly C １ ~C ４ 2. The method of claim 1, wherein the alcohol is an aliphatic alcohol, preferably ethanol.

3. 3. The method according to claim 1 or 2, wherein the polyamide is polyamide 11, polyamide 6, or polyamide 10.10, or polyamide 10.12, or polyamide 6.

10.

4. In step iv), the mixture is heated to a temperature of at most T over a period of at least 2 hours, in particular between 3 and 12 hours, starting from the end of the precipitation of the polyamide. ｐ 4. The method of claim 1, wherein the temperature is maintained at a temperature equal to

5. The monomodal melting endotherm and single melting temperature (T ｆ１ ｍａｘ ).

6. 6. Polyamide powder according to claim 5, characterized in that it has a median diameter Dv50 between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 30 μm and 90 μm.

7. 7. Polyamide powder according to claim 5, characterized in that it has a span factor between 0.1 and 1.5, preferably between 0.1 and 1.0, more preferably between 0.5 and 1.

0.

8. 8. Powder according to any one of claims 5 to 7, wherein the polyamide is polyamide 11.

9. Melting temperature (T) between 195°C and 205°C ｆ１ ｍａｘ 9. The powder according to claim 8, characterized in that it has a molecular weight of 1.001 or more.

10. Melting temperature (T ｆ１ ｍａｘ ) and crystallization temperature (T ｃ 10. The powder according to claim 8, wherein the difference between the temperature of the powder and the temperature of the container is between 35°C and 45°C.

11. A unimodal melting endotherm and a single melting temperature (T ｆ１ ｍａｘ ) and further having the following properties: a volume-average diameter between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 40 μm and 80 μm; a diameter Dv10 of more than 5 μm, in particular between 10 μm and 70 μm, preferably between 20 μm and 60 μm; a volume median diameter Dv50 between 10 μm and 200 μm, in particular between 20 μm and 100 μm, preferably between 30 μm and 90 μm; a diameter Dv90 of less than 350 μm, in particular between 30 μm and 200 μm, preferably between 50 μm and 150 μm; a span factor between 0.1 and 1.5, preferably between 0.1 and 1, more preferably between 0.5 and 1.0; an enthalpy of fusion greater than 100 J / g, preferably between 110 J / g and 160 J / g; and / or an intrinsic viscosity between 0.8 and 1.8, preferably between 1.0 and 1.5 The polyamide 11 powder has at least one of:

12. A composition in powder form, in particular for 3D printing by laser sintering, comprising: - a polyamide powder according to any one of claims 5 to 11; and - at least one filler or additive A composition comprising:

13. 13. A method for producing a polyamide article by powder agglomeration of the powder according to any one of claims 5 to 12 by melting using electromagnetic radiation.

14. 13. An article of manufacture obtained by melting a powder according to any one of claims 5 to 11 or a composition according to claim 12 with the aid of electromagnetic radiation.

15. Polyamide melting temperature (Tf １ ｍｉｎ ) and crystallization temperature (T ｃ ) and the difference (Tf １ ｍｉｎ -T ｃ 5. Use of the method according to any one of claims 1 to 4 to increase the amount of erythrocytes in the blood.

Images